Forecast Discussions mentioning any of "HRRR" "RR" "RUC13" "RUC" received at GSD on 12/06/11


AREA FORECAST DISCUSSION
NWS DENVER CO
250 PM MST SUN DEC 4 2011 .SHORT TERM...BROAD UPPER TROF COVERS MUCH OF THE WESTERN U.S. WHILE WATER VAPOR IMAGERY SHOWING NEXT DISTURBANCE DROPPING SOUTH INTO THE MEAN TROF POSITION OVER UTAH. RUC QG FIELDS SHOWING BEST UPWARD FORCING OVER WESTERN CO AND WESTERN WYOMING. THE ASSOCIATED COLD FRONT IS MOVING SOUTH FROM SOUTHERN WYOMING INTO NORTHERN COLORADO WITH GUSTY NORTHERLY WINDS DEVELOPING BEHIND THE FRONT. CEILINGS ARE BEGINNING TO LOWER OVER THE FRONT RANGE WITH SOME VERY LIGHT ECHOES DEVELOPING OVER THE FOOTHILLS. OVERALL...FORECAST IS STILL ON TRACK WITH MAIN CONCERN SNOW AMOUNTS FOR UPCOMING STORM. SNOW AMOUNTS EXPECTED TO BE A BIT LOWER THAN THE LAST STORM...AS QG VERTICAL VELOCITY FIELDS SHOWING THE BEST FORCING ACROSS WESTERN COLORADO WITH LESSER FORCING OVER NORTHEAST COLORADO AND OVERALL MOISTURE IS A BIT LOWER. HIGHEST SNOW AMOUNTS WILL BE OVER THE EAST SLOPE FRONT RANGE FOOTHILLS WITH LESSER AMOUNTS AS YOU MOVE EAST AWAY FROM THE FOOTHILLS. THERE IS SOME GOOD LOW LEVEL INSTABILITY WITH UPSLOPE UP TO AROUND 600MB. WILL KEEP THE CURRENT 3-6 SNOWFALL RANGE OVER THE URBAN CORRIDOR BUT WOULDN`T BE SURPRISED IF AMOUNTS END UP BEING A BIT LOWER. BIG DROPOFF OF SNOW EAST OF INTERSTATE 25 AND AM CONCERNED THAT THERE WON`T BE MUCH SNOW OVER EASTERN WELD COUNTY AND ZONE 45 AND 46 WITH CURRENT ADVISORIES. WILL LEAVE IN PLACE FOR NOW. FOR THE FOOTHILLS WILL STILL GO WITH 5 TO 10 INCHES. EVEN COLDER TEMPERATURES FOR TONIGHT AND MONDAY WITH READINGS IN THE SINGLE DIGITS AND LOWER TEENS FOR THE NEXT 24 HOURS. .LONG TERM...COULD STILL SEE A FEW FLURRIES OCCURRING SOUTH ON INTERSTATE 70 AS THE STORM CONTINUES TO MOVE SOUTH AND COLD HIGH PRESSURE SETTLES IN. TEMPERATURES WILL CONTINUE TO PLUMMET TO BELOW ZERO ACROSS THE AREA. WILL LIKELY SEE VERY COLD TEMPERATURES IN THE HIGH MOUNTAIN VALLEYS...DROPPING TO AROUND -20 TO -30 BY EARLY TUESDAY MORNING. THE PERSISTENT UPPER TROUGH WILL FINALLY MOVE SOUTHEAST OF THE AREA WITH A SHORT WAVE UPPER RIDGE MOVING OVERHEAD HOWEVER FLOW ALOFT WILL STILL BE NORTHERLY. TEMPERATURES WILL WARM SLIGHTLY...BUT HAVE KEPT TEMPERATURES COOLER THAN GUIDANCE AS THE RECENT COLD AIRMASS WILL BE HARD TO SCOUR OUT AND THE SNOW ON THE GROUND WILL LIKELY HAVE AN AFFECT AS WELL. HAVE KEPT HIGHS IN THE TEENS TO UPPER 20S FOR TUESDAY. ON WEDNESDAY...FLOW ALOFT WILL TURN WESTERLY AS A BROAD UPPER TROUGH OVER CANADA DROPS SOUTH. THE WEST WINDS WILL HELP TEMPERATURES WARM DURING THE DAY...THEN A WEAK COLD FRONT WILL DROP SOUTH DURING THE NIGHT. NO REAL PRECIPITATION EXPECT THAT NIGHT...HOWEVER IT WILL RESULT IN COOLER TEMPERATURES AND A SLIGHT CHANCE OF SNOW THURSDAY AS ANOTHER SHORTWAVE TROUGH ROUNDS THE BOTTOM OF THE LARGER TROUGH. THE LARGE SCALE PATTERN WILL CONTINUE TO TRANSITION EAST FRIDAY TO BRING A STRONGER UPPER RIDGE OVER THE ROCKIES BRINGING DRIER WEATHER AND RELATIVELY WARMER AIR FRIDAY AND SATURDAY. INTRODUCING A SLIGHT CHANCE OF PRECIPITATION FOR SUNDAY AS MODELS DISAGREEING ON WHETHER THERE WILL BE ANOTHER TROUGH OR RIDGE OVER THE AREA. && .AVIATION...CEILINGS BEGINNING TO LOWER NORTH OF THE LOCAL TERMINALS WITH CIGS OF 5000-7000 FEET AGL UPSTREAM OVER FNL AND GXY. THIS WILL RESULT IN ILS APPROACHES AROUND 23Z AT DEN AND BJC. THE LIGHT SNOW NOT FAR BEHIND WITH SNOW NOW AT CYS. MORE WIDESPREAD SNOW AT LOCAL AIRPORTS DEVELOPING BETWEEN 02-3Z AND CONTINUING THROUGH ABOUT 08Z. THIS WILL BE THE WINDOW OF MOST OF THE ACCUMULATION SNOW. MOST OF THE SNOW WILL BECOME VERY LIGHT AND JUST FLURRIES DURING THE DAY ON MONDAY WITH ACCUMULATIONS UNDER AN INCH. STILL TOTAL ACCUMULATIONS OF 3 TO 6 INCHES...WITH 2-3 AT DIA...3-4 AT APA AND 4 TO 6 AT BJC. && .BOU WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 11 AM MST MONDAY FOR THE URBAN CORRIDOR...PALMER DIVIDE AND ADJACENT PLAINS...ZONES COZ038>041-043-045-046. WINTER WEATHER ADVISORY UNTIL 11 AM MST MONDAY FOR THE FOOTHILLS AND SOUTH PARK...ZONES COZ035>037. && $$ SHORT TERM...ENTREKIN LONG TERM....KRIEDERMAN AVIATION...ENTREKIN
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
310 AM EST SUN DEC 4 2011 .SYNOPSIS... HIGH PRESSURE WILL REMAIN CENTERED NORTH OF THE REGION THROUGH EARLY THIS WEEK AS A WEAK TROUGH OF LOW PRESSURE LINGERS OFFSHORE. A COLD FRONT WILL IMPACT THE AREA DURING MID WEEK FOLLOWED BY HIGH PRESSURE FOR LATE IN THE WEEK. && .NEAR TERM /THROUGH TODAY/... IT IS CONSIDERABLY WARMER ACROSS SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA EARLY THIS MORNING WITH 24 HOUR TEMPERATURE CHANGES AVERAGING BETWEEN +15 AND +20 DEGREES PER 04/07Z REGIONAL OBSERVATIONS. THIS TREND WILL CONTINUE THROUGH SUNRISE WITH LITTLE CHANGE IN TEMPERATURES EXPECTED. DEEP LAYERED HIGH PRESSURE WILL HOLD FIRM ACROSS THE CAROLINAS AND EASTERN GEORGIA TODAY AS AN IMPRESSIVE UPPER LEVEL TROUGH DOMINATES MUCH OF THE WESTERN AND CENTRAL PORTIONS OF THE COUNTRY. CLOUD COVER IS EXPECTED TO THICKEN THROUGH THE DAY AS 290-295K ISENTROPIC LIFT PERSISTS ATOP THE LOW-LEVEL SURFACE WEDGE. ALTHOUGH THE LOWEST 4000 FT OF THE COLUMN WILL BE QUITE MOIST... THE REMAINDER OF THE LOWER TROPOSPHERE WILL REMAIN TOO DRY TO SUPPORT MUCH IN THE WAY OF SIGNIFICANT RAINFALL. ALTHOUGH A FEW SPRINKLES COULD OCCUR AT VARIOUS LOCATIONS THROUGH THE DAY... ESPECIALLY AT THE COAST CLOSER TO THE COASTAL TROUGH...THE PROSPECTS FOR MEASURABLE RAINFALL ARE TOO LOW TO JUSTIFY ANY MENTION OF RAIN CHANCES THROUGH SUNSET. HIGH TEMPERATURES WILL BE TEMPERED BY A STRENGTHENING ONSHORE FLOW AND INCREASED CLOUD COVER. MODEL SOUNDINGS SUGGEST A SLIGHT LOWERING OF OUR HIGH TEMPERATURE FORECAST IS NEEDED FOR MOST LOCATIONS...BUT ONLY BY 1-2 DEGREES. STILL EXPECT AT OR SLIGHTLY ABOVE NORMAL TEMPERATURES FOR EARLY DECEMBER WITH HIGHS GENERALLY TOPPING OUT IN THE MID-UPPER 60S. IT SHOULD BE NOTED THAT SOME GRIDDED GUIDANCE SUGGESTS TEMPERATURES MAY BE CONFINED TO THE LOWER-MID 60S. WILL HAVE TO SEE HOW IF THESE TRENDS CONTINUE AND IF THEY DO A SLIGHTLY LOWERING MAY BE CONSIDERED LATER TODAY. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY/... THE UPPER RIDGE WILL BEGIN TO RAPIDLY ERODE TONIGHT AS THE UPPER TROUGH TO THE WEST DRAWS CLOSER. THE LOW-LEVEL LOOKS TO HOLD FIRM WITH THE COASTAL TROUGH LURKING JUST OFFSHORE FOR MUCH OF THE NIGHT. CONTINUED ISENTROPIC LIFT WILL HELP MAINTAIN QUITE A BIT OF CLOUD COVER OVERNIGHT WITH AN OUTSIDE CHANCE FOR A BRIEF SPRINKLE OR LIGHT SHOWER POTENTIALLY MOVING ONSHORE AT THE COAST. WE CONTINUE TO FAVOR A DRY FORECAST WITH GRIDDED POPS GENERALLY RANGING BETWEEN 5-10 PERCENT. SIMILAR TO THIS MORNING...THE INCREASED CLOUD COVER AND A BIT MORE WIND WILL YIELD A RELATIVELY WARM NIGHT WITH LOWS RANGING FROM THE LOWER 50S INLAND TO THE UPPER 50S/NEAR 60 AT THE COAST. THERE IS SOME CONCERN FOR FOG TO DEVELOP AFTER MIDNIGHT AS STRATUS TRIES TO BUILD DOWN...BUT CONFIDENCE THIS FAR OUT IS NOT HIGH ENOUGH TO JUSTIFY A MENTION ATTM. AT MID LEVELS...A STRONG RIDGE WILL DOMINATE THE SOUTHEAST MONDAY AND TUESDAY...WHILE SURFACE HIGH PRESSURE SLOWLY RETREATS INTO THE ATLANTIC. TEMPERATURES WILL BE ABOVE NORMAL THE FIRST HALF OF THE WEEK...EXCEPT ALONG THE IMMEDIATE COAST WHERE SURFACE WINDS WILL GENERALLY BE FROM THE SOUTHEAST DURING THIS PERIOD. THERE IS A CHANCE OF A FEW SHOWERS AROUND BY TUESDAY AS A COLD FRONT MAKES SLOW PROGRESS INTO NORTHERN GEORGIA AND UPSTATE SOUTH CAROLINA...BUT MOST OF THE ACTIVITY SHOULD REMAIN TO THE NORTHWEST OF THE AREA. THE FORECAST BECOMES MUCH MORE DIFFICULT FOR WEDNESDAY. THE MAIN QUESTION WILL BE THE SPEED OF THE FRONT APPROACHING FROM THE WEST. THE 00Z GFS ESSENTIALLY STALLS THE FRONT FROM UPSTATE SOUTH CAROLINA TO CENTRAL GEORGIA...KEEPING THE FORECAST AREA ON THE WARM SIDE OF THE SYSTEM. HOWEVER...BOTH THE CMC AND ECMWF ARE A LITTLE MORE PROGRESSIVE AND HAVE THE FRONT MOVING SLOWLY THROUGH THE CWA LATER WEDNESDAY. THE DIFFERENCES IN FRONTAL TIMING ARE MAINLY MODULATED BY THE EXPECTED DEVELOPMENT OF A SURFACE LOW PRESSURE AREA ALONG THE FRONT. THE GFS IS FURTHEST WEST WITH THE DEVELOPMENT...AND ACTUALLY BRINGS A LOW OUT OF THE EASTERN GULF OF MEXICO INTO GEORGIA THURSDAY MORNING AND DOES NOT DRAG THE FRONT THROUGH THE CWA UNTIL THURSDAY. RIGHT NOW THIS IS AN OUTLIER...AND NOT ONLY DO THE OTHER GLOBAL MODELS BRING THE FRONT THROUGH FASTER...THERE ARE SEVERAL MEMBERS OF THE GFS ENSEMBLE WHICH ARE ALSO FASTER. THEREFORE...I HAVE GONE MORE WITH A MIDDLE OF THE ROAD SOLUTION...KEEPING MOST OF THE AREA ON THE WARM SIDE WEDNESDAY...BUT WITH THE FRONT KNOCKING ON THE DOOR BY AFTERNOON. I HAVE CONTINUED CHANCE POPS ON WEDNESDAY ACROSS THE AREA...BUT FRONTAL TIMING MAY CAUSE AN INCREASE OR DECREASE OF THESE VALUES WITH TIME. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... BASED ON THE THINKING MENTIONED ABOVE...I AM GOING FOR A SCENARIO WITH A FRONTAL PASSAGE WEDNESDAY NIGHT ACROSS THE CWA FROM WEST TO EAST. THIS IS NOT MUCH DIFFERENT THAN THE PREVIOUS FORECAST WAS SHOWING...ALTHOUGH I DID HAVE TO MAKE SOME APPROPRIATE ADJUSTMENTS TO THE TEMPS AND DEW POINTS TO ACCOUNT FOR THE SPEED OF THE FRONT. FOR PRECIP...DUE TO THE UNCERTAINTY IN THE TIMING I AM JUST GOING WITH CHANCE POPS WEDNESDAY NIGHT. THOSE MIGHT HAVE TO BE RAISED IN A DAY OR TWO WHEN THE TIMING IS A BIT MORE CERTAIN. COOLER AND DRIER WEATHER WILL MOVE IN BEHIND THE FRONT FOR THE END OF THE WEEK. && .AVIATION /07Z SUNDAY THROUGH THURSDAY/... EXTREMELY TRICKY AVIATION FORECAST FOR THE NEXT 24 HOURS. OF MOST IMPORTANCE IS THE NEXT 6-9 HOURS WHERE THE GREATEST AVIATION IMPACTS CAN BE EXPECTED. SATELLITE SHOWS LOW/MID-LEVEL CLOUD DECKS RAPIDLY EXPANDING ACROSS THE REGION COINCIDENT WITH INCREASING ISENTROPIC ASSENT. EXPECT MVFR CIGS TO OVERSPREAD KCHS/KSAV WITHIN THE NEXT FEW HOURS WITH BOTH RUC AND NAM SOUNDINGS INDICATING A POTENTIAL FOR IFR CIGS AFTER 09Z...IF NOT SOONER. GIVEN CURRENT CIG TRENDS SOUTH OF THE ALTAMAHA RIVER...WE SUSPECT KSAV HAS THE HIGHEST CHANCE FOR SEEING IFR CONDITIONS OVER THE NEXT FEW HOURS SO WILL INTRODUCE A TEMPO GROUP FROM 09-12Z TO TAKE THIS INTO ACCOUNT. CONFIDENCE IS NOT AS HIGH AT KCHS SO WILL ONLY UTILIZE A TEMPO 09-12Z FOR LOW-END MVFR CIGS AT THIS POINT. SHOULD TRENDS SUGGEST IFR CONDITIONS WILL DEVELOP AND AMENDMENT WILL BE ISSUED. LOW CONFIDENCE ON EXACTLY WHEN CIGS WILL RISE BACK TO VFR LEVELS WITH GUIDANCE ESSENTIALLY SPLIT. SOME KEEP CIGS IN MVFR TERRITORY FOR MUCH OF THE 06Z TAF PERIOD WHILE OTHERS BRING CONDITIONS BACK TO VFR BY LATE MORNING/EARLY AFTERNOON. WILL TAKE THE MORE CONSERVATIVE ROUTE AT THIS POINT GIVEN ALL OF THE UNCERTAINTIES AND SHOW VFR CIGS RETURNING TO BOTH TERMINALS BY 15-16Z. EXTENDED AVIATION OUTLOOK...CAN NOT RULE OUT MVFR CIGS ON OCCASION AT THE TERMINALS MONDAY AND TUESDAY MORNINGS WITH THE ONSHORE FLOW POTENTIALLY BRINGING IN A MARINE STRATUS DECK...BUT THE BEST CHANCE OF REDUCED CIGS/VSBYS WILL BE LATER WEDNESDAY INTO THURSDAY MORNING WITH THE COLD FRONT PASSAGE. && .MARINE... WINDS AND SEAS CONTINUE TO BUILD ACROSS THE WATERS EARLY THIS MORNING. THE COASTAL THROUGH RECENTLY PUSHED WEST OF BUOY 41004 SO EXPECT WINDS TO GRADUALLY DIMINISH SOUTH OF EDISTO BEACH OVER THE NEXT FEW HOURS. A PINCHED GRADIENT WILL LIKELY CONTINUE OVER THE CHARLESTON COUNTY COASTAL WATERS WHERE WINDS OF 15-20 KT WITH HIGHER GUSTS WILL LIKELY PERSIST THROUGH AT LEAST LATE MORNING. BUOY AND WW4 OUTPUT SUGGEST SEAS RANGE FROM 4-6 NEARSHORE AND 6-8 FT OFFSHORE. THE SMALL CRAFT ADVISORY LOOKS WELL PLACED FOR ALL BUT THE CHARLESTON HARBOR. THE PRESSURE GRADIENT IS EXPECTED TO RE-TIGHTEN THIS EVENING AS INLAND AREAS COOL AND THE COASTAL THROUGH MEANDERS EVEN CLOSER TO THE BEACHES. THE MOST ENHANCED GRADIENT LOOKS TO OCCUR OVER THE FAVORED CHARLESTON COUNTY COASTAL WATERS WHERE SPEEDS COULD REACH AS HIGH AS 15-20 KT. THE FAVORED NORTHEAST FETCH WILL KEEP SEAS ELEVATED...BUT THE LATEST WW4 OUTPUT KEEPS SEAS BELOW 6 FT OVER THE NEARSHORE WATERS. SEAS LOOK TO REMAIN ABOVE 6 FT OVER THE GEORGIA OFFSHORE LEG THROUGH THE NIGHT. WINDS SHOULD BE GENERALLY 15 KNOTS OR LESS OUT OF THE EAST AND SOUTHEAST MONDAY AND TUESDAY WITH HIGH PRESSURE IN THE WESTERN ATLANTIC SLOW TO MOVE EASTWARD. WINDS WILL PICK UP WEDNESDAY AHEAD OF THE APPROACHING COLD FRONT...THEN STAY UP BEHIND THE FRONT ON THURSDAY...WITH WINDS VEERING TO WEST AND NORTHWEST. SCAS ARE EXPECTED AT SOME POINT MID WEEK. SEAS WILL BE A BIT MORE OF A PROBLEM DUE TO THE EXTENDED FETCH FROM THE EAST. HEIGHTS OF 6 FEET OR MORE ARE EXPECTED IN THE OUTER GEORGIA WATERS FOR A FEW DAYS NEXT WEEK...WHILE SEAS WILL BE COMING UP IN THE NEARSHORE WATERS BUT MAY NOT REACH THE SCA CRITERIA OF 6 FEET. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR AMZ350- 352-354. SMALL CRAFT ADVISORY UNTIL 5 PM EST THURSDAY FOR AMZ374. && $$
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
1231 AM EST SUN DEC 4 2011 .SYNOPSIS... HIGH PRESSURE WILL REMAIN CENTERED NORTH OF THE REGION THROUGH EARLY NEXT WEEK...WHILE A WEAK TROUGH OF LOW PRESSURE WILL DEVELOP AND PERSIST ACROSS THE NEARBY COASTAL WATERS DURING THIS TIME. A COLD FRONT WILL IMPACT THE AREA DURING MID WEEK...FOLLOWED BY HIGH PRESSURE FOR LATE IN THE WEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... SATELLITE SHOWS LOW/MID-LEVEL CLOUDS RAPIDLY EXPANDING. SHOULD SEE MOST AREAS GO MOSTLY CLOUDY IF NOT CLOUDY OVER THE NEXT FEW HOURS. WILL NEED TO MAKE SOME ADJUSTMENT TO TEMPERATURES WITH THE EARLY MORNING UPDATE. && .SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY/... MODELS ARE GENERALLY IN GOOD AGREEMENT...SHOWING A DEEP LAYERED RIDGE EXTENDING FROM THE EASTERN GULF OF MEXICO TO NOVA SCOTIA AND A BROAD POSITIVELY TILTED TROUGH FROM THE NORTHERN PLAINS INTO THE FOUR CORNERS REGION ON SUNDAY. THIS SYNOPTIC PATTERN WILL GRADUALLY SHIFT EASTWARD THROUGH THE SHORT TERM PERIOD. SUNDAY...SURFACE HIGH PRESSURE WILL CONTINUE TO WEDGE INTO THE REGION FROM THE NORTH. SKIES SHOULD BE PARTLY TO MOSTLY CLOUDY FOR THE MAJORITY OF THE DAY WITH AMPLE MOISTURE TRAPPED BENEATH A MID LEVEL INVERSION ACCORDING TO MODEL SOUNDINGS. THESE CLOUDS WILL LIKELY STICK AROUND THROUGH SUNDAY NIGHT AS THE LOW LEVEL FLOW REMAINS ONSHORE. DAYTIME TEMPERATURES MIGHT BE HELD DOWN A BIT DUE TO THE CLOUD COVER...BUT STILL EXPECT HIGHS TO REACH THE UPPER 60S. TEMPERATURES SUNDAY NIGHT WILL ONLY FALL INTO THE UPPER 40S OR LOWER 50S GIVEN THE CLOUD COVER AS WELL. MONDAY...THE SURFACE RIDGE WILL SHIFT OFFSHORE ALLOWING THE LOW LEVEL FLOW TO VEER SOUTHEASTERLY. WHILE LOW LEVEL MOISTURE WILL CONTINUE TO ADVECT INTO THE AREA MAINTAINING PARTLY TO PERHAPS MOSTLY CLOUDY SKIES...THE MOISTURE SHOULD BE TOO SHALLOW AND SUBSIDENCE TOO STRONG TO SUPPORT ANY PRECIPITATION. HIGHS WILL REMAIN IN THE UPPER 60S WITH LOWS MONDAY NIGHT EVEN MILDER IN THE MID 50S. TUESDAY...THERE IS NOW BETTER MODEL AGREEMENT INDICATING THAT THE UPPER LEVEL PATTERN WILL BE LESS PROGRESSIVE...DELAYING THE APPROACH OF A COLD FRONT FROM THE WEST. HAVE LOWERED THE POTENTIAL FOR PRECIPITATION AS A RESULT...ONLY SHOWING A SLIGHT CHANCE OF SHOWERS FOR INLAND AREAS. TEMPERATURES AHEAD OF THE FRONT SHOULD WARM WELL INTO THE 70S. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... HE PATTERN FOR THIS PERIOD CONTINUES TO BE SOMEWHAT UNCERTAIN... ALTHOUGH THE LATEST TRENDS SUGGEST A DELAYED PROGRESSION OF THE SYNOPTIC FLOW. MODELS ARE STRUGGLING WITH HOW TO HANDLE THE EVOLUTION OF THE LARGE UPPER LEVEL TROUGH OVER THE WEST. THE GENERAL CONSENSUS SEEMS TO BE POINTING TOWARD EJECTING THE TROUGH ENE ON WEDNESDAY...PUSHING THE FRONT THROUGH SOMETIME WEDNESDAY NIGHT. THE FORECAST WILL SHOW A CHANCE OF SHOWERS THROUGH WEDNESDAY NIGHT...WITH DRYING THEN OCCURRING BEHIND THE FRONT AS HIGH PRESSURE BUILDS IN FOR LATE IN THE WEEK. THE AIRMASS AHEAD OF THE FRONT WILL REMAIN UNSEASONABLY WARM...WITH COOLER CONDITIONS IN ITS WAKE. THE GFS IS INDICATING THAT THE UPPER FLOW WILL BE QUITE PROGRESSIVE...WITH ANOTHER DEEP UPPER TROUGH DEVELOPING OVER THE WESTERN U.S. BY FRIDAY...THEN PUSHING ANOTHER COLD FRONT THROUGH THE REGION FRIDAY NIGHT/EARLY SATURDAY. CONFIDENCE IN THIS SOLUTION IS RATHER LOW GIVEN THE UNCERTAINTY BEFORE THIS PERIOD. HAVE GONE WITH SLIGHTLY COOLER THAN NORMAL TEMPS FRIDAY NIGHT AND SATURDAY FOR NOW. THE GFS WAS NOT SHOWING MUCH MOISTURE ASSOCIATED WITH THIS FRONT. THUS HAVE KEPT POPS BELOW 15 PERCENT. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... EXTREMELY TRICKY AVIATION FORECAST FOR THE NEXT 24 HOURS. OF MOST IMPORTANCE IS THE NEXT 6-9 HOURS WHERE THE GREATEST AVIATION IMPACTS CAN BE EXPECTED. SATELLITE SHOWS LOW/MID-LEVEL CLOUD DECKS RAPIDLY EXPANDING ACROSS THE REGION COINCIDENT WITH INCREASING ISENTROPIC ASSENT. EXPECT MVFR CIGS TO OVERSPREAD KCHS/KSAV WITHIN THE NEXT FEW HOURS WITH BOTH RUC AND NAM SOUNDINGS INDICATING A POTENTIAL FOR IFR CIGS AFTER 09Z...IF NOT SOONER. GIVEN CURRENT CIG TRENDS SOUTH OF THE ALTAMAHA RIVER...WE SUSPECT KSAV HAS THE HIGHEST CHANCE FOR SEEING IFR CONDITIONS OVER THE NEXT FEW HOURS SO WILL INTRODUCE A TEMPO GROUP FROM 09-12Z TO TAKE THIS INTO ACCOUNT. CONFIDENCE IS NOT AS HIGH AT KCHS SO WILL ONLY UTILIZE A TEMPO 09-12Z FOR LOW-END MVFR CIGS AT THIS POINT. SHOULD TRENDS SUGGEST IFR CONDITIONS WILL DEVELOP AND AMENDMENT WILL BE ISSUED. LOW CONFIDENCE ON EXACTLY WHEN CIGS WILL RISE BACK TO VFR LEVELS WITH GUIDANCE ESSENTIALLY SPLIT. SOME KEEP CIGS IN MVFR TERRITORY FOR MUCH OF THE 06Z TAF PERIOD WHILE OTHERS BRING CONDITIONS BACK TO VFR BY LATE MORNING/EARLY AFTERNOON. WILL TAKE THE MORE CONSERVATIVE ROUTE AT THIS POINT GIVEN ALL OF THE UNCERTAINTIES AND SHOW VFR CIGS RETURNING TO BOTH TERMINALS BY 15-16Z. EXTENDED AVIATION OUTLOOK...THERE IS A POTENTIAL FOR PERIODIC MVFR CIGS SUNDAY NIGHT INTO TUESDAY IN ASSOCIATION WITH A COASTAL TROUGH AND INCREASING LOW LEVEL MOISTURE. MVFR OR LOWER VSBYS ARE ALSO POSSIBLE IN FOG DURING THE LATE NIGHT/EARLY MORNING HOURS THROUGH THE FIRST PART OF THE WEEK. THERE COULD BE SOME BRIEF PERIODS OF MVFR CIGS AGAIN WITH SCATTERED SHOWERS ASSOCIATED WITH THE NEXT FRONT WEDNESDAY AND WEDNESDAY NIGHT. && .MARINE... BUOY OBSERVATIONS AND WW4 OUTPUT SUGGESTS SEAS HAVE BREACHED 6 FT ACROSS THE SOUTH CAROLINA MARINE ZONES. HAVE EXPANDED THE SMALL CRAFT ADVISORY TO THESE ZONES. A TIGHT SURFACE PRESSURE GRADIENT WILL CONTINUE TO SUPPORT NE WINDS 15-20 KT INTO THE OVERNIGHT...WITH GUSTS TO 25 KT ACROSS GA WATERS. PER THE LATEST OPC DEPICTION OF THE WAVE HEIGHT GRADIENT... CAPPED SEAS AT 5 FT WITH NO SCA/S ACROSS SC NEARSHORE WATERS...BUT 6 FT SEAS WILL IMPACT AREAS AT OR JUST BEYOND THE 20 NM BENCHMARK. LATER TONIGHT...NAM GUIDANCE CONTINUES TO DEPICT WEAK TROUGH DEVELOPMENT ACCOMPANIED BY GRADUAL RELAXATION OF THE PRESSURE GRADIENT. CONFIDENCE IN THIS SCENARIO REMAINS LESS THAN IDEAL...BUT FORECASTS CONTINUE TO DEPICT DECREASING WINDS LATER TONIGHT. HIGH PRESSURE TO THE NORTHEAST OF THE REGION WILL CONTINUE TO PRODUCE LONG FETCH NE FLOW THROUGH SUNDAY. WINDS WILL VEER TO SE FOR MONDAY THEN MORE SOUTHERLY BY TUESDAY AS A COLD FRONT GRADUALLY APPROACHES FROM THE WEST. THERE IS STILL SOME UNCERTAINTY WITH RESPECT TO THE TIMING/STRENGTH OF THE FRONT...BUT MODEL CONSENSUS SHOWS IT PUSHING OFFSHORE WEDNESDAY NIGHT. WINDS AHEAD AND IMMEDIATELY IN WAKE OF THE FRONT COULD APPROACH SMALL CRAFT ADVISORY LEVELS. MEANWHILE...MARGINAL SMALL CRAFT ADVISORY CONDITIONS DUE TO SEAS IN THE OUTER GEORGIA WATERS SHOULD CONTINUE THROUGH MID WEEK. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR AMZ350- 352-354. SMALL CRAFT ADVISORY UNTIL NOON EST THURSDAY FOR AMZ374. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1001 PM CST MON DEC 5 2011 .DISCUSSION... 852 PM CST A FEW CHALLENGES REVOLVING AROUND THE LAKE EFFECT PRECIPITATION THIS EVENING. RADAR IMAGERY SHOWS PRECIPITATION FROM MILWAUKEE SOUTH INTO NORTHERN WILL COUNTY. WATER VAPOR IMAGERY SHOWS DEFORMATION ZONE MOVING EAST OF THE FORECAST AREA WITH SUBSIDENCE AND MID LEVEL DRY AIR MOVING IN FROM THE SOUTHWEST. HAVE SEEN OVERALL INTENSITY OF RETURNS OFF THE LAKE DECREASE SOMEWHAT AS THIS FEATURE PROGRESSES THROUGH...BUT FORECAST SOUNDINGS SHOW LITTLE CHANGE IN THE LOW AND MID LEVELS OVERNIGHT AND SUSPECT AREA OF PRECIPITATION WILL CONTINUE THROUGH THE REMAINDER OF THE EVENING AND OVERNIGHT. SOUNDINGS DO SHOW A SLIGHT DECREASE IN THE INVERSION HEIGHTS BETWEEN 06-09Z...AND MOST OF THE HIGH-RES GUIDANCE...WITH THE RUC BEING THE EXCEPTION...SHOWS PRECIP DIMINISHING LATE TONIGHT. SUSPECT THE RUC MAY BE ONTO SOMETHING THOUGH...WITH NO REAL SENSE OF WHAT MAY CAUSE LAKE EFFECT TO SHUT OFF OVERNIGHT...THUS WILL BUMP UP POPS FOR TONIGHT. PRECIP TYPE ALSO A BIG QUESTION MARK. THE 129DM LINE ON THE 1000-850MB THICKNESS LINES UP WELL WITH CURRENT RAIN-SNOW LINE AND DOES GRADUALLY SHIFT SOUTH THROUGH COOK COUNTY TONIGHT...BUT LOCALIZED EFFECTS WITH WARM AIR OFF THE LAKE AND URBAN HEAT ISLAND WILL DELAY THE CHANGE OVER TO SNOW FOR AREAS ALONG THE LAKESHORE AND PORTIONS OF COOK COUNTY DESPITE THE GRADUAL COOL ADVECTION. HOWEVER...WET-BULBING EFFECTS UNDER THE HEAVIER SHOWERS MAY DOMINATE...AND HAS ALREADY BEEN EVIDENT ON DUAL-POL IMAGERY WITH SOME OF THE SHOWERS THAT PASSED OVER SOUTHERN DUPAGE COUNTY EARLIER TONIGHT WHERE SNOW BRIEFLY MADE ITS WAY TO THE SURFACE. SO DO EXPECT A CHANGE OVER TO SNOW AT SOME POINT...BUT HAVE VERY LOW CONFIDENCE ON PRECISE TIMING. PRECIP AMOUNT REPORTS HAVE BEEN ON THE ORDER OF A FEW HUNDREDTHS THUS FAR UNDER THE STRONGEST RETURNS...AND SEE NO REASON FOR THIS TO CHANGE OVERNIGHT NOR HAVE ANY CONCERNS FOR ACCUMULATIONS. FORECAST UPDATES TO FOLLOW SHORTLY...BMD //PREV DISCUSSION... NEAR TERM....THIS AFTERNOON THROUGH TONIGHT... VISIBLE IMAGERY CONTINUES TO SHOW A THICK STRATUS LAYER OVERHEAD. VERTICAL GROWTH OF THE CLOUD DESK REMAINS WELL SOUTH OF THE REGION OVER THE OZARKS AND WESTERN TENNESSEE. WITH THE ABUNDANT SOLAR SHIELDING...TEMPERATURES THIS AFTERNOON HAVE NOT WARMED MUCH. THUS EXPECT TEMPS TO REMAIN IN THE MID/UPR 30S. BETTER COLD AIR ADVECTION HAS CONTINUED TO OCCUR ACROSS WEST CENTRAL ILLINOIS WHERE TEMPERATURES HAVE HELD AROUND 30...AND IN THE MID 20S ACROSS CENTRAL MISSOURI. IR IMAGERY THIS AFTERNOON ALSO CONTINUES TO INDICATE MUCH THICKER CLOUD COVER OVER ILLINOIS/INDIANA. WSR-88D RADAR WAS DEPICTING PRECIPITATION PUSHING INLAND ACROSS BOTH COOK AND LAKE COUNTY ILLINOIS...AS LAKE MOISTURE SLOWLY SLIDES SOUTH/SOUTHWEST. MOISTURE REMAINS VERY SHALLOW AND MINIMAL LIFT...SUPPORTING PRECIP TO REMAIN AS LIQUID WITH PATCHY DRIZZLE. FURTHER NORTH A FEW OBSERVATIONS ACROSS WISCONSIN HAVE REPORTED LGT SN. FOR FAR NORTHEAST ILLINOIS TEMPERATURES ARE WARM ENOUGH TO MAINTAIN A LIQUID STATE OF PRECIPITATION. QUASI-STATIONARY BOUNDARY REMAINS TO OUR SOUTHEAST ACROSS THE OZARKS STRETCHING NORTHEAST THROUGH THE OHIO VALLEY. OVERNIGHT THE CHALLENGE WILL CONTINUE TO BE COVERAGE OF PRECIP...AND TEMPERATURES. GUIDANCE HAS SUGGESTED THAT TEMPERATURES WILL COOL MORE EFFICIENTLY TONIGHT WITH BETTER COLD AIR ADVECTION INTO NORTHERN IL/NORTHWEST IN...HOWEVER FEEL THIS IS TOO OVERDONE. THUS HAVE ADJUSTED OVERNIGHT LOWS UP A FEW DEGREES GIVEN THE EXPECTED THICK CLOUD COVER. WINDS START TO TURN NORTHEASTERLY THIS EVENING AND CONTINUE OVERNIGHT...WHICH SHOULD AID IN BENDING THE LAKE MOISTURE SOUTHWEST OR OVER NORTHEAST ILLINOIS. THUS HAVE MAINTAINED MENTION OF SLIGHT CHANCE WORDING. VERTICAL LIFT APPEARS TO BUMP UP A TAD OVERNIGHT...WITH SFC TEMPS PUSHING CLOSER TO FREEZING. MODEL SOUNDINGS INDICATE THAT ANY PRECIP THAT FALLS THIS EVENING WOULD START AS LIQUID...THEN POSSIBLY START TO MIX WITH LGT SNOW. AS PREVIOUSLY MENTIONED ABOUT THE MINIMAL LIFTING MECHANISM...IT IS POSSIBLE THAT PATCHY DRIZZLE COULD OCCUR BEFORE LGT SNOW WOULD OCCUR. QPF REMAINS MINIMAL...OR LESS THAN 0.05 THROUGH THE NEXT 24HRS. MORE THAN LIKELY IT IS CLOSER TO 0.01 TO 0.03. BASED ON THE EXPECTED TEMPERATURES AND MINIMAL LIFT...ANY SNOW THAT DOES FALL MAY ACCUMULATE UP TO A QUARTER OF AN INCH. ALTHOUGH THAT BEING SAID...CONFIDENCE IS LOW THAT THIS SCENARIO WOULD PAN OUT. TUESDAY THROUGH THURSDAY... A WEAK WAVE IS PROGGED TO DEVELOP ALONG THE QUASI-STATIONARY BOUNDARY AND SLIDE NORTHEAST THROUGH MISSOURI. ANTI-CYCLONIC FLOW REMAINS UPSTREAM ACROSS IOWA/MINNESOTA/WISCONSIN...WHICH SHOULD START TO TURN OFF LAKE MOISTURE SOMETIME TUE AFTN/EVE. HAVE HELD ONTO MENTION OF LGT RA/SN THRU THE MORNING HOURS. AFTN TEMPS SHOULD WARM MARGINALLY TO AROUND THE MID 30S ACROSS MOST OF THE CWFA. BY TUE AFTN/EVE THE INFLUENCE FROM THE UPSTREAM RIDGE SHOULD FINALLY ERODE THE THICK STRATUS AND ALLOW PARTLY CLOUD SKIES TO DEVELOP BY THE LATE AFTN/EVE. THIS COUPLED WITH 850MB THERMAL TROUGH OF -10 TO -12 DEG...WILL SET THE STAGE FOR OVERNIGHT LOWS IN THE TEENS TO LOWER 20S. AS WINDS SLOWLY SHIFT FROM THE NORTHWEST TO THE WEST/SOUTHWEST WED...THE LAKE MOISTURE WILL BECOME ORIENTED OVER LOWER MICHIGAN. 500MB VORT SLOWLY SLIDES EAST ALONG THE SOUTHERN STREAM...WHILE THE NORTHERN STREAM REMAINS IN PROGRESSIVE. THE FOCUS WED WILL CONTINUE TO BE ON THE ARRIVAL OF A POTENT FRONTAL BOUNDARY...THAT IS COUPLED WITH AN 850MB THERMAL TROUGH OF -20 TO -22 DEG C. THIS WILL PROVIDE THE COOLEST AIR OF THE SEASON LATER IN THE WEEK TO NORTHERN IL/NORTHWEST IN. PRIOR TO THE ARRIVAL OF THIS AIRMASS...MOISTURE IS EXPECTED TO POOL ALONG THE FRONT AS IT SLOWLY PUSHES SOUTHEAST ACROSS THE PLAINS THURSDAY. GUIDANCE HAS FLUCTUATED ON HOW THIS FEATURE WILL UNFOLD...AND IT REMAINS POSSIBLE THAT A WEAK WAVE WILL DEVELOP ALONG THE LEE-SIDE OF THE 500MB TROUGH AXIS. THIS SCENARIO COULD RESULT IN LGT SNOW OVERSPREADING NORTHERN IL/NORTHWEST IN THUR AFTN AS THE POTENT THERMAL TROUGH ARRIVES ALOFT. TEMPS THUR WILL REMAIN IN THE LOW/MID 30S. BEACHLER LONG TERM...THURSDAY NIGHT THROUGH MONDAY MAIN CONCERNS IN THE EXTENDED PORTION OF THE FORECAST ARE LIGHT SNOW POTENTIAL THURSDAY NIGHT INTO EARLY FRIDAY...FOLLOWED BY THE FIRST BLAST OF ARCTIC AIR OF THE SEASON FOR FRIDAY INTO EARLY SATURDAY. ON THURSDAY NIGHT...AS MENTIONED ABOVE...DIGGING H5 TROUGH WILL SPAWN A WEAK SURFACE LOW WHICH WILL TRACK ACROSS NORTHERN GREAT LAKES AND SEND AN ARCTIC FRONTAL BOUNDARY TOWARD AREA. MODELS HAVE BEEN CONSISTENT IN SPITTING OUT A STRIPE OF VERY LIGHT QPF NEAR OR OVER CWA IN RESPONSE TO THIS FEATURE. WITH NEGATIVE TEEN AIR AT H85 BUILDING IN FROM THE NORTH BEHIND ARCTIC FRONT...SUSPECT WAVE WILL RIDE ALONG LOW LEVEL BAROCLINIC ZONE. A PEEK AT GFS TIME HEIGHT AT ORD FOR THURSDAY NIGHT PERIOD SHOWS SATURATION AND ADEQUATE LIFT INTO -15C FAVORED SNOW GROWTH ZONE. THEREFORE...DESPITE QPF ONLY IN THE HUNDREDTHS UP TO MAYBE A TENTH OR SLIGHTLY MORE...WITH VERY COLD AIR MASS...SNOW WOULD BE HIGH RATIO AND POSSIBLY RESULT IN FIRST WIDESPREAD LIGHT ACCUMULATING SNOW OF THE SEASON FOR MANY (IF SCENARIO PANS OUT...POTENTIAL FOR AN INCH OR TWO OF SNOW). FOR NOW...HAVE BUMPED UP POPS IN GRIDS TO CHANCE ACROSS THE AREA GIVEN SOME UNCERTAINTY IN EXACTLY WHERE BEST SNOW POTENTIAL WILL OCCUR. LIGHT SNOW MAY LINGER INTO EARLY FRIDAY FOR EASTERN PORTION OF CWA BEFORE WAVE SHIFTS OFF TO THE EAST. THEREAFTER...ON FRIDAY...STRONG CAA WILL BE IN FULL FORCE WITH SHARP THERMAL TROUGH ARRIVING OVERHEAD LATE IN THE DAY. OPERATIONAL MODELS AND ENSEMBLES HAVE BACKED OFF EVER SO SLIGHTLY ON JUST HOW COLD ARCTIC AIR MASS WILL BE...BUT -15C OR SO AT H85 AND -8 TO -10 AT H95 WILL BE PLENTY COLD. TEMPERATURES WILL STRUGGLE INTO THE MID TO UPPER 20S FRIDAY AFTERNOON WITH A PERSISTENT WNW BREEZE LEADING TO LOW WIND CHILL VALUES. AXIS OF ARCTIC HIGH WILL PASS CLOSEST ON FRIDAY NIGHT...LEADING TO STRONG RADIATIONAL COOLING. IF MINOR SNOW COVER IS PRESENT...LOW TO MID TEENS...UPPER TEENS IN DOWNTOWN CHICAGO...IN GRIDS FOR LOW EARLY SATURDAY MORNING MIGHT BE A FEW DEGREES TOO HIGH. SW FLOW...STEADY WARMING ALOFT AND LIKELY FULL SUNSHINE ON SATURDAY WILL ALLOW FOR SOME RECOVERY FROM VERY COLD START TO DAY...BUT SUSPECT IT WILL BE TOUGH TO MAKE UP A LOT OF GROUND DUE TO LIMITED DAYLIGHT THIS TIME OF YEAR. THUS SHAVED OFF A DEGREE FROM MODEL BLEND FOR MAX TEMPERATURES ON SATURDAY...YIELDING HIGHS IN THE UPPER 20S TO AROUND 30 DEGREES. SUNDAY AND MONDAY LOOK TO BE MAINLY DRY WITH TEMPERATURES RETURNING TO CLOSE TO SEASONAL NORMS DUE TO SOUTHERLY FLOW AND CONTINUED WARMING OF THE COLUMN. A FRONTAL BOUNDARY MAY DROP SOUTH THROUGH THE AREA LATE MONDAY... BRINGING NEXT CHANCE FOR LIGHT PRECIP...BUT LARGE MODEL UNCERTAINTY THIS FAR OUT PRECLUDES ANYTHING MORE THAN SLIGHT POPS FOR MONDAY NIGHT. RC && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 04Z... * LAKE EFFECT RAIN/SNOW SHOWERS THIS EVENING. * POTENTIAL FOR LAKE EFFECT RAIN/SNOW SHOWERS THROUGH THE REMAINDER OF THE PERIOD. * MVFR CIGS POSSIBLY LIFTING TO VFR OVERNIGHT. * WIND SPEEDS/GUSTS THIS EVENING. CMS //DISCUSSION...UPDATED 02Z... LAKE EFFECT SHOWERS INCREASED IN COVERAGE AND INTENSITY EARLIER THIS EVENING AND FIRST WAVE PASSED THROUGH ORD AND WILL SOON BE AT MDW. PRECIP TYPE FROM UGN TO PWK TO ORD HAS BEEN ALL RAIN. THOUGH FURTHER INLAND WHERE TEMPS ARE COOLER...RAIN HAS MIXED WITH AND IN SOME AREAS CHANGED OVER TO SNOW. TEMPERATURES NEAR THE LAKE HOLDING STEADY WITH CGX HOLDING AT 42 FOR THE PAST FEW HRS. SO STILL THINK PRECIP TYPE AT ORD/MDW WILL REMAIN MAINLY RAIN BUT WITH TIME... ADDITIONAL LAKE EFFECT SHOWERS NOW DEVELOPING FROM NORTHEAST IL ACROSS SOUTHWEST WI MAY MIX WITH OR EVEN CHANGE OVER TO SNOW AS THEY MOVE SOUTH LATER THIS EVENING. WITH LITTLE CHANGE TO THE AIRMASS AND SOUNDING PROFILES THROUGH THE NIGHT...POTENTIAL FOR SCATTERED SHOWERS CONTINUING OVERNIGHT INTO TUESDAY MORNING EXISTS. THOUGH OVERALL CONFIDENCE REGARDING PRECIP TRENDS IS LOW. CMS PREVIOUS 00Z DISCUSSION... LAKE EFFECT RAIN/SNOW SHOWERS STILL OCCURRING ACROSS FAR SOUTHEAST WI INTO FAR NORTHEAST IL EARLY THIS EVENING. WINDS HAVE BECOME MORE NORTHEAST AND WITH A BIT OF CONVERGENCE ALONG THE WESTERN SIDE OF THE LAKE...THIS ACTIVITY MAY MAINTAIN ITSELF THROUGH THE EVENING HRS...PERHAPS LONGER. DIFFICULT TO PIN DOWN THE BEST TIME PERIOD AT ORD...SHOULD IT OCCUR. FOR NOW WILL CARRY VCSH AT ORD/DPA AND WILL MONITOR TRENDS THIS EVENING. WITH AIR TEMPS STILL IN THE UPPER 30S/NEAR 40...LIKELY TO STILL BE SOME RAIN BUT WITH TEMPS SLOWLY COOLING THROUGH THE EVENING...POTENTIAL FOR MORE SNOW SHOWERS EXISTS. CONTINUED NORTHEAST FLOW TUESDAY WITH LITTLE CHANGE TO THE AIR MASS WILL SUPPORT AT LEAST THE CHANCE FOR LAKE EFFECT RAIN/SNOW SHOWERS INTO THE AFTERNOON. BY LATE AFTERNOON...WINDS ALOFT START TURNING MORE NORTHWESTERLY WHICH SHOULD BRING AN END TO ANY LAKE EFFECT PRECIP. CIGS HAVE LIFTED TO MVFR AT MOST LOCATIONS...WITH SOME PATCHY IFR ACROSS PARTS OF WESTERN IL. PREVAILING MVFR STILL LOOKS ON TRACK THOUGH COULD SEE SOME LOW END MVFR...NEAR 1KFT WITH ANY OF THE HEAVIER LAKE EFFECT SHOWERS. DRIER AIR SPREADING ACROSS THE LAKE FROM LOWER MICHIGAN WILL LIKELY BE MODIFIED SOME AND MVFR CIGS MAY CONTINUE WELL INTO TUESDAY MORNING. THE GRADIENT HAS TIGHTENED SOME AND SHOULD REMAIN SOMEWHAT TIGHT THIS EVENING BEFORE SLOWLY RELAXING OVERNIGHT INTO TUESDAY MORNING. AS A RESULT...EXPECT NORTHEAST WINDS 10-15KTS THROUGH MUCH OF THE NIGHT WITH SOME HIGHER GUSTS...15-20KTS POSSIBLE THIS EVENING. WINDS WILL SLOWLY TURN BACK NORTHERLY TUESDAY AND THEN NORTHWEST OR WEST TUESDAY EVENING AS SPEEDS DIMINISH TO 5KTS OR LESS. CMS //ORD AND MDW CONFIDENCE...UPDATED 04Z... * LOW CONFIDENCE REGARDING LAKE EFFECT RAIN/SNOW SHOWERS... INCLUDING DURATION AND INTENSITY. * HIGH CONFIDENCE FOR MVFR CIGS THIS EVENING...MEDIUM CONFIDENCE CIGS WILL LIFT TO VFR OVERNIGHT OR TUESDAY MORNING. * HIGH CONFIDENCE IN WIND DIRECTION/SPEEDS/GUSTS THIS EVENING. CMS //OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z... WEDNESDAY AND THURSDAY...VFR. THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE. FRIDAY THROUGH SUNDAY...VFR. CMS && .MARINE... 147 PM CST HIGH PRESSURE ACROSS THE PLAINS WILL SLOWLY SAG SOUTHWARD TUESDAY AND TUESDAY NIGHT AS A STRONG AREA OF LOW PRESSURE MOVES ACROSS NORTHERN MANITOBA INTO THE HUDSON BAY. AS A CONSEQUENCE OF THIS...WINDS ARE EXPECTED TO BECOME WEST SOUTHWESTERLY AND INCREASE TO NEAR 30 KT LATE TUESDAY NIGHT AND ON WEDNESDAY. THEN WEDNESDAY NIGHT A STRONG COLD FRONT...ASSOCIATED WITH THE LOW ACROSS NORTHERN CANADA...WILL PUSH SOUTH ACROSS LAKE MICHIGAN. WEST TO NORTHWEST WINDS WILL OCCUR IN THE WAKE OF THIS FRONT. FOLLOWING THIS FRONT...ANOTHER CANADIAN HIGH PRESSURE SYSTEM WILL DROP SOUTHEAST ACROSS THE PLAINS THURSDAY AND FRIDAY. THIS SHOULD HELP SUPPORT A DECENT PRESSURE GRADIENT ACROSS THE GREAT LAKES. THUS...IN COMBINATION WITH A VERY COLD AIR MASS OVER THE RELATIVELY WARM WATERS OF LAKE MICHIGAN...WINDS WILL LIKELY REMAIN ELEVATED IN THE 20 TO 25 KT RANGE DURING THIS PERIOD. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
854 PM CST MON DEC 5 2011 .DISCUSSION... 852 PM CST A FEW CHALLENGES REVOLVING AROUND THE LAKE EFFECT PRECIPITATION THIS EVENING. RADAR IMAGERY SHOWS PRECIPITATION FROM MILWAUKEE SOUTH INTO NORTHERN WILL COUNTY. WATER VAPOR IMAGERY SHOWS DEFORMATION ZONE MOVING EAST OF THE FORECAST AREA WITH SUBSIDENCE AND MID LEVEL DRY AIR MOVING IN FROM THE SOUTHWEST. HAVE SEEN OVERALL INTENSITY OF RETURNS OFF THE LAKE DECREASE SOMEWHAT AS THIS FEATURE PROGRESSES THROUGH...BUT FORECAST SOUNDINGS SHOW LITTLE CHANGE IN THE LOW AND MID LEVELS OVERNIGHT AND SUSPECT AREA OF PRECIPITATION WILL CONTINUE THROUGH THE REMAINDER OF THE EVENING AND OVERNIGHT. SOUNDINGS DO SHOW A SLIGHT DECREASE IN THE INVERSION HEIGHTS BETWEEN 06-09Z...AND MOST OF THE HIGH-RES GUIDANCE...WITH THE RUC BEING THE EXCEPTION...SHOWS PRECIP DIMINISHING LATE TONIGHT. SUSPECT THE RUC MAY BE ONTO SOMETHING THOUGH...WITH NO REAL SENSE OF WHAT MAY CAUSE LAKE EFFECT TO SHUT OFF OVERNIGHT...THUS WILL BUMP UP POPS FOR TONIGHT. PRECIP TYPE ALSO A BIG QUESTION MARK. THE 129DM LINE ON THE 1000-850MB THICKNESS LINES UP WELL WITH CURRENT RAIN-SNOW LINE AND DOES GRADUALLY SHIFT SOUTH THROUGH COOK COUNTY TONIGHT...BUT LOCALIZED EFFECTS WITH WARM AIR OFF THE LAKE AND URBAN HEAT ISLAND WILL DELAY THE CHANGE OVER TO SNOW FOR AREAS ALONG THE LAKESHORE AND PORTIONS OF COOK COUNTY DESPITE THE GRADUAL COOL ADVECTION. HOWEVER...WET-BULBING EFFECTS UNDER THE HEAVIER SHOWERS MAY DOMINATE...AND HAS ALREADY BEEN EVIDENT ON DUAL-POL IMAGERY WITH SOME OF THE SHOWERS THAT PASSED OVER SOUTHERN DUPAGE COUNTY EARLIER TONIGHT WHERE SNOW BRIEFLY MADE ITS WAY TO THE SURFACE. SO DO EXPECT A CHANGE OVER TO SNOW AT SOME POINT...BUT HAVE VERY LOW CONFIDENCE ON PRECISE TIMING. PRECIP AMOUNT REPORTS HAVE BEEN ON THE ORDER OF A FEW HUNDREDTHS THUS FAR UNDER THE STRONGEST RETURNS...AND SEE NO REASON FOR THIS TO CHANGE OVERNIGHT NOR HAVE ANY CONCERNS FOR ACCUMULATIONS. FORECAST UPDATES TO FOLLOW SHORTLY...BMD && .PREV DISCUSSION... NEAR TERM....THIS AFTERNOON THROUGH TONIGHT... VISIBLE IMAGERY CONTINUES TO SHOW A THICK STRATUS LAYER OVERHEAD. VERTICAL GROWTH OF THE CLOUD DESK REMAINS WELL SOUTH OF THE REGION OVER THE OZARKS AND WESTERN TENNESSEE. WITH THE ABUNDANT SOLAR SHIELDING...TEMPERATURES THIS AFTERNOON HAVE NOT WARMED MUCH. THUS EXPECT TEMPS TO REMAIN IN THE MID/UPR 30S. BETTER COLD AIR ADVECTION HAS CONTINUED TO OCCUR ACROSS WEST CENTRAL ILLINOIS WHERE TEMPERATURES HAVE HELD AROUND 30...AND IN THE MID 20S ACROSS CENTRAL MISSOURI. IR IMAGERY THIS AFTERNOON ALSO CONTINUES TO INDICATE MUCH THICKER CLOUD COVER OVER ILLINOIS/INDIANA. WSR-88D RADAR WAS DEPICTING PRECIPITATION PUSHING INLAND ACROSS BOTH COOK AND LAKE COUNTY ILLINOIS...AS LAKE MOISTURE SLOWLY SLIDES SOUTH/SOUTHWEST. MOISTURE REMAINS VERY SHALLOW AND MINIMAL LIFT...SUPPORTING PRECIP TO REMAIN AS LIQUID WITH PATCHY DRIZZLE. FURTHER NORTH A FEW OBSERVATIONS ACROSS WISCONSIN HAVE REPORTED LGT SN. FOR FAR NORTHEAST ILLINOIS TEMPERATURES ARE WARM ENOUGH TO MAINTAIN A LIQUID STATE OF PRECIPITATION. QUASI-STATIONARY BOUNDARY REMAINS TO OUR SOUTHEAST ACROSS THE OZARKS STRETCHING NORTHEAST THROUGH THE OHIO VALLEY. OVERNIGHT THE CHALLENGE WILL CONTINUE TO BE COVERAGE OF PRECIP...AND TEMPERATURES. GUIDANCE HAS SUGGESTED THAT TEMPERATURES WILL COOL MORE EFFICIENTLY TONIGHT WITH BETTER COLD AIR ADVECTION INTO NORTHERN IL/NORTHWEST IN...HOWEVER FEEL THIS IS TOO OVERDONE. THUS HAVE ADJUSTED OVERNIGHT LOWS UP A FEW DEGREES GIVEN THE EXPECTED THICK CLOUD COVER. WINDS START TO TURN NORTHEASTERLY THIS EVENING AND CONTINUE OVERNIGHT...WHICH SHOULD AID IN BENDING THE LAKE MOISTURE SOUTHWEST OR OVER NORTHEAST ILLINOIS. THUS HAVE MAINTAINED MENTION OF SLIGHT CHANCE WORDING. VERTICAL LIFT APPEARS TO BUMP UP A TAD OVERNIGHT...WITH SFC TEMPS PUSHING CLOSER TO FREEZING. MODEL SOUNDINGS INDICATE THAT ANY PRECIP THAT FALLS THIS EVENING WOULD START AS LIQUID...THEN POSSIBLY START TO MIX WITH LGT SNOW. AS PREVIOUSLY MENTIONED ABOUT THE MINIMAL LIFTING MECHANISM...IT IS POSSIBLE THAT PATCHY DRIZZLE COULD OCCUR BEFORE LGT SNOW WOULD OCCUR. QPF REMAINS MINIMAL...OR LESS THAN 0.05 THROUGH THE NEXT 24HRS. MORE THAN LIKELY IT IS CLOSER TO 0.01 TO 0.03. BASED ON THE EXPECTED TEMPERATURES AND MINIMAL LIFT...ANY SNOW THAT DOES FALL MAY ACCUMULATE UP TO A QUARTER OF AN INCH. ALTHOUGH THAT BEING SAID...CONFIDENCE IS LOW THAT THIS SCENARIO WOULD PAN OUT. TUESDAY THROUGH THURSDAY... A WEAK WAVE IS PROGGED TO DEVELOP ALONG THE QUASI-STATIONARY BOUNDARY AND SLIDE NORTHEAST THROUGH MISSOURI. ANTI-CYCLONIC FLOW REMAINS UPSTREAM ACROSS IOWA/MINNESOTA/WISCONSIN...WHICH SHOULD START TO TURN OFF LAKE MOISTURE SOMETIME TUE AFTN/EVE. HAVE HELD ONTO MENTION OF LGT RA/SN THRU THE MORNING HOURS. AFTN TEMPS SHOULD WARM MARGINALLY TO AROUND THE MID 30S ACROSS MOST OF THE CWFA. BY TUE AFTN/EVE THE INFLUENCE FROM THE UPSTREAM RIDGE SHOULD FINALLY ERODE THE THICK STRATUS AND ALLOW PARTLY CLOUD SKIES TO DEVELOP BY THE LATE AFTN/EVE. THIS COUPLED WITH 850MB THERMAL TROUGH OF -10 TO -12 DEG...WILL SET THE STAGE FOR OVERNIGHT LOWS IN THE TEENS TO LOWER 20S. AS WINDS SLOWLY SHIFT FROM THE NORTHWEST TO THE WEST/SOUTHWEST WED...THE LAKE MOISTURE WILL BECOME ORIENTED OVER LOWER MICHIGAN. 500MB VORT SLOWLY SLIDES EAST ALONG THE SOUTHERN STREAM...WHILE THE NORTHERN STREAM REMAINS IN PROGRESSIVE. THE FOCUS WED WILL CONTINUE TO BE ON THE ARRIVAL OF A POTENT FRONTAL BOUNDARY...THAT IS COUPLED WITH AN 850MB THERMAL TROUGH OF -20 TO -22 DEG C. THIS WILL PROVIDE THE COOLEST AIR OF THE SEASON LATER IN THE WEEK TO NORTHERN IL/NORTHWEST IN. PRIOR TO THE ARRIVAL OF THIS AIRMASS...MOISTURE IS EXPECTED TO POOL ALONG THE FRONT AS IT SLOWLY PUSHES SOUTHEAST ACROSS THE PLAINS THURSDAY. GUIDANCE HAS FLUCTUATED ON HOW THIS FEATURE WILL UNFOLD...AND IT REMAINS POSSIBLE THAT A WEAK WAVE WILL DEVELOP ALONG THE LEE-SIDE OF THE 500MB TROUGH AXIS. THIS SCENARIO COULD RESULT IN LGT SNOW OVERSPREADING NORTHERN IL/NORTHWEST IN THUR AFTN AS THE POTENT THERMAL TROUGH ARRIVES ALOFT. TEMPS THUR WILL REMAIN IN THE LOW/MID 30S. BEACHLER LONG TERM...THURSDAY NIGHT THROUGH MONDAY MAIN CONCERNS IN THE EXTENDED PORTION OF THE FORECAST ARE LIGHT SNOW POTENTIAL THURSDAY NIGHT INTO EARLY FRIDAY...FOLLOWED BY THE FIRST BLAST OF ARCTIC AIR OF THE SEASON FOR FRIDAY INTO EARLY SATURDAY. ON THURSDAY NIGHT...AS MENTIONED ABOVE...DIGGING H5 TROUGH WILL SPAWN A WEAK SURFACE LOW WHICH WILL TRACK ACROSS NORTHERN GREAT LAKES AND SEND AN ARCTIC FRONTAL BOUNDARY TOWARD AREA. MODELS HAVE BEEN CONSISTENT IN SPITTING OUT A STRIPE OF VERY LIGHT QPF NEAR OR OVER CWA IN RESPONSE TO THIS FEATURE. WITH NEGATIVE TEEN AIR AT H85 BUILDING IN FROM THE NORTH BEHIND ARCTIC FRONT...SUSPECT WAVE WILL RIDE ALONG LOW LEVEL BAROCLINIC ZONE. A PEEK AT GFS TIME HEIGHT AT ORD FOR THURSDAY NIGHT PERIOD SHOWS SATURATION AND ADEQUATE LIFT INTO -15C FAVORED SNOW GROWTH ZONE. THEREFORE...DESPITE QPF ONLY IN THE HUNDREDTHS UP TO MAYBE A TENTH OR SLIGHTLY MORE...WITH VERY COLD AIR MASS...SNOW WOULD BE HIGH RATIO AND POSSIBLY RESULT IN FIRST WIDESPREAD LIGHT ACCUMULATING SNOW OF THE SEASON FOR MANY (IF SCENARIO PANS OUT...POTENTIAL FOR AN INCH OR TWO OF SNOW). FOR NOW...HAVE BUMPED UP POPS IN GRIDS TO CHANCE ACROSS THE AREA GIVEN SOME UNCERTAINTY IN EXACTLY WHERE BEST SNOW POTENTIAL WILL OCCUR. LIGHT SNOW MAY LINGER INTO EARLY FRIDAY FOR EASTERN PORTION OF CWA BEFORE WAVE SHIFTS OFF TO THE EAST. THEREAFTER...ON FRIDAY...STRONG CAA WILL BE IN FULL FORCE WITH SHARP THERMAL TROUGH ARRIVING OVERHEAD LATE IN THE DAY. OPERATIONAL MODELS AND ENSEMBLES HAVE BACKED OFF EVER SO SLIGHTLY ON JUST HOW COLD ARCTIC AIR MASS WILL BE...BUT -15C OR SO AT H85 AND -8 TO -10 AT H95 WILL BE PLENTY COLD. TEMPERATURES WILL STRUGGLE INTO THE MID TO UPPER 20S FRIDAY AFTERNOON WITH A PERSISTENT WNW BREEZE LEADING TO LOW WIND CHILL VALUES. AXIS OF ARCTIC HIGH WILL PASS CLOSEST ON FRIDAY NIGHT...LEADING TO STRONG RADIATIONAL COOLING. IF MINOR SNOW COVER IS PRESENT...LOW TO MID TEENS...UPPER TEENS IN DOWNTOWN CHICAGO...IN GRIDS FOR LOW EARLY SATURDAY MORNING MIGHT BE A FEW DEGREES TOO HIGH. SW FLOW...STEADY WARMING ALOFT AND LIKELY FULL SUNSHINE ON SATURDAY WILL ALLOW FOR SOME RECOVERY FROM VERY COLD START TO DAY...BUT SUSPECT IT WILL BE TOUGH TO MAKE UP A LOT OF GROUND DUE TO LIMITED DAYLIGHT THIS TIME OF YEAR. THUS SHAVED OFF A DEGREE FROM MODEL BLEND FOR MAX TEMPERATURES ON SATURDAY...YIELDING HIGHS IN THE UPPER 20S TO AROUND 30 DEGREES. SUNDAY AND MONDAY LOOK TO BE MAINLY DRY WITH TEMPERATURES RETURNING TO CLOSE TO SEASONAL NORMS DUE TO SOUTHERLY FLOW AND CONTINUED WARMING OF THE COLUMN. A FRONTAL BOUNDARY MAY DROP SOUTH THROUGH THE AREA LATE MONDAY... BRINGING NEXT CHANCE FOR LIGHT PRECIP...BUT LARGE MODEL UNCERTAINTY THIS FAR OUT PRECLUDES ANYTHING MORE THAN SLIGHT POPS FOR MONDAY NIGHT. RC && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 02Z... * LAKE EFFECT RAIN/SNOW SHOWERS THIS EVENING. * POTENTIAL FOR LAKE EFFECT RAIN/SNOW SHOWERS THROUGH THE REMAINDER OF THE PERIOD. * MVFR CIGS POSSIBLY LIFTING TO VFR OVERNIGHT. * WIND SPEEDS/GUSTS THIS EVENING. CMS //DISCUSSION...UPDATED 02Z... LAKE EFFECT SHOWERS INCREASED IN COVERAGE AND INTENSITY EARLIER THIS EVENING AND FIRST WAVE PASSED THROUGH ORD AND WILL SOON BE AT MDW. PRECIP TYPE FROM UGN TO PWK TO ORD HAS BEEN ALL RAIN. THOUGH FURTHER INLAND WHERE TEMPS ARE COOLER...RAIN HAS MIXED WITH AND IN SOME AREAS CHANGED OVER TO SNOW. TEMPERATURES NEAR THE LAKE HOLDING STEADY WITH CGX HOLDING AT 42 FOR THE PAST FEW HRS. SO STILL THINK PRECIP TYPE AT ORD/MDW WILL REMAIN MAINLY RAIN BUT WITH TIME... ADDITIONAL LAKE EFFECT SHOWERS NOW DEVELOPING FROM NORTHEAST IL ACROSS SOUTHWEST WI MAY MIX WITH OR EVEN CHANGE OVER TO SNOW AS THEY MOVE SOUTH LATER THIS EVENING. WITH LITTLE CHANGE TO THE AIRMASS AND SOUNDING PROFILES THROUGH THE NIGHT...POTENTIAL FOR SCATTERED SHOWERS CONTINUING OVERNIGHT INTO TUESDAY MORNING EXISTS. THOUGH OVERALL CONFIDENCE REGARDING PRECIP TRENDS IS LOW. CMS PREVIOUS 00Z DISCUSSION... LAKE EFFECT RAIN/SNOW SHOWERS STILL OCCURRING ACROSS FAR SOUTHEAST WI INTO FAR NORTHEAST IL EARLY THIS EVENING. WINDS HAVE BECOME MORE NORTHEAST AND WITH A BIT OF CONVERGENCE ALONG THE WESTERN SIDE OF THE LAKE...THIS ACTIVITY MAY MAINTAIN ITSELF THROUGH THE EVENING HRS...PERHAPS LONGER. DIFFICULT TO PIN DOWN THE BEST TIME PERIOD AT ORD...SHOULD IT OCCUR. FOR NOW WILL CARRY VCSH AT ORD/DPA AND WILL MONITOR TRENDS THIS EVENING. WITH AIR TEMPS STILL IN THE UPPER 30S/NEAR 40...LIKELY TO STILL BE SOME RAIN BUT WITH TEMPS SLOWLY COOLING THROUGH THE EVENING...POTENTIAL FOR MORE SNOW SHOWERS EXISTS. CONTINUED NORTHEAST FLOW TUESDAY WITH LITTLE CHANGE TO THE AIR MASS WILL SUPPORT AT LEAST THE CHANCE FOR LAKE EFFECT RAIN/SNOW SHOWERS INTO THE AFTERNOON. BY LATE AFTERNOON...WINDS ALOFT START TURNING MORE NORTHWESTERLY WHICH SHOULD BRING AN END TO ANY LAKE EFFECT PRECIP. CIGS HAVE LIFTED TO MVFR AT MOST LOCATIONS...WITH SOME PATCHY IFR ACROSS PARTS OF WESTERN IL. PREVAILING MVFR STILL LOOKS ON TRACK THOUGH COULD SEE SOME LOW END MVFR...NEAR 1KFT WITH ANY OF THE HEAVIER LAKE EFFECT SHOWERS. DRIER AIR SPREADING ACROSS THE LAKE FROM LOWER MICHIGAN WILL LIKELY BE MODIFIED SOME AND MVFR CIGS MAY CONTINUE WELL INTO TUESDAY MORNING. THE GRADIENT HAS TIGHTENED SOME AND SHOULD REMAIN SOMEWHAT TIGHT THIS EVENING BEFORE SLOWLY RELAXING OVERNIGHT INTO TUESDAY MORNING. AS A RESULT...EXPECT NORTHEAST WINDS 10-15KTS THROUGH MUCH OF THE NIGHT WITH SOME HIGHER GUSTS...15-20KTS POSSIBLE THIS EVENING. WINDS WILL SLOWLY TURN BACK NORTHERLY TUESDAY AND THEN NORTHWEST OR WEST TUESDAY EVENING AS SPEEDS DIMINISH TO 5KTS OR LESS. CMS //ORD AND MDW CONFIDENCE...UPDATED 02Z... * LOW CONFIDENCE REGARDING LAKE EFFECT RAIN/SNOW SHOWERS... INCLUDING DURATION AND INTENSITY. * HIGH CONFIDENCE FOR MVFR CIGS THIS EVENING...MEDIUM CONFIDENCE CIGS WILL LIFT TO VFR OVERNIGHT OR TUESDAY MORNING. * HIGH CONFIDENCE IN WIND DIRECTION/SPEEDS/GUSTS THIS EVENING. CMS //OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z... WEDNESDAY AND THURSDAY...VFR. THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE. FRIDAY THROUGH SUNDAY...VFR. CMS && .MARINE... 147 PM CST HIGH PRESSURE ACROSS THE PLAINS WILL SLOWLY SAG SOUTHWARD TUESDAY AND TUESDAY NIGHT AS A STRONG AREA OF LOW PRESSURE MOVES ACROSS NORTHERN MANITOBA INTO THE HUDSON BAY. AS A CONSEQUENCE OF THIS...WINDS ARE EXPECTED TO BECOME WEST SOUTHWESTERLY AND INCREASE TO NEAR 30 KT LATE TUESDAY NIGHT AND ON WEDNESDAY. THEN WEDNESDAY NIGHT A STRONG COLD FRONT...ASSOCIATED WITH THE LOW ACROSS NORTHERN CANADA...WILL PUSH SOUTH ACROSS LAKE MICHIGAN. WEST TO NORTHWEST WINDS WILL OCCUR IN THE WAKE OF THIS FRONT. FOLLOWING THIS FRONT...ANOTHER CANADIAN HIGH PRESSURE SYSTEM WILL DROP SOUTHEAST ACROSS THE PLAINS THURSDAY AND FRIDAY. THIS SHOULD HELP SUPPORT A DECENT PRESSURE GRADIENT ACROSS THE GREAT LAKES. THUS...IN COMBINATION WITH A VERY COLD AIR MASS OVER THE RELATIVELY WARM WATERS OF LAKE MICHIGAN...WINDS WILL LIKELY REMAIN ELEVATED IN THE 20 TO 25 KT RANGE DURING THIS PERIOD. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
154 PM CST SUN DEC 4 2011 .DISCUSSION... 1125 AM CST FRONTAL BOUNDARY CONTINUES TO STEADILY PUSH EAST ACROSS THE CWFA...EXPECTED BY MIDDAY TO PUSH THROUGH NORTHWEST INDIANA. BEHIND THIS BOUNDARY TEMPERATURES IN MANY LOCATIONS HAVE FALLEN INTO THE UPPER 30S TO LOWER 40S. EXPECT TEMPERATURES TO REMAIN NEARLY STEADY THROUGHOUT THE REMAINDER OF THE DAY...THEN SLOWLY BEGIN TO FALL THIS EVENING. ONE CAVEAT FOR HOW LOW TEMPERATURES MAY FALL TONIGHT WILL BE THE POSSIBILITY OF ABUNDANT CLOUD COVER. CURRENT GUIDANCE CONTINUES TO INDICATE THAT SKIES WILL STEADILY BREAK-UP THIS AFTERNOON AND POSSIBLY TURN SCATTERED TONIGHT. HOWEVER...LOOKING AT THE CURRENT VISIBLE IMAGERY ACROSS THE ENTIRE REGION AND MANY LOCATIONS UPSTREAM THIS SCENARIO OF THINNING SKIES LOOKS TO BE IN JEOPARDY. THUS HAVE CONCERNS ABOUT HOW COLD WE WILL SEE TEMPERATURES FALL TONIGHT. NONETHELESS 850MB THERMAL TROUGH CONTINUES TO PIVOT EAST...AND REMAIN OVERHEAD TONIGHT. AIDING IN TEMPERATURES FALLING INTO THE UPPER 20S TO LOWER 30S TONIGHT WILL BE THE STEADY COLD AIR ADVECTION WITH NORTHERLY WINDS TURNING NORHTEASTERLY. WITH AN INCREASING THERMAL DIFFERENTIAL ACROSS THE RELATIVELY WARMER MARINE ENVIRONMENT...AND MUCH COOLER AIR ALOFT EXPECT A NARROW CHANNEL OF LAKE MOISTURE TO FORM FROM THE NORTH/NORTHEAST WINDS. THIS WILL AID IN THE POSSIBILITY OF LAKE EFFECT FLURRIES/LGT SN. THEN BECOMING MIXED WITH LGT RA AFTER DAYBREAK MON. THROWING A POTENTIAL MONKEY WRENCH IN THIS SCENARIO COULD BE THE DEPTH OF THE FAVORED DENDRITIC GROWTH ZONE AND MOISTURE. VERY MINIMAL VERTICAL ENERGY MAY LIMIT THIS TO POSSIBLY JUST SOME DRIZZLE. THIS WILL BE THE FIRST CHALLENGE OF THE EVENING FORECAST. AS THIS COULD END UP BEING FROZEN DRIZZLE WITH TEMPERATURES POSSIBLY IN THE LOWER 30S. BEACHLER //PREV DISCUSSION... 340 AM CST HIGHLIGHTS THIS WEEK WILL INCLUDE RAIN COMING TO AN END...POSSIBLE SN/RASN/RA ACROSS THE SOUTHEAST MONDAY...LES POTENTIAL FOR LAKE/COOK LATE SUNDAY NIGHT INTO MONDAY...TRANSITIONING SOUTH TO LAKE/PORTER INDIANA BY TUESDAY...A FEW DAYS OF QUIET...FOLLOWED BY A LATE CLIPPER AND SNOW POTENTIAL AND FINALLY A BLAST OF COLD BY NEXT WEEKEND. THE EARLY MORNING SURFACE MAP SHOWED THE SURFACE LOW THAT HAS BEEN BRINGING THE WET AND ACTIVE WEATHER TO THE AREA TODAY...CONTINUING TO LIFTING NORTH THROUGH CENTRAL WISCONSIN. MEANWHILE AN ATTENDANT COLD FRONT LAY ROUGHLY ACROSS THE MISSISSIPPI RIVER...SOUTHWEST NEARLY TO ST LOUIS. THIS FRONT WILL CONTINUE TO SLOWLY SWEEP FROM WEST TO EAST THIS MORNING EVENTUALLY PUSHING ITSELF AND THE PRECIP EAST. THE MOST WIDE SPREAD ECHOES HAVE PUSHED EAST AND ONLY A FEW SCATTERED SHOWERS ARE LOCATED WITH THE ACTUAL FRONT. ACROSS EAST CENTRAL IOWA...TEMPERATURES HAVE DROPPED ENOUGH THAT -SN WAS REPORTED...BUT CLOUD TOPS HAVE WARMED ENOUGH AND ARE WARMER THAN -10C. THIS MEANS THAT THERE IS NO LONGER ICE INTRODUCTION INTO THE SATURATED LAYERS BELOW...AND A FEW LOCATIONS REPORTED U.P. AND OR FZDZ. FOR OUR AREA...AFTER THE FRONT MOVES THROUGH...LOWER LEVEL MOISTURE WILL REMAIN BUT PROFILES ARE STILL INDICATIVE OF LIQUID PRECIP AND SURFACE TEMPS WILL REMAIN ABOVE FREEZING. THE HRRR AND RUC BOTH HAVE A GOOD HANDLE ON THE WESTERN EDGE OF THE PRECIP AND FRONTAL LOCATION...AND MOST OF IT SHOULD CLEAR THE ROCKFORD CORRIDOR NEAR SUNRISE...WITH CHICAGO AND EAST JUST A FEW HOURS BEYOND. WHILE LOWER LEVEL RH WILL REMAIN PREVALENT WITH AND SHORTLY BEYOND FROPA...MOISTURE ABOVE -10C WILL DISAPPEAR AND THERE MAY BE SOME LINGERING DZ INTO THE EARLY MORNING HOURS. THE BIG PUSH OF COLDER AIR ISNT EXPECTED UNTIL LATER THIS EVENING AND TEMPERATURES WILL REMAIN ABOVE FREEZING...SO NO CONCERN OVER ANY OTHER PRECIP TYPES THIS MORNING. HIGH TEMPS WILL GENERALLY BE SEEN EARLY TODAY...AND SLOWLY FALL THROUGH THE DAY. WINDS WILL ABATE AS HIGH PRESSURE AND A PERIOD OF DRY...SLOWLY MOVE IN. THE MAIN UPPER LEVEL TROUGHING THAT STRETCHES FROM ROUGHLY SASKATCHEWAN...SOUTHWEST THROUGH THE FOUR CORNERS REGION WILL NOT HAVE MUCH REASON TO MOVE UNTIL THE START OF THE WORKWEEK. PRESENT SHORTWAVE SEEN ON WATER VAPOR IMAGERY ROUNDING THE BASE OF THE TROUGH...ACROSS SOUTHERN ARIZONA...WILL DAMPEN SOME AS IT GETS EJECTED ON THE EASTERN FLANK TODAY AND TONIGHT. AS IT DOES THIS...IT WILL HELP TO AMPLIFY AN INVERTED TROUGH THAT WILL NOSE ITS WAY TOWARDS THE OHIO VALLEY...EVENTUALLY SPAWNING A WEAK LOW ACROSS THE TENNESSEE VALLEY. GUIDANCE HAS BEEN HEMMING AND HAWING WITH JUST HOW FAR NORTH TO BRING THE PRECIP WITH THIS FEATURE...AND JUST HOW MUCH OF IT WILL REACH INTO THE SOUTHEASTERN CORNER OF THE CWA. THE LATEST FORECAST TRENDS HAVE BACKED OFF FROM PREVIOUS...AND DID SCALE BACK ON POPS AS WELL AS COVERAGE. STILL A LITTLE UNCERTAIN WITH WHERE THE RASN VS STRAIGHT RA LINE WOULD BE AND WILL MAINTAIN A SORT OF MIX. ALSO OF NOTE FOR COASTAL LOCATIONS IN THIS SAME TIME FRAME /AS THE INV TROF-LOW SLIDE EAST/ IS THE CHANCE FOR LES. THERMAL PROFILES ACROSS THE SOUTHERN LAKE WILL BECOME INCREASINGLY UNSTABLE WITH LAKE SURFACE TO H85 DELTA T`S REACHING THE 12-15C RANGE. EXPECT WEAK SHOWERS TO BEGIN TO STRETCH FROM LAKE COUNTY IL...EVENTUALLY SOUTH TO COOK AND GRADUALLY INTO THE MORE TYPICAL LAKE/PORTER IN ORIENTATION. QPF AMOUNTS NOT LOOKING VERY IMPRESSIVE DURING THE SHORT DURATION AND WOULD ONLY EXPECT ANYWHERE FROM A TRACE TO MAYBE A TENTH OR TWO OF ACCUMULATION CLOSE TO THE LAKE TOMORROW AND INTO TOMORROW NIGHT. THIS WILL ALL BE FOLLOWED BY A FEW DAYS OF QUIET AS ANOTHER RIDGE OF HIGH PRESSURE SWINGS IN FROM THE NORTHWEST. A LATE WEEK SYSTEM IS STILL PART OF A LOW CONFIDENCE FORECAST. GFS HAD BEEN ADVERTISING A WEAK CLIPPER DROPPING FROM THE NORTHERN PLAINS... AND PREVIOUS EC SOLNS HAD SIMILAR...BUT THE 12Z FLIPPED AND DEVELOPED A SURFACE LOW THAT LIFTS THROUGH THE MISSISSIPPI VALLEY...INTO NORTHERN INDIANA...NORTHEAST THROUGH EASTERN ONTARIO. CONFIDENCE AT THIS POINT ON THAT EURO SOLN IS LOW AND WILL KEEP THE CHANCE OF SNOW AND NOT BUMP UP (OR DOWN) ANY CATEGORY UNTIL THE PICTURE IS A LITTLE CLEARER. THE 00Z SOLN BEGAN TO COME IN AND WAS BACK TO THE ORIGINAL PICTURE WITH THE CLIPPER RACING THROUGH. DESPITE THE LOWER CONFIDENCE IN THAT FEATURE LATE THIS WEEK...THE ONE PICTURE OF CLARITY WHAT WILL FOLLOW IT. ALL LONG RANGE GUIDANCE IS STILL INDICATING THAT THERE WILL BE A LARGE SURGE OF COLD AIR ENCROACHING AS AN UPPER LEVEL TROUGH SWINGS THROUGH. THERE ARE STILL SOME TIMING DIFFERENCES WITH HOW QUICKLY THE COLD AIR WILL DUMP IN...WHICH IS DUE IN PART TO THE LARGE MODEL DIFFERENCES MENTIONED MOMENTS AGO...BUT THE ONE THING THEY ALL AGREE ON IS HOW COLD THE LOWER LEVELS WILL GET INTO THE WEEKEND. EVEN A WEEK OUT...THE EC/GFS/GEFS/DGEX/GEM(NHEM THROUGH F144) ALL HIGHLIGHT H85 TEMPS PLUMMETING TO -16 TO -18 DEGREES...OR EVEN A FEW DEGREES COLDER. TRANSLATE THAT TO THE SURFACE AND IT WOULD BE POSSIBLE THAT HIGHS WOULD STRUGGLE TO GET OUT OF THE TEENS FOR MANY LOCATIONS AND OVERNIGHT LOWS LEADING INTO THE WEEKEND WOULD DIVE BOMB TO THE SINGLE DIGITS /BUT LIKELY A SMIDGEN WARMER IN THE CHICAGO METRO/. WITH THAT FORECAST STILL BEING OUT 6-7 DAYS...AND A SLEW OF OTHER WEATHER GOING ON THROUGH THE EARLY WEEK... WILL ONLY CONTINUE TO TREND DOWN FROM THE INHERITED LONG RANGE FORECAST. THE BIG SAVING GRACE IS THE LACK OF SOLID SNOW PACK. IF THAT WERE PRESENT...IT WOULD BE MUCH COLDER. SHEA && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 18Z... * CIG TRENDS THIS AFTERNOON. * POTENTIAL FOR SOME LAKE EFFECT RAIN/SNOW SHOWERS ON MONDAY. KJB //DISCUSSION...UPDATED 18Z... THE MAIN CONCERNS THIS AFTERNOON ARE THE IFR CIGS MOVING ACROSS NORTHEASTERN ILLINOIS. A COLD FRONT IS CURRENTLY MOVING ACROSS NORTHEASTERN ILLINOIS. CIGS ALONG AND BEHIND THIS FRONT HAVE DROPPED INTO THE IFR RANGE. I EXPECT THESE CIGS TO LAST FOR A COUPLE OF HOURS THIS AFTERNOON BEFORE THEY BEGIN TO IMPROVE SOME BY MID TO LATE AFTERNOON. WINDS WILL PRIMARILY BE WESTERLY WITH A FEW GUSTS AROUND 18KT POSSIBLE EARLY THIS AFTERNOON. THE NEXT WEATHER CONCERN WILL BE ON MONDAY AS NORTH TO NORTHEASTERLY FLOW SETS UP AHEAD OF HIGH PRESSURE ACROSS THE PLAINS STATES. THIS FLOW PATTERN...IN COMBINATION WITH THE RELATIVELY COLD TEMPERATURES OVER LAKE MICHIGAN COULD SET THE STAGE FOR SOME LOWER MVFR CIGS AND SOME LAKE EFFECT RAIN AND SNOW SHOWERS BEGINNING EARLY MONDAY MORNING. KJB //ORD AND MDW CONFIDENCE...UPDATED 18Z... * MEDIUM CONFIDENCE IN CIGS IMPROVING TO LOW END MVFR AROUND 21 UTC. KJB //OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z... MONDAY NIGHT...MVFR CIG. CHANCE LIGHT LAKE EFFECT SNOW SHOWERS. TUESDAY...VFR. WEDNESDAY...VFR. THURSDAY...VFR. FRIDAY...VFR. SATURDAY...VFR. ALLSOPP && .MARINE... 153 PM CST HIGH PRESSURE WILL BUILD ACROSS THE PLAINS STATES ON MONDAY...SETTING UP NORTH TO NORTHEASTERLY FLOW DOWN LAKE MICHIGAN. THE FLOW WILL TURN MORE WESTERLY LATE TUESDAY INTO WEDNESDAY AS A POTENT STORM SYSTEM MOVES EAST ACROSS NORTHERN CANADA. THIS LOW WILL PUSH A COLD FRONT ACROSS LAKE MICHIGAN WEDNESDAY NIGHT. VERY COLD AIR BEHIND THIS FRONT LOOKS TO SET UP AN UNSTABLE ATMOSPHERE ACROSS THE LAKE LATER THIS WEEK. THIS LOOKS TO SET UP CONDITIONS FAVORABLE FOR SOME LAKE EFFECT SNOW SHOWERS. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 3 PM SUNDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1149 AM CST SUN DEC 4 2011 .DISCUSSION... 1125 AM CST FRONTAL BOUNDARY CONTINUES TO STEADILY PUSH EAST ACROSS THE CWFA...EXPECTED BY MIDDAY TO PUSH THROUGH NORTHWEST INDIANA. BEHIND THIS BOUNDARY TEMPERATURES IN MANY LOCATIONS HAVE FALLEN INTO THE UPPER 30S TO LOWER 40S. EXPECT TEMPERATURES TO REMAIN NEARLY STEADY THROUGHOUT THE REMAINDER OF THE DAY...THEN SLOWLY BEGIN TO FALL THIS EVENING. ONE CAVEAT FOR HOW LOW TEMPERATURES MAY FALL TONIGHT WILL BE THE POSSIBILITY OF ABUNDANT CLOUD COVER. CURRENT GUIDANCE CONTINUES TO INDICATE THAT SKIES WILL STEADILY BREAK-UP THIS AFTERNOON AND POSSIBLY TURN SCATTERED TONIGHT. HOWEVER...LOOKING AT THE CURRENT VISIBLE IMAGERY ACROSS THE ENTIRE REGION AND MANY LOCATIONS UPSTREAM THIS SCENARIO OF THINNING SKIES LOOKS TO BE IN JEOPARDY. THUS HAVE CONCERNS ABOUT HOW COLD WE WILL SEE TEMPERATURES FALL TONIGHT. NONETHELESS 850MB THERMAL TROUGH CONTINUES TO PIVOT EAST...AND REMAIN OVERHEAD TONIGHT. AIDING IN TEMPERATURES FALLING INTO THE UPPER 20S TO LOWER 30S TONIGHT WILL BE THE STEADY COLD AIR ADVECTION WITH NORTHERLY WINDS TURNING NORHTEASTERLY. WITH AN INCREASING THERMAL DIFFERENTIAL ACROSS THE RELATIVELY WARMER MARINE ENVIRONMENT...AND MUCH COOLER AIR ALOFT EXPECT A NARROW CHANNEL OF LAKE MOISTURE TO FORM FROM THE NORTH/NORTHEAST WINDS. THIS WILL AID IN THE POSSIBILITY OF LAKE EFFECT FLURRIES/LGT SN. THEN BECOMING MIXED WITH LGT RA AFTER DAYBREAK MON. THROWING A POTENTIAL MONKEY WRENCH IN THIS SCENARIO COULD BE THE DEPTH OF THE FAVORED DENDRITIC GROWTH ZONE AND MOISTURE. VERY MINIMAL VERTICAL ENERGY MAY LIMIT THIS TO POSSIBLY JUST SOME DRIZZLE. THIS WILL BE THE FIRST CHALLENGE OF THE EVENING FORECAST. AS THIS COULD END UP BEING FROZEN DRIZZLE WITH TEMPERATURES POSSIBLY IN THE LOWER 30S. BEACHLER //PREV DISCUSSION... 340 AM CST HIGHLIGHTS THIS WEEK WILL INCLUDE RAIN COMING TO AN END...POSSIBLE SN/RASN/RA ACROSS THE SOUTHEAST MONDAY...LES POTENTIAL FOR LAKE/COOK LATE SUNDAY NIGHT INTO MONDAY...TRANSITIONING SOUTH TO LAKE/PORTER INDIANA BY TUESDAY...A FEW DAYS OF QUIET...FOLLOWED BY A LATE CLIPPER AND SNOW POTENTIAL AND FINALLY A BLAST OF COLD BY NEXT WEEKEND. THE EARLY MORNING SURFACE MAP SHOWED THE SURFACE LOW THAT HAS BEEN BRINGING THE WET AND ACTIVE WEATHER TO THE AREA TODAY...CONTINUING TO LIFTING NORTH THROUGH CENTRAL WISCONSIN. MEANWHILE AN ATTENDANT COLD FRONT LAY ROUGHLY ACROSS THE MISSISSIPPI RIVER...SOUTHWEST NEARLY TO ST LOUIS. THIS FRONT WILL CONTINUE TO SLOWLY SWEEP FROM WEST TO EAST THIS MORNING EVENTUALLY PUSHING ITSELF AND THE PRECIP EAST. THE MOST WIDE SPREAD ECHOES HAVE PUSHED EAST AND ONLY A FEW SCATTERED SHOWERS ARE LOCATED WITH THE ACTUAL FRONT. ACROSS EAST CENTRAL IOWA...TEMPERATURES HAVE DROPPED ENOUGH THAT -SN WAS REPORTED...BUT CLOUD TOPS HAVE WARMED ENOUGH AND ARE WARMER THAN -10C. THIS MEANS THAT THERE IS NO LONGER ICE INTRODUCTION INTO THE SATURATED LAYERS BELOW...AND A FEW LOCATIONS REPORTED U.P. AND OR FZDZ. FOR OUR AREA...AFTER THE FRONT MOVES THROUGH...LOWER LEVEL MOISTURE WILL REMAIN BUT PROFILES ARE STILL INDICATIVE OF LIQUID PRECIP AND SURFACE TEMPS WILL REMAIN ABOVE FREEZING. THE HRRR AND RUC BOTH HAVE A GOOD HANDLE ON THE WESTERN EDGE OF THE PRECIP AND FRONTAL LOCATION...AND MOST OF IT SHOULD CLEAR THE ROCKFORD CORRIDOR NEAR SUNRISE...WITH CHICAGO AND EAST JUST A FEW HOURS BEYOND. WHILE LOWER LEVEL RH WILL REMAIN PREVALENT WITH AND SHORTLY BEYOND FROPA...MOISTURE ABOVE -10C WILL DISAPPEAR AND THERE MAY BE SOME LINGERING DZ INTO THE EARLY MORNING HOURS. THE BIG PUSH OF COLDER AIR ISNT EXPECTED UNTIL LATER THIS EVENING AND TEMPERATURES WILL REMAIN ABOVE FREEZING...SO NO CONCERN OVER ANY OTHER PRECIP TYPES THIS MORNING. HIGH TEMPS WILL GENERALLY BE SEEN EARLY TODAY...AND SLOWLY FALL THROUGH THE DAY. WINDS WILL ABATE AS HIGH PRESSURE AND A PERIOD OF DRY...SLOWLY MOVE IN. THE MAIN UPPER LEVEL TROUGHING THAT STRETCHES FROM ROUGHLY SASKATCHEWAN...SOUTHWEST THROUGH THE FOUR CORNERS REGION WILL NOT HAVE MUCH REASON TO MOVE UNTIL THE START OF THE WORKWEEK. PRESENT SHORTWAVE SEEN ON WATER VAPOR IMAGERY ROUNDING THE BASE OF THE TROUGH...ACROSS SOUTHERN ARIZONA...WILL DAMPEN SOME AS IT GETS EJECTED ON THE EASTERN FLANK TODAY AND TONIGHT. AS IT DOES THIS...IT WILL HELP TO AMPLIFY AN INVERTED TROUGH THAT WILL NOSE ITS WAY TOWARDS THE OHIO VALLEY...EVENTUALLY SPAWNING A WEAK LOW ACROSS THE TENNESSEE VALLEY. GUIDANCE HAS BEEN HEMMING AND HAWING WITH JUST HOW FAR NORTH TO BRING THE PRECIP WITH THIS FEATURE...AND JUST HOW MUCH OF IT WILL REACH INTO THE SOUTHEASTERN CORNER OF THE CWA. THE LATEST FORECAST TRENDS HAVE BACKED OFF FROM PREVIOUS...AND DID SCALE BACK ON POPS AS WELL AS COVERAGE. STILL A LITTLE UNCERTAIN WITH WHERE THE RASN VS STRAIGHT RA LINE WOULD BE AND WILL MAINTAIN A SORT OF MIX. ALSO OF NOTE FOR COASTAL LOCATIONS IN THIS SAME TIME FRAME /AS THE INV TROF-LOW SLIDE EAST/ IS THE CHANCE FOR LES. THERMAL PROFILES ACROSS THE SOUTHERN LAKE WILL BECOME INCREASINGLY UNSTABLE WITH LAKE SURFACE TO H85 DELTA T`S REACHING THE 12-15C RANGE. EXPECT WEAK SHOWERS TO BEGIN TO STRETCH FROM LAKE COUNTY IL...EVENTUALLY SOUTH TO COOK AND GRADUALLY INTO THE MORE TYPICAL LAKE/PORTER IN ORIENTATION. QPF AMOUNTS NOT LOOKING VERY IMPRESSIVE DURING THE SHORT DURATION AND WOULD ONLY EXPECT ANYWHERE FROM A TRACE TO MAYBE A TENTH OR TWO OF ACCUMULATION CLOSE TO THE LAKE TOMORROW AND INTO TOMORROW NIGHT. THIS WILL ALL BE FOLLOWED BY A FEW DAYS OF QUIET AS ANOTHER RIDGE OF HIGH PRESSURE SWINGS IN FROM THE NORTHWEST. A LATE WEEK SYSTEM IS STILL PART OF A LOW CONFIDENCE FORECAST. GFS HAD BEEN ADVERTISING A WEAK CLIPPER DROPPING FROM THE NORTHERN PLAINS... AND PREVIOUS EC SOLNS HAD SIMILAR...BUT THE 12Z FLIPPED AND DEVELOPED A SURFACE LOW THAT LIFTS THROUGH THE MISSISSIPPI VALLEY...INTO NORTHERN INDIANA...NORTHEAST THROUGH EASTERN ONTARIO. CONFIDENCE AT THIS POINT ON THAT EURO SOLN IS LOW AND WILL KEEP THE CHANCE OF SNOW AND NOT BUMP UP (OR DOWN) ANY CATEGORY UNTIL THE PICTURE IS A LITTLE CLEARER. THE 00Z SOLN BEGAN TO COME IN AND WAS BACK TO THE ORIGINAL PICTURE WITH THE CLIPPER RACING THROUGH. DESPITE THE LOWER CONFIDENCE IN THAT FEATURE LATE THIS WEEK...THE ONE PICTURE OF CLARITY WHAT WILL FOLLOW IT. ALL LONG RANGE GUIDANCE IS STILL INDICATING THAT THERE WILL BE A LARGE SURGE OF COLD AIR ENCROACHING AS AN UPPER LEVEL TROUGH SWINGS THROUGH. THERE ARE STILL SOME TIMING DIFFERENCES WITH HOW QUICKLY THE COLD AIR WILL DUMP IN...WHICH IS DUE IN PART TO THE LARGE MODEL DIFFERENCES MENTIONED MOMENTS AGO...BUT THE ONE THING THEY ALL AGREE ON IS HOW COLD THE LOWER LEVELS WILL GET INTO THE WEEKEND. EVEN A WEEK OUT...THE EC/GFS/GEFS/DGEX/GEM(NHEM THROUGH F144) ALL HIGHLIGHT H85 TEMPS PLUMMETING TO -16 TO -18 DEGREES...OR EVEN A FEW DEGREES COLDER. TRANSLATE THAT TO THE SURFACE AND IT WOULD BE POSSIBLE THAT HIGHS WOULD STRUGGLE TO GET OUT OF THE TEENS FOR MANY LOCATIONS AND OVERNIGHT LOWS LEADING INTO THE WEEKEND WOULD DIVE BOMB TO THE SINGLE DIGITS /BUT LIKELY A SMIDGEN WARMER IN THE CHICAGO METRO/. WITH THAT FORECAST STILL BEING OUT 6-7 DAYS...AND A SLEW OF OTHER WEATHER GOING ON THROUGH THE EARLY WEEK... WILL ONLY CONTINUE TO TREND DOWN FROM THE INHERITED LONG RANGE FORECAST. THE BIG SAVING GRACE IS THE LACK OF SOLID SNOW PACK. IF THAT WERE PRESENT...IT WOULD BE MUCH COLDER. SHEA && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 18Z... * CIG TRENDS THIS AFTERNOON. * POTENTIAL FOR SOME LAKE EFFECT RAIN/SNOW SHOWERS ON MONDAY. KJB //DISCUSSION...UPDATED 18Z... THE MAIN CONCERNS THIS AFTERNOON ARE THE IFR CIGS MOVING ACROSS NORTHEASTERN ILLINOIS. A COLD FRONT IS CURRENTLY MOVING ACROSS NORTHEASTERN ILLINOIS. CIGS ALONG AND BEHIND THIS FRONT HAVE DROPPED INTO THE IFR RANGE. I EXPECT THESE CIGS TO LAST FOR A COUPLE OF HOURS THIS AFTERNOON BEFORE THEY BEGIN TO IMPROVE SOME BY MID TO LATE AFTERNOON. WINDS WILL PRIMARILY BE WESTERLY WITH A FEW GUSTS AROUND 18KT POSSIBLE EARLY THIS AFTERNOON. THE NEXT WEATHER CONCERN WILL BE ON MONDAY AS NORTH TO NORTHEASTERLY FLOW SETS UP AHEAD OF HIGH PRESSURE ACROSS THE PLAINS STATES. THIS FLOW PATTERN...IN COMBINATION WITH THE RELATIVELY COLD TEMPERATURES OVER LAKE MICHIGAN COULD SET THE STAGE FOR SOME LOWER MVFR CIGS AND SOME LAKE EFFECT RAIN AND SNOW SHOWERS BEGINNING EARLY MONDAY MORNING. KJB //ORD AND MDW CONFIDENCE...UPDATED 18Z... * MEDIUM CONFIDENCE IN CIGS IMPROVING TO LOW END MVFR AROUND 21 UTC. KJB //OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z... MONDAY NIGHT...MVFR CIG. CHANCE LIGHT LAKE EFFECT SNOW SHOWERS. TUESDAY...VFR. WEDNESDAY...VFR. THURSDAY...VFR. FRIDAY...VFR. SATURDAY...VFR. ALLSOPP && .MARINE... 133 AM CST A POWERFUL STORM WAS MOVING THROUGH THE GREAT LAKES THIS MORNING. LOW PRESSURE WILL MOVE QUICKLY FROM WISCONSIN TO NORTHERN LAKE MICHIGAN THIS MORNING...THEN ON TO QUEBEC BY EVENING. EAST OF THE TRACK OF THE LOW A VERY STRONG SOUTHERLY LOW LEVEL JET WAS OCCURRING...WITH 50 KT WINDS JUST 1 TO 2 THOUSAND FEET OFF THE SURFACE. A STRONG INVERSION WAS LIMITING MIXING BUT GALE FORCE WINDS WERE WORKING DOWN TO THE LAKE SURFACE OVER THE SOUTH HALF WITH SOME GALE FORCE GUSTS ON THE EAST SIDE OF THE NORTH HALF OF THE LAKE. WINDS SHOULD DROP OFF PRETTY QUICKLY AS THE LOW MOVES RAPIDLY NORTHEAST TODAY AND GALES SHOULD END BY ABOUT NOON. PRESENTLY GALE WARNING GOES THROUGH MID AFTERNOON BUT IT MAY BE CANCELED EARLY. WINDS WILL VEER FROM SOUTH TO NORTHWEST THROUGH THE COURSE OF THE DAY. TONIGHT THROUGH MONDAY ANOTHER LOW WILL MOVE FROM THE TEXAS COAST UP THROUGH THE OHIO VALLEY WHILE STRONG HIGH PRESSURE BUILDS INTO THE NORTHERN PLAINS. THIS WILL PRODUCE A PERIOD OF NORTHERLY WINDS ON LAKE MICHIGAN. THE REST OF THE WEEK HIGH PRESSURE WILL DOMINATE THE CENTRAL U.S. WHILE LOW PRESSURE BECOMES ANCHORED OVER NORTHEAST CANADA. THIS WILL PRODUCE A PROLONGED PERIOD OF WESTERLY WINDS OVER LAKE MICHIGAN FROM MID WEEK INTO THE WEEKEND. ALLSOPP && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779- LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 3 PM SUNDAY. SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 3 PM SUNDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1135 AM CST SUN DEC 4 2011 .DISCUSSION... 1125 AM CST FRONTAL BOUNDARY CONTINUES TO STEADILY PUSH EAST ACROSS THE CWFA...EXPECTED BY MIDDAY TO PUSH THROUGH NORTHWEST INDIANA. BEHIND THIS BOUNDARY TEMPERATURES IN MANY LOCATIONS HAVE FALLEN INTO THE UPPER 30S TO LOWER 40S. EXPECT TEMPERATURES TO REMAIN NEARLY STEADY THROUGHOUT THE REMAINDER OF THE DAY...THEN SLOWLY BEGIN TO FALL THIS EVENING. ONE CAVEAT FOR HOW LOW TEMPERATURES MAY FALL TONIGHT WILL BE THE POSSIBILITY OF ABUNDANT CLOUD COVER. CURRENT GUIDANCE CONTINUES TO INDICATE THAT SKIES WILL STEADILY BREAK-UP THIS AFTERNOON AND POSSIBLY TURN SCATTERED TONIGHT. HOWEVER...LOOKING AT THE CURRENT VISIBLE IMAGERY ACROSS THE ENTIRE REGION AND MANY LOCATIONS UPSTREAM THIS SCENARIO OF THINNING SKIES LOOKS TO BE IN JEOPARDY. THUS HAVE CONCERNS ABOUT HOW COLD WE WILL SEE TEMPERATURES FALL TONIGHT. NONETHELESS 850MB THERMAL TROUGH CONTINUES TO PIVOT EAST...AND REMAIN OVERHEAD TONIGHT. AIDING IN TEMPERATURES FALLING INTO THE UPPER 20S TO LOWER 30S TONIGHT WILL BE THE STEADY COLD AIR ADVECTION WITH NORTHERLY WINDS TURNING NORHTEASTERLY. WITH AN INCREASING THERMAL DIFFERENTIAL ACROSS THE RELATIVELY WARMER MARINE ENVIRONMENT...AND MUCH COOLER AIR ALOFT EXPECT A NARROW CHANNEL OF LAKE MOISTURE TO FORM FROM THE NORTH/NORTHEAST WINDS. THIS WILL AID IN THE POSSIBILITY OF LAKE EFFECT FLURRIES/LGT SN. THEN BECOMING MIXED WITH LGT RA AFTER DAYBREAK MON. THROWING A POTENTIAL MONKEY WRENCH IN THIS SCENARIO COULD BE THE DEPTH OF THE FAVORED DENDRITIC GROWTH ZONE AND MOISTURE. VERY MINIMAL VERTICAL ENERGY MAY LIMIT THIS TO POSSIBLY JUST SOME DRIZZLE. THIS WILL BE THE FIRST CHALLENGE OF THE EVENING FORECAST. AS THIS COULD END UP BEING FROZEN DRIZZLE WITH TEMPERATURES POSSIBLY IN THE LOWER 30S. BEACHLER && .PREV DISCUSSION... 340 AM CST HIGHLIGHTS THIS WEEK WILL INCLUDE RAIN COMING TO AN END...POSSIBLE SN/RASN/RA ACROSS THE SOUTHEAST MONDAY...LES POTENTIAL FOR LAKE/COOK LATE SUNDAY NIGHT INTO MONDAY...TRANSITIONING SOUTH TO LAKE/PORTER INDIANA BY TUESDAY...A FEW DAYS OF QUIET...FOLLOWED BY A LATE CLIPPER AND SNOW POTENTIAL AND FINALLY A BLAST OF COLD BY NEXT WEEKEND. THE EARLY MORNING SURFACE MAP SHOWED THE SURFACE LOW THAT HAS BEEN BRINGING THE WET AND ACTIVE WEATHER TO THE AREA TODAY...CONTINUING TO LIFTING NORTH THROUGH CENTRAL WISCONSIN. MEANWHILE AN ATTENDANT COLD FRONT LAY ROUGHLY ACROSS THE MISSISSIPPI RIVER...SOUTHWEST NEARLY TO ST LOUIS. THIS FRONT WILL CONTINUE TO SLOWLY SWEEP FROM WEST TO EAST THIS MORNING EVENTUALLY PUSHING ITSELF AND THE PRECIP EAST. THE MOST WIDE SPREAD ECHOES HAVE PUSHED EAST AND ONLY A FEW SCATTERED SHOWERS ARE LOCATED WITH THE ACTUAL FRONT. ACROSS EAST CENTRAL IOWA...TEMPERATURES HAVE DROPPED ENOUGH THAT -SN WAS REPORTED...BUT CLOUD TOPS HAVE WARMED ENOUGH AND ARE WARMER THAN -10C. THIS MEANS THAT THERE IS NO LONGER ICE INTRODUCTION INTO THE SATURATED LAYERS BELOW...AND A FEW LOCATIONS REPORTED U.P. AND OR FZDZ. FOR OUR AREA...AFTER THE FRONT MOVES THROUGH...LOWER LEVEL MOISTURE WILL REMAIN BUT PROFILES ARE STILL INDICATIVE OF LIQUID PRECIP AND SURFACE TEMPS WILL REMAIN ABOVE FREEZING. THE HRRR AND RUC BOTH HAVE A GOOD HANDLE ON THE WESTERN EDGE OF THE PRECIP AND FRONTAL LOCATION...AND MOST OF IT SHOULD CLEAR THE ROCKFORD CORRIDOR NEAR SUNRISE...WITH CHICAGO AND EAST JUST A FEW HOURS BEYOND. WHILE LOWER LEVEL RH WILL REMAIN PREVALENT WITH AND SHORTLY BEYOND FROPA...MOISTURE ABOVE -10C WILL DISAPPEAR AND THERE MAY BE SOME LINGERING DZ INTO THE EARLY MORNING HOURS. THE BIG PUSH OF COLDER AIR ISNT EXPECTED UNTIL LATER THIS EVENING AND TEMPERATURES WILL REMAIN ABOVE FREEZING...SO NO CONCERN OVER ANY OTHER PRECIP TYPES THIS MORNING. HIGH TEMPS WILL GENERALLY BE SEEN EARLY TODAY...AND SLOWLY FALL THROUGH THE DAY. WINDS WILL ABATE AS HIGH PRESSURE AND A PERIOD OF DRY...SLOWLY MOVE IN. THE MAIN UPPER LEVEL TROUGHING THAT STRETCHES FROM ROUGHLY SASKATCHEWAN...SOUTHWEST THROUGH THE FOUR CORNERS REGION WILL NOT HAVE MUCH REASON TO MOVE UNTIL THE START OF THE WORKWEEK. PRESENT SHORTWAVE SEEN ON WATER VAPOR IMAGERY ROUNDING THE BASE OF THE TROUGH...ACROSS SOUTHERN ARIZONA...WILL DAMPEN SOME AS IT GETS EJECTED ON THE EASTERN FLANK TODAY AND TONIGHT. AS IT DOES THIS...IT WILL HELP TO AMPLIFY AN INVERTED TROUGH THAT WILL NOSE ITS WAY TOWARDS THE OHIO VALLEY...EVENTUALLY SPAWNING A WEAK LOW ACROSS THE TENNESSEE VALLEY. GUIDANCE HAS BEEN HEMMING AND HAWING WITH JUST HOW FAR NORTH TO BRING THE PRECIP WITH THIS FEATURE...AND JUST HOW MUCH OF IT WILL REACH INTO THE SOUTHEASTERN CORNER OF THE CWA. THE LATEST FORECAST TRENDS HAVE BACKED OFF FROM PREVIOUS...AND DID SCALE BACK ON POPS AS WELL AS COVERAGE. STILL A LITTLE UNCERTAIN WITH WHERE THE RASN VS STRAIGHT RA LINE WOULD BE AND WILL MAINTAIN A SORT OF MIX. ALSO OF NOTE FOR COASTAL LOCATIONS IN THIS SAME TIME FRAME /AS THE INV TROF-LOW SLIDE EAST/ IS THE CHANCE FOR LES. THERMAL PROFILES ACROSS THE SOUTHERN LAKE WILL BECOME INCREASINGLY UNSTABLE WITH LAKE SURFACE TO H85 DELTA T`S REACHING THE 12-15C RANGE. EXPECT WEAK SHOWERS TO BEGIN TO STRETCH FROM LAKE COUNTY IL...EVENTUALLY SOUTH TO COOK AND GRADUALLY INTO THE MORE TYPICAL LAKE/PORTER IN ORIENTATION. QPF AMOUNTS NOT LOOKING VERY IMPRESSIVE DURING THE SHORT DURATION AND WOULD ONLY EXPECT ANYWHERE FROM A TRACE TO MAYBE A TENTH OR TWO OF ACCUMULATION CLOSE TO THE LAKE TOMORROW AND INTO TOMORROW NIGHT. THIS WILL ALL BE FOLLOWED BY A FEW DAYS OF QUIET AS ANOTHER RIDGE OF HIGH PRESSURE SWINGS IN FROM THE NORTHWEST. A LATE WEEK SYSTEM IS STILL PART OF A LOW CONFIDENCE FORECAST. GFS HAD BEEN ADVERTISING A WEAK CLIPPER DROPPING FROM THE NORTHERN PLAINS... AND PREVIOUS EC SOLNS HAD SIMILAR...BUT THE 12Z FLIPPED AND DEVELOPED A SURFACE LOW THAT LIFTS THROUGH THE MISSISSIPPI VALLEY...INTO NORTHERN INDIANA...NORTHEAST THROUGH EASTERN ONTARIO. CONFIDENCE AT THIS POINT ON THAT EURO SOLN IS LOW AND WILL KEEP THE CHANCE OF SNOW AND NOT BUMP UP (OR DOWN) ANY CATEGORY UNTIL THE PICTURE IS A LITTLE CLEARER. THE 00Z SOLN BEGAN TO COME IN AND WAS BACK TO THE ORIGINAL PICTURE WITH THE CLIPPER RACING THROUGH. DESPITE THE LOWER CONFIDENCE IN THAT FEATURE LATE THIS WEEK...THE ONE PICTURE OF CLARITY WHAT WILL FOLLOW IT. ALL LONG RANGE GUIDANCE IS STILL INDICATING THAT THERE WILL BE A LARGE SURGE OF COLD AIR ENCROACHING AS AN UPPER LEVEL TROUGH SWINGS THROUGH. THERE ARE STILL SOME TIMING DIFFERENCES WITH HOW QUICKLY THE COLD AIR WILL DUMP IN...WHICH IS DUE IN PART TO THE LARGE MODEL DIFFERENCES MENTIONED MOMENTS AGO...BUT THE ONE THING THEY ALL AGREE ON IS HOW COLD THE LOWER LEVELS WILL GET INTO THE WEEKEND. EVEN A WEEK OUT...THE EC/GFS/GEFS/DGEX/GEM(NHEM THROUGH F144) ALL HIGHLIGHT H85 TEMPS PLUMMETING TO -16 TO -18 DEGREES...OR EVEN A FEW DEGREES COLDER. TRANSLATE THAT TO THE SURFACE AND IT WOULD BE POSSIBLE THAT HIGHS WOULD STRUGGLE TO GET OUT OF THE TEENS FOR MANY LOCATIONS AND OVERNIGHT LOWS LEADING INTO THE WEEKEND WOULD DIVE BOMB TO THE SINGLE DIGITS /BUT LIKELY A SMIDGEN WARMER IN THE CHICAGO METRO/. WITH THAT FORECAST STILL BEING OUT 6-7 DAYS...AND A SLEW OF OTHER WEATHER GOING ON THROUGH THE EARLY WEEK... WILL ONLY CONTINUE TO TREND DOWN FROM THE INHERITED LONG RANGE FORECAST. THE BIG SAVING GRACE IS THE LACK OF SOLID SNOW PACK. IF THAT WERE PRESENT...IT WOULD BE MUCH COLDER. SHEA && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 14Z... * LOW MVFR TO IFR POST FRONTAL CIGS MOVING BACK ACROSS THE TERMINALS LATER THIS MORNING. KJB //DISCUSSION...UPDATED 12Z... LOW PRESSURE OVER NORTHERN LAKE MICHIGAN MOVING QUICKLY NORTHEAST THIS MORNING. MOST OF THE RAIN HAS MOVED OUT OF THE AREA. ONLY A FEW LIGHT SHOWERS REMAIN ALONG THE COLD FRONT...WHICH STRETCHES FROM THE LOW TO JUST WEST OF RFD TO STL. JUST KEPT A VCSH IN FOR A FEW HOURS TO COVER A POSSIBLE BRIEF LIGHT SHOWER THROUGH MID MORNING. STRONG SSW WINDS STILL GUSTING TO AROUND 25 KTS EARLY THIS MORNING. WINDS WILL SHIFT WEST WITH COLD FRONTAL PASSAGE MID MORNING AND DIMINISH. MAY STILL SEE SOME GUSTS TO AROUND 20 KT OR SO THROUGH MIDDAY. WINDS WILL BECOME NORTHWEST AND FALL TO LESS THAN 10 KT BY LATE AFTERNOON. MAIN ISSUE TODAY WILL BE LOW CEILINGS...PRESENTLY RUNNING AROUND 1000-1500 FT. SOME IFR NOTED OVER IA AND WESTERN IL BEHIND THE COLD FRONT. BUT WITH EVERYTHING LIFTING NORTHEAST...AND LOOKING AT MODEL SOUNDINGS...DONT EXPECT IFR CIGS TO IMPACT THE CHICAGO AREA TERMINALS. RFD MY FLIRT WITH IFR THROUGH THE MORNING HOURS AND HAVE COVERED THIS WITH A TEMPO GROUP. SHOULD SEE AN IMPROVING TREND THROUGH THE AFTERNOON. THE BACK EDGE OF THE STRATUS OVER THE DAKOTAS...NEB...INTO NW MO IS PUSHING EAST ON SATELLITE IMAGERY. THERE IS A POSSIBILITY OF STRATUS SCATTERING OUT OVER NORTHERN IL TOWARDS EVENING OR OVERNIGHT...BUT CONFIDENCE IN THAT HAPPENING IS LOW AND WILL HANG ON TO MVFR CIGS THROUGH THE NIGHT AT THIS POINT. WINDS WILL GRADUALLY VEER NORTH NORTHEAST LATE TONIGHT INTO MONDAY MORNING. AS COLDER AIR MOVES DOWN THE LAKE...SOME LAKE EFFECT CLOUDS AND LIGHT SNOW SHOWERS ARE POSSIBLE MONDAY BUT AT THIS TIME IT APPEARS THE CLOUD DEPTH WILL BE TOO SHALLOW TO SUPPORT ANY SIGNIFICANT LAKE EFFECT FOR MONDAY. ALLSOPP //ORD AND MDW CONFIDENCE...UPDATED 14Z... * HIGH CONFIDENCE IN MVFR CIGS. * LOW CONFIDENCE IN CIGS DROPPING INTO THE IFR CATEGORY. KJB //OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z... MONDAY NIGHT...MVFR CIG. CHANCE LIGHT LAKE EFFECT SNOW SHOWERS. TUESDAY...VFR. WEDNESDAY...VFR. THURSDAY...VFR. FRIDAY...VFR. SATURDAY...VFR. ALLSOPP && .MARINE... 133 AM CST A POWERFUL STORM WAS MOVING THROUGH THE GREAT LAKES THIS MORNING. LOW PRESSURE WILL MOVE QUICKLY FROM WISCONSIN TO NORTHERN LAKE MICHIGAN THIS MORNING...THEN ON TO QUEBEC BY EVENING. EAST OF THE TRACK OF THE LOW A VERY STRONG SOUTHERLY LOW LEVEL JET WAS OCCURRING...WITH 50 KT WINDS JUST 1 TO 2 THOUSAND FEET OFF THE SURFACE. A STRONG INVERSION WAS LIMITING MIXING BUT GALE FORCE WINDS WERE WORKING DOWN TO THE LAKE SURFACE OVER THE SOUTH HALF WITH SOME GALE FORCE GUSTS ON THE EAST SIDE OF THE NORTH HALF OF THE LAKE. WINDS SHOULD DROP OFF PRETTY QUICKLY AS THE LOW MOVES RAPIDLY NORTHEAST TODAY AND GALES SHOULD END BY ABOUT NOON. PRESENTLY GALE WARNING GOES THROUGH MID AFTERNOON BUT IT MAY BE CANCELED EARLY. WINDS WILL VEER FROM SOUTH TO NORTHWEST THROUGH THE COURSE OF THE DAY. TONIGHT THROUGH MONDAY ANOTHER LOW WILL MOVE FROM THE TEXAS COAST UP THROUGH THE OHIO VALLEY WHILE STRONG HIGH PRESSURE BUILDS INTO THE NORTHERN PLAINS. THIS WILL PRODUCE A PERIOD OF NORTHERLY WINDS ON LAKE MICHIGAN. THE REST OF THE WEEK HIGH PRESSURE WILL DOMINATE THE CENTRAL U.S. WHILE LOW PRESSURE BECOMES ANCHORED OVER NORTHEAST CANADA. THIS WILL PRODUCE A PROLONGED PERIOD OF WESTERLY WINDS OVER LAKE MICHIGAN FROM MID WEEK INTO THE WEEKEND. ALLSOPP && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779- LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 3 PM SUNDAY. SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 3 PM SUNDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
912 AM CST SUN DEC 4 2011 .DISCUSSION... 340 AM CST HIGHLIGHTS THIS WEEK WILL INCLUDE RAIN COMING TO AN END...POSSIBLE SN/RASN/RA ACROSS THE SOUTHEAST MONDAY...LES POTENTIAL FOR LAKE/COOK LATE SUNDAY NIGHT INTO MONDAY...TRANSITIONING SOUTH TO LAKE/PORTER INDIANA BY TUESDAY...A FEW DAYS OF QUIET...FOLLOWED BY A LATE CLIPPER AND SNOW POTENTIAL AND FINALLY A BLAST OF COLD BY NEXT WEEKEND. THE EARLY MORNING SURFACE MAP SHOWED THE SURFACE LOW THAT HAS BEEN BRINGING THE WET AND ACTIVE WEATHER TO THE AREA TODAY...CONTINUING TO LIFTING NORTH THROUGH CENTRAL WISCONSIN. MEANWHILE AN ATTENDANT COLD FRONT LAY ROUGHLY ACROSS THE MISSISSIPPI RIVER...SOUTHWEST NEARLY TO ST LOUIS. THIS FRONT WILL CONTINUE TO SLOWLY SWEEP FROM WEST TO EAST THIS MORNING EVENTUALLY PUSHING ITSELF AND THE PRECIP EAST. THE MOST WIDE SPREAD ECHOES HAVE PUSHED EAST AND ONLY A FEW SCATTERED SHOWERS ARE LOCATED WITH THE ACTUAL FRONT. ACROSS EAST CENTRAL IOWA...TEMPERATURES HAVE DROPPED ENOUGH THAT -SN WAS REPORTED...BUT CLOUD TOPS HAVE WARMED ENOUGH AND ARE WARMER THAN -10C. THIS MEANS THAT THERE IS NO LONGER ICE INTRODUCTION INTO THE SATURATED LAYERS BELOW...AND A FEW LOCATIONS REPORTED U.P. AND OR FZDZ. FOR OUR AREA...AFTER THE FRONT MOVES THROUGH...LOWER LEVEL MOISTURE WILL REMAIN BUT PROFILES ARE STILL INDICATIVE OF LIQUID PRECIP AND SURFACE TEMPS WILL REMAIN ABOVE FREEZING. THE HRRR AND RUC BOTH HAVE A GOOD HANDLE ON THE WESTERN EDGE OF THE PRECIP AND FRONTAL LOCATION...AND MOST OF IT SHOULD CLEAR THE ROCKFORD CORRIDOR NEAR SUNRISE...WITH CHICAGO AND EAST JUST A FEW HOURS BEYOND. WHILE LOWER LEVEL RH WILL REMAIN PREVALENT WITH AND SHORTLY BEYOND FROPA...MOISTURE ABOVE -10C WILL DISAPPEAR AND THERE MAY BE SOME LINGERING DZ INTO THE EARLY MORNING HOURS. THE BIG PUSH OF COLDER AIR ISNT EXPECTED UNTIL LATER THIS EVENING AND TEMPERATURES WILL REMAIN ABOVE FREEZING...SO NO CONCERN OVER ANY OTHER PRECIP TYPES THIS MORNING. HIGH TEMPS WILL GENERALLY BE SEEN EARLY TODAY...AND SLOWLY FALL THROUGH THE DAY. WINDS WILL ABATE AS HIGH PRESSURE AND A PERIOD OF DRY...SLOWLY MOVE IN. THE MAIN UPPER LEVEL TROUGHING THAT STRETCHES FROM ROUGHLY SASKATCHEWAN...SOUTHWEST THROUGH THE FOUR CORNERS REGION WILL NOT HAVE MUCH REASON TO MOVE UNTIL THE START OF THE WORKWEEK. PRESENT SHORTWAVE SEEN ON WATER VAPOR IMAGERY ROUNDING THE BASE OF THE TROUGH...ACROSS SOUTHERN ARIZONA...WILL DAMPEN SOME AS IT GETS EJECTED ON THE EASTERN FLANK TODAY AND TONIGHT. AS IT DOES THIS...IT WILL HELP TO AMPLIFY AN INVERTED TROUGH THAT WILL NOSE ITS WAY TOWARDS THE OHIO VALLEY...EVENTUALLY SPAWNING A WEAK LOW ACROSS THE TENNESSEE VALLEY. GUIDANCE HAS BEEN HEMMING AND HAWING WITH JUST HOW FAR NORTH TO BRING THE PRECIP WITH THIS FEATURE...AND JUST HOW MUCH OF IT WILL REACH INTO THE SOUTHEASTERN CORNER OF THE CWA. THE LATEST FORECAST TRENDS HAVE BACKED OFF FROM PREVIOUS...AND DID SCALE BACK ON POPS AS WELL AS COVERAGE. STILL A LITTLE UNCERTAIN WITH WHERE THE RASN VS STRAIGHT RA LINE WOULD BE AND WILL MAINTAIN A SORT OF MIX. ALSO OF NOTE FOR COASTAL LOCATIONS IN THIS SAME TIME FRAME /AS THE INV TROF-LOW SLIDE EAST/ IS THE CHANCE FOR LES. THERMAL PROFILES ACROSS THE SOUTHERN LAKE WILL BECOME INCREASINGLY UNSTABLE WITH LAKE SURFACE TO H85 DELTA T`S REACHING THE 12-15C RANGE. EXPECT WEAK SHOWERS TO BEGIN TO STRETCH FROM LAKE COUNTY IL...EVENTUALLY SOUTH TO COOK AND GRADUALLY INTO THE MORE TYPICAL LAKE/PORTER IN ORIENTATION. QPF AMOUNTS NOT LOOKING VERY IMPRESSIVE DURING THE SHORT DURATION AND WOULD ONLY EXPECT ANYWHERE FROM A TRACE TO MAYBE A TENTH OR TWO OF ACCUMULATION CLOSE TO THE LAKE TOMORROW AND INTO TOMORROW NIGHT. THIS WILL ALL BE FOLLOWED BY A FEW DAYS OF QUIET AS ANOTHER RIDGE OF HIGH PRESSURE SWINGS IN FROM THE NORTHWEST. A LATE WEEK SYSTEM IS STILL PART OF A LOW CONFIDENCE FORECAST. GFS HAD BEEN ADVERTISING A WEAK CLIPPER DROPPING FROM THE NORTHERN PLAINS... AND PREVIOUS EC SOLNS HAD SIMILAR...BUT THE 12Z FLIPPED AND DEVELOPED A SURFACE LOW THAT LIFTS THROUGH THE MISSISSIPPI VALLEY...INTO NORTHERN INDIANA...NORTHEAST THROUGH EASTERN ONTARIO. CONFIDENCE AT THIS POINT ON THAT EURO SOLN IS LOW AND WILL KEEP THE CHANCE OF SNOW AND NOT BUMP UP (OR DOWN) ANY CATEGORY UNTIL THE PICTURE IS A LITTLE CLEARER. THE 00Z SOLN BEGAN TO COME IN AND WAS BACK TO THE ORIGINAL PICTURE WITH THE CLIPPER RACING THROUGH. DESPITE THE LOWER CONFIDENCE IN THAT FEATURE LATE THIS WEEK...THE ONE PICTURE OF CLARITY WHAT WILL FOLLOW IT. ALL LONG RANGE GUIDANCE IS STILL INDICATING THAT THERE WILL BE A LARGE SURGE OF COLD AIR ENCROACHING AS AN UPPER LEVEL TROUGH SWINGS THROUGH. THERE ARE STILL SOME TIMING DIFFERENCES WITH HOW QUICKLY THE COLD AIR WILL DUMP IN...WHICH IS DUE IN PART TO THE LARGE MODEL DIFFERENCES MENTIONED MOMENTS AGO...BUT THE ONE THING THEY ALL AGREE ON IS HOW COLD THE LOWER LEVELS WILL GET INTO THE WEEKEND. EVEN A WEEK OUT...THE EC/GFS/GEFS/DGEX/GEM(NHEM THROUGH F144) ALL HIGHLIGHT H85 TEMPS PLUMMETING TO -16 TO -18 DEGREES...OR EVEN A FEW DEGREES COLDER. TRANSLATE THAT TO THE SURFACE AND IT WOULD BE POSSIBLE THAT HIGHS WOULD STRUGGLE TO GET OUT OF THE TEENS FOR MANY LOCATIONS AND OVERNIGHT LOWS LEADING INTO THE WEEKEND WOULD DIVE BOMB TO THE SINGLE DIGITS /BUT LIKELY A SMIDGEN WARMER IN THE CHICAGO METRO/. WITH THAT FORECAST STILL BEING OUT 6-7 DAYS...AND A SLEW OF OTHER WEATHER GOING ON THROUGH THE EARLY WEEK... WILL ONLY CONTINUE TO TREND DOWN FROM THE INHERITED LONG RANGE FORECAST. THE BIG SAVING GRACE IS THE LACK OF SOLID SNOW PACK. IF THAT WERE PRESENT...IT WOULD BE MUCH COLDER. SHEA && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 14Z... * LOW MVFR TO IFR POST FRONTAL CIGS MOVING BACK ACROSS THE TERMINALS LATER THIS MORNING. KJB //DISCUSSION...UPDATED 12Z... LOW PRESSURE OVER NORTHERN LAKE MICHIGAN MOVING QUICKLY NORTHEAST THIS MORNING. MOST OF THE RAIN HAS MOVED OUT OF THE AREA. ONLY A FEW LIGHT SHOWERS REMAIN ALONG THE COLD FRONT...WHICH STRETCHES FROM THE LOW TO JUST WEST OF RFD TO STL. JUST KEPT A VCSH IN FOR A FEW HOURS TO COVER A POSSIBLE BRIEF LIGHT SHOWER THROUGH MID MORNING. STRONG SSW WINDS STILL GUSTING TO AROUND 25 KTS EARLY THIS MORNING. WINDS WILL SHIFT WEST WITH COLD FRONTAL PASSAGE MID MORNING AND DIMINISH. MAY STILL SEE SOME GUSTS TO AROUND 20 KT OR SO THROUGH MIDDAY. WINDS WILL BECOME NORTHWEST AND FALL TO LESS THAN 10 KT BY LATE AFTERNOON. MAIN ISSUE TODAY WILL BE LOW CEILINGS...PRESENTLY RUNNING AROUND 1000-1500 FT. SOME IFR NOTED OVER IA AND WESTERN IL BEHIND THE COLD FRONT. BUT WITH EVERYTHING LIFTING NORTHEAST...AND LOOKING AT MODEL SOUNDINGS...DONT EXPECT IFR CIGS TO IMPACT THE CHICAGO AREA TERMINALS. RFD MY FLIRT WITH IFR THROUGH THE MORNING HOURS AND HAVE COVERED THIS WITH A TEMPO GROUP. SHOULD SEE AN IMPROVING TREND THROUGH THE AFTERNOON. THE BACK EDGE OF THE STRATUS OVER THE DAKOTAS...NEB...INTO NW MO IS PUSHING EAST ON SATELLITE IMAGERY. THERE IS A POSSIBILITY OF STRATUS SCATTERING OUT OVER NORTHERN IL TOWARDS EVENING OR OVERNIGHT...BUT CONFIDENCE IN THAT HAPPENING IS LOW AND WILL HANG ON TO MVFR CIGS THROUGH THE NIGHT AT THIS POINT. WINDS WILL GRADUALLY VEER NORTH NORTHEAST LATE TONIGHT INTO MONDAY MORNING. AS COLDER AIR MOVES DOWN THE LAKE...SOME LAKE EFFECT CLOUDS AND LIGHT SNOW SHOWERS ARE POSSIBLE MONDAY BUT AT THIS TIME IT APPEARS THE CLOUD DEPTH WILL BE TOO SHALLOW TO SUPPORT ANY SIGNIFICANT LAKE EFFECT FOR MONDAY. ALLSOPP //ORD AND MDW CONFIDENCE...UPDATED 14Z... * HIGH CONFIDENCE IN MVFR CIGS. * LOW CONFIDENCE IN CIGS DROPPING INTO THE IFR CATEGORY. KJB //OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z... MONDAY NIGHT...MVFR CIG. CHANCE LIGHT LAKE EFFECT SNOW SHOWERS. TUESDAY...VFR. WEDNESDAY...VFR. THURSDAY...VFR. FRIDAY...VFR. SATURDAY...VFR. ALLSOPP && .MARINE... 133 AM CST A POWERFUL STORM WAS MOVING THROUGH THE GREAT LAKES THIS MORNING. LOW PRESSURE WILL MOVE QUICKLY FROM WISCONSIN TO NORTHERN LAKE MICHIGAN THIS MORNING...THEN ON TO QUEBEC BY EVENING. EAST OF THE TRACK OF THE LOW A VERY STRONG SOUTHERLY LOW LEVEL JET WAS OCCURRING...WITH 50 KT WINDS JUST 1 TO 2 THOUSAND FEET OFF THE SURFACE. A STRONG INVERSION WAS LIMITING MIXING BUT GALE FORCE WINDS WERE WORKING DOWN TO THE LAKE SURFACE OVER THE SOUTH HALF WITH SOME GALE FORCE GUSTS ON THE EAST SIDE OF THE NORTH HALF OF THE LAKE. WINDS SHOULD DROP OFF PRETTY QUICKLY AS THE LOW MOVES RAPIDLY NORTHEAST TODAY AND GALES SHOULD END BY ABOUT NOON. PRESENTLY GALE WARNING GOES THROUGH MID AFTERNOON BUT IT MAY BE CANCELED EARLY. WINDS WILL VEER FROM SOUTH TO NORTHWEST THROUGH THE COURSE OF THE DAY. TONIGHT THROUGH MONDAY ANOTHER LOW WILL MOVE FROM THE TEXAS COAST UP THROUGH THE OHIO VALLEY WHILE STRONG HIGH PRESSURE BUILDS INTO THE NORTHERN PLAINS. THIS WILL PRODUCE A PERIOD OF NORTHERLY WINDS ON LAKE MICHIGAN. THE REST OF THE WEEK HIGH PRESSURE WILL DOMINATE THE CENTRAL U.S. WHILE LOW PRESSURE BECOMES ANCHORED OVER NORTHEAST CANADA. THIS WILL PRODUCE A PROLONGED PERIOD OF WESTERLY WINDS OVER LAKE MICHIGAN FROM MID WEEK INTO THE WEEKEND. ALLSOPP && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779- LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 3 PM SUNDAY. SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 3 PM SUNDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
549 AM CST SUN DEC 4 2011 .DISCUSSION... 340 AM CST HIGHLIGHTS THIS WEEK WILL INCLUDE RAIN COMING TO AN END...POSSIBLE SN/RASN/RA ACROSS THE SOUTHEAST MONDAY...LES POTENTIAL FOR LAKE/COOK LATE SUNDAY NIGHT INTO MONDAY...TRANSITIONING SOUTH TO LAKE/PORTER INDIANA BY TUESDAY...A FEW DAYS OF QUIET...FOLLOWED BY A LATE CLIPPER AND SNOW POTENTIAL AND FINALLY A BLAST OF COLD BY NEXT WEEKEND. THE EARLY MORNING SURFACE MAP SHOWED THE SURFACE LOW THAT HAS BEEN BRINGING THE WET AND ACTIVE WEATHER TO THE AREA TODAY...CONTINUING TO LIFTING NORTH THROUGH CENTRAL WISCONSIN. MEANWHILE AN ATTENDANT COLD FRONT LAY ROUGHLY ACROSS THE MISSISSIPPI RIVER...SOUTHWEST NEARLY TO ST LOUIS. THIS FRONT WILL CONTINUE TO SLOWLY SWEEP FROM WEST TO EAST THIS MORNING EVENTUALLY PUSHING ITSELF AND THE PRECIP EAST. THE MOST WIDE SPREAD ECHOES HAVE PUSHED EAST AND ONLY A FEW SCATTERED SHOWERS ARE LOCATED WITH THE ACTUAL FRONT. ACROSS EAST CENTRAL IOWA...TEMPERATURES HAVE DROPPED ENOUGH THAT -SN WAS REPORTED...BUT CLOUD TOPS HAVE WARMED ENOUGH AND ARE WARMER THAN -10C. THIS MEANS THAT THERE IS NO LONGER ICE INTRODUCTION INTO THE SATURATED LAYERS BELOW...AND A FEW LOCATIONS REPORTED U.P. AND OR FZDZ. FOR OUR AREA...AFTER THE FRONT MOVES THROUGH...LOWER LEVEL MOISTURE WILL REMAIN BUT PROFILES ARE STILL INDICATIVE OF LIQUID PRECIP AND SURFACE TEMPS WILL REMAIN ABOVE FREEZING. THE HRRR AND RUC BOTH HAVE A GOOD HANDLE ON THE WESTERN EDGE OF THE PRECIP AND FRONTAL LOCATION...AND MOST OF IT SHOULD CLEAR THE ROCKFORD CORRIDOR NEAR SUNRISE...WITH CHICAGO AND EAST JUST A FEW HOURS BEYOND. WHILE LOWER LEVEL RH WILL REMAIN PREVALENT WITH AND SHORTLY BEYOND FROPA...MOISTURE ABOVE -10C WILL DISAPPEAR AND THERE MAY BE SOME LINGERING DZ INTO THE EARLY MORNING HOURS. THE BIG PUSH OF COLDER AIR ISNT EXPECTED UNTIL LATER THIS EVENING AND TEMPERATURES WILL REMAIN ABOVE FREEZING...SO NO CONCERN OVER ANY OTHER PRECIP TYPES THIS MORNING. HIGH TEMPS WILL GENERALLY BE SEEN EARLY TODAY...AND SLOWLY FALL THROUGH THE DAY. WINDS WILL ABATE AS HIGH PRESSURE AND A PERIOD OF DRY...SLOWLY MOVE IN. THE MAIN UPPER LEVEL TROUGHING THAT STRETCHES FROM ROUGHLY SASKATCHEWAN...SOUTHWEST THROUGH THE FOUR CORNERS REGION WILL NOT HAVE MUCH REASON TO MOVE UNTIL THE START OF THE WORKWEEK. PRESENT SHORTWAVE SEEN ON WATER VAPOR IMAGERY ROUNDING THE BASE OF THE TROUGH...ACROSS SOUTHERN ARIZONA...WILL DAMPEN SOME AS IT GETS EJECTED ON THE EASTERN FLANK TODAY AND TONIGHT. AS IT DOES THIS...IT WILL HELP TO AMPLIFY AN INVERTED TROUGH THAT WILL NOSE ITS WAY TOWARDS THE OHIO VALLEY...EVENTUALLY SPAWNING A WEAK LOW ACROSS THE TENNESSEE VALLEY. GUIDANCE HAS BEEN HEMMING AND HAWING WITH JUST HOW FAR NORTH TO BRING THE PRECIP WITH THIS FEATURE...AND JUST HOW MUCH OF IT WILL REACH INTO THE SOUTHEASTERN CORNER OF THE CWA. THE LATEST FORECAST TRENDS HAVE BACKED OFF FROM PREVIOUS...AND DID SCALE BACK ON POPS AS WELL AS COVERAGE. STILL A LITTLE UNCERTAIN WITH WHERE THE RASN VS STRAIGHT RA LINE WOULD BE AND WILL MAINTAIN A SORT OF MIX. ALSO OF NOTE FOR COASTAL LOCATIONS IN THIS SAME TIME FRAME /AS THE INV TROF-LOW SLIDE EAST/ IS THE CHANCE FOR LES. THERMAL PROFILES ACROSS THE SOUTHERN LAKE WILL BECOME INCREASINGLY UNSTABLE WITH LAKE SURFACE TO H85 DELTA T`S REACHING THE 12-15C RANGE. EXPECT WEAK SHOWERS TO BEGIN TO STRETCH FROM LAKE COUNTY IL...EVENTUALLY SOUTH TO COOK AND GRADUALLY INTO THE MORE TYPICAL LAKE/PORTER IN ORIENTATION. QPF AMOUNTS NOT LOOKING VERY IMPRESSIVE DURING THE SHORT DURATION AND WOULD ONLY EXPECT ANYWHERE FROM A TRACE TO MAYBE A TENTH OR TWO OF ACCUMULATION CLOSE TO THE LAKE TOMORROW AND INTO TOMORROW NIGHT. THIS WILL ALL BE FOLLOWED BY A FEW DAYS OF QUIET AS ANOTHER RIDGE OF HIGH PRESSURE SWINGS IN FROM THE NORTHWEST. A LATE WEEK SYSTEM IS STILL PART OF A LOW CONFIDENCE FORECAST. GFS HAD BEEN ADVERTISING A WEAK CLIPPER DROPPING FROM THE NORTHERN PLAINS... AND PREVIOUS EC SOLNS HAD SIMILAR...BUT THE 12Z FLIPPED AND DEVELOPED A SURFACE LOW THAT LIFTS THROUGH THE MISSISSIPPI VALLEY...INTO NORTHERN INDIANA...NORTHEAST THROUGH EASTERN ONTARIO. CONFIDENCE AT THIS POINT ON THAT EURO SOLN IS LOW AND WILL KEEP THE CHANCE OF SNOW AND NOT BUMP UP (OR DOWN) ANY CATEGORY UNTIL THE PICTURE IS A LITTLE CLEARER. THE 00Z SOLN BEGAN TO COME IN AND WAS BACK TO THE ORIGINAL PICTURE WITH THE CLIPPER RACING THROUGH. DESPITE THE LOWER CONFIDENCE IN THAT FEATURE LATE THIS WEEK...THE ONE PICTURE OF CLARITY WHAT WILL FOLLOW IT. ALL LONG RANGE GUIDANCE IS STILL INDICATING THAT THERE WILL BE A LARGE SURGE OF COLD AIR ENCROACHING AS AN UPPER LEVEL TROUGH SWINGS THROUGH. THERE ARE STILL SOME TIMING DIFFERENCES WITH HOW QUICKLY THE COLD AIR WILL DUMP IN...WHICH IS DUE IN PART TO THE LARGE MODEL DIFFERENCES MENTIONED MOMENTS AGO...BUT THE ONE THING THEY ALL AGREE ON IS HOW COLD THE LOWER LEVELS WILL GET INTO THE WEEKEND. EVEN A WEEK OUT...THE EC/GFS/GEFS/DGEX/GEM(NHEM THROUGH F144) ALL HIGHLIGHT H85 TEMPS PLUMMETING TO -16 TO -18 DEGREES...OR EVEN A FEW DEGREES COLDER. TRANSLATE THAT TO THE SURFACE AND IT WOULD BE POSSIBLE THAT HIGHS WOULD STRUGGLE TO GET OUT OF THE TEENS FOR MANY LOCATIONS AND OVERNIGHT LOWS LEADING INTO THE WEEKEND WOULD DIVE BOMB TO THE SINGLE DIGITS /BUT LIKELY A SMIDGEN WARMER IN THE CHICAGO METRO/. WITH THAT FORECAST STILL BEING OUT 6-7 DAYS...AND A SLEW OF OTHER WEATHER GOING ON THROUGH THE EARLY WEEK... WILL ONLY CONTINUE TO TREND DOWN FROM THE INHERITED LONG RANGE FORECAST. THE BIG SAVING GRACE IS THE LACK OF SOLID SNOW PACK. IF THAT WERE PRESENT...IT WOULD BE MUCH COLDER. SHEA && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 12Z... * MVFR CIGS. * STRONG GUSTY SSW WINDS VEERING WEST AND DIMINISHING BY AFTERNOON. * FEW LIGHT SHOWERS THROUGH ABOUT 15Z. ALLSOPP //DISCUSSION...UPDATED 12Z... LOW PRESSURE OVER NORTHERN LAKE MICHIGAN MOVING QUICKLY NORTHEAST THIS MORNING. MOST OF THE RAIN HAS MOVED OUT OF THE AREA. ONLY A FEW LIGHT SHOWERS REMAIN ALONG THE COLD FRONT...WHICH STRETCHES FROM THE LOW TO JUST WEST OF RFD TO STL. JUST KEPT A VCSH IN FOR A FEW HOURS TO COVER A POSSIBLE BRIEF LIGHT SHOWER THROUGH MID MORNING. STRONG SSW WINDS STILL GUSTING TO AROUND 25 KTS EARLY THIS MORNING. WINDS WILL SHIFT WEST WITH COLD FRONTAL PASSAGE MID MORNING AND DIMINISH. MAY STILL SEE SOME GUSTS TO AROUND 20 KT OR SO THROUGH MIDDAY. WINDS WILL BECOME NORTHWEST AND FALL TO LESS THAN 10 KT BY LATE AFTERNOON. MAIN ISSUE TODAY WILL BE LOW CEILINGS...PRESENTLY RUNNING AROUND 1000-1500 FT. SOME IFR NOTED OVER IA AND WESTERN IL BEHIND THE COLD FRONT. BUT WITH EVERYTHING LIFTING NORTHEAST...AND LOOKING AT MODEL SOUNDINGS...DONT EXPECT IFR CIGS TO IMPACT THE CHICAGO AREA TERMINALS. RFD MY FLIRT WITH IFR THROUGH THE MORNING HOURS AND HAVE COVERED THIS WITH A TEMPO GROUP. SHOULD SEE AN IMPROVING TREND THROUGH THE AFTERNOON. THE BACK EDGE OF THE STRATUS OVER THE DAKOTAS...NEB...INTO NW MO IS PUSHING EAST ON SATELLITE IMAGERY. THERE IS A POSSIBILITY OF STRATUS SCATTERING OUT OVER NORTHERN IL TOWARDS EVENING OR OVERNIGHT...BUT CONFIDENCE IN THAT HAPPENING IS LOW AND WILL HANG ON TO MVFR CIGS THROUGH THE NIGHT AT THIS POINT. WINDS WILL GRADUALLY VEER NORTH NORTHEAST LATE TONIGHT INTO MONDAY MORNING. AS COLDER AIR MOVES DOWN THE LAKE...SOME LAKE EFFECT CLOUDS AND LIGHT SNOW SHOWERS ARE POSSIBLE MONDAY BUT AT THIS TIME IT APPEARS THE CLOUD DEPTH WILL BE TOO SHALLOW TO SUPPORT ANY SIGNIFICANT LAKE EFFECT FOR MONDAY. ALLSOPP //ORD AND MDW CONFIDENCE...UPDATED 12Z... * HIGH CONFIDENCE IN WIND FORECAST. * MEDIUM CONFIDENCE ON CIGS REMAINING 1000-1500 THROUGH THE MORNING...THEN LIFTING IN THE AFTERNOON. THERE IS A SLIGHT CHANCE OF IFR CIGS THIS MORNING BUT CONFIDENCE IN THAT HAPPENING AT ORD/MDW IS LOW. * MEDIUM CONFIDENCE IN MVFR CIGS HANGING IN THROUGH THE NIGHT. * HIGH CONFIDENCE IN LIGHT SHOWERS ENDING WITH COLD FRONT PASSAGE AROUND MID THIS MORNING. ALLSOPP //OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z... MONDAY NIGHT...MVFR CIG. CHANCE LIGHT LAKE EFFECT SNOW SHOWERS. TUESDAY...VFR. WEDNESDAY...VFR. THURSDAY...VFR. FRIDAY...VFR. SATURDAY...VFR. ALLSOPP && .MARINE... 133 AM CST A POWERFUL STORM WAS MOVING THROUGH THE GREAT LAKES THIS MORNING. LOW PRESSURE WILL MOVE QUICKLY FROM WISCONSIN TO NORTHERN LAKE MICHIGAN THIS MORNING...THEN ON TO QUEBEC BY EVENING. EAST OF THE TRACK OF THE LOW A VERY STRONG SOUTHERLY LOW LEVEL JET WAS OCCURRING...WITH 50 KT WINDS JUST 1 TO 2 THOUSAND FEET OFF THE SURFACE. A STRONG INVERSION WAS LIMITING MIXING BUT GALE FORCE WINDS WERE WORKING DOWN TO THE LAKE SURFACE OVER THE SOUTH HALF WITH SOME GALE FORCE GUSTS ON THE EAST SIDE OF THE NORTH HALF OF THE LAKE. WINDS SHOULD DROP OFF PRETTY QUICKLY AS THE LOW MOVES RAPIDLY NORTHEAST TODAY AND GALES SHOULD END BY ABOUT NOON. PRESENTLY GALE WARNING GOES THROUGH MID AFTERNOON BUT IT MAY BE CANCELED EARLY. WINDS WILL VEER FROM SOUTH TO NORTHWEST THROUGH THE COURSE OF THE DAY. TONIGHT THROUGH MONDAY ANOTHER LOW WILL MOVE FROM THE TEXAS COAST UP THROUGH THE OHIO VALLEY WHILE STRONG HIGH PRESSURE BUILDS INTO THE NORTHERN PLAINS. THIS WILL PRODUCE A PERIOD OF NORTHERLY WINDS ON LAKE MICHIGAN. THE REST OF THE WEEK HIGH PRESSURE WILL DOMINATE THE CENTRAL U.S. WHILE LOW PRESSURE BECOMES ANCHORED OVER NORTHEAST CANADA. THIS WILL PRODUCE A PROLONGED PERIOD OF WESTERLY WINDS OVER LAKE MICHIGAN FROM MID WEEK INTO THE WEEKEND. ALLSOPP && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779- LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 3 PM SUNDAY. SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 3 PM SUNDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
341 AM CST SUN DEC 4 2011 .DISCUSSION... 340 AM CST HIGHLIGHTS THIS WEEK WILL INCLUDE RAIN COMING TO AN END...POSSIBLE SN/RASN/RA ACROSS THE SOUTHEAST MONDAY...LES POTENTIAL FOR LAKE/COOK LATE SUNDAY NIGHT INTO MONDAY...TRANSITIONING SOUTH TO LAKE/PORTER INDIANA BY TUESDAY...A FEW DAYS OF QUIET...FOLLOWED BY A LATE CLIPPER AND SNOW POTENTIAL AND FINALLY A BLAST OF COLD BY NEXT WEEKEND. THE EARLY MORNING SURFACE MAP SHOWED THE SURFACE LOW THAT HAS BEEN BRINGING THE WET AND ACTIVE WEATHER TO THE AREA TODAY...CONTINUING TO LIFTING NORTH THROUGH CENTRAL WISCONSIN. MEANWHILE AN ATTENDANT COLD FRONT LAY ROUGHLY ACROSS THE MISSISSIPPI RIVER...SOUTHWEST NEARLY TO ST LOUIS. THIS FRONT WILL CONTINUE TO SLOWLY SWEEP FROM WEST TO EAST THIS MORNING EVENTUALLY PUSHING ITSELF AND THE PRECIP EAST. THE MOST WIDE SPREAD ECHOES HAVE PUSHED EAST AND ONLY A FEW SCATTERED SHOWERS ARE LOCATED WITH THE ACTUAL FRONT. ACROSS EAST CENTRAL IOWA...TEMPERATURES HAVE DROPPED ENOUGH THAT -SN WAS REPORTED...BUT CLOUD TOPS HAVE WARMED ENOUGH AND ARE WARMER THAN -10C. THIS MEANS THAT THERE IS NO LONGER ICE INTRODUCTION INTO THE SATURATED LAYERS BELOW...AND A FEW LOCATIONS REPORTED U.P. AND OR FZDZ. FOR OUR AREA...AFTER THE FRONT MOVES THROUGH...LOWER LEVEL MOISTURE WILL REMAIN BUT PROFILES ARE STILL INDICATIVE OF LIQUID PRECIP AND SURFACE TEMPS WILL REMAIN ABOVE FREEZING. THE HRRR AND RUC BOTH HAVE A GOOD HANDLE ON THE WESTERN EDGE OF THE PRECIP AND FRONTAL LOCATION...AND MOST OF IT SHOULD CLEAR THE ROCKFORD CORRIDOR NEAR SUNRISE...WITH CHICAGO AND EAST JUST A FEW HOURS BEYOND. WHILE LOWER LEVEL RH WILL REMAIN PREVALENT WITH AND SHORTLY BEYOND FROPA...MOISTURE ABOVE -10C WILL DISAPPEAR AND THERE MAY BE SOME LINGERING DZ INTO THE EARLY MORNING HOURS. THE BIG PUSH OF COLDER AIR ISNT EXPECTED UNTIL LATER THIS EVENING AND TEMPERATURES WILL REMAIN ABOVE FREEZING...SO NO CONCERN OVER ANY OTHER PRECIP TYPES THIS MORNING. HIGH TEMPS WILL GENERALLY BE SEEN EARLY TODAY...AND SLOWLY FALL THROUGH THE DAY. WINDS WILL ABATE AS HIGH PRESSURE AND A PERIOD OF DRY...SLOWLY MOVE IN. THE MAIN UPPER LEVEL TROUGHING THAT STRETCHES FROM ROUGHLY SASKATCHEWAN...SOUTHWEST THROUGH THE FOUR CORNERS REGION WILL NOT HAVE MUCH REASON TO MOVE UNTIL THE START OF THE WORKWEEK. PRESENT SHORTWAVE SEEN ON WATER VAPOR IMAGERY ROUNDING THE BASE OF THE TROUGH...ACROSS SOUTHERN ARIZONA...WILL DAMPEN SOME AS IT GETS EJECTED ON THE EASTERN FLANK TODAY AND TONIGHT. AS IT DOES THIS...IT WILL HELP TO AMPLIFY AN INVERTED TROUGH THAT WILL NOSE ITS WAY TOWARDS THE OHIO VALLEY...EVENTUALLY SPAWNING A WEAK LOW ACROSS THE TENNESSEE VALLEY. GUIDANCE HAS BEEN HEMMING AND HAWING WITH JUST HOW FAR NORTH TO BRING THE PRECIP WITH THIS FEATURE...AND JUST HOW MUCH OF IT WILL REACH INTO THE SOUTHEASTERN CORNER OF THE CWA. THE LATEST FORECAST TRENDS HAVE BACKED OFF FROM PREVIOUS...AND DID SCALE BACK ON POPS AS WELL AS COVERAGE. STILL A LITTLE UNCERTAIN WITH WHERE THE RASN VS STRAIGHT RA LINE WOULD BE AND WILL MAINTAIN A SORT OF MIX. ALSO OF NOTE FOR COASTAL LOCATIONS IN THIS SAME TIME FRAME /AS THE INV TROF-LOW SLIDE EAST/ IS THE CHANCE FOR LES. THERMAL PROFILES ACROSS THE SOUTHERN LAKE WILL BECOME INCREASINGLY UNSTABLE WITH LAKE SURFACE TO H85 DELTA T`S REACHING THE 12-15C RANGE. EXPECT WEAK SHOWERS TO BEGIN TO STRETCH FROM LAKE COUNTY IL...EVENTUALLY SOUTH TO COOK AND GRADUALLY INTO THE MORE TYPICAL LAKE/PORTER IN ORIENTATION. QPF AMOUNTS NOT LOOKING VERY IMPRESSIVE DURING THE SHORT DURATION AND WOULD ONLY EXPECT ANYWHERE FROM A TRACE TO MAYBE A TENTH OR TWO OF ACCUMULATION CLOSE TO THE LAKE TOMORROW AND INTO TOMORROW NIGHT. THIS WILL ALL BE FOLLOWED BY A FEW DAYS OF QUIET AS ANOTHER RIDGE OF HIGH PRESSURE SWINGS IN FROM THE NORTHWEST. A LATE WEEK SYSTEM IS STILL PART OF A LOW CONFIDENCE FORECAST. GFS HAD BEEN ADVERTISING A WEAK CLIPPER DROPPING FROM THE NORTHERN PLAINS... AND PREVIOUS EC SOLNS HAD SIMILAR...BUT THE 12Z FLIPPED AND DEVELOPED A SURFACE LOW THAT LIFTS THROUGH THE MISSISSIPPI VALLEY...INTO NORTHERN INDIANA...NORTHEAST THROUGH EASTERN ONTARIO. CONFIDENCE AT THIS POINT ON THAT EURO SOLN IS LOW AND WILL KEEP THE CHANCE OF SNOW AND NOT BUMP UP (OR DOWN) ANY CATEGORY UNTIL THE PICTURE IS A LITTLE CLEARER. THE 00Z SOLN BEGAN TO COME IN AND WAS BACK TO THE ORIGINAL PICTURE WITH THE CLIPPER RACING THROUGH. DESPITE THE LOWER CONFIDENCE IN THAT FEATURE LATE THIS WEEK...THE ONE PICTURE OF CLARITY WHAT WILL FOLLOW IT. ALL LONG RANGE GUIDANCE IS STILL INDICATING THAT THERE WILL BE A LARGE SURGE OF COLD AIR ENCROACHING AS AN UPPER LEVEL TROUGH SWINGS THROUGH. THERE ARE STILL SOME TIMING DIFFERENCES WITH HOW QUICKLY THE COLD AIR WILL DUMP IN...WHICH IS DUE IN PART TO THE LARGE MODEL DIFFERENCES MENTIONED MOMENTS AGO...BUT THE ONE THING THEY ALL AGREE ON IS HOW COLD THE LOWER LEVELS WILL GET INTO THE WEEKEND. EVEN A WEEK OUT...THE EC/GFS/GEFS/DGEX/GEM(NHEM THROUGH F144) ALL HIGHLIGHT H85 TEMPS PLUMMETING TO -16 TO -18 DEGREES...OR EVEN A FEW DEGREES COLDER. TRANSLATE THAT TO THE SURFACE AND IT WOULD BE POSSIBLE THAT HIGHS WOULD STRUGGLE TO GET OUT OF THE TEENS FOR MANY LOCATIONS AND OVERNIGHT LOWS LEADING INTO THE WEEKEND WOULD DIVE BOMB TO THE SINGLE DIGITS /BUT LIKELY A SMIDGEN WARMER IN THE CHICAGO METRO/. WITH THAT FORECAST STILL BEING OUT 6-7 DAYS...AND A SLEW OF OTHER WEATHER GOING ON THROUGH THE EARLY WEEK... WILL ONLY CONTINUE TO TREND DOWN FROM THE INHERITED LONG RANGE FORECAST. THE BIG SAVING GRACE IS THE LACK OF SOLID SNOW PACK. IF THAT WERE PRESENT...IT WOULD BE MUCH COLDER. SHEA && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 09Z... * LIGHT SHOWERS ENDING * MVFR CIGS...POSSIBLY DROPPING TO AROUND 1000 FT THIS MORNING. * STRONG GUSTY SSW WINDS AND POTENTIAL FOR LLWS EARLY...WINDS VEERING WEST AND DIMINISHING BY MIDDAY. ALLSOPP //DISCUSSION...UPDATED 06Z... SHIELD OF RAIN CONTINUES TO LIFT NORTHEASTWARD ACROSS THE TERMINALS WITH COVERAGE BECOMING MORE BROKEN JUST TO THE SOUTHWEST. LOW PRESSURE RESPONSIBLE FOR THE RAIN IS MOVING NORTHEAST ACROSS EASTERN IOWA AND WILL CROSS NORTHERN LAKE MICHIGAN SUNDAY MORNING. SOUTH WINDS HAVE INCREASED MARKEDLY AHEAD OF THE LOW WITH GUSTS CURRENTLY IN THE 25-30 KT RANGE BUT THESE WILL DIMINISH TO 20-25 KT OVERNIGHT. LOWER CEILINGS NOW MAKING IT INTO THE TERMINALS WITH LOW END MVFR EXPECTED TO ARRIVE IN THE NEXT FEW HOURS WHERE IT HAS NOT ALREADY. RFD WILL LIKELY SEE IFR SOON WITH SOME POTENTIAL FOR PERIODS OF IFR ACROSS THE CHI METRO TERMINALS WITH A LOWER CHANCE AT GYY. LATEST TRENDS SHOW MVFR VSBY TO BE RATHER SPOTTY BUT STILL EXPECT IT TO OCCUR TONIGHT THOUGH CONFIDENCE IS REDUCED IN WHETHER OR NOT IT WILL BE STEADY OR MORE INTERMITTENT. SHOWERS SHOULD BEGIN TO WANE IN THE 9-12Z TIME FRAME...POSSIBLY A LITTLE LATER AT GYY. ANOTHER CONCERN IS LOW LEVEL WIND SHEAR. WINDS INCREASE TO 50-55 KT AT 2000 FT ACROSS THE AREA...THOUGH SURFACE GUSTS OF 25-30 KT AT THE CURRENT TIME ARE LIKELY LIMITING THE SHEAR FOR NOW...BUT AS GUSTS DIMINISH A BIT IN A FEW HOURS SHEAR RISK WILL AGAIN INCREASE. MVFR CEILINGS WILL CONTINUE THROUGH SUNDAY MORNING WITH IFR EXPECTED TO IMPROVE TO MVFR AT RFD DURING THE MORNING. SOUTH WINDS WILL TURN SOUTHWEST THEN WEST THROUGH THE MORNING WITH SOME GUSTS CONTINUING. EXPECT THAT CEILINGS WILL SLOWLY LIFT...THOUGH REMAIN MVFR...INTO EARLY AFTERNOON AS THE WEST WINDS USHER IN DRIER LOW LEVEL AIR. TOUGH TO SAY IF VFR WILL BE REACHED BUT IT WOULD LIKELY TAKE UNTIL LATE AFTERNOON IF IT DOES...IF NOT EARLY EVENING. WINDS THEN SHIFT NORTHWEST EARLY SUNDAY EVENING. MDB //ORD AND MDW CONFIDENCE...UPDATED 09Z... * MEDIUM CONFIDENCE IN CIGS DROPPING TO 1000-1500 FT THIS MORNING THEN INCREASING TO 2000 FT OR BETTER THIS AFTERNOON. * HIGH CONFIDENCE IN VISIBILITY REMAINING 6 PLUS WITH JUST A FEW SPRINKLES THROUGH 12Z. * MEDIUM TO HIGH CONFIDENCE IN WIND FORECAST. ALLSOPP //OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z... MONDAY...VFR BUT POTENTIAL FOR IFR/MVFR IN LAKE EFFECT SNOW SHOWERS. TUESDAY...VFR. WEDNESDAY...VFR. THURSDAY...VFR. FRIDAY...VFR. SLIGHT CHANCE OF LIGHT SNOW. MDB && .MARINE... 133 AM CST A POWERFUL STORM WAS MOVING THROUGH THE GREAT LAKES THIS MORNING. LOW PRESSURE WILL MOVE QUICKLY FROM WISCONSIN TO NORTHERN LAKE MICHIGAN THIS MORNING...THEN ON TO QUEBEC BY EVENING. EAST OF THE TRACK OF THE LOW A VERY STRONG SOUTHERLY LOW LEVEL JET WAS OCCURRING...WITH 50 KT WINDS JUST 1 TO 2 THOUSAND FEET OFF THE SURFACE. A STRONG INVERSION WAS LIMITING MIXING BUT GALE FORCE WINDS WERE WORKING DOWN TO THE LAKE SURFACE OVER THE SOUTH HALF WITH SOME GALE FORCE GUSTS ON THE EAST SIDE OF THE NORTH HALF OF THE LAKE. WINDS SHOULD DROP OFF PRETTY QUICKLY AS THE LOW MOVES RAPIDLY NORTHEAST TODAY AND GALES SHOULD END BY ABOUT NOON. PRESENTLY GALE WARNING GOES THROUGH MID AFTERNOON BUT IT MAY BE CANCELED EARLY. WINDS WILL VEER FROM SOUTH TO NORTHWEST THROUGH THE COURSE OF THE DAY. TONIGHT THROUGH MONDAY ANOTHER LOW WILL MOVE FROM THE TEXAS COAST UP THROUGH THE OHIO VALLEY WHILE STRONG HIGH PRESSURE BUILDS INTO THE NORTHERN PLAINS. THIS WILL PRODUCE A PERIOD OF NORTHERLY WINDS ON LAKE MICHIGAN. THE REST OF THE WEEK HIGH PRESSURE WILL DOMINATE THE CENTRAL U.S. WHILE LOW PRESSURE BECOMES ANCHORED OVER NORTHEAST CANADA. THIS WILL PRODUCE A PROLONGED PERIOD OF WESTERLY WINDS OVER LAKE MICHIGAN FROM MID WEEK INTO THE WEEKEND. ALLSOPP && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779- LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 3 PM SUNDAY. SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 3 PM SUNDAY. && $$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
539 AM CST SUN DEC 4 2011 .UPDATE... RADAR AND RUC TRENDS INDICATE THE DEFORMATION ZONE PRECIPITATION HAS FALLEN APART AND MOST SFC OBS INDICATE NO PRECIPITATION IS OCCURRING. ISOLATED FLURRIES OR VERY LOCALIZED FZDZ MAY BE OCCURRING IN THE NORTHWEST PART OF THE CWFA BUT MUCH OF THE AREA NOW LOOKS TO REMAIN DRY. THE COLD FRONT IS NOW IN THE EASTERN PART OF THE CWFA AND WILL CLEAR IT BY 14Z AND TAKE WHAT LINGERING RA/SHRA WITH IT. THUS THE CURRENT TREND OF ENDING ALL PRECIP IN THE EASTERN CWFA BY 15Z LOOKS ON TARGET. AS FOR THE CLOUDS...NOT ONE MODEL HAS A HANDLE ON WHAT IS CURRENTLY GOING ON. THE OPENING IN WESTERN IOWA APPEARS TO BE SLOWLY SHRINKING BASED ON RECENT SATELLITE TRENDS. THE CAA POURING INTO THE AREA IS NOT STEEPENING LOW LEVEL LAPSE RATES ALL THAT MUCH BASED ON RECENT RUC TRENDS. EXTRAPOLATION OF THE POCKET OF CLEAR SKIES IN WESTERN IOWA SUGGESTS THAT IT WOULD REMAIN WEST OF THE CWFA DURING THE DAY. TEMPERATURE WISE...HIGH TEMPERATURES IN THE FAR EASTERN CWFA WILL OCCUR OVER THE NEXT 1-2 HRS AND THEN SLOWLY FALL THE REMAINDER OF THE DAY. LOW TEMPERATURES THIS MORNING WILL BE RIGHT AROUND THE 14-15Z TIME FRAME. AN UPDATE TO THE OVERALL FCST FOR TODAY WILL BE AVAILABLE SHORTLY. ..08.. && .AVIATION... NOT ONE MODEL IS CURRENTLY HANDLING THE CLOUD COVER ACROSS THE MIDWEST. CIGS BLO 1KFT AGL WILL SLOWLY RISE AND ACHIEVE 1KFT CIGS 15Z-18Z. THE HOLE OF VFR TO UNLIMITED CIGS IN WESTERN IOWA PER SATELLITE IS A CONCERN BUT RECENT TRENDS SUGGEST THIS HOLE IS FILLING. AFT 18Z CIGS WILL CONTINUE TO SLOWLY RISE BUT SHOULD REMAIN IN THE 1-2KFT AGL RANGE. AFT 02Z/05 CIGS AT ALL TAF SITES SHOULD CLIMB TO 2-3KFT AGL. VSBYS SHOULD REMAIN VFR THROUGH 12Z/05. ..08.. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
313 AM CST SUN DEC 4 2011 .SYNOPSIS... 06Z SFC ANALYSIS HAD A LOW SOUTHEAST OF KVOK AND ANOTHER AROUND KMXO. THE FRONT RAN BETWEEN THE TWO LOWS AND INTO NORTHERN MISSOURI. A WEAK TROF RAN FROM THE KMXO LOW TO NEAR KUIN. RADAR TRENDS SHOW THE STRATIFORM PRECIP HAS EXITED THE AREA WITH A NARROW BAND OF RAIN ASSOCIATED WITH THE FRONT MOVING INTO ILLINOIS FROM IOWA. DEFORMATION PRECIPITATION CONTINUES ACROSS IOWA BUT IS DECREASING IN OVERALL COVERAGE. DEW POINTS AHEAD OF THE FRONT WERE IN THE 40S AND 50S WITH 20S AND 30S BEHIND THE FRONT. && .SHORT TERM...TODAY AND TONIGHT... THE RUC 285K OMEGA AND 295K CONDENSATION PRESSURE DEFICIT FIELDS ALONG WITH F VECTOR CONVERGENCE DEPICTS REASONABLY WELL WHAT IS CURRENTLY GOING ON. THE COLD FRONT WILL BE OVER THE EXTREME EASTERN CWFA JUST PRIOR TO SUNRISE WITH ITS ASSOCIATED RAIN BAND. THIS RAIN BAND WILL EXIT THE EASTERN CWFA 13-15Z. ACROSS THE WESTERN CWFA WET BULB SFC TEMPERATURES ARE DROPPING BELOW 34 DEGREES AND CONDENSATION PRESSURE DEFICITS ARE RISING. WHERE THE WET BULB SFC TEMPERATURES ARE 32 OR BELOW THE PRECIP CHANGES TO SNOW WITH SOME PATCHY FZDZ. RUC TRENDS SHOW WET BULB TEMPERATURES DROPPING THROUGH SUNRISE SO THERE IS A POTENTIAL FOR SOME LIGHT SNOW AND PATCHY FREEZING DRIZZLE ROUGHLY WEST OF A DUBUQUE TO FAIRFIELD LINE. HOWEVER...WITH THE DEFORMATION ZONE AND FORCING WEAKENING ALONG WITH CONDENSATION PRESSURE DEFICITS RISING THE PRECIPITATION WILL LIKELY BE MORE FLURRIES AND PATCHY FREEZING DRIZZLE. RUC TRENDS INDICATE THE PRECIPITATION IN THIS AREA WILL END BY MID MORNING. THUS TO HANDLE THE CURRENT TRENDS...THERE WILL BE A PRE-FIRST PERIOD TO REFLECT PRECIPITATION TRENDS. TEMPERATURES WILL CONTINUE TO FALL WITH MINS BEING ACHIEVED AROUND 14Z. BASED ON THE CAA...TEMPERATURES WILL LIKELY CONTINUE FALLING THROUGH MID MORNING BEFORE STARTING A SLOW RISE. MAX TEMPERATURES IN THE EASTERN CWFA WILL BE EARLY THIS MORNING WHILE WESTERN AREAS WILL SEE MAX TEMPERATURES THIS AFTERNOON. TONIGHT...QUIET AND DRY WX IS EXPECTED WITH A VERY SLOW CLEARING OF THE CLOUDS. ..08.. .LONG TERM...MONDAY THROUGH SATURDAY MONDAY THROUGH TUESDAY WE WILL BE ON THE COLD SIDE THAT MOVES THROUGH THE AREA TODAY AND SHOULD BE DRAPED FROM LOUISIANA NORTHEAST TO OHIO AND FARTHER NORTHEAST. THE UPPER LEVEL TROUGH WILL STILL BE WORKING THROUGH THE AREA...AND THE 500MB TROUGH AXIS IS NOT DUE TO GET PAST THE AREA UNTIL TUESDAY NIGHT. WHILE WE LOSE THE MID AND UPPER LEVEL MOISTURE...SOME TRAPPED MOISTURE HANGING AROUND 900MB AND BELOW WILL KEEP THE TIME PERIOD MOSTLY CLOUDY IF NOT CLOUDY ...NOT CLEARING UNTIL TUESDAY AFTERNOON. THE MODELS ARE INDICATING SOME CLEARING ON MONDAY MORNING...BUT THIS FILLS BACK IN AS NORTH WINDS ADVECT CLOUDS BACK OVER THE AREA IN THE CYCLONIC FLOW. WILL HAVE TO WATCH THESE TRENDS...AND WILL TREND PESSIMISTIC FOR NOW AS IT IS THE TIME OF YEAR FOR GLOOMY CONDITIONS. TEMPERATURES TO BE MODERATED BY THESE CLOUDS...BUT BELOW NORMAL VALUES CAN BE EXPECTED WITH THE COLD AIR ADVECTION GOING ON. HIGHS MONDAY IN THE 30S TO DROP INTO THE MID 20S TO MID 30S FOR TUESDAY. WITH ALL THE LOW CLOUDS AROUND...WE MAY GET A FEW FLURRIES OR EVEN PATCHY DRIZZLE...BUT HAVE ONLY PUT IN FLURRIES FOR NOW. TUESDAY NIGHT THE CLOUDS SHOULD FINALLY CLEAR...HAVE HAVE GONE WITH MUCH COLDER MIN TEMPS IN THE TEENS AND LOWER 20S. BY WEDNESDAY THE MAIN UPPER LEVEL TROUGH AXIS SWINGS EAST OF THE AREA...LEAVING US WITH CYCLONIC NORTHWEST FLOW. ALREADY...A COLD FRONT IS EXPECTED TO SWING THROUGH ON WEDNESDAY...AND WITH LITTLE MOISTURE AVAILABLE DO NOT EXPECT ANY PRECIPITATION. A SECOND COLD FRONT ALONG WITH AN UPPER LEVEL SHORTWAVE IS EXPECTED THROUGH THURSDAY OR THURSDAY EVENING...AGAIN SOMEWHAT LACKING IN MOISTURE...BUT IT MAY BE ABLE TO PRODUCE SOME PRECIPITATION THURSDAY NIGHT ALONG AND BEHIND IT. HOWEVER...THE MODELS HAVE LITTLE IN THE WAY OF RUN TO RUN CONSISTENCY WITH THIS FEATURE RIGHT NOW...AND HAVE STAYED FAIRLY CLOSE TO A CONSENSUS FORECAST FOR THIS TIME RANGE. TEMPERATURES IN THE NORTHWEST FLOW TO BE COLDER THAN NORMAL...WITH HIGHS ONLY GETTING INTO THE 30S...AND MINS IN THE TEENS AND 20S. FRIDAY WE WILL BE IN DEEP NORTHWEST FLOW ON THE WEST SIDE OF THE LONGWAVE TROUGH WITH SOME WEAK RIDGING AT THE SURFACE. BY SATURDAY THE LONGWAVE TROUGH WILL HAVE SHIFTED FURTHER EAST...AND WARM AIR ADVECTING BEGINS AGAIN AT MID LEVELS...WITH SOUTHWEST FLOW DEVELOPING AT THE SURFACE. THESE PERIODS SHOULD BE DRY WITH COLDER TEMPERATURES AGAIN. ..LE.. && .AVIATION... /ISSUED 1142 PM CST SAT DEC 3 2011/ A SURFACE LOW OVER NORTHEAST IOWA WILL CONTINUE TO MOVE NORTHEAST AWAY FROM THE AREA. EXPECT SOME IFR OR LIFR CIGS/VSBYS FOR A FEW HOURS EARLY THIS MORNING THEN WITH WEST TO NORTHWEST WINDS SPREADING OVER THE AREA THE CIGS/VSBYS SHOULD BE IMPROVING TO MVFR BY 12Z TO 15Z. THE RAIN WILL BE TAPERING OFF OVER THE AREA BY 09Z. A RN/SN MIX IS STILL POSSIBLE AT CID/DBQ BEFORE THE PRECIPITATION ENDS. FOR THE REST OF THE PERIOD EXPECT MVFR TO LOW END VFR CIGS SUNDAY AFTERNOON AND EVENING. ..DLF.. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1142 PM CST SAT DEC 3 2011 .AVIATION... A SURFACE LOW OVER NORTHEAST IOWA WILL CONTINUE TO MOVE NORTHEAST AWAY FROM THE AREA. EXPECT SOME IFR OR LIFR CIGS/VSBYS FOR A FEW HOURS EARLY THIS MORNING THEN WITH WEST TO NORTHWEST WINDS SPREADING OVER THE AREA THE CIGS/VSBYS SHOULD BE IMPROVING TO MVFR BY 12Z TO 15Z. THE RAIN WILL BE TAPERING OFF OVER THE AREA BY 09Z. A RN/SN MIX IS STILL POSSIBLE AT CID/DBQ BEFORE THE PRECIPITATION ENDS. FOR THE REST OF THE PERIOD EXPECT MVFR TO LOW END VFR CIGS SUNDAY AFTERNOON AND EVENING. ..DLF.. && .PREV DISCUSSION... /ISSUED 308 PM CST SAT DEC 3 2011/ SYNOPSIS... MAIN FEATURE OF INTEREST IS THE UPPER LEVEL LOW OVER LAS VEGAS WITH A LEAD WAVE EJECTING OVER WESTERN KANSAS AT 18Z. MEANWHILE... SURFACE LOW IS LOCATED IN SOUTH-CENTRAL KANSAS WITH THE COLD FRONT EXTENDING NORTH TO FORT DODGE /KFOD/ AND THE UPPER PENINSULA. TEMPS BEHIND THE FRONT DIVE FROM THE MID AND SOME UPPER 40S INTO THE LOWER 30S. LARGE AREA OF RAIN IN THE WARM SECTOR LIFTED NORTH TODAY WITH PRECIP AMOUNTS TYPICALLY IN THE ONE HALF TO ONE INCH RANGE. NEXT ROUND OF PRECIP ASSOCIATED WITH THE MAIN COLD FRONT NOW SPANNING CENTRAL IOWA AND MUCH OF MISSOURI. SHORT TERM...TONIGHT AND SUNDAY... MAIN FORECAST CONCERN TONIGHT IS THE BEHAVIOR OF THE NEXT ROUND OF PRECIP. RUC BRINGS THE SURFACE LOW OVER VINTON /KVTI/ BY 03Z THIS EVENING. THIS IS SLIGHTLY FASTER AND FARTHER NORTHWEST THAN MODEL FORECASTS HAD BEEN BUT IS IN LINE WITH THE OVERALL TREND TO A WARMER FORECAST. IN TERMS OF PRECIP...THIS MORE WESTERN TRACK...AS SEEN IN THE RUC AND CURRENT RADAR TRENDS...SUGGESTS RAIN THROUGH THE EVENING WITH ONLY A BRIEF CHANGE TO SNOW IN THE FAR NORTHERN COUNTIES BEFORE PRECIP ENDS LATE TONIGHT/EARLY SUNDAY MORNING. MUCH OF THE AREA TO BE DRY-SLOTTED OVERNIGHT WITH ONLY THE NORTHERN AND WESTERN SECTIONS EXPECTED TO SEE WRAP-AROUND PRECIP AS THE LOW RACES OFF TO THE NORTHEAST. EVEN SO...BUFKIT SOUNDINGS FOR KCID AND KDBQ LIMIT ANY FROZEN PRECIP TO ONLY AN HOUR OR TWO BEFORE ENDING ALTOGETHER. THUS HAVE REDUCED SNOW AMOUNTS AND ENDED PRECIP A FEW HOURS EARLIER THAN PREVIOUS FORECAST. ..DMD.. LONG TERM...SUNDAY NIGHT THROUGH NEXT SATURDAY HIGH PRESSURE AT THE SURFACE MIGRATING THROUGH THE NORTHERN PLAINS INTO THE UPPER MS VALLEY TO BRING NEAR TO SLIGHTLY BELOW NORMAL TEMPERATURES FROM SUNDAY NIGHT THROUGH WEDNESDAY. THROUGH THIS PERIOD...MODELS IN GENERAL AGREEMENT FEATURING AN UPPER LEVEL POSITIVE TILT LONG WAVE TROUGH TRANSITIONING EAST THROUGH THE CENTRAL U.S....SUPPRESSING THE MAIN BAROCLINIC AXIS AND STORM TRACK WELL TO THE SOUTHEAST. A WAVE OF LOW PRESSURE TRACKING ALONG THE OHIO RIVER MONDAY WILL SPREAD SNOW INTO PORTIONS OF MO AND IL...AND WILL KEEP ONLY SLIGHT CHANCE POPS CONFINED TO THE FAR EAST AND SOUTH MONDAY NIGHT ON THE EXTREME NW EDGE OF THIS SYSTEM. OTHERWISE...NO PRECIPITATION IS EXPECTED...BUT HIGH LEVEL LIFT AND MOISTURE ALOFT AHEAD OF THE UPPER TROUGH AXIS WILL FAVOR MOSTLY CLOUDY SKIES FOR MUCH OF MON THROUGH WED. THU THROUGH SAT...MODEL CONSENSUS INDICATES A COLD FRONT DROPPING SOUTH THROUGH THE REGION LATE THURSDAY...FOLLOWED BY MUCH COLDER TEMPERATURES FRIDAY AND SATURDAY FOLLOWING A FRESH INFLUX OF COLD AIR AT 850 MB THAT HAS BEEN BUILDING WELL TO THE NORTH. THERE CONTINUES TO BE CONSIDERABLE DIFFERENCES WITH THE TIMING AND PLACEMENT OF CRITICAL UPPER LEVEL TROUGHS AND SURFACE FEATURES IN THIS TIME FRAME...THUS THE POTENTIAL FOR PRECIPITATION REMAINS LOW CONFIDENCE. THE CURRENT SUITE OF MODELS USED IN THE EXTENDED SUPPORTS OUR SLIGHT TO LOW END CHANCES FOR LIGHT SNOW FOR THU NIGHT FOLLOWING THE PASSAGE OF THE COLD FRONT. AHEAD OF THIS FRONT...HIGHS THURSDAY SHOULD REACH INTO THE 30S IN MOST AREAS. THIS IS FOLLOWED BY 20S FRIDAY AND SATURDAY WITH OVERNIGHT LOWS IN THE SINGLE DIGITS AND TEENS. ..SHEETS.. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$
AREA FORECAST DISCUSSION
NWS GOODLAND KS
850 PM MST MON DEC 5 2011 .UPDATE... 850 PM MDT MON DEC 5 2011 LATEST RUC HRRR HAS A BIT BETTER HANDLE ON COLDER TEMPS PRESENTLY AND THROUGH THE REST OF THE OVERNIGHT REALLY TANKS TEMPS IN AREAS SUCH AS MCCOOK AND NORTON WITH READINGS IN THE -10F TO -14F RANGE AFTER 12Z. 00Z MET GUIDANCE FOR KMCK SHOWING -9F. KMCK DROPPED TO -1F 2 MORNINGS AGO. HAVE UPDATED MINS TO DROP THEM TO AROUND -11F WHILE IN NORTON HAVE LOWERED THEM TO THE -10F RANGE. FOR NORTON COUNTY COMBINATION OF THE 10F FORECAST AND WEST WIND OF 5 MPH OR LESS PUTS THEM IN WIND CHILL ADVISORY CRITERIA. WILL CONTINUE TO MONITOR 03Z RUN OF THE HRRR AND SEE WHAT IT DOES FOR TEMPS AND WINDS. 007 && .DISCUSSION... 221 PM MST MON DEC 5 2011 EARLY AFTERNOON WV IMAGERY AND RUC H5 ANALYSIS SHOW LARGE SCALE TROUGH EXTENDING FROM GREAT LAKES REGION...ACROSS CENTRAL COLORADO...WITH BASE OF TROUGH OVER SOUTHERN ARIZONA/NEW MEXICO. THROUGH TONIGHT...SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE CENTRAL HIGH PLAINS AS A WEAK SHORTWAVE TROUGH CONTINUES TO PUSH AWAY FROM THE FORECAST AREA. COMBINATION OF CLEARING SKY...VERY LIGHT WINDS AND WIDESPREAD SNOW COVER WILL CONTRIBUTE TO VERY COLD TEMPERATURES OVERNIGHT. AMBIENT TEMPERATURES WILL FALL BELOW ZERO FOR ALL BUT THE FAR SOUTHEAST PORTION OF THE FORECAST AREA WHICH WILL REMAIN AT OR SLIGHTLY ABOVE ZERO. DESPITE THE LIGHT WINDS...WIND CHILL READINGS WILL FALL TO AS LOW AS 20 BELOW ZERO FOR A PERIOD OF TIME PRIMARILY OVER THE NORTHWEST HALF OF THE FORECAST AREA. AS SUCH...WILL ISSUE A WIND CHILL ADVISORY. FOLTZ TUESDAY-WEDNESDAY...SHORTWAVE RIDGING WILL BUILD OVER THE CWA TUESDAY QUICKLY FOLLOWED BY WESTERLY FLOW ALOFT WEDNESDAY...WHICH WILL FAVOR DRY CONDITIONS OVER CWA. SHALLOW COLD AIR MASS WILL BEGIN TO MODERATE...WITH HIGH/LOW TEMP FORECAST COMPLICATED BY LINGERING SNOW PACK. CONTINUED TO UNDERCUT GUIDANCE THROUGH THESE PERIODS....NOT EXPECTING TEMPS TO MAKE IT ABOVE FREEZING UNTIL WED AFTERNOON. WEDNESDAY NIGHT-THURSDAY NIGHT...COLD FRONT PUSHES SOUTH ACROSS CWA WEDNESDAY NIGHT...WITH SHORTWAVE TROUGH PASSING NORTH OF CWA THURSDAY/THURSDAY NIGHT. BEST LIFT/MOISTURE LOOKS TO REMAIN OVER CENTRAL NEBRASKA...HOWEVER MODEL POINT SOUNDINGS DO SHOW DENDRITIC LAYER BEGINNING TO SATURATE IN EXTREME NORTHERN PART OF CWA IN THE 21Z-00Z TIME FRAME. WENT AHEAD AND ADDED SLIGHT CHANCE POPS TO SW NEBRASKA COUNTIES 18Z-00Z WHERE A DUSTING COULDNT BE RULED OUT. ALSO EXPANDED FLURRIES FURTHER SOUTH...AND MADE CONDITIONS DRY AFTER 06Z. FRIDAY-MONDAY...WARMING TREND WILL START UP AGAIN FRIDAY...AND CONTINUE THROUGH THE WEEKEND WITH SHORTWAVE RIDGING ACROSS WESTERN CONUS THROUGH SATURDAY. TEMPERATURES SHOULD MODERATE TO NEAR NORMAL VALUES IN THE UPPER 30S/LOW 40S SAT/SUN. CLOSED LOW BEGINS TO DEVELOP OVER SW CONUS BY SUNDAY NIGHT/MONDAY WITH W/SW FLOW DEVELOPING OVER CWA AHEAD OF THIS FEATURE. GUIDANCE IN GENERAL AGREEMENT ON ARRIVAL OF COLD FRONT SUN NIGHT/MON...WHICH SHOULD SUPPORT A RETURN TO BELOW NORMAL TEMPERATURES EARLY NEXT WEEK. NOT EXPECTING ANY PRECIP THROUGH EXTENDED PERIODS...WITH DRY AIR MASS IN PLACE OVER CWA. DR && .AVIATION... 420 PM MST MON DEC 5 2011 FOR THE 00Z TAFS...VFR EXPECTED THROUGH THE PERIOD AT BOTH KGLD AND KMCK. SFC HIGH OVER THE AREA PRODUCING VRY LIGHT WINDS WILL SLOWLY MOVE EAST TUESDAY WITH A LEE TROUGH DEVELOPING TO THE WEST. SOUTHWEST WINDS AROUND 10KTS TO DEVELOP SHORTLY AFTER SUNRISE AND CONTINUE THROUGH THE DAY UNDER A CLEAR SKY. 007 && .GLD WATCHES/WARNINGS/ADVISORIES... KS...WIND CHILL ADVISORY UNTIL 8 AM MST /9 AM CST/ TUESDAY FOR KSZ001>003-013-014-027. NE...WIND CHILL ADVISORY UNTIL 8 AM MST /9 AM CST/ TUESDAY FOR NEZ079>081. CO...WIND CHILL ADVISORY UNTIL 8 AM MST TUESDAY FOR COZ090>092. && $$
AREA FORECAST DISCUSSION...CORRECTED
NWS GOODLAND KS
705 PM MST MON DEC 5 2011 .UPDATE... 705 PM MDT MON DEC 5 2011 AT 02Z WIND CHILL READINGS HAVE ALREADY DROPPED TO -15F IN FAR EASTERN COLORADO AND WESTERN KANSAS AS TEMPERATURES OF -3F TO -5F COMBINE WITH WEST WINDS OF 5-7 MPH. AS A RESULT...HAVE STARTED THE WIND ADVISORY NOW VS THE ORIGINAL 06Z STARTING TIME. NO LARGE CHANGES TO TONIGHTS GRIDS. MIN TEMPS LOOK PRETTY GOOD WHEN COMPARED TO LATEST MOS AND 00Z NAM TEMP FORECASTS. 007 && .DISCUSSION... 221 PM MST MON DEC 5 2011 EARLY AFTERNOON WV IMAGERY AND RUC H5 ANALYSIS SHOW LARGE SCALE TROUGH EXTENDING FROM GREAT LAKES REGION...ACROSS CENTRAL COLORADO...WITH BASE OF TROUGH OVER SOUTHERN ARIZONA/NEW MEXICO. THROUGH TONIGHT...SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE CENTRAL HIGH PLAINS AS A WEAK SHORTWAVE TROUGH CONTINUES TO PUSH AWAY FROM THE FORECAST AREA. COMBINATION OF CLEARING SKY...VERY LIGHT WINDS AND WIDESPREAD SNOW COVER WILL CONTRIBUTE TO VERY COLD TEMPERATURES OVERNIGHT. AMBIENT TEMPERATURES WILL FALL BELOW ZERO FOR ALL BUT THE FAR SOUTHEAST PORTION OF THE FORECAST AREA WHICH WILL REMAIN AT OR SLIGHTLY ABOVE ZERO. DESPITE THE LIGHT WINDS...WIND CHILL READINGS WILL FALL TO AS LOW AS 20 BELOW ZERO FOR A PERIOD OF TIME PRIMARILY OVER THE NORTHWEST HALF OF THE FORECAST AREA. AS SUCH...WILL ISSUE A WIND CHILL ADVISORY. FOLTZ TUESDAY-WEDNESDAY...SHORTWAVE RIDGING WILL BUILD OVER THE CWA TUESDAY QUICKLY FOLLOWED BY WESTERLY FLOW ALOFT WEDNESDAY...WHICH WILL FAVOR DRY CONDITIONS OVER CWA. SHALLOW COLD AIR MASS WILL BEGIN TO MODERATE...WITH HIGH/LOW TEMP FORECAST COMPLICATED BY LINGERING SNOW PACK. CONTINUED TO UNDERCUT GUIDANCE THROUGH THESE PERIODS....NOT EXPECTING TEMPS TO MAKE IT ABOVE FREEZING UNTIL WED AFTERNOON. WEDNESDAY NIGHT-THURSDAY NIGHT...COLD FRONT PUSHES SOUTH ACROSS CWA WEDNESDAY NIGHT...WITH SHORTWAVE TROUGH PASSING NORTH OF CWA THURSDAY/THURSDAY NIGHT. BEST LIFT/MOISTURE LOOKS TO REMAIN OVER CENTRAL NEBRASKA...HOWEVER MODEL POINT SOUNDINGS DO SHOW DENDRITIC LAYER BEGINNING TO SATURATE IN EXTREME NORTHERN PART OF CWA IN THE 21Z-00Z TIME FRAME. WENT AHEAD AND ADDED SLIGHT CHANCE POPS TO SW NEBRASKA COUNTIES 18Z-00Z WHERE A DUSTING COULDNT BE RULED OUT. ALSO EXPANDED FLURRIES FURTHER SOUTH...AND MADE CONDITIONS DRY AFTER 06Z. FRIDAY-MONDAY...WARMING TREND WILL START UP AGAIN FRIDAY...AND CONTINUE THROUGH THE WEEKEND WITH SHORTWAVE RIDGING ACROSS WESTERN CONUS THROUGH SATURDAY. TEMPERATURES SHOULD MODERATE TO NEAR NORMAL VALUES IN THE UPPER 30S/LOW 40S SAT/SUN. CLOSED LOW BEGINS TO DEVELOP OVER SW CONUS BY SUNDAY NIGHT/MONDAY WITH W/SW FLOW DEVELOPING OVER CWA AHEAD OF THIS FEATURE. GUIDANCE IN GENERAL AGREEMENT ON ARRIVAL OF COLD FRONT SUN NIGHT/MON...WHICH SHOULD SUPPORT A RETURN TO BELOW NORMAL TEMPERATURES EARLY NEXT WEEK. NOT EXPECTING ANY PRECIP THROUGH EXTENDED PERIODS...WITH DRY AIR MASS IN PLACE OVER CWA. DR && .AVIATION... 420 PM MST MON DEC 5 2011 FOR THE 00Z TAFS...VFR EXPECTED THROUGH THE PERIOD AT BOTH KGLD AND KMCK. SFC HIGH OVER THE AREA PRODUCING VRY LIGHT WINDS WILL SLOWLY MOVE EAST TUESDAY WITH A LEE TROUGH DEVELOPING TO THE WEST. SOUTHWEST WINDS AROUND 10KTS TO DEVELOP SHORTLY AFTER SUNRISE AND CONTINUE THROUGH THE DAY UNDER A CLEAR SKY. 007 && .GLD WATCHES/WARNINGS/ADVISORIES... KS...WIND CHILL ADVISORY UNTIL 8 AM MST /9 AM CST/ TUESDAY FOR KSZ001>003-013-014-027. NE...WIND CHILL ADVISORY UNTIL 8 AM MST /9 AM CST/ TUESDAY FOR NEZ079>081. CO...WIND CHILL ADVISORY UNTIL 8 AM MST TUESDAY FOR COZ090>092. && $$
AREA FORECAST DISCUSSION
NWS TOPEKA KS
551 PM CST MON DEC 5 2011 ...UPDATE TO AVIATION... .DISCUSSION... TONIGHT THROUGH TUESDAY... MAIN FOCUS TONIGHT WILL BE THE POTENTIAL FOR SCATTERED FLURRIES OVER PORTIONS OF THE CWA. SHORTWAVE TROUGH ANALYZED OVER NEW MEXICO WILL LIFT ACROSS THE SOUTHERN/CENTRAL PLAINS TONIGHT. BEST LIFT WILL REMAIN MAINLY SOUTH OF THE CWA...WITH MODEST ASCENT OVER THE SOUTHERN HALF OF THE CWA. THE BIGGEST LIMITING FACTOR FOR PRECIPITATION PRODUCTION WILL BE A PERSISTENT DRY LAYER AT H85-H7...AS SEEN IN CROSS SECTIONS THROUGH THE AREA. EXPECT AN AREA OF LIGHT SNOW OR FLURRIES TO DEVELOP ACROSS THE TX PANHANDLE INTO SW KS THIS EVENING...WITH ACTIVITY WEAKENING AS THE UPPER SUPPORT LIFTS TO THE NORTHEAST. SCATTERED FLURRIES WILL BE POSSIBLE ACROSS EAST CENTRAL KS TONIGHT AS THE ASCENT SPREADS INTO THE AREA AND COLUMN ATTEMPTS TO SATURATE. MEASURABLE SNOWFALL LOOKS UNLIKELY AT THIS TIME ALTHOUGH A FEW AREAS IN EAST CENTRAL SECTIONS MIGHT SEE A TRACE. PRECIPITATION SHOULD END BY MID MORNING TUESDAY AS THE SHORTWAVE TROUGH SHEARS AND DEPARTS TO THE EAST. TEMPERATURES WILL REMAIN CHILLY WITH LOWS IN THE MIDDLE TEENS TO LOWER 20S AND HIGHS TUESDAY IN THE MIDDLE 20S TO LOWER 30S. BLAIR TUESDAY EVENING THROUGH FRIDAY EVENING... THE BROAD H5 LONGWAVE TROUGH WILL CONTINUE TO MAKE ITS PROGRESSION EASTWARD...GENERATING PRECIP OVER THE SOUTHEASTERN CONUS. DRY SUBSIDENCE AIR FILLS IN ON THE BACKSIDE OF THE TROUGH AS INFLUENCE FROM A SURFACE RIDGE CENTERED OVER THE CENTRAL PLAINS WILL CALM WINDS TUESDAY EVENING. STRONG BOUNDARY LAYER DECOUPLING AND CLEAR SKIES WILL ALLOW TEMPERATURES TO QUICKLY FALL INTO THE LOWER TEENS. WEDNESDAY AFTERNOON STILL APPEARS ON TRACK AS SFC HIGH PRESSURE REIGNS AND CLEAR SKIES ALLOW TEMPS TO PEAK IN THE MIDDLE TO UPPER 30S. NO MAJOR CHANGES WERE MADE ON THURSDAY IN REGARDS TO THE TRACK OF THE OPEN H5 TROUGH PROGGED TO DIP SOUTHWARD OVER THE INTER-MOUNTAIN WEST AND NORTHERN PLAINS REGION. THE NAM/GEM CONTINUES TO DEVELOP A LIGHT BAND OF SNOW WHERE STRONGEST ASCENT IS PRESENT FROM SOUTHERN NEBRASKA TO SOUTHWEST IOWA. ATTM...INSTABILITY APPEARS FAIRLY WEAK WITH BUFKIT SOUNDINGS INDICATING ENOUGH LIFT FOR POSSIBLE LIGHT FLURRIES THURSDAY EVENING ACROSS THE FAR NORTHERN COUNTIES OF THE CWA. AS THE DISTURBANCE LIFTS EAST TOWARDS THE MIDWEST...SURFACE RIDGING BUILDS SOUTHWARD TOWARDS THE CENTRAL PLAINS ON FRIDAY. PERSISTENT COLD AIR ADVECTION WILL NOT MODERATE TEMPS MUCH WITH HIGHS IN THE 30S AND LOWS IN THE TEENS TO NEAR 20 DEGREES. SATURDAY THROUGH MONDAY... AS THE SURFACE RIDGE SHIFTS EASTWARD...WINDS BACK TO THE SOUTHWEST AS A LEE SURFACE TROUGH DEVELOPS OVER COLORADO. INCREASING SOUTHERLY WINDS ON SATURDAY AND SUNDAY WILL PUSH TEMPERATURES SLIGHTLY WARMER IN THE UPPER 30S TO LOWER 40S DURING THIS PERIOD. AS THE LEE TROUGH SHIFTS EAST...A COLD FRONT MOVES EAST ACROSS KANSAS WITH ANOTHER SHOT OF COLDER AIR POSSIBLE MONDAY EVENING. BOWEN && .AVIATION... LATEST RUC SOUNDINGS AND SATELLITE TRENDS DEPICT THE MVFR STRATUS TO HOLD OVER THE TERMINAL SITES THROUGH THE EVENING HOURS. LIGHT SNOW FLURRIES ARE POSSIBLE MONDAY EVENING HOWEVER BETTER MOISTURE AND LIFT IS WELL SOUTH OF TERMINALS AND WITH LOW CONFIDENCE OF ANY MEASURABLE SNOW...DECIDED TO NOT INCLUDE IN THE TAF. NORTH WINDS REMAIN AT OR ABOVE 10 KTS BEFORE WEAKENING TUESDAY MORNING AS THE PRESSURE GRADIENT RELAXES. SUBSIDENCE BEHIND THE SYSTEM IS EXPECTED TO LIFT AND SCATTER STRATUS TO VFR BY TUES AFTERNOON. BOWEN && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS GOODLAND KS
420 PM MST MON DEC 5 2011 .DISCUSSION... 221 PM MST MON DEC 5 2011 EARLY AFTERNOON WV IMAGERY AND RUC H5 ANALYSIS SHOW LARGE SCALE TROUGH EXTENDING FROM GREAT LAKES REGION...ACROSS CENTRAL COLORADO...WITH BASE OF TROUGH OVER SOUTHERN ARIZONA/NEW MEXICO. THROUGH TONIGHT...SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE CENTRAL HIGH PLAINS AS A WEAK SHORTWAVE TROUGH CONTINUES TO PUSH AWAY FROM THE FORECAST AREA. COMBINATION OF CLEARING SKY...VERY LIGHT WINDS AND WIDESPREAD SNOW COVER WILL CONTRIBUTE TO VERY COLD TEMPERATURES OVERNIGHT. AMBIENT TEMPERATURES WILL FALL BELOW ZERO FOR ALL BUT THE FAR SOUTHEAST PORTION OF THE FORECAST AREA WHICH WILL REMAIN AT OR SLIGHTLY ABOVE ZERO. DESPITE THE LIGHT WINDS...WIND CHILL READINGS WILL FALL TO AS LOW AS 20 BELOW ZERO FOR A PERIOD OF TIME PRIMARILY OVER THE NORTHWEST HALF OF THE FORECAST AREA. AS SUCH...WILL ISSUE A WIND CHILL ADVISORY. FOLTZ TUESDAY-WEDNESDAY...SHORTWAVE RIDGING WILL BUILD OVER THE CWA TUESDAY QUICKLY FOLLOWED BY WESTERLY FLOW ALOFT WEDNESDAY...WHICH WILL FAVOR DRY CONDITIONS OVER CWA. SHALLOW COLD AIR MASS WILL BEGIN TO MODERATE...WITH HIGH/LOW TEMP FORECAST COMPLICATED BY LINGERING SNOW PACK. CONTINUED TO UNDERCUT GUIDANCE THROUGH THESE PERIODS....NOT EXPECTING TEMPS TO MAKE IT ABOVE FREEZING UNTIL WED AFTERNOON. WEDNESDAY NIGHT-THURSDAY NIGHT...COLD FRONT PUSHES SOUTH ACROSS CWA WEDNESDAY NIGHT...WITH SHORTWAVE TROUGH PASSING NORTH OF CWA THURSDAY/THURSDAY NIGHT. BEST LIFT/MOISTURE LOOKS TO REMAIN OVER CENTRAL NEBRASKA...HOWEVER MODEL POINT SOUNDINGS DO SHOW DENDRITIC LAYER BEGINNING TO SATURATE IN EXTREME NORTHERN PART OF CWA IN THE 21Z-00Z TIME FRAME. WENT AHEAD AND ADDED SLIGHT CHANCE POPS TO SW NEBRASKA COUNTIES 18Z-00Z WHERE A DUSTING COULDNT BE RULED OUT. ALSO EXPANDED FLURRIES FURTHER SOUTH...AND MADE CONDITIONS DRY AFTER 06Z. FRIDAY-MONDAY...WARMING TREND WILL START UP AGAIN FRIDAY...AND CONTINUE THROUGH THE WEEKEND WITH SHORTWAVE RIDGING ACROSS WESTERN CONUS THROUGH SATURDAY. TEMPERATURES SHOULD MODERATE TO NEAR NORMAL VALUES IN THE UPPER 30S/LOW 40S SAT/SUN. CLOSED LOW BEGINS TO DEVELOP OVER SW CONUS BY SUNDAY NIGHT/MONDAY WITH W/SW FLOW DEVELOPING OVER CWA AHEAD OF THIS FEATURE. GUIDANCE IN GENERAL AGREEMENT ON ARRIVAL OF COLD FRONT SUN NIGHT/MON...WHICH SHOULD SUPPORT A RETURN TO BELOW NORMAL TEMPERATURES EARLY NEXT WEEK. NOT EXPECTING ANY PRECIP THROUGH EXTENDED PERIODS...WITH DRY AIR MASS IN PLACE OVER CWA. DR && .AVIATION... 420 PM MST MON DEC 5 2011 FOR THE 00Z TAFS...VFR EXPECTED THROUGH THE PERIOD AT BOTH KGLD AND KMCK. SFC HIGH OVER THE AREA PRODUCING VRY LIGHT WINDS WILL SLOWLY MOVE EAST TUESDAY WITH A LEE TROUGH DEVELOPING TO THE WEST. SOUTHWEST WINDS AROUND 10KTS TO DEVELOP SHORTLY AFTER SUNRISE AND CONTINUE THROUGH THE DAY UNDER A CLEAR SKY. 007 && .GLD WATCHES/WARNINGS/ADVISORIES... KS...WIND CHILL ADVISORY FROM 11 PM MST /MIDNIGHT CST/ THIS EVENING TO 8 AM MST /9 AM CST/ TUESDAY FOR KSZ001>003-013-014-027. NE...WIND CHILL ADVISORY FROM 11 PM MST /MIDNIGHT CST/ THIS EVENING TO 8 AM MST /9 AM CST/ TUESDAY FOR NEZ079>081. CO...WIND CHILL ADVISORY FROM 11 PM THIS EVENING TO 8 AM MST TUESDAY FOR COZ090>092. && $$
AREA FORECAST DISCUSSION
NWS CARIBOU ME
917 PM EST MON DEC 5 2011 .SYNOPSIS... A SLOW MOVING COLD FRONT WILL APPROACH NORTHERN MAINE THIS EVENING AND THEN MOVE ACROSS THE STATE BY LATE TONIGHT. THE FRONT WILL MOVE OFF THE COAST LATER TUESDAY WITH A SERIES OF WEAK LOW PRESSURES TRACKING ALONG THE COASTAL FRONT TUESDAY NIGHT INTO WEDNESDAY.&& .NEAR TERM /THROUGH TUESDAY/... UPDATE 2: BEEFED UP CLOUDS ACROSS FAR SERN AREAS...OTHERWISE CURRENT FCST APPEARS IN GOOD SHAPE. UPDATE 1: SFC COLD FRONT CONTS TO SLOWLY SAG SEWRD AND SHOULD ENTER OUR FAR NWRN AREAS NEXT HOUR OR TWO... TEMPS AHEAD OF THIS FRONT WARMER THAN ORIGINALLY FCST SO HAVE ADJUSTED HOURLY TEMPS UPWARD AND MODIFIED WX GRIDS AS WELL - SLOWING THE CHANGEOVER TO SNOW ACROSS FAR NWRN AREAS. PREV DISC: FIRST SURGE OF RAIN HAS MOVED OUT OF NORTHERN MAINE EARLY THIS AFTERNOON AS DEPICTED BY THE HRRR MODEL. THE HRRR MODEL DOES NOT BRING THE NEXT SURGE BACK INTO NORTHERN MAINE UNTIL EARLY THIS EVENING SO WILL START OUT WITH LOWER POPS ACROSS THE NORTH AND THEN GRADUALLY INCREASE POPS BACK TO CATEGORICAL THIS EVENING. AS THE COLD FRONT CROSSES NORTHERN MAINE AFTER MIDNIGHT, RAIN WILL MIX WITH SNOW AND THEN CHANGE TO ALL SNOW ACROSS MAINLY NORTHERN AROOSTOOK COUNTY. SNOW WILL CONTINUE INTO THE MORNING HOURS BUT EXPECT SNOW TO BE LIGHT. AT THIS TIME STILL EXPECTING 1 TO 3 INCHES OF SNOW ACROSS NORTHERN SECTIONS WITH THE HIGHEST VALUES ACROSS THE ST. JOHN VALLEY. EXPECT RAIN TO MOVE INTO CENTRAL REGIONS AFTER MIDNIGHT AND THEN INTO DOWNEAST JUST BEFORE SUNRISE TUESDAY. RAIN WILL CONTINUE FOR MOST OF THE DAY OVER DOWNEAST AS LOW PRESSURE MOVES ALONG THE FRONT AS IT SLIDES OFF THE COAST. HIGH TEMPERATURES ON TUESDAY WILL ONLY RISE 1 TO 3 DEGREES FROM THE MORNING LOWS AS COLDER AIR MOVES IN WITH THE NORTH WINDS BEHIND THE COLD FRONT. FOR RAINFALL AMOUNTS EXPECTING BETWEEN A QUARTER TO HALF AN INCH ACROSS THE REGION BY TUESDAY AFTERNOON.&& .SHORT TERM /TUESDAY NIGHT THROUGH FRIDAY/... THE UNSETTLED PATTERN WILL CONTINUE THROUGH THE SHORT TERM. A COLD FRONT WILL BE STRETCHED ACROSS THE GULF OF MAINE TUESDAY NIGHT WITH A WAVE OF LOW PRESSURE POSITIONED NEAR NOVA SCOTIA TUESDAY EVENING. PRECIPITATION...MOSTLY IN THE FORM OF SNOW THOUGH MIXED WITH RAIN DOWNEAST AND ESPECIALLY ALONG THE COAST... WILL BEGIN TO WIND DOWN OVERNIGHT AS THIS LOW CONTINUES TO TREK TO THE EAST. HOWEVER ANOTHER WEAK WAVE...THIS ONE FURTHER SOUTH...WILL KEEP AT LEAST THE SLIGHT CHANCE OF RAIN/SNOW SHOWERS ACROSS THE REGION THROUGH WEDNESDAY MORNING. HIGH PRESSURE WILL FINALLY BE ABLE TO TAKE HOLD WEDNESDAY NIGHT...BUT YET ANOTHER LOW WILL MOVE TO THE SOUTH OF THE GULF OF MAINE THURSDAY. THE 12Z ECMWF IS THE MOST AGGRESSIVE AND THE FURTHEST NORTH WITH THIS SYSTEM AND INDICATES THAT MUCH OF DOWNEAST MAINE WOULD SEE A RAIN/SNOW MIX. THE 12Z NAM AND GFS MEANWHILE KEEP THE LOW SOUTH AND ONLY BRUSH THE COAST WITH PRECIPITATION. HAVE GONE WITH SLIGHT CHANCE POPS FOR NOW. ALSO KEPT SLIGHT CHANCE POPS ACROSS THE NORTH AS A COLD FRONT APPROACHES FROM CANADA. DAYTIME TEMPERATURES WEDNESDAY AND THURSDAY WILL RANGE FROM THE LOWER 30S NORTH TO AROUND 40 SOUTH WHILE THE NIGHTS DIP DOWN INTO THE 20S. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... THE START OF THE LONG TERM FINDS THE GFS AND THE ECMWF WITH A SIMILAR SOLUTION...HOWEVER THE GFS APPEARS ABOUT 6HRS BEHIND THE ECMWF ON MOVEMENT OF THE MAIN LOW. A LOW PRESSURE (GFS) IN THE N ATLANTIC SE OF NOVA SCOTIA...A DEEP COLD CORE LOW OVER HUDSON BAY WITH A TROUGH EXTENDING S THROUGH THE CENTRAL GREAT LAKES REGION. A CANADIAN HIGH PRESSURE RIDGE THAT DUG INTO THE SOUTHERN STATES WILL BEGIN TO SPREAD TOWARDS NEW ENGLAND. THE ECMWF THE PRIMARY LOW IS FARTHER NORTH INTO THE CANADIAN MARITIMES. AND THE BUILDING RIDGE EXTEND FARTHER NORTH INTO SOUTHERN NEW ENGLAND. BY FRIDAY MORNING THE HIGH MOVES INTO THE ATLANTIC... THE GFS DIGS THE TROUGH ACROSS THE GREAT LAKE FARTHER SOUTH. THE ECMWF DEVELOPS A WEAK LOW OVER EASTERN ILLINOIS. BY FRIDAY EVENING BOTH MODELS ARE INDICATING A LOW OVER THE NORTHERN GREAT LAKES...WITH A TROUGH OF LOWER PRESSURE EXTENDING SOUTH ALONG THE EASTERN SEABOARD. BY EARLY SATURDAY MORNING BOTH MODELS MOVES THE LOW EAST...THE GFS TO NRN MAINE...THE ECMWF TO SRN QUEBEC. BY SATURDAY MORNING THE GFS MOVES THE LOW AND FRONT EAST OF THE AREA...THE ECMWF TO ERN MAINE. BY SATURDAY EVENING THE LOW WILL BE WELL EAST AND A HIGH PRESSURE RIDGE WILL BUILD IN. HIGHER PRESSURE WILL BUILD IN THROUGH THE END OF THE PERIOD...HOWEVER THE COLD LOW OVER HUDSON BAY WILL REMAIN THROUGH THE PERIOD AND WILL PERIODICALLY KICK OFF SHORT WAVES THAT WILL MOVE THROUGH NORTHERN AND CENTRAL MAINE THROUGH THE END OF THE PERIOD. LOADED GMOS...WITH SOME HAND SMOOTHING. PLUS 15 PERCENT FOR GUST OVER LAND 20 PERCENT OVER WATER. NAWAVE 4 FOR SEAS IN THE COASTAL WATERS. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... NEAR TERM: VFR CONDITIONS ACROSS THE NORTH WILL LOWER TO MVFR THIS EVENING AND THEN IFR BY LATER TONIGHT AND REMAIN IFR THROUGH TUESDAY. VFR CONDITIONS ACROSS DOWNEAST WILL LOWER TO IFR AFTER SUNRISE TUESDAY AND REMAIN IFR FOR THE REMAINDER OF THE DAY. SHORT TERM: WIDESPREAD IFR IN SNOW /MIXED WITH RAIN SOUTH/ EXPECTED INTO WEDNESDAY MORNING...THEN GRADUALLY IMPROVING CONDITIONS FROM NORTH TO SOUTH WEDNESDAY AFTERNOON AS HIGH PRESSURE BUILDS OVER THE REGION. CLOUDS WILL INCREASE LATE WEDNESDAY NIGHT AND THURSDAY AS A COLD FRONT APPROACHES FROM CANADA AND A LOW PRESSURE SYSTEM MOVES TO THE SOUTH OF THE GULF OF MAINE. THERE IS A SLIGHT CHANCE THAT THESE SYSTEMS WILL BRING SNOW AND MVFR/IFR CONDITIONS TO THE REGION THURSDAY. MORE RAIN/SNOW IS POSSIBLE FRIDAY AND FRIDAY NIGHT AS ANOTHER LOW MOVES ACROSS NORTHERN MAINE. && .MARINE... NEAR TERM: WINDS AND SEAS WILL REMAIN BELOW SCA CRITERIA THROUGH TUESDAY. A COLD FRONT WILL APPROACH FROM THE NORTH TONIGHT AND TUESDAY AND THEN CROSS THE WATERS BY TUESDAY EVENING. SHORT TERM: NO HEADLINES EXPECTED OVER THE WATERS AS WINDS REMAIN BELOW 25 KT AND WAVES LESS THAN 5 FT. THE WEATHER WILL BE UNSETTLED HOWEVER AS A SERIES OF LOW PRESSURE WAVES MOVE OVER OR JUST TO THE SOUTH OF THE GULF OF MAINE THROUGH MID WEEK. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...NONE. MARINE...NONE. && $$ NEAR TERM...KHW/FOSTER SHORT TERM...HASTINGS LONG TERM...NORTON AVIATION...KHW MARINE...KHW/HASTINGS
AREA FORECAST DISCUSSION
NWS CARIBOU ME
622 PM EST MON DEC 5 2011 .SYNOPSIS... A SLOW MOVING COLD FRONT WILL APPROACH NORTHERN MAINE THIS EVENING AND THEN MOVE ACROSS THE STATE BY LATE TONIGHT. THE FRONT WILL MOVE OFF THE COAST LATER TUESDAY WITH A SERIES OF WEAK LOW PRESSURES TRACKING ALONG THE COASTAL FRONT TUESDAY NIGHT INTO WEDNESDAY.&& .NEAR TERM /THROUGH TUESDAY/... UPDATE: SFC COLD FRONT CONTS TO SLOWLY SAG SEWRD AND SHOULD ENTER OUR FAR NWRN AREAS NEXT HOUR OR TWO... TEMPS AHEAD OF THIS FRONT WARMER THAN ORIGINALLY FCST SO HAVE ADJUSTED HOURLY TEMPS UPWARD AND MODIFIED WX GRIDS AS WELL - SLOWING THE CHANGEOVER TO SNOW ACROSS FAR NWRN AREAS. PREV DISC: FIRST SURGE OF RAIN HAS MOVED OUT OF NORTHERN MAINE EARLY THIS AFTERNOON AS DEPICTED BY THE HRRR MODEL. THE HRRR MODEL DOES NOT BRING THE NEXT SURGE BACK INTO NORTHERN MAINE UNTIL EARLY THIS EVENING SO WILL START OUT WITH LOWER POPS ACROSS THE NORTH AND THEN GRADUALLY INCREASE POPS BACK TO CATEGORICAL THIS EVENING. AS THE COLD FRONT CROSSES NORTHERN MAINE AFTER MIDNIGHT, RAIN WILL MIX WITH SNOW AND THEN CHANGE TO ALL SNOW ACROSS MAINLY NORTHERN AROOSTOOK COUNTY. SNOW WILL CONTINUE INTO THE MORNING HOURS BUT EXPECT SNOW TO BE LIGHT. AT THIS TIME STILL EXPECTING 1 TO 3 INCHES OF SNOW ACROSS NORTHERN SECTIONS WITH THE HIGHEST VALUES ACROSS THE ST. JOHN VALLEY. EXPECT RAIN TO MOVE INTO CENTRAL REGIONS AFTER MIDNIGHT AND THEN INTO DOWNEAST JUST BEFORE SUNRISE TUESDAY. RAIN WILL CONTINUE FOR MOST OF THE DAY OVER DOWNEAST AS LOW PRESSURE MOVES ALONG THE FRONT AS IT SLIDES OFF THE COAST. HIGH TEMPERATURES ON TUESDAY WILL ONLY RISE 1 TO 3 DEGREES FROM THE MORNING LOWS AS COLDER AIR MOVES IN WITH THE NORTH WINDS BEHIND THE COLD FRONT. FOR RAINFALL AMOUNTS EXPECTING BETWEEN A QUARTER TO HALF AN INCH ACROSS THE REGION BY TUESDAY AFTERNOON. && .SHORT TERM /TUESDAY NIGHT THROUGH FRIDAY/... THE UNSETTLED PATTERN WILL CONTINUE THROUGH THE SHORT TERM. A COLD FRONT WILL BE STRETCHED ACROSS THE GULF OF MAINE TUESDAY NIGHT WITH A WAVE OF LOW PRESSURE POSITIONED NEAR NOVA SCOTIA TUESDAY EVENING. PRECIPITATION...MOSTLY IN THE FORM OF SNOW THOUGH MIXED WITH RAIN DOWNEAST AND ESPECIALLY ALONG THE COAST... WILL BEGIN TO WIND DOWN OVERNIGHT AS THIS LOW CONTINUES TO TREK TO THE EAST. HOWEVER ANOTHER WEAK WAVE...THIS ONE FURTHER SOUTH...WILL KEEP AT LEAST THE SLIGHT CHANCE OF RAIN/SNOW SHOWERS ACROSS THE REGION THROUGH WEDNESDAY MORNING. HIGH PRESSURE WILL FINALLY BE ABLE TO TAKE HOLD WEDNESDAY NIGHT...BUT YET ANOTHER LOW WILL MOVE TO THE SOUTH OF THE GULF OF MAINE THURSDAY. THE 12Z ECMWF IS THE MOST AGGRESSIVE AND THE FURTHEST NORTH WITH THIS SYSTEM AND INDICATES THAT MUCH OF DOWNEAST MAINE WOULD SEE A RAIN/SNOW MIX. THE 12Z NAM AND GFS MEANWHILE KEEP THE LOW SOUTH AND ONLY BRUSH THE COAST WITH PRECIPITATION. HAVE GONE WITH SLIGHT CHANCE POPS FOR NOW. ALSO KEPT SLIGHT CHANCE POPS ACROSS THE NORTH AS A COLD FRONT APPROACHES FROM CANADA. DAYTIME TEMPERATURES WEDNESDAY AND THURSDAY WILL RANGE FROM THE LOWER 30S NORTH TO AROUND 40 SOUTH WHILE THE NIGHTS DIP DOWN INTO THE 20S. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... THE START OF THE LONG TERM FINDS THE GFS AND THE ECMWF WITH A SIMILAR SOLUTION...HOWEVER THE GFS APPEARS ABOUT 6HRS BEHIND THE ECMWF ON MOVEMENT OF THE MAIN LOW. A LOW PRESSURE (GFS) IN THE N ATLANTIC SE OF NOVA SCOTIA...A DEEP COLD CORE LOW OVER HUDSON BAY WITH A TROUGH EXTENDING S THROUGH THE CENTRAL GREAT LAKES REGION. A CANADIAN HIGH PRESSURE RIDGE THAT DUG INTO THE SOUTHERN STATES WILL BEGIN TO SPREAD TOWARDS NEW ENGLAND. THE ECMWF THE PRIMARY LOW IS FARTHER NORTH INTO THE CANADIAN MARITIMES. AND THE BUILDING RIDGE EXTEND FARTHER NORTH INTO SOUTHERN NEW ENGLAND. BY FRIDAY MORNING THE HIGH MOVES INTO THE ATLANTIC... THE GFS DIGS THE TROUGH ACROSS THE GREAT LAKE FARTHER SOUTH. THE ECMWF DEVELOPS A WEAK LOW OVER EASTERN ILLINOIS. BY FRIDAY EVENING BOTH MODELS ARE INDICATING A LOW OVER THE NORTHERN GREAT LAKES...WITH A TROUGH OF LOWER PRESSURE EXTENDING SOUTH ALONG THE EASTERN SEABOARD. BY EARLY SATURDAY MORNING BOTH MODELS MOVES THE LOW EAST...THE GFS TO NRN MAINE...THE ECMWF TO SRN QUEBEC. BY SATURDAY MORNING THE GFS MOVES THE LOW AND FRONT EAST OF THE AREA...THE ECMWF TO ERN MAINE. BY SATURDAY EVENING THE LOW WILL BE WELL EAST AND A HIGH PRESSURE RIDGE WILL BUILD IN. HIGHER PRESSURE WILL BUILD IN THROUGH THE END OF THE PERIOD...HOWEVER THE COLD LOW OVER HUDSON BAY WILL REMAIN THROUGH THE PERIOD AND WILL PERIODICALLY KICK OFF SHORT WAVES THAT WILL MOVE THROUGH NORTHERN AND CENTRAL MAINE THROUGH THE END OF THE PERIOD. LOADED GMOS...WITH SOME HAND SMOOTHING. PLUS 15 PERCENT FOR GUST OVER LAND 20 PERCENT OVER WATER. NAWAVE 4 FOR SEAS IN THE COASTAL WATERS. && .AVIATION /23Z MONDAY THROUGH SATURDAY/... NEAR TERM: VFR CONDITIONS ACROSS THE NORTH WILL LOWER TO MVFR THIS EVENING AND THEN IFR BY LATER TONIGHT AND REMAIN IFR THROUGH TUESDAY. VFR CONDITIONS ACROSS DOWNEAST WILL LOWER TO IFR AFTER SUNRISE TUESDAY AND REMAIN IFR FOR THE REMAINDER OF THE DAY. SHORT TERM: WIDESPREAD IFR IN SNOW /MIXED WITH RAIN SOUTH/ EXPECTED INTO WEDNESDAY MORNING...THEN GRADUALLY IMPROVING CONDITIONS FROM NORTH TO SOUTH WEDNESDAY AFTERNOON AS HIGH PRESSURE BUILDS OVER THE REGION. CLOUDS WILL INCREASE LATE WEDNESDAY NIGHT AND THURSDAY AS A COLD FRONT APPROACHES FROM CANADA AND A LOW PRESSURE SYSTEM MOVES TO THE SOUTH OF THE GULF OF MAINE. THERE IS A SLIGHT CHANCE THAT THESE SYSTEMS WILL BRING SNOW AND MVFR/IFR CONDITIONS TO THE REGION THURSDAY. MORE RAIN/SNOW IS POSSIBLE FRIDAY AND FRIDAY NIGHT AS ANOTHER LOW MOVES ACROSS NORTHERN MAINE. && .MARINE... NEAR TERM: WINDS AND SEAS WILL REMAIN BELOW SCA CRITERIA THROUGH TUESDAY. A COLD FRONT WILL APPROACH FROM THE NORTH TONIGHT AND TUESDAY AND THEN CROSS THE WATERS BY TUESDAY EVENING. SHORT TERM: NO HEADLINES EXPECTED OVER THE WATERS AS WINDS REMAIN BELOW 25 KT AND WAVES LESS THAN 5 FT. THE WEATHER WILL BE UNSETTLED HOWEVER AS A SERIES OF LOW PRESSURE WAVES MOVE OVER OR JUST TO THE SOUTH OF THE GULF OF MAINE THROUGH MID WEEK. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...NONE. MARINE...NONE. && $$ NEAR TERM...KHW/FOSTER SHORT TERM...HASTINGS LONG TERM...NORTON AVIATION...KHW MARINE...KHW/HASTINGS
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
736 AM EST SUN DEC 4 2011 .SYNOPSIS... RAIN CHANCES WILL BE ON THE INCREASE FOR THE UPPER OHIO VALLEY REGION AS A COLD FRONT MOVES TOWARD...AND THEN ACROSS THE AREA EARLY THIS WEEK. COLDER WEATHER WILL RETURN BY MID WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... MADE MINIMAL ALTERATIONS TO TEMPERATURE, CLOUDS, AND WIND BASED ON RECENT SURFACE DATA AND HRRR MODEL OUTPUT. CONTINUE TO EXPECT SOME INCREASE IN CLOUDS WEST TO EAST TOWARD AFTERNOON, AS HIGH PRESSURE EXITS TO THE COAST. LOW PRESSURE CROSSING THE GREAT LAKES WILL DRAG A COLD FRONT TOWARD THE PBZ AREA BY TONIGHT...AND RAIN CHANCES WILL DEVELOP FOR THE WESTERN TIER OF COUNTIES AS THE AFTERNOON PROGRESSES. WITH WARM ADVECTION UNDER SOUTHERLY FLOW...TODAYS HIGHS ARE FORECAST APPROXIMATELY 10 DEGREES ABOVE NORMAL USING GFS MOS GUIDANCE. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... MODELS IN GENERAL AGREEMENT IN SLOWING EASTWARD PROGRESS OF THE FRONT...WITH ONLY LOW...OR NO CHANCE OF RAIN FOR WV/MD/ AND MUCH OF PA WELL INTO MONDAY. CROSSING SHORTWAVE SHOULD DRAG THE FRONT ACROSS MOST OF THE AREA ON TUESDAY...AND POPS WERE INCREASED TO CATEGORICAL NUMBERS FOR THE FINAL ADVANCE AND PASSAGE OF THE BOUNDARY. PROGGED PRECIP AMOUNTS HAVE FALLEN AND DO NOT EXPECT THOSE TOTALS TO EXCEED THE INCH TO INCH AND A HALF RANGE. TEMPERATURES THROUGH TUESDAY WERE FORECAST ABOVE THE NORMALS USING A BLEND OF PERSISTENCE AND GFS MOS. PRECIP CHANCES WERE MAINTAINED THROUGH WEDNESDAY AS UPPER TROUGH IS FORECAST TO DEVELOP ACROSS THE GREAT LAKES...WITH SNOW SHOWERS INCLUDED IN THE COOLER AIR UNDER THAT FEATURE. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... NOT MUCH RUN-TO-RUN CONSISTENCY WITH MODELS IN THE LAST DAY. 00Z GFS PUSHED FRONT OUT TO SEA BY THURSDAY MORNING...THEN THE 12Z GFS BRINGS A HUGE LOW UP THE EAST COAST. 00Z ECMWF HANGS THE FRONT UP ALONG THE COASTLINE...WITH THE 12Z ECMWF SLIGHTLY FARTHER OFFSHORE. 00Z CANADIAN/UKMET SUPPORT THE IDEA OF A BIG LOW DEVELOPING ALONG THE FRONT...BUT HAVE 24-HOUR DIFFERENCES IN THE TIMING. WITH VARYING SOLUTIONS...WILL STICK CLOSE TO HPC SOLUTION...WHICH BLENDS GFS/ECMWF ENSEMBLES...WHICH QUICKLY MOVES THE FRONT OFFSHORE. NEXT FRONT WILL CROSS THE GREAT LAKES FRIDAY INTO SATURDAY...AGAIN WITH VARYING SOLUTIONS AS TO THE INTENSITY. WILL GO WITH CHANCE POPS DURING THIS TIME PERIOD. TEMPS WILL BE ABOUT 5 DEGREES BELOW NORMAL THROUGHOUT THE EXTENDED FORECAST. && .AVIATION /13Z SUNDAY THROUGH THURSDAY/... VFR TO CONTINUE INTO TONIGHT, ALTHOUGH RAIN SHOWERS MAY AFFECT KZZV LATE TONIGHT. EXPECT SOUTHERLY WINDS TO INCREASE LATE THIS MORNING WITH GUSTS TO 20 KTS THIS AFTERNOON. OUTLOOK...MONDAY THROUGH THURSDAY... FRONT WILL STALL OUT ALONG WESTERN BORDER OF THE FORECAST AREA INTO MONDAY. THIS MAY LIMIT RESTRICTIONS IN SHOWERS DURING THIS TIME PERIOD TO KFKL AND KZZV. THE FRONT WILL AFFECT ALL TERMINALS BY MONDAY NIGHT, BRINGING RESTRICTIONS IN SHOWERS. THE FRONT WILL REMAIN ACROSS THE AREA UNTIL AT LEAST TUESDAY NIGHT. MODELS THEN DIVERGE...WITH LITTLE CONFIDENCE IN WHETHER THE FRONT WILL REMAIN OVER THE AREA OR PUSH OFF TO THE EAST. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$
AREA FORECAST DISCUSSION...UPDATED
NWS TWIN CITIES/CHANHASSEN MN
1211 AM CST SUN DEC 4 2011 .UPDATE... UPDATED FOR THE 06Z AVIATION DISCUSSION BELOW. .DISCUSSION... SNOW HAS BEGUN TO SPREAD INTO S MN AND WILL CONTINUE TO EXPAND NE RAPIDLY DURING THE REMAINDER OF THE AFTERNOON. A BIT OF SATURATION LEFT TO DO IN LOWER LEVELS BUT CIGS ARE BEGINNING TO LOWER ACROSS S MN. IR SATELLITE SHOWS ELONGATED VORT FROM W KS INTO SC NEB LIFTING NE. GFS/NAM SIMILAR ON TIMING BRINGING MAIN VORT INTO SC MN BY 00Z AND THEN LIFTING INTO CENTRAL WI BY 06Z. GFS HAS INCREASED QPF VALUES A BIT MORE TOWARD THE NAM SOLUTION. INCREASED SNOW AMOUNTS A BIT ACROSS AREAS FROM MKT TO SE METRO BASED LARGELY ON TRACK OF SURFACE/850 MB LOW CENTERS. HEAVY SNOW OFTEN SETS UP 70 TO 90 MILES N OF 850 MB LOW TRACK..AND 850 MB LOW TRACKS FROM SW IA TO JUST S OF LSE BY 06Z THEN INTO E UPR MICHIGAN BY 12Z. KEPT SNOW AMOUNTS IN THE 3 TO 6 INCH ADVISORY. FAVORABLE ISENTROPIC LIFT COMES THRU RATHER QUICKLY WITH 3-3.5G/KG SO HESITATE TO GO ANY HIGHER. WILL BE A PERIOD FROM AROUND 22Z TO 05Z WHERE ADVISORY AREA WILL BE UNDER STRONG UPPER DIVERGENGE FROM COUPLED UPPER JET... FAVORABLE DENDRITIC TEMPERATURES AND STRONG 600 MB FULL WIND FRONTOGENSIS WHICH COULD BRING A PERIOD OF A FEW HOURS OF VISIBILITY INTO THE 1/2 SM RANGE AS FAR N AS MSP. LIKE THE TIMING OF THE RUC BUFKIT SNOW ACCUMS IN THAT WINDOW. DECREASED SNOW AMOUNTS SLIGHTLY IN W SIDE OF ADVY AREA AROUND SPRINGFIELD AND GAYLORD. ADVISORY WILL LIKELY BE ABLE TO BE EXPIRED BY 06Z ACROSS MUCH OF THE MN CWA WITH NO SIGNIFICANT WIND EXPECTED IN WAKE OF SNOW. COOLER FOR SUNDAY...BUT TROF DROPPING OUT OF CANADA WILL BACK WINDS ENUF TO KEEP MAIN PUSH OF COLD AIR NORTH OF AREA. AS THIS SYSTEM MOVES THRU COLD AIR WILL MOVE IN FOR MONDAY WITH HIGHS ONLY IN THE TEEN TO MID 20S. SLIGHT MODERATION FOR WEDNESDAY AS WEAK TROF MOVES ACROSS AREA. AFTER THAT AREA REMAINS IN COLD AND DRY NW FLOW AT LEAST UNTIL NEXT WEEKEND. WITH SNOW COVER EXPECTED TONIGHT ACROSS S MN INTO WC WI WILL BE SOME SOME MORNINGS WHERE WE SHOULD GET MIN TEMPS DOWN NEAR ZERO...TUESDAY AND PROBABLY AGAIN FRIDAY/SATURDAY. .AVIATION.../06Z TAF ISSUANCE/ HAVE THE SNOW CLEARING EAST CENTRAL MN BY ROUGHLY 09Z PER THE SHARP CLEARING EDGE TO THE BACK OF THE RADAR NOW. LIKELY LOSE IFR VISIBILITY BY AROUND 08Z IN MN DUE TO THE DECREASING SNOW RATES. KEAU MAY STILL SEE CONDITIONS GET POORER FOR A COUPLE HOUR WINDOW THIS MORNING BEFORE IMPROVING CLOSER TO SUNRISE. IN TERMS OF CLOUDS...THE CONDITIONAL CEILINGS WHEN SNOW IS FALLING COULD CREATE SHORT PERIODS OF IFR CEILINGS OVER THE NEXT FEW HOURS...BUT OVERALL WE ARE MAINLY STUCK WITH A MVFR DECK. THIS MIGHT BE WITH US FOR SOME TIME. DOING A SIMPLE EXTRAPOLATION OF THE BACK EDGE OF THE STRATUS GETS CLEARING INTO WESTERN MN BY AROUND 12Z. HOWEVER...GIVEN THE TIME OF YEAR AND DUE TO THE FACT WE REALLY DON`T SEE MUCH OF A PATTERN CHANCE UNTIL MONDAY...TRENDED PESSIMISTIC WITH THE MVFR CEILINGS. KMSP...VISIBILITY HAS IMPROVED OVER THE LAST HOUR AT THE AIRPORT AND SHOULD SEE THE SNOW TAPER TO NOTHING BY AROUND 09Z. THE CEILINGS HAVE TEMPORARILY JUMPED UP TO 3500FT...BUT WITH LOWER CEILINGS TO THE WEST...IT SHOULD ONLY BE A MATTER OF TIME BEFORE MVFR STRATUS MOVES BACK IN AND LINGERS FOR MOST OF THE DAY. HOWEVER...FAIRLY CONFIDENT WE`LL REMAIN ABOVE 2000FT MUCH OF THE TAF PERIOD. WIND DIRECTION WILL REMAIN OUT OF THE NORTHWEST AND GRADUALLY DECREASE AFTER SUNRISE. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...WINTER WEATHER ADVISORY UNTIL 6 AM CST SUNDAY FOR ANOKA-BLUE EARTH-BROWN-CARVER-CHISAGO-DAKOTA-FARIBAULT-FREEBORN- GOODHUE-HENNEPIN-LE SUEUR-MARTIN-NICOLLET-RAMSEY-RICE-SCOTT- SIBLEY-STEELE-WASECA-WASHINGTON-WATONWAN. WI...WINTER WEATHER ADVISORY UNTIL 6 AM CST SUNDAY FOR BARRON- CHIPPEWA-DUNN-EAU CLAIRE-PEPIN-PIERCE-POLK-RUSK-ST. CROIX. && $$ BAP/CLF
AREA FORECAST DISCUSSION...UPDATED
NWS ST LOUIS MO
952 PM CST MON DEC 5 2011 .UPDATE... /952 PM CST MON DEC 5 2011/ ANOTHER SHORTWAVE EXPECTED TO APPROACH CNTRL MO BY 12Z AND WILL WEAKEN AND BECOME SHEARED OUT AS IT PUSHES INTO CNTRL AND NERN IL ON LATE TUESDAY. MODEL SOUNDINGS SUGGEST THAT MUCH OF THE LIFECYCLE OF THIS SHORTWAVE MOVING THRU THE FA WILL BE CHARACTERIZED BY A SEEDER-FEEDER SCENARIO...WHERE A WELL DEVELOPED MID CLOUD DECK SEEDS A LOWER CLOUD DECK BELOW WITH A FAIRLY CONIDERABLE DRY LAYER IN-BETWEEN. THIS TYPICALLY TRANSLATES TO FLURRIES EXCEPT IN AND CLOSE TO THE APPROACH OF THIS SHORTWAVE WHERE SOME AREAS MAY BE ABLE TO PICK UP A LIGHT DUSTING OF SNOW... NOTABLY IN PARTS OF CNTRL/NERN MO. TEMPS WILL MOVE LITTLE TONIGHT WITH A LO OVERCAST CLOUD DECK IN PLACE AND WEAKENING LO LEVEL CAA...AND WILL LIKELY STRUGGLE TO GET MUCH OVER 35F TOMORROW MUCH LIKE TODAY WITH LITTLE CHANGING. TES && .DISCUSSION... /356 PM CST MON DEC 5 2011/ SE SECTIONS OF THE CWA RECEIVED A GLANCING BLOW OF WINTER WEATHER TODAY AS FINAL SURGE OF PRECIP WORKED FAR ENOUGH INTO THE COLD AIR TO TURN PRECIP INTO A WINTRY MIX. AT ONE TIME OR ANOTHER JUST ABOUT EVERY WINTER WEATHER PRECIP TYPE WAS REPORTED...BUT AS OF 21Z AMS HAD COOLED ENOUGH THAT THE PRECIP WAS ALL IN THE FORM OF SNOW. NO REPORTS OF ANY MAJOR ACCUMULATIONS...BUT A FEW WEB CAMS AND SPOTTY REPORTS WE HAVE GOTTEN SUGGEST ACCUMULATIONS OF AROUND AN INCH ALONG AND SOUTH OF A BISMARCK...CENTRALIA LINE. SHORTWAVE THAT AIDED THIS ROUND OF WINTER WEATHER HAS RACED INTO S CENTRAL MO...WITH A CORRESPONDING RAPID DECREASE IN PRECIP OVER THIS AREA. EXPECT THIS TREND TO CONTINUE OVER THE NEXT FEW HOURS...SO THAT BY 00Z PRECIPITATION IN OUR SE COUNTIES SHOULD BE DOWN TO JUST FLURRIES. HOWEVER...WITH UPPER TROF STILL LAGGING WELL TO THE WEST NOT SURE WE ARE TOTALLY DONE WITH THE PRECIP WITH THIS SYSTEM. ALL OF THE SHORT RANGE MODELS ARE EJECTING A SHORTWAVE OUT OF THE TROF AND INTO OUR AREA LATE TONIGHT AND TUESDAY...AND THEY ARE ALL PRINTING OUT SMALL AMOUNTS OF QPF. SO...HAVE REINTRODUCED LOW CHANCE POPS FOR SCATTERED SNOW SHOWERS LATE TONIGHT AND TUESDAY FOR ABOUT THE SW HALF OF THE CWA...WHILE CONTINUING A MENTION OF FLURRIES IN THE REMAINDER OF THE FA. CHILLY AIRMASS WILL REMAIN LOCKED IN PLACE THROUGH TUESDAY...ALONG WITH LOTS OF CLOUDS. THE CLOUD COVER WILL HELP HOLD UP TEMPS SOMEWHAT TONIGHT BUT WILL LIKELY MAKE FOR ANOTHER CHILLY DAY ON TUESDAY...AND HAVE KEPT HIGHS LOCKED IN THE 30S. PROGS ARE INDICATING A SLOW EWD PROGRESSION OF THE UPPER TROF...WHILE A SERIES OF SHORTWAVES DROPPING DOWN THE BACK SIDE OF THE TROF LEAD TO THE DEVELOPMENT OF ANOTHER AND MUCH BROADER UPPER TROF THAT WILL DOMINATE MOST OF THE CONUS HEADING INTO THE WEEKEND. MEDIUM RANGE SOLUTIONS HAVE BEEN CONSISTENTLY ADVERTISING THAT AMS THAT DROPS INTO THE AREA DUE TO THIS PATTERN SHIFT WILL BE QUITE CHILLY...SO AFTER A MODEST MODERATION IN TEMPS AT MIDWEEK FRIDAY AND FRIDAY NIGHT WILL BRING ANOTHER TASTE OF WINTER TEMPS...WITH HIGHS ON FRIDAY STRUGGLING TO REACH THE LM30S AND LOWS BY SATURDAY MORNING PRIMARILY IN THE TEENS AND LOWER 20S. NOT LOOKING FOR MUCH IN THE WAY OF PRECIP DURING THIS TIME...BUT A FEW FLURRIES ARE CERTAINLY POSSIBLE WITH THE ARRIVAL OF THE COLD FRONT ON THURSDAY NIGHT. IN SPITE OF THE DEVELOPMENT OF THE BROAD TROF...UA PATTERN IS ALSO FORECAST TO BE PROGRESSIVE HEADING INTO EARLY NEXT WEEK. MEDIUM RANGE SOLUTIONS ARE IN GOOD AGREEMENT THAT UA PATTERN OVER THE CENTRAL U.S. WILL TRANSITION TO A ZONAL FLOW REGIME...WHICH SHOULD RESULT IN A MODERATION OF TEMPS. TRUETT && .AVIATION... /542 PM CST MON DEC 5 2011/ MVFR CIGS WILL PREVAIL ACROSS THE AREA THIS EVENING...PRIMARILY BELOW 2000FT EXCEPT OVER CENTRAL MISSOURI. CIGS OUT THERE SHOULD ALSO FALL BELOW 2000FT...AND POSSIBLY DOWN TO IFR ALONG WITH MUCH OF THE REST OF THE AREA TONIGHT. MODEL GUIDANCE IS PRINTING OUT SOME VERY LIGHT PRECIPITATION BEGINNING EARLY TUESDAY MORNING AND CONTINUING ON AND OFF THROUGH THE DAY. TEMPERATURES ARE COLD ENOUGH THAT THIS SHOULD BE SNOW IF IT OCCURS. DID NOT INCLUDE IN TAFS AT THIS POINT...BUT WILL REEVALUATE FOR THE 06Z ISSUANCE. IFR CIGS SHOULD RISE THROUGH THE LATE MORNING INTO THE AFTERNOON TO MVFR LEVELS. SPECIFICS FOR KSTL...MVFR CIGS BELOW 2000FT WILL PREVAIL AT LAMBERT THIS EVENING. MODEL FORECAST SOUNDINGS FROM THE RUC ARE INDICATING THAT THE CIGS WILL DROP BELOW 1000FT AFTER MIDNIGHT TONIGHT. THIS SEEMS REASONABLE GIVEN THE WEATHER PATTERN WE`RE IN...BUT TIMING IS NOT CERTAIN AT THIS POINT. REGARDLESS...EXPECT IFR CIGS TO RISE BACK TO MVFR BY MID-LATE MORNING. MODELS ARE INDICATING SOME LIGHT SNOW AT THE TERMINAL BEGINNING AS EARLY AS 12Z AND PERSISTING ON AND OFF THROUGH THE DAY. DID NOT INCLUDE THIS PRECIPITATION AT THIS TIME AS IT LOOKS TO BE VERY LIGHT IF IT OCCURS AT ALL. WILL REEVALUATE FOR THE SCHEDULED 06Z TAF WHEN NEW GUIDANCE IS AVAILABLE. CARNEY && .LSX WATCHES/WARNINGS/ADVISORIES... MO...NONE. IL...NONE. && $$ WFO LSX
AREA FORECAST DISCUSSION
NWS KANSAS CITY/PLEASANT HILL MO
943 PM CST MON DEC 5 2011 .DISCUSSION... Have raised snow chances a bit overnight, mainly over the far southern counties and for later in the night. However, did increase snow chances markedly over the eastern 1/4 of the CWA on Tuesday. Mid/upper level system ejecting out of NM tonight. Latest RUC is a bit stronger and further north with the 700mb vorticity center. Looks like a seeded-feeder setup to start out where a snow from a higher level of clouds falls into a lower cloud deck and "seed" it resulting in light snow and/or flurries. However, increasing dynamics, weak frontogenetic forcing and weak isentropic lift could generate areas/bands of light snow towards sunrise tomorrow. A better bet for measurable snow will occur Tuesday morning when the drier sub-cloud regions have become saturated. Initial thoughts are a tenth of an inch of snow is possible across the far southern counties, but possibly enough to make roads slick as this will be a dry/fluffy snow. Have a bit of concern that a region of upward vertical motion progged just above a nearly saturated layer dendritic snow growth region between 12-z15z over the far eastern counties could yield more than the current half inch of snow currently forecast. Since confidence in models has been low of late on how they have handled the cloud structures of late will go the conservative route and let the mid shift make any changes. MJ && .PREV DISCUSSION... /318 PM CST Mon Dec 5 2011/ Brisk northerly winds continues to advect colder air into Missouri with chilly temperatures the next couple of days. The main concern is a shortwave in southern New Mexico, south of the Four Corners Low. Short term high resolution models (NAM and RUC) are indicating that this wave will progress northeast into west central Missouri on Tuesday. light to moderate snow has been occurring in the TX panhandle, aided by upslope, with development toward the northeast. The models are showing very weak isentropic upglide along with weak deformation ahead of a weak 700 mb low in eastern Kansas late tonight and early Tuesday. Moisture is quite limited but have inserted sct snow showers for much of the area late tonight and Tuesday. Cannot rule out a narrow band of more persistent snow, producing very light accumulations. Later shifts will have to monitor the progress of this system. Otherwise, the trough axis will pass late Tuesday and Wednesday with dry conditions. DB Medium Range (Thursday through Monday)... Operational and ensemble members are in good agreement through the majority of the period depicting primarily stagnant longwave features over the western hemisphere. Most notable are a seasonably deep polar vortex centered across northern Hudson Bay and the Nunavut archipelago and an equally intense ridge through the Gulf of Alaska (both features in the 1-2 normalized standard deviations away from average range). This scenario will result in broad nwly/quasi-zonal flow for locations east of the Rockies with largely dry conditions and temperature slightly below average into the weekend. By the end of the period, models also indicate energy spilling over the top of the western ridge, causing a slight retrogressive phase, placing much of the central and southern plains into a warming, swly flow regime. There is naturally uncertainty into the depth and positioning of swrn conus energy late in the period, however the effect on weather through the forecast area would not be felt until after this valid period. Only real potential sensible weather during this medium range period still appears to be very light snow/snow flurries Thursday night into Friday morning across far northern Missouri. 21 && .AVIATION... For the 00Z TAFs, MVFR cigs and snow potential are the two primary concerns. NAM and GFS have been poor performers of late in handling the cold air stratocu deck so will put on ignore. Latest RUC is preferable and keeps the MVFR cigs in through the night. AVNFPS climate program supports this. In addition, with a 700mb shortwave approaching don`t see any subsidence to erode these cigs until afternoon so will keep the MVFR cigs in till then. That being said there could be a brief period or two where MVFR cigs scatter out between now and 18z Tuesday but it should fill back in. As for snow potential the above mentioned 700mb shortwave will lift newd tonight with weak downstream isentropic lift supporting bands of snow spreading across sern KS and parts of west central MO later tonight. While the better chance for any accumulating snow will most likely be south of the terminals the latest RUC and 18z NAM show a weaker/more elongated vorticity maxima further north that could result in snow flurries or snow showers to affect KMCI/KMKC. However, relatively high confidence that it will not be measurable snow. That plus it is a rather long window for occurrence, 07z-15z so will not include in the terminals. Will monitor south central and central KS as that should give a clue as to how far north any snow will reach. MJ && .EAX WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ WFO EAX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NWS ST LOUIS MO
558 PM CST MON DEC 5 2011 .DISCUSSION... /356 PM CST MON DEC 5 2011/ SE SECTIONS OF THE CWA RECEIVED A GLANCING BLOW OF WINTER WEATHER TODAY AS FINAL SURGE OF PRECIP WORKED FAR ENOUGH INTO THE COLD AIR TO TURN PRECIP INTO A WINTRY MIX. AT ONE TIME OR ANOTHER JUST ABOUT EVERY WINTER WEATHER PRECIP TYPE WAS REPORTED...BUT AS OF 21Z AMS HAD COOLED ENOUGH THAT THE PRECIP WAS ALL IN THE FORM OF SNOW. NO REPORTS OF ANY MAJOR ACCUMULATIONS...BUT A FEW WEB CAMS AND SPOTTY REPORTS WE HAVE GOTTEN SUGGEST ACCUMULATIONS OF AROUND AN INCH ALONG AND SOUTH OF A BISMARCK...CENTRALIA LINE. SHORTWAVE THAT AIDED THIS ROUND OF WINTER WEATHER HAS RACED INTO S CENTRAL MO...WITH A CORRESPONDING RAPID DECREASE IN PRECIP OVER THIS AREA. EXPECT THIS TREND TO CONTINUE OVER THE NEXT FEW HOURS...SO THAT BY 00Z PRECIPITATION IN OUR SE COUNTIES SHOULD BE DOWN TO JUST FLURRIES. HOWEVER...WITH UPPER TROF STILL LAGGING WELL TO THE WEST NOT SURE WE ARE TOTALLY DONE WITH THE PRECIP WITH THIS SYSTEM. ALL OF THE SHORT RANGE MODELS ARE EJECTING A SHORTWAVE OUT OF THE TROF AND INTO OUR AREA LATE TONIGHT AND TUESDAY...AND THEY ARE ALL PRINTING OUT SMALL AMOUNTS OF QPF. SO...HAVE REINTRODUCED LOW CHANCE POPS FOR SCATTERED SNOW SHOWERS LATE TONIGHT AND TUESDAY FOR ABOUT THE SW HALF OF THE CWA...WHILE CONTINUING A MENTION OF FLURRIES IN THE REMAINDER OF THE FA. CHILLY AIRMASS WILL REMAIN LOCKED IN PLACE THROUGH TUESDAY...ALONG WITH LOTS OF CLOUDS. THE CLOUD COVER WILL HELP HOLD UP TEMPS SOMEWHAT TONIGHT BUT WILL LIKELY MAKE FOR ANOTHER CHILLY DAY ON TUESDAY...AND HAVE KEPT HIGHS LOCKED IN THE 30S. PROGS ARE INDICATING A SLOW EWD PROGRESSION OF THE UPPER TROF...WHILE A SERIES OF SHORTWAVES DROPPING DOWN THE BACK SIDE OF THE TROF LEAD TO THE DEVELOPMENT OF ANOTHER AND MUCH BROADER UPPER TROF THAT WILL DOMINATE MOST OF THE CONUS HEADING INTO THE WEEKEND. MEDIUM RANGE SOLUTIONS HAVE BEEN CONSISTENTLY ADVERTISING THAT AMS THAT DROPS INTO THE AREA DUE TO THIS PATTERN SHIFT WILL BE QUITE CHILLY...SO AFTER A MODEST MODERATION IN TEMPS AT MIDWEEK FRIDAY AND FRIDAY NIGHT WILL BRING ANOTHER TASTE OF WINTER TEMPS...WITH HIGHS ON FRIDAY STRUGGLING TO REACH THE LM30S AND LOWS BY SATURDAY MORNING PRIMARILY IN THE TEENS AND LOWER 20S. NOT LOOKING FOR MUCH IN THE WAY OF PRECIP DURING THIS TIME...BUT A FEW FLURRIES ARE CERTAINLY POSSIBLE WITH THE ARRIVAL OF THE COLD FRONT ON THURSDAY NIGHT. IN SPITE OF THE DEVELOPMENT OF THE BROAD TROF...UA PATTERN IS ALSO FORECAST TO BE PROGRESSIVE HEADING INTO EARLY NEXT WEEK. MEDIUM RANGE SOLUTIONS ARE IN GOOD AGREEMENT THAT UA PATTERN OVER THE CENTRAL U.S. WILL TRANSITION TO A ZONAL FLOW REGIME...WHICH SHOULD RESULT IN A MODERATION OF TEMPS. TRUETT && .AVIATION... /542 PM CST MON DEC 5 2011/ MVFR CIGS WILL PREVAIL ACROSS THE AREA THIS EVENING...PRIMARILY BELOW 2000FT EXCEPT OVER CENTRAL MISSOURI. CIGS OUT THERE SHOULD ALSO FALL BELOW 2000FT...AND POSSIBLY DOWN TO IFR ALONG WITH MUCH OF THE REST OF THE AREA TONIGHT. MODEL GUIDANCE IS PRINTING OUT SOME VERY LIGHT PRECIPITATION BEGINNING EARLY TUESDAY MORNING AND CONTINUING ON AND OFF THROUGH THE DAY. TEMPERATURES ARE COLD ENOUGH THAT THIS SHOULD BE SNOW IF IT OCCURS. DID NOT INCLUDE IN TAFS AT THIS POINT...BUT WILL REEVALUATE FOR THE 06Z ISSUANCE. IFR CIGS SHOULD RISE THROUGH THE LATE MORNING INTO THE AFTERNOON TO MVFR LEVELS. SPECIFICS FOR KSTL... MVFR CIGS BELOW 2000FT WILL PREVAIL AT LAMBERT THIS EVENING. MODEL FORECAST SOUNDINGS FROM THE RUC ARE INDICATING THAT THE CIGS WILL DROP BELOW 1000FT AFTER MIDNIGHT TONIGHT. THIS SEEMS REASONABLE GIVEN THE WEATHER PATTERN WE`RE IN...BUT TIMING IS NOT CERTAIN AT THIS POINT. REGARDLESS...EXPECT IFR CIGS TO RISE BACK TO MVFR BY MID-LATE MORNING. MODELS ARE INDICATING SOME LIGHT SNOW AT THE TERMINAL BEGINNING AS EARLY AS 12Z AND PERSISTING ON AND OFF THROUGH THE DAY. DID NOT INCLUDE THIS PRECIPITATION AT THIS TIME AS IT LOOKS TO BE VERY LIGHT IF IT OCCURS AT ALL. WILL REEVALUATE FOR THE SCHEDULED 06Z TAF WHEN NEW GUIDANCE IS AVAILABLE. CARNEY && .LSX WATCHES/WARNINGS/ADVISORIES... MO...NONE. IL...NONE. && $$ WFO LSX
AREA FORECAST DISCUSSION
NWS KANSAS CITY/PLEASANT HILL MO
544 PM CST MON DEC 5 2011 ...UPDATED AVIATION DISCUSSION... .DISCUSSION... /318 PM CST Mon Dec 5 2011/ Brisk northerly winds continues to advect colder air into Missouri with chilly temperatures the next couple of days. The main concern is a shortwave in southern New Mexico, south of the Four Corners Low. Short term high resolution models (NAM and RUC) are indicating that this wave will progress northeast into west central Missouri on Tuesday. light to moderate snow has been occurring in the TX panhandle, aided by upslope, with development toward the northeast. The models are showing very weak isentropic upglide along with weak deformation ahead of a weak 700 mb low in eastern Kansas late tonight and early Tuesday. Moisture is quite limited but have inserted sct snow showers for much of the area late tonight and Tuesday. Cannot rule out a narrow band of more persistent snow, producing very light accumulations. Later shifts will have to monitor the progress of this system. Otherwise, the trough axis will pass late Tuesday and Wednesday with dry conditions. DB Medium Range (Thursday through Monday)... Operational and ensemble members are in good agreement through the majority of the period depicting primarily stagnant longwave features over the western hemisphere. Most notable are a seasonably deep polar vortex centered across northern Hudson Bay and the Nunavut archipelago and an equally intense ridge through the Gulf of Alaska (both features in the 1-2 normalized standard deviations away from average range). This scenario will result in broad nwly/quasi-zonal flow for locations east of the Rockies with largely dry conditions and temperature slightly below average into the weekend. By the end of the period, models also indicate energy spilling over the top of the western ridge, causing a slight retrogressive phase, placing much of the central and southern plains into a warming, swly flow regime. There is naturally uncertainty into the depth and positioning of swrn conus energy late in the period, however the effect on weather through the forecast area would not be felt until after this valid period. Only real potential sensible weather during this medium range period still appears to be very light snow/snow flurries Thursday night into Friday morning across far northern Missouri. 21 && .AVIATION... For the 00Z TAFs, MVFR cigs and snow potential are the two primary concerns. NAM and GFS have been poor performers of late in handling the cold air stratocu deck so will put on ignore. Latest RUC is preferable and keeps the MVFR cigs in through the night. AVNFPS climate program supports this. In addition, with a 700mb shortwave approaching don`t see any subsidence to erode these cigs until afternoon so will keep the MVFR cigs in till then. That being said there could be a brief period or two where MVFR cigs scatter out between now and 18z Tuesday but it should fill back in. As for snow potential the above mentioned 700mb shortwave will lift newd tonight with weak downstream isentropic lift supporting bands of snow spreading across sern KS and parts of west central MO later tonight. While the better chance for any accumulating snow will most likely be south of the terminals the latest RUC and 18z NAM show a weaker/more elongated vorticity maxima further north that could result in snow flurries or snow showers to affect KMCI/KMKC. However, relatively high confidence that it will not be measurable snow. That plus it is a rather long window for occurrence, 07z-15z so will not include in the terminals. Will monitor south central and central KS as that should give a clue as to how far north any snow will reach. MJ && .EAX WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ WFO EAX
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
1059 PM EST MON DEC 5 2011 .SYNOPSIS... A MOIST SOUTHWEST FLOW ALOFT WILL INTERACT WITH A SLOW MOVING FRONTAL BOUNDARY AND ONE OR MORE WAVES OF LOW PRESSURE TO BRING UNSETTLED CONDITIONS TO THE AREA THROUGH MID WEEK. COLD AND BRISK WEATHER IS ANTICIPATED FROM LATER THIS WEEK INTO THE WEEKEND. && .NEAR TERM /UNTIL 8 AM TUESDAY MORNING/... SFC COLD FRONT HAS STALLED OUT TEMPORARILY THIS EVENING...JUST TO THE SE OF INTERSTATE 90 IN FAR NWRN PENN. 03Z SFC OBS...AND THE 02Z RUC DISPLAY A VERY TIGHT...MEAN SFC-925 MB TEMP GRADIENT FROM KERI...SW TO KCMH. RUC INDICATES THAT THIS BOUNDARY WILL CRAWL EAST TO NEAR A KELZ...TO KDUJ AND KPIT LINE BY THE 10-12Z TUESDAY TIMEFRAME. THE RAIN AREA /THAT HAS BEEN STREAMING NE AND CONFINED NEAR...AND JUST IN THE WAKE OF THE FRONT/ HAS STARTED TO QUICKLY EXPAND EAST AHEAD OF THIS BOUNDARY /NEARING KUNV ATTM AND LIKELY BEGINNING IN KIPT BY 05Z/...AS THE NOSE OF A STRENGTHENING 50-55KT/850 MB SWRLY JET MOVES NORTH ACROSS THE ALLEGHENY PLATEAU. THIS LLJ ENERGY WILL BE AIDED BY INCREASING 850-700 UVVEL BENEATH PULSES OF UPPER LEVEL DIVERGENCE BENEATH THE RIGHT ENTRANCE REGION OF A 110 KT JET LIFTING INTO NEW YORK STATE TOWARD DAYBREAK. RUC AND SREF MEAN...12-HOUR QPF IS AROUND 0.50 OF AN INCH ACROSS OUR FAR NW ZONES /NEAR KBFD/...AND BETWEEN 0.10 AND 0.25 OF AN INCH THROUGHOUT THE CENTRAL COUNTIES. RAINFL AMOUNTS OVER MUCH OF THE LOWER SUSQUEHANNA VALLEY REGION WILL STAY AOB 0.10 IF AN INCH THROUGH 12Z TUESDAY. LATEST NAM/HRRR SPREADS THE PRECIP GRADUALLY TO THE EAST ACROSS THE REST OF THE SCENT MTNS AND SUSQ VALLEY THROUGH THE PREDAWN HOURS. TIMING OF HIGHEST CHCS FOR PRECIP IS BETWEEN 05-10Z TUES ACROSS THE NW HALF OF THE CWA...AND DURING THE MID TO LATE MORNING IN THE SE ZONES. RUC 925 MB WET BULB TEMPS SINK TO A MIN OF ABOUT PLUS 1-2C ACROSS THE FAR NW BY 12Z TUESDAY...SO A CHANG-OVER TO SLEET/WET SNOW IS NOT EXPECTED AS FAR EAST AS WARREN OR KBFD. POPS WILL DECREASE AROUND OR SHORTLY AFTER DAYBREAK TUESDAY IN THE FAR NW. THE EXTENSIVE CLOUD COVER AND CONTINUED LIGHT SOUTH TO SOUTHEAST SFC WINDS ACROSS MOST OF THE AREA SHOULD KEEP TEMPS FROM FALLING VERY MUCH TONIGHT. TEMPS WILL FALL AN ADDITIONAL SEVERAL DEG F ACROSS THE HIGHER TERRAIN OF THE NORTH AND WEST...BUT WILL BE STEADY OR FALL JUST A FEW DEGREES ELSEWHERE AS MOISTURE BUILDS AND CLOUDS LOWER SUBSTANTIALLY. WILL JUST MENTION PATCHY 2-3SM FOG IN THE WHOLE AREA FOR THE TIME BEING. && .SHORT TERM /8 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... FRONT INCHES IT/S WAY ACROSS THE REST OF CENTRAL/ERN PENN ON TUES. NO SIGNIFICANT WAVES DEVELOP ALONG IT...SO GENERALLY SCT SHRA WILL FALL THROUGH THE DAY ON TUESDAY. LIKELIHOOD OF SHOWERS FAIRLY HIGH DURING THE WHOLE DAY...AND PINNING A TIME FOR HIGHEST POPS NOT EASY. WILL PAINT THE HIGHER POPS IN THE AFTN AS PRESSURE LOWER ON THE FRONT SLIGHTLY. THE MORE-ORGANIZED SHOWERS AND HIGHER POPS SHOULD BE IN THE SERN HALF OF THE FORECAST AREA. UPPER TROUGH STAYS HIGHLY POSITIVE AND DRAGS ALONG. THUS...LITTLE CHANGE IN THE SFC PATTERN AND FORCING IS SEEN FOR EARLY TUES NIGHT. HOWEVER...THE SFC BOUNDARY DOES SEEM TO CLEAR THE FORECAST AREA TUES NIGHT...AND WILL LOWER POPS OVER MUCH OF THE AREA IN THE SECOND HALF OF THE NIGHT. UPSLOPE IN THE WEST COULD FORCE ENOUGH MOISTURE UP INTO THE HILLS TO GENERATE SHOWERS...BUT P-TYPE IS QUESTIONABLE. 8H TEMPS ARE ABOVE FZG THROUGH 06-09Z IN THE WRN HIGHLANDS...BUT SFC TEMPS SHOULD FOLLOW ALONG IN LOCK STEP AND GET INTO THE 20S NW AND NEAR FZG IN THE LAURELS. WILL THEREFORE MENTION SHSN MIXING IN TO THE SCT SHRA IN THE W AFTER MIDNIGHT. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... A POSITIVE TILTED LONG WAVE TROUGH EXTENDING FROM THE GREAT LAKES INTO TX ON WED WILL BRING DEEP BROAD SWLY FLOW ALOFT. NAM/EC AND GEFS MODEL/ENSEMBLE GUIDANCE HAS TRENDED TOWARD GOOD AGREEMENT FOR A WAVE OF LOW PRESSURE TO DEVELOP OVER THE SE STATES WEDNESDAY /ALONG THE STALLED OUT FRONT THAT/S PROGGED TO EXTEND NE TO THE NEW JERSEY COAST/. GFS /WHICH SEVERAL RUNS AGO...DISPLAYED PRACTICALLY THE LONE CHC OF A LIGHT TO MODERATE WINTER WEATHER EVENT ACROSS OUR SE AND PERHAPS CENTRAL CWA/ HAS BECOME ONE OF THE FEW OUTLIER SOLUTIONS. /THE OTHER BEING THE 12Z CANADIAN GEM MODEL/. 12Z EC...18Z GEFS...AND THE 18Z/00Z NAM ARE IN PRETTY GOOD AGREEMENT AND INDICATE THE POTENTIAL FOR A FEW TO SVRL INCHES OF WET SNOW NEAR THE I-81 CORRIDOR. THE 21Z SREF HASN/T CHANGED MUCH FROM THE 15Z VERSION...WITH THE NW EDGE OF ITS 0.25 INCH STORM TOTAL LEQ QPF CONTOUR FROM KMRB...TO NEAR KMUI AND KABE. THE COMPACT...OPEN /AND PERHAPS SLIGHTLY NEG TILT/ UPPER SHORTWAVE THAT WILL BE LIFTING QUICKLY NE OUT OF THE SOUTHERN U.S. WILL NOT HAVE A CHANCE TO AMPLIFY SIGNIFICANTLY...CONSIDERING THE DEEP VORTEX DRIFTING OVER HUDSON BAY...WITH A FAST WESTERLY UPPER FLOW ACROSS THE NRN U.S. AND UPPER GLAKES REGION. HOWEVER...THE WELL- DEFINED ENTRANCE REGION OF A POTENT 140 KT UPPER JET FROM PENN TO SRN NEW ENGLAND WILL HELP TO CREATE A POTENTIAL PERIOD OF MODERATE TO STRONG UVVEL AS JET MAX WITH THE LIFTING SHORTWAVE LINKS UP. BUMPED UP POPS TO LIKELY ACROSS THE FAR SE WITH A TIGHT POP GRADIENT BETWEEN I-81 AND A KAOO...KUNV AND KIPT LINE. PRECIP TYPE WILL LIKELY START AS A COLD LIGHT RAIN IN THE SOUT...WITH SOME AREAS OF LIGHT RAIN/WET SNOW DEVELOPING FROM THE HIGHER MID CLOUD BASE ACROSS THE REGION NORTHWEST OF I-81 BY LATE EVENING. MENTIONED THE CHC FOR A LIGHT TO MDT WET SNOW FOR OUR SE ZONES IN THE HAZ WEATHER OUTLOOK. MODELS REBOUND WITH BETTER CONSENSUS AFTER THIS SYSTEM HEADED INTO THE WEEKEND. A NORTHERN STREAM COLD FRONT MOVES THROUGH FRI TURNING FLOW WESTERLY AND BRINGING COLD AND BRISK CONDITIONS TO START THE WEEKEND. TEMPS WILL BE ABOUT 5F BELOW NORMAL /WHICH WILL BE NOTICEABLE AFTER OUR RUN OF RELATIVELY MILD TEMPS/ AND LAKE EFFECT/OROGRAPHIC SNOW SHOWERS WILL DEVELOP FRI NIGHT INTO SAT...MAINLY CONFINED TO THE NW MTNS. HIGH PRES RETURNS FOR SUNDAY/MONDAY WHICH WILL ALLOW TEMPERATURES TO GRADUALLY MODERATE WITH FAIR WEATHER. && .AVIATION /04Z TUESDAY THROUGH SATURDAY/... A COLD FRONT...LOCATED OVER NW PA AT 00Z...WILL PUSH SLOWLY SOUTHEAST ACROSS PENNSYLVANIA LATE TONIGHT. CURRENT ANALYSIS SHOWS WIDESPREAD VFR CONDS ACROSS THE BULK OF CENTRAL PA. HOWEVER...AS THE FRONT PUSHES EAST...EXPECT DETERIORATING FLYING CONDS. PERIODS OF RAIN WILL DEVELOP OVR THE ENTIRE REGION AND SHORT RANGE MDL DATA SUPPORTS WIDESPREAD IFR CIGS/VSBYS DEVELOPING AFTER MIDNIGHT. MODEST IMPROVEMENT IS EXPECTED BY TUESDAY AFTN...AS FRONT BEGINS TO PUSH EAST OF THE REGION. MANY LOCATIONS WILL LIKELY IMPROVE TO MVFR CONDS. HOWEVER...RESIDUAL MOISTURE ASCENDING THE W MTNS COULD LEAD TO LINGERING IFR CIGS AT JST AND BFD THRU TUE NIGHT. OUTLOOK... WED...AM LOW CIGS POSSIBLE W MTNS. WED NIGHT...RAIN/SNOW AND LOW CIGS POSSIBLE SOUTHEAST. THU...NO SIG WX EXPECTED. FRI...PM SHSN POSSIBLE NW MTNS. SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...DANGELO/LAMBERT LONG TERM...LAMBERT/RXR/STEINBUGL AVIATION...FITZGERALD
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
839 PM EST MON DEC 5 2011 .SYNOPSIS... A MOIST SOUTHWEST FLOW ALOFT WILL INTERACT WITH A SLOW MOVING FRONTAL BOUNDARY AND ONE OR MORE WAVES OF LOW PRESSURE TO BRING UNSETTLED CONDITIONS TO THE AREA THROUGH MID WEEK. COLD AND BRISK WEATHER IS ANTICIPATED FROM LATER THIS WEEK INTO THE WEEKEND. && .NEAR TERM /UNTIL 8 AM TUESDAY MORNING/... SFC COLD FRONT HAS MADE IT JUST TO THE SE OF INTERSTATE 90 IN FAR NWRN PENN THIS EVENING. 21Z RUC AND LATEST 22Z HRRR INDICATES THAT THIS BOUNDARY WILL CRAWL EAST TO NEAR A KELZ...TO KDUJ AND KPIT LINE AROUND 10Z TUESDAY. THE RAIN AREA /THAT HAS BEEN STREAMING NE AND CONFINED NEAR...AND JUST IN THE WAKE OF THE FRONT/ SHOULD BEGIN TO EXPAND EASTWARD AHEAD OF THIS BOUNDARY LATE TONIGHT AS A STRENGTHENING 50-55KT/850 MB SWRLY JET MOVES NORTH ACROSS THE ALLEGHENY PLATEAU. THIS LLJ ENERGY WILL BE AIDED BY INCREASING 850-700 UVVEL BENEATH PULSES OF UPPER LEVEL DIVERGENCE BENEATH THE RIGHT ENTRANCE REGION OF A 110 KT JET LIFTING INTO NEW YORK STATE TOWARD DAYBREAK. RUC AND SREF MEAN...12-HOUR QPF IS AROUND 0.50 OF AN INCH ACROSS OUR FAR NW ZONES /NEAR KBFD/...AND BETWEEN 0.10 AND 0.25 OF AN INCH THROUGHOUT THE CENTRAL COUNTIES. RAINFL AMOUNTS OVER MUCH OF THE LOWER SUSQUEHANNA VALLEY REGION WILL STAY AOB 0.10 IF AN INCH THROUGH 12Z TUESDAY. LATEST NAM/HRRR PUSH SCT SHOWERS INTO THE CENTRAL MTS BETWEEN 04-06Z TUESDAY...THEN SPREADS THE PRECIP GRADUALLY TO THE EAST ACROSS THE REST OF THE AREA THROUGH THE PREDAWN HOURS. TIMING OF HIGHEST CHCS FOR PRECIP IS BETWEEN 05-10Z TUES ACROSS THE NW HALF OF THE CWA...AND DURING THE MID TO LATE MORNING IN THE SE ZONES POPS WILL DECREASE AROUND OR SHORTLY AFTER DAYBREAK TUESDAY IN THE FAR NW. THE EXTENSIVE CLOUD COVER AND CONTINUED LIGHT SOUTH TO SOUTHEAST SFC WINDS ACROSS MOST OF THE AREA SHOULD KEEP TEMPS FROM FALLING VERY MUCH TONIGHT. TEMPS WILL FALL AN ADDITIONAL SEVERAL DEG F ACROSS THE HIGHER TERRAIN OF THE NORTH AND WEST...BUT WILL BE STEADY OR FALL JUST A FEW DEGREES ELSEWHERE AS MOISTURE BUILDS AND CLOUDS LOWER SUBSTANTIALLY. WILL JUST MENTION PATCHY 2-3SM FOG IN THE WHOLE AREA FOR THE TIME BEING. && .SHORT TERM /8 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... FRONT INCHES IT/S WAY ACROSS THE REST OF THE STATE ON TUES. NO SIGNIFICANT WAVES DEVELOP ALONG IT...SO GENERALLY SCT SHRA WILL FALL THROUGH THE DAY ON TUESDAY. LIKELIHOOD OF SHOWERS FAIRLY HIGH DURING THE WHOLE DAY...AND PINNING A TIME FOR HIGHEST POPS NOT EASY. WILL PAINT THE HIGHER POPS IN THE AFTN AS PRESSURE LOWER ON THE FRONT SLIGHTLY. THE MORE-ORGANIZED SHOWERS AND HIGHER POPS SHOULD BE IN THE SERN HALF OF THE FORECAST AREA. UPPER TROUGH STAYS HIGHLY POSITIVE AND DRAGS ALONG. THUS...LITTLE CHANGE IN THE SFC PATTERN AND FORCING IS SEEN FOR EARLY TUES NIGHT. HOWEVER...THE SFC BOUNDARY DOES SEEM TO CLEAR THE FORECAST AREA TUES NIGHT...AND WILL LOWER POPS OVER MUCH OF THE AREA IN THE SECOND HALF OF THE NIGHT. UPSLOPE IN THE WEST COULD FORCE ENOUGH MOISTURE UP INTO THE HILLS TO GENERATE SHOWERS...BUT P-TYPE IS QUESTIONABLE. 8H TEMPS ARE ABOVE FZG THROUGH 06-09Z IN THE WRN HIGHLANDS...BUT SFC TEMPS SHOULD FOLLOW ALONG IN LOCK STEP AND GET INTO THE 20S NW AND NEAR FZG IN THE LAURELS. WILL THEREFORE MENTION SHSN MIXING IN TO THE SCT SHRA IN THE W AFTER MIDNIGHT. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... A POSITIVE TILTED LONG WAVE TROUGH EXTENDING FROM THE GREAT LAKES INTO TX ON WED WILL BRING DEEP BROAD SWLY FLOW ALOFT. MODEL/ENSEMBLE GUIDANCE CONTINUING TO STRUGGLE ON A CONSENSUS CONCERNING ULTIMATE EVOLUTION OF THIS SYSTEM...MAINLY THE HANDLING OF UPSTREAM SHORTWAVE ENERGY...THOUGH GFS/ECMWF IN SLIGHTLY BETTER AGREEMENT ON MORE SOUTHERN TRACK OF SFC LOW WED NIGHT BUT WITH TIMING DIFF CONTINUING. WITH THIS IN MIND...MAINTAINED BASIC THEME OF PREVIOUS FORECAST OF LEANING TOWARDS THE FASTER MORE SOUTHERLY SOLUTION OF THE ECMWF...KEEPING POPS HIGHEST IN THE SE WITH QUICKLY DECREASING POPS TO THE NW. PRECIP TYPE WILL REMAIN ALL RAIN WED AFT AND EVE...BUT COULD MIX/TURN TO SNOW LATER WED NIGHT WITH LIGHT ACCUM POSSIBLE. ONE CAVEAT...WITH SUCH LOW CONFIDENCE...THIS SYSTEM AND QPF AMOUNTS /AS WELL AS THE GENERAL IMPACT OVERALL/ COULD POSS BE GREATER THAN CURRENTLY PREDICTED. DEPENDING ON THE OUTCOME...THERE MAY BE ENOUGH COLD AIR IN PLACE TO PRODUCE SNOW ACCUMULATIONS. MODELS REBOUND WITH BETTER CONSENSUS AFTER THIS SYSTEM HEADED INTO THE WEEKEND. A NORTHERN STREAM COLD FRONT MOVES THROUGH FRI TURNING FLOW WESTERLY AND BRINGING COLD AND BRISK CONDITIONS TO START THE WEEKEND. TEMPS WILL BE ABOUT 5F BELOW NORMAL /WHICH WILL BE NOTICABLE AFTER OUR RUN OF RELATIVELY MILD TEMPS/ AND LAKE EFFECT/OROGRAPHIC SNOW SHOWERS WILL DEVELOP FRI NIGHT INTO SAT...MAINLY CONFINED TO THE NW MTNS. HIGH PRES RETURNS FOR SUNDAY/MONDAY WHICH WILL ALLOW TEMPERATURES TO GRADUALLY MODERATE WITH FAIR WEATHER. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... A COLD FRONT...LOCATED OVER NW PA AT 00Z...WILL PUSH SLOWLY SOUTHEAST ACROSS PENNSYLVANIA LATE TONIGHT. CURRENT ANALYSIS SHOWS WIDESPREAD VFR CONDS ACROSS THE BULK OF CENTRAL PA. HOWEVER...AS THE FRONT PUSHES EAST...EXPECT DETERIORATING FLYING CONDS. PERIODS OF RAIN WILL DEVELOP OVR THE ENTIRE REGION AND SHORT RANGE MDL DATA SUPPORTS WIDESPREAD IFR CIGS/VSBYS DEVELOPING AFTER MIDNIGHT. MODEST IMPROVEMENT IS EXPECTED BY TUESDAY AFTN...AS FRONT BEGINS TO PUSH EAST OF THE REGION. MANY LOCATIONS WILL LIKELY IMPROVE TO MVFR CONDS. HOWEVER...RESIDUAL MOISTURE ASCENDING THE W MTNS COULD LEAD TO LINGERING IFR CIGS AT JST AND BFD THRU TUE NIGHT. OUTLOOK... WED...AM LOW CIGS POSSIBLE W MTNS. WED NIGHT...RAIN/SNOW AND LOW CIGS POSSIBLE SOUTHEAST. THU...NO SIG WX EXPECTED. FRI...PM SHSN POSSIBLE NW MTNS. SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...DANGELO LONG TERM...RXR/STEINBUGL AVIATION...FITZGERALD
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
547 PM EST SUN DEC 4 2011 .SYNOPSIS... WITH HIGH PRESSURE EAST OF THE REGION OUR ATTENTION TURNS TO A SLOW MOVING FRONTAL SYSTEM APPROACHING PENNSYLVANIA. CLOUDS FROM THIS FRONT WILL OVERSPREAD TONIGHT. ON MONDAY RAINFALL WILL INCREASE IN COVERAGE AND INTENSITY OVER THE WEST AND SPREAD ACROSS CENTRAL PENNSYLVANIA OVERNIGHT. TEMPERATURES WILL CONTINUE WELL ABOVE AVERAGE WITH THIS SYSTEM...UNTIL A STRONG COLD FRONT BRING TEMPERATURES BACK DOWN TO AVERAGE READINGS LATE TUESDAY AND WEDNESDAY. ANOTHER STORM SYSTEM WILL APPROACH THE REGION FROM THE SOUTH ON THURSDAY. THIS STORM HAS THE POTENTIAL TO BRING SOME WINTRY OR MIXED PRECIPITATION DEPENDING ON THE TRACK. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... TRANQUIL WEATHER WILL PERSIST OVERNIGHT ACROSS MOST OF THE REGION WITH JUST AREAS OF MAINLY CIRROSTRATUS...AND SOME HIGH-BASED ALTO CU DRIFTING NE. 15Z SREF AND 21Z RUC SHOWS SOME LIGHT SHOWERS EDGING INTO WARREN AND PERHAPS ELK/MCKEAN COUNTIES AFTER 07Z. EVEN THERE...QPF WILL BE LIGHT AND LESS THAN 0.10 BY 12Z MONDAY. VERY MILD TEMPS FOR EARLY DECEMBER WILL CONTINUE THROUGH TONIGHT. THANKS TO THE GENERALLY LIGHT SOUTHERLY BREEZE...AND FAIR AMOUNT OF CLOUD COVER...TEMPS WILL ONLY REACH THE UPPER 30S TO LOWER 40S FOR MINS /WHICH WILL BE 10-15F ABOVE NORMAL...WITH THE GREATEST DEPARTURES OCCURRING ACROSS THE MOUNTAINS/. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... CLOUDS LOWER AND THICKEN AS FRONTAL BOUNDARY APPROACHES. PRECIPITATION WILL INCREASE IN THE AFTERNOON HOURS AND BECOME A STEADY LIGHT RAIN OVERNIGHT. FRONT STILL WEST OF AREA SO MILD TEMPERATURES CONTINUE THROUGH THE PERIOD. && .LONG TERM /TUESDAY THROUGH SUNDAY/... MODELS AGREE ON A COLD FRONT PUSHING ACROSS PA ON TUE...KEEPING RAIN CHANCES HIGH...ESPECIALLY ACROSS THE SOUTHERN MTNS AND SUSQ VALLEY. TEMPS TUE START OFF MILD...BUT WILL LIKELY REMAIN STEADY OR FALL A BIT IN THE AFTERNOON...ESP IN THE NW. NO LARGE PUSH OF COLD AIR BEHIND FRONT EVIDENT THOUGH. LINGERING CHANCE FOR LIGHT RAIN/SNOW SHOWERS TUE NIGHT INTO WED AS NARROW TROUGH AND COOLER AIR SLIDES OVERHEAD. MUCH UNCERTAINTY IN LATE WEEK SOLUTIONS AS LARGE MODEL DIVERGENCE CONTINUES. WAVE OF LOW PRESSURE SLIDES UP/EAST OF THE APPALACHIANS THU...WITH ECMWF CONTINUING TO TRACK THIS TO OUR SE...THOUGH THE GFS SOLUTION CONTINUES TO BECOME GRADUALLY MORE INTERESTING WITH A MORE NORTHERLY TRACK. TOUGH TO RESOLVE THIS IN THE GRIDS OTHER THAN TO EDGE POPS UPWARD A BIT ON THU AND SEE HOW THIS PLAYS OUT. COULD BRING POTENTIAL FOR 0.50 INCH QPF...WITH SOME OF THAT FALLING AS SNOW IF THE GFS SOLUTION WINS OUT...THOUGH AM STILL LEANING MORE TOWARD THE ECMWF SOLUTION AT THIS TIME. TROUGH DIGS IN FROM THE NW FRI NIGHT INTO SAT...BRINGING NOTICABLY COLDER TEMPS AND WESTERLY FLOW. THIS WILL ALSO BRING A GOOD CHANCE FOR LAKE EFFECT SNOW SHOWERS IN THE NW MTNS SAT. TEMPS SHOULD BEGIN TO REBOUND EARLY NEXT WEEK. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... SOME ISOLATED PRE-FRONTAL SHOWERS MAY MOVE INTO BFD EARLY TOMORROW MORNING...ALONG WITH SOME MVFR VSBYS. CALM WINDS AND LOW LEVEL MOISTURE WILL ALLOW FOR FOG FORMATION ACROSS THE SUSQ VALLEY OVERNIGHT. LATEST MDL DATA SUGGEST IFR VSBYS ARE LIKELY AT IPT/MDT/LNS LATE TONIGHT. FOG OVER THE SUSQ VALLEY SHOULD DISSIPATE BY MIDDAY MONDAY. OUTLOOK... MON...RAIN/LOW CIGS POSSIBLE...MAINLY NW. TUE...RAIN/LOW CIGS POSSIBLE. WED...RAIN AREA WIDE TRANSITIONS TO SHSN NW. THU...LOW CIGS...SHSN NW. FRI...LOW CIGS/LAKE EFFECT SHOWERS POSSIBLE MAINLY NW. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...ROSS/LAMBERT NEAR TERM...LAMBERT SHORT TERM...ROSS/LAMBERT LONG TERM...RXR AVIATION...FITZGERALD/KREKELER
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
519 PM EST SUN DEC 4 2011 .SYNOPSIS... WITH HIGH PRESSURE EAST OF THE REGION OUR ATTENTION TURNS TO A SLOW MOVING FRONTAL SYSTEM APPROACHING PENNSYLVANIA. CLOUDS FROM THIS FRONT WILL OVERSPREAD TONIGHT. ON MONDAY RAINFALL WILL INCREASE IN COVERAGE AND INTENSITY OVER THE WEST AND SPREAD ACROSS CENTRAL PENNSYLVANIA OVERNIGHT. TEMPERATURES WILL CONTINUE WELL ABOVE AVERAGE WITH THIS SYSTEM...UNTIL A STRONG COLD FRONT BRING TEMPERATURES BACK DOWN TO AVERAGE READINGS LATE TUESDAY AND WEDNESDAY. ANOTHER STORM SYSTEM WILL APPROACH THE REGION FROM THE SOUTH ON THURSDAY. THIS STORM HAS THE POTENTIAL TO BRING SOME WINTRY OR MIXED PRECIPITATION DEPENDING ON THE TRACK. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... TRANQUIL WEATHER WILL PERSIST OVERNIGHT ACROSS MOST OF THE REGION WITH JUST AREAS OF MAINLY CIRROSTRATUS...AND SOME HIGH-BASED ALTO CU DRIFTING NE. 15Z SREF AND 21Z RUC SHOWS SOME LIGHT SHOWERS EDGING INTO WARREN AND PERHAPS ELK/MCKEAN COUNTIES AFTER 07Z. EVEN THERE...QPF WILL BE LIGHT AND LESS THAN 0.10 BY 12Z MONDAY. VERY MILD TEMPS FOR EARLY DECEMBER WILL CONTINUE THROUGH TONIGHT. THANKS TO THE GENERALLY LIGHT SOUTHERLY BREEZE...AND FAIR AMOUNT OF CLOUD COVER...TEMPS WILL ONLY REACH THE UPPER 30S TO LOWER 40S FOR MINS /WHICH WILL BE 10-15F ABOVE NORMAL...WITH THE GREATEST DEPARTURES OCCURRING ACROSS THE MOUNTAINS/. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... CLOUDS LOWER AND THICKEN AS FRONTAL BOUNDARY APPROACHES. PRECIPITATION WILL INCREASE IN THE AFTERNOON HOURS AND BECOME A STEADY LIGHT RAIN OVERNIGHT. FRONT STILL WEST OF AREA SO MILD TEMPERATURES CONTINUE THROUGH THE PERIOD. && .LONG TERM /TUESDAY THROUGH SUNDAY/... MODELS AGREE ON A COLD FRONT PUSHING ACROSS PA ON TUE...KEEPING RAIN CHANCES HIGH...ESPECIALLY ACROSS THE SOUTHERN MTNS AND SUSQ VALLEY. TEMPS TUE START OFF MILD...BUT WILL LIKELY REMAIN STEADY OR FALL A BIT IN THE AFTERNOON...ESP IN THE NW. NO LARGE PUSH OF COLD AIR BEHIND FRONT EVIDENT THOUGH. LINGERING CHANCE FOR LIGHT RAIN/SNOW SHOWERS TUE NIGHT INTO WED AS NARROW TROUGH AND COOLER AIR SLIDES OVERHEAD. MUCH UNCERTAINTY IN LATE WEEK SOLUTIONS AS LARGE MODEL DIVERGENCE CONTINUES. WAVE OF LOW PRESSURE SLIDES UP/EAST OF THE APPALACHIANS THU...WITH ECMWF CONTINUING TO TRACK THIS TO OUR SE...THOUGH THE GFS SOLUTION CONTINUES TO BECOME GRADUALLY MORE INTERESTING WITH A MORE NORTHERLY TRACK. TOUGH TO RESOLVE THIS IN THE GRIDS OTHER THAN TO EDGE POPS UPWARD A BIT ON THU AND SEE HOW THIS PLAYS OUT. COULD BRING POTENTIAL FOR 0.50 INCH QPF...WITH SOME OF THAT FALLING AS SNOW IF THE GFS SOLUTION WINS OUT...THOUGH AM STILL LEANING MORE TOWARD THE ECMWF SOLUTION AT THIS TIME. TROUGH DIGS IN FROM THE NW FRI NIGHT INTO SAT...BRINGING NOTICABLY COLDER TEMPS AND WESTERLY FLOW. THIS WILL ALSO BRING A GOOD CHANCE FOR LAKE EFFECT SNOW SHOWERS IN THE NW MTNS SAT. TEMPS SHOULD BEGIN TO REBOUND EARLY NEXT WEEK. && .AVIATION /22Z SUNDAY THROUGH FRIDAY/... LLWS IS POSSIBLE OVER BFD EARLY THIS AFTERNOON...MAINLY OVER THE NW MTNS. SOME ISOLATED PRE-FRONTAL SHOWERS MAY MOVE INTO BFD EARLY TOMORROW MORNING...ALONG WITH SOME MVFR VSBYS. CALM WINDS AND LOW LEVEL MOISTURE WILL ALLOW FOR MVFR CONDITIONS ALONG THE LOWER SUSQ TOMORROW MORNING. THESE CONDITIONS SHOULD CONTINUE UNTIL 15Z BEFORE LIFTING. OUTLOOK... MON...RAIN/LOW CIGS POSSIBLE...MAINLY NW. TUE...RAIN/LOW CIGS POSSIBLE. WED...RAIN AREA WIDE TRANSITIONS TO SHSN NW. THU...LOW CIGS...SHSN NW. FRI...LOW CIGS/LAKE EFFECT SHOWERS POSSIBLE MAINLY NW. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...ROSS/LAMBERT NEAR TERM...LAMBERT SHORT TERM...ROSS/LAMBERT LONG TERM...RXR AVIATION...KREKELER
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
1020 AM CST SUN DEC 4 2011 .DISCUSSION... STRATUS SLOW TO EXIT THIS MORNING SO HAVE SLOWED THE EASTWARD PROGRESSION. THIS OF COURSE ALSO MEANS A LITTLE SLOWER RISE IN TEMPERATURES IN THESE AREAS WHICH WILL MEAN TEMPERATURES STUCK IN THE LOWER TO MID 20S. NOT MUCH WIND TO SPEAK OF FOR THE NEXT SEVERAL HOURS HOWEVER SO NOT QUITE AS COLD AS IT COULD BE. LOW PRESSURE IS DEVELOPING ACROSS THE WESTERN HIGH PLAINS AND WILL MOVE ACROSS SOUTH DAKOTA THROUGH THE NIGHT. THIS WILL BRING A STRONG NORTH TO NORTHWEST WIND TONIGHT WHICH WILL CARRY INTO TOMORROW. OTHERWISE...A WEAK THERMAL/THETA E RIDGE IN THE LOW AND MID LEVELS WILL SPREAD INTO CENTRAL SOUTH DAKOTA LATE THIS AFTERNOON AND EARLY THIS EVENING ALONG WITH WEAK PV ADVECTION ALOFT SO WILL NEED TO WATCH THIS AREA FOR A LITTLE LIGHT SNOW FROM ABOUT 6 PM THROUGH 2 AM. WILL HAVE TO OVERCOME QUITE A BIT OF DRY AIR IN THE WAKE OF YESTERDAYS SYSTEM SO CONFIDENCE NOT EXCEEDINGLY HIGH ON ACCUMULATIONS. THINKING THAT THE BETTER CHANCES FOR ACCUMULATIONS WILL BE TONIGHT AND MORE COUPLED WITH FORCING FROM ABOUT 850-800MB WHERE THE BETTER DENDRITIC LAYER RESIDES. WHILE LAYERS ABOVE...ESPECIALLY FROM ABOUT 700MB ON UP...WILL BE QUITE DRY WE SHOULD BE STILL GET A LITTLE LIGHT SNOW WITH THE FAVORABLE FORCING/THERMAL FIELDS IN THE LOW LEVELS. /08 && .AVIATION.../FOR THE 18Z TAF ISSUANCE/ LARGE AREA OF MVFR STRATUS SLOWLY SHIFTING EAST THIS MORNING...BUT THE WESTERN EDGE FINALLY STARTING TO SHOW SIGNS OF DISSIPATION. WILL KEEP FSD AND SUX WITHIN THE STRATUS THROUGH ABOUT 18-20Z THEN EXPECTING MAINLY MID AND HIGH CLOUDS...VFR...THROUGH THE PERIOD. HON WILLS SEE THE BEST CHANCE FOR A RETURN OF MVFR CEILINGS AFTER ABOUT 10Z AS COLDER AIR SURGES SOUTHWARD. SOME PATCHY LIGHT SNOW...MAINLY VFR BUT SOME PATCHY MVFR...WILL ALSO BE POSSIBLE FROM ABOUT THE JAMES VALLEY WEST WITH THE BETTER CHANCE FROM ABOUT 2Z THROUGH 10Z. /08 && .PREV DISCUSSION.../ISSUED AT 311 AM CST/ LIGHT SNOW WHICH AFFECTED PORTIONS OF OUR AREA ON SATURDAY HAS PUSHED INTO CENTRAL MINNESOTA AND CENTRAL IOWA VERY EARLY THIS MORNING. BEHIND THE EXITING SYSTEM...A BROAD AREA OF STRATUS HAS DEVELOPED ACROSS THE EASTERN DAKOTAS INTO EASTERN NEBRASKA...THOUGH MODELS NOT PICKING UP ON THIS AT ALL. 06Z RUC 925 MB RH TIME SECTION HINTING AT IT...AND HAS IT PULLING EASTWARD THROUGH THE MORNING...EXITING OVER OUR FAR EAST BY 18Z. OTHERWISE...A RELATIVELY QUIET DAY IN STORE...WITH CLOUDS INCREASING IN OUR WEST IN THE AFTERNOON AS A WEAK SHORTWAVE DROPS SOUTHWARD ON A NORTHWESTERLY UPPER LEVEL FLOW. NOT MUCH IN THE WAY OF DYNAMICS WITH THIS FEATURE...BUT COULD SPIT OUT SOME VERY LIGHT SNOW IN OUR WEST BY LATE THIS AFTERNOON INTO TONIGHT. TEMPERATURES A BIT TRICKY TODAY IN BETWEEN CLOUD COVER...THOUGH WHAT IS MORE CERTAIN IS THAT READINGS WILL NOT WARM A WHOLE LOT OVER SNOW COVERED AREAS...WITH HIGHS GENERALLY IN THE MID 20S THROUGH NORTHWESTERN IOWA AND PORTIONS OF SOUTHWESTERN MINNESOTA. TO THE WEST...WITH MORE SUN AND BETTER MIXING IN A TRANSITIONING SOUTHWESTERLY LOW LEVEL FLOW...HIGHS WILL REACH THE MID 30S ACROSS THE MUCH OF THE JAMES RIVER VALLEY INTO SOUTH CENTRAL SOUTH DAKOTA. WINDS WILL BECOME NORTHWESTERLY AND PICK UP FROM WEST TO EAST TONIGHT IN A TIGHTENING GRADIENT AND COLD AIR ADVECTION BEHIND THE EXITING SHORTWAVE AND SURFACE LOW/ASSOCIATED FRONTAL BOUNDARY. THE WINDS AND CLOUD COVER WILL KEEP OVERNIGHT LOWS SOMEWHAT IN CHECK...THOUGH WILL STILL DROP INTO THE TEENS...EXCEPT SINGLE DIGITS OVER SNOW COVER. COLDER AIR WILL CONTINUE TO FILTER INTO THE REGION ON MONDAY WITH A SURFACE HIGH BUILDING INTO THE REGION. TEMPERATURES WILL NOT RISE MUCH FROM EARLY MORNING LOWS...WITH HIGHS ONLY IN THE UPPER TEENS TO LOWER 20S. SOUTHERLY FLOW RETURNS TO THE REGION ON TUESDAY BEHIND THE EXITING HIGH...AND TEMPERATURES TRY TO WARM A BIT IN THE WEST...INTO THE MID AND UPPER 20S...WHILE READINGS OVER SNOW COVERED AREAS MAY ACTUALLY BE A LITTLE COOLER THAN MONDAYS HIGHS WITH LESS MIXING...REMAINING ONLY IN THE UPPER TEENS. EVEN WARMER ON WEDNESDAY AHEAD OF THE NEXT ARCTIC SURGE WHICH WILL DIVE SOUTHWARD ON WEDNESDAY NIGHT AND THURSDAY. COULD GET A LITTLE SNOW ALONG THE LEADING EDGE OF THIS SURGE/FRONTAL GRADIENT DURING THAT TIME FRAME...THOUGH ANY SNOW SHOULD BE LIGHT. HIGHS ON WEDNESDAY WILL BE IN THE UPPER 20S TO MID 30S...THEN DROP BACK TO THE LOWER TO MID 20S ON THURSDAY. FRIDAY LOOKS TO BE THE COLDEST DAY OF THE WEEK...WITH HIGHS MID TEENS TO AROUND 20...FOLLOWED BY SOME WARMING ON SATURDAY. LOOKS TO REMAIN DRY BOTH DAYS. && .FSD WATCHES/WARNINGS/ADVISORIES... IA...NONE. MN...NONE. NE...NONE. SD...NONE. && $$
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
515 AM CST SUN DEC 4 2011 .DISCUSSION.../ISSUED AT 311 AM CST/ LIGHT SNOW WHICH AFFECTED PORTIONS OF OUR AREA ON SATURDAY HAS PUSHED INTO CENTRAL MINNESOTA AND CENTRAL IOWA VERY EARLY THIS MORNING. BEHIND THE EXITING SYSTEM...A BROAD AREA OF STRATUS HAS DEVELOPED ACROSS THE EASTERN DAKOTAS INTO EASTERN NEBRASKA...THOUGH MODELS NOT PICKING UP ON THIS AT ALL. 06Z RUC 925 MB RH TIME SECTION HINTING AT IT...AND HAS IT PULLING EASTWARD THROUGH THE MORNING...EXITING OVER OUR FAR EAST BY 18Z. OTHERWISE...A RELATIVELY QUIET DAY IN STORE...WITH CLOUDS INCREASING IN OUR WEST IN THE AFTERNOON AS A WEAK SHORTWAVE DROPS SOUTHWARD ON A NORTHWESTERLY UPPER LEVEL FLOW. NOT MUCH IN THE WAY OF DYNAMICS WITH THIS FEATURE...BUT COULD SPIT OUT SOME VERY LIGHT SNOW IN OUR WEST BY LATE THIS AFTERNOON INTO TONIGHT. TEMPERATURES A BIT TRICKY TODAY IN BETWEEN CLOUD COVER...THOUGH WHAT IS MORE CERTAIN IS THAT READINGS WILL NOT WARM A WHOLE LOT OVER SNOW COVERED AREAS...WITH HIGHS GENERALLY IN THE MID 20S THROUGH NORTHWESTERN IOWA AND PORTIONS OF SOUTHWESTERN MINNESOTA. TO THE WEST...WITH MORE SUN AND BETTER MIXING IN A TRANSITIONING SOUTHWESTERLY LOW LEVEL FLOW...HIGHS WILL REACH THE MID 30S ACROSS THE MUCH OF THE JAMES RIVER VALLEY INTO SOUTH CENTRAL SOUTH DAKOTA. WINDS WILL BECOME NORTHWESTERLY AND PICK UP FROM WEST TO EAST TONIGHT IN A TIGHTENING GRADIENT AND COLD AIR ADVECTION BEHIND THE EXITING SHORTWAVE AND SURFACE LOW/ASSOCIATED FRONTAL BOUNDARY. THE WINDS AND CLOUD COVER WILL KEEP OVERNIGHT LOWS SOMEWHAT IN CHECK...THOUGH WILL STILL DROP INTO THE TEENS...EXCEPT SINGLE DIGITS OVER SNOW COVER. COLDER AIR WILL CONTINUE TO FILTER INTO THE REGION ON MONDAY WITH A SURFACE HIGH BUILDING INTO THE REGION. TEMPERATURES WILL NOT RISE MUCH FROM EARLY MORNING LOWS...WITH HIGHS ONLY IN THE UPPER TEENS TO LOWER 20S. SOUTHERLY FLOW RETURNS TO THE REGION ON TUESDAY BEHIND THE EXITING HIGH...AND TEMPERATURES TRY TO WARM A BIT IN THE WEST...INTO THE MID AND UPPER 20S...WHILE READINGS OVER SNOW COVERED AREAS MAY ACTUALLY BE A LITTLE COOLER THAN MONDAYS HIGHS WITH LESS MIXING...REMAINING ONLY IN THE UPPER TEENS. EVEN WARMER ON WEDNESDAY AHEAD OF THE NEXT ARCTIC SURGE WHICH WILL DIVE SOUTHWARD ON WEDNESDAY NIGHT AND THURSDAY. COULD GET A LITTLE SNOW ALONG THE LEADING EDGE OF THIS SURGE/FRONTAL GRADIENT DURING THAT TIME FRAME...THOUGH ANY SNOW SHOULD BE LIGHT. HIGHS ON WEDNESDAY WILL BE IN THE UPPER 20S TO MID 30S...THEN DROP BACK TO THE LOWER TO MID 20S ON THURSDAY. FRIDAY LOOKS TO BE THE COLDEST DAY OF THE WEEK...WITH HIGHS MID TEENS TO AROUND 20...FOLLOWED BY SOME WARMING ON SATURDAY. LOOKS TO REMAIN DRY BOTH DAYS. && .AVIATION.../FOR THE 12Z TAF ISSUANCE/ LARGE AREA OF STRATUS FROM THE JAMES RIVER EASTWARD AT SUNRISE WILL CONTINUE MOVING EAST AND DISSIPATING ON THE WEST EDGE THROUGH MID MORNING. CEILINGS ARE MVFR WITH NO VISIBILITY RESTRICTIONS IN THIS AREA...AND CLOUDS CHOULD BECOME SCATTERED AT ALL TAF SITES BY 16Z. LIGHT NORTHWEST SURFACE WINDS AT 12Z WILL BECOME SOUTHERLY AT 5 TO 10 KTS THIS AFTERNOON BEFORE SWITCHING BACK TO THE NORTH OR NORTHWEST AT 5 TO 10 KTS THIS EVENING BEHIND A LOW PRESSURE SYSTEM THAT WILL BE MOVING THROUGH THE WESTERN AND CENTRAL DAKOTAS. THERE WILL BE A CHANCE OF LIGHT SNOW MAKING IT AS FAR EAST AS KHON OVERNIGHT BEHIND THE LOW. /MG && .FSD WATCHES/WARNINGS/ADVISORIES... IA...NONE. MN...NONE. NE...NONE. SD...NONE. && $$
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
311 AM CST SUN DEC 4 2011 .DISCUSSION... LIGHT SNOW WHICH AFFECTED PORTIONS OF OUR AREA ON SATURDAY HAS PUSHED INTO CENTRAL MINNESOTA AND CENTRAL IOWA VERY EARLY THIS MORNING. BEHIND THE EXITING SYSTEM...A BROAD AREA OF STRATUS HAS DEVELOPED ACROSS THE EASTERN DAKOTAS INTO EASTERN NEBRASKA...THOUGH MODELS NOT PICKING UP ON THIS AT ALL. 06Z RUC 925 MB RH TIME SECTION HINTING AT IT...AND HAS IT PULLING EASTWARD THROUGH THE MORNING...EXITING OVER OUR FAR EAST BY 18Z. OTHERWISE...A RELATIVELY QUIET DAY IN STORE...WITH CLOUDS INCREASING IN OUR WEST IN THE AFTERNOON AS A WEAK SHORTWAVE DROPS SOUTHWARD ON A NORTHWESTERLY UPPER LEVEL FLOW. NOT MUCH IN THE WAY OF DYNAMICS WITH THIS FEATURE...BUT COULD SPIT OUT SOME VERY LIGHT SNOW IN OUR WEST BY LATE THIS AFTERNOON INTO TONIGHT. TEMPERATURES A BIT TRICKY TODAY IN BETWEEN CLOUD COVER...THOUGH WHAT IS MORE CERTAIN IS THAT READINGS WILL NOT WARM A WHOLE LOT OVER SNOW COVERED AREAS...WITH HIGHS GENERALLY IN THE MID 20S THROUGH NORTHWESTERN IOWA AND PORTIONS OF SOUTHWESTERN MINNESOTA. TO THE WEST...WITH MORE SUN AND BETTER MIXING IN A TRANSITIONING SOUTHWESTERLY LOW LEVEL FLOW...HIGHS WILL REACH THE MID 30S ACROSS THE MUCH OF THE JAMES RIVER VALLEY INTO SOUTH CENTRAL SOUTH DAKOTA. WINDS WILL BECOME NORTHWESTERLY AND PICK UP FROM WEST TO EAST TONIGHT IN A TIGHTENING GRADIENT AND COLD AIR ADVECTION BEHIND THE EXITING SHORTWAVE AND SURFACE LOW/ASSOCIATED FRONTAL BOUNDARY. THE WINDS AND CLOUD COVER WILL KEEP OVERNIGHT LOWS SOMEWHAT IN CHECK...THOUGH WILL STILL DROP INTO THE TEENS...EXCEPT SINGLE DIGITS OVER SNOW COVER. COLDER AIR WILL CONTINUE TO FILTER INTO THE REGION ON MONDAY WITH A SURFACE HIGH BUILDING INTO THE REGION. TEMPERATURES WILL NOT RISE MUCH FROM EARLY MORNING LOWS...WITH HIGHS ONLY IN THE UPPER TEENS TO LOWER 20S. SOUTHERLY FLOW RETURNS TO THE REGION ON TUESDAY BEHIND THE EXITING HIGH...AND TEMPERATURES TRY TO WARM A BIT IN THE WEST...INTO THE MID AND UPPER 20S...WHILE READINGS OVER SNOW COVERED AREAS MAY ACTUALLY BE A LITTLE COOLER THAN MONDAYS HIGHS WITH LESS MIXING...REMAINING ONLY IN THE UPPER TEENS. EVEN WARMER ON WEDNESDAY AHEAD OF THE NEXT ARCTIC SURGE WHICH WILL DIVE SOUTHWARD ON WEDNESDAY NIGHT AND THURSDAY. COULD GET A LITTLE SNOW ALONG THE LEADING EDGE OF THIS SURGE/FRONTAL GRADIENT DURING THAT TIME FRAME...THOUGH ANY SNOW SHOULD BE LIGHT. HIGHS ON WEDNESDAY WILL BE IN THE UPPER 20S TO MID 30S...THEN DROP BACK TO THE LOWER TO MID 20S ON THURSDAY. FRIDAY LOOKS TO BE THE COLDEST DAY OF THE WEEK...WITH HIGHS MID TEENS TO AROUND 20...FOLLOWED BY SOME WARMING ON SATURDAY. LOOKS TO REMAIN DRY BOTH DAYS. && .AVIATION.../FOR THE 06Z TAF ISSUANCE/ DRIER AIR MASS SETTLING INTO THE AREA TONIGHT. SNOW BAND LINGERING IN THE EXTREME SOUTHEAST CORNER OF THE CWA SHOULD EXIT THE AREA WITHIN THE NEXT HOUR OR SO. LATEST SATELLITE IMAGERY SHOWS RELATIVELY FAST MOVING AND NARROW TONGUE OF LOW STRATUS TRACKING SOUTHEAST ACROSS EASTERN NORTH DAKOTA AND INTO NORTHEAST AND SOUTH CENTRAL SOUTH DAKOTA. MVFR CEILINGS AROUND 2500 TO 3000 FEET WILL BE ASSOCIATED WITH THIS BAND WHICH WILL TRACK ACROSS THE ENTIRE CWA INTO THE EARLY MORNING HOURS. DESPITE A FRESH SNOWPACK ACROSS THE SOUTHEASTERN HALF...RELATIVELY LIGHT WINDS AND LATE CLEARING TONIGHT...THINK THAT THE AIRMASS WILL BE TOO DRY TO SUPPORT FOG ALTHOUGH IT WILL BE SOMETHING TO CONTINUE TO MONITOR. VFR CONDITIONS AND RELATIVELY LIGHT WINDS ON TAP FOR SUNDAY. && .FSD WATCHES/WARNINGS/ADVISORIES... IA...NONE. MN...NONE. NE...NONE. SD...NONE. && $$
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
801 PM CST MON DEC 5 2011 .UPDATE... THERE IS SOME TIME THIS EVENING FOR A RELEVANT METEOROLOGY LESSON FOR WEATHER ENTHUSIASTS. OFTEN THESE DISCUSSIONS WILL TALK ABOUT ICE CRYSTAL ACTIVATION AND SPECIFICALLY REFERENCE THE AVAILABILITY OF MOISTURE AT -10 C WHEN TRYING TO FORECAST PRECIP TYPE. SIMPLY STATED...PURE LIQUID WATER DROPLETS DO NOT FREEZE UNTIL -40 DEGREES. THIS IS BECAUSE THEY DO NOT KNOW HOW TO FORM INTO A CRYSTAL WITHOUT SOME HELP ON THE MOLECULAR LEVEL FROM OTHER CHEMICAL COMPOUNDS...OR OTHER ICE CRYSTALS THAT HAVE ALREADY BEEN TAUGHT HOW TO CRYSTALLIZE BY ONE OF THESE COMPOUNDS. THESE SPECIAL COMPOUNDS RANGE FROM DIRT...TO SALTS...TO POLLUTION AEROSOLS AND EVEN SOME BACTERIA...AND ARE CALLED CLOUD CONDENSATION NUCLEI. ESSENTIALLY THE FORMATION OF ICE CRYSTALS DEPENDS ON THE PROBABILITY THAT SOME OF THESE COMPOUNDS ARE AVAILABLE IN THE CLOUD. THE BEST WE CAN SAY...IS THAT AROUND -8C...40 PERCENT OF THE TIME SUPERCOOLED DROPLETS WILL BECOME CRYSTALS...AND SATURATION AT -10C...MEANS THAT PROBABILITY INCREASES TO GREATER THAN 70 PERCENT. THAT IS WHY WE LIKE TO USE MOISTURE AT THE -10C AS A GOOD RULE OF THUMB FOR SUPERCOOLED LIQUID DROPS VERSUS SNOW CRYSTALS. ONCE A WATER MOLECULE FIGURES OUT HOW TO FORM INTO A CRYSTAL...ANY NEARBY SUPERCOOLED WATER DROPLETS WILL QUICKLY PILE ONTO THAT CRYSTAL CHAIN...FORMING THE LONG SIX-SIDED ICE CRYSTAL DENDRITES WE CALL SNOWFLAKES. ANYWAY...BACK TO TONIGHTS FORECAST...THE EVENING SOUNDING SHOWED SATURATION AT -5C...WITH VERY DRY AIR IN THE COLDER LEVELS ABOVE 700MB. FURTHER COOLING OF THE AIR MASS NEAR 900MB MAY MEAN SATURATION AT -8C GENERALLY NORTH OF A CISCO TO DENTON TO PARIS LINE. THIS WOULD BE THE REGION WHERE SNOW FLURRIES WOULD BE POSSIBLE...BUT AGAIN FLUCTUATIONS BETWEEN FREEZING DRIZZLE AND SNOW FLURRIES WOULD OCCUR. TO THE SOUTH OF THAT LINE...ANY PRECIPITATION WOULD FALL AS DRIZZLE OR FREEZING DRIZZLE. RUC/HRRR FORECASTS KEEP THE BRUNT OF ANY OF THE LIGHT PRECIPITATION ACROSS THE NORTHERN TWO ROWS OF COUNTIES THROUGH 3 AM. SUPERCOOLED PRECIPITATION IS VERY HAZARDOUS AS THESE DROPS FREEZE THE INSTANT THEY COME IN CONTACT WITH AN OBJECT ON THE GROUND...EVEN IF THAT OBJECT IS SLIGHTLY ABOVE FREEZING. THANKFULLY THE AIR AT THE SURFACE REMAINS FAIRLY DRY AND MUCH OF THE RADAR RETURNS ARE EVAPORATING BEFORE REACHING THE GROUND. SHOULD REFLECTIVITY INCREASE AND LOW LEVEL MOISTENING TAKE PLACE DURING THE NEXT FEW HOURS...MAY HAVE TO THINK ABOUT AN ADVISORY FOR FREEZING DRIZZLE DUE TO IMPACTS FROM ICY BRIDGES. TR.92 && .AVIATION... /00Z TAFS/ CIGS HAVE IMPROVED IN THE METROPLEX TO LOW END VFR RANGE AND BASED ON ALL THE LATEST GUIDANCE THINK THIS TREND WILL CONTINUE INTO THE OVERNIGHT WITH ONE CAVEAT TO BE DISCUSSED BELOW. FARTHER SOUTH AT WACO MVFR CIGS OVC016 WILL PERSIST THROUGH THE EVENING WITH GRADUAL IMPROVEMENT THROUGH THE NIGHT. MOISTURE IS EXPECTED TO LINGER IN A THICK LAYER ABOVE THE SURFACE FOR MOST OF THE NIGHT HOWEVER NEAR THE SURFACE IT CONTINUES TO DRY OUT FROM NORTH TO SOUTH WITH TEMP/DEWPOINT SPREADS GREATER THAN 10 DEGREES AT DFW. ALTHOUGH NO SIGNIFICANT FORCING IS EXPECTED...EVEN WEAK ASCENT ANYWHERE IN THIS MOIST LAYER MAY RESULT IN SOME ENHANCED DRIZZLE PATCHES. THE LATEST RUC GUIDANCE SUGGESTS THAT DRIZZLE WILL OCCUR AND RESATURATE THE NEAR SURFACE DRY LAYER. THIS WOULD RESULT IN TWO PROBLEMS...CIGS WOULD LIKELY QUICKLY FALL TO IFR AND TEMPS NEAR OR BELOW FREEZING WOULD RESULT IN SOME LIGHT ICING. GIVEN THE AMOUNT OF DRYING ONGOING AND UPSTREAM DEWPOINT TEMPERATURES...THINK THIS SCENARIO IS NOT VERY LIKELY AT THIS TIME. IF RADAR/TEMP/DEWPOINT TRENDS THROUGH THE EVENING SUGGEST OTHERWISE...WILL MAKE QUICK AMENDMENTS TO THE CURRENT FORECAST. OTHERWISE...VFR CONDITIONS EXPECTED ON TUESDAY WITH GRADUAL SCATTERING OF CIGS BY LATE IN THE DAY. DUNN && .PREV DISCUSSION... /ISSUED 333 PM CST MON DEC 5 2011/ THE SHORTWAVE THAT WAS RESPONSIBLE FOR THIS MORNING/S SNOWFALL ACROSS THE WESTERN AND NORTHWESTERN COUNTIES OF NORTH TEXAS IS NOW MOVING INTO MISSOURI. A DEEP TROUGH REMAINS OVER THE DESERT SOUTHWEST WITH ANOTHER DISTURBANCE MOVING THROUGH SOUTHERN ARIZONA/NEW MEXICO. VERY LIGHT RETURNS CONTINUE TO SHOW ON AREA RADARS BUT ONLY ONE LOCAL OBSERVATION SITE HAS REPORTED PRECIP DURING THE LAST SEVERAL HOURS. HOWEVER...THERE IS SOME WEAK ISENTROPIC LIFT OVER THE REGION THAT IS LIKELY CONTRIBUTING TO THE LIGHT RETURNS ON RADAR. THINK SOME DRIZZLE OR POSSIBLY LIGHT SNOW FLAKES MAY OCCUR OVER ROUGHLY THE NORTHWESTERN HALF OF NORTH TEXAS THROUGH THE EVENING HOURS AS THE WEAK ISENTROPIC LIFT CONTINUES. THE NEXT SHORTWAVE TO OUR WEST IS FORECAST TO LIFT ACROSS THE TEXAS PANHANDLE AND INTO OKLAHOMA...MISSING NORTH TEXAS...BUT WILL CARRY A SMALL CHANCE FOR DRIZZLE/LIGHT FREEZING DRIZZLE/LIGHT SNOW FLAKES THROUGH THE OVERNIGHT HOURS ALONG AND NORTHWEST OF A LINE FROM COMANCHE TO DALLAS TO BONHAM. THE EASTWARD EXTENT OF THIS LINE COULD BE TOO AGGRESSIVE AND MAY HAVE TO BE TRIMMED BACK LATER TONIGHT. THE MAIN CONCERN FOR TONIGHT IS THE FREEZING TEMPERATURES ACROSS ALL BUT THE SOUTHEASTERN COUNTIES WITH THE POTENTIAL FOR ANY RESIDUAL WATER TO REFREEZE ON THE ROADWAYS LATE TONIGHT. DESPITE PERSISTENT CLOUD COVER THROUGH THE NIGHT...COLD AIR ADVECTION IS EXPECTED TO OCCUR TONIGHT RESULTING IN TEMPERATURES DROPPING INTO THE MID 20S IN THE NORTHWEST TO AROUND 33 DEGREES IN THE SOUTHEAST. THE MOST LIKELY LOCATION FOR WATER TO FREEZE ON ROADWAYS TONIGHT WOULD BE ACROSS THE WESTERN AND NORTHWESTERN COUNTIES WHERE TEMPERATURES ARE FORECAST TO DROP INTO THE MID AND UPPER 20S FOR SEVERAL HOURS. TEMPERATURES ON WEDNESDAY WILL NOT WARM MUCH MORE THAN VALUES REACHED TODAY...RANGING FROM THE MID 30S IN THE NORTHWEST TO THE MID 40S IN THE SOUTHEAST. THE UPPER LEVEL TROUGH TO OUR WEST WILL FINALLY EJECT EAST TOMORROW NIGHT WITH A STRONG SHORTWAVE IN THE BASE OF THE TROUGH MOVING OVER NORTH TEXAS. MAJORITY OF THE MODELS ARE CONSISTENT WITH INCREASING MOISTURE IN THE DENDRITIC GROWTH ZONE ALONG THE PATH OF THIS SHORTWAVE WHICH INCREASES THE POTENTIAL FOR SNOW FLURRIES TUESDAY NIGHT THROUGH WEDNESDAY MORNING. HAVE MENTIONED A CHANCE FOR FLURRIES DURING THIS TIME FRAME MAINLY NORTH OF I-20 WHERE IT APPEARS MID LEVEL MOISTURE WILL BE THE HIGHEST. HOWEVER...THIS COULD BE EXPANDED FARTHER SOUTH DEPENDING ON THE DATA OVER THE NEXT 24 HOURS. RIGHT NOW...THE LOWER LEVELS OF THE ATMOSPHERE LOOK TOO DRY TO SUPPORT MORE THAN FLURRIES WITH NOT ENOUGH TIME FOR TOP-DOWN SEEDING...BUT CANNOT COMPLETELY RULE OUT A SMALL CHANCE FOR SOME LIGHT SNOW TO OCCUR. IF THIS WERE TO OCCUR...THE MOST LIKELY LOCATIONS TO RECEIVE LIGHT SNOW WOULD BE EAST OF INTERSTATE 35 AND NORTH OF INTERSTATE 20. ACCUMULATIONS WOULD MOST LIKELY BE LIMITED TO A DUSTING. AFTER THE UPPER LEVEL TROUGH PASSES ON WEDNESDAY...WEAK TROUGHING WILL CONTINUE OVER THE REGION THROUGH THE END OF THE WEEKEND WITH A FEW WEAK SHORTWAVES PASSING OVERHEAD. HOWEVER...THE ATMOSPHERIC COLUMN WILL BE TOO DRY BY THAT TIME FOR ANY MORE PRECIPITATION AND THE FORECAST REMAINS DRY THROUGH THE WEEKEND. TEMPERATURES WILL CONTINUE TO REMAIN WELL BELOW NORMAL WITH SEVERAL NIGHTS OF SUBFREEZING OR NEAR FREEZING OVERNIGHT LOWS. ANOTHER FRONT WILL ARRIVE ON FRIDAY BRINGING ANOTHER SHOT OF COOL AND DRY AIR TO NORTH TEXAS. OUR NEXT CHANCE FOR RAIN MAY COME EARLY NEXT WEEK BUT DISCREPANCIES IN THE MODELS AND LOW CONFIDENCE IN THE OVERALL PATTERN NEXT WEEK PREVENT RAIN CHANCES FROM BEING MENTIONED AT THIS TIME. 82/JLD && .PRELIMINARY POINT TEMPS/POPS... DALLAS-FT. WORTH, TX 29 40 26 47 28 / 10 5 10 10 5 WACO, TX 30 41 24 48 26 / 10 5 10 10 5 PARIS, TX 30 41 27 44 26 / 10 5 10 10 5 DENTON, TX 25 38 22 44 24 / 10 5 10 10 5 MCKINNEY, TX 25 39 24 44 25 / 10 5 10 10 5 DALLAS, TX 30 40 27 47 29 / 10 5 10 10 5 TERRELL, TX 29 42 25 45 26 / 10 5 10 10 5 CORSICANA, TX 31 42 28 47 28 / 10 5 5 10 5 TEMPLE, TX 29 41 24 49 25 / 10 5 5 10 5 MINERAL WELLS, TX 25 38 21 48 25 / 10 10 10 10 5 && .FWD WATCHES/WARNINGS/ADVISORIES... NONE. && $$ /
AREA FORECAST DISCUSSION...UPDATED
NWS LUBBOCK TX
604 PM CST MON DEC 5 2011 .AVIATION... SNOW HAS LET UP AT KLBB AND CEILINGS HAVE GONE VFR BRIEFLY... HOWEVER EXPECT THAT WE WILL CONTINUE TO SEE PERIODS OF SNOW AT KLBB AND CEILINGS BOUNCING AROUND MVFR TO VFR THROUGH THE OVERNIGHT HOURS. IFR CONDITIONS ARE HARD TO FIGURE OUT RIGHT NOW AT KLBB BUT FEEL THE CEILINGS SHOULD REMAIN ABOVE THIS. EXPECT SNOW TO END AT KLBB BEFORE MIDNIGHT ALTHOUGH PERIODS OF LIGHT FLURRIES MAY PERSIST INTO TUESDAY MORNING. KCDS SHOULD REMAIN VFR WITH NO PRECIPITATION ALTHOUGH THERE MAY BE BRIEF PERIODS OF MVFR THROUGH THE OVERNIGHT HOURS. EXPECT VFR CONDITIONS BY LATE TOMORROW MORNING INTO EARLY TUESDAY AFTERNOON FOR KLBB. JORDAN && .PREV DISCUSSION... /ISSUED 334 PM CST MON DEC 5 2011/ SHORT TERM... THE MAIN FOCUS FOR THE SHORT TERM WILL CONTINUE TO BE THE WINTER WEATHER IMPACTS ASSOCIATED WITH A STRONG UPPER-LOW PRESSURE SYSTEM STILL PUSHING THROUGH THE FOUR CORNERS REGION. OVER THE COURSE OF THE DAY...LIGHT SNOW SHOWERS HAVE PERSISTED ACROSS THE CAPROCK...THOUGH VERY MINOR ACCUMULATIONS HAVE OCCURRED SINCE THE MID-MORNING HOURS. HOWEVER...CURRENT OBS...SATELLITE AND RADAR IMAGERY AND MODEL PROJECTIONS ARE SHOWING THE POTENTIAL FOR SOME ADDITIONAL AREAS OF LIGHT SNOWFALL TO MOVE INTO THE AREA LATE THIS AFTERNOON AND THIS EVENING AS ANOTHER LOBE OF ENERGY FROM THE AFOREMENTIONED UPPER-LOW ROTATES OVER THE REGION. MOST OF THE QPF SIGNALS SHOWN ARE FAIRLY LIGHT...BUT THE TTU WRF AND THE HRRR BOTH SHOW SOME ENHANCED PRECIPITATION BANDS DEVELOPING ACROSS THE NORTHWESTERN ZONES THIS EVENING. THIS THINKING SEEMS TO BE PLAUSIBLE AS IR SATELLITE DATA IS INDICATING A BAND OF COLDER CLOUD TOPS PUSHING INTO THE WESTERN PANHANDLE...WITH SURFACE OBS AT CLOVIS DROPPING DOWN TO 1-2 SM DUE TO SNOW. THUS...SOME LOCALIZED BURSTS OF MODERATE SNOW WILL BE POSSIBLE /PARTICULARLY ACROSS THE SW PANHANDLE/ WHERE AN ADDITIONAL INCH OF SNOW MAY BE POSSIBLE TONIGHT. HAVE INCREASED POPS TO LIKELY TO CHANCE ACROSS MUCH OF THE AREA THIS EVENING...BEFORE LOWERING THEM AFTER MIDNIGHT AS PRECIPITATION BEGINS TO WANE. THE OTHER BIG CONCERN FOR THIS EVENING WILL BE THE BRISK NORTHERLY WINDS AND STRONG COLD AIR ADVECTION OCCURRING...WHICH WILL DROP TEMPERATURES INTO THE SINGLE DIGITS ACROSS THE SW PANHANDLE AND INTO THE TEENS ACROSS THE REST OF THE AREA. GIVEN THE BITTERLY COLD TEMPERATURES AND WINDS THAT SHOULD REMAIN ABOVE 10 MPH OVERNIGHT SOME LOW WIND CHILLS WILL DEVELOP AFTER SUNSET. GIVEN THE POTENTIAL FOR SOME DANGEROUSLY COLD WINDS CHILLS AT OR AROUND -5 DEGREES OCCURRING LATER TONIGHT ACROSS THE NORTHWEST ZONES...HAVE PLACED THAT AREA IN A WIND CHILL ADVISORY THROUGH 15Z TOMORROW. GIVEN THE POTENTIAL FOR SOME ADDITIONAL /ALBEIT GENERALLY LIGHT/ SNOWFALL ACCUMULATIONS ON THE CAPROCK THIS EVENING AND ALREADY HAZARDOUS DRIVING CONDITIONS FROM BLACK ICE AND SNOW ON AREA ROADWAYS...HAVE OPTED TO EXTEND THE WINTER WEATHER ADVISORY ON THE CAPROCK UNTIL 12Z. TOMORROW WILL BE A BITTERLY COLD DAY ACROSS THE AREA...AS HIGHS WILL GENERALLY REMAIN WELL BELOW FREEZING IN THE 20S DUE TO VERY LOW THICKNESS VALUES AND A CONTINUED NORTHERLY WIND. LONG TERM... AMPLIFIED PATTERN THROUGHOUT THE CONUS WILL SLOWLY RELAX BY MIDWEEK RESULTING IN BRIEFLY ZONAL FLOW AND SLIGHTLY MILDER TEMPS ON THE SOUTH PLAINS. THIS PATTERN HOWEVER STILL LOOKS TO BREAK DOWN ON FRIDAY YIELDING BROADLY CYCLONIC FLOW COURTESY OF A DEEP POLAR VORTEX TAKING RESIDENCE IN THE HUDSON BAY. JUST A GLANCING BLOW FROM THIS BROAD TROUGH WILL YIELD A DRY POLAR FRONT LATE THU NIGHT/EARLY FRI SERVING TO KNOCK HIGHS ON FRI 15-20 DEG BELOW CLIMO. MEDIUM RANGE MODELS INSIST ON DEEPER WEST OR SWLY FLOW BY THE WEEKEND INDICATIVE OF MORE SEASONABLE TEMPS. GREATEST FORECAST CHALLENGE THIS PERIOD INVOLVES LO TEMPS TUE NIGHT AS STRATUS CLEARS AND WINDS SLACKEN WITHIN AN ELONGATED SURFACE RIDGE. CHOSE NOT TO LOWER INHERITED MIN TEMPS MUCH BELOW GUIDANCE FOR NOW AS ALL NUMERICAL DATA INDICATE LIGHT WESTERLY FLOW OVERNIGHT. SHOULD THESE LIGHT WINDS VEER MORE NLY IN LATER FORECASTS...THEN THE RECORD DAILY LOW AT LBB /8 SET IN 2005/ MAY BE IN JEOPARDY. && .PRELIMINARY POINT TEMPS/POPS... FRIONA 8 21 7 40 17 / 60 10 0 0 0 TULIA 12 22 11 41 18 / 50 10 0 0 0 PLAINVIEW 13 23 10 40 18 / 50 10 0 0 0 LEVELLAND 13 22 9 40 19 / 50 10 0 0 0 LUBBOCK 15 25 11 40 19 / 40 10 0 0 0 DENVER CITY 14 26 16 40 20 / 50 10 0 0 0 BROWNFIELD 14 26 13 40 20 / 50 10 0 0 0 CHILDRESS 20 30 17 42 21 / 20 10 0 0 0 SPUR 20 30 15 44 20 / 30 10 0 0 0 ASPERMONT 21 33 20 45 22 / 20 10 10 0 0 && .LUB WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 6 AM CST TUESDAY FOR THE FOLLOWING ZONES: TXZ021>024-027>030-033>036-039>042. WIND CHILL ADVISORY FROM 9 PM THIS EVENING TO 9 AM CST TUESDAY FOR THE FOLLOWING ZONES: TXZ021>023-027-028. && $$
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
244 PM CST SUN DEC 4 2011 ...A BRIEF TRANSITION TO A WINTRY MIX POSSIBLE FAR NORTHWEST LATE TONIGHT EARLY MONDAY...OTHERWISE JUST A COLD RAIN EXPECTED... .DISCUSSION... WIDESPREAD LIGHT TO MODERATE RAIN WITH ISOLATED/EMBEDDED THUNDERSTORMS ARE CONTINUING THIS AFTERNOON SOUTHEAST OF A CISCO TO DECATUR...TO GAINESVILLE LINE. MAIN DRIVING FORCE HAS BEEN WARM ADVECTION/ISENTROPIC LIFT OVER A SHALLOW FRONTAL INVERSION CURRENTLY OVER NORTH TEXAS. WILL CONTINUE THE HIGH RAIN CHANCES ACROSS THE MAJORITY OF NORTH TEXAS TONIGHT AS THE NEXT STRONG SHORTWAVE BEGINS TO APPROACH NORTH TEXAS. MODERATE RAIN IS OCCURRING ACROSS THE EASTERN COUNTIES AND 1 TO 2 INCHES..WITH LOCALIZED AMOUNTS ACROSS NORTHEAST COUNTIES POSSIBLY NEARING 3 INCHES...IS EXPECTED THROUGH MONDAY MORNING. THE 850MB FRONT IS CURRENTLY SITUATED FROM NEAR LUBBOCK TO OKLAHOMA CITY THIS AFTERNOON AND SHOULD PROGRESS SOUTHWARD..REACHING OUR NORTHWEST COUNTIES BY DAYBREAK MONDAY MORNING PER THE WRF AND HRRR MODELS. MODEL FORECAST SOUNDINGS FOR THIS AREA HAVE SATURATION AT/ABOVE 800MB WITH THE THERMAL PROFILE STRADDLING THE 0 DEG C ISOTHERM THROUGH THE MORNING HOURS MONDAY. BOTH MODELS SHOW SOME DRY POCKETS...PARTICULARLY BELOW 850MB WHICH SHOULD KEEP ANY PRECIPITATION VERY LIGHT WITH A VERY LIGHT RAIN/SNOW MIX POSSIBLE. THE SHORTWAVE DISTURBANCE PASSES EAST OF NORTH TEXAS MONDAY AFTERNOON WITH SUBSIDENCE AND ISENTROPIC DOWNGLIDE IN ITS WAKE. THIS PROCESS WILL RAPIDLY SHUT OFF MOST PRECIPITATION FROM WEST TO EAST THROUGH TUESDAY EVENING WITH BRISK AND COLD CONDITIONS CONTINUING THROUGH THE NIGHT TUESDAY. WITH THE POSITIVELY TILTED UPPER TROUGH TO OUR WEST...PLENTY OF MID-HIGH CLOUDINESS SHOULD REMAIN MONDAY NIGHT THROUGH WEDNESDAY MORNING. THE COMBINATION OF MOSTLY CLOUDY SKIES AND CONTINUED CAA IN THE LOWER LEVELS WILL MAINTAIN A COLD START TO THE FIRST HALF OF THE WEEK. STUBBORN UPPER LOW WILL OPEN AND LIFT OUT TUES NIGHT AND WEDNESDAY MORNING AS STRONG JET STREAK ROUNDS ITS BASE. MODELS SHOW SOME ELEVATED LIFT AND SHALLOW SATURATED LAYER ACROSS THE NORTHERN HALF OF NORTH TEXAS AS THE UPPER TROUGH LIFTS OUT. IT APPEARS A FEW FLURRIES COULD OCCUR CLOSER TO THE RED RIVER...BUT WILL LEAVE OUT FOR NOW UNTIL MOISTURE PROFILES ARE BETTER RESOLVED. IN WAKE OF OUR UPPER TROUGH...BRIEF MID LEVEL HEIGHT RISES OCCUR LATER WEDNESDAY INTO THURSDAY ALLOWING FOR A MOSTLY CLEAR FORECAST. CHILLY NIGHTS AND COOL DAYS WILL BE THE RULE LATE WEEK. ANOTHER REINFORCING COLD FRONT ARRIVES BY FRIDAY AND WILL KEEP THE AREA COOL INTO NEXT WEEKEND...AS ZONAL FLOW ALOFT PREVAILS. 05/42 && .PRELIMINARY POINT TEMPS/POPS... DALLAS-FT. WORTH, TX 38 42 32 40 28 / 100 60 10 10 10 WACO, TX 42 44 32 42 28 / 100 60 10 10 10 PARIS, TX 39 43 34 44 28 / 100 80 20 10 10 DENTON, TX 37 41 29 40 25 / 80 40 10 10 10 MCKINNEY, TX 38 42 31 42 26 / 100 60 10 10 10 DALLAS, TX 39 43 33 42 27 / 100 60 10 10 10 TERRELL, TX 40 43 31 43 28 / 100 80 10 10 10 CORSICANA, TX 41 44 35 44 30 / 100 70 10 10 10 TEMPLE, TX 41 43 32 43 28 / 100 60 10 10 10 MINERAL WELLS, TX 34 41 25 41 24 / 70 40 10 10 10 && .FWD WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 82/05/42
AREA FORECAST DISCUSSION
NWS AUSTIN/SAN ANTONIO TX
1149 PM CST SAT DEC 3 2011 .AVIATION... A WIDESPREAD AREA OF SHRA WITH EMBEDDED TSRA HAS DEVELOPED ACROSS CENTRAL TEXAS. ADDITIONAL DEVELOPMENT IS EXPECTED THROUGH THE OVERNIGHT HOURS AS THIS SYSTEM PROGRESSES SOUTHWARD AHEAD OF AN APPROACHING COLD FRONT WITH THE POTENTIAL FOR PERIODS OF -SHRA AND TEMPO -TSRA. A PRE-FRONTAL TROUGH AHEAD OF THE COLD FRONT WILL ENABLE SFC WINDS TO GRADUALLY BACK FROM SE TO E THROUGH THE NEXT FEW HOURS BEFORE THE FRONT ARRIVES BETWEEN 09-12Z ACROSS THE REGION. MVFR CIGS STRETCH FROM KJCT TO KBMQ TO KTPL AND ARE EXPECTED TO REACH THE SOUTH CENTRAL TEXAS TAF SITES BY 07Z. CIGS WILL DETERIORATE TO IFR AND POTENTIALLY LIFR THROUGH THE OVERNIGHT HOURS. ADDITIONALLY...AHEAD OF THE FRONT...A MIX OF -DZ/BR/-SHRA WILL LOWER VSBYS TO MVFR/IFR PARTICULARLY AT KAUS/KSAT/KSSF. THE COLD FRONT WILL ARRIVE SUNDAY MORNING...BUT IMPROVEMENTS TO CIGS AND VSBYS WILL BE SLOW WITH VFR CONDITIONS STILL NOT EXPECTED TO RETURN DURING THE 24-HR NOR 30-HR TAF PERIODS. && .PREV DISCUSSION... /ISSUED 933 PM CST SAT DEC 3 2011/ UPDATE... PRE-FRONTAL TROUGH EXTENDS FROM WACO TO LAMPASAS TO JUNCTION TO DRYDEN WHILE CANADIAN COLD FRONT EXTENDS FROM WICHITA FALLS TO ABILENE TO MIDLAND. TROUGH AND FRONT HAVE SPEED UP SLIGHTLY AND NEW 00Z NAM AND RUC BRING THESE FEATURES THROUGH SOUTH CENTRAL TEXAS A LITTLE EARLIER THAN PREVIOUSLY FORECAST WHICH SEEMS REASONABLE. MAIN IMPACTS ARE TO GO WITH COOLER TEMPERATURES AND EARLIER WIND SHIFTS TO NORTHERLY ON SUNDAY...ESPECIALLY DURING THE LATE MORNING AND AFTERNOON ALONG WITH LOWER POST-FRONTAL DEWPOINTS FOR SUNDAY THROUGH MONDAY. REMAINDER OF YOUR SOUTH CENTRAL TEXAS FORECAST IS ON TRACK. PREV DISCUSSION... /ISSUED 538 PM CST SAT DEC 3 2011/ AVIATION... A BRIEF WINDOW OF VFR CONDITIONS WILL CONTINUE THROUGH THE NEXT FEW HOURS BEFORE THE ONSET OF MVFR CIGS BY ABOUT 03Z. STREAMER SHOWERS WILL CONTINUE TO DEVELOP MAINLY EAST OF A LINE FROM KERV TO KHDO TO KCOT THROUGH THE EVENING HOURS AS WARM AIR ADVECTION PERSISTS IN ADVANCE OF AN APPROACHING COLD FRONT. THE DEEP MOISTURE IN THE LOWER LEVELS WILL PROMOTE THE DETERIORATION OF CIGS TO IFR AND POTENTIALLY LIFR CONDITIONS OVERNIGHT. AHEAD OF THE FRONT...A MIX OF -DZ/BR/-SHRA IS EXPECTED TO LOWER VSBYS TO MVFR/IFR PARTICULARLY AT KAUS/KSAT/KSSF. THE COLD FRONT WILL ARRIVE SUNDAY MORNING...BUT IMPROVEMENTS TO CIGS AND VSBYS WILL BE SLOW WITH VFR CONDITIONS NOT EXPECTED TO RETURN DURING THE 24-HR NOR 30-HR TAF PERIODS. PREV DISCUSSION... /ISSUED 314 PM CST SAT DEC 3 2011/ DISCUSSION... PRE-FRONTAL TROUGH/DRY LINE HAS PUSHED INTO THE FAR WESTERN CWA THIS AFTERNOON WITH GOOD MIXING/CLEARING ACROSS THE WESTERN COUNTIES. THE SKIES OVER THE EASTERN COUNTIES GENERALLY ALONG AND EAST OF I35 HAVE REMAINED MOSTLY CLOUDY WITH PATCHY LIGHT RAIN AND DRIZZLE CONTINUING IN THE DEEP SLY GULF FLOW. RAIN CHANCES WILL INCREASE AGAIN LATER THIS EVENING INTO THE OVERNIGHT HOURS AND SUNDAY. COMBINATION OF UPPER AIR DISTURBANCES IN THE SWLY FLOW ALOFT...CONVERGENCE ALONG THE PRE-FRONTAL SURFACE TROF...AND THE INCREASING LOW LEVEL GULF FLOW WILL RESULT IN GOOD CHANCES FOR DEEP CONVECTION. BECAUSE OF THE DEEP GULF INFLOW AHEAD OF THE TROUGH...WILL SEE GENEROUS QPF VALUES ESPECIALLY ACROSS THE NE/ERN COUNTIES. RAINFALL AMOUNTS OF ONE HALF TO ONE INCH OVER THE NEXT 24 HOURS WITH ISOLATED STORM TOTALS OF NEAR 2 INCHES POSSIBLE. THE COLD FRONT WAS PUSHING THROUGH THE TX PANHANDLE THIS AFTERNOON AND MODELS HAVE SLOWED THE PROGRESSION THRU S TX ON DURING THE DAY ON SUNDAY. CURRENT THINKING IS A FRONTAL PASSAGE INTO THE NRN HILL COUNTRY/EDWARDS PLATEAU BY 6 AM AND TO NEAR I10/HIGHWAY 90 BY AROUND NOON...AND THRU THE REMAINDER OF THE CWA BY 5 PM. HIGH TEMPERATURES WILL OCCUR JUST AHEAD OF THE COLD FRONT AND TEMPS ACROSS THE SRN CWA COULD REACH THE MID OR UPPER 70S. WILL SEE SLOWLY FALLING TEMPERATURES BEHIND THE FRONT AS COLD AIR ADVECTION WILL BEHIND TO INCREASE LATE SUNDAY NIGHT INTO MONDAY. MONDAY WILL BE THE MORE BONE CHILLING DAY WITH THE COMBINATION OF COLD...WIND AND POST FRONTAL OVERRUNNING LIGHT RAIN. WINTER PRECIPITATION FOR THE FAR NRN COUNTIES APPEARS UNLIKELY GIVEN THE WARMER 12Z SOUNDING TEMP PROFILE FOR MONDAY NIGHT/TUESDAY MORNING...AND MOST PRECIPITATION WILL BE ENDING FROM THE WEST BY SUNRISE TUESDAY MORNING. GRADUAL CLEARING TUESDAY WITH ALLOW FOR A COUPLE OF NIGHTS OF FREEZING TEMPERATURES AREA WIDE TUESDAY NIGHT AND WEDNESDAY NIGHT. STRONG WESTERLY FLOW ALOFT WILL RESULT IN A QUICK RETURN OF MOISTURE AND OVERRUNNING SETTING UP FOR LATE THURSDAY INTO FRIDAY AHEAD OF THE NEXT COLD FRONT. ANOTHER FAIRLY GOOD SHOT OF COLD CANADIAN AIR WILL ARRIVE FRIDAY NIGHT INTO SATURDAY...HOWEVER IT DOES NOT APPEAR THERE WILL BE ANY POST FRONTAL PRECIPITATION AS A DRY WNWLY FLOW DEVELOP BEHIND A SHORT WAVE AS THE COLD AIR ADVECTION BEGINS. && .PRELIMINARY POINT TEMPS/POPS... AUSTIN CAMP MABRY 54 58 44 49 36 / 80 80 90 60 20 AUSTIN BERGSTROM INTL AIRPORT 57 59 43 50 34 / 80 80 90 60 30 NEW BRAUNFELS MUNI AIRPORT 62 63 44 50 35 / 70 70 80 50 20 BURNET MUNI AIRPORT 47 49 40 47 35 / 80 80 90 50 20 DEL RIO INTL AIRPORT 55 56 45 52 36 / 50 30 50 20 10 GEORGETOWN MUNI AIRPORT 52 55 40 47 34 / 80 80 90 60 20 HONDO MUNI AIRPORT 63 63 45 53 35 / 70 50 80 30 20 SAN MARCOS MUNI AIRPORT 61 63 45 48 36 / 70 70 90 50 30 LA GRANGE - FAYETTE REGIONAL 64 67 48 50 38 / 70 80 90 70 30 SAN ANTONIO INTL AIRPORT 62 63 46 53 37 / 70 60 80 40 20 STINSON MUNI AIRPORT 64 64 47 52 38 / 70 60 80 40 20 && .EWX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ MESOSCALE/AVIATION...25 SYNOPTIC/GRIDS...04
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
1130 PM CST SAT DEC 3 2011 .AVIATION... SOME SLIGHTLY DRIER AIR IN THE LOW LEVELS HAS MOVED INTO THE REGION BEHIND THE INITIAL WIND SHIFT/WEAK FRONT. THIS HAS ALLOWED CIGS TO GO VFR EVERYWHERE BUT WACO. WITH MORE RAIN ON THE WAY OVERNIGHT EXPECT LOW LEVEL SATURATION TO OCCUR AND HELP BRING BACK MVFR CIGS AROUND SUNRISE...WITH IFR CIGS BY TOMORROW AFTERNOON. LIGHT RAIN WILL BE ALMOST CONTINUOUS THROUGH THE NEXT 24 HOURS BUT AGAIN WILL NEED LOW LEVEL SATURATION BEFORE VIS GETS AFFECTED. A COUPLE STORMS HAVE FORMED SW OF DFW TRACON AND WILL SHOW VCTS THROUGH 9Z THIS MORNING AS THESE CELLS MOVE THROUGH. AFTER THAT ANY THUNDER SHOULD BE VERY ISOLATED AND WILL KEEP WEATHER TYPE AS SHRA. GENERALLY IFR CIGS AND MVFR VIS EXPECTED SUNDAY AFTERNOON THROUGH MONDAY MORNING. WINTER POTENTIAL FOR DFW TRACON CONTINUES TO LOOK LOW WITH SUBFREEZING TEMPS NOT EXPECTED SUNDAY NIGHT OR MONDAY WHEN PRECIP IS OCCURRING. RAIN/SNOW LINE EARLY MONDAY MORNING SHOULD STAY JUST NW OF DFW TRACON. TR.92 && .UPDATE... PRECIP CONTINUES TO EXPAND IN AREAL COVERAGE OVER THE NORTHEAST QUADRANT OF THE CWA. LATEST RUC ANALYSIS SHOWS THE STRONG LIFT RESPONSIBLE FOR THE PRECIP ON THE 295K ISENTROPIC SURFACE. 35 KNOT SOUTHERLY WINDS ARE QUICKLY LIFTING MOIST PARCELS FROM 975 MB TO 875 MB AS THE COLDER AIR MASS MOVES EAST. UPPED POPS IN THE 0-6Z TIMEFRAME TO 100 PERCENT FOR AREAS EAST AND NORTH OF A SHERMAN TO DALLAS TO CANTON LINE GIVEN THE EXPECTED INTENSITY OF THIS LIFT AND CURRENT RADAR TRENDS. THE RUC SHIFTS THE BEST LIFT ASSOCIATED WITH THE COLD AIR WEDGE TO THE SOUTH LATER TONIGHT AND WILL HAVE 80 POPS FOR THE SOUTHERN ZONES AFTER 6Z. WIDESPREAD PRECIP IS EXPECTED TOMORROW BEHIND THE FRONTAL BOUNDARY AS WARM/MOIST AIR IS LIFTED OVER THE COLD AIR. BUMPED UP POPS TO 100 PERCENT FOR MOST OF THE CWA EXCEPT FOR THE NORTHWESTERN ZONES FOR THE SUNDAY PERIOD. 85/NH && .PREV DISCUSSION... /ISSUED 321 PM CST SAT DEC 3 2011/ SHORTWAVE DISTURBANCE CONTINUES TO LIFT UP THROUGH THE SOUTHERN PLAINS THIS AFTERNOON RESULTING IN THE SLOW EASTWARD PROGRESSION OF A BAND OF LIGHT TO MODERATE RAIN CURRENTLY ALONG A LINE FROM COMANCHE TO WEATHERFORD TO GAINESVILLE. LOW RAINFALL AMOUNTS FOR MOST AREAS...BUT SOME ISOLATED AMOUNTS TO BETWEEN A QUARTER AND HALF INCH WILL BE POSSIBLE AS THIS BAND MOVES ACROSS NORTH TEXAS. THE RAIN-COOLED AIR HAS RESULTED IN THE OLD FRONT SAGGING TO A GAINESVILLE TO DECATUR TO CISCO LINE THIS AFTERNOON WITH TEMPERATURES IN THE 50S BEHIND THE FRONT WHILE REMAINING IN THE 60S TO LOWER 70S AHEAD OF IT. A FEW EMBEDDED THUNDERSTORMS ARE POSSIBLE...BUT NOT LIKELY THROUGH THIS EVENING. A STRONGER COLD FRONT CAN BE SEEN NOW MOVING THROUGH THE HIGH PLAINS OF EASTERN CO/WESTERN KS THIS AFTERNOON. THE FRONT SHOULD ARRIVE INTO OUR FAR NORTHWEST COUNTIES BY MIDNIGHT...THEN QUICKLY PUSH TO AN ATHENS...WACO...LAMPASAS LINE BY SUNRISE SUNDAY. THE FRONT WILL CLEAR THE REMAINDER OF NORTH TEXAS BY LATE MORNING SUNDAY. THE STRONG COLD FRONT WILL OVERTAKE OUR CURRENT FRONT WITH THE BULK OF MODERATE RAIN AND ISOLATED THUNDERSTORMS OCCURRING AHEAD OF THE FRONT. SOME LIGHT RAIN WILL LIKELY REMAIN BEHIND THE FRONT. HIGHS SUNDAY WILL OCCUR BETWEEN MIDNIGHT AND MIDDAY SUNDAY...WITH FALLING AFTERNOON TEMPERATURES AND GUSTY NORTH WINDS 15 TO 20 MPH AFTER FROPA. THE GUSTY WINDS AND LIGHT RAIN WILL MAKE FOR A RAW AND WET DAY ACROSS NORTH TEXAS...THOUGH OVERALL HEAVIER RAINFALL SHOULD SHIFT TO THE SOUTH AND EAST OF OUR AREA LATE SUNDAY AFTERNOON AND EVENING. A MORE ROBUST SHORTWAVE DISTURBANCE ARRIVES LATE SUNDAY NIGHT INTO MONDAY AND WILL INDUCE ISENTROPIC ASCENT ONCE AGAIN WITH A COLD AND AT TIMES MODERATE RAIN ACROSS NORTH TEXAS. TEMPERATURES WILL LIKELY FALL INTO THE MID 30S BY DAYBREAK MONDAY MORNING ACROSS AREAS TO THE NORTHWEST OF THE DFW METROPLEX. MOST MODELS...INCLUDING SREF AND WRF ...ARE HOLDING THE DEEPER COLD AIR OFF TO THE NORTHWEST OF THIS AREA THROUGH MIDDAY MONDAY. DESPITE TEMPERATURES JUST ABOVE FREEZING...A RAIN/SNOW MIX COULD OCCUR ACROSS THIS AREA MONDAY MORNING AS THERMAL PROFILES COOL QUICKLY TO OR JUST BELOW FREEZING. COLD RAIN IS EXPECTED ELSEWHERE. REGARDING THE WINTER WEATHER POTENTIAL...AS THE SHORTWAVE MOVES QUICKLY ACROSS THE AREA...DRYING ABOVE THE BOUNDARY LAYER WILL FOLLOW IN ITS WAKE. AS A RESULT OF THIS DRYING...ICE CRYSTAL PRODUCTION WILL BE LIMITED AND A MIXTURE OF VERY LIGHT RAIN/ DRIZZLE/FLURRIES IS LIKELY. ISENTROPIC DOWNSLOPE CONTINUES DURING THE OVERNIGHT HOURS INTO TUESDAY MORNING WITH CLOUDS GRADUALLY DECREASING. NORTH TEXAS WILL REMAIN UNDER THE INFLUENCE OF CYCLONIC FLOW ALOFT THROUGH THE WEEK...RESULTING IN PARTLY CLOUDY SKIES AND COLD CONDITIONS. THE STUBBORN UPPER LOW FINALLY OPENS UP AND LIFTS OUT TUES NIGHT AND EARLY WEDNESDAY WITH SOME LIFT RETURNING TO THE NORTH TEXAS. AT THIS TIME...WE FEEL MOISTURE WILL BE TOO LIMITED FOR PRECIPITATION BUT WILL MONITOR CLOSELY. WE CONTINUE TO UNDERCUT MOS HIGH TEMPERATURES SINCE THE COLD AIRMASS IS 5-7 KFT DEEP WITH ONLY A SLOW MODIFICATION BY THURSDAY. NEXT COLD FRONT IS EXPECTED TO ARRIVE FRIDAY...AS ANOTHER SHORTWAVE DISTURBANCE MOVES SOUTHEAST ACROSS THE FRONT RANGE OF THE ROCKIES. GFS IS THE FASTEST WITH THE COLD FRONT...WHILE THE SREF/CANADIAN/AND ARE ECMWF SLOWER. FOR NOW...WILL LEAN TOWARD A SLOW CONSENSUS ON THE FRONT WITH WARMER TEMPERATURES FRIDAY THAN WHAT THE MAV MOS GUIDANCE. WE WILL ALSO LEAVE THIS PERIOD DRY WITH UNCERTAINTIES ON MOISTURE AVAILABILITY AND TIMING OF BOTH SURFACE AND UPPER LEVEL FEATURES. 05/42 && .PRELIMINARY POINT TEMPS/POPS... DALLAS-FT. WORTH, TX 41 45 38 40 29 / 80 100 90 60 20 WACO, TX 48 49 39 44 30 / 70 100 90 60 20 PARIS, TX 49 50 38 44 29 / 100 100 80 70 20 DENTON, TX 38 42 37 38 27 / 70 100 80 60 20 MCKINNEY, TX 42 45 37 41 29 / 100 100 80 60 20 DALLAS, TX 43 47 38 41 30 / 90 100 90 60 20 TERRELL, TX 49 49 39 44 30 / 100 100 90 70 20 CORSICANA, TX 52 52 40 45 31 / 70 100 90 70 20 TEMPLE, TX 54 54 40 46 30 / 80 100 90 60 20 MINERAL WELLS, TX 37 41 34 36 26 / 40 90 70 60 20 && .FWD WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
607 PM CST MON DEC 5 2011 UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE .SHORT TERM...TONIGHT AND TUESDAY. LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW THE STATE OF WISCONSIN LOCATED BETWEEN A COLD FRONT RUNNING UP THE EASTERN SIDE OF THE APPALACHIANS...AND A POLAR SURFACE HIGH STRETCHING ACROSS THE DAKOTAS EARLY THIS AFTERNOON. A WEAK SURFACE TROUGH REMAINS A NUISANCE WHICH HANGS BACK FROM JUST SOUTH OF MILWAUKEE TO EAU CLAIRE. RADAR RETURNS HAVE GRADUALLY ERODED OVER CENTRAL AND EAST-CENTRAL WISCONSIN OVER THE COURSE OF THE DAY...THOUGH BEEFIER RETURNS AND SURFACE OBS SHOW LIGHT SNOW SHOWERS OCCURRING OVER WESTERN WISCONSIN. SOME HOLES IN THE CLOUDS ARE TRYING TO DEVELOP OVER NORTHEAST WISCONSIN...AND PERHAPS INTO CENTRAL WISCONSIN AS WELL. AS THE SURFACE HIGH SHIFTS EAST TONIGHT...CLOUD TRENDS AND TEMPS ARE THE MAIN FORECAST CONCERNS. TONIGHT...HIGH PRESSURE OVER THE NORTHERN PLAINS WILL BUILD EAST OVER THE NORTHERN MISSISSIPPI VALLEY. HOWEVER...FLOW WILL CONTINUE TO BE OUT OF THE NORTH AND LIGHTLY ADVECTING CLOUDS OFF LAKE SUPERIOR. IN ADDITION...12Z GUIDANCE SUPPORTS LINGERING LOW LEVEL CONVERGENCE OVER CENTRAL WISCONSIN THAT WILL KEEP AN AREA OF ENHANCED RH IN PLACE. KEPT A FLURRY MENTION OVER THE FAR WESTERN CWA TO ACCOUNT FOR THIS. WITH PLENTY OF CLOUDS UPSTREAM...HAVE A HARD TIME GOING BELOW MOSTLY CLOUDY CONDITIONS. THERE WILL BE UNDOUBTEDLY SUCKER HOLES THAT WILL DEVELOP WITHIN THE STRATUS...MOSTLY LIKELY WITHIN THE DOWNSLOPING AREAS OF NORTHEAST WISCONSIN. WILL PLAY THE PROBABILITY THAT SCT CONDITIONS DEVELOP THERE...BUT LEAVE MOSTLY CLOUDY CONDITIONS ELSEWHERE...WITH SCT SNOW SHOWERS OVER THE SNOW BELT OF N-C WISCONSIN. LOWS IN THE LOWER TEENS NORTH TO MIDDLE 20S SOUTHEAST. TEMPS COULD BE MUCH COLDER OVER THE SNOW PACK OF N-C WISCONSIN IF HOLES IN THE CLOUDS DO DEVELOP THERE. TUESDAY...HIGH PRESSURE BUILDS INTO THE REGION TOMORROW. ANY SURFACE CONVERGENCE ALONG THE LINGERING TROUGH OVER CENTRAL WISCONSIN IS PROGGED TO DISSIPATE IN THE MORNING...BUT MODELS INDICATE THE REMNANTS OF THE ENHANCED RH MOVING EAST AS LIGHT SW FLOW DEVELOPS. ALSO SEE SIGNS OF STEEP LOW LEVEL LAPSE RATES WITH HEATING OF THE DAY THAT POINTS TOWARDS STRATO-CU DEVELOPING. WITH CLOUDS UNDER THE HIGH CURRENTLY...WILL SIDE MORE PESSIMISTICALLY WITH CLOUD COVER...WHICH WILL KEEP MOSTLY CLOUDY CONDITIONS OVER NORTH-CENTRAL WISCONSIN FOR THE MORNING...AND PARTLY CLOUDY CONDITIONS EVERYWHERE FOR THE AFTERNOON. HIGHS RANGING FROM THE LOWER 20S NORTH TO AROUND 30 DEGREES SOUTHEAST. .LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...THE MAIN FCST CONCERN IS THE ARRIVAL OF ARCTIC AIR LATER IN THE WEEK. SHORT-WAVE ENERGY CURRENTLY OVER THE GULF OF ALASKA WILL TOP THE WEST COAST RIDGE...THEN HELP TO CARVE A BROAD TROF OVER THE CENTRAL U.S. BY THURSDAY. A SURGE OF ARCTIC AIR IS EXPECTED TO ARRIVE IN WI ON THURSDAY...WITH H8 TEMPS PLUMMETING TO -16 TO -20 C BY FRIDAY. THIS WILL LEAD TO OUR COLDEST TEMPERATURES SO FAR THIS SEASON. THE COLDER WEATHER WILL NOT LAST LONG...AS SOUTHWEST WINDS DEVELOP IN THE WAKE OF THE RETREATING ARCTIC HIGH OVER THE WEEKEND. H8 TEMPS ARE EXPECTED TO SURGE TO 0 TO +4 C BY SATURDAY NIGHT/SUNDAY. A WEAK COLD FRONT IS EXPECTED TO MOVE THROUGH THE REGION ON WEDNESDAY...WITH A STRONGER ARCTIC FRONT ARRIVING ON THURSDAY. HAVE BEEN WATCHING FOR POSSIBLE SNOW DEVELOPMENT AS THE RRQ OF A STG UPPER JET INTERACTS WITH THE ARCTIC FRONT THURSDAY NIGHT INTO FRIDAY...BUT THE CONCENSUS OF THE MODELS...INCLUDING THE 12Z/MON ECMWF...IS THAT SNOW WILL DEVELOP TO OUR SOUTH AND EAST. WILL NOT CARRY ANY POPS AT THIS TIME...BUT SUBSEQUENT SHIFTS WILL STILL NEED TO KEEP AN EYE ON THIS. DESPITE THE PRESENCE OF A COLD AIR MASS FROM WEDNESDAY THROUGH FRIDAY NIGHT...WIND TRAJECTORIES WILL BE TOO WESTERLY FOR ANY APPRECIABLE LK-EFFECT SNOW. MODELS HAVE BACKED OFF SLIGHTLY ON THE MAGNITUDE OF THE COLD SNAP LATE IN THE WORK WEEK...WITH H8 TEMPS TRENDING A FEW DEGREES WARMER. EVEN SO...STILL EXPECT MAX TEMPS TO BE ABOUT 10 DEGREES BLO NORMAL ON FRIDAY. THE COLDER WEATHER WILL BE SHORT-LIVED... WITH ABOVE NORMAL TEMPERATURES QUICKLY RETURNING BY SUNDAY. A WEAK COLD FRONT MAY IMPACT THE REGION ON MONDAY...BUT SHOULD NOT HAVE ANY SIGNIFICANT IMPACT ON OUR WEATHER. && .AVIATION...A VFR SCT SKY CONDITION DEVELOPING OVER NORTHEAST WISCONSIN OR JUST NORTH OF GRB LATE THIS AFTERNOON. SCATTERED MVFR CIGS AND VSBYS WILL ALSO PERSIST OVER FAR NORTH CENTRAL WISCONSIN TONIGHT. OTHERWISE THE REST OF THE REGION CAN EXPECT MAINLY VFR CIGS WITH SOME PATCHY MFR CIGS OVER CENTRAL WISCONSIN TUESDAY MORNING. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
515 PM CST MON DEC 5 2011 .SHORT TERM... 245 PM CST MON DEC 5 2011 BIGGEST FORECAST CONCERN IS ON CLOUDS AND TEMPERATURES...WITH LIGHT PRECIPITATION CHANCES THIS EVENING ALSO A CONCERN. 18Z WATER VAPOR IMAGERY SHOWS SHORTWAVE TROUGH OVER MINNESOTA...WHILE AT THE SURFACE A WEAK TROUGH WAS WORKING ITS WAY THROUGH THE FORECAST AREA...BUT WAS WEAKENING WITH TIME. THIS COMBINATION WAS PRODUCING WEAK LIFT THROUGH SATURATED LOWER LAYER AND THUS SURFACE REPORTS INDICATING MAINLY LIGHT SNOW AND FLURRIES...WITH SOME PATCHY FREEZING DRIZZLE. 05.12Z MODELS AGAIN IN GOOD AGREEMENT WITH THEIR MASS FIELDS. THERE IS SOME DIFFERENCES IN SPEED OF COLDER PLUNGE OF AIR ON THURSDAY...WITH THE NAM THE FASTEST. ONLY OTHER DIFFERENCE NOTED IS GFS A LITTLE FASTER IN PUSHING THE STRATUS OUT ON TUESDAY. FOR TONIGHT...SHORTWAVE IN MINNESOTA ROTATES INTO NORTHWEST WISCONSIN. MODEL SOUNDINGS INDICATE WEAK LIFT CONTINUES IN THE SATURATED LOWER LAYER DURING THE EVENING. 05.15Z RUC SOUNDINGS QUESTIONABLE WITH REGARDS TO ICE IN THE CLOUD LAYER...WHILE NAM SOUNDINGS SUGGEST MORE ICE. BASED ON REPORTS FROM THIS AFTERNOON MENTION FLURRIES AND PATCHY FREEZING DRIZZLE FOR THE EVENING HOURS. WITH THE CLOUDS DID GO ON THE WARMER SIDE OF THE GUIDANCE NUMBERS FOR LOWS TONIGHT. ON TUESDAY...GFS A LITTLE FASTER IN PUSHING THE STRATUS OUT OF THE AREA...WHILE THE NAM KEEPS 850MB-925MB MOISTURE OVER THE AREA THROUGHOUT THE DAY AND NOT CLEARING UNTIL EVENING. DID TAKE A COMPROMISE...WITH A CLEARING TREND FROM WEST TO EAST DURING THE AFTERNOON HOURS. TEMPERATURES WILL BE TRICKY WITH THE CLOUDS...BUT WITH THE MORE PESSIMISTIC OUTLOOK DID GO WITH THE COOLER OF THE GUIDANCE NUMBERS. DO EXPECT CLEAR SKIES...AT LEAST FOR A SHORT PERIOD OF TIME TUESDAY NIGHT. HOWEVER...ANOTHER SHORTWAVE BEGINS TO DROP SOUTHWARD OUT OF SOUTHERN CANADA LATE TUESDAY NIGHT...AND MODELS HINT AT AN INCREASE IN HIGH LEVEL CLOUDS. THESE CLOUDS THEN DROP ACROSS THE AREA ON WEDNESDAY AND WEDNESDAY NIGHT AHEAD OF THE ASSOCIATED COLD FRONT. TEMPERATURES LOOK TO BE A LITTLE MILDER AHEAD OF THE FRONT...BUT STILL BELOW NORMAL WITH HIGHS FROM THE MIDDLE 20S IN THE SNOW COVERED LOCATIONS...TO THE LOWER 30S IN THE NON SNOW COVERED AREAS. ON THURSDAY COLD AIR BEGINS TO SURGE INTO THE AREA BEHIND THE FRONT. AS MENTIONED BEFORE NAM QUICKER IN MOVING THIS COLD AIR INTO THE REGION AND AGAIN USED A MODEL CONSENSUS FOR HIGHS. 05.12 GFS AND ECMWF ALSO GENERATING SOME LIGHT PRECIPITATION ALONG THE LEADING EDGE OF THE COLD AIR ACROSS IOWA IN BAND OF WEAK FRONTOGENESIS. WITH THE BULK OF PUSH OF COLD AIR THURSDAY NIGHT...DID ADD SOME LOWER END SNOW PROBABILITIES ACROSS NORTHEAST IOWA AND SOUTHWEST WISCONSIN. .LONG TERM... 245 PM CST MON DEC 5 2011 A DRY NORTHWEST LOW PATTERN WILL CONTINUE FOR FRIDAY AND SATURDAY AND THIS WILL LEAD TO BELOW NORMAL TEMPERATURES. THE FLOW WILL BECOME MORE ZONAL ON SUNDAY AS A TROUGH BUILDS INTO THE WESTERN CONUS. AS THE TROUGH PROGRESSES INTO THE CENTRAL SECTIONS OF THE COUNTRY...THE FLOW WILL BECOME MORE SOUTHWESTERLY. DRY CONDITIONS WILL CONTINUE THROUGH MONDAY...BUT WITH A MORE SOUTHERLY WIND...TEMPERATURES WILL WARM SATURDAY AND SUNDAY...WITH HIGHS EXPECTED IN THE 30S BOTH SUNDAY AND MONDAY. && .AVIATION... 515 PM CST MON DEC 5 2011 PERSISTENT LOW LEVEL SATURATION...PER RH FIELDS AND BUFKIT SOUNDINGS...SUGGEST THAT THE MVFR CIGS WILL HOLD INTO TUE AFTERNOON/EVENING. AN UPPER LEVEL SHORTWAVE TROUGH WILL HELP SWEEP THE LOW STRATUS TO THE EAST...AND MOST OF TUE NIGHT LOOKS SCT-SKC. BY WED MORNING CLOUDS ASSOCIATED WITH THE TROUGH WILL SLIDE IN...AND THERE COULD BE ANOTHER PERIOD OF MVFR CIGS IN THE AFTERNOON. COULD SEE SOME FLURRIES AT KLSE TONIGHT...AND BUFKIT SOUNDINGS STILL SUGGEST THAT ICE MAY NOT BE IN THE TOP OF THE CLOUD AT TIMES... BRINGING THE POTENTIAL FOR FREEZING DRIZZLE. FEEL -SN IS MORE LIKELY AT THIS MOMENT...AND WILL HOLD WITH THAT FOR NOW. NORTHWEST WINDS WILL SWING TO THE SOUTHWEST BY LATE TUE AFTERNOON...AHEAD OF THAT SHORTWAVE...BUT SHIFT BACK TO THE NORTHWEST ON WED AS THE SYSTEM PASSES EAST. && .ARX WATCHES/WARNINGS/ADVISORIES... 245 PM CST MON DEC 5 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM... RABERDING LONG TERM.... RABERDING AVIATION..... RIECK
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
224 PM CST SUN DEC 4 2011 .SHORT TERM...TONIGHT AND MONDAY. LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A DOUBLE BARRELED LOW PRESSURE MOVING ACROSS THE ONTARIO-QUEBEC BORDER AND THE STRAITS OF MACKINAC...AND A COLD FRONT STRETCHING FROM NORTHERN LOWER MICHIGAN TO THE SOUTHERN MISSISSIPPI VALLEY. WITH NORTHWEST FLOW IN PLACE AND DELTA T/S INCREASING TO 14C...CLOUD COVER HAS BEEN STUBBORN TO DISSIPATE THOUGH PRECIP HAS EXITED TO THE NORTHEAST BY MIDDAY. A SURFACE TROUGH IS TRYING TO DEVELOP OVER NORTHEAST AND CENTRAL WISCONSIN THIS AFTERNOON AND A FEW SNOW SHOWERS/FLURRIES HAVE DEVELOPED OVER THE PAST HOUR. SOME CLEARING NOTED OVER NORTHERN MINNESOTA WHERE DEWPOINTS HAVE FALLEN TO THE LOWER TEENS. WITH NORTHERLY FLOW IN PLACE OVER THE NEXT 24 HOURS...SMALL PRECIP CHANCES AND CLOUD TRENDS ARE THE MAIN FORECAST CONCERNS. TONIGHT... AS HIGH PRESSURE BUILDS OVER THE NORTHERN PLAINS...WEAK CYCLONIC FLOW WILL LINGER ACROSS THE REGION. LOW LEVEL FLOW WILL VEER FROM THE NORTHWEST TO THE NORTH...WHICH WILL KEEP MOISTURE STREAMING OFF LAKE SUPERIOR. AS A RESULT...SCT LAKE EFFECT SNOW SHOWERS WILL PREVAIL OVER THE SNOW BELT OF N-C WISCONSIN FOR THE ENTIRE NIGHT. FARTHER SOUTH...A WEAK SURFACE TROUGH WILL MOVE SOUTH OVER CENTRAL WISCONSIN THIS EVENING. MOISTURE DEPTH WILL EXTEND BEYOND 800MB AND -10C...SO IT SEEMS PLAUSIBLE THAT FLURRIES OR VERY LIGHT SNOW SHOWERS ARE POSSIBLE ALONG THE TROUGH. HAVE ADDED SLIGHTLY MORE TEMPORAL RESOLUTION TO ACCOUNT FOR THIS. OTHERWISE...DO NOT SEE MUCH OF AN OPPORTUNITY FOR CLEARING...EXCEPT IN THE DOWN SLOPING REGIONS OF NORTHEAST WISCONSIN WHERE SOME HOLES MAY DEVELOP...ESPECIALLY LATE TONIGHT. LOWS IN THE UPPER TEENS NORTH TO UPPER 20S SOUTHEAST. MONDAY...ONLY SOME SUBTLE CHANGES HEADING INTO MONDAY. SHORTWAVE ENERGY OVER THE PLAINS WILL LIFT TO THE NORTHEAST OVER NW WISCONSIN...BUT WITH VERY LITTLE IMPACT ON OUR WEATHER. WILL CONTINUE TO HAVE NORTHERLY FLOW TOMORROW WITH SOME MINOR COLD ADVECTION THAT WILL DROP 850MB TEMPS IN THE NEGATIVE LOW TO MID TEENS. LIGHT LAKE EFFECT SNOW SHOWERS WILL PREVAIL OVER THE SNOW BELT OF N-C WISCONSIN...WHILE MOSTLY CLOUDY CONDITIONS WILL BE THE RULE ELSEWHERE. HIGHS IN THE MIDDLE 20S NORTH TO MIDDLE 30S SOUTHEAST. .LONG TERM...MONDAY NIGHT THROUGH NEXT SUNDAY...THE MAIN FCST CONCERN IS THE ARRIVAL OF COLDER ARCTIC AIR LATE IN THE NEXT WORK WEEK. A STRONG UPPER RIDGE WILL COVER THE EASTERN PACIFIC...SOUTHWEST CANADA AND THE WEST COAST OF THE U.S. EARLY IN THE PERIOD...WITH A POSITIVELY-TILTED UPPER TROF MOVG OUT OF THE NORTHERN PLAINS INTO THE WESTERN GREAT LAKES. THIS UPPER TROF WILL MOVE THROUGH WISCONSIN ON MONDAY NIGHT AND TUESDAY...BUT WITH A SFC RIDGE OF HIGH PRESSURE IN PLACE...EXPECT MINIMAL IMPACT ON OUR WEATHER. SHORT-WAVE ENERGY TOPPING THE WESTERN RIDGE AND DIVING INTO THE NORTHERN PLAINS WILL HELP TO CARVE A BROAD TROF OVER THE CENTRAL U.S. BY THURSDAY. A SURGE OF ARCTIC AIR IS EXPECTED TO ARRIVE IN WI ON THURSDAY...WITH H8 TEMPS PLUMMETING TO AROUND -20 C LATE THURSDAY NIGHT INTO FRIDAY. THIS WILL LEAD TO OUR COLDEST TEMPERATURES SO FAR THIS SEASON. THE COLD SNAP WILL BE BRIEF... AS SOUTHWEST WINDS DEVELOP IN THE WAKE OF THE RETREATING ARCTIC HIGH OVER THE WEEKEND. A LARGE RIDGE OF HIGH PRESSURE WILL BUILD INTO NW WI ON MONDAY NIGHT...THEN MOVE THROUGH GRB CWA ON TUESDAY. LINGERING LAKE-EFFECT SNOW SHOWERS OVER NC WI SHOULD COME TO AN END AS THE RIDGE AXIS ARRIVES ON TUESDAY. A WEAK COLD FRONT IS EXPECTED TO MOVE THROUGH THE REGION ON WEDNESDAY...WITH A STRONGER ARCTIC FRONT ARRIVING ON THURSDAY. THE ECMWF HAS BACKED OFF ON THE POTENTIAL FOR SNOW ALONG THE ARCTIC FRONT ON THU NGT/FRI...AND IS FOCUSING FARTHER SE...FROM SOUTHERN WI INTO LOWER MICHIGAN. WILL NEED TO KEEP AN EYE ON THIS OVER THE NEXT FEW DAYS TO SEE IF THIS TREND WILL HOLD. CONFIDENCE IS FAIRLY HIGH FOR THE ARRIVAL OF MUCH COLDER TEMPERATURES LATE IN THE WORK WEEK...ALTHOUGH THE COLD IS EXPECTED TO BE SHORT-LIVED. A WARM FRONT IS EXPECTED TO ARRIVE ON SUNDAY...WITH TEMPERATURES CLIMBING BACK TO ABOVE NORMAL. DESPITE THE PRESENCE OF A COLD AIR MASS FROM WEDNESDAY THROUGH SATURDAY...WIND TRAJECTORIES WILL NOT BE FAVORABLE FOR LK-EFFECT SNOW. && .AVIATION...CYCLONIC FLOW VEERING FROM NORTHWEST TO NORTH WILL BE PREVAILING ACROSS THE REGION THROUGH TOMORROW. WITH FLOW OFF LAKE SUPERIOR...WILL BE HARD PRESSED TO SEE SOME CLEARING OVER THE TAF SITES. SOME HOLES WILL LIKELY DEVELOP OVER THE FOX VALLEY WITH TEMPORARY VFR CIGS...BUT MVFR CIGS WILL PREVAIL THROUGH LATE TONIGHT. SOME SNOW SHOWERS/FLURRIES WILL OCCASIONALLY IMPACT RHI...AND POSSIBLY AUW/CWA THIS EVENING WHEN A WEAK SURFACE TROUGH DROPS SOUTH. SOME MINOR IMPROVEMENT OF CIGS EXPECTED ON MONDAY. MPC && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ MPC/KIECKBUSCH
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1141 AM CST SUN DEC 4 2011 .SHORT TERM...TODAY THROUGH TUESDAY NIGHT 324 AM CST SUN DEC 4 2011 MAIN FORECAST CONCERN NOW THAT THE PRECIPITATION IS EXITING/DIMINISHING IS WHEN CLOUDS WILL CLEAR. CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED RIDGING STILL OVER THE EAST PACIFIC AND ALONG THE EAST COAST OF THE U.S....AND TROUGHING IN-BETWEEN FROM HUDSON BAY SOUTHWEST INTO ARIZONA. IMPORTANT FEATURES TO NOTE INCLUDE A SHORTWAVE NEAR EAU CLAIRE WI ON THE EAST SIDE OF THE UPPER TROUGH...AND TWO SHORTWAVES OVER MONTANA ON THE BACK SIDE OF THE UPPER TROUGH. THE FORMER SHORTWAVE IN CONJUNCTION WITH PLENTIFUL MOISTURE AND LOW TO MID-LEVEL FRONTOGENESIS BROUGHT THE WIDESPREAD PRECIPITATION TO THE AREA LAST NIGHT. DRY SLOT NOTED IN WATER VAPOR COMBINED NOW WITH THE SHORTWAVE MOVED THROUGH...RESULTING IN SOME SUBSIDENCE...HAS ALLOWED PRECIPITATION TO REALLY DIMINISH DURING THE PAST 4-6 HOURS. IT APPEARS MODELS YESTERDAY MAY HAVE OVERDONE THE LOW LEVEL ISENTROPIC LIFT FOR THE CURRENT EARLY MORNING HOURS... GIVEN THAT THEY NOW SHOW NO ISENTROPIC LIFT AND SEEING THE PRECIPITATION DIMINISH ON RADAR. THEREFORE...THE CONCERN ABOUT THE DRY SLOT CLEARING OUT ICE AND RESULTING IN FREEZING PRECIPITATION IS NOT AS GREAT. IN ADDITION... SURFACE TEMPERATURES HAVE STRUGGLED TO FALL BELOW FREEZING WHERE IR CLOUD TOP TEMPERATURES INDICATE ICE HAS BEEN LOST. REGARDING THE SURFACE...SEA LEVEL PRESSURE ANALYSIS SHOWS A 1008MB LOW NEAR MANITOWOC WI. PLENTY OF CLOUDS EXTEND WEST FROM THE LOW...BACK INTO THE EASTERN DAKOTAS. UPSTREAM...ANOTHER BUT MUCH WEAKER SURFACE LOW IS NOTED NEAR WILLISTON ASSOCIATED WITH ONE OF THE MONTANA SHORTWAVES. TODAY AND TONIGHT...A SHORTWAVE IN EASTERN MONTANA IS PROGGED TO MOVE INTO SOUTH DAKOTA TODAY AND INTO NORTHWEST WISCONSIN TONIGHT. THE TRACK OF THE SHORTWAVE SUGGESTS ALL OF THE FORCING WILL STAY NORTH AND WEST OF THE AREA. THIS IS CONFIRMED TOO BY QG PLOTS. IN ADDITION...IT APPEARS MUCH OF THE CLOUD COVER ASSOCIATED WITH THE SHORTWAVE WILL STAY TO THE NORTHWEST. SO THIS LEAVES THE CURRENT CLOUD COVER AND SYSTEM GOING THROUGH THE MAIN CONCERN. WITH STRATUS EXTENDING SO FAR WEST...GRADUAL SUBSIDENCE OCCURRING TODAY IN THE WAKE OF THE SYSTEM AND THE LOW SUN ANGLE...THINKING A VERY PESSIMISTIC TREND MIGHT BE THE WAY TO GO. LIKE THE 04.00Z NAM INDICATING THE STRATUS STAYS IN PUT ACROSS THE AREA TODAY WITH ONLY SLOW CLEARING TONIGHT FOR WESTERN AREAS. CONCERNED THAT EVEN THE NAM MIGHT BE TOO FAST TONIGHT AS THE 900-950MB WINDS TURN FROM THE NORTHWEST TO NORTH. COMBINED WITH THE RECENT MOISTURE...CLOUDS MAY ACTUALLY LOWER IN CEILING HEIGHT VERSUS CLEARING. LAST CONCERN IS PRECIPITATION...BOTH THIS MORNING AND POSSIBLY OUT OF THE STRATUS DECK TONIGHT. GIVEN DIMINISHING RADAR RETURNS AND DRY FORECASTS INDICATED BY THE 04.00Z NAM/GFS/ECMWF FOR 12-18Z TODAY...HAVE REALLY DRIED OUT THIS MORNING. IN FACT...THERE MAY NOT BE MUCH GOING ON AFTER 12Z. WITH PRECIPITATION RAPIDLY DIMINISHING...WILL CANCEL THE ADVISORY HERE AT 4 AM. TONIGHT...THE 04.00Z NAM/GFS SHOW SOME LIGHT QPF OVER THE NORTH HALF OF WISCONSIN. APPEARS TO RESULT FROM LOW LEVEL CONVERGENCE...ASSOCIATED WITH SURFACE TROUGHING LINGERING BACK FROM THE CURRENT AREA OF LOW PRESSURE NEAR GRB. HAVE ADDED A 20 PERCENT CHANCE OF SNOW INTO THE FORECAST TO ACCOUNT FOR THIS POSSIBILITY. OTHERWISE...TEMPERATURES LOOK LIKE THEY SHOULD STRUGGLE TO RISE TODAY WITH 850MB TEMPS FALLING TO AT LEAST -6 TO -8C AND CLOUDS STAYING PUT. MAYBE A 1 OR 3 DEGREE F RISE IS POSSIBLE FROM THE 6 AM TEMPERATURE. WITH MORE CLOUDS ANTICIPATED TONIGHT...BROUGHT LOW TEMPERATURES UP A FEW DEGREES...ESPECIALLY ALONG AND EAST OF THE MISSISSIPPI RIVER WHERE CLOUDS ARE MORE CERTAIN. WHERE CLOUDS CLEAR OUT...TEMPERATURES COULD FALL INTO THE UPPER SINGLE DIGITS. MONDAY THROUGH TUESDAY NIGHT...BIG STORY/CONCERN HERE IS FORECASTING WHEN THE STRATUS WILL DISSIPATE AND ANY POTENTIAL PRECIPITATION OUT OF IT. UPPER TROUGH SITUATED OVER THE NORTHERN PLAINS IS FORECAST TO MARCH SOUTHEAST DURING THIS PERIOD...IN RESPONSE TO A POWERFUL UPPER TROUGH DIGGING FORMING OVER CENTRAL CANADA. NORTH TO NORTHEAST LOW LEVEL FLOW IS LIKELY MONDAY INTO MONDAY NIGHT WITH HIGH PRESSURE BUILDING INTO THE NORTHERN PLAINS. THIS FLOW SHOULD DO A DECENT JOB IN HOLDING IN THE STRATUS BELOW THE SUBSIDENCE INVERSION...UNTIL MAYBE LATE MONDAY NIGHT WHEN THERE IS SUGGESTION THE FLOW BACKS NORTHWEST TO BRING IN SOME DRIER LOW LEVEL AIR. IN ADDITION...THAT TROUGH MENTIONED IN THE TONIGHT DISCUSSION IS PROGGED TO DROP SOUTHWEST DUE TO THE LOW LEVEL FLOW. CONVERGENCE ALONG THIS TROUGH COULD RESULT IN SOME FLURRY ACTIVITY AND HAVE ADDED IT TO THE FORECAST. 04.00Z CANADIAN MODEL IS EVEN MORE AGGRESSIVE AND SHOWING A FEW HUNDREDTHS. IF OTHER MODELS...SUCH AS THE NAM/GFS START TO SHOW THIS IN LATER RUNS...MAY NEED TO HAVE SOME HIGHER CHANCES ADDED. BETTER POTENTIAL FOR CLEARING EXISTS TUESDAY AS THE SURFACE RIDGE MOVES IN AT THE SAME TIME WITH DAYTIME HEATING...SO INDICATED CLEARING STARTING HERE. UPPER RIDGING THEN BUILDS OVER THE AREA FOR TUESDAY NIGHT AHEAD OF THE POWERFUL UPPER TROUGH...MAINTAINING DRY CONDITIONS WITH GENERALLY MOSTLY CLEAR SKIES. FOR TEMPERATURES... LOOK FOR A COOLING TREND AS THE UPPER TROUGH MOVES IN. DID RAISE LOW TEMPERATURES UP MONDAY NIGHT IN THE CLOUDY SKY AREA...CLOSER TO THE 2 METER NAM12 GUIDANCE. OTHERWISE...A BLEND OF GUIDANCE SEEMED REASONABLE. .LONG TERM...WEDNESDAY THROUGH SATURDAY NIGHT 324 AM CST SUN DEC 4 2011 AFTER WHAT WAS SOME UNCERTAINTY IN THE LONG TERM FORECAST...CAUSED ESPECIALLY BY THE 03.12Z ECMWF SUGGESTING A POSSIBLE ADVISORY-TYPE SNOW MOVING THROUGH FRIDAY/FRIDAY NIGHT...ALL MODELS HAVE COME BACK INTO GREAT AGREEMENT ON THE UPPER AND SURFACE PATTERNS THROUGHOUT THE LONG TERM. IN FACT...THEY LOOK A LOT LIKE WHAT WAS SHOWN BY THE 03.00Z CYCLE. SO FOR NOW WILL CONSIDER THE 03.12Z ECMWF AN ODD OUTLIER. A WEST-NORTHWEST FLOW UPPER PATTERN BEGINS THE LONG TERM...ON THE SOUTH SIDE OF THE POWERFUL TROUGH DROPPING INTO SOUTHERN CANADA. A COLD FRONT LOOKS TO SLIDE THROUGH THE FORECAST AREA ON WEDNESDAY...ENDING A BRIEF WARM SURGE ALOFT CAUSED BY THE UPPER RIDGE. THEN FOR WEDNESDAY NIGHT AND THURSDAY...A SHORTWAVE TROUGH IS FORECAST TO DIG DOWN THE WEST SIDE OF THE CANADA UPPER TROUGH...CAUSING AN UPPER JET TO STRENGTHEN DOWNSTREAM OVER NORTHERN WISCONSIN. RIGHT ENTRANCE REGION FORCING OF THIS JET SHOULD INDUCE SOME MID-LEVEL FRONTOGENESIS...AND COMBINED WITH A LITTLE MOISTURE MAY PRODUCE A BAND OF LIGHT SNOW OVER FAR SOUTHERN SECTION THURSDAY NIGHT. INCLUDED A 20 PERCENT CHANCE FOR THIS. BIGGER IMPACT IS ON FRIDAY WHEN THE SHORTWAVE TROUGH MOVES ACROSS...CAUSING 850MB TEMPS TO TANK FROM -9 TO -13C ON THURSDAY TO AROUND -20C ON FRIDAY. NEEDLESS TO SAY...BELOW NORMAL TEMPERATURES LIKELY. A DRY AND SLOW WARMING TREND SHOULD THEN ENSUE HEADING INTO THE WEEKEND IN RESPONSE TO THE MODELS FORECASTING THE UPPER FLOW BECOMING MORE ZONAL. IN FACT...THE LATEST 04.00Z ECMWF SUGGESTS HIGHS APPROACHING 40 FOR NEXT SUNDAY AS A SURGE OF DOWNSLOPED WARMED PACIFIC AIR FLOWS INTO THE AREA. && .AVIATION...THROUGH 18Z MONDAY 1141 AM CST SUN DEC 4 2011 LOW LEVEL MOISTURE IN PLACE ACROSS THE REGION WILL CONTINUE TO PRODUCE MAINLY MVFR CEILINGS AT THE TAF SITES THROUGH LATE TONIGHT...WITH CEILINGS IN THE 1000 TO 1500 FT RANGE. AN UPPER LEVEL SHORTWAVE MOVING ACROSS THE AREA MAY PRODUCE SOME FLURRIES ACROSS THE TAF SITES AS IT MOVES THROUGH DURING THE EVENING AND OVERNIGHT HOURS. FORECAST SOUNDINGS SHOW A SMALL POSSIBILITY OF LOSING ICE ALOFT...WHICH COULD LEAD TO LIGHT FREEZING DRIZZLE. CONFIDENCE LOW ON THIS OCCURRING SO HAVE NOT INCLUDED IT IN THE TAFS AT THIS TIME. PLAN ON MVFR CONDITIONS AT KLSE THROUGH THE FORECAST PERIOD. THE STRATUS IS EXPECTED TO BECOME BKN TO SCT AT KRST AROUND 08Z TONIGHT...WHICH MAY PROVIDE A PERIOD OF VFR CONDITIONS LATE TONIGHT INTO EARLY MONDAY MORNING. LOOK FOR NORTHWEST WINDS AT 6 TO 10 KTS THROUGH THE FORECAST PERIOD. && .ARX WATCHES/WARNINGS/ADVISORIES... 324 AM CST SUN DEC 4 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...AJ LONG TERM....AJ AVIATION.....WETENKAMP
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
603 AM CST SUN DEC 4 2011 UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE .UPDATED...CONCERNING HEADLINES. AVAILABLE REPORTS IN THE ADVISORY AREA SO FAR THIS EVENING RANGE UP TO 2 INCHES. IR LOOP SHOWS BEST ENHANCEMENT HAS QUICKLY SHIFTED NORTHEASTWARD INTO UPPER MICHIGAN. RADAR AND OBS ACROSS THE REGION INDICATE THE RAIN SNOW LINE EXTENDS FROM NORTHWEST IOWA TO RST TO STE TO JUST SOUTH OF IMT. A SURFACE LOW WAS OVER SOUTHERN IOWA EARLY THIS EVENING AND WILL BE ENTERING SOUTHWEST WISCONSIN LATE THIS EVENING AND NEARLY TRACKING ALONG THE RAIN SNOW LINE OVERNIGHT. A LARGE AREA OF RAIN WAS IN THE WARM SECTOR OF THE LOW OVER IOWA AND SOUTHERN WISCONSIN MOVING TOWARD EASTERN WISCONSIN. PARTS OF EASTERN WISCONSIN MAY SEE UP TO AN ADDITIONAL INCH OF RAIN OVERNIGHT. BUT BACK TO THE ADVISORY...BEST SNOW GROWTH REGION WAS OVER NORTHWEST WISCONSIN AND MAY INCLUDE WESTERN PORTIONS OF ONEIDA AND VILAS COUNTIES. THIS SNOW GROWTH REGION IS PROGGED TO SAG INTO NORTH CENTRAL WISCONSIN OVERNIGHT AS THE H8 LOW AND SURFACE LOW TRACKS OVER. NOT OUT OF THE QUESTION A WARNING MAY BE NEEDED AS THESE MORE FAVORABLE DYNAMICS PLAY A ROLE...BUT FOR NOW WILL CONTINUE THE HIGH END ADVISORY. TDH && .PREV DISCUSSION...ISSUED AT 505 PM CST SAT DEC 3 2011... SHORT TERM...TONIGHT AND SUNDAY. LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A DEVELOPING LOW PRESSURE SYSTEM MOVING NORTHEAST OVER SOUTH-CENTRAL KANSAS JUST AHEAD OF A SHORTWAVE TROUGH. ATTACHED TO THE SURFACE LOW TO THE NORTHEAST RUNS A COLD FRONT OVER CENTRAL IOWA INTO NORTHWEST WISCONSIN. FIRST BATCH OF PRECIP IS RIDING ALONG THE 850MB BAROCLINIC ZONE OVER THE SOUTHEASTERN HALF OF WISCONSIN THOUGH SOME BREAKS ARE SPREADING OVER EASTERN IOWA AND NORTHERN ILLINOIS...THAT MAY SPELL A BREAK IN THE PRECIP FOR A BRIEF PERIOD LATE THIS AFTERNOON OVER E-C WISCONSIN. THE MAIN AXIS OF PRECIP...HOWEVER... EXISTS JUST TO THE EAST OF THE SURFACE LOW ON THE NOSE OF A 60 KT LLJ AND UPPER DIVERGENT AREA WITHIN THE COUPLED JET. SOME HIGHER REFLECTIVITIES ARE ALSO DEVELOPING OVER WESTERN WISCONSIN WITHIN A STRENGTHENING FGEN ZONE...SO WILL JUST START THE WINTER HEADLINES WITH THE AFTERNOON PACKAGE. AS THE LOW TRACKS NORTHEAST OVER THE NEXT 24 HOURS...THE OBVIOUS CONCERNS ARE SNOW AMOUNTS AND HEADLINES. TONIGHT...FOLLOWED A SREF/GFS BLEND TONIGHT...WHICH SPLITS THE DIFFERENCE BETWEEN THE STRONGER NAM AND WEAKER ECMWF WHILE KEEPING THE CONSENSUS TRACK. LOW PRESSURE OVER THE CENTRAL PLAINS WILL RAPIDLY MOVE NE TOWARDS THE MID-MISSISSIPPI VALLEY THIS EVENING...AND NORTHERN LAKE MICHIGAN BY 12Z SUNDAY. AHEAD OF THE LOW...A BEEFY LLJ WILL SHIFT INTO SOUTHERN WISCONSIN THIS EVENING...THEREBY INCREASING CONVERGENCE ALONG THE STALLED BAROCLINIC ZONE STRETCHING ACROSS THE STATE...AND 850-700MB FGEN IN THE PROCESS. COMBINED WITH STRONG QG FORCING FROM SHORTWAVE ENERGY AND A WIDE OPEN GULF (PWATS 150-200 PCT OF NORMAL)...THE BEEFY SLUG OF PRECIP OVER THE PLAINS WILL HAVE NO TROUBLE SPREADING ACROSS THE STATE THIS EVENING. PTYPE REMAINS PROBLEMATIC AS THE 12Z MODEL RUNS HAVE TRENDED SLIGHTLY WARMER WITH THE THERMAL PROFILE AS THE LOW PUSHES WARMER AIR ALOFT SLIGHTLY FARTHER NORTH THAN PREVIOUS RUNS. THIS WILL PLACE THE RAIN-SNOW MIX AREA FROM WOOD COUNTY TO NORTHERN OCONTO AND MARINETTE. NORTH OF THE RAIN-SNOW LINE SHOULD RESIDE THE AXIS OF HEAVIEST SNOWFALL...WHICH LINES UP WITH THE EXTRAPOLATED SOUTHERN EDGE OF THE COMMA HEAD FROM APPROX MERRILL TO CRANDON. WITH SLIGHTLY COLDER AIR IN PLACE COMPARED TO THE FIRST SNOW STORM IN NOVEMBER...SNOW RATIOS WILL RUN BETWEEN 10-14:1 OVER THIS AREA ACCORDING TO THE COBB SNOWFALL ALGORITHM. WITH QPFS AROUND 0.4 TO 0.5 INCHES...THIS AMOUNTS TO A GOOD 4-6 INCH SWATH OF SNOW TONIGHT (5 TO 7 INCHES OVERALL)...THOUGH THE BULK OF THE PRECIP WILL LIKELY FALL THIS EVENING. THE FOX VALLEY AND LAKESHORE WILL RESIDE WITHIN THE WARM SECTOR OF THE STORM...WHICH MEANS MOSTLY RAIN TONIGHT...THOUGH SOME SNOW MAY MIX IN LATE. ENTERTAINED SOME THOUGHTS OF UPGRADING TO A WARNING GIVEN THE HEAVY SNOW OBS UPSTREAM...BUT GIVEN THE RELATIVELY LOW IMPACT OF THE SNOW (DURING THE NIGHT ON A WEEKEND)...WILL STICK WITH ADVISORY HEADLINES. ALSO THOUGHT ABOUT TRIMMING THE ADVISORY TO THE NW BY A ROW OF COUNTIES...BUT COORDINATION WITH SURROUNDING OFFICES YIELDED A RELUCTANCE...DUE TO THE SLOPPINESS OF THE MIX AND POTENTIAL FOR FREEZING DRIZZLE. AS A RESULT...WILL KEEP CURRENT HEADLINES AS THEY CURRENTLY STAND BUT STRESS THE HEAVY SNOWFALL RATES ARRIVING THIS EVENING. SUNDAY...THE LOW PRESSURE WILL QUICKLY EXIT TO SOUTHEAST ONTARIO BY 18Z SUNDAY BUT WILL HAVE THE BACK EDGE OF THE COMMA HEAD SHIFTING NE OVER N-C AND FAR NORTHEAST WISCONSIN. SOME MID-LEVEL FGEN WILL LINGER WHICH WILL RESULT IN ANOTHER HALF INCH TO AN INCH OVER N-C WISCONSIN EARLY IN THE MORNING. BUT OTHERWISE...SNOW WILL BE TAPERING DOWN TO JUST FLURRIES IN THE MORNING...WHILE COLDER AIR FILTERS ACROSS THE REGION. LOW LEVEL TROUGHINESS AND CYCLONIC FLOW WILL HANG AROUND FOR MUCH OF THE DAY...SO NOT ANTICIPATING MUCH CLEARING TOMORROW. HIGHS MAINLY IN THE LOW TO MIDDLE 30S. LONG TERM...SUNDAY NIGHT THROUGH NEXT SATURDAY...THE MAIN FCST CONCERNS WILL BE MINOR LAKE EFFECT SNOW POTENTIAL OVER NORTHERN WI EARLY IN THE PERIOD...THEN THE POTENTIAL FOR SNOW AND MUCH COLDER TEMPERATURES WITH AN ARCTIC FRONTAL PASSAGE LATE NEXT WEEK. A STRONG...HIGH AMPLITUDE RIDGE WILL COVER THE EASTERN PACIFIC... WESTERN CANADA AND THE WEST COAST OF THE U.S. EARLY IN THE PERIOD... WITH A POSITIVELY-TILTED UPPER TROF EXTENDING FROM CENTRAL CANADA INTO THE SOUTHWEST UNITED STATES. THIS UPPER TROF WILL MOVE THROUGH WISCONSIN ON TUESDAY...WITH LITTLE IMPACT ON OUR WEATHER. SHORT-WAVE ENERGY WILL TOP THE WESTERN RIDGE EARLY NEXT WEEK...THEN EVENTUALLY HELP TO CARVE A BROAD TROF OVER THE CENTRAL U.S. BY THU/FRI. A SURGE OF ARCTIC AIR IS EXPECTED TO ARRIVE IN WI LATE IN THE WEEK... WITH H8 TEMPS PLUMMETING TO AROUND -20 C. THIS WILL LEAD TO OUR COLDEST TEMPERATURES SO FAR THIS SEASON. A LARGE RIDGE OF HIGH PRESSURE WILL BE CENTERED OVER THE NORTHERN ROCKIES AND NORTHERN PLAINS SUN NGT INTO MON...WITH COLD NORTH FLOW RESULTING IN SCT LAKE-EFFECT SNOW SHOWERS OVER MAINLY NC WI. THE SNOW SHOWERS MAY LINGER INTO MONDAY NIGHT...BUT SHOULD COME TO AN END ON TUESDAY AS THE RIDGE AXIS PUSHES ACROSS WI. A WEAK COLD FRONT IS EXPECTED TO MOVE THROUGH THE REGION ON WEDNESDAY...WITH A STRONGER ARCTIC FRONT ARRIVING SOMETIME DURING THE THU/FRI TIME FRAME. DURING THIS PERIOD...LLVL FLOW IS EXPECTED TO BE TOO WESTERLY FOR LK-EFFECT. THE ECMWF AND A FEW OF THE GFS ENSEMBLE MEMBERS SUGGEST THAT A SFC WAVE WILL DEVELOP ALONG THE ARCTIC BOUNDARY LATE IN THE WEEK...AS THE RRQ OF A STRONG UPPER LEVEL JET PULLS THROUGH THE REGION. IF THIS PLAYS OUT...WE COULD BRING SEE SEVERAL INCHES OF POWDERY SNOW SOMETIME DURING THE THURSDAY NIGHT TO SATURDAY PERIOD. FOR NOW...WILL FOLLOW THE CONCENSUS OF AREA OFFICES...AND JUST MENTION SMALL POPS ACROSS OUR SOUTHERN AND EASTERN COUNTIES ON THU NGT/FRI. THERE IS A HIGHER DEGREE OF CONFIDENCE IN A TREND TOWARD MUCH COLDER TEMPERATURES LATE IN THE WEEK...ALTHOUGH THE NEW ECMWF IS SLOWER WITH THE TIMING OF THE ARCTIC BOUNDARY. SUBSEQUENT FCSTS SHOULD BE BETTER ABLE TO PINPOINT THE FRONTAL TIMING AND SNOWFALL POTENTIAL LATE NEXT WEEK. && .AVIATION...SNOW IS ENDING BUT IFR CIGS WILL LIKELY REMAIN OVER MOST OF THE REGION THROUGH EARLY AFTERNOON AND THEN MVFR IN MOST PLACES. RDM && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
548 AM CST SUN DEC 4 2011 .SHORT TERM...TODAY THROUGH TUESDAY NIGHT 324 AM CST SUN DEC 4 2011 MAIN FORECAST CONCERN NOW THAT THE PRECIPITATION IS EXITING/DIMINISHING IS WHEN CLOUDS WILL CLEAR. CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED RIDGING STILL OVER THE EAST PACIFIC AND ALONG THE EAST COAST OF THE U.S....AND TROUGHING IN-BETWEEN FROM HUDSON BAY SOUTHWEST INTO ARIZONA. IMPORTANT FEATURES TO NOTE INCLUDE A SHORTWAVE NEAR EAU CLAIRE WI ON THE EAST SIDE OF THE UPPER TROUGH...AND TWO SHORTWAVES OVER MONTANA ON THE BACK SIDE OF THE UPPER TROUGH. THE FORMER SHORTWAVE IN CONJUNCTION WITH PLENTIFUL MOISTURE AND LOW TO MID-LEVEL FRONTOGENESIS BROUGHT THE WIDESPREAD PRECIPITATION TO THE AREA LAST NIGHT. DRY SLOT NOTED IN WATER VAPOR COMBINED NOW WITH THE SHORTWAVE MOVED THROUGH...RESULTING IN SOME SUBSIDENCE...HAS ALLOWED PRECIPITATION TO REALLY DIMINISH DURING THE PAST 4-6 HOURS. IT APPEARS MODELS YESTERDAY MAY HAVE OVERDONE THE LOW LEVEL ISENTROPIC LIFT FOR THE CURRENT EARLY MORNING HOURS... GIVEN THAT THEY NOW SHOW NO ISENTROPIC LIFT AND SEEING THE PRECIPITATION DIMINISH ON RADAR. THEREFORE...THE CONCERN ABOUT THE DRY SLOT CLEARING OUT ICE AND RESULTING IN FREEZING PRECIPITATION IS NOT AS GREAT. IN ADDITION... SURFACE TEMPERATURES HAVE STRUGGLED TO FALL BELOW FREEZING WHERE IR CLOUD TOP TEMPERATURES INDICATE ICE HAS BEEN LOST. REGARDING THE SURFACE...SEA LEVEL PRESSURE ANALYSIS SHOWS A 1008MB LOW NEAR MANITOWOC WI. PLENTY OF CLOUDS EXTEND WEST FROM THE LOW...BACK INTO THE EASTERN DAKOTAS. UPSTREAM...ANOTHER BUT MUCH WEAKER SURFACE LOW IS NOTED NEAR WILLISTON ASSOCIATED WITH ONE OF THE MONTANA SHORTWAVES. TODAY AND TONIGHT...A SHORTWAVE IN EASTERN MONTANA IS PROGGED TO MOVE INTO SOUTH DAKOTA TODAY AND INTO NORTHWEST WISCONSIN TONIGHT. THE TRACK OF THE SHORTWAVE SUGGESTS ALL OF THE FORCING WILL STAY NORTH AND WEST OF THE AREA. THIS IS CONFIRMED TOO BY QG PLOTS. IN ADDITION...IT APPEARS MUCH OF THE CLOUD COVER ASSOCIATED WITH THE SHORTWAVE WILL STAY TO THE NORTHWEST. SO THIS LEAVES THE CURRENT CLOUD COVER AND SYSTEM GOING THROUGH THE MAIN CONCERN. WITH STRATUS EXTENDING SO FAR WEST...GRADUAL SUBSIDENCE OCCURRING TODAY IN THE WAKE OF THE SYSTEM AND THE LOW SUN ANGLE...THINKING A VERY PESSIMISTIC TREND MIGHT BE THE WAY TO GO. LIKE THE 04.00Z NAM INDICATING THE STRATUS STAYS IN PUT ACROSS THE AREA TODAY WITH ONLY SLOW CLEARING TONIGHT FOR WESTERN AREAS. CONCERNED THAT EVEN THE NAM MIGHT BE TOO FAST TONIGHT AS THE 900-950MB WINDS TURN FROM THE NORTHWEST TO NORTH. COMBINED WITH THE RECENT MOISTURE...CLOUDS MAY ACTUALLY LOWER IN CEILING HEIGHT VERSUS CLEARING. LAST CONCERN IS PRECIPITATION...BOTH THIS MORNING AND POSSIBLY OUT OF THE STRATUS DECK TONIGHT. GIVEN DIMINISHING RADAR RETURNS AND DRY FORECASTS INDICATED BY THE 04.00Z NAM/GFS/ECMWF FOR 12-18Z TODAY...HAVE REALLY DRIED OUT THIS MORNING. IN FACT...THERE MAY NOT BE MUCH GOING ON AFTER 12Z. WITH PRECIPITATION RAPIDLY DIMINISHING...WILL CANCEL THE ADVISORY HERE AT 4 AM. TONIGHT...THE 04.00Z NAM/GFS SHOW SOME LIGHT QPF OVER THE NORTH HALF OF WISCONSIN. APPEARS TO RESULT FROM LOW LEVEL CONVERGENCE...ASSOCIATED WITH SURFACE TROUGHING LINGERING BACK FROM THE CURRENT AREA OF LOW PRESSURE NEAR GRB. HAVE ADDED A 20 PERCENT CHANCE OF SNOW INTO THE FORECAST TO ACCOUNT FOR THIS POSSIBILITY. OTHERWISE...TEMPERATURES LOOK LIKE THEY SHOULD STRUGGLE TO RISE TODAY WITH 850MB TEMPS FALLING TO AT LEAST -6 TO -8C AND CLOUDS STAYING PUT. MAYBE A 1 OR 3 DEGREE F RISE IS POSSIBLE FROM THE 6 AM TEMPERATURE. WITH MORE CLOUDS ANTICIPATED TONIGHT...BROUGHT LOW TEMPERATURES UP A FEW DEGREES...ESPECIALLY ALONG AND EAST OF THE MISSISSIPPI RIVER WHERE CLOUDS ARE MORE CERTAIN. WHERE CLOUDS CLEAR OUT...TEMPERATURES COULD FALL INTO THE UPPER SINGLE DIGITS. MONDAY THROUGH TUESDAY NIGHT...BIG STORY/CONCERN HERE IS FORECASTING WHEN THE STRATUS WILL DISSIPATE AND ANY POTENTIAL PRECIPITATION OUT OF IT. UPPER TROUGH SITUATED OVER THE NORTHERN PLAINS IS FORECAST TO MARCH SOUTHEAST DURING THIS PERIOD...IN RESPONSE TO A POWERFUL UPPER TROUGH DIGGING FORMING OVER CENTRAL CANADA. NORTH TO NORTHEAST LOW LEVEL FLOW IS LIKELY MONDAY INTO MONDAY NIGHT WITH HIGH PRESSURE BUILDING INTO THE NORTHERN PLAINS. THIS FLOW SHOULD DO A DECENT JOB IN HOLDING IN THE STRATUS BELOW THE SUBSIDENCE INVERSION...UNTIL MAYBE LATE MONDAY NIGHT WHEN THERE IS SUGGESTION THE FLOW BACKS NORTHWEST TO BRING IN SOME DRIER LOW LEVEL AIR. IN ADDITION...THAT TROUGH MENTIONED IN THE TONIGHT DISCUSSION IS PROGGED TO DROP SOUTHWEST DUE TO THE LOW LEVEL FLOW. CONVERGENCE ALONG THIS TROUGH COULD RESULT IN SOME FLURRY ACTIVITY AND HAVE ADDED IT TO THE FORECAST. 04.00Z CANADIAN MODEL IS EVEN MORE AGGRESSIVE AND SHOWING A FEW HUNDREDTHS. IF OTHER MODELS...SUCH AS THE NAM/GFS START TO SHOW THIS IN LATER RUNS...MAY NEED TO HAVE SOME HIGHER CHANCES ADDED. BETTER POTENTIAL FOR CLEARING EXISTS TUESDAY AS THE SURFACE RIDGE MOVES IN AT THE SAME TIME WITH DAYTIME HEATING...SO INDICATED CLEARING STARTING HERE. UPPER RIDGING THEN BUILDS OVER THE AREA FOR TUESDAY NIGHT AHEAD OF THE POWERFUL UPPER TROUGH...MAINTAINING DRY CONDITIONS WITH GENERALLY MOSTLY CLEAR SKIES. FOR TEMPERATURES... LOOK FOR A COOLING TREND AS THE UPPER TROUGH MOVES IN. DID RAISE LOW TEMPERATURES UP MONDAY NIGHT IN THE CLOUDY SKY AREA...CLOSER TO THE 2 METER NAM12 GUIDANCE. OTHERWISE...A BLEND OF GUIDANCE SEEMED REASONABLE. .LONG TERM...WEDNESDAY THROUGH SATURDAY NIGHT 324 AM CST SUN DEC 4 2011 AFTER WHAT WAS SOME UNCERTAINTY IN THE LONG TERM FORECAST...CAUSED ESPECIALLY BY THE 03.12Z ECMWF SUGGESTING A POSSIBLE ADVISORY-TYPE SNOW MOVING THROUGH FRIDAY/FRIDAY NIGHT...ALL MODELS HAVE COME BACK INTO GREAT AGREEMENT ON THE UPPER AND SURFACE PATTERNS THROUGHOUT THE LONG TERM. IN FACT...THEY LOOK A LOT LIKE WHAT WAS SHOWN BY THE 03.00Z CYCLE. SO FOR NOW WILL CONSIDER THE 03.12Z ECMWF AN ODD OUTLIER. A WEST-NORTHWEST FLOW UPPER PATTERN BEGINS THE LONG TERM...ON THE SOUTH SIDE OF THE POWERFUL TROUGH DROPPING INTO SOUTHERN CANADA. A COLD FRONT LOOKS TO SLIDE THROUGH THE FORECAST AREA ON WEDNESDAY...ENDING A BRIEF WARM SURGE ALOFT CAUSED BY THE UPPER RIDGE. THEN FOR WEDNESDAY NIGHT AND THURSDAY...A SHORTWAVE TROUGH IS FORECAST TO DIG DOWN THE WEST SIDE OF THE CANADA UPPER TROUGH...CAUSING AN UPPER JET TO STRENGTHEN DOWNSTREAM OVER NORTHERN WISCONSIN. RIGHT ENTRANCE REGION FORCING OF THIS JET SHOULD INDUCE SOME MID-LEVEL FRONTOGENESIS...AND COMBINED WITH A LITTLE MOISTURE MAY PRODUCE A BAND OF LIGHT SNOW OVER FAR SOUTHERN SECTION THURSDAY NIGHT. INCLUDED A 20 PERCENT CHANCE FOR THIS. BIGGER IMPACT IS ON FRIDAY WHEN THE SHORTWAVE TROUGH MOVES ACROSS...CAUSING 850MB TEMPS TO TANK FROM -9 TO -13C ON THURSDAY TO AROUND -20C ON FRIDAY. NEEDLESS TO SAY...BELOW NORMAL TEMPERATURES LIKELY. A DRY AND SLOW WARMING TREND SHOULD THEN ENSUE HEADING INTO THE WEEKEND IN RESPONSE TO THE MODELS FORECASTING THE UPPER FLOW BECOMING MORE ZONAL. IN FACT...THE LATEST 04.00Z ECMWF SUGGESTS HIGHS APPROACHING 40 FOR NEXT SUNDAY AS A SURGE OF DOWNSLOPED WARMED PACIFIC AIR FLOWS INTO THE AREA. && .AVIATION...TODAY INTO MONDAY 548 AM CST SUN DEC 4 2011 LOW PRESSURE THAT BROUGHT SNOW AND MVFR/IFR CIGS/VSBYS TO THE TAF SITE SAT/SAT NIGHT WILL CONTINUE TO MOVE AWAY FROM THE AREA TODAY. VFR VSBYS WILL PREVAIL ACROSS MN/WI TODAY/TONIGHT AS DRYER BOUNDARY LAYER AIR SPREADS ACROSS THE AREA ON NORTHWEST WINDS. SUBSIDENCE BEHIND THE LOW IS ON THE WEAK SIDE AND ANOTHER SHORTWAVE WILL BE DROPPING SOUTH INTO THE UPPER MIDWEST FOR TONIGHT/MONDAY. WITH CONSIDERABLE MOISTURE IN THE 925-850MB LAYER LINGERING OVER MN/IA/WI AND SOME WEAK LIFT FROM THE SHORTWAVE DROPPING INTO THE REGION... MVFR CLOUD DECKS ARE EXPECTED TO REMAIN OVER THE TAF SITES THRU TONIGHT AND MONDAY. THERE MAY BE ENOUGH DEPTH OF MOISTURE/CLOUDS AND WEAK CONVERGENCE/LIFT TO PRODUCE SCT FLURRIES ON MON. THESE NOT EXPECTED TO HAVE AN IMPACT ON VSBYS MON. && .ARX WATCHES/WARNINGS/ADVISORIES... 324 AM CST SUN DEC 4 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...AJ LONG TERM....AJ AVIATION.....RRS
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
325 AM CST SUN DEC 4 2011 .SHORT TERM...TODAY THROUGH TUESDAY NIGHT 324 AM CST SUN DEC 4 2011 MAIN FORECAST CONCERN NOW THAT THE PRECIPITATION IS EXITING/DIMINISHING IS WHEN CLOUDS WILL CLEAR. CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED RIDGING STILL OVER THE EAST PACIFIC AND ALONG THE EAST COAST OF THE U.S....AND TROUGHING IN-BETWEEN FROM HUDSON BAY SOUTHWEST INTO ARIZONA. IMPORTANT FEATURES TO NOTE INCLUDE A SHORTWAVE NEAR EAU CLAIRE WI ON THE EAST SIDE OF THE UPPER TROUGH...AND TWO SHORTWAVES OVER MONTANA ON THE BACK SIDE OF THE UPPER TROUGH. THE FORMER SHORTWAVE IN CONJUNCTION WITH PLENTIFUL MOISTURE AND LOW TO MID-LEVEL FRONTOGENESIS BROUGHT THE WIDESPREAD PRECIPITATION TO THE AREA LAST NIGHT. DRY SLOT NOTED IN WATER VAPOR COMBINED NOW WITH THE SHORTWAVE MOVED THROUGH...RESULTING IN SOME SUBSIDENCE...HAS ALLOWED PRECIPITATION TO REALLY DIMINISH DURING THE PAST 4-6 HOURS. IT APPEARS MODELS YESTERDAY MAY HAVE OVERDONE THE LOW LEVEL ISENTROPIC LIFT FOR THE CURRENT EARLY MORNING HOURS... GIVEN THAT THEY NOW SHOW NO ISENTROPIC LIFT AND SEEING THE PRECIPITATION DIMINISH ON RADAR. THEREFORE...THE CONCERN ABOUT THE DRY SLOT CLEARING OUT ICE AND RESULTING IN FREEZING PRECIPITATION IS NOT AS GREAT. IN ADDITION... SURFACE TEMPERATURES HAVE STRUGGLED TO FALL BELOW FREEZING WHERE IR CLOUD TOP TEMPERATURES INDICATE ICE HAS BEEN LOST. REGARDING THE SURFACE...SEA LEVEL PRESSURE ANALYSIS SHOWS A 1008MB LOW NEAR MANITOWIC WI. PLENTY OF CLOUDS EXTEND WEST FROM THE LOW...BACK INTO THE EASTERN DAKOTAS. UPSTREAM...ANOTHER BUT MUCH WEAKER SURFACE LOW IS NOTED NEAR WILLISTON ASSOCIATED WITH ONE OF THE MONTANA SHORTWAVES. TODAY AND TONIGHT...A SHORTWAVE IN EASTERN MONTANA IS PROGGED TO MOVE INTO SOUTH DAKOTA TODAY AND INTO NORTHWEST WISCONSIN TONIGHT. THE TRACK OF THE SHORTWAVE SUGGESTS ALL OF THE FORCING WILL STAY NORTH AND WEST OF THE AREA. THIS IS CONFIRMED TOO BY QG PLOTS. IN ADDITION...IT APPEARS MUCH OF THE CLOUD COVER ASSOCIATED WITH THE SHORTWAVE WILL STAY TO THE NORTHWEST. SO THIS LEAVES THE CURRENT CLOUD COVER AND SYSTEM GOING THROUGH THE MAIN CONCERN. WITH STRATUS EXTENDING SO FAR WEST...GRADUAL SUBSIDENCE OCCURRING TODAY IN THE WAKE OF THE SYSTEM AND THE LOW SUN ANGLE...THINKING A VERY PESSIMISTIC TREND MIGHT BE THE WAY TO GO. LIKE THE 04.00Z NAM INDICATING THE STRATUS STAYS IN PUT ACROSS THE AREA TODAY WITH ONLY SLOW CLEARING TONIGHT FOR WESTERN AREAS. CONCERNED THAT EVEN THE NAM MIGHT BE TOO FAST TONIGHT AS THE 900-950MB WINDS TURN FROM THE NORTHWEST TO NORTH. COMBINED WITH THE RECENT MOISTURE...CLOUDS MAY ACTUALLY LOWER IN CEILING HEIGHT VERSUS CLEARING. LAST CONCERN IS PRECIPITATION...BOTH THIS MORNING AND POSSIBLY OUT OF THE STRATUS DECK TONIGHT. GIVEN DIMINISHING RADAR RETURNS AND DRY FORECASTS INDICATED BY THE 04.00Z NAM/GFS/ECMWF FOR 12-18Z TODAY...HAVE REALLY DRIED OUT THIS MORNING. IN FACT...THERE MAY NOT BE MUCH GOING ON AFTER 12Z. WITH PRECIPITATION RAPIDLY DIMINISHING...WILL CANCEL THE ADVISORY HERE AT 4 AM. TONIGHT...THE 04.00Z NAM/GFS SHOW SOME LIGHT QPF OVER THE NORTH HALF OF WISCONSIN. APPEARS TO RESULT FROM LOW LEVEL CONVERGENCE...ASSOCIATED WITH SURFACE TROUGHING LINGERING BACK FROM THE CURRENT AREA OF LOW PRESSURE NEAR GRB. HAVE ADDED A 20 PERCENT CHANCE OF SNOW INTO THE FORECAST TO ACCOUNT FOR THIS POSSIBILITY. OTHERWISE...TEMPERATURES LOOK LIKE THEY SHOULD STRUGGLE TO RISE TODAY WITH 850MB TEMPS FALLING TO AT LEAST -6 TO -8C AND CLOUDS STAYING PUT. MAYBE A 1 OR 3 DEGREE F RISE IS POSSIBLE FROM THE 6 AM TEMPERATURE. WITH MORE CLOUDS ANTICIPATED TONIGHT...BROUGHT LOW TEMPERATURES UP A FEW DEGREES...ESPECIALLY ALONG AND EAST OF THE MISSISSIPPI RIVER WHERE CLOUDS ARE MORE CERTAIN. WHERE CLOUDS CLEAR OUT...TEMPERATURES COULD FALL INTO THE UPPER SINGLE DIGITS. MONDAY THROUGH TUESDAY NIGHT...BIG STORY/CONCERN HERE IS FORECASTING WHEN THE STRATUS WILL DISSIPATE AND ANY POTENTIAL PRECIPITATION OUT OF IT. UPPER TROUGH SITUATED OVER THE NORTHERN PLAINS IS FORECAST TO MARCH SOUTHEAST DURING THIS PERIOD...IN RESPONSE TO A POWERFUL UPPER TROUGH DIGGING FORMING OVER CENTRAL CANADA. NORTH TO NORTHEAST LOW LEVEL FLOW IS LIKELY MONDAY INTO MONDAY NIGHT WITH HIGH PRESSURE BUILDING INTO THE NORTHERN PLAINS. THIS FLOW SHOULD DO A DECENT JOB IN HOLDING IN THE STRATUS BELOW THE SUBSIDENCE INVERSION...UNTIL MAYBE LATE MONDAY NIGHT WHEN THERE IS SUGGESTION THE FLOW BACKS NORTHWEST TO BRING IN SOME DRIER LOW LEVEL AIR. IN ADDITION...THAT TROUGH MENTIONED IN THE TONIGHT DISCUSSION IS PROGGED TO DROP SOUTHWEST DUE TO THE LOW LEVEL FLOW. CONVERGENCE ALONG THIS TROUGH COULD RESULT IN SOME FLURRY ACTIVITY AND HAVE ADDED IT TO THE FORECAST. 04.00Z CANADIAN MODEL IS EVEN MORE AGGRESSIVE AND SHOWING A FEW HUNDREDTHS. IF OTHER MODELS...SUCH AS THE NAM/GFS START TO SHOW THIS IN LATER RUNS...MAY NEED TO HAVE SOME HIGHER CHANCES ADDED. BETTER POTENTIAL FOR CLEARING EXISTS TUESDAY AS THE SURFACE RIDGE MOVES IN AT THE SAME TIME WITH DAYTIME HEATING...SO INDICATED CLEARING STARTING HERE. UPPER RIDGING THEN BUILDS OVER THE AREA FOR TUESDAY NIGHT AHEAD OF THE POWERFUL UPPER TROUGH...MAINTAINING DRY CONDITIONS WITH GENERALLY MOSTLY CLEAR SKIES. FOR TEMPERATURES... LOOK FOR A COOLING TREND AS THE UPPER TROUGH MOVES IN. DID RAISE LOW TEMPERATURES UP MONDAY NIGHT IN THE CLOUDY SKY AREA...CLOSER TO THE 2 METER NAM12 GUIDANCE. OTHERWISE...A BLEND OF GUIDANCE SEEMED REASONABLE. .LONG TERM...WEDNESDAY THROUGH SATURDAY NIGHT 324 AM CST SUN DEC 4 2011 AFTER WHAT WAS SOME UNCERTAINTY IN THE LONG TERM FORECAST...CAUSED ESPECIALLY BY THE 03.12Z ECMWF SUGGESTING A POSSIBLE ADVISORY-TYPE SNOW MOVING THROUGH FRIDAY/FRIDAY NIGHT...ALL MODELS HAVE COME BACK INTO GREAT AGREEMENT ON THE UPPER AND SURFACE PATTERNS THROUGHOUT THE LONG TERM. IN FACT...THEY LOOK A LOT LIKE WHAT WAS SHOWN BY THE 03.00Z CYCLE. SO FOR NOW WILL CONSIDER THE 03.12Z ECMWF AN ODD OUTLIER. A WEST-NORTHWEST FLOW UPPER PATTERN BEGINS THE LONG TERM...ON THE SOUTH SIDE OF THE POWERFUL TROUGH DROPPING INTO SOUTHERN CANADA. A COLD FRONT LOOKS TO SLIDE THROUGH THE FORECAST AREA ON WEDNESDAY...ENDING A BRIEF WARM SURGE ALOFT CAUSED BY THE UPPER RIDGE. THEN FOR WEDNESDAY NIGHT AND THURSDAY...A SHORTWAVE TROUGH IS FORECAST TO DIG DOWN THE WEST SIDE OF THE CANADA UPPER TROUGH...CAUSING AN UPPER JET TO STRENGTHEN DOWNSTREAM OVER NORTHERN WISCONSIN. RIGHT ENTRANCE REGION FORCING OF THIS JET SHOULD INDUCE SOME MID-LEVEL FRONTOGENESIS...AND COMBINED WITH A LITTLE MOISTURE MAY PRODUCE A BAND OF LIGHT SNOW OVER FAR SOUTHERN SECTION THURSDAY NIGHT. INCLUDED A 20 PERCENT CHANCE FOR THIS. BIGGER IMPACT IS ON FRIDAY WHEN THE SHORTWAVE TROUGH MOVES ACROSS...CAUSING 850MB TEMPS TO TANK FROM -9 TO -13C ON THURSDAY TO AROUND -20C ON FRIDAY. NEEDLESS TO SAY...BELOW NORMAL TEMPERATURES LIKELY. A DRY AND SLOW WARMING TREND SHOULD THEN ENSUE HEADING INTO THE WEEKEND IN RESPONSE TO THE MODELS FORECASTING THE UPPER FLOW BECOMING MORE ZONAL. IN FACT...THE LATEST 04.00Z ECMWF SUGGESTS HIGHS APPROACHING 40 FOR NEXT SUNDAY AS A SURGE OF DOWNSLOPED WARMED PACIFIC AIR FLOWS INTO THE AREA. && .AVIATION...THROUGH 18Z SUNDAY 1130 PM CST SAT DEC 3 2011 SNOW WILL CONTINUE TO DIMINISH OVERNIGHT AS THE STORM SYSTEM PULLS NORTHEAST. VSBYS SHOULD HOLD IN THE 3-5SM WITH -SN OR BR FOR MUCH OF SUNDAY MORNING THOUGH. -FZDZ DOESN/T LOOK LIKE A CONCERN FOR KRST/KLSE NOW AS SATELLITE TRENDS AND RH FIELDS SUGGEST THE DRIER MID LEVELS WOULD STAY SOUTH OF THE TAF SITES...AND THUS KEEP THE ICE FREE CLOUDS - AND POTENTIAL FZDZ MAKERS - SOUTH. STILL...SOMETHING TO MONITOR. CIGS WILL BE A BIGGER CONCERN AS THE LOW LEVEL MOISTURE REMAINS ENTRENCHED ACROSS THE AREA. 00Z NAM NOW MORE SUGGESTIVE OF HANGING ONTO MVFR/IFR CONDITIONS FOR MUCH OF TODAY INTO TONIGHT. SOME HINTS OF A BRIEF BREAK INTO SCT SUN NIGHT...BUT CONFIDENCE ISN/T HIGH ENOUGH AND WILL HOLD WITH CIGS THROUGH 06Z MON. && .ARX WATCHES/WARNINGS/ADVISORIES... 324 AM CST SUN DEC 4 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...AJ LONG TERM...AJ AVIATION..... RIECK
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
1037 PM CST SAT DEC 3 2011 UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE .UPDATED...CONCERNING HEADLINES. AVAILABLE REPORTS IN THE ADVISORY AREA SO FAR THIS EVENING RANGE UP TO 2 INCHES. IR LOOP SHOWS BEST ENHANCEMENT HAS QUICKLY SHIFTED NORTHEASTWARD INTO UPPER MICHIGAN. RADAR AND OBS ACROSS THE REGION INDICATE THE RAIN SNOW LINE EXTENDS FROM NORTHWEST IOWA TO RST TO STE TO JUST SOUTH OF IMT. A SURFACE LOW WAS OVER SOUTHERN IOWA EARLY THIS EVENING AND WILL BE ENTERING SOUTHWEST WISCONSIN LATE THIS EVENING AND NEARLY TRACKING ALONG THE RAIN SNOW LINE OVERNIGHT. A LARGE AREA OF RAIN WAS IN THE WARM SECTOR OF THE LOW OVER IOWA AND SOUTHERN WISCONSIN MOVING TOWARD EASTERN WISCONSIN. PARTS OF EASTERN WISCONSIN MAY SEE UP TO AN ADDITIONAL INCH OF RAIN OVERNIGHT. BUT BACK TO THE ADVISORY...BEST SNOW GROWTH REGION WAS OVER NORTHWEST WISCONSIN AND MAY INCLUDE WESTERN PORTIONS OF ONEIDA AND VILAS COUNTIES. THIS SNOW GROWTH REGION IS PROGGED TO SAG INTO NORTH CENTRAL WISCONSIN OVERNIGHT AS THE H8 LOW AND SURFACE LOW TRACKS OVER. NOT OUT OF THE QUESTION A WARNING MAY BE NEEDED AS THESE MORE FAVORABLE DYNAMICS PLAY A ROLE...BUT FOR NOW WILL CONTINUE THE HIGH END ADVISORY. TDH && .PREV DISCUSSION...ISSUED AT 505 PM CST SAT DEC 3 2011... SHORT TERM...TONIGHT AND SUNDAY. LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A DEVELOPING LOW PRESSURE SYSTEM MOVING NORTHEAST OVER SOUTH-CENTRAL KANSAS JUST AHEAD OF A SHORTWAVE TROUGH. ATTACHED TO THE SURFACE LOW TO THE NORTHEAST RUNS A COLD FRONT OVER CENTRAL IOWA INTO NORTHWEST WISCONSIN. FIRST BATCH OF PRECIP IS RIDING ALONG THE 850MB BAROCLINIC ZONE OVER THE SOUTHEASTERN HALF OF WISCONSIN THOUGH SOME BREAKS ARE SPREADING OVER EASTERN IOWA AND NORTHERN ILLINOIS...THAT MAY SPELL A BREAK IN THE PRECIP FOR A BRIEF PERIOD LATE THIS AFTERNOON OVER E-C WISCONSIN. THE MAIN AXIS OF PRECIP...HOWEVER... EXISTS JUST TO THE EAST OF THE SURFACE LOW ON THE NOSE OF A 60 KT LLJ AND UPPER DIVERGENT AREA WITHIN THE COUPLED JET. SOME HIGHER REFLECTIVITIES ARE ALSO DEVELOPING OVER WESTERN WISCONSIN WITHIN A STRENGTHENING FGEN ZONE...SO WILL JUST START THE WINTER HEADLINES WITH THE AFTERNOON PACKAGE. AS THE LOW TRACKS NORTHEAST OVER THE NEXT 24 HOURS...THE OBVIOUS CONCERNS ARE SNOW AMOUNTS AND HEADLINES. TONIGHT...FOLLOWED A SREF/GFS BLEND TONIGHT...WHICH SPLITS THE DIFFERENCE BETWEEN THE STRONGER NAM AND WEAKER ECMWF WHILE KEEPING THE CONSENSUS TRACK. LOW PRESSURE OVER THE CENTRAL PLAINS WILL RAPIDLY MOVE NE TOWARDS THE MID-MISSISSIPPI VALLEY THIS EVENING...AND NORTHERN LAKE MICHIGAN BY 12Z SUNDAY. AHEAD OF THE LOW...A BEEFY LLJ WILL SHIFT INTO SOUTHERN WISCONSIN THIS EVENING...THEREBY INCREASING CONVERGENCE ALONG THE STALLED BAROCLINIC ZONE STRETCHING ACROSS THE STATE...AND 850-700MB FGEN IN THE PROCESS. COMBINED WITH STRONG QG FORCING FROM SHORTWAVE ENERGY AND A WIDE OPEN GULF (PWATS 150-200 PCT OF NORMAL)...THE BEEFY SLUG OF PRECIP OVER THE PLAINS WILL HAVE NO TROUBLE SPREADING ACROSS THE STATE THIS EVENING. PTYPE REMAINS PROBLEMATIC AS THE 12Z MODEL RUNS HAVE TRENDED SLIGHTLY WARMER WITH THE THERMAL PROFILE AS THE LOW PUSHES WARMER AIR ALOFT SLIGHTLY FARTHER NORTH THAN PREVIOUS RUNS. THIS WILL PLACE THE RAIN-SNOW MIX AREA FROM WOOD COUNTY TO NORTHERN OCONTO AND MARINETTE. NORTH OF THE RAIN-SNOW LINE SHOULD RESIDE THE AXIS OF HEAVIEST SNOWFALL...WHICH LINES UP WITH THE EXTRAPOLATED SOUTHERN EDGE OF THE COMMA HEAD FROM APPROX MERRILL TO CRANDON. WITH SLIGHTLY COLDER AIR IN PLACE COMPARED TO THE FIRST SNOW STORM IN NOVEMBER...SNOW RATIOS WILL RUN BETWEEN 10-14:1 OVER THIS AREA ACCORDING TO THE COBB SNOWFALL ALGORITHM. WITH QPFS AROUND 0.4 TO 0.5 INCHES...THIS AMOUNTS TO A GOOD 4-6 INCH SWATH OF SNOW TONIGHT (5 TO 7 INCHES OVERALL)...THOUGH THE BULK OF THE PRECIP WILL LIKELY FALL THIS EVENING. THE FOX VALLEY AND LAKESHORE WILL RESIDE WITHIN THE WARM SECTOR OF THE STORM...WHICH MEANS MOSTLY RAIN TONIGHT...THOUGH SOME SNOW MAY MIX IN LATE. ENTERTAINED SOME THOUGHTS OF UPGRADING TO A WARNING GIVEN THE HEAVY SNOW OBS UPSTREAM...BUT GIVEN THE RELATIVELY LOW IMPACT OF THE SNOW (DURING THE NIGHT ON A WEEKEND)...WILL STICK WITH ADVISORY HEADLINES. ALSO THOUGHT ABOUT TRIMMING THE ADVISORY TO THE NW BY A ROW OF COUNTIES...BUT COORDINATION WITH SURROUNDING OFFICES YIELDED A RELUCTANCE...DUE TO THE SLOPPINESS OF THE MIX AND POTENTIAL FOR FREEZING DRIZZLE. AS A RESULT...WILL KEEP CURRENT HEADLINES AS THEY CURRENTLY STAND BUT STRESS THE HEAVY SNOWFALL RATES ARRIVING THIS EVENING. SUNDAY...THE LOW PRESSURE WILL QUICKLY EXIT TO SOUTHEAST ONTARIO BY 18Z SUNDAY BUT WILL HAVE THE BACK EDGE OF THE COMMA HEAD SHIFTING NE OVER N-C AND FAR NORTHEAST WISCONSIN. SOME MID-LEVEL FGEN WILL LINGER WHICH WILL RESULT IN ANOTHER HALF INCH TO AN INCH OVER N-C WISCONSIN EARLY IN THE MORNING. BUT OTHERWISE...SNOW WILL BE TAPERING DOWN TO JUST FLURRIES IN THE MORNING...WHILE COLDER AIR FILTERS ACROSS THE REGION. LOW LEVEL TROUGHINESS AND CYCLONIC FLOW WILL HANG AROUND FOR MUCH OF THE DAY...SO NOT ANTICIPATING MUCH CLEARING TOMORROW. HIGHS MAINLY IN THE LOW TO MIDDLE 30S. LONG TERM...SUNDAY NIGHT THROUGH NEXT SATURDAY...THE MAIN FCST CONCERNS WILL BE MINOR LAKE EFFECT SNOW POTENTIAL OVER NORTHERN WI EARLY IN THE PERIOD...THEN THE POTENTIAL FOR SNOW AND MUCH COLDER TEMPERATURES WITH AN ARCTIC FRONTAL PASSAGE LATE NEXT WEEK. A STRONG...HIGH AMPLITUDE RIDGE WILL COVER THE EASTERN PACIFIC... WESTERN CANADA AND THE WEST COAST OF THE U.S. EARLY IN THE PERIOD... WITH A POSITIVELY-TILTED UPPER TROF EXTENDING FROM CENTRAL CANADA INTO THE SOUTHWEST UNITED STATES. THIS UPPER TROF WILL MOVE THROUGH WISCONSIN ON TUESDAY...WITH LITTLE IMPACT ON OUR WEATHER. SHORT-WAVE ENERGY WILL TOP THE WESTERN RIDGE EARLY NEXT WEEK...THEN EVENTUALLY HELP TO CARVE A BROAD TROF OVER THE CENTRAL U.S. BY THU/FRI. A SURGE OF ARCTIC AIR IS EXPECTED TO ARRIVE IN WI LATE IN THE WEEK... WITH H8 TEMPS PLUMMETING TO AROUND -20 C. THIS WILL LEAD TO OUR COLDEST TEMPERATURES SO FAR THIS SEASON. A LARGE RIDGE OF HIGH PRESSURE WILL BE CENTERED OVER THE NORTHERN ROCKIES AND NORTHERN PLAINS SUN NGT INTO MON...WITH COLD NORTH FLOW RESULTING IN SCT LAKE-EFFECT SNOW SHOWERS OVER MAINLY NC WI. THE SNOW SHOWERS MAY LINGER INTO MONDAY NIGHT...BUT SHOULD COME TO AN END ON TUESDAY AS THE RIDGE AXIS PUSHES ACROSS WI. A WEAK COLD FRONT IS EXPECTED TO MOVE THROUGH THE REGION ON WEDNESDAY...WITH A STRONGER ARCTIC FRONT ARRIVING SOMETIME DURING THE THU/FRI TIME FRAME. DURING THIS PERIOD...LLVL FLOW IS EXPECTED TO BE TOO WESTERLY FOR LK-EFFECT. THE ECMWF AND A FEW OF THE GFS ENSEMBLE MEMBERS SUGGEST THAT A SFC WAVE WILL DEVELOP ALONG THE ARCTIC BOUNDARY LATE IN THE WEEK...AS THE RRQ OF A STRONG UPPER LEVEL JET PULLS THROUGH THE REGION. IF THIS PLAYS OUT...WE COULD BRING SEE SEVERAL INCHES OF POWDERY SNOW SOMETIME DURING THE THURSDAY NIGHT TO SATURDAY PERIOD. FOR NOW...WILL FOLLOW THE CONCENSUS OF AREA OFFICES...AND JUST MENTION SMALL POPS ACROSS OUR SOUTHERN AND EASTERN COUNTIES ON THU NGT/FRI. THERE IS A HIGHER DEGREE OF CONFIDENCE IN A TREND TOWARD MUCH COLDER TEMPERATURES LATE IN THE WEEK...ALTHOUGH THE NEW ECMWF IS SLOWER WITH THE TIMING OF THE ARCTIC BOUNDARY. SUBSEQUENT FCSTS SHOULD BE BETTER ABLE TO PINPOINT THE FRONTAL TIMING AND SNOWFALL POTENTIAL LATE NEXT WEEK. && .AVIATION...IFR TO LIFR CIGS AND VSBYS WILL CONTINUE OVER CENTRAL AND NORTH CENTRAL WISCONSIN AS STEADY SNOWS CONTINUE TO AFFECT THE AREA OVERNIGHT. MAINLY LIFR TO IFR CIGS WITH IFR VSBYS WITH RAIN AND FOG TO IMPACT EASTERN WISCONSIN. PERSISTENT RAIN/SNOW LINE CONTINUES TO RUN FROM AROUND ISW TO JUST SOUTH OF IMT LATE THIS EVENING. CIGS AND VSBYS TO GRADUALLY IMPROVE TO MVFR CONDITIONS SUNDAY AS THE LOW PRESSURE SYSTEM DEPARTS TO THE NORTHEAST. TDH && .GRB WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 6 AM CST SUNDAY FOR WIZ005-010>013- 018-019-021-030-035. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
249 AM CST TUE DEC 6 2011 .DISCUSSION... 852 PM CST A FEW CHALLENGES REVOLVING AROUND THE LAKE EFFECT PRECIPITATION THIS EVENING. RADAR IMAGERY SHOWS PRECIPITATION FROM MILWAUKEE SOUTH INTO NORTHERN WILL COUNTY. WATER VAPOR IMAGERY SHOWS DEFORMATION ZONE MOVING EAST OF THE FORECAST AREA WITH SUBSIDENCE AND MID LEVEL DRY AIR MOVING IN FROM THE SOUTHWEST. HAVE SEEN OVERALL INTENSITY OF RETURNS OFF THE LAKE DECREASE SOMEWHAT AS THIS FEATURE PROGRESSES THROUGH...BUT FORECAST SOUNDINGS SHOW LITTLE CHANGE IN THE LOW AND MID LEVELS OVERNIGHT AND SUSPECT AREA OF PRECIPITATION WILL CONTINUE THROUGH THE REMAINDER OF THE EVENING AND OVERNIGHT. SOUNDINGS DO SHOW A SLIGHT DECREASE IN THE INVERSION HEIGHTS BETWEEN 06-09Z...AND MOST OF THE HIGH-RES GUIDANCE...WITH THE RUC BEING THE EXCEPTION...SHOWS PRECIP DIMINISHING LATE TONIGHT. SUSPECT THE RUC MAY BE ONTO SOMETHING THOUGH...WITH NO REAL SENSE OF WHAT MAY CAUSE LAKE EFFECT TO SHUT OFF OVERNIGHT...THUS WILL BUMP UP POPS FOR TONIGHT. PRECIP TYPE ALSO A BIG QUESTION MARK. THE 129DM LINE ON THE 1000-850MB THICKNESS LINES UP WELL WITH CURRENT RAIN-SNOW LINE AND DOES GRADUALLY SHIFT SOUTH THROUGH COOK COUNTY TONIGHT...BUT LOCALIZED EFFECTS WITH WARM AIR OFF THE LAKE AND URBAN HEAT ISLAND WILL DELAY THE CHANGE OVER TO SNOW FOR AREAS ALONG THE LAKESHORE AND PORTIONS OF COOK COUNTY DESPITE THE GRADUAL COOL ADVECTION. HOWEVER...WET-BULBING EFFECTS UNDER THE HEAVIER SHOWERS MAY DOMINATE...AND HAS ALREADY BEEN EVIDENT ON DUAL-POL IMAGERY WITH SOME OF THE SHOWERS THAT PASSED OVER SOUTHERN DUPAGE COUNTY EARLIER TONIGHT WHERE SNOW BRIEFLY MADE ITS WAY TO THE SURFACE. SO DO EXPECT A CHANGE OVER TO SNOW AT SOME POINT...BUT HAVE VERY LOW CONFIDENCE ON PRECISE TIMING. PRECIP AMOUNT REPORTS HAVE BEEN ON THE ORDER OF A FEW HUNDREDTHS THUS FAR UNDER THE STRONGEST RETURNS...AND SEE NO REASON FOR THIS TO CHANGE OVERNIGHT NOR HAVE ANY CONCERNS FOR ACCUMULATIONS. FORECAST UPDATES TO FOLLOW SHORTLY...BMD //PREV DISCUSSION... NEAR TERM....THIS AFTERNOON THROUGH TONIGHT... VISIBLE IMAGERY CONTINUES TO SHOW A THICK STRATUS LAYER OVERHEAD. VERTICAL GROWTH OF THE CLOUD DESK REMAINS WELL SOUTH OF THE REGION OVER THE OZARKS AND WESTERN TENNESSEE. WITH THE ABUNDANT SOLAR SHIELDING...TEMPERATURES THIS AFTERNOON HAVE NOT WARMED MUCH. THUS EXPECT TEMPS TO REMAIN IN THE MID/UPR 30S. BETTER COLD AIR ADVECTION HAS CONTINUED TO OCCUR ACROSS WEST CENTRAL ILLINOIS WHERE TEMPERATURES HAVE HELD AROUND 30...AND IN THE MID 20S ACROSS CENTRAL MISSOURI. IR IMAGERY THIS AFTERNOON ALSO CONTINUES TO INDICATE MUCH THICKER CLOUD COVER OVER ILLINOIS/INDIANA. WSR-88D RADAR WAS DEPICTING PRECIPITATION PUSHING INLAND ACROSS BOTH COOK AND LAKE COUNTY ILLINOIS...AS LAKE MOISTURE SLOWLY SLIDES SOUTH/SOUTHWEST. MOISTURE REMAINS VERY SHALLOW AND MINIMAL LIFT...SUPPORTING PRECIP TO REMAIN AS LIQUID WITH PATCHY DRIZZLE. FURTHER NORTH A FEW OBSERVATIONS ACROSS WISCONSIN HAVE REPORTED LGT SN. FOR FAR NORTHEAST ILLINOIS TEMPERATURES ARE WARM ENOUGH TO MAINTAIN A LIQUID STATE OF PRECIPITATION. QUASI-STATIONARY BOUNDARY REMAINS TO OUR SOUTHEAST ACROSS THE OZARKS STRETCHING NORTHEAST THROUGH THE OHIO VALLEY. OVERNIGHT THE CHALLENGE WILL CONTINUE TO BE COVERAGE OF PRECIP...AND TEMPERATURES. GUIDANCE HAS SUGGESTED THAT TEMPERATURES WILL COOL MORE EFFICIENTLY TONIGHT WITH BETTER COLD AIR ADVECTION INTO NORTHERN IL/NORTHWEST IN...HOWEVER FEEL THIS IS TOO OVERDONE. THUS HAVE ADJUSTED OVERNIGHT LOWS UP A FEW DEGREES GIVEN THE EXPECTED THICK CLOUD COVER. WINDS START TO TURN NORTHEASTERLY THIS EVENING AND CONTINUE OVERNIGHT...WHICH SHOULD AID IN BENDING THE LAKE MOISTURE SOUTHWEST OR OVER NORTHEAST ILLINOIS. THUS HAVE MAINTAINED MENTION OF SLIGHT CHANCE WORDING. VERTICAL LIFT APPEARS TO BUMP UP A TAD OVERNIGHT...WITH SFC TEMPS PUSHING CLOSER TO FREEZING. MODEL SOUNDINGS INDICATE THAT ANY PRECIP THAT FALLS THIS EVENING WOULD START AS LIQUID...THEN POSSIBLY START TO MIX WITH LGT SNOW. AS PREVIOUSLY MENTIONED ABOUT THE MINIMAL LIFTING MECHANISM...IT IS POSSIBLE THAT PATCHY DRIZZLE COULD OCCUR BEFORE LGT SNOW WOULD OCCUR. QPF REMAINS MINIMAL...OR LESS THAN 0.05 THROUGH THE NEXT 24HRS. MORE THAN LIKELY IT IS CLOSER TO 0.01 TO 0.03. BASED ON THE EXPECTED TEMPERATURES AND MINIMAL LIFT...ANY SNOW THAT DOES FALL MAY ACCUMULATE UP TO A QUARTER OF AN INCH. ALTHOUGH THAT BEING SAID...CONFIDENCE IS LOW THAT THIS SCENARIO WOULD PAN OUT. TUESDAY THROUGH THURSDAY... A WEAK WAVE IS PROGGED TO DEVELOP ALONG THE QUASI-STATIONARY BOUNDARY AND SLIDE NORTHEAST THROUGH MISSOURI. ANTI-CYCLONIC FLOW REMAINS UPSTREAM ACROSS IOWA/MINNESOTA/WISCONSIN...WHICH SHOULD START TO TURN OFF LAKE MOISTURE SOMETIME TUE AFTN/EVE. HAVE HELD ONTO MENTION OF LGT RA/SN THRU THE MORNING HOURS. AFTN TEMPS SHOULD WARM MARGINALLY TO AROUND THE MID 30S ACROSS MOST OF THE CWFA. BY TUE AFTN/EVE THE INFLUENCE FROM THE UPSTREAM RIDGE SHOULD FINALLY ERODE THE THICK STRATUS AND ALLOW PARTLY CLOUD SKIES TO DEVELOP BY THE LATE AFTN/EVE. THIS COUPLED WITH 850MB THERMAL TROUGH OF -10 TO -12 DEG...WILL SET THE STAGE FOR OVERNIGHT LOWS IN THE TEENS TO LOWER 20S. AS WINDS SLOWLY SHIFT FROM THE NORTHWEST TO THE WEST/SOUTHWEST WED...THE LAKE MOISTURE WILL BECOME ORIENTED OVER LOWER MICHIGAN. 500MB VORT SLOWLY SLIDES EAST ALONG THE SOUTHERN STREAM...WHILE THE NORTHERN STREAM REMAINS IN PROGRESSIVE. THE FOCUS WED WILL CONTINUE TO BE ON THE ARRIVAL OF A POTENT FRONTAL BOUNDARY...THAT IS COUPLED WITH AN 850MB THERMAL TROUGH OF -20 TO -22 DEG C. THIS WILL PROVIDE THE COOLEST AIR OF THE SEASON LATER IN THE WEEK TO NORTHERN IL/NORTHWEST IN. PRIOR TO THE ARRIVAL OF THIS AIRMASS...MOISTURE IS EXPECTED TO POOL ALONG THE FRONT AS IT SLOWLY PUSHES SOUTHEAST ACROSS THE PLAINS THURSDAY. GUIDANCE HAS FLUCTUATED ON HOW THIS FEATURE WILL UNFOLD...AND IT REMAINS POSSIBLE THAT A WEAK WAVE WILL DEVELOP ALONG THE LEE-SIDE OF THE 500MB TROUGH AXIS. THIS SCENARIO COULD RESULT IN LGT SNOW OVERSPREADING NORTHERN IL/NORTHWEST IN THUR AFTN AS THE POTENT THERMAL TROUGH ARRIVES ALOFT. TEMPS THUR WILL REMAIN IN THE LOW/MID 30S. BEACHLER LONG TERM...THURSDAY NIGHT THROUGH MONDAY MAIN CONCERNS IN THE EXTENDED PORTION OF THE FORECAST ARE LIGHT SNOW POTENTIAL THURSDAY NIGHT INTO EARLY FRIDAY...FOLLOWED BY THE FIRST BLAST OF ARCTIC AIR OF THE SEASON FOR FRIDAY INTO EARLY SATURDAY. ON THURSDAY NIGHT...AS MENTIONED ABOVE...DIGGING H5 TROUGH WILL SPAWN A WEAK SURFACE LOW WHICH WILL TRACK ACROSS NORTHERN GREAT LAKES AND SEND AN ARCTIC FRONTAL BOUNDARY TOWARD AREA. MODELS HAVE BEEN CONSISTENT IN SPITTING OUT A STRIPE OF VERY LIGHT QPF NEAR OR OVER CWA IN RESPONSE TO THIS FEATURE. WITH NEGATIVE TEEN AIR AT H85 BUILDING IN FROM THE NORTH BEHIND ARCTIC FRONT...SUSPECT WAVE WILL RIDE ALONG LOW LEVEL BAROCLINIC ZONE. A PEEK AT GFS TIME HEIGHT AT ORD FOR THURSDAY NIGHT PERIOD SHOWS SATURATION AND ADEQUATE LIFT INTO -15C FAVORED SNOW GROWTH ZONE. THEREFORE...DESPITE QPF ONLY IN THE HUNDREDTHS UP TO MAYBE A TENTH OR SLIGHTLY MORE...WITH VERY COLD AIR MASS...SNOW WOULD BE HIGH RATIO AND POSSIBLY RESULT IN FIRST WIDESPREAD LIGHT ACCUMULATING SNOW OF THE SEASON FOR MANY (IF SCENARIO PANS OUT...POTENTIAL FOR AN INCH OR TWO OF SNOW). FOR NOW...HAVE BUMPED UP POPS IN GRIDS TO CHANCE ACROSS THE AREA GIVEN SOME UNCERTAINTY IN EXACTLY WHERE BEST SNOW POTENTIAL WILL OCCUR. LIGHT SNOW MAY LINGER INTO EARLY FRIDAY FOR EASTERN PORTION OF CWA BEFORE WAVE SHIFTS OFF TO THE EAST. THEREAFTER...ON FRIDAY...STRONG CAA WILL BE IN FULL FORCE WITH SHARP THERMAL TROUGH ARRIVING OVERHEAD LATE IN THE DAY. OPERATIONAL MODELS AND ENSEMBLES HAVE BACKED OFF EVER SO SLIGHTLY ON JUST HOW COLD ARCTIC AIR MASS WILL BE...BUT -15C OR SO AT H85 AND -8 TO -10 AT H95 WILL BE PLENTY COLD. TEMPERATURES WILL STRUGGLE INTO THE MID TO UPPER 20S FRIDAY AFTERNOON WITH A PERSISTENT WNW BREEZE LEADING TO LOW WIND CHILL VALUES. AXIS OF ARCTIC HIGH WILL PASS CLOSEST ON FRIDAY NIGHT...LEADING TO STRONG RADIATIONAL COOLING. IF MINOR SNOW COVER IS PRESENT...LOW TO MID TEENS...UPPER TEENS IN DOWNTOWN CHICAGO...IN GRIDS FOR LOW EARLY SATURDAY MORNING MIGHT BE A FEW DEGREES TOO HIGH. SW FLOW...STEADY WARMING ALOFT AND LIKELY FULL SUNSHINE ON SATURDAY WILL ALLOW FOR SOME RECOVERY FROM VERY COLD START TO DAY...BUT SUSPECT IT WILL BE TOUGH TO MAKE UP A LOT OF GROUND DUE TO LIMITED DAYLIGHT THIS TIME OF YEAR. THUS SHAVED OFF A DEGREE FROM MODEL BLEND FOR MAX TEMPERATURES ON SATURDAY...YIELDING HIGHS IN THE UPPER 20S TO AROUND 30 DEGREES. SUNDAY AND MONDAY LOOK TO BE MAINLY DRY WITH TEMPERATURES RETURNING TO CLOSE TO SEASONAL NORMS DUE TO SOUTHERLY FLOW AND CONTINUED WARMING OF THE COLUMN. A FRONTAL BOUNDARY MAY DROP SOUTH THROUGH THE AREA LATE MONDAY... BRINGING NEXT CHANCE FOR LIGHT PRECIP...BUT LARGE MODEL UNCERTAINTY THIS FAR OUT PRECLUDES ANYTHING MORE THAN SLIGHT POPS FOR MONDAY NIGHT. RC && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 08Z... * POTENTIAL FOR LAKE EFFECT RAIN/SNOW SHOWERS THROUGH THE AFTERNOON * PERIODS OF MVFR CIGS THROUGH TUESDAY EVENING. SHEA //DISCUSSION...UPDATED 06Z... MAIN FORECAST CONCERN AND CHALLENGE REMAINS THE LAKE EFFECT RAIN/ SNOW SHOWERS. OVERALL INTENSITY HAS DIMINISHED SOME FROM EARLIER THIS EVENING BUT STILL MANY SHOWERS FROM FAR SOUTHEAST WI INTO NORTHEAST IL. COOLER AIR SLOWLY FILTERING IN FROM THE NORTH HAS CHANGED PRECIP TO MAINLY SNOW ACROSS SOUTHEAST WI INTO FAR NORTHEAST IL...AS WELL AS LOCATIONS FARTHER INLAND...SUCH AS DPA WHERE TEMPS HAVE ALSO COOLED A FEW DEGREES. FORECAST SOUNDINGS CONTINUE TO SHOW THE INVERSION HEIGHT LOWERING SOME THROUGH THE OVERNIGHT HRS AND THIS SHOULD LIMIT THE COVERAGE AND INTENSITY OF THE LAKE EFFECT SHOWERS OVERNIGHT. WHILE THERE WILL STILL LIKELY BE PERIODS OF LIGHT RAIN AND/OR LIGHT SNOW...CONFIDENCE IN TRYING TO TIME ANY OF THIS PRECIP IS VERY LOW. AND FOR THAT REASON...HAVE GONE WITH A VICINITY MENTION...THOUGH LATER UPDATES FOR PREVAILING OR TEMPO PRECIP MAY BE NEEDED. LITTLE CHANGE TO THE AIRMASS OR LOW LEVEL PROFILES INTO TUESDAY AFTERNOON AND THERE COULD BE ADDITIONAL LAKE EFFECT SHOWERS THROUGH SUNSET...PERHAPS AIDED BY DIURNAL WARMING BY MID/LATE MORNING. CONFIDENCE VERY LOW HERE AS WELL. OUTSIDE OF PRECIP AREAS...CIGS HAVE GENERALLY LIFTED INTO LOW VFR WITH A FEW PATCHES OF HIGH MVFR CIGS. EXPECT THIS OVERALL TREND TO CONTINUE WITH MVFR POSSIBLE IN AREAS OF HEAVIER PRECIP. THOUGH AM CONCERNED THAT THERE COULD BE ANOTHER PERIOD OF MVFR CIGS TUESDAY AFTERNOON. WITH A RIDGE OF HIGH PRESSURE MOVING ACROSS THE AREA TUESDAY NIGHT...ANY MVFR CIGS MAY GET TRAPPED BELOW THE INVERSION AND COULD PERSIST WELL INTO TUESDAY NIGHT. NORTHEAST WINDS WILL SLOWLY TURN MORE NORTHERLY TUESDAY AFTERNOON THEN SHOULD FLOP WESTERLY TUESDAY EVENING AS THE ABOVE MENTIONED RIDGE BUILDS ACROSS THE AREA. WINDS COULD POTENTIALLY BECOME LIGHT AND VRB OR EVEN CALM TUESDAY EVENING. IN THE SHORT TERM...GRADIENT WILL SLOWLY RELAX OVERNIGHT AND THINK THE PREVAILING GUSTS HAVE ENDED EXCEPT AT GYY AND ALONG THE LAKE...WITH PREVAILING SPEEDS IN THE 9-13KT RANGE. CMS //ORD AND MDW CONFIDENCE...UPDATED 08Z... * LOW CONFIDENCE REGARDING PRECIP TYPE/TIMING/DURATION/INTENSITY THROUGH THE PERIOD * MEDIUM CONFIDENCE PREVAILING CIGS WILL BECOME/REMAIN VFR THROUGH TUESDAY MORNING...LOW CONFIDENCE PREVAILING MVFR CIGS MAY RETURN TUESDAY MORNING/AFTERNOON SHEA //OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z... WEDNESDAY AND THURSDAY...VFR. THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE. FRIDAY THROUGH SUNDAY...VFR. CMS && .MARINE... 248 AM CST HIGH PRESSURE EXTENDING FROM THE UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS WILL SLOWLY SAG ACROSS THE GREAT LAKES REGION TODAY AND TONIGHT AS A STRONG LOW PRESSURE SYSTEM MOVES ACROSS NORTHERN MANITOBA INTO THE HUDSON BAY. THIS LOW WILL DRAG A COLD FRONT ACROSS LAKE MICHIGAN WEDNESDAY. DURING THIS PERIOD...WINDS OVER THE LAKE WILL GRADUALLY SHIFT FROM NORTHERLY TO SOUTHWESTERLY. WIND SPEEDS WILL DIMINISH TO AS LOW AS TO TO 15 KT LATE TONIGHT AS THE SFC RIDGE AXIS CROSSES THE LAKE...BUT AS THE RIDGE PUSHES TO THE SOUTH AND A SFC TROUGH ASSOCIATED WITH THE COLD FRONT DROPS THROUGH THE NORTHERN PLAINS LATE TONIGHT...WINDS WILL QUICKLY INCREASE AGAIN TO AROUND 30 KT. FOLLOWING THE PASSAGE OF THE COLD FRONT...ANOTHER CANADIAN HIGH PRESSURE SYSTEM WILL DROP SOUTHEAST ACROSS THE PLAINS THURSDAY AND FRIDAY. THIS SHOULD MAINTAIN A MODERATE PRESSURE GRADIENT OVER THE GREAT LAKES. THE COMBINATION OF THE MODERATELY STRONG PRESSURE GRADIENT AND STRONG COLD ADVECTION BEHIND THE EXITING FRONT WILL KEEP WINDS AROUND 25 TO 30KT OVER THE LAKE FROM WEDNESDAY THROUGH SATURDAY. KREIN && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
201 AM CST TUE DEC 6 2011 .DISCUSSION... 852 PM CST A FEW CHALLENGES REVOLVING AROUND THE LAKE EFFECT PRECIPITATION THIS EVENING. RADAR IMAGERY SHOWS PRECIPITATION FROM MILWAUKEE SOUTH INTO NORTHERN WILL COUNTY. WATER VAPOR IMAGERY SHOWS DEFORMATION ZONE MOVING EAST OF THE FORECAST AREA WITH SUBSIDENCE AND MID LEVEL DRY AIR MOVING IN FROM THE SOUTHWEST. HAVE SEEN OVERALL INTENSITY OF RETURNS OFF THE LAKE DECREASE SOMEWHAT AS THIS FEATURE PROGRESSES THROUGH...BUT FORECAST SOUNDINGS SHOW LITTLE CHANGE IN THE LOW AND MID LEVELS OVERNIGHT AND SUSPECT AREA OF PRECIPITATION WILL CONTINUE THROUGH THE REMAINDER OF THE EVENING AND OVERNIGHT. SOUNDINGS DO SHOW A SLIGHT DECREASE IN THE INVERSION HEIGHTS BETWEEN 06-09Z...AND MOST OF THE HIGH-RES GUIDANCE...WITH THE RUC BEING THE EXCEPTION...SHOWS PRECIP DIMINISHING LATE TONIGHT. SUSPECT THE RUC MAY BE ONTO SOMETHING THOUGH...WITH NO REAL SENSE OF WHAT MAY CAUSE LAKE EFFECT TO SHUT OFF OVERNIGHT...THUS WILL BUMP UP POPS FOR TONIGHT. PRECIP TYPE ALSO A BIG QUESTION MARK. THE 129DM LINE ON THE 1000-850MB THICKNESS LINES UP WELL WITH CURRENT RAIN-SNOW LINE AND DOES GRADUALLY SHIFT SOUTH THROUGH COOK COUNTY TONIGHT...BUT LOCALIZED EFFECTS WITH WARM AIR OFF THE LAKE AND URBAN HEAT ISLAND WILL DELAY THE CHANGE OVER TO SNOW FOR AREAS ALONG THE LAKESHORE AND PORTIONS OF COOK COUNTY DESPITE THE GRADUAL COOL ADVECTION. HOWEVER...WET-BULBING EFFECTS UNDER THE HEAVIER SHOWERS MAY DOMINATE...AND HAS ALREADY BEEN EVIDENT ON DUAL-POL IMAGERY WITH SOME OF THE SHOWERS THAT PASSED OVER SOUTHERN DUPAGE COUNTY EARLIER TONIGHT WHERE SNOW BRIEFLY MADE ITS WAY TO THE SURFACE. SO DO EXPECT A CHANGE OVER TO SNOW AT SOME POINT...BUT HAVE VERY LOW CONFIDENCE ON PRECISE TIMING. PRECIP AMOUNT REPORTS HAVE BEEN ON THE ORDER OF A FEW HUNDREDTHS THUS FAR UNDER THE STRONGEST RETURNS...AND SEE NO REASON FOR THIS TO CHANGE OVERNIGHT NOR HAVE ANY CONCERNS FOR ACCUMULATIONS. FORECAST UPDATES TO FOLLOW SHORTLY...BMD //PREV DISCUSSION... NEAR TERM....THIS AFTERNOON THROUGH TONIGHT... VISIBLE IMAGERY CONTINUES TO SHOW A THICK STRATUS LAYER OVERHEAD. VERTICAL GROWTH OF THE CLOUD DESK REMAINS WELL SOUTH OF THE REGION OVER THE OZARKS AND WESTERN TENNESSEE. WITH THE ABUNDANT SOLAR SHIELDING...TEMPERATURES THIS AFTERNOON HAVE NOT WARMED MUCH. THUS EXPECT TEMPS TO REMAIN IN THE MID/UPR 30S. BETTER COLD AIR ADVECTION HAS CONTINUED TO OCCUR ACROSS WEST CENTRAL ILLINOIS WHERE TEMPERATURES HAVE HELD AROUND 30...AND IN THE MID 20S ACROSS CENTRAL MISSOURI. IR IMAGERY THIS AFTERNOON ALSO CONTINUES TO INDICATE MUCH THICKER CLOUD COVER OVER ILLINOIS/INDIANA. WSR-88D RADAR WAS DEPICTING PRECIPITATION PUSHING INLAND ACROSS BOTH COOK AND LAKE COUNTY ILLINOIS...AS LAKE MOISTURE SLOWLY SLIDES SOUTH/SOUTHWEST. MOISTURE REMAINS VERY SHALLOW AND MINIMAL LIFT...SUPPORTING PRECIP TO REMAIN AS LIQUID WITH PATCHY DRIZZLE. FURTHER NORTH A FEW OBSERVATIONS ACROSS WISCONSIN HAVE REPORTED LGT SN. FOR FAR NORTHEAST ILLINOIS TEMPERATURES ARE WARM ENOUGH TO MAINTAIN A LIQUID STATE OF PRECIPITATION. QUASI-STATIONARY BOUNDARY REMAINS TO OUR SOUTHEAST ACROSS THE OZARKS STRETCHING NORTHEAST THROUGH THE OHIO VALLEY. OVERNIGHT THE CHALLENGE WILL CONTINUE TO BE COVERAGE OF PRECIP...AND TEMPERATURES. GUIDANCE HAS SUGGESTED THAT TEMPERATURES WILL COOL MORE EFFICIENTLY TONIGHT WITH BETTER COLD AIR ADVECTION INTO NORTHERN IL/NORTHWEST IN...HOWEVER FEEL THIS IS TOO OVERDONE. THUS HAVE ADJUSTED OVERNIGHT LOWS UP A FEW DEGREES GIVEN THE EXPECTED THICK CLOUD COVER. WINDS START TO TURN NORTHEASTERLY THIS EVENING AND CONTINUE OVERNIGHT...WHICH SHOULD AID IN BENDING THE LAKE MOISTURE SOUTHWEST OR OVER NORTHEAST ILLINOIS. THUS HAVE MAINTAINED MENTION OF SLIGHT CHANCE WORDING. VERTICAL LIFT APPEARS TO BUMP UP A TAD OVERNIGHT...WITH SFC TEMPS PUSHING CLOSER TO FREEZING. MODEL SOUNDINGS INDICATE THAT ANY PRECIP THAT FALLS THIS EVENING WOULD START AS LIQUID...THEN POSSIBLY START TO MIX WITH LGT SNOW. AS PREVIOUSLY MENTIONED ABOUT THE MINIMAL LIFTING MECHANISM...IT IS POSSIBLE THAT PATCHY DRIZZLE COULD OCCUR BEFORE LGT SNOW WOULD OCCUR. QPF REMAINS MINIMAL...OR LESS THAN 0.05 THROUGH THE NEXT 24HRS. MORE THAN LIKELY IT IS CLOSER TO 0.01 TO 0.03. BASED ON THE EXPECTED TEMPERATURES AND MINIMAL LIFT...ANY SNOW THAT DOES FALL MAY ACCUMULATE UP TO A QUARTER OF AN INCH. ALTHOUGH THAT BEING SAID...CONFIDENCE IS LOW THAT THIS SCENARIO WOULD PAN OUT. TUESDAY THROUGH THURSDAY... A WEAK WAVE IS PROGGED TO DEVELOP ALONG THE QUASI-STATIONARY BOUNDARY AND SLIDE NORTHEAST THROUGH MISSOURI. ANTI-CYCLONIC FLOW REMAINS UPSTREAM ACROSS IOWA/MINNESOTA/WISCONSIN...WHICH SHOULD START TO TURN OFF LAKE MOISTURE SOMETIME TUE AFTN/EVE. HAVE HELD ONTO MENTION OF LGT RA/SN THRU THE MORNING HOURS. AFTN TEMPS SHOULD WARM MARGINALLY TO AROUND THE MID 30S ACROSS MOST OF THE CWFA. BY TUE AFTN/EVE THE INFLUENCE FROM THE UPSTREAM RIDGE SHOULD FINALLY ERODE THE THICK STRATUS AND ALLOW PARTLY CLOUD SKIES TO DEVELOP BY THE LATE AFTN/EVE. THIS COUPLED WITH 850MB THERMAL TROUGH OF -10 TO -12 DEG...WILL SET THE STAGE FOR OVERNIGHT LOWS IN THE TEENS TO LOWER 20S. AS WINDS SLOWLY SHIFT FROM THE NORTHWEST TO THE WEST/SOUTHWEST WED...THE LAKE MOISTURE WILL BECOME ORIENTED OVER LOWER MICHIGAN. 500MB VORT SLOWLY SLIDES EAST ALONG THE SOUTHERN STREAM...WHILE THE NORTHERN STREAM REMAINS IN PROGRESSIVE. THE FOCUS WED WILL CONTINUE TO BE ON THE ARRIVAL OF A POTENT FRONTAL BOUNDARY...THAT IS COUPLED WITH AN 850MB THERMAL TROUGH OF -20 TO -22 DEG C. THIS WILL PROVIDE THE COOLEST AIR OF THE SEASON LATER IN THE WEEK TO NORTHERN IL/NORTHWEST IN. PRIOR TO THE ARRIVAL OF THIS AIRMASS...MOISTURE IS EXPECTED TO POOL ALONG THE FRONT AS IT SLOWLY PUSHES SOUTHEAST ACROSS THE PLAINS THURSDAY. GUIDANCE HAS FLUCTUATED ON HOW THIS FEATURE WILL UNFOLD...AND IT REMAINS POSSIBLE THAT A WEAK WAVE WILL DEVELOP ALONG THE LEE-SIDE OF THE 500MB TROUGH AXIS. THIS SCENARIO COULD RESULT IN LGT SNOW OVERSPREADING NORTHERN IL/NORTHWEST IN THUR AFTN AS THE POTENT THERMAL TROUGH ARRIVES ALOFT. TEMPS THUR WILL REMAIN IN THE LOW/MID 30S. BEACHLER LONG TERM...THURSDAY NIGHT THROUGH MONDAY MAIN CONCERNS IN THE EXTENDED PORTION OF THE FORECAST ARE LIGHT SNOW POTENTIAL THURSDAY NIGHT INTO EARLY FRIDAY...FOLLOWED BY THE FIRST BLAST OF ARCTIC AIR OF THE SEASON FOR FRIDAY INTO EARLY SATURDAY. ON THURSDAY NIGHT...AS MENTIONED ABOVE...DIGGING H5 TROUGH WILL SPAWN A WEAK SURFACE LOW WHICH WILL TRACK ACROSS NORTHERN GREAT LAKES AND SEND AN ARCTIC FRONTAL BOUNDARY TOWARD AREA. MODELS HAVE BEEN CONSISTENT IN SPITTING OUT A STRIPE OF VERY LIGHT QPF NEAR OR OVER CWA IN RESPONSE TO THIS FEATURE. WITH NEGATIVE TEEN AIR AT H85 BUILDING IN FROM THE NORTH BEHIND ARCTIC FRONT...SUSPECT WAVE WILL RIDE ALONG LOW LEVEL BAROCLINIC ZONE. A PEEK AT GFS TIME HEIGHT AT ORD FOR THURSDAY NIGHT PERIOD SHOWS SATURATION AND ADEQUATE LIFT INTO -15C FAVORED SNOW GROWTH ZONE. THEREFORE...DESPITE QPF ONLY IN THE HUNDREDTHS UP TO MAYBE A TENTH OR SLIGHTLY MORE...WITH VERY COLD AIR MASS...SNOW WOULD BE HIGH RATIO AND POSSIBLY RESULT IN FIRST WIDESPREAD LIGHT ACCUMULATING SNOW OF THE SEASON FOR MANY (IF SCENARIO PANS OUT...POTENTIAL FOR AN INCH OR TWO OF SNOW). FOR NOW...HAVE BUMPED UP POPS IN GRIDS TO CHANCE ACROSS THE AREA GIVEN SOME UNCERTAINTY IN EXACTLY WHERE BEST SNOW POTENTIAL WILL OCCUR. LIGHT SNOW MAY LINGER INTO EARLY FRIDAY FOR EASTERN PORTION OF CWA BEFORE WAVE SHIFTS OFF TO THE EAST. THEREAFTER...ON FRIDAY...STRONG CAA WILL BE IN FULL FORCE WITH SHARP THERMAL TROUGH ARRIVING OVERHEAD LATE IN THE DAY. OPERATIONAL MODELS AND ENSEMBLES HAVE BACKED OFF EVER SO SLIGHTLY ON JUST HOW COLD ARCTIC AIR MASS WILL BE...BUT -15C OR SO AT H85 AND -8 TO -10 AT H95 WILL BE PLENTY COLD. TEMPERATURES WILL STRUGGLE INTO THE MID TO UPPER 20S FRIDAY AFTERNOON WITH A PERSISTENT WNW BREEZE LEADING TO LOW WIND CHILL VALUES. AXIS OF ARCTIC HIGH WILL PASS CLOSEST ON FRIDAY NIGHT...LEADING TO STRONG RADIATIONAL COOLING. IF MINOR SNOW COVER IS PRESENT...LOW TO MID TEENS...UPPER TEENS IN DOWNTOWN CHICAGO...IN GRIDS FOR LOW EARLY SATURDAY MORNING MIGHT BE A FEW DEGREES TOO HIGH. SW FLOW...STEADY WARMING ALOFT AND LIKELY FULL SUNSHINE ON SATURDAY WILL ALLOW FOR SOME RECOVERY FROM VERY COLD START TO DAY...BUT SUSPECT IT WILL BE TOUGH TO MAKE UP A LOT OF GROUND DUE TO LIMITED DAYLIGHT THIS TIME OF YEAR. THUS SHAVED OFF A DEGREE FROM MODEL BLEND FOR MAX TEMPERATURES ON SATURDAY...YIELDING HIGHS IN THE UPPER 20S TO AROUND 30 DEGREES. SUNDAY AND MONDAY LOOK TO BE MAINLY DRY WITH TEMPERATURES RETURNING TO CLOSE TO SEASONAL NORMS DUE TO SOUTHERLY FLOW AND CONTINUED WARMING OF THE COLUMN. A FRONTAL BOUNDARY MAY DROP SOUTH THROUGH THE AREA LATE MONDAY... BRINGING NEXT CHANCE FOR LIGHT PRECIP...BUT LARGE MODEL UNCERTAINTY THIS FAR OUT PRECLUDES ANYTHING MORE THAN SLIGHT POPS FOR MONDAY NIGHT. RC && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 08Z... * POTENTIAL FOR LAKE EFFECT RAIN/SNOW SHOWERS THROUGH THE AFTERNOON * PERIODS OF MVFR CIGS THROUGH TUESDAY EVENING. SHEA //DISCUSSION...UPDATED 06Z... MAIN FORECAST CONCERN AND CHALLENGE REMAINS THE LAKE EFFECT RAIN/ SNOW SHOWERS. OVERALL INTENSITY HAS DIMINISHED SOME FROM EARLIER THIS EVENING BUT STILL MANY SHOWERS FROM FAR SOUTHEAST WI INTO NORTHEAST IL. COOLER AIR SLOWLY FILTERING IN FROM THE NORTH HAS CHANGED PRECIP TO MAINLY SNOW ACROSS SOUTHEAST WI INTO FAR NORTHEAST IL...AS WELL AS LOCATIONS FARTHER INLAND...SUCH AS DPA WHERE TEMPS HAVE ALSO COOLED A FEW DEGREES. FORECAST SOUNDINGS CONTINUE TO SHOW THE INVERSION HEIGHT LOWERING SOME THROUGH THE OVERNIGHT HRS AND THIS SHOULD LIMIT THE COVERAGE AND INTENSITY OF THE LAKE EFFECT SHOWERS OVERNIGHT. WHILE THERE WILL STILL LIKELY BE PERIODS OF LIGHT RAIN AND/OR LIGHT SNOW...CONFIDENCE IN TRYING TO TIME ANY OF THIS PRECIP IS VERY LOW. AND FOR THAT REASON...HAVE GONE WITH A VICINITY MENTION...THOUGH LATER UPDATES FOR PREVAILING OR TEMPO PRECIP MAY BE NEEDED. LITTLE CHANGE TO THE AIRMASS OR LOW LEVEL PROFILES INTO TUESDAY AFTERNOON AND THERE COULD BE ADDITIONAL LAKE EFFECT SHOWERS THROUGH SUNSET...PERHAPS AIDED BY DIURNAL WARMING BY MID/LATE MORNING. CONFIDENCE VERY LOW HERE AS WELL. OUTSIDE OF PRECIP AREAS...CIGS HAVE GENERALLY LIFTED INTO LOW VFR WITH A FEW PATCHES OF HIGH MVFR CIGS. EXPECT THIS OVERALL TREND TO CONTINUE WITH MVFR POSSIBLE IN AREAS OF HEAVIER PRECIP. THOUGH AM CONCERNED THAT THERE COULD BE ANOTHER PERIOD OF MVFR CIGS TUESDAY AFTERNOON. WITH A RIDGE OF HIGH PRESSURE MOVING ACROSS THE AREA TUESDAY NIGHT...ANY MVFR CIGS MAY GET TRAPPED BELOW THE INVERSION AND COULD PERSIST WELL INTO TUESDAY NIGHT. NORTHEAST WINDS WILL SLOWLY TURN MORE NORTHERLY TUESDAY AFTERNOON THEN SHOULD FLOP WESTERLY TUESDAY EVENING AS THE ABOVE MENTIONED RIDGE BUILDS ACROSS THE AREA. WINDS COULD POTENTIALLY BECOME LIGHT AND VRB OR EVEN CALM TUESDAY EVENING. IN THE SHORT TERM...GRADIENT WILL SLOWLY RELAX OVERNIGHT AND THINK THE PREVAILING GUSTS HAVE ENDED EXCEPT AT GYY AND ALONG THE LAKE...WITH PREVAILING SPEEDS IN THE 9-13KT RANGE. CMS //ORD AND MDW CONFIDENCE...UPDATED 08Z... * LOW CONFIDENCE REGARDING PRECIP TYPE/TIMING/DURATION/INTENSITY THROUGH THE PERIOD * MEDIUM CONFIDENCE PREVAILING CIGS WILL BECOME/REMAIN VFR THROUGH TUESDAY MORNING...LOW CONFIDENCE PREVAILING MVFR CIGS MAY RETURN TUESDAY MORNING/AFTERNOON SHEA //OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z... WEDNESDAY AND THURSDAY...VFR. THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE. FRIDAY THROUGH SUNDAY...VFR. CMS && .MARINE... 147 PM CST HIGH PRESSURE ACROSS THE PLAINS WILL SLOWLY SAG SOUTHWARD TUESDAY AND TUESDAY NIGHT AS A STRONG AREA OF LOW PRESSURE MOVES ACROSS NORTHERN MANITOBA INTO THE HUDSON BAY. AS A CONSEQUENCE OF THIS...WINDS ARE EXPECTED TO BECOME WEST SOUTHWESTERLY AND INCREASE TO NEAR 30 KT LATE TUESDAY NIGHT AND ON WEDNESDAY. THEN WEDNESDAY NIGHT A STRONG COLD FRONT...ASSOCIATED WITH THE LOW ACROSS NORTHERN CANADA...WILL PUSH SOUTH ACROSS LAKE MICHIGAN. WEST TO NORTHWEST WINDS WILL OCCUR IN THE WAKE OF THIS FRONT. FOLLOWING THIS FRONT...ANOTHER CANADIAN HIGH PRESSURE SYSTEM WILL DROP SOUTHEAST ACROSS THE PLAINS THURSDAY AND FRIDAY. THIS SHOULD HELP SUPPORT A DECENT PRESSURE GRADIENT ACROSS THE GREAT LAKES. THUS...IN COMBINATION WITH A VERY COLD AIR MASS OVER THE RELATIVELY WARM WATERS OF LAKE MICHIGAN...WINDS WILL LIKELY REMAIN ELEVATED IN THE 20 TO 25 KT RANGE DURING THIS PERIOD. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1101 PM CST MON DEC 5 2011 .DISCUSSION... 852 PM CST A FEW CHALLENGES REVOLVING AROUND THE LAKE EFFECT PRECIPITATION THIS EVENING. RADAR IMAGERY SHOWS PRECIPITATION FROM MILWAUKEE SOUTH INTO NORTHERN WILL COUNTY. WATER VAPOR IMAGERY SHOWS DEFORMATION ZONE MOVING EAST OF THE FORECAST AREA WITH SUBSIDENCE AND MID LEVEL DRY AIR MOVING IN FROM THE SOUTHWEST. HAVE SEEN OVERALL INTENSITY OF RETURNS OFF THE LAKE DECREASE SOMEWHAT AS THIS FEATURE PROGRESSES THROUGH...BUT FORECAST SOUNDINGS SHOW LITTLE CHANGE IN THE LOW AND MID LEVELS OVERNIGHT AND SUSPECT AREA OF PRECIPITATION WILL CONTINUE THROUGH THE REMAINDER OF THE EVENING AND OVERNIGHT. SOUNDINGS DO SHOW A SLIGHT DECREASE IN THE INVERSION HEIGHTS BETWEEN 06-09Z...AND MOST OF THE HIGH-RES GUIDANCE...WITH THE RUC BEING THE EXCEPTION...SHOWS PRECIP DIMINISHING LATE TONIGHT. SUSPECT THE RUC MAY BE ONTO SOMETHING THOUGH...WITH NO REAL SENSE OF WHAT MAY CAUSE LAKE EFFECT TO SHUT OFF OVERNIGHT...THUS WILL BUMP UP POPS FOR TONIGHT. PRECIP TYPE ALSO A BIG QUESTION MARK. THE 129DM LINE ON THE 1000-850MB THICKNESS LINES UP WELL WITH CURRENT RAIN-SNOW LINE AND DOES GRADUALLY SHIFT SOUTH THROUGH COOK COUNTY TONIGHT...BUT LOCALIZED EFFECTS WITH WARM AIR OFF THE LAKE AND URBAN HEAT ISLAND WILL DELAY THE CHANGE OVER TO SNOW FOR AREAS ALONG THE LAKESHORE AND PORTIONS OF COOK COUNTY DESPITE THE GRADUAL COOL ADVECTION. HOWEVER...WET-BULBING EFFECTS UNDER THE HEAVIER SHOWERS MAY DOMINATE...AND HAS ALREADY BEEN EVIDENT ON DUAL-POL IMAGERY WITH SOME OF THE SHOWERS THAT PASSED OVER SOUTHERN DUPAGE COUNTY EARLIER TONIGHT WHERE SNOW BRIEFLY MADE ITS WAY TO THE SURFACE. SO DO EXPECT A CHANGE OVER TO SNOW AT SOME POINT...BUT HAVE VERY LOW CONFIDENCE ON PRECISE TIMING. PRECIP AMOUNT REPORTS HAVE BEEN ON THE ORDER OF A FEW HUNDREDTHS THUS FAR UNDER THE STRONGEST RETURNS...AND SEE NO REASON FOR THIS TO CHANGE OVERNIGHT NOR HAVE ANY CONCERNS FOR ACCUMULATIONS. FORECAST UPDATES TO FOLLOW SHORTLY...BMD //PREV DISCUSSION... NEAR TERM....THIS AFTERNOON THROUGH TONIGHT... VISIBLE IMAGERY CONTINUES TO SHOW A THICK STRATUS LAYER OVERHEAD. VERTICAL GROWTH OF THE CLOUD DESK REMAINS WELL SOUTH OF THE REGION OVER THE OZARKS AND WESTERN TENNESSEE. WITH THE ABUNDANT SOLAR SHIELDING...TEMPERATURES THIS AFTERNOON HAVE NOT WARMED MUCH. THUS EXPECT TEMPS TO REMAIN IN THE MID/UPR 30S. BETTER COLD AIR ADVECTION HAS CONTINUED TO OCCUR ACROSS WEST CENTRAL ILLINOIS WHERE TEMPERATURES HAVE HELD AROUND 30...AND IN THE MID 20S ACROSS CENTRAL MISSOURI. IR IMAGERY THIS AFTERNOON ALSO CONTINUES TO INDICATE MUCH THICKER CLOUD COVER OVER ILLINOIS/INDIANA. WSR-88D RADAR WAS DEPICTING PRECIPITATION PUSHING INLAND ACROSS BOTH COOK AND LAKE COUNTY ILLINOIS...AS LAKE MOISTURE SLOWLY SLIDES SOUTH/SOUTHWEST. MOISTURE REMAINS VERY SHALLOW AND MINIMAL LIFT...SUPPORTING PRECIP TO REMAIN AS LIQUID WITH PATCHY DRIZZLE. FURTHER NORTH A FEW OBSERVATIONS ACROSS WISCONSIN HAVE REPORTED LGT SN. FOR FAR NORTHEAST ILLINOIS TEMPERATURES ARE WARM ENOUGH TO MAINTAIN A LIQUID STATE OF PRECIPITATION. QUASI-STATIONARY BOUNDARY REMAINS TO OUR SOUTHEAST ACROSS THE OZARKS STRETCHING NORTHEAST THROUGH THE OHIO VALLEY. OVERNIGHT THE CHALLENGE WILL CONTINUE TO BE COVERAGE OF PRECIP...AND TEMPERATURES. GUIDANCE HAS SUGGESTED THAT TEMPERATURES WILL COOL MORE EFFICIENTLY TONIGHT WITH BETTER COLD AIR ADVECTION INTO NORTHERN IL/NORTHWEST IN...HOWEVER FEEL THIS IS TOO OVERDONE. THUS HAVE ADJUSTED OVERNIGHT LOWS UP A FEW DEGREES GIVEN THE EXPECTED THICK CLOUD COVER. WINDS START TO TURN NORTHEASTERLY THIS EVENING AND CONTINUE OVERNIGHT...WHICH SHOULD AID IN BENDING THE LAKE MOISTURE SOUTHWEST OR OVER NORTHEAST ILLINOIS. THUS HAVE MAINTAINED MENTION OF SLIGHT CHANCE WORDING. VERTICAL LIFT APPEARS TO BUMP UP A TAD OVERNIGHT...WITH SFC TEMPS PUSHING CLOSER TO FREEZING. MODEL SOUNDINGS INDICATE THAT ANY PRECIP THAT FALLS THIS EVENING WOULD START AS LIQUID...THEN POSSIBLY START TO MIX WITH LGT SNOW. AS PREVIOUSLY MENTIONED ABOUT THE MINIMAL LIFTING MECHANISM...IT IS POSSIBLE THAT PATCHY DRIZZLE COULD OCCUR BEFORE LGT SNOW WOULD OCCUR. QPF REMAINS MINIMAL...OR LESS THAN 0.05 THROUGH THE NEXT 24HRS. MORE THAN LIKELY IT IS CLOSER TO 0.01 TO 0.03. BASED ON THE EXPECTED TEMPERATURES AND MINIMAL LIFT...ANY SNOW THAT DOES FALL MAY ACCUMULATE UP TO A QUARTER OF AN INCH. ALTHOUGH THAT BEING SAID...CONFIDENCE IS LOW THAT THIS SCENARIO WOULD PAN OUT. TUESDAY THROUGH THURSDAY... A WEAK WAVE IS PROGGED TO DEVELOP ALONG THE QUASI-STATIONARY BOUNDARY AND SLIDE NORTHEAST THROUGH MISSOURI. ANTI-CYCLONIC FLOW REMAINS UPSTREAM ACROSS IOWA/MINNESOTA/WISCONSIN...WHICH SHOULD START TO TURN OFF LAKE MOISTURE SOMETIME TUE AFTN/EVE. HAVE HELD ONTO MENTION OF LGT RA/SN THRU THE MORNING HOURS. AFTN TEMPS SHOULD WARM MARGINALLY TO AROUND THE MID 30S ACROSS MOST OF THE CWFA. BY TUE AFTN/EVE THE INFLUENCE FROM THE UPSTREAM RIDGE SHOULD FINALLY ERODE THE THICK STRATUS AND ALLOW PARTLY CLOUD SKIES TO DEVELOP BY THE LATE AFTN/EVE. THIS COUPLED WITH 850MB THERMAL TROUGH OF -10 TO -12 DEG...WILL SET THE STAGE FOR OVERNIGHT LOWS IN THE TEENS TO LOWER 20S. AS WINDS SLOWLY SHIFT FROM THE NORTHWEST TO THE WEST/SOUTHWEST WED...THE LAKE MOISTURE WILL BECOME ORIENTED OVER LOWER MICHIGAN. 500MB VORT SLOWLY SLIDES EAST ALONG THE SOUTHERN STREAM...WHILE THE NORTHERN STREAM REMAINS IN PROGRESSIVE. THE FOCUS WED WILL CONTINUE TO BE ON THE ARRIVAL OF A POTENT FRONTAL BOUNDARY...THAT IS COUPLED WITH AN 850MB THERMAL TROUGH OF -20 TO -22 DEG C. THIS WILL PROVIDE THE COOLEST AIR OF THE SEASON LATER IN THE WEEK TO NORTHERN IL/NORTHWEST IN. PRIOR TO THE ARRIVAL OF THIS AIRMASS...MOISTURE IS EXPECTED TO POOL ALONG THE FRONT AS IT SLOWLY PUSHES SOUTHEAST ACROSS THE PLAINS THURSDAY. GUIDANCE HAS FLUCTUATED ON HOW THIS FEATURE WILL UNFOLD...AND IT REMAINS POSSIBLE THAT A WEAK WAVE WILL DEVELOP ALONG THE LEE-SIDE OF THE 500MB TROUGH AXIS. THIS SCENARIO COULD RESULT IN LGT SNOW OVERSPREADING NORTHERN IL/NORTHWEST IN THUR AFTN AS THE POTENT THERMAL TROUGH ARRIVES ALOFT. TEMPS THUR WILL REMAIN IN THE LOW/MID 30S. BEACHLER LONG TERM...THURSDAY NIGHT THROUGH MONDAY MAIN CONCERNS IN THE EXTENDED PORTION OF THE FORECAST ARE LIGHT SNOW POTENTIAL THURSDAY NIGHT INTO EARLY FRIDAY...FOLLOWED BY THE FIRST BLAST OF ARCTIC AIR OF THE SEASON FOR FRIDAY INTO EARLY SATURDAY. ON THURSDAY NIGHT...AS MENTIONED ABOVE...DIGGING H5 TROUGH WILL SPAWN A WEAK SURFACE LOW WHICH WILL TRACK ACROSS NORTHERN GREAT LAKES AND SEND AN ARCTIC FRONTAL BOUNDARY TOWARD AREA. MODELS HAVE BEEN CONSISTENT IN SPITTING OUT A STRIPE OF VERY LIGHT QPF NEAR OR OVER CWA IN RESPONSE TO THIS FEATURE. WITH NEGATIVE TEEN AIR AT H85 BUILDING IN FROM THE NORTH BEHIND ARCTIC FRONT...SUSPECT WAVE WILL RIDE ALONG LOW LEVEL BAROCLINIC ZONE. A PEEK AT GFS TIME HEIGHT AT ORD FOR THURSDAY NIGHT PERIOD SHOWS SATURATION AND ADEQUATE LIFT INTO -15C FAVORED SNOW GROWTH ZONE. THEREFORE...DESPITE QPF ONLY IN THE HUNDREDTHS UP TO MAYBE A TENTH OR SLIGHTLY MORE...WITH VERY COLD AIR MASS...SNOW WOULD BE HIGH RATIO AND POSSIBLY RESULT IN FIRST WIDESPREAD LIGHT ACCUMULATING SNOW OF THE SEASON FOR MANY (IF SCENARIO PANS OUT...POTENTIAL FOR AN INCH OR TWO OF SNOW). FOR NOW...HAVE BUMPED UP POPS IN GRIDS TO CHANCE ACROSS THE AREA GIVEN SOME UNCERTAINTY IN EXACTLY WHERE BEST SNOW POTENTIAL WILL OCCUR. LIGHT SNOW MAY LINGER INTO EARLY FRIDAY FOR EASTERN PORTION OF CWA BEFORE WAVE SHIFTS OFF TO THE EAST. THEREAFTER...ON FRIDAY...STRONG CAA WILL BE IN FULL FORCE WITH SHARP THERMAL TROUGH ARRIVING OVERHEAD LATE IN THE DAY. OPERATIONAL MODELS AND ENSEMBLES HAVE BACKED OFF EVER SO SLIGHTLY ON JUST HOW COLD ARCTIC AIR MASS WILL BE...BUT -15C OR SO AT H85 AND -8 TO -10 AT H95 WILL BE PLENTY COLD. TEMPERATURES WILL STRUGGLE INTO THE MID TO UPPER 20S FRIDAY AFTERNOON WITH A PERSISTENT WNW BREEZE LEADING TO LOW WIND CHILL VALUES. AXIS OF ARCTIC HIGH WILL PASS CLOSEST ON FRIDAY NIGHT...LEADING TO STRONG RADIATIONAL COOLING. IF MINOR SNOW COVER IS PRESENT...LOW TO MID TEENS...UPPER TEENS IN DOWNTOWN CHICAGO...IN GRIDS FOR LOW EARLY SATURDAY MORNING MIGHT BE A FEW DEGREES TOO HIGH. SW FLOW...STEADY WARMING ALOFT AND LIKELY FULL SUNSHINE ON SATURDAY WILL ALLOW FOR SOME RECOVERY FROM VERY COLD START TO DAY...BUT SUSPECT IT WILL BE TOUGH TO MAKE UP A LOT OF GROUND DUE TO LIMITED DAYLIGHT THIS TIME OF YEAR. THUS SHAVED OFF A DEGREE FROM MODEL BLEND FOR MAX TEMPERATURES ON SATURDAY...YIELDING HIGHS IN THE UPPER 20S TO AROUND 30 DEGREES. SUNDAY AND MONDAY LOOK TO BE MAINLY DRY WITH TEMPERATURES RETURNING TO CLOSE TO SEASONAL NORMS DUE TO SOUTHERLY FLOW AND CONTINUED WARMING OF THE COLUMN. A FRONTAL BOUNDARY MAY DROP SOUTH THROUGH THE AREA LATE MONDAY... BRINGING NEXT CHANCE FOR LIGHT PRECIP...BUT LARGE MODEL UNCERTAINTY THIS FAR OUT PRECLUDES ANYTHING MORE THAN SLIGHT POPS FOR MONDAY NIGHT. RC && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 06Z... * POTENTIAL FOR LAKE EFFECT RAIN/SNOW SHOWERS THROUGH TUESDAY AFTERNOON. * PERIODS OF MVFR CIGS THROUGH TUESDAY EVENING. CMS //DISCUSSION...UPDATED 06Z... MAIN FORECAST CONCERN AND CHALLENGE REMAINS THE LAKE EFFECT RAIN/ SNOW SHOWERS. OVERALL INTENSITY HAS DIMINISHED SOME FROM EARLIER THIS EVENING BUT STILL MANY SHOWERS FROM FAR SOUTHEAST WI INTO NORTHEAST IL. COOLER AIR SLOWLY FILTERING IN FROM THE NORTH HAS CHANGED PRECIP TO MAINLY SNOW ACROSS SOUTHEAST WI INTO FAR NORTHEAST IL...AS WELL AS LOCATIONS FARTHER INLAND...SUCH AS DPA WHERE TEMPS HAVE ALSO COOLED A FEW DEGREES. FORECAST SOUNDINGS CONTINUE TO SHOW THE INVERSION HEIGHT LOWERING SOME THROUGH THE OVERNIGHT HRS AND THIS SHOULD LIMIT THE COVERAGE AND INTENSITY OF THE LAKE EFFECT SHOWERS OVERNIGHT. WHILE THERE WILL STILL LIKELY BE PERIODS OF LIGHT RAIN AND/OR LIGHT SNOW...CONFIDENCE IN TRYING TO TIME ANY OF THIS PRECIP IS VERY LOW. AND FOR THAT REASON...HAVE GONE WITH A VICINITY MENTION...THOUGH LATER UPDATES FOR PREVAILING OR TEMPO PRECIP MAY BE NEEDED. LITTLE CHANGE TO THE AIRMASS OR LOW LEVEL PROFILES INTO TUESDAY AFTERNOON AND THERE COULD BE ADDITIONAL LAKE EFFECT SHOWERS THROUGH SUNSET...PERHAPS AIDED BY DIURNAL WARMING BY MID/LATE MORNING. CONFIDENCE VERY LOW HERE AS WELL. OUTSIDE OF PRECIP AREAS...CIGS HAVE GENERALLY LIFTED INTO LOW VFR WITH A FEW PATCHES OF HIGH MVFR CIGS. EXPECT THIS OVERALL TREND TO CONTINUE WITH MVFR POSSIBLE IN AREAS OF HEAVIER PRECIP. THOUGH AM CONCERNED THAT THERE COULD BE ANOTHER PERIOD OF MVFR CIGS TUESDAY AFTERNOON. WITH A RIDGE OF HIGH PRESSURE MOVING ACROSS THE AREA TUESDAY NIGHT...ANY MVFR CIGS MAY GET TRAPPED BELOW THE INVERSION AND COULD PERSIST WELL INTO TUESDAY NIGHT. NORTHEAST WINDS WILL SLOWLY TURN MORE NORTHERLY TUESDAY AFTERNOON THEN SHOULD FLOP WESTERLY TUESDAY EVENING AS THE ABOVE MENTIONED RIDGE BUILDS ACROSS THE AREA. WINDS COULD POTENTIALLY BECOME LIGHT AND VRB OR EVEN CALM TUESDAY EVENING. IN THE SHORT TERM...GRADIENT WILL SLOWLY RELAX OVERNIGHT AND THINK THE PREVAILING GUSTS HAVE ENDED EXCEPT AT GYY AND ALONG THE LAKE...WITH PREVAILING SPEEDS IN THE 9-13KT RANGE. CMS //ORD AND MDW CONFIDENCE...UPDATED 06Z... * LOW CONFIDENCE REGARDING PRECIP TYPE/TIMING/DURATION/INTENSITY THROUGH THE PERIOD. * MEDIUM CONFIDENCE PREVAILING CIGS WILL BECOME/REMAIN VFR THROUGH TUESDAY MORNING...LOW CONFIDENCE PREVAILING MVFR CIGS MAY RETURN TUESDAY MORNING/AFTERNOON. CMS //OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z... WEDNESDAY AND THURSDAY...VFR. THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE. FRIDAY THROUGH SUNDAY...VFR. CMS && .MARINE... 147 PM CST HIGH PRESSURE ACROSS THE PLAINS WILL SLOWLY SAG SOUTHWARD TUESDAY AND TUESDAY NIGHT AS A STRONG AREA OF LOW PRESSURE MOVES ACROSS NORTHERN MANITOBA INTO THE HUDSON BAY. AS A CONSEQUENCE OF THIS...WINDS ARE EXPECTED TO BECOME WEST SOUTHWESTERLY AND INCREASE TO NEAR 30 KT LATE TUESDAY NIGHT AND ON WEDNESDAY. THEN WEDNESDAY NIGHT A STRONG COLD FRONT...ASSOCIATED WITH THE LOW ACROSS NORTHERN CANADA...WILL PUSH SOUTH ACROSS LAKE MICHIGAN. WEST TO NORTHWEST WINDS WILL OCCUR IN THE WAKE OF THIS FRONT. FOLLOWING THIS FRONT...ANOTHER CANADIAN HIGH PRESSURE SYSTEM WILL DROP SOUTHEAST ACROSS THE PLAINS THURSDAY AND FRIDAY. THIS SHOULD HELP SUPPORT A DECENT PRESSURE GRADIENT ACROSS THE GREAT LAKES. THUS...IN COMBINATION WITH A VERY COLD AIR MASS OVER THE RELATIVELY WARM WATERS OF LAKE MICHIGAN...WINDS WILL LIKELY REMAIN ELEVATED IN THE 20 TO 25 KT RANGE DURING THIS PERIOD. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS TOPEKA KS
339 AM CST TUE DEC 6 2011 .DISCUSSION... SHORT RANGE FORECAST (TODAY AND WEDNESDAY)... 8Z WATER VAPOR IMAGERY AND ASSOCIATED 500 MB RUC ANALYSIS SHOWS A HIGHLY AMPLIFIED POSITIVELY TILTED TROUGH OVER THE CENTRAL PLAINS WITH ITS AXIS EXTENDING FROM LAKE SUPERIOR AND RUNNING SOUTHWESTWARD THROUGH NEBRASKA AND INTO THE FOUR CORNER REGION. CURRENTLY TEMPERATURES ACROSS CENTRAL NEBRASKA ARE BELOW ZERO AS THE SURFACE RIDGE OF HIGH PRESSURE IS CENTERED OVER NEBRASKA. THE COLDEST LOCATION REMAINS KBBW WHERE THE TEMP AT 9Z WAS -11. ACROSS NORTHEAST KANSAS TEMPERATURES REMAIN IN THE MID TEENS WITH WIND CHILLS IN THE SINGLE DIGITS. ACROSS SOUTHEAST KANSAS MEAGER FRONTOGENETICAL AND ISENTROPIC LIFT HAS BROUGHT SOME LIGHT SNOW...MAINLY IN THE FORM OF NON-ACCUMULATING FLURRIES. BY MID-DAY ON TUESDAY EXPECT THE LOW/MID LEVEL LIFT AND SATURATED CONDITIONS TO MOVE OFF THE EAST OF THE FORECAST AREA ALLOWING A GRADUAL BREAKDOWN OF THE STRATUS DECK. EXPECT VERY LIGHT COLD AIR ADVECTION TO PERSIST THROUGHOUT THE DAY AS WINDS STAY FROM THE NORTH WHERE THE SURFACE HIGH WILL RESIDE. AS A RESULT OF THE COLD AIR ADVECTION AND THE ABBREVIATED DURATION OF CLEAR SKIES EXPECT TEMPS ON TUESDAY TO REMAIN IN THE MID TO UPPER 20S ACROSS AREAS NORTH OF THE KANSAS TURNPIKE...WITH TEMPS SOUTH AND EAST OF THE TURNPIKE REACHING THE LOWER 30S. FOR TUESDAY NIGHT THE SURFACE HIGH MOVES EASTWARD AND CENTERS OVER NORTHEAST KANSAS. EXPECT SKIES TO CLEAR OUT AND WINDS TO GO CALM OVERNIGHT. EXPECT TUESDAY NIGHT/WED MORNING TO BE THE COLDEST PERIOD FOR THIS FORECAST PACKAGE AS TEMPS WILL DROP TO THE LOWER TEENS ACROSS THE ENTIRE AREA...WITH THE LOWER TERRAIN OF RIVER VALLEYS PERHAPS DROPPING INTO THE SINGLE DIGITS. BY WEDNESDAY THE ARCTIC AIRMASS WHICH BROUGHT THE FRIGID TEMPS FOR THE EARLY PART OF THE WEEK WILL SHIFT EAST AND WARMER AIR WILL ADVECT INTO THE AREA...ALLOWING WEDNESDAY`S TEMPS TO REACH THE UPPER 30S TO LOWER 40S. MID-RANGE AND EXTENDED FORECAST (THURSDAY THROUGH MONDAY)... FAIRLY INACTIVE WEATHER PATTERN SHAPING UP FOR THE MIDDLE TO LATE PART OF THE WEEK AND INTO THE WEEKEND...AS NO REAL MID OR UPPER LEVEL FORCING ENTERS THE AREA. ALTHOUGH THE DAY TIME HOURS WILL BE SLIGHTLY WARMER FOR THE MIDDLE TO LATE PART OF THE WEEK OVERNIGHT LOWS WILL STILL DROP TO THE MID TEENS TO UPPER 20S AS ANOTHER MASS OF COLD AIR DIPS INTO THE AREA. PERHAPS THE ONLY WEATHER TO AFFECT NORTHEAST KANSAS WILL BE LATE IN THE WEEK AS AN UPPER LEVEL LOW DIGS SOUTHWARD THROUGH NEBRASKA BUT ITS SOUTHWARD PROGRESS STOPS IN SOUTHERN NEBRASKA BEFORE IT EJECTS EASTWARD. WITH LITTLE MOISTURE FOR THE SYSTEM TO WORK WITH EXPECT ONLY A FEW FLURRIES ACROSS AREAS NORTH OF HIGHWAY 24 THURSDAY NIGHT/FRIDAY MORNING. THEREAFTER EXPECT A DRY FORECAST FOR THE REST OF THE WEEK AND THROUGH THE WEEKEND WITH DAYTIME HIGHS IN THE 40S AND OVERNIGHT LOWS IN THE UPPER 20S TO LOWER 30S. JL && .AVIATION... FORECAST SOUNDINGS AND SATELLITE TRENDS SUGGEST MVFR CIGS TO REMAIN OVER THE TERMINALS THROUGH 12Z OR SO. EXPECT MHK TO BREAK OUT EARLIER WITH TOP AND FOE TO FOLLOW AS SUBSIDENCE ERODES THE CLOUDS BY 18Z. WINDS CONTINUE NORTH NEAR 10 KTS THEN DECREASE AS SURFACE HIGH MOVES EAST. 53 && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS GOODLAND KS
1020 PM MST MON DEC 5 2011 .UPDATE... 850 PM MDT MON DEC 5 2011 LATEST RUC HRRR HAS A BIT BETTER HANDLE ON COLDER TEMPS PRESENTLY AND THROUGH THE REST OF THE OVERNIGHT REALLY TANKS TEMPS IN AREAS SUCH AS MCCOOK AND NORTON WITH READINGS IN THE -10F TO -14F RANGE AFTER 12Z. 00Z MET GUIDANCE FOR KMCK SHOWING -9F. KMCK DROPPED TO -1F 2 MORNINGS AGO. HAVE UPDATED MINS TO DROP THEM TO AROUND -11F WHILE IN NORTON HAVE LOWERED THEM TO THE -10F RANGE. FOR NORTON COUNTY COMBINATION OF THE 10F FORECAST AND WEST WIND OF 5 MPH OR LESS PUTS THEM IN WIND CHILL ADVISORY CRITERIA. WILL CONTINUE TO MONITOR 03Z RUN OF THE HRRR AND SEE WHAT IT DOES FOR TEMPS AND WINDS. 007 && .DISCUSSION... 221 PM MST MON DEC 5 2011 EARLY AFTERNOON WV IMAGERY AND RUC H5 ANALYSIS SHOW LARGE SCALE TROUGH EXTENDING FROM GREAT LAKES REGION...ACROSS CENTRAL COLORADO...WITH BASE OF TROUGH OVER SOUTHERN ARIZONA/NEW MEXICO. THROUGH TONIGHT...SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE CENTRAL HIGH PLAINS AS A WEAK SHORTWAVE TROUGH CONTINUES TO PUSH AWAY FROM THE FORECAST AREA. COMBINATION OF CLEARING SKY...VERY LIGHT WINDS AND WIDESPREAD SNOW COVER WILL CONTRIBUTE TO VERY COLD TEMPERATURES OVERNIGHT. AMBIENT TEMPERATURES WILL FALL BELOW ZERO FOR ALL BUT THE FAR SOUTHEAST PORTION OF THE FORECAST AREA WHICH WILL REMAIN AT OR SLIGHTLY ABOVE ZERO. DESPITE THE LIGHT WINDS...WIND CHILL READINGS WILL FALL TO AS LOW AS 20 BELOW ZERO FOR A PERIOD OF TIME PRIMARILY OVER THE NORTHWEST HALF OF THE FORECAST AREA. AS SUCH...WILL ISSUE A WIND CHILL ADVISORY. FOLTZ TUESDAY-WEDNESDAY...SHORTWAVE RIDGING WILL BUILD OVER THE CWA TUESDAY QUICKLY FOLLOWED BY WESTERLY FLOW ALOFT WEDNESDAY...WHICH WILL FAVOR DRY CONDITIONS OVER CWA. SHALLOW COLD AIR MASS WILL BEGIN TO MODERATE...WITH HIGH/LOW TEMP FORECAST COMPLICATED BY LINGERING SNOW PACK. CONTINUED TO UNDERCUT GUIDANCE THROUGH THESE PERIODS....NOT EXPECTING TEMPS TO MAKE IT ABOVE FREEZING UNTIL WED AFTERNOON. WEDNESDAY NIGHT-THURSDAY NIGHT...COLD FRONT PUSHES SOUTH ACROSS CWA WEDNESDAY NIGHT...WITH SHORTWAVE TROUGH PASSING NORTH OF CWA THURSDAY/THURSDAY NIGHT. BEST LIFT/MOISTURE LOOKS TO REMAIN OVER CENTRAL NEBRASKA...HOWEVER MODEL POINT SOUNDINGS DO SHOW DENDRITIC LAYER BEGINNING TO SATURATE IN EXTREME NORTHERN PART OF CWA IN THE 21Z-00Z TIME FRAME. WENT AHEAD AND ADDED SLIGHT CHANCE POPS TO SW NEBRASKA COUNTIES 18Z-00Z WHERE A DUSTING COULDNT BE RULED OUT. ALSO EXPANDED FLURRIES FURTHER SOUTH...AND MADE CONDITIONS DRY AFTER 06Z. FRIDAY-MONDAY...WARMING TREND WILL START UP AGAIN FRIDAY...AND CONTINUE THROUGH THE WEEKEND WITH SHORTWAVE RIDGING ACROSS WESTERN CONUS THROUGH SATURDAY. TEMPERATURES SHOULD MODERATE TO NEAR NORMAL VALUES IN THE UPPER 30S/LOW 40S SAT/SUN. CLOSED LOW BEGINS TO DEVELOP OVER SW CONUS BY SUNDAY NIGHT/MONDAY WITH W/SW FLOW DEVELOPING OVER CWA AHEAD OF THIS FEATURE. GUIDANCE IN GENERAL AGREEMENT ON ARRIVAL OF COLD FRONT SUN NIGHT/MON...WHICH SHOULD SUPPORT A RETURN TO BELOW NORMAL TEMPERATURES EARLY NEXT WEEK. NOT EXPECTING ANY PRECIP THROUGH EXTENDED PERIODS...WITH DRY AIR MASS IN PLACE OVER CWA. DR && .AVIATION... 1020 PM MST MON DEC 5 2011 FOR THE 06Z TAFS...VFR THROUGH THE PERIOD AT BOTH KGLD AND KMCK. SFC HIGH OVER THE AREA PRODUCING SOUTHEST WINDS OF 5 TO 10 KTS. THESE WINDS WILL CONTINUE THROUGH THE DAY TUESDAY BEFORE BECOMING WEST TOWARD THE END OF THE PERIOD WITH AN INCREASE IN MID LEVEL CLOUDS AS WELL. 007 && .GLD WATCHES/WARNINGS/ADVISORIES... KS...WIND CHILL ADVISORY UNTIL 8 AM MST /9 AM CST/ TUESDAY FOR KSZ001>003-013-014-027. NE...WIND CHILL ADVISORY UNTIL 8 AM MST /9 AM CST/ TUESDAY FOR NEZ079>081. CO...WIND CHILL ADVISORY UNTIL 8 AM MST TUESDAY FOR COZ090>092. && $$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
1113 PM CST MON DEC 5 2011 .AVIATION... FOR THE 06Z TAF ISSUANCE. VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES THROUGH LATE TUESDAY AFTERNOON. SURFACE HIGH PRESSURE WILL PREVAIL ACROSS THE NORTHERN ROCKIES LATE TONIGHT INFLUENCING NORTHERLY WINDS 5 TO 10KT THROUGH EARLY TUESDAY MORNING. A LEE SIDE TROUGH OF LOW PRESSURE WILL DEVELOP ACROSS EASTERN COLORADO TUESDAY MORNING TURNING WINDS WESTERLY 5 TO 10KT BY EARLY TUESDAY AFTERNOON. && .PREV DISCUSSION... /ISSUED 500 PM CST MON DEC 5 2011/ SYNOPSIS... THE 15.12Z 250 HPA MAP CONTINUED TO SHOW A LARGE TROUGH BISECTING THE CONUS WITH A STRONG 100 KT JET EXTENDING SOUTHWARD FROM SASKATCHEWAN AND ACROSS MONTANA. AN EVEN FASTER JET NEAR 150 KT WAS MOVING ACROSS SE CANADA WITH AN EXTENSION OF THIS JET, ALBEIT WEAKER WINDS, TOWARDS KANSAS. AT 500 HPA, VERY COLD AIR OF -40 DEG C WAS OBSERVED AT KABR WITH -30S DEG C SOUTHWARD ACROSS COLORADO. THE ARCTIC AIR AT 700 HPA WITH TEMPERATURES AT LEAST -20 DEG C EXTENDED ACROSS THE NORTHERN PLAINS. 5 DEGREES OF COOLING WAS NOTED BETWEEN THE 00Z AND 12Z RAOB FOR KDDC AT 850 HPA. AT THE SURFACE, ARCTIC AIR EXTENDED ACROSS THE PLAINS WITH TEENS AND 20S DEG F CONTINUING AT 21Z ACROSS THE SUNFLOWER STATE. -SUGDEN DISCUSSION... DAYS 1-2... TONIGHT: THE VERY SHORT TERM CONCERN FOR THIS EVENING IS THE SNOW POTENTIAL ACROSS THE CENTRAL AND SOUTHERN HALF OF THE CWFA WITH A MORE APPRECIABLE CHANCE FOR "HEAVIER" SNOW ACROSS THE SE CWFA. THE SATELLITE WATER VAPOR CHANNEL SHOWS A WEAK DISTURBANCE MOVING NEW MEXICO AT THE BASE OF AN UPPER LEVEL TROUGH. A PV ANOMALY ASSOCIATED WITH THE PASSAGE OF THE UPPER LEVEL TROUGH AND ISENTROPIC LIFT IN THE 290-295K THETA LAYER WILL PROVIDE ENOUGH LIFT FOR SOME SNOW SHOWERS, PARTICULARLY ACROSS THE SE FA. AS A RESULT, HAVE INCREASED POPS UP TO CHANCE AND UPPED SNOWFALL AMOUNTS TO 0.6-1.0 INCHES TOWARDS MEDICINE LODGE. HRRR ALSO IS SHOWING SOME ACCUMULATIONS WHICH AGREES WITH THE QPF OUTPUT FROM THE THE NAM, GFS, GEM, ECMWF, ARW, AND NMM...WHICH ALL PAINT A LITTLE QPF IN THIS REGION. OTHERWISE, MID AND LOW LEVEL CLOUDS WILL EVENTUALLY CLEAR TONIGHT AS THE COLD SURFACE HIGH PRESSURE CENTER SETTLES ACROSS KANSAS AND THE TROF CONTINUES EAST. THIS WILL RESULT IN WEAKENING OF WINDS AND ALLOW TEMPERATURES TO PLUMMET. I HAVE -2 TO -4 DEG F TO THE NORTHWEST AND AROUND 16 DEG F SE AS THE NW WILL HAVE WEAKER WINDS AND LESS CLOUD COVER THAN COMPARED TO THE SE. HAVE CONTINUED THE TREND OF HIGHLIGHTING THE LOW WIND CHILL VALUES IN THE HWO. THESE VALUES ARE NOT EXPECTED TO REACH WIND CHILL ADVISORY CRITERIA. TUESDAY: HAVE ZERO POPS IN TUESDAY AS THE CWFA WILL BE ON THE BACKSIDE (SUBSIDENCE) OF THE UPPER LEVEL TROUGH AND HIGH PRESSURE WILL CONTINUE AT THE SURFACE. THINK THE NAM MODEL IS BEING TOO INFLUENCED BY THE SNOWFIELD ACROSS WEST CENTRAL AND NORTHWEST KANSAS SO HAVE STEERED AWAY FROM THIS RUN. TEMPERATURES WILL SLIGHTLY MODERATE COMPARED TO MONDAYS HIGHS AND BE IN THE 20S DEG F. BY TOMORROW EVENING, A WEAK LEE SURFACE TROUGH WILL DEVELOP ACROSS EASTERN COLORADO WHICH WILL TURN OUR WINDS MORE SOUTHWESTERLY TO WESTERLY. SKIES SHOULD BE CLEAR WITH A DRY AIRMASS OVERHEAD. WEDNESDAY: THE DAY WILL START COLD WITH SINGLE DIGITS TO LOW TEENS DEG F DURING THE MORNING. DURING THE DAY, THE WEAK LEE SIDE TROUGH WILL MOVE EASTWARDS ACROSS WESTERN KANSAS USHERED BY A SHORTWAVE TROUGH MOVING ACROSS THE NORTHERN PLAINS. THIS WILL TURN OUR WINDS MORE NORTHWESTERLY SO WE COULD SEE SOME DOWNSLOPE CONDITIONS AND RESULT WARMER TEMPERATURES. MEX GUIDANCE HAS KDDC IN THE 40S AND THE ECMWF IS PARTICULARLY WARM WITH MID 40S DEG F ACROSS THE CENTRAL AND SE FA. HAVE NOT WARMED TEMPERATURES UP TO THIS BUT DID TWEAK THEM UP HIGHER WEDNESDAY. -SUGDEN DAYS 3-7... A SPLIT JET STREAM IS EXPECTED TO PREVAIL ACROSS THE CONUS WITH BENIGN WEATHER AS A RESULT THROUGH THE EXTENDED FORECAST. WEDNESDAY NIGHT THROUGH FRIDAY: A NORTHWEST TO SOUTHEAST ORIENTED SURFACE HIGH WILL MOVE THROUGH THE NORTHERN PLAINS THURSDAY AS A SHORTWAVE TROUGH IN THE NORTHERN BRANCH OF THE JET SWINGS SOUTHEASTWARD AROUND THE SOUTHERN EDGE OF THE LARGER HUDSON BAY . ANY NORTHWEST FLOW FRONTOGENESIS AND ATTENDANT SNOW TIED TO THIS FEATURE WILL BE NORTH AND EAST OF THE SOUTHWEST KANSAS REGION SO NO POPS ARE IN THE FORECAST. A GLANCING BLOW OF ARCTIC AIR WILL ONLY RESULT IN A MINIMAL IMPACT ON TEMPERATURES WITH HIGHS GENERALLY IN THE UPPER 30S FOR BOTH THURSDAY AND FRIDAY. SATURDAY THROUGH MONDAY: THE NORTHERN POLAR JET WILL BE SHIFTED NORTH DURING THIS TIME FRAME WITH VERY WEAK FLOW IN THE MID AND UPPER LEVELS OVER THE CENTRAL ROCKIES AND GREAT PLAINS. MEANWHILE...THE SOUTHERN JET WILL REMAIN ALONG AN AXIS FROM THE NORTHERN BAJA OF CALIFORNIA THROUGH SOUTHWEST TEXAS TO THE GULF COAST REGION. THE DETERMINISTIC GFS AND ECMWF MODELS BOTH SHOW A MINOR SHORTWAVE TROUGH WITHIN THE SOUTHERN JET MOVING ACROSS SOUTHERN CALIFORNIA/NORTHERN BAJA CALIFORNIA ENTERING THE DESERT SOUTHWEST REGION. A JET STREAM IN THE NORTHERN POLAR JET IS EXPECTED TO DIG SOUTHWARD DOWN THE WEST COAST AROUND SUNDAY...WHICH WILL BECOME INVOLVED WITH THE SOUTHERN JET IN SOME FASHION. INTERACTION OF SOUTHERN AND NORTHERN BRANCHES OF THE JET IS SOMETHING THAT MODELS WILL STRUGGLE WITH AT THIS TIME FRAME...SO THERE IS A LOT OF UNCERTAINTY GOING INTO LATE WEEKEND/EARLY NEXT WEEK CONCERNING HOW A POTENTIAL MEAN TROUGH IN THE WEST WILL EVOLVE...AND JUST HOW IT WILL IMPACT SOUTHWEST KANSAS WEATHER AS A RESULT. -UMSCHEID && .PRELIMINARY POINT TEMPS/POPS... DDC 8 27 10 41 / 20 0 0 0 GCK 4 24 8 39 / 10 0 0 0 EHA 6 25 9 41 / 20 0 0 0 LBL 8 27 9 41 / 20 0 0 0 HYS 7 24 9 37 / 10 0 0 0 P28 16 30 14 42 / 40 0 0 0 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ FN12/99/99
AREA FORECAST DISCUSSION
NWS CARIBOU ME
1227 AM EST TUE DEC 6 2011 .SYNOPSIS... A SLOW MOVING COLD FRONT WILL MOVE ACROSS THE STATE BY LATE TONIGHT. THE FRONT WILL MOVE OFF THE COAST LATER TUESDAY WITH A SERIES OF WEAK LOW PRESSURES TRACKING ALONG THE COASTAL FRONT TUESDAY NIGHT INTO WEDNESDAY. && .NEAR TERM /THROUGH TUESDAY/... HAVE ADJUSTED TEMPERATURE...POP AND WEATHER GRIDS. THE HRRR MODEL DOES NOT BRING THE NEXT SURGE BACK INTO NORTHERN MAINE UNTIL EARLY THIS EVENING SO WILL START OUT WITH LOWER POPS ACROSS THE NORTH AND THEN GRADUALLY INCREASE POPS BACK TO CATEGORICAL THIS EVENING. AS THE COLD FRONT CROSSES NORTHERN MAINE AFTER MIDNIGHT, RAIN WILL MIX WITH SNOW AND THEN CHANGE TO ALL SNOW ACROSS MAINLY NORTHERN AROOSTOOK COUNTY. SNOW WILL CONTINUE INTO THE MORNING HOURS BUT EXPECT SNOW TO BE LIGHT. AT THIS TIME STILL EXPECTING 1 TO 3 INCHES OF SNOW ACROSS NORTHERN SECTIONS WITH THE HIGHEST VALUES ACROSS THE ST. JOHN VALLEY. EXPECT RAIN TO MOVE INTO CENTRAL REGIONS AFTER MIDNIGHT AND THEN INTO DOWNEAST JUST BEFORE SUNRISE TUESDAY. RAIN WILL CONTINUE FOR MOST OF THE DAY OVER DOWNEAST AS LOW PRESSURE MOVES ALONG THE FRONT AS IT SLIDES OFF THE COAST. HIGH TEMPERATURES ON TUESDAY WILL ONLY RISE 1 TO 3 DEGREES FROM THE MORNING LOWS AS COLDER AIR MOVES IN WITH THE NORTH WINDS BEHIND THE COLD FRONT. FOR RAINFALL AMOUNTS EXPECTING BETWEEN A QUARTER TO HALF AN INCH ACROSS THE REGION BY TUESDAY AFTERNOON. && .SHORT TERM /TUESDAY NIGHT THROUGH FRIDAY/... THE UNSETTLED PATTERN WILL CONTINUE THROUGH THE SHORT TERM. A COLD FRONT WILL BE STRETCHED ACROSS THE GULF OF MAINE TUESDAY NIGHT WITH A WAVE OF LOW PRESSURE POSITIONED NEAR NOVA SCOTIA TUESDAY EVENING. PRECIPITATION...MOSTLY IN THE FORM OF SNOW THOUGH MIXED WITH RAIN DOWNEAST AND ESPECIALLY ALONG THE COAST... WILL BEGIN TO WIND DOWN OVERNIGHT AS THIS LOW CONTINUES TO TREK TO THE EAST. HOWEVER ANOTHER WEAK WAVE...THIS ONE FURTHER SOUTH...WILL KEEP AT LEAST THE SLIGHT CHANCE OF RAIN/SNOW SHOWERS ACROSS THE REGION THROUGH WEDNESDAY MORNING. HIGH PRESSURE WILL FINALLY BE ABLE TO TAKE HOLD WEDNESDAY NIGHT...BUT YET ANOTHER LOW WILL MOVE TO THE SOUTH OF THE GULF OF MAINE THURSDAY. THE 12Z ECMWF IS THE MOST AGGRESSIVE AND THE FURTHEST NORTH WITH THIS SYSTEM AND INDICATES THAT MUCH OF DOWNEAST MAINE WOULD SEE A RAIN/SNOW MIX. THE 12Z NAM AND GFS MEANWHILE KEEP THE LOW SOUTH AND ONLY BRUSH THE COAST WITH PRECIPITATION. HAVE GONE WITH SLIGHT CHANCE POPS FOR NOW. ALSO KEPT SLIGHT CHANCE POPS ACROSS THE NORTH AS A COLD FRONT APPROACHES FROM CANADA. DAYTIME TEMPERATURES WEDNESDAY AND THURSDAY WILL RANGE FROM THE LOWER 30S NORTH TO AROUND 40 SOUTH WHILE THE NIGHTS DIP DOWN INTO THE 20S.&& && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... THE START OF THE LONG TERM FINDS THE GFS AND THE ECMWF WITH A SIMILAR SOLUTION...HOWEVER THE GFS APPEARS ABOUT 6HRS BEHIND THE ECMWF ON MOVEMENT OF THE MAIN LOW. A LOW PRESSURE (GFS) IN THE N ATLANTIC SE OF NOVA SCOTIA...A DEEP COLD CORE LOW OVER HUDSON BAY WITH A TROUGH EXTENDING S THROUGH THE CENTRAL GREAT LAKES REGION. A CANADIAN HIGH PRESSURE RIDGE THAT DUG INTO THE SOUTHERN STATES WILL BEGIN TO SPREAD TOWARDS NEW ENGLAND. THE ECMWF THE PRIMARY LOW IS FARTHER NORTH INTO THE CANADIAN MARITIMES. AND THE BUILDING RIDGE EXTEND FARTHER NORTH INTO SOUTHERN NEW ENGLAND. BY FRIDAY MORNING THE HIGH MOVES INTO THE ATLANTIC... THE GFS DIGS THE TROUGH ACROSS THE GREAT LAKE FARTHER SOUTH. THE ECMWF DEVELOPS A WEAK LOW OVER EASTERN ILLINOIS. BY FRIDAY EVENING BOTH MODELS ARE INDICATING A LOW OVER THE NORTHERN GREAT LAKES...WITH A TROUGH OF LOWER PRESSURE EXTENDING SOUTH ALONG THE EASTERN SEABOARD. BY EARLY SATURDAY MORNING BOTH MODELS MOVES THE LOW EAST...THE GFS TO NRN MAINE...THE ECMWF TO SRN QUEBEC. BY SATURDAY MORNING THE GFS MOVES THE LOW AND FRONT EAST OF THE AREA...THE ECMWF TO ERN MAINE. BY SATURDAY EVENING THE LOW WILL BE WELL EAST AND A HIGH PRESSURE RIDGE WILL BUILD IN. HIGHER PRESSURE WILL BUILD IN THROUGH THE END OF THE PERIOD...HOWEVER THE COLD LOW OVER HUDSON BAY WILL REMAIN THROUGH THE PERIOD AND WILL PERIODICALLY KICK OFF SHORT WAVES THAT WILL MOVE THROUGH NORTHERN AND CENTRAL MAINE THROUGH THE END OF THE PERIOD. LOADED GMOS...WITH SOME HAND SMOOTHING. PLUS 15 PERCENT FOR GUST OVER LAND 20 PERCENT OVER WATER. NAWAVE 4 FOR SEAS IN THE COASTAL WATERS. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... NEAR TERM: VFR CONDITIONS ACROSS THE NORTH WILL LOWER TO MVFR THIS EVENING AND THEN IFR BY LATER TONIGHT AND REMAIN IFR THROUGH TUESDAY. VFR CONDITIONS ACROSS DOWNEAST WILL LOWER TO IFR AFTER SUNRISE TUESDAY AND REMAIN IFR FOR THE REMAINDER OF THE DAY. SHORT TERM: WIDESPREAD IFR IN SNOW /MIXED WITH RAIN SOUTH/ EXPECTED INTO WEDNESDAY MORNING...THEN GRADUALLY IMPROVING CONDITIONS FROM NORTH TO SOUTH WEDNESDAY AFTERNOON AS HIGH PRESSURE BUILDS OVER THE REGION. CLOUDS WILL INCREASE LATE WEDNESDAY NIGHT AND THURSDAY AS A COLD FRONT APPROACHES FROM CANADA AND A LOW PRESSURE SYSTEM MOVES TO THE SOUTH OF THE GULF OF MAINE. THERE IS A SLIGHT CHANCE THAT THESE SYSTEMS WILL BRING SNOW AND MVFR/IFR CONDITIONS TO THE REGION THURSDAY. MORE RAIN/SNOW IS POSSIBLE FRIDAY AND FRIDAY NIGHT AS ANOTHER LOW MOVES ACROSS NORTHERN MAINE. && .MARINE... NEAR TERM: WINDS AND SEAS WILL REMAIN BELOW SCA CRITERIA THROUGH TUESDAY. A COLD FRONT WILL APPROACH FROM THE NORTH TONIGHT AND TUESDAY AND THEN CROSS THE WATERS BY TUESDAY EVENING. SHORT TERM: NO HEADLINES EXPECTED OVER THE WATERS AS WINDS REMAIN BELOW 25 KT AND WAVES LESS THAN 5 FT. THE WEATHER WILL BE UNSETTLED HOWEVER AS A SERIES OF LOW PRESSURE WAVES MOVE OVER OR JUST TO THE SOUTH OF THE GULF OF MAINE THROUGH MID WEEK. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...NONE. MARINE...NONE. && $$ NEAR TERM...MIGNONE
AREA FORECAST DISCUSSION...UPDATED FOR 06Z TAFS
NWS MARQUETTE MI
1118 PM EST MON DEC 5 2011 .SYNOPSIS... WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROUGH FROM HUDSON BAY AND NRN ONTARIO THROUGH THE NRN PLAINS TO THE SRN ROCKIES. LITTLE LOW OR MID LEVEL FORCING WAS ASSOCIATED WITH THE TROUGH IN THE VERY DRY AIRMASS UPSTREAM. AT THE SFC...A RIDGE EXTENDED FROM NRN ONTARIO INTO THE NRN PLAINS RESULTING IN WEAK NRLY LOW LEVEL FLOW ACROSS LAKE SUPERIOR INTO UPPER MI. RADAR INDICATED LIGHT DISORGANIZED LES INTO UPPER MI. ACYC FLOW INTO THE REGION AND SHEAR WITHIN THE SFC-850 MB LAYER HAS LIMITED INTENSITY WITH GENERALLY LIGHT ACCUMULATIONS OF AN INCH OR LESS OBSERVED IN WEST AND NORTH CENTRAL UPPER MI. SNOW RATIO HAS BEEN HIGH...TYPICAL OF MOST LES...WITH THE CLOUD LAYER IN THE 2K-6K FT DGZ. && .SHORT TERM...TONIGHT AND TUESDAY SOME INCREASE IN LES INTENSITY MAY BE POSSIBLE THIS EVENING AS THE MID LEVEL TROUGH MOVES INTO THE AREA AND 850 MB TEMPS DROP SLIGHTLY TO NEAR -15C. HOWEVER...THE CBL FLOW WILL ALSO BECOME INCREASINGLY ANTICYCLONIC AS THE SFC RIDGE AXIS SHIFTS OVER THE AREA. THIS WILL ALLOW THE WINDS TO BACK OVERNIGHT WHICH WILL SHIFT THE BEST SNOWFALL BY MORNING TO THE ONTONAGON TO THE KEWEENAW AS WELL AS ALGER COUNTY. DESPITE THE FAVORABLE INSTABILITY AND MOISTURE...THE SHEAR COMBINED WITH THE SHIFTING NATURE OF THE BANDS SHOULD LIMIT SNOWFALL TO 1-2 INCHES...MAINLY FROM IWD-CMX AND FROM MQT-P53. THE LIGHT WINDS MAY ALLOW THE DEVELOPMENT OF A BAND ALONG THE SHORELINE INTO THE WEST ANE NEAR MARQUETTE AS THE LAND BREEZE STRENGTHENS...PER HIGH RES WRF/ARW BUT CONFIDENCE IN DETAILS FOR LES BAND EVOLUTION IN THE LIGHT WIND REGIME IS LOW. A BRIEF PERIOD OF HEAVIER SNOW WOULD BE POSSIBLE IF SUCH A BAND DEVELOPS. ANY LES ACROSS THE KEWEENAW AND EAST OF MARQUETTE SHOULD RAPIDLY SHIFT OFFSHORE ON TUESDAY AS THE RIDGE AXIS MOVES SOUTHEAST. CONDITIONS SHOULD BE MORE PLEASANT BY AFTERNOON WITH SOME SUNSHINE OVER THE AREA ALONG WITH RELATIVELY LIGHT SW WINDS. .LONG TERM /TUES NIGHT THROUGH NEXT MONDAY/... AT THE START OF THE PERIOD...AN ELONGATED UPPER TROUGH WILL BE STRETCHING FROM JAMES BAY TO THE SRN PLAINS AND QUICKLY SHIFTING E OF THE AREA. THIS WILL ALLOW A WEAK RIDGE...AHEAD OF THE MAIN UPPER LOW TO AFFECT THE AREA DURING THE LONG TERM OVER THE NW TERRITORIES OF CANADA. THIS WEAK UPPER RIDGE WILL CAUSE SFC RIDGE TO SLIDE E ACROSS THE CWA TUES EVENING. MIGHT SEE A QUICK COOL DOWN TUES EVENING WITH THE CLEAR SKIES AND LIGHT WINDS...ESPECIALLY OVER THE CNTRL/ERN CWA...BUT INCREASING SWRLY FLOW AND MID LEVEL CLOUDS AHEAD OF THE NEXT FRONT WILL LEVEL TEMPS OFF AND MAY EVEN CAUSE THEM TO RISE SOME OVER THE WRN CWA. WITH THE DEEPER MOISTURE AND H850-700 Q-VECTOR CONV ARRIVING LATE TUES NIGHT...COULD SEE A FEW SNOW SHOWERS LATE TUES NIGHT OVER THE KEWEENAW. BUT WITH THE BEST FORCING/MOISTURE OVER NRN LK SUPERIOR...WILL KEEP THE CHANCES THERE. STRONGER PRESSURE GRADIENT AHEAD OF THE FRONT WILL LIKELY LEAD TO SOME GALES OVER LK SUPERIOR TUES NIGHT. EVEN WITH THE WAA ALOFT...LLVL WINDS BELOW THE INVERSION LOOK TO BE IN THE 30-40KT RANGE AND WILL LIKELY ALSO LEAD TO A GUSTY OVERNIGHT FOR THE HIGHER TERRAIN OF KEWEENAW PENINSULA. WILL CONTINUE THE GALE WATCH OVER W/CNTRL LK SUPERIOR. COLD FRONT MOVING THROUGH ON WED AND WILL USHER IN THE COLDEST AIR OF THE SEASON. EXPECT THE MID LVL FORCING/MOISTURE TO BE THROUGH THE AREA BY WED AFTN...AND WILL MOVE UP THE POP TIMING FROM THE PREVIOUS SHIFT TO BE MORE IN THE MORNING FROM THE AFTN. MAY TAKE A LITTLE WHILE FOR THE LES TO GET GOING BEHIND THE FRONT...AS INVERSION HEIGHTS FALL TO 4.5-5.5KFT AND LLVL DRY AIR LIMITS ANY POTENTIAL CLOUD DEPTH. THUS...WILL GO WITH SLIGHTS OVER THE WNW WIND FAVORED LOCATIONS OVER THE WEST AND KEEP CHANCES OVER THE EAST WHERE THE LOW-MID LVL MOISTURE WILL TRY TO LINGER LONGER. THINK THESE LIMITED CONDITIONS WILL CONTINUE INTO THE EVENING HOURS BEFORE REALLY INTENSIFYING THROUGH THE NIGHT. THIS INTENSIFICATION WILL LARGELY BE DUE TO A SHORTWAVE MOVING THROUGH ON WED NIGHT...WHICH WILL INCREASE THE LOW-MID LVL MOISTURE AND PULL EVEN COLDER H850 TEMPS OVER THE AREA /STEADILY FALLING TO NEAR -20C BY THURS EVENING/. THIS WILL INCREASE DELTA-T/S TO SOME FAIRLY IMPRESSIVE VALUES /LOW-MID 20S BY THURS EVENING/. IN ADDITION...WITH INVERSION HEIGHTS RISING TO 7-10KFT AND LK INDUCED CAPES IN THE 500-700 J/KG RANGE...LOOKS TO BE A GOOD POTENTIAL FOR AREAS TO RECEIVE MOD/HEAVY LES LATE WED NIGHT INTO THURS. LAKE EFFECT SNOW PARAMATER SUPPORTS THIS POTENTIAL...RISING ABOVE 2...WHICH SUPPORTS A HIGH POTENTIAL FOR HEAVY SNOWFALL RATES...OVER THE W WED NIGHT AND THE E ON THURS. WINDS LOOK TO BE OUT OF THE WNW WED NIGHT INTO THURS...SO HAVE THE HIGHEST POPS IN THOSE FAVORED LOCATIONS. ONE ITEM TO NOTE ON WIND DIRECTIONS IS THAT THE NAM/GEM HINTING AT A MESO LOW FORMING OVER ERN LK SUPERIOR ON THURS...WHICH COULD END UP FORCING WINDS MORE TO THE NW OVER THE WRN CWA. OVER THE E...THIS COULD CAUSE A DOMINATE BAND TO SETUP SOMEWHERE OVER THE SERN LAKE...POTENTIALLY RIGHT ALONG THE SHORELINE E OF GRAND MARAIS DUE TO THE WSW WINDS AROUND THE MESO LOW. FINALLY...COULD BE A SLIGHT LULL OVER THE W IN THE AFTN...AS SLIGHTLY DRIER AIR MOVES THROUGH...AND HAVE SLIGHTLY LOWERED POPS FOR THAT TIMEFRAME. DAYS 4 THROUGH 7 /THURS NIGHT THROUGH NEXT MONDAY/... ARCTIC TROUGH DROPPING SE ACROSS THE AREA THURS NIGHT INTO SAT WILL PROVIDE REINFORCING COLD AIR TO THE AREA AND CONTINUE THE LES. EXPECT THE -16 TO -20C H850 TEMPS TO CONTINUE THURS NIGHT INTO FRI NIGHT AS BL WINDS ARE FROM THE WNW THURS NIGHT INTO FRI AND THEN START TO SHIFT TO THE WSW FRI NIGHT. WITH THE ABUNDANT LOW-MID LVL MOISTURE UNDER THE UPPER TROUGH...THE INGREDIENTS ARE COMING TOGETHER FOR A POTENTIALLY SIGNIFICANT LES PERIOD THURS NIGHT INTO FRI FOR WNW WIND FAVORED LOCATIONS. AS MENTIONED PREVIOUSLY...LES PARAMETER CONTINUES TO HIGHLIGHT THE HEAVY SNOW POTENTIAL...VALUES ABOVE 2...THROUGH FRI FOR WNW WIND LOCATIONS. THIS IS ALSO SEEN IN BUFKIT LK INDUCED CAPE VALUES EXCEEDING 700 J/KG AND EQL LVLS BETWEEN 7-10KFT. IT IS A WAYS OUT...BUT BUFKIT SOUNDINGS ARE SHOWING THE CLOUD BASES TO BE AT OR ABOVE THE DGZ AND LIMIT DENDRITES. EITHER WAY...SHOULD SEE A HIGH SLR VALUE AND ALLOW FOR EASY BLOWING/DRIFTING FOR AREAS NEAR LK SUPERIOR WHERE THE WINDS WILL BE STRONGEST. IN ADDITION...THIS DRIER AIR IN THE LLVLS COULD ALSO LEAD TO A COUPLE MAIN/DOMINATE BANDS. WILL STICK TO OUR LES CLIMO POP/SKY GRIDS FOR THIS TIME FRAME AND WILL CONTINUE TO MENTION THE HEAVY SNOW POTENTIAL IN THE HWO. WITH THE WINDS SHIFTING TO THE SW AND WAA DEVELOPING ON SAT...EXPECT THE LES TO DIMINISH. THIS WAA IS DUE TO A WEAK SHORTWAVE AND CLIPPER SYSTEM SLIDES THROUGH SOUTHERN ONTARIO...WITH THE MAIN ENERGY/MOISTURE STAYING N OF THE CWA. UPPER FLOW TRANSITIONS TO MORE ZONAL NRN STREAM ALONG THE U.S./CANADA BORDER FOR SUN INTO MON. THIS ALLOWS WARMER H850 TEMPS...AROUND -1 TO 1C...TO MOVE OVER THE AREA AND LEAD TO A PERIOD OF SLIGHTLY ABOVE NORMAL TEMPERATURES WITH HIGHS IN THE UPPER 20S AND LOWER 30S. MODELS CONSISTENT ON SFC TROUGH SETTLING OVER THE AREA SUN NIGHT INTO MON...AS SFC HIGHS ARE SETUP OVER THE NRN PLAINS AND OHIO VALLEY. LIMITED UPPER LVL FORCING...SO HAVE KEPT THE FCST DRY FOR NOW. && .AVIATION /FOR THE 06Z TAF ISSUANCE/ FOR EARLY IN THIS FCST PERIOD...WEATHER AT TAF SITES WILL BE DOMINATED BY LAKE EFFECT CLOUDS/SNOW SHOWERS WITH PREDOMINANT MVFR CIGS. AS IS TYPICAL FOR LAKE EFFECT SNOW SHOWERS...VSBY WILL BE QUITE VARIABLE...GENERALLY RANGING FROM MVFR TONIGHT. SOME IMPROVEMENT IN VIS IS EXPECTED TUE MORNING AS WINDS BACK MORE WNW AHEAD OF BUILDING HIGH PRES RDG DIMINISHING SHSN. VFR CONDITIONS WILL OCCUR IN THE LATE MORNING TO EARLY AFTERNOON AT ALL SITES. COULD BE SOME STRONGER WINDS AND LLWS IN THE LATER PERIODS AT ALL SITES...BUT THAT IS WAY OUT THERE AND CONFIDENCE IN PUTTING IT INTO FORECAST IS PRETTY LOW AT THIS TIME. && .MARINE /FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE/... EXPECT WINDS MOSTLY IN THE 10-20 KT RANGE INTO TUE MORNING AS A HIGH PRES RIDGE OVER NORTHERN ONTARIO AND THE NRN PLAINS SLOWLY BUILDS ACROSS LAKE SUPERIOR. AS THE RIDGE SLIPS SE OF THE LAKE AND A COLD FRONT APPROACHES...SW WINDS ARE EXPECTED TO INCREASE TO GALE FORCE TUE NIGHT INTO EARLY WED...MAINLY OVER WESTERN AND NCNTRL LAKE SUPERIOR. A WINTRY PATTERN OF W-NW WINDS WILL THEN PERSIST THRU LATE WEEK WITH LAKE EFFECT SNOW SHOWERS. GIVEN ARCTIC AIR PASSING OVER THE LAKE...EFFICIENT MIXING WITH 20-30 KT AND SOME GALE FORCE GUSTS AT TIMES LATE IN THE WEEK. WITH ARCTIC AIRMASS INTO THE AREA SOME FREEZING SPRAY MAY ALSO DEVELOP. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... NONE. LAKE SUPERIOR... GALE WARNING FROM 7 PM TUESDAY TO 10 AM EST WEDNESDAY FOR LSZ266. GALE WARNING FROM 5 PM EST /4 PM CST/ TUESDAY TO 7 AM EST / 6 AM CST WEDNESDAY FOR LSZ162. GALE WATCH FROM 5 PM EST TUESDAY TO 10 AM EST WEDNESDAY FOR LSZ263-264. LAKE MICHIGAN... NONE. && $$ SYNOPSIS...JLB SHORT TERM...JLB LONG TERM...SRF AVIATION...07 MARINE...JLB
AREA FORECAST DISCUSSION
NWS KANSAS CITY/PLEASANT HILL MO
357 AM CST Tue Dec 6 2011 .DISCUSSION... Water vapor imagery early this morning shows us that Kansas and Missouri remain under the direct influence of a large, positively tilled and shearing, trough. It is evident that a dry wedge, that rotated under the base of the trough early Monday, has quickly stretched northeast, effectively detaching the moisture feed of the Pineapple Express from much of the dynamics of the slowly shearing trough. Which, is not to say moisture isn`t available, just that there will be less to work with in the coming days. Otherwise, of note is a subtle shortwave that has rounded the base of the trough, and is heading towards central Missouri via south central Kansas. Light snow has been observed with this features in Wichita, with a few tenths of an inch of accumulation this morning. For today, of primary concern is the shortwave and potential for snow. Upper air sounding from Monday evening in Topeka shows a nice dry layer between 900mb and 700mb, which any snow will have to overcome in order to reach the surface. But, a variety of models advertise that this should not be much of a problem as the top-down seeder-feeder process gets to work as the shortwave moves through central Missouri this morning. Current snow observations noted at Wichita, and now Springfield and Columbia, back this idea up. Still, lack of quality deep layer moisture, and the limited residency time of the shortwave, should limit accumulations to something around or under one inch. As for location, best potential for any accumulation looks to be along a line from Clinton northeast through Moberly, where the shearing vorticity axis of the shortwave is expected to traverse. Some flurries will be possible father north and west, think Kansas City to Bethany line. Have continued to highlight snow across central Missouri by inserting likely POPs for this morning. After todays fleeting snow flakes stop falling, our next potential shot at snow will arrive across the Missouri-Iowa border Thursday night. The longwave polar low, currently in the process of shifting across northern Canada towards the Hudson Bay, will send another reinforcing cold shot of air south into the Plains States starting Wednesday, which will insure that temperatures stay well below normal through the remainder of the work week. However, looking at Thursday nights precipitation potential, the entrance region to the jet streak rounding the base of the mean trough, carved out by the polar low across the central plains, would be coincident with enough moisture to squeeze some flakes out along the Iowa border. As for the weekend, currently it looks dry, and like a warming trend will prevail, though we will only be warming back to around normal. As Saturday arrives a ridge across the west coast will be shifting farther east. This should allow for temperatures to moderate a bit through the weekend as synoptic level height gains, and a modest south wind on the back side of a surface high to our east, take the edge off the cold temperatures. CUTTER && .AVIATION... For the 06Z TAFs, MVFR cigs are likely to persist through the night and probably Tuesday morning. Since the NAM and to a lesser extent the GFS have shown to be unreliable on handling the cold air stratocu deck have relied on the RUC and AVNFPS climatology. An approaching mid level shortwave will pass just south of the terminals but can`t rule out scattered flurries from time to time. But lacking definite timing and they not likely to be an obscuration to visibilities will not mention in the TAFs. Passage of shortwave trough axis should see clearing skies in the afternoon with VFR conditions. MJ && .EAX WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ WFO EAX
AREA FORECAST DISCUSSION
NWS KANSAS CITY/PLEASANT HILL MO
1137 PM CST MON DEC 5 2011 ...UPDATED AVIATION DISCUSSION... .DISCUSSION... /943 PM CST MON DEC 5 2011/ Have raised snow chances a bit overnight, mainly over the far southern counties and for later in the night. However, did increase snow chances markedly over the eastern 1/4 of the CWA on Tuesday. Mid/upper level system ejecting out of NM tonight. Latest RUC is a bit stronger and further north with the 700mb vorticity center. Looks like a seeded-feeder setup to start out where a snow from a higher level of clouds falls into a lower cloud deck and "seed" it resulting in light snow and/or flurries. However, increasing dynamics, weak frontogenetic forcing and weak isentropic lift could generate areas/bands of light snow towards sunrise tomorrow. A better bet for measurable snow will occur Tuesday morning when the drier sub-cloud regions have become saturated. Initial thoughts are a tenth of an inch of snow is possible across the far southern counties, but possibly enough to make roads slick as this will be a dry/fluffy snow. Have a bit of concern that a region of upward vertical motion progged just above a nearly saturated layer dendritic snow growth region between 12-z15z over the far eastern counties could yield more than the current half inch of snow currently forecast. Since confidence in models has been low of late on how they have handled the cloud structures of late will go the conservative route and let the mid shift make any changes. MJ && .PREV DISCUSSION... /318 PM CST Mon Dec 5 2011/ Brisk northerly winds continues to advect colder air into Missouri with chilly temperatures the next couple of days. The main concern is a shortwave in southern New Mexico, south of the Four Corners Low. Short term high resolution models (NAM and RUC) are indicating that this wave will progress northeast into west central Missouri on Tuesday. light to moderate snow has been occurring in the TX panhandle, aided by upslope, with development toward the northeast. The models are showing very weak isentropic upglide along with weak deformation ahead of a weak 700 mb low in eastern Kansas late tonight and early Tuesday. Moisture is quite limited but have inserted sct snow showers for much of the area late tonight and Tuesday. Cannot rule out a narrow band of more persistent snow, producing very light accumulations. Later shifts will have to monitor the progress of this system. Otherwise, the trough axis will pass late Tuesday and Wednesday with dry conditions. DB Medium Range (Thursday through Monday)... Operational and ensemble members are in good agreement through the majority of the period depicting primarily stagnant longwave features over the western hemisphere. Most notable are a seasonably deep polar vortex centered across northern Hudson Bay and the Nunavut archipelago and an equally intense ridge through the Gulf of Alaska (both features in the 1-2 normalized standard deviations away from average range). This scenario will result in broad nwly/quasi-zonal flow for locations east of the Rockies with largely dry conditions and temperature slightly below average into the weekend. By the end of the period, models also indicate energy spilling over the top of the western ridge, causing a slight retrogressive phase, placing much of the central and southern plains into a warming, swly flow regime. There is naturally uncertainty into the depth and positioning of swrn conus energy late in the period, however the effect on weather through the forecast area would not be felt until after this valid period. Only real potential sensible weather during this medium range period still appears to be very light snow/snow flurries Thursday night into Friday morning across far northern Missouri. 21 && .AVIATION... For the 06Z TAFs, MVFR cigs are likely to persist through the night and probably Tuesday morning. Since the NAM and to a lesser extent the GFS have shown to be unreliable on handling the cold air stratocu deck have relied on the RUC and AVNFPS climatology. An approaching mid level shortwave will pass just south of the terminals but can`t rule out scattered flurries from time to time. But lacking definite timing and they not likely to be an obscuration to visibilities will not mention in the TAFs. Passage of shortwave trough axis should see clearing skies in the afternoon with VFR conditions. MJ && .EAX WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ WFO EAX
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
403 AM EST TUE DEC 6 2011 .SYNOPSIS... LIGHT RAIN SHOWERS EXPECTED TO LINGER THIS MORNING WITH A SLOW MOVING COLD FRONT IN THE VICINITY. STRONG SYSTEM BRINGS RAIN AND SNOW WEDNESDAY AND WEDNESDAY NIGHT. HIGH PRESSURE THURSDAY. CLIPPER FRIDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... 330 AM UPDATE... MAIN CHANGE WITH THIS ISSUANCE IS THE UPDATE TO POPS BASED ON REGIONAL RADAR TRENDS. HRRR MODEL APPEARS TO BE HANDLING THE CURRENT SITUATION WELL...WILL BE STICKING WITH THIS SOLN FOR NEXT WAVE THAT IS TRAVELING ALONG THE FRONT...CURRENTLY IN EAST CENTRAL TN. 1230 AM UPDATE... TWEAKED POPS TO BE MORE REPRESENTATIVE OF RADAR ECHOES...HEAVIEST PRECIPITATION HAS MOVED JUST EAST OF CWA WITH LIGHT SHOWERS LINGERING BACK ALONG THE COLD FRONT. HEAVIEST RATES SEEM TO BE .10 TO .20 IN/HR...SO NO CONCERN WITH WATER PROBLEMS. LOW STRATUS DECK APPEARING RIGHT ON TIME BEHIND THE COLD FRONT...EXPECTING STRATUS TO CONTINUE CREEPING EAST THROUGH THE EARLY MORNING. PREV DISCN... MODELS IN FAIRLY GOOD AGREEMENT WITH FRONTAL BOUNDARY PUSHING THROUGH THE REGION EARLY TUESDAY. LOW TEMPERATURES DEPEND ON PERFECT TIMING OF THE FRONT. LOOKING AT CURRENT TEMPERATURES AROUND THE FRONT...WILL GO WITH COOLER MOS IN THE FAR WEST...AND WARMER MOS IN THE FAR EAST. EXPECTING A LOW STRATUS DECK BEHIND THE FRONT ON TUESDAY. WITH SUCH A SHALLOW LAYER OF COLD AIR...DO NOT THINK THE MOS GUIDANCE IS HANDLING IT WELL. THEREFORE...WILL GO ON THE LOWER SIDE OF MOS GUIDANCE FOR HIGHS. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... MUCH BETTER CONSENSUS IN THE MODELS TONIGHT COMPARED TO THE RUNS LAST NIGHT REGARDING THE VIGOROUS SYSTEM SLATED FOR WEDNESDAY AND WEDNESDAY NIGHT. MOISTURE WILL HAVE ALREADY OVERSPREAD THE AREA SOUTH OF THE OHIO RIVER BY 12Z WEDNESDAY...AND EXPECT STEADY RAIN THROUGH THE FIRST PART OF THAT TIME PERIOD. THE ENTIRE KEY TO THIS FORECAST IS THE RATE OF THE COLD AIR ADVECTION AND THE SURFACE TEMPERATURES FALLING BELOW FREEZING. THIS WILL OCCUR FIRST IN THE HIGHEST ELEVATIONS WHERE THE MOST SIGNIFICANT ACCUMULATIONS ARE LIKELY. 925MB TEMPERATURE GRADIENT WILL TIGHTEN UP OVER THE EASTERN MOUNTAINS AND FINALLY KICK THROUGH AFTER AROUND 21Z WEDNESDAY...WHICH WILL SUBSEQUENTLY ALLOW THE CHANGE OVER TO SNOW FOR THE REMAINDER OF THE MOUNTAINS. WHILE THE OPERATIONAL MODELS GO EASY ON THE SPEED OF THE COLD AIR ADVECTION...STRENGTH OF THE DYNAMICS IN PLAY DO LEAVE SOME QUESTION AS TO WHETHER THIS PARAMETER IS BEING REPRESENTED WELL BY THESE MODELS...OR IF THERE WILL BE AN EARLIER TRANSITION TIME TO COME OVER THE NEXT COUPLE OF RUNS. SYSTEM WILL BE EFFICIENT WHEN IT COMES TO CREATING PRECIPITATION. JET STREAK OVER 140KTS EXISTS OVER SOUTHEAST OHIO WEDNESDAY...AND THE 500MB WAVE INDICATES A SHIFT TO A NEGATIVE TILT UPON PASSAGE THROUGH THE CENTRAL AND SOUTHERN APPALACHIANS. ROBUST FRONTOGENETIC FORCING WILL COUPLE WITH Q VECTOR CONVERGENCE IN THE UPPER LEVELS...CREATING ENHANCED OMEGA THROUGH THE DENDRITIC GROWTH LAYERS...WITH SATURATION OF THE COLUMN EXTENDING FROM THE SURFACE TO ABOVE 500MB. THE 03Z RUN OF THE SREF BRINGS PROBABILITIES OF SNOW EXCEEDING 4 INCHES AT ABOUT THE 30 TO 40 PERCENT RANGE FOR POCAHONTAS COUNTY. CURRENT STATE OF THE FORECAST GRIDS DOES BRING AROUND 4 TO 8 INCHES TOTAL SNOW ACCUMULATION...RELEGATED TO THE HIGHEST PEAKS OF THE CWA...ABOVE ROUGHLY 4000FT. WITH THE SLOWER CHANGE OVER TO SNOW IN THE MOUNTAINS BELOW 4000FT...ABOUT 2 TO 4 INCHES OF SNOW ARE IN THE FORECAST FOR THIS ISSUANCE. ANOTHER VARIABLE IN THIS OVERALL EQUATION IS THE MILD AIR THAT HAS BEEN IN PLACE...THE RAIN THAT WILL PRECEDE THE SNOW...AND THE LENGTH OF TIME NECESSARY FOR THE SNOW TO ACCUMULATE. GIVEN THE FACT THAT THIS IS A LATE 3RD PERIOD TO EARLY 4TH PERIOD EVENT...WILL NOT COMMIT TO THE WATCH FOR NOW. ANY VARIABILITY IN THE TIMING OF THE BELOW FREEZING AIR COULD ALTER THE SNOWFALL TOTAL FORECAST SIGNIFICANTLY...IN EITHER DIRECTION. NOT COMFORTABLE WITH THIS POTENTIAL VOLATILITY TO THE FORECAST AND WILL DRAW ATTENTION TO THIS SYSTEM IN THE HWO AND RWS TEXT PRODUCTS. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... A SHARP AMPLIFYING TROF WILL BE THE MAIN FEATURE EARLY IN THE EXTENDED. THIS TROF WILL SETTLE INTO EASTERN CONUS...ADVERTISED BY A CLIPPER FOR FRI NIGHT. BEST LIFT WITH THIS FEATURE WILL SKIRT BY MAINLY TO NORTH. HOWEVER...GIVEN SOME MOISTURE AND MAGNITUDE OF COLD AIR BEHIND IT...CANT RULE OUT SOME FLURRIES ABOUT ANYWHERE WITH FROPA. WILL MENTION FLURRIES IN WX GRIDS FOR LOWLANDS AND CARRY CHC POPS NORTHERN MTNS. H85 TEMPS COME DOWN TO ARND -10C BY SAT MORNING. NOT MUCH IN THE WAY OF UPSLOPE AS ATMOSPHERIC COLUMN WILL QUICKLY DRY OUT AND NW FLOW MEAGER. WILL DRY THINGS OUT QUICKLY SAT...WITH A RETURN TO SUNSHINE FOR ALL BY AFTN...ALBEIT COLD. DESPITE THE SUNSHINE...THINK 40F WILL BE HARD TO COME BY IN THE LOWLANDS...WITH GUIDANCE SUGGESTING MID 30S IS ABOUT IT...WITH 20S IN THE MTNS. UPR TROF DOESNT STICK ARND IN THIS PROGRESSIVE PATTERN...AS WAA QUICKLY ALLOWS H85 TEMPS TO RECOVER. HOWEVER...COLD NIGHT WILL BE ON TAP SAT WITH SFC HIGH BUILDING OVERHEAD. WILL GO WITH AN EARLY LOW HIGHEST ELEVATIONS AND LEVEL OFF OR SLIGHTLY REBOUND BY SUN MORNING...WITH LOWLANDS DIPPING DOWN INTO LWR 20S. TOOK TYPICAL COLD SPOTS INTO TEENS...IE NORTHERN MTN VALLEYS/NE KY. MODERATING TEMPS WILL CARRY THE WAY EARLY NEXT WEEK...THOUGH STILL REMAINING ON THE CHILLY SIDE. SHOULD STAY DRY THROUGH TUES. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... COLD FRONT CURRENTLY JUST WEST OF HTS AND PKB AND SHOULD CONTINUE TO SLOWLY MOVE EAST OVERNIGHT. SHRA AHEAD OF FRONT MAY CAUSE BORDERLINE MVFR CONDITIONS...BUT FOR THE MOST PART VFR STILL PREDOMINANT EAST OF OHIO RIVER. ONCE THE FRONT PASSES...CIGS DROP TO MVFR IN LOW STRATUS DECK. BY DAWN...IFR CIGS AND VSBY WILL BE COMMON IN WIDESPREAD RAIN. THE RAIN WILL TAPER OFF FROM W TO E TUE...ALLOWING VSBY TO IMPROVE TO VFR IN THE LOWLANDS AND MVFR IN THE MOUNTAINS BY AFTERNOON. HOWEVER...CIGS WILL STRUGGLE TO CLIMB TO LOW MVFR ION THE LOWLANDS. IN THE MOUNTAINS...IT WILL TAKE UNTIL ABOUT DAWN FOR CIGS TO GET DOWN TO IFR BUT THEN CIGS WILL REMAIN IFR OR CLOSE TO IT THROUGH THE DAY TUE. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z WEDNESDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: TIMING OF THE FRONT COULD VARY...CAUSING TIMING OF IFR/LIFR CONDITIONS TO VARY. DENSITY OF THE FOG TONIGHT COULD ALSO VARY. TIMING AND DEGREE OF IMPROVEMENT TUE ALSO COULD VARY. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. DATE TUE 12/06/11 UTC 1HRLY 08 09 10 11 12 13 14 15 16 17 18 19 EST 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14 CRW CONSISTENCY M M L L M M M L M M M M HTS CONSISTENCY L M M M M M L L M H H H BKW CONSISTENCY M M L M M M M M L L L L EKN CONSISTENCY H L L L L L L L M M M M PKB CONSISTENCY M M M M M M L L H M H H CKB CONSISTENCY L L L L M M M M M M M M AFTER 06Z WEDNESDAY... IFR IN PERIODS OF RAIN INTO TUE NT...AND IN THE MOUNTAINS IN SNOW WED NT. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...26/TAX NEAR TERM...RPY/TAX SHORT TERM...26 LONG TERM...30 AVIATION...TAX
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
344 AM EST TUE DEC 6 2011 .SYNOPSIS... LIGHT RAIN SHOWERS EXPECTED TO LINGER THIS MORNING WITH A SLOW MOVING COLD FRONT IN THE VICINITY. COLDER WEDNESDAY WITH TROUGH AXIS ALOFT CROSSING WEDNESDAY NIGHT. HIGH PRESSURE THURSDAY. CLIPPER FRIDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... 330 AM UPDATE... MAIN CHANGE WITH THIS ISSUANCE IS THE UPDATE TO POPS BASED ON REGIONAL RADAR TRENDS. HRRR MODEL APPEARS TO BE HANDLING THE CURRENT SITUATION WELL...WILL BE STICKING WITH THIS SOLN FOR NEXT WAVE THAT IS TRAVELING ALONG THE FRONT...CURRENTLY IN EAST CENTRAL TN. 1230 AM UPDATE... TWEAKED POPS TO BE MORE REPRESENTATIVE OF RADAR ECHOES...HEAVIEST PRECIPITATION HAS MOVED JUST EAST OF CWA WITH LIGHT SHOWERS LINGERING BACK ALONG THE COLD FRONT. HEAVIEST RATES SEEM TO BE .10 TO .20 IN/HR...SO NO CONCERN WITH WATER PROBLEMS. LOW STRATUS DECK APPEARING RIGHT ON TIME BEHIND THE COLD FRONT...EXPECTING STRATUS TO CONTINUE CREEPING EAST THROUGH THE EARLY MORNING. PREV DISCN... MODELS IN FAIRLY GOOD AGREEMENT WITH FRONTAL BOUNDARY PUSHING THROUGH THE REGION EARLY TUESDAY. LOW TEMPERATURES DEPEND ON PERFECT TIMING OF THE FRONT. LOOKING AT CURRENT TEMPERATURES AROUND THE FRONT...WILL GO WITH COOLER MOS IN THE FAR WEST...AND WARMER MOS IN THE FAR EAST. EXPECTING A LOW STRATUS DECK BEHIND THE FRONT ON TUESDAY. WITH SUCH A SHALLOW LAYER OF COLD AIR...DO NOT THINK THE MOS GUIDANCE IS HANDLING IT WELL. THEREFORE...WILL GO ON THE LOWER SIDE OF MOS GUIDANCE FOR HIGHS. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY/... RECENT MODEL RUNS HAVE COME INTO BETTER AGREEMENT IN THE SHORT TERM PERIOD. PROGRESSION OF SURFACE FRONT ACROSS THE CWA HAS BEEN TRENDING SLOWER. NAM EVEN APPEARS TO HANG UP THE FRONT OVER THE MOUNTAINS WEDNESDAY...WITH SEVERAL WAVES RIDING ALONG THE FRONT...WHILE GFS FOR EXAMPLE...APPEARS TO CLEAR THE SURFACE FRONT EAST OF THE MOUNTAINS LATE TUESDAY NIGHT OR WEDNESDAY. MUCH OF THE INITIAL PRECIPITATION IN THE SHORT TERM WILL START OUT AS RAIN...BUT BY WEDNESDAY NIGHT/THURSDAY...A MORE SIGNIFICANT SHORTWAVE TROUGH WILL APPROACH FROM THE WEST. STILL SOME DIFFERENCES IN THE EXACT TRACK...TIMING...AND THUS NORTHWARD EXTEND OF THE PRECIPITATION SHIELD ASSOCIATED WITH THIS...SO FOR NOW...KIND OF WENT WITH A SPLIT BETWEEN THE 12Z NAM AND 12Z GFS. THINKING ENOUGH COLD AIR WILL BE IN PLACE LATE WEDNESDAY NIGHT/EARLY THURSDAY FOR PRECIPITATION TO GRADUALLY CHANGE OVER TO SNOW CWA WIDE. WITH 1000-500MB THICKNESSES HOVERING AROUND 540 AND RATHER MOIST SOUNDINGS WITH MUCH OF THE SOUNDING NEAR 0C...EXPECTING A HEAVIER...WET SNOW. ACCUMULATIONS ARE STILL UP IN THE AIR A BIT...BUT REALLY ONLY EXPECTING ACCUMULATIONS IN THE HIGHER TERRAIN...PARTICULARLY NORTHERN MOUNTAIN ZONES. ANY SNOW IN THE LOWLANDS WILL LIKELY NOT ACCUMULATE DUE TO WARM GROUND. FOR NOW...DECIDED TO BE CONSERVATIVE ON SNOWFALL ACCUMULATIONS...AND HAVE GENERALLY 2-4 INCHES IN THE NORTHERN MOUNTAIN ZONES...WITH GENERALLY 1-3 INCHES IN SURROUNDING HIGHER TERRAIN COUNTIES. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... A SHARP AMPLIFYING TROF WILL BE THE MAIN FEATURE EARLY IN THE EXTENDED. THIS TROF WILL SETTLE INTO EASTERN CONUS...ADVERTISED BY A CLIPPER FOR FRI NIGHT. BEST LIFT WITH THIS FEATURE WILL SKIRT BY MAINLY TO NORTH. HOWEVER...GIVEN SOME MOISTURE AND MAGNITUDE OF COLD AIR BEHIND IT...CANT RULE OUT SOME FLURRIES ABOUT ANYWHERE WITH FROPA. WILL MENTION FLURRIES IN WX GRIDS FOR LOWLANDS AND CARRY CHC POPS NORTHERN MTNS. H85 TEMPS COME DOWN TO ARND -10C BY SAT MORNING. NOT MUCH IN THE WAY OF UPSLOPE AS ATMOSPHERIC COLUMN WILL QUICKLY DRY OUT AND NW FLOW MEAGER. WILL DRY THINGS OUT QUICKLY SAT...WITH A RETURN TO SUNSHINE FOR ALL BY AFTN...ALBEIT COLD. DESPITE THE SUNSHINE...THINK 40F WILL BE HARD TO COME BY IN THE LOWLANDS...WITH GUIDANCE SUGGESTING MID 30S IS ABOUT IT...WITH 20S IN THE MTNS. UPR TROF DOESNT STICK ARND IN THIS PROGRESSIVE PATTERN...AS WAA QUICKLY ALLOWS H85 TEMPS TO RECOVER. HOWEVER...COLD NIGHT WILL BE ON TAP SAT WITH SFC HIGH BUILDING OVERHEAD. WILL GO WITH AN EARLY LOW HIGHEST ELEVATIONS AND LEVEL OFF OR SLIGHTLY REBOUND BY SUN MORNING...WITH LOWLANDS DIPPING DOWN INTO LWR 20S. TOOK TYPICAL COLD SPOTS INTO TEENS...IE NORTHERN MTN VALLEYS/NE KY. MODERATING TEMPS WILL CARRY THE WAY EARLY NEXT WEEK...THOUGH STILL REMAINING ON THE CHILLY SIDE. SHOULD STAY DRY THROUGH TUES. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... COLD FRONT CURRENTLY JUST WEST OF HTS AND PKB AND SHOULD CONTINUE TO SLOWLY MOVE EAST OVERNIGHT. SHRA AHEAD OF FRONT MAY CAUSE BORDERLINE MVFR CONDITIONS...BUT FOR THE MOST PART VFR STILL PREDOMINANT EAST OF OHIO RIVER. ONCE THE FRONT PASSES...CIGS DROP TO MVFR IN LOW STRATUS DECK. BY DAWN...IFR CIGS AND VSBY WILL BE COMMON IN WIDESPREAD RAIN. THE RAIN WILL TAPER OFF FROM W TO E TUE...ALLOWING VSBY TO IMPROVE TO VFR IN THE LOWLANDS AND MVFR IN THE MOUNTAINS BY AFTERNOON. HOWEVER...CIGS WILL STRUGGLE TO CLIMB TO LOW MVFR ION THE LOWLANDS. IN THE MOUNTAINS...IT WILL TAKE UNTIL ABOUT DAWN FOR CIGS TO GET DOWN TO IFR BUT THEN CIGS WILL REMAIN IFR OR CLOSE TO IT THROUGH THE DAY TUE. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z WEDNESDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: TIMING OF THE FRONT COULD VARY...CAUSING TIMING OF IFR/LIFR CONDITIONS TO VARY. DENSITY OF THE FOG TONIGHT COULD ALSO VARY. TIMING AND DEGREE OF IMPROVEMENT TUE ALSO COULD VARY. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. DATE TUE 12/06/11 UTC 1HRLY 08 09 10 11 12 13 14 15 16 17 18 19 EST 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14 CRW CONSISTENCY M M L L M M M L M M M M HTS CONSISTENCY L M M M M M L L M H H H BKW CONSISTENCY M M L M M M M M L L L L EKN CONSISTENCY H L L L L L L L M M M M PKB CONSISTENCY M M M M M M L L H M H H CKB CONSISTENCY L L L L M M M M M M M M AFTER 06Z WEDNESDAY... IFR IN PERIODS OF RAIN INTO TUE NT...AND IN THE MOUNTAINS IN SNOW WED NT. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...SL/30/TAX NEAR TERM...RPY/TAX SHORT TERM...SL LONG TERM...30 AVIATION...TAX
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
229 AM EST TUE DEC 6 2011 .SYNOPSIS... A MOIST SOUTHWEST FLOW ALOFT WILL INTERACT WITH A SLOW MOVING WAVY FRONTAL BOUNDARY TO BRING UNSETTLED CONDITIONS TO THE AREA THROUGH MID WEEK. UPPER LEVEL ENERGY MIGRATING FROM THE ROCKIES EASTWARD ACROSS THE CENTRAL PLAINS STATES INTO THE APPALACHIANS SHOULD INDUCE A MORE DEFINED AREA OF LOW PRESSURE OVER THE SOUTHERN MID-ATLANTIC REGION BY WEDNESDAY NIGHT BEFORE LIFTING NORTHEAST OFF THE SOUTHERN NEW ENGLAND COAST EARLY THURSDAY MORNING. COLD AND BRISK WEATHER IS ANTICIPATED FROM LATER THIS WEEK INTO THE FIRST PART OF THE WEEKEND...WITH SOME MODERATION IN TEMPERATURES LIKELY HEADING INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... AT 0530Z THE SFC COLD FRONT WAS LOCATED JUST E OF A JHW-YNG-ZZV LINE. RDR SHOWS GREATEST CVRG OR LGT/MOD RNFL MOVG ACRS THE NW AND NCNTRL MTNS. MDL AND CIWS DATA SUGGEST PCPN WILL BECOME DISORGANIZED THROUGH THE PREDAWN HOURS AS BEST MID/UPPER FORCING SLIDES OFF TO THE NORTH AND FNTL WAVE LIFTS NEWD FM SW PA. WV/IR SATL DATA ALSO SHOWS DRY SLOT SURGING NEWD INTO THE UPPER OH VLY WHICH SHOULD ALSO HELP TO CUT OFF PCPN TO SOME EXTENT. AN UNSEASONABLY MILD EARLY DEC NIGHT WILL CONTINUE OVR MUCH OF THE CWA WITH READINGS IN THE MID 40S TO MID 50S. THE EXCEPTION WILL BE OVR THE FAR NW AS COLDER AIR WRAPS IN FM THE NORTH. MARGINAL BL AND LLVL WET BULBS SUGGEST A LOW CHANCE FOR RA/SN MIX WITH SFC TEMPS BOTTOMING OUT IN THE MID TO UPPER 30S. PREVIOUS DISC FROM 1059 PM... SFC COLD FRONT HAS STALLED OUT TEMPORARILY THIS EVENING...JUST TO THE SE OF INTERSTATE 90 IN FAR NWRN PENN. 03Z SFC OBS...AND THE 02Z RUC DISPLAY A VERY TIGHT...MEAN SFC-925 MB TEMP GRADIENT FROM KERI...SW TO KCMH. RUC INDICATES THAT THIS BOUNDARY WILL CRAWL EAST TO NEAR A KELZ...TO KDUJ AND KPIT LINE BY THE 10-12Z TUESDAY TIMEFRAME. THE RAIN AREA /THAT HAS BEEN STREAMING NE AND CONFINED NEAR...AND JUST IN THE WAKE OF THE FRONT/ HAS STARTED TO QUICKLY EXPAND EAST AHEAD OF THIS BOUNDARY /NEARING KUNV ATTM AND LIKELY BEGINNING IN KIPT BY 05Z/...AS THE NOSE OF A STRENGTHENING 50-55KT/850 MB SWRLY JET MOVES NORTH ACROSS THE ALLEGHENY PLATEAU. THIS LLJ ENERGY WILL BE AIDED BY INCREASING 850-700 UVVEL BENEATH PULSES OF UPPER LEVEL DIVERGENCE BENEATH THE RIGHT ENTRANCE REGION OF A 110 KT JET LIFTING INTO NEW YORK STATE TOWARD DAYBREAK. RUC AND SREF MEAN...12-HOUR QPF IS AROUND 0.50 OF AN INCH ACROSS OUR FAR NW ZONES /NEAR KBFD/...AND BETWEEN 0.10 AND 0.25 OF AN INCH THROUGHOUT THE CENTRAL COUNTIES. RAINFL AMOUNTS OVER MUCH OF THE LOWER SUSQUEHANNA VALLEY REGION WILL STAY AOB 0.10 IF AN INCH THROUGH 12Z TUESDAY. LATEST NAM/HRRR SPREADS THE PRECIP GRADUALLY TO THE EAST ACROSS THE REST OF THE SCENT MTNS AND SUSQ VALLEY THROUGH THE PREDAWN HOURS. TIMING OF HIGHEST CHCS FOR PRECIP IS BETWEEN 05-10Z TUES ACROSS THE NW HALF OF THE CWA...AND DURING THE MID TO LATE MORNING IN THE SE ZONES. RUC 925 MB WET BULB TEMPS SINK TO A MIN OF ABOUT PLUS 1-2C ACROSS THE FAR NW BY 12Z TUESDAY...SO A CHANG-OVER TO SLEET/WET SNOW IS NOT EXPECTED AS FAR EAST AS WARREN OR KBFD. POPS WILL DECREASE AROUND OR SHORTLY AFTER DAYBREAK TUESDAY IN THE FAR NW. THE EXTENSIVE CLOUD COVER AND CONTINUED LIGHT SOUTH TO SOUTHEAST SFC WINDS ACROSS MOST OF THE AREA SHOULD KEEP TEMPS FROM FALLING VERY MUCH TONIGHT. TEMPS WILL FALL AN ADDITIONAL SEVERAL DEG F ACROSS THE HIGHER TERRAIN OF THE NORTH AND WEST...BUT WILL BE STEADY OR FALL JUST A FEW DEGREES ELSEWHERE AS MOISTURE BUILDS AND CLOUDS LOWER SUBSTANTIALLY. WILL JUST MENTION PATCHY 2-3SM FOG IN THE WHOLE AREA FOR THE TIME BEING. && .SHORT TERM /8 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... FRONT INCHES IT/S WAY ACROSS THE REST OF CENTRAL/ERN PENN ON TUES. NO SIGNIFICANT WAVES DEVELOP ALONG IT...SO GENERALLY SCT SHRA WILL FALL THROUGH THE DAY ON TUESDAY. LIKELIHOOD OF SHOWERS FAIRLY HIGH DURING THE WHOLE DAY...AND PINNING A TIME FOR HIGHEST POPS NOT EASY. WILL PAINT THE HIGHER POPS IN THE AFTN AS PRESSURE LOWER ON THE FRONT SLIGHTLY. THE MORE-ORGANIZED SHOWERS AND HIGHER POPS SHOULD BE IN THE SERN HALF OF THE FORECAST AREA. UPPER TROUGH STAYS HIGHLY POSITIVE AND DRAGS ALONG. THUS...LITTLE CHANGE IN THE SFC PATTERN AND FORCING IS SEEN FOR EARLY TUES NIGHT. HOWEVER...THE SFC BOUNDARY DOES SEEM TO CLEAR THE FORECAST AREA TUES NIGHT...AND WILL LOWER POPS OVER MUCH OF THE AREA IN THE SECOND HALF OF THE NIGHT. UPSLOPE IN THE WEST COULD FORCE ENOUGH MOISTURE UP INTO THE HILLS TO GENERATE SHOWERS...BUT P-TYPE IS QUESTIONABLE. 8H TEMPS ARE ABOVE FZG THROUGH 06-09Z IN THE WRN HIGHLANDS...BUT SFC TEMPS SHOULD FOLLOW ALONG IN LOCK STEP AND GET INTO THE 20S NW AND NEAR FZG IN THE LAURELS. WILL THEREFORE MENTION SHSN MIXING IN TO THE SCT SHRA IN THE W AFTER MIDNIGHT. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... A POSITIVE TILTED LONG WAVE TROUGH EXTENDING FROM THE GREAT LAKES INTO TX ON WED WILL BRING DEEP BROAD SWLY FLOW ALOFT. NAM/EC AND GEFS MODEL/ENSEMBLE GUIDANCE HAS TRENDED TOWARD GOOD AGREEMENT FOR A WAVE OF LOW PRESSURE TO DEVELOP OVER THE SE STATES WEDNESDAY /ALONG THE STALLED OUT FRONT THAT/S PROGGED TO EXTEND NE TO THE NEW JERSEY COAST/. GFS /WHICH SEVERAL RUNS AGO...DISPLAYED PRACTICALLY THE LONE CHC OF A LIGHT TO MODERATE WINTER WEATHER EVENT ACROSS OUR SE AND PERHAPS CENTRAL CWA/ HAS BECOME ONE OF THE FEW OUTLIER SOLUTIONS. /THE OTHER BEING THE 12Z CANADIAN GEM MODEL/. 12Z EC...18Z GEFS...AND THE 18Z/00Z NAM ARE IN PRETTY GOOD AGREEMENT AND INDICATE THE POTENTIAL FOR A FEW TO SVRL INCHES OF WET SNOW NEAR THE I-81 CORRIDOR. THE 21Z SREF HASN/T CHANGED MUCH FROM THE 15Z VERSION...WITH THE NW EDGE OF ITS 0.25 INCH STORM TOTAL LEQ QPF CONTOUR FROM KMRB...TO NEAR KMUI AND KABE. THE COMPACT...OPEN /AND PERHAPS SLIGHTLY NEG TILT/ UPPER SHORTWAVE THAT WILL BE LIFTING QUICKLY NE OUT OF THE SOUTHERN U.S. WILL NOT HAVE A CHANCE TO AMPLIFY SIGNIFICANTLY...CONSIDERING THE DEEP VORTEX DRIFTING OVER HUDSON BAY...WITH A FAST WESTERLY UPPER FLOW ACROSS THE NRN U.S. AND UPPER GLAKES REGION. HOWEVER...THE WELL- DEFINED ENTRANCE REGION OF A POTENT 140 KT UPPER JET FROM PENN TO SRN NEW ENGLAND WILL HELP TO CREATE A POTENTIAL PERIOD OF MODERATE TO STRONG UVVEL AS JET MAX WITH THE LIFTING SHORTWAVE LINKS UP. BUMPED UP POPS TO LIKELY ACROSS THE FAR SE WITH A TIGHT POP GRADIENT BETWEEN I-81 AND A KAOO...KUNV AND KIPT LINE. PRECIP TYPE WILL LIKELY START AS A COLD LIGHT RAIN IN THE SOUTH...WITH SOME AREAS OF LIGHT RAIN/WET SNOW DEVELOPING FROM THE HIGHER MID CLOUD BASE ACROSS THE REGION NORTHWEST OF I-81 BY LATE EVENING. MENTIONED THE CHC FOR A LIGHT TO MDT WET SNOW FOR OUR SE ZONES IN THE HAZ WEATHER OUTLOOK. MODELS REBOUND WITH BETTER CONSENSUS AFTER THIS SYSTEM HEADED INTO THE WEEKEND. A NORTHERN STREAM COLD FRONT MOVES THROUGH FRI TURNING FLOW WESTERLY AND BRINGING COLD AND BRISK CONDITIONS TO START THE WEEKEND. TEMPS WILL BE ABOUT 5F BELOW NORMAL /WHICH WILL BE NOTICEABLE AFTER OUR RUN OF RELATIVELY MILD TEMPS/ AND LAKE EFFECT/OROGRAPHIC SNOW SHOWERS WILL DEVELOP FRI NIGHT INTO SAT...MAINLY CONFINED TO THE NW MTNS. HIGH PRES RETURNS FOR SUNDAY/MONDAY WHICH WILL ALLOW TEMPERATURES TO GRADUALLY MODERATE WITH FAIR WEATHER. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... A COLD FRONT...LOCATED EXTENDING ACROSS THE WESTERN HALF OF PA AT 07Z...WILL PUSH SLOWLY SOUTHEAST ACROSS PENNSYLVANIA LATE TONIGHT...ACCOMPANIED BY OCNL LGT RAIN. CURRENT ANALYSIS SHOWS IFR CONDS CONFINED TO NW PA...BEHIND FRONT. HOWEVER...AS THE FRONT PUSHES EAST...EXPECT DETERIORATING FLYING CONDS TO SPREAD OVER THE REST OF PA. SHORT RANGE MDL DATA SUPPORTS IFR CONDS BECOMING WIDESPREAD ACROSS THE REST OF CENTRAL PA AFTER 09Z. MODEST IMPROVEMENT IS EXPECTED BY TUESDAY AFTN...AS FRONT BEGINS TO PUSH EAST OF THE REGION. MANY LOCATIONS WILL LIKELY IMPROVE TO MVFR CONDS. HOWEVER...RESIDUAL MOISTURE ASCENDING THE W MTNS COULD LEAD TO LINGERING IFR CIGS AT JST AND BFD THRU TUE NIGHT. OUTLOOK... WED...AM LOW CIGS POSSIBLE W MTNS. WED NIGHT...RAIN/SNOW AND LOW CIGS POSSIBLE SOUTHEAST. THU...NO SIG WX EXPECTED. FRI...PM SHSN POSSIBLE NW MTNS. SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT/STEINBUGL NEAR TERM...LAMBERT/STEINBUGL SHORT TERM...DANGELO/LAMBERT LONG TERM...LAMBERT/RXR/STEINBUGL AVIATION...FITZGERALD/CERU
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
1254 AM EST TUE DEC 6 2011 .SYNOPSIS... A MOIST SOUTHWEST FLOW ALOFT WILL INTERACT WITH A SLOW MOVING WAVY FRONTAL BOUNDARY TO BRING UNSETTLED CONDITIONS TO THE AREA THROUGH MID WEEK. UPPER LEVEL ENERGY MIGRATING FROM THE ROCKIES EASTWARD ACROSS THE CENTRAL PLAINS STATES INTO THE APPALACHIANS SHOULD INDUCE A MORE DEFINED AREA OF LOW PRESSURE OVER THE SOUTHERN MID-ATLANTIC REGION BY WEDNESDAY NIGHT BEFORE LIFTING NORTHEAST OFF THE SOUTHERN NEW ENGLAND COAST EARLY THURSDAY MORNING. COLD AND BRISK WEATHER IS ANTICIPATED FROM LATER THIS WEEK INTO THE FIRST PART OF THE WEEKEND...WITH SOME MODERATION IN TEMPERATURES LIKELY HEADING INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... AT 0530Z THE SFC COLD FRONT WAS LOCATED JUST E OF A JHW-YNG-ZZV LINE. RDR SHOWS GREATEST CVRG OR LGT/MOD RNFL MOVG ACRS THE NW AND NCNTRL MTNS. MDL AND CIWS DATA SUGGEST PCPN WILL BECOME DISORGANIZED THROUGH THE PREDAWN HOURS AS BEST MID/UPPER FORCING SLIDES OFF TO THE NORTH AND FNTL WAVE LIFTS NEWD FM SW PA. WV/IR SATL DATA ALSO SHOWS DRY SLOT SURGING NEWD INTO THE UPPER OH VLY WHICH SHOULD ALSO HELP TO CUT OFF PCPN TO SOME EXTENT. AN UNSEASONABLY MILD EARLY DEC NIGHT WILL CONTINUE OVR MUCH OF THE CWA WITH READINGS IN THE MID 40S TO MID 50S. THE EXCEPTION WILL BE OVR THE FAR NW AS COLDER AIR WRAPS IN FM THE NORTH. MARGINAL BL AND LLVL WET BULBS SUGGEST A LOW CHANCE FOR RA/SN MIX WITH SFC TEMPS BOTTOMING OUT IN THE MID TO UPPER 30S. PREVIOUS DISC FROM 1059 PM... SFC COLD FRONT HAS STALLED OUT TEMPORARILY THIS EVENING...JUST TO THE SE OF INTERSTATE 90 IN FAR NWRN PENN. 03Z SFC OBS...AND THE 02Z RUC DISPLAY A VERY TIGHT...MEAN SFC-925 MB TEMP GRADIENT FROM KERI...SW TO KCMH. RUC INDICATES THAT THIS BOUNDARY WILL CRAWL EAST TO NEAR A KELZ...TO KDUJ AND KPIT LINE BY THE 10-12Z TUESDAY TIMEFRAME. THE RAIN AREA /THAT HAS BEEN STREAMING NE AND CONFINED NEAR...AND JUST IN THE WAKE OF THE FRONT/ HAS STARTED TO QUICKLY EXPAND EAST AHEAD OF THIS BOUNDARY /NEARING KUNV ATTM AND LIKELY BEGINNING IN KIPT BY 05Z/...AS THE NOSE OF A STRENGTHENING 50-55KT/850 MB SWRLY JET MOVES NORTH ACROSS THE ALLEGHENY PLATEAU. THIS LLJ ENERGY WILL BE AIDED BY INCREASING 850-700 UVVEL BENEATH PULSES OF UPPER LEVEL DIVERGENCE BENEATH THE RIGHT ENTRANCE REGION OF A 110 KT JET LIFTING INTO NEW YORK STATE TOWARD DAYBREAK. RUC AND SREF MEAN...12-HOUR QPF IS AROUND 0.50 OF AN INCH ACROSS OUR FAR NW ZONES /NEAR KBFD/...AND BETWEEN 0.10 AND 0.25 OF AN INCH THROUGHOUT THE CENTRAL COUNTIES. RAINFL AMOUNTS OVER MUCH OF THE LOWER SUSQUEHANNA VALLEY REGION WILL STAY AOB 0.10 IF AN INCH THROUGH 12Z TUESDAY. LATEST NAM/HRRR SPREADS THE PRECIP GRADUALLY TO THE EAST ACROSS THE REST OF THE SCENT MTNS AND SUSQ VALLEY THROUGH THE PREDAWN HOURS. TIMING OF HIGHEST CHCS FOR PRECIP IS BETWEEN 05-10Z TUES ACROSS THE NW HALF OF THE CWA...AND DURING THE MID TO LATE MORNING IN THE SE ZONES. RUC 925 MB WET BULB TEMPS SINK TO A MIN OF ABOUT PLUS 1-2C ACROSS THE FAR NW BY 12Z TUESDAY...SO A CHANG-OVER TO SLEET/WET SNOW IS NOT EXPECTED AS FAR EAST AS WARREN OR KBFD. POPS WILL DECREASE AROUND OR SHORTLY AFTER DAYBREAK TUESDAY IN THE FAR NW. THE EXTENSIVE CLOUD COVER AND CONTINUED LIGHT SOUTH TO SOUTHEAST SFC WINDS ACROSS MOST OF THE AREA SHOULD KEEP TEMPS FROM FALLING VERY MUCH TONIGHT. TEMPS WILL FALL AN ADDITIONAL SEVERAL DEG F ACROSS THE HIGHER TERRAIN OF THE NORTH AND WEST...BUT WILL BE STEADY OR FALL JUST A FEW DEGREES ELSEWHERE AS MOISTURE BUILDS AND CLOUDS LOWER SUBSTANTIALLY. WILL JUST MENTION PATCHY 2-3SM FOG IN THE WHOLE AREA FOR THE TIME BEING. && .SHORT TERM /8 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... FRONT INCHES IT/S WAY ACROSS THE REST OF CENTRAL/ERN PENN ON TUES. NO SIGNIFICANT WAVES DEVELOP ALONG IT...SO GENERALLY SCT SHRA WILL FALL THROUGH THE DAY ON TUESDAY. LIKELIHOOD OF SHOWERS FAIRLY HIGH DURING THE WHOLE DAY...AND PINNING A TIME FOR HIGHEST POPS NOT EASY. WILL PAINT THE HIGHER POPS IN THE AFTN AS PRESSURE LOWER ON THE FRONT SLIGHTLY. THE MORE-ORGANIZED SHOWERS AND HIGHER POPS SHOULD BE IN THE SERN HALF OF THE FORECAST AREA. UPPER TROUGH STAYS HIGHLY POSITIVE AND DRAGS ALONG. THUS...LITTLE CHANGE IN THE SFC PATTERN AND FORCING IS SEEN FOR EARLY TUES NIGHT. HOWEVER...THE SFC BOUNDARY DOES SEEM TO CLEAR THE FORECAST AREA TUES NIGHT...AND WILL LOWER POPS OVER MUCH OF THE AREA IN THE SECOND HALF OF THE NIGHT. UPSLOPE IN THE WEST COULD FORCE ENOUGH MOISTURE UP INTO THE HILLS TO GENERATE SHOWERS...BUT P-TYPE IS QUESTIONABLE. 8H TEMPS ARE ABOVE FZG THROUGH 06-09Z IN THE WRN HIGHLANDS...BUT SFC TEMPS SHOULD FOLLOW ALONG IN LOCK STEP AND GET INTO THE 20S NW AND NEAR FZG IN THE LAURELS. WILL THEREFORE MENTION SHSN MIXING IN TO THE SCT SHRA IN THE W AFTER MIDNIGHT. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... A POSITIVE TILTED LONG WAVE TROUGH EXTENDING FROM THE GREAT LAKES INTO TX ON WED WILL BRING DEEP BROAD SWLY FLOW ALOFT. NAM/EC AND GEFS MODEL/ENSEMBLE GUIDANCE HAS TRENDED TOWARD GOOD AGREEMENT FOR A WAVE OF LOW PRESSURE TO DEVELOP OVER THE SE STATES WEDNESDAY /ALONG THE STALLED OUT FRONT THAT/S PROGGED TO EXTEND NE TO THE NEW JERSEY COAST/. GFS /WHICH SEVERAL RUNS AGO...DISPLAYED PRACTICALLY THE LONE CHC OF A LIGHT TO MODERATE WINTER WEATHER EVENT ACROSS OUR SE AND PERHAPS CENTRAL CWA/ HAS BECOME ONE OF THE FEW OUTLIER SOLUTIONS. /THE OTHER BEING THE 12Z CANADIAN GEM MODEL/. 12Z EC...18Z GEFS...AND THE 18Z/00Z NAM ARE IN PRETTY GOOD AGREEMENT AND INDICATE THE POTENTIAL FOR A FEW TO SVRL INCHES OF WET SNOW NEAR THE I-81 CORRIDOR. THE 21Z SREF HASN/T CHANGED MUCH FROM THE 15Z VERSION...WITH THE NW EDGE OF ITS 0.25 INCH STORM TOTAL LEQ QPF CONTOUR FROM KMRB...TO NEAR KMUI AND KABE. THE COMPACT...OPEN /AND PERHAPS SLIGHTLY NEG TILT/ UPPER SHORTWAVE THAT WILL BE LIFTING QUICKLY NE OUT OF THE SOUTHERN U.S. WILL NOT HAVE A CHANCE TO AMPLIFY SIGNIFICANTLY...CONSIDERING THE DEEP VORTEX DRIFTING OVER HUDSON BAY...WITH A FAST WESTERLY UPPER FLOW ACROSS THE NRN U.S. AND UPPER GLAKES REGION. HOWEVER...THE WELL- DEFINED ENTRANCE REGION OF A POTENT 140 KT UPPER JET FROM PENN TO SRN NEW ENGLAND WILL HELP TO CREATE A POTENTIAL PERIOD OF MODERATE TO STRONG UVVEL AS JET MAX WITH THE LIFTING SHORTWAVE LINKS UP. BUMPED UP POPS TO LIKELY ACROSS THE FAR SE WITH A TIGHT POP GRADIENT BETWEEN I-81 AND A KAOO...KUNV AND KIPT LINE. PRECIP TYPE WILL LIKELY START AS A COLD LIGHT RAIN IN THE SOUTH...WITH SOME AREAS OF LIGHT RAIN/WET SNOW DEVELOPING FROM THE HIGHER MID CLOUD BASE ACROSS THE REGION NORTHWEST OF I-81 BY LATE EVENING. MENTIONED THE CHC FOR A LIGHT TO MDT WET SNOW FOR OUR SE ZONES IN THE HAZ WEATHER OUTLOOK. MODELS REBOUND WITH BETTER CONSENSUS AFTER THIS SYSTEM HEADED INTO THE WEEKEND. A NORTHERN STREAM COLD FRONT MOVES THROUGH FRI TURNING FLOW WESTERLY AND BRINGING COLD AND BRISK CONDITIONS TO START THE WEEKEND. TEMPS WILL BE ABOUT 5F BELOW NORMAL /WHICH WILL BE NOTICEABLE AFTER OUR RUN OF RELATIVELY MILD TEMPS/ AND LAKE EFFECT/OROGRAPHIC SNOW SHOWERS WILL DEVELOP FRI NIGHT INTO SAT...MAINLY CONFINED TO THE NW MTNS. HIGH PRES RETURNS FOR SUNDAY/MONDAY WHICH WILL ALLOW TEMPERATURES TO GRADUALLY MODERATE WITH FAIR WEATHER. && .AVIATION /05Z TUESDAY THROUGH SATURDAY/... A COLD FRONT...LOCATED OVER NW PA AT 03Z...WILL PUSH SLOWLY SOUTHEAST ACROSS PENNSYLVANIA LATE TONIGHT...ACCOMPANIED BY OCNL LGT RAIN. CURRENT ANALYSIS SHOWS IFR CONDS CONFINED TO NW PA...BEHIND FRONT. HOWEVER...AS THE FRONT PUSHES EAST...EXPECT DETERIORATING FLYING CONDS TO SPREAD OVER THE REST OF PA. SHORT RANGE MDL DATA SUPPORTS IFR CONDS DEVELOPING AT BFD BY 06Z...THEN BECOMING WIDESPREAD ACROSS THE REST OF CENTRAL PA TOWARDS DAWN. MODEST IMPROVEMENT IS EXPECTED BY TUESDAY AFTN...AS FRONT BEGINS TO PUSH EAST OF THE REGION. MANY LOCATIONS WILL LIKELY IMPROVE TO MVFR CONDS. HOWEVER...RESIDUAL MOISTURE ASCENDING THE W MTNS COULD LEAD TO LINGERING IFR CIGS AT JST AND BFD THRU TUE NIGHT. OUTLOOK... WED...AM LOW CIGS POSSIBLE W MTNS. WED NIGHT...RAIN/SNOW AND LOW CIGS POSSIBLE SOUTHEAST. THU...NO SIG WX EXPECTED. FRI...PM SHSN POSSIBLE NW MTNS. SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT/STEINBUGL NEAR TERM...LAMBERT/STEINBUGL SHORT TERM...DANGELO/LAMBERT LONG TERM...LAMBERT/RXR/STEINBUGL AVIATION...FITZGERALD
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
1152 PM EST MON DEC 5 2011 .SYNOPSIS... A MOIST SOUTHWEST FLOW ALOFT WILL INTERACT WITH A SLOW MOVING FRONTAL BOUNDARY AND ONE OR MORE WAVES OF LOW PRESSURE TO BRING UNSETTLED CONDITIONS TO THE AREA THROUGH MID WEEK. COLD AND BRISK WEATHER IS ANTICIPATED FROM LATER THIS WEEK INTO THE WEEKEND. && .NEAR TERM /UNTIL 8 AM TUESDAY MORNING/... SFC COLD FRONT HAS STALLED OUT TEMPORARILY THIS EVENING...JUST TO THE SE OF INTERSTATE 90 IN FAR NWRN PENN. 03Z SFC OBS...AND THE 02Z RUC DISPLAY A VERY TIGHT...MEAN SFC-925 MB TEMP GRADIENT FROM KERI...SW TO KCMH. RUC INDICATES THAT THIS BOUNDARY WILL CRAWL EAST TO NEAR A KELZ...TO KDUJ AND KPIT LINE BY THE 10-12Z TUESDAY TIMEFRAME. THE RAIN AREA /THAT HAS BEEN STREAMING NE AND CONFINED NEAR...AND JUST IN THE WAKE OF THE FRONT/ HAS STARTED TO QUICKLY EXPAND EAST AHEAD OF THIS BOUNDARY /NEARING KUNV ATTM AND LIKELY BEGINNING IN KIPT BY 05Z/...AS THE NOSE OF A STRENGTHENING 50-55KT/850 MB SWRLY JET MOVES NORTH ACROSS THE ALLEGHENY PLATEAU. THIS LLJ ENERGY WILL BE AIDED BY INCREASING 850-700 UVVEL BENEATH PULSES OF UPPER LEVEL DIVERGENCE BENEATH THE RIGHT ENTRANCE REGION OF A 110 KT JET LIFTING INTO NEW YORK STATE TOWARD DAYBREAK. RUC AND SREF MEAN...12-HOUR QPF IS AROUND 0.50 OF AN INCH ACROSS OUR FAR NW ZONES /NEAR KBFD/...AND BETWEEN 0.10 AND 0.25 OF AN INCH THROUGHOUT THE CENTRAL COUNTIES. RAINFL AMOUNTS OVER MUCH OF THE LOWER SUSQUEHANNA VALLEY REGION WILL STAY AOB 0.10 IF AN INCH THROUGH 12Z TUESDAY. LATEST NAM/HRRR SPREADS THE PRECIP GRADUALLY TO THE EAST ACROSS THE REST OF THE SCENT MTNS AND SUSQ VALLEY THROUGH THE PREDAWN HOURS. TIMING OF HIGHEST CHCS FOR PRECIP IS BETWEEN 05-10Z TUES ACROSS THE NW HALF OF THE CWA...AND DURING THE MID TO LATE MORNING IN THE SE ZONES. RUC 925 MB WET BULB TEMPS SINK TO A MIN OF ABOUT PLUS 1-2C ACROSS THE FAR NW BY 12Z TUESDAY...SO A CHANG-OVER TO SLEET/WET SNOW IS NOT EXPECTED AS FAR EAST AS WARREN OR KBFD. POPS WILL DECREASE AROUND OR SHORTLY AFTER DAYBREAK TUESDAY IN THE FAR NW. THE EXTENSIVE CLOUD COVER AND CONTINUED LIGHT SOUTH TO SOUTHEAST SFC WINDS ACROSS MOST OF THE AREA SHOULD KEEP TEMPS FROM FALLING VERY MUCH TONIGHT. TEMPS WILL FALL AN ADDITIONAL SEVERAL DEG F ACROSS THE HIGHER TERRAIN OF THE NORTH AND WEST...BUT WILL BE STEADY OR FALL JUST A FEW DEGREES ELSEWHERE AS MOISTURE BUILDS AND CLOUDS LOWER SUBSTANTIALLY. WILL JUST MENTION PATCHY 2-3SM FOG IN THE WHOLE AREA FOR THE TIME BEING. && .SHORT TERM /8 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... FRONT INCHES IT/S WAY ACROSS THE REST OF CENTRAL/ERN PENN ON TUES. NO SIGNIFICANT WAVES DEVELOP ALONG IT...SO GENERALLY SCT SHRA WILL FALL THROUGH THE DAY ON TUESDAY. LIKELIHOOD OF SHOWERS FAIRLY HIGH DURING THE WHOLE DAY...AND PINNING A TIME FOR HIGHEST POPS NOT EASY. WILL PAINT THE HIGHER POPS IN THE AFTN AS PRESSURE LOWER ON THE FRONT SLIGHTLY. THE MORE-ORGANIZED SHOWERS AND HIGHER POPS SHOULD BE IN THE SERN HALF OF THE FORECAST AREA. UPPER TROUGH STAYS HIGHLY POSITIVE AND DRAGS ALONG. THUS...LITTLE CHANGE IN THE SFC PATTERN AND FORCING IS SEEN FOR EARLY TUES NIGHT. HOWEVER...THE SFC BOUNDARY DOES SEEM TO CLEAR THE FORECAST AREA TUES NIGHT...AND WILL LOWER POPS OVER MUCH OF THE AREA IN THE SECOND HALF OF THE NIGHT. UPSLOPE IN THE WEST COULD FORCE ENOUGH MOISTURE UP INTO THE HILLS TO GENERATE SHOWERS...BUT P-TYPE IS QUESTIONABLE. 8H TEMPS ARE ABOVE FZG THROUGH 06-09Z IN THE WRN HIGHLANDS...BUT SFC TEMPS SHOULD FOLLOW ALONG IN LOCK STEP AND GET INTO THE 20S NW AND NEAR FZG IN THE LAURELS. WILL THEREFORE MENTION SHSN MIXING IN TO THE SCT SHRA IN THE W AFTER MIDNIGHT. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... A POSITIVE TILTED LONG WAVE TROUGH EXTENDING FROM THE GREAT LAKES INTO TX ON WED WILL BRING DEEP BROAD SWLY FLOW ALOFT. NAM/EC AND GEFS MODEL/ENSEMBLE GUIDANCE HAS TRENDED TOWARD GOOD AGREEMENT FOR A WAVE OF LOW PRESSURE TO DEVELOP OVER THE SE STATES WEDNESDAY /ALONG THE STALLED OUT FRONT THAT/S PROGGED TO EXTEND NE TO THE NEW JERSEY COAST/. GFS /WHICH SEVERAL RUNS AGO...DISPLAYED PRACTICALLY THE LONE CHC OF A LIGHT TO MODERATE WINTER WEATHER EVENT ACROSS OUR SE AND PERHAPS CENTRAL CWA/ HAS BECOME ONE OF THE FEW OUTLIER SOLUTIONS. /THE OTHER BEING THE 12Z CANADIAN GEM MODEL/. 12Z EC...18Z GEFS...AND THE 18Z/00Z NAM ARE IN PRETTY GOOD AGREEMENT AND INDICATE THE POTENTIAL FOR A FEW TO SVRL INCHES OF WET SNOW NEAR THE I-81 CORRIDOR. THE 21Z SREF HASN/T CHANGED MUCH FROM THE 15Z VERSION...WITH THE NW EDGE OF ITS 0.25 INCH STORM TOTAL LEQ QPF CONTOUR FROM KMRB...TO NEAR KMUI AND KABE. THE COMPACT...OPEN /AND PERHAPS SLIGHTLY NEG TILT/ UPPER SHORTWAVE THAT WILL BE LIFTING QUICKLY NE OUT OF THE SOUTHERN U.S. WILL NOT HAVE A CHANCE TO AMPLIFY SIGNIFICANTLY...CONSIDERING THE DEEP VORTEX DRIFTING OVER HUDSON BAY...WITH A FAST WESTERLY UPPER FLOW ACROSS THE NRN U.S. AND UPPER GLAKES REGION. HOWEVER...THE WELL- DEFINED ENTRANCE REGION OF A POTENT 140 KT UPPER JET FROM PENN TO SRN NEW ENGLAND WILL HELP TO CREATE A POTENTIAL PERIOD OF MODERATE TO STRONG UVVEL AS JET MAX WITH THE LIFTING SHORTWAVE LINKS UP. BUMPED UP POPS TO LIKELY ACROSS THE FAR SE WITH A TIGHT POP GRADIENT BETWEEN I-81 AND A KAOO...KUNV AND KIPT LINE. PRECIP TYPE WILL LIKELY START AS A COLD LIGHT RAIN IN THE SOUT...WITH SOME AREAS OF LIGHT RAIN/WET SNOW DEVELOPING FROM THE HIGHER MID CLOUD BASE ACROSS THE REGION NORTHWEST OF I-81 BY LATE EVENING. MENTIONED THE CHC FOR A LIGHT TO MDT WET SNOW FOR OUR SE ZONES IN THE HAZ WEATHER OUTLOOK. MODELS REBOUND WITH BETTER CONSENSUS AFTER THIS SYSTEM HEADED INTO THE WEEKEND. A NORTHERN STREAM COLD FRONT MOVES THROUGH FRI TURNING FLOW WESTERLY AND BRINGING COLD AND BRISK CONDITIONS TO START THE WEEKEND. TEMPS WILL BE ABOUT 5F BELOW NORMAL /WHICH WILL BE NOTICEABLE AFTER OUR RUN OF RELATIVELY MILD TEMPS/ AND LAKE EFFECT/OROGRAPHIC SNOW SHOWERS WILL DEVELOP FRI NIGHT INTO SAT...MAINLY CONFINED TO THE NW MTNS. HIGH PRES RETURNS FOR SUNDAY/MONDAY WHICH WILL ALLOW TEMPERATURES TO GRADUALLY MODERATE WITH FAIR WEATHER. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... A COLD FRONT...LOCATED OVER NW PA AT 03Z...WILL PUSH SLOWLY SOUTHEAST ACROSS PENNSYLVANIA LATE TONIGHT...ACCOMPANIED BY OCNL LGT RAIN. CURRENT ANALYSIS SHOWS IFR CONDS CONFINED TO NW PA...BEHIND FRONT. HOWEVER...AS THE FRONT PUSHES EAST...EXPECT DETERIORATING FLYING CONDS TO SPREAD OVER THE REST OF PA. SHORT RANGE MDL DATA SUPPORTS IFR CONDS DEVELOPING AT BFD BY 06Z...THEN BECOMING WIDESPREAD ACROSS THE REST OF CENTRAL PA TOWARDS DAWN. MODEST IMPROVEMENT IS EXPECTED BY TUESDAY AFTN...AS FRONT BEGINS TO PUSH EAST OF THE REGION. MANY LOCATIONS WILL LIKELY IMPROVE TO MVFR CONDS. HOWEVER...RESIDUAL MOISTURE ASCENDING THE W MTNS COULD LEAD TO LINGERING IFR CIGS AT JST AND BFD THRU TUE NIGHT. OUTLOOK... WED...AM LOW CIGS POSSIBLE W MTNS. WED NIGHT...RAIN/SNOW AND LOW CIGS POSSIBLE SOUTHEAST. THU...NO SIG WX EXPECTED. FRI...PM SHSN POSSIBLE NW MTNS. SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...DANGELO/LAMBERT LONG TERM...LAMBERT/RXR/STEINBUGL AVIATION...FITZGERALD
AREA FORECAST DISCUSSION...UPDATED
NWS LUBBOCK TX
1141 PM CST MON DEC 5 2011 .AVIATION... UNCERTAINTY REMAINS HIGH AS TO WHEN SNOW WILL END AT KLBB AND WHAT CEILINGS WILL DO ONCE THE SNOW ENDS. OCCASIONAL PERIODS OF SNOW CONTINUE AT KLBB AS BANDS REDEVELOP NEAR THE TERMINAL BUT CEILINGS HAVE BEEN FAIRLY CONSISTENT. ALL INDICATIONS ARE THAT MVFR CONDITIONS WILL CONTINUE THROUGH THE OVERNIGHT HOURS AND SNOW SHOULD FINALLY SHUT OFF A FEW HOURS AFTER MIDNIGHT LOCAL TIME. EXPECT TO SEE VFR CEILINGS DEVELOP BY MID-MORNING TUESDAY AND CONTINUE THROUGH THE END OF THIS TAF CYCLE. JORDAN && .PREV DISCUSSION... /ISSUED 604 PM CST MON DEC 5 2011/ AVIATION... SNOW HAS LET UP AT KLBB AND CEILINGS HAVE GONE VFR BRIEFLY... HOWEVER EXPECT THAT WE WILL CONTINUE TO SEE PERIODS OF SNOW AT KLBB AND CEILINGS BOUNCING AROUND MVFR TO VFR THROUGH THE OVERNIGHT HOURS. IFR CONDITIONS ARE HARD TO FIGURE OUT RIGHT NOW AT KLBB BUT FEEL THE CEILINGS SHOULD REMAIN ABOVE THIS. EXPECT SNOW TO END AT KLBB BEFORE MIDNIGHT ALTHOUGH PERIODS OF LIGHT FLURRIES MAY PERSIST INTO TUESDAY MORNING. KCDS SHOULD REMAIN VFR WITH NO PRECIPITATION ALTHOUGH THERE MAY BE BRIEF PERIODS OF MVFR THROUGH THE OVERNIGHT HOURS. EXPECT VFR CONDITIONS BY LATE TOMORROW MORNING INTO EARLY TUESDAY AFTERNOON FOR KLBB. JORDAN PREV DISCUSSION... /ISSUED 334 PM CST MON DEC 5 2011/ SHORT TERM... THE MAIN FOCUS FOR THE SHORT TERM WILL CONTINUE TO BE THE WINTER WEATHER IMPACTS ASSOCIATED WITH A STRONG UPPER-LOW PRESSURE SYSTEM STILL PUSHING THROUGH THE FOUR CORNERS REGION. OVER THE COURSE OF THE DAY...LIGHT SNOW SHOWERS HAVE PERSISTED ACROSS THE CAPROCK...THOUGH VERY MINOR ACCUMULATIONS HAVE OCCURRED SINCE THE MID-MORNING HOURS. HOWEVER...CURRENT OBS...SATELLITE AND RADAR IMAGERY AND MODEL PROJECTIONS ARE SHOWING THE POTENTIAL FOR SOME ADDITIONAL AREAS OF LIGHT SNOWFALL TO MOVE INTO THE AREA LATE THIS AFTERNOON AND THIS EVENING AS ANOTHER LOBE OF ENERGY FROM THE AFOREMENTIONED UPPER-LOW ROTATES OVER THE REGION. MOST OF THE QPF SIGNALS SHOWN ARE FAIRLY LIGHT...BUT THE TTU WRF AND THE HRRR BOTH SHOW SOME ENHANCED PRECIPITATION BANDS DEVELOPING ACROSS THE NORTHWESTERN ZONES THIS EVENING. THIS THINKING SEEMS TO BE PLAUSIBLE AS IR SATELLITE DATA IS INDICATING A BAND OF COLDER CLOUD TOPS PUSHING INTO THE WESTERN PANHANDLE...WITH SURFACE OBS AT CLOVIS DROPPING DOWN TO 1-2 SM DUE TO SNOW. THUS...SOME LOCALIZED BURSTS OF MODERATE SNOW WILL BE POSSIBLE /PARTICULARLY ACROSS THE SW PANHANDLE/ WHERE AN ADDITIONAL INCH OF SNOW MAY BE POSSIBLE TONIGHT. HAVE INCREASED POPS TO LIKELY TO CHANCE ACROSS MUCH OF THE AREA THIS EVENING...BEFORE LOWERING THEM AFTER MIDNIGHT AS PRECIPITATION BEGINS TO WANE. THE OTHER BIG CONCERN FOR THIS EVENING WILL BE THE BRISK NORTHERLY WINDS AND STRONG COLD AIR ADVECTION OCCURRING...WHICH WILL DROP TEMPERATURES INTO THE SINGLE DIGITS ACROSS THE SW PANHANDLE AND INTO THE TEENS ACROSS THE REST OF THE AREA. GIVEN THE BITTERLY COLD TEMPERATURES AND WINDS THAT SHOULD REMAIN ABOVE 10 MPH OVERNIGHT SOME LOW WIND CHILLS WILL DEVELOP AFTER SUNSET. GIVEN THE POTENTIAL FOR SOME DANGEROUSLY COLD WINDS CHILLS AT OR AROUND -5 DEGREES OCCURRING LATER TONIGHT ACROSS THE NORTHWEST ZONES...HAVE PLACED THAT AREA IN A WIND CHILL ADVISORY THROUGH 15Z TOMORROW. GIVEN THE POTENTIAL FOR SOME ADDITIONAL /ALBEIT GENERALLY LIGHT/ SNOWFALL ACCUMULATIONS ON THE CAPROCK THIS EVENING AND ALREADY HAZARDOUS DRIVING CONDITIONS FROM BLACK ICE AND SNOW ON AREA ROADWAYS...HAVE OPTED TO EXTEND THE WINTER WEATHER ADVISORY ON THE CAPROCK UNTIL 12Z. TOMORROW WILL BE A BITTERLY COLD DAY ACROSS THE AREA...AS HIGHS WILL GENERALLY REMAIN WELL BELOW FREEZING IN THE 20S DUE TO VERY LOW THICKNESS VALUES AND A CONTINUED NORTHERLY WIND. LONG TERM... AMPLIFIED PATTERN THROUGHOUT THE CONUS WILL SLOWLY RELAX BY MIDWEEK RESULTING IN BRIEFLY ZONAL FLOW AND SLIGHTLY MILDER TEMPS ON THE SOUTH PLAINS. THIS PATTERN HOWEVER STILL LOOKS TO BREAK DOWN ON FRIDAY YIELDING BROADLY CYCLONIC FLOW COURTESY OF A DEEP POLAR VORTEX TAKING RESIDENCE IN THE HUDSON BAY. JUST A GLANCING BLOW FROM THIS BROAD TROUGH WILL YIELD A DRY POLAR FRONT LATE THU NIGHT/EARLY FRI SERVING TO KNOCK HIGHS ON FRI 15-20 DEG BELOW CLIMO. MEDIUM RANGE MODELS INSIST ON DEEPER WEST OR SWLY FLOW BY THE WEEKEND INDICATIVE OF MORE SEASONABLE TEMPS. GREATEST FORECAST CHALLENGE THIS PERIOD INVOLVES LO TEMPS TUE NIGHT AS STRATUS CLEARS AND WINDS SLACKEN WITHIN AN ELONGATED SURFACE RIDGE. CHOSE NOT TO LOWER INHERITED MIN TEMPS MUCH BELOW GUIDANCE FOR NOW AS ALL NUMERICAL DATA INDICATE LIGHT WESTERLY FLOW OVERNIGHT. SHOULD THESE LIGHT WINDS VEER MORE NLY IN LATER FORECASTS...THEN THE RECORD DAILY LOW AT LBB /8 SET IN 2005/ MAY BE IN JEOPARDY. && .PRELIMINARY POINT TEMPS/POPS... FRIONA 8 21 7 40 17 / 60 10 0 0 0 TULIA 12 22 11 41 18 / 50 10 0 0 0 PLAINVIEW 13 23 10 40 18 / 50 10 0 0 0 LEVELLAND 13 22 9 40 19 / 50 10 0 0 0 LUBBOCK 15 25 11 40 19 / 40 10 0 0 0 DENVER CITY 14 26 16 40 20 / 50 10 0 0 0 BROWNFIELD 14 26 13 40 20 / 50 10 0 0 0 CHILDRESS 20 30 17 42 21 / 20 10 0 0 0 SPUR 20 30 15 44 20 / 30 10 0 0 0 ASPERMONT 21 33 20 45 22 / 20 10 10 0 0 && .LUB WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 6 AM CST TUESDAY FOR THE FOLLOWING ZONES: TXZ021>024-027>030-033>036-039>042. WIND CHILL ADVISORY UNTIL 9 AM CST TUESDAY FOR THE FOLLOWING ZONES: TXZ021>023-027-028. && $$ 99/99/99
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
332 AM CST TUE DEC 6 2011 .SHORT TERM...TODAY THROUGH THURSDAY NIGHT 332 AM CST TUE DEC 6 2011 MAIN FORECAST CONCERNS THIS PACKAGE...CLOUDS AND TEMPERATURES THRU THE PERIOD. DATA ANALYSIS AT 06Z HAD A RIDGE OF HIGH PRESSURE EXTENDING FROM NORTH OF LK SUPERIOR ACROSS MN TO NEB AND WESTERN KS. A LARGE AREA OF LOW PRESSURE WAS LOCATED OVER NORTH-CENTRAL CAN WITH FALLING PRESSURES IN THE NORTHERN PLAINS. STRATUS CLOUDS REMAINS TRAPPED ACROSS THE AREA...UNDER AN INVERSION BETWEEN 850-800MB AND EAST OF THE SFC RIDGE AXIS. WEST EDGE OF THE CLOUDS WAS NEAR A KDLH-KOTG LINE...MAKING VERY SLOW PROGRESS EAST/SOUTH. WEAK SFC-925MB TROUGH AND CONVERGENCE...ALONG WITH THE SLOWLY COOLING LOWER LEVELS CONTINUED TO SQUEEZE SOME FLURRIES/VERY LIGHT SNOW OUT OF THE COLUMN OVER MUCH OF WESTERN WI INTO EXTREME EASTERN MN. NO PROBLEMS NOTED WITH 06.00Z MODEL INITIALIZATIONS. SOLUTIONS QUITE SIMILAR FOR TODAY THRU THU NIGHT...AT LEAST WITH THE SHORTWAVES AND LARGER SCALE FEATURES. MODELS STILL STRUGGLING WITH THE LOWER LEVEL MOISTURE/RH FIELDS AND STRATUS CLOUDS ACROSS THE AREA. DPROG/DT OF 500MB HGTS AT 06.00Z SHOWED MODEL RUNS OF 04.00Z AND 05.00Z VERIFIED QUITE WELL ACROSS NOAM...FAVORING STRONGER OF EARLIER MODELS WITH THE NORTHERN PORTION OF THE TROUGH AND FASTER OF EARLIER MODELS WITH THE SOUTHWEST CONUS PORTION OF THE TROUGH. THRU TODAY/TONIGHT MODELS TREND TOWARD A TIGHTER/FASTER CONSENSUS WITH THE SOUTHERN PORTION OF THE TROUGH MOVING EAST INTO THE MID/LOWER MS VALLEY AND WEAKENING OF THE NORTHERN PORTION OF THE TROUGH AS IT MOVES EAST OF THE REGION. TREND CONTINUES FASTER WITH THE LOWER MS VALLEY TROUGH WED/WED NIGHT AS IT TO THE EAST COAST BY 12Z THU. BETTER CONSENSUS FOR BROAD TROUGHING/NORTHWEST FLOW TO DEVELOP OVER THE NORTH-CENTRAL CONUS/ GREAT LAKES REGION. THIS TROUGH DEEPENS OVER THE MID/UPPER MS VALLEY THU/THU NIGHT...BUT MINOR DIFFERENCES IN THE TIMING/STRENGTH DETAILS DEVELOP BY 12Z FRI. OVERALL BETTER RUN-TO-RUN CONSISTENCY FOR TODAY THRU THU NIGHT SHOWN BY ECMWF...ESPECIALLY WITH THE SOUTHERN STREAM ENERGY EARLY IN THE PERIOD. CHECK OF OBS VS. MODEL DATA AT 06Z SHOWED MODELS ALL QUITE GOOD WITH THE CENTRAL CONUS SFC MASS FIELDS...THOUGH AGAIN CONTINUED TO STRUGGLE WITH THE LOWER LEVEL RH AND STRATUS DECKS TRAPPED ACROSS THE REGION. ECMWF/ RUC LOOK TO BE DOING BEST WITH THE 925MB RH/STATUS CLOUDS OVER MN/ WI/IA WHILE ONLY MODEL SOME INDICATION OF THE FLURRIES WAS THE GFS. THUS NO CLEAR DETERMINISTIC MODEL FAVORITE. WITH MODELS TRENDING TOWARD A TIGHTER CONSENSUS MUCH OF THE PERIOD...FAVORED THE CONSENSUS. SHORT TERM FCST CONFIDENCE AVERAGE TO GOOD THIS CYCLE. IN THE SHORT TERM...LOW CLOUDS/CLEARING REMAIN PROBLEMATIC TODAY/ TONIGHT WITH TYPICAL POOR MODEL PERFORMANCE ON THIS AND THE TIME OF YEAR WHEN LOW CLOUDS LIKE TO HANG TOUGH. MODEL CONSENSUS KEEPS 70+ PERCENT 925MB RH OVER THE CENTRAL/EAST PARTS OF THE FCST AREA THRU THE DAY WITH ONLY SLOW EROSION/ADVECTION ON THE WESTERN SIDE. RAISED CLOUD COVER IN SKY GRIDS TO REFLECT A SLOWER/NON CLEARING TODAY. MOVED THE CLEARING INTO TONIGHT WITH INCREASING WEST SFC- 850MB FLOW NORTH OF THE LOW LEVEL RIDGE AXIS TO FINALLY ADVECT THE MOISTURE EAST AND OUT OF THE AREA. SFC-925MB TROUGH WEAKENS THRU THIS MORNING...BUT GIVEN SLOW MOVEMENT OF THE LOW LEVEL FEATURES... LINGERED SCT FLURRIES OVER THE NORTH HALF OF THE FCST AREA WHERE RADAR REFLECTIVITY/SFC OBS CONTINUED TO DETECT/REPORT FLURRIES AS OF 09Z. REST OF SHORT-TERM PERIOD GENERALLY COOL/QUIET. SHORTWAVE ENERGY PASSES NORTH OF THE FCST AREA WED/WED NIGHT WITH BULK OF FORCING/LIFT AND 850-500MB MOISTURE/SATURATION REMAINING NORTH OF THE FCST AREA. COLD/DRY AIRMASS SETTLES ACROSS THE AREA IN THE WAKE OF THIS SHORTWAVE TROUGH FOR THU/THU NIGHT. THIS AS MORE SHORTWAVE ENERGY DROPS SOUTHEAST ACROSS THE NORTHERN PLAINS FOR THU/THU NIGHT. BULK OF THE LOWER LEVEL THERMO-DYNAMIC FORCING AND INCREASE OF MOISTURE IN THE 925-700MB LAYER REMAINS SOUTH OF THE FCST AREA THU/THU NIGHT. ONLY LINGERED A SMALL -SN CHANCE ACROSS THE EXTREME SOUTH END OF THE FCST AREA THU NIGHT TO BLEND WITH NEIGHBORING GRIDS. SATURATION OF THE COLUMN OVER THE NORTH END OF THE FCST AREA THU/THU NIGHT...NORTH OF THE SHORTWAVE TRACK...AN ISSUE IN THE COLDER COLUMN THERE. MAY YET SEE SCT FLURRIES ALONG/NORTH OF HWY 29 THU/THU NIGHT BUT LEFT THIS DRY FOR NOW. GENERALLY CARRIED PARTLY CLOUDY TO MOSTLY CLEAR SKIES FOR WED THRU THU NIGHT. HIGH/LOW TEMPERATURES PROBLEMATIC WITH SNOW COVERING THE NORTHWEST HALF OF THE FCST AREA WHILE THE SOUTHEAST HALF IS SNOW-FREE. WITH MORE CLOUDS/OVERCAST TODAY...TRENDED HIGHS FOR MINIMAL DIURNAL SWING AND AT OR BELOW NUMERICAL GUIDANCE. WITH PARTLY CLOUDY SKIES TONIGHT BUT SOME SOUTHWEST GRADIENT WINDS...FAVORED A BLEND OF THE GUIDANCE LOWS. SOUTHWEST/WEST WINDS AHEAD OF THE NEXT COLD FRONT AND SOME SUNSHINE WED...TRENDED TOWARD WARMER OF GUIDANCE HIGHS... ESPECIALLY OVER THE SNOW-FREE SOUTHEAST HALF OF THE FCST AREA. APPEARS BOUNDARY LAYER WINDS WILL KEEP LOW LEVELS STIRRED WED NIGHT AND TRENDED TOWARD WARMER OF GUIDANCE LOWS. FAVORED A MODEL CONSENSUS OF HIGHS FOR THU...WHICH BLENDS WELL WITH NEIGHBORING GRIDS BUT MAY BE TOO WARM WITH MDT/STRONG LOW LEVEL COLD ADVECTION OVER THE REGION BY MID-DAY. FAVORED THE MODEL CONSENSUS FOR LOWS THU NIGHT...WHICH ALSO MAY BE TOO WARM IF WINDS ARE LIGHTER THAN EXPECTED ESPECIALLY OVER THE SNOW-COVERED PORTIONS OF THE FCST AREA. .LONG TERM...FRIDAY THROUGH MONDAY 332 AM CST TUE DEC 6 2011 LONG-TERM FCST CONFIDENCE AVERAGE. 06.00Z MEDIUM RANGE MODELS IN REASONABLE AGREEMENT WITH EACH OTHER AND THEIR PREVIOUS RUNS FRI THRU SUNDAY WITH THE LONGWAVE TROUGH BEING PROGRESSIVE AND HGTS RISING OVER THE UPPER MIDWEST FRIDAY INTO SUNDAY. COLD SFC HIGH PRESSURE DRIFTS OVER THE AREA FRI THEN MOVES SOUTH OF THE AREA FOR SAT/SUN. STRONG LOW LEVEL WARM ADVECTION SPREADS ACROSS THE AREA SAT INTO SAT NIGHT WITH 925MB TEMPS IN THE 0 TO +4C RANGE BY 12Z SUN. BELOW/MUCH BELOW NORMAL TEMPS FRI LOOK TO WARM TO ABOVE/MUCH ABOVE NORMAL BY SUN AS BULK OF THE WARM ADVECTION GOES INTO WARMING UNDER PARTLY CLOUDY/MOSTLY SUNNY SKIES. RAISED HIGHS A BIT OVER THE SOUTHEAST HALF OF THE FCST AREA SUN WITH THE LACK OF SNOW COVER. GFS/ECMWF SOLUTIONS DIVERGE FOR MON. ECMWF SLIDES A COLD FRONT AND WEAK LOW LEVEL COLD ADVECTION ACROSS THE AREA WHILE GFS TRACKS A LOW INTO NORTHWEST MN KEEPING THE AREA UNDER LOW LEVEL WARM ADVECTION. EITHER WAY...APPEARS SOME OF THE SNOW COVER WILL MELT SUN AND MON WILL SEE CONTINUED ABOVE NORMAL TEMPS. BIGGEST LONG-TERM QUESTION LOOKS TO BE WILL THERE BE ENOUGH LOWER LEVEL MOISTURE FOR A SMALL PRECIP CHANCE FOR PARTS OF THE AREA BY LATER MON. MODEL CONSENSUS DATA USED IN THE DAY 4-7 FCST GRIDS LOOKS TO HAVE ALL OF THIS WELL TRENDED FOR NOW. && .AVIATION...THROUGH 06Z WEDNESDAY 1045 PM CST MON DEC 5 2011 PERSISTENT LOW LEVEL SATURATION...PER RH FIELDS AND BUFKIT SOUNDINGS...SUGGEST THAT THE MVFR CIGS WILL HOLD INTO TUE AFTERNOON/EVENING. AN UPPER LEVEL SHORTWAVE TROUGH WILL HELP SWEEP THE LOW STRATUS TO THE EAST...AND MOST OF TUE NIGHT LOOKS SCT-SKC. BY WED MORNING CLOUDS ASSOCIATED WITH THE TROUGH WILL SLIDE IN...AND THERE COULD BE ANOTHER PERIOD OF MVFR CIGS IN THE AFTERNOON. A FEW FLURRIES WILL CONTINUE THROUGH THE OVERNIGHT HOURS...BUT DON/T SEE ANY REDUCTIONS TO VSBY. BELIEVE ANY THREAT FOR -FZDZ HAS ALSO ENDED. NORTHWEST WINDS WILL SWING TO THE SOUTHWEST BY LATE TUE AFTERNOON...AHEAD OF THAT SHORTWAVE...BUT SHIFT BACK TO THE NORTHWEST ON WED AS THE SYSTEM PASSES EAST. && .ARX WATCHES/WARNINGS/ADVISORIES... 332 AM CST TUE DEC 6 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM... RRS LONG TERM.... RRS AVIATION..... RIECK
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
1057 PM CST MON DEC 5 2011 UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE .SHORT TERM...TONIGHT AND TUESDAY. LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW THE STATE OF WISCONSIN LOCATED BETWEEN A COLD FRONT RUNNING UP THE EASTERN SIDE OF THE APPALACHIANS...AND A POLAR SURFACE HIGH STRETCHING ACROSS THE DAKOTAS EARLY THIS AFTERNOON. A WEAK SURFACE TROUGH REMAINS A NUISANCE WHICH HANGS BACK FROM JUST SOUTH OF MILWAUKEE TO EAU CLAIRE. RADAR RETURNS HAVE GRADUALLY ERODED OVER CENTRAL AND EAST-CENTRAL WISCONSIN OVER THE COURSE OF THE DAY...THOUGH BEEFIER RETURNS AND SURFACE OBS SHOW LIGHT SNOW SHOWERS OCCURRING OVER WESTERN WISCONSIN. SOME HOLES IN THE CLOUDS ARE TRYING TO DEVELOP OVER NORTHEAST WISCONSIN...AND PERHAPS INTO CENTRAL WISCONSIN AS WELL. AS THE SURFACE HIGH SHIFTS EAST TONIGHT...CLOUD TRENDS AND TEMPS ARE THE MAIN FORECAST CONCERNS. TONIGHT...HIGH PRESSURE OVER THE NORTHERN PLAINS WILL BUILD EAST OVER THE NORTHERN MISSISSIPPI VALLEY. HOWEVER...FLOW WILL CONTINUE TO BE OUT OF THE NORTH AND LIGHTLY ADVECTING CLOUDS OFF LAKE SUPERIOR. IN ADDITION...12Z GUIDANCE SUPPORTS LINGERING LOW LEVEL CONVERGENCE OVER CENTRAL WISCONSIN THAT WILL KEEP AN AREA OF ENHANCED RH IN PLACE. KEPT A FLURRY MENTION OVER THE FAR WESTERN CWA TO ACCOUNT FOR THIS. WITH PLENTY OF CLOUDS UPSTREAM...HAVE A HARD TIME GOING BELOW MOSTLY CLOUDY CONDITIONS. THERE WILL BE UNDOUBTEDLY SUCKER HOLES THAT WILL DEVELOP WITHIN THE STRATUS...MOSTLY LIKELY WITHIN THE DOWNSLOPING AREAS OF NORTHEAST WISCONSIN. WILL PLAY THE PROBABILITY THAT SCT CONDITIONS DEVELOP THERE...BUT LEAVE MOSTLY CLOUDY CONDITIONS ELSEWHERE...WITH SCT SNOW SHOWERS OVER THE SNOW BELT OF N-C WISCONSIN. LOWS IN THE LOWER TEENS NORTH TO MIDDLE 20S SOUTHEAST. TEMPS COULD BE MUCH COLDER OVER THE SNOW PACK OF N-C WISCONSIN IF HOLES IN THE CLOUDS DO DEVELOP THERE. TUESDAY...HIGH PRESSURE BUILDS INTO THE REGION TOMORROW. ANY SURFACE CONVERGENCE ALONG THE LINGERING TROUGH OVER CENTRAL WISCONSIN IS PROGGED TO DISSIPATE IN THE MORNING...BUT MODELS INDICATE THE REMNANTS OF THE ENHANCED RH MOVING EAST AS LIGHT SW FLOW DEVELOPS. ALSO SEE SIGNS OF STEEP LOW LEVEL LAPSE RATES WITH HEATING OF THE DAY THAT POINTS TOWARDS STRATO-CU DEVELOPING. WITH CLOUDS UNDER THE HIGH CURRENTLY...WILL SIDE MORE PESSIMISTICALLY WITH CLOUD COVER...WHICH WILL KEEP MOSTLY CLOUDY CONDITIONS OVER NORTH-CENTRAL WISCONSIN FOR THE MORNING...AND PARTLY CLOUDY CONDITIONS EVERYWHERE FOR THE AFTERNOON. HIGHS RANGING FROM THE LOWER 20S NORTH TO AROUND 30 DEGREES SOUTHEAST. .LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...THE MAIN FCST CONCERN IS THE ARRIVAL OF ARCTIC AIR LATER IN THE WEEK. SHORT-WAVE ENERGY CURRENTLY OVER THE GULF OF ALASKA WILL TOP THE WEST COAST RIDGE...THEN HELP TO CARVE A BROAD TROF OVER THE CENTRAL U.S. BY THURSDAY. A SURGE OF ARCTIC AIR IS EXPECTED TO ARRIVE IN WI ON THURSDAY...WITH H8 TEMPS PLUMMETING TO -16 TO -20 C BY FRIDAY. THIS WILL LEAD TO OUR COLDEST TEMPERATURES SO FAR THIS SEASON. THE COLDER WEATHER WILL NOT LAST LONG...AS SOUTHWEST WINDS DEVELOP IN THE WAKE OF THE RETREATING ARCTIC HIGH OVER THE WEEKEND. H8 TEMPS ARE EXPECTED TO SURGE TO 0 TO +4 C BY SATURDAY NIGHT/SUNDAY. A WEAK COLD FRONT IS EXPECTED TO MOVE THROUGH THE REGION ON WEDNESDAY...WITH A STRONGER ARCTIC FRONT ARRIVING ON THURSDAY. HAVE BEEN WATCHING FOR POSSIBLE SNOW DEVELOPMENT AS THE RRQ OF A STG UPPER JET INTERACTS WITH THE ARCTIC FRONT THURSDAY NIGHT INTO FRIDAY...BUT THE CONCENSUS OF THE MODELS...INCLUDING THE 12Z/MON ECMWF...IS THAT SNOW WILL DEVELOP TO OUR SOUTH AND EAST. WILL NOT CARRY ANY POPS AT THIS TIME...BUT SUBSEQUENT SHIFTS WILL STILL NEED TO KEEP AN EYE ON THIS. DESPITE THE PRESENCE OF A COLD AIR MASS FROM WEDNESDAY THROUGH FRIDAY NIGHT...WIND TRAJECTORIES WILL BE TOO WESTERLY FOR ANY APPRECIABLE LK-EFFECT SNOW. MODELS HAVE BACKED OFF SLIGHTLY ON THE MAGNITUDE OF THE COLD SNAP LATE IN THE WORK WEEK...WITH H8 TEMPS TRENDING A FEW DEGREES WARMER. EVEN SO...STILL EXPECT MAX TEMPS TO BE ABOUT 10 DEGREES BLO NORMAL ON FRIDAY. THE COLDER WEATHER WILL BE SHORT-LIVED... WITH ABOVE NORMAL TEMPERATURES QUICKLY RETURNING BY SUNDAY. A WEAK COLD FRONT MAY IMPACT THE REGION ON MONDAY...BUT SHOULD NOT HAVE ANY SIGNIFICANT IMPACT ON OUR WEATHER. && .AVIATION...A FEW FLURRIES OR SNOW SHOWERS CONTINUE OVER A CONVERGENT REGION OVER WEST CENTRAL WISCONSIN. OBSERVATIONS OVER CENTRAL WISCONSIN REPORTING 10 MILES WITH NO WEATHER PRESENT BUT ANTICIPATE FLURRY ACTIVITY OCCURRING WEST OF A LINE FROM RIB FALLS TO WISCONSIN RAPIDS INTO WAUSHARA COUNTY. RADARS ALSO SHOWING SOME RETURNS OVER THE LAKE MICHIGAN SHORELINE WITH NO GROUND TRUTH AND FINALLY SCATTERED SNOW SHOWERS WERE NOTED OVER VILAS. AS FAR AS CLOUDS...A SUCKER HOLE OPENED UP NORTHEAST WISCONSIN INCLUDING THE GRB VICINITY. BUT STILL EXPECT VFR CIGS TO DOMINATE OVERNIGHT INTO TUESDAY WITH SOME DECREASE IN CLOUDS LATER TUESDAY. TDH && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1045 PM CST MON DEC 5 2011 .SHORT TERM... 245 PM CST MON DEC 5 2011 BIGGEST FORECAST CONCERN IS ON CLOUDS AND TEMPERATURES...WITH LIGHT PRECIPITATION CHANCES THIS EVENING ALSO A CONCERN. 18Z WATER VAPOR IMAGERY SHOWS SHORTWAVE TROUGH OVER MINNESOTA...WHILE AT THE SURFACE A WEAK TROUGH WAS WORKING ITS WAY THROUGH THE FORECAST AREA...BUT WAS WEAKENING WITH TIME. THIS COMBINATION WAS PRODUCING WEAK LIFT THROUGH SATURATED LOWER LAYER AND THUS SURFACE REPORTS INDICATING MAINLY LIGHT SNOW AND FLURRIES...WITH SOME PATCHY FREEZING DRIZZLE. 05.12Z MODELS AGAIN IN GOOD AGREEMENT WITH THEIR MASS FIELDS. THERE IS SOME DIFFERENCES IN SPEED OF COLDER PLUNGE OF AIR ON THURSDAY...WITH THE NAM THE FASTEST. ONLY OTHER DIFFERENCE NOTED IS GFS A LITTLE FASTER IN PUSHING THE STRATUS OUT ON TUESDAY. FOR TONIGHT...SHORTWAVE IN MINNESOTA ROTATES INTO NORTHWEST WISCONSIN. MODEL SOUNDINGS INDICATE WEAK LIFT CONTINUES IN THE SATURATED LOWER LAYER DURING THE EVENING. 05.15Z RUC SOUNDINGS QUESTIONABLE WITH REGARDS TO ICE IN THE CLOUD LAYER...WHILE NAM SOUNDINGS SUGGEST MORE ICE. BASED ON REPORTS FROM THIS AFTERNOON MENTION FLURRIES AND PATCHY FREEZING DRIZZLE FOR THE EVENING HOURS. WITH THE CLOUDS DID GO ON THE WARMER SIDE OF THE GUIDANCE NUMBERS FOR LOWS TONIGHT. ON TUESDAY...GFS A LITTLE FASTER IN PUSHING THE STRATUS OUT OF THE AREA...WHILE THE NAM KEEPS 850MB-925MB MOISTURE OVER THE AREA THROUGHOUT THE DAY AND NOT CLEARING UNTIL EVENING. DID TAKE A COMPROMISE...WITH A CLEARING TREND FROM WEST TO EAST DURING THE AFTERNOON HOURS. TEMPERATURES WILL BE TRICKY WITH THE CLOUDS...BUT WITH THE MORE PESSIMISTIC OUTLOOK DID GO WITH THE COOLER OF THE GUIDANCE NUMBERS. DO EXPECT CLEAR SKIES...AT LEAST FOR A SHORT PERIOD OF TIME TUESDAY NIGHT. HOWEVER...ANOTHER SHORTWAVE BEGINS TO DROP SOUTHWARD OUT OF SOUTHERN CANADA LATE TUESDAY NIGHT...AND MODELS HINT AT AN INCREASE IN HIGH LEVEL CLOUDS. THESE CLOUDS THEN DROP ACROSS THE AREA ON WEDNESDAY AND WEDNESDAY NIGHT AHEAD OF THE ASSOCIATED COLD FRONT. TEMPERATURES LOOK TO BE A LITTLE MILDER AHEAD OF THE FRONT...BUT STILL BELOW NORMAL WITH HIGHS FROM THE MIDDLE 20S IN THE SNOW COVERED LOCATIONS...TO THE LOWER 30S IN THE NON SNOW COVERED AREAS. ON THURSDAY COLD AIR BEGINS TO SURGE INTO THE AREA BEHIND THE FRONT. AS MENTIONED BEFORE NAM QUICKER IN MOVING THIS COLD AIR INTO THE REGION AND AGAIN USED A MODEL CONSENSUS FOR HIGHS. 05.12 GFS AND ECMWF ALSO GENERATING SOME LIGHT PRECIPITATION ALONG THE LEADING EDGE OF THE COLD AIR ACROSS IOWA IN BAND OF WEAK FRONTOGENESIS. WITH THE BULK OF PUSH OF COLD AIR THURSDAY NIGHT...DID ADD SOME LOWER END SNOW PROBABILITIES ACROSS NORTHEAST IOWA AND SOUTHWEST WISCONSIN. .LONG TERM... 245 PM CST MON DEC 5 2011 A DRY NORTHWEST LOW PATTERN WILL CONTINUE FOR FRIDAY AND SATURDAY AND THIS WILL LEAD TO BELOW NORMAL TEMPERATURES. THE FLOW WILL BECOME MORE ZONAL ON SUNDAY AS A TROUGH BUILDS INTO THE WESTERN CONUS. AS THE TROUGH PROGRESSES INTO THE CENTRAL SECTIONS OF THE COUNTRY...THE FLOW WILL BECOME MORE SOUTHWESTERLY. DRY CONDITIONS WILL CONTINUE THROUGH MONDAY...BUT WITH A MORE SOUTHERLY WIND...TEMPERATURES WILL WARM SATURDAY AND SUNDAY...WITH HIGHS EXPECTED IN THE 30S BOTH SUNDAY AND MONDAY. && .AVIATION... 1045 PM CST MON DEC 5 2011 PERSISTENT LOW LEVEL SATURATION...PER RH FIELDS AND BUFKIT SOUNDINGS...SUGGEST THAT THE MVFR CIGS WILL HOLD INTO TUE AFTERNOON/EVENING. AN UPPER LEVEL SHORTWAVE TROUGH WILL HELP SWEEP THE LOW STRATUS TO THE EAST...AND MOST OF TUE NIGHT LOOKS SCT-SKC. BY WED MORNING CLOUDS ASSOCIATED WITH THE TROUGH WILL SLIDE IN...AND THERE COULD BE ANOTHER PERIOD OF MVFR CIGS IN THE AFTERNOON. A FEW FLURRIES WILL CONTINUE THROUGH THE OVERNIGHT HOURS...BUT DON/T SEE ANY REDUCTIONS TO VSBY. BELIEVE ANY THREAT FOR -FZDZ HAS ALSO ENDED. NORTHWEST WINDS WILL SWING TO THE SOUTHWEST BY LATE TUE AFTERNOON...AHEAD OF THAT SHORTWAVE...BUT SHIFT BACK TO THE NORTHWEST ON WED AS THE SYSTEM PASSES EAST. && .ARX WATCHES/WARNINGS/ADVISORIES... 245 PM CST MON DEC 5 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM... RABERDING LONG TERM.... RABERDING AVIATION..... RIECK
AREA FORECAST DISCUSSION
NWS TOPEKA KS
536 AM CST TUE DEC 6 2011 ...UPDATE TO AVIATION... .DISCUSSION... SHORT RANGE FORECAST (TODAY AND WEDNESDAY)... 8Z WATER VAPOR IMAGERY AND ASSOCIATED 500 MB RUC ANALYSIS SHOWS A HIGHLY AMPLIFIED POSITIVELY TILTED TROUGH OVER THE CENTRAL PLAINS WITH ITS AXIS EXTENDING FROM LAKE SUPERIOR AND RUNNING SOUTHWESTWARD THROUGH NEBRASKA AND INTO THE FOUR CORNER REGION. CURRENTLY TEMPERATURES ACROSS CENTRAL NEBRASKA ARE BELOW ZERO AS THE SURFACE RIDGE OF HIGH PRESSURE IS CENTERED OVER NEBRASKA. THE COLDEST LOCATION REMAINS KBBW WHERE THE TEMP AT 9Z WAS -11. ACROSS NORTHEAST KANSAS TEMPERATURES REMAIN IN THE MID TEENS WITH WIND CHILLS IN THE SINGLE DIGITS. ACROSS SOUTHEAST KANSAS MEAGER FRONTOGENETICAL AND ISENTROPIC LIFT HAS BROUGHT SOME LIGHT SNOW...MAINLY IN THE FORM OF NON-ACCUMULATING FLURRIES. BY MID-DAY ON TUESDAY EXPECT THE LOW/MID LEVEL LIFT AND SATURATED CONDITIONS TO MOVE OFF THE EAST OF THE FORECAST AREA ALLOWING A GRADUAL BREAKDOWN OF THE STRATUS DECK. EXPECT VERY LIGHT COLD AIR ADVECTION TO PERSIST THROUGHOUT THE DAY AS WINDS STAY FROM THE NORTH WHERE THE SURFACE HIGH WILL RESIDE. AS A RESULT OF THE COLD AIR ADVECTION AND THE ABBREVIATED DURATION OF CLEAR SKIES EXPECT TEMPS ON TUESDAY TO REMAIN IN THE MID TO UPPER 20S ACROSS AREAS NORTH OF THE KANSAS TURNPIKE...WITH TEMPS SOUTH AND EAST OF THE TURNPIKE REACHING THE LOWER 30S. FOR TUESDAY NIGHT THE SURFACE HIGH MOVES EASTWARD AND CENTERS OVER NORTHEAST KANSAS. EXPECT SKIES TO CLEAR OUT AND WINDS TO GO CALM OVERNIGHT. EXPECT TUESDAY NIGHT/WED MORNING TO BE THE COLDEST PERIOD FOR THIS FORECAST PACKAGE AS TEMPS WILL DROP TO THE LOWER TEENS ACROSS THE ENTIRE AREA...WITH THE LOWER TERRAIN OF RIVER VALLEYS PERHAPS DROPPING INTO THE SINGLE DIGITS. BY WEDNESDAY THE ARCTIC AIRMASS WHICH BROUGHT THE FRIGID TEMPS FOR THE EARLY PART OF THE WEEK WILL SHIFT EAST AND WARMER AIR WILL ADVECT INTO THE AREA...ALLOWING WEDNESDAY`S TEMPS TO REACH THE UPPER 30S TO LOWER 40S. MID-RANGE AND EXTENDED FORECAST (THURSDAY THROUGH MONDAY)... FAIRLY INACTIVE WEATHER PATTERN SHAPING UP FOR THE MIDDLE TO LATE PART OF THE WEEK AND INTO THE WEEKEND...AS NO REAL MID OR UPPER LEVEL FORCING ENTERS THE AREA. ALTHOUGH THE DAY TIME HOURS WILL BE SLIGHTLY WARMER FOR THE MIDDLE TO LATE PART OF THE WEEK OVERNIGHT LOWS WILL STILL DROP TO THE MID TEENS TO UPPER 20S AS ANOTHER MASS OF COLD AIR DIPS INTO THE AREA. PERHAPS THE ONLY WEATHER TO AFFECT NORTHEAST KANSAS WILL BE LATE IN THE WEEK AS AN UPPER LEVEL LOW DIGS SOUTHWARD THROUGH NEBRASKA BUT ITS SOUTHWARD PROGRESS STOPS IN SOUTHERN NEBRASKA BEFORE IT EJECTS EASTWARD. WITH LITTLE MOISTURE FOR THE SYSTEM TO WORK WITH EXPECT ONLY A FEW FLURRIES ACROSS AREAS NORTH OF HIGHWAY 24 THURSDAY NIGHT/FRIDAY MORNING. THEREAFTER EXPECT A DRY FORECAST FOR THE REST OF THE WEEK AND THROUGH THE WEEKEND WITH DAYTIME HIGHS IN THE 40S AND OVERNIGHT LOWS IN THE UPPER 20S TO LOWER 30S. JL && .AVIATION... STRATUS WITH MVFR CEILINGS...AROUND 1600 FT...WERE OBSERVED AT THE TAF SITES THIS MORNING. ISENTROPIC DOWN-GLIDE WILL INCREASE THROUGH MID MORNING AND SHOULD SCATTER OUT THE MVFR CEILINGS BY 16Z. EXPECT VFR CONDITIONS THROUGH THE REMAINDER OF THE TAF PERIOD. NORTH WINDS OF 8 TO 12 KTS WILL SLOWLY DIMINISH THROUGH THE DAY. GARGAN && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS CARIBOU ME
858 AM EST TUE DEC 6 2011 .SYNOPSIS... A COLD FRONT WILL MOVE OFF THE COAST LATE TODAY WITH A SERIES OF WEAK LOW PRESSURE SYSTEMS TRACKING ALONG THE FRONT TONIGHT INTO WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... UPDATE: USING HRRR MODEL WILL END PRECIPITATION FROM WEST TO EAST ACROSS THE REGION THIS AFTERNOON. REGION WILL START OUT PRECIP FREE THIS EVENING THEN NEXT LOW PRESSURE MOVING ALONG STATIONARY FRONT OVER THE GULF OF MAINE WILL BRING PRECIP BACK ACROSS THE AREA LATER TONIGHT. A COLD FRONT IS EXPECTED TO MOVE THROUGH THE STATE DURING THE DAY TODAY. CURRENT GUIDANCE APPEARS TO MOVE THIS FRONTAL SYSTEM TOO FAST AND EXPECT THE FRONT TO REMAIN STATIONARY DURING THE EARLY MORNING AS A WAVE MOVES NORTHEASTWARD ALONG THE FRONT. AFTER THE WAVE MOVES OFF TO THE NORTHEAST THE COLD AIR SHOULD MOVE IN DURING THE MID MORNING. HAVE USED THE NAM12 AND GFS40 TO INITIALIZE THE POP GRIDS THEN HAVE MANUALLY ADJUSTED TO BETTER FIT THE TIMING OF THE COLD FRONT. HAVE ALSO INCREASE THE POPS TO NEAR 100 PERCENT IN THE VICINITY OF THE FRONT. BY LATE IN THE AFTERNOON AND EARLY EVENING THE FRONT SHOULD BE CLEARING THE COAST. ANOTHER LOW IS EXPECTED TO DEVELOP ALONG THE FRONT TO THE SOUTH LATER TONIGHT AND AS A RESULT PRECIPITATION WILL SPREAD BACK INTO SOUTH TOWARDS WEDNESDAY MORNING. HAVE USED A BLEND OF NAM12 AND GMOS FOR WIND AND USED THE NAM12 FOR TEMPERATURE AND DEW POINT. ALSO BLENDED NAM12 AND GFS40 FOR QPF WITH SOME MANUAL ADJUSTMENTS. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY/... AN INTERESTING FORECAST IN STORE FOR THIS TERM. A SECOND WAVE OF LOW PRES IS EXPECTED TO MOVE ALONG THE STALLED FRONTAL BOUNDARY AND PASS THROUGH THE COAST ON WEDNESDAY. DECIDED TO USE THE SREF POPS BLENDED IN W/THE GFS FOR EARLY WEDNESDAY WHICH SHOWED 60-80% POPS ACROSS THE NORTHERN AND EASTERN AREAS W/. BLYR TEMPERATURES DO LOOK TO BE COLD ENOUGH ACROSS THE NORTHERN AND NORTHWESTERN AREAS FOR ALL SNOW WHILE CENTRAL AND DOWNEAST AREAS WILL SEE MAINLY RAIN. THE PRECIP WILL WIND DOWN BY THE AFTERNOON W/COLDER AIR SLOWLY SEEPING SOUTHWARD. QPF IS A BLEND OF HPC/GFS AND THE NAM WHICH SHOWS .05 TO .15". ANY SNOWFALL ACCUMULATIONS WILL BE ACROSS THE FAR NORTH AND NORTHWEST W/UP TO AN INCH OF ADDITIONAL ACCUMULATION. THE TEMPERATURES WERE ADJUSTED UPWARD USING A BLEND OF THE BCGMOS AND NAM12 GIVEN THE PROXIMITY OF THE FRONT AND HOW THE COLD AIR HAS BEEN HELD BACK THIS MORNING AS DISCUSSED ABOVE IN NEAR TERM SECTION. A BRIEF BREAK IN THINGS AS SOME WEAK RIDGING IS SHOWN TO WORK ACROSS THE CWA FOR WEDNESDAY NIGHT W/SOME PARTIAL CLEARING AND COLDER TEMPERATURES ESPECIALLY ACROSS THE NORTHERN 3RD OF THE CWA. ONCE AGAIN, PREVIOUS MINS WERE RAISED DUE TO SLOWER PROGRESSION OF THE COLD AIR. NOW THE ATTENTION TURNS TO THURSDAY W/THE APCH OF LOW PRES FROM THE MID ATLC REGION. THE 00Z RUN OF THE ECMWF ALONG THE 5 OUT 10 GFS ENSEMBLE MEMBERS SHOW THE LOW FURTHER W AND PASSING THROUGH THE GULF OF MAINE AND THEN ACROSS NOVA SCOTIA. THE ECMWF IS THE FURTHEST WEST BRINGING THE LOW THROUGH THE BAY OF FUNDY WHICH WOULD MEAN A SIGNIFICANT SNOWSTORM FOR JUST ABOUT THE ENTIRE CWA. THE 00Z RUN OF THE NAM WAS FURTHER EAST AND BRINGS THE HEAVIEST QPF INTO THE DOWNEAST AND THE COAST. THE CANADIAN HEMISPHERIC IS CLOSER TO THE NAM AND OPERATIONAL RUN OF THE GFS W/A TRACK ACROSS NOVA SCOTIA. SINCE THE TRENDS HAVE BEEN A MORE WESTERN TRACK ESPECIALLY FROM THE ECMWF AND THE GFS ENSEMBLE, CONFIDENCE IS BUILDING TO RAISE THE BAR AND BRING LIKELY POPS INTO THE DOWNEAST AND COAST ON THURSDAY AND CHC POPS UP INTO NORTHERN MAINE. THE CONFIDENCE IS NOT HIGH ENOUGH THOUGH TO BRING HIGHER PERCENTAGES FURTHER NORTH AS SHOWN BY THE ECMWF. IT WILL BE INTERESTING TO SEE HOW THE LATER MODEL RUNS HANDLE THIS SYSTEM. TEMPERATURES DO LOOK LIKE THEY COULD BE COLD ENOUGH FOR SNOW EVEN AS FAR SOUTH AS BANGOR AND PERHAPS BAR HARBOR. DECIDED TO BLEND THE GMOS AND BCGMOS FOR MAX TEMPERATURES ON THURSDAY WHICH SHOW LOW TO MID 30S. WE WILL ADD A SECTION TO THE HWO ADDRESSING THIS POTENTIAL STORM. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... THE STORM SYSTEM APPEARS TO BE A FAST MOVER PULLING THROUGH THE MARITIMES W/MUCH COLDER AIR SET TO POUR INTO THE REGION THROUGH THE WEEKEND. INITIALIZED THE LONGER TERM W/THE GMOS AND THEN ADJUSTED MAINLY FOR THE POPS AND WINDS. A DISTURBANCE IS SHOWN BY THE GFS AND THE ECMWF TO AFFECT THE CWA ON SATURDAY W/THE POSSIBILITY OF LIGHT SNOW AND MINOR ACCUMULATIONS. AFTER THIS SYSTEM PULLS THROUGH SATURDAY EVENING, MUCH COLDER AIR IS SHOWN TO PUSH INTO THE REGION W/SOME OF THE COLDEST TEMPERATURES OF THE SEASON SO FAR. GMOS TEMPERATURES LOOKED TO BE HANDLING THIS WELL AND SO NO REASON TO DEVIATE FROM THEM. THE PRECIP CHCS LOOKED OVERDONE ON SUNDAY AND DECIDED TO DROP THEM BACK W/HIGH PRES SHOWN TO RIDGE ACROSS THE REGION. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... NEAR TERM: EXPECT MVFR/IFR CONDITIONS TODAY AND TONIGHT. SHORT TERM: IFR/MVFR LOOKS TO BE THE GOING RATE FOR WEDNESDAY W/SNOW ACROSS THE NORTHERN TERMINALS ESPECIALLY KCAR AND KPQI. A BREAK TO MVFR AND EVEN VFR POSSIBLE FOR KBGR AND KBHB WEDNESDAY EVENING W/MVFR HOLDING FOR THE NORTHERN TERMINALS. THERE IS THE POTENTIAL FOR CIGS AND VSBYS TO DROP BACK TO IFR AND EVEN LIFR COME THURSDAY FOR ALL THE TAF SITES AS A STORM SYSTEM APCHS FROM THE SOUTH. && .MARINE... NEAR TERM: HAVE USED A BLEND OF THE NAM12 AND GFS40 FOR WINDS. FOR WAVES USED SWAN/NAM. LONG PERIOD INCOMING WAVE APPEARS TO BE 1 FOOT OR LESS BASED ON BUOY SPECTRAL AND WNA SPECTRAL BULLETIN...SO MOST OF COMBINED SEA RESULTING FROM LOCAL WINDS. SWAN BRING SEAS CLOSE TO SCA AGAIN LATER TODAY. MY THINKING IS THAT WAVE HEIGHT WILL TOP OFF JUST UNDER 5 FEET SO WILL NOT ISSUE SCA AT THIS TIME. SHORT TERM: THERE IS POTENTIAL FOR SCA CONDITIONS ON THURSDAY INTO THURSDAY NIGHT AS LOW PRES INTENSIFIES AS IS IT MOVES THROUGH THE GULF OF MAINE INTO THE MARITIMES. BLENDED THE GEM/NAM12 AND GFS FOR WEDNESDAY INTO WEDNESDAY NIGHT AND THEN FOLLOWED W/THE GFS AND GMOS FROM THURSDAY ONWARD. THEREFORE, WINDS WERE BROUGHT UP TO 20 TO 25 KTS FOR AFOREMENTIONED TIME-FRAME AND THEN SPEEDS COME DOWN AS HIGH PRES RIDGES IN FOR FRIDAY. WNAWAVE AND THE SWAN GUIDANCE WAS USED FOR WAVES WHICH KEEP HEIGHTS AOB 5 FT. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...NONE. MARINE...NONE. && $$ NEAR TERM...FOSTER/MIGNONE SHORT TERM...HEWITT LONG TERM...HEWITT AVIATION...FOSTER/MIGNONE MARINE...FOSTER/MIGNONE/HEWITT
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
519 AM EST TUE DEC 6 2011 .SYNOPSIS... LIGHT RAIN SHOWERS EXPECTED TO LINGER THIS MORNING WITH A SLOW MOVING COLD FRONT IN THE VICINITY. STRONG SYSTEM BRINGS RAIN AND SNOW WEDNESDAY AND WEDNESDAY NIGHT. HIGH PRESSURE THURSDAY. CLIPPER FRIDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... EARLY MORNING RADAR TRENDS INDICATE TWO POINTS OF FOCUS FOR PRECIPITATION. COLD FRONT JUST EAST OF OH RIVER VALLEY HAS BEEN THE IMPETUS FOR SCT SHOWERS OVERNIGHT INTO THE EARLY MORNING. NOT EXPECTING THIS TO CHANGE MUCH...SAVE FOR THE EVENTUAL EASTWARD CREEP OF THE FRONTAL BOUNDARY. SECOND FOCUS IS A WAVE RIDING NORTH ALONG THE FRONT...CURRENTLY LOCATED IN EAST-CENTRAL TN. EXPECTING SHOWERS ASSOCIATED WITH THIS FEATURE TO BE A LITTLE MORE ORGANIZED AS THEY ENTER OUR SW VA AND WV MNT COUNTIES IN THE COMING HOURS. HRRR HAS HANDLED ONGOING PRECIPITATION TRENDS THE BEST...STICKING WITH THIS SOLN THIS MORNING. LOW CIGS AND VSBYS HAVE BEEN REPORTED ALONG THE FRONT AS IT MADE IT SLOW JOURNEY THROUGH SE OHIO...EXPECTING THIS TREND TO CONTINUE IN CRW AND CKB VICINITIES BEFORE ANY DAYTIME MIXING CAN IMPROVE CONDITIONS. LOW STRATUS SHOULD HANG AROUND CWA THROUGH AT LEAST MIDDAY WITH THE GREATEST IMPACT EVIDENT IN MNT COUNTIES. TEMPS REMAIN COOLER THAN MOS WEST OF TROF AXIS...TWEAKED TEMPS TO ACCOUNT FOR THIS. GOING WITH A NEAR NON-DIURNAL TREND TO HIGH TEMPS WITH COLD FRONT STILL IN THE REGION. KEEPING WITH THE TREND OF AOA MOS TEMPS IN WV MNTS TODAY...WHILE AOB MOS IN THE LOWLANDS. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... MUCH BETTER CONSENSUS IN THE MODELS TONIGHT COMPARED TO THE RUNS LAST NIGHT REGARDING THE VIGOROUS SYSTEM SLATED FOR WEDNESDAY AND WEDNESDAY NIGHT. MOISTURE WILL HAVE ALREADY OVERSPREAD THE AREA SOUTH OF THE OHIO RIVER BY 12Z WEDNESDAY...AND EXPECT STEADY RAIN THROUGH THE FIRST PART OF THAT TIME PERIOD. THE ENTIRE KEY TO THIS FORECAST IS THE RATE OF THE COLD AIR ADVECTION AND THE SURFACE TEMPERATURES FALLING BELOW FREEZING. THIS WILL OCCUR FIRST IN THE HIGHEST ELEVATIONS WHERE THE MOST SIGNIFICANT ACCUMULATIONS ARE LIKELY. 925MB TEMPERATURE GRADIENT WILL TIGHTEN UP OVER THE EASTERN MOUNTAINS AND FINALLY KICK THROUGH AFTER AROUND 21Z WEDNESDAY...WHICH WILL SUBSEQUENTLY ALLOW THE CHANGE OVER TO SNOW FOR THE REMAINDER OF THE MOUNTAINS. WHILE THE OPERATIONAL MODELS GO EASY ON THE SPEED OF THE COLD AIR ADVECTION...STRENGTH OF THE DYNAMICS IN PLAY DO LEAVE SOME QUESTION AS TO WHETHER THIS PARAMETER IS BEING REPRESENTED WELL BY THESE MODELS...OR IF THERE WILL BE AN EARLIER TRANSITION TIME TO COME OVER THE NEXT COUPLE OF RUNS. SYSTEM WILL BE EFFICIENT WHEN IT COMES TO CREATING PRECIPITATION. JET STREAK OVER 140KTS EXISTS OVER SOUTHEAST OHIO WEDNESDAY...AND THE 500MB WAVE INDICATES A SHIFT TO A NEGATIVE TILT UPON PASSAGE THROUGH THE CENTRAL AND SOUTHERN APPALACHIANS. ROBUST FRONTOGENETIC FORCING WILL COUPLE WITH Q VECTOR CONVERGENCE IN THE UPPER LEVELS...CREATING ENHANCED OMEGA THROUGH THE DENDRITIC GROWTH LAYERS...WITH SATURATION OF THE COLUMN EXTENDING FROM THE SURFACE TO ABOVE 500MB. THE 03Z RUN OF THE SREF BRINGS PROBABILITIES OF SNOW EXCEEDING 4 INCHES AT ABOUT THE 30 TO 40 PERCENT RANGE FOR POCAHONTAS COUNTY. CURRENT STATE OF THE FORECAST GRIDS DOES BRING AROUND 4 TO 8 INCHES TOTAL SNOW ACCUMULATION...RELEGATED TO THE HIGHEST PEAKS OF THE CWA...ABOVE ROUGHLY 4000FT. WITH THE SLOWER CHANGE OVER TO SNOW IN THE MOUNTAINS BELOW 4000FT...ABOUT 2 TO 4 INCHES OF SNOW ARE IN THE FORECAST FOR THIS ISSUANCE. ANOTHER VARIABLE IN THIS OVERALL EQUATION IS THE MILD AIR THAT HAS BEEN IN PLACE...THE RAIN THAT WILL PRECEDE THE SNOW...AND THE LENGTH OF TIME NECESSARY FOR THE SNOW TO ACCUMULATE. GIVEN THE FACT THAT THIS IS A LATE 3RD PERIOD TO EARLY 4TH PERIOD EVENT...WILL NOT COMMIT TO THE WATCH FOR NOW. ANY VARIABILITY IN THE TIMING OF THE BELOW FREEZING AIR COULD ALTER THE SNOWFALL TOTAL FORECAST SIGNIFICANTLY...IN EITHER DIRECTION. NOT COMFORTABLE WITH THIS POTENTIAL VOLATILITY TO THE FORECAST AND WILL DRAW ATTENTION TO THIS SYSTEM IN THE HWO AND RWS TEXT PRODUCTS. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... A SHARP AMPLIFYING TROF WILL BE THE MAIN FEATURE EARLY IN THE EXTENDED. THIS TROF WILL SETTLE INTO EASTERN CONUS...ADVERTISED BY A CLIPPER FOR FRI NIGHT. BEST LIFT WITH THIS FEATURE WILL SKIRT BY MAINLY TO NORTH. HOWEVER...GIVEN SOME MOISTURE AND MAGNITUDE OF COLD AIR BEHIND IT...CANT RULE OUT SOME FLURRIES ABOUT ANYWHERE WITH FROPA. WILL MENTION FLURRIES IN WX GRIDS FOR LOWLANDS AND CARRY CHC POPS NORTHERN MTNS. H85 TEMPS COME DOWN TO ARND -10C BY SAT MORNING. NOT MUCH IN THE WAY OF UPSLOPE AS ATMOSPHERIC COLUMN WILL QUICKLY DRY OUT AND NW FLOW MEAGER. WILL DRY THINGS OUT QUICKLY SAT...WITH A RETURN TO SUNSHINE FOR ALL BY AFTN...ALBEIT COLD. DESPITE THE SUNSHINE...THINK 40F WILL BE HARD TO COME BY IN THE LOWLANDS...WITH GUIDANCE SUGGESTING MID 30S IS ABOUT IT...WITH 20S IN THE MTNS. UPR TROF DOESNT STICK ARND IN THIS PROGRESSIVE PATTERN...AS WAA QUICKLY ALLOWS H85 TEMPS TO RECOVER. HOWEVER...COLD NIGHT WILL BE ON TAP SAT WITH SFC HIGH BUILDING OVERHEAD. WILL GO WITH AN EARLY LOW HIGHEST ELEVATIONS AND LEVEL OFF OR SLIGHTLY REBOUND BY SUN MORNING...WITH LOWLANDS DIPPING DOWN INTO LWR 20S. TOOK TYPICAL COLD SPOTS INTO TEENS...IE NORTHERN MTN VALLEYS/NE KY. MODERATING TEMPS WILL CARRY THE WAY EARLY NEXT WEEK...THOUGH STILL REMAINING ON THE CHILLY SIDE. SHOULD STAY DRY THROUGH TUES. && .AVIATION /10Z TUESDAY THROUGH SATURDAY/... COLD FRONT CURRENTLY JUST EAST OF HTS AND PKB AND SHOULD CONTINUE TO SLOWLY MOVE EAST THIS MORNING. IFR/LIFR CONDITIONS ALONG THE FRONT...WITH IMPROVEMENT TO MVFR/IFR BEHIND THE FRONT IN LOW STRATUS DECK. CONDITIONS SHOULD IMPROVE TO PREDOMINANTLY MVFR CONDITONS BASED ON CIGS. EXPECTING ADDITIONAL SHRA TODAY ALONG THE FRONT AND IN MNT COUNTIES. POSSIBLE IFR CONDITIONS COULD EXIST IN ANY SHOWERS THAT OCCUR WITH LOWERED VSBYS. RAIN WILL EVENTUALLY TAPER OFF FROM W TO E TUES AFTERNOON THIS SHOULD ALLOW VSBYS TO IMPROVE WHILE CIGS WILL BE SLOWER TO RESPOND. EXPECTING CONDITIONS TO DETERIORATE AGAIN TONIGHT WITH MVFR CIGS AND VSBYS...PRIMARILY IN THE MOUNTAINS. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z WEDNESDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: CONDITIONS ALONG THE FRONT HAVE CAUSED BOUNCING CIGS AND VSBYS TO LESS THAN FORECAST...ANY VARIANCE IN TIMING COULD CAUSE TIMING CHANGES OF WORSENING CONDITIONS. DEGREE AND TIMING OF IMPROVEMENT TODAY COULD ALSO VARY. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. DATE TUE 12/06/11 UTC 1HRLY 08 09 10 11 12 13 14 15 16 17 18 19 EST 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14 CRW CONSISTENCY M M L L M M M L M M M M HTS CONSISTENCY L M M M M M L L M H H H BKW CONSISTENCY M M L M M M M M L L L L EKN CONSISTENCY H L L L L L L L M M M M PKB CONSISTENCY M M M M M M L L H M H H CKB CONSISTENCY L L L L M M M M M M M M AFTER 12Z WEDNESDAY... IFR IN PERIODS OF RAIN INTO WEDS...ALSO WITH SNOW EXPECTED IN THE MOUNTAINS. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...26/TAX NEAR TERM...TAX SHORT TERM...26 LONG TERM...30 AVIATION...TAX
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
509 AM EST TUE DEC 6 2011 .SYNOPSIS... A MOIST SOUTHWEST FLOW ALOFT WILL INTERACT WITH A SLOW MOVING WAVY FRONTAL BOUNDARY TO BRING UNSETTLED CONDITIONS TO THE AREA THROUGH MID WEEK. UPPER LEVEL ENERGY MIGRATING FROM THE ROCKIES EASTWARD ACROSS THE CENTRAL PLAINS STATES INTO THE APPALACHIANS SHOULD INDUCE A MORE DEFINED AREA OF LOW PRESSURE OVER THE CAROLINAS BY WEDNESDAY NIGHT. THIS SYSTEM MAY SPREAD A SWATH OF LIGHT TO MODERATE SNOW ACROSS SOUTHERN AND EASTERN PENNSYLVANIA AS IT TRACKS NORTHEAST NEAR THE MID-ATLANTIC COAST. SEASONABLY COLD AND BRISK BUT MAINLY DRY WEATHER IS ANTICIPATED FROM LATER THIS WEEK INTO THE FIRST PART OF THE WEEKEND...WITH SOME MODERATION IN TEMPERATURES LIKELY HEADING INTO EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AT 0530Z THE SFC COLD FRONT WAS LOCATED JUST E OF A JHW-YNG-ZZV LINE. RDR SHOWS GREATEST CVRG OR LGT/MOD RNFL MOVG ACRS THE NW AND NCNTRL MTNS. MDL AND CIWS DATA SUGGEST PCPN WILL BECOME DISORGANIZED THROUGH THE PREDAWN HOURS AS BEST MID/UPPER FORCING SLIDES OFF TO THE NORTH AND FNTL WAVE LIFTS NEWD FM SW PA. WV/IR SATL DATA ALSO SHOWS DRY SLOT SURGING NEWD INTO THE UPPER OH VLY WHICH SHOULD ALSO HELP TO CUT OFF PCPN TO SOME EXTENT. AN UNSEASONABLY MILD EARLY DEC NIGHT WILL CONTINUE OVR MUCH OF THE CWA WITH READINGS IN THE MID 40S TO MID 50S. THE EXCEPTION WILL BE OVR THE FAR NW AS COLDER AIR WRAPS IN FM THE NORTH. MARGINAL BL AND LLVL WET BULBS SUGGEST A LOW CHANCE FOR RA/SN MIX WITH SFC TEMPS BOTTOMING OUT IN THE MID TO UPPER 30S. PREVIOUS DISC FROM 1059 PM... SFC COLD FRONT HAS STALLED OUT TEMPORARILY THIS EVENING...JUST TO THE SE OF INTERSTATE 90 IN FAR NWRN PENN. 03Z SFC OBS...AND THE 02Z RUC DISPLAY A VERY TIGHT...MEAN SFC-925 MB TEMP GRADIENT FROM KERI...SW TO KCMH. RUC INDICATES THAT THIS BOUNDARY WILL CRAWL EAST TO NEAR A KELZ...TO KDUJ AND KPIT LINE BY THE 10-12Z TUESDAY TIMEFRAME. THE RAIN AREA /THAT HAS BEEN STREAMING NE AND CONFINED NEAR...AND JUST IN THE WAKE OF THE FRONT/ HAS STARTED TO QUICKLY EXPAND EAST AHEAD OF THIS BOUNDARY /NEARING KUNV ATTM AND LIKELY BEGINNING IN KIPT BY 05Z/...AS THE NOSE OF A STRENGTHENING 50-55KT/850 MB SWRLY JET MOVES NORTH ACROSS THE ALLEGHENY PLATEAU. THIS LLJ ENERGY WILL BE AIDED BY INCREASING 850-700 UVVEL BENEATH PULSES OF UPPER LEVEL DIVERGENCE BENEATH THE RIGHT ENTRANCE REGION OF A 110 KT JET LIFTING INTO NEW YORK STATE TOWARD DAYBREAK. RUC AND SREF MEAN...12-HOUR QPF IS AROUND 0.50 OF AN INCH ACROSS OUR FAR NW ZONES /NEAR KBFD/...AND BETWEEN 0.10 AND 0.25 OF AN INCH THROUGHOUT THE CENTRAL COUNTIES. RAINFL AMOUNTS OVER MUCH OF THE LOWER SUSQUEHANNA VALLEY REGION WILL STAY AOB 0.10 IF AN INCH THROUGH 12Z TUESDAY. LATEST NAM/HRRR SPREADS THE PRECIP GRADUALLY TO THE EAST ACROSS THE REST OF THE SCENT MTNS AND SUSQ VALLEY THROUGH THE PREDAWN HOURS. TIMING OF HIGHEST CHCS FOR PRECIP IS BETWEEN 05-10Z TUES ACROSS THE NW HALF OF THE CWA...AND DURING THE MID TO LATE MORNING IN THE SE ZONES. RUC 925 MB WET BULB TEMPS SINK TO A MIN OF ABOUT PLUS 1-2C ACROSS THE FAR NW BY 12Z TUESDAY...SO A CHANG-OVER TO SLEET/WET SNOW IS NOT EXPECTED AS FAR EAST AS WARREN OR KBFD. POPS WILL DECREASE AROUND OR SHORTLY AFTER DAYBREAK TUESDAY IN THE FAR NW. THE EXTENSIVE CLOUD COVER AND CONTINUED LIGHT SOUTH TO SOUTHEAST SFC WINDS ACROSS MOST OF THE AREA SHOULD KEEP TEMPS FROM FALLING VERY MUCH TONIGHT. TEMPS WILL FALL AN ADDITIONAL SEVERAL DEG F ACROSS THE HIGHER TERRAIN OF THE NORTH AND WEST...BUT WILL BE STEADY OR FALL JUST A FEW DEGREES ELSEWHERE AS MOISTURE BUILDS AND CLOUDS LOWER SUBSTANTIALLY. WILL JUST MENTION PATCHY 2-3SM FOG IN THE WHOLE AREA FOR THE TIME BEING. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... A FAIRLY PROGRESSIVE AND DYNAMIC H5/H7 SHORTWAVE TROUGH WILL STREAK EWD FM THE LWR MS VLY ACRS THE SRN APPALACHIANS TO THE MID- ATLC SEABOARD WED/WED NGT INTO EARLY THURS. AS THE MID/UPPER LEVEL TROUGH TAKES ON A NEGATIVE TILT...STRONG HEIGHT FALLS AND UPPER LEVEL DIVERGENCE WILL INDUCE SFC LOW DEVELOPMENT INVOF THE CAROLINAS/VA VCNTY WED NGT. THE DEEP LAYER ASCENT AND FAVORABLE JET DYNAMICS WILL LEAD TO LOWERING SNOW LEVELS AS COLD AIR WRAPS INTO THE SYS AS IT ROTATES UP ACRS ERN NY INTO NEW ENGLAND. GUID INDICATES DECENT CLUSTERING WITH THE SFC LOW BUT LINGERING TIMING AND TRACK UNCERTAINTY STILL REMAINS...ALTHOUGH THE SPREADS HAVE NARROWED CONSIDERABLY FROM 24 HOURS AGO. THE PREFERENCE IS STILL TWD A FASTER PROGRESSION OF THE SYS OVERALL AND THE SREF AND GEFS MEANS APPEAR TO BE ADJUSTING IN THIS DIRECTION. WHILE THERE IS A MODEST INCREASE IN FORECASTER CONFIDENCE IN LIGHT OF THE NARROWING SPREADS AND GENERAL TREND TWD A CONSENSUS SOLN...THE RECENT POOR CONTINUITY AND LINGERING UNCERTAINTY /ESPECIALLY IN THE TRACK OF THE LOW/ LEADS TO BELOW AVG CONFIDENCE. IT APPEARS THAT A 12-HR PD OF MOD TO PERHAPS HVY PCPN WILL BE POSSIBLE OVR THE SRN AND ERN ZONES IN THE DEFORMATION ZONE AND COMMA HEAD LOCATED ON THE NW EDGE OF THE EVENTUAL SFC LOW TRACK. PCPN SHOULD CHANGEOVER FROM RAIN TO SNOW AS COLD AIR FILLS IN ON THE BACKSIDE OF THE DEEPENING SYS. THE GFS SFC LOW TRACK IS FURTHER EAST/OFFSHORE COMPARED TO THE NAM/ECMWF/CAN/GEFS...THUS BRINGING THE THREAT OF LESS SNOW COMPARED TO THE OTHER GUID...WHICH IS INDICATING A SOLID 0.50 TO 1 INCH OF LIQUID IN 12 HRS OVR MUCH OF SERN PA ENDING 12Z THURS. THE LOWER ELEVATIONS/VALLEYS WILL LKLY START AS RAIN AND TRANSITION OVR TO SNOW WHICH COULD LIMIT ACCUMS. MEANWHILE HIGHER ELEVATIONS SHOULD SEE HIGH PROBABILITIES FOR MORE SIGNIFICANT ACCUMS GIVEN LONGER DURATION. OVERALL... CONFIDENCE DID NOT QUITE MEET THE WATCH ISSUANCE THRESHOLD ALTHOUGH CONSIDERED ISSUING WSW WITH COLLABORATION FROM LWX AND PHI. FOR NOW WILL KEEP MENTION IN THE HWO MENTIONING LIGHT TO MODERATE ACCUMS POSSIBLE. IT SHOULD BE NOTED THAT MOD TO HVY ACCUMS IN EXCESS OF 6 INCHES ARE ALSO POSSIBLE GIVEN MDL QPFS...WITH A LOWER RISK/PROBABILITY OUTCOME DUE TO THE AFOREMENTIONED UNCERTAINTY IN THE TRACK/TIMING AND THERMAL PROFILES/ELEVATION DEPENDENCE. THE LOW WILL MOVE OFF THE SOUTHERN NEW ENGLAND COAST BY DAYBREAK THURS WITH A BRISK AND COLD WLY FLOW REGIME PREVAILING OVR CNTRL PA DURING THE DAY. THIS SHOULD TRANSLATE INTO A BRIEF PD OF MTN SNOW SHOWERS EARLY GIVEN FAVORABLE DOWNWIND LAKE TRAJECTORIES AND COLD CYC FLOW ALOFT. THE LLVL FLOW WILL BACK MORE TO THE WSW THURS NGT INTO FRI AS A NRN STREAM TROUGH ROTATES INTO THE UPPER MIDWEST AROUND THE BASE OF HUDSON BAY VORTEX. && .LONG TERM /FRIDAY THROUGH MONDAY/... A MSTR-STARVED COLD FNT MARKING THE LEADING EDGE OF THE UPPER MIDWEST H5 TROUGH AND ACCOMPANYING SEASONABLY COLD /-12 TO -14C AT 850MB/ AIR ALOFT WILL CROSS THE AREA FRI NGT...WITH LITTLE FANFARE OTHER THAN SOME LAKE ENHANCED/UPSLOPE SNOW SHOWERS ALONG THE ALLEGHENIES. TEMPERATURES SHOULD BOTTOM ON SATURDAY AS THE CORE UPPER TROUGH AXIS MOVES OVERHEAD. HIGH PRES WILL OVERSPREAD THE REGION ON SUN AND DOMINATE THE PATTERN INTO EARLY NEXT WEEK. RETURN FLOW AROUND THE HIGH SHOULD LEAD TO MODERATING TEMPS WITH FAIR WEATHER PERSISTING THROUGH MONDAY. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... A COLD FRONT...LOCATED EXTENDING ACROSS THE WESTERN HALF OF PA AT 07Z...WILL PUSH SLOWLY SOUTHEAST ACROSS PENNSYLVANIA LATE TONIGHT...ACCOMPANIED BY OCNL LGT RAIN. CURRENT ANALYSIS SHOWS IFR CONDS CONFINED TO NW PA...BEHIND FRONT. HOWEVER...AS THE FRONT PUSHES EAST...EXPECT DETERIORATING FLYING CONDS TO SPREAD OVER THE REST OF PA. SHORT RANGE MDL DATA SUPPORTS IFR CONDS BECOMING WIDESPREAD ACROSS THE REST OF CENTRAL PA AFTER 09Z. MODEST IMPROVEMENT IS EXPECTED BY TUESDAY AFTN...AS FRONT BEGINS TO PUSH EAST OF THE REGION. MANY LOCATIONS WILL LIKELY IMPROVE TO MVFR CONDS. HOWEVER...RESIDUAL MOISTURE ASCENDING THE W MTNS COULD LEAD TO LINGERING IFR CIGS AT JST AND BFD THRU TUE NIGHT. OUTLOOK... WED...AM LOW CIGS POSSIBLE W MTNS. WED NIGHT...RAIN/SNOW AND LOW CIGS POSSIBLE SOUTHEAST. THU...NO SIG WX EXPECTED. FRI...PM SHSN POSSIBLE NW MTNS. SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...STEINBUGL NEAR TERM...LAMBERT/STEINBUGL SHORT TERM...STEINBUGL LONG TERM...STEINBUGL AVIATION...FITZGERALD/CERU
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
607 AM CST TUE DEC 6 2011 UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE .SHORT TERM...TODAY THROUGH WEDNESDAY. FORECAST CONCERNS THIS PERIOD...CLOUDS LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH PRESSURE STRETCHING FROM WESTERN LAKE SUPERIOR INTO WESTERN IA. LOWER CLOUD CLEARING OVER MUCH OF EASTERN WI AS DRIER AIR...SEEN ON GRB SOUNDING...WORKING IN. CLOUDS HANGING TOUGH OVER WESTERN PART OF STATE. SURFACE HIGH WILL CONTINUE TO SHIFT OVER STATE TODAY...EXITING TONIGHT WITH COLD FRONT ASSOCIATED WITH LOW MOVING THROUGH NORTHERN CANADA MOVING THROUGH STATE ON WED. QUESTION IS WHAT WILL HAPPEN WITH CLOUDS TODAY. AREA OF CONVERGENCE ASSOCIATED WITH WEAK SURFACE TROF OVER WESTERN WI TO WEAKEN THIS MORNING. SOME MODELS SHOW LOWER CLOUD MOVING BACK INTO EASTERN WI LATE TODAY AS LOW LEVEL WINDS SHIFT TO THE SOUTHWEST LATE. SOME SHOW CLOUD DISSIPATING THROUGH THE DAY AS SUPPORT WEAKENS. HAVE LEANED TOWARDS CANADIAN THAT SHOWS CURRENT CLEARING OVER EASTERN AND NORTH CENTRAL WI...THOUGH WILL STAY WITH PARTLY CLOUDY/PARTLY SUNNY WORDING GIVEN CIRRUS MOVING THROUGH AND SOME UNCERTAINTY. CLOUDS CONTINUE TO MOVE SOUTH OFF LAKE SUPERIOR/MICHIGAN IN THE FAR EAST. THUS CLEARING SLOWED A BIT FROM PREVIOUS FORECAST...THOUGH LITTLE CHANGE MADE IN TEMPERATURE FORECAST. .LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY. MODELS HAD AN UPPER TROUGH OVER MUCH OF THE CONUS EARLY IN THE PERIOD...WITH THE FLOW BECOMING ZONAL OVER THE UPPER GREAT LAKES BY EARLY NEXT WEEK. AN ARCTIC FRONT WILL BRING MUCH COLDER AIR INTO THE FORECAST AREA ON THURSDAY. HAVE A SLIGHT CHANCE OF SNOW SHOWERS IN VILAS COUNTY FOR THE END OF THE WORK WEEK. LAPSE RATES OVER LAKE SUPERIOR SHOULD BE STEEP...BUT WINDS APPEARED TO HAVE TOO MUCH OF A WESTERLY COMPONENT TO GO AS HIGH AS CHANCE POPS. NEAR OR ABOVE NORMAL TEMPERATURES CAN BE EXPECTED BY SUNDAY AS A SURFACE RIDGE PASSES EAST OF THE AREA AND SOUTHWEST WINDS BRING WARMER AIR INTO THE STATE. HAVE SOME SLIGHT CHANCE POPS LATE IN THE PERIOD WITH SHORT WAVE ENERGY AND A SURFACE LOW APPROACHING WISCONSIN. MAY NEED TO GO WITH HIGHER POPS IN THE AFTERNOON FORECAST PACKAGE OR TOMORROW MORNING IF CONDITIONS APPEAR MORE FAVORABLE FOR PRECIPITATION. && .AVIATION...DRIER AIR WORKING IN OVER EASTERN WI HAS CLEARED SKIES FOR MUCH OF EASTERN WI AND NORTH CENTRAL WI...NOW WORKING INTO CENTRAL WI. SUPPORT FOR FLURRIES/CLOUDS JUST WEST OF CWA/AUW TO DIMINISH THIS MORNING. THOUGHTS ARE CLOUDS WILL CONTINUE TO DIMINISH OVER WEST. INCREASING SOUTHWEST WINDS THIS EVENING...30 KTS AT 2K FT. THOUGH NOT STRONG ENOUGH DIFFERENCE FROM SURFACE FOR LLWS AT THIS TIME. TE && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
537 AM CST TUE DEC 6 2011 .SHORT TERM...TODAY THROUGH THURSDAY NIGHT 332 AM CST TUE DEC 6 2011 MAIN FORECAST CONCERNS THIS PACKAGE...CLOUDS AND TEMPERATURES THRU THE PERIOD. DATA ANALYSIS AT 06Z HAD A RIDGE OF HIGH PRESSURE EXTENDING FROM NORTH OF LK SUPERIOR ACROSS MN TO NEB AND WESTERN KS. A LARGE AREA OF LOW PRESSURE WAS LOCATED OVER NORTH-CENTRAL CAN WITH FALLING PRESSURES IN THE NORTHERN PLAINS. STRATUS CLOUDS REMAINS TRAPPED ACROSS THE AREA...UNDER AN INVERSION BETWEEN 850-800MB AND EAST OF THE SFC RIDGE AXIS. WEST EDGE OF THE CLOUDS WAS NEAR A KDLH-KOTG LINE...MAKING VERY SLOW PROGRESS EAST/SOUTH. WEAK SFC-925MB TROUGH AND CONVERGENCE...ALONG WITH THE SLOWLY COOLING LOWER LEVELS CONTINUED TO SQUEEZE SOME FLURRIES/VERY LIGHT SNOW OUT OF THE COLUMN OVER MUCH OF WESTERN WI INTO EXTREME EASTERN MN. NO PROBLEMS NOTED WITH 06.00Z MODEL INITIALIZATIONS. SOLUTIONS QUITE SIMILAR FOR TODAY THRU THU NIGHT...AT LEAST WITH THE SHORTWAVES AND LARGER SCALE FEATURES. MODELS STILL STRUGGLING WITH THE LOWER LEVEL MOISTURE/RH FIELDS AND STRATUS CLOUDS ACROSS THE AREA. DPROG/DT OF 500MB HGTS AT 06.00Z SHOWED MODEL RUNS OF 04.00Z AND 05.00Z VERIFIED QUITE WELL ACROSS NOAM...FAVORING STRONGER OF EARLIER MODELS WITH THE NORTHERN PORTION OF THE TROUGH AND FASTER OF EARLIER MODELS WITH THE SOUTHWEST CONUS PORTION OF THE TROUGH. THRU TODAY/TONIGHT MODELS TREND TOWARD A TIGHTER/FASTER CONSENSUS WITH THE SOUTHERN PORTION OF THE TROUGH MOVING EAST INTO THE MID/LOWER MS VALLEY AND WEAKENING OF THE NORTHERN PORTION OF THE TROUGH AS IT MOVES EAST OF THE REGION. TREND CONTINUES FASTER WITH THE LOWER MS VALLEY TROUGH WED/WED NIGHT AS IT TO THE EAST COAST BY 12Z THU. BETTER CONSENSUS FOR BROAD TROUGHING/NORTHWEST FLOW TO DEVELOP OVER THE NORTH-CENTRAL CONUS/ GREAT LAKES REGION. THIS TROUGH DEEPENS OVER THE MID/UPPER MS VALLEY THU/THU NIGHT...BUT MINOR DIFFERENCES IN THE TIMING/STRENGTH DETAILS DEVELOP BY 12Z FRI. OVERALL BETTER RUN-TO-RUN CONSISTENCY FOR TODAY THRU THU NIGHT SHOWN BY ECMWF...ESPECIALLY WITH THE SOUTHERN STREAM ENERGY EARLY IN THE PERIOD. CHECK OF OBS VS. MODEL DATA AT 06Z SHOWED MODELS ALL QUITE GOOD WITH THE CENTRAL CONUS SFC MASS FIELDS...THOUGH AGAIN CONTINUED TO STRUGGLE WITH THE LOWER LEVEL RH AND STRATUS DECKS TRAPPED ACROSS THE REGION. ECMWF/ RUC LOOK TO BE DOING BEST WITH THE 925MB RH/STATUS CLOUDS OVER MN/ WI/IA WHILE ONLY MODEL SOME INDICATION OF THE FLURRIES WAS THE GFS. THUS NO CLEAR DETERMINISTIC MODEL FAVORITE. WITH MODELS TRENDING TOWARD A TIGHTER CONSENSUS MUCH OF THE PERIOD...FAVORED THE CONSENSUS. SHORT TERM FCST CONFIDENCE AVERAGE TO GOOD THIS CYCLE. IN THE SHORT TERM...LOW CLOUDS/CLEARING REMAIN PROBLEMATIC TODAY/ TONIGHT WITH TYPICAL POOR MODEL PERFORMANCE ON THIS AND THE TIME OF YEAR WHEN LOW CLOUDS LIKE TO HANG TOUGH. MODEL CONSENSUS KEEPS 70+ PERCENT 925MB RH OVER THE CENTRAL/EAST PARTS OF THE FCST AREA THRU THE DAY WITH ONLY SLOW EROSION/ADVECTION ON THE WESTERN SIDE. RAISED CLOUD COVER IN SKY GRIDS TO REFLECT A SLOWER/NON CLEARING TODAY. MOVED THE CLEARING INTO TONIGHT WITH INCREASING WEST SFC- 850MB FLOW NORTH OF THE LOW LEVEL RIDGE AXIS TO FINALLY ADVECT THE MOISTURE EAST AND OUT OF THE AREA. SFC-925MB TROUGH WEAKENS THRU THIS MORNING...BUT GIVEN SLOW MOVEMENT OF THE LOW LEVEL FEATURES... LINGERED SCT FLURRIES OVER THE NORTH HALF OF THE FCST AREA WHERE RADAR REFLECTIVITY/SFC OBS CONTINUED TO DETECT/REPORT FLURRIES AS OF 09Z. REST OF SHORT-TERM PERIOD GENERALLY COOL/QUIET. SHORTWAVE ENERGY PASSES NORTH OF THE FCST AREA WED/WED NIGHT WITH BULK OF FORCING/LIFT AND 850-500MB MOISTURE/SATURATION REMAINING NORTH OF THE FCST AREA. COLD/DRY AIRMASS SETTLES ACROSS THE AREA IN THE WAKE OF THIS SHORTWAVE TROUGH FOR THU/THU NIGHT. THIS AS MORE SHORTWAVE ENERGY DROPS SOUTHEAST ACROSS THE NORTHERN PLAINS FOR THU/THU NIGHT. BULK OF THE LOWER LEVEL THERMO-DYNAMIC FORCING AND INCREASE OF MOISTURE IN THE 925-700MB LAYER REMAINS SOUTH OF THE FCST AREA THU/THU NIGHT. ONLY LINGERED A SMALL -SN CHANCE ACROSS THE EXTREME SOUTH END OF THE FCST AREA THU NIGHT TO BLEND WITH NEIGHBORING GRIDS. SATURATION OF THE COLUMN OVER THE NORTH END OF THE FCST AREA THU/THU NIGHT...NORTH OF THE SHORTWAVE TRACK...AN ISSUE IN THE COLDER COLUMN THERE. MAY YET SEE SCT FLURRIES ALONG/NORTH OF HWY 29 THU/THU NIGHT BUT LEFT THIS DRY FOR NOW. GENERALLY CARRIED PARTLY CLOUDY TO MOSTLY CLEAR SKIES FOR WED THRU THU NIGHT. HIGH/LOW TEMPERATURES PROBLEMATIC WITH SNOW COVERING THE NORTHWEST HALF OF THE FCST AREA WHILE THE SOUTHEAST HALF IS SNOW-FREE. WITH MORE CLOUDS/OVERCAST TODAY...TRENDED HIGHS FOR MINIMAL DIURNAL SWING AND AT OR BELOW NUMERICAL GUIDANCE. WITH PARTLY CLOUDY SKIES TONIGHT BUT SOME SOUTHWEST GRADIENT WINDS...FAVORED A BLEND OF THE GUIDANCE LOWS. SOUTHWEST/WEST WINDS AHEAD OF THE NEXT COLD FRONT AND SOME SUNSHINE WED...TRENDED TOWARD WARMER OF GUIDANCE HIGHS... ESPECIALLY OVER THE SNOW-FREE SOUTHEAST HALF OF THE FCST AREA. APPEARS BOUNDARY LAYER WINDS WILL KEEP LOW LEVELS STIRRED WED NIGHT AND TRENDED TOWARD WARMER OF GUIDANCE LOWS. FAVORED A MODEL CONSENSUS OF HIGHS FOR THU...WHICH BLENDS WELL WITH NEIGHBORING GRIDS BUT MAY BE TOO WARM WITH MDT/STRONG LOW LEVEL COLD ADVECTION OVER THE REGION BY MID-DAY. FAVORED THE MODEL CONSENSUS FOR LOWS THU NIGHT...WHICH ALSO MAY BE TOO WARM IF WINDS ARE LIGHTER THAN EXPECTED ESPECIALLY OVER THE SNOW-COVERED PORTIONS OF THE FCST AREA. .LONG TERM...FRIDAY THROUGH MONDAY 332 AM CST TUE DEC 6 2011 LONG-TERM FCST CONFIDENCE AVERAGE. 06.00Z MEDIUM RANGE MODELS IN REASONABLE AGREEMENT WITH EACH OTHER AND THEIR PREVIOUS RUNS FRI THRU SUNDAY WITH THE LONGWAVE TROUGH BEING PROGRESSIVE AND HGTS RISING OVER THE UPPER MIDWEST FRIDAY INTO SUNDAY. COLD SFC HIGH PRESSURE DRIFTS OVER THE AREA FRI THEN MOVES SOUTH OF THE AREA FOR SAT/SUN. STRONG LOW LEVEL WARM ADVECTION SPREADS ACROSS THE AREA SAT INTO SAT NIGHT WITH 925MB TEMPS IN THE 0 TO +4C RANGE BY 12Z SUN. BELOW/MUCH BELOW NORMAL TEMPS FRI LOOK TO WARM TO ABOVE/MUCH ABOVE NORMAL BY SUN AS BULK OF THE WARM ADVECTION GOES INTO WARMING UNDER PARTLY CLOUDY/MOSTLY SUNNY SKIES. RAISED HIGHS A BIT OVER THE SOUTHEAST HALF OF THE FCST AREA SUN WITH THE LACK OF SNOW COVER. GFS/ECMWF SOLUTIONS DIVERGE FOR MON. ECMWF SLIDES A COLD FRONT AND WEAK LOW LEVEL COLD ADVECTION ACROSS THE AREA WHILE GFS TRACKS A LOW INTO NORTHWEST MN KEEPING THE AREA UNDER LOW LEVEL WARM ADVECTION. EITHER WAY...APPEARS SOME OF THE SNOW COVER WILL MELT SUN AND MON WILL SEE CONTINUED ABOVE NORMAL TEMPS. BIGGEST LONG-TERM QUESTION LOOKS TO BE WILL THERE BE ENOUGH LOWER LEVEL MOISTURE FOR A SMALL PRECIP CHANCE FOR PARTS OF THE AREA BY LATER MON. MODEL CONSENSUS DATA USED IN THE DAY 4-7 FCST GRIDS LOOKS TO HAVE ALL OF THIS WELL TRENDED FOR NOW. && .AVIATION...TODAY AND TONIGHT 537 AM CST TUE DEC 6 2011 MAIN AVIATION CONCERN IS CEILINGS. A VARIETY OF CEILINGS CURRENTLY ENCOMPASS THE AREA...RANGING FROM IFR TO VFR. WITH A LIGHT WIND REGIME IN PLACE...IT IS EASILY POSSIBLE CEILINGS AT THE TAF SITES COULD VARY FOR A WHILE...RISING AND FALLING FROM TIME TO TIME. HOWEVER...AS THE DAY PROGRESSES...DAYTIME MIXING SHOULD PROMOTE A GRADUAL RISE IN CEILINGS. ANY CLEARING OF CLOUDS LOOKS TO WAIT UNTIL THIS EVENING...ASSOCIATED WITH A SURFACE HIGH PRESSURE RIDGE MOVING WEST TO EAST ACROSS THE TAF SITES. ONCE CLEAR...VFR CONDITIONS SHOULD THEN PERSIST THROUGH THE REST OF THE NIGHT. ANOTHER CONCERN IS WINDS LATE TONIGHT. IN THE WAKE OF THE RIDGE...SOUTHWEST WINDS ARE FORECAST TO INCREASE TO 10-15 KT AT BOTH TAF SITES. HOWEVER... 35-40 KT WINDS ARE PROGGED 1500-2000 FT ABOVE THE SURFACE. RIGHT NOW THERE IS NOT ENOUGH WIND TO INSERT LOW LEVEL WIND SHEAR...BUT IT IS SOMETHING TO MONITOR. && .ARX WATCHES/WARNINGS/ADVISORIES... 332 AM CST TUE DEC 6 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM... RRS LONG TERM.... RRS AVIATION...AJ
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
405 AM CST TUE DEC 6 2011 .SHORT TERM...TODAY THROUGH WEDNESDAY. FORECAST CONCERNS THIS PERIOD...CLOUDS LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH PRESSURE STRETCHING FROM WESTERN LAKE SUPERIOR INTO WESTERN IA. LOWER CLOUD CLEARING OVER MUCH OF EASTERN WI AS DRIER AIR...SEEN ON GRB SOUNDING...WORKING IN. CLOUDS HANGING TOUGH OVER WESTERN PART OF STATE. SURFACE HIGH WILL CONTINUE TO SHIFT OVER STATE TODAY...EXITING TONIGHT WITH COLD FRONT ASSOCIATED WITH LOW MOVING THROUGH NORTHERN CANADA MOVING THROUGH STATE ON WED. QUESTION IS WHAT WILL HAPPEN WITH CLOUDS TODAY. AREA OF CONVERGENCE ASSOCIATED WITH WEAK SURFACE TROF OVER WESTERN WI TO WEAKEN THIS MORNING. SOME MODELS SHOW LOWER CLOUD MOVING BACK INTO EASTERN WI LATE TODAY AS LOW LEVEL WINDS SHIFT TO THE SOUTHWEST LATE. SOME SHOW CLOUD DISSIPATING THROUGH THE DAY AS SUPPORT WEAKENS. HAVE LEANED TOWARDS CANADIAN THAT SHOWS CURRENT CLEARING OVER EASTERN AND NORTH CENTRAL WI...THOUGH WILL STAY WITH PARTLY CLOUDY/PARTLY SUNNY WORDING GIVEN CIRRUS MOVING THROUGH AND SOME UNCERTAINTY. CLOUDS CONTINUE TO MOVE SOUTH OFF LAKE SUPERIOR/MICHIGAN IN THE FAR EAST. THUS CLEARING SLOWED A BIT FROM PREVIOUS FORECAST...THOUGH LITTLE CHANGE MADE IN TEMPERATURE FORECAST. .LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY. MODELS HAD AN UPPER TROUGH OVER MUCH OF THE CONUS EARLY IN THE PERIOD...WITH THE FLOW BECOMING ZONAL OVER THE UPPER GREAT LAKES BY EARLY NEXT WEEK. AN ARCTIC FRONT WILL BRING MUCH COLDER AIR INTO THE FORECAST AREA ON THURSDAY. HAVE A SLIGHT CHANCE OF SNOW SHOWERS IN VILAS COUNTY FOR THE END OF THE WORK WEEK. LAPSE RATES OVER LAKE SUPERIOR SHOULD BE STEEP...BUT WINDS APPEARED TO HAVE TOO MUCH OF A WESTERLY COMPONENT TO GO AS HIGH AS CHANCE POPS. NEAR OR ABOVE NORMAL TEMPERATURES CAN BE EXPECTED BY SUNDAY AS A SURFACE RIDGE PASSES EAST OF THE AREA AND SOUTHWEST WINDS BRING WARMER AIR INTO THE STATE. HAVE SOME SLIGHT CHANCE POPS LATE IN THE PERIOD WITH SHORT WAVE ENERGY AND A SURFACE LOW APPROACHING WISCONSIN. MAY NEED TO GO WITH HIGHER POPS IN THE AFTERNOON FORECAST PACKAGE OR TOMORROW MORNING IF CONDITIONS APPEAR MORE FAVORABLE FOR PRECIPITATION. && .AVIATION...A FEW FLURRIES OR SNOW SHOWERS CONTINUE OVER A CONVERGENT REGION OVER WEST CENTRAL WISCONSIN. OBSERVATIONS OVER CENTRAL WISCONSIN REPORTING 10 MILES WITH NO WEATHER PRESENT BUT ANTICIPATE FLURRY ACTIVITY OCCURRING WEST OF A LINE FROM RIB FALLS TO WISCONSIN RAPIDS INTO WAUSHARA COUNTY. RADARS ALSO SHOWING SOME RETURNS OVER THE LAKE MICHIGAN SHORELINE WITH NO GROUND TRUTH AND FINALLY SCATTERED SNOW SHOWERS WERE NOTED OVER VILAS. AS FAR AS CLOUDS...A SUCKER HOLE OPENED UP NORTHEAST WISCONSIN INCLUDING THE GRB VICINITY. BUT STILL EXPECT VFR CIGS TO DOMINATE OVERNIGHT INTO TUESDAY WITH SOME DECREASE IN CLOUDS LATER TUESDAY. TDH && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ TE/MG
AREA FORECAST DISCUSSION
NWS MOUNT HOLLY NJ
1238 PM EST TUE DEC 6 2011 .SYNOPSIS... A COLD FRONT STRETCHING FROM NORTHERN MAINE INTO LOW PRESSURE OVER WESTERN PENNSYLVANIA WILL SLOWLY SAG SOUTHEAST ACROSS OUR AREA TONIGHT. A STRONGER LOW WILL FORM OVER THE CAROLINAS WEDNESDAY AND INTENSIFY RAPIDLY AS IT PASSES CAPE COD EARLY THURSDAY. SOUTHERN PLAINS HIGH PRESSURE WILL BUILD INTO THE MID ATLANTIC STATES FRIDAY THEN BE FOLLOWED BY A COLD FRONTAL PASSAGE EARLY SATURDAY. THERE IS A CHANCE THAT LOW PRESSURE WILL FORM ON THAT FRONT TO THE EAST OF NEW JERSEY. ANOTHER SOUTHERN PLAINS HIGH PRESSURE SYSTEM WILL BUILD INTO THE MID ATLANTIC STATES NEXT SUNDAY AND MONDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A 14Z SURFACE ANALYSIS PLACED A FRONTAL BOUNDARY DRAPED FROM NORTHERN NEW ENGLAND TO WESTERN PENNSYLVANIA THEN DOWN TO THE NORTH-CENTRAL GULF OF MEXICO. A FEW WEAK AREAS OF LOW PRESSURE WERE ALONG THIS FRONT. ANOTHER MILD DAY ON TAP ACROSS THE REGION AS A SOUTHERLY FLOW IS MAINTAINED AHEAD OF A SLOWLY APPROACHING COLD FRONT. THIS BOUNDARY SHOULD TEND TO TAKE ITS TIME AS THE UPPER-LEVEL FLOW IS NEARLY PARALLEL TO IT. SOME MAINLY LIGHTER POCKETS OF RAIN HAVE BEEN MOVING ACROSS PARTS OF THE CWA THIS MORNING, WITH SOME HEAVIER SHOWERS LOCATES TO OUR SOUTHWEST OVER VIRGINIA. RAINFALL AMOUNTS TODAY ARE ANTICIPATED TO BE ON THE LIGHTER SIDE. DID RAISE QPF SLIGHTLY FOR SHOWERS MOVING FROM DOVER INTO SOUTHERN NJ IN THE NEXT FEW HOURS. LOOKING AT THE 14Z RUC AND 15Z SREF EXPECT MAJORITY OF RAINFALL TO BE NORTH OF PHILLY METRO AFTER 20Z, QPF AND POPS REFLECT THAT. AS FOR TEMPERATURES, WE MOSTLY USED AN EVENLY WEIGHTED BLEND OF THE GFS/NAM MOS. IF WE GET SOME SUNSHINE TO OCCUR, THE LOCAL TEMPERATURES ESPECIALLY ACROSS THE EASTERN/SOUTHERN AREAS COULD GET TO 70 DEGREES AS 925 MB TEMPERATURES ARE FORECAST TO BE NEAR +13C. MAXIMUM TEMPERATURES ACROSS SOUTHERN SECTIONS HAVE BEEN RAISED SLIGHTLY BASED ON 17Z METAR OBS. DEWPOINTS HAVE ALSO BEEN RAISED SLIGHTLY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... THE FRONTAL BOUNDARY MENTIONED ABOVE WILL GRADUALLY SETTLE EASTWARD ACROSS THE REGION DURING THE NIGHT. BASED ON THE SLOW EASTWARD PROGRESSION AND THE CAA HOLDING OFF UNTIL NEAR DAYBREAK, MOST OF THE REGION WILL HAVE ANOTHER MILD NIGHT. THERE WILL BE PLENTY OF MOISTURE ACROSS THE CWA WITHIN THE SOUTHERLY FLOW AHEAD OF THE BOUNDARY. AS THE THERMAL GRADIENT STARTS TO TIGHTEN ALOFT DURING THE NIGHT, FRONTOGENETIC FORCING SHOULD RESPOND AND PRODUCE A RIBBON OF RAIN ACROSS THE AREA. THIS MAY END UP BEING FAIRLY NARROW BUT AT THIS POINT WE CONTINUED WITH CATEGORICAL POPS SLIDING SOUTHEASTWARD ACROSS THE REGION DURING THE COURSE OF THE NIGHT. OVERALL, THE RAINFALL AMOUNTS SHOULD BE ON THE LIGHTER SIDE WITH THE EXCEPTION OF A MORE FOCUSED AREA OF RAIN DEVELOPING LATE AS SOME OF THE MODEL GUIDANCE SUGGESTS /ESPECIALLY ACROSS THE CENTRAL AND SOUTHERN AREAS/. SOME OF THE MODEL PARAMETERS /I.E. SHOWALTER INDEX/ HINTS AT SOME POSSIBLE INSTABILITY DEVELOPING TONIGHT, HOWEVER FORECAST SOUNDINGS SHOW LITTLE IN THE WAY OF INSTABILITY GIVEN A RATHER SATURATED PROFILE. THEREFORE, ANY CONVECTIVE TYPE CONTRIBUTION SHOULD NOT BE DEEP ENOUGH TO PRODUCE CHARGE SEPARATION DUE TO THE RATHER LOW INSTABILITY POTENTIAL. IT APPEARS THAT THE COLD AIR LAGS FOR AWHILE, THEREFORE WE REMOVED ANY MENTION OF SNOW ACROSS THE FAR NORTHWEST. OTHERWISE, PATCHY FOG MAY ONCE AGAIN BE ACROSS THE REGION ESPECIALLY ACROSS THE HIGHER TERRAIN. HOWEVER, GIVEN THE FLOW NOT TO FAR ABOVE THE SURFACE IT WAS DECIDED TO NOT INCLUDE IT ATTM AS THE OVERALL VISIBILITIES OUTSIDE OF THE RAIN MAY NOT BE A REAL IMPACT. AS FOR TEMPERATURES, WE WENT WITH A BLEND OF THE NAM/GFS MOS TO SPLIT SOMEWHAT OF A DIFFERENCE AT SOME LOCALES. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... PATTERN ALOFT: CHARACTERIZED BY A GENERAL SENSE OF TROUGHING OVER CENTRAL NORTH AMERICA WITH SEVERAL STRONG SHORT WAVES ROLLING THROUGH THE TROUGH...ULTIMATELY SHOVING THE CURRENT PLUS 1 SD 500 MB WARM RIDGE EASTWARD INTO THE CENTRAL ATLC. THEREFORE...THE LONG PERIOD OF ABOVE NORMAL TEMPERATURES LASTING MORE THAN TWO WEEKS...WILL GIVE WAY TO SEASONABLY COOL TEMPERATURES THURSDAY AFTERNOON ONWARD THROUGH THE PERIOD. THE BEST CHANCE FOR A BELOW NORMAL DAY OR TWO IS SLATED FOR THIS COMING SUNDAY AND MONDAY. THE PRIMARY WEATHER MAKER IN THIS FCST PERIOD APPEARS TO BE WEDNESDAY AND IT MAY RESULT IN MULTIPLE HEADLINES INCLUSIVE OF ADVISORY SNOW IN E PA AND NW NJ...TO A POSSIBLE FLOOD WATCH FOR SPOTTY SMALL STREAM FLOODING ALONG THE I95 CORRIDOR TO A BRIEF NW GALE THU MORNING. THE DAILIES BELOW... WEDNESDAY...STRONG SHORT WAVE LIFTING ENE FROM THE SW USA PROMISES TO BRING HEAVY PRECIPITATION TO THE AREA...MOST OF IT RAIN BUT NEEDS TO BE CAREFULLY WATCHED FOR A MODERATE SNOW EVENT IN THE NW SECTOR OF OUR FCST AREA...PARTICULARLY READING TO ALLENTOWN TO MORRISTOWN NWWD AND ESPECIALLY HIGH TERRAIN WHICH FEATURES THE POCONOS. SUSPECT 2 TO 4 HRS OF SNOW GROWTH POTENTIAL OF 1 INCH/HR WHICH IS HIGHLIGHTED IN BOTH THE 00Z/6 GFS/NAM. DEFORMATION ZONE HEAVY PCPN IN E PA. SNOW ACCUMULATION...IF ANY SHOULD OCCUR PRIMARILY WED NIGHT. THERE IS CHC OF SPOTTY 6 INCH AMOUNTS ABOVE 1000 FT IN THE POCONOS AND POSSIBLY EXTREME NW NJ NEAR WANTAGE AND HIGH POINT. NO WATCH ATTM BUT WE MAY NEED TO ISSUE ONE LATER TODAY. TOP DOWN AND BOX WX TOOLS OFFERED ALMOST IDENTICAL WX GRIDS AS POSTED AT 315 AM THIS MORNING. THIS SYSTEM HAS A LIKELIHOOD OF PRODUCING 1 TO NEARLY 2.5 INCHES OF RAIN IN 12 HRS NEAR I95 WHERE 6 HR FFG VALUES RANGE FROM 1.6 TO 2.6 INCHES AND 12 HR HEADWATER GUIDANCE IS NEAR 2 INCHES. THIS FLAGS THE POTENTIAL OF SOME SMALL STREAM FLOODING IF 2 INCH VALUES OCCUR AND AN AFTERNOON ISSUANCE OF A FLOOD WATCH MAY BE NEEDED FOR THE ALREADY VULNERABLE LOWER FFG AREA INTO THE ILG-PHL-NE NJ METRO REGION. COLLABORATION PREFERRED TO WAIT ONE MORE FCST CYCLE. WE DO NOTE THE SREF IS AWFULLY LOW ON ITS QPF FOR THIS EVENT AND FEEL SOMETHING IS VERY WRONG WITH THE SREF WHEN THE 00Z/6 UK/EC/GGEM OP RUNS AS WELL AS THE GEFS ARE SO HEAVY. TEMPS/DEWPOINTS/WINDS WERE GENERALLY 50/50 BLENDED 00Z/6 NCEP MOS GUIDANCE EXCEPT IN THE 00Z-09Z TIME FRAME WHEN LEANED HEAVILY ON THE NAM 2M TEMPS PRESUMING PCPN WOULD BE TURNING OVER TO SNOW NW TO SE. WE COULD SEE RAIN END AS A MIX TO PHL BUT FOR NOW...MORE CONSERVATIVE. THURSDAY...P/S AND BRISK DURING THE DAY AND A MO CLEAR NIGHT. GFS MEX GUIDANCE LOOKED GOOD. FRIDAY...A CHILLY START AS HIGH PRESSURE BRIEFLY BUILDS OVERHEAD WITH LIGHT WIND. HIGH CLOUDS MAY ALREADY BE INCREASING AT DAYBREAK... AHEAD OF THE NEXT INTENSIFYING TROUGH ALOFT APPROACHING FROM THE WEST. DID NOT ADJUST POPS FROM THE 330PM KPHI MONDAY FCST SINCE MOST OF THE POP AND WX ENERGY ON THIS SHIFT WAS DEVOTED TO WEDNESDAY. SATURDAY...MAY BE BRIEFLY UNSETTLED WITH THE CFP BUT FOR NOW A CONSERVATIVE FCST. 00Z/6 MEX GUIDANCE TEMPS BLENDED WITH THE 330 PM FCST FROM YDY. THERE COULD BE A FLY IN THE OINTMENT...IN THE FORM OF A COASTAL LOW DEVELOPING WHICH IF OCCURRED WOULD REQUIRE A HEAVIER CLOUD FCST THAN NOW ISSUED AS WELL AS A CHANCE OF PCPN. FOR NOW...THE CONSERVATIVE NO CHANGE MODE BUT SOME MODEL GUIDANCE FLAGS THIS LATTER MORE UNSETTLED IDEA. SUNDAY AND MONDAY...FAIR WX AS SOUTHERN PLAINS HIGH PRESSURE ARRIVES AND DOMINATES. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. A FRONTAL BOUNDARY WILL GRADUALLY APPROACH THE AREA TODAY INTO TONIGHT AS A COUPLE OF WEAK AREA OF LOW PRESSURE SYSTEMS TRAVEL ALONG IT. A MILD AND MOIST SOUTHERLY FLOW REMAINS IN PLACE ACROSS OUR REGION AHEAD OF THIS FRONT, WHICH WILL RESULT IN WIDESPREAD CLOUDINESS THROUGH THE PERIOD. THE CEILINGS ARE EXPECTED TO LOWER AND EXPAND EASTWARD THROUGH THE DAY BECOMING MVFR ACROSS THE TAF SITES WITH SOME IFR POSSIBLE IN HEAVIER SHOWERS. AHEAD OF THE FRONTAL BOUNDARY, WE ARE EXPECTING SOME RAIN TO MOVE ACROSS A PORTION OF THE AREA AT TIMES THROUGH TONIGHT. THIS MAY BE IN THE FORM OF A FEW PERIODS OF RAIN FROM WEST TO EAST AND SHOULD BE MOSTLY ON THE LIGHTER SIDE. WE THEREFORE CONTINUED THE IDEA OF SOME RAIN AROUND AT TIMES THROUGH THE PERIOD. THE VISIBILITIES ARE PROBLEMATIC AS IT WILL MAINLY BE DEPENDENT ON THE RAIN AND THE ASSOCIATED INTENSITY. GIVEN THE AMOUNT OF MOISTURE IN THE AIR, WE FOCUSED THE REDUCTION IN THE VISIBILITY WITH THE RAIN MENTION AND THIS MAY SETTLE LOWER ESPECIALLY TONIGHT. IN SUMMARY, LOWERING CONDITIONS ARE EXPECTED THROUGH THE DAY AND TONIGHT WITH BOUTS OF RAIN AT TIMES. THE FRONT ITSELF IS EXPECTED TO GRADUALLY CROSS MOST OF THE TERMINALS TOWARD DAYBREAK WEDNESDAY WITH A SOUTHERLY WIND UP TO 10 KNOTS SHIFTING TO THE WEST. OUTLOOK... WEDNESDAY...ANY MORNING IFR MAY BECOME MVFR OR VFR CIGS FOR A TIME... MAINLY FAR N PTN OF THE AREA BEFORE DETERIORATING TO IFR IN RAIN LATE IN THE DAY FROM S TO N. A CHANGE TO 1 TO 6 HRS OF SNOW APPEARS PROBABLE IN THE KRDG/KABE REGION WED NIGHT WITH BRIEF LIFR CONDS POCONOS TO KABE WHERE A WET SNOWFALL RATE OF 1/HR IS POSSIBLE FOR A SHORT TIME. STRONGEST WINDS PROBABLY LATE WED NIGHT WHEN A WSHIFT TO NW IS EXPECTED BEHIND RAPIDLY DEEPENING AND FAST DEPARTING COASTAL LOW PRES. NW GUSTS 15 TO 25 KTS BY DAWN THU. THURSDAY...VFR. NW WIND GUSTS TO 20 OR 25 KTS BECOMING LIGHT AT NIGHT. FRIDAY...VFR. LIGHT WIND. SATURDAY...VFR THOUGH THERE MAY BE A SHORT PERIOD OF MVFR CIGS DURING THE MORNING. && .MARINE... A SOUTHERLY FLOW WILL CONTINUE TODAY AND TONIGHT AHEAD OF A SLOW MOVING COLD FRONT. THIS BOUNDARY IS NOT EXPECTED TO REACH THE WATERS UNTIL ABOUT DAYBREAK WEDNESDAY. THE FLOW AROUND 925 MB WILL INCREASE TO ABOUT 35 KNOTS THROUGH TONIGHT. GIVEN THE WAA THOUGH, THIS IS EXPECTED TO NOT MIX DOWN ALL THAT EFFICIENTLY. THEREFORE, THE WINDS ARE ANTICIPATED TO REMAIN BELOW ADVISORY CRITERIA. THE SOUTHERLY FLOW HOWEVER COULD EDGE THE SEAS UP TO 5 FEET ESPECIALLY FOR THE OFFSHORE WATERS THROUGH TONIGHT. THIS DOES NOT LOOK SOLID, THEREFORE WE HELD OFF ON AN ADVISORY FOR NOW. OUTLOOK... WED/THU...POSSIBLE SCA CONDS ON THE ATLC WATERS FOR A TIME WEDNESDAY HEADLINED A GALE WATCH FOR LATE WED NIGHT-THU MORNING WHICH WAS THE MORE IMPORTANT HEADLINE HAZARD. OTRW WIDESPREAD SCA THURSDAY MORNING WITH A LOW TO MDT PROB OF A 3 TO 6 HR PERIOD OF NW GALES IN THE 08Z-14Z THURSDAY TIME FRAME. FRI...QUIET. NO HEADLINE. SAT...A LITTLE CHOPPY WITH NEXT CFP AND CHC OF SCA CONDS DEVELOPING. && .HYDROLOGY... THIS SYSTEM HAS A LIKELIHOOD OF PRODUCING 1 TO NEARLY 2.5 INCHES OF RAIN IN 12 HRS NEAR I95 WHERE 6 HR FFG VALUES RANGE FROM 1.6 TO 2.6 INCHES AND 12 HR HEADWATER GUIDANCE IS NEAR 2 INCHES. THIS FLAGS THE POTENTIAL OF SOME SMALL STREAM FLOODING IF 2 INCH VALUES OCCUR AND AN AFTERNOON ISSUANCE OF A FLOOD WATCH MAY BE NEEDED FOR THE ALREADY VULNERABLE LOWER FFG AREA INTO THE ILG-PHL-NE NJ METRO REGION. COLLABORATION PREFERRED TO WAIT ONE MORE FCST CYCLE. WE DO NOTE THE SREF IS AWFULLY LOW ON ITS QPF FOR THIS EVENT AND FEEL SOMETHING IS VERY WRONG WITH THE SREF WHEN THE 00Z/6 UK/EC/GGEM OP RUNS AS WELL AS THE GEFS ARE SO HEAVY. && .CLIMATE... ALLENTOWN YEARLY RECORD 67.69. SOON TO BE REESTABLISHED WITH SIGNIFICANTLY HIGHER RECORD VALUES IN 2011. AS OF 5 AM...67.62. MEANWHILE THROUGH THE 5TH OF DECEMBER... KPHL 16 CONSEC DAYS ABOVE NORMAL KABE 16 CONSEC DAYS ABOVE NORMAL KTTN 16 CONSEC DAYS AT OR ABOVE NORMAL. NORMAL ON 12/3 KMPO 16 CONSEC DAYS AT OR ABOVE NORMAL. NORMAL ON 12/3 ALL OTHER CLIMO SITES NOT MENTIONED HAD A BELOW NORMAL DAY AT LEAST ON THE 3RD OF DEC. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...GALE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY MORNING FOR ANZ450>455. && $$ SYNOPSIS...DRAG NEAR TERM...GAINES/GORSE/MEOLA SHORT TERM...GORSE LONG TERM...DRAG AVIATION...DRAG/GORSE/MEOLA MARINE...DRAG/GORSE HYDROLOGY... CLIMATE...
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
200 PM CST TUE DEC 6 2011 .DISCUSSION... 304 AM CST FORECAST HIGHLIGHTS TODAY INCLUDE LAKE EFFECT PRECIP TODAY...CLOUD TRENDS THROUGH TONIGHT...POTENTIAL LIGHT SNOW EVENT THURSDAY NIGHT PRIOR TO THE ARRIVAL OF SEASONS COLDEST AIR MASS LATE IN THE WEEK. VERY LITTLE CHANGE IS EXPECTED TO WINDS/STABILITY OVER THE LAKE THROUGH MIDDAY...SO GENERALLY EXPECTING A CONTINUATION OF LIGHT NUISANCE TYPE LAKE EFFECT RAIN/SNOW SHOWERS THROUGH THIS MORNING OVER NORTHEAST ILLINOIS. P-TYPE SHOULD BE MOSTLY RAIN NEAR THE LAKE WITH GREATER THREAT OF SNOW MIXTURE INLAND. EVEN WHERE PRECIP CHANGES TO ALL SNOW TEMPS SHOULD MOSTLY BE TOO WARM TO ALLOW FOR ANYTHING MORE THAN A BRIEF DUSTING AT WORST. WINDS WILL BEGIN BACKING THIS AFTERNOON SENDING THE SCATTERED LIGHT LAKE EFFECT PRECIP EASTWARD MORE INTO NW INDY THIS AFTERNOON BEFORE MOVING EAST AND OUT OF OUR CWA TOWARD EVENING. REGARDING CLOUDINESS TODAY...TIS THE SEASON FOR STRATUS AS EVENING RAOBS ACROSS THE REGION SHOWED A RATHER TEXT BOOK STRATUS SOUNDING WITH MOISTURE BENEATH A SHARP FRONTAL INVERSION. HAVE SEEN SOME BREAKS IN THE STRATUS OVER IN EASTERN WI AND COULD SEE A FEW HOLES FROM TODAY OVER MAINLY NE IL...BUT AS FLOW BACKS TO THE NORTHWEST WOULD ANTICIPATE THE STRATUS DECK TO OUR WEST TO ADVECT EASTWARD AND KEEP US FAIRLY SOCKED IN THROUGH TODAY AND INTO THIS EVENING. HAVE OPTED TO GO SOMEWHAT OPTIMISTIC WITH CLEARING TONIGHT FROM THE WEST...AND HANG ONTO CLOUDS LONGER THAN ANY GUIDANCE WOULD SUGGEST AS MODELS ARE NOTORIOUS FOR STRUGGLING WITH SHALLOW COOL SEASON STRATUS. GIVEN THE EXPECTATION OF CLOUD COVER HAVE GONE AHEAD AND RAISED LOW TEMPS TONIGHT...PARTICULARLY SOUTHEAST CWA. STRONG SHORTWAVE PASSES WELL TO OUR SOUTH WEDNESDAY AS LONG WAVE TROUGH RELOADS TO OUR NORTHWEST AND IS PREPARED TO TAKE AN ARCTIC DUMP ON US LATER THIS WEEK. PROBABLY THE MOST CONTENTIOUS PART OF THE FORECAST REVOLVES AROUND THE POTENTIAL FOR SOME ACCUMULATING SNOW THURSDAY NIGHT. GLOBAL MODELS ALL GENERALLY AGREE ON DEVELOPING A TIGHTENING LOW/MID LEVEL BAROCLINIC ZONE IN ADVANCE OF VIGOROUS SHORTWAVE MOVING INTO THE WESTERN GREAT LAKES REGION THURSDAY NIGHT. MODELS CONTINUE TO HINT AT THE DEVELOPMENT OF BAND OF LIGHT FRONTOGENTICALLY DRIVEN PRECIP IN ADVANCE OF THIS SHORTWAVE WHICH COULD BE ENOUGH TO PRODUCE A NARROW BAND OF AN INCH OR SO OF SNOW. THE DEVIL IS IN THE DETAILS HOWEVER AS THE AREA TO SEE THAT SNOWFALL WOULD LIKELY TO BE FAIRLY SMALL AND MODELS HAVE BEEN BOUNCING AROUND A BIT WITH RESPECT TO THE PLACEMENT OF THE HEAVIEST (ALBEIT STILL LIGHT) PRECIP. THE WRF-NMM AND WRF-ARW SUGGEST MOISTURE WILL BE TOO LIMITED AND FORCING TOO FAR SOUTH TO SERIOUSLY THREATEN OUR CWA WITH SUPPORT FROM THE CANADIAN MODEL. HAVING SAID ALL OF THIS...IT REALLY EQUATES TO LITTLE CHANGE FROM PREVIOUS FORECAST WITH SLIGHT CHANCE TO LOW END CHANCE POPS ACROSS THE CWA THURSDAY NIGHT. CWA WILL THEN GET SIDE-SWIPED BY A BITTERLY COLD EARLY SEASON SHOT OF ARCTIC AIR FRIDAY INTO FRIDAY NIGHT WITH H8 TEMPS PROGGED TO DROP TO -15C OR COLDER. TEMPS FRIDAY LOOK TO BE FAIRLY STEADY AND MAY EVEN FALL A BIT AS HEART OF ARCTIC AIR ARRIVES. SAVING GRACE WITH THIS COLD SNAP IS THE LACK OF SNOW COVER HERE AND UPSTREAM LIKELY ALLOWING IT TO MODIFY SOMEWHAT. EVEN SO TEMPS IN THE 20 LOOK LIKELY FRIDAY WITH LOWS IN THE TEENS FRIDAY NIGHT AWAY FROM THE CITY. PATTERN PROGGED TO REMAIN VERY PROGRESSIVE WITH BITTER COLD GETTING SHOVED QUICKLY EASTWARD OVER THE WEEKEND AS A UPPER FLOW TRANSITIONS TO MORE ZONAL. INCREASINGLY STRONG SOUTHWESTERLY WINDS SHOULD SEND TEMPS BACK TO NEAR IF NOT ABOVE NORMAL BY SUNDAY INTO MONDAY WITH LITTLE TO NO THREAT OF ANY PRECIP FRIDAY AFTERNOON THROUGH MONDAY. IZZI && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 18Z... * POTENTIAL LAKE EFFECT SNOW SHOWERS EARLY-MID AFTERNOON. * LIGHT SNOW APPROACHING FROM THE SW. * VARIABLE VFR/MVFR CIGS INTO THIS EVENING. TRS //DISCUSSION...UPDATED 18Z... AREA OF RADAR ECHOES CONTINUES TO MOVE NORTHEASTWARD OVER N CENTRAL IL AND APPROACHING METRO NE IL. LIGHT SNOW HAS BEEN REPORTED AT DVN...MLI...GBG...PIA...C75 WHERE SURFACE DEW POINT DEPRESSIONS ONLY 1 TO 3 DEG F. WITH MODELS DAMPENING OUT THE SHORT WAVE FORCING THIS -SN AS IT CONTINUES NORTHEASTWARD FROM NW MO...SE IA...W CENTRAL IL THIS AFTERNOON AND AN INCREASINGLY ANTICYCLONIC LOW LEVEL FLOW AS THE SURFACE RIDGE CONTINUES TO BUILD SOUTHEASTWARD FROM THE UPPER MIDWEST AND MID MO VALLEY...ALONG WITH MUCH DRIER LOW LEVEL AIR WITH DEW POINTS ONLY IN THE TEENS TO LOWER 20S F ACROSS NORTHERN IL DO NOT ANTICIPATE ANY OF THIS PRECIP TO REACH THE GROUND AT THE LOCAL TERMINALS. TRAJECTORY OF COLD AIR DOWN LAKE MI HAS POTENTIAL TO BRING LAKE EFFECT SNOW SHOWERS TO NE IL THIS AFTERNOON. VISIBLE SATELLITE LOOP SHOWING A LAKE EFFECT BAND HAS SPREAD SOUTHWARD FROM E OF MTW TO E OF ETB LAST COUPLE HOURS. LATEST RUNS OF RUC13 CONTINUE TO BRING LIGHT PRECIP TO THE IL SHORE 1BETWEEN 18Z AND 19Z. OTHER HIGH RESOLUTION MODELS LESS AGGRESSIVE AND ONLY SPIT OUT SPOTTY 0.01 QPF AMOUNTS OVER THE WATER. TEMPERATURE INVERSION PER FORECAST TEMPERATURE PROFILES AND VERIFIED BY ACARS DATA SHOW BASE TO BE LOCATED BETWEEN 050 AND 060 AGL WHICH WOULD BE DEEP ENOUGH FOR SOME LIGHT LAKE EFFECT THOUGH AS MENTIONED ABOVE LOW LEVEL FLOW BECOMES MORE ANTICYCLONIC WITH TIME THIS AFTERNOON AND DRY AIR IN PLACE OVER FAR NE IL AND UPSTREAM. RAC HAS HAD A PERSISTENT NNE WIND OFF THE LAKE ALL MORNING AND DEW POINT THERE HELD AT ONLY 22Z UNTIL 17Z WHEN IT DROPPED TO 20F. A LOW CHANCE OF SOME LAKE EFFECT SHOWERS REACHING VC ORD AND/OR MDW STILL EXISTS SO HAVE KEPT MENTION OF VCSH THESE SITES 20Z-23Z. REGARDING CEILINGS THIS AFTERNOON...METARS FROM NEAR THE SE WI AND NE IL SHORES SHOW THEM CONTINUING TO HOVER AROUND 030. EXPECT AT LEAST AREAS OF CIGS AROUND 030 THESE AREAS UNTIL FLOW AT CLOUD LEVEL BACKS TO N AND NW LATER AFTERNOON AND THIS EVENING. A PERSISTENT AREA OF MVFR STRATUS/STRATOCU HAS BEEN IN PLACE OVER NW WI...FARR SE MN...EASTERN IA...AND NE THROUGH SOUTHERN MO AHEAD OF THE SURFACE RIDGE AXIS. EXPECT THESE CLOUDS TO SHIFT E TO SE AS DOES THE RIDGE DURING THE AFTERNOON AND EVENING BUT BASED ON MODEL INDICATIONS AND MOS OUTPUT ANTICIPATE ONLY SCT AREAS OF MVFR WITH VFR PREVAILING THIS EVENING. SURFACE WINDS CLOSER TO THE RIDGE AXIS UPSTREAM PRETTY UNIFORMLY OUT OF THE NE AND AOB 10KT. WINDS AT LOCAL TERMINALS TO BACK DURING THE FIRST PART OF THE EVENING BOTH DIURNALLY AND AS RIDGE AXIS NEARS OVERHEAD...WITH WINDS TURNING TO OUT OF THE W TO WSW BY MIDNIGHT AS THE RIDGE AXIS SLIPS S OF THE TERMINALS. TRS //ORD AND MDW CONFIDENCE...UPDATED 18Z... * MEDIUM CONFIDENCE IN CIG TRENDS THRU THIS EVE. * LOW CONFIDENCE IN LAKE EFFECT SHOWERS IMPACTING CHI TERMINALS MID AFTERNOON-EARLY EVENING. * MEDIUM CONFIDENCE IN WIND FORECASTS THROUGH THIS EVE. TRS //OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z... * WEDNESDAY NIGHT AND THURSDAY...VFR * THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE * FRIDAY THROUGH MONDAY...VFR SHEA && .MARINE... 158 PM CST A SURFACE RIDGE OF HIGH PRESSURE EXTENDING FROM THE PLAINS NORTHEASTWARD ACROSS THE UPPER GREAT LAKES REGION WILL SLOWLY SAG SOUTHWARD TONIGHT AS A STRONG AREA OF LOW PRESSURE MOVES INTO THE HUDSON BAY. AS THIS SURFACE RIDGE MOVES ACROSS LAKE MICHIGAN THERE WILL BE A PERIOD OF LIGHTER WINDS THIS EVENING. HOWEVER...THIS WILL BE SHORT LIVED AS THE WINDS WILL BECOME WEST SOUTHWESTERLY AND INCREASE TO NEAR 30 KT LATER TONIGHT ACROSS THE NORTHERN HALF OF THE LAKE. THESE WINDS WILL CONTINUE LAKE-WIDE DURING THE DAY ON WEDNESDAY AS A COLD FRONT MOVES SOUTH ACROSS THE LAKE. THERE COULD BE A PERIOD OF LOW END GALES AS THE COLD AIR BEGINS TO PUSH ACROSS THE LAKE WEDNESDAY NIGHT INTO THURSDAY. HOWEVER...WIDESPREAD 30 KT WITH SOME GALE FORCE GUSTS APPEARS TO BE THE MOST LIKELY AT THIS TIME. WINDS ACROSS LAKE MICHIGAN LOOK TO REMAIN IN THE 15 TO 25 KT RANGE INTO FRIDAY AS THE PRESSURE GRADIENT BETWEEN THE LOW ACROSS THE HUDSON BAY AND HIGH PRESSURE ACROSS THE PLAINS REMAINS ELEVATED. ANOTHER SURGE OF HIGHER WINDS...POTENTIALLY GALE FORCE...LOOKS TO OCCUR ON SATURDAY AS ANOTHER AREA OF LOW PRESSURE TRACKS ACROSS SOUTHERN CANADA. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1153 AM CST TUE DEC 6 2011 .DISCUSSION... 304 AM CST FORECAST HIGHLIGHTS TODAY INCLUDE LAKE EFFECT PRECIP TODAY...CLOUD TRENDS THROUGH TONIGHT...POTENTIAL LIGHT SNOW EVENT THURSDAY NIGHT PRIOR TO THE ARRIVAL OF SEASONS COLDEST AIR MASS LATE IN THE WEEK. VERY LITTLE CHANGE IS EXPECTED TO WINDS/STABILITY OVER THE LAKE THROUGH MIDDAY...SO GENERALLY EXPECTING A CONTINUATION OF LIGHT NUISANCE TYPE LAKE EFFECT RAIN/SNOW SHOWERS THROUGH THIS MORNING OVER NORTHEAST ILLINOIS. P-TYPE SHOULD BE MOSTLY RAIN NEAR THE LAKE WITH GREATER THREAT OF SNOW MIXTURE INLAND. EVEN WHERE PRECIP CHANGES TO ALL SNOW TEMPS SHOULD MOSTLY BE TOO WARM TO ALLOW FOR ANYTHING MORE THAN A BRIEF DUSTING AT WORST. WINDS WILL BEGIN BACKING THIS AFTERNOON SENDING THE SCATTERED LIGHT LAKE EFFECT PRECIP EASTWARD MORE INTO NW INDY THIS AFTERNOON BEFORE MOVING EAST AND OUT OF OUR CWA TOWARD EVENING. REGARDING CLOUDINESS TODAY...TIS THE SEASON FOR STRATUS AS EVENING RAOBS ACROSS THE REGION SHOWED A RATHER TEXT BOOK STRATUS SOUNDING WITH MOISTURE BENEATH A SHARP FRONTAL INVERSION. HAVE SEEN SOME BREAKS IN THE STRATUS OVER IN EASTERN WI AND COULD SEE A FEW HOLES FROM TODAY OVER MAINLY NE IL...BUT AS FLOW BACKS TO THE NORTHWEST WOULD ANTICIPATE THE STRATUS DECK TO OUR WEST TO ADVECT EASTWARD AND KEEP US FAIRLY SOCKED IN THROUGH TODAY AND INTO THIS EVENING. HAVE OPTED TO GO SOMEWHAT OPTIMISTIC WITH CLEARING TONIGHT FROM THE WEST...AND HANG ONTO CLOUDS LONGER THAN ANY GUIDANCE WOULD SUGGEST AS MODELS ARE NOTORIOUS FOR STRUGGLING WITH SHALLOW COOL SEASON STRATUS. GIVEN THE EXPECTATION OF CLOUD COVER HAVE GONE AHEAD AND RAISED LOW TEMPS TONIGHT...PARTICULARLY SOUTHEAST CWA. STRONG SHORTWAVE PASSES WELL TO OUR SOUTH WEDNESDAY AS LONG WAVE TROUGH RELOADS TO OUR NORTHWEST AND IS PREPARED TO TAKE AN ARCTIC DUMP ON US LATER THIS WEEK. PROBABLY THE MOST CONTENTIOUS PART OF THE FORECAST REVOLVES AROUND THE POTENTIAL FOR SOME ACCUMULATING SNOW THURSDAY NIGHT. GLOBAL MODELS ALL GENERALLY AGREE ON DEVELOPING A TIGHTENING LOW/MID LEVEL BAROCLINIC ZONE IN ADVANCE OF VIGOROUS SHORTWAVE MOVING INTO THE WESTERN GREAT LAKES REGION THURSDAY NIGHT. MODELS CONTINUE TO HINT AT THE DEVELOPMENT OF BAND OF LIGHT FRONTOGENTICALLY DRIVEN PRECIP IN ADVANCE OF THIS SHORTWAVE WHICH COULD BE ENOUGH TO PRODUCE A NARROW BAND OF AN INCH OR SO OF SNOW. THE DEVIL IS IN THE DETAILS HOWEVER AS THE AREA TO SEE THAT SNOWFALL WOULD LIKELY TO BE FAIRLY SMALL AND MODELS HAVE BEEN BOUNCING AROUND A BIT WITH RESPECT TO THE PLACEMENT OF THE HEAVIEST (ALBEIT STILL LIGHT) PRECIP. THE WRF-NMM AND WRF-ARW SUGGEST MOISTURE WILL BE TOO LIMITED AND FORCING TOO FAR SOUTH TO SERIOUSLY THREATEN OUR CWA WITH SUPPORT FROM THE CANADIAN MODEL. HAVING SAID ALL OF THIS...IT REALLY EQUATES TO LITTLE CHANGE FROM PREVIOUS FORECAST WITH SLIGHT CHANCE TO LOW END CHANCE POPS ACROSS THE CWA THURSDAY NIGHT. CWA WILL THEN GET SIDE-SWIPED BY A BITTERLY COLD EARLY SEASON SHOT OF ARCTIC AIR FRIDAY INTO FRIDAY NIGHT WITH H8 TEMPS PROGGED TO DROP TO -15C OR COLDER. TEMPS FRIDAY LOOK TO BE FAIRLY STEADY AND MAY EVEN FALL A BIT AS HEART OF ARCTIC AIR ARRIVES. SAVING GRACE WITH THIS COLD SNAP IS THE LACK OF SNOW COVER HERE AND UPSTREAM LIKELY ALLOWING IT TO MODIFY SOMEWHAT. EVEN SO TEMPS IN THE 20 LOOK LIKELY FRIDAY WITH LOWS IN THE TEENS FRIDAY NIGHT AWAY FROM THE CITY. PATTERN PROGGED TO REMAIN VERY PROGRESSIVE WITH BITTER COLD GETTING SHOVED QUICKLY EASTWARD OVER THE WEEKEND AS A UPPER FLOW TRANSITIONS TO MORE ZONAL. INCREASINGLY STRONG SOUTHWESTERLY WINDS SHOULD SEND TEMPS BACK TO NEAR IF NOT ABOVE NORMAL BY SUNDAY INTO MONDAY WITH LITTLE TO NO THREAT OF ANY PRECIP FRIDAY AFTERNOON THROUGH MONDAY. IZZI && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 18Z... * POTENTIAL LAKE EFFECT SNOW SHOWERS EARLY-MID AFTERNOON. * LIGHT SNOW APPROACHING FROM THE SW. * VARIABLE VFR/MVFR CIGS INTO THIS EVENING. TRS //DISCUSSION...UPDATED 18Z... AREA OF RADAR ECHOES CONTINUES TO MOVE NORTHEASTWARD OVER N CENTRAL IL AND APPROACHING METRO NE IL. LIGHT SNOW HAS BEEN REPORTED AT DVN...MLI...GBG...PIA...C75 WHERE SURFACE DEW POINT DEPRESSIONS ONLY 1 TO 3 DEG F. WITH MODELS DAMPENING OUT THE SHORT WAVE FORCING THIS -SN AS IT CONTINUES NORTHEASTWARD FROM NW MO...SE IA...W CENTRAL IL THIS AFTERNOON AND AN INCREASINGLY ANTICYCLONIC LOW LEVEL FLOW AS THE SURFACE RIDGE CONTINUES TO BUILD SOUTHEASTWARD FROM THE UPPER MIDWEST AND MID MO VALLEY...ALONG WITH MUCH DRIER LOW LEVEL AIR WITH DEW POINTS ONLY IN THE TEENS TO LOWER 20S F ACROSS NORTHERN IL DO NOT ANTICIPATE ANY OF THIS PRECIP TO REACH THE GROUND AT THE LOCAL TERMINALS. TRAJECTORY OF COLD AIR DOWN LAKE MI HAS POTENTIAL TO BRING LAKE EFFECT SNOW SHOWERS TO NE IL THIS AFTERNOON. VISIBLE SATELLITE LOOP SHOWING A LAKE EFFECT BAND HAS SPREAD SOUTHWARD FROM E OF MTW TO E OF ETB LAST COUPLE HOURS. LATEST RUNS OF RUC13 CONTINUE TO BRING LIGHT PRECIP TO THE IL SHORE 1BETWEEN 18Z AND 19Z. OTHER HIGH RESOLUTION MODELS LESS AGGRESSIVE AND ONLY SPIT OUT SPOTTY 0.01 QPF AMOUNTS OVER THE WATER. TEMPERATURE INVERSION PER FORECAST TEMPERATURE PROFILES AND VERIFIED BY ACARS DATA SHOW BASE TO BE LOCATED BETWEEN 050 AND 060 AGL WHICH WOULD BE DEEP ENOUGH FOR SOME LIGHT LAKE EFFECT THOUGH AS MENTIONED ABOVE LOW LEVEL FLOW BECOMES MORE ANTICYCLONIC WITH TIME THIS AFTERNOON AND DRY AIR IN PLACE OVER FAR NE IL AND UPSTREAM. RAC HAS HAD A PERSISTENT NNE WIND OFF THE LAKE ALL MORNING AND DEW POINT THERE HELD AT ONLY 22Z UNTIL 17Z WHEN IT DROPPED TO 20F. A LOW CHANCE OF SOME LAKE EFFECT SHOWERS REACHING VC ORD AND/OR MDW STILL EXISTS SO HAVE KEPT MENTION OF VCSH THESE SITES 20Z-23Z. REGARDING CEILINGS THIS AFTERNOON...METARS FROM NEAR THE SE WI AND NE IL SHORES SHOW THEM CONTINUING TO HOVER AROUND 030. EXPECT AT LEAST AREAS OF CIGS AROUND 030 THESE AREAS UNTIL FLOW AT CLOUD LEVEL BACKS TO N AND NW LATER AFTERNOON AND THIS EVENING. A PERSISTENT AREA OF MVFR STRATUS/STRATOCU HAS BEEN IN PLACE OVER NW WI...FARR SE MN...EASTERN IA...AND NE THROUGH SOUTHERN MO AHEAD OF THE SURFACE RIDGE AXIS. EXPECT THESE CLOUDS TO SHIFT E TO SE AS DOES THE RIDGE DURING THE AFTERNOON AND EVENING BUT BASED ON MODEL INDICATIONS AND MOS OUTPUT ANTICIPATE ONLY SCT AREAS OF MVFR WITH VFR PREVAILING THIS EVENING. SURFACE WINDS CLOSER TO THE RIDGE AXIS UPSTREAM PRETTY UNIFORMLY OUT OF THE NE AND AOB 10KT. WINDS AT LOCAL TERMINALS TO BACK DURING THE FIRST PART OF THE EVENING BOTH DIURNALLY AND AS RIDGE AXIS NEARS OVERHEAD...WITH WINDS TURNING TO OUT OF THE W TO WSW BY MIDNIGHT AS THE RIDGE AXIS SLIPS S OF THE TERMINALS. TRS //ORD AND MDW CONFIDENCE...UPDATED 18Z... * MEDIUM CONFIDENCE IN CIG TRENDS THRU THIS EVE. * LOW CONFIDENCE IN LAKE EFFECT SHOWERS IMPACTING CHI TERMINALS MID AFTERNOON-EARLY EVENING. * MEDIUM CONFIDENCE IN WIND FORECASTS THROUGH THIS EVE. TRS //OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z... * WEDNESDAY NIGHT AND THURSDAY...VFR * THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE * FRIDAY THROUGH MONDAY...VFR SHEA && .MARINE... 248 AM CST HIGH PRESSURE EXTENDING FROM THE UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS WILL SLOWLY SAG ACROSS THE GREAT LAKES REGION TODAY AND TONIGHT AS A STRONG LOW PRESSURE SYSTEM MOVES ACROSS NORTHERN MANITOBA INTO THE HUDSON BAY. THIS LOW WILL DRAG A COLD FRONT ACROSS LAKE MICHIGAN WEDNESDAY. DURING THIS PERIOD...WINDS OVER THE LAKE WILL GRADUALLY SHIFT FROM NORTHERLY TO SOUTHWESTERLY. WIND SPEEDS WILL DIMINISH TO AS LOW AS TO TO 15 KT LATE TONIGHT AS THE SFC RIDGE AXIS CROSSES THE LAKE...BUT AS THE RIDGE PUSHES TO THE SOUTH AND A SFC TROUGH ASSOCIATED WITH THE COLD FRONT DROPS THROUGH THE NORTHERN PLAINS LATE TONIGHT...WINDS WILL QUICKLY INCREASE AGAIN TO AROUND 30 KT. FOLLOWING THE PASSAGE OF THE COLD FRONT...ANOTHER CANADIAN HIGH PRESSURE SYSTEM WILL DROP SOUTHEAST ACROSS THE PLAINS THURSDAY AND FRIDAY. THIS SHOULD MAINTAIN A MODERATE PRESSURE GRADIENT OVER THE GREAT LAKES. THE COMBINATION OF THE MODERATELY STRONG PRESSURE GRADIENT AND STRONG COLD ADVECTION BEHIND THE EXITING FRONT WILL KEEP WINDS AROUND 25 TO 30KT OVER THE LAKE FROM WEDNESDAY THROUGH SATURDAY. KREIN && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1105 AM CST TUE DEC 6 2011 .DISCUSSION... 304 AM CST FORECAST HIGHLIGHTS TODAY INCLUDE LAKE EFFECT PRECIP TODAY...CLOUD TRENDS THROUGH TONIGHT...POTENTIAL LIGHT SNOW EVENT THURSDAY NIGHT PRIOR TO THE ARRIVAL OF SEASONS COLDEST AIR MASS LATE IN THE WEEK. VERY LITTLE CHANGE IS EXPECTED TO WINDS/STABILITY OVER THE LAKE THROUGH MIDDAY...SO GENERALLY EXPECTING A CONTINUATION OF LIGHT NUISANCE TYPE LAKE EFFECT RAIN/SNOW SHOWERS THROUGH THIS MORNING OVER NORTHEAST ILLINOIS. P-TYPE SHOULD BE MOSTLY RAIN NEAR THE LAKE WITH GREATER THREAT OF SNOW MIXTURE INLAND. EVEN WHERE PRECIP CHANGES TO ALL SNOW TEMPS SHOULD MOSTLY BE TOO WARM TO ALLOW FOR ANYTHING MORE THAN A BRIEF DUSTING AT WORST. WINDS WILL BEGIN BACKING THIS AFTERNOON SENDING THE SCATTERED LIGHT LAKE EFFECT PRECIP EASTWARD MORE INTO NW INDY THIS AFTERNOON BEFORE MOVING EAST AND OUT OF OUR CWA TOWARD EVENING. REGARDING CLOUDINESS TODAY...TIS THE SEASON FOR STRATUS AS EVENING RAOBS ACROSS THE REGION SHOWED A RATHER TEXT BOOK STRATUS SOUNDING WITH MOISTURE BENEATH A SHARP FRONTAL INVERSION. HAVE SEEN SOME BREAKS IN THE STRATUS OVER IN EASTERN WI AND COULD SEE A FEW HOLES FROM TODAY OVER MAINLY NE IL...BUT AS FLOW BACKS TO THE NORTHWEST WOULD ANTICIPATE THE STRATUS DECK TO OUR WEST TO ADVECT EASTWARD AND KEEP US FAIRLY SOCKED IN THROUGH TODAY AND INTO THIS EVENING. HAVE OPTED TO GO SOMEWHAT OPTIMISTIC WITH CLEARING TONIGHT FROM THE WEST...AND HANG ONTO CLOUDS LONGER THAN ANY GUIDANCE WOULD SUGGEST AS MODELS ARE NOTORIOUS FOR STRUGGLING WITH SHALLOW COOL SEASON STRATUS. GIVEN THE EXPECTATION OF CLOUD COVER HAVE GONE AHEAD AND RAISED LOW TEMPS TONIGHT...PARTICULARLY SOUTHEAST CWA. STRONG SHORTWAVE PASSES WELL TO OUR SOUTH WEDNESDAY AS LONG WAVE TROUGH RELOADS TO OUR NORTHWEST AND IS PREPARED TO TAKE AN ARCTIC DUMP ON US LATER THIS WEEK. PROBABLY THE MOST CONTENTIOUS PART OF THE FORECAST REVOLVES AROUND THE POTENTIAL FOR SOME ACCUMULATING SNOW THURSDAY NIGHT. GLOBAL MODELS ALL GENERALLY AGREE ON DEVELOPING A TIGHTENING LOW/MID LEVEL BAROCLINIC ZONE IN ADVANCE OF VIGOROUS SHORTWAVE MOVING INTO THE WESTERN GREAT LAKES REGION THURSDAY NIGHT. MODELS CONTINUE TO HINT AT THE DEVELOPMENT OF BAND OF LIGHT FRONTOGENTICALLY DRIVEN PRECIP IN ADVANCE OF THIS SHORTWAVE WHICH COULD BE ENOUGH TO PRODUCE A NARROW BAND OF AN INCH OR SO OF SNOW. THE DEVIL IS IN THE DETAILS HOWEVER AS THE AREA TO SEE THAT SNOWFALL WOULD LIKELY TO BE FAIRLY SMALL AND MODELS HAVE BEEN BOUNCING AROUND A BIT WITH RESPECT TO THE PLACEMENT OF THE HEAVIEST (ALBEIT STILL LIGHT) PRECIP. THE WRF-NMM AND WRF-ARW SUGGEST MOISTURE WILL BE TOO LIMITED AND FORCING TOO FAR SOUTH TO SERIOUSLY THREATEN OUR CWA WITH SUPPORT FROM THE CANADIAN MODEL. HAVING SAID ALL OF THIS...IT REALLY EQUATES TO LITTLE CHANGE FROM PREVIOUS FORECAST WITH SLIGHT CHANCE TO LOW END CHANCE POPS ACROSS THE CWA THURSDAY NIGHT. CWA WILL THEN GET SIDE-SWIPED BY A BITTERLY COLD EARLY SEASON SHOT OF ARCTIC AIR FRIDAY INTO FRIDAY NIGHT WITH H8 TEMPS PROGGED TO DROP TO -15C OR COLDER. TEMPS FRIDAY LOOK TO BE FAIRLY STEADY AND MAY EVEN FALL A BIT AS HEART OF ARCTIC AIR ARRIVES. SAVING GRACE WITH THIS COLD SNAP IS THE LACK OF SNOW COVER HERE AND UPSTREAM LIKELY ALLOWING IT TO MODIFY SOMEWHAT. EVEN SO TEMPS IN THE 20 LOOK LIKELY FRIDAY WITH LOWS IN THE TEENS FRIDAY NIGHT AWAY FROM THE CITY. PATTERN PROGGED TO REMAIN VERY PROGRESSIVE WITH BITTER COLD GETTING SHOVED QUICKLY EASTWARD OVER THE WEEKEND AS A UPPER FLOW TRANSITIONS TO MORE ZONAL. INCREASINGLY STRONG SOUTHWESTERLY WINDS SHOULD SEND TEMPS BACK TO NEAR IF NOT ABOVE NORMAL BY SUNDAY INTO MONDAY WITH LITTLE TO NO THREAT OF ANY PRECIP FRIDAY AFTERNOON THROUGH MONDAY. IZZI && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 16Z... * POTENTIAL LAKE EFFECT SNOW SHOWERS EARLY-MID AFTERNOON. * LIGHT SNOW APPROACHING FROM THE SW. * VARIABLE VFR/MVFR CIGS INTO THIS EVENING. TRS //DISCUSSION...UPDATED 16Z... AREA OF RADAR ECHOES CONTINUES TO MOVE NORTHEASTWARD OVER N CENTRAL IL AND APPROACHING METRO NE IL. LIGHT SNOW HAS BEEN REPORTED AT DVN...MLI...PIA...C75 WHERE SURFACE DEW POINT DEPRESSIONS 1-3 DEG F. WITH MODELS DAMPENING OUT THE SHORT WAVE FORCING THIS -SN THIS AFTERNOON AS IT CONTINUES NORTHEASTWARD FROM NW MO AND SE IA...INCREASINGLY ANTICYCLONIC LOW LEVEL FLOW AS THE SURFACE RIDGE CONTINUES TO BUILD SOUTHEASTWARD FROM THE UPPER MIDWEST AND MID MO VALLEY...AND WITH MUCH DRIER LOW LEVEL AIR WITH DEW POINTS ONLY IN THE TEENS TO LOWER 20S F ACROSS NORTHERN IL DO NOT ANTICIPATE ANY OF THIS PRECIP TO REACH THE GROUND AT THE LOCAL TERMINALS. TRAJECTORY OF COLD AIR DOWN LAKE MI HAS POTENTIAL TO BRING LAKE EFFECT SNOW SHOWERS TO NE IL THIS AFTERNOON. VISIBLY SATELLITE LOOP SHOWING A LAKE EFFECT BAND HAS SPREAD SOUTHWARD FROM E OF MTW TO E OF ETB LAST COUPLE HOURS. LATEST RUNS OF RUC13 CONTINUE TO BRING LIGHT PRECIP TO THE IL SHORE AROUND 19Z. OTHER HIGH RESOLUTION MODELS LESS AGGRESSIVE AND ONLY SPIT OUT SPOTTY 0.01 QPF AMOUNTS OVER THE WATER. BASE OF INVERSION PER FORECAST TEMPERATURE PROFILES AND VERIFIED BY ACARS DATA SHOW IT TO BE LOCATED 5500-6000 FT AGL WHICH WOULD DEEP ENOUGH FOR SOME LIGHT LAKE EFFECT THOUGH AS MENTIONED ABOVE LOW LEVEL FLOW BECOMES MORE ANTICYCLONIC WITH TIME THIS AFTERNOON AND DRY AIR IN PLACE OVER FAR NE IL AND UPSTREAM. RAC HAS HAD A PERSISTENT NNE WIND OFF THE LAKE ALL MORNING AND DEW POINT THERE STILL ONLY 22F. A LOW CHANCE OF SOME LAKE EFFECT SHOWERS REACHING VC ORD AND/OR MDW STILL EXISTS SO HAVE KEPT MENTION OF VCSH THESE SITES 18Z-21Z. REGARDING CEILINGS LATE MORNING THROUGH AFTERNOON...METARS FROM NEAR THE SE WI AND NE IL SHORES HOVER AROUND 030. EXPECT AT LEAST AREAS OF CIGS AROUND 030 THESE AREAS UNTIL FLOW AT CLOUD LEVEL BACKS TO N TO NW. A PERSISTENT AREA OF MVFR STRATUS/STRATOCU HAS BEEN IN PLACE AHEAD OF THE SURFACE RIDGE AXIS. EXPECT THESE CLOUDS TO SHIFT E TO SE AS DOES THE RIDGE THIS AFTERNOON AND EVENING BUT BASED ON MODEL INDICATIONS AND MOS OUTPUT ANTICIPATE ONLY PREVAILING SCT AREAS OF MVFR THIS EVENING. SLIGHT BACKING OF WINDS AT ORD AND MDW LAST HOUR OR TWO LIKELY IN RESPONSE TO INCREASING CONVERGENT BAND MOVING DOWN FROM MID LAKE SO HAVE KEPT WITH THIS NOTION THROUGH THE AFTERNOON AND THEN FURTHER BACKING DUE TO APPROACHING SURFACE RIDGE OCCURS THIS EVE. TRS //ORD AND MDW CONFIDENCE...UPDATED 14Z... * MEDIUM CONFIDENCE IN CIG TRENDS INTO THIS EVE. * LOW CONFIDENCE IN LAKE EFFECT SHOWERS IMPACTING CHI TERMINALS THIS AFTERNOON. * MEDIUM CONFIDENCE IN WIND FORECASTS INTO THIS EVE. TRS //OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z... * WEDNESDAY NIGHT AND THURSDAY...VFR * THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE * FRIDAY THROUGH MONDAY...VFR SHEA && .MARINE... 248 AM CST HIGH PRESSURE EXTENDING FROM THE UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS WILL SLOWLY SAG ACROSS THE GREAT LAKES REGION TODAY AND TONIGHT AS A STRONG LOW PRESSURE SYSTEM MOVES ACROSS NORTHERN MANITOBA INTO THE HUDSON BAY. THIS LOW WILL DRAG A COLD FRONT ACROSS LAKE MICHIGAN WEDNESDAY. DURING THIS PERIOD...WINDS OVER THE LAKE WILL GRADUALLY SHIFT FROM NORTHERLY TO SOUTHWESTERLY. WIND SPEEDS WILL DIMINISH TO AS LOW AS TO TO 15 KT LATE TONIGHT AS THE SFC RIDGE AXIS CROSSES THE LAKE...BUT AS THE RIDGE PUSHES TO THE SOUTH AND A SFC TROUGH ASSOCIATED WITH THE COLD FRONT DROPS THROUGH THE NORTHERN PLAINS LATE TONIGHT...WINDS WILL QUICKLY INCREASE AGAIN TO AROUND 30 KT. FOLLOWING THE PASSAGE OF THE COLD FRONT...ANOTHER CANADIAN HIGH PRESSURE SYSTEM WILL DROP SOUTHEAST ACROSS THE PLAINS THURSDAY AND FRIDAY. THIS SHOULD MAINTAIN A MODERATE PRESSURE GRADIENT OVER THE GREAT LAKES. THE COMBINATION OF THE MODERATELY STRONG PRESSURE GRADIENT AND STRONG COLD ADVECTION BEHIND THE EXITING FRONT WILL KEEP WINDS AROUND 25 TO 30KT OVER THE LAKE FROM WEDNESDAY THROUGH SATURDAY. KREIN && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS TOPEKA KS
1139 AM CST TUE DEC 6 2011 ...UPDATE TO AVIATION... && .AVIATION... VFR CONDITIONS EXPECTED THROUGH THE PERIOD. NORTH WINDS BECOME VARIABLE OVERNIGHT AND SHIFT AROUND TO THE SOUTHWEST ON WEDNESDAY. SPEEDS REMAIN BELOW 12 KTS. 67 && .PREV DISCUSSION... /ISSUED 536 AM CST TUE DEC 6 2011/ SHORT RANGE FORECAST (TODAY AND WEDNESDAY)... 8Z WATER VAPOR IMAGERY AND ASSOCIATED 500 MB RUC ANALYSIS SHOWS A HIGHLY AMPLIFIED POSITIVELY TILTED TROUGH OVER THE CENTRAL PLAINS WITH ITS AXIS EXTENDING FROM LAKE SUPERIOR AND RUNNING SOUTHWESTWARD THROUGH NEBRASKA AND INTO THE FOUR CORNER REGION. CURRENTLY TEMPERATURES ACROSS CENTRAL NEBRASKA ARE BELOW ZERO AS THE SURFACE RIDGE OF HIGH PRESSURE IS CENTERED OVER NEBRASKA. THE COLDEST LOCATION REMAINS KBBW WHERE THE TEMP AT 9Z WAS -11. ACROSS NORTHEAST KANSAS TEMPERATURES REMAIN IN THE MID TEENS WITH WIND CHILLS IN THE SINGLE DIGITS. ACROSS SOUTHEAST KANSAS MEAGER FRONTOGENETICAL AND ISENTROPIC LIFT HAS BROUGHT SOME LIGHT SNOW...MAINLY IN THE FORM OF NON-ACCUMULATING FLURRIES. BY MID-DAY ON TUESDAY EXPECT THE LOW/MID LEVEL LIFT AND SATURATED CONDITIONS TO MOVE OFF THE EAST OF THE FORECAST AREA ALLOWING A GRADUAL BREAKDOWN OF THE STRATUS DECK. EXPECT VERY LIGHT COLD AIR ADVECTION TO PERSIST THROUGHOUT THE DAY AS WINDS STAY FROM THE NORTH WHERE THE SURFACE HIGH WILL RESIDE. AS A RESULT OF THE COLD AIR ADVECTION AND THE ABBREVIATED DURATION OF CLEAR SKIES EXPECT TEMPS ON TUESDAY TO REMAIN IN THE MID TO UPPER 20S ACROSS AREAS NORTH OF THE KANSAS TURNPIKE...WITH TEMPS SOUTH AND EAST OF THE TURNPIKE REACHING THE LOWER 30S. FOR TUESDAY NIGHT THE SURFACE HIGH MOVES EASTWARD AND CENTERS OVER NORTHEAST KANSAS. EXPECT SKIES TO CLEAR OUT AND WINDS TO GO CALM OVERNIGHT. EXPECT TUESDAY NIGHT/WED MORNING TO BE THE COLDEST PERIOD FOR THIS FORECAST PACKAGE AS TEMPS WILL DROP TO THE LOWER TEENS ACROSS THE ENTIRE AREA...WITH THE LOWER TERRAIN OF RIVER VALLEYS PERHAPS DROPPING INTO THE SINGLE DIGITS. BY WEDNESDAY THE ARCTIC AIRMASS WHICH BROUGHT THE FRIGID TEMPS FOR THE EARLY PART OF THE WEEK WILL SHIFT EAST AND WARMER AIR WILL ADVECT INTO THE AREA...ALLOWING WEDNESDAY`S TEMPS TO REACH THE UPPER 30S TO LOWER 40S. MID-RANGE AND EXTENDED FORECAST (THURSDAY THROUGH MONDAY)... FAIRLY INACTIVE WEATHER PATTERN SHAPING UP FOR THE MIDDLE TO LATE PART OF THE WEEK AND INTO THE WEEKEND...AS NO REAL MID OR UPPER LEVEL FORCING ENTERS THE AREA. ALTHOUGH THE DAY TIME HOURS WILL BE SLIGHTLY WARMER FOR THE MIDDLE TO LATE PART OF THE WEEK OVERNIGHT LOWS WILL STILL DROP TO THE MID TEENS TO UPPER 20S AS ANOTHER MASS OF COLD AIR DIPS INTO THE AREA. PERHAPS THE ONLY WEATHER TO AFFECT NORTHEAST KANSAS WILL BE LATE IN THE WEEK AS AN UPPER LEVEL LOW DIGS SOUTHWARD THROUGH NEBRASKA BUT ITS SOUTHWARD PROGRESS STOPS IN SOUTHERN NEBRASKA BEFORE IT EJECTS EASTWARD. WITH LITTLE MOISTURE FOR THE SYSTEM TO WORK WITH EXPECT ONLY A FEW FLURRIES ACROSS AREAS NORTH OF HIGHWAY 24 THURSDAY NIGHT/FRIDAY MORNING. THEREAFTER EXPECT A DRY FORECAST FOR THE REST OF THE WEEK AND THROUGH THE WEEKEND WITH DAYTIME HIGHS IN THE 40S AND OVERNIGHT LOWS IN THE UPPER 20S TO LOWER 30S. JL && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
429 PM EST TUE DEC 6 2011 .SYNOPSIS... COLDER AIR WILL ENTER THE UPPER OHIO VALLEY IN THE WAKE OF A SLOWLY MOVING COLD FRONT. A LOW PRESSURE CENTER WILL DEEPEN OVER THE WESTERN CAROLINAS WEDNESDAY MORNING AND CAUSE PRECIPITATION TO LINGER LONG ENOUGH ACROSS THE MOUNTAINS, FOR RAIN TO CHANGE TO HEAVY WET SNOW WEDNESDAY AFTERNOON INTO EARLY THURSDAY. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... PER RECENT SURFACE AND RADAR DATA AND HRRR AND NAM MODEL OUTPUT, MAINTAINED SHOWERS SOUTHEAST OF PITTSBURGH THIS PERIOD. EXPECT DRIZZLE NORTH AND WEST OF PITTSBURGH AND AREAS OF FOG ACROSS THE MOUNTAINS OVERNIGHT. FORECASTED LOWS USING BLEND OF GFS AND NAM MOS VALUES. MOST SPOTS WILL REMAIN ABOVE FREEZING OVERNIGHT, AND WITH THE GROUND STILL WARM, IT SEEMED UNLIKELY ANY OF THIS LIQUID PRECIPITATION WOULD FREEZE. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/... RECENT MODEL SUITE CONTINUES TO SHOW A LOW PRESSURE CENTER DEEPENING OVER THE WESTERN CAROLINAS EARLY WEDNESDAY AND THEN MOVING NORTHEAST PAST THE DELMARVA PENINSULA EARLY THURSDAY. THIS WILL MAINTAIN PRECIPITATION ACROSS THE MOUNTAINS INTO EARLY THURSDAY, WITH RAIN CHANGING TO SNOW DUE TO THE COOLING TEMPERATURES. THE PRECIPITATION, CHANGING TO SNOW, CAN BECOME HEAVY MIDDAY WEDNESDAY INTO THE WEE HOURS OF THURSDAY ACROSS THE WV-MD MOUNTAINS. HENCE HAVE UPGRADED THE WINTER STORM WATCH TO A WINTER STORM WARNING AS SNOW AMOUNTS CAN EXCEED 6 INCHES. THE DENSITY OF THE SNOW CAN HAVE THE ADDED IMPACT OF CAUSING DOWNED TREES AND POWER LINES. COLD WEST WINDS ACROSS THE LAKE ERIE COUPLED WITH A SECONDARY COLD FRONT MAY CAUSE SNOW SHOWERS ACROSS THE I-80 CORRIDOR THURSDAY. ISOLATED SNOW SHOWERS CAN REDEVELOP ACROSS THE HIGHER MOUNTAINS DUE TO THE RESULTING UPSLOPE FLOW. PASSING HIGH PRESSURE SHOULD PROVIDE A DRY BREAK THURSDAY NIGHT AND MOST OF FRIDAY. FORECASTED TEMPERATURE DETAILS USING BLEND OF GFS AND NAM MOS WHICH SHOWED VALUES ABOUT 5 DEGREES COLDER THAN NORMAL. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... THE MODELS ARE IN A GENERAL AGREEMENT FOR THE START OF THE LONG TERM PERIOD WITH A WAVE DROPPING THROUGH THE GREAT LAKES SPAWNING SOME SNOW SHOWERS ON SATURDAY AND REINFORCING THE COLD AIR ACROSS THE REGION THROUGH THE WEEKEND. 850HPA TEMPS OF -16C ACCOMPANY THIS TROUGH SO KEPT TEMPERATURES BELOW NORMAL FOR THE FIRST HALF OF THE LONG TERM PERIOD... MODERATING A FEW DEGREES EACH DAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES A HOLD OVER THE EAST COAST. KEPT CLOSE TO HPC GUIDANCE FOR THE LATTER HALF OF THE PERIOD DUE TO LOW END MODEL CONFIDENCE. && .AVIATION /21Z TUESDAY THROUGH SUNDAY/... NORTHWEST FLOW BEHIND A VERY SLOW MOVING FRONTAL BOUNDARY WILL KEEP IFR CONDITIONS THROUGH A MAJORITY OF THE 24-30 HOUR TAF PERIOD. SINCE BUFKIT SOUNDINGS SUGGEST THAT MANY OF THE PORTS WILL IMPROVE TO AT LEAST LOW-END MVFR FOR A FEW HOURS THIS AFTERNOON AND UPSTREAM OBSERVATIONS INDICATE THIS IMPROVEMENT...DECIDED TO MENTION THIS IN MOST OF THE TAF LOCATIONS. THE SITES CLOSER TO THE FRONTAL BOUNDARY...MGW AND LBE...MAY NOT EXPERIENCE THIS TEMPORARY IMPROVEMENT. CONDITIONS SHOULD DETERIORATE BACK TO IFR FOR THE REST OF THE OVERNIGHT PERIOD INTO WEDNESDAY AS NORTHWEST FLOW AT THE SURFACE AND SOUTHWEST FLOW ALOFT HOLD STRATUS IN PLACE. A SHORTWAVE MOVING THROUGH THE UPPER LEVEL FLOW WILL BRING THE CHANCE FOR ADDITIONAL SHOWERS TOMORROW. OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY... RESTRICTIONS WILL BE POSSIBLE THROUGH WED NIGHT BEFORE HIGH PRESSURE BUILDS IN FOR THURSDAY AND FRIDAY. NEXT CHANCE FOR RESTRICTIONS WILL BE WITH THE SHORTWAVE PASSAGE SATURDAY. VFR WILL RETURN SUNDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WINTER STORM WARNING FROM 11 AM WEDNESDAY TO 4 AM EST THURSDAY FOR MDZ001. OH...NONE. PA...NONE. WV...WINTER STORM WARNING FROM 11 AM WEDNESDAY TO 4 AM EST THURSDAY FOR WVZ023-041. && $$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
1106 AM EST TUE DEC 6 2011 .SYNOPSIS... COLDER AIR WILL ENTER THE UPPER OHIO VALLEY IN THE WAKE OF A SLOWLY MOVING COLD FRONT. PRECIPITATION WILL LINGER LONG ENOUGH ACROSS THE MOUNTAINS FOR RAIN TO CHANGE TO SNOW WEDNESDAY INTO EARLY THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... PER RECENT SURFACE AND RADAR DATA AND HRRR AND NAM MODEL OUTPUT, MAINTAINED SHOWERS SOUTHEAST OF PITTSBURGH THIS PERIOD, WHILE ADJUSTING TEMPERATURES SLIGHTLY LOWER. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/... CONTINUE TO EXPECT COLDER THAN NORMAL TEMPERATURES TO SWEEP ACROSS THE UPPER OHIO VALLEY THIS PERIOD. HAVE MAINTAINED WINTER STORM WATCH ACROSS THE WV-MD MOUNTAINS WEDNESDAY INTO THURSDAY. TRAILING SURFACE LOW PRESSURE CENTER ALONG SLOW EASTBOUND COLD FRONT WILL CAUSE PRECIPITATION TO LINGER ACROSS THE WV-MD MOUNTAINS, WHERE IT CAN CHANGE FROM RAIN TO WET SNOW DURING WEDNESDAY. STILL UNCERTAINTY REGARDING PRECIPITATION AMOUNTS AND TEMPERATURES DETAILS, WHICH WILL VARY BY ELEVATION. HENCE HAVE HELD OFF ON MORE SPECIFIC WINTER WEATHER ISSUANCES. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... ANOTHER TROUGH WILL CROSS THE AREA ON FRIDAY, SERVING TO INSTIGATE A CHANCE OF SNOW SHOWERS THROUGH FRIDAY NIGHT AND PROVIDE A REINFORCING SHOT OF COLD AIR. AFTERWARD, FORECAST IS CLOSEST TO THE ECMWF ENSEMBLE MEAN. A STRONG AREA OF HIGH PRESSURE WILL BUILD INTO THE AREA AND KEEP THE FORECAST DRY FOR THE WEEKEND INTO MONDAY. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/... EXPECT COLD NORTH TO NORTHWEST WINDS TO MAINTAIN IFR STRATUS ACROSS MUCH OF THE UPPER OHIO VALLEY INTO AFTERNOON. THERE MAY BE TEMPORARY IMPROVEMENT TO MVFR LATER THIS AFTERNOON. HOWEVER, DETERIORATION BACK TO IFR IS EXPECTED TNGT AS FRONT/POOLED MSTR IS NOT EXPECTED TO MAKE MUCH SWD PROGRESS UNDER SWLY FLOW ALOFT. OUTLOOK...WEDNESDAY THROUGH SATURDAY... A SHORTWV IS FORECAST TO MOVE THRU THE SW FLOW OVR THE REGION AND SPAWN SOME PCPN IN MGW AREA ON WED. CIG RESTRICTIONS ARE POSSIBLE FOR MUCH OF WED AT OTHER TERMINALS. THEREAFTER...A BROAD UPR TROUGH IS FORECAST TO DEVELOP OVR THE GREAT LAKES. PERIODIC RESTRICTIONS AND SOME SHSN SHOULD BE ANTICIPATED IN THE COLD FLOW OVR THE REGION. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR MDZ001. OH...NONE. PA...NONE. WV...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR WVZ023-041. && $$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
415 PM EST TUE DEC 6 2011 .SYNOPSIS... WV IMAGERY AND RUC ANALYSIS INDICATED A SHEARED MID/UPPER LEVEL TROUGH FROM NRN ONTARIO THROUGH NW WI AND IA INTO THE CNTRL PLAINS. AN UPSTREAM SHORTWAVE TROUGH WAS MOVING THROUGH CNTRL MANITOBA. AT THE SFC...SW FLOW WAS INCREASING OVER WRN LAKE SUPERIOR AND W UPPER MI BTWN A DEPARTING RIDGE FROM QUEBEC INTO EAST UPPER MI AND A TROUGH OVER MANITOBA. ALTHOUGH THE BACKING WINDS HAVE PUSHED THE LAKE CLOUDS OFFSHORE OVER THE CNTRL AND WEST CWA...LOWER LEVEL MOISTURE OVER WRN WI WAS STREAMING BACK INTO THE WEST...PER VIS LOOP. MID LEVEL CLOUDS WERE ADVANCING THROUGH NW ONTARIO AND NRN MN ASSOCIATED WITH WAA/295K ISENTROPIC LIFT AHEAD OF THE TROUGH. && .SHORT TERM...TONIGHT AND WEDNESDAY MAIN FCST CONCERN IS LES POTENTIAL WITH THE FRONT/TROUGH MOVING THROUGH THE AREA. SATELLITE TRENDS AND NAM/RUC 925-900 MB RH FCST SUGGESTS THAT THE LOWER CLOUDS WILL CONTINUE TO SPREAD TO THE EAST THIS EVENING AND THEN MOVE OUT OVERNIGHT AS WINDS BEGIN TO VEER MORE TO THE WNW. MODERATE MID LEVEL QVECTOR CONV ASSOCIATED WITH THE TROUGH MOVING INTO THE AREA WED MORNING WILL BRING AN INCREASE IN 850-700 MB MOISTURE. WITH WINDS VEERING WRLY AND 850 MB TEMPS TO AROUND -11C...CONDITIONS WILL BECOME MORE FAVORABLE FOR LES INTO THE KEWEENAW LATE TONIGHT INTO WED MORNING. CAA DROPS 850 MB TEMPS TO AROUND -14C DURING THE AFTERNOON...BUT THE DEEPER MOISTURE IS EXPECTED TO DEPART. SINCE THE PERIOD WITH THE COMBINATION OF LOW LEVEL CONV AND 850-700 MB MOISTURE IS BRIEF...ANY LES ACCUMULATIONS ARE EXPECTED TO BE LIGHT...GENERALLY AN INCH OR LESS. SCT -SHSN WILL ALSO AFFECT LOCATIONS E OF MUNISING DURING THE AFTERNOON BUT AGAIN ACCUMULATIONS SHOULD BE LIGHT. .LONG TERM /WED NIGHT THROUGH NEXT TUESDAY/... COLD FRONT THAT WILL START THE COOLING TREND WILL BE EAST OF THE AREA AT THE START OF THE PERIOD...WHICH WILL PRODUCED A PROLONGED LAKE EFFECT SNOW PERIOD FOR PORTIONS OF UPPER MICHIGAN. EXPECT SFC LOW TO BE STATIONED OVER HUDSON BAY THROUGH SAT...WHILE A SFC HIGH SHIFTS FROM THE NRN PLAINS ON THURS TO THE OHIO RIVER VALLEY BY FRI NIGHT. THIS WILL LEAD TO WINDS OUT OF A WNW DIRECTION ON WED NIGHT INTO THURS...THEN BACKING TO THE W FOR THURS NIGHT INTO FRI NIGHT. THIS A LITTLE MORE WESTERLY THAN SHOWN YESTERDAY AND WILL LIKELY FOCUS PCPN OVER THE ERN CWA TO BE FROM GRAND MARAIS EASTWARD...RIGHT ALONG THE SHORELINE. THINK LAND BREEZES WILL HELP FOCUS A DOMINATE BAND EITHER RIGHT ALONG THE SHORELINE OR JUST OFFSHORE AT TIMES DURING THE PERIOD. OVER THE WEST...FAVORABLE LOCATIONS WILL BE FROM ROCKLAND THROUGH COPPER HARBOR...ESPECIALLY OVER THE HIGHER TERRAIN. EXPECT LES TO BE ONGOING AT THE START OF THE PERIOD...BUT WILL REALLY BEGIN TO RAMP UP OVERNIGHT WED INTO THURS MORNING...AS SHORTWAVE AND SECONDARY SFC TROUGH SWEEP ACROSS THE AREA. THIS WILL INCREASE MID LVL MOISTURE AND START A DOWNWARD TREND IN H850 TEMPS FROM -14C /DELTA-T OF 19/ TO -20C OVER THE W AND -18C OVER THE E. THESE VALUES DON/T LOOK AS COLD AS YESTERDAY FOR THE THURS/FRI TIME FRAME...WHICH WILL BE MORE FAVORABLE FOR THE LES POTENTIAL...AS THE DGZ WILL BE RIGHT IN THE BEST OMEGA. IN ADDITION...MODELS SHOWING A MORE MOIST LLVL...WITH LESS SUB CLOUD LAYER DRY AIR. THIS ALLOWS THE BEST LK INDUCED FORCING TO BE LOCATED DIRECTLY IN OR THE TOP HALF OF THE DGZ AND AID FOR FASTER ACCUMULATION. THUS...HAVE BUMPED UP SLR UP SLIGHTLY INTO THE LOW/MID 20S...ALTHOUGH NOT QUITE AS HIGH AS SEEN ON SOME OF THE CARIBOU SLR VALUES. MIGHT BE A LITTLE LULL IN LES OVER THE WEST ON THURS AFTN...AS DRIER AIR ABOVE H800 MOVES THROUGH AND LOWERS THE INVERSION HEIGHTS. THIS WILL BE SHORT LIVED AS NEXT WAVE OF DEEPER MOISTURE MOVES IN AND INVERSION HEIGHTS RISE ON THURS NIGHT WITH THE UPPER TROUGH MOVING OVERHEAD. EVEN WITH THIS LULL...THERE WILL STILL BE GUSTY WINDS THAT WILL CREATE BLOWING/DRIFTING SNOW ALONG THE LK SUPERIOR SHORELINE WITH THE FAIRLY FLUFFY SNOW THAT WILL HAVE FALLEN WED NIGHT INTO THURS MORNING. FRI DEEPER MOISTURE STARTS TO DEPART THE WEST DURING THE DAY...STARTING TO DIMINISH LES INSTENSITY...BUT WILL STILL BE ONGOING THROUGH FRI NIGHT. WITH WINDS SHIFTING MORE OUT OF THE WSW...EXPECT BEST BANDS TO BE OVER THE KEWEENAW AND OFFSHORE OVER THE E /ALTHOUGH A WEAK TROUGH COULD SLIDE THE BAND BACK ONSHORE FRI NIGHT/. AS FOR SNOWFALL AMOUNTS...LES PARAMETER EXCEEDS 2 FOR MUCH OF THE PERIOD...WHICH ALONG WITH LK INDUCED CAPE VALUES EXCEEDING 700 J/KG AND EQL/S IN THE 9-12KFT RANGE...THE POTENTIAL IS THERE FOR HEAVY SNOWFALL ACCUMULATIONS. CURRENT FCST FROM 6Z THURS TO 6Z SAT HAS 12-20 INCHES OVER THE HIGHER TERRAIN FROM ROCKLAND TO CALUMET AND SIMILAR TOTALS RIGHT ALONG THE LK SUPERIOR SHORELINE E OF GRAND MARAIS. WILL LIKELY SEE A COUPLE PERIODS WHERE OUR 8IN/12HR WARN CRITERIA WILL BE REACHED OVER THE WEST...SO HAVE PUT OUT A LES WATCH FOR ONTONAGON THROUGH KEWEENAW COUNTIES. HAVE LIMITED CONFIDENCE IN THE EAST WITH BAND LOCATION DUE TO THE LITTLE MORE WRLY WINDS AND SOME LIKELY WANDERING OF THE BAND ON/OFF SHORE THROUGH THE PERIOD...SO HELD OFF ON A WATCH FOR TIME BEING. DAYS 4 THROUGH 7 /FRI NIGHT THROUGH NEXT TUESDAY/... EXPECT LES TO COME TO AN END ON SAT...AS A CLIPPER SYSTEM DROPS THROUGH SOUTHERN ONTARIO AND SHIFTS WINDS TO THE SW AND PRODUCES WAA ALOFT. FINE DETAILS BECOME A LITTLE MORE MUDDLED FOR SUN THROUGH TUES...AS NO MAJOR DISTURBANCES OR FEATURES AFFECT THE REGION. THIS LEAVES THE AREA UNDER ZONAL FLOW ALOFT FOR SUN...AHEAD OF A SHORTWAVE MOVING ACROSS THE AREA MON INTO MON NIGHT. WITH H850 TEMPS AROUND -1C ON SUN...EXPECT TEMPS TO BE SLIGHTLY ABOVE NORMAL WITH HIGHS IN THE LOWER 30S. SUN NIGHT INTO MON NIGHT SHOULD SEE A SFC TROUGH NEAR THE UPPER GREAT LKS REGION...BUT WITH HOW WEAK IT APPEARS TO BE WITH THE ZONAL FLOW...HAVE LIMITED CONFIDENCE ON PCPN. THUS...WILL GO WITH A MOSTLY CLOUDY PERIOD...ALTHOUGH THE BEST CHANCE FOR PCPN WILL BE MON INTO MON NIGHT. THESE CLOUDS WILL KEEP OVERNIGHT LOWS FROM BEING TOO COLD AND KEEP TEMPS NEAR NORMAL FOR MON INTO TUES. && .AVIATION /FOR THE 18Z TAF ISSUANCE/ ANY LEFTOVER MVFR CIGS WITH LAKE EFFECT CLOUDS ARE EXPECTED TO MOVE OUT BY MID TO LATE AFTERNOON AS WINDS BACK TO THE SW. SW GRADIENT WINDS INCREASING THIS EVENING AHEAD OF APPROACHING COLD FRONT WILL SUPPORT LLWS AT ALL TAF SITES TONIGHT. WINDS VEERING WRLY LATE TONIGHT BEHIND THE FRONT SHOULD BRING MVFR CIGS BACK INTO KIWD AND KCMX. FAVORABLE WRLY FLOW AT KCMX MAY RESULT IN WIND GUSTS AOA 30 KTS AS WELL AS POSSIBLE LAKE EFFECT SNOW SHOWERS. && .MARINE /FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE/... SW WINDS ARE EXPECTED TO INCREASE TO GALE FORCE TONIGHT INTO EARLY WED...MAINLY OVER WESTERN AND NCNTRL LAKE SUPERIOR AHEAD OF A TROUGH MOVING TOWARD THE REGION. AS WINDS VEER NW BEHIND THE TROUGH...WINDS ARE EXPECTED TO DIMINISH INTO THE 20-30 KT RANGE. A WINTRY PATTERN OF W-NW WINDS WILL THEN PERSIST THRU LATE WEEK WITH LAKE EFFECT SNOW SHOWERS. GIVEN ARCTIC AIR PASSING OVER THE LAKE AND EFFICIENT MIXING...EXPECT WINDS CONSISTENTLY 20-30 KT WITH ANOTHER PERIOD OF GALES POSSIBLE AGAIN LATE WED NIGHT AND THURSDAY. COMBINATION OF ARCTIC AIR AND STRONG WIND SHOULD RESULT IN FREEZING SPRAY WED NIGHT INTO FRIDAY. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW WATCH FROM LATE WEDNESDAY NIGHT THROUGH LATE FRIDAY NIGHT FOR MIZ001>003. LAKE SUPERIOR... GALE WARNING UNTIL 10 AM EST WEDNESDAY FOR LSZ266. GALE WARNING UNTIL 7 AM EST /6 AM CST/ WEDNESDAY FOR LSZ162. GALE WARNING UNTIL 10 AM EST WEDNESDAY FOR LSZ263-264. LAKE MICHIGAN... NONE. && $$ SYNOPSIS...JLB SHORT TERM...JLB LONG TERM...SRF AVIATION...JLB MARINE...JLB
AREA FORECAST DISCUSSION
NWS GRAND FORKS ND
1043 AM CST TUE DEC 6 2011 .DISCUSSION... CONCERN FOR THE UPDATE IS THE WIND SPEED. ALL INDICATIONS ARE THE LOW LEVEL INVERSION WILL HOLD PREVENTING 40KT - 45KT 925MB WIND FROM MIXING DOWN. HRRR HAS BEEN CONSISTENT IN DEVELOPING SFC GUSTS TO 40KTS OVER NORTH RRV AND NORTHWEST MINNESOTA COUNTIES 18Z-23Z. RUC13 AND NAM12 LAPSE RATES REMAIN STRONGLY NEGATIVE...YET MOMENTUM TRANSFER WILL PROBABLY PUSH TRANSIENT GUSTS TO THE SURFACE. PLAN TO UP THE WIND GUSTS MORE IN LINE WITH THE HRRR BUT NOT QUITE AS STRONG. OTRW THE PREVIOUS FORECAST IS IN GOOD SHAPE. WILL HOLD OFF ON WIND ADVISORY ALTHOUGH IT COULD BE CLOSE PARTICULARLY IN THE HIGHER TERRAIN FAVORED AREAS OF THE DEVILS LAKE BASIN AND NORTHWEST MINNESOTA. && .AVIATION...MAIN CONCERN FOR TODAY WILL BE WIND SPEEDS. BUMPED UP WINDS PER PUBLIC FCST COORDINATION. EXPECT SOUTHWEST WINDS WITH GUSTS UP TO 35 KNOTS. CIRRUS EXPECTED INTO TONIGHT. PROBABILITY FOR MVFR CIGS INCREASE BY WEDNESDAY MORNING ALONG COLD FRONT. && .PREV DISCUSSION... /ISSUED 337 AM CST TUE DEC 6 2011/ SHORT TERM...CHALLENGES INCLUDE WINDS TODAY ALONG WITH CLOUD COVER AND TEMPERATURES THROUGH THE PERIOD. 00Z MODELS IN DECENT AGREEMENT AND WILL USE A BLEND FOR DETAILS. TODAY-TONIGHT...STRONG SYSTEM WILL PROPAGATE ACROSS CANADA...WELL NORTH OF THE REGION. SOUTHWEST WINDS WILL INCREASE INTO THE AFTERNOON HOURS. MODEL SOUNDINGS SUGGEST MIXING TO 925MB...WITH 30-40KNTS AVAILABLE TO MIX...WITH 20-30 DEGREE DIFFERENCE FROM THE SFC TO 925MB. CONSIDERING THESE FACTORS SUSTAINED WINDS WILL LIKELY BE JUST BELOW ADVISORY CRITERIA. STRONGEST WINDS EXPECTED IN FAVORABLE CROOKSTON TO HALLOCK AREA. SIMILAR SITUATION LAST FRIDAY PROVED MOST TEMPERATURE GUIDANCE TOO COLD...WITH ECMWF VERIFYING BEST. FOLLOWING ECMWF...INCREASED MAX TEMPS 3-6F. 850MB THERMAL RIDGE WILL PROPAGATE THROUGH THE FA 00Z-06Z WED...AND COLD FROPA THROUGH THE REGION BY 12Z. LIKELY WILL BE SOME SORT OF NON-DIURNAL TEMPERATURE TREND. INCREASED SKY COVER AS MODEL GUIDANCE SUGGESTING LOW-LEVEL STRATUS IN COLD AIR ADVECTION JUST AHEAD OF UPPER WAVE. VERY LIGHT PRECIP ALSO POSSIBLE ACROSS NE FA. MODEL SOUNDINGS SUGGEST FZDZ POSSIBLE. LOW-LEVEL SATURATED LAYER AVERAGE TEMP WILL BE AROUND -8C WITH DRY LAYER ABOVE SUGGESTING SUPERCOOLED WATER DROPLETS. INCLUDED FLURRY/FZDZ AFT 06Z. WED-THUR NIGHT...UPPER FLOW BECOMES NORTHWEST WITH MULTIPLE WEAK/FAST MOVING SYSTEMS. COLDER AIRMASS SHOULD CONTINUE TO FILTER INTO THE REGION WITH COLDEST AIRMASS ON THUR. THERE WILL LIKELY BE PARTLY CLOUDY PERIODS...BUT BEGINNING TO THINK THAT MUCH OF THIS PERIOD WILL BE CLOUDY (ESPECIALLY THE NE HALF OF THE FA WHERE COLDEST 850MB TEMPS WILL BE LOCATED)...AND INCREASED SKY COVER ACROSS THE NE HALF OF THE FA. DID NOT INSERT PRECIP...BUT WOULD NOT BE SURPRISED TO SEE PERIODIC FLURRIES. BREEZY WINDS LIKELY. LONG TERM (FRIDAY-MONDAY)... MODELS IN THE EXTENDED ARE IN GOOD AGREEMENT AS UPPER LEVEL NW FLOW DOMINATES THE WEATHER PATTERN. CONTINUED DRY WEATHER WITH TEMPERATURES REBOUNDING TO ABOVE NORMAL FOR THE WEEKEND WITH HIGHER THICKNESSES BUILDING INTO THE NORTHERN PLAINS. AVIATION...MAIN CONCERN FOR TODAY WILL BE WIND SPEEDS. EXPECT SOUTHWEST WINDS WITH GUSTS UP TO 25 KNOTS. CIRRUS EXPECTED INTO TONIGHT. PROBABILITY FOR MVFR CIGS INCREASE BY WEDNESDAY MORNING ALONG COLD FRONT. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ EWENS
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
1247 PM EST TUE DEC 6 2011 .SYNOPSIS... A SLOW MOVING COLD FRONT WILL GRADUALLY SLIDE EASTWARD TODAY. STRONG SYSTEM BRINGS RAIN WEDNESDAY...CHANGING TO SNOW WEDNESDAY NIGHT. HIGH PRESSURE THURSDAY. CLIPPER FRIDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... EARLY MORNING RADAR TRENDS INDICATE TWO POINTS OF FOCUS FOR PRECIPITATION. COLD FRONT JUST EAST OF OH RIVER VALLEY HAS BEEN THE IMPETUS FOR SCT SHOWERS OVERNIGHT INTO THE EARLY MORNING. NOT EXPECTING THIS TO CHANGE MUCH...SAVE FOR THE EVENTUAL EASTWARD CREEP OF THE FRONTAL BOUNDARY. SECOND FOCUS IS A WAVE RIDING NORTH ALONG THE FRONT...CURRENTLY LOCATED IN EAST-CENTRAL TN. EXPECTING SHOWERS ASSOCIATED WITH THIS FEATURE TO BE A LITTLE MORE ORGANIZED AS THEY ENTER OUR SW VA AND WV MOUNTAIN COUNTIES IN THE COMING HOURS. HRRR HAS HANDLED ONGOING PRECIPITATION TRENDS THE BEST...STICKING WITH THIS SOLUTION THIS MORNING. LOW CIGS AND VSBYS HAVE BEEN REPORTED ALONG THE FRONT AS IT MADE IT SLOW JOURNEY THROUGH SE OHIO...EXPECTING THIS TREND TO CONTINUE IN CRW AND CKB VICINITIES BEFORE ANY DAYTIME MIXING CAN IMPROVE CONDITIONS. LOW STRATUS SHOULD HANG AROUND CWA THROUGH AT LEAST MIDDAY WITH THE GREATEST IMPACT EVIDENT IN MOUNTAIN COUNTIES. TEMPS REMAIN COOLER THAN MOS WEST OF TROF AXIS...TWEAKED TEMPS TO ACCOUNT FOR THIS. GOING WITH A NEAR NON-DIURNAL TREND TO HIGH TEMPS WITH COLD FRONT STILL IN THE REGION. KEEPING WITH THE TREND OF AOA MOS TEMPS IN WV MNTS TODAY...WHILE AOB MOS IN THE LOWLANDS. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... MUCH BETTER CONSENSUS IN THE MODELS TONIGHT COMPARED TO THE RUNS LAST NIGHT REGARDING THE VIGOROUS SYSTEM SLATED FOR WEDNESDAY AND WEDNESDAY NIGHT. MOISTURE WILL HAVE ALREADY OVERSPREAD THE AREA SOUTH OF THE OHIO RIVER BY 12Z WEDNESDAY...AND EXPECT STEADY RAIN THROUGH THE FIRST PART OF THAT TIME PERIOD. THE ENTIRE KEY TO THIS FORECAST IS THE RATE OF THE COLD AIR ADVECTION AND THE SURFACE TEMPERATURES FALLING BELOW FREEZING. THIS WILL OCCUR FIRST IN THE HIGHEST ELEVATIONS WHERE THE MOST SIGNIFICANT ACCUMULATIONS ARE LIKELY. 925MB TEMPERATURE GRADIENT WILL TIGHTEN UP OVER THE EASTERN MOUNTAINS AND FINALLY KICK THROUGH AFTER AROUND 21Z WEDNESDAY...WHICH WILL SUBSEQUENTLY ALLOW THE CHANGE OVER TO SNOW FOR THE REMAINDER OF THE MOUNTAINS. WHILE THE OPERATIONAL MODELS GO EASY ON THE SPEED OF THE COLD AIR ADVECTION...STRENGTH OF THE DYNAMICS IN PLAY DO LEAVE SOME QUESTION AS TO WHETHER THIS PARAMETER IS BEING REPRESENTED WELL BY THESE MODELS...OR IF THERE WILL BE AN EARLIER TRANSITION TIME TO COME OVER THE NEXT COUPLE OF RUNS. SYSTEM WILL BE EFFICIENT WHEN IT COMES TO CREATING PRECIPITATION. JET STREAK OVER 140KTS EXISTS OVER SOUTHEAST OHIO WEDNESDAY...AND THE 500MB WAVE INDICATES A SHIFT TO A NEGATIVE TILT UPON PASSAGE THROUGH THE CENTRAL AND SOUTHERN APPALACHIANS. ROBUST FRONTOGENETIC FORCING WILL COUPLE WITH Q VECTOR CONVERGENCE IN THE UPPER LEVELS...CREATING ENHANCED OMEGA THROUGH THE DENDRITIC GROWTH LAYERS...WITH SATURATION OF THE COLUMN EXTENDING FROM THE SURFACE TO ABOVE 500MB. THE 03Z RUN OF THE SREF BRINGS PROBABILITIES OF SNOW EXCEEDING 4 INCHES AT ABOUT THE 30 TO 40 PERCENT RANGE FOR POCAHONTAS COUNTY. CURRENT STATE OF THE FORECAST GRIDS DOES BRING AROUND 4 TO 8 INCHES TOTAL SNOW ACCUMULATION...RELEGATED TO THE HIGHEST PEAKS OF THE CWA...ABOVE ROUGHLY 4000FT. WITH THE SLOWER CHANGE OVER TO SNOW IN THE MOUNTAINS BELOW 4000FT...ABOUT 2 TO 4 INCHES OF SNOW ARE IN THE FORECAST FOR THIS ISSUANCE. ANOTHER VARIABLE IN THIS OVERALL EQUATION IS THE MILD AIR THAT HAS BEEN IN PLACE...THE RAIN THAT WILL PRECEDE THE SNOW...AND THE LENGTH OF TIME NECESSARY FOR THE SNOW TO ACCUMULATE. GIVEN THE FACT THAT THIS IS A LATE 3RD PERIOD TO EARLY 4TH PERIOD EVENT...WILL NOT COMMIT TO THE WATCH FOR NOW. ANY VARIABILITY IN THE TIMING OF THE BELOW FREEZING AIR COULD ALTER THE SNOWFALL TOTAL FORECAST SIGNIFICANTLY...IN EITHER DIRECTION. NOT COMFORTABLE WITH THIS POTENTIAL VOLATILITY TO THE FORECAST AND WILL DRAW ATTENTION TO THIS SYSTEM IN THE HWO AND RWS TEXT PRODUCTS. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... A SHARP AMPLIFYING TROF WILL BE THE MAIN FEATURE EARLY IN THE EXTENDED. THIS TROF WILL SETTLE INTO EASTERN CONUS...ADVERTISED BY A CLIPPER FOR FRI NIGHT. BEST LIFT WITH THIS FEATURE WILL SKIRT BY MAINLY TO NORTH. HOWEVER...GIVEN SOME MOISTURE AND MAGNITUDE OF COLD AIR BEHIND IT...CANT RULE OUT SOME FLURRIES ABOUT ANYWHERE WITH FROPA. WILL MENTION FLURRIES IN WX GRIDS FOR LOWLANDS AND CARRY CHC POPS NORTHERN MTNS. H85 TEMPS COME DOWN TO ARND -10C BY SAT MORNING. NOT MUCH IN THE WAY OF UPSLOPE AS ATMOSPHERIC COLUMN WILL QUICKLY DRY OUT AND NW FLOW MEAGER. WILL DRY THINGS OUT QUICKLY SAT...WITH A RETURN TO SUNSHINE FOR ALL BY AFTN...ALBEIT COLD. DESPITE THE SUNSHINE...THINK 40F WILL BE HARD TO COME BY IN THE LOWLANDS...WITH GUIDANCE SUGGESTING MID 30S IS ABOUT IT...WITH 20S IN THE MTNS. UPR TROF DOESNT STICK ARND IN THIS PROGRESSIVE PATTERN...AS WAA QUICKLY ALLOWS H85 TEMPS TO RECOVER. HOWEVER...COLD NIGHT WILL BE ON TAP SAT WITH SFC HIGH BUILDING OVERHEAD. WILL GO WITH AN EARLY LOW HIGHEST ELEVATIONS AND LEVEL OFF OR SLIGHTLY REBOUND BY SUN MORNING...WITH LOWLANDS DIPPING DOWN INTO LWR 20S. TOOK TYPICAL COLD SPOTS INTO TEENS...IE NORTHERN MTN VALLEYS/NE KY. MODERATING TEMPS WILL CARRY THE WAY EARLY NEXT WEEK...THOUGH STILL REMAINING ON THE CHILLY SIDE. SHOULD STAY DRY THROUGH TUES. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... A COLD FRONT CURRENTLY LOCATED JUST WEST OF BKW AND EKN IS VERY SLOWLY MOVING EASTWARD. LIFR/IFR CONDITIONS CAN BE EXPECTED WEST OF THE FRONT...WITH VFR/MVFR EAST OF THE FRONT. A LOW WILL FORM ALONG THIS FRONT AND MOVE NORTHWARD LATE TONIGHT AND WEDNESDAY. THIS WILL BRING MORE RAIN TO THE AREA. WITH THE REGION ON THE WEST SIDE OF THE FRONT...EXPECT LIFR/IFR CONDITIONS. COLD AIR ON THE BACK SIDE OF THIS SYSTEM COULD CAUSE A BURST OF SNOW LATE WEDNESDAY. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z WEDNESDAY... FORECAST CONFIDENCE: HIGH WEST OF THE FRONT...LOW FOR TIMING OF FRONT IN THE EAST. ALTERNATE SCENARIOS: TIMING OF THE FRONT CONTROLS THE COLLAPSE OF CEILINGS IN THE EASTERN COUNTIES. THIS TIMING COULD VARY. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. UTC 1HRLY 18 19 20 21 22 23 00 01 02 03 04 05 EST 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00 CRW CONSISTENCY M M M M M M M M M L L L HTS CONSISTENCY H H H H H L L L L M M M BKW CONSISTENCY M L M M M L L L M L L L EKN CONSISTENCY L M M M M M M L L L L L PKB CONSISTENCY M H H M M L L L L M M M CKB CONSISTENCY M H H H H H H H H L L L AFTER 18Z WEDNESDAY... IFR IN PERIODS OF PRECIPITATION AND FOG INTO WEDNESDAY NIGHT. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...26/TAX NEAR TERM...TAX SHORT TERM...26 LONG TERM...30 AVIATION...RPY
AREA FORECAST DISCUSSION
NWS BROWNSVILLE TX
1158 AM CST TUE DEC 6 2011 .DISCUSSION...SEE THE AVIATION SEGMENT BELOW FOR THE DISCUSSION OF THE 18Z TAF ISSUANCE. && .AVIATION...THE 12Z BRO SOUNDING SHOWS THAT THE CURRENT ATMS IS PRETTY SATURATED AND A FAIRLY STRONG INVERSION IS EVIDENT AT AND BELOW THE 850 MB LEVEL. AS A RESULT VSBL IMAGERY OVER DEEP SOUTH TX SHOWS AN LARGE AREA OF OVC CLD DECKS. HOWEVER A LARGE HOLE IN THE LOW CLD DECKS IS EVIDENT OVER SOUTH CENTRAL TX AND APPEARS TO BE MOVING S-SE AT A PRETTY GOOD CLIP. THE LATEST RUC AND NAM12 RH FIELDS SHOWS MUCH DRIER AIR FILTERING IN OVER THE REGION THROUGHOUT THE EVENING AND OVERNIGHT HOURS WHICH WILL RESULT IN THE LIFTING OF THE CEILINGS THROUGHOUT THE UPCOMING TAF PERIOD. ACCORDINGLY EXPECT VFR VSBYS AND CEILINGS THROUGH 18Z TOMORROW WITH LIGHT TO MODERATE NORTHERLY SURFACE FLOW PERSISTING AS THE SURFACE RIDGING SPREADS OVER THE REGION. && .PREV DISCUSSION... /ISSUED 427 AM CST TUE DEC 6 2011/ SHORT TERM /TODAY THROUGH WEDNESDAY/...THE UPPER TROUGH AXIS CURRENTLY EXTENDING TO THE DESERT SOUTHWEST WILL LIFT OUT ACROSS NORTH TEXAS LATE TUESDAY NIGHT. WEAK ISENTROPIC LIFT AHEAD OF THE UPPER TROUGH WILL RESULT IN CLOUDY SKIES...COOL TEMPERATURES...AND A SLIGHT CHANCE OF LIGHT RAIN/SPRINKLES THIS MORNING THROUGH EARLY THIS AFTERNOON. CLOUDS WILL BEGIN TO DECREASE LATER THIS AFTERNOON AND TONIGHT AS THE UPPER TROUGH LIFTS OUT OVER THE SOUTHERN PLAINS. SURFACE HIGH PRESSURE WILL SETTLE INTO DEEP SOUTH TEXAS LATE TONIGHT THROUGH WEDNESDAY. THE MAIN CHALLENGE WILL BE HOW LOW THE TEMPERATURES DROP TONIGHT/WEDNESDAY MORNING. LIGHT WINDS... CLEARING SKIES...AND MUCH DRIER AIR FILTERING INTO THE AREA WOULD SUGGEST A COLD NIGHT IN DEEP SOUTH TEXAS AND IN THE RIO GRANDE VALLEY. CURRENT MODEL DATA CONSENSUS IS ALSO INDICATING A COLD NIGHT ACROSS THE AREA. THE ONLY CONCERN IS THAT THE WINDS MAY NOT DROP OFF AS QUICKLY AS THE MODEL GUIDANCE IS INDICATING. AFTER A LONG IN OFFICE DISCUSSION...PONDERING OVER THE AVAILABLE GUIDANCE ONE LAST TIME...AND COORDINATING WITH WFO CRP...HAVE DECIDED TO ISSUE A FREEZE WATCH FOR A GOOD PORTION OF THE CWA. THE FREEZE WATCH WILL INCLUDE ALL OF THE COUNTIES OF BRO CWA EXCEPT FOR HIDALGO AND CAMERON COUNTIES AND THE COASTAL PORTION OF WILLACY COUNTY. WIDESPREAD TEMPERATURES ARE EXPECTED TO BE IN THE UPPER 20S TO LOWER 30S ACROSS DEEP SOUTH TEXAS AND THE VALLEY WEDNESDAY MORNING. PLEASE REFER TO THE NPW BRO PRODUCT. THANKS WFO CORPUS CHRISTI FOR THE COORDINATION REGARDING THE FREEZE WATCH. LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...CLEAR SKIES WILL COMBINE WITH LIGHT WINDS AND DRIER AIR TO PRODUCE ANOTHER ROUND OF FREEZING TEMPERATURES ACROSS MOST OF DEEP SOUTH TEXAS AND THE RIO GRANDE VALLEY LATE WEDNESDAY NIGHT THROUGH EARLY THURSDAY MORNING .AND A FREEZE WARNING MAY BE NEEDED FOR THAT TIME. PLEASANT AND DRY WEATHER WITH MODERATING TEMPERATURES IS EXPECTED THURSDAY AND THURSDAY NIGHT AS SURFACE HIGH PRESSURE YIELDS TO AN INVERTED SURFACE TROUGH OF LOW PRESSURE DEVELOPING OVER THE WESTERN GULF OF MEXICO. ISOLATED TO SCATTERED AREAS OF RAIN WITH OVERCAST SKIES WILL THEN PREVAIL FOR FRIDAY THROUGH EARLY NEXT WEEK AS THE TROUGH INTENSIFIES AND PERSISTS. TEMPERATURES WILL BE HELD AT BELOW NORMAL LEVELS FROM FRIDAY THROUGH SUNDAY DUE TO THE INCREASED CLOUD COVER AND FLOW FROM THE NORTHEAST AND EAST...HOWEVER TEMPERATURES WILL BEGIN TO RECOVER ON MONDAY AS THE FLOW SHIFTS FROM OUT OF THE SOUTHEAST. MARINE...TODAY THROUGH WEDNESDAY...OBS AT BUOY 020 CURRENTLY REFLECT NNW WINDS AT AROUND 19 KNOTS WITH HIGHER GUSTS AND WAVE HEIGHTS AROUND 7 FEET WITH A 5 SECOND PERIOD. STRONG WINDS WILL PERSIST TODAY AS HIGH PRESSURE CONTINUES TO SURGE ACROSS THE LOWER TEXAS COAST. THE SMALL CRAFT ADVISORY ON THE BAY IS IN EFFECT UNTIL 1 PM TODAY AND MAY LIKELY BE EXTENDED THROUGH LATE THIS AFTERNOON OR INTO EARLY THIS EVENING. A SMALL CRAFT ADVISORY HAS BEEN EXTENDED ON THE GULF WATERS THROUGH 6 AM WEDNESDAY. LITTLE CHANGE IS OTHERWISE EXPECTED IN THE SHORT TERM MARINE FORECAST. WEDNESDAY NIGHT THROUGH MONDAY...MARINE CONDITIONS ARE EXPECTED TO STEADILY IMPROVE WEDNESDAY NIGHT THROUGH FRIDAY...WITH SMALL CRAFT ADVISORIES NOT ANTICIPATED TO BE NEEDED...AS SURFACE HIGH PRESSURE SHIFTS EAST FROM THE TEXAS COASTLINE TO THE MID-ATLANTIC REGION. WINDS AND SEAS WILL THEN INCREASE FOR FRIDAY NIGHT THROUGH EARLY NEXT WEEK...WITH SMALL CRAFT ADVISORIES INCREASINGLY POSSIBLE...AS THE HIGH PRESSURE SYSTEM INTERACTS WITH LOW PRESSURE OVER THE BAY OF CAMPECHE AND SOUTHERN GULF OF MEXICO. && .BRO WATCHES/WARNINGS/ADVISORIES... TX...FREEZE WATCH FROM LATE TONIGHT THROUGH WEDNESDAY MORNING FOR TXZ248>252-254. GM...SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM CST THIS AFTERNOON FOR GMZ130-132-135. SMALL CRAFT ADVISORY UNTIL 6 AM CST WEDNESDAY FOR GMZ150-155-170- 175. && $$ THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT: HTTP://WWW.WEATHER.GOV/BROWNSVILLE SHORT TERM...60 LONG TERM...54 GRAPHICAST/UPPER AIR...VEGA
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
219 PM CST TUE DEC 6 2011 .SYNOPSIS...SEASONABLY COLD AND VERY QUIET FOR THE EARLY PART OF DECEMBER. AMPLIFIED LNGWV PATTERN IN PLACE...WITH LARGE SCALE FLOW DOMINATED BY MASSIVE RIDGE OVER THE ERN PAC. THE FLOW DOWNSTREAM WAS SOMEWHAT SPLIT...WITH NRN STREAM MUCH STRONGER THAN THE SRN...AND WITH TROFFING OVER ERN NOAM. THE TREND DURING THE FIRST PART OF THE FCST PERIOD WL BE FOR BROAD ERN NOAM TROF TO EXPAND SWD FM VORTEX IN THE HUDSON BAY RGN. THE SAME FEATURES SHOULD REMAIN IN PLACE FOR THE LATTER HALF OF THE PERIOD...BUT WITH A GRADUAL DECR IN AMPLITUDE. TEMPS ACRS THE AREA HAVE COOLED TO NR NORMAL...AND WL CONT THE DOWNSLIDE TO SOMEWHAT BLO NORMAL LEVELS AS THE UPR TROF DEEPENS OVER THE RGN. ALTHOUGH THE N NOW HAS A DECENT SNOWCOVER...THE LACK OF A WIDESPREAD DEEP SNOWCOVER ACRS THE ENTIRE REGION WL PREVENT THIS FROM TURNING INTO A VERY COLD PERIOD. READINGS SHOULD REBOUND DURING THE LATTER PART OF THE PERIOD AS UPR FLOW BECOMES MORE WLY. GULF MOISTURE WL REMAIN TRAPPED WELL S OF THE AREA...AND DON/T SEE ANY STG SYSTEMS IN THE FAST NWLY/WNWLY FLOW EITHER. EVEN THE PROSPECT FOR LAKE-EFFECT LOOKS LOW AS FLOW WL BE RATHER WLY. SO DON/T EXPECT MUCH PCPN DURING THE PERIOD. && .SHORT TERM...TONIGHT AND WEDNESDAY. LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH PRESSURE STRETCHING FROM THE CENTRAL GREAT PLAINS...ACROSS THE GREAT LAKES...AND INTO QUEBEC THIS AFTERNOON. DESPITE THE SURFACE HIGH...LOW CLOUDS OVER WESTERN AND CENTRAL WISCONSIN ARE STUBBORNLY MOVING TO THE NORTHEAST. EARLIER FLURRY ACTIVITY OVER THE DOOR PENINSULA IS ALSO FINALLY STARTING TO MOVE TO THE EAST AS WELL. MEANWHILE...OVER THE LAKE WINNIPEG REGION...A DIVING SHORTWAVE IS SENDING A WARM FRONT TO THE SOUTHEAST. AS THE SURFACE HIGH DRIFTS TO THE SOUTH TONIGHT...CLOUDS AND TEMPS REMAIN THE MAIN FORECAST CONCERNS. TONIGHT...SURFACE HIGH PRESSURE WILL DRIFT TO THE SOUTH AS HEIGHT FALLS OCCUR OVER SOUTH-CENTRAL CANADA AND THE FAR NORTHERN PLAINS. LOW LEVEL SW WINDS WILL STRENGTHEN AND CONTINUE TO PUSH THE LOW STRATUS TO THE NE. BASED ON THE LATEST SATELLITE OBS...TEND TO THINK THE LOW STRATUS WILL STAY IN TACT OVER CENTRAL INTO EAST- CENTRAL WISCONSIN THROUGH MID-EVENING WHILE NORTH- CENTRAL WISCONSIN MAY ACTUALLY TURN PARTLY CLOUDY. UNLESS SOME HOLES DEVELOP LATER THIS AFTERNOON...WILL TREND THE FORECAST THIS DIRECTION. DRIER AIR IS THEN PROGGED TO PUSH THE STUBBORN STRATUS TO THE EAST LATE THIS EVENING AND OVERNIGHT. SOME HIGH CLOUDS MAY ARRIVE LATE AHEAD OF A SHEAR SHORTWAVE DIVING OVER SOUTH-CENTRAL CANADA. THE STRENGTHENING WIND FIELD AND CLOUD COVER WILL KEEP TEMPS WARMER THAN LAST NIGHT...AND WILL GO UPPER SINGLE DIGITS NORTH TO LOWER 20S SE. WEDNESDAY...THE SHEARED WAVE WILL SLIDE SOUTHEAST OVER LAKE SUPERIOR...AND PUSH A WEAKENING COLD FRONT ACROSS THE FORECAST AREA DURING THE MORNING. WILL SEE SOME SCT TO BKN MID CLOUDS WITH THE FRONT...BUT NO REAL THREAT OF SNOW SHOWERS EXCEPT OVER NORTHERN VILAS WHERE WNW WINDS MAY SEND A SCT SNOW SHOWERS ALONG THE U.P.-WISCONSIN BORDER. TEMPS A COUPLE DEGREES WARMER THAN TODAY OFF OF A WARMER START IN THE MORNING. .LONG TERM...WED NGT THROUGH NEXT TUE. TRENDED TEMPS DOWN A LITTLE BOTH THU AND FRI AS FCST AREA WL BE DOMINATED BY COLD AIR FLOWING SEWD FM CANADA. WLY FLOW SHOULD KEEP SIG LAKE-EFFECT NE OF THE AREA. THE CANADIAN GLOBAL MODEL BROUGHT SOME PCPN ACRS E-C WI ON THU NGT INTO FRI AS BAROCLINIC LEAF TYPE FEATURES SLIDES ACRS THE AREA. THE FEATURE WAS ALSO AT LEAST HINTED AT ON THE REST OF THE MODELS...BUT THEY WERE ALL WEAKER AND FARTHER S. SO CANADIAN SEEMS LIKE AN OUTLIER AND WL STICK WITH DRY FCST. && .AVIATION...LOW CLOUDS ARE HANGING TOUGH LATE THIS MORNING OVER WESTERN AND CENTRAL WISCONSIN...THOUGH THERE MAY BE A SLIGHT DIMINISHING TREND OF THE FLURRY ACTIVITY. LOW LEVEL WINDS WILL TURN TO THE SOUTHWEST THIS AFTERNOON...WHICH WILL TEND TO PUSH THE LOW CLOUDS TO THE EAST. AS A RESULT...HAVE MAINTAINED THE LOW END VFR BKN CONDITIONS OVER CENTRAL AND NORTH-CENTRAL TAF SITES THROUGH LATE THIS AFTERNOON AND EARLY THIS EVENING. SOME EROSION IS LIKELY THIS AFTERNOON...BUT QUITE DIFFICULT TO DETERMINE WHERE IT WILL OCCUR. LOW LEVEL DRY AIR WILL FINALLY SURGE INTO THE AREA THIS EVENING WHICH WILL CLEAR SKIES OUT. MID AND HIGH CLOUDS WILL ARRIVE LATE TONIGHT AHEAD OF THE UPPER LEVEL WAVE. THOUGH DO NOT SEE LOW CLOUDS REDEVELOPING...STRENGTHENING SW FLOW WILL LEAD TO LLWS DEVELOPING 09-15Z TOMORROW. MPC && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ MPC/SKOWRONSKI
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
146 PM CST TUE DEC 6 2011 UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE. .SHORT TERM...TODAY THROUGH WEDNESDAY. FORECAST CONCERNS THIS PERIOD...CLOUDS LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH PRESSURE STRETCHING FROM WESTERN LAKE SUPERIOR INTO WESTERN IA. LOWER CLOUD CLEARING OVER MUCH OF EASTERN WI AS DRIER AIR...SEEN ON GRB SOUNDING...WORKING IN. CLOUDS HANGING TOUGH OVER WESTERN PART OF STATE. SURFACE HIGH WILL CONTINUE TO SHIFT OVER STATE TODAY...EXITING TONIGHT WITH COLD FRONT ASSOCIATED WITH LOW MOVING THROUGH NORTHERN CANADA MOVING THROUGH STATE ON WED. QUESTION IS WHAT WILL HAPPEN WITH CLOUDS TODAY. AREA OF CONVERGENCE ASSOCIATED WITH WEAK SURFACE TROF OVER WESTERN WI TO WEAKEN THIS MORNING. SOME MODELS SHOW LOWER CLOUD MOVING BACK INTO EASTERN WI LATE TODAY AS LOW LEVEL WINDS SHIFT TO THE SOUTHWEST LATE. SOME SHOW CLOUD DISSIPATING THROUGH THE DAY AS SUPPORT WEAKENS. HAVE LEANED TOWARDS CANADIAN THAT SHOWS CURRENT CLEARING OVER EASTERN AND NORTH CENTRAL WI...THOUGH WILL STAY WITH PARTLY CLOUDY/PARTLY SUNNY WORDING GIVEN CIRRUS MOVING THROUGH AND SOME UNCERTAINTY. CLOUDS CONTINUE TO MOVE SOUTH OFF LAKE SUPERIOR/MICHIGAN IN THE FAR EAST. THUS CLEARING SLOWED A BIT FROM PREVIOUS FORECAST...THOUGH LITTLE CHANGE MADE IN TEMPERATURE FORECAST. .LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY. MODELS HAD AN UPPER TROUGH OVER MUCH OF THE CONUS EARLY IN THE PERIOD...WITH THE FLOW BECOMING ZONAL OVER THE UPPER GREAT LAKES BY EARLY NEXT WEEK. AN ARCTIC FRONT WILL BRING MUCH COLDER AIR INTO THE FORECAST AREA ON THURSDAY. HAVE A SLIGHT CHANCE OF SNOW SHOWERS IN VILAS COUNTY FOR THE END OF THE WORK WEEK. LAPSE RATES OVER LAKE SUPERIOR SHOULD BE STEEP...BUT WINDS APPEARED TO HAVE TOO MUCH OF A WESTERLY COMPONENT TO GO AS HIGH AS CHANCE POPS. NEAR OR ABOVE NORMAL TEMPERATURES CAN BE EXPECTED BY SUNDAY AS A SURFACE RIDGE PASSES EAST OF THE AREA AND SOUTHWEST WINDS BRING WARMER AIR INTO THE STATE. HAVE SOME SLIGHT CHANCE POPS LATE IN THE PERIOD WITH SHORT WAVE ENERGY AND A SURFACE LOW APPROACHING WISCONSIN. MAY NEED TO GO WITH HIGHER POPS IN THE AFTERNOON FORECAST PACKAGE OR TOMORROW MORNING IF CONDITIONS APPEAR MORE FAVORABLE FOR PRECIPITATION. && .AVIATION...LOW CLOUDS ARE HANGING TOUGH LATE THIS MORNING OVER WESTERN AND CENTRAL WISCONSIN...THOUGH THERE MAY BE A SLIGHT DIMINISHING TREND OF THE FLURRY ACTIVITY. LOW LEVEL WINDS WILL TURN TO THE SOUTHWEST THIS AFTERNOON...WHICH WILL TEND TO PUSH THE LOW CLOUDS TO THE EAST. AS A RESULT...HAVE MAINTAINED THE LOW END VFR BKN CONDITIONS OVER CENTRAL AND NORTH-CENTRAL TAF SITES THROUGH LATE THIS AFTERNOON AND EARLY THIS EVENING. SOME EROSION IS LIKELY THIS AFTERNOON...BUT QUITE DIFFICULT TO DETERMINE WHERE IT WILL OCCUR. LOW LEVEL DRY AIR WILL FINALLY SURGE INTO THE AREA THIS EVENING WHICH WILL CLEAR SKIES OUT. MID AND HIGH CLOUDS WILL ARRIVE LATE TONIGHT AHEAD OF THE UPPER LEVEL WAVE. THOUGH DO NOT SEE LOW CLOUDS REDEVELOPING...STRENGTHENING SW FLOW WILL LEAD TO LLWS DEVELOPING 09-15Z TOMORROW. MPC && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1151 AM CST TUE DEC 6 2011 .SHORT TERM...TODAY THROUGH THURSDAY NIGHT 332 AM CST TUE DEC 6 2011 MAIN FORECAST CONCERNS THIS PACKAGE...CLOUDS AND TEMPERATURES THRU THE PERIOD. DATA ANALYSIS AT 06Z HAD A RIDGE OF HIGH PRESSURE EXTENDING FROM NORTH OF LK SUPERIOR ACROSS MN TO NEB AND WESTERN KS. A LARGE AREA OF LOW PRESSURE WAS LOCATED OVER NORTH-CENTRAL CAN WITH FALLING PRESSURES IN THE NORTHERN PLAINS. STRATUS CLOUDS REMAINS TRAPPED ACROSS THE AREA...UNDER AN INVERSION BETWEEN 850-800MB AND EAST OF THE SFC RIDGE AXIS. WEST EDGE OF THE CLOUDS WAS NEAR A KDLH-KOTG LINE...MAKING VERY SLOW PROGRESS EAST/SOUTH. WEAK SFC-925MB TROUGH AND CONVERGENCE...ALONG WITH THE SLOWLY COOLING LOWER LEVELS CONTINUED TO SQUEEZE SOME FLURRIES/VERY LIGHT SNOW OUT OF THE COLUMN OVER MUCH OF WESTERN WI INTO EXTREME EASTERN MN. NO PROBLEMS NOTED WITH 06.00Z MODEL INITIALIZATIONS. SOLUTIONS QUITE SIMILAR FOR TODAY THRU THU NIGHT...AT LEAST WITH THE SHORTWAVES AND LARGER SCALE FEATURES. MODELS STILL STRUGGLING WITH THE LOWER LEVEL MOISTURE/RH FIELDS AND STRATUS CLOUDS ACROSS THE AREA. DPROG/DT OF 500MB HGTS AT 06.00Z SHOWED MODEL RUNS OF 04.00Z AND 05.00Z VERIFIED QUITE WELL ACROSS NOAM...FAVORING STRONGER OF EARLIER MODELS WITH THE NORTHERN PORTION OF THE TROUGH AND FASTER OF EARLIER MODELS WITH THE SOUTHWEST CONUS PORTION OF THE TROUGH. THRU TODAY/TONIGHT MODELS TREND TOWARD A TIGHTER/FASTER CONSENSUS WITH THE SOUTHERN PORTION OF THE TROUGH MOVING EAST INTO THE MID/LOWER MS VALLEY AND WEAKENING OF THE NORTHERN PORTION OF THE TROUGH AS IT MOVES EAST OF THE REGION. TREND CONTINUES FASTER WITH THE LOWER MS VALLEY TROUGH WED/WED NIGHT AS IT TO THE EAST COAST BY 12Z THU. BETTER CONSENSUS FOR BROAD TROUGHING/NORTHWEST FLOW TO DEVELOP OVER THE NORTH-CENTRAL CONUS/ GREAT LAKES REGION. THIS TROUGH DEEPENS OVER THE MID/UPPER MS VALLEY THU/THU NIGHT...BUT MINOR DIFFERENCES IN THE TIMING/STRENGTH DETAILS DEVELOP BY 12Z FRI. OVERALL BETTER RUN-TO-RUN CONSISTENCY FOR TODAY THRU THU NIGHT SHOWN BY ECMWF...ESPECIALLY WITH THE SOUTHERN STREAM ENERGY EARLY IN THE PERIOD. CHECK OF OBS VS. MODEL DATA AT 06Z SHOWED MODELS ALL QUITE GOOD WITH THE CENTRAL CONUS SFC MASS FIELDS...THOUGH AGAIN CONTINUED TO STRUGGLE WITH THE LOWER LEVEL RH AND STRATUS DECKS TRAPPED ACROSS THE REGION. ECMWF/ RUC LOOK TO BE DOING BEST WITH THE 925MB RH/STATUS CLOUDS OVER MN/ WI/IA WHILE ONLY MODEL SOME INDICATION OF THE FLURRIES WAS THE GFS. THUS NO CLEAR DETERMINISTIC MODEL FAVORITE. WITH MODELS TRENDING TOWARD A TIGHTER CONSENSUS MUCH OF THE PERIOD...FAVORED THE CONSENSUS. SHORT TERM FCST CONFIDENCE AVERAGE TO GOOD THIS CYCLE. IN THE SHORT TERM...LOW CLOUDS/CLEARING REMAIN PROBLEMATIC TODAY/ TONIGHT WITH TYPICAL POOR MODEL PERFORMANCE ON THIS AND THE TIME OF YEAR WHEN LOW CLOUDS LIKE TO HANG TOUGH. MODEL CONSENSUS KEEPS 70+ PERCENT 925MB RH OVER THE CENTRAL/EAST PARTS OF THE FCST AREA THRU THE DAY WITH ONLY SLOW EROSION/ADVECTION ON THE WESTERN SIDE. RAISED CLOUD COVER IN SKY GRIDS TO REFLECT A SLOWER/NON CLEARING TODAY. MOVED THE CLEARING INTO TONIGHT WITH INCREASING WEST SFC- 850MB FLOW NORTH OF THE LOW LEVEL RIDGE AXIS TO FINALLY ADVECT THE MOISTURE EAST AND OUT OF THE AREA. SFC-925MB TROUGH WEAKENS THRU THIS MORNING...BUT GIVEN SLOW MOVEMENT OF THE LOW LEVEL FEATURES... LINGERED SCT FLURRIES OVER THE NORTH HALF OF THE FCST AREA WHERE RADAR REFLECTIVITY/SFC OBS CONTINUED TO DETECT/REPORT FLURRIES AS OF 09Z. REST OF SHORT-TERM PERIOD GENERALLY COOL/QUIET. SHORTWAVE ENERGY PASSES NORTH OF THE FCST AREA WED/WED NIGHT WITH BULK OF FORCING/LIFT AND 850-500MB MOISTURE/SATURATION REMAINING NORTH OF THE FCST AREA. COLD/DRY AIRMASS SETTLES ACROSS THE AREA IN THE WAKE OF THIS SHORTWAVE TROUGH FOR THU/THU NIGHT. THIS AS MORE SHORTWAVE ENERGY DROPS SOUTHEAST ACROSS THE NORTHERN PLAINS FOR THU/THU NIGHT. BULK OF THE LOWER LEVEL THERMO-DYNAMIC FORCING AND INCREASE OF MOISTURE IN THE 925-700MB LAYER REMAINS SOUTH OF THE FCST AREA THU/THU NIGHT. ONLY LINGERED A SMALL -SN CHANCE ACROSS THE EXTREME SOUTH END OF THE FCST AREA THU NIGHT TO BLEND WITH NEIGHBORING GRIDS. SATURATION OF THE COLUMN OVER THE NORTH END OF THE FCST AREA THU/THU NIGHT...NORTH OF THE SHORTWAVE TRACK...AN ISSUE IN THE COLDER COLUMN THERE. MAY YET SEE SCT FLURRIES ALONG/NORTH OF HWY 29 THU/THU NIGHT BUT LEFT THIS DRY FOR NOW. GENERALLY CARRIED PARTLY CLOUDY TO MOSTLY CLEAR SKIES FOR WED THRU THU NIGHT. HIGH/LOW TEMPERATURES PROBLEMATIC WITH SNOW COVERING THE NORTHWEST HALF OF THE FCST AREA WHILE THE SOUTHEAST HALF IS SNOW-FREE. WITH MORE CLOUDS/OVERCAST TODAY...TRENDED HIGHS FOR MINIMAL DIURNAL SWING AND AT OR BELOW NUMERICAL GUIDANCE. WITH PARTLY CLOUDY SKIES TONIGHT BUT SOME SOUTHWEST GRADIENT WINDS...FAVORED A BLEND OF THE GUIDANCE LOWS. SOUTHWEST/WEST WINDS AHEAD OF THE NEXT COLD FRONT AND SOME SUNSHINE WED...TRENDED TOWARD WARMER OF GUIDANCE HIGHS... ESPECIALLY OVER THE SNOW-FREE SOUTHEAST HALF OF THE FCST AREA. APPEARS BOUNDARY LAYER WINDS WILL KEEP LOW LEVELS STIRRED WED NIGHT AND TRENDED TOWARD WARMER OF GUIDANCE LOWS. FAVORED A MODEL CONSENSUS OF HIGHS FOR THU...WHICH BLENDS WELL WITH NEIGHBORING GRIDS BUT MAY BE TOO WARM WITH MDT/STRONG LOW LEVEL COLD ADVECTION OVER THE REGION BY MID-DAY. FAVORED THE MODEL CONSENSUS FOR LOWS THU NIGHT...WHICH ALSO MAY BE TOO WARM IF WINDS ARE LIGHTER THAN EXPECTED ESPECIALLY OVER THE SNOW-COVERED PORTIONS OF THE FCST AREA. .LONG TERM...FRIDAY THROUGH MONDAY 332 AM CST TUE DEC 6 2011 LONG-TERM FCST CONFIDENCE AVERAGE. 06.00Z MEDIUM RANGE MODELS IN REASONABLE AGREEMENT WITH EACH OTHER AND THEIR PREVIOUS RUNS FRI THRU SUNDAY WITH THE LONGWAVE TROUGH BEING PROGRESSIVE AND HGTS RISING OVER THE UPPER MIDWEST FRIDAY INTO SUNDAY. COLD SFC HIGH PRESSURE DRIFTS OVER THE AREA FRI THEN MOVES SOUTH OF THE AREA FOR SAT/SUN. STRONG LOW LEVEL WARM ADVECTION SPREADS ACROSS THE AREA SAT INTO SAT NIGHT WITH 925MB TEMPS IN THE 0 TO +4C RANGE BY 12Z SUN. BELOW/MUCH BELOW NORMAL TEMPS FRI LOOK TO WARM TO ABOVE/MUCH ABOVE NORMAL BY SUN AS BULK OF THE WARM ADVECTION GOES INTO WARMING UNDER PARTLY CLOUDY/MOSTLY SUNNY SKIES. RAISED HIGHS A BIT OVER THE SOUTHEAST HALF OF THE FCST AREA SUN WITH THE LACK OF SNOW COVER. GFS/ECMWF SOLUTIONS DIVERGE FOR MON. ECMWF SLIDES A COLD FRONT AND WEAK LOW LEVEL COLD ADVECTION ACROSS THE AREA WHILE GFS TRACKS A LOW INTO NORTHWEST MN KEEPING THE AREA UNDER LOW LEVEL WARM ADVECTION. EITHER WAY...APPEARS SOME OF THE SNOW COVER WILL MELT SUN AND MON WILL SEE CONTINUED ABOVE NORMAL TEMPS. BIGGEST LONG-TERM QUESTION LOOKS TO BE WILL THERE BE ENOUGH LOWER LEVEL MOISTURE FOR A SMALL PRECIP CHANCE FOR PARTS OF THE AREA BY LATER MON. MODEL CONSENSUS DATA USED IN THE DAY 4-7 FCST GRIDS LOOKS TO HAVE ALL OF THIS WELL TRENDED FOR NOW. && .AVIATION...THROUGH 18Z WEDNESDAY 1151 AM CST TUE DEC 6 2011 BIGGEST CHALLENGE THIS TAF PERIOD ARE CEILINGS AND CLEARING TRENDS AT BOTH TAF SITES. CURRENTLY BAND OF MVFR CEILINGS STRETCHES FROM NORTHEAST IOWA...SOUTHEAST MINNESOTA...AND WESTERN WISCONSIN. INCLUDED A SHORT TEMPO GROUP AT KRST FOR SCATTERED FLURRIES AND SUB-MVFR CONDITIONS UNTIL MAIN RIDGE AXIS PUSHES THROUGH. EXPECTING CLEARING AND VFR CONDITIONS TO EDGE CLOSER TO KRST BY 02Z AND TO KLSE BY 05Z. WESTERN EDGE OF CLOUD COVER SEEMS TO BE MIXING BETTER THIS AFTERNOON...AND CLEARING TREND MAY BE FASTER IF THIS CONTINUES. VFR CONDITIONS WILL PERSIST OVERNIGHT AS WINDS SHIFT TO SOUTHWEST...AHEAD OF A COLD FRONT PROGGED TO MOVE THROUGH THE REGION. FRONTAL PASSAGE EXPECTED AT KRST AT 12Z WED AND AT KLSE AT 15Z. BROKEN MID TO HIGH LEVEL CLOUDS CURRENTLY OVER NORTH DAKOTA WILL MOVE IN THE WAKE OF FRONTAL PASSAGE AND WINDS AHEAD AND BEHIND THE FRONT WILL INCREASE TO 10-15 KT. && .ARX WATCHES/WARNINGS/ADVISORIES... 332 AM CST TUE DEC 6 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM... RRS LONG TERM.... RRS AVIATION...ZT/MW