Forecast Discussions mentioning any of "HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 09/07/12


AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
351 AM PDT WED SEP 5 2012 .SYNOPSIS... TWO SOURCES OF MONSOON MOISTURE WILL MOVE ACROSS SOUTHWEST CALIFORNIA THROUGH THURSDAY. ONE IS COMING FROM THE SOUTHWEST...AND WILL BRING ABUNDANT CLOUDS AND INTERMITTENT LIGHT RAIN SHOWERS THIS MORNING. THE OTHER IS COMING FROM THE SOUTHEAST. THIS SHOULD LEAD TO AFTERNOON AND EVENING THUNDERSTORMS OVER THE MOUNTAINS AND DESERTS WITH LOCALLY HEAVY RAINS. A HIGH PRESSURE RIDGE WILL BUILD WESTWARD ACROSS THE AREA ON FRIDAY...TEMPORARILY BRINGING A DRYING TREND. ANOTHER SURGE OF MONSOON MOISTURE IS POSSIBLE OVER THIS COMING WEEKEND. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .THIS MORNING THROUGH EARLY AFTERNOON... EMBEDDED SHORT WAVE IN THE MID/HIGH LEVEL MONSOON MOISTURE STREAM COMING IN FROM THE SOUTHWEST IS CAUSING 40-45 DBZ RADAR ECHOES OVER THE SOUTHERN CALIFORNIA BIGHT. USING LAST NIGHT AS AN ANALOG WHEN SIMILAR STRENGTH ECHOES MOVED ACROSS SANTA BARBARA/VENTURA/LOS ANGELES/KERN COUNTIES...THEN SHOULD ONLY SEE LIGHT INTERMITTENT RAIN WEST OF THE MOUNTAINS THIS MORNING. THE HRRR MODEL COMPOSITE REFLECTIVITY MATCHES HAS BEEN DOING VERY WELL WITH THE POSITION AND OBSERVED STRENGTH OF THE RADAR ECHOES. USING THIS MODEL ALSO YIELDS LIGHT RAINFALL...STARTING AROUND 0700 PDT FOR THE ORANGE COUNTY COAST...SPREADING INLAND BY 1100 PDT TO INLAND EMPIRE AND NORTH SAN DIEGO COUNTY. FOR THE EARLY AFTERNOON...SUBSIDENCE FOLLOWING THE SHORT WAVE SHOULD RESULT IN LESS MID/HIGH LEVEL CLOUDS AND END SHOWER ACTIVITY WEST OF MOUNTAINS. OVER MOUNTAINS AND DESERTS...WETTER MID/LOW LEVELS DUE TO MONSOON MOISTURE STREAM FROM THE SOUTHEAST SHOULD YIELD MEASURABLE RAINFALL AMOUNTS THIS MORNING...BUT THUNDERSTORM DEVELOPMENT WILL LIKELY BE DELAYED UNTIL MID AFTERNOON DUE TO EXTENSIVE CLOUD COVER THIS MORNING. .MID AFTERNOON THROUGH EARLY EVENING... MOUNTAINS AND DESERTS HAVE A SLIGHTLY GREATER RISK OF FLASH FLOODING TODAY...ASSUMING ENOUGH CLEARING TAKES PLACE TO ALLOW DEVELOPMENT OF CONVERGING DIURNAL WINDS AND RESULTANT LIFTING. THE PRECIPITABLE WATER VALUES RANGE FROM 1.25 TO ALMOST 2 INCHES. THE STEERING WINDS WILL INITIALLY BE FROM THE SOUTH AND THEN SHIFT TO SOUTHWEST. THIS WOULD CARRY THE THUNDERSTORMS DOWN THE DESERT SLOPES...ADDING ADDITIONAL RAINFALL TO THE LOWER END OF DRAINAGE BASINS AT THE SAME TIME THAT RUNOFF IS COMING DOWN FROM THE HEADWATERS. NO FLASH FLOOD WATCH AT THIS TIME BUT STAY TUNED FOR UPDATE LATE THIS MORNING. .TONIGHT THROUGH THURSDAY... PRETTY MUCH FORECASTING PERSISTENCE...ALTHOUGH WITHOUT THE THREAT OF MORNING RAIN WEST OF THE MOUNTAINS. AS NOTED IN PREVIOUS FORECAST DISCUSSION...AMPLE MID-LEVEL MOISTURE REMAINS THROUGH THURSDAY WITH PRECIPITABLE WATER VALUES GREATER THE 1.5 INCHES...TRANSPORT WINDS ARE LIGHT SOUTHWESTERLY SO THUNDERSTORMS THAT DO FORM THURSDAY AFTERNOON COULD STILL PRODUCE LOCALLY HEAVY DOWNPOURS. FRIDAY/SATURDAY... FORECASTING LESS THUNDERSTORM ACTIVITY AND SLIGHT INCREASE IN LATE NIGHT/EARLY MORNING LOW CLOUDS WEST OF MOUNTAINS DUE TO HIGH PRESSURE RIDGE BUILDING ALOFT AND CLOSING DOOR ON MONSOON MOISTURE. HOWEVER ENOUGH RESIDUAL MID LEVEL MOISTURE AND DAYTIME HEATING FOR ISOLATED THUNDERSTORM DEVELOPMENT. SUNDAY/MONDAY... MONSOON DOOR REOPENS FOR ANOTHER SURGE AS AN EASTERLY WAVE/UPPER LOW TRACKS AROUND THE SW QUADRANT OF THE HIGH CELL AND MOVES ACROSS NORTHERN BAJA CALIFORNIA/SOUTHWEST CALIFORNIA. HAVE ADDED SOME POPS...AROUND 20 PERCENT...AND MENTION OF THUNDERSTORMS FOR MOUNTAINS AND DESERTS ON THESE DAYS. TUESDAY... GOING WITH THE TROUGH IN THE WESTERLIES FINALLY MOVING CLOSE ENOUGH TO BRING DRIER AIR IN FROM THE WEST. LOOK FOR MOSTLY SUNNY/CLEAR SKIES OVER MOUNTAINS AND DESERTS WITH SLIGHT COOLING...AND MORE NIGHT/MORNING CLOUDS FOR COASTS AND WESTERN VALLEYS. && .AVIATION... 050930Z...PATCHY STRATUS...WITH BASES AROUND 800 FT MSL AND TOPS NEAR 1100 FT MSL...IS HAVING DIFFICULTY DEVELOPING AND MAY STEER CLEAR OF COASTAL AERODROMES THIS MORNING. VERY LIGHT SHOWERS ARE CURRENTLY OVER THE PACIFIC...MOVING TOWARD THE COAST THIS MORNING. PRECIPITATION FALLING FROM THESE SHOWERS WILL MOST LIKELY ONLY CREATE A TRACE AT THE SURFACE. ISOLATED TO SCATTERED SHOWERS AND TSTMS ARE EXPECTED THIS AFTERNOON AND EVENING OVER THE MTNS AND DESERTS...WITH BASES AROUND 8K FT MSL AND TOPS AROUND 40K FT MSL. OTHERWISE...VFR CONDS WITH SCT/BKN CLOUDS AOA 10K FT AND UNRESTRICTED VIS THROUGH THU MORNING. && .FIRE WEATHER... A POCKET OF VERY DRY AIR REMAINS OVER THE FOOTHILLS AND LOWER COASTAL SLOPES AT ELEVATIONS BETWEEN 1000 FEET AND 3500 FEET MSL. RELATIVE HUMIDITY IN THIS LAYER HAS BEEN IN THE SINGLE DIGITS WITH LITTLE TO NO RECOVERY OVERNIGHT FOR AT LEAST THE PAST 6 DAYS. THIS DRY AIR MAY FINALLY BE MODIFIED TODAY IF THE INTERMITTENT LIGHT RAIN SHOWERS DO OCCUR AS FORECAST. ELSEWHERE RELATIVE HUMIDITY SHOULD BE HIGH ENOUGH TO RETARD FIRE GROWTH FROM ANY LIGHTNING OUTSIDE OF WETTING RAIN AREAS...AND INITIAL ATTACK FORCES MAY BE NEED TO ASSIST WITH OTHER HAZARDS ASSOCIATED WITH THUNDERSTORMS...SUCH AS FLASH FLOODING. .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE AT THIS TIME. PZ...NONE. && $$ PUBLIC/FIRE WEATHER...BALFOUR AVIATION/MARINE...JJT
AREA FORECAST DISCUSSION
NWS SAN JOAQUIN VALLEY - HANFORD CA
120 AM PDT WED SEP 5 2012 .SYNOPSIS... MOISTURE FROM THE TROPICS WILL STREAM INTO THE REGION THROUGH THURSDAY PRODUCING ISOLATED SHOWERS AND THUNDERSTORMS TO PARTS OF THE AREA. BY FRIDAY, DRIER AIR WILL MOVE IN FROM THE WEST, BRINGING AN END TO THE THUNDERSTORM THREAT. && .DISCUSSION...I VERY COMPLICATED PATTERN THIS MORNING TO SAY THE LEAST. SATELLITE IMAGERY SHOWS ONE OF THE MORE PRONOUNCED INFLUXES OF TROPICAL MOISTURE INTO SOUTHERN CALIFORNIA IN QUITE A WHILE. OF NOTE IS THE WIND SHEAR DEPICTED BY LOWER LEVEL CLOUDS MOVING NORTHWEST ON SOUTHEAST WINDS WHILE THE MAIN CLOUD AND MOISTURE LAYER MOVES NORTHEAST ON SOUTHWEST WINDS. IF THIS ISN`T ENOUGH DIRECTIONS TO MAKE YOU DIZZY I DON`T KNOW WHAT WILL! ANYWAY, THE MAIN MOISTURE FEED IS COMING FROM THE REMNANTS OF TROPICAL SYSTEM JOHN AND PER THE SAN DIEGO SOUNDING THE LAYER IS RATHER DEEP, EXTENDING FROM AROUND 9000 FEET AT THE BOTTOM TO AROUND 16000 FEET AT THE TOP. THE MAIN FORECAST PROBLEM IS JUST HOW FAR NORTH THIS MOISTURE RICH BAND WILL MIGRATE AND THE ASSOCIATED THREAT OF ELEVATED CONVECTION AS WELL AS THE THREAT OF RAIN SHOWERS OVER THE ENTIRE CENTRAL CALIFORNIA INTERIOR. IN THE VERY SHORT TERM, THE RUC13 MATCHES UP WELL WITH THE SAN DIEGO SOUNDING IN SHOWING THE MOISTURE SITTING JUST ABOVE 700 MB. THE RUC TRANSPORT WINDS AT 700 MB ARE PRONOUNCED SOUTHEAST AND IF MOISTURE WAS ABUNDANT AT THIS LEVEL THE ADVECTION INTO CENTRAL CALIFORNIA WOULD BE SIMPLE. GIVEN THAT THE DEEPER MOISTURE LIES ABOVE 700 MB FOR TODAY THE PROBLEM IS GETTING THIS DEEPER MOISTURE NORTHWARD INTO THE FORECAST AREA FOR ANY CONVECTIVE THREAT. WATER VAPOR IMAGERY SHOWS SOME INTERESTING THINGS OCCURRING OFF OF THE CENTRAL COAST. IT APPEARS A BAROCLINIC LEAF IS DEVELOPING AND A BACKING OF THE FLOW FROM THE WEST TO THE SOUTH IS OCCURRING. THIS WILL HELP TO PULL THE MID LEVEL MOISTURE FROM SOUTH OF POINT CONCEPTION NORTHWARD AND LIFT THE SOUTHWEST FLOW "MOISTURE FETCH" (REMEMBER ALL SOUTHWEST FLOW IS NOT DRY) WELL INTO CENTRAL CALIFORNIA BY TONIGHT. FOR THURSDAY FORECAST MODELS ARE NOW BRINGING MUCH MORE MOISTURE INTO CENTRAL CALIFORNIA WITH THE BRUNT MOVING UP THE COASTAL RANGE AND WEST SIDE OF THE FORECAST AREA. WILL OPT TO INTRODUCE THE CHANCE OF THUNDERSTORMS TO EVEN THE SAN JOAQUIN VALLEY TONIGHT AND CONTINUE THROUGH THURSDAY. GIVEN THE TREND OF MODELS TO HOLD ON TO THE MOISTURE INTO FRIDAY. TEMPERATURES WILL BE HIGHLY DEPENDENT ON CLOUD COVER SO WILL LIKELY HAVE ISSUES PINNING DOWN MAX TEMPS FOR THE NEXT COUPLE OF DAYS. WILL GIVE IT MY BEST SHOT AND SEE HOW IT GOES. WITH THIS FRONT LOADED FORECAST, A QUICK GLIMPSE INTO NEXT WEEK SHOWS A RIDGE THAT JUST DOESN`T WANT TO GIVE UP. MAYBE SOME COOLING BY MID WEEK BUT I AM NOT THAT CONFIDENT. && .AVIATION... ISOLATED THUNDERSTORMS ARE POSSIBLE IN THE MOUNTAINS THIS AFTERNOON AND TONIGHT IN ADDITION TO THE FOOTHILLS WEST OF INTERSTATE 5 AND THE KERN COUNTY DESERT. OTHERWISE...VFR CONDITIONS WILL PREVAIL ACROSS THE CENTRAL CALIFORNIA INTERIOR UNTIL 12Z THURSDAY.&& .AIR QUALITY ISSUES... ON WEDNESDAY SEPTEMBER 5 2012... UNHEALTHY FOR SENSITIVE GROUPS IN FRESNO AND KERN COUNTIES AND SEQUOIA NATIONAL PARK AND FOREST. FURTHER INFORMATION IS AVAILABLE AT VALLEYAIR.ORG && .CERTAINTY... THE LEVEL OF CERTAINTY FOR DAYS 1 AND 2 IS LOW. THE LEVEL OF CERTAINTY FOR DAYS 3 THROUGH 7 IS MEDIUM. THIS INFORMATION IS PROVIDED AS PART OF A TRIAL PROJECT CONDUCTED BY THE NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD. CERTAINTY LEVELS INCLUDE LOW...MEDIUM...AND HIGH. PLEASE VISIT WWW.WEATHER.GOV/HNX/CERTAINTY.PHP /ALL LOWER CASE/ FOR ADDITIONAL INFORMATION AND/OR TO PROVIDE FEEDBACK. && .HNX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ PUBLIC...DUDLEY AVN/FW...DURFEE SYNOPSIS...WP WEATHER.GOV/HANFORD
AREA FORECAST DISCUSSION
NWS SAN JOAQUIN VALLEY - HANFORD CA
931 PM PDT TUE SEP 4 2012 .SYNOPSIS... MOISTURE FROM THE TROPICS WILL STREAM INTO THE REGION THROUGH THURSDAY PRODUCING ISOLATED SHOWERS AND THUNDERSTORMS TO PARTS OF THE AREA. BY FRIDAY, DRIER AIR WILL MOVE IN FROM THE WEST, BRINGING AN END TO THE THUNDERSTORM THREAT. && .DISCUSSION... NO UPDATE THIS EVE. MID LEVEL MOISTURE...PARTIALLY FROM THE REMNANTS OF FORMER TS/S ILEANA AND JOHN...ARE VERY SLOWLY WORKING N-NE. ISOLD CONVECTION IN THE SRN SIERRA THIS AFTN SHOULD REPEAT WED. SEVERAL SITES IN THE SJV AND HIGH DESERT RECORDED AFTN HIGHS OF 100(+) TODAY. LITTLE CHANGE EXPECTED WED...THO THERE COULD BE A FEW MORE CLOUDS TO HOLD TEMPS UNDER 100. THATS A BIG IFFF. NOT A CONFIDENCE BUILDING UPPER LEVEL PATTERN ACROSS CENTRAL CA...AS REGION IS LOCKED BETWEEN THE LARGE DOMINANT E-W RIDGE STRADDLING THE U.S./MEX BRDR FROM TX TO SOCAL...AND A SEEMINGLY PERMANENT LOW OFF THE NORCAL COAST. THE FCST PROBLEM IS WHERE WILL THE DRY/MOIST INTERFACE BE WITH TIME...AND PRECIP/NO PRECIP LINE. && .PREV DISCUSSION... /ISSUED 324 PM PDT TUE SEP 4 2012/ SCT TO BKN CLOUDS ACROSS THE CENTRAL SJV AND INTO THE TULARE COUNTY MOUNTAINS TODAY. TEMPERATURES ACROSS THE SJV ARE APPROACHING THE CENTURY MARK IN A FEW LOCATIONS. NO PRECIP HAS BEEN REPORTED WITH THE CLOUD COVER THIS AFTERNOON IN THE VALLEY AND ONLY A FEW HUNDREDTHS IN THE TULARE COUNTY FOOTHILLS AND MOUNTAINS. THE FORECAST CALLS FOR PARTLY CLOUDY SKIES TONIGHT OVER THE CENTRAL CA INTERIOR. VISIBLE SATELLITE IMAGERY INDICATES A LINE OF SHOWERS OFF THE NRN BAJA COAST THAT IS MOVING NORTH. SOME SHOWERS HAVE DEVELOPED IN THE SOUTH LAND THIS AFTERNOON. THE KERN DESERT AND MOUNTAINS REMAIN RAIN FREE THIS AFTERNOON AS RUC SHOWS STABLE ATMS. A FEW LIGHTNING STRIKES ARE OCCURRING IN THE FRESNO COUNTY MOUNTAINS ATTM AS A CLUSTER OF STORMS QUICKLY MOVES EAST. SW FLOW ALOFT IS FORECAST TO CONTINUE THIS WEEK WITH RISING HEIGHTS AND TEMPERATURES CONTINUING ABOVE NORMAL THROUGH THE WEEKEND. THE UPPER RIDGE WILL MOVE INTO SRN CA BY SAT AND REMAIN THERE UNTIL MONDAY BEFORE IT DRIFTS BACK TO THE EAST AS ANOTHER SURGE OF MOISTURE APPROACHES THE AREA BY NEXT TUESDAY. THE ECMWF IS MORE AGGRESSIVE WITH THE MOISTURE ON NEXT TUESDAY THAN THE GFS. && .AVIATION... VFR CONDITIONS WILL PREVAIL ACROSS THE CENTRAL CALIFORNIA INTERIOR THROUGH 18Z WED. AFTER 18Z WED...A SLIGHT CHANCE OF THUNDERSTORMS WILL BEGIN DEVELOPING OVER THE COAST RANGE...SOUTHERN SIERRA NEVADA...TEHACHAPI RANGE AND KERN COUNTY DESERTS AND CONTINUE THRU 06Z THU. && .AIR QUALITY ISSUES... ON WEDNESDAY SEPTEMBER 5 2012... UNHEALTHY FOR SENSITIVE GROUPS IN FRESNO AND KERN COUNTIES AND SEQUOIA NATIONAL PARK AND FOREST. FURTHER INFORMATION IS AVAILABLE AT VALLEYAIR.ORG && .CERTAINTY... THE LEVEL OF CERTAINTY FOR DAYS 1 AND 2 IS MEDIUM. THE LEVEL OF CERTAINTY FOR DAYS 3 THROUGH 7 IS LOW. THIS INFORMATION IS PROVIDED AS PART OF A TRIAL PROJECT CONDUCTED BY THE NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD. CERTAINTY LEVELS INCLUDE LOW...MEDIUM...AND HIGH. PLEASE VISIT WWW.WEATHER.GOV/HNX/CERTAINTY.PHP /ALL LOWER CASE/ FOR ADDITIONAL INFORMATION AND/OR TO PROVIDE FEEDBACK. && .HNX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ PUBLIC...BINGHAM AVN/FW...DS SYNOPSIS...WP WEATHER.GOV/HANFORD
AREA FORECAST DISCUSSION
NWS NEW YORK NY
1025 PM EDT THU SEP 6 2012 .SYNOPSIS... A WEAK COLD FRONT APPROACHES THIS EVENING AND THEN DISSIPATES ACROSS THE TRI-STATE AREA ON FRIDAY. A MUCH STRONGER COLD FRONT THEN APPROACHES ON SATURDAY...PASSING THROUGH THE AREA LATE SATURDAY NIGHT INTO EARLY SUNDAY MORNING. HIGH PRESSURE WILL FOLLOW THROUGH THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 955 PM UPDATE...CONVECTION WEAKENING OVER UPSTATE NY...BUT THE REMNANTS ARE STILL ROBUST ENOUGH TO PERHAPS SURVIVE AS THEY REACH THE PORT JERVIS AREA. RADAR TIMING IS JUST BEFORE 3Z. HAVE MAINTAINED SLIGHT CHANCES IN THIS AREA TIL 4Z. ELSEWHERE...SOME STRATUS ALREADY VISIBLE ON 11-3.9 STLT OVER SERN CT...SO THE FOG IS EXPECTED TO NOT BE TOO FAR BEHIND. CLEAR SLOT OVER THE CWA SHOULD HELP DEVELOPMENT THRU MIDNIGHT...BUT CONVECTIVE DEBRIS IS ON THE DOORSTEP. THIS MAY LIMIT THE FOG THREAT LATE IF ENOUGH OF THIS HOLDS TOGETHER. FCST THEREFORE CONTINUES ONLY PATCHY WORDING. MID LVL WAVE ACROSS NRN PA MAY PROVIDE ENOUGH LIFT FOR AN ISOLD ELEVATED TSTM OVERNIGHT...BUT WITH THE HRRR TRENDING DRY AND THE 00Z NAM JUST ROLLING IN DRY...WILL CONCUR WITH THE PREV FCST AND KEEP THE CWA DRY THRU THE OVERNIGHT. USED A BLEND OF MET/MAV FOR OVERNIGHT LOWS...RANGING FROM THE LOW TO MID 60S IN THE SUBURBS...TO AROUND 70 METRO NY. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... WEAK FRONT DISSIPATES AND/OR LIFTS BACK TO THE NORTH OF THE AREA AS A WARM FRONT BY EARLY AFT. ONCE AGAIN...LIFT AND INSTABILITY ARE WEAK WITH THE POSSIBILITY OF AN ISOLATED SHOWER/THUNDERSTORM AT ANYTIME. PREFERENCE REMAINS TO KEEP IT OUT OF THE FORECAST. PARTLY TO MOSTLY CLOUDY SKIES IN THE MORNING WILL GIVE WAY TO MOSTLY SUNNY SKIES IN THE AFT. IT LOOKS LIKE ANOTHER WARM...MUGGY DAY FOR THE TRI-STATE AREA WITH HIGHS TOPPING OUT 5 TO 8 DEGREES ABOVE NORMAL...LOWER 80S COAST TO NEAR INLAND/METRO NY. LOWS FRI NIGHT WILL BE AROUND 70 FOR MOST LOCATIONS. LOW CLOUDS/PATCHY FOG ONCE AGAIN POSSIBLE SAT MORNING...ESPECIALLY WITH A STRENGTHENING SLY FLOW. USED A BLEND OF MAV/MET MOS AS EACH WAS WITHIN A COUPLE OF DEGREES OF ONE ANOTHER...WITH MODELS IN GENERALLY GOOD AGREEMENT. AN AIR QUALITY ALERT FOR OZONE HAS BEEN ISSUED BY CT FOR FAIRFIELD COUNTY ON FRIDAY. THERE IS A HIGH RISK FOR RIP CURRENTS AT OCEAN BEACHES THROUGH FRIDAY. && .LONG TERM /SATURDAY THROUGH THURSDAY/... DEEP BROAD TROUGH OVER THE MIDWEST AND OHIO VALLEY ON SAT WILL TRACK TOWARDS THE EAST COAST SAT NIGHT INTO SUNDAY. MEANWHILE...HURRICANE LESLIE OVER THE OPEN ATLANTIC WATERS...WILL TURN TO THE NORTH AND INCREASE IN FORWARD SPEED THIS WEEKEND INTO EARLY NEXT WEEK AS SHE IS PICKED UP IN THE STRONGER UPPER FLOW. MEDIUM RANGE MODELS ARE IN DECENT AGREEMENT WITH UPPER PATTERN...EC BEING THE SLOWEST TO LIFT THE TROUGH THROUGH AND GFS THE FASTEST ALTHOUGH IT HAS SLOWED SOME SINCE YESTERDAYS RUNS. DOWNSTREAM AMPLIFICATION OF A BROAD UPPER RIDGE WOULD TEND TO SUPPORT THE SLOWER SOLNS AND HAVE GIVEN MORE WEIGHT. STRENGTHENING SFC LOW PRES NEAR THE LOWER GREAT LAKES SAT MORNING WILL LIFT INTO SOUTHERN QUEBEC BY SUN MORNING. WAA SHOWERS AND POSSIBLY A FEW TSTMS ON SAT WITH A WEAK WARM FROPA...BUT INCREASING LLJ AND RRQ OF 90+ KT UPPER LEVEL JET AND A DECENT MID LEVEL VORT APPROACHING WITH A SFC COLD FRONT WILL RESULT IN AN INCREASED LIKELIHOOD FOR SHOWERS AND TSTMS SAT NIGHT. MAIN THREAT WILL BE HEAVY RAINFALL WITH PWATS INCREASING TO 1.5 TO 2 INCHES DURING THE EVENING HOURS AND TALL SKINNY CAPE PROFILES. HOWEVER...SOME STRONG STORMS CANNOT BE RULED OUT WITH A WEAK CAPE STRONG SHEAR TYPE ENVIRONMENT THAT IS EXPECTED TO BE PRESENT. EASTERN PORTIONS OF THE FORECAST AREA MAY HAVE SHOWERS/TSTMS LINGER INTO SUN...BUT THE MAIN ACTIVITY SHOULD BE EAST OF THE AREA WITH DRYING CONDITIONS AS A RESULT OF DEEP NW FLOW FROM W TO E. LESLIE PASSES WELL TO THE EAST OF THE FORECAST AREA EARLY NEXT WEEK...MAKING HER CLOSEST APPROACH ON MON. THE IMPACTS EXPECTED THROUGH THIS TIME ARE HIGH SURF...BEACH EROSION...AND DANGEROUS RIP CURRENTS. FOR THE LATEST INFORMATION ON LESLIE...PLEASE REFER TO THE NATIONAL HURRICANE CENTERS FORECAST PRODUCTS. BREEZY CONDITIONS LIKELY ON MONDAY AS THE AREA IS CAUGHT BETWEEN LESLIE PASSING TO THE EAST AND HIGH PRES BUILDING IN FROM THE WEST. OTHERWISE...THE FIRST HALF OF NEXT WEEK LOOKS DRY AS THE HIGH DOMINATES. ABOVE NORMAL TEMPS AND HUMID CONDITIONS LIKELY THROUGH SAT NIGHT...NEAR SEASONABLE SUN...THEN SLIGHTLY BELOW NORMAL LEVELS THROUGH THE REST OF THE FORECAST PERIOD. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... FOR OVERNIGHT...LOW STRATUS WITH IFR CIGS IS BEGINNING TO EXPAND WESTWARD ACROSS SOUTHERN CT FROM KGON TO NEAR KBDR...AS LIGHT ONSHORE FLOW OF MOIST AIR EXPERIENCES WEAK LIFT ALONG COASTLINES. WILL HAVE TO KEEP AN EYE ON KISP/KJFK FOR BRIEF OCCURRENCE OF THESE CONDS AS WELL. EXCEPT FOR KGON...THESE LOW CIGS MAY NOT LAST VERY LONG...AS STRONGER W-NW WINDS JUST OFF THE SFC IN THE WAKE OF A WEAK SFC TROUGH PASSAGE MAY SCATTER THEM OUT AFTER ABOUT 05Z. OTHERWISE...RADIATIONAL COOLING UNDER MOSTLY CLEAR SKIES MAY PRODUCE SOME LATE NIGHT MIST WITH MVFR VSBY AT SOME OUTLYING TERMINALS. FOR FRIDAY...VFR THROUGHOUT BY 13Z-14Z. A SLIGHTLY STRONGER S FLOW WILL DEVELOP AHEAD OF AN APPROACHING FRONTAL SYSTEM. A LATE DAY TSTM IS POSSIBLE NW OF NYC. KSWF MOST LIKELY TO EXPERIENCE IMPACTS. OUTLOOK FOR 00Z SAT THROUGH TUE... .FRI NIGHT-SAT MORNING...MVFR OR LOWER CONDS LIKELY IN LOW STRATUS AND/OR FOG...ESPECIALLY ALONG THE COAST. .SAT AFTERNOON-NIGHT...GUSTY S-SW FLOW AT NYC METRO AND COASTAL SITES. COLD FROPA SAT NIGHT SHOULD BE PRECEDED BY LINE OF TSTMS THAT COULD BRING IFR CONDS IN HEAVY RAIN AND STRONG WINDS. .SUNDAY...MORNING MVFR CONDS IN SHOWERS MAINLY E OF NYC METRO...OTHERWISE VFR. .MON-TUE...VFR. && .MARINE... SE SWELL FROM HURRICANES LESLIE AND MICHAEL WELL OUT IN THE ATLANTIC WILL KEEP SEAS ON THE OCEAN WATERS AT MARGINAL SCA LEVELS THE NEXT COUPLE OF DAYS. IN ADDITION...THE SWELL WILL PROVIDE FOR ROUGH CONDITIONS IN AND AROUND INLETS. FOR FURTHER DETAILS...REFER TO THE LATEST FORECASTS/ADVISORIES ISSUED FROM THE NATIONAL HURRICANE CENTER. SWELLS ARE EXPECTED TO CONTINUE TO AFFECT THE OCEAN WATERS THIS WEEKEND AND INTO EARLY NEXT WEEK WITH SCA CONDITIONS LIKELY. LESLIE MAKES HER CLOSEST APPROACH ON MON...BUT WILL REMAIN WELL E OF THE WATERS. OTHERWISE...A STRONG COLD FRONT WILL TRACK THROUGH THE WATERS SAT NIGHT. AN INCREASING PRESSURE GRADIENT WILL LIKELY RESULT IN SCA WIND GUSTS ON THE WATERS...BUT THERE IS THE POSSIBILITY THAT WIND GUSTS COULD REACH GALE FORCE. MODEL DISCREPANCIES BETWEEN STRENGTH OF LLJ AND HOW MUCH OF IT CAN MIX TO THE SFC WILL PLAY A ROLE. HIGH PRES BUILDS IN BEHIND THE FRONT WITH SUB-ADVY CONDS EXPECTED ON NON-OCEAN WATERS FOR THE REMAINDER OF THE PERIOD. && .HYDROLOGY... MOST LOCATIONS WILL SEE LITTLE OR NO PRECIPITATION THROUGH FRIDAY. HOWEVER...THERE IS THE POTENTIAL FOR LOCALLY MODERATE TO HEAVY RAINFALL AT ANY LOCATION EXPERIENCING ISOLATED STRONG CONVECTION DURING THIS TIME FRAME. A COLD FRONT MOVING THROUGH THE AREA THIS WEEKEND HAS THE POTENTIAL TO PRODUCE A GENERAL ONE INCH RAINFALL...WITH LOCALLY UP TO 2 INCHES. THERE IS STILL SOME UNCERTAINTY ON THE PROGRESSION OF THE FRONT AND THEREFORE QPF AMOUNTS. A SLOWER PROGRESSION WOULD INCREASE THE POTENTIAL FOR INTERACTION WITH DEEP TROPICAL MOISTURE WELL AHEAD OF LESLIE...AND AN ENHANCED RAINFALL EVENT. THIS IS A REMOTE POSSIBILITY AT THIS TIME. OVERALL THOUGH...HEAVY DOWNPOURS AND ISOLATED CONVECTION SAT EVE INTO SAT NIGHT WILL MAINLY PRESENT A MINOR URBAN AND SMALL STREAM FLOODING THREAT...AND AN ISOLATED FLASH FLOOD THREAT FROM TRAINING CONVECTION. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT SATURDAY FOR ANZ350-353-355. && $$ SYNOPSIS...24/DW NEAR TERM...JMC/DW SHORT TERM...DW LONG TERM...24 AVIATION...GOODMAN MARINE...24/DW HYDROLOGY...24/DW
AREA FORECAST DISCUSSION
NWS COLUMBIA SC
1055 AM EDT WED SEP 5 2012 .SYNOPSIS... UPPER LEVEL TROUGH ASSOCIATED WITH THE REMNANTS OF ISAAC WILL CONTINUE TO GIVE OUR AREA WARM AND HUMID WEATHER WITH CHANCES OF SHOWERS AND THUNDERSTORMS THROUGH THURSDAY. THE UPPER TROUGH WILL SHIFT OFFSHORE BY THURSDAY AS A COLD FRONT APPROACHES FROM THE WEST ON FRIDAY. THIS WILL BRING ANOTHER CHANCE OF SHOWERS AND THUNDERSTORMS TO THE AREA FOR THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A FEW SHOWERS STARTING TO DEVELOP IN THE UPSTATE LATE THIS MORNING. IR/WV SATELLITE IMAGERY SHOWS MAINLY LOW AND MID LEVEL CLOUDINESS ASSOCIATED WITH UPPER TROUGH WHICH HAS WEAKENED AND NOW CONTAINS LESS DEEP TROPICAL MOISTURE. THE WV CURVE ACTUALLY SHOWS SOME DRIER AIR INTERACTING WITH UPPER LOW IN THE WESTERN PORTION OF THE FORECAST AREA. DECIDED TO LOWER POPS ABOUT 4-5 PERCENT BECAUSE EXPECT LESS COVERAGE. WILL CONFINE 40 PERCENT TO NORTH AND WEST OF CAE AREA AND KEEP CLOSE TO 30 PERCENT REST OF AREA. AFTERNOON HIGHS MAINLY IN THE UPPER 80S STILL OK. SPC HAS REGION IN SEE TEXT BUT WITH RUC AND NAM FORECAST SOUNDINGS SHOWING SOME DRYING ALOFT...COULD NOT RULE OUT ISOLATED STORMS WITH STRONG DOWNDRAFTS IF ATMOSPHERE BECOMES UNSTABLE ENOUGH. RIGHT NOW MODELS ONLY SHOW MEAGER INSTABILITY WITH LIS -2/-4 AND CAPES AROUND 1000 J/KG. SPC DOWNDRAFT CAPES LOW LESS THAN 800. SO CHANCES FOR SEVERE STORMS REMAIN QUITE LOW. OTHERWISE...PWS ARE STILL UP AROUND 2 INCHES. SO THE THREAT FOR SOME HEAVY RAIN CONTINUES MUCH LIKE PREVIOUS DAYS. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... CONVECTIVE ACTIVITY WILL DIMINISH WITH SUNSET AS THE MOISTURE PLUME AND UPPER LEVEL TROUGH CONTINUE TO SLOWLY SWING INTO THE FORECAST AREA. BY THURSDAY AFTERNOON THE UPPER LEVEL TROUGH WILL BE CENTERED OVER THE REGION AND SLIDE TO THE COAST THURSDAY NIGHT. THIS WILL ALLOW SLIGHTLY DRIER AIR TO MOVE INTO THE NORTHERN MIDLANDS ON FRIDAY AS THE CHANCE OF SHOWERS MOVES TOWARD THE COAST. THIS WILL RESULT IN MAINLY DIURNAL SHOWERS AND THUNDERSTORMS OVER THE AREA EACH AFTERNOON WITH ACTIVITY DIMINISHING WITH THE LOSS OF HEATING. WITH THE MOISTURE PLUME ALSO WEAKENING THE CHANCE OF LOCALIZED HEAVY RAINFALL WILL CONTINUE TO LESSEN. TEMPERATURES WILL GENERALLY BE IN THE UPPER 80S TO AROUND 90 WITH OVERNIGHT LOWS IN THE LOWER 70S. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... MODELS ARE IN GOOD AGREEMENT THROUGH THE LONG TERM WITH SOME MINOR DIFFERENCES IN TIMING WITH THE FRONTAL SYSTEM FOR THE WEEKEND. PATTERN WILL REMAIN ACTIVE THROUGH THE FIRST HALF OF THE LONG TERM AS LOW PRESSURE PUSHES THROUGH THE GREAT LAKES REGION AND A COLD FRONT CROSSES THE EASTERN US SATURDAY AND SUNDAY. THIS WILL RESULT IN A CHANCE OF SHOWERS AND THUNDERSTORMS SATURDAY AND SUNDAY WITH THE FRONT MOVING OFFSHORE SUNDAY NIGHT. BEHIND THE FRONT HIGH PRESSURE ALONG WITH COOLER AND DRIER AIR WILL MOVE INTO THE REGION WITH OVERNIGHT LOW TEMPERATURES EXPECTED TO FALL IN TO THE LOWER 60S. THE HIGH PRESSURE WILL REMAIN DOMINANT OVER THE AREA FROM SUNDAY NIGHT THROUGH TUESDAY. TEMPERATURES THROUGH THE LONG TERM WILL BE NEAR TO SLIGHTLY ABOVE NORMAL FOR FRIDAY THROUGH SUNDAY...THEN SLIGHTLY BELOW NORMAL SUNDAY NIGHT THROUGH TUESDAY. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... STRATUS AND STRATOCU CONTINUE TO LIFT AS SURFACE HEATING HAS BROUGHT TEMPERATURES INTO THE UPPER 70S AND LOWER 80S. MAYBE 1-2 MORE HOURS OF MVFR CEILINGS BUT SHOULD BECOME MOSTLY VFR BY NOON. WITH AFTERNOON HEATING...ATMOSPHERE WILL BECOME MORE UNSTABLE BUT MODELS NOT SHOWING BECOMING VERY UNSTABLE. MODELS GIVE ONLY MEAGER INSTABILITY WITH LIS -2/-4 AND CAPES AROUND 1000 J/KG BUT EXPECT STRONG LOW LEVEL LAPSE RATES WHICH MAY ALLOW SHOWERS AND THUNDERSTORMS TO DEVELOP. IT LOOKS LIKE THE COVERAGE SHOULD BE LESS THAN YESTERDAY. DUE TO UNCERTAINTY AS TO THE TIMING AND LOCATION...DECIDED NOT TO INCLUDE AT TAF SITES. ANY THAT DO AFFECT ANY TAF SITE MAY HAVE BRIEF IFR-MVFR CONDITIONS. A FEW SHOWERS AND THUNDERSTORMS MAY LINGER INTO THE EVENING HOURS BUT ARE EXPECTED TO BE GONE BY 04Z OR MIDNIGHT. AFTER MIDNIGHT... NAM BUFKIT IS SHOWING LOW LEVEL WINDS SOUTHWEST AT 10-15 KNOTS BELOW 1 KFT. SO NOT MUCH IN THE WAY OF FOG EXPECTED BUT MVFR VSBYS STILL POSSIBLE AT AGS AND OGB NEAR SUNRISE THURSDAY. ANOTHER ISSUE IS STRATUS CEILINGS. RIGHT NOW...MODELS SUGGEST LESS LOW LEVEL MOISTURE THAN PREVIOUS DAYS. SO THE POTENTIAL FOR LOW CEILINGS HAS DIMINISHED. WITH LOW CONFIDENCE...DECIDED NOT TO INCLUDE IFR CEILINGS THURSDAY MORNING AT TAF SITES. EXTENDED AVIATION OUTLOOK...RESTRICTIONS MAINLY FOR AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...NONE. GA...NONE. && $$ 07
AREA FORECAST DISCUSSION
NWS LINCOLN IL
901 PM CDT THU SEP 6 2012 .DISCUSSION... ISSUED 900 PM CDT THU SEP 6 2012 DRY AIR MIXING THIS AFTERNOON DROPPED SURFACE DEWPOINTS INTO THE LOW TO MID 50S IN SOME WESTERN AREAS...WITH EAST AND SOUTHEAST AREA DEWPOINTS STILL IN THE 60S. ANY FOG FORMATION UNDER THE CLEAR SKIES AND LIGHT WINDS WILL BE IN THE ESE COUNTIES. WESTERN AREAS SHOULD SEE LIMITED FOG IF AT ALL. THE NEXT ISSUE WILL BE WHEN THE STORM COMPLEX WILL ARRIVE FROM IOWA. THE LATEST HRRR MODEL OUTPUT KEEPS ALL STORMS IN IOWA THROUGH 6 AM...SO CONFIDENCE IS DROPPING THAT ANY STORMS WILL REACH OUR NW COUNTIES BEFORE SUNRISE. WE REMAIN IN THE DAY 1 SPC SEVERE OUTLOOK FOR KNOX AND FAR NW FULTON COUNTIES VALID THROUGH 12Z. WILL KEEP LIKELY POPS IN THAT AREA FOR LATE TONIGHT...BUT PULLED OUT POPS THROUGH 9Z...THEN KEPT LIMITED POPS FROM 9Z-12Z LATER TONIGHT. THE MAIN SHOW FOR STORMS WILL BE ON FRIDAY...ESPECIALLY FRIDAY AFTERNOON EAST OF I-55 WHEN PEAK HEATING AND INSTABILITY/SHEAR BECOME MORE FAVORABLE FOR SEVERE STORMS. UPDATED GRIDS AND FORECAST INFO WILL BE AVAILABLE SHORTLY. SHIMON && .AVIATION... ISSUED 635 PM CDT THU SEP 6 2012...FOR THE 00Z TAFS THE MCS IN SOUTH CENTRAL MISSOURI TOOK AN ESE PATH INTO ILLINOIS AND WILL REMAIN WELL SOUTH OF OUR TERMINAL LOCATIONS. SOME CIRRUS BLOW-OFF FROM THE STORMS WILL BRUSH BY THE DEC/SPI/CMI LOCATIONS...OTHERWISE CLEAR SKIES ARE EXPECTED FOR MUCH OF THE NIGHT. THE NEXT STORM COMPLEX FROM THE PLAINS IS EXPECTED TO ARRIVE LATE TONIGHT...WITH A FEW STORMS POSSIBLY AS EARLY AS 09Z IN PIA. A LATER TREND IS PREFERRED WITH THE ARRIVAL OF STORMS FROM THAT SYSTEM...SO MOST OF THE THUNDERSTORM ACTIVITY SHOULD COME IN A 2-3 HOUR WINDOW STARTING MID MORNING IN PIA AND CONTINUE EAST THROUGH CMI EARLIER IN THE AFTERNOON. STRONG TO SEVERE STORMS WILL BE MAINLY CONFINED TO AREAS EAST OF I-55...WITH CMI/DEC HAVING THE BEST CHANCES OF SEVERE LEVEL STORMS. THE AFTERNOON TIME FRAME LOOKS TO BE MOST FAVORABLE FOR SEVERE WEATHER DUE TO PEAK HEATING AND AVAILABLE INSTABILITY AND WIND SHEAR. WE DID NOT SPECULATE A TEMPO PERIOD FOR THE STRONGEST STORMS WITH THIS TAF ISSUANCE. WINDS WILL BE LIGHT AND VARIABLY OVERNIGHT. ENOUGH MIXING OF DRY AIR OCCURRED TODAY THAT SHOULD PRECLUDE ANY DENSE FOG OVERNIGHT. HOWEVER...SOME PATCHY MVFR FOG CAN NOT BE RULED OUT. WINDS TOMORROW WILL START OUT SOUTHEAST AHEAD OF THE COLD FRONT...THEN VEER TO THE SW LATE MORNING AND EVENTUALLY NW BEHIND THE FRONT IN THE AFTERNOON. THAT SCENARIO WILL PLAY OUT AT EACH TERMINAL WITH THE PASSAGE OF THE FRONT/STORM COMPLEX. SHIMON && .PREV DISCUSSION... ISSUED 250 PM CDT THU SEP 6 2012 HIGH PRESSURE CENTERED OVER EASTERN IOWA EARLY THIS AFTERNOON. MOST OF THE FOG ACROSS THE SOUTHEAST HALF OF THE CWA BURNED OFF BY 9 AM OR SO...BUT THE CLOUDS HAVE LINGERED THERE INTO THIS AFTERNOON. THIS IS ALONG A BOUNDARY/SURFACE FRONT THAT DIVIDES DEW POINTS IN THE 50S TO THE NORTHWEST...AND AROUND 70 TO THE SOUTHEAST. THE LARGER SURFACE PICTURE SHOWS LOW PRESSURE IN NORTH CENTRAL NEBRASKA...WITH A WARM FRONT ARCHING NORTHEAST INTO CENTRAL MINNESOTA AND A COLD FRONT EXTENDING WESTWARD. THIS PARTICULAR STORM SYSTEM IS THE FEATURE OF INTEREST FOR OUR AREA OVER THE NEXT 36 HOURS. THE MAIN CONCERNS WILL BE WITH RAINFALL TIMING AND AMOUNTS...AS WELL AS SEVERE WEATHER POTENTIAL. SHORT TERM...TONIGHT THROUGH SATURDAY... DIGGING UPPER TROUGH CURRENTLY MOVING INTO NORTH DAKOTA WILL PUSH STORM SYSTEM IN THE PLAINS EASTWARD. STILL LOOKING LIKE THE WESTERN HALF OF THE CWA WILL BE SEEING SOME SHOWERS AND STORMS SPREADING IN AFTER MIDNIGHT...ESPECIALLY NORTHWEST OF THE ILLINOIS RIVER. HAVE ADDED SOME SLIGHT CHANCE POPS AS FAR EAST AS I-57 FOR LATE TONIGHT. REASONABLE AGREEMENT EXISTS AMONG MODEL SOLUTIONS ON SWEEPING THE COLD FRONT ACROSS THE FORECAST AREA FRIDAY AFTERNOON AND EARLY EVENING...ALTHOUGH THE NAM IS A TAD FASTER IN THIS REGARD. ALL MODEL SOLUTIONS SHOWING PRECIPITABLE WATER VALUES AROUND 2-2.1 INCHES AHEAD OF THE FRONT...WHICH IS AROUND THE 99TH PERCENTILE FOR EARLY SEPTEMBER...SO SOME AREAS OF HEAVIER RAIN ARE LIKELY. IN TERMS OF THE SEVERE POTENTIAL...CAPES PROGGED TO RISE TO AT LEAST 2000 J/KG EAST OF THE RAIN SHIELD...WHERE SOME SUN MAY OCCUR DURING THE MORNING...AND BULK SHEAR VALUES AHEAD OF THE FRONT PROGGED TO RISE TO AROUND 40-45 KNOTS. MAINLY LOOKING AT A WIND DAMAGE AND HAIL THREAT IN THIS AREA. LATEST SPC DAY2 OUTLOOK HAS AREAS FROM THE ILLINOIS RIVER SOUTHEAST IN A SLIGHT RISK...WITH THE GREATEST PROBABILITIES SOUTH OF A TAYLORVILLE TO DANVILLE LINE. RAIN CHANCES SHOULD QUICKLY TAPER OFF FROM WEST TO EAST FOLLOWING THE PASSAGE OF THE FRONT...WITH MOST AREAS WEST OF I-57 DRY BY LATE FRIDAY EVENING. UPPER TROUGH WILL CONTINUE TO DEEPEN AS IT SWEEPS ACROSS THE GREAT LAKES SATURDAY. WILL CONTINUE WITH HIGHS IN THE LOWER 70S ACROSS MOST OF THE CWA AS THE COLDER AND DRIER AIR IS DRAWN SOUTHWARD. LONG TERM...SUNDAY THROUGH THURSDAY... HIGH TEMPERATURES REMAIN IN THE 70S SUNDAY AND MONDAY...AS THE UPPER TROUGH GRADUALLY LIFTS NORTHEAST INTO CANADA...WITH SOME GRADUAL WARMING AFTER THAT. MAIN CONCERN IN THE LONGER TERM REMAINS WITH A SHORTWAVE WHICH WILL TRACK ALONG THE CANADIAN BORDER EARLY IN THE WEEK. ECMWF AND GFS MODELS HAVING SOME DIFFICULTY WITH THE FAST UPPER FLOW...AND WHEN TO BRING THIS INTO OUR GENERAL REGION. BOTH MODELS SHOW A SLOWING OF THE ASSOCIATED SURFACE FRONT BY MIDWEEK AS IT STARTS TO PARALLEL THE UPPER FLOW... DUE TO A 500 MB HIGH STRETCHED EAST-WEST ACROSS THE SOUTHEASTERN STATES. MAIN PRECIPITATION FOCUS WOULD LIKELY HOLD OFF UNTIL THURSDAY IN OUR AREA...BUT A FAIR AMOUNT OF DRY AIR WILL STILL BE OVER THE CWA. THEREFORE...WILL ONLY GO WITH SOME SLIGHT CHANCE POPS ACROSS THE NORTHWEST FOR NOW. GEELHART && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
218 AM CDT WED SEP 5 2012 .MESOSCALE DISCUSSION... 728 PM CDT CLOSELY MONITORING CONVECTION OVER WESTERN WISCONSIN EARLY THIS EVENING FOR ANY POTENTIAL IMPACTS ON OUR CWA TONIGHT. CLUSTER OF STRONG TO SEVERE THUNDERSTORMS OVER SOUTHWEST WISCONSIN APPEARS TO BE CONGEALING IN A LARGE MASS OF STORMS WHICH COULD RESULT IN FORMATION OF COLD POOL AND A MORE ACCELERATED MOTION. FORWARD PROPAGATING CORFIDI VECTORS FROM WRF-NAM AND RUC BOTH SUGGEST CONVECTION WOULD RACE QUICKLY EAST-SOUTHEAST TOWARD CHGO METRO...HOWEVER SPC OBJECTIVE MESOANALYSIS DATA SHOWS A REGION OR MUCH LESSER INSTABILITY AND GREATER INHIBITION OVER SOUTHERN WISCONSIN. VISIBLE SATELLITE IMAGERY TUES AFTERNOON SHOWED A DISTINCT ABSENCE OF CUMULUS IN A SWATH FROM NE IL (AHEAD OF LAKE BREEZE) NNW INTO CENTRAL WISCONSIN...WHICH WOULD LEND SOME CREDENCE TO THE WEAKER INSTABILITY/STRONGER CAPPING SHOWN IN THE SPC OBJECTIVE ANALYSIS DATA. RELATIVELY WEAK LOW LEVEL FLOW SUGGESTS ANY RAPID NORTHEASTWARD TRANSPORT OF MOISTURE OR INSTABILITY IS UNLIKELY THIS EVENING...SO WOULD ANTICIPATE CONVECTION TO WEAKEN AS IT PROGRESSES EASTWARD INTO THE LESS UNSTABLE ENVIRONMENT OVER SOUTHERN WISCONSIN. LOOKING LIKE A MORE PLAUSIBLE SCENARIO WOULD BE FOR MOST INTENSE VIGOROUS CONVECTION TO FAVOR THE WESTERN PORTIONS OF THIS DEVELOPING MCS AND FOR THE STRONGER CELLS TO TEND TO PROPAGATE MORE SOUTHWARD INTO THE AXIS OF GREATER MOISTURE/INSTABILITY WHICH WAS NICELY DEPICTED BY THE CUMULUS FIELD THIS AFTERNOON. MODELS REALLY NOT SHOWING ANY SIGNIFICANT LOW LEVEL JET OR LOW LEVEL WARM AIR ADVECTION OVERNIGHT SO ITS QUESTIONABLE HOW WELL SUSTAINED THIS CONVECTION WILL BE INTO THE MID TO LATE EVENING...BUT REGARDLESS GIVEN ITS ALREADY RATHER CLOSE PROXIMITY FEEL SOME UPWARD ADJUSTMENTS TO POP GRIDS FOR TONIGHT ARE WARRANTED...ESPECIALLY WESTERN CWA. IZZI && .DISCUSSION... 307 PM CDT MAIN FORECAST CONCERN FOR THE NEXT FEW DAYS WILL FOCUS ON THE INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS TONIGHT AND TOMORROW ASSOCIATED WITH A COLD FRONT DROPPING SEWD OUT OF THE UPPER MISSISSIPPI VALLEY. FOR THE REMAINDER OF THE AFTERNOON AND THIS EVENING...CONDITIONS WILL REMAIN GENERALLY QUIET...HOWEVER...WITH AMPLE LOW LEVEL MOISTURE LINGERING OVER THE REGION FOLLOWING THE PASSAGE OF TROPICAL CYCLONE ISAAC...DAYTIME WARMING COMBINED WITH A LAKE BREEZE BOUNDARY PUSHING INLAND FROM LAKE MICHIGAN WILL ALLOW FOR AT LEAST A SMALL CHANCE OF SHOWERS OR THUNDERSTORMS OVER THE AREA THROUGH EARLY THIS EVENING. FOR THE LARGER SCALE...A PERSISTENT POLAR LOW CONTINUES TO SIT AND SPIN OVER NRN MANITOBA WHILE A SERIES OF WEAK IMPULSES TRACK ALONG THE SRN PERIPHERY. INITIALLY...THE SFC PRESSURE PATTERN REMAINS VERY DIFFUSE WITH LITTLE SFC FORCING. HOWEVER...BY LATE TONIGHT...THE SHORT RANGE GUIDANCE IS IN GOOD AGREEMENT ON INCREASING THE PCPN THREAT AS A STRONG SHORTWAVE DROPS OUT OF THE NORTHERN ROCKIES AND PUSHES INTO THE NORTHERN PLAINS TONIGHT AND ACROSS THE UPPER MISSISSIPPI VALLEY TOMORROW. THIS SHORT WAVE WILL REINFORCE A WEAK SFC COLD FRONT...WHICH WILL PROVIDE THE SFC FORCING TO IGNITE THUNDERSTORMS. THE MAIN FORECAST CONCERN WITH THIS SYSTEM WILL BE HOW FAR SOUTH TO EXTEND THE HIGHER POPS THROUGH THE MIDWEST AND INTO THE MIDDLE MISSISSIPPI VALLEY. WHILE THE STRONGEST FORCING SHOULD REMAIN TO THE NORTH OF THE LOCAL AREA IN WISCONSIN WITH THE TRACK OF THE MAIN VORT MAX...THERE SHOULD BE ENOUGH UPPER LEVEL FORCING EXTENDING SWD...COINCIDENT WITH THE SFC COLD FRONT TO WARRANT KEEPING LIKELY POPS ACROSS THE CWA BEGINNING EARLY TOMORROW MORNING OVER THE ROCKFORD AREA AND THEN SPREADING EWD THROUGH THE DAY AS THE COLD FRONT PUSHES EWD. THE WARM SECTOR ENVIRONMENT SHOULD BE PRIMED FOR THUNDERSTORMS BY LATE MORNING/EARLY AFTERNOON AS TEMPERATURES SHOULD REACH INTO THE UPPER 80S TO CLOSE TO 90 DEGREES WITH SFC DEW POINTS IN THE UPPER 60S TO LOWER 70S. DEEP LAYER INSTABILITY WILL ALSO BE MORE THAN ADEQUATE FOR THUNDERSTORM DEVELOPMENT AS IS EVIDENCED BY BUFKIT SOUNDS FROM THE NAM12 ADVERTISING CAPE VALUES EXCEEDING 1500 J/KG BY THE LATE MORNING HOURS AND INCREASING TO ARND 2500 J/KG DURING THE AFTERNOON. THE GIVEN THE ELEMENTS EXPECTED TO BE IN PLACE TOMORROW...THE ;LATEST SPC DAY 2 OUTLOOK KEEPS THE CWA IN A SLIGHT RISK AREA FOR SEVERE THUNDERSTORMS. THE GREATEST THREAT SHOULD BE DURING THE LATE AFTERNOON HOURS AS THE COLD FRONT CROSSES THE AREA DURING THE TIME OF PEAK HEATING. THE MAIN SEVERE THREAT SHOULD BE STRONG...DAMAGING STRAIGHT LINE WINDS GIVEN A RELATIVELY DRY LAYER EXPECTED BETWEEN 850MB-700MB...THOUGH THERE MAY ALSO BE A LARGE HAIL THREAT AS COOLER AIR MOVES IN ALOFT WITH FREEZING LEVELS DROPPING TO ARND 12KFT. LOCALLY HEAVY RAINFALL WILL BE LESS OF A CONCERN AS THE COLD FRONT WILL BE PROGRESSIVE THROUGH THE DAY AND PWATS ARE EXPECTED TO BE 1.5 INCHES OR LESS. THURSDAY IS SHAPING UP TO BE DRY AND THE NEXT CHANCE FOR PCPN WILL COME BY EARLY FRIDAY MORNING AS A LONG WAVE TROUGH DROPS INTO THE UPPER MISSISSIPPI VALLEY. A WEAK FRONT ASSOCIATED WITH THE UPPER TROUGH IS EXPECTED TO MOVE INTO NWRN IL EARLY FRIDAY...BUT THE MAIN CONCERN WILL BE SFC WAVE DEVELOPMENT ALONG THE COLD FRONT. THE LONGER RANGE GUIDANCE IS IN GOOD AGREEMENT ON THE FORMATION OF A DECENT SFC WAVE ON THE FRONT...BUT THERE IS LESSER AGREEMENT ON THE STRENGTH AND LOCATION OF THE SFC WAVE DEVELOPMENT. HOWEVER...THERE IS ENOUGH CONFIDENCE TO CARRY LIKELY POPS FOR THE SRN PORTIONS OF THE CWA...WITH A CHANCE OF THUNDERSTORMS...BUT LESSER CONFIDENCE TO THE NORTH...SO WILL ONLY CARRY CHANCE POPS FOR THE NORTHERN PORTIONS OF THE CWA. FOR TEMPERATURES...FOLLOWING THE PASSAGE OF THE COLD FRONT TOMORROW...HIGHS WILL DROP BACK INTO UPPER 70S TO LOWER 80S FOR THURSDAY. FOR FRIDAY AND SATURDAY...AS THE LONG WAVE UPPER TROUGH MOVES ACROSS THE REGION...HIGHS SHOULD ONLY BE IN THE MIDDLE 70S FOR FRIDAY/ THE COOLEST AIR WILL MOVE OVER THE AREA FOR THE WEEKEND WITH TEMPS ONLY REACHING INTO THE UPPER 60S TO AROUND 70F ON SATURDAY AND THE LOWER 70S FOR SUNDAY. WEAK UPPER RIDGING SHOULD RETURN TO THE AREA BY EARLY NEXT WEEK...BRINGING SLIGHTLY WARMER WEATHER WITH HIGHS IN THE MIDDLE 70S. KREIN && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 06Z... * CHANCE FOR SHRA/TSRA AFTER SUNRISE. * CHANCE FOR TSRA THIS AFTERNOON. * POTENTIAL FOR GUSTY SOUTH/SOUTHWEST WINDS. CMS //DISCUSSION...UPDATED 06Z... LINE OF TSRA CONTINUES TO WEAKEN AS IT MOVES SOUTHEAST OF THE TERMINALS WITH SHOWERS EXPECTED TO END OVER THE CHICAGO AREA TERMINALS IN THE NEXT 1-2 HRS. A SMALL SCALE HIGH PRESSURE HAS FORMED ON THE BACK SIDE OF THE PRECIPITATION. AS A RESULT... WINDS WILL TURN NORTHEAST...EAST...SOUTHEAST THEN BACK LIGHT SOUTHERLY OVER THE NEXT FEW HOURS AS THIS HIGH MOVES SOUTHEAST. SPEEDS LIKELY TO BE IN THE 10-15 KT RANGE WITH HIGHER GUSTS POSSIBLE BUT THE OVERALL TREND WILL BE FOR SPEEDS TO SLOWLY DIMINISH. FOCUS THEN SHIFTS TO A LINE OF TSRA NOW MOVING ACROSS NORTH CENTRAL IA AND SOUTHERN MN. SHORT TERM GUIDANCE WOULD SUGGEST THIS LINE WILL CONTINUE MOVING EAST AND SHOULD BEGIN TO WEAKEN AFTER SUNRISE. WHILE THE BULK OF THIS ACTIVITY MAY MOVE ACROSS SOUTHERN WI...HAVE OPTED TO INCLUDE A TEMPO FOR TSRA AT RFD AND SHRA AT DPA AND TRENDS WILL NEED TO BE MONITORED EARLY THIS MORNING WITH TSRA POSSIBLY NEEDED TO BE ADDED FOR THE CHICAGO TERMINALS AFTER SUNRISE. THIS ACTIVITY MAY THEN AFFECT ANY ADDITIONAL TSRA DEVELOPMENT LATER THIS AFTERNOON WITH A POSSIBLE OUTFLOW PUSHING SOUTH ACROSS THE TERMINALS DURING THE MORNING AND BECOMING THE FOCUS FOR NEW DEVELOPMENT...WELL AHEAD OF THE COLD FRONT WITH PERHAPS WEAKER CONVECTION DEVELOPING WITH THE FRONT. AT THIS POINT...CONFIDENCE IS TOO LOW TO MAKE ANY SIGNIFICANT CHANGES AND HAVE MAINTAINED PREVIOUS TSRA TIMING FOR THIS AFTERNOON. IF CONVECTION DOES MATERIALIZE...STRONG/GUSTY WINDS WILL BE POSSIBLE. UNCERTAINTY ALSO REMAINS REGARDING HOW STRONG SOUTH/SOUTHWEST WINDS WILL BECOME LATER THIS MORNING INTO THIS AFTERNOON AS WELL. NEWEST FORECAST SOUNDINGS WOULD SUGGEST LOW LEVEL WINDS WILL NOT BE QUITE AS STRONG AS PREVIOUSLY THOUGHT...BUT GUSTS TO 20 KTS STILL POSSIBLE IN THE AFTERNOON. CMS //ORD AND MDW CONFIDENCE...UPDATED 06Z... * LOW CONFIDENCE REGARDING POTENTIAL SHRA/TSRA AFTER SUNRISE. * MEDIUM CONFIDENCE REGARDING TSRA THIS AFTERNOON...LOW CONFIDENCE REGARDING TIMING/DURATION. * MEDIUM CONFIDENCE REGARDING WIND SPEEDS/DIRECTIONS THROUGH THE PERIOD...LOW CONFIDENCE REGARDING GUSTS. CMS //OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z... * THURSDAY...VFR. * FRIDAY THROUGH SATURDAY...CHANCE OF SHRA. MVFR POSSIBLE. * SUNDAY...SLIGHT CHANCE OF SHRA. * MONDAY...VFR. && .MARINE... 217 AM CDT THE WINDS EARLY THIS MORNING ACROSS THE SOUTHERN HALF OF THE LAKE HAVE BEEN AFFECTED BY THE OVERNIGHT CONVECTION. THIS HAS LEAD TO THE DEVELOPMENT OF A SMALLER SCALE AREA OF SURFACE HIGH PRESSURE ACROSS THE SOUTHERN TIP OF THE LAKE. THE RESULT OF THIS HAS BEEN VARYING WIND DIRECTIONS...WITH PRIMARILY A NORTHWESTERN WIND UP TO 30 KT ACROSS THE NEAR SHORES OF INDIANA AND THE OPEN WATERS. HOWEVER...ACROSS THE ILLINOIS NEAR SHORES THE WINDS HAVE BECOME EASTERLY ON THE BACK SIDE OF THE HIGH. I EXPECT THE WIND SPEED TO SUBSIDE THROUGH THE EARLY MORNING HOURS AND THE PRIMARILY DIRECTION SHOULD BECOME SOUTHERLY DURING THE MORNING. THE MAIN CONCERN FOR TODAY WILL BE THE THREAT FOR ADDITIONAL THUNDERSTORMS...WITH A VERY GOOD CHANCE OF SEVERE WEATHER WITH WINDS OVER 50 KT. THIS WILL OCCUR AHEAD OF A COLD FRONT THAT SHOULD PASS ACROSS THE LAKE BY EARLY THIS EVENING. THIS WILL SWITCH THE WINDS OUT OF THE NORTH NORTHWEST AROUND 20 KT OVERNIGHT TONIGHT. THE WINDS SHOULD GRADUALLY ABATE DURING THE DAY ON THURSDAY AS SURFACE HIGH PRESSURE BUILDS ACROSS THE LAKE. THE NEXT SYSTEM OF CONCERN LOOKS TO OCCUR LATER FRIDAY AND INTO THE WEEKEND. THERE REMAINS UNCERTAINTY ON HOW STRONG THIS SYSTEM WILL GET...AND THUS THE WIND FORECAST REMAINS A BIT UNCERTAIN DURING THIS TIME. HOWEVER...IT DOES APPEARS THAT A PERIOD OF STRONGER NORTHERLY WINDS UP TO 30 KT ARE POSSIBLE LATE FRIDAY NIGHT INTO SATURDAY AS SURFACE LOW PRESSURE TAKES SHAPE ACROSS THE OHIO VALLEY. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1253 AM CDT WED SEP 5 2012 .MESOSCALE DISCUSSION... 728 PM CDT CLOSELY MONITORING CONVECTION OVER WESTERN WISCONSIN EARLY THIS EVENING FOR ANY POTENTIAL IMPACTS ON OUR CWA TONIGHT. CLUSTER OF STRONG TO SEVERE THUNDERSTORMS OVER SOUTHWEST WISCONSIN APPEARS TO BE CONGEALING IN A LARGE MASS OF STORMS WHICH COULD RESULT IN FORMATION OF COLD POOL AND A MORE ACCELERATED MOTION. FORWARD PROPAGATING CORFIDI VECTORS FROM WRF-NAM AND RUC BOTH SUGGEST CONVECTION WOULD RACE QUICKLY EAST-SOUTHEAST TOWARD CHGO METRO...HOWEVER SPC OBJECTIVE MESOANALYSIS DATA SHOWS A REGION OR MUCH LESSER INSTABILITY AND GREATER INHIBITION OVER SOUTHERN WISCONSIN. VISIBLE SATELLITE IMAGERY TUES AFTERNOON SHOWED A DISTINCT ABSENCE OF CUMULUS IN A SWATH FROM NE IL (AHEAD OF LAKE BREEZE) NNW INTO CENTRAL WISCONSIN...WHICH WOULD LEND SOME CREDENCE TO THE WEAKER INSTABILITY/STRONGER CAPPING SHOWN IN THE SPC OBJECTIVE ANALYSIS DATA. RELATIVELY WEAK LOW LEVEL FLOW SUGGESTS ANY RAPID NORTHEASTWARD TRANSPORT OF MOISTURE OR INSTABILITY IS UNLIKELY THIS EVENING...SO WOULD ANTICIPATE CONVECTION TO WEAKEN AS IT PROGRESSES EASTWARD INTO THE LESS UNSTABLE ENVIRONMENT OVER SOUTHERN WISCONSIN. LOOKING LIKE A MORE PLAUSIBLE SCENARIO WOULD BE FOR MOST INTENSE VIGOROUS CONVECTION TO FAVOR THE WESTERN PORTIONS OF THIS DEVELOPING MCS AND FOR THE STRONGER CELLS TO TEND TO PROPAGATE MORE SOUTHWARD INTO THE AXIS OF GREATER MOISTURE/INSTABILITY WHICH WAS NICELY DEPICTED BY THE CUMULUS FIELD THIS AFTERNOON. MODELS REALLY NOT SHOWING ANY SIGNIFICANT LOW LEVEL JET OR LOW LEVEL WARM AIR ADVECTION OVERNIGHT SO ITS QUESTIONABLE HOW WELL SUSTAINED THIS CONVECTION WILL BE INTO THE MID TO LATE EVENING...BUT REGARDLESS GIVEN ITS ALREADY RATHER CLOSE PROXIMITY FEEL SOME UPWARD ADJUSTMENTS TO POP GRIDS FOR TONIGHT ARE WARRANTED...ESPECIALLY WESTERN CWA. IZZI && .DISCUSSION... 307 PM CDT MAIN FORECAST CONCERN FOR THE NEXT FEW DAYS WILL FOCUS ON THE INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS TONIGHT AND TOMORROW ASSOCIATED WITH A COLD FRONT DROPPING SEWD OUT OF THE UPPER MISSISSIPPI VALLEY. FOR THE REMAINDER OF THE AFTERNOON AND THIS EVENING...CONDITIONS WILL REMAIN GENERALLY QUIET...HOWEVER...WITH AMPLE LOW LEVEL MOISTURE LINGERING OVER THE REGION FOLLOWING THE PASSAGE OF TROPICAL CYCLONE ISAAC...DAYTIME WARMING COMBINED WITH A LAKE BREEZE BOUNDARY PUSHING INLAND FROM LAKE MICHIGAN WILL ALLOW FOR AT LEAST A SMALL CHANCE OF SHOWERS OR THUNDERSTORMS OVER THE AREA THROUGH EARLY THIS EVENING. FOR THE LARGER SCALE...A PERSISTENT POLAR LOW CONTINUES TO SIT AND SPIN OVER NRN MANITOBA WHILE A SERIES OF WEAK IMPULSES TRACK ALONG THE SRN PERIPHERY. INITIALLY...THE SFC PRESSURE PATTERN REMAINS VERY DIFFUSE WITH LITTLE SFC FORCING. HOWEVER...BY LATE TONIGHT...THE SHORT RANGE GUIDANCE IS IN GOOD AGREEMENT ON INCREASING THE PCPN THREAT AS A STRONG SHORTWAVE DROPS OUT OF THE NORTHERN ROCKIES AND PUSHES INTO THE NORTHERN PLAINS TONIGHT AND ACROSS THE UPPER MISSISSIPPI VALLEY TOMORROW. THIS SHORT WAVE WILL REINFORCE A WEAK SFC COLD FRONT...WHICH WILL PROVIDE THE SFC FORCING TO IGNITE THUNDERSTORMS. THE MAIN FORECAST CONCERN WITH THIS SYSTEM WILL BE HOW FAR SOUTH TO EXTEND THE HIGHER POPS THROUGH THE MIDWEST AND INTO THE MIDDLE MISSISSIPPI VALLEY. WHILE THE STRONGEST FORCING SHOULD REMAIN TO THE NORTH OF THE LOCAL AREA IN WISCONSIN WITH THE TRACK OF THE MAIN VORT MAX...THERE SHOULD BE ENOUGH UPPER LEVEL FORCING EXTENDING SWD...COINCIDENT WITH THE SFC COLD FRONT TO WARRANT KEEPING LIKELY POPS ACROSS THE CWA BEGINNING EARLY TOMORROW MORNING OVER THE ROCKFORD AREA AND THEN SPREADING EWD THROUGH THE DAY AS THE COLD FRONT PUSHES EWD. THE WARM SECTOR ENVIRONMENT SHOULD BE PRIMED FOR THUNDERSTORMS BY LATE MORNING/EARLY AFTERNOON AS TEMPERATURES SHOULD REACH INTO THE UPPER 80S TO CLOSE TO 90 DEGREES WITH SFC DEW POINTS IN THE UPPER 60S TO LOWER 70S. DEEP LAYER INSTABILITY WILL ALSO BE MORE THAN ADEQUATE FOR THUNDERSTORM DEVELOPMENT AS IS EVIDENCED BY BUFKIT SOUNDS FROM THE NAM12 ADVERTISING CAPE VALUES EXCEEDING 1500 J/KG BY THE LATE MORNING HOURS AND INCREASING TO ARND 2500 J/KG DURING THE AFTERNOON. THE GIVEN THE ELEMENTS EXPECTED TO BE IN PLACE TOMORROW...THE ;LATEST SPC DAY 2 OUTLOOK KEEPS THE CWA IN A SLIGHT RISK AREA FOR SEVERE THUNDERSTORMS. THE GREATEST THREAT SHOULD BE DURING THE LATE AFTERNOON HOURS AS THE COLD FRONT CROSSES THE AREA DURING THE TIME OF PEAK HEATING. THE MAIN SEVERE THREAT SHOULD BE STRONG...DAMAGING STRAIGHT LINE WINDS GIVEN A RELATIVELY DRY LAYER EXPECTED BETWEEN 850MB-700MB...THOUGH THERE MAY ALSO BE A LARGE HAIL THREAT AS COOLER AIR MOVES IN ALOFT WITH FREEZING LEVELS DROPPING TO ARND 12KFT. LOCALLY HEAVY RAINFALL WILL BE LESS OF A CONCERN AS THE COLD FRONT WILL BE PROGRESSIVE THROUGH THE DAY AND PWATS ARE EXPECTED TO BE 1.5 INCHES OR LESS. THURSDAY IS SHAPING UP TO BE DRY AND THE NEXT CHANCE FOR PCPN WILL COME BY EARLY FRIDAY MORNING AS A LONG WAVE TROUGH DROPS INTO THE UPPER MISSISSIPPI VALLEY. A WEAK FRONT ASSOCIATED WITH THE UPPER TROUGH IS EXPECTED TO MOVE INTO NWRN IL EARLY FRIDAY...BUT THE MAIN CONCERN WILL BE SFC WAVE DEVELOPMENT ALONG THE COLD FRONT. THE LONGER RANGE GUIDANCE IS IN GOOD AGREEMENT ON THE FORMATION OF A DECENT SFC WAVE ON THE FRONT...BUT THERE IS LESSER AGREEMENT ON THE STRENGTH AND LOCATION OF THE SFC WAVE DEVELOPMENT. HOWEVER...THERE IS ENOUGH CONFIDENCE TO CARRY LIKELY POPS FOR THE SRN PORTIONS OF THE CWA...WITH A CHANCE OF THUNDERSTORMS...BUT LESSER CONFIDENCE TO THE NORTH...SO WILL ONLY CARRY CHANCE POPS FOR THE NORTHERN PORTIONS OF THE CWA. FOR TEMPERATURES...FOLLOWING THE PASSAGE OF THE COLD FRONT TOMORROW...HIGHS WILL DROP BACK INTO UPPER 70S TO LOWER 80S FOR THURSDAY. FOR FRIDAY AND SATURDAY...AS THE LONG WAVE UPPER TROUGH MOVES ACROSS THE REGION...HIGHS SHOULD ONLY BE IN THE MIDDLE 70S FOR FRIDAY/ THE COOLEST AIR WILL MOVE OVER THE AREA FOR THE WEEKEND WITH TEMPS ONLY REACHING INTO THE UPPER 60S TO AROUND 70F ON SATURDAY AND THE LOWER 70S FOR SUNDAY. WEAK UPPER RIDGING SHOULD RETURN TO THE AREA BY EARLY NEXT WEEK...BRINGING SLIGHTLY WARMER WEATHER WITH HIGHS IN THE MIDDLE 70S. KREIN && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 06Z... * CHANCE FOR SHRA/TSRA AFTER SUNRISE. * CHANCE FOR TSRA THIS AFTERNOON. * POTENTIAL FOR GUSTY SOUTH/SOUTHWEST WINDS. CMS //DISCUSSION...UPDATED 06Z... LINE OF TSRA CONTINUES TO WEAKEN AS IT MOVES SOUTHEAST OF THE TERMINALS WITH SHOWERS EXPECTED TO END OVER THE CHICAGO AREA TERMINALS IN THE NEXT 1-2 HRS. A SMALL SCALE HIGH PRESSURE HAS FORMED ON THE BACK SIDE OF THE PRECIPITATION. AS A RESULT... WINDS WILL TURN NORTHEAST...EAST...SOUTHEAST THEN BACK LIGHT SOUTHERLY OVER THE NEXT FEW HOURS AS THIS HIGH MOVES SOUTHEAST. SPEEDS LIKELY TO BE IN THE 10-15 KT RANGE WITH HIGHER GUSTS POSSIBLE BUT THE OVERALL TREND WILL BE FOR SPEEDS TO SLOWLY DIMINISH. FOCUS THEN SHIFTS TO A LINE OF TSRA NOW MOVING ACROSS NORTH CENTRAL IA AND SOUTHERN MN. SHORT TERM GUIDANCE WOULD SUGGEST THIS LINE WILL CONTINUE MOVING EAST AND SHOULD BEGIN TO WEAKEN AFTER SUNRISE. WHILE THE BULK OF THIS ACTIVITY MAY MOVE ACROSS SOUTHERN WI...HAVE OPTED TO INCLUDE A TEMPO FOR TSRA AT RFD AND SHRA AT DPA AND TRENDS WILL NEED TO BE MONITORED EARLY THIS MORNING WITH TSRA POSSIBLY NEEDED TO BE ADDED FOR THE CHICAGO TERMINALS AFTER SUNRISE. THIS ACTIVITY MAY THEN AFFECT ANY ADDITIONAL TSRA DEVELOPMENT LATER THIS AFTERNOON WITH A POSSIBLE OUTFLOW PUSHING SOUTH ACROSS THE TERMINALS DURING THE MORNING AND BECOMING THE FOCUS FOR NEW DEVELOPMENT...WELL AHEAD OF THE COLD FRONT WITH PERHAPS WEAKER CONVECTION DEVELOPING WITH THE FRONT. AT THIS POINT...CONFIDENCE IS TOO LOW TO MAKE ANY SIGNIFICANT CHANGES AND HAVE MAINTAINED PREVIOUS TSRA TIMING FOR THIS AFTERNOON. IF CONVECTION DOES MATERIALIZE...STRONG/GUSTY WINDS WILL BE POSSIBLE. UNCERTAINTY ALSO REMAINS REGARDING HOW STRONG SOUTH/SOUTHWEST WINDS WILL BECOME LATER THIS MORNING INTO THIS AFTERNOON AS WELL. NEWEST FORECAST SOUNDINGS WOULD SUGGEST LOW LEVEL WINDS WILL NOT BE QUITE AS STRONG AS PREVIOUSLY THOUGHT...BUT GUSTS TO 20 KTS STILL POSSIBLE IN THE AFTERNOON. CMS //ORD AND MDW CONFIDENCE...UPDATED 06Z... * LOW CONFIDENCE REGARDING POTENTIAL SHRA/TSRA AFTER SUNRISE. * MEDIUM CONFIDENCE REGARDING TSRA THIS AFTERNOON...LOW CONFIDENCE REGARDING TIMING/DURATION. * MEDIUM CONFIDENCE REGARDING WIND SPEEDS/DIRECTIONS THROUGH THE PERIOD...LOW CONFIDENCE REGARDING GUSTS. CMS //OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z... * THURSDAY...VFR. * FRIDAY THROUGH SATURDAY...CHANCE OF SHRA. MVFR POSSIBLE. * SUNDAY...SLIGHT CHANCE OF SHRA. * MONDAY...VFR. && .MARINE... 323 PM CDT LIGHT VARIABLE WINDS WILL BEGIN TO FAVOR A SOUTHERLY DIRECTION TONIGHT AND GRADUALLY FRESHEN AS A COLD FRONT ADVANCES EASTWARD INTO THE UPPER MIDWEST OVERNIGHT. THE COLD FRONT WILL MOVE ACROSS NORTHERN LAKE MI BY MID AFTERNOON WED AND ACROSS SOUTHERN LAKE MI BY MID EVENING...WITH WINDS VEERING TO SOUTHWEST THEN WEST AND NORTHWEST WITH THE PASSAGE OF THE COLD FRONT. A SECOND COLD FRONT WILL MOVE ACROSS LAKE MI LATE THU NIGHT AND FRI. WINDS WILL BECOME SOUTHWESTERLY AS THE FRONT NEARS...THEN VEER TO OUT OF THE WEST AND NORTHWEST AGAIN WITH THE COLD FRONT PASSAGE. HIGH PRESSURE OF OVER SASKATCHEWAN AND MANITOBA WILL EXPAND OVER THE PLAINS AND NORTHERN GREAT LAKES FRIDAY NIGHT. WINDS WILL INCREASE TO STRONG NORTH TO NORTHEAST BREEZES FOR SAT AND SUN...WITH SOME GUSTS NEAR GALE FORCE ON SOUTHERN LAKE MI AS THE PRESSURE GRADIENT ACROSS THE REGION INCREASES BETWEEN THE HIGH PRESSURE RIDGE TO THE N AND W...AND A LOW MOVING FROM THE MID MS VALLEY UP THE OH VALLEY. TRS && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
423 PM EDT WED SEP 5 2012 .SHORT TERM... TONIGHT THROUGH THURSDAY NIGHT. SHORT/SMALL WINDOW OF OPPORTUNITY WRT DESTABILIZATION INADOV SFC FNTL BNDRY ACRS XTRM SERN WI/NRN IL/ERN IA/MO LATE THIS AFTN. OF NOTE HAS BEEN SPC RAP FAILURE TO ADEQUATELY ASSESS DOWNSTREAM STABILIZATION AMID WAKE OF MATURE BUBBLE MESOHIGH BEHIND LATE AM/ERLY AFTN LINEAR CONVECTION THAT NOW ARCHES FM NRN OH TO OH RVR VALLEY. WHILE EWD ADVANCE OF STEEP 7-5H LAPSE RATES OF 8-9 C/KM OMINOUS...THE CERTAINLY FAR FROM PRISTINE 0-3KM THERMODYNAMIC ENVIRON ACRS NERN IL/CWA AMID DENSE CONVECTIVE DEBRIS AND WELL OVERTURNED ATMOS...WL LKLY QUELL ALL BUT JUST A FLEETING HOPE FOR ANY FIRM CONVECTIVE MAINTENANCE WITH ERN EXTENT. GIVEN CONDITIONALITY WRT LATE AFTN INITIATION WITH MODEST LLVL WIND PROFILE/LWST 100 MB CONVERGENCE AHEAD OF FNT...AND ADDED CONDITIONALITY FURTHER DOWNSTREAM...HAVE CHOSE LOWER END GUID WITH NO HIER THAN MID RANGE CHC POPS AFT 02 UTC. SEVERE RISK ALSO APPEARS TO BE WANING...BUT WL LET HWO CONTINUE TO COVER WITH HIEST RISKS ACRS SRN CWA/ALONG PROGGED OVERLAP OF SFC CAPE RESERVOIR AND MODERATE DEEP LYR SHEAR/INCRSG THIS EVE AS 50 KT 5H WNWLY FLOW ACRS IL/WI SURGES EWD. NIL WX AFTER TONIGHT IN DRYING LLVL ATMOS. HAVE LWRD TEMPS INVOF KBEH SUBSTANTIALLY TMWR NIGHT IN WEAKENING SFC FLOW AS 1018 MB PLAINS HIGH SETTLES ACRS SRN GRTLKS...FAVORING COOL DRAINAGE ALONG LAKESHORE NEAR DAYBREAK FRI. && .LONG TERM... FRIDAY THROUGH WEDNESDAY...A SIGNIFICANT TROF WILL MOVE ACROSS THE WESTERN GREAT LAKES REGION EARLY IN THE PERIOD. BOTH THE GFS AND THE ECMWF HAVE ABANDONED THE EARLY CUT OFF LOW SOLUTION FROM MANY PREVIOUS RUNS IN LIEU OF A MORE PROGRESSIVE OPEN WAVE SOLUTION DUE TO MORE PHASING WITH THE NORTHERN STREAM AND THE APPROACH OF ANOTHER UPSTREAM UPPER TROF. HOWEVER...THE ONGOING TIMING OF THE ARRIVAL OF THE MAIN TROF OVER THE WESTERN GREAT LAKES REGION STILL APPEARS ON TRACK WITH THE BEST CHANCE FOR RAIN FRIDAY NIGHT. KEPT SHOWERS LIKELY FRIDAY NIGHT. ADDED A CHANCE FOR THUNDER SOUTHEAST HALF PER ECMWF WITH EMBEDDED STORMS POSSIBLE GIVEN MOISTURE AND LIFT AVAILABLE. OTHERWISE...COOLER AND DRY CONDITIONS SUNDAY AND MONDAY FOLLOWED BY A RETURN TO ABOVE NORMAL TEMPERATURES WEDNESDAY AND THE UPPER LEVEL RIDGE BUILDS EAST AHEAD OF THE NEXT UPPER LEVEL TROF CAN BE EXPECTED. THE 500 MB CANADIAN AND GFS ANALOGS ALSO SUPPORT TEMPERATURES RISING ABOVE NORMAL. && .AVIATION... /18 UTC TAF/ UPSTREAM DESTABILIZATION RATHER SLOW TO RECOMMENCE HAS PLACED ADDED CONDITIONALITY UPON CONVECTION ASSOCD WITH PRIMARY FRONTAL BOUNDARY XTNDG FM SCNTL WI SEWD THROUGH IA TO NWRN MO LATER THIS AFTN. TIMING WOULD PLACE THIS INTO NWRN IN AFTER SUNSET. ADDED UNCERTAINTY WRT UNFAVORABLE CONVECTION MAINTENANCE WITH DOWNSTREAM EXTENT WITH SFC STABILIZATION INCRSG AND MEAGER LLVL WIND FIELD. FOR NOW HAVE COVERED GRTST POTNL TIMEFRAME WITH 4 HOUR VCTS GROUPINGS AS GRTR CONFIDENCE FOR TEMPO LACKING ATTM. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM...MURPHY LONG TERM...SKIPPER AVIATION...MURPHY
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
200 AM EDT WED SEP 5 2012 .AVIATION... 06Z TAFS...AVIATION CONCERNS CENTER ON EVOLUTION OF MCS ACROSS NORTHEAST ILLINOIS/FAR NORTHWEST INDIANA...FOG POTENTIAL THROUGH EARLY WEDNESDAY MORNING...AND THUNDERSTORM CHANCES WEDNESDAY AFTERNOON AND EVENING. IR SATELLITE/RADAR TRENDS CONTINUE TO INDICATE WEAKENING TREND TO CONVECTIVE SYSTEM ACROSS FAR NORTHWEST INDIANA/NORTHEAST ILLINOIS AND EXPECT THIS TREND TO CONTINUE AS CONDITIONS DOWNSTREAM ARE NOT AS UNSTABLE. NONETHELESS...A MATURE OUTFLOW BOUNDARY RACING WELL AHEAD WILL CONTINUE TO ALLOW ISOLATED TO SCATTERED SHOWERS TO DEVELOP...AND PERHAPS A THUNDERSTORMS OVER THE NEXT SEVERAL HOURS. HAVE INCLUDED A WIND GUST GROUP AT KSBN TO AROUND 20 KNOTS TO ACCOUNT FOR THIS OUTFLOW BOUNDARY THROUGH 08Z...BUT WILL CONFINE PRECIP MENTION TO VCSH AT THIS TIME. OTHERWISE FOR THE OVERNIGHT HOURS...FOG POTENTIAL WILL BE THE BIGGEST CONCERN AND HAVE MADE NO CHANGES TO PREVIOUS TAFS WHICH FOCUS THE LIFR CONDITIONS AT KFWA WHERE CROSSOVER TEMPS ARE HIGHER AND LESS INFLUENCE FROM CONVECTIVE DEBRIS CLOUDINESS IS EXPECTED. FOR WEDNESDAY...NEXT UPSTREAM SHORT WAVE ACROSS THE DAKOTAS WILL APPROACH THE WESTERN GREAT LAKES BY EVENING...WITH A POTENTIAL FOR SMALLER SCALE CONVECTIVE VORTS TO REACH NORTHWEST INDIANA DURING THE AFTERNOON. MODERATELY TO STRONGLY UNSTABLE CONDITIONS ARE ALSO EXPECTED TO DEVELOP ESPECIALLY FOR KSBN AND HAVE INCLUDED VCTS MENTION IN THE 20Z-04Z TIMEFRAME. && PREV DISCUSSION... /ISSUED 339 PM EDT TUE SEP 4 2012/ SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT. SEVERAL CONCERNS TO DEAL WITH OVER THE NEXT 36 HOURS FROM CONVECTION/SVR WX TO FOG. WEAK FRONTAL BOUNDARY WAS ROUGHLY LOCATED FROM MONTICELLO TO FORT WAYNE TO DEFIANCE WITH ISOL TO SCT SHOWERS STRUGGLING TO TAKE SHAPE ALONG WITH GIVEN WEAK CONVERGENCE AND LIMITED INSTABILITY. WILL KEEP A PRE 1ST PERIOD TO ADDRESS THIS ACTIVITY WHICH SHOULD EXIT BY 00Z. WITH MOIST BOUNDARY LAYER AND LITTLE CHANCE FOR MIXING ACROSS THE AREA TODAY...FOG/STRATUS POTENTIAL WILL REMAIN HIGH ACROSS MOST IF NOT ALL OF THE FORECAST AREA. COULD SEE WIDESPREAD DENSE FOG LATER TONIGHT IN MANY SPOTS WITH TEMPS FALLING PASS CROSSOVER TEMPS IN THE UPPER 60S TO AROUND 70 AND CALM WINDS/CLEAR SKIES. POTENTIAL ISSUES ARISE FROM ANTICIPATED UPSTREAM CONVECTION ACROSS MINN/WI/IOWA. SEVERAL RUNS OF THE HRRR HAVE SHOWN DEVELOPMENT ACROSS THIS AREA DROPPING TOWARDS POSSIBLE WESTERN PARTS OF THE FORECAST AREA LATER TONIGHT/WEDS MORNING...POSSIBLY CAUSING ISSUES WITH FOG DEVELOPMENT. FOR NOW...HAVE BUMPED UP WORDING IN ZONES TO PATCHY DENSE FOG AND WILL DEFER TO EVENING/OVERNIGHT SHIFTS TO ADJUST BASED ON UPSTREAM TRENDS. STRONGER UPPER LEVEL TROUGH AND SFC COLD FRONT STILL POISED TO MOVE INTO THE REGION WEDS/WEDS NGT. STRONG DYNAMICS WILL ACCOMPANY THE SYSTEM WITH A FAVORABLE TIMING OF LIFT AND MSTR CONVERGENCE IN THE LATE AFTERNOON/EARLY EVENING. GIVEN 0-6 KM SHEAR IN THE 30 TO 40 KT RANGE SVR THREAT IS STILL POSSIBLE...IF SUFFICIENT HEATING CAN OCCUR AHEAD OF THE ACTUAL FRONT. THE FLY IN THE OINTMENT FOR THIS MAY BE ANY LATE NIGHT/MORNING CONVECTION NOTED ABOVE THAT COULD STABILIZE THE AREA THROUGH OPTIMAL PEAK HEATING...THEREBY REDUCING CHANCES FOR SVR WX. DO STILL FEEL THAT CONVECTION WILL FIRE TO THE WEST ALONG THE FRONT IN ILLINOIS DURING THE AFTERNOON AND MOVE EAST TOWARDS THE AREA. HAVE THEREFORE CAUTIOUSLY HELD WITH LIKELY POPS IN NW AREAS WEDS AFTERNOON BUT FOR NOW BACKED OFF ON POP TIMING EARLIER IN THE DAY ASSUMING THAT MODEL INDICATIONS OF IA/WI/MN COMPLEX DYING AS IT APPROACHES OCCUR. THIS SAME REASONING WARRANTS A SLIGHT INCREASE IN POPS WEDS NGT WITH POTENTIAL FOR SOMEWHAT SLOWER DEPARTURE OF PRECIP...BUT NOT A RAMP UP TO LIKELY IN EASTERN AREAS GIVEN LESS FAVORABLE TIME FRAME FOR CONVECTION TO MAINTAIN ITSELF UNLESS ALREADY WELL ESTABLISHED. LONG TERM... THURSDAY THROUGH TUESDAY...THE MAIN CHALLENGES THIS PERIOD CONCERN THE CHANCES FOR THE DEVELOPMENT OF A CUT OFF LOW OVER THE OHIO VALLEY REGION THIS WEEKEND. ADDITIONAL CHALLENGES INCLUDE THE TIMING AND EXTENT OF PRECIPITATION AND THE EFFECT ON TEMPERATURES IF THE LOW DEVELOPS AND LINGERS OVER OR NEAR THE REGION. FOR THIS PACKAGE...FAVOR THE ECMWF...ALTHOUGH THE 12Z RUN WAS AN OUTLIER COMPARED TO THE PAST SEVERAL RUNS. THE 12Z ECMWF RUN WAS NOT USED FOR THIS PACKAGE. THE PAST SEVERAL ECMWF RUNS HAVE HAD REASONABLE RUN TO RUN CONSISTENCY. AS A WHOLE THE NEW 12Z GFS SOLUTION HAS TRENDED TOWARD THE SLOWER...FARTHER WEST 00Z ECMWF SOLUTION. ALSO...THE 00Z ECMWF HAS HAD BETTER SUPPORT WITH THE SURFACE LOW/SURFACE REFLECTION CLOSER TO THE UPPER LOW THAN THE GFS. HAVE RAISED RAIN CHANCES FRIDAY NIGHT GIVEN REASONABLE CONFIDENCE IN THE TIMING OF THE SHORT WAVE TROF AND ASSOCIATED COLD FRONT. FOR THE REST OF THE PERIOD...WENT WITH PERSISTENCE AND ATTEMPTED TO HOLD TO THE PREVIOUS FORECAST WITH DRY CONDITIONS STARTING SUNDAY NIGHT. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR INZ006>009- 017-018-024>027-032>034. MI...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR MIZ080-081. OH...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR OHZ001-002- 004-005-015-016-024-025. LM...NONE. && $$ SHORT TERM...FISHER LONG TERM...SKIPPER AVIATION...MARSILI
AREA FORECAST DISCUSSION
NWS DES MOINES IA
1225 AM CDT WED SEP 5 2012 ...UPDATED AVIATION DISCUSSION... .SHORT TERM /TONIGHT/... PRIMARY CONCERN TONIGHT WILL BE CONVECTIVE TRENDS BUT CONFIDENCE IN THAT EVOLUTION IS DECREASING AS MOST MODELS...HIGH RES EXPLICIT AND PARAMETERIZED...ARE CURRENTLY OVERZEALOUS IN THEIR DEPICTION OF PRECIP. PRESENT SITUATION HAS 80KT JET FROM ROCKIES INTO IA ENHANCING DEEP/EFFECTIVE SHEAR. LITTLE IN THE WAY OF LARGE SCALE FORCING NOTED IMMEDIATELY UPSTREAM HOWEVER WITH RAP ANALYSIS AND WATER VAPOR IMAGERY FAIRLY BENIGN. ONLY SIGN OF LARGER SCALE UPWARD VERTICAL MOTION /UVM/ SEEMS TO BE ACROSS CENTRAL NE NEAR H85/H7 SHORT WAVE PER VISIBLE IMAGERY. OUR FORECAST AREA SEEMS PRIMED FOR DEVELOPMENT THERMODYNAMICALLY WITH UNCAPPED 2000-4000 J/KG MLCAPES. HOWEVER SPOTTY CONVERGENCE AND LITTLE TO NO UVM OVERHEAD HAVE RESULTED IN NO DEVELOPMENT AS OF YET. SMALL CELL ALONG HIGHWAY 20 DISSIPATED WHICH IS A SIGNAL THAT WE ARE NOT READY TO GO SURFACE BASED AND/OR HAVE INSUFFICIENT UPPER LEVEL SUPPORT. AT THE MOMENT FEEL THAT CONVECTIVE INITIATION IS GOING TO WAIT FOR AFOREMENTIONED NE UVM ALONG WITH INCREASED SYNOPTIC SCALE FORCING AHEAD OF MT/DAKOTAS SHORT WAVE AS IT MOVES EAST THIS EVENING. ECMWF/GFS QG FORCING INCREASES AS IT REACHES MN BY 06Z. 18Z RAP SUGGESTS WEAKLY CAPPED ELEVATED CAPES 2000 J/KG OR MORE WILL BE IN PLACE AND CERTAINLY CAPABLE OF SUPPORTING SEVERE WEATHER CONSIDERING OUR PROXIMITY TO THE JET. DCAPES SHOULD REMAIN QUITE HIGH OVERNIGHT WITH SOUNDINGS SHOWING PLENTY OF DRY AIR BELOW 3KM. THUS EXPECT NE CONVECTION TO SLOWLY DEVELOP AND MATURE AS IT REACHES IA MUCAPE AXIS WITH DAMAGING WINDS AND HAIL QUITE POSSIBLE. .LONG TERM /WEDNESDAY THROUGH TUESDAY/... FORECAST CONCERNS FOR WEDNESDAY WILL DEAL WITH A STRONG COLD FRONT PUSHING ACROSS THE FORECAST AREA DURING THE MORNING AIDED BY A POTENT SHORT WAVE SWEEPING ACROSS THE NORTHERN PLAINS INTO IA. MOST OF THE CAPE AND SHEAR ARE AHEAD OF THE BOUNDARY SO ONGOING CONVECTION FROM THE OVERNIGHT WILL AFFECT THE EASTERN HALF OR SO OF THE FORECAST AREA. BEHIND THE FRONT MUCH COOLER AND DRIER AIR WILL PUSH INTO CENTRAL IOWA DURING THE AFTERNOON SO ANY THUNDERSTORM THREAT IN THE AFTERNOON WILL BE CONFINED TO THE FAR SOUTHEAST PORTION OF CENTRAL IOWA ON EAST. BEYOND WEDNESDAY WE BEGIN OUR SLIDE IN TEMPS AS HIGH PRESSURE BUILDS IN WEDNESDAY NIGHT THROUGH LATE THURSDAY. WARM ADVECTION OCCURS THURSDAY NIGHT AHEAD OF THE NEXT SYSTEM TO AFFECT THE AREA. ON FRIDAY THETA ADVECTION INCREASES AND A SECOND SHORT WAVE ROTATES THROUGH THE NORTHERN AND CENTRAL PLAINS BRINGING AND ANOTHER FRONT WILL PUSH ACROSS IOWA BRINGING A REINFORCING SHOT OF COLD AIR. SHOWERS AND ISOLATED THUNDERSTORMS WILL OCCUR WITH THIS FOLLOWED BY SOME VERY COOL AIR. TEMPERATURES OVER THE WEEKEND WILL ACTUALLY BE BELOW NORMAL BUT IT WILL BE DRY. && .AVIATION...05/06Z ONGOING CONVECTION ACROSS NORTHERN IOWA WILL AFFECT NORTHERN SITES...KFOD/KMCW/KALO THROUGH 12Z. WITH STRONGER THUNDERSTORMS WINDS COULD GUST UP TO 40KTS OR HIGHER...AND WITH HEAVY RAIN COULD SEE VISIBILITIES DROP TO MVFR OR IFR. HOWEVER...CEILINGS WILL PRIMARILY REMAIN VFR WITH HIGH BASED STORMS. COULD SEE PRECIPITATION SPREADING FURTHER SOUTH TO KDSM...AND HAVE VCTS MENTIONED. PRECIPITATION WILL QUICKLY PUSH OUT OF SITES...BUT COULD SEE SOME BR OR HZ DEVELOPMENT NEAR 12Z AT SITES. HOWEVER...BELIEVE WINDS WILL REMAIN STRONG AND HAVE NOT INCLUDED MENTION ATTM. WINDS WILL SHIFT TO THE N/NE AND WILL BE STRONG AND GUSTY THROUGHOUT THE DAY WEDNESDAY. OTHERWISE...CEILINGS WILL BE VFR. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...SMALL LONG TERM...FAB AVIATION...AWB
AREA FORECAST DISCUSSION
NWS GOODLAND KS
838 PM MDT THU SEP 6 2012 .UPDATE... ISSUED AT 828 PM MDT THU SEP 6 2012 JUST COMPLETED ANOTHER UPDATE. TRIMMED OFF ALL BUT THE EASTERN PORTION OF THE WATCH AND COULD HAVE TRIMMED IT ALL BUT JUST ENOUGH THERE FOR ME TO KEEP IT IN UNTIL 04Z. LOOKING THE UPSTREAM 00Z SOUNDING IT DOES NOT LOOK FAVORABLE FOR REDEVELOPMENT WITH A DRY AIR MASS IN PLACE. MID LEVEL MOISTURE DOES INCREASE AFTER 06Z. MODELS INSIST ON KEEPING A CONSIDERABLE AMOUNT OF ELEVATED CAPE INTO TOMORROW MORNING WITH LOW CINH UNTIL AFTER 12Z. LIGHTNING DETECTION NETWORK IS SHOWING SOME INCREASE IN LIGHTING WELL TO THE NORTHWEST AND ESPECIALLY WEST AS A RATHER STRONGER SHORTWAVE TROUGH MOVES IN. ALSO AREA COMES UNDER THE INFLUENCE OF RIGHT REAR QUADRANT OF THE JET BY LATE TONIGHT INTO TOMORROW MORNING. AM NOT VERY EXCITED ABOUT THE PROSPECT OF MEASURABLE BUT CANNOT IGNORE WHAT IS GOING ON UPSTREAM COMBINED WITH WHAT THE LIFT AND INSTABILITY IS SHOWING ME. SO AFTER AFTER THE WATCH IS OVER KEPT A SLIGHT CHANCE TO LOW CHANCE OF PRECIPITATION INTO TOMORROW MORNING. AT THIS TIME IT LOOKS LIKE WILL STAY BELOW WIND ADVISORY CRITERIA BUT WILL CONTINUE TO MONITOR TRENDS AND NEWER DATA. UPDATE ISSUED AT 629 PM MDT THU SEP 6 2012 JUST COMPLETED AN UPDATE MAINLY TO REFINE THUNDERSTORM FORECAST. MAIN LINE OF THUNDERSTORMS HAS PUSHED OFF TO THE EAST OF THE FORECAST AREA AT THIS TIME. BOUNDARY IS STILL OVER THE AREA THAT IS IN THE SEVERE THUNDERSTORM WATCH WITH IT PROGGED TO MOVE BACK TO THE WEST THIS EVENING. PROBLEM AT THIS TIME...MAIN MID/UPR LEVEL SUPPORT HAS PUSHED OFF TO THE EAST. AM VERY PESSIMISTIC ABOUT ANY REDEVELOPMENT AT THIS TIME. HOWEVER...WILL CONTINUE TO WATCH TRENDS AND ALLOW NEWER MODEL DATA TO COME IN. SO AT THIS TIME...REDUCED POPS AND REDUCED AREA OF PRECIPITATION. ALSO REDUCED TH SKY COVER AS WELL BECAUSE OF THIS. WIND FIELD IS ALL OVER THE PLACE DUE TO THE ABOVE MENTIONED BOUNDARY AND AS A RESULT MODELS HAVING A HARD TIME IN RESOLVING THE DEWPOINT FIELD AS WELL. LOWER DEWPOINTS ARE MUCH FURTHER EAST BUT SHOULD COME BACK TO WEST THROUGH THE EVENING. FRONT STILL LOOKS ON TRACK IN THE NORTH AROUND 06Z. DEFINITELY NOT THE LAST UPDATE FOR THE EVENING. UPDATE ISSUED AT 259 PM MDT THU SEP 6 2012 UPDATED FORECAST TO INCLUDE THE SEVERE THUNDERSTORM WATCH THIS AFTERNOON AND EVENING. && .SHORT TERM...(THIS EVENING THROUGH FRIDAY) ISSUED AT 149 PM MDT THU SEP 6 2012 LATEST WV IMAGERY AND RUC H5 ANALYSIS CONTINUE TO INDICATE WESTERLY FLOW ACROSS THE INTER-MOUNTAIN WEST AND HIGH PLAINS JUST NORTH OF SOUTHWESTERN CONUS RIDGE. AT THE SURFACE A TROUGH/DRY LINE HAS SHIFTED EAST TO LIE FROM JUST WEST OF MCCOOK NEBRASKA...BETWEEN GOODLAND AND COLBY KANSAS...AND THEN WEST OF TRIBUNE KANSAS. TD VALUES IN THE UPPER 50S/LOW 60S AND MIXED LAYER CAPES IN EXCESS OF 1000 J/KG ARE CURRENTLY EAST OF THIS DRY LINE...WITH MUCH MORE STABLE AIR MASS TO THE WEST OF THIS FEATURE. SURFACE CONVERGENCE AHEAD OF THIS DRY LINE SHOULD HELP OVERCOME WEAKENING CAP LATER THIS AFTERNOON AND EARLY THIS EVENING...WITH THUNDERSTORM COVERAGE INCREASING FURTHER EAST WHERE BETTER LARGE SCALE FORCING IS EXPECTED. BASED ON MODEL SOUNDINGS LCL VALUES REMAIN HIGH...WITH DEEP MIXED LAYER TO ABOUT 650 MB INDICATIVE OF MICROBURST POTENTIAL WITH THUNDERSTORMS. IN ADDITION...SUPERCELL THUNDERSTORMS WILL BE A POSSIBILITY....WITH 0-6KM BULK SHEAR VALUES PROGGED TO BE AROUND 40KT OR HIGHER...AND WITH MIXED LAYER CAPE IN EXCESS OF 1500 J/KG. LCL VALUES WILL BE FAIRLY HIGH IN THE 8-10KFT RANGE...SO IM NOT AS CONCERNED ABOUT A TORNADO THREAT WITH THIS ACTIVITY. A COLD FRONT IS EXPECTED TO MOVE ACROSS THE CWA FROM THE NW AFTER MIDNIGHT...WITH LARGE PRESSURE RISES AND INCREASING H85 WINDS BEHIND THE FRONT POSSIBLY RESULTING IN ADVISORY CRITERIA WINDS. OTHER THAN THE 12Z NAM...MOST GUIDANCE IS VERY MARGINAL ON THIS...SO I DECIDED AGAINST ISSUING AN ADVISORY THIS FORECAST CYCLE. AHEAD OF THIS FRONT ELEVATED INSTABILITY AND MOISTURE WILL BEGIN TO BUILD BACK TO THE WEST...WITH ISOLATED THREAT FOR CONVECTION RETURNING AFTER MIDNIGHT THROUGH FRIDAY MORNING AS THE FRONT MOVES ACROSS THE REGION. CONFIDENCE IS LOW AT THIS TIME...AND MOST GUIDANCE IS NOT CURRENTLY INITIATING ANYTHING WITH THIS FROPA...SO I LIMITED POPS TO SLIGHT CHANCE CATEGORY. LARGE SCALE SUBSIDENCE SHOULD BRING DRY CONDITIONS BACK TO THE CWA FRIDAY. .LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY) ISSUED AT 215 PM MDT THU SEP 6 2012 DRY AND MILD CONDITIONS ON FRIDAY NIGHT AND SATURDAY WILL TRANSITION TO DRY AND WARM CONDITIONS DURING THE FIRST PART OF NEXT WEEK AS THE UPPER RIDGE MOVES FROM THE ROCKIES TO THE HIGH PLAINS AND THE COOLER AREA OF HIGH PRESSURE AT THE SURFACE SLIDES INTO THE SOUTHERN PLAINS. SOUTHERLY SURFACE RETURN FLOW ESTABLISHES OVER THE CENTRAL HIGH PLAINS ON SUNDAY AND CONTINUES THROUGH MONDAY AS THE SURFACE LEE TROUGH DEEPENS AND THE UPPER RIDGE TRANSITIONS OVER THE PLAINS STATES. TEMPERATURES ARE EXPECTED TO WARM BACK UP INTO THE 90S BY MONDAY AS A RESULT AHEAD OF THE NEXT FRONT DUE THROUGH THE REGION DURING THE DAY ON TUESDAY. ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ON TUESDAY IN THE VICINITY OF THE FRONT. STORMS WILL BECOME MORE WIDESPREAD AND CONTINUE THROUGH TUESDAY NIGHT AND INTO WEDNESDAY AS THE FLOW OVER THE CENTRAL HIGH PLAINS BECOMES MORE ZONAL AND A SERIES OF SHORT WAVE TROUGHS MOVES THROUGH THE FLOW. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING) ISSUED AT 540 PM MDT THU SEP 6 2012 VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. AT THIS TIME INITIAL ROUND OF THUNDERSTORMS WILL BE TO THE EAST OF BOTH TAF SITES. THERE IS A LOW PROBABILITY OF THUNDERSTORMS AFTER 06Z BUT AT THIS TIME TO KEEP THEM OUT. WILL CONTINUE TO MONITOR CLOSELY WITH LATEST DATA FOR POSSIBLE UPDATES. STRONG COLD FRONT BEGINS TO MOVE THROUGH THE AREA IN THE 06Z TO 08Z TIME FRAME WITH VERY GUSTY WINDS EXPECTED THROUGH THE MORNING HOURS. AFTER THAT WINDS WILL BEGIN TO GRADUALLY DECREASE. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...BULLER SHORT TERM...DR LONG TERM...LOCKHART AVIATION...BULLER
AREA FORECAST DISCUSSION
NWS GOODLAND KS
634 PM MDT THU SEP 6 2012 .UPDATE... ISSUED AT 629 PM MDT THU SEP 6 2012 JUST COMPLETED AN UPDATE MAINLY TO REFINE THUNDERSTORM FORECAST. MAIN LINE OF THUNDERSTORMS HAS PUSHED OFF TO THE EAST OF THE FORECAST AREA AT THIS TIME. BOUNDARY IS STILL OVER THE AREA THAT IS IN THE SEVERE THUNDERSTORM WATCH WITH IT PROGGED TO MOVE BACK TO THE WEST THIS EVENING. PROBLEM AT THIS TIME...MAIN MID/UPR LEVEL SUPPORT HAS PUSHED OFF TO THE EAST. AM VERY PESSIMISTIC ABOUT ANY REDEVELOPMENT AT THIS TIME. HOWEVER...WILL CONTINUE TO WATCH TRENDS AND ALLOW NEWER MODEL DATA TO COME IN. SO AT THIS TIME...REDUCED POPS AND REDUCED AREA OF PRECIPITATION. ALSO REDUCED TH SKY COVER AS WELL BECAUSE OF THIS. WIND FIELD IS ALL OVER THE PLACE DUE TO THE ABOVE MENTIONED BOUNDARY AND AS A RESULT MODELS HAVING A HARD TIME IN RESOLVING THE DEWPOINT FIELD AS WELL. LOWER DEWPOINTS ARE MUCH FURTHER EAST BUT SHOULD COME BACK TO WEST THROUGH THE EVENING. FRONT STILL LOOKS ON TRACK IN THE NORTH AROUND 06Z. DEFINITELY NOT THE LAST UPDATE FOR THE EVENING. UPDATE ISSUED AT 259 PM MDT THU SEP 6 2012 UPDATED FORECAST TO INCLUDE THE SEVERE THUNDERSTORM WATCH THIS AFTERNOON AND EVENING. && .SHORT TERM...(THIS EVENING THROUGH FRIDAY) ISSUED AT 149 PM MDT THU SEP 6 2012 LATEST WV IMAGERY AND RUC H5 ANALYSIS CONTINUE TO INDICATE WESTERLY FLOW ACROSS THE INTER-MOUNTAIN WEST AND HIGH PLAINS JUST NORTH OF SOUTHWESTERN CONUS RIDGE. AT THE SURFACE A TROUGH/DRY LINE HAS SHIFTED EAST TO LIE FROM JUST WEST OF MCCOOK NEBRASKA...BETWEEN GOODLAND AND COLBY KANSAS...AND THEN WEST OF TRIBUNE KANSAS. TD VALUES IN THE UPPER 50S/LOW 60S AND MIXED LAYER CAPES IN EXCESS OF 1000 J/KG ARE CURRENTLY EAST OF THIS DRY LINE...WITH MUCH MORE STABLE AIR MASS TO THE WEST OF THIS FEATURE. SURFACE CONVERGENCE AHEAD OF THIS DRY LINE SHOULD HELP OVERCOME WEAKENING CAP LATER THIS AFTERNOON AND EARLY THIS EVENING...WITH THUNDERSTORM COVERAGE INCREASING FURTHER EAST WHERE BETTER LARGE SCALE FORCING IS EXPECTED. BASED ON MODEL SOUNDINGS LCL VALUES REMAIN HIGH...WITH DEEP MIXED LAYER TO ABOUT 650 MB INDICATIVE OF MICROBURST POTENTIAL WITH THUNDERSTORMS. IN ADDITION...SUPERCELL THUNDERSTORMS WILL BE A POSSIBILITY....WITH 0-6KM BULK SHEAR VALUES PROGGED TO BE AROUND 40KT OR HIGHER...AND WITH MIXED LAYER CAPE IN EXCESS OF 1500 J/KG. LCL VALUES WILL BE FAIRLY HIGH IN THE 8-10KFT RANGE...SO IM NOT AS CONCERNED ABOUT A TORNADO THREAT WITH THIS ACTIVITY. A COLD FRONT IS EXPECTED TO MOVE ACROSS THE CWA FROM THE NW AFTER MIDNIGHT...WITH LARGE PRESSURE RISES AND INCREASING H85 WINDS BEHIND THE FRONT POSSIBLY RESULTING IN ADVISORY CRITERIA WINDS. OTHER THAN THE 12Z NAM...MOST GUIDANCE IS VERY MARGINAL ON THIS...SO I DECIDED AGAINST ISSUING AN ADVISORY THIS FORECAST CYCLE. AHEAD OF THIS FRONT ELEVATED INSTABILITY AND MOISTURE WILL BEGIN TO BUILD BACK TO THE WEST...WITH ISOLATED THREAT FOR CONVECTION RETURNING AFTER MIDNIGHT THROUGH FRIDAY MORNING AS THE FRONT MOVES ACROSS THE REGION. CONFIDENCE IS LOW AT THIS TIME...AND MOST GUIDANCE IS NOT CURRENTLY INITIATING ANYTHING WITH THIS FROPA...SO I LIMITED POPS TO SLIGHT CHANCE CATEGORY. LARGE SCALE SUBSIDENCE SHOULD BRING DRY CONDITIONS BACK TO THE CWA FRIDAY. .LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY) ISSUED AT 215 PM MDT THU SEP 6 2012 DRY AND MILD CONDITIONS ON FRIDAY NIGHT AND SATURDAY WILL TRANSITION TO DRY AND WARM CONDITIONS DURING THE FIRST PART OF NEXT WEEK AS THE UPPER RIDGE MOVES FROM THE ROCKIES TO THE HIGH PLAINS AND THE COOLER AREA OF HIGH PRESSURE AT THE SURFACE SLIDES INTO THE SOUTHERN PLAINS. SOUTHERLY SURFACE RETURN FLOW ESTABLISHES OVER THE CENTRAL HIGH PLAINS ON SUNDAY AND CONTINUES THROUGH MONDAY AS THE SURFACE LEE TROUGH DEEPENS AND THE UPPER RIDGE TRANSITIONS OVER THE PLAINS STATES. TEMPERATURES ARE EXPECTED TO WARM BACK UP INTO THE 90S BY MONDAY AS A RESULT AHEAD OF THE NEXT FRONT DUE THROUGH THE REGION DURING THE DAY ON TUESDAY. ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ON TUESDAY IN THE VICINITY OF THE FRONT. STORMS WILL BECOME MORE WIDESPREAD AND CONTINUE THROUGH TUESDAY NIGHT AND INTO WEDNESDAY AS THE FLOW OVER THE CENTRAL HIGH PLAINS BECOMES MORE ZONAL AND A SERIES OF SHORT WAVE TROUGHS MOVES THROUGH THE FLOW. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING) ISSUED AT 540 PM MDT THU SEP 6 2012 VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. AT THIS TIME INITIAL ROUND OF THUNDERSTORMS WILL BE TO THE EAST OF BOTH TAF SITES. THERE IS A LOW PROBABILITY OF THUNDERSTORMS AFTER 06Z BUT AT THIS TIME TO KEEP THEM OUT. WILL CONTINUE TO MONITOR CLOSELY WITH LATEST DATA FOR POSSIBLE UPDATES. STRONG COLD FRONT BEGINS TO MOVE THROUGH THE AREA IN THE 06Z TO 08Z TIME FRAME WITH VERY GUSTY WINDS EXPECTED THROUGH THE MORNING HOURS. AFTER THAT WINDS WILL BEGIN TO GRADUALLY DECREASE. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...BULLER SHORT TERM...DR LONG TERM...LOCKHART AVIATION...BULLER
AREA FORECAST DISCUSSION
NWS GOODLAND KS
545 PM MDT THU SEP 6 2012 .UPDATE... ISSUED AT 259 PM MDT THU SEP 6 2012 UPDATED FORECAST TO INCLUDE THE SEVERE THUNDERSTORM WATCH THIS AFTERNOON AND EVENING. && .SHORT TERM...(THIS EVENING THROUGH FRIDAY) ISSUED AT 149 PM MDT THU SEP 6 2012 LATEST WV IMAGERY AND RUC H5 ANALYSIS CONTINUE TO INDICATE WESTERLY FLOW ACROSS THE INTER-MOUNTAIN WEST AND HIGH PLAINS JUST NORTH OF SOUTHWESTERN CONUS RIDGE. AT THE SURFACE A TROUGH/DRY LINE HAS SHIFTED EAST TO LIE FROM JUST WEST OF MCCOOK NEBRASKA...BETWEEN GOODLAND AND COLBY KANSAS...AND THEN WEST OF TRIBUNE KANSAS. TD VALUES IN THE UPPER 50S/LOW 60S AND MIXED LAYER CAPES IN EXCESS OF 1000 J/KG ARE CURRENTLY EAST OF THIS DRY LINE...WITH MUCH MORE STABLE AIR MASS TO THE WEST OF THIS FEATURE. SURFACE CONVERGENCE AHEAD OF THIS DRY LINE SHOULD HELP OVERCOME WEAKENING CAP LATER THIS AFTERNOON AND EARLY THIS EVENING...WITH THUNDERSTORM COVERAGE INCREASING FURTHER EAST WHERE BETTER LARGE SCALE FORCING IS EXPECTED. BASED ON MODEL SOUNDINGS LCL VALUES REMAIN HIGH...WITH DEEP MIXED LAYER TO ABOUT 650 MB INDICATIVE OF MICROBURST POTENTIAL WITH THUNDERSTORMS. IN ADDITION...SUPERCELL THUNDERSTORMS WILL BE A POSSIBILITY....WITH 0-6KM BULK SHEAR VALUES PROGGED TO BE AROUND 40KT OR HIGHER...AND WITH MIXED LAYER CAPE IN EXCESS OF 1500 J/KG. LCL VALUES WILL BE FAIRLY HIGH IN THE 8-10KFT RANGE...SO IM NOT AS CONCERNED ABOUT A TORNADO THREAT WITH THIS ACTIVITY. A COLD FRONT IS EXPECTED TO MOVE ACROSS THE CWA FROM THE NW AFTER MIDNIGHT...WITH LARGE PRESSURE RISES AND INCREASING H85 WINDS BEHIND THE FRONT POSSIBLY RESULTING IN ADVISORY CRITERIA WINDS. OTHER THAN THE 12Z NAM...MOST GUIDANCE IS VERY MARGINAL ON THIS...SO I DECIDED AGAINST ISSUING AN ADVISORY THIS FORECAST CYCLE. AHEAD OF THIS FRONT ELEVATED INSTABILITY AND MOISTURE WILL BEGIN TO BUILD BACK TO THE WEST...WITH ISOLATED THREAT FOR CONVECTION RETURNING AFTER MIDNIGHT THROUGH FRIDAY MORNING AS THE FRONT MOVES ACROSS THE REGION. CONFIDENCE IS LOW AT THIS TIME...AND MOST GUIDANCE IS NOT CURRENTLY INITIATING ANYTHING WITH THIS FROPA...SO I LIMITED POPS TO SLIGHT CHANCE CATEGORY. LARGE SCALE SUBSIDENCE SHOULD BRING DRY CONDITIONS BACK TO THE CWA FRIDAY. .LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY) ISSUED AT 215 PM MDT THU SEP 6 2012 DRY AND MILD CONDITIONS ON FRIDAY NIGHT AND SATURDAY WILL TRANSITION TO DRY AND WARM CONDITIONS DURING THE FIRST PART OF NEXT WEEK AS THE UPPER RIDGE MOVES FROM THE ROCKIES TO THE HIGH PLAINS AND THE COOLER AREA OF HIGH PRESSURE AT THE SURFACE SLIDES INTO THE SOUTHERN PLAINS. SOUTHERLY SURFACE RETURN FLOW ESTABLISHES OVER THE CENTRAL HIGH PLAINS ON SUNDAY AND CONTINUES THROUGH MONDAY AS THE SURFACE LEE TROUGH DEEPENS AND THE UPPER RIDGE TRANSITIONS OVER THE PLAINS STATES. TEMPERATURES ARE EXPECTED TO WARM BACK UP INTO THE 90S BY MONDAY AS A RESULT AHEAD OF THE NEXT FRONT DUE THROUGH THE REGION DURING THE DAY ON TUESDAY. ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ON TUESDAY IN THE VICINITY OF THE FRONT. STORMS WILL BECOME MORE WIDESPREAD AND CONTINUE THROUGH TUESDAY NIGHT AND INTO WEDNESDAY AS THE FLOW OVER THE CENTRAL HIGH PLAINS BECOMES MORE ZONAL AND A SERIES OF SHORT WAVE TROUGHS MOVES THROUGH THE FLOW. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING) ISSUED AT 540 PM MDT THU SEP 6 2012 VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. AT THIS TIME INITIAL ROUND OF THUNDERSTORMS WILL BE TO THE EAST OF BOTH TAF SITES. THERE IS A LOW PROBABILITY OF THUNDERSTORMS AFTER 06Z BUT AT THIS TIME TO KEEP THEM OUT. WILL CONTINUE TO MONITOR CLOSELY WITH LATEST DATA FOR POSSIBLE UPDATES. STRONG COLD FRONT BEGINS TO MOVE THROUGH THE AREA IN THE 06Z TO 08Z TIME FRAME WITH VERY GUSTY WINDS EXPECTED THROUGH THE MORNING HOURS. AFTER THAT WINDS WILL BEGIN TO GRADUALLY DECREASE. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...LOCKHART SHORT TERM...DR LONG TERM...LOCKHART AVIATION...BULLER
AREA FORECAST DISCUSSION
NWS PADUCAH KY
929 PM CDT THU SEP 6 2012 .UPDATE... ISSUED AT 930 PM CDT THU SEP 6 2012 EARLY EVENING MCS WAS IN THE PROCESS OF DISSIPATING OVER WESTERN KY...WITH VERY LITTLE LEFT IN THE WAY OF DEEP CONVECTION AT 02Z. SOME ISOLATED WEAK STORMS WERE OBSERVED UPSTREAM OVER CENTRAL MISSOURI. THESE STORMS APPEAR TO BE RELATED TO WARM MOIST ADVECTION OVER THE TOP OF THE COLD DOME LEFT BY AFTERNOON STORMS. THE 00Z RUC MODEL INDICATES THAT LOW LEVEL WARM MOIST ADVECTION WILL SPREAD SOUTH AND EAST OVERNIGHT AS THE MESOHIGH RETREATS EASTWARD. THEREFORE...WOULD NOT BE SURPRISED TO SEE ISOLATED TO SCATTERED STORMS FORM OR SPREAD SOUTHEAST INTO SE MISSOURI AND SRN ILLINOIS OVERNIGHT. UPDATE TO FORECAST COMING AROUND 03Z WILL NOT CONTAIN ANY BIG CHANGES. && .SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)... ISSUED AT 219 PM CDT THU SEP 6 2012 TOWERING CUMULUS ALONG AND NORTH OF A MARBLE HILL...JACKSON SHOULD ENHANCE THUNDERSTORM DEVELOPMENT AHEAD OF THE MCS OVER CENTRAL MISSOURI AS OF 19Z THURSDAY DURING THE MIDDLE/LATE AFTERNOON HOURS. THIS CONVECTION WILL LIKELY DISTURB THE ENVIRONMENT AHEAD OF THE MCS...BUT ENHANCE POCKETS OF CONVECTION JUST AHEAD OF IT. I AM CONCERNED THAT THE SOUTHERN END OF THE BOWING MCS STRUCTURE MAY DIVE MOVE SOUTH TOWARD BUTLER COUNTY...LIMITING EASTWARD MOVEMENT BEYOND THE MISSISSIPPI RIVER THROUGH SUNSET. LAPS DATA INDICATE BETTER CAPE AND THETA-E CONVERGENCE ACROSS THAT AREA. THE 3KM HRRR 1KM REFLECTIVITY FIELDS SEEM TO HAVE A GOOD HANDLE ON THE MCS THIS AFTERNOON. THIS FIELD WAS UTILIZED IN DEVELOP POP/WEATHER CHANCES ACROSS SOUTHEAST MISSOURI IN COLLABORATION WITH THE NWS OFFICES IN SPRINGFIELD AND SAINT LOUIS MO. ONCE THIS MCS DECAYS AND DIES OUT THIS EVENING...THE MAIN FOCUS FOR CONVECTIVE ACTIVITY WILL SHIFT BACK TO THE WEST WITH ANOTHER COLD FRONT MOVING TOWARD THE AREA FRIDAY AFTERNOON. SATELLITE INITIALIZATION OF THE HEMISPHERIC SCALE MODELS HAS SHOWN THAT THE CLOSED CYCLONIC VORTEX THAT WAS ADVERTISED OVER THE ONTARIO CANADIAN PROVINCE...WAS ACTUALLY SHOWING UP FURTHER WEST IN THE MANITOBA CANADIAN PROVINCE. THE NET EFFECT FOR THE WFO PAH FORECAST AREA IS THAT THE TIMING OF THE SYSTEM MOVEMENT OF THE COLD FRONT WILL BE SHIFTED TO THE LATE AFTERNOON AND EVENING HOURS ON FRIDAY. THERE SHOULD BE SUFFICIENT IMMEDIATE POST-FRONTAL...WITH FAIRLY GOOD PRECIPITATION EFFICIENCY. GOES SOUNDER DATA ALREADY SHOW LAYER PRECIPITABLE WATER BETWEEN 1.6 TO 2.0 INCHES...ALREADY NEARLY 100 PERCENT OF NORMAL. THERE IS DEEPER PLUME OF PRECIPITABLE WATER IN ARKANSAS AT THIS TIME AND THIS SHOULD TRANSLATE OVER THE WFO PAH FORECAST AREA FRIDAY AFTERNOON AND EVENING. PLAN TO EMPHASIZE LOCALLY HEAVY RAIN WITH THE SYSTEM ON FRIDAY. AFTER THE COLD FRONT MOVES THROUGH FRIDAY NIGHT...EARLY SATURDAY MORNING...STRONG COLD AIR ADVECTION SHOULD BRING MAX TEMPERATURES DOWN SOME 1O TO 15 DEGREES BELOW NORMAL FOR SATURDAY...A WELCOME RELIEF TO THE RECORD SETTING SUMMER HEAT. .LONG TERM...(SATURDAY THROUGH THURSDAY) ISSUED AT 219 PM CDT THU SEP 6 2012 DEEP EASTERN U.S. TROF IS FORECAST TO MOVE OFFSHORE FOLLOWED BY RISING MID LEVEL HEIGHTS OVER THE MISSISSIPPI AND OHIO VALLEY REGIONS EARLY NEXT WEEK. AT THE SURFACE...LARGE AREA OF HIGH PRESSURE WILL MOVE SLOWLY EAST OF THE REGION. THE AIR MASS IS FORECAST TO REMAIN VERY DRY THROUGH WEDNESDAY. SO NO PRECIPITATION FORECAST...WITH TEMPERATURES MODERATING EACH DAY. WEDNESDAY NIGHT INTO THURSDAY...THE MODELS DROP A FRONTAL BOUNDARY SOUTH TOWARD THE REGION. STILL SOME QUESTION AS TO WHETHER OR NOT IT WILL MAKE IT INTO THE AREA LATE IN THE DAY 7 PERIOD. SO ELECTED TO LEAVE IT OUT FOR NOW...AND WILL CONTINUE TO MONITOR LONG RANGE MODEL FORECAST TRENDS. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING) ISSUED AT 659 PM CDT THU SEP 6 2012 STRONG BOW OF THUNDERSTORMS WILL CROSS THE KPAH REGION IN THE FIRST COUPLE HOURS OF THE 00Z FORECAST PERIOD. WILL LIKELY BE WIND GUSTS FROM 40 TO 60 MPH WITH THIS BOW OF STORMS. THE STORMS ALSO AFFECTED KCGI AN HOUR OR SO AGO...AND THESE ARE THE ONLY TWO SITES THAT RECEIVED HEAVY RAINS TODAY. LIKE LAST NIGHT...I WILL CONCENTRATE THE IFR TO LIFR FOG IN THOSE TWO SITES DUE TO THE WET GROUND/CLEARING SHIES/LIGHT WINDS. SHOULD BEGIN TO GO DOWN AROUND MIDNIGHT OR SO LOCAL TIME. DENSE STUFF WOULD LIKELY BE 09Z-13Z FRAME. KEVV/KOWB HAD DENSE FOG LAST NIGHT...BUT HAVE HAD A CHANCE TO DRY OUT TODAY. THEREFORE...WILL KEEP MORE LIKE MVFR CONDITIONS THERE LATE TONIGHT. WILL NEED TO MONITOR THO FOR POSSIBLE LOWER CONDITIONS TOWARD DAWN. && .PAH WATCHES/WARNINGS/ADVISORIES... KY...NONE. MO...NONE. IL...NONE. IN...NONE. && $$ UPDATE...MY SHORT TERM...SMITH LONG TERM....CN AVIATION...GM
AREA FORECAST DISCUSSION...UPDATED
NWS GRAY ME
1155 PM EDT THU SEP 6 2012 .SYNOPSIS... A WEAK LOW PRESSURE SYSTEM WILL APPROACH FROM THE WEST THIS EVENING...THEN SLIDE OFFSHORE OVERNIGHT. A WEAK RIDGE OF HIGH PRESSURE FOLLOWS FOR FRIDAY. ANOTHER COLD FRONT WILL IMPACT THE AREA SATURDAY NIGHT THROUGH SUNDAY. HIGH PRESSURE WILL BUILD IN FOR THE FIRST HALF OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... .UPDATE... RADAR SHOWS SHOWERS AND ISOLATED THUNDERSTORMS ARE FILLING IN ALONG A COLD FRONT WHICH HAS NOW ENTERED OUR NORTHERN COUNTIES. HAVE ADJUSTED POPS AS WELL AS CLOUD COVER FOR THE NEXT FEW HOURS AS THE BOUNDARY MOVES EAST. THE LATEST HRRR SHOWS PRECIPITATION WANING OVERNIGHT AS IT DOES SO WITH ONLY A FEW HUNDREDTHS OF QPF AT MOST. AREAS OF DENSE FOG ARE ALREADY DEVELOPING AND EXPECT THAT TREND TO CONTINUE. && PREVIOUS DISCUSSION... A WEAK SHORT WAVE TROUGH AND ASSOCIATED WEAK COLD FRONT WILL PUSH ACROSS THE CWA TONIGHT. SCATTERED SHOWERS AND THUNDERSTORMS ARE ASSOCIATED WITH THESE FEATURES ACROSS UPSTATE NY AND WESTERN VT AS OF 19Z. A FEW OF THESE MAY SURVIVE AS THEY MOVE EASTWARD INTO NEW HAMPSHIRE AND ADJACENT WESTERN MAINE THIS EVENING. WIND SHEAR AND INSTABILITY IN WESTERN NH SEEMS SUFFICIENT ENOUGH TO ALLOW FOR ONE OR TWO STRONG STORMS WITH GUSTY WINDS AND SOME HAIL...MAINLY IN THE CT VALLEY. DID NOT INCLUDE ANY POPS FOR THE MAINE COASTLINE AS ANY ACTIVITY SHOULD DISSIPATE BEFORE REACHING THAT AREA. OTHERWISE...ANY SHOWER ACTIVITY WANES THIS EVENING...ALLOWING FOR SOME CLEARING. AREAS OF FOG...LOCALLY DENSE...SHOULD FORM WELL AFTER MIDNIGHT. MINS BASED ON A BLEND OF THE MET/MAV GUIDANCE. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... SURFACE HIGH PRESSURE RIDGING OVER THE AREA ON FRIDAY. CANNOT COMPLETELY RULE OUT AN ISOLATED SHOWER...BUT THE BULK OF THE DAY SHOULD BE DRY AND QUITE WARM FOR THAT MATTER. FRIDAY NIGHT SHOULD CONTINUE TO BE DRY AS WELL...ALTHOUGH LOW LEVEL MOISTURE MAY RESULT IN THE FORMATION OF LOW CLOUDS AND PERHAPS A LITTLE LIGHT RAIN OR DRIZZLE. && .LONG TERM /SATURDAY THROUGH THURSDAY/... COMPLICATED FCST EVOLVES ON SAT...AS POTENT UPR TROF DIGS ACROSS THE GREAT LAKES. AHEAD OF THIS FEATURE...LLVL SLY FLOW WILL INCREASE THRU THE DAY. THIS WILL TRANSPORT RICH MOISTURE NWD...AS WELL AS INCREASE TEMPS ALOFT TO NEAR 15-16 C. NORMALLY THIS WOULD MEAN A WARM AND HUMID DAY...HOWEVER...SUSTAINED LLVL ONSHORE FLOW IN THE PRESENCE OF WEAK LIFT IN WAA REGIME COULD SPELL MOSTLY LOW CLOUDS WITH DZ LATER IN THE DAY. IN THIS SCENARIO...SUBSTANTIAL DESTABILIZATION OF THE CWA WOULD BE UNLIKELY. SAFEST BET FOR WARMER SFC TEMPS WOULD BE ACROSS THE FAR SWRN ZONES...IN SRN AND WRN NH. TSTMS DEVELOPING ACROSS ERN NY WILL LIKELY HOLD TOGETHER...GIVEN THE STRENGTH OF FORCING ALOFT...AND COULD POSE A SMALL RISK FOR STRONG TSTMS LATE IN THE DAY FOR THE CT RIVER VALLEY. THIS WILL ALSO IMPACT WIND FCST...AS STRONG HEATING AND MIXING COULD RESULT IN SOME GUSTY SLY FLOW AHEAD OF THE FNT. WITH 100 KT JET MOVING OVERHEAD...CONVECTION SHOULD REMAIN INTACT THRU NH AND INTO ME. IT MAY NOT EVEN PRODUCE MUCH IF ANY LIGHTNING...BUT WILL CONTAIN EMBEDDED POCKETS OF +RA...DUE TO PWAT VALUES APPROACHING 1.75 INCHES. THE TIMING OF FNT/OCCLUSION THRU THE CWA VARIES ACROSS AVAILABLE GUIDANCE...WITH THE GFS OFFERING A FAST SOLN AND ECMWF/UKMET ON THE SLOWER SIDE. HIGHEST POP WILL MOST LIKELY BE LATE SAT INTO EARLY SUN...WITH RAPID CLEARING LATE SUN AS DOWNSLOPING NWLY FLOW TAKES OVER. WITH CONCENTRATED FORCING ALONG THE FNT AND RELATIVELY PROGRESSIVE NATURE...EXPECT QPF TO GENERALLY REMAIN AROUND 1 INCH...ESPECIALLY ACROSS THE MTNS. EMBEDDED CONVECTION COULD YIELD SOME LOCALLY HIGHER AMOUNTS. UPR TROF REMAINS OVERHEAD INTO MON...WHERE DIURNAL HEATING WILL FUEL CU DEVELOPMENT AND A FEW ISOLD TO SCT SHRA. HIGH PRES BUILDS IN THRU MIDWEEK...WITH THE NEXT S/WV TROF TO APPROACH THE CWA FROM THE W LATE THU. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... SHORT TERM /THROUGH FRIDAY/...LOCALIZED SHOWERS AND POSSIBLY A THUNDERSTORM EARLY THIS EVENING IN NH WITH LOCALLY LOWER CONDITIONS. OTHERWISE...MAINLY VFR. HOWEVER...AREAS OF FOG AND SOME STRATUS ARE EXPECTED LATER TONIGHT INTO EARLY FRIDAY MORNING AT MOST TERMINALS...BRINGING CONDITIONS DOWN TO IFR OR LOWER FOR A TIME. OTHERWISE...VFR EXPECTED DURING THE DAY ON FRIDAY. IFR CONDITIONS EXPECTED TO ONCE AGAIN DEVELOP FRIDAY NIGHT. LONG TERM...IFR/LIFR CONDITIONS SATURDAY INTO SUNDAY MORNING IN HEAVY SHOWERS AND ISOLATED THUNDERSTORMS IMPROVING GENERALLY FROM WEST TO EAST BY LATE SUN MORNING. PATCHY MVFR FOG MONDAY MORNING BUT OTHERWISE VFR. && .MARINE... SHORT TERM /THROUGH FRIDAY/...SEAS WILL GRADUALLY DIMINISH THIS EVENING. HOWEVER...LONG PERIOD SWELLS TO CONTINUE THROUGH FRIDAY NIGHT. LONG TERM...SOUTHEAST SWELL FROM LESLIE WILL IMPACT THE COAST THROUGH TUE. LONG PERIOD SWELL AROUND 13 SECONDS WILL BUILD TO NEAR 10 FT ON THE OUTER WATERS AS THE STORM REMAINS OUTSIDE THE GULF OF MAINE. RIP CURRENTS AND BEACH EROSION APPEAR TO BE THE BIGGEST THREATS. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ UPDATE...HANES
AREA FORECAST DISCUSSION
NWS CARIBOU ME
1213 AM EDT WED SEP 5 2012 .SYNOPSIS... LOW PRESSURE WILL APPROACH FROM THE WEST TONIGHT THEN TRACK ACROSS COASTAL MAINE WEDNESDAY. WEAK HIGH PRESSURE WILL RETURN THURSDAY INTO FRIDAY. && .NEAR TERM /THROUGH WEDNESDAY/... MIDNIGHT UPDATE...NUDGED LIKELY POPS FURTHER NORTH JUST A BIT AS RAIN IS MOVING INTO WESTERN AROOSTOOK COUNTY AND NORTHERN SOMERSET AND PISCATAQUIS COUNTY AND MESOSCALE MODELS LIKE THE HRRR INDICATE RAIN SHOULD EXTEND NORTH INTO CENTRAL AROOSTOOK COUNTY. OTHERWISE FORECAST REMAINS ON TRACK. PREV DISC: PRIMARY LOW PRESSURE WILL MOVE INTO THE EASTERN GREAT LAKES THIS EVENING. LATER TONIGHT A SECONDARY LOW PRESSURE SYSTEM WILL DEVELOP ON A BOUNDARY RUNNING ALONG THE MAINE COAST. THIS SYSTEM WHICH IS ACCOMPANIED BY TROPICAL MOISTURE WILL PRODUCE HEAVY AMOUNTS OF RAIN. ADDITIONAL RAIN IS EXPECTED WEDNESDAY AS THE PRIMARY LOW MOVES ACROSS THE STATE. FOR POPS HAVE USED A BLEND OF THE NAM12...GFS40...SREF AND ECMWF. WILL USE SAME BLEND FOR QPF EXCEPT EXCHANGE NAM80 FOR NAM12. FOR WINDS HAVE BLENDED NAM12 AND GMOS. USED THE GMOS FOR THE TEMPERATURE AND DEW POINTS.&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... RAIN WILL BE WINDING DOWN WEDNESDAY NIGHT AS ISAAC`S REMNANT LOW CONTINUES TO MOVE AWAY FROM NEW ENGLAND AND INTO THE CANADIAN MARITIMES. HIGH PRESSURE WILL BRIEFLY BUILD OVER THE REGION ON THURSDAY, BRINGING PARTLY SUNNY SKIES AND FAIR WEATHER TO THE AREA. THIS WILL BE SHORT-LIVED HOWEVER AS A COLD FRONT WILL APPROACH FROM OUR WEST LATE THURSDAY AND CROSS THE STATE ON FRIDAY. EXPECT SHOWERS TO DEVELOP AHEAD/ALONG OF THIS BOUNDARY AS IT MOVES THROUGH FROM NORTHWEST TO SOUTHEAST. MODEL GUIDANCE DOES INDICATE THERE SHOULD BE ENOUGH INSTABILITY FOR THUNDERSTORMS FRIDAY AFTERNOON WITH CAPES PROGGED TO BE 500-1200 J/KG. TEMPERATURES WILL BE SEASONABLE BOTH THURSDAY AND FRIDAY; HIGHS WILL BE IN THE MID 70S AND LOWS IN THE LOWER TO MID 50S. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... THE BIG CONCERN FOR THE LONG TERM PERIOD IS AN UPPER TROUGH THAT IS PROGGED TO DEVELOP OVER THE UPPER MIDWEST AND ITS EFFECT ON WHAT WILL THEN BE HURRICANE LESLIE. CURRENT INDICATIONS ARE THAT THE TROUGH WILL CUTOFF INTO A LOW OVER THE OHIO RIVER VALLEY SOMETIME ON SUNDAY WHICH WILL THEN SLOWLY SHIFT EASTWARD THROUGH THE MIDDLE OF NEXT WEEK. AS IT DOES SO, LESLIE WILL BE PULLED NORTHWARD THROUGH THE WESTERN ATLANTIC ALONG THE LOW`S EASTERN PERIPHERY. MODEL GUIDANCE KEEPS THE TROPICAL SYSTEM WELL OFF THE US EAST COAST AND SOUTH OF NOVA SCOTIA, THOUGH THE 04/00Z RUN OF THE ECMWF BRINGS IT CLOSE ENOUGH TO BRUSH OUR FAR SOUTHEASTERN ZONES WITH SOME RAIN. EVEN IF LESLIE STAYS FAR OUT TO SEA AS IS CURRENTLY EXPECTED, IT WILL STILL IMPACT OUR FORECAST AREA IN TWO WAYS. FIRST, TROPICAL MOISTURE WILL FEED INTO THE SOUTHWEST FLOW AHEAD OF THE PRIMARY UPPER LOW. THIS MOISTURE WILL OVERSPREAD NEW ENGLAND, BRINGING WIDESPREAD SHOWERS TO THE REGION FOR LATE SATURDAY THROUGH MONDAY. SECOND, LARGE SWELLS AND HEAVY SURF WILL IMPACT THE MAINE COASTLINE AND COASTAL WATERS SUNDAY AND MONDAY. THIS WILL POSE A RISK FOR PERSONS LIVING ALONG THE IMMEDIATE COAST AND TO ANY MARITIME PROPERTY. PERSONS WITH COASTAL OR MARITIME INTERESTS SHOULD STAY TUNED FOR LATER UPDATES ON THIS SITUATION. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... NEAR TERM: EXPECT IFR CONDITIONS ALL AREAS TONIGHT DUE TO LOW CEILING ...FOG AND RAIN. SHORT TERM: MVFR/IFR CONDITIONS ARE EXPECTED AT ALL TERMINALS THROUGH WEDNESDAY NIGHT AS RAIN ENDS AND FOG DEVELOPS. CONDITIONS WILL IMPROVE TO VFR THURSDAY MORNING AND SHOULD REMAIN SO THROUGH THURSDAY NIGHT. THEN MVFR RETURNS IN SHOWERS AND THUNDERSTORMS FRIDAY AND ESPECIALLY FRIDAY AFTERNOON ASSOCIATED WITH COLD FRONT PASSAGE. BRIEF LOCALIZED IFR CONDITIONS ARE POSSIBLE IN ANY THUNDERSTORMS. VFR IS THEN EXPECTED SATURDAY WITH MORE SHOWERS AND MVFR ON SUNDAY. && .MARINE... NEAR TERM: FOR WINDS HAVE USED A BLEND OF THE NAM12 AND GFS40. WILL ADJUST WINDS INTO EARLY EVENING A LITTLE HIGHER. FOR WAVES: PRIMARY WAVE GROUPS SPLIT BETWEEN INCREASING LONG PERIOD WAVES FROM TROPICAL STORM LESLIE ...FROM 155 DEGREES/13-14 SECONDS... AND DEVELOPING SOUTHEAST FETCH IN GULF OF MAINE ..FROM 190 DEGREES/5 SECONDS... HAVE INITIALIZED GRIDS WITH NAM/SWAN. WILL LOWER WAVE HEIGHTS 1 FOOT BELOW MODEL NUMBER AS GULF OF MAINE FETCH LOOKS A LITTLE TOO HIGH. WILL ADJUST SCA TO START AT 0300Z FOR SAME REASON. SHORT TERM: SMALL CRAFT ADVISORIES FOR HAZARDOUS SEAS HAVE BEEN EXTENDED INTO THURSDAY MORNING AS WAVES WILL REMAIN ABOVE 5 FT IN RESPONSE TO LOW PRESSURE MOVING THROUGH THE CANADIAN MARITIMES. THOUGH THERE MAY BE A BRIEF BREAK FOR A FEW HOURS ON THURSDAY WHEN WAVES WILL SUBSIDE TO BELOW 5 FT, SCA FOR SEAS WILL MOST LIKELY BE NEEDED RIGHT THROUGH THE WEEKEND AS SWELLS FROM TROPICAL STORM LESLIE AFFECT THE GULF OF MAINE WATERS. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM EDT THURSDAY FOR ANZ050>052. && $$ NEAR TERM...KHW/MCB SHORT TERM...HASTINGS LONG TERM...HASTINGS AVIATION...KHW MARINE...KHW/HASTINGS
AREA FORECAST DISCUSSION
NWS KANSAS CITY/PLEASANT HILL MO
931 PM CDT THU SEP 6 2012 .DISCUSSION... Overnight rain chances diminishing with a much better bet starting Friday morning. The convection which formed along the dryline from north central KS through the TX Panhandle has steadily weakened after pulling away from the boundary while the low level jet has refocused west of ICT and is enhancing the activity headed for south central KS. Latest HRRR finally caught on while 00Z NAM continues to be basically dry overnight. Cold front is now over central NE and dropping southeast. Will cut back on pops with chance wording held back until after 09z. Eastern counties looking dry overnight. Much stronger forcing aloft arrives Friday mid/late morning as a shortwave deepens as it drops southeast through NE. High PoPs for Friday morning/afternoon with rain threat quickly ending from nw-se. MJ && .PREV DISCUSSION... /340 PM CDT Thu Sep 6 2012/ Short term concerns remain focused on precipitation potential overnight and into Friday. Early this afternoon, shortwave energy interacting with a well-defined corridor of 850:700 mb moisture and prevailing westerly 700:500 mb flow produced a large complex of thunderstorms in areas just south of the CWA boundary. Subsidence behind this shortwave has allowed temperatures to jump back into the lower 90s in the southern CWA and should stabilize the southeastern zones into this evening. Further northwest, eyes begin to turn towards an autumn-like cold front stretching from north to south from central South Dakota through central Nebraska and northwestern Kansas. A strong EML continues to advect into area along and ahead of this surface boundary, with 700 mb temperatures of 11-12C common into eastern Nebraska. That said, a small CU field has developed over north central Kansas this afternoon, which could be enhanced by a weak shortwave exiting eastern Colorado. Should this activity develop, it would track into south central Kansas this evening. While 19Z aircraft sounding indicated 700mb temps of only 9-10C, latest RAP/HRRR continue to advect warmer air aloft into the CWA which should prevent an extensive eastward track of activity. The primary focus for thunderstorms this evening appears to be turning towards northeastern Nebraska, northwestern Iowa and southeast South Dakota, where strong moisture transport has been pointed through the daytime hours. Initial thoughts are that convection will begin to break out early this evening along a weak surface low near Sioux Falls as cooling aloft and lift on the nose of a 35 knot LLJ allows convection to overcome a weaker cap. With low level winds remaining focused well away from the CWA this evening, have significantly trimmed back PoPs through 06z. Beyond 06z, some questions continue to linger as to whether weak lift will be able to overcome a stronger cap over southern Nebraska. Latest guidance continues to propagate an MCS into portions of central Iowa and northern Illinois after midnight with much of the area remaining dry through nearly 09z. Will still begin to increase PoPs after midnight as lingering moisture axis will begin to interact more directly with veering LLJ which could produce scattered thunderstorms. Higher instability does begin to advect northeast after midnight, creating some potential for an elevated hail threat. While boundary layer will stabilize to some degree, surface winds should remain fairly mixy, which could also promote a localized damaging wind threat given LLJ running nearly parallel to the surface boundary. A better chance for thunderstorm development looks to begin after the 09Z timeframe when 850mb trough begins to surge southeast and frontogenesis intensifies. By 12Z the surface front should have already reached the St. Joseph area, with precipitation rapidly beginning to increase. Strong pressure rises behind the front will push the boundary through the CWA by the noon hour, with period of showers and embedded thunder through early afternoon. Will bump up PoPs further. While PWAT values will be higher than normal, the rapid storm movement should limit the heavy rainfall threat. Precipitation will rapidly come to an end Friday afternoon, with the surface high plunging southward. Beyond Friday night, the only concerns will be with temperatures as high pressure dominates the weekend. Readings on Saturday will be nearly perfect, with 70s expected and a light northerly wind. Have lowered overnight lows heading into Sunday as winds turn light and variable. Wouldn`t be shocked to see 40 degree readings fairly widespread. Dux Sunday - Wednesday: The region will still be under the influence of a modified Canadian high pressure area Sunday resulting in quiet and seasonally cool conditions. That high will gradually shift east of the region late Sunday and into Monday with winds becoming southerly by Monday. Temperatures should still be cooler than normal Monday but a rebound is expected by Tuesday and Wednesday as thickness values increase and temperatures aloft warm. The high will have swept moisture into the central Gulf of Mexico, so despite warmer temperatures, moisture will be limited and the chances for precipitation will be very small through Tuesday night or Wednesday morning. By Wednesday afternoon, another wave will track across the Northern Plains with its associated cold front moving into Missouri Wednesday evening or night. This will bring us our next chance for showers and storms, though chances don`t look especially good at this point. CDB && .AVIATION... For the 00Z TAFs: Plenty of timing issues in this forecast period. Will start off with VFR conditions with SKC and gradually see an increase in convective blowoff high clouds courtesy of a broken line of thunderstorms moving towards central KS. Models insist that despite the low level jet increasing tonight it will veer to the southwest with time. Such a scenario tends to be non-supportive of maintaining convection downstream or slows its overall net eastward push. Some of the short term convective models do allow this activity to flourish but follows the 700mb thermal gradient and tracks more towards the southeast and just south of the KMCI/KMKC terminals. With such uncertainty feel it best to use VCTS until Friday morning when rain chances increase markedly within a post frontal environment. Also believe thunder will be embedded and not a continuous event. Convection will push south of the terminals early Friday afternoon. Gusty north winds will gradually subside by mid to late afternoon. MJ && .EAX WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ WFO EAX
AREA FORECAST DISCUSSION...UPDATED
NWS ST LOUIS MO
107 PM CDT WED SEP 5 2012 .UPDATE... ISSUED AT 1240 PM CDT WED SEP 5 2012 SHOWERS AND THUNDERSTORMS OVERSPREAD THE AREA THIS MORNING COINCIDENT WITH MULTIPLE OUTFLOW BOUNDARIES AND AN MCV DRIFTING ACROSS THE REGION FROM SW MISSOURI. THUS FAR...RAINFALL AND CLOUDCOVER HAVE KEPT TEMPERATURES QUITE A BIT COOLER THAN ORIGINALLY EXPECTED...AND DESPITE A REBOUND ON TAP FOR THIS AFTERNOON AS THE CLOUDS DISSIPATE...CURRENTLY DO NOT EXPECT THE METRO AREA TO REACH HEAT ADVISORY CRITERIA. LOCATIONS ACROSS SOUTHEASTERN MISSOURI AND SOUTHERN ILLINOIS HOWEVER...WHERE PRECIPITATION AND CLOUDCOVER HAD LESS OF AN IMPACT...COULD VERY WELL SEE HEAT INDICES IN THE 100-105 DEGREE RANGE. SO HAVE CONTINUED THE ADVISORY FOR THOSE AREAS. THE BIG QUESTION THAT REMAINS IS WHETHER ENOUGH DESTABILIZATION WILL OCCUR TO SUPPORT CONVECTIVE DEVELOPMENT THIS AFTERNOON AND EVENING IN THE WARM SECTOR AHEAD OF THE APPROACHING COLD FRONT. MODELS DID NOT CAPTURE THIS MORNINGS ACTIVITY VERY WELL...THOUGH THE MOST RECENT RUN OF THE HRRR DOES FIRE SOME STORMS LATE THIS AFTERNOON AHEAD OF THE FRONT. GIVEN UNCERTAINTY...HAVE CONTINUED CHANCE-HIGH CHANCE POPS FOR THE AREA THIS AFTERNOON AND EARLY THIS EVENING. JP && .SHORT TERM... ISSUED AT 331 AM CDT WED SEP 5 2012 (TODAY AND TONIGHT) CHALLENGING FORECAST FOR TODAY...MULTIPLE OUTFLOW BOUNDARIES ARE MOVING INTO THE CWFA FROM THE WEST...THE NORTH-NORTHWEST..AND THE NORTHEAST THIS MORNING. THE AFFECTS OF WHICH MAY BE MANIFOLD. THE OVERALL SYNOPTIC PATTERN LOOKS QUITE HOT. AM DISCOUNTING THE GFS/MAV TEMPERATURES FOR TODAY SINCE IT`S BEEN TOO COLD ALL SUMMER. THE NAM LOOKS MORE REASONABLE WITH HIGHS OF 95 TO 103 ACROSS THE CWFA. 00Z 850MB ANALYSIS FROM LAST NIGHT SHOWS 24-25C AIR LURKING JUST TO OUR SOUTHWEST AND HIGHS REACHED THE 96-105F RANGE ACROSS SOUTHWEST MISSOURI...ARKANSAS...EASTERN KANSAS...AND OKLAHOMA YESTERDAY. I SEE NO REASON THAT WE WON`T GET THAT WARM TODAY...EXCEPT FOR THOSE PESKY OUTFLOW BOUNDARIES AND CONVECTIVE DEBRIS FROM NOCTURNAL CONVECTION. HOWEVER...AM GOING TO STICK WITH A WARM FORECAST TODAY. AM THINKING THAT THE CONVECTIVE DEBRIS WILL CLEAR THE AREA BY MID MORNING AND SHOULDN`T HAVE THAT MUCH IMPACT ON TEMPERATURES. THE OUTFLOW BOUNDARIES AREN`T COOLING THINGS OFF EITHER...ALL THEY`RE DOING IS MIXING DOWN WARMER AIR ALOFT...AND TEMPERATURES ARE ACTUALLY RISING AS THEY PASS. OUTFLOW BOUNDARIES COULD SERVE AS FOCI FOR CONVECTIVE DEVELOPMENT THIS AFTERNOON...AND IF CONVECTIVE INITIATION OCCURS TOO EARLY WOULD BE THE PRIMARY REASON FOR A HIGH TEMPERATURE BUST. REGARDLESS...HIGH DEWPOINTS AHEAD OF THE COLD FRONT OVER EASTERN MISSOURI AND PARTS OF SOUTHWEST ILLINOIS COMBINED WITH TEMPERATURES NEAR 100 WILL LIKELY CAUSE HEAT INDEX VALUES AROUND 105. HAVE GONE AHEAD AND ISSUED A HEAT ADVISORY TO COVER THIS. EXPECTING SOME DRIER AIR TO MIX DOWN ACROSS CENTRAL AND NORTHEAST MISSOURI/WEST CENTRAL ILLINOIS WHICH SHOULD HEAT INDEX VALUES BELOW 105. TONIGHT SHOULD BE INTERESTING...NAM IS HINTING THAT A STRONG THUNDERSTORM COMPLEX WILL DEVELOP SOMEWHERE OVER NORTHERN/WEST CENTRAL ILLINOIS OR EASTERN IOWA AND DROP SOUTHEAST. NAM AND RAP DEVELOP EYE-POPPING MUCAPE VALUES IN EXCESS OF 4800 J/KG IN THOSE AREAS AHEAD OF THE FRONT EARLY THIS AFTERNOON TO SUPPORT THE CONVECTION...AND 0-6KM SHEAR VALUES IN EXCESS OF 30KTS ARE MORE THAN ENOUGH TO SUPPORT SEVERE WEATHER. THINK A LARGE SEVERE MCS IS LIKELY UP THERE...JUST UNSURE HOW FAR SOUTH INTO OUR AREA IT WILL EXTEND. THINK THAT SOME PARTS OF OUR AREA WILL DEFINITELY SEE THUNDERSTORMS...IF NOT SOME SEVERE WEATHER...JUST UNSURE WHAT THE AREAL EXTENT WILL BE...SO HAVE KEPT CHANCE-HIGH CHANCE GOING FOR NOW. CARNEY && .LONG TERM... ISSUED AT 357 AM CDT WED SEP 5 2012 (THURSDAY THROUGH TUESDAY) CURRENT THINKING REMAINS BASICALLY UNCHANGED THROUGH EARLY NEXT WEEK. TONIGHT`S COLD FRONT SHOULD BE THROUGH MOST OF THE AREA BY 12Z THURSDAY MORNING. THE FRONT HANGS UP ACROSS EXTREME SOUTHERN MISSOURI OR NORTHERN ARKANSAS THURSDAY TEMPERATURES SHOULD BE 8-10 DEGREES COOLER THURSDAY BEHIND THE FRONT...AND BOTH THE GFS AND NAM HAVE IT FAR ENOUGH SOUTH THAT ONLY EXTREME SOUTHEAST MISSOURI SHOULD HAVE ANY POSSIBILITY OF RAIN. THURSDAY NIGHT THE MAJOR SHORTWAVE DROPS INTO THE NORTHERN PLAINS CAUSING THE LOW LEVEL JET TO TO RAMP UP OVER KANSAS AND MISSOURI. ALL MODELS SHOW GOOD LOW LEVEL MOISTURE CONVERGENCE AND SPREAD PRECIP OVER MUCH OF WESTERN AND NORTHERN MISSOURI OVERNIGHT. BY FRIDAY AS THE SHORTWAVE SWINGS INTO NEBRASKA THERE SHOULD BE WIDESPREAD PRECIP ACROSS THE AREA. RAIN AND THUNDERSTORMS SHOULD COME END BEHIND THE COLD FRONT LATE FRIDAY NIGHT. STILL THINK THERE COULD BE SOME SCATTERED AFTERNOON SHOWERS SATURDAY AS COLD ADVECTION CONTINUES...THOUGH LATEST RUNS OF THE ECMWF AND GFS ARE DRIER THAN YESTERDAY`S. SHOULD HAVE A STRETCH OF BEAUTIFUL EARLY-FALL WEATHER SUNDAY AND MONDAY WITH HIGHS IN THE 70S AND LOWS IN THE 50S. COULD SEE SOME WARMER TEMPERATURES BUILD BACK INTO THE AREA BY TUESDAY AS THE ECMWF DEVELOPS AN UPPER LEVEL RIDGE OVER THE AREA. CARNEY && .AVIATION... ISSUED AT 1240 PM CDT WED SEP 5 2012 QUITE A BIT OF UNCERTAINTY THROUGH THIS FORECAST PERIOD. ONGOING CONVECTION ACROSS THE REGION HAS TAPERED OFF ACROSS MISSOURI AND CONTINUES TO MOVE EASTWARD THROUGH ILLINOIS...AND WAS NOT CAPTURED WELL BY ANY OF THE MODELS. HENCE...THE POSSIBILITY OF THUNDERSTORMS THIS AFTERNOON REMAINS UNCERTAIN DUE TO LINGERING CLOUDCOVER AND STABLILZATION. THUS...HAVE CARRIED VFR CONDITIONS THROUGH THE VALID TAF PERIOD FOR ALL SITES...WITH TEMPOS FOR SOME LIGHT RAIN AS SHOWERS SLOWLY PERCOLATE ACROSS THE METRO AREA TAF SITES. A COLD FRONT IS STILL PROGGED TO MOVE THROUGH THE AREA THIS EVENING AND TONIGHT...WHICH WILL VEER WINDS AROUND TO THE NORTHWEST TONIGHT...AND NORTH ON THURSDAY. WILL CONTINUE TO MONITOR CONDITIONS AND REASSESS THE FORECAST AS NEEDED DEPENDING ON ANY CONVECTIVE DEVELOPMENT ALONG AND AHEAD OF THE APPROACHING FRONT. SPECIFICS FOR KSTL... JUST A FEW SHOWERS LINGERING ACROSS THE METRO AREA THIS AFTERNOON IN THE WAKE OF MORNING CONVECTION...THUS HAVE INCLUDED A BRIEF TEMPO FROM 18-19Z THIS AFTERNOON FOR SOME LIGHT RAIN AT THE TERMINAL. STABLIZATION DUE TO CLOUDCOVER AND COOLER TEMPERATURES COULD HINDER CONVECTIVE DEVELOPMENT THIS AFTERNOON AHEAD OF THE APPROACHING COLD FRONT...THOUGH CONDITIONS WILL CONTINUE TO BE CLOSELY MONITORED. CONDIFENCE IS TOO LOW AT THE MOMENT TO INCLUDE MENTION OF PRECIPITATION IN THE TAF BEYOND THE TEMPO GROUP...WITH VFR CONDITIONS EXPECTED THROUGH THE FORECAST AND WINDS VEERING TO THE NORTH BEHIND THE APPROACHING FRONT WHICH SHOULD MAKE IT THROUGH THE TERMINAL BY 00-03Z THIS EVENING. JP && .LSX WATCHES/WARNINGS/ADVISORIES... MO...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR IRON MO-MADISON MO- REYNOLDS MO-ST. FRANCOIS MO-STE. GENEVIEVE MO. IL...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR RANDOLPH IL. && $$ WFO LSX
AREA FORECAST DISCUSSION
NWS ELKO NV
314 PM PDT WED SEP 5 2012 .SYNOPSIS...CURRENTLY...HIGH PRESSURE IS HOVERING OVER THE SILVER STATE. MEANWHILE AN AREA OF LOW PRESSURE IS MOVING INTO CALIFORNIA AND WILL CLIP NORTHWESTERN NEVADA TONIGHT. ISOLATED THUNDERSTORMS POSSIBLE LATE THIS EVENING. OVER NORTHEASTERN NEVADA...THE LOWS WILL DIP INTO THE FORTIES LATE TONIGHT AND EARLY THURSDAY. THUNDERSTORMS POSSIBLE THURSDAY AFTERNOON. && .SHORT TERM...TONIGHT THROUGH THURSDAY. THE NAM12 DEPICTS ENHANCED CAPES AND PWS OVER CENTRAL NEVADA TODAY. ISOLATED CONVECTION POSSIBLE ALTHOUGH THE BEST INGREDIENTS WILL MATERIALIZE JUST SOUTH OF THE LKN CWA. AS TIME ELAPSES...PACIFIC ENERGY WILL CLIP THE NORTHWEST PORTION OF THE LKN CWA TONIGHT...POSSIBLY FUELING A FEW DRY THUNDERSTORMS. THE FGEN FORCING WITH THIS SYSTEM LOOKS ANEMIC BUT THE UPPER LEVEL DIFFLUENCE WILL BE THERE...EVEN IF TEMPORARILY. THE NAM12 AND THE HRRR ARE BOTH PINGING INTO CONVECTION AGAIN TOMORROW OVER THE CENTRAL ZONES AS MOISTURE GETS ENTRAINED INTO THE BACK SIDE OF THE MID-LEVEL LOW. THE NAM12 IS PROJECTING NEGATIVE VALUES OF LI FROM TONOPAH TO CEDAR CITY BY 21Z AND WELL UP TO DENIO AND JACKPOT BY 00Z...COUPLED WITH A SURGE IN PWS AND +200 J/KG OF CAPE. THE ELY SOUNDING...IS BY FAR...THE MOST IMPRESSIVE WITH TOMORROWS ROUND OF CONVECTION...COMPLETE WITH A CLASSIC INVERTED-V PROFILE AND THE DEEPEST LAYER OF MOISTURE. .LONG TERM...THURSDAY NIGHT THROUGH NEXT WEDNESDAY. DRY AND QUIET TO START...BUT RAMPING UP AS FOUR CORNERS LOW AND NORTHEAST PACIFIC HIGH WORK IN TANDEM TO BRING YET MORE SUBTROPICAL MOISTURE INTO THE GREAT BASIN ON THE WEEKEND. THE UPPER LOW DRIFTS TO THE NORTHEAST ALLOWING THE RIDGE TO COME WEST ON FRIDAY AND SATURDAY...WHICH INHIBITS MOISTURE FLOW INTO THE REGION. AS THE LOW MOVE OVER THE RIDGE...THE RIDGE FLATTENS AND CREEPS EAST A BIT ALLOWING PW`S TO SHOOT BACK INTO CENTRAL AND NORTHERN NEVADA. BY SUNDAY AFTERNOON...LOOKING AT PW`S IN THE 0.75" TO 0.90" RANGE OVER MOST OF THE AREA. THIS PW AREA ACTUALLY CREEPS BACK IN SOONER THAN THE WEEKEND...BUT LI`S ARE NOT FAVORABLE FOR CONVECTION UNTIL SUNDAY. THEREAFTER...THUNDERSTORMS ARE IN THE FORECAST FOR THE SOUTHEAST HALF OF THE FORECAST AREA...EAST OF LINE FROM ROUGHLY JACKPOT TO TONOPAH THROUGH THE REST OF THE LONG RANGE PERIOD. TEMPS WILL REMAIN ABOVE NORMAL IN THE DAY...WITH NEAR TO SLIGHTLY ABOVE NORMAL AT NIGHT. THE FROST/FREEZE PROGRAM ENDS ON SEP 15...AND IT APPEARS THAT WE MAY NOT BE ISSUING ANY WARNINGS OR ADVISORIES...UNLESS THINGS REALLY CHANGE. && .AVIATION...VFR THROUGH 00Z FRIDAY. ISOLATED -TSRA WILL AFFECT THE VICINITY OF KTPH AND KELY 00Z THURSDAY THROUGH ABOUT 04Z THURSDAY. ANOTHER ROUND OF VICINITY -TSRA WILL AFFECT KTPH...KELY...AND KWMC ON THURSDAY AFTERNOON. AROUND KEKO...SOME CU BUILDUPS BUT NOT BECOMING TS. DRAINAGE WINDS OVERNIGHT...BECOMING SW TO W 10-20 KNOTS AT ALL SITES AFTER 20Z THURSDAY. && .FIRE WEATHER...A LOW PRESSURE SYSTEM WILL CLIP NORTHWEST NEVADA TONIGHT PRODUCING ISOLATED DRY THUNDERSTORMS OVER THE WESTERN PORTION OF 467. NEW STARTS POSSIBLE. A SECOND AREA OF CONCERN WILL BE OVER CENTRAL NEVADA WHERE MOISTURE IS PRESENT. LIGHTNING STRIKES ALREADY OBSERVED OVER THE SOUTHERN PORTION OF 457 WHERE THE BEST PWS HAVE BEEN PROGGED FOR THIS EVENING. ISOLATED THUNDERSTORMS EXPECTED OVER CENTRAL ZONES...HOWEVER...EXPECTING A MIX OF DRY AND WET THUNDERSTORMS. MODELS DEPICT A MORE ROBUST ROUND OF MOISTURE OVER 457 AND 455 TOMORROW AFTERNOON. && .LKN WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 97/98/98/97
AREA FORECAST DISCUSSION
NWS RALEIGH NC
744 AM EDT WED SEP 5 2012 .SYNOPSIS... A MOIST AIRMASS WILL PERSIST OVER THE AREA THROUGH THURSDAY IN ASSOCIATION WITH A STALLED SURFACE TROUGH OVER THE CAROLINAS. A BRIEF DRY PERIOD IS EXPECTED ON FRIDAY...FOLLOWED BY A RETURN TO UNSETTLED WEATHER OVER THE WEEKEND AS AN UNSEASONABLY DEEP UPPER LEVEL TROUGH APPROACHES FROM THE WEST. && .NEAR TERM /TODAY AND TONIGHT/... AS OF 245 AM WEDNESDAY... PRECIPITATION CHANCES: AN H5 DISTURBANCE WAS NOTED IN WV IMAGERY AND RAP/MESOANALYSIS DATA OVER THE WESTERN PIEDMONT AT 06Z THIS MORNING. THE DISTURBANCE IS EXPECTED TO PROGRESSES SLOWLY EAST TO THE HWY 1 CORRIDOR BY 15-18Z AND THE COASTAL PLAIN BY 18-21Z. THE LATEST RAP GUIDANCE INDICATES THIS FEATURE WILL BECOME INCREASINGLY SHEARED/DEAMPLIFIED BY THE AFTERNOON HOURS...AND IT IS DIFFICULT TO ASCERTAIN WHAT (IF ANY) CONTRIBUTION TO ASCENT MAY BE ASSOCIATED WITH IT. LIGHT MID-LEVEL FLOW WILL BE PRESENT OVER THE CAROLINAS TODAY...SOUTH OF THE PRIMARY BELT OF WESTERLIES WHERE A WEAKNESS HAS DEVELOPED IN H5 RIDGE EXTENDING WEST-EAST ACROSS THE SOUTHERN 1/3 OF THE CONUS...AND IT WILL BE DIFFICULT FOR ANY ADDITIONAL MID/UPPER LEVEL DISTURBANCES TO TRACK INTO THE AREA THROUGH TONIGHT. LOWER-LEVEL FORCING WILL BE CONFINED TO CONVERGENCE ASSOC/W A WEAKENING SFC-H85 TROUGH OVER WESTERN PORTIONS OF THE STATE TODAY...WITH THE BEST LOW-LEVEL CONVERGENCE SHIFTING EAST INTO PORTIONS OF THE NW/NORTHERN PIEDMONT OVERNIGHT. RELATIVELY SPEEDY (20-30 KT) SW LOW-LEVEL FLOW WILL BE PRESENT ON THE EASTERN PERIPHERY OF THE TROUGH OVER CENTRAL NC. WEAK MID-LEVEL LAPSE RATES AND BROKEN CLOUD COVER WILL LIMIT DIURNAL DESTABILIZATION IN THE WEST TODAY...WITH MLCAPE VALUES OF ~1000 J/KG OR LESS. ALTHOUGH STRONGER INSOLATION MAY BE PRESENT IN EASTERN PORTIONS...WEAK MID-LEVEL LAPSE RATES COUPLED WITH A RELATIVELY DRIER BOUNDARY LAYER SHOULD LIMIT MLCAPE VALUES TO 1000-1500 J/KG...THOUGH UP TO 2000 J/KG WILL BE POSSIBLE IF BOUNDARY LAYER MOISTURE IS GREATER THAN PROGGED. ABOVE NORMAL MOISTURE WILL BE PRESENT THROUGHOUT THE COLUMN TODAY/TONIGHT...WITH PWAT VALUES PROGGED NEAR 2.00" EVERYWHERE. THE LATEST 00Z CONVECTION ALLOWING MODELS (CAMS) INDICATE CONVECTION DEVELOPING ON THE EASTERN PERIPHERY OF THE WEAKENING H5 DISTURBANCE IN VICINITY OF THE HWY 1 CORRIDOR BETWEEN 12-18Z TODAY...SHIFTING EAST INTO THE COASTAL PLAIN BY MID/LATE AFTERNOON. THE CAMS ALSO INDICATE CONVECTION DEVELOPING IN VICINITY OF THE SFC-H85 TROUGH OVER THE FOOTHILLS/MOUNTAINS THIS AFTERNOON...SHIFTING INTO PORTIONS OF THE NW/NORTHERN PIEDMONT OVERNIGHT IN ASSOCIATION WITH WEAK LOW-LEVEL CONVERGENCE IN THE PRESENCE OF A VERY MOIST AND MARGINALLY UNSTABLE AIRMASS. WILL BASE PRECIP CHANCES THROUGH TONIGHT ON THE AFOREMENTIONED REASONING...HOWEVER...CONFIDENCE IN THE TIMING/ COVERAGE OF CONVECTION REMAINS RELATIVELY LOW GIVEN THE PRESENCE OF WEAK STEERING FLOW. TEMPERATURES: WITH RELATIVELY LITTLE CHANGE IN AIRMASS...HIGHS TODAY WILL BE SIMILAR TO PREVIOUS DAYS...DEPENDING PRIMARILY ON CLOUD COVER AND CONVECTION. WILL INDICATE HIGHS RANGING FROM THE LOWER/MID 80S WEST TO MID/UPPER 80S EAST. LOWS TONIGHT WILL ALSO BE BASED ON PERSISTENCE...IN THE LOWER 70S. HAZARDOUS WEATHER: VERY WEAK DEEP-LAYER SHEAR WILL BE UNSUPPORTIVE OF CONVECTIVE ORGANIZATION TODAY. GIVEN AN INCREASINGLY DEAMPLIFIED PATTERN OVER THE CAROLINAS...A THERMODYNAMIC ENVIRONMENT CHARACTERIZED BY LOW DCAPE AND WEAK MID-LEVEL LAPSE RATES...THE THREAT FOR AN ISOLD SEVERE STORM WILL BE VERY LOW...THOUGH NON-ZERO (AS LONG AS DEEP CONVECTION IS PRESENT) GIVEN ENHANCED (~25 KT) LOW-LEVEL FLOW AND A VERY MOIST COLUMN SUPPORTIVE OF PRECIP LOADING. LOCALLY HEAVY RAINFALL AND ISOLD FLOODING CANNOT BE RULED OUT IN URBAN AREAS... THOUGH THE THREAT APPEARS LOWER THAN PREVIOUS DAYS. -VINCENT && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 230 AM WEDNESDAY... THERE IS A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS AGAIN THURSDAY AFTERNOON AND EVENING AS A WEAKENING COLD FRONT IS FORECAST TO STALL ACROSS CENTRAL NORTH CAROLINA THURSDAY. THE UPPER DYNAMICS WILL BE VERY WEAK. HOWEVER... CONTINUED HI PW`S AND STRONG HEATING ESPECIALLY IN THE SOUTH AND EAST WILL SUPPORT SCATTERED STRONG THUNDERSTORMS... WITH THE PRIMARY THREATS OF LOCALLY HEAVY RAIN AND GUSTY WIND. WE WILL CARRY THE HIGHEST POP IN THE EAST AND SOUTH... BUT EVEN THE NW WILL HAVE LOW CHANCE POPS. HIGHS IN THE MID TO UPPER 80S NW RANGING TO AROUND 90 SE. THE POPS WILL BECOME SLIGHT CHANCE BY LATE EVENING THURSDAY... SUPPORTED BY THE LINGERING NEARLY STATIONARY BOUNDARY. LOWS GENERALLY 70-73. FRIDAY AND FRIDAY NIGHT... THIS MAY BE THE DAY WHEN WE HAVE THE LOWEST POPS... ESPECIALLY OVER THE PIEDMONT WHERE SOME DRIER AIR (VERY SLIGHTLY DRIER AIR MAY FILTER IN WITH DEW POINTS IN THE MID 60S). THAT IS... IF... THE LOW LEVEL BOUNDARY DRIFTS INTO THE COASTAL PLAIN OR WASHES OUT ENTIRELY PER SOME MODEL SOLUTIONS. THIS APPEARS POSSIBLE... YET BY LATE IN THE DAY EXPECT THE SEA BREEZE/OLD FRONT COMBO TO DRIFT BACK WNW INTO THE EASTERN PIEDMONT BY EARLY EVENING BRINGING BACK 70+ DEW POINTS. WE WILL STILL CARRY SLIGHT TO LOW CHANCE POP FOR SHOWERS AND THUNDERSTORMS... MAINLY FROM FAY AND RDU EASTWARD DURING FRIDAY AFTERNOON AND EARLY EVENING. OTHERWISE... PARTLY SUNNY WARM AND HUMID. HIGHS 88-94 NW TO SANDHILLS. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 245 AM WEDNESDAY... BIG PATTERN CHANGE IN THE OFFING... A FAIRLY DEEP MID-UPPER LEVEL TROUGH IS FORECAST TO DEVELOP OVER THE GREAT LAKES AND SWING EASTWARD OVER THE WEEKEND. THE ACTUAL COLD FRONT IS PROJECTED FOR SATURDAY. THIS WILL SWEEP THE VERY MUGGY OPPRESSIVE AIR MASS CURRENTLY OVER THE AREA OUT TO SEA SUNDAY AND MONDAY. THE MODELS HAVE BEEN TRENDING TOWARD A MORE PROGRESSIVE TROUGH PASSAGE FOR OUR REGION AND LATITUDE. THIS WOULD MEAN LESS IN THE WAY OF SEVERE AND FLOODING POTENTIAL OVER THE WEEKEND. STAY TUNED. WE WILL CONTINUE TO CARRY INCREASING CHANCES OF SHOWERS AND STORMS SAT-SAT NIGHT... SHIFTING EAST MORE QUICKLY SUNDAY. MODELS NOW PROJECT THE ACTUAL FRONT TO PUSH EAST THROUGH OUR REGION BY LATE SATURDAY. THIS WOULD MEAN LOWERING HUMIDITIES AND MUCH LOWER POP FOR SUNDAY (A DAY TO A DAY AND A HALF EARLIER THAN PROJECTED 24 HOURS AGO). WE WILL TREND THAT WAY... BUT KEEP A CHANCE POP MAINLY EAST SUNDAY. TURNING COOLER AND MUCH DRIER MONDAY AND TUESDAY. LOWS 55-60. HIGHS 77-82. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... AS OF 730 AM WEDNESDAY... 24-HR TAF PERIOD: IFR CEILINGS THIS MORNING ARE EXPECTED TO LIFT TO MVFR AND EVENTUALLY SCATTER OUT TO VFR AT MOST LOCATIONS BY 15Z. MVFR CEILINGS COULD PERSIST INTO THE AFTERNOON AT THE INT/GSO TERMINALS WHERE SHOWER ACTIVITY WILL BE MORE LIKELY AS THE DAY PROGRESSES. EXPECT THE BEST CHANCE OF CONVECTION AT THE INT/GSO TERMINALS BETWEEN 15Z THIS MORNING AND 03Z THIS EVENING...WHERE VCSH WILL BE MENTIONED. AT THE RDU/FAY/RWI TERMINALS...CONFIDENCE IN AFTERNOON CONVECTION IS LOWER THAN AT INT/GSO. AS A RESULT...WILL KEEP VFR CONDITIONS IN PLACE AT RDU/FAY/RWI ONCE MORNING FOG AND STRATUS HAS LIFTED AND SCATTERED OUT. OTHERWISE...ANTICIPATE A CHANCE FOR SUB-VFR CEILINGS/VISBYS ONCE AGAIN BY THE END OF THE TAF PERIOD...06-12Z THURSDAY MORNING. LOOKING AHEAD: SUB-VFR STRATUS OR FOG WILL BE POSSIBLE DURING THE EARLY MORNING HOURS (07-13Z) ON BOTH FRI/SAT...ALONG WITH ISOLD SHOWERS AND STORMS DURING THE AFTERNOON AND EARLY EVENING HOURS...PRIMARILY AT THE FAY/RWI TAF SITES. MORE WIDESPREAD SHOWERS/STORMS WILL BE POSSIBLE SATURDAY NIGHT/SUNDAY AS AN UNSEASONABLY DEEP UPPER LEVEL TROUGH APPROACHES FROM THE WEST. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM....VINCENT SHORT TERM...BADGETT LONG TERM...BADGETT AVIATION...VINCENT
AREA FORECAST DISCUSSION
NWS RALEIGH NC
331 AM EDT WED SEP 5 2012 .SYNOPSIS... A MOIST AIRMASS WILL PERSIST OVER THE AREA THROUGH THURSDAY IN ASSOCIATION WITH A STALLED SURFACE TROUGH OVER THE CAROLINAS. A BRIEF DRY PERIOD IS EXPECTED ON FRIDAY...FOLLOWED BY A RETURN TO UNSETTLED WEATHER OVER THE WEEKEND AS AN UNSEASONABLY DEEP UPPER LEVEL TROUGH APPROACHES FROM THE WEST. && .NEAR TERM /TODAY AND TONIGHT/... AS OF 245 AM WEDNESDAY... PRECIPITATION CHANCES: AN H5 DISTURBANCE WAS NOTED IN WV IMAGERY AND RAP/MESOANALYSIS DATA OVER THE WESTERN PIEDMONT AT 06Z THIS MORNING. THE DISTURBANCE IS EXPECTED TO PROGRESSES SLOWLY EAST TO THE HWY 1 CORRIDOR BY 15-18Z AND THE COASTAL PLAIN BY 18-21Z. THE LATEST RAP GUIDANCE INDICATES THIS FEATURE WILL BECOME INCREASINGLY SHEARED/DEAMPLIFIED BY THE AFTERNOON HOURS...AND IT IS DIFFICULT TO ASCERTAIN WHAT (IF ANY) CONTRIBUTION TO ASCENT MAY BE ASSOCIATED WITH IT. LIGHT MID-LEVEL FLOW WILL BE PRESENT OVER THE CAROLINAS TODAY...SOUTH OF THE PRIMARY BELT OF WESTERLIES WHERE A WEAKNESS HAS DEVELOPED IN H5 RIDGE EXTENDING WEST-EAST ACROSS THE SOUTHERN 1/3 OF THE CONUS...AND IT WILL BE DIFFICULT FOR ANY ADDITIONAL MID/UPPER LEVEL DISTURBANCES TO TRACK INTO THE AREA THROUGH TONIGHT. LOWER-LEVEL FORCING WILL BE CONFINED TO CONVERGENCE ASSOC/W A WEAKENING SFC-H85 TROUGH OVER WESTERN PORTIONS OF THE STATE TODAY...WITH THE BEST LOW-LEVEL CONVERGENCE SHIFTING EAST INTO PORTIONS OF THE NW/NORTHERN PIEDMONT OVERNIGHT. RELATIVELY SPEEDY (20-30 KT) SW LOW-LEVEL FLOW WILL BE PRESENT ON THE EASTERN PERIPHERY OF THE TROUGH OVER CENTRAL NC. WEAK MID-LEVEL LAPSE RATES AND BROKEN CLOUD COVER WILL LIMIT DIURNAL DESTABILIZATION IN THE WEST TODAY...WITH MLCAPE VALUES OF ~1000 J/KG OR LESS. ALTHOUGH STRONGER INSOLATION MAY BE PRESENT IN EASTERN PORTIONS...WEAK MID-LEVEL LAPSE RATES COUPLED WITH A RELATIVELY DRIER BOUNDARY LAYER SHOULD LIMIT MLCAPE VALUES TO 1000-1500 J/KG...THOUGH UP TO 2000 J/KG WILL BE POSSIBLE IF BOUNDARY LAYER MOISTURE IS GREATER THAN PROGGED. ABOVE NORMAL MOISTURE WILL BE PRESENT THROUGHOUT THE COLUMN TODAY/TONIGHT...WITH PWAT VALUES PROGGED NEAR 2.00" EVERYWHERE. THE LATEST 00Z CONVECTION ALLOWING MODELS (CAMS) INDICATE CONVECTION DEVELOPING ON THE EASTERN PERIPHERY OF THE WEAKENING H5 DISTURBANCE IN VICINITY OF THE HWY 1 CORRIDOR BETWEEN 12-18Z TODAY...SHIFTING EAST INTO THE COASTAL PLAIN BY MID/LATE AFTERNOON. THE CAMS ALSO INDICATE CONVECTION DEVELOPING IN VICINITY OF THE SFC-H85 TROUGH OVER THE FOOTHILLS/MOUNTAINS THIS AFTERNOON...SHIFTING INTO PORTIONS OF THE NW/NORTHERN PIEDMONT OVERNIGHT IN ASSOCIATION WITH WEAK LOW-LEVEL CONVERGENCE IN THE PRESENCE OF A VERY MOIST AND MARGINALLY UNSTABLE AIRMASS. WILL BASE PRECIP CHANCES THROUGH TONIGHT ON THE AFOREMENTIONED REASONING...HOWEVER...CONFIDENCE IN THE TIMING/ COVERAGE OF CONVECTION REMAINS RELATIVELY LOW GIVEN THE PRESENCE OF WEAK STEERING FLOW. TEMPERATURES: WITH RELATIVELY LITTLE CHANGE IN AIRMASS...HIGHS TODAY WILL BE SIMILAR TO PREVIOUS DAYS...DEPENDING PRIMARILY ON CLOUD COVER AND CONVECTION. WILL INDICATE HIGHS RANGING FROM THE LOWER/MID 80S WEST TO MID/UPPER 80S EAST. LOWS TONIGHT WILL ALSO BE BASED ON PERSISTENCE...IN THE LOWER 70S. HAZARDOUS WEATHER: VERY WEAK DEEP-LAYER SHEAR WILL BE UNSUPPORTIVE OF CONVECTIVE ORGANIZATION TODAY. GIVEN AN INCREASINGLY DEAMPLIFIED PATTERN OVER THE CAROLINAS...A THERMODYNAMIC ENVIRONMENT CHARACTERIZED BY LOW DCAPE AND WEAK MID-LEVEL LAPSE RATES...THE THREAT FOR AN ISOLD SEVERE STORM WILL BE VERY LOW...THOUGH NON-ZERO (AS LONG AS DEEP CONVECTION IS PRESENT) GIVEN ENHANCED (~25 KT) LOW-LEVEL FLOW AND A VERY MOIST COLUMN SUPPORTIVE OF PRECIP LOADING. LOCALLY HEAVY RAINFALL AND ISOLD FLOODING CANNOT BE RULED OUT IN URBAN AREAS... THOUGH THE THREAT APPEARS LOWER THAN PREVIOUS DAYS. -VINCENT && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 230 AM WEDNESDAY... THERE IS A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS AGAIN THURSDAY AFTERNOON AND EVENING AS A WEAKENING COLD FRONT IS FORECAST TO STALL ACROSS CENTRAL NORTH CAROLINA THURSDAY. THE UPPER DYNAMICS WILL BE VERY WEAK. HOWEVER... CONTINUED HI PW`S AND STRONG HEATING ESPECIALLY IN THE SOUTH AND EAST WILL SUPPORT SCATTERED STRONG THUNDERSTORMS... WITH THE PRIMARY THREATS OF LOCALLY HEAVY RAIN AND GUSTY WIND. WE WILL CARRY THE HIGHEST POP IN THE EAST AND SOUTH... BUT EVEN THE NW WILL HAVE LOW CHANCE POPS. HIGHS IN THE MID TO UPPER 80S NW RANGING TO AROUND 90 SE. THE POPS WILL BECOME SLIGHT CHANCE BY LATE EVENING THURSDAY... SUPPORTED BY THE LINGERING NEARLY STATIONARY BOUNDARY. LOWS GENERALLY 70-73. FRIDAY AND FRIDAY NIGHT... THIS MAY BE THE DAY WHEN WE HAVE THE LOWEST POPS... ESPECIALLY OVER THE PIEDMONT WHERE SOME DRIER AIR (VERY SLIGHTLY DRIER AIR MAY FILTER IN WITH DEW POINTS IN THE MID 60S). THAT IS... IF... THE LOW LEVEL BOUNDARY DRIFTS INTO THE COASTAL PLAIN OR WASHES OUT ENTIRELY PER SOME MODEL SOLUTIONS. THIS APPEARS POSSIBLE... YET BY LATE IN THE DAY EXPECT THE SEA BREEZE/OLD FRONT COMBO TO DRIFT BACK WNW INTO THE EASTERN PIEDMONT BY EARLY EVENING BRINGING BACK 70+ DEW POINTS. WE WILL STILL CARRY SLIGHT TO LOW CHANCE POP FOR SHOWERS AND THUNDERSTORMS... MAINLY FROM FAY AND RDU EASTWARD DURING FRIDAY AFTERNOON AND EARLY EVENING. OTHERWISE... PARTLY SUNNY WARM AND HUMID. HIGHS 88-94 NW TO SANDHILLS. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 245 AM WEDNESDAY... BIG PATTERN CHANGE IN THE OFFING... A FAIRLY DEEP MID-UPPER LEVEL TROUGH IS FORECAST TO DEVELOP OVER THE GREAT LAKES AND SWING EASTWARD OVER THE WEEKEND. THE ACTUAL COLD FRONT IS PROJECTED FOR SATURDAY. THIS WILL SWEEP THE VERY MUGGY OPPRESSIVE AIR MASS CURRENTLY OVER THE AREA OUT TO SEA SUNDAY AND MONDAY. THE MODELS HAVE BEEN TRENDING TOWARD A MORE PROGRESSIVE TROUGH PASSAGE FOR OUR REGION AND LATITUDE. THIS WOULD MEAN LESS IN THE WAY OF SEVERE AND FLOODING POTENTIAL OVER THE WEEKEND. STAY TUNED. WE WILL CONTINUE TO CARRY INCREASING CHANCES OF SHOWERS AND STORMS SAT-SAT NIGHT... SHIFTING EAST MORE QUICKLY SUNDAY. MODELS NOW PROJECT THE ACTUAL FRONT TO PUSH EAST THROUGH OUR REGION BY LATE SATURDAY. THIS WOULD MEAN LOWERING HUMIDITIES AND MUCH LOWER POP FOR SUNDAY (A DAY TO A DAY AND A HALF EARLIER THAN PROJECTED 24 HOURS AGO). WE WILL TREND THAT WAY... BUT KEEP A CHANCE POP MAINLY EAST SUNDAY. TURNING COOLER AND MUCH DRIER MONDAY AND TUESDAY. LOWS 55-60. HIGHS 77-82. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 200 AM WEDNESDAY... 24-HR TAF PERIOD: A MOIST/SPEEDY (25 KT AT 1000 FT AGL) LOW-LEVEL FLOW IS EXPECTED TO RESULT IN THE DEVELOPMENT OF IFR CEILINGS AT ALL AVIATION TERMINALS BETWEEN 08-10Z THIS MORNING...PERSISTING THROUGH 13Z...THEN LIFTING TO MVFR AND EVENTUALLY SCATTERING OUT TO VFR IN MOST LOCATIONS BY 15Z. EXCEPTIONS INCLUDE THE INT/GSO TERMINALS WHERE MVFR CEILINGS COULD PERSIST THROUGH THE AFTERNOON. LIFR FOG HAS DEVELOPED THE PAST SEVERAL MORNINGS BETWEEN 10-12Z AT THE FAY/RWI TERMINALS AND PERSISTENCE WOULD SUGGEST SIMILAR CONDITIONS THIS MORNING... HOWEVER...A SOMEWHAT TIGHTER MSLP GRADIENT AND PERSISTENT SOUTHERLY BREEZE MAY PREVENT VISBYS FROM FALLING BELOW MVFR. EXPECT THE BEST CHANCE OF CONVECTION AT THE INT/GSO TERMINALS BETWEEN 15Z THIS MORNING AND 03Z THIS EVENING...WHERE VCSH WILL BE MENTIONED. AT THE RDU/FAY/RWI TERMINALS...CONFIDENCE IN AFTERNOON CONVECTION IS LOWER THAN AT INT/GSO. AS A RESULT...WILL KEEP VFR CONDITIONS IN PLACE AT RDU/FAY/RWI ONCE MORNING FOG AND STRATUS HAS LIFTED AND SCATTERED OUT. OTHERWISE...ANTICIPATE A CHANCE FOR IFR CEILINGS/VISBYS ONCE AGAIN BY THE END OF THE TAF PERIOD...06-12Z THURSDAY MORNING. LOOKING AHEAD: SUB-VFR STRATUS OR FOG WILL BE POSSIBLE DURING THE EARLY MORNING HOURS (07-13Z) ON BOTH FRI/SAT...ALONG WITH ISOLD SHOWERS AND STORMS DURING THE AFTERNOON AND EARLY EVENING HOURS...PRIMARILY AT THE FAY/RWI TAF SITES. MORE WIDESPREAD SHOWERS/STORMS WILL BE POSSIBLE SATURDAY NIGHT/SUNDAY AS AN UNSEASONABLY DEEP UPPER LEVEL TROUGH APPROACHES FROM THE WEST. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM....VINCENT SHORT TERM...BADGETT LONG TERM...BADGETT AVIATION...VINCENT
AREA FORECAST DISCUSSION
NWS RALEIGH NC
245 AM EDT WED SEP 5 2012 .SYNOPSIS... A WARM AND MOIST AIR MASS WILL PERSIST OVER THE AREA THROUGH THURSDAY... AS A LINGERING TROUGH OF LOW PRESSURE HOLDS OVERHEAD. A BIG PATTERN CHANGE IS EXPECTED BY LATE IN THE WEEKEND AND EARLY NEXT WEEK AS MUCH DRIER AND COOLER AIR WILL ARRIVE FROM THE UPPER MIDWEST. && .NEAR TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... AS OF 805 PM TUESDAY... THE LATEST SURFACE ANALYSIS SHOWED A WEAK SURFACE TROUGH OVER THE FAR WESTERN PIEDMONT...ALSO SHOWING UP ON MSAS AS AN AREA OF WEAK SURFACE CONVERGENCE. HOWEVER...PARTIALLY DUE TO LIMITED INSTABILITY...A RELATIVE MINIMUM OF THAT IN VICINITY OF THE TROUGH ON THE LATEST MSAS...STORMS WERE HAVING A HARD TIME BECOMING ROBUST. WHERE THE GREATER INSTABILITY WAS OVER THE COASTAL PLAIN...WITH MSAS LIFTED INDEX VALUES NEARLY TO -5C...SLIGHTLY DRIER AIR AND MORE OVERALL CIN AS NOTED ON NEAR-TERM NAM AND GFS BUFR SOUNDINGS WERE LIKELY CONTRIBUTING TO SCANT DEVELOPMENT AS OF THIS WRITING. OVERNIGHT...BOTH THE 18Z AND THE LATEST RAP DIMINISH LIFT BY 06Z... AND EVEN THE GFS...WITH QPF LINGERING LONGER THROUGH THE OVERNIGHT DESPITE STABILIZING BUFR SOUNDINGS IN CENTRAL NORTH CAROLINA...HAS 850MB LIFT DIMINISHING AS CONVERGENCE ALOFT INCREASES. THE LATEST RADAR TRENDS SUPPORT THE LATEST HRRR WRF...WITH MUCH OF THE DEEP CONVECTION HAVING DIMINISHED BY 05Z. HIGHER PRECIPITABLE WATER AIR SPREADS EAST OVERNIGHT...SO THAT BY 12Z BASICALLY ALL OF CENTRAL NORTH CAROLINA IS IN A SIMILAR AIR MASS WITH PRECIPITABLE WATER VALUES AROUND TWO INCHES AND K INDICES AT OR APPROACHING THE MID 30S. SURFACE-BASED AND DCAPE VALUES FALL...AND THE NAM ACTUALLY SEEMS TO FORECAST A SLIGHT INCREASE IN SURFACE RIDGING THAT MAY HELP TO LIMIT DEVELOPMENT OVERNIGHT. IN THE MOIST AIR MASS...AND WITH A SHEAR AXIS ALOFT OR JUST OFF TO OUR WEST... WILL CONTINUE THE ISOLATED SHOWERS OVERNIGHT IN THE FORECAST...BUT CURRENTLY IT IS EXPECTED MOST LOCATIONS LATE TONIGHT SHOULD REMAIN DRY. SREF PROBABILITIES OF VISIBILITIES BELOW 3 MILES ARE LIMITED OVERNIGHT...IN CONCERT WITH THE LATEST MOS GUIDANCE...WHILE SREF PROBABILITIES OF LOW CLOUDS ARE MOSTLY ABOVE 50 PERCENT BY 12Z WEDNESDAY. THIS IS CONSISTENT WITH THE LATEST GFS AND NAM BUFR SOUNDINGS. SHOULD BE PATCHY FOG AT BEST TOWARD THE COASTAL PLAIN WHERE THE INCREASING CLOUDS SHOULD BE NOTED LATER...WITH FOG LIMITED BY SOME WIND...ALBEIT LIGHT...CONTINUING OVERNIGHT. OVERNIGHT LOWS NEAR PERSISTENCE...MAINLY 70 TO 73. -DJF WEDNESDAY AND WEDNESDAY NIGHT: STRONG DAYTIME HEATING WILL SERVE TO RENEW CONVECTIVE INITIATION ACROSS CENTRAL NC WEDNESDAY AFTERNOON...FOCUSED ALONG THE LINGERING SUBTROPICAL MOISTURE PLUME CONFINED WITHIN THE LOWER-MID LEVEL TROUGH AXIS RESIDING OVER THE AREA. VERY SIMILAR TO THE PAST FEW DAYS...THE MAIN CONCERN WILL BE FROM TRAINING...HEAVY RAIN PRODUCING THUNDERSTORMS...WITH A SECONDARY/ISOLATED SEVERE THREAT DUE TO WEAK WINDS ALOFT AND WEAK FORCING. HIGHS WILL DEPEND ON HOW SOON WE GET CONVECTION TO POP...BUT WESTERN PIEDMONT PORTIONS OF THE AREA SHOULD BE A GOOD 2 TO 3 DEGREES COOLER THAN CENTRAL AND EASTERN AREAS WITH DELAYED HEATING FROM SLOWER BREAKUP/BURN OFF OF MORNING STRATUS/FOG. HIGHS IN THE MID 80S NW TO NEAR 90 JUST ABOUT EVERYWHERE ELSE. LOWS WEDNESDAY NIGHT THE LOWER 70S WITH AREAS OF STRATUS AND FOG. -CBL && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 230 AM WEDNESDAY... THERE IS A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS AGAIN THURSDAY AFTERNOON AND EVENING AS A WEAKENING COLD FRONT IS FORECAST TO STALL ACROSS CENTRAL NORTH CAROLINA THURSDAY. THE UPPER DYNAMICS WILL BE VERY WEAK. HOWEVER... CONTINUED HI PW`S AND STRONG HEATING ESPECIALLY IN THE SOUTH AND EAST WILL SUPPORT SCATTERED STRONG THUNDERSTORMS... WITH THE PRIMARY THREATS OF LOCALLY HEAVY RAIN AND GUSTY WIND. WE WILL CARRY THE HIGHEST POP IN THE EAST AND SOUTH... BUT EVEN THE NW WILL HAVE LOW CHANCE POPS. HIGHS IN THE MID TO UPPER 80S NW RANGING TO AROUND 90 SE. THE POPS WILL BECOME SLIGHT CHANCE BY LATE EVENING THURSDAY... SUPPORTED BY THE LINGERING NEARLY STATIONARY BOUNDARY. LOWS GENERALLY 70-73. FRIDAY AND FRIDAY NIGHT... THIS MAY BE THE DAY WHEN WE HAVE THE LOWEST POPS... ESPECIALLY OVER THE PIEDMONT WHERE SOME DRIER AIR (VERY SLIGHTLY DRIER AIR MAY FILTER IN WITH DEW POINTS IN THE MID 60S). THAT IS... IF... THE LOW LEVEL BOUNDARY DRIFTS INTO THE COASTAL PLAIN OR WASHES OUT ENTIRELY PER SOME MODEL SOLUTIONS. THIS APPEARS POSSIBLE... YET BY LATE IN THE DAY EXPECT THE SEA BREEZE/OLD FRONT COMBO TO DRIFT BACK WNW INTO THE EASTERN PIEDMONT BY EARLY EVENING BRINGING BACK 70+ DEW POINTS. WE WILL STILL CARRY SLIGHT TO LOW CHANCE POP FOR SHOWERS AND THUNDERSTORMS... MAINLY FROM FAY AND RDU EASTWARD DURING FRIDAY AFTERNOON AND EARLY EVENING. OTHERWISE... PARTLY SUNNY WARM AND HUMID. HIGHS 88-94 NW TO SANDHILLS. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 245 AM WEDNESDAY... BIG PATTERN CHANGE IN THE OFFING... A FAIRLY DEEP MID-UPPER LEVEL TROUGH IS FORECAST TO DEVELOP OVER THE GREAT LAKES AND SWING EASTWARD OVER THE WEEKEND. THE ACTUAL COLD FRONT IS PROJECTED FOR SATURDAY. THIS WILL SWEEP THE VERY MUGGY OPPRESSIVE AIR MASS CURRENTLY OVER THE AREA OUT TO SEA SUNDAY AND MONDAY. THE MODELS HAVE BEEN TRENDING TOWARD A MORE PROGRESSIVE TROUGH PASSAGE FOR OUR REGION AND LATITUDE. THIS WOULD MEAN LESS IN THE WAY OF SEVERE AND FLOODING POTENTIAL OVER THE WEEKEND. STAY TUNED. WE WILL CONTINUE TO CARRY INCREASING CHANCES OF SHOWERS AND STORMS SAT-SAT NIGHT... SHIFTING EAST MORE QUICKLY SUNDAY. MODELS NOW PROJECT THE ACTUAL FRONT TO PUSH EAST THROUGH OUR REGION BY LATE SATURDAY. THIS WOULD MEAN LOWERING HUMIDITIES AND MUCH LOWER POP FOR SUNDAY (A DAY TO A DAY AND A HALF EARLIER THAN PROJECTED 24 HOURS AGO). WE WILL TREND THAT WAY... BUT KEEP A CHANCE POP MAINLY EAST SUNDAY. TURNING COOLER AND MUCH DRIER MONDAY AND TUESDAY. LOWS 55-60. HIGHS 77-82. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... AS OF 745 PM TUESDAY... CONFIDENCE IS HIGH THAT AVIATION CONDITIONS WILL DETERIORATE AFTER NIGHTFALL... AND PARTICULARLY AFTER MIDNIGHT... AT ALL CENTRAL NC TERMINAL FORECAST SITES. THE RISK OF A SHOWER OR ISOLATED STORM WILL PERSIST NEAR INT/GSO THROUGH 04Z BUT THE CHANCE WILL QUICKLY DIMINISH AFTER 02Z. ELSEWHERE AT RDU/FAY/RWI... THE CHANCE OF A SHOWER OR STORM FOR THE REMAINDER OF THE NIGHT IS VERY SMALL. AFTER 04Z... THE RECENT RAINS AND RESULTANT WET GROUND COMBINED WITH VERY LIGHT WIND FROM THE SE OR SOUTH WILL FAVOR DEVELOPMENT OF LOW STRATUS AFTER MIDNIGHT. SREF AVIATION PROBABILITIES SHOW A VERY GOOD CHANCE OF CIGS UNDER 1 KFT OVERNIGHT... ESPECIALLY AT INT/GSO... AND FORECAST SOUNDINGS SUGGEST THAT CIGS COULD BE LOWER THAN 600 FT AGL. EXPECT AROUND A 200-500 FT CIG AT ALL SITES AFTER 07Z OR 08Z TONIGHT... HOLDING THROUGH AROUND 13Z WHEN THE CLOUDS WILL BEGIN TO LIFT AND MIX OUT TO SCATTERED. VSBYS WILL BE GENERALLY MVFR BETWEEN 07Z AND 13Z... ALTHOUGH VSBYS COULD GET LOWER AT TOWERS... AS CIGS LOWER. VFR CONDITIONS ARE EXPECTED TO RETURN AFTER 13Z OR 14Z WEDNESDAY MORNING. THE CHANCE FOR STORMS WEDNESDAY AFTERNOON DOES NOT APPEAR TO BE HIGH ENOUGH TO INCLUDE AS A PREVAILING CONDITION AT THIS TIME... BUT THE MOST LIKELY LOCATION OF ANY STORMS WEDNESDAY AFTERNOON WILL BE AT INT/GSO/RDU. LOOKING BEYOND 00Z THURSDAY (WEDNESDAY EVENING)... ANOTHER ROUND OF LOW CIGS AND VSBYS IS EXPECTED LATE WEDNESDAY NIGHT INTO THURSDAY MORNING AREAWIDE. WE MAY SEE A BRIEF RESPITE FROM THE DAILY SLOW-MOVING HEAVY-RAIN-PRODUCING STORMS FROM FRIDAY INTO SATURDAY... HOWEVER MORE RAIN AND STORMS ARE EXPECTED SUNDAY. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BADGETT NEAR TERM....DJF/CBL SHORT TERM...BADGETT LONG TERM...BADGETT AVIATION...HARTFIELD
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
951 PM EDT THU SEP 6 2012 .SYNOPSIS... A WEAK DISTURBANCE WILL BRING A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS TO NORTHERN PORTIONS OF THE AREA TODAY. HIGH PRESSURE WILL WORK INTO THE AREA TONIGHT AND REMAIN ACROSS THE AREA THROUGH FRIDAY MORNING. A LOW PRESSURE SYSTEM...AND A STRONG COLD FRONT...WILL BRING PRECIPITATION BACK TO THE AREA FROM FRIDAY AFTERNOON THROUGH SATURDAY MORNING. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... ISOLATED SHOWERS AND THUNDERSTORMS CONTINUE NEAR A WEAK FRONTAL BOUNDARY ACROSS THE NORTHERN PORTIONS OF THE FORECAST AREA. HAVE EXTENDED SLIGHT CHANCE POPS UNTIL MIDNIGHT FOR PORTIONS OF THE AREA. THE LATEST HRRR INDICATES THAT SOME OF THIS ACTIVITY MAY TRY TO REDEVELOP FARTHER SOUTH...LIKELY OUTFLOW INITIATED...WHERE THE BETTER ELEVATED INSTABILITY IS LOCATED. HOWEVER...KEPT THESE ZONES DRY FOR NOW. IN THE SOUTH...SURFACE DEWPOINTS IN THE UPPER 60S WILL ALLOW FOR SOME FOG TO DEVELOP...BUT NOT LIKELY AS WIDESPREAD AS THE PAST TWO NIGHTS. HAVE LIMITED THE MENTION OF FOG IN THE ZONES MAINLY TO VALLEY LOCATIONS ACROSS THE SOUTHERN HALF OF THE FORECAST AREA. ACROSS THE NORTH...SLIGHTLY DRIER CONDITIONS AND A MORE CLOUDY START TO THE OVERNIGHT PERIOD SHOULD LIMIT FOG DEVELOPMENT. MINIMUM TEMPERATURES WERE NOT ADJUSTED ON THIS UPDATE AS EVENTUAL LATE NIGHT CLEARING ACROSS THE NORTH WILL ALLOW FOR TEMPERATURES TO DROP INTO THE LOW 60S. SOUTH OF THE FRONT...TEMPERATURES WILL REMAIN IN THE UPPER 60S. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/... SURFACE LOW PRESSURE IS EXPECTED TO DEVELOP OVER NORTHERN ILLINOIS ON FRIDAY AFTERNOON. THIS LOW WILL MOVE QUICKLY TO THE ENE AS IT DEEPENS...AND ROUNDS THE FRONT EDGE OF A VERY SHARP MID LEVEL TROUGH OVER THE GREAT LAKES. A STRONG COLD FRONT WILL TRAIL SOUTHWEST FROM THIS LOW PRESSURE CENTER...MOVING EAST THROUGH THE OHIO VALLEY THROUGH SATURDAY MORNING. FRONTAL TIMING IS IN DECENT AGREEMENT BETWEEN THE MODELS...ALTHOUGH BY THE END OF ITS PASSAGE...THE SURFACE LOW POSITION AND STRENGTH ARE HANDLED SLIGHTLY DIFFERENTLY. DESPITE THE DIFFERING POSITIONS OF THE SURFACE LOW (WHICH WILL NOT DIRECTLY IMPACT THE ILN CWA)...THE RIBBON OF DEEP MOISTURE AND EXPECTED PRECIPITATION SEEM TO BE WITHIN 3 HOURS OF EACH OTHER EVEN BY SATURDAY AFTERNOON. THIS HAS LED TO A VERY DETERMINISTIC POP/WX FORECAST...WITH A 100 PERCENT CHANCE OF TS/RA THAT SPREAD ACROSS THE ENTIRE FORECAST AREA. FORCING WILL NOT BE IN QUESTION WITH THIS SYSTEM...WITH PLENTY OF SUPPORT FROM THE COLD FRONT AND UPPER TROUGH. THE POTENTIAL FOR HAZARDOUS WEATHER WITH THIS SYSTEM IS THE PRIMARY CONCERN OF THE SHORT TERM FORECAST. THE FRONT WILL BE MOVING INTO AN ENVIRONMENT WITH 30-40 KNOTS OF 0-6KM SHEAR...AND 15-25 KNOTS IN THE LOWEST KILOMETER OR TWO. MLCAPE DURING PEAK HEATING WILL BE IN THE 1500-2000 J/KG RANGE. GIVEN THE STRONG FORCING...THESE PARAMETERS CERTAINLY SUPPORT A SEVERE WEATHER THREAT. THE BIGGEST NEGATIVE FOR SEVERE POTENTIAL IS THE TIMING...SINCE MUCH OF THE ACTIVITY IS EXPECTED TO TAKE PLACE AFTER 00Z. THERE IS NO BIG PUSH OF MOISTURE IN THE BOUNDARY LAYER...WITH THE HIGHEST DEWPOINTS BEING RELEGATED TO A RIBBON ALONG AND NEAR THE FRONT. WANING INSTABILITY AFTER SUNSET (A FACTOR PARTIALLY CONNECTED TO THE ABOVE) WILL LIMIT THE STRENGTH OF THE CONVECTION. IN ADDITION...THE FRONT IS EXPECTED TO BE FORWARD PROPAGATING AT AROUND 30 MPH...NOT FAST ENOUGH TO KEEP UP WITH THE MOVEMENT OF INDIVIDUAL STORM CELLS OR LINES (OR THEIR OUTFLOW BOUNDARIES). THE END RESULT IS THAT A LINE (OR BROKEN LINE) OF STRONG TO SEVERE CONVECTION IS EXPECTED TO MOVE INTO THE ILN CWA LATE TOMORROW AFTERNOON. THE GREATER THREAT IS IN THE WESTERN HALF OF THE CWA...WITH A PROJECTED WEAKENING TREND IN THE CONVECTION DURING THE EVENING AND OVERNIGHT HOURS. DAMAGING WINDS WILL BE THE PRIMARY THREAT...WITH SOME LARGE HAIL ALSO POSSIBLE. THE LOW LEVEL SHEAR WILL SUPPORT SOME POSSIBILITY OF TORNADOES BEFORE THE BOUNDARY LAYER BEGINS TO DECOUPLE...THOUGH THIS THREAT WOULD LIKELY BE TIED TO THE EVOLUTION OF THE INDIVIDUAL QLCS ELEMENTS WITHIN THE CONVECTION. HEAVY RAIN IS ALSO A POSSIBILITY. ALTHOUGH WIDESPREAD QPF TOTALS WILL PROBABLY BE IN THE 0.75-1.25 INCH RANGE...PWATS NEAR TWO INCHES AND MOISTURE TRANSPORT THAT PARALLELS THE FRONT WILL RESULT IN SOME POSSIBILITY OF TRAINING AND POTENTIAL LOCALIZED FLOODING. THE FRONT DOES SLOW DOWN SOMEWHAT AS IT MOVES INTO THE UPPER OHIO VALLEY...AS ITS ORIENTATION BECOMES MORE SSW/NNE AND THE SURFACE LOW ALSO GAINS MORE OF A NORTHERLY COMPONENT TO ITS MOTION. EVEN STILL...THE SYSTEM IS LARGELY A PROGRESSIVE ONE. THIS FORECAST PACKAGE WILL BE SLIGHTLY AGGRESSIVE IN CLEARING POPS OUT BEHIND THE FRONT...WITH THE EXPECTATION THAT MOST OF THE WESTERN HALF OF THE CWA WILL HAVE A DRY SATURDAY. HOWEVER...SOME LOW LEVEL MOISTURE BEHIND THE FRONT WILL KEEP CLOUDS AROUND FOR A WHILE. ESPECIALLY GIVEN THE COLD ADVECTION PROVIDED BY THE FRONT...A SIGNIFICANT COOL DOWN IS EXPECTED...WITH HIGHS ONLY REACHING THE LOWER 70S. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... SHORT WAVE ENERGY WILL ROTATE DOWN ACROSS THE GREAT LAKES SATURDAY NIGHT INTO SUNDAY. MOISTURE IS PRETTY LIMITED...BUT THE COMBINATION OF THIS AND SOME DAYTIME HEATING...MAY BE ENOUGH TO SQUEEZE OUT A FEW SHOWERS OR SPRINKLES ACROSS OUR NORTH SUNDAY AFTERNOON. OTHERWISE...RIDGING AT THE SURFACE AND ALOFT WILL BUILD INTO THE AREA THROUGH TUESDAY BEFORE SHIFTING OFF TO THE EAST THROUGH THE END OF THE LONG TERM PERIOD. THIS WILL PROVIDE DRY CONDITIONS AND MAINLY CLEAR SKIES THROUGH AT LEAST MID WEEK. AS THE SURFACE HIGH SLIDES OVERHEAD...CLEAR SKIES AND LIGHT WINDS WILL LEAD TO SOME SEASONABLY COOL NIGHTS. EXPECT OVERNIGHT LOWS TO DIP DOWN INTO THE 40S IN SOME OF THE OUTLYING AREAS THROUGH THE FIRST PART OF THE WEEK WITH DAYTIME HIGHS GENERALLY IN THE 70S. WE WILL THEN SEE A GRADUAL MODERATION IN TEMPS WEDNESDAY INTO THURSDAY AS THE HIGH BEGINS TO PUSH OFF TO THE EAST AND WE GET INTO RETURN FLOW. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... ISOLATED THUNDERSTORMS MAINLY NEAR KDAY WILL DIMINISH BY SUNSET. MOSTLY CLEAR SKIES WILL ALLOW FOR SHALLOW FOG TO DEVELOP AROUND THE AREA TONIGHT...LIFTING SHORTLY AFTER SUNRISE. THIS FOG WILL AFFECT TAF SITES MAINLY ACROSS THE SOUTH...KCVG/KLUK/KILN...WHERE BETTER SURFACE MOISTURE IS LOCATED. CLOUD COVER WILL INCREASE AHEAD OF A STORM SYSTEM DURING THE DAY. BY THE EVENING HOURS EXPECT WIDESPREAD RAIN AND THUNDERSTORMS TO BEGIN MOVING INTO THE WESTERN TERMINALS...BRINGING WITH THEM MVFR TO IFR CONDITIONS. .OUTLOOK...MVFR CEILINGS AND VISIBILITIES POSSIBLE FRIDAY NIGHT INTO SATURDAY MORNING. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HATZOS NEAR TERM...LATTO SHORT TERM...HATZOS LONG TERM...JGL AVIATION...LATTO
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
611 PM EDT WED SEP 5 2012 .SYNOPSIS... AFTERNOON CONVECTION...FOLLOWED BY DYING MCS MOVING INTO NORTHEAST KY AND EXTREME SOUTHERN WV THIS EVENING. COLD FRONT ARRIVES THURSDAY FOLLOWED BY AN UPPER LEVEL LOW AND SURFACE COLD FRONT FOR THE WEEKEND. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... UPDATED POPS/WX PER LATEST RADAR IMAGES SHOWING DIURNAL CONVECTION DEVELOPING ACROSS THE SOUTHERN THIRD OF WV. SO...WENT MORE DETERMINISTIC WITH HIGH LIKELIES. ONLY THE OLD RUN FROM THE HRRR DEPICTED THIS ACTIVITY WITH THE REST OF MODELS OVERDOING THE REST OF THE AREA WHICH REMAINS CLEAR SKIES AND DRY. THE NAM SHOWS FORCING IN THE MID LEVEL OMEGA REACHING THE SOUTHERN COAL FIELDS LATE THIS EVENING BY 00Z THU...BUT BELIEVE THAT IS ASSOCIATED WITH THE APPROACHING MCS FEATURE INTO NORTHEAST KY...WELL AHEAD OF A COLD FRONT. PREVIOUS DISCUSSION BELOW... ALMOST LIKE A MID SUMMER PATTERN WHERE WEAK FLOW IS DOMINATED BY MESOSCALE INFLUENCES...BEFORE COLD FRONT APPROACHES FROM THE WEST LATER THURSDAY. THE HI RES MODELS HAVE DONE A POOR JOB INITIALIZING MCS OVER INDIANA THIS MORNING...AND APPARENTLY TOO AGGRESSIVE IN PUSHING WEAK FRONT AND DEEPER MOISTURE OUT OF AREA THIS AFTERNOON. THE NAM HAS DONE A BETTER JOB THAN THE GFS...AND WILL USE NAM DETAILS. STILL...WILL HAVE TO BE MORE AGGRESSIVE THAN MODELS EARLY IN TONIGHT PERIOD FOR EFFECTS OF THE INDIANA MCS AS IT MOVES EAST AND WEAKENS. WILL INTRODUCE LOW POPS OVER SOUTHWEST THIRD OF AREA EARLY TONIGHT TO ACCOUNT FOR POSSIBLE MCS BEFORE IN SINKS SOUTH OUT OF THE AREA LATE TONIGHT. ALSO...WILL DOWN PLAY NAM AGGRESSIVENESS ON ANOTHER MCS DROPPING SOUTHEAST OUT OF NORTHERN INDIANA LATER TONIGHT...UNTIL WE SEE EFFECTS OF PRECEDING MCS. IN SHORT...HAVE SOME SORT OF LOW POPS OVER THE WESTERN AND SOUTHERN PORTIONS OVERNIGHT. TEMPS AGAIN OVERNIGHT WILL BE HIGHER THAN GUIDANCE WITH THE HIGH MOISTURE...CLOSER TO MET NUMBERS. FOR THURSDAY...COLD FRONT COMES ACROSS FROM THE NORTHWEST...MANLY AFFECTING THE AREA IN THE AFTERNOON. AGAIN...UNCERTAINTY ON HOW VIGOROUS THIS FRONT AND CONVECTION WILL BE PROMPTS A CHANCE POP WITH THE FRONT. TEMPS WILL BE ON THE HIGH SIDE OF GUIDANCE...HITTING 90 MANY LOCATIONS. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY NIGHT/... PRECIP WILL COME TO AN END FROM WEST TO EAST THURSDAY NIGHT AS WEAK FRONT PULLS AWAY/DISSIPATES. NAM LINGERS MOISTURE INTO FRIDAY...WHILE GFS IS A BIT FASTER MOVING IT OUT. HAVE SLIGHT CHANCE POPS IN THE MOUNTAINS FRIDAY AFTERNOON TO ACCOUNT FOR ANY ISOLATED DIURNAL CONVECTION THAT MAY DEVELOP. ONLY A SHORT BREAK BEFORE THE NEXT SYSTEM MOVES IN FOR THE WEEKEND. MODELS AND ENSEMBLES HAVE CONTINUED TRENDING TOWARDS THE IDEA OF AN OPEN TROUGH...AND KEEP IT FAIRLY PROGRESSIVE. WITH THIS IN MIND...SPED UP ENTIRE SYSTEM A BIT...WITH SLIGHT CHANCE POPS ENTERING SE OHIO LATE FRIDAY EVENING AND INTO THE WV MOUNTAINS OVERNIGHT. THEN HAVE LIKELY POPS INTO SE OHIO BY SATURDAY MORNING AND THE WV MOUNTAINS EARLY SATURDAY AFTERNOON. KEPT THE HIGHEST POPS ALONG AND IN FRONT OF THE SURFACE COLD FRONT...WHICH SHOULD CROSS THE OHIO RIVER 18Z-20Z AND EXIT EAST OF FORECAST AREA SATURDAY NIGHT. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... MADE WHOLESALE CHANGES TO THE LONG TERM FORECAST AS MODELS COMING INTO BETTER AGREEMENT THAN YESTERDAY...NOW SHOWING OPEN WAVE SWINGING THROUGH OVER THE WEEKEND...AND A THING OF THE PAST AS WE HEAD INTO THE WORK WEEK. LINGER CHANCE AND SLIGHT CHANCE POPS THROUGH SUNDAY...MOVING OUT SUNDAY NIGHT AS THE UPPER TROUGH MOVES EAST AND OUT TO SEA. THIS WILL PROVIDE A MAINLY DRY FORECAST FOR THE REST OF THE LONG TERM. DID NOT INCLUDE ANY POPS FOR THE WORK WEEK AT THIS TIME DUE TO LACKING MOISTURE...BUT WITH NORTHWEST FLOW IT MAY BE POSSIBLE TO GET A LITTLE SHORTWAVE RIPPLE THAT COULD POP A SHOWER OR TWO AT SOME POINT. TEMPERATURES WILL START OFF BELOW NORMAL ON MONDAY...WITH A GRADUAL WARMING TREND TO NEAR NORMAL BY MID TO LATE WEEK AS UPPER RIDGE MOVES INTO SOUTHERN PLAINS. && .AVIATION /22Z WEDNESDAY THROUGH MONDAY/... 18Z WEDNESDAY THRU 12Z THURSDAY... INCREASED CONVECTION THRU EARLY AFTERNOON OVER SOUTHEASTERN WV AND SOUTHWEST VA AS EASTWARD MOVING SHORT WAVE AND WEAK FRONTAL BOUNDARY COLLIDE WITH DEEPER MOISTURE. MAIN EFFECT WILL BE AT BKW. THIS SHORT WAVE WILL EXIT MOUNTAINS BY 21Z WITH CONVECTION DIMINISHING. VFR OUTSIDE OF CONVECTION THIS AFTERNOON AND EVENING. DYING EASTWARD MOVING MCS FROM INDIANA MAY CLIP THE SOUTHWESTERN THIRD OF THE AREA EARLY TONIGHT AS IT TRIES TO DROP SOUTHEAST...POSSIBLY AFFECTING HTS. ANOTHER MCS MAY DEVELOP AND TRACK SOUTHEAST FROM NORTHERN INDIANA TO AFFECT NORTHWEST PORTIONS OF AREA AFTER 08Z. ALL THIS OVERNIGHT ACTIVITY FORECAST IS WITH LOW CONFIDENCE...AND WILL GO OPTIMISTIC FOR MAINLY MID CLOUDS WITH THESE SYSTEMS. HOWEVER...FOG WILL FROM LATER TONIGHT AFTER 06Z...ESPECIALLY EAST PORTIONS WITH LESSER CLOUDS. WILL GO WITH MVFR TO LOCALLY IFR FOG UNTIL 12Z. AFTER 12Z...VFR CEILINGS WITH INCREASING CHANCE FOR JUST AFTER THIS PERIOD AS COLD FRONT APPROACHES. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z FRIDAY... FORECAST CONFIDENCE: LOW. ALTERNATE SCENARIOS: EVOLUTION OF ANY OVERNIGHT COMPLEXES WILL DETERMINE AMOUNT OF CLOUD AND FOG. 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 20 21 22 23 00 01 02 03 04 05 06 07 EDT 1HRLY 16 17 18 19 20 21 22 23 00 01 02 03 CRW CONSISTENCY H H H H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H M H BKW CONSISTENCY H H H H H H H H H H H H EKN CONSISTENCY H H H H H H H H H H H L PKB CONSISTENCY H H H H H H H H H H M H CKB CONSISTENCY H H H H H H H H H H M H AFTER 00Z FRIDAY... IFR FOG EXPECTED AT MOST TERMINALS 06 TO 12Z THURSDAY. BRIEF IFR POSSIBLE IN THUNDERSTORMS SATURDAY. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...ARJ/JMV/MZ NEAR TERM...JMV SHORT TERM...MZ LONG TERM...MZ AVIATION...JMV
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
732 PM EDT THU SEP 6 2012 .SYNOPSIS... A WEAK COLD FRONT WILL MOVE SLOWLY ACROSS THE STATE TODAY AND TONIGHT. AN UPPER TROUGH WILL FORM OVER THE GREAT LAKES AND MIDWEST AND AMPLIFY AS IT APPROACHES PENNSYLVANIA...BRINGING UNSETTLED WEATHER INTO THE WEEKEND. HIGH PRESSURE WILL BUILD INTO THE AREA LATE MONDAY...BRINGING IN COOLER TEMPERATURES...BEFORE MOVING OFF THE COAST LATER IN THE WEEK. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... ANOTHER UPDATE TO UP POPS ACROSS THE FAR NE...BUT CUT BACK TO THE FAR NW AND SW. STILL STORMS FORMING ACROSS THE NORTHERN TIER PORTION OF PA. STP FOR NORTHERN LYCOMING ABOUT 16 INCHES. SOME OF THIS HAIL...BUT STILL A LOT OF RAIN...WITH FLOODING OF SOME ROADS. WILL CONTINUE TO MONITOR AND UPDATE PRODUCTS AS NEEDED. EARLIER DISCUSSION BELOW. A WEAK COLD FRONT ENTERING WESTERN PA WILL BE THE FOCUS FOR SOME SCATTERED CONVECTION THIS AFTERNOON. BEHIND THE DEPARTING SHORTWAVE CURRENTLY BRINGING SOME CLOUDS TO SERN ZONES...SATELLITE AND RUC DATA SUPPORT A MSUNNY DAY ACROSS THE NWRN 2/3 OR SO OF THE FCST AREA...WITH INCREASING SUNSHINE FOR THE AFTERNOON ACROSS THE SE PART OF THE CWA. THE SUNSHINE AND MDL 8H TEMPS ARND 17C WILL ALLOW TEMPS TO CLIMB QUICKLY INTO THE 80S BY AFTN...WITH THE LOWER SUSQ VALLEY NEARING 90F. RUC INDICATES STEEPENING MID LEVEL LAPSE RATES ALREADY DEVELOPING OVER WESTERN PA IN RESPONSE TO STRONG HEATING AND SLOWLY FALLING MID LEVEL TAMPS AND HEIGHTS. SPC RAP SHOWS CAPES EXCEEDING 3000J OVER WRN PA. MOISTURE CONVERGENCE IS WEAK HOWEVER AND VIZ SHOTS ARE JUST STARTING TO SHOW THE DEVELOPMENT OF A CU FIELD BACK OVER THE LOWER LAKES. THIS SHOULD CONTINUE TO DEVELOP AS THE DAY HEATS UP...WITH THE BEST CHANCES FOR STORMS BEING OVER MY NWRN COUNTIES. THE INSTABILITY COMBINED WITH SOME MODEST WIND SHEAR COULD BE ENOUGH TO SUPPORT ISOLATED STRONG WIND GUSTS IN SOME OF THE THUNDERSTORMS. ACTIVITY SHOULD WANE AFTER THE LOSS OF HEATING...LEADING TO A MAINLY DRY OVERNIGHT WITH MORE OF THE KIND OF LATE NIGHT FOG AND LOW CLOUDS WE HAVE SEEN OVER THE LAST FEW NIGHTS. IT WILL REMAIN QUITE MILD...IN THE 60S. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... A WEAK HIGH WILL BUILD INTO THE AREA BY LATE FRIDAY AS THE FRONTAL BOUNDARY LIFTS BACK NORTH AS A WARM FRONT INTO NEW YORK STATE. SW FLOW AT THE SFC AND ALOFT WILL MAINTAIN VERY WARM AND SOMEWHAT HUMID CONDITIONS...ESP IN THE SOUTH WHERE TEMPS WILL TOP OUT IN THE U80S TO LOWER 90S WITH SFC DEWPOINTS IN THE U60S TO AROUND 70F. HIGH TEMPS IN ALL AREAS FRIDAY WILL ONCE AGAIN BE 10-12F ABOVE NORMAL. GFS AND THE NEW NAM KEEP US DRY THRU THE DAY FRIDAY. THIS LOOKS MORE REASONABLE THAN THE SMALL CHC POPS OF THE 09Z SREF. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... CLOUDS THICKEN UP WITH SHRA/TSRA WELL AFTER MIDNIGHT ACROSS THE ALLEGHENY PLATEAU OF NRN AND WRN PENN. LOW LEVEL WIND SHEAR COULD IMPACT AVIATION AND BE FELT ACRS THE HIGHER TERRAIN FRIDAY NIGHT INTO SATURDAY...AS THE SSW FLOW IN THE 1-2 KFT AGL LAYER STRENGTHENS TO 35-40 KTS. DEEP LOW FCST TO DRAG A WARM FRONT...THEN A COLD FRONT ACROSS THE AREA ON SAT. MODELS DO NOT CLOSE LOW OFF NOW...BUT STILL LOOKS WET. SOME CHC OF STRONG TO PERHAPS SEVERE STORMS ACROSS THE EAST LATE. LESS CHC FOR WIDESPREAD HEAVY RAIN NOW...AS SYSTEM DOES NOT CLOSE OFF AND GO NEGATIVE. STILL WILL BE WET FOR MUCH OF THE DAY. RATHER STRONG UPPER LVL LOW MOVING ACROSS THE REGION ON SUNDAY... THUS EXPECT CU TO DEVELOP FAST...LIMIT MAX TEMPS...AND RESULT IN SHOWERS AND STORMS. BASED ON THIS...LEFT CHC POPS IN...MORE IN LINE WITH THE GFS...THAN THE NAM MODEL. ON THE COOL SIDE FOR SAT ACROSS THE FAR WEST...AND THE AREA SUNDAY INTO TUE AM...BUT NOTHING ABNORMAL FOR LATE AUG... EARLY SEPT. TUE AM COULD BE AS COOL ACROSS THE SE...AS OTHER AREAS. MINOR ADJUSTMENTS TO TEMPS. TOOK OUT SHOWERS FOR SUNDAY NIGHT. TUE AND WED LOOK DRY WITH HIGH PRESSURE OVER WV. A SW FLOW FOR THU...BUT STILL DRY...AS THE HIGH MOVES EAST. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... STILL SHOWING MDT/LNS HANGING DOGGEDLY ONTO CIGS AROUND 3000```BUT I EXPECT THESE TO LIFT QUICKLY SO HAVE STARTED THE NEW TAF PACKAGE OFF AS VFR AT ALL SITES. THE REST OF THE AFTERNOON WILL SEE SCATTERED CONVECTION BECOMING THE THREAT WITH LOCALIZED RESTRICTIONS IN THE SHOWERS/STORMS AS WELL AS THE POTENTIAL FOR ISOLATED STRONG WIND GUSTS IN STRONGER THUNDERSTORMS. MOST LIKLEY AREAS TO SEE THIS SHOULD BE ALONG NY...PA BORDER. EXPECT MORE LATE NIGHT FOG AND LOW CLOUDS TONIGHT. OUTLOOK... FRI...MAINLY VFR AFTER EARLY MORNING FOG/LOW CLOUD RESTRICTIONS. SAT...DETERIORATING CONDITIONS WITH THE APPROACH OF A WAVE OF LOW PRESSURE AND COLD FRONT. SUN...MVFR EARLY...IMPROVING DURING THE DAY. MON-TUE...NO SIG WX. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LA CORTE NEAR TERM...LA CORTE/MARTIN SHORT TERM...LA CORTE LONG TERM...MARTIN AVIATION...LA CORTE
AREA FORECAST DISCUSSION
NWS GREENVILLE-SPARTANBURG SC
1018 PM EDT THU SEP 6 2012 .SYNOPSIS... SLIGHTLY DRIER AIR WILL PREVAIL ACROSS OUR REGION ON FRIDAY UNDER WEAK HIGH PRESSURE. A STRONG COLD FRONT WILL MOVE ACROSS THE AREA SATURDAY AND SATURDAY NIGHT WITH DRY AIR OVERSPREADING THE REGION ON SUNDAY. DRY HIGH PRESSURE WILL SETTLE OVER THE REGION FOR MUCH OF NEXT WEEK. && .NEAR TERM /THROUGH FRIDAY/... EVENING UPDATE...NO MAJOR CHANGES WERE MADE TO THE GOING FCST. THE BIGGEST CHANGE WAS TO LOWER POPS TO ISOL FOR THE PERSISTENT -SHRA/TSTMS ACROSS THE ERN HALF OF THE FA. RADAR TRENDS AND ENVIRONMENTAL CONDS FAVOR A CONTINUED WEAKENING OF THESE STORMS...HOWEVER A PULSE PATTERN HAS BEEN EXHIBITED THROUGHOUT THE PAST COUPLE OF HRS AS THEY INTERACT WITH REMNANT OUTFLOWS. THE LATEST HRRR OUTPUT INDICATED A STORM COULD DEVELOP INTO THE CLT AREA AROUND 04Z...BUT THE ACTUAL INITIAL CELL HAS SINCE DISSIPATED. SO LONG STORY SHORT...NO CONFIDENT STORM THREAT IS HAD ATTM ACROSS THE CLT AREA...YET ISOL -SHRA WILL CONTINUE TO DEVELOP ACROSS THE NC PIEDMONT. SMALL SCALE DEBRIS CLOUDS SHOULD BECOME LESS AND LESS THROUGH THE OVERNIGHT AND GOOD RADIATIONAL COOLING CONDS AND STEEP SFC/BASED INVERSIONS SETTING UP BY DAYBREAK. THIS WILL LEAD TO A PATCHY FG PATTERN ACROSS THE NON/MTNS AND PERHAPS AREAS OF DENSE FG ACROSS THE MTN VALLEYS. AN MCS RACING ACROSS SRN KY MAY DISRUPT FG FORMATION ACROSS THE MTNS IF ENOUGH OF ITS CLOUDINESS MAKES IT INTO THE AREA. MIN TEMPS WILL BE ABOVE NORMAL BY A COUPLE DEGREES AS SFC TD/S HAVE REMAINED RELATIVELY HIGH ACROSS THE AREA THIS EVENING. PREVIOUS DISCUSSION... THE 16 UTC RAP AND WATER VAPOR IMAGERY CONTINUE TO INDICATE A WELL DEFINED SHORT WAVE TROF SLOWLY PROGRESSING ACROSS THE NC MTNS. AHEAD OF THE TROUGH...A STOUT AREA OF PVA EXITS OVER THE FOOTHILLS AND WESTERN PIEDMONT. THE WAVE WILL CONTINUE TO SLOWLY TRANSLATE TO THE ESE OVER THE NEXT SEVERAL HOURS. DEWPOINTS ARE QUITE HIGH OVER THE WESTERN CAROLINAS AND NE GA...AND NOW THAT TEMPS HAVE WARMED INTO THE L-M80S...SBCAPE VALUES HAVE RISEN TO 2000 J/KG OR HIGH IN MANY AREAS. THIS HAS RESULTED IN THE DEVELOPMENT OF SHRA/TSTMS OVER THE ERN UPSTATE AND SRN NC PIEDMONT. THE ACTIVITY SHOULD INCREASE IN COVERAGE OVER THE NEXT COUPLE HOURS...THEN MOVE EAST OF THE REGION BY EARLY EVENING. THE LATEST SPC MESOANALYSIS SHOWS A DCAPE MINIMUM ACROSS THE REGION. FREEZING LEVELS ARE ALSO OVER 15KFT. THEREFORE...NEITHER DAMAGING WINDS OR NOR HAIL WILL BE MUCH OF A THREAT WITH STORMS THIS AFTN. THE STORMS SHOULD NOT BECOME VERY ORGANIZED AND 30 TO 40 PERCENT COVERAGE...MAINLY OVER THE ERN ZONES...STILL LOOKS REASONABLE. THE EXCEPTION TO THIS COULD BE THE SRN NC PIEDMONT WHERE THE WAVE IS ALSO RESULTING IS INCREASED LLVL CONVERGENCE. LATE TONIGHT WIDESPREAD DENSE VALLEY FOG IS EXPECTED OVER THE NC MTNS. WITH THE MID-LEVELS DRY OUT...FOR SHOULD ALSO BE A LITTLE MORE WIDESPREAD ACROSS THE FOOTHILLS AND PIEDMONT...PARTICULARLY ALONG THE LARGER RIVER VALLEYS. SLIGHTLY DRIER AIR WILL WORK INTO THE REGION TOMORROW. A SHORT WAVE RIDGE WILL ALSO SLOWLY TRANSLATE ACROSS THE FA. WITH MUCH DRIER AIR ALOFT AND WARM H7 TEMPS CONVECTION WILL HAVE DIFFICULTLY DEVELOPING TOMORROW AND I HAVE A DRY FORECAST FOR THE FOOTHILLS AND PIEDMONT. ISOLATED STORMS ARE POSSIBLE OVER THE MTNS...PARTICULARLY OVER THE HIGHER ELEVATIONS. WITH DRIER AIR AND LIGHT DOWNSLOPE FLOW...TEMPERATURES WILL RISE INTO THE L90S ACROSS MUCH OF FOOTHILLS AND PIEDMONT. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... COLD FROPA AND ASSOCIATED PRECIPITATION ARE THE BIG CONCERN FOR FRIDAY NIGHT AND SATURDAY. 850MB WINDS WERE STRONGER ON 00Z NAM THAN ON 06Z GFS...WHICH LED THE NAM TO PRODUCE STRONGER THETA-E ADVECTION AND MOISTURE TRANSPORT AHEAD OF THE FRONT. 12Z NAM HAS WEAKER WINDS MORE IN LINE WITH THE GFS AND ITS MOISTURE FIELDS REFLECT THE WEAKER ADVECTION. DECENT AGREEMENT BETWEEN MODELS IN TIMING OF FROPA...WHICH APPEARS TO OCCUR BETWEEN 12Z AND 18Z. PRECIPITABLE WATER VALUES INCREASE AS THE FRONT ENTERS THE PIEDMONT...BUT THE VALUES OVER THE MOUNTAINS ARE MORE EXTREME WITH RESPECT TO CLIMATOLOGY. IF THE DYNAMICS ALONG THE FRONT WERE MORE IMPRESSIVE I WOULD BE INCLINED TO GO WITH HIGHER QPF...BUT KEPT IT IN CHECK FOR NOW. WITH THE FRONT MOVING THROUGH EARLY IN THE DAY...INSTABILITY WILL BE LIMITED...BUT FORECAST SOUNDINGS INDICATE ENOUGH CAPE TO WARRANT A THUNDER MENTION. HOWEVER THE BETTER CHANCES FOR THUNDER WILL BE OVER THE SC PIEDMONT ZONES DURING THE AFTERNOON AS THAT AREA WILL HAVE MORE TIME TO DESTABILIZE. COLD ADVECTION AND SUBSIDENCE SET IN QUICKLY BEHIND THE FRONT AND MODELS AGREE PRECIP SHOULD END BY LATE SATURDAY EVENING. COULD SEE SOME STRONG GAP WINDS IN THE MOUNTAIN VALLEYS OVERNIGHT SATURDAY NIGHT GIVEN STRONG WINDS IN 1000-3000 FT LAYER AND WEAK INVERSION PROFILE EXPECTED WITH PARTLY CLOUDY SKIES STILL IN PLACE. SUNDAY LOOKS TO BE REFRESHINGLY COOLER AND LESS HUMID WITH HIGHS IN THE MID 70S OVER THE MOUNTAINS TO THE LOWER 80S OVER THE PIEDMONT. ONE ITEM OF NOTE IS THAT THE 00Z EC DEVELOPS THE TROUGH INTO A CUTOFF UPPER LOW OVER THE NORTHEAST CONUS...WITH A WEAK LOBE OF VORTICITY REACHING THE MOUNTAINS LATE SUNDAY. HOWEVER THE MODEL DOES NOT PRODUCE ANY PRECIP AND THE WHOLE TROUGH IS LONG GONE ON THE GFS AT THIS TIME ANYWAY...SO STILL FEEL PRETTY CONFIDENT WITH DRY FORECAST SUNDAY. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 200 PM EDT THURSDAY...BY 00Z MONDAY ALL MODELS ARE INDICATING THAT DRY AIR WILL BE WELL ESTABLISHED AS THE AXIS OF THE UPPER TROUGH WILL BE OVER OUR AREA AND MOVING EAST. COOLER CANADIAN HIGH PRESSURE WILL BE MOVING FROM THE MISSISSIPPI VALLEY SUNDAY EVENING TO BE POSITIONED OVER WEST VIRGINIA BY AROUND 00Z TUESDAY. HIGH PRESSURE WILL SLOWLY SLIDE OFF THE EAST COAST IN MID WEEK AS THE NEXT COLD FRONT APPROACHES FROM THE NORTHWEST. HPC HAS THE FRONT OVER THE OHIO RIVER THURSDAY MORNING AS THAT POSITION MORE CLOSELY FOLLOWS THE ECMWF WHICH HAS A MUCH MORE SHALLOW TROUGH CROSSING THE GREAT LAKES AND HAS VERY LITTLE MOISTURE. THE GFS IS MUCH SLOWER WITH A SHARPER UPPER TROUGH AND DEEPER MOISTURE. THEREFORE...ONLY INCREASING THE CLOUDS A BIT OVER THE MOUNTAINS AT THE END OF THE CURRENT FORECAST WHICH AT THIS POINT IS THURSDAY NIGHT. TEMPERATURES WILL BE A FEW DEGREES BELOW NORMAL DURING THE FIRST HALF OF THE WEEK AND WARMING TO JUST BELOW NORMAL BY THURSDAY. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... AT KCLT...A LINE OF SHOWERS AND THUNDERSTORMS MOVING INTO NRN IREDELL COUNTY COULD REACH THE TERMINAL AROUND 02Z. HOWEVER...THE GENERAL WEANING SEEN ON THE HRRR AND WRF PRECLUDE A TEMPO INCLUSION AT THIS TIME. HOWEVER...A TEMPO COULD BE ADDED LATER ON IF NEEDED. AFTER THAT....EXPECT A CLEARING SKY TREND THROUGH THE MORNING AND THE DEVELOPMENT OF MFVR VSBY...LIFTING BY 13Z. LIGHT N/LY WINDS VEERING NE/LY IN THE AFTERNOON WILL PREVAIL THROUGH THE REMAINDER OF THE TAF PERIOD. ELSEWHERE...KEPT VCTS IN THE UPSTATE SC SITES THROUGH AROUND 02Z WITH AN ONGOING LINE CONVECTION PUSHING SOUTH. MVFR VSBYS WILL DEVELOP ACROSS THE NON/MTN SITES...WITH IFR VSBY SETTING UP UP AT KAVL BEFORE SUNRISE. EXPECT A RATHER QUICK BURN OFF OF FG...LIKELY AROUND 13Z OR 14Z. LIGHT N/Y TO NE/LY WINDS THROUGH THE AFTERNOON PERIOD. OUTLOOK...BRIEF DRYING FROM THE WEST IS EXPECTED INTO FRIDAY. A COLD FRONT WILL APPROACH THE REGION FROM THE NORTHWEST ON SATURDAY AND MOVE EAST OF THE AREA ON SUNDAY. A LINE OF THUNDERSTORMS IS POSSIBLE WITH THE FRONT ON SATURDAY. DRY AUTUMNAL HIGH PRES WILL DOMINATE THE AREA EARLY NEXT WEEK. AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)... WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...DEO NEAR TERM...SBK SHORT TERM...JW LONG TERM...DEO AVIATION...SBK
AREA FORECAST DISCUSSION
NWS GREENVILLE-SPARTANBURG SC
749 PM EDT THU SEP 6 2012 .SYNOPSIS... SLIGHTLY DRIER AIR WILL PREVAIL ACROSS OUR REGION ON FRIDAY UNDER WEAK HIGH PRESSURE. A STRONG COLD FRONT WILL MOVE ACROSS THE AREA SATURDAY AND SATURDAY NIGHT WITH DRY AIR OVERSPREADING THE REGION ON SUNDAY. DRY HIGH PRESSURE WILL SETTLE OVER THE REGION FOR MUCH OF NEXT WEEK. && .NEAR TERM /THROUGH FRIDAY/... 730 PM EDT UPDATE...POPS WERE ADJUSTED SPATIALLY AND TEMPORARILY ONCE AGAIN WITH NEW LINE OF STORMS PUSHING IN FROM THE NORTH ACROSS THE NW PIEDMONT. THESE STORMS HAVE REMAINED RELATIVELY WEAK AND THEY ARE HEADING DIRECTLY FOR THE CLT AREA...PROBABLY REACHING THAT AREA AROUND 02Z. THE 3 KM HRRR MODEL IS SORTA CAPTURING THESE STORMS AND THE OVERALL MESO ENVIRON...YET NO REAL DEFINITIVE GUIDANCE IS HAD AS THE WRF ALSO LACKS MESOSCALE DEFINITION. SO...WILL COUNT ON A GENERAL WEAKENING TREND AS THESE STORMS MOVE SOUTH INTO A WORKED OVER ATMOS...YET ONE FULL OF EXISTING OUTFLOW BNDRYS. NO...BIG CHANGES WERE NEEDED TO TEMPS/TDS...BUT SKY WILL BE ADJ DOWN QUITE A BIT BASED ON IR TRENDS. 430 PM EDT UPDATE...THE BIGGEST CHANGE FOR THE UPDATE INCLUDED ADDING A NUMEROUS -SHRA/TS AREA ACROSS THE EASTERN UPSTATE AND INTO THE NC PIEDMONT AROUND KCLT...PER THE LATEST 88D TRENDS AND SFC CONVERGENCE FIELDS. THERE COULD BE SOME TRAINING HYDRO ISSUES LATER ON...DEPENDING ON TRANSLATION OF THE UPPER TROF EASTWARD. SKY COVER WAS ADJUSTED USING THE LATEST VSBL LOOP AND INTERPOLATED HR/LY THROUGH THE EVENING. MINOR CHANGES WERE MADE TO TEMPS/TDS...MAINLY ACROSS THE EASTERN PIEDMONT WHERE CONVECTIVE CLOUD COVER HAS KEPT HR/LY VALUES LOWER THAN FORECASTED. THE 16 UTC RAP AND WATER VAPOR IMAGERY CONTINUE TO INDICATE A WELL DEFINED SHORT WAVE TROF SLOWLY PROGRESSING ACROSS THE NC MTNS. AHEAD OF THE TROUGH...A STOUT AREA OF PVA EXITS OVER THE FOOTHILLS AND WESTERN PIEDMONT. THE WAVE WILL CONTINUE TO SLOWLY TRANSLATE TO THE ESE OVER THE NEXT SEVERAL HOURS. DEWPOINTS ARE QUITE HIGH OVER THE WESTERN CAROLINAS AND NE GA...AND NOW THAT TEMPS HAVE WARMED INTO THE L-M80S...SBCAPE VALUES HAVE RISEN TO 2000 J/KG OR HIGH IN MANY AREAS. THIS HAS RESULTED IN THE DEVELOPMENT OF SHRA/TSTMS OVER THE ERN UPSTATE AND SRN NC PIEDMONT. THE ACTIVITY SHOULD INCREASE IN COVERAGE OVER THE NEXT COUPLE HOURS...THEN MOVE EAST OF THE REGION BY EARLY EVENING. THE LATEST SPC MESOANALYSIS SHOWS A DCAPE MINIMUM ACROSS THE REGION. FREEZING LEVELS ARE ALSO OVER 15KFT. THEREFORE...NEITHER DAMAGING WINDS OR NOR HAIL WILL BE MUCH OF A THREAT WITH STORMS THIS AFTN. THE STORMS SHOULD NOT BECOME VERY ORGANIZED AND 30 TO 40 PERCENT COVERAGE...MAINLY OVER THE ERN ZONES...STILL LOOKS REASONABLE. THE EXCEPTION TO THIS COULD BE THE SRN NC PIEDMONT WHERE THE WAVE IS ALSO RESULTING IS INCREASED LLVL CONVERGENCE. LATE TONIGHT WIDESPREAD DENSE VALLEY FOG IS EXPECTED OVER THE NC MTNS. WITH THE MID-LEVELS DRY OUT...FOR SHOULD ALSO BE A LITTLE MORE WIDESPREAD ACROSS THE FOOTHILLS AND PIEDMONT...PARTICULARLY ALONG THE LARGER RIVER VALLEYS. SLIGHTLY DRIER AIR WILL WORK INTO THE REGION TOMORROW. A SHORT WAVE RIDGE WILL ALSO SLOWLY TRANSLATE ACROSS THE FA. WITH MUCH DRIER AIR ALOFT AND WARM H7 TEMPS CONVECTION WILL HAVE DIFFICULTLY DEVELOPING TOMORROW AND I HAVE A DRY FORECAST FOR THE FOOTHILLS AND PIEDMONT. ISOLATED STORMS ARE POSSIBLE OVER THE MTNS...PARTICULARLY OVER THE HIGHER ELEVATIONS. WITH DRIER AIR AND LIGHT DOWNSLOPE FLOW...TEMPERATURES WILL RISE INTO THE L90S ACROSS MUCH OF FOOTHILLS AND PIEDMONT. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... COLD FROPA AND ASSOCIATED PRECIPITATION ARE THE BIG CONCERN FOR FRIDAY NIGHT AND SATURDAY. 850MB WINDS WERE STRONGER ON 00Z NAM THAN ON 06Z GFS...WHICH LED THE NAM TO PRODUCE STRONGER THETA-E ADVECTION AND MOISTURE TRANSPORT AHEAD OF THE FRONT. 12Z NAM HAS WEAKER WINDS MORE IN LINE WITH THE GFS AND ITS MOISTURE FIELDS REFLECT THE WEAKER ADVECTION. DECENT AGREEMENT BETWEEN MODELS IN TIMING OF FROPA...WHICH APPEARS TO OCCUR BETWEEN 12Z AND 18Z. PRECIPITABLE WATER VALUES INCREASE AS THE FRONT ENTERS THE PIEDMONT...BUT THE VALUES OVER THE MOUNTAINS ARE MORE EXTREME WITH RESPECT TO CLIMATOLOGY. IF THE DYNAMICS ALONG THE FRONT WERE MORE IMPRESSIVE I WOULD BE INCLINED TO GO WITH HIGHER QPF...BUT KEPT IT IN CHECK FOR NOW. WITH THE FRONT MOVING THROUGH EARLY IN THE DAY...INSTABILITY WILL BE LIMITED...BUT FORECAST SOUNDINGS INDICATE ENOUGH CAPE TO WARRANT A THUNDER MENTION. HOWEVER THE BETTER CHANCES FOR THUNDER WILL BE OVER THE SC PIEDMONT ZONES DURING THE AFTERNOON AS THAT AREA WILL HAVE MORE TIME TO DESTABILIZE. COLD ADVECTION AND SUBSIDENCE SET IN QUICKLY BEHIND THE FRONT AND MODELS AGREE PRECIP SHOULD END BY LATE SATURDAY EVENING. COULD SEE SOME STRONG GAP WINDS IN THE MOUNTAIN VALLEYS OVERNIGHT SATURDAY NIGHT GIVEN STRONG WINDS IN 1000-3000 FT LAYER AND WEAK INVERSION PROFILE EXPECTED WITH PARTLY CLOUDY SKIES STILL IN PLACE. SUNDAY LOOKS TO BE REFRESHINGLY COOLER AND LESS HUMID WITH HIGHS IN THE MID 70S OVER THE MOUNTAINS TO THE LOWER 80S OVER THE PIEDMONT. ONE ITEM OF NOTE IS THAT THE 00Z EC DEVELOPS THE TROUGH INTO A CUTOFF UPPER LOW OVER THE NORTHEAST CONUS...WITH A WEAK LOBE OF VORTICITY REACHING THE MOUNTAINS LATE SUNDAY. HOWEVER THE MODEL DOES NOT PRODUCE ANY PRECIP AND THE WHOLE TROUGH IS LONG GONE ON THE GFS AT THIS TIME ANYWAY...SO STILL FEEL PRETTY CONFIDENT WITH DRY FORECAST SUNDAY. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 200 PM EDT THURSDAY...BY 00Z MONDAY ALL MODELS ARE INDICATING THAT DRY AIR WILL BE WELL ESTABLISHED AS THE AXIS OF THE UPPER TROUGH WILL BE OVER OUR AREA AND MOVING EAST. COOLER CANADIAN HIGH PRESSURE WILL BE MOVING FROM THE MISSISSIPPI VALLEY SUNDAY EVENING TO BE POSITIONED OVER WEST VIRGINIA BY AROUND 00Z TUESDAY. HIGH PRESSURE WILL SLOWLY SLIDE OFF THE EAST COAST IN MID WEEK AS THE NEXT COLD FRONT APPROACHES FROM THE NORTHWEST. HPC HAS THE FRONT OVER THE OHIO RIVER THURSDAY MORNING AS THAT POSITION MORE CLOSELY FOLLOWS THE ECMWF WHICH HAS A MUCH MORE SHALLOW TROUGH CROSSING THE GREAT LAKES AND HAS VERY LITTLE MOISTURE. THE GFS IS MUCH SLOWER WITH A SHARPER UPPER TROUGH AND DEEPER MOISTURE. THEREFORE...ONLY INCREASING THE CLOUDS A BIT OVER THE MOUNTAINS AT THE END OF THE CURRENT FORECAST WHICH AT THIS POINT IS THURSDAY NIGHT. TEMPERATURES WILL BE A FEW DEGREES BELOW NORMAL DURING THE FIRST HALF OF THE WEEK AND WARMING TO JUST BELOW NORMAL BY THURSDAY. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... AT KCLT...A LINE OF SHOWERS AND THUNDERSTORMS MOVING INTO NRN IREDELL COUNTY COULD REACH THE TERMINAL AROUND 02Z. HOWEVER...THE GENERAL WEANING SEEN ON THE HRRR AND WRF PRECLUDE A TEMPO INCLUSION AT THIS TIME. HOWEVER...A TEMPO COULD BE ADDED LATER ON IF NEEDED. AFTER THAT....EXPECT A CLEARING SKY TREND THROUGH THE MORNING AND THE DEVELOPMENT OF MFVR VSBY...LIFTING BY 13Z. LIGHT N/LY WINDS VEERING NE/LY IN THE AFTERNOON WILL PREVAIL THROUGH THE REMAINDER OF THE TAF PERIOD. ELSEWHERE...KEPT VCTS IN THE UPSTATE SC SITES THROUGH AROUND 02Z WITH AN ONGOING LINE CONVECTION PUSHING SOUTH. MVFR VSBYS WILL DEVELOP ACROSS THE NON/MTN SITES...WITH IFR VSBY SETTING UP UP AT KAVL BEFORE SUNRISE. EXPECT A RATHER QUICK BURN OFF OF FG...LIKELY AROUND 13Z OR 14Z. LIGHT N/Y TO NE/LY WINDS THROUGH THE AFTERNOON PERIOD. OUTLOOK...BRIEF DRYING FROM THE WEST IS EXPECTED INTO FRIDAY. A COLD FRONT WILL APPROACH THE REGION FROM THE NORTHWEST ON SATURDAY AND MOVE EAST OF THE AREA ON SUNDAY. A LINE OF THUNDERSTORMS IS POSSIBLE WITH THE FRONT ON SATURDAY. DRY AUTUMNAL HIGH PRES WILL DOMINATE THE AREA EARLY NEXT WEEK. AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)... WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...DEO NEAR TERM...MCAVOY/SBK SHORT TERM...JW LONG TERM...DEO AVIATION...SBK
AREA FORECAST DISCUSSION
NWS GREENVILLE-SPARTANBURG SC
530 PM EDT WED SEP 5 2012 .SYNOPSIS... DEEP TROPICAL MOISTURE CURRENTLY OVER THE REGION WILL BEGIN TO PROGRESSIVELY LESSENING THURSDAY INTO FRIDAY. A STRONG COLD FRONT WILL MOVE OVER THE CAROLINAS THIS WEEKEND FOLLOWED BY HIGH PRESSURE THAT WILL PROVIDE COOLER AND DRYER WEATHER INTO THE FIRST OF NEXT WEEK. && .NEAR TERM /THROUGH THURSDAY/... 530 PM EDT UPDATE...MADE LOWERING CHANGES TO THE POPS/QPF BASED ON RADAR TRENDS WV IMAGERY AND WRF/ARW OUTPUT. VERY WEAK FORCING ACROSS THE NRN ZONES AND ACTUAL SUBSIDENCE SOUTH ACROSS THE UPSTATE AND NE GA HAVE PRECLUDED A SIGFNT CONVECTIVE THREAT IN STRENGTH AND SPATIALLY THIS EVENING FOR AREAS OUTSIDE THE CENT/NRN NC MTNS AS WELL AS AREAS SOUTH OF I40. MADE COSMETIC CHANGES TO THE SKY GRIDS AND MINOR TWEAKS TO TEMPS/TDS...MAINLY ACROSS THE NC MTNS. THE LATEST WATER VAPOR IMAGERY SHOWS DRIER MID LEVEL AIR SPREADING ACROSS THE FORECAST AREA SOUTH OF INTERSTATE 40. THE MID LEVEL FLOW IS QUITE WEAK OVER THE UPSTATE...NE GA AND FAR SRN NC AS A SPUR OF DEEP LAYER RIDGING HAS PUSHED INTO THE FA FROM THE WEST...FINALLY DISPLACING THE WEAK...MOIST TROUGH THAT HAD BEEN OVER THE REGION FOR THE PAST SEVERAL DAYS. THE RAP BRINGS A WEAK SHORT WAVE ACROSS WESTERN NC THIS EVENING. LLVL CONVERGENCE IS INCREASING OVER THE NC MTNS AND FOOTHILLS AHEAD OF THE WAVE. THE MODELS ARE SPLIT ON HOW FAR SOUTHEAST THIS CONVECTION GETS. THE GFS KEEPS IT OVER THE MTNS AND FOOTHILLS...WHILE THE RAP AND NAM PUSH IT INTO THE NRN SUBURBS OF CHARLOTTE. WITH THE FINGER OF DRIER AIR PUSHING INTO THE SRN PIEDMONT I/VE GONE WITH A FORECAST THAT KEEPS THE BEST CONVECTIVE CHANCES OVER THE MTNS AND FOOTHILLS WITH LOWER POPS ALONG AND SOUTH OF I-85 AND BACK ACROSS THE SW NC MTNS. THIS IS NOT TO SAY THAT STORMS WON/T PUSH INTO CHARLOTTE LATER THIS EVENING AS THE ATMOSPHERE IS NOT CAPPED AND IS MODERATELY UNSTABLE. HOWEVER...THIS DOES NOT LOOK LIKE THE MOST PROBABLE SOLUTION ATTM. PATCHY DENSE VALLEY FOG IS EXPECTED OVER THE MTNS TONIGHT. ACROSS THE FOOTHILLS AND PIEDMONT CONSIDERABLY LESS LOW CLOUD COVER IS ANTICIPATED OWNING TO A MORE WESTERLY COMPONENT TO THE LLVL WIND FIELD. A SHORT WAVE CURRENTLY OVER CENTRAL MISSOURI IS EXPECTED TO CROSS THE FORECAST AREA DURING THE AFTERNOON HOURS ON THURSDAY. THE DEEP LAYER RH IS CONSIDERABLY HIGHER ON THU THAN TODAY ALONG AND AHEAD OF THIS WAVE. BY 21 UTC THE FEATURE IS EXPECTED TO BE OVER THE I-77 CORRIDOR AND IT WILL MOVE EAT OF CHARLOTTE BY THE EARLY EVENING. THE NAM AND GFS BOTH DEVELOP PCPN BY LATE MORNING AHEAD OF THE SHORT WAVE. THE NAM HAS PCPN ENDING WITH WEAKLY DIVERGENT LLVL FLOW OVER MOST OF THE FA DEVELOPING BETWEEN 21-00 UTC. THE WAY IT APPEARS NOW...A BAND OF SHRA AND A FEW TSTMS WILL DEVELOP DEVELOP OVER THE FOOTHILLS BY LATE MORNING...OR THEY MAY MOVE INTO THE MTNS AS A REMNANT OF A WEAKENING MCS. THE CONVECTION WILL MOVE ACROSS THE REST OF THE FOOTHILLS FROM EARLY TO MID AFTN AND EXIT TO THE EAST BY 6 OR 7 PM. THE SHEAR IS WEAK AND CONVECTION ISN/T EXPECTED TO BE HIGHLY ORGANIZED AND MOST OF THE STORMS SHOULD BE SUB-SEVERE. THIS IS GENERALLY SUPPORTED BY THE 12 UTC 4KM SPC WRF AS WELL. FOR NOW I/LL CAP POPS ARE 40 PERCENT...WITH POPS FALLING OFF QUICKLY TOWARD SUNSET. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... AS OF 2 PM EDT WEDNESDAY...THE CONSENSUS OF THE MODEL GUIDANCE MAINTAINS THAT THE PLUME OF DEEPER MOISTURE WILL HAVE SHIFTED EASTWARD TO THE COASTAL PLAIN. IN THE WAKE OF A WEAK UPPER WAVE... THE ENVIRONMENT SHOULD BE LESS FAVORABLE FOR DEEP CONVECTION. THE CHANCE FOR SHOWERS AND STORMS SHOULD DROP IN THE EARLY EVENING AS THE FORCING AND MOISTURE MOVE OFF TO THE EAST...TO THE POINT WHERE THE FCST IS DRY EAST OF THE MTNS FROM 03Z ONWARD. THERE COULD BE A FEW LINGERING SHOWERS OVER THE MTNS UNTIL LATE EVENING. FRIDAY LOOKS LIKE A RELATIVELY QUIET TRANSITION DAY WHILE WE WAIT FOR THE FORCING AND MOISTURE TO RELOAD. A STRONG SHORT WAVE OVER THE UPPER MS VALLEY WILL DIG AN UPPER TROF DOWN OVER THE UPPER MIDWEST AND GREAT LAKES THROUGH THE DAY...WHICH WILL GRADUALLY TURN THE FLOW ALOFT MORE SW. UPPER FORCING WILL BE MINIMAL. THERE SHOULD BE ENOUGH LOW LEVEL MOISTURE AND BUOYANCY TO SUPPORT SCATTERED SHOWERS AND STORMS DEVELOPING OVER THE HIGHER TERRAIN WITH DIFFERENTIAL HEATING...WITH SOME OF THE STORMS MOVING OUT OVER THE FOOTHILLS AND PIEDMONT IN THE AFTERNOON AND EARLY EVENING. THE STORMS EAST OF THE BLUE RIDGE WILL DIE OFF WITH SUNSET...BUT WILL KEEP THE CHANCE OF PRECIP GOING OVERNIGHT ON THE W SIDE OF THE MTNS IN CASE SOME ACTIVITY MOVES IN FROM THE WEST AHEAD OF THE NEXT FRONT. THE UPPER TROF CONTINUES TO DIG OVER THE MIDWEST/OH VALLEY ON SATURDAY AS THE WAVE DROPS SOUTHEASTWARD. DEEP MOISTURE MOVES IN AHEAD OF THE WAVE TO BE ACTED UPON BY IMPROVED UPPER FORCING AS WE WORK THROUGH THE DAY. THE OPERATIONAL RUNS FROM ALL THREE MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE TIMING OF THE MAIN VORT AXIS REACHING THE GREAT VALLEY LATE IN THE DAY. THE NEW GFS SWEEPS THE UPPER TROF AXIS ACROSS THE WESTERN CAROLINAS OVERNIGHT WHILE THE 00Z RUN PUSHES IT THROUGH SUNDAY MORNING. EITHER WAY...BOTH MODELS SUGGEST AN EARLIER TIMING OF THE MAIN FRONTAL PRECIP BAND. WILL LIMIT THE PRECIP TO THE CHANCE RANGE FOR THE TIME BEING BUT WILL PROBABLY NEED A LIKELY POP FOR AT LEAST THE MTNS...BUT IT IS A MATTER OF WHICH PERIOD TO FOCUS ON...SATURDAY AFTERNOON OR SATURDAY NIGHT. WILL NOT RULE OUT SOME SEVERE STORMS IF THE FRONT WILL MOVE THROUGH EARLY ENOUGH. AT THIS POINT...THINK MOST OF THE PRECIP WILL HAVE MOVED EAST OF THE FCST AREA BY SUNRISE ON SUNDAY...WHICH AGREES WITH THE HPC POSITION OF THE MAIN FRONT ON THE COAST AT THAT TIME. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... AS OF 1130 AM EDT WEDNESDAY...AFTER DEALING WITH A SEMI-TROPICAL AIR MASS FOR THE LAST TWO WEEKS...IT APPEARS AS THOUGH WE ARE IN FOR A PERIOD OF SPECTACULAR EARLY AUTUMN-LIKE WEATHER EARLY NEXT WEEK. BUT FIRST...WE HAVE TO GET A FRONT THROUGH THE CAROLINAS EARLY ON SUNDAY. THE GFS MOVES THE MAIN SHORT WAVE LOBE ACROSS THE WESTERN CAROLINAS EARLY SUNDAY MORNING WHILE THE ECMWF HAS THIS FEATURE CROSSING SUNDAY AFTERNOON. THE TIMING IS FASTER THAN PREVIOUSLY INDICATED...WITH THE MAIN SFC FRONT POTENTIALLY MOVING ACROSS THE AREA SATURDAY NIGHT. WILL BACK OFF TO A SLIGHT CHANCE ACROSS THE REGION ON SUNDAY AS A FEW SHOWERS COULD BE TRIGGERED BY A SECONDARY FRONT. EITHER WAY...THERE IS A STRONG INDICATION THAT THE PRECIP WILL BE LONG GONE BY SUNSET SUNDAY...SO THE PRECIP CHANCES ARE ELIMINATED ALTOGETHER AFTER 00Z MONDAY. THE UPPER TROF AXIS WILL REACH THE EASTERN SEABOARD BY MONDAY MORNING AND MOVE SLOWLY OFFSHORE THROUGH MIDWEEK...WHILE AN UPPER ANTICYCLONE REMAINS PARKED OVER THE SRN PLAINS. THE RESULTING UPPER RIDGE TO OUR NW WILL BRING DRY HIGH PRESSURE BUILDING IN SUNDAY NIGHT AND MONDAY. ONCE ESTABLISHED...THIS SURFACE HIGH WILL DOMINATE OUR WEATHER AS IT MOVES SLOWLY PAST TO THE NORTH THROUGH WEDNESDAY. THIS SHOULD BRING MOSTLY CLEAR SKY...DRY AIR...HIGH TEMPS IN THE MID/UPPER 70S AND LOW TEMPS IN THE MID/UPPER 50S. THUS...MONDAY AND TUESDAY WILL FEEL MORE LIKE LATE SEPTEMBER OR EARLY OCTOBER. THE AIR MASS SHOULD START TO MODIFY A BIT BY WEDNESDAY. && .AVIATION /22Z WEDNESDAY THROUGH MONDAY/... AT KCLT 21Z UPDATE...BASED ON THE FAIRLY DEEP STABLE LAYER GENERALLY ACROSS THE I-85 CORRIDOR...DECIDED TO REMOVE TEMPO -SHRA/VSBY AND REPLACE WITH A VCSH. A FEW TOWERS COULD GO UP AROUND THE AIRFIELD...BUT NO GOOD EVIDENCE IS HAD TO EXPECT A DIRECT TERMINAL IMPACT. ALSO...BASED ON COORDINATION WITH THE NATIONAL GUARD AND ZLT...AN MVFR CIG WAS INTRODUCED PRE/SUNRISE THROUGH 14Z. AT KCLT...THE BULK OF THE TSTM ACTIVITY IS EXPECTED TO DEVELOP OVER THE FOOTHILLS AND STAY 30 TO 50 MILES NORTHWEST OF THE AIRFIELD THIS AFTERNOON AND EVENING. HOWEVER...THERE IS A LINE OF TCU BACK ACROSS THE UPSTATE AND INTO THE SRN NC PIEDMONT THAT HAS BEEN PRODUCING OCCASIONAL LIGHT SHRA. ATTM I HAVE REPLACED TEMPO THUNDER WITH TEMPO SHRA IN THE TAF. IF STORMS DEVELOP FROM THE LINE OF TOWERS OVER THE UPSTATE WE SHOULD STILL HAVE A COUPLE OF HOURS OF LEAD TIME BEFORE THE STORMS AFFECT THE AIRFIELD. THE MODELS BRING SOME MID LEVEL MOISTURE INTO THE REGION TONIGHT. THE LLVL FLOW ALSO VEERS TO THE WEST. IF WE DON/T SEE ANY PCPN THIS EVENING...I THINK THE TWO FACTORS ABOVE SHOULD KEEP STRATUS FROM DEVELOPING OVER THE REGION TONIGHT. ELSEWHERE...OVER THE UPSTATE ONLY ISOLATED SHRA ARE EXPECTED THE REST OF THE AFTN. THERE IS A SMALL CHANCE THAT THE SHRA WILL BUILD INTO TSTMS...BUT FOR NOW I THINK THE RISK IS TOO SMALL TO INCLUDE THUNDER IN THE TAFS. WINDS WILL BE OUT OF THE SOUTHWEST AT SPEEDS UNDER 10 KTS. THERE WILL BE A BETTER CHANCE OF SHRA/TSTMS AT KAVL AND KHKY CLOSER TO A WEAK SFC TROUGH OF LOW PRESSURE. THE FOG AND STRATUS FORECAST IS TRICKIER TONIGHT THAN IT HAS BEEN THE PAST COUPLE DAYS. WINDS WILL VEER TO THE WEST OVERNIGHT. STRATUS MAY APPROACH THE UPSTATE FROM THE SOUTHWEST LATE...BUT OVERALL I ONLY SEE SOME MVFR FOG DEVELOPING. THE EXCEPTION WILL BE THE FRENCH BROAD VALLEY WHERE VALLEY FOG AND STRATUS WILL BE MORE WIDESPREAD...PARTICULARLY IF THERE IS A PERIOD OF CLEARING OVERNIGHT. SHRA MAY SPREAD ACROSS THE MTNS AND FOOTHILLS SHORTLY AFTER SUNRISE AHEAD OF A COLD FRONT THOUGH I/VE TONED THIS BACK IN THE TAFS. OUTLOOK...GRADUAL DRYING FROM THE WEST IS EXPECTED ON THURSDAY...WITH DEEPER DRYING ON FRIDAY. A COLD FRONT WILL APPROACH THE REGION FROM THE NORTHWEST ON SATURDAY AND MOVE EAST OF THE AREA ON SUNDAY. AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)... WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...PM NEAR TERM...MCAVOY/SBK SHORT TERM...PM LONG TERM...PM AVIATION...MCAVOY/SBK
AREA FORECAST DISCUSSION
NWS GREENVILLE-SPARTANBURG SC
459 PM EDT WED SEP 5 2012 .SYNOPSIS... DEEP TROPICAL MOISTURE CURRENTLY OVER THE REGION WILL BEGIN TO PROGRESSIVELY LESSENING THURSDAY INTO FRIDAY. A STRONG COLD FRONT WILL MOVE OVER THE CAROLINAS THIS WEEKEND FOLLOWED BY HIGH PRESSURE THAT WILL PROVIDE COOLER AND DRYER WEATHER INTO THE FIRST OF NEXT WEEK. && .NEAR TERM /THROUGH THURSDAY/... THE LATEST WATER VAPOR IMAGERY SHOWS DRIER MID LEVEL AIR SPREADING ACROSS THE FORECAST AREA SOUTH OF INTERSTATE 40. THE MID LEVEL FLOW IS QUITE WEAK OVER THE UPSTATE...NE GA AND FAR SRN NC AS A SPUR OF DEEP LAYER RIDGING HAS PUSHED INTO THE FA FROM THE WEST...FINALLY DISPLACING THE WEAK...MOIST TROUGH THAT HAD BEEN OVER THE REGION FOR THE PAST SEVERAL DAYS. THE RAP BRINGS A WEAK SHORT WAVE ACROSS WESTERN NC THIS EVENING. LLVL CONVERGENCE IS INCREASING OVER THE NC MTNS AND FOOTHILLS AHEAD OF THE WAVE. THE MODELS ARE SPLIT ON HOW FAR SOUTHEAST THIS CONVECTION GETS. THE GFS KEEPS IT OVER THE MTNS AND FOOTHILLS...WHILE THE RAP AND NAM PUSH IT INTO THE NRN SUBURBS OF CHARLOTTE. WITH THE FINGER OF DRIER AIR PUSHING INTO THE SRN PIEDMONT I/VE GONE WITH A FORECAST THAT KEEPS THE BEST CONVECTIVE CHANCES OVER THE MTNS AND FOOTHILLS WITH LOWER POPS ALONG AND SOUTH OF I-85 AND BACK ACROSS THE SW NC MTNS. THIS IS NOT TO SAY THAT STORMS WON/T PUSH INTO CHARLOTTE LATER THIS EVENING AS THE ATMOSPHERE IS NOT CAPPED AND IS MODERATELY UNSTABLE. HOWEVER...THIS DOES NOT LOOK LIKE THE MOST PROBABLE SOLUTION ATTM. PATCHY DENSE VALLEY FOG IS EXPECTED OVER THE MTNS TONIGHT. ACROSS THE FOOTHILLS AND PIEDMONT CONSIDERABLY LESS LOW CLOUD COVER IS ANTICIPATED OWNING TO A MORE WESTERLY COMPONENT TO THE LLVL WIND FIELD. A SHORT WAVE CURRENTLY OVER CENTRAL MISSOURI IS EXPECTED TO CROSS THE FORECAST AREA DURING THE AFTERNOON HOURS ON THURSDAY. THE DEEP LAYER RH IS CONSIDERABLY HIGHER ON THU THAN TODAY ALONG AND AHEAD OF THIS WAVE. BY 21 UTC THE FEATURE IS EXPECTED TO BE OVER THE I-77 CORRIDOR AND IT WILL MOVE EAT OF CHARLOTTE BY THE EARLY EVENING. THE NAM AND GFS BOTH DEVELOP PCPN BY LATE MORNING AHEAD OF THE SHORT WAVE. THE NAM HAS PCPN ENDING WITH WEAKLY DIVERGENT LLVL FLOW OVER MOST OF THE FA DEVELOPING BETWEEN 21-00 UTC. THE WAY IT APPEARS NOW...A BAND OF SHRA AND A FEW TSTMS WILL DEVELOP DEVELOP OVER THE FOOTHILLS BY LATE MORNING...OR THEY MAY MOVE INTO THE MTNS AS A REMNANT OF A WEAKENING MCS. THE CONVECTION WILL MOVE ACROSS THE REST OF THE FOOTHILLS FROM EARLY TO MID AFTN AND EXIT TO THE EAST BY 6 OR 7 PM. THE SHEAR IS WEAK AND CONVECTION ISN/T EXPECTED TO BE HIGHLY ORGANIZED AND MOST OF THE STORMS SHOULD BE SUB-SEVERE. THIS IS GENERALLY SUPPORTED BY THE 12 UTC 4KM SPC WRF AS WELL. FOR NOW I/LL CAP POPS ARE 40 PERCENT...WITH POPS FALLING OFF QUICKLY TOWARD SUNSET. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... AS OF 2 PM EDT WEDNESDAY...THE CONSENSUS OF THE MODEL GUIDANCE MAINTAINS THAT THE PLUME OF DEEPER MOISTURE WILL HAVE SHIFTED EASTWARD TO THE COASTAL PLAIN. IN THE WAKE OF A WEAK UPPER WAVE... THE ENVIRONMENT SHOULD BE LESS FAVORABLE FOR DEEP CONVECTION. THE CHANCE FOR SHOWERS AND STORMS SHOULD DROP IN THE EARLY EVENING AS THE FORCING AND MOISTURE MOVE OFF TO THE EAST...TO THE POINT WHERE THE FCST IS DRY EAST OF THE MTNS FROM 03Z ONWARD. THERE COULD BE A FEW LINGERING SHOWERS OVER THE MTNS UNTIL LATE EVENING. FRIDAY LOOKS LIKE A RELATIVELY QUIET TRANSITION DAY WHILE WE WAIT FOR THE FORCING AND MOISTURE TO RELOAD. A STRONG SHORT WAVE OVER THE UPPER MS VALLEY WILL DIG AN UPPER TROF DOWN OVER THE UPPER MIDWEST AND GREAT LAKES THROUGH THE DAY...WHICH WILL GRADUALLY TURN THE FLOW ALOFT MORE SW. UPPER FORCING WILL BE MINIMAL. THERE SHOULD BE ENOUGH LOW LEVEL MOISTURE AND BUOYANCY TO SUPPORT SCATTERED SHOWERS AND STORMS DEVELOPING OVER THE HIGHER TERRAIN WITH DIFFERENTIAL HEATING...WITH SOME OF THE STORMS MOVING OUT OVER THE FOOTHILLS AND PIEDMONT IN THE AFTERNOON AND EARLY EVENING. THE STORMS EAST OF THE BLUE RIDGE WILL DIE OFF WITH SUNSET...BUT WILL KEEP THE CHANCE OF PRECIP GOING OVERNIGHT ON THE W SIDE OF THE MTNS IN CASE SOME ACTIVITY MOVES IN FROM THE WEST AHEAD OF THE NEXT FRONT. THE UPPER TROF CONTINUES TO DIG OVER THE MIDWEST/OH VALLEY ON SATURDAY AS THE WAVE DROPS SOUTHEASTWARD. DEEP MOISTURE MOVES IN AHEAD OF THE WAVE TO BE ACTED UPON BY IMPROVED UPPER FORCING AS WE WORK THROUGH THE DAY. THE OPERATIONAL RUNS FROM ALL THREE MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE TIMING OF THE MAIN VORT AXIS REACHING THE GREAT VALLEY LATE IN THE DAY. THE NEW GFS SWEEPS THE UPPER TROF AXIS ACROSS THE WESTERN CAROLINAS OVERNIGHT WHILE THE 00Z RUN PUSHES IT THROUGH SUNDAY MORNING. EITHER WAY...BOTH MODELS SUGGEST AN EARLIER TIMING OF THE MAIN FRONTAL PRECIP BAND. WILL LIMIT THE PRECIP TO THE CHANCE RANGE FOR THE TIME BEING BUT WILL PROBABLY NEED A LIKELY POP FOR AT LEAST THE MTNS...BUT IT IS A MATTER OF WHICH PERIOD TO FOCUS ON...SATURDAY AFTERNOON OR SATURDAY NIGHT. WILL NOT RULE OUT SOME SEVERE STORMS IF THE FRONT WILL MOVE THROUGH EARLY ENOUGH. AT THIS POINT...THINK MOST OF THE PRECIP WILL HAVE MOVED EAST OF THE FCST AREA BY SUNRISE ON SUNDAY...WHICH AGREES WITH THE HPC POSITION OF THE MAIN FRONT ON THE COAST AT THAT TIME. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... AS OF 1130 AM EDT WEDNESDAY...AFTER DEALING WITH A SEMI-TROPICAL AIR MASS FOR THE LAST TWO WEEKS...IT APPEARS AS THOUGH WE ARE IN FOR A PERIOD OF SPECTACULAR EARLY AUTUMN-LIKE WEATHER EARLY NEXT WEEK. BUT FIRST...WE HAVE TO GET A FRONT THROUGH THE CAROLINAS EARLY ON SUNDAY. THE GFS MOVES THE MAIN SHORT WAVE LOBE ACROSS THE WESTERN CAROLINAS EARLY SUNDAY MORNING WHILE THE ECMWF HAS THIS FEATURE CROSSING SUNDAY AFTERNOON. THE TIMING IS FASTER THAN PREVIOUSLY INDICATED...WITH THE MAIN SFC FRONT POTENTIALLY MOVING ACROSS THE AREA SATURDAY NIGHT. WILL BACK OFF TO A SLIGHT CHANCE ACROSS THE REGION ON SUNDAY AS A FEW SHOWERS COULD BE TRIGGERED BY A SECONDARY FRONT. EITHER WAY...THERE IS A STRONG INDICATION THAT THE PRECIP WILL BE LONG GONE BY SUNSET SUNDAY...SO THE PRECIP CHANCES ARE ELIMINATED ALTOGETHER AFTER 00Z MONDAY. THE UPPER TROF AXIS WILL REACH THE EASTERN SEABOARD BY MONDAY MORNING AND MOVE SLOWLY OFFSHORE THROUGH MIDWEEK...WHILE AN UPPER ANTICYCLONE REMAINS PARKED OVER THE SRN PLAINS. THE RESULTING UPPER RIDGE TO OUR NW WILL BRING DRY HIGH PRESSURE BUILDING IN SUNDAY NIGHT AND MONDAY. ONCE ESTABLISHED...THIS SURFACE HIGH WILL DOMINATE OUR WEATHER AS IT MOVES SLOWLY PAST TO THE NORTH THROUGH WEDNESDAY. THIS SHOULD BRING MOSTLY CLEAR SKY...DRY AIR...HIGH TEMPS IN THE MID/UPPER 70S AND LOW TEMPS IN THE MID/UPPER 50S. THUS...MONDAY AND TUESDAY WILL FEEL MORE LIKE LATE SEPTEMBER OR EARLY OCTOBER. THE AIR MASS SHOULD START TO MODIFY A BIT BY WEDNESDAY. && .AVIATION /21Z WEDNESDAY THROUGH MONDAY/... AT KCLT 21Z UPDATE...BASED ON THE FAIRLY DEEP STABLE LAYER GENERALLY ACROSS THE I-85 CORRIDOR...DECIDED TO REMOVE TEMPO -SHRA/VSBY AND REPLACE WITH A VCSH. A FEW TOWERS COULD GO UP AROUND THE AIRFIELD...BUT NO GOOD EVIDENCE IS HAD TO EXPECT A DIRECT TERMINAL IMPACT. ALSO...BASED ON COORDINATION WITH THE NATIONAL GUARD AND ZLT...AN MVFR CIG WAS INTRODUCED PRE/SUNRISE THROUGH 14Z. AT KCLT...THE BULK OF THE TSTM ACTIVITY IS EXPECTED TO DEVELOP OVER THE FOOTHILLS AND STAY 30 TO 50 MILES NORTHWEST OF THE AIRFIELD THIS AFTERNOON AND EVENING. HOWEVER...THERE IS A LINE OF TCU BACK ACROSS THE UPSTATE AND INTO THE SRN NC PIEDMONT THAT HAS BEEN PRODUCING OCCASIONAL LIGHT SHRA. ATTM I HAVE REPLACED TEMPO THUNDER WITH TEMPO SHRA IN THE TAF. IF STORMS DEVELOP FROM THE LINE OF TOWERS OVER THE UPSTATE WE SHOULD STILL HAVE A COUPLE OF HOURS OF LEAD TIME BEFORE THE STORMS AFFECT THE AIRFIELD. THE MODELS BRING SOME MID LEVEL MOISTURE INTO THE REGION TONIGHT. THE LLVL FLOW ALSO VEERS TO THE WEST. IF WE DON/T SEE ANY PCPN THIS EVENING...I THINK THE TWO FACTORS ABOVE SHOULD KEEP STRATUS FROM DEVELOPING OVER THE REGION TONIGHT. ELSEWHERE...OVER THE UPSTATE ONLY ISOLATED SHRA ARE EXPECTED THE REST OF THE AFTN. THERE IS A SMALL CHANCE THAT THE SHRA WILL BUILD INTO TSTMS...BUT FOR NOW I THINK THE RISK IS TOO SMALL TO INCLUDE THUNDER IN THE TAFS. WINDS WILL BE OUT OF THE SOUTHWEST AT SPEEDS UNDER 10 KTS. THERE WILL BE A BETTER CHANCE OF SHRA/TSTMS AT KAVL AND KHKY CLOSER TO A WEAK SFC TROUGH OF LOW PRESSURE. THE FOG AND STRATUS FORECAST IS TRICKIER TONIGHT THAN IT HAS BEEN THE PAST COUPLE DAYS. WINDS WILL VEER TO THE WEST OVERNIGHT. STRATUS MAY APPROACH THE UPSTATE FROM THE SOUTHWEST LATE...BUT OVERALL I ONLY SEE SOME MVFR FOG DEVELOPING. THE EXCEPTION WILL BE THE FRENCH BROAD VALLEY WHERE VALLEY FOG AND STRATUS WILL BE MORE WIDESPREAD...PARTICULARLY IF THERE IS A PERIOD OF CLEARING OVERNIGHT. SHRA MAY SPREAD ACROSS THE MTNS AND FOOTHILLS SHORTLY AFTER SUNRISE AHEAD OF A COLD FRONT THOUGH I/VE TONED THIS BACK IN THE TAFS. OUTLOOK...GRADUAL DRYING FROM THE WEST IS EXPECTED ON THURSDAY...WITH DEEPER DRYING ON FRIDAY. A COLD FRONT WILL APPROACH THE REGION FROM THE NORTHWEST ON SATURDAY AND MOVE EAST OF THE AREA ON SUNDAY. AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)... WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...PM NEAR TERM...MCAVOY SHORT TERM...PM LONG TERM...PM AVIATION...MCAVOY/SBK
AREA FORECAST DISCUSSION
NWS GREENVILLE-SPARTANBURG SC
238 PM EDT WED SEP 5 2012 .SYNOPSIS... DEEP TROPICAL MOISTURE CURRENTLY OVER THE REGION WILL BEGIN TO PROGRESSIVELY LESSENING THURSDAY INTO FRIDAY. A STRONG COLD FRONT WILL MOVE OVER THE CAROLINAS THIS WEEKEND FOLLOWED BY HIGH PRESSURE THAT WILL PROVIDE COOLER AND DRYER WEATHER INTO THE FIRST OF NEXT WEEK. && .NEAR TERM /THROUGH THURSDAY/... THE LATEST WATER VAPOR IMAGERY SHOWS DRIER MID LEVEL AIR SPREADING ACROSS THE FORECAST AREA SOUTH OF INTERSTATE 40. THE MID LEVEL FLOW IS QUITE WEAK OVER THE UPSTATE...NE GA AND FAR SRN NC AS A SPUR OF DEEP LAYER RIDGING HAS PUSHED INTO THE FA FROM THE WEST...FINALLY DISPLACING THE WEAK...MOIST TROUGH THAT HAD BEEN OVER THE REGION FOR THE PAST SEVERAL DAYS. THE RAP BRINGS A WEAK SHORT WAVE ACROSS WESTERN NC THIS EVENING. LLVL CONVERGENCE IS INCREASING OVER THE NC MTNS AND FOOTHILLS AHEAD OF THE WAVE. THE MODELS ARE SPLIT ON HOW FAR SOUTHEAST THIS CONVECTION GETS. THE GFS KEEPS IT OVER THE MTNS AND FOOTHILLS...WHILE THE RAP AND NAM PUSH IT INTO THE NRN SUBURBS OF CHARLOTTE. WITH THE FINGER OF DRIER AIR PUSHING INTO THE SRN PIEDMONT I/VE GONE WITH A FORECAST THAT KEEPS THE BEST CONVECTIVE CHANCES OVER THE MTNS AND FOOTHILLS WITH LOWER POPS ALONG AND SOUTH OF I-85 AND BACK ACROSS THE SW NC MTNS. THIS IS NOT TO SAY THAT STORMS WON/T PUSH INTO CHARLOTTE LATER THIS EVENING AS THE ATMOSPHERE IS NOT CAPPED AND IS MODERATELY UNSTABLE. HOWEVER...THIS DOES NOT LOOK LIKE THE MOST PROBABLE SOLUTION ATTM. PATCHY DENSE VALLEY FOG IS EXPECTED OVER THE MTNS TONIGHT. ACROSS THE FOOTHILLS AND PIEDMONT CONSIDERABLY LESS LOW CLOUD COVER IS ANTICIPATED OWNING TO A MORE WESTERLY COMPONENT TO THE LLVL WIND FIELD. A SHORT WAVE CURRENTLY OVER CENTRAL MISSOURI IS EXPECTED TO CROSS THE FORECAST AREA DURING THE AFTERNOON HOURS ON THURSDAY. THE DEEP LAYER RH IS CONSIDERABLY HIGHER ON THU THAN TODAY ALONG AND AHEAD OF THIS WAVE. BY 21 UTC THE FEATURE IS EXPECTED TO BE OVER THE I-77 CORRIDOR AND IT WILL MOVE EAT OF CHARLOTTE BY THE EARLY EVENING. THE NAM AND GFS BOTH DEVELOP PCPN BY LATE MORNING AHEAD OF THE SHORT WAVE. THE NAM HAS PCPN ENDING WITH WEAKLY DIVERGENT LLVL FLOW OVER MOST OF THE FA DEVELOPING BETWEEN 21-00 UTC. THE WAY IT APPEARS NOW...A BAND OF SHRA AND A FEW TSTMS WILL DEVELOP DEVELOP OVER THE FOOTHILLS BY LATE MORNING...OR THEY MAY MOVE INTO THE MTNS AS A REMNANT OF A WEAKENING MCS. THE CONVECTION WILL MOVE ACROSS THE REST OF THE FOOTHILLS FROM EARLY TO MID AFTN AND EXIT TO THE EAST BY 6 OR 7 PM. THE SHEAR IS WEAK AND CONVECTION ISN/T EXPECTED TO BE HIGHLY ORGANIZED AND MOST OF THE STORMS SHOULD BE SUB-SEVERE. THIS IS GENERALLY SUPPORTED BY THE 12 UTC 4KM SPC WRF AS WELL. FOR NOW I/LL CAP POPS ARE 40 PERCENT...WITH POPS FALLING OFF QUICKLY TOWARD SUNSET. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... AS OF 2 PM EDT WEDNESDAY...THE CONSENSUS OF THE MODEL GUIDANCE MAINTAINS THAT THE PLUME OF DEEPER MOISTURE WILL HAVE SHIFTED EASTWARD TO THE COASTAL PLAIN. IN THE WAKE OF A WEAK UPPER WAVE... THE ENVIRONMENT SHOULD BE LESS FAVORABLE FOR DEEP CONVECTION. THE CHANCE FOR SHOWERS AND STORMS SHOULD DROP IN THE EARLY EVENING AS THE FORCING AND MOISTURE MOVE OFF TO THE EAST...TO THE POINT WHERE THE FCST IS DRY EAST OF THE MTNS FROM 03Z ONWARD. THERE COULD BE A FEW LINGERING SHOWERS OVER THE MTNS UNTIL LATE EVENING. FRIDAY LOOKS LIKE A RELATIVELY QUIET TRANSITION DAY WHILE WE WAIT FOR THE FORCING AND MOISTURE TO RELOAD. A STRONG SHORT WAVE OVER THE UPPER MS VALLEY WILL DIG AN UPPER TROF DOWN OVER THE UPPER MIDWEST AND GREAT LAKES THROUGH THE DAY...WHICH WILL GRADUALLY TURN THE FLOW ALOFT MORE SW. UPPER FORCING WILL BE MINIMAL. THERE SHOULD BE ENOUGH LOW LEVEL MOISTURE AND BUOYANCY TO SUPPORT SCATTERED SHOWERS AND STORMS DEVELOPING OVER THE HIGHER TERRAIN WITH DIFFERENTIAL HEATING...WITH SOME OF THE STORMS MOVING OUT OVER THE FOOTHILLS AND PIEDMONT IN THE AFTERNOON AND EARLY EVENING. THE STORMS EAST OF THE BLUE RIDGE WILL DIE OFF WITH SUNSET...BUT WILL KEEP THE CHANCE OF PRECIP GOING OVERNIGHT ON THE W SIDE OF THE MTNS IN CASE SOME ACTIVITY MOVES IN FROM THE WEST AHEAD OF THE NEXT FRONT. THE UPPER TROF CONTINUES TO DIG OVER THE MIDWEST/OH VALLEY ON SATURDAY AS THE WAVE DROPS SOUTHEASTWARD. DEEP MOISTURE MOVES IN AHEAD OF THE WAVE TO BE ACTED UPON BY IMPROVED UPPER FORCING AS WE WORK THROUGH THE DAY. THE OPERATIONAL RUNS FROM ALL THREE MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE TIMING OF THE MAIN VORT AXIS REACHING THE GREAT VALLEY LATE IN THE DAY. THE NEW GFS SWEEPS THE UPPER TROF AXIS ACROSS THE WESTERN CAROLINAS OVERNIGHT WHILE THE 00Z RUN PUSHES IT THROUGH SUNDAY MORNING. EITHER WAY...BOTH MODELS SUGGEST AN EARLIER TIMING OF THE MAIN FRONTAL PRECIP BAND. WILL LIMIT THE PRECIP TO THE CHANCE RANGE FOR THE TIME BEING BUT WILL PROBABLY NEED A LIKELY POP FOR AT LEAST THE MTNS...BUT IT IS A MATTER OF WHICH PERIOD TO FOCUS ON...SATURDAY AFTERNOON OR SATURDAY NIGHT. WILL NOT RULE OUT SOME SEVERE STORMS IF THE FRONT WILL MOVE THROUGH EARLY ENOUGH. AT THIS POINT...THINK MOST OF THE PRECIP WILL HAVE MOVED EAST OF THE FCST AREA BY SUNRISE ON SUNDAY...WHICH AGREES WITH THE HPC POSITION OF THE MAIN FRONT ON THE COAST AT THAT TIME. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... AS OF 1130 AM EDT WEDNESDAY...AFTER DEALING WITH A SEMI-TROPICAL AIR MASS FOR THE LAST TWO WEEKS...IT APPEARS AS THOUGH WE ARE IN FOR A PERIOD OF SPECTACULAR EARLY AUTUMN-LIKE WEATHER EARLY NEXT WEEK. BUT FIRST...WE HAVE TO GET A FRONT THROUGH THE CAROLINAS EARLY ON SUNDAY. THE GFS MOVES THE MAIN SHORT WAVE LOBE ACROSS THE WESTERN CAROLINAS EARLY SUNDAY MORNING WHILE THE ECMWF HAS THIS FEATURE CROSSING SUNDAY AFTERNOON. THE TIMING IS FASTER THAN PREVIOUSLY INDICATED...WITH THE MAIN SFC FRONT POTENTIALLY MOVING ACROSS THE AREA SATURDAY NIGHT. WILL BACK OFF TO A SLIGHT CHANCE ACROSS THE REGION ON SUNDAY AS A FEW SHOWERS COULD BE TRIGGERED BY A SECONDARY FRONT. EITHER WAY...THERE IS A STRONG INDICATION THAT THE PRECIP WILL BE LONG GONE BY SUNSET SUNDAY...SO THE PRECIP CHANCES ARE ELIMINATED ALTOGETHER AFTER 00Z MONDAY. THE UPPER TROF AXIS WILL REACH THE EASTERN SEABOARD BY MONDAY MORNING AND MOVE SLOWLY OFFSHORE THROUGH MIDWEEK...WHILE AN UPPER ANTICYCLONE REMAINS PARKED OVER THE SRN PLAINS. THE RESULTING UPPER RIDGE TO OUR NW WILL BRING DRY HIGH PRESSURE BUILDING IN SUNDAY NIGHT AND MONDAY. ONCE ESTABLISHED...THIS SURFACE HIGH WILL DOMINATE OUR WEATHER AS IT MOVES SLOWLY PAST TO THE NORTH THROUGH WEDNESDAY. THIS SHOULD BRING MOSTLY CLEAR SKY...DRY AIR...HIGH TEMPS IN THE MID/UPPER 70S AND LOW TEMPS IN THE MID/UPPER 50S. THUS...MONDAY AND TUESDAY WILL FEEL MORE LIKE LATE SEPTEMBER OR EARLY OCTOBER. THE AIR MASS SHOULD START TO MODIFY A BIT BY WEDNESDAY. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... AT KCLT...THE BULK OF THE TSTM ACTIVITY IS EXPECTED TO DEVELOP OVER THE FOOTHILLS AND STAY 30 TO 50 MILES NORTHWEST OF THE AIRFIELD THIS AFTERNOON AND EVENING. HOWEVER...THERE IS A LINE OF TCU BACK ACROSS THE UPSTATE AND INTO THE SRN NC PIEDMONT THAT HAS BEEN PRODUCING OCCASIONAL LIGHT SHRA. ATTM I HAVE REPLACED TEMPO THUNDER WITH TEMPO SHRA IN THE TAF. IF STORMS DEVELOP FROM THE LINE OF TOWERS OVER THE UPSTATE WE SHOULD STILL HAVE A COUPLE OF HOURS OF LEAD TIME BEFORE THE STORMS AFFECT THE AIRFIELD. THE MODELS BRING SOME MID LEVEL MOISTURE INTO THE REGION TONIGHT. THE LLVL FLOW ALSO VEERS TO THE WEST. IF WE DON/T SEE ANY PCPN THIS EVENING...I THINK THE TWO FACTORS ABOVE SHOULD KEEP STRATUS FROM DEVELOPING OVER THE REGION TONIGHT. ELSEWHERE...OVER THE UPSTATE ONLY ISOLATED SHRA ARE EXPECTED THE REST OF THE AFTN. THERE IS A SMALL CHANCE THAT THE SHRA WILL BUILD INTO TSTMS...BUT FOR NOW I THINK THE RISK IS TOO SMALL TO INCLUDE THUNDER IN THE TAFS. WINDS WILL BE OUT OF THE SOUTHWEST AT SPEEDS UNDER 10 KTS. THERE WILL BE A BETTER CHANCE OF SHRA/TSTMS AT KAVL AND KHKY CLOSER TO A WEAK SFC TROUGH OF LOW PRESSURE. THE FOG AND STRATUS FORECAST IS TRICKIER TONIGHT THAN IT HAS BEEN THE PAST COUPLE DAYS. WINDS WILL VEER TO THE WEST OVERNIGHT. STRATUS MAY APPROACH THE UPSTATE FROM THE SOUTHWEST LATE...BUT OVERALL I ONLY SEE SOME MVFR FOG DEVELOPING. THE EXCEPTION WILL BE THE FRENCH BROAD VALLEY WHERE VALLEY FOG AND STRATUS WILL BE MORE WIDESPREAD...PARTICULARLY IF THERE IS A PERIOD OF CLEARING OVERNIGHT. SHRA MAY SPREAD ACROSS THE MTNS AND FOOTHILLS SHORTLY AFTER SUNRISE AHEAD OF A COLD FRONT THOUGH I/VE TONED THIS BACK IN THE TAFS. OUTLOOK...GRADUAL DRYING FROM THE WEST IS EXPECTED ON THURSDAY...WITH DEEPER DRYING ON FRIDAY. A COLD FRONT WILL APPROACH THE REGION FROM THE NORTHWEST ON SATURDAY AND MOVE EAST OF THE AREA ON SUNDAY. AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)... WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...PM NEAR TERM...MCAVOY SHORT TERM...PM LONG TERM...PM AVIATION...MCAVOY
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
1105 PM CDT TUE SEP 4 2012 .DISCUSSION.../ISSUED AT 1005 PM CDT/ THUNDERSTORMS WITH SEVERE WEATHER HAVE BEEN MOVING EAST OVER AREA THIS EVENING INCLUDING CURRENT DAMAGING WIND EVENT IN NORTHWEST IOWA AND SOUTHWEST MINNESOTA. IF TRENDS CONTINUE AND NOTHING DEVELOPS BEHIND THESE STORMS WE MAY BE ABLE TO CUT THEM BACK SOONER BUT FOR NOW WILL HOLD IN. && .AVIATION.../FOR THE 06Z TAF ISSUANCE/ THUNDERSTORMS EASTERN PART OF AREA SHOULD BE JUST EAST OF KSUX AND WELL EAST OF KHON AND KFSD AT START 0F FORECAST PERIOD/ 06Z. VERY LOCAL VISIBILITIES AND STRONG WINDS IN THUNDERSTORMS FAR EASTERN PART OF AREA IN SOUTHWEST MN AND NORTHWEST IA SHOULD END BY 09Z. OTHERWISE VFR OVER AREA THROUGH 06/06Z. A FEW SURFACE GUSTS AROUND 25 KNOTS FROM THE NORTHWEST OVER AREA 15Z-22Z. && .PREV DISCUSSION.../ISSUED AT 325 PM CDT/ DIFFUSE BOUNDARY IN NORTHWEST IOWA BEGINNING TO LIFT NORTHWARD AS A WARM FRONT THIS AFTERNOON AS SURFACE LOW PRESSURE STRENGTHENS OVER THE BLACK HILLS. MIXING HAS ALLOWED DEWPOINTS TO DRAMATICALLY FALL THIS AFTERNOON ACROSS THE NORTHWESTERN TWO THIRDS OF THE CWA...WHILE DEEPER MOISTURE HAS ALLOWED DEWPOINTS TO REMAIN IN THE 60S ACROSS NORTHWEST IOWA. INSTABILITY CONTINUES TO INCREASE THIS AFTERNOON...ESPECIALLY ACROSS OUR SOUTHEASTERN HALF OF THE FORECAST AREA WHERE CAPE VALUES ARE GREATER THAN 1500 J/KG...WITH INCREASING LAPSE RATES AND STRENGTHENING WESTERLIES BRINGING SHEAR UP AROUND 40 KT. SO FAR...CAPPING IS PREVENTING CONVECTION FROM DEVELOPING...HOWEVER WITH KSUX ALREADY 95/65 EXPECT THE CAPPING TO BE SURPASSED SOON. THE HRRR AND NAM CONTINUE TO DEPICT CONVECTION MOVING NORTHEASTWARD INTO THE MISSOURI VALLEY...EXTREME SOUTHEAST SOUTH DAKOTA AND NORTHWEST IOWA LATE THIS AFTERNOON THROUGH THE EVENING. IF CONVECTION DOES MANAGE TO FIRE IN THIS AREA...STORMS COULD POTENTIALLY BECOME SEVERE WITH LARGE HAIL TO AROUND WALNUT SIZE AND WIND GUSTS TO 70 MPH. FURTHER WEST...HIGH BASED CUMULUS FIELD NOW MOVING INTO OUR WESTERN BORDER. ISOLATED HIGH BASED CONVECTION WILL BE POSSIBLE IN OUR WESTERN HALF THIS AFTERNOON AND EVENING...BUT EXPECT LITTLE TO NO SEVERE WEATHER IN THIS AREA WITH SUCH DRY LOW AND MID LEVELS. AS THE LOW BEGINS TRACKING EAST NORTHEAST ACROSS THE FORECAST AREA THIS EVENING AND OVERNIGHT...THE TRAILING COLD FRONT WILL SHIFT THE CONVECTION INTO CENTRAL AND EASTERN PORTIONS OF THE FORECAST AREA WHERE CONDITIONS ARE MORE FAVORABLE FOR PRECIPITATION. WINDS WILL LIKELY BECOME FAIRLY BREEZY FROM THE WEST NORTHWEST LATE TONIGHT. LOWS TONIGHT WILL RANGE FROM THE MID 50S FAR NORTHWEST TO THE MID 60S FAR SOUTHEAST. RELATIVELY QUIET WEATHER WITH MILDER TEMPERATURES EXPECTED FOR WEDNESDAY AS SURFACE HIGH PRESSURE SETTLES IN BEHIND THE EXITING SYSTEM. NORTH NORTHWEST WINDS WILL REMAIN A LITTLE BREEZY THROUGH THE DAY...BUT SKIES WILL BE SUNNY AND HIGHS ARE EXPECTED IN THE 70S. / HIGH PRESSURE WILL BUILD IN OVER THE AREA FOR WEDNESDAY NIGHT. THUS TRENDED LOWS TOWARDS THE COOLER SIDE OF GUIDANCE...GENERALLY UPPER 40S TO LOWER 50S. A MID LEVEL WAVE AND SOME CLOUD COVER MAY BEGIN ENTERING OUR WEST BY LATE NIGHT...THUS DID NOT GO QUITE AS COOL AS I WOULD HAVE IF COMPLETELY CLEAR SKIES WERE MORE LIKELY. MID LEVEL FORCING OVERHEAD ON THURSDAY OUT AHEAD OF OUR NEXT WAVE...ALSO SHOULD SEE DECENT ISENTROPIC LIFT. ATMOSPHERE WILL BE ON THE DRY SIDE THOUGH...THUS FOLLOWED THE NAM AND GFS IDEA OF A DRY DAY. HOWEVER SHOULD SEE AT LEAST SOME MID LEVEL CLOUD COVER...AND WITH DECENT MID LEVEL LAPSE RATES...WOULD NOT BE SURPRISED TO SEE A FEW ELEVATED SHOWERS AND THUNDERSTORMS. THINK THE ECMWF IS PROBABLY OVERDOING CONVECTION THURSDAY...BUT LOW POPS MAY NEED TO BE ADDED ON FUTURE SHIFTS IF MODELS TREND A LITTLE MOISTER IN THE MID LEVELS. WITH UNCERTAINTY ON CLOUD COVER...FOLLOWED A BLEND OF THE COOLER MOS AND THE WARMER BIAS CORRECTED NAM FOR HIGHS...GENERALLY MID 70S SOUTHWEST MINNESOTA TO LOW TO MID 80S ELSEWHERE. SURFACE LOW TO OUR WEST ON THURSDAY WILL PRODUCE BLUSTERY SOUTH SOUTHEAST WINDS WEST OF THE JAMES RIVER...WITH GUSTS AROUND 25 TO 30 MPH POSSIBLE. THE BETTER MOISTURE AND DEEP LAYER FORCING MOVES ACROSS THE CWA THURSDAY NIGHT. THUS LOOKS LIKE A GOOD CHANCE OF SEEING SOME SHOWERS IN MOST AREAS. INSTABILITY IS ON THE LOW SIDE...BUT SHOULD SEE AT LEAST A COUPLE HUNDRED J/KG OF ELEVATED CAPE. SO THINKING WE SEE AT LEAST SOME EMBEDDED THUNDER. WITH THE CLOUDS AND SHOWERS AROUND...LOWS WILL STAY A BIT WARMER THAN WEDNESDAY NIGHT...MAINLY IN THE 50S. COULD SEE SOME LINGERING SHOWERS ACROSS NORTHWEST IOWA FRIDAY MORNING...BUT THESE SHOULD EXIT THE AREA BY AFTERNOON AS THE TROUGH AXIS AND DEEPER MOISTURE PUSHES EAST. EXPECT TO SEE GRADUAL CLEARING FROM NORTH TO SOUTH DURING THE DAY. MUCH COOLER AIR WILL BE ADVECTED IN BEHIND THE FRONT FOR FRIDAY...AND THIS COMBINED WITH THE LINGERING CLOUD COVER...SHOULD HOLD HIGHS IN THE MID 60S TO LOWER 70S. AS WE HEAD INTO THE WEEKEND...OUR UPPER LEVEL LOW WILL PUSH EAST AND DIG A DEEP TROUGH INTO THE EASTERN PART OF THE COUNTRY. MEANWHILE A STRONG RIDGE WILL BUILD INTO THE ROCKIES. OUR AREA WILL REMAIN IN BETWEEN THE TWO MAKING TEMPERATURES A BIT TRICKY. WE WILL TEND TO SEE A WARMING TREND INTO EARLY NEXT WEEK...BUT HOW WARM DEPENDS ON THE STRENGTH AND POSITION OF THE ABOVE MENTIONED FEATURES. TRENDED HIGHS A BIT ABOVE CONSENSUS SUNDAY THROUGH TUESDAY CLOSER TO THE 0Z ECMWF AND HPC GUIDANCE. THIS GIVES 70S ON SATURDAY...AND UPPER 70S TO MID 80S SUNDAY THROUGH TUESDAY. THE NEW 12Z ECMWF HAS TRENDED STRONGER WITH THE RIDGE AND THUS WARMER WITH TEMPERATURES...SO WILL HAVE TO MONITOR MODEL TRENDS THIS PERIOD. LOWS FRIDAY AND SATURDAY NIGHT LOOK TO BE ON THE COOL SIDE...WITH LIGHT WINDS AND CLEAR SKIES EXPECTED. LOWERED THEM A LITTLE BELOW CONSENSUS...WITH MAINLY MID AND UPPER 40S EXPECTED. AS THE RIDGE BUILDS CLOSER...LOWS SHOULD WARM INTO THE 50S BY SUNDAY NIGHT. LOOKS DRY SATURDAY THROUGH TUESDAY. PROBABLY WILL SEE OUR NEXT COLD FRONT APPROACH SOMETIME AROUND TUESDAY...HOWEVER AT THIS TIME DOES NOT UPPER TO BE MUCH MOISTURE WITH IT. /CHENARD && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. $$
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
625 PM CDT THU SEP 6 2012 .SHORT TERM...TONIGHT THROUGH SUNDAY 322 PM CDT THU SEP 6 2012 MAIN FORECAST CONCERNS ARE ON SHOWER AND THUNDERSTORMS TONIGHT THROUGH FRIDAY MORNING...FOCUS THEN TURNS TO TEMPERATURES. LATEST WATER VAPOR IMAGERY SHOWED AND ELONGATED UPPER LEVEL TROUGH EXTENDING FROM NEAR JAMES BAY SOUTHWEST TO ALONG THE CONUS/CANADA BORDER ALL THE WAY INTO THE PACIFIC NORTHWEST. SURFACE OBSERVATIONS SHOWED PRESSURE OVER NORTHEAST NEBRASKA MOVING EAST. THE SURFACE LOW WILL MOVE EAST INTO THE UPPER MISSISSIPPI RIVER VALLEY TONIGHT AS THE TROUGH DIGS INTO THE UPPER MIDWEST. SEVERAL INTERESTING FEATURES TO KEY IN ON OVERNIGHT. THE FIRST STRONG WARM AIR ADVECTION AHEAD OF THE SURFACE LOW...FOCUSED INTO NORTHERN IOWA. ALSO...THERE ARE TWO 250 MB JET STREAKS MOVING INTO THE FORECAST AREA OVERNIGHT. THE FIRST HAS THE LEFT EXIT REGION FOCUSED ACROSS NORTHERN WISCONSIN THIS EVENING THEN QUICKLY SHIFTS NORTHEAST OF THE AREA AS ANOTHER JET STREAK DEVELOPS ACROSS NORTHERN NEBRASKA INTO NORTHERN IOWA AS THE TROUGH DIGS SOUTH. THE LAST FEATURE AS FRONTOGENESIS MOVING NORTHWEST TO SOUTHEAST ACROSS THE AREA OVERNIGHT...LOCATED FROM JUST ABOVE THE SURFACE THROUGH AROUND 600 MB. THE NORTHERN STREAM JET AND THE FRONTOGENESIS WILL PROVIDE THE SUPPORT FOR SHOWERS ACROSS NORTHERN WISCONSIN TONIGHT INTO FRIDAY MORNING. THE BEST SUPPORT WILL BE ALONG AND NORTH OF INTERSTATE 94 SO HAVE HIGHER PRECIPITATION CHANCES AND AMOUNTS ACROSS THESE AREAS. THE STRONG WARM AIR ADVECTION/MOISTURE TRANSPORT MOVING INTO NORTHERN IOWA ALONG WITH THE DEVELOPING SOUTHERN STREAM JET WILL PROVIDE THE FORCING FOR SHOWERS AND THUNDERSTORMS ACROSS NORTHEAST IOWA...PORTIONS OF SOUTHEAST MINNESOTA INTO FAR SOUTHWEST WISCONSIN. BULK SHEAR VALUES OF 40 TO 50 KTS...IN 1-7 KM LAYER...AND ELEVATED CAPE OF 1500 J/KG WHEN LIFTING FROM 1.5 KM...WILL SUPPORT THE POTENTIAL FOR SEVERE THUNDERSTORMS WITH LARGE HAIL. AT THIS TIME THE HIGHEST CHANCES FOR SEVERE WEATHER LOOKS TO BE ALONG AND SOUTH OF THE INTERSTATE 80 CORRIDOR. A FEW SEVERE STORMS MAY EDGE INTO PORTIONS OF NORTHEAST IOWA AND INTO GRANT COUNTY WISCONSIN...WITH THE MAIN THREAT BEING LARGE HAIL. COULD SEE AN MCS DEVELOP IN NORTH CENTRAL INTO NORTHERN IOWA IN THE 6 TO 9Z TIMEFRAME. IF THE MCS DEVELOPS IT WOULD FOLLOW THE CORFIDI VECTORS TO THE SOUTHEAST INTO EASTERN IA AND WESTERN ILLINOIS. LOOK FOR SHOWERS TO OVERSPREAD MUCH OF THE AREA LATE THIS EVENING INTO THE OVERNIGHT HOURS AS THE TROUGH MOVES IN. SHOWERS AND THUNDERSTORMS WILL BE COMMON ACROSS NORTHEAST IOWA INTO FAR SOUTHWEST WISCONSIN THROUGH THE OVERNIGHT. HAVE INCREASES PRECIPITATION CHANCES THROUGH OVERNIGHT HOURS INTO EARLY FRIDAY MORNING. SHOWERS WILL CONTINUE EARLY FRIDAY MORNING AHEAD OF A POTENT COLD FRONT. THE SHOWERS WILL END FROM WEST TO EAST ACROSS THE REGION FRIDAY AFTERNOON. HAVE INCREASED RAIN CHANCES IN THE 12-15Z TIME FRAME FRIDAY TO ACCOUNT FOR LINGERING FRONTOGENESIS...IN THE 850 TO 500 MB LAYER...ALONG AND SOUTH OF INTERSTATE 90. MUCH COOLER TEMPERATURES ARE IN STORE FOR FRIDAY...WITH 850 MB TEMPS FALLING TO AROUND 8C. PLAN ON BREEZY NORTHWEST WINDS OF 15 TO 25 MPH WITH GUSTS TO AROUND 30 MPH POSSIBLE IN THE OPEN AREAS OF SOUTHEAST MINNESOTA AND NORTHEAST IOWA. CLOUDS WILL DECREASE ACROSS THE REGION THROUGH THE AFTERNOON HOURS AS HIGH PRESSURE ATTEMPTS TO EDGE INTO THE REGION FROM THE HORTEN PLAINS. LOOK FOR HIGHS MAINLY IN THE 60S. COOL HIGH PRESSURE WILL BE OVERHEAD FRIDAY NIGHT WITH LOWS FALLING INTO THE 40S. A TIGHT PRESSURE GRADIENT WILL REMAIN IN PLACE AND SHOULD MITIGATE VALLEY FOG DEVELOPMENT. A SECONDARY TROUGH LOOKS TO DIVE INTO THE WESTERN GREAT LAKES ON SATURDAY. THE MAIN IMPACT ACROSS THE FORECAST AREA WILL BE INCREASING CLOUDS ACROSS NORTH CENTRAL WISCONSIN. THE TROUGH COULD SPARK ISOLATED SHOWERS ACROSS NORTHERN INTO CENTRAL WISCONSIN SATURDAY AFTERNOON INTO SATURDAY EVENING. HAVE MAINTAINED SLIGHT CHANCES FOR RAIN SHOWERS ACROSS THESE AREAS. PLAN ON HIGHS ON SATURDAY IN THE THE 60S TO AROUND 70. HIGH PRESSURE WILL FINALLY BUILD IN ON SUNDAY AS AN UPPER RIDGE MOVES INTO THE NORTHERN PLAINS. PLAN ON WARMER TEMPERATURES ON SUNDAY WITH HIGHS IN THE LOWER TO MIDDLE 70S. .LONG TERM...MONDAY THROUGH THURSDAY 322 PM CDT THU SEP 6 2012 06.12 MEDIUM RANGE MODELS IN AGREEMENT ON MONDAY SHOWING AN UPPER RIDGE OVER THE FORECAST AREA. SOUTHERLY FLOW WILL USHER IN SLIGHTLY WARMER TEMPERATURES WITH HIGHS IN THE UPPER 70S TO AROUND 80. THE RIDGE WILL REMAIN IN PLACE THROUGH EARLY TUESDAY WITH SOUTHERLY FLOW PERSISTING. A TROUGH IS EXPECTED TO RACE ACROSS THE NORTHERN PLAINS TUESDAY ...THEN PUSH INTO THE UPPER MISSISSIPPI RIVER VALLEY TUESDAY INTO WEDNESDAY. THIS SYSTEM WILL BRING A CHANCES OF SHOWERS AND THUNDERSTORMS TO THE AREA TUESDAY INTO WEDNESDAY. ZONAL FLOW IS EXPECTED TO DEVELOP IN THE WAKE OF THE TROUGH WEDNESDAY NIGHT INTO THURSDAY. A SHORTWAVE TROUGH LOOKS TO MOVE ACROSS LOCATIONS SOUTH OF INTERSTATE 90 ON THURSDAY BRINGING A LIGHT CHANCES OF SHOWERS AND THUNDERSTORMS TO THESE AREAS. && .AVIATION... 625 PM CDT THU SEP 6 2012 A COUPLE UPPER LEVEL SYSTEMS WILL SPIN ACROSS THE UPPER MISSISSIPPI RIVER VALLEY TONIGHT/FRIDAY...BRINGING AREAS OF SHRA/TS. TO THE NORTH...SCT -SHRA WERE TRACKING EAST ACROSS CENTRAL/NORTHERN MN IN RESPONSE TO A NORTHERN PIECE OF UPPER LEVEL ENERGY. VERY WEAK INSTABILITY A LOFT HAS LED TO A FEW LIGHTNING STRIKES ON THE SOUTHERN FRINGES. LATEST HRRR AND RAP SUGGESTS THAT THIS ACTIVITY WILL STAY NORTH OF KRST/KLSE...ALTHOUGH SOME OF THE RADAR TRENDS POINT TO A FARTHER SOUTHERN EXTENT...WHICH COULD IMPACT KRST. THE LOW LEVEL JET/MOISTURE TRANSPORT WILL FOCUS INTO NORTHERN IA BY 06Z TONIGHT...INTERACTING WITH SHORTWAVE ENERGY THERE...WITH AN AREA OF SHRA/TS BLOSSOMING AS A RESULT. MESO MODELS ALSO FAVOR KEEPING THE BULK OF THIS ACTIVITY SOUTH OF KRST/KLSE. WHILE THE TAF SITES WILL BE SPLIT IN BETWEEN THE TWO SHORTWAVES...THERE WILL BE ENOUGH FRONTOGENETIC FORCING/SFC FRONT AND SATURATION FOR SCT -SHRA...PERHAPS A TS EARLY ON. MOST OF THESE CIGS WILL BE AROUND 8 KFT INITIALLY. LOOK FOR LOWERING CIGS AS THE SFC FRONT MOVES THROUGH THOUGH...WITH BUFKIT SOUNDINGS AND RH FIELDS SHOWING AN INCREASE IN LOW LEVEL SATURATION. THESE LOWER CIGS WILL LINGER FRI MORNING...WITH GRADUAL IMPROVEMENT THROUGH THE DAY. && .ARX WATCHES/WARNINGS/ADVISORIES... 322 PM CDT THU SEP 6 2012 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...WETENKAMP LONG TERM....WETENKAMP AVIATION.....RIECK
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
330 PM CDT WED SEP 5 2012 .SHORT TERM...TONIGHT THROUGH SATURDAY 329 PM CDT WED SEP 5 2012 FOCUS THIS FORECAST PERIOD WAS ON THE NEXT WEATHER SYSTEM COMING INTO THE AREA THURSDAY NIGHT AND FRIDAY. CHANCES ARE INCREASING FOR A SHOWER PRODUCER. CURRENT FRONTAL POSITION TOUGH TO DISCERN RIGHT NOW...BUT MAYBE THE MORE IMPORTANT ELEMENT IS WHERE THE CONVERGENCE AND INSTABILITY IS. SURFACE MOISTURE CONVERGENCE CURRENTLY LIES ACROSS THE SOUTHERNMOST FORECAST AREA PER SPC 19Z ANALYSIS. MLCAPE IS UP TO 1500 J/KG THERE WITH CIN ABOUT 50 J/KG. THERE IS SOME WEAKER CONVERGENCE ACROSS NERN IA ALONG ANOTHER WEAK WIND SHIFT FROM WEST TO N-NW. THE NEXT FEW HOURS HOLD A CHANCE FOR ISOLATED TSRA ACROSS NERN IA AND SWRN WI BUT THIS CHANCE SHOULD SHIFT SOUTHEAST BY EVENING. CURRENTLY DO NOT HAVE A TSRA CHANCE IN THE FORECAST THIS AFTERNOON OR EVENING. 12Z 250 MB RAOB INFORMATION SHOWING A NICE HEIGHT FALL/RISE/FALL SIGNAL OVERHEAD AND UPSTREAM INTO WRN ALBERTA...WITH THE WESTERNMOST FALL OF OVER 100M/12HR ASSOCIATED WITH THE FRIDAY SHORTWAVE TROUGH SHIFTING SOUTHEAST. A NICE WARM POOL OF AIR SEEN WITH THAT SHORTWAVE TROUGH OVER ALBERTA/BRITISH COLUMBIA THERE TOO..AND 100KT JET CORE...WITH LATEST RUC ANALYSIS SHOWING THE TROPOPAUSE FOLD DOWN TO 500MB OVER CENTRAL BC. SHORTWAVE RIDGE TO BUILD IN FOR TONIGHT/THURSDAY IS CENTERED NEAR KGGW WITH 80M/12HR HEIGHT RISES AT 250 MB. RIDGE BUILDING WILL CONTINUE OVERNIGHT WITH ENOUGH 0-2KM AGL FLOW /GREATER THAN 10KTS/ TO KEEP MISSISSIPPI RIVER VALLEY FOG OUT OF THE PICTURE. HOWEVER...HAVE KEPT THE WI RIVER VALLEY FOG IN FOR THU MORNING AS MORE ORTHOGONAL NW FLOW WILL ALLOW FOR DECOUPLING IN THE BOUNDARY LAYER. PLUS...DEWPOINTS WILL BE HIGHEST IN THAT AREA OVERNIGHT...HAVE SLOWED THE DRIER AIR ADVECTION. ALBERTA/BC SHORTWAVE TROUGH TO BRING FALL-LIKE DYNAMICS TO THE AREA THURSDAY NIGHT AND INTO FRIDAY. PRETTY GOOD CONSISTENCY IN THE LARGER SCALE FORCING PRESENTED IN THE 05.12Z NAM/GFS THIS MORNING AND BECAUSE OF THIS...HAVE RAISED RAIN CHANCES LATE THURSDAY NIGHT INTO FRIDAY. THE SHORTWAVE ROUGH ENERGY SPLITS AS IT HEADS SOUTHEAST WITH A PORTION MOVING IN FROM THE DAKOTAS AND THE SECOND COMING IN FROM THE SOUTHWEST. THESE EACH HAVE A SMALL JET CORE ASSOCIATED WITH THEM AND BY LATER THU NIGHT-FRIDAY...IT APPEARS THEY INTERACT IN A COUPLED JET SCENARIO OVER THE AREA FOR GOOD DIVERGENCE ALOFT. A STRONG BAROCLINIC ZONE IN THE 700-850MB LAYER WITH THE INITIAL SHORTWAVE TROUGH WILL ALSO CREATE A W-E RAIN BAND WITH ITS FORCING IN FRONTOGENESIS FROM CENTRAL MN-NRN WI...WHICH SLOWLY SHIFTS INTO THE NWRN FORECAST AREA BY FRIDAY MORNING. THIS IS SOMEWHAT IN CONCERT WITH 500-300MB QVECTOR CONVERGENCE. MEANWHILE...BACK AT THE RANCH...THETA-E CONVERGENCE IN THE LOW- LEVELS WILL ALSO START INCREASING IN THE WRN AND NRN FORECAST BY 12Z FRIDAY. THEN...QG FORCING INCREASES AS SECOND SHORTWAVE TROUGH ENERGY PIECE SHIFTS ACROSS THE SOUTHERN FORECAST AREA. 05.12Z ECMWF HAS THESE COMPONENTS...JUST FURTHER NORTH AND SOUTH...SPLITTING AROUND THE FORECAST AREA. 05.09Z SREF DATA SUGGESTS ANY CAPE OVER 500 J/KG SHOULD REMAIN SOUTH OF THE FORECAST AREA WITH DEWPOINTS STRUGGLING TO REACH MIDDLE 50S. HOWEVER...WITH STEEPER LAPSE RATES IN THE MID-LEVELS AND STRONGER FRONTOGENESIS...COULD SEE SOME THUNDER THU NIGHT UNTIL IT IS USED UP. OVERALL...THE SIGNALS ARE BEST IN THE NRN AND SRN FORECAST AREA...BUT LARGE ENOUGH SIGNALS EXIST TO MOVE TOWARD A LIGHT RAIN SHOWER SOLUTION FOR LATE THURSDAY NIGHT AND INTO FRIDAY. AMOUNTS MAY NOT BE LARGE WITH LIMITED INSTABILITY IN THE FORECAST AREA...AROUND A QUARTER OF AN INCH TOTAL. RAIN SHOULD CLEAR QUICKLY EAST LATER ON FRIDAY. CURRENTLY THE FORECAST TEMPERATURES HAVE A 10F DIURNAL RANGE FRIDAY...AND IF IT SHOWERS ALL DAY...IT WOULD LIKELY BE ABOUT 5F. CONFIDENCE IS INCREASING ON THE RAIN EVENT...BUT NOT HIGH ENOUGH TO CUT HIGHS FRIDAY MORE. THIS WILL BE NEEDED IF WE INCREASE THE RAIN CHANCES MORE IN COMING FORECASTS. NOTE...THE NCEP GFS MODEL WAS CHANGED TODAY AT 12Z TO TRY AND SOLVE THE COLD/MOIST BIAS IN THE LOWEST 3KM AGL THAT HAS BEEN EVIDENT SINCE LAST YEAR. IT APPEARED BETTER WITH ITS INITIALIZATION IN THE LOW LEVELS. .LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY 329 PM CDT WED SEP 5 2012 WITH NORTHWEST FLOW OVER THE AREA FOR THE WEEKEND...THERE IS SOME SIGNAL FOR A SHORTWAVE TROUGH TO SHIFT THROUGH THE GREAT LAKES SATURDAY NIGHT. AT THIS TIME THE 05.00Z ECMWF AND 05.12 GEM/GFS/ECMWF REMAIN CONSISTENT IN SHOWERS OVERNIGHT IN EASTERN WISCONSIN. THERE IS A VERY DEEP TROPOSPHERIC QG FORCING SIGNAL MOVING THROUGH EASTERN WI PER THE 05.12Z ECMWF. THUS...HAVE ADDED SOME SMALL SHOWER CHANCES TO CENTRAL WI AREAS. IF THIS SIGNAL CONTINUES...MORE CLOUD AND HIGHER RAIN CHANCES WILL BE NEEDED. IT LOOKS LIKE A FAST MOVER TO LIMIT THE IMPACT ON THE WEEKEND WEATHER. RIDGE BUILDING THEN IN CONTROL OF WEATHER SUN-TUE WITH TEMPERATURES WARMING. THERE ARE SOME SIGNALS THAT TUESDAY COULD BE IN A PREFRONTAL SOUTHWESTERLY FLOW WITH 90F POSSIBLE. HAVE BUMPED HIGHS ABOUT 3F AND THE ONLY THING HOLDING OFF THE FORECAST OF WARMER HIGHS IS THE TIMING OF A STRONG FRONT AT DAY 6 CAN GET TRICKY. && .AVIATION...THROUGH 18Z THURSDAY 1222 PM CDT WED SEP 5 2012 VFR CONDITIONS EXPECTED AT KRST/KLSE THROUGH THE PERIOD AND MAIN FORECAST CONCERN IS WHETHER RIVER VALLEY FOG WILL DEVELOP AT KLSE. LATEST SURFACE ANALYSIS DEPICTS COLD FRONT DRAPED FROM NORTHEAST WISCONSIN DOWN INTO NORTHERN IOWA. FOR THIS AFTERNOON...MIXING SHOULD CONTINUE UNTIL AROUND 01Z AND HAVE CONTINUED GUSTS UP TO 18 KTS AT BOTH TAF SITES. REGARDING VALLEY FOG OVERNIGHT...WINDS IN THE 850 TO 925 MB LAYER ARE EXPECTED TO BE IN THE 10-15 KT RANGE. COMBINED WITH PLENTY OF DAYTIME MIXING...AND 03Z T/TD SPREADS BETWEEN 12-15F...ALL OF THESE FACTORS SHOULD PRECLUDE DENSE FOG DEVELOPMENT. THOUGH BY 12Z THE GRADIENT DOES RELAX A BIT AS THE SURFACE HIGH BUILDS IN...SO IF THERE WERE TO BE ANY FOG CONCERNS IT WOULD BE SHORT LIVED...PATCHY AND IN THE 13-14Z TIME FRAME. FOR THURSDAY...NO CONCERNS WITH SURFACE HIGH PRESSURE IN PLACE...AMPLE SUNSHINE AND LIGHT WINDS. && .ARX WATCHES/WARNINGS/ADVISORIES... 329 PM CDT WED SEP 5 2012 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...BAUMGARDT LONG TERM...BAUMGARDT AVIATION...ZT
AREA FORECAST DISCUSSION...UPDATED
NWS MILWAUKEE/SULLIVAN WI
957 AM CDT WED SEP 5 2012 .UPDATE...CLEARING CONTINUES TO PROGRESS WEST TO EAST ACROSS SOUTHERN WISCONSIN THIS MORNING. WITH THE COLD FRONT REMAINING TO THE WEST...THE SUN SHOULD PUSHING TEMPERATURES INTO THE 80S FOR AFTERNOON HIGHS. BIG QUESTION IS WHEN THUNDERSTORMS REDEVELOP AHEAD OF THE FRONT. GIVEN THE EXPECTED TIMING OF THE FRONT...THE BEST CHANCE FOR MORE STORMS WILL BE ACROSS THE SOUTHEAST FORECAST AREA...MAINLY SOUTHEAST OF A LINE FROM DARLINGTON TO SHEBOYGAN. MODELS SOUNDINGS STILL SHOWING PLENTY OF CAPE AND SHEAR THIS AFTERNOON...SO SEVERE STORMS CERTAINLY POSSIBLE IF THINGS GET GOING BEFORE THE FRONT GETS THROUGH THE FORECAST AREA. && .AVIATION/18Z TAFS/...WILL CONTINUE TO SEE CLEARING SKIES THROUGH THIS MORNING. ATTENTION THEN TURNS TO POSSIBLE REDEVELOPMENT OF STORMS AHEAD OF AN APPROACHING COLD FRONT. THINK BEST CHANCE OF STORMS THIS AFTERNOON WILL BE ALONG AND SOUTHEAST OF A LINE FROM DARLINGTON TO SHEBOYGAN. STRONG TO SEVERE STORMS ONCE AGAIN POSSIBLE...ESPECIALLY FARTHER TO THE SOUTHEAST. LOWER VSBYS LIKELY WITHIN MODERATE TO HEAVY RAINFALL...OTHERWISE VFR CONDITIONS WILL PREVAIL THROUGH THE DAY. IF SKIES CLEAR UP AND WINDS ARE LIGHT ENOUGH...COULD SEE SOME PATCHY FOG DEVELOP TONIGHT. QUIET WEATHER THEN EXPECTED THURSDAY UNDER HIGH PRESSURE. && .PREV DISCUSSION... /ISSUED 328 AM CDT WED SEP 5 2012/ SHORT TERM... TODAY AND TONIGHT...FORECAST CONFIDENCE...MEDIUM MAIN FORECAST CONCERN IS THE APPROACHING SHORTWAVE EXITING THE NORTHERN PLAINS AND MINNESOTA REGION BEFORE REACHING WESTERN LAKE SUPERIOR AROUND NOON. 90 KNOT 250 MB JET MAX ROUNDING THE BASE OF THE SHORTWAVE INCREASES TO 100 KNOTS NEAR LAKE SUPERIOR BY SUNRISE AND TOWARDS JAMES BAY THIS AFTERNOON. STRONG UPPER DIVERGENCE MOVES ACROSS NORTHERN WISCONSIN THIS MORNING WITH LESSER VALUES OF DIVERGENCE ACROSS SOUTHERN WISCONSIN...THAT DIMINISHES EVEN MORE THIS AFTERNOON. A RATHER STRONG 700 MB WIND MAX PUSHES INTO WEST CENTRAL WISCONSIN BY SUNRISE BEFORE LIFTING INTO NORTHEAST WISCONSIN BY NOON. THE BEST 700 MB MOISTURE CONVERGENCE AND UPWARD MOTION FOLLOWS THIS FEATURE. 850 MB MOISTURE REMAIN HIGH NEAR 15 CELSIUS THROUGHOUT THE DAY. WHILE THE BEST DYNAMICS REMAIN NORTH...THE THERMODYNAMICS ARE BETTER SOUTH WITH ALMOST 20 CELSIUS 850 MB THERMAL RIDGE INTO SOUTHEAST WISCONSIN BY NOON. THAT DROPS TO NEAR THE ILLINOIS BORDER BY EARLY EVENING. ZERO TO 1 KM RESULTING IN 2000 J/KG OF CAPE INTO THE EARLY EVENING IN THE FAR SOUTHEAST AS THE SURFACE FRONT FINALLY EXITS THE FAR SOUTHEAST. THEREFORE EXPECT THE MINNESOTA MCS THAT HAS MERGED WITH THE THUNDERSTORMS ON THE BACK SIDE OF THE OUTFLOW BOUNDARY FROM LAST EVENINGS MCS TO PUSH EAST AS THE 700 MB WIND MAX MOVES THROUGH. BEST LIFT NORTH BUT BEST INSTABILITY WELL SOUTH AS THIS MCS MOVES OUT OF THE HIGH CAPE ENVIRONMENT. THEREFORE EXPECT THE STORMS FROM THIS MCS TO CONTINUE TO WEAKEN AS IT MOVES ACROSS THE FORECAST AREA EARLY THIS MORNING. RAP SOUNDINGS ARE QUITE STABLE WITH MID LEVEL DRY AIR OVER MOST OF THE FORECAST AREA.. THEN THERE WILL BE A CHANCE FOR MORE THUNDERSTORMS THIS AFTERNOON WITH THE COLD FRONT. HOWEVER BEST DYNAMICS ARE NORTHEAST...WITH BEST INSTABILITY TO OUR SOUTH. NAM FORECAST SOUNDINGS DO SHOW STEEP LAPSE RATES IN THE LOW TO MID LEVELS AGAIN THIS AFTERNOON...ESPECIALLY SOUTHEAST WITH 10C/KM AT 900 MB TO 8 C/KM AT 500 MB. WITH PRECIPITABLE WATER VALUES AROUND 1.6 INCHES...MORE STORMS ARE POSSIBLE...ALTHOUGH THE BEST SEVERE THREAT SHOULD BE TO OUR SOUTH AND EAST. INTERESTING IS THE LOCAL SEVERE ENVIRONMENT PROBABILITY CWASP OFF THE NAM HAS HIGHER VALUES THIS AFTERNOON 75 PCT THAN IT DID YESTERDAY WITH THE FIRST MCS 65 PCT. STRONG MID LEVEL DRYING LATE TONIGHT BEHIND THE COLD FRONT. THURSDAY...FORECAST CONFIDENCE IS HIGH. A DRIER AND COOLER AIRMASS WILL SETTLE INTO SOUTHERN WI WITH HIGH PRESSURE IN THE WAKE OF THE FRONT. THE MAJORITY OF MODELS AGREE THAT THE SURFACE COLD FRONT AND 850MB BAROCLINIC ZONE WILL BE SOUTH OF THE WI BORDER BY 12Z THU SO KEPT THU DRY. EXPECTING A PLEASANTLY MOSTLY SUNNY DAY WITH HIGHS IN THE UPPER 70S AND LOW DEWPOINTS. THURSDAY NIGHT THROUGH FRIDAY...FORECAST CONFIDENCE IS MEDIUM. A LARGE UPPER TROUGH WILL SWING ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION FRIDAY AND FRIDAY NIGHT. SHOWERS COULD SPREAD INTO SOUTHERN WI AS EARLY AS THU NIGHT WITH WEAK WARM AIR ADVECTION AND THE NOSE OF THE UPPER JET INTO THE AREA. BY AROUND 18Z FRIDAY IT LOOKS LIKE THE STRONGER FORCING WITH THE RIGHT ENTRANCE REGION OF THE UPPER JET AND STRONGEST FRONTOGENESIS WILL BE MAINLY SOUTH OF THE WISCONSIN BORDER. THE OTHER BETTER AREA OF FORCING WITH THE MAIN UPPER TROUGH AND VORT MAX WILL BE CLOSER TO NORTHERN WISCONSIN AND UPPER MICHIGAN. REDUCED THE POPS SLIGHTLY...BUT KEPT THE CHANCE OF SHOWERS WORDING FOR FRIDAY. EXPECTING RAIN TO BE LIGHT AND NOT AMOUNT TO MUCH. OVERALL FRIDAY WILL BE CLOUDY AND COOL WITH OFF AND ON RAIN SHOWERS. MAX TEMPS EXPECTED AROUND 70. THE SURFACE COLD FRONT SHOULD PUSH SOUTH OF THE WI BORDER BY LATE FRI AFTERNOON. SHOWERS COULD LINGER INTO THE EVENING UNTIL THE UPPER TROUGH CLEARS THE AREA...BUT DRY AIR WORKING IN BEHIND THE SYSTEM SHOULD CUT PRECIP CHANCES SIGNIFICANTLY AFTER MIDNIGHT. LONG TERM... SATURDAY...FORECAST CONFIDENCE MEDIUM TO HIGH. MUCH COOLER AIR WILL SETTLE INTO WI BEHIND THIS UPPER TROUGH AND SURFACE COLD FRONT BY SATURDAY MORNING AND PERSIST THROUGH THE WEEKEND. ONE MORE LOBE OF VORTICITY IS FORECAST TO SWING DOWN ACROSS WI SAT NIGHT. ECMWF AND GFS SPIT OUT SMALL QPF AMOUNTS...BUT EXPECTING THE ATMOSPHERE TO BE TOO DRY SO LEFT OUT POPS. 925MB TEMPS SHOULD DIP DOWN TO AROUND 12C ON SATURDAY...YIELDING MAX TEMPS IN THE UPPER 60S WITH AMPLE SUNSHINE. THERE COULD BE A BIT OF A NORTHWEST BREEZE DURING THE AFTERNOON. SUNDAY THROUGH WEDNESDAY...FORECAST CONFIDENCE HIGH. ECMWF AND GFS ARE NOW ON THE SAME TRACK WITH AN OPEN-WAVE 500MB LOW THAT REMAINS PROGRESSIVE AND MOVES EAST OVER THE WEEKEND. A STRONG HIGH PRESSURE RIDGE WILL BUILD BACK INTO THE UPPER MIDWEST THROUGH THE FIRST HALF OF THE WEEK. MAX TEMPS WILL BE IN THE LOW TO MID 70S WITH LOW DEWPOINTS. NO PRECIP EXPECTED AND THERE SHOULD BE PLENTY OF SUNSHINE. AVIATION/12Z TAFS/... ONE COMPLEX OF THUNDERSTORMS HAS PUSHED EAST...BUT A SECOND AREA OF STRONG STORMS OVER SOUTHEAST MINNESOTA WILL PUSH EAST ACROSS MUCH OF THE FORECAST AREA BUT WEAKEN DUE TO MORE STABLE AIR OVER SOUTH CENTRAL AND SOUTHEAST WISCONSIN. THEN ANOTHER CHANCE OF THUNDERSTORMS WITH A COLD FRONT THAT WILL PUSH ACROSS SOUTHERN WISCONSIN TODAY. SOME OF THESE COULD BE STRONG LATER THIS AFTERNOON IN THE SOUTHEAST. MAINLY VFR CIGS...BUT MVFR/IFR IN THE THUNDERSTORMS. && .MKX WATCHES/WARNINGS/ADVISORIES... WI...NONE. LM...NONE. && $$ UPDATE...DDV TODAY/TONIGHT AND AVIATION/MARINE...HENTZ THURSDAY THROUGH TUESDAY...MRC
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
328 AM CDT WED SEP 5 2012 .SHORT TERM... TODAY AND TONIGHT...FORECAST CONFIDENCE...MEDIUM MAIN FORECAST CONCERN IS THE APPROACHING SHORTWAVE EXITING THE NORTHERN PLAINS AND MINNESOTA REGION BEFORE REACHING WESTERN LAKE SUPERIOR AROUND NOON. 90 KNOT 250 MB JET MAX ROUNDING THE BASE OF THE SHORTWAVE INCREASES TO 100 KNOTS NEAR LAKE SUPERIOR BY SUNRISE AND TOWARDS JAMES BAY THIS AFTERNOON. STRONG UPPER DIVERGENCE MOVES ACROSS NORTHERN WISCONSIN THIS MORNING WITH LESSER VALUES OF DIVERGENCE ACROSS SOUTHERN WISCONSIN...THAT DIMINISHES EVEN MORE THIS AFTERNOON. A RATHER STRONG 700 MB WIND MAX PUSHES INTO WEST CENTRAL WISCONSIN BY SUNRISE BEFORE LIFTING INTO NORTHEAST WISCONSIN BY NOON. THE BEST 700 MB MOISTURE CONVERGENCE AND UPWARD MOTION FOLLOWS THIS FEATURE. 850 MB MOISTURE REMAIN HIGH NEAR 15 CELSIUS THROUGHOUT THE DAY. WHILE THE BEST DYNAMICS REMAIN NORTH...THE THERMODYNAMICS ARE BETTER SOUTH WITH ALMOST 20 CELSIUS 850 MB THERMAL RIDGE INTO SOUTHEAST WISCONSIN BY NOON. THAT DROPS TO NEAR THE ILLINOIS BORDER BY EARLY EVENING. ZERO TO 1 KM RESULTING IN 2000 J/KG OF CAPE INTO THE EARLY EVENING IN THE FAR SOUTHEAST AS THE SURFACE FRONT FINALLY EXITS THE FAR SOUTHEAST. THEREFORE EXPECT THE MINNESOTA MCS THAT HAS MERGED WITH THE THUNDERSTORMS ON THE BACK SIDE OF THE OUTFLOW BOUNDARY FROM LAST EVENINGS MCS TO PUSH EAST AS THE 700 MB WIND MAX MOVES THROUGH. BEST LIFT NORTH BUT BEST INSTABILITY WELL SOUTH AS THIS MCS MOVES OUT OF THE HIGH CAPE ENVIRONMENT. THEREFORE EXPECT THE STORMS FROM THIS MCS TO CONTINUE TO WEAKEN AS IT MOVES ACROSS THE FORECAST AREA EARLY THIS MORNING. RAP SOUNDINGS ARE QUITE STABLE WITH MID LEVEL DRY AIR OVER MOST OF THE FORECAST AREA.. THEN THERE WILL BE A CHANCE FOR MORE THUNDERSTORMS THIS AFTERNOON WITH THE COLD FRONT. HOWEVER BEST DYNAMICS ARE NORTHEAST...WITH BEST INSTABILITY TO OUR SOUTH. NAM FORECAST SOUNDINGS DO SHOW STEEP LAPSE RATES IN THE LOW TO MID LEVELS AGAIN THIS AFTERNOON...ESPECIALLY SOUTHEAST WITH 10C/KM AT 900 MB TO 8 C/KM AT 500 MB. WITH PRECIPITABLE WATER VALUES AROUND 1.6 INCHES...MORE STORMS ARE POSSIBLE...ALTHOUGH THE BEST SEVERE THREAT SHOULD BE TO OUR SOUTH AND EAST. INTERESTING IS THE LOCAL SEVERE ENVIRONMENT PROBABILITY CWASP OFF THE NAM HAS HIGHER VALUES THIS AFTERNOON 75 PCT THAN IT DID YESTERDAY WITH THE FIRST MCS 65 PCT. STRONG MID LEVEL DRYING LATE TONIGHT BEHIND THE COLD FRONT. THURSDAY...FORECAST CONFIDENCE IS HIGH. A DRIER AND COOLER AIRMASS WILL SETTLE INTO SOUTHERN WI WITH HIGH PRESSURE IN THE WAKE OF THE FRONT. THE MAJORITY OF MODELS AGREE THAT THE SURFACE COLD FRONT AND 850MB BAROCLINIC ZONE WILL BE SOUTH OF THE WI BORDER BY 12Z THU SO KEPT THU DRY. EXPECTING A PLEASANTLY MOSTLY SUNNY DAY WITH HIGHS IN THE UPPER 70S AND LOW DEWPOINTS. THURSDAY NIGHT THROUGH FRIDAY...FORECAST CONFIDENCE IS MEDIUM. A LARGE UPPER TROUGH WILL SWING ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION FRIDAY AND FRIDAY NIGHT. SHOWERS COULD SPREAD INTO SOUTHERN WI AS EARLY AS THU NIGHT WITH WEAK WARM AIR ADVECTION AND THE NOSE OF THE UPPER JET INTO THE AREA. BY AROUND 18Z FRIDAY IT LOOKS LIKE THE STRONGER FORCING WITH THE RIGHT ENTRANCE REGION OF THE UPPER JET AND STRONGEST FRONTOGENESIS WILL BE MAINLY SOUTH OF THE WISCONSIN BORDER. THE OTHER BETTER AREA OF FORCING WITH THE MAIN UPPER TROUGH AND VORT MAX WILL BE CLOSER TO NORTHERN WISCONSIN AND UPPER MICHIGAN. REDUCED THE POPS SLIGHTLY...BUT KEPT THE CHANCE OF SHOWERS WORDING FOR FRIDAY. EXPECTING RAIN TO BE LIGHT AND NOT AMOUNT TO MUCH. OVERALL FRIDAY WILL BE CLOUDY AND COOL WITH OFF AND ON RAIN SHOWERS. MAX TEMPS EXPECTED AROUND 70. THE SURFACE COLD FRONT SHOULD PUSH SOUTH OF THE WI BORDER BY LATE FRI AFTERNOON. SHOWERS COULD LINGER INTO THE EVENING UNTIL THE UPPER TROUGH CLEARS THE AREA...BUT DRY AIR WORKING IN BEHIND THE SYSTEM SHOULD CUT PRECIP CHANCES SIGNIFICANTLY AFTER MIDNIGHT. .LONG TERM... SATURDAY...FORECAST CONFIDENCE MEDIUM TO HIGH. MUCH COOLER AIR WILL SETTLE INTO WI BEHIND THIS UPPER TROUGH AND SURFACE COLD FRONT BY SATURDAY MORNING AND PERSIST THROUGH THE WEEKEND. ONE MORE LOBE OF VORTICITY IS FORECAST TO SWING DOWN ACROSS WI SAT NIGHT. ECMWF AND GFS SPIT OUT SMALL QPF AMOUNTS...BUT EXPECTING THE ATMOSPHERE TO BE TOO DRY SO LEFT OUT POPS. 925MB TEMPS SHOULD DIP DOWN TO AROUND 12C ON SATURDAY...YIELDING MAX TEMPS IN THE UPPER 60S WITH AMPLE SUNSHINE. THERE COULD BE A BIT OF A NORTHWEST BREEZE DURING THE AFTERNOON. SUNDAY THROUGH WEDNESDAY...FORECAST CONFIDENCE HIGH. ECMWF AND GFS ARE NOW ON THE SAME TRACK WITH AN OPEN-WAVE 500MB LOW THAT REMAINS PROGRESSIVE AND MOVES EAST OVER THE WEEKEND. A STRONG HIGH PRESSURE RIDGE WILL BUILD BACK INTO THE UPPER MIDWEST THROUGH THE FIRST HALF OF THE WEEK. MAX TEMPS WILL BE IN THE LOW TO MID 70S WITH LOW DEWPOINTS. NO PRECIP EXPECTED AND THERE SHOULD BE PLENTY OF SUNSHINE. && .AVIATION/12Z TAFS/... ONE COMPLEX OF THUNDERSTORMS HAS PUSHED EAST...BUT A SECOND AREA OF STRONG STORMS OVER SOUTHEAST MINNESOTA WILL PUSH EAST ACROSS MUCH OF THE FORECAST AREA BUT WEAKEN DUE TO MORE STABLE AIR OVER SOUTH CENTRAL AND SOUTHEAST WISCONSIN. THEN ANOTHER CHANCE OF THUNDERSTORMS WITH A COLD FRONT THAT WILL PUSH ACROSS SOUTHERN WISCONSIN TODAY. SOME OF THESE COULD BE STRONG LATER THIS AFTERNOON IN THE SOUTHEAST. MAINLY VFR CIGS...BUT MVFR/IFR IN THE THUNDERSTORMS. && .MKX WATCHES/WARNINGS/ADVISORIES... WI...NONE. LM...NONE. && $$ TODAY/TONIGHT AND AVIATION/MARINE...HENTZ THURSDAY THROUGH TUESDAY...MRC
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1145 PM CDT TUE SEP 4 2012 .SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT 256 PM CDT TUE SEP 4 2012 MAIN FORECAST CONCERNS ARE ON CONVECTION THROUGH WEDNESDAY MORNING AND ASSOCIATED SEVERE WEATHER POTENTIAL. CURRENTLY AS OF 20Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS SHOWED A POTENT SHORTWAVE TROUGH OVER SOUTHERN SASKATCHEWAN INTO EASTERN MONTANA...THEN NEAR ZONAL TO SLIGHT SOUTHWEST FLOW STREAMING EAST INTO NEW ENGLAND. WITHIN THIS FLOW...A SHORTWAVE WAS PRESENT OVER FAR WESTERN WISCONSIN...WITH SOME WEAK RIDGING RIGHT BEHIND IT OVER MINNESOTA. MOSTLY SUNNY SKIES AFTER THE FOG BURNED OFF THIS MORNING HAS ALLOWED FOR STRONG HEATING ACROSS THE AREA. WITH 12Z RAOBS HAVING 850MB TEMPS AROUND 18C...TEMPERATURES HAVE CLIMBED INTO THE MID TO UPPER 80S. DEWPOINTS REMAIN MUGGY FOR THIS TIME OF YEAR...IN THE MID 60S TO AROUND 70. THE COMBINATION OF THE TEMPERATURES AND DEWPOINTS HAS RESULTED IN MLCAPE VALUES OF 2000-3000 J/KG WITH LITTLE CIN. AT THE SURFACE...LOW PRESSURE WAS NEAR AITKIN MN WITH A DRY-LINE ARCING THROUGH NORTHWEST WI INTO SOUTHEAST MN. PLENTY OF CUMULUS GOING UP AHEAD OF THIS DRY LINE. STORMS ARE EXPECTED TO DEVELOP IN THE NEXT HOUR OR TWO OUT OF THIS CUMULUS FIELD. BIG CONCERN FOR SEVERE WEATHER IS WIND GIVEN MID-LEVEL DRY AIR PRESENT...SEEN ON BOTH WATER VAPOR AND THE 12Z MPX SOUNDING. TO THE WEST...FAIRLY QUIET ACROSS THE DAKOTAS AHEAD OF THE POTENT TROUGH. HOWEVER...ANOTHER SURFACE LOW HAS DEVELOPED AHEAD OF IT NEAR PIERRE. IN ADDITION... GOES PRECIPITABLE WATER IMAGERY SHOWS MOISTURE BEGINNING TO SURGE TO THE NORTHWEST THROUGH EASTERN NEBRASKA AHEAD OF THE SURFACE LOW/UPPER TROUGH. REST OF THE AFTERNOON...ASSUMING CONVECTION FIRES IN THE CUMULUS FIELD...WHICH IS INDICATED BY MANY MESO-MODELS...EXPECTING IT TO PROPAGATE EAST-SOUTHEAST QUICKLY DURING THE NEXT FEW HOURS. THIS IS DUE TO THE DRY MID LEVEL AIR ALLOWING FOR RAPID MOVING OUTFLOW AS WELL AS THE MAIN SHORTWAVE ACCOMPANYING IT SHIFTING INTO EASTERN WISCONSIN BY 00Z. THEREFORE...THINKING THE SEVERE THREAT AND PROBABLY MUCH OF THE PRECIPITATION WILL END BY 00Z. ONLY CAVEAT COULD BE IN FAR SOUTHWEST WI AND FAR NORTHEAST IA WHERE THERE ARE HINTS THE TAIL END OF CONVECTION COULD STALL OUT. KEPT SOME HIGHER CHANCES OF PRECIPITATION DOWN THERE JUST IN CASE. TONIGHT AND WEDNESDAY...THE POTENT SHORTWAVE OVER EASTERN MONTANA IS FORECAST TO MOVE INTO WESTERN MINNESOTA BY 12Z WEDNESDAY. AS THIS OCCURS...THE MOISTURE SEEN LIFTING UP THROUGH EASTERN NEBRASKA RIGHT NOW IS GOING TO GET ISENTROPICALLY LIFTED UP TOWARDS US. SO AFTER SOME BRIEF SHORTWAVE RIDGING AND SUBSIDENCE THIS EVENING...ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS LOOKS LIKELY. DEVELOPMENT MAY OCCUR SOUTH OF I-90 AS EARLY AS 03Z AS SUGGESTED BY THE 04.12Z NAM/GFS. BETTER POTENTIAL FOR PRECIPITATION FOR THE ENTIRE AREA IS AFTER MIDNIGHT AS THE SHORTWAVE APPROACHES AND 850MB MOISTURE TRANSPORT REALLY INCREASES. MID-LEVEL FLOW IS NICELY DIFFLUENT TOO AHEAD OF THE WAVE...AIDING IN FORCING. MCS DEVELOPMENT IS CERTAINLY POSSIBLE...AS NOTED BY THE 04.12Z ECMWF/UKMET/CANADIAN/NAM. REGARDING SEVERE CONCERN...1-6KM SHEAR VALUES VARY FROM MODEL TO MODEL. NAM IS ON THE ORDER OF 30-40 KT WHILE THE GFS IS 20-30KT. THE NAM WOULD DEFINITELY GIVE A SEVERE WEATHER CONCERN...WITH BOTH HAIL AND DAMAGING WINDS POSSIBLE. THE GFS NOT AS MUCH SO. THEREFORE... THINK THE SPCS DAY 1 OUTLOOK SLIGHT RISK IDEA IS APPROPRIATE. A BIG NOTE...THERE IS A POSSIBILITY MCS DEVELOPMENT COULD OCCUR FARTHER SOUTH SAY MORE OVER IOWA. IF IT DOES...CORFIDI VECTORS WOULD TAKE IT SOUTHEAST...LIMITING SOME OF THE CONVECTIVE ACTIVITY OVER THE FORECAST AREA. SHORTWAVE TROUGH IS PROGGED TO HEAD EAST TO CENTRAL UPPER MICHIGAN AND LAKE MICHIGAN BY 18Z...ALLOWING STRONG ISENTROPIC DESCENT TO FILTER INTO THE AREA AND CLEAR OUT THE PRECIPITATION/CLOUDS. COLD FRONTAL BOUNDARY TOO LOOKS TO BE THROUGH THE AREA AROUND 18Z. 850MB TEMPS FALL QUITE A BIT WITH THE PASSAGE OF THE TROUGH. THROUGH 12Z WEDNESDAY...THEY HOVER BETWEEN 18-20C. BY 00Z THURSDAY...THOUGH... THEY FALL TO 12-14C. THUS...ANTICIPATE A COOLER DAY TOMORROW...MORE AROUND SEASONABLE NORMALS. WEDNESDAY NIGHT AND THURSDAY...TROUGHING OVER THE FORECAST AREA AS A RESULT OF THAT POTENT SHORTWAVE MOVING THROUGH WEDNESDAY LOOKS TO BE SHORT-LIVED. THAT IS BECAUSE ANOTHER POTENT TROUGH IS PROGGED TO DROP SOUTH INTO MONTANA BY 12Z THURSDAY. THERE WILL BE ENOUGH SUBSIDENCE AND DRY AIR PERSISTING IN THE WAKE OF WEDNESDAYS SHORTWAVE SUCH THAT WEDNESDAY NIGHT STAYS DRY. AT THE SURFACE...A HIGH PRESSURE RIDGE IS PROGGED TO BUILD INTO WESTERN PORTIONS OF THE FORECAST AREA BY 12Z THURSDAY. GIVEN THE RIDGE POSITION...ENOUGH OF A NORTHWESTERLY BREEZE SHOULD OCCUR TO PREVENT ANY FOG AT LEAST IN THE MISSISSIPPI RIVER VALLEY. OTHER SMALLER VALLEYS LIKE THE WISCONSIN MAY STILL BE SUSCEPTIBLE...THOUGH. COOLER NIGHT LIKELY WITH WINDS LIGHTENING UP THROUGH THE NIGHT AS WELL AS CLEAR SKIES. SOME OF THE TYPICAL COLD SPOTS COULD FALL INTO THE MID 40S. ON THURSDAY...THAT POTENT TROUGH DIGS DOWN A LITTLE MORE THROUGH MONTANA...SETTING UP WEST-SOUTHWEST MID LEVEL FLOW OVER THE AREA. WITHIN THIS FLOW...THERE COULD BE A SHORTWAVE SKIMMING ACROSS NORTHERN WISCONSIN IN THE AFTERNOON...BUT OTHERWISE MODELS DO NOT SHOW ANY OTHER SHORTWAVES OF SIGNIFICANCE. HOWEVER..WITH THAT POTENT TROUGH DIGGING A LITTLE MORE...IT SETS UP A 310-315K ISENTROPIC LIFT/MID-LEVEL FRONTOGENESIS ZONE DOWNSTREAM ACROSS THE NORTHERN PLAINS INTO OUR REGION. LOOKS LIKE ANY PRECIPITATION RESULTING FROM THIS FORCING WILL STAY WEST OF OUR AREA...BUT AN INCREASE IN MID/HIGH CLOUDS IS LIKELY...ESPECIALLY IN THE AFTERNOON. 850MB TEMPS OF 12-14C COMBINED WITH A DECENT AMOUNT OF SUN AND THE DRY AIR SHOULD ALLOW FOR TEMPERATURES TO CLIMB INTO THE MID TO UPPER 70S. THURSDAY NIGHT AND FRIDAY...THE POTENT TROUGH OVER MONTANA IS FORECAST TO DIG SOUTHEAST DURING THIS PERIOD...BEING PUSHED BY RIDGING DROPPING DOWN INTO SOUTH CENTRAL CANADA. BY 00Z SATURDAY...A LONG WAVE TROUGH SHOULD EXTEND FROM NORTHEAST ONTARIO...INTO THE FORECAST AREA AND INTO NEBRASKA. THE MAIN ISSUE WITH THIS POTENT TROUGH COMING TOWARDS THE AREA IS WHERE DOES THE FRONTOGENESIS ZONE AHEAD OF IT LAY UP...AND THUS THE ASSOCIATED PRECIPITATION. THE 04.00Z ECMWF KEPT THE BULK OF IT ACROSS IOWA THURSDAY NIGHT AND INTO ILLINOIS AND MISSOURI ON FRIDAY...THUS FOR THE MOST PART OUR FORECAST AREA ENDS UP DRY. THE 04.12Z NAM IS FARTHER NORTH...HAVING PRECIPITATION FALL SOUTH OF INTERSTATE 94 AFTER MIDNIGHT THURSDAY NIGHT AND FRIDAY. 04.12Z GFS IS A LITTLE MORE INTERESTING. THE MODEL SUGGESTS SOME HIGHER LEVEL FRONTOGENESIS PRODUCING A BAND OF MOSTLY LIGHT RAIN...WHICH SLOWLY DROPS SOUTH THROUGH THE AREA AFTER MIDNIGHT THURSDAY NIGHT THROUGH FRIDAY. THESE BANDS SOMETIMES VERIFY AND OTHER TIMES NOT. OVERALL...THE BULK OF THE PRECIPITATION IN THE GFS FALLS TO THE SOUTH. IN ANY EVENT...ALL MODELS SUGGEST A NEED TO INCREASE PRECIPITATION CHANCES UP TO 40 FOR NOW...MAINLY SOUTH OF I-90. FURTHER REFINEMENTS WILL BE NEEDED AS WE GET CLOSER TO THIS PERIOD. WITH MORE CLOUDS AS WELL AS COOLER AIR COMING IN WITH THE UPPER TROUGH...ANTICIPATE THIS PERIOD TO BE MUCH COOLER THAN AS OF LATE. THIS WILL BE ESPECIALLY TRUE ON FRIDAY AS 850MB TEMPS FALL TO 6-9C. HIGHS ON FRIDAY MAY GET STUCK IN THE 60S...ESPECIALLY IF IT RAINS ALL DAY LIKE THE NAM. .LONG TERM...FRIDAY NIGHT THROUGH TUESDAY 256 PM CDT TUE SEP 4 2012 04.12Z ECMWF/GFS/CANADIAN AND GFS ENSEMBLES ARE A LITTLE DIFFERENT AMONGST EACH OTHER TODAY COMPARED TO YESTERDAY...MOSTLY WITH REGARDS TO HANDLING WHETHER THE UPPER TROUGH COMING THROUGH THE FORECAST AREA FRIDAY ENDS UP CLOSING OFF IN THE OHIO RIVER VALLEY. INTERESTINGLY...THE 04.12Z ECMWF/CANADIAN AND GFS HAVE NOW FLIP-FLOPPED WITH EACH OTHER...WITH THE ECMWF/CANADIAN NOW MORE PROGRESSIVE AND THE GFS CLOSING OFF. FOR OUR AREA...THOUGH...WHICH EVER SOLUTION PANS OUT REALLY DOESNT MATTER...AS BOTH SCENARIOS BUILD HIGH PRESSURE INTO THE FORECAST AREA FOR THE WEEKEND. SO MAYBE AFTER A FEW LINGERING SHOWERS IN NORTHEAST IA/SOUTHWEST WI FRIDAY NIGHT...EXPECT DECREASING CLOUDS AND DRY WEATHER FOR THE WEEKEND. CERTAINLY LOOKS COOL COMPARED TO WHAT HAS BEEN SEEN RECENTLY... THANKS TO 850MB TEMPS OF 6-8C ON SATURDAY AND 10-12C ON SUNDAY. WOULD NOT BE SURPRISED IF SOME OF THE TYPICAL COLD SPOTS END UP SEEING SOME UPPER 30S. FOR EARLY NEXT WEEK...UPPER RIDGING OVER THE WESTERN U.S. IS FORECAST TO BUILD UP INTO THE FORECAST AREA...BUT FLATTEN PRETTY QUICKLY BY TUESDAY AS A SHORTWAVE TROUGH CROSSING SOUTHERN CANADA. WILL SEE A WARM UP WITH THE RIDGING COMING IN...AT LEAST BACK TO NORMAL. DRY CONDITIONS SHOULD CONTINUE AS WELL WITH THE HIGH PRESSURE OVER THE WEEKEND BLOCKING GULF OF MEXICO MOISTURE RETURN. && .AVIATION... 1145 PM CDT TUE SEP 4 2012 ANOTHER ROUND OF THUNDERSTORMS WILL IMPACT THE AREA AS AN ORGANIZED MCS DRIVES ACROSS THE REGION BETWEEN 05-09Z. STRONG WINDS WILL ACCOMPANY THE STORMS INITIALLY...LIKELY IMPACTING KRST BETWEEN 0530-07Z AND 07-08Z AT KLSE. THE STRONGEST WINDS COULD BE ON A WEAKENING TREND AS THE STORMS REACH KLSE...HOWEVER. SHRA/TS COULD LINGER THROUGH WED MORNING...BUT THE BULK OF THIS ACTIVITY SHOULD HAVE EXITED EAST BY 18Z AS A COLD FRONT SWEEPS ACROSS THE UPPER MISSISSIPPI RIVER VALLEY. TIMING IS ROUGHLY 16Z AT KRST AND 18Z AT KLSE. CLEARING FOR WED NIGHT...AND CONSIDERING THE RAINFALL...SOME INGREDIENTS FOR FOG. AS OF NOW...THINK LOW LEVEL WINDS WILL BE STIRRING TOO MUCH...THUS INHIBITING THE FOG. OF COURSE THIS WILL BE RE-EVALUATED FOR LATER TAF ISSUANCES. && .ARX WATCHES/WARNINGS/ADVISORIES... 256 PM CDT TUE SEP 4 2012 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...AJ LONG TERM....AJ AVIATION.....RIECK
AREA FORECAST DISCUSSION
NWS LINCOLN IL
1154 PM CDT THU SEP 6 2012 .DISCUSSION... ISSUED 900 PM CDT THU SEP 6 2012 DRY AIR MIXING THIS AFTERNOON DROPPED SURFACE DEWPOINTS INTO THE LOW TO MID 50S IN SOME WESTERN AREAS...WITH EAST AND SOUTHEAST AREA DEWPOINTS STILL IN THE 60S. ANY FOG FORMATION UNDER THE CLEAR SKIES AND LIGHT WINDS WILL BE IN THE ESE COUNTIES. WESTERN AREAS SHOULD SEE LIMITED FOG IF AT ALL. THE NEXT ISSUE WILL BE WHEN THE STORM COMPLEX WILL ARRIVE FROM IOWA. THE LATEST HRRR MODEL OUTPUT KEEPS ALL STORMS IN IOWA THROUGH 6 AM...SO CONFIDENCE IS DROPPING THAT ANY STORMS WILL REACH OUR NW COUNTIES BEFORE SUNRISE. WE REMAIN IN THE DAY 1 SPC SEVERE OUTLOOK FOR KNOX AND FAR NW FULTON COUNTIES VALID THROUGH 12Z. WILL KEEP LIKELY POPS IN THAT AREA FOR LATE TONIGHT...BUT PULLED OUT POPS THROUGH 9Z...THEN KEPT LIMITED POPS FROM 9Z-12Z LATER TONIGHT. THE MAIN SHOW FOR STORMS WILL BE ON FRIDAY...ESPECIALLY FRIDAY AFTERNOON EAST OF I-55 WHEN PEAK HEATING AND INSTABILITY/SHEAR BECOME MORE FAVORABLE FOR SEVERE STORMS. UPDATED GRIDS AND FORECAST INFO WILL BE AVAILABLE SHORTLY. SHIMON && .AVIATION... ISSUED 1154 PM CDT THU SEP 6 2012...FOR THE 06Z TAFS STORMS HAVE BEGUN TO FIRE IN CENTRAL IOWA UNDER A SHORTWAVE AHEAD OF THE COLD FRONT. UNLESS THAT LINE HAS DEVELOPMENT TO THE SOUTHWEST...THE CURRENT BAND OF CONVECTION WOULD MISS OUR NORTHERN COUNTIES TO THE NORTH. ASSUMING THE LINE DOES EXPAND TO THE SW...THE TIMING OF ARRIVAL IN KNOX COUNTY WOULD BE AROUND 1030Z/0520 CDT. BASED ON THAT...THE PIA TERMINAL COULD SEE CONVECTION AROUND 12Z...SO I BUMPED THE VCTS TO 12Z AND THE STEADY -SHRA TO 15Z. LIKEWISE...I TRENDED STORMS/PRECIP LATER WITH THE DOWNSTREAM TAFS. THE STRONGEST CONVECTION STILL APPEARS TARGETED FOR THE AFTERNOON NEAR THE EASTERN TERMINALS OF DEC/CMI AND POSSIBLY BMI/SPI. AS A SURFACE WAVE TRAVELS UP THE FRONT DURING THE AFTERNOON...IT WILL COMBINE WITH FAVORABLE SHEAR AND INSTABILITY TO PRODUCE STRONG TO SEVERE STORMS. DAMAGING WINDS WILL BE THE PRIMARY HAZARD FOR THE EASTERN TERMINAL LOCATIONS...WITH LARGE HAIL ALSO POSSIBLE. STILL A TOUGH CALL ON THE 2-3 HOUR WINDOW OF PEAK SEVERE STORM CHANCES...SO WILL NOT INCLUDE AN AFTERNOON TEMPO JUST YET. WINDS WILL INCREASE OUT OF THE SW IN THE MORNING...THEN VEER TO THE W-NW AS THE FRONT MOVES THROUGH. NW WINDS WILL DEVELOP IN THE POST-FRONTAL AIRMASS...WITH STRATIFORM RAIN FOR A FEW HOURS BEHIND THE FRONT. IFR LOW CLOUDS AND MVFR FOG ARE POSSIBLE FOR THE EVENING...AS COOLER AIR FILTERS INTO THE MOIST AIRMASS. SOME LOCALLY DENSE FOG MAY DEVELOP ALREADY IN THE EVENING...BUT WILL HOLD OFF ON VLIFR CONDITIONS THIS FAR OUT. SHIMON && .PREV DISCUSSION... ISSUED 250 PM CDT THU SEP 6 2012 HIGH PRESSURE CENTERED OVER EASTERN IOWA EARLY THIS AFTERNOON. MOST OF THE FOG ACROSS THE SOUTHEAST HALF OF THE CWA BURNED OFF BY 9 AM OR SO...BUT THE CLOUDS HAVE LINGERED THERE INTO THIS AFTERNOON. THIS IS ALONG A BOUNDARY/SURFACE FRONT THAT DIVIDES DEW POINTS IN THE 50S TO THE NORTHWEST...AND AROUND 70 TO THE SOUTHEAST. THE LARGER SURFACE PICTURE SHOWS LOW PRESSURE IN NORTH CENTRAL NEBRASKA...WITH A WARM FRONT ARCHING NORTHEAST INTO CENTRAL MINNESOTA AND A COLD FRONT EXTENDING WESTWARD. THIS PARTICULAR STORM SYSTEM IS THE FEATURE OF INTEREST FOR OUR AREA OVER THE NEXT 36 HOURS. THE MAIN CONCERNS WILL BE WITH RAINFALL TIMING AND AMOUNTS...AS WELL AS SEVERE WEATHER POTENTIAL. SHORT TERM...TONIGHT THROUGH SATURDAY... DIGGING UPPER TROUGH CURRENTLY MOVING INTO NORTH DAKOTA WILL PUSH STORM SYSTEM IN THE PLAINS EASTWARD. STILL LOOKING LIKE THE WESTERN HALF OF THE CWA WILL BE SEEING SOME SHOWERS AND STORMS SPREADING IN AFTER MIDNIGHT...ESPECIALLY NORTHWEST OF THE ILLINOIS RIVER. HAVE ADDED SOME SLIGHT CHANCE POPS AS FAR EAST AS I-57 FOR LATE TONIGHT. REASONABLE AGREEMENT EXISTS AMONG MODEL SOLUTIONS ON SWEEPING THE COLD FRONT ACROSS THE FORECAST AREA FRIDAY AFTERNOON AND EARLY EVENING...ALTHOUGH THE NAM IS A TAD FASTER IN THIS REGARD. ALL MODEL SOLUTIONS SHOWING PRECIPITABLE WATER VALUES AROUND 2-2.1 INCHES AHEAD OF THE FRONT...WHICH IS AROUND THE 99TH PERCENTILE FOR EARLY SEPTEMBER...SO SOME AREAS OF HEAVIER RAIN ARE LIKELY. IN TERMS OF THE SEVERE POTENTIAL...CAPES PROGGED TO RISE TO AT LEAST 2000 J/KG EAST OF THE RAIN SHIELD...WHERE SOME SUN MAY OCCUR DURING THE MORNING...AND BULK SHEAR VALUES AHEAD OF THE FRONT PROGGED TO RISE TO AROUND 40-45 KNOTS. MAINLY LOOKING AT A WIND DAMAGE AND HAIL THREAT IN THIS AREA. LATEST SPC DAY2 OUTLOOK HAS AREAS FROM THE ILLINOIS RIVER SOUTHEAST IN A SLIGHT RISK...WITH THE GREATEST PROBABILITIES SOUTH OF A TAYLORVILLE TO DANVILLE LINE. RAIN CHANCES SHOULD QUICKLY TAPER OFF FROM WEST TO EAST FOLLOWING THE PASSAGE OF THE FRONT...WITH MOST AREAS WEST OF I-57 DRY BY LATE FRIDAY EVENING. UPPER TROUGH WILL CONTINUE TO DEEPEN AS IT SWEEPS ACROSS THE GREAT LAKES SATURDAY. WILL CONTINUE WITH HIGHS IN THE LOWER 70S ACROSS MOST OF THE CWA AS THE COLDER AND DRIER AIR IS DRAWN SOUTHWARD. LONG TERM...SUNDAY THROUGH THURSDAY... HIGH TEMPERATURES REMAIN IN THE 70S SUNDAY AND MONDAY...AS THE UPPER TROUGH GRADUALLY LIFTS NORTHEAST INTO CANADA...WITH SOME GRADUAL WARMING AFTER THAT. MAIN CONCERN IN THE LONGER TERM REMAINS WITH A SHORTWAVE WHICH WILL TRACK ALONG THE CANADIAN BORDER EARLY IN THE WEEK. ECMWF AND GFS MODELS HAVING SOME DIFFICULTY WITH THE FAST UPPER FLOW...AND WHEN TO BRING THIS INTO OUR GENERAL REGION. BOTH MODELS SHOW A SLOWING OF THE ASSOCIATED SURFACE FRONT BY MIDWEEK AS IT STARTS TO PARALLEL THE UPPER FLOW... DUE TO A 500 MB HIGH STRETCHED EAST-WEST ACROSS THE SOUTHEASTERN STATES. MAIN PRECIPITATION FOCUS WOULD LIKELY HOLD OFF UNTIL THURSDAY IN OUR AREA...BUT A FAIR AMOUNT OF DRY AIR WILL STILL BE OVER THE CWA. THEREFORE...WILL ONLY GO WITH SOME SLIGHT CHANCE POPS ACROSS THE NORTHWEST FOR NOW. GEELHART && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS GOODLAND KS
1059 PM MDT THU SEP 6 2012 .UPDATE... ISSUED AT 1004 PM MDT THU SEP 6 2012 UPDATE DUE TO EXPIRATION OF WATCH. ALSO MADE MINOR ADJUSTMENTS ON REMAINING HOURLY GRIDS. UPDATE ISSUED AT 828 PM MDT THU SEP 6 2012 JUST COMPLETED ANOTHER UPDATE. TRIMMED OFF ALL BUT THE EASTERN PORTION OF THE WATCH AND COULD HAVE TRIMMED IT ALL BUT JUST ENOUGH THERE FOR ME TO KEEP IT IN UNTIL 04Z. LOOKING THE UPSTREAM 00Z SOUNDING IT DOES NOT LOOK FAVORABLE FOR REDEVELOPMENT WITH A DRY AIR MASS IN PLACE. MID LEVEL MOISTURE DOES INCREASE AFTER 06Z. MODELS INSIST ON KEEPING A CONSIDERABLE AMOUNT OF ELEVATED CAPE INTO TOMORROW MORNING WITH LOW CINH UNTIL AFTER 12Z. LIGHTNING DETECTION NETWORK IS SHOWING SOME INCREASE IN LIGHTING WELL TO THE NORTHWEST AND ESPECIALLY WEST AS A RATHER STRONGER SHORTWAVE TROUGH MOVES IN. ALSO AREA COMES UNDER THE INFLUENCE OF RIGHT REAR QUADRANT OF THE JET BY LATE TONIGHT INTO TOMORROW MORNING. AM NOT VERY EXCITED ABOUT THE PROSPECT OF MEASURABLE BUT CANNOT IGNORE WHAT IS GOING ON UPSTREAM COMBINED WITH WHAT THE LIFT AND INSTABILITY IS SHOWING ME. SO AFTER AFTER THE WATCH IS OVER KEPT A SLIGHT CHANCE TO LOW CHANCE OF PRECIPITATION INTO TOMORROW MORNING. AT THIS TIME IT LOOKS LIKE WILL STAY BELOW WIND ADVISORY CRITERIA BUT WILL CONTINUE TO MONITOR TRENDS AND NEWER DATA. UPDATE ISSUED AT 629 PM MDT THU SEP 6 2012 JUST COMPLETED AN UPDATE MAINLY TO REFINE THUNDERSTORM FORECAST. MAIN LINE OF THUNDERSTORMS HAS PUSHED OFF TO THE EAST OF THE FORECAST AREA AT THIS TIME. BOUNDARY IS STILL OVER THE AREA THAT IS IN THE SEVERE THUNDERSTORM WATCH WITH IT PROGGED TO MOVE BACK TO THE WEST THIS EVENING. PROBLEM AT THIS TIME...MAIN MID/UPR LEVEL SUPPORT HAS PUSHED OFF TO THE EAST. AM VERY PESSIMISTIC ABOUT ANY REDEVELOPMENT AT THIS TIME. HOWEVER...WILL CONTINUE TO WATCH TRENDS AND ALLOW NEWER MODEL DATA TO COME IN. SO AT THIS TIME...REDUCED POPS AND REDUCED AREA OF PRECIPITATION. ALSO REDUCED TH SKY COVER AS WELL BECAUSE OF THIS. WIND FIELD IS ALL OVER THE PLACE DUE TO THE ABOVE MENTIONED BOUNDARY AND AS A RESULT MODELS HAVING A HARD TIME IN RESOLVING THE DEWPOINT FIELD AS WELL. LOWER DEWPOINTS ARE MUCH FURTHER EAST BUT SHOULD COME BACK TO WEST THROUGH THE EVENING. FRONT STILL LOOKS ON TRACK IN THE NORTH AROUND 06Z. DEFINITELY NOT THE LAST UPDATE FOR THE EVENING. UPDATE ISSUED AT 259 PM MDT THU SEP 6 2012 UPDATED FORECAST TO INCLUDE THE SEVERE THUNDERSTORM WATCH THIS AFTERNOON AND EVENING. && .SHORT TERM...(THIS EVENING THROUGH FRIDAY) ISSUED AT 149 PM MDT THU SEP 6 2012 LATEST WV IMAGERY AND RUC H5 ANALYSIS CONTINUE TO INDICATE WESTERLY FLOW ACROSS THE INTER-MOUNTAIN WEST AND HIGH PLAINS JUST NORTH OF SOUTHWESTERN CONUS RIDGE. AT THE SURFACE A TROUGH/DRY LINE HAS SHIFTED EAST TO LIE FROM JUST WEST OF MCCOOK NEBRASKA...BETWEEN GOODLAND AND COLBY KANSAS...AND THEN WEST OF TRIBUNE KANSAS. TD VALUES IN THE UPPER 50S/LOW 60S AND MIXED LAYER CAPES IN EXCESS OF 1000 J/KG ARE CURRENTLY EAST OF THIS DRY LINE...WITH MUCH MORE STABLE AIR MASS TO THE WEST OF THIS FEATURE. SURFACE CONVERGENCE AHEAD OF THIS DRY LINE SHOULD HELP OVERCOME WEAKENING CAP LATER THIS AFTERNOON AND EARLY THIS EVENING...WITH THUNDERSTORM COVERAGE INCREASING FURTHER EAST WHERE BETTER LARGE SCALE FORCING IS EXPECTED. BASED ON MODEL SOUNDINGS LCL VALUES REMAIN HIGH...WITH DEEP MIXED LAYER TO ABOUT 650 MB INDICATIVE OF MICROBURST POTENTIAL WITH THUNDERSTORMS. IN ADDITION...SUPERCELL THUNDERSTORMS WILL BE A POSSIBILITY....WITH 0-6KM BULK SHEAR VALUES PROGGED TO BE AROUND 40KT OR HIGHER...AND WITH MIXED LAYER CAPE IN EXCESS OF 1500 J/KG. LCL VALUES WILL BE FAIRLY HIGH IN THE 8-10KFT RANGE...SO IM NOT AS CONCERNED ABOUT A TORNADO THREAT WITH THIS ACTIVITY. A COLD FRONT IS EXPECTED TO MOVE ACROSS THE CWA FROM THE NW AFTER MIDNIGHT...WITH LARGE PRESSURE RISES AND INCREASING H85 WINDS BEHIND THE FRONT POSSIBLY RESULTING IN ADVISORY CRITERIA WINDS. OTHER THAN THE 12Z NAM...MOST GUIDANCE IS VERY MARGINAL ON THIS...SO I DECIDED AGAINST ISSUING AN ADVISORY THIS FORECAST CYCLE. AHEAD OF THIS FRONT ELEVATED INSTABILITY AND MOISTURE WILL BEGIN TO BUILD BACK TO THE WEST...WITH ISOLATED THREAT FOR CONVECTION RETURNING AFTER MIDNIGHT THROUGH FRIDAY MORNING AS THE FRONT MOVES ACROSS THE REGION. CONFIDENCE IS LOW AT THIS TIME...AND MOST GUIDANCE IS NOT CURRENTLY INITIATING ANYTHING WITH THIS FROPA...SO I LIMITED POPS TO SLIGHT CHANCE CATEGORY. LARGE SCALE SUBSIDENCE SHOULD BRING DRY CONDITIONS BACK TO THE CWA FRIDAY. .LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY) ISSUED AT 215 PM MDT THU SEP 6 2012 DRY AND MILD CONDITIONS ON FRIDAY NIGHT AND SATURDAY WILL TRANSITION TO DRY AND WARM CONDITIONS DURING THE FIRST PART OF NEXT WEEK AS THE UPPER RIDGE MOVES FROM THE ROCKIES TO THE HIGH PLAINS AND THE COOLER AREA OF HIGH PRESSURE AT THE SURFACE SLIDES INTO THE SOUTHERN PLAINS. SOUTHERLY SURFACE RETURN FLOW ESTABLISHES OVER THE CENTRAL HIGH PLAINS ON SUNDAY AND CONTINUES THROUGH MONDAY AS THE SURFACE LEE TROUGH DEEPENS AND THE UPPER RIDGE TRANSITIONS OVER THE PLAINS STATES. TEMPERATURES ARE EXPECTED TO WARM BACK UP INTO THE 90S BY MONDAY AS A RESULT AHEAD OF THE NEXT FRONT DUE THROUGH THE REGION DURING THE DAY ON TUESDAY. ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ON TUESDAY IN THE VICINITY OF THE FRONT. STORMS WILL BECOME MORE WIDESPREAD AND CONTINUE THROUGH TUESDAY NIGHT AND INTO WEDNESDAY AS THE FLOW OVER THE CENTRAL HIGH PLAINS BECOMES MORE ZONAL AND A SERIES OF SHORT WAVE TROUGHS MOVES THROUGH THE FLOW. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT) ISSUED AT 1055 PM MDT THU SEP 6 2012 VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. IT LOOKS LIKE THE BEST CHANCE FOR PRECIPITATION WILL BE TO THE EAST OF BOTH TAF SITES SO LEFT ALL MENTION OUT. COLD FRONT IS BEGINNING TO MOVE THROUGH THE AREA AT THIS TIME. NORTH WINDS WILL BE GUSTY THROUGH THE DAY WITH THE HIGHEST SPEEDS/GUSTS THROUGH EARLY IN THE AFTERNOON. AFTER THAT WINDS WILL BECOME MUCH LIGHTER. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...BULLER SHORT TERM...DR LONG TERM...LOCKHART AVIATION...BULLER
AREA FORECAST DISCUSSION
NWS GOODLAND KS
1005 PM MDT THU SEP 6 2012 .UPDATE... ISSUED AT 1004 PM MDT THU SEP 6 2012 UPDATE DUE TO EXPIRATION OF WATCH. ALSO MADE MINOR ADJUSTMENTS ON REMAINING HOURLY GRIDS. UPDATE ISSUED AT 828 PM MDT THU SEP 6 2012 JUST COMPLETED ANOTHER UPDATE. TRIMMED OFF ALL BUT THE EASTERN PORTION OF THE WATCH AND COULD HAVE TRIMMED IT ALL BUT JUST ENOUGH THERE FOR ME TO KEEP IT IN UNTIL 04Z. LOOKING THE UPSTREAM 00Z SOUNDING IT DOES NOT LOOK FAVORABLE FOR REDEVELOPMENT WITH A DRY AIR MASS IN PLACE. MID LEVEL MOISTURE DOES INCREASE AFTER 06Z. MODELS INSIST ON KEEPING A CONSIDERABLE AMOUNT OF ELEVATED CAPE INTO TOMORROW MORNING WITH LOW CINH UNTIL AFTER 12Z. LIGHTNING DETECTION NETWORK IS SHOWING SOME INCREASE IN LIGHTING WELL TO THE NORTHWEST AND ESPECIALLY WEST AS A RATHER STRONGER SHORTWAVE TROUGH MOVES IN. ALSO AREA COMES UNDER THE INFLUENCE OF RIGHT REAR QUADRANT OF THE JET BY LATE TONIGHT INTO TOMORROW MORNING. AM NOT VERY EXCITED ABOUT THE PROSPECT OF MEASURABLE BUT CANNOT IGNORE WHAT IS GOING ON UPSTREAM COMBINED WITH WHAT THE LIFT AND INSTABILITY IS SHOWING ME. SO AFTER AFTER THE WATCH IS OVER KEPT A SLIGHT CHANCE TO LOW CHANCE OF PRECIPITATION INTO TOMORROW MORNING. AT THIS TIME IT LOOKS LIKE WILL STAY BELOW WIND ADVISORY CRITERIA BUT WILL CONTINUE TO MONITOR TRENDS AND NEWER DATA. UPDATE ISSUED AT 629 PM MDT THU SEP 6 2012 JUST COMPLETED AN UPDATE MAINLY TO REFINE THUNDERSTORM FORECAST. MAIN LINE OF THUNDERSTORMS HAS PUSHED OFF TO THE EAST OF THE FORECAST AREA AT THIS TIME. BOUNDARY IS STILL OVER THE AREA THAT IS IN THE SEVERE THUNDERSTORM WATCH WITH IT PROGGED TO MOVE BACK TO THE WEST THIS EVENING. PROBLEM AT THIS TIME...MAIN MID/UPR LEVEL SUPPORT HAS PUSHED OFF TO THE EAST. AM VERY PESSIMISTIC ABOUT ANY REDEVELOPMENT AT THIS TIME. HOWEVER...WILL CONTINUE TO WATCH TRENDS AND ALLOW NEWER MODEL DATA TO COME IN. SO AT THIS TIME...REDUCED POPS AND REDUCED AREA OF PRECIPITATION. ALSO REDUCED TH SKY COVER AS WELL BECAUSE OF THIS. WIND FIELD IS ALL OVER THE PLACE DUE TO THE ABOVE MENTIONED BOUNDARY AND AS A RESULT MODELS HAVING A HARD TIME IN RESOLVING THE DEWPOINT FIELD AS WELL. LOWER DEWPOINTS ARE MUCH FURTHER EAST BUT SHOULD COME BACK TO WEST THROUGH THE EVENING. FRONT STILL LOOKS ON TRACK IN THE NORTH AROUND 06Z. DEFINITELY NOT THE LAST UPDATE FOR THE EVENING. UPDATE ISSUED AT 259 PM MDT THU SEP 6 2012 UPDATED FORECAST TO INCLUDE THE SEVERE THUNDERSTORM WATCH THIS AFTERNOON AND EVENING. && .SHORT TERM...(THIS EVENING THROUGH FRIDAY) ISSUED AT 149 PM MDT THU SEP 6 2012 LATEST WV IMAGERY AND RUC H5 ANALYSIS CONTINUE TO INDICATE WESTERLY FLOW ACROSS THE INTER-MOUNTAIN WEST AND HIGH PLAINS JUST NORTH OF SOUTHWESTERN CONUS RIDGE. AT THE SURFACE A TROUGH/DRY LINE HAS SHIFTED EAST TO LIE FROM JUST WEST OF MCCOOK NEBRASKA...BETWEEN GOODLAND AND COLBY KANSAS...AND THEN WEST OF TRIBUNE KANSAS. TD VALUES IN THE UPPER 50S/LOW 60S AND MIXED LAYER CAPES IN EXCESS OF 1000 J/KG ARE CURRENTLY EAST OF THIS DRY LINE...WITH MUCH MORE STABLE AIR MASS TO THE WEST OF THIS FEATURE. SURFACE CONVERGENCE AHEAD OF THIS DRY LINE SHOULD HELP OVERCOME WEAKENING CAP LATER THIS AFTERNOON AND EARLY THIS EVENING...WITH THUNDERSTORM COVERAGE INCREASING FURTHER EAST WHERE BETTER LARGE SCALE FORCING IS EXPECTED. BASED ON MODEL SOUNDINGS LCL VALUES REMAIN HIGH...WITH DEEP MIXED LAYER TO ABOUT 650 MB INDICATIVE OF MICROBURST POTENTIAL WITH THUNDERSTORMS. IN ADDITION...SUPERCELL THUNDERSTORMS WILL BE A POSSIBILITY....WITH 0-6KM BULK SHEAR VALUES PROGGED TO BE AROUND 40KT OR HIGHER...AND WITH MIXED LAYER CAPE IN EXCESS OF 1500 J/KG. LCL VALUES WILL BE FAIRLY HIGH IN THE 8-10KFT RANGE...SO IM NOT AS CONCERNED ABOUT A TORNADO THREAT WITH THIS ACTIVITY. A COLD FRONT IS EXPECTED TO MOVE ACROSS THE CWA FROM THE NW AFTER MIDNIGHT...WITH LARGE PRESSURE RISES AND INCREASING H85 WINDS BEHIND THE FRONT POSSIBLY RESULTING IN ADVISORY CRITERIA WINDS. OTHER THAN THE 12Z NAM...MOST GUIDANCE IS VERY MARGINAL ON THIS...SO I DECIDED AGAINST ISSUING AN ADVISORY THIS FORECAST CYCLE. AHEAD OF THIS FRONT ELEVATED INSTABILITY AND MOISTURE WILL BEGIN TO BUILD BACK TO THE WEST...WITH ISOLATED THREAT FOR CONVECTION RETURNING AFTER MIDNIGHT THROUGH FRIDAY MORNING AS THE FRONT MOVES ACROSS THE REGION. CONFIDENCE IS LOW AT THIS TIME...AND MOST GUIDANCE IS NOT CURRENTLY INITIATING ANYTHING WITH THIS FROPA...SO I LIMITED POPS TO SLIGHT CHANCE CATEGORY. LARGE SCALE SUBSIDENCE SHOULD BRING DRY CONDITIONS BACK TO THE CWA FRIDAY. .LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY) ISSUED AT 215 PM MDT THU SEP 6 2012 DRY AND MILD CONDITIONS ON FRIDAY NIGHT AND SATURDAY WILL TRANSITION TO DRY AND WARM CONDITIONS DURING THE FIRST PART OF NEXT WEEK AS THE UPPER RIDGE MOVES FROM THE ROCKIES TO THE HIGH PLAINS AND THE COOLER AREA OF HIGH PRESSURE AT THE SURFACE SLIDES INTO THE SOUTHERN PLAINS. SOUTHERLY SURFACE RETURN FLOW ESTABLISHES OVER THE CENTRAL HIGH PLAINS ON SUNDAY AND CONTINUES THROUGH MONDAY AS THE SURFACE LEE TROUGH DEEPENS AND THE UPPER RIDGE TRANSITIONS OVER THE PLAINS STATES. TEMPERATURES ARE EXPECTED TO WARM BACK UP INTO THE 90S BY MONDAY AS A RESULT AHEAD OF THE NEXT FRONT DUE THROUGH THE REGION DURING THE DAY ON TUESDAY. ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ON TUESDAY IN THE VICINITY OF THE FRONT. STORMS WILL BECOME MORE WIDESPREAD AND CONTINUE THROUGH TUESDAY NIGHT AND INTO WEDNESDAY AS THE FLOW OVER THE CENTRAL HIGH PLAINS BECOMES MORE ZONAL AND A SERIES OF SHORT WAVE TROUGHS MOVES THROUGH THE FLOW. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING) ISSUED AT 540 PM MDT THU SEP 6 2012 VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. AT THIS TIME INITIAL ROUND OF THUNDERSTORMS WILL BE TO THE EAST OF BOTH TAF SITES. THERE IS A LOW PROBABILITY OF THUNDERSTORMS AFTER 06Z BUT AT THIS TIME TO KEEP THEM OUT. WILL CONTINUE TO MONITOR CLOSELY WITH LATEST DATA FOR POSSIBLE UPDATES. STRONG COLD FRONT BEGINS TO MOVE THROUGH THE AREA IN THE 06Z TO 08Z TIME FRAME WITH VERY GUSTY WINDS EXPECTED THROUGH THE MORNING HOURS. AFTER THAT WINDS WILL BEGIN TO GRADUALLY DECREASE. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...BULLER SHORT TERM...DR LONG TERM...LOCKHART AVIATION...BULLER
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
252 AM CDT FRI SEP 7 2012 .DISCUSSION... THE LEADING EDGE OF A COOL CANADIAN AIR MASS WAS JUST SOUTH OF A KFRM TO KEAU LINE EARLY THIS MORNING. AS EXPECTED...THE LLJ AND ASSOCIATED MOISTURE ADVECTION WAS JUST SOUTH OF THE FA GENERATED TSRA JUST SOUTH OF THE IOWA BORDER. THE OTHER FORCING ACROSS CENTRAL MN/NORTHERN WI WHICH WAS ASSOCIATED WITH A STRONG JET STREAK OF 120-130 KTS MOVING ACROSS SD EARLY THIS MORNING. THE ACTIVITY IN CENTRAL MN/N WI HAS BEEN RELATIVELY LIGHT IN RESPECT TO QPF AMTS...BUT COVERAGE HAS BEEN FAIRLY CONSISTENT FROM NEAR KBRD TO SOUTH OF KDLH. ALTHOUGH THE JET STREAK WILL CONTINUE TO ENHANCE PRECIPITATION ACROSS N WI/WC MN THRU SUNRISE...HOW FAR SOUTH THIS BAND EXPANDS REMAINS IN QUESTION. ANOTHER VIGOROUS SHRTWV JUST SOUTH OF WINNIPEG IS PROGGED TO MOVE S/SE ACROSS MN OVER THE NEXT 6 TO 12 HRS. THIS AREA OF ENHANCED LIFT SHOULD CONTINUE AT LEAST A SMALL CHC OF SHRA ACROSS FAR S MN/WC WI. IN ADDITION...ANOTHER JET STREAK ACROSS WESTERN NEBRASKA MAY CONTRIBUTE TO ADDITIONAL LIFT ACROSS FAR S MN AFT 12Z. SIMILAR SCENARIOS WITH -SHRA EXPANDING ACROSS FAR S MN AFT 12Z IS DEPICTED IN THE LATEST WRF REFLECTIVITY MODEL ALONG WITH MPX LOCAL MODEL DEPICTION OF THE REFLECTIVITY PATTERN. ONCE THE MEAN UPPER WAVE MOVES ACROSS MN...EXPECT THE PRECIPITATION TO END...WITH SOME ISOLD -SHRA ACROSS THE FAR EASTERN FA DUE TO RESIDUAL MOISTURE AND AMPLE COLD AIR ALOFT TO GENERATE INSTABILITY SHRA IF SOME BREAKS IN THE OVERCAST DEVELOP. ONE MINOR CHG IN THE UPCOMING WEEKEND FORECAST IS BASED ON ANOTHER SHRTWV MOVING SE ACROSS THE WESTERN GREAT LAKES SATURDAY AFTN/EVENING. ALTHOUGH DEEP MOISTURE WILL BE LIMITED...STRONG ISENTROPIC LIFT ASSOCIATED WITH THE DIVING SHRTWV SHOULD AT LEAST GENERATE A FEW SHRA OVER PORTIONS OF WC WI. EVEN SOME LAKE EFFECT SHRA MAY CLIP SOME OF OUR EASTERN FA DUE TO THE STRENGTH OF THIS SHRTWV. TEMPS WILL BE TRICKY FOR SATURDAY MORNING...AND AGAIN SUNDAY MORNING DUE TO WIND SPDS INCREASING AHEAD OF SATURDAY SYSTEM. EXPECT THAT SATURDAY MAY NOT BE THE COLDEST MORNING WITH SOME MIXING IN THE LOW LEVELS. SUNDAY MORNING LOOKS TO BE THE COOLEST AS THE RIDGE BUILDS OVERHEAD. ALTHOUGH AM NOT EXPECTING ANY WIDESPREAD FROST SUNDAY MORNING...THERE WILL BE THE TYPICAL LOW LYING AREAS IN CENTRAL MN...AND WC WI WHERE THE MERCURY WILL DIP INTO THE MID 30S. LATER FORECASTS CAN START TO INTRODUCE PATCHY FROST IF THIS SCENARIO DEVELOPS. AFT SUNDAY...A STRONG RETURN FLOW WILL COMMENCE WITH FIRE WX CONCERNS MONDAY AFTN DUE TO THE STRENGTH OF THE SFC WINDS...AND RH FIELDS DROPPING INTO THE CRITICAL RANGES. WILL HIGHLIGHT THE HWO WITH FIRE WX CONCERNS FOR MON...AND POSSIBLY TUE IN THE SE FA. ..JLT.. && .AVIATION.../06Z TAF ISSUANCE/ SFC LOW TAKING SHAPE THIS EVENING NEAR OMAHA...WITH COLD FRONT AT 4Z STILL HUNG UP FROM NEAR RWF UP TOWARD CAMBRIDGE. THIS FRONT WILL START MAKING PROGRESS SE AFTER 6Z AS THE LOW HEADS INTO CENTRAL IA. HRRR HAS PICKED UP ON CURRENT CONDITIONS WELL...AND IN GENERAL FOLLOWED IT FOR SHRA TIMING IN TAFS...WHICH RESULTED IN PUSHING -SHRA MENTION BACK A COUPLE OF HOURS IN MOST CASES. STILL EXPECT TWO PRIMARY AREAS OF PRECIP TONIGHT...A BAND OF RAIN MAINLY NORTH OF I-94 WITH THUNDERSTORMS ACROSS IA. CONFIDENCE DECREASING IN SEEING MVFR CIGS OVERNIGHT...AS MODELS SHOWING THERE SHOULD ALREADY BE SUCH CIGS OVER CENTRAL MN...BUT ALL CIGS ARE STILL OVER 050. LEFT A BRIEF MENTION FOR MVFR CIGS ONLY AT WI TERMINALS... WHERE HEAVIEST PRECIP LOOKS TO FALL. FOR TOMORROW...STRONG COLD AIR ADVECTION WILL SUPPORT BKN-OVC CIGS BETWEEN 040 AND 060 THROUGH MUCH OF THE AFTERNOON. FOR WINDS...E-NE WINDS WILL QUICKLY SWING AROUND TO THE NW THIS TONIGHT AS THE SFC LOW WORKS ACROSS IA. NW SPEEDS WILL QUICKLY PICK UP IN THE MORNING...WITH GUSTS INTO THE 20S STILL LOOKING GOOD. KMSP...WILL CONTINUE TO SEE BOUTS OF VFR SHOWERS THROUGH ABOUT 10Z. WITH LACK OF MVFR CIGS ACROSS CENTRAL MN...AND VERY DRY LOW LEVELS IN 00Z KMPX SOUNDING...REMOVED MVFR CIG MENTION...THOUGH AN 020 TO 030 CIG CAN NOT BE RULED OUT MAINLY BETWEEN 10Z AND 13Z. /OUTLOOK FOR KMSP/ SATURDAY THROUGH TUESDAY...VFR CONDITIONS EXPECTED. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ JLT/MPG
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1105 PM CDT THU SEP 6 2012 .UPDATE... 06Z AVIATION DISCUSSION ADDED BELOW. && .DISCUSSION... /ISSUED 332 PM CDT THU SEP 6 2012/ AT 3 PM...A COLD FRONT WAS ANALYZED ROUGHLY FROM KHYR...TO KAXN...AND KHON. TEMPERATURES NORTH HAVE FALLEN INTO THE 50S AND 60S WITH 70S AND 80S COMMON SOUTH. THIS FRONT WILL CONTINUE TO TREK SOUTH THIS EVENING AND CLEAR THE FORECAST AREA BY MIDNIGHT. TONIGHT...POSITIVELY TILTED UPPER LEVEL WAVE WILL TRAVERSE THE REGION OVER THE NEXT 24 HOURS. AS IT DOES SO...UPPER LEVEL FORCING ASSOCIATED WITH THE POSITIVE VORTICITY ADVECTION WILL RESULT IN LOW/MID LEVEL CONVERGENCE AS ALREADY SEEN IN THE H850 SPC MESOANALYSIS. THIS NORTH/SOUTH CONVERGENCE ALONG THE LATITUDINALLY ORIENTED ISENTROPES WILL INDUCE AN AREA OF FRONTOGENESIS ACROSS CENTRAL MN AND NORTHERN WI. PRECIPITATION IS EXPECTED TO INCREASE IN COVERAGE THIS EVENING...WITH THE HEAVIEST BAND SETTING UP NORTH OF I-94. HAVE LEFT ISOLATED THUNDER MENTION IN THE GRIDS GIVEN THE STRONG SYNOPTIC FORCING AND THIN AREA OF CAPE AS SEEN IN THE FORECAST SOUNDINGS. AS OF THIS AFTERNOON...ALREADY HAD A FEW THUNDERSTORMS DEVELOPING ACROSS THE WESTERN CWA. FURTHER TO THE SOUTH THE LOW LEVEL JET WILL INCREASE OVERNIGHT WITH ELEVATED THUNDERSTORMS EXPECTED ACROSS IOWA LATE THIS EVENING. THE BEST MOISTURE CONVERGENCE AS SEEN IN THE H925 FIELDS IS SOUTH OF THE IA/MN BORDER...BUT HAVE A SECOND AREA OF CONCENTRATED POPS ACROSS THE SOUTH TONIGHT. PRECIPITATION WILL RAPIDLY END FRIDAY MORNING AS DRIER MID LEVEL AIR PROPAGATES SOUTHWARD. STEEP LOW LEVEL LAPSE RATES IN STRONG CAA ENVIRONMENT WILL MAINTAIN STRATOCU FIELD INTO LATE AFTERNOON. REMOVED SCHC POPS OVER WCTRL WI DURING THE AFTERNOON WITH A VERY SHALLOW CLOUD DEPTH. GUSTY WINDS EXPECTED WITH FORECAST SOUNDINGS INDICATING A FEW GUSTS OF 25 TO 30 MPH POSSIBLE. MIXING 925 MB TEMPS DOWN TO THE SURFACE INDICATE TEMPERATURES MAXING OUT ONLY IN THE MID 60S. CLEAR AND COLD NIGHT EXPECTED FRIDAY NIGHT. HIGH PRESSURE SLIDING WELL SOUTH INTO THE CENTRAL PLAINS SHOULD KEEP WINDS SOMEWHAT MIXED THROUGH THE NIGHT IN MOST LOCATIONS...PREVENTING TEMPERATURES FROM BOTTOMING OUT TOO MUCH. STILL COULD SEE A FEW STATIONS FALL INTO THE UPPER 30S...BUT THE THREAT OF ANY FROST IS NEGLIGIBLE. A HIGHLY AMPLIFIED PATTERN WILL PLAY OUT FOR THE WEEKEND WITH THE CWA STUCK BETWEEN THE TROUGH AND THE RIDGE. A WEAK UPPER DISTURBANCE EMBEDDED IN THE STRONG NORTH FLOW MAY BRING A THREAT FOR A SHOWER OVER WCTRL WI SATURDAY AFTERNOON. OTHERWISE...DRY CONDITIONS ARE EXPECTED. THE WHOLE PATTERN WILL SHIFT EAST EARLY NEXT WEEK WITH MUCH WARMER TEMPERATURES RETURNING. THICKNESSES WILL RISE FROM AROUND 560 DAM SATURDAY AFTERNOON TO 576+ DAM BY TUESDAY. SHOULD SEE HIGHS APPROACHING 90 IN SWRN MN MONDAY...AND UPPER 80S AT LEAST ACROSS WCTRL WI/SERN MN TUESDAY AS THE THERMAL RIDGE SETTLES OVERHEAD. THESE HIGHS ARE SEVERAL DEGREES ABOVE GUIDANCE VALUES WHICH SEEM TOO COOL IN SUCH A PATTERN. THE NEXT FRONT WILL ARRIVE TUESDAY AFTERNOON/NIGHT BUT SHOULD SWING THROUGH MOSTLY DRY. MAINTAINED SCHC POPS WITH IT. A MILD/WARM ZONAL FLOW RETURNS FOR THE MIDDLE OF NEXT WEEK WITH NO REAL COLD AIR INTRUSIONS IN SIGHT. && .AVIATION.../06Z TAF ISSUANCE/ SFC LOW TAKING SHAPE THIS EVENING NEAR OMAHA...WITH COLD FRONT AT 4Z STILL HUNG UP FROM NEAR RWF UP TOWARD CAMBRIDGE. THIS FRONT WILL START MAKING PROGRESS SE AFTER 6Z AS THE LOW HEADS INTO CENTRAL IA. HRRR HAS PICKED UP ON CURRENT CONDITIONS WELL...AND IN GENERAL FOLLOWED IT FOR SHRA TIMING IN TAFS...WHICH RESULTED IN PUSHING -SHRA MENTION BACK A COUPLE OF HOURS IN MOST CASES. STILL EXPECT TWO PRIMARY AREAS OF PRECIP TONIGHT...A BAND OF RAIN MAINLY NORTH OF I-94 WITH THUNDERSTORMS ACROSS IA. CONFIDENCE DECREASING IN SEEING MVFR CIGS OVERNIGHT...AS MODELS SHOWING THERE SHOULD ALREADY BE SUCH CIGS OVER CENTRAL MN...BUT ALL CIGS ARE STILL OVER 050. LEFT A BRIEF MENTION FOR MVFR CIGS ONLY AT WI TERMINALS... WHERE HEAVIEST PRECIP LOOKS TO FALL. FOR TOMORROW...STRONG COLD AIR ADVECTION WILL SUPPORT BKN-OVC CIGS BETWEEN 040 AND 060 THROUGH MUCH OF THE AFTERNOON. FOR WINDS...E-NE WINDS WILL QUICKLY SWING AROUND TO THE NW THIS TONIGHT AS THE SFC LOW WORKS ACROSS IA. NW SPEEDS WILL QUICKLY PICK UP IN THE MORNING...WITH GUSTS INTO THE 20S STILL LOOKING GOOD. KMSP...WILL CONTINUE TO SEE BOUTS OF VFR SHOWERS THROUGH ABOUT 10Z. WITH LACK OF MVFR CIGS ACROSS CENTRAL MN...AND VERY DRY LOW LEVELS IN 00Z KMPX SOUNDING...REMOVED MVFR CIG MENTION...THOUGH AN 020 TO 030 CIG CAN NOT BE RULED OUT MAINLY BETWEEN 10Z AND 13Z. /OUTLOOK FOR KMSP/ SATURDAY THROUGH TUESDAY...VFR CONDITIONS EXPECTED. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$
AREA FORECAST DISCUSSION
NWS KANSAS CITY/PLEASANT HILL MO
1211 AM CDT FRI SEP 7 2012 ...UPDATED AVIATION DISCUSSION... .DISCUSSION... Overnight rain chances diminishing with a much better bet starting Friday morning. The convection which formed along the dryline from north central KS through the TX Panhandle has steadily weakened after pulling away from the boundary while the low level jet has refocused west of ICT and is enhancing the activity headed for south central KS. Latest HRRR finally caught on while 00Z NAM continues to be basically dry overnight. Cold front is now over central NE and dropping southeast. Will cut back on pops with chance wording held back until after 09z. Eastern counties looking dry overnight. Much stronger forcing aloft arrives Friday mid/late morning as a shortwave deepens as it drops southeast through NE. High PoPs for Friday morning/afternoon with rain threat quickly ending from nw-se. MJ && .PREV DISCUSSION... /340 PM CDT Thu Sep 6 2012/ Short term concerns remain focused on precipitation potential overnight and into Friday. Early this afternoon, shortwave energy interacting with a well-defined corridor of 850:700 mb moisture and prevailing westerly 700:500 mb flow produced a large complex of thunderstorms in areas just south of the CWA boundary. Subsidence behind this shortwave has allowed temperatures to jump back into the lower 90s in the southern CWA and should stabilize the southeastern zones into this evening. Further northwest, eyes begin to turn towards an autumn-like cold front stretching from north to south from central South Dakota through central Nebraska and northwestern Kansas. A strong EML continues to advect into area along and ahead of this surface boundary, with 700 mb temperatures of 11-12C common into eastern Nebraska. That said, a small CU field has developed over north central Kansas this afternoon, which could be enhanced by a weak shortwave exiting eastern Colorado. Should this activity develop, it would track into south central Kansas this evening. While 19Z aircraft sounding indicated 700mb temps of only 9-10C, latest RAP/HRRR continue to advect warmer air aloft into the CWA which should prevent an extensive eastward track of activity. The primary focus for thunderstorms this evening appears to be turning towards northeastern Nebraska, northwestern Iowa and southeast South Dakota, where strong moisture transport has been pointed through the daytime hours. Initial thoughts are that convection will begin to break out early this evening along a weak surface low near Sioux Falls as cooling aloft and lift on the nose of a 35 knot LLJ allows convection to overcome a weaker cap. With low level winds remaining focused well away from the CWA this evening, have significantly trimmed back PoPs through 06z. Beyond 06z, some questions continue to linger as to whether weak lift will be able to overcome a stronger cap over southern Nebraska. Latest guidance continues to propagate an MCS into portions of central Iowa and northern Illinois after midnight with much of the area remaining dry through nearly 09z. Will still begin to increase PoPs after midnight as lingering moisture axis will begin to interact more directly with veering LLJ which could produce scattered thunderstorms. Higher instability does begin to advect northeast after midnight, creating some potential for an elevated hail threat. While boundary layer will stabilize to some degree, surface winds should remain fairly mixy, which could also promote a localized damaging wind threat given LLJ running nearly parallel to the surface boundary. A better chance for thunderstorm development looks to begin after the 09Z timeframe when 850mb trough begins to surge southeast and frontogenesis intensifies. By 12Z the surface front should have already reached the St. Joseph area, with precipitation rapidly beginning to increase. Strong pressure rises behind the front will push the boundary through the CWA by the noon hour, with period of showers and embedded thunder through early afternoon. Will bump up PoPs further. While PWAT values will be higher than normal, the rapid storm movement should limit the heavy rainfall threat. Precipitation will rapidly come to an end Friday afternoon, with the surface high plunging southward. Beyond Friday night, the only concerns will be with temperatures as high pressure dominates the weekend. Readings on Saturday will be nearly perfect, with 70s expected and a light northerly wind. Have lowered overnight lows heading into Sunday as winds turn light and variable. Wouldn`t be shocked to see 40 degree readings fairly widespread. Dux Sunday - Wednesday: The region will still be under the influence of a modified Canadian high pressure area Sunday resulting in quiet and seasonally cool conditions. That high will gradually shift east of the region late Sunday and into Monday with winds becoming southerly by Monday. Temperatures should still be cooler than normal Monday but a rebound is expected by Tuesday and Wednesday as thickness values increase and temperatures aloft warm. The high will have swept moisture into the central Gulf of Mexico, so despite warmer temperatures, moisture will be limited and the chances for precipitation will be very small through Tuesday night or Wednesday morning. By Wednesday afternoon, another wave will track across the Northern Plains with its associated cold front moving into Missouri Wednesday evening or night. This will bring us our next chance for showers and storms, though chances don`t look especially good at this point. CDB && .AVIATION... For the 06Z TAFs: Rain chances have diminished considerably through 12z as upstream convection over KS fell apart as earlier thought. Will need to await the arrival of the cold front which will track southeast and move through the terminals between 12-16Z. While isolated convection is possible in the pre-frontal zone will need to await the arrival of much better upper support as a sharpening shortwave swings through NE. Frontogenetical forcing aloft will also play a role in generating widespread convection by late morning and lasting through mid afternoon. How much thunder will accompany the showers is debatable but still believe it best to keep it in a TEMPO group vs prevailing. Some potential for MVFR ceilings with the heavier showers as the rain band fills in by the noon hour. Gusty north winds will gradually subside by late afternoon with rapidly clearing skies by sunset. MJ && .EAX WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ WFO EAX
AREA FORECAST DISCUSSION
NWS ELKO NV
1056 PM PDT THU SEP 6 2012 .SYNOPSIS...A FEW SHOWERS WILL MOVE ACROSS MUCH OF EASTERN NEVADA THROUGH EARLY FRIDAY MORNING. FRIDAY AND SATURDAY WILL BE MILD AND MAINLY DRY WITH THUNDERSTORMS CONFINED TO SOUTH OF HIGHWAY 50. THUNDERSTORMS WILL INCREASE AGAIN SUNDAY AND MONDAY AS A LOW PRESSURE SYSTEM MOVES THROUGH. && .UPDATE...ADDED SHOWERS IN THE 06Z-12Z PERIOD...NONE OF THE MODELS PICKED UP ON THE ACTIVITY. CONVECTION HAS ENDED FOR THE NIGHT SO REMOVED MENTION OF THUNDERSTORMS. && .PREV DISCUSSION... /ISSUED AT 303 PM / SYNOPSIS...LOW PRESSURE SYSTEM BRINGS PARTLY TO MOSTLY CLOUDY SKIES TO NORTHERN AND CENTRAL NEVADA THIS AFTERNOON AND EVENING. ISOLATED TO SCATTERED THUNDERSTORMS EXPECTED OVER WHITE PINE COUNTY THIS AFTERNOON. FRIDAY AND SATURDAY WILL BE MILD AND DRY. NEXT ROUND OF THUNDERSTORMS EXPECTED SUNDAY AFTERNOON. SHORT TERM...TONIGHT THROUGH FRIDAY. THE REMNANTS OF A PACIFIC LOW ARE PUSHING ACROSS THE GREAT BASIN BRINGING CLOUD COVERAGE...SLIGHTLY COOLER TEMPS AND A BAND OF CONVECTION TO PORTIONS OF CENTRAL NEVADA...NAMELY WHITE PINE COUNTY. NUMEROUS LIGHTNING STRIKES AND PEA SIZED HAIL HAVE ALREADY BEEN OBSERVED FROM SOUTHEASTERN ELKO COUNTY TO LUND ALONG A NORTHEAST TO SOUTHWEST ORIENTED AXIS. THE NAM12 AND HRRR PINGED INTO UNSTABLE CONDITIONS OVER CENTRAL NEVADA...DEPICTING +400 J/KG OVER WHITE PINE AND THE EASTERN PORTION OF NORTHERN NYE COINCIDENT WITH NEGATIVE LIFTED INDICES. MORE CONVECTION ON TAP FOR TONIGHT. THE NAM12 AND THE GFS40 ARE BOTH DRIER AND SLIGHTLY MORE STABLE TOMORROW...AS THE RIDGE AXIS BUILDS BACK INTO THE LKN CWA. LONG TERM...FRIDAY NIGHT THROUGH NEXT THURSDAY. LOW PRESSURE SYSTEM OFF PACIFIC NORTHWEST COAST. HIGH PRESSURE RIDGE OVER GREAT BASIN. LONG RANGE MODELS HAVE THE LOW TRACKING NORTH UP THE COAST BEFORE BEING KICKED NORTHEAST LATE SATURDAY. THIS WILL RESULT IN RELATIVELY DRY AIR FRIDAY NIGHT AND SATURDAY OVER THE GREAT BASIN WITH RIDGE AXIS OVERHEAD. WHEN THE LOW KICKS OUT...THE RIDGE FIRST FLATTENS...THEN DRIFTS EAST ON SUNDAY. THIS WILL OPEN UP MOISTURE FROM THE SUB-TROPICS TO MOVE NORTH INTO NEVADA...ESPECIALLY OVER THE SOUTHEAST HALF OF THE FORECAST AREA ON SATURDAY NIGHT THROUGH TUESDAY. TEMPS WILL START NEAR 90 AT MOST VALLEY LOCATIONS...DROPPING TO NEAR NORMAL...THE 80S...BY EARLY IN THE WEEK. LOW TEMPS WILL START IN THE 50S...AND END UP IN THE 40S IN THE POPULATED VALLEY LOCATIONS. A FEW 30S COULD CREEP IN AS SKIES CLEAR OUT MID WEEK. AVIATION...SCT/BKN MID CLOUDS ACROSS NEVADA THROUGH 03Z FRI. AREA OF CONVERGING WINDS WILL FIRE UP THUNDERSTORMS IN WHITE PINE COUNTY AND AFFECT KELY THROUGH SUNSET. SOME SHOWERS MAY AFFECT KEKO. KWMC AND KTPH SHOULD REMAIN STORM FREE. GUSTY WINDS AT ALL BUT KEKO WILL REDUCE CLOUD COVER AFTER SUNSET AND ON FRIDAY. FIRE WEATHER...THIS AFTERNOON THUNDERSTORM ACTIVITY WILL BE CONCENTRATED OVER 455 AS A WELL DEFINED BAND MOVES THROUGH. THE PWS HAVE BEEN OVER .80 OF AN INCH IN 455 ON THE MODELS...SUFFICIENT TO PRODUCE WETTING RAINS. NUMEROUS LIGHTNING STRIKES ALREADY OBSERVED OVER WHITE PINE COUNTY TODAY. MOSTLY DRY AND MILD CONDITIONS EXPECTED FRIDAY AND SATURDAY. NEXT WAVE OF THUNDERSTORM ACTIVITY EXPECTED SUNDAY AND MONDAY AFTERNOONS. && .LKN WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 92/99
AREA FORECAST DISCUSSION
NWS RALEIGH NC
547 AM EDT FRI SEP 7 2012 .SYNOPSIS... A WEAK SURFACE TROUGH WILL STALL OVER THE EASTERN CAROLINAS TODAY. A DEEPENING LOW PRESSURE SYSTEM OVER THE GREAT LAKES WILL PUSH A STRONG COLD FRONT THROUGH THE CAROLINAS SATURDAY AFTERNOON AND EVENING. COOLER AND DRIER CONDITIONS WILL PREVAIL IN THE WAKE OF THE FRONT SUNDAY THROUGH EARLY NEXT WEEK AS HIGH PRESSURE BUILDS INTO THE REGION. && .NEAR TERM /TODAY AND TONIGHT/... AS OF 330 AM FRIDAY... OVERVIEW: AN H5 SHORTWAVE CENTERED NEAR THE HWY 1 CORRIDOR AT 06Z THIS MORNING IS EXPECTED TO TRACK SLOWLY EAST TOWARD THE CAROLINA COAST THIS AFTERNOON BEFORE FURTHER WEAKENING AND SHIFTING OFFSHORE THIS EVENING/TONIGHT. A SFC-H85 TROUGH ATTENDANT THE SHORTWAVE IS PROGGED TO STALL OUT OVER THE COASTAL PLAIN TODAY...THEN DISSIPATE TONIGHT AS HEIGHT FALLS OVERSPREAD THE AREA FROM WEST-EAST IN ADVANCE OF AN AMPLIFYING UPPER LEVEL TROUGH AND ASSOCIATED SURFACE COLD FRONT PROGRESSING INTO THE OH VALLEY. PRECIPITATION CHANCES: MOISTURE THROUGHOUT THE COLUMN WILL VARY WIDELY ACROSS THE AREA TODAY...BETWEEN A DRY AIRMASS (PWAT VALUES ~1.00") OVER THE MOUNTAINS AND A VERY MOIST AIRMASS (PWAT VALUES ~2.00") OVER THE COASTAL CAROLINAS WHERE THE AFOREMENTIONED SFC-H85 TROUGH IS PROGGED TO STALL OUT. THE LATEST GFS/RAP MODEL GUIDANCE INDICATES THE DRIER AIRMASS TO THE NORTH AND WEST ADVECTING INTO CENTRAL NC THROUGHOUT THE MORNING...WITH PWAT VALUES FALLING TO 1.00-1.25" OVER THE BULK OF THE AREA...EXCEPT THE SOUTHEAST COASTAL PLAIN WHERE PWAT VALUES MAY LINGER NEAR ~1.75". THE LATEST 00Z NAM APPEARS TO BE AN OUTLIER...INDICATING DEEPER MOISTURE LINGERING MUCH FURTHER WEST (TO THE TRIANGLE/HWY 1 CORRIDOR) THAN EITHER THE 00Z GFS OR 06Z RAP. GIVEN THAT THE GFS HAS SUPPORT FROM THE MOST RECENT RAP MODEL RUN... THE NAM WILL BE DISREGARD AT THIS TIME. ANTICIPATE THAT INSTABILITY WILL GENERALLY BE CONFINED TO AREAS SOUTH AND EAST OF THE TRIANGLE DURING PEAK HEATING...WITH MLCAPE VALUES RANGING FROM 500-1500 J/KG IN THE SOUTHEAST COASTAL PLAIN...PRIMARILY IN CUMBERLAND/SAMPSON/ WAYNE COUNTIES. SOME UNCERTAINTY IS PRESENT...AND THE INSTABILITY AXIS COULD BE SLIGHTLY FURTHER TO THE EAST OR WEST...DEPENDING ON THE LOCATION OF THE SFC-H85 TROUGH. FORCING FOR ASCENT TODAY WILL PRIMARILY BE ASSOCIATED WITH LOW-LEVEL CONVERGENCE IN VICINITY OF THE SEABREEZE AND THE SFC-H85 TROUGH OVER THE COASTAL CAROLINAS. SHORTWAVE ENERGY PROGRESSING INTO ILLINOIS AT 06Z WILL PROGRESS EAST THROUGH THE MID-ATLANTIC THIS AFTERNOON...RESULTING IN WEAK DPVA OVER NORTHERN PORTIONS OF THE STATE. WITH THE ABOVE IN MIND...WILL INDICATE A 20-30% CHANCE OF SHOWERS/STORMS IN THE SOUTHEAST COASTAL PLAIN CLOSER TO THE BEST MOISTURE/INSTABILITY AND LOW-LEVEL FORCING DURING PEAK HEATING. ANTICIPATE THAT THE DRIER /MORE STABLE/ AIRMASS IN PLACE OVER NORTHERN PORTIONS OF THE AREA WILL PRECLUDE A CHANCE FOR CONVECTION WITH THE AFOREMENTIONED SHORTWAVE ENERGY. WILL KEEP THE FORECAST DRY OVERNIGHT. TEMPERATURES: GIVEN LESS CLOUD COVER AND 1000-850 MB THICKNESSES SIMILAR TO PREVIOUS DAYS...EXPECT HIGHS IN THE UPPER 80S TO 90-91F. LOWS TONIGHT IN THE UPPER 60S TO LOWER 70S...WARMEST WHERE A LIGHT SOUTHERLY BREEZE IS PRESENT AS THE MSLP GRADIENT BEGINS TO TIGHTEN FROM THE WEST PRIOR TO SUNRISE. HAZARDOUS WEATHER: CONVECTION ALLOWING MODELS DEVELOP ISOLD CONVECTION OVER THE FAR SOUTHEAST COASTAL PLAIN THIS AFTERNOON...IN ASSOC/W THE LINGERING SFC-H85 TROUGH AND/OR THE SEABREEZE. DEEP-LAYER SHEAR WILL BE NEGLIGIBLE TODAY (< 15 KT IN SOUTHEAST NC)...AND DESTABILIZATION IS EXPECTED TO YIELD RELATIVELY MARGINAL INSTABILITY WITH MLCAPE VALUES IN THE 500-1500 J/KG RANGE...SO ANY CONVECTION THAT DEVELOPS WILL BE UNORGANIZED AND SHORT-LIVED. HOWEVER...THE ADVECTION OF A DRIER MID-LEVEL AIRMASS INTO THE AREA WILL RESULT IN A MARKED INCREASE IN DCAPE THIS AFTERNOON...EVEN IN THE SOUTHEAST COASTAL PLAIN...WHERE VIRTUALLY ALL MODEL GUIDANCE INDICATE VALUES IN THE 1000-1500 J/KG RANGE. WITH THIS IN MIND...AN ISOLD UPDRAFT INTERACTING WITH OR ENHANCED BY OUTFLOW IN THE PRESENCE OF RELATIVELY HIGH DCAPE COULD YIELD A BRIEF/ISOLD INSTANCE OF DAMAGING WIND...PRIMARILY IN CUMBERLAND/SAMPSON/WAYNE COUNTIES...THOUGH THE PROBABILITY IS TOO LOW TO MENTION IN THE HAZARDOUS WEATHER OUTLOOK. -VINCENT && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 303 AM FRIDAY... ...SLIGHT CHANCE OF SEVERE THUNDERSTORMS SATURDAY AFTERNOON AND EARLY EVENING... THE BIG PATTERN CHANGE THAT HAS BEEN ADVERTISED FOR DAYS WILL START WITH A BANG SATURDAY AFTERNOON. A POSITIVELY TILTED MID-UPPER TROUGH IS FORECAST TO AMPLIFY AS IT DIVES SE ACROSS THE CENTRAL APPALACHIANS AND MID-ATLANTIC STATES SATURDAY AFTERNOON. THE ASSOCIATED COLD FRONT WILL PUSH INTO THE REGION DURING PEAK HEATING. THE THE MOST FAVORABLE WINDS ALOFT FOR ORGANIZED SEVERE STORMS MAY REMAIN JUST TO OUR NORTH. HOWEVER... STRONG SURFACE HEATING IS EXPECTED TO DESTABILIZE THE BOUNDARY LAYER BY EARLY AFTERNOON OUT AHEAD OF A PRE-FRONTAL TROUGH/REMNANT CONVECTIVE OUTFLOW BOUNDARY. THIS BOUNDARY SHOULD BEGIN TO ARRIVE DURING PEAK HEATING FOR MUCH OF CENTRAL NORTH CAROLINA. WITH STRONG HEATING... TEMPERATURES SHOULD REACH AROUND 90 BY EARLY AFTERNOON THROUGHOUT MOST OF THE REGION. THIS WILL COMBINE WITH DEW POINTS FORECAST TO BE IN THE LOWER 70S TO PRODUCE FAVORABLE PARAMETERS FOR MULTICELL STORM CLUSTERS. A FEW OF THESE STORMS MAY BECOME SEVERE WITH THE MAIN THREAT BEING DAMAGING WET DOWNBURSTS. THE MULTICELL CLUSTERS MAY EVOLVE INTO A LINE BY LATE AFTERNOON AGAIN FAVORING ISOLATED DAMAGING WIND GUSTS ALONG LEWP/BOWING SEGMENTS. THERE MAY BE A FINAL LINE OF CONVECTION WITH THE MAIN COLD FRONT LATER IN THE DAY OR EVENING. REGARDLESS... SATURDAY AFTERNOON AND EVENING IS EXPECTED TO BE ACTIVE ONCE AGAIN. IN ADDITION TO THE SLIGHT CHANCE OF SEVERE STORMS... FREQUENT CG LIGHTNING AND LOCALLY HEAVY RAIN IS AGAIN EXPECTED WITH THE STORMS. EARLY MORNING STRATUS WILL GIVE WAY TO PARTLY SUNNY SKIES. WE WILL CARRY LIKELY POP FOR SHOWERS AND THUNDERSTORMS IN THE AFTERNOON AND EVENING. HIGHS 90-93 EXCEPT UPPER 80S NW. THE STORMS WILL GRADUALLY END SATURDAY EVENING NW... AND ELSEWHERE OVERNIGHT WITH THE ACTUAL COLD FRONTAL PASSAGE. GOOD DRY/COOL AIR ADVECTION WILL ARRIVE MAINLY BETWEEN 06Z-12Z. THIS LATE CAA ARRIVAL COMBINED WITH LINGER CLOUDS SHOULD KEEP LOWS MILD AND LIKELY ABOVE GUIDANCE. WE WILL CARRY 60-65 MOST AREAS. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 303 AM FRIDAY... A LONG AWAITED BREATHER FROM ALL THE VERY WARM/HUMID/THUNDERY WEATHER WILL BEGIN SUNDAY. A REFRESHING BREEZE WILL COMBINE WITH AMPLE SUNSHINE TO BRING A SPRING-LIKE FEEL. HIGHS OF 78-83 EXPECTED (WITH DEW POINTS IN THE 40S NW AND LOWER 50S SE). A NORTHERLY BREEZE AT 10-15 MPH WILL MAKE IT FEEL APRIL-FRESH AT TIMES. MONDAY THROUGH THURSDAY... EXPECT DRY AND SEASONABLY COOL CONDITIONS MONDAY AND TUESDAY... WITH MODERATING DAYTIME TEMPS WED AND THUR. MOSTLY CLEAR/MOSTLY SUNNY WITH LOWS IN THE 50S EACH DAY. HIGHS 75 TO 80 MON-TUE... WARMING INTO THE LOWER TO MID 80S BY THURSDAY. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 155 AM FRIDAY... 24-HR TAF PERIOD: IFR TO VLIFR CEILINGS AND VISBYS ARE PRESENT OVER PORTIONS OF THE NORTHERN PIEDMONT (INCLUDING RDU/RWI) AS OF 06Z. GIVEN A VERY MOIST LOW-LEVEL AIRMASS...LIGHT/CALM WINDS...AND A DRIER MID-LEVEL AIRMASS PROGRESSING INTO THE AREA FROM THE NORTHWEST...EXPECT THAT ALL TAF SITES WILL SEE CONDITIONS DETERIORATE INTO THE IFR TO VLIFR RANGE BETWEEN 06-12Z THIS MORNING. FOG AND LOW CEILINGS ARE EXPECTED TO LIFT AND SCATTER TO VFR BETWEEN 12-15Z AT INT/GSO/RDU. CONDITIONS SHOULD BE SLOWER TO IMPROVE AT THE FAY/RWI TERMINALS WHERE MOISTURE IS DEEPER AND MVFR CEILINGS MAY PERSIST THROUGH ~18Z. ISOLATED SHOWERS AND STORMS WILL BE POSSIBLE DURING THE AFTERNOON...THOUGH CHANCES WILL MOST LIKELY BE LIMITED TO THE FAY TERMINAL. OTHERWISE...EXPECT VFR CONDITIONS TO PREVAIL THIS AFTERNOON THROUGH 06Z TONIGHT. LOW-LEVEL SOUTHERLY FLOW WILL STRENGTHEN PRIOR TO SUNRISE SATURDAY IN ADVANCE OF AN APPROACHING COLD FRONT...AND IT IS POSSIBLE THAT MVFR/IFR CEILINGS MAY DEVELOP BETWEEN 09-12Z SAT. LOOKING AHEAD: A STRONG COLD FRONT WILL TRACK EAST INTO CENTRAL NC SATURDAY AFT/EVE. A LINE OF SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ALONG AND AHEAD OF THE FRONT. RAIN MAY LINGER INTO SATURDAY NIGHT AND EARLY SUNDAY MORNING IN THE WAKE OF THE FRONTAL PASSAGE...PRIMARILY AT THE FAY/RWI TERMINALS. VFR CONDITIONS WILL RULE IN THE WAKE OF THE COLD FRONT SUNDAY THROUGH EARLY NEXT WEEK AS COOL AND DRY HIGH PRESSURE BUILDS INTO THE CAROLINAS. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM....VINCENT SHORT TERM...BADGETT LONG TERM...BADGETT AVIATION...VINCENT
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
402 AM EDT FRI SEP 7 2012 .SYNOPSIS... LONG PERIOD SWELLS FROM LESLIE WILL IMPACT THE BEACHES THROUGH THE WEEKEND...INCREASING THE RISK FOR STRONG AND FREQUENT RIP CURRENTS AND LARGER THAN NORMAL BREAKERS. SOME BEACH EROSION MAY EVEN BE OBSERVED. A WEAK RIDGE OF HIGH PRESSURE WILL REMAIN ALONG THE COAST AS A TROUGH OF LOW PRESSURE SLOWLY APPROACHES THE CAROLINAS FROM THE WEST TODAY. A STRONGER FRONTAL SYSTEM WILL USHER IN FALL-LIKE WEATHER SUNDAY...WITH DRIER AND COOLER HIGH PRESSURE BUILDING IN THROUGH NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 300 AM FRIDAY...A WEAK 500 MB DISTURBANCE AND SURFACE TROUGH/ OUTFLOW BOUNDARY HAVE BEEN MAINTAINING SCATTERED CONVECTION THROUGH THE EARLY MORNING HOURS. ACTIVITY HAS BEEN MOST PREVALENT IN THE SC PEE DEE REGION WHERE RADAR ESTIMATES UP TO 4.50 INCHES OF RAIN EXIST ACROSS PORTIONS OF FLORENCE...MARION AND WILLIAMSBURG COUNTIES. THERMODYNAMICALLY THIS CONVECTION IS ELEVATED...ROOTED IN A LAYER 4000-7000 FT ABOVE THE GROUND. AS THE UPPER DISTURBANCES WEAKENS AND PRESSES OFFSHORE IN THE NEXT COUPLE OF HOURS THE CONVECTION SHOULD WEAKEN AS WELL. THE 04Z HRRR DID NOT INITIALIZE WELL...BUT EARLIER RUNS (PARTICULARLY THE 01Z RUN) MODEL THE CURRENTLY OBSERVED PATTERNS ON RADAR WELL. LOW STRATUS CLOUDS ARE FILLING IN NORTH OF THE RAIN AREA AND MAY SPREAD DOWN AS FAR SOUTH AS FLORENCE...MARION...WHITEVILLE AND WILMINGTON BY DAYBREAK. AFTER PROVIDING A GLOOMY SUNRISE THESE CLOUDS SHOULD BURN OFF BY 10:00 AM WITH AN EXPANSIVE CUMULUS FIELD DEVELOPING IN ITS PLACE. TRIGGERS FOR AFTERNOON CONVECTION SHOULD INCLUDE A WELL-DEFINED SEABREEZE...THE REMNANT OUTFLOW BOUNDARY FROM THE EARLY MORNING CONVECTION ACROSS SOUTH CAROLINA...AND A DIFFERENTIAL HEATING BOUNDARY AROUND THE EDGE OF THE MORNING LOW STRATUS DECK. DESPITE NO SUPPORT FROM THE UPPER LEVELS AND A FORECAST STORM CELL MOTION OF LESS THAN 5 MPH...I`M STILL INCLUDING 20 POPS INLAND AND 30 POPS NEAR THE COAST FOR THIS AFTERNOON GIVEN ALL THE SURFACE BOUNDARIES AND WIDESPREAD 1500 J/KG SURFACE-BASED CAPE EXPECTED. ANY LINGERING CONVECTION SHOULD DIE AWAY QUICKLY THIS EVENING AS THE BOUNDARY LAYER COOLS. THE ATMOSPHERE WILL BEGIN TO RESPOND TO AN APPROACHING UPPER LEVEL TROUGH THAT WILL DRIVE A STRONG COLD FRONT THROUGH THE CAROLINAS THIS WEEKEND. DEEP-LAYER FLOW THAT IS ESSENTIALLY LIGHT AND VARIABLE THIS AFTERNOON WILL TURN SOUTHWEST AND STEADILY INCREASE THROUGH THE NIGHT. SURFACE WINDS WILL NOT INCREASE APPRECIABLY GIVEN THE STABLE LOW-LEVEL THERMAL PROFILES AT NIGHT...BUT WINDS 1000 FT AGL AND HIGHER WILL PICK UP SPEED AFTER MIDNIGHT. HIGHS TODAY SHOULD REACH 90 OR SO INLAND...WITH UPPER 80S NEAR THE COAST AND MID 80S ON THE BEACHES. LOWS TONIGHT WILL FALL INTO THE LOWER TO MID 70S. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY...STRONG COLD FRONT WILL APPROACH THE AREA SATURDAY MOVING THROUGH BY SUNDAY. LOCAL AREA WILL BE IN WARM SECTOR ON SAT WITH DEEP LAYER MOISTURE MAKING ITS WAY IN A SW FLOW LATER IN THE DAY AS MOISTURE POOLS AHEAD OF FRONT. GFS ACTUAL SHOWS SOME DRIER AIR IN PLACE IN THE MID LEVELS INITIALLY THROUGH THE AFTERNOON AND THEN PCP WATER VALUES SHOOT UP OVER 2 INCHES THROUGH SAT EVENING. EXPECT BEST LIFT AND MOISTURE THROUGH THE LATE EVENING AND OVERNIGHT AS MID TO UPPER TROUGH PUSHES COLD FRONT THROUGH. POTENTIAL FOR STRONG TO SEVERE STORMS ESPECIALLLY JUST AHEAD OF FRONT. THE FRONT WILL MAKE IT THROUGH AFTER THE BEST HEATING OF THE DAY AND THIS MAY WORK IN OUR FAVOR LIMITING MORE WIDESPREAD STORMS. THE SFC FRONT SHOULD MAKE IT OFF SHORE BY SUN MORNING BUT WINDS IN THE LOW TO MID LEVELS WILL TAKE A LITTLE WHILE LONGER TO VEER AROUND. PCP WATER VALUES WILL DROP OUT THROUGH SUNDAY DOWN LESS THAN 1.5 INCHES BY SUN AFTN AND DROPPING EVEN FURTHER TO LESS THAN AN INCH BY END OF THE PERIOD. OVERALL EXPECT MORE LOCALIZED CONVECTION THROUGH SAT AFTN WITH MORE WIDESPREAD ACTIVITY WITH APPROACH OF FRONT LATE SAT INTO EARLY SUNDAY. THEN CLEARING THROUGH SUNDAY BEHIND FRONT AS PLENTY OF DRY AIR MAKES IT WAY IN. SAT WILL BE THE LAST DAY OF VERY WARM TEMPS AS 850 TEMPS REMAIN UP NEAR 18 C BUT AS COOLER AIR ADVECTS IN ON SUNDAY...850 TEMPS WILL FALL THROUGH THE DAY REACHING DOWN TO 10 C BY MON MORNING. MAX TEMPS ON SAT WILL BE UP AROUND 90 OR SO WHILE SUNDAY THE TEMPS WILL BE BETWEEN 80 AND 85 MOST PLACES WHILE DEWPOINT TEMPS DROP ABOUT 10 DEGREES DOWN TO 60. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 300 AM FRIDAY...FALL LIKE WEATHER WILL EXIST THROUGH MUCH OF NEXT WEEK AS COOL AND DRY HIGH PRESSURE BUILDS DOWN OVER THE SOUTHEAST. BRIGHT SEPTEMBER SUN WILL PRODUCE MAX TEMPS BETWEEN 80 AND 85 MOST PLACES BUT THE VERY DRY AIR MASS WILL PRODUCE SOME LARGE DIURNAL SWINGS. WITH DEWPOINT TEMPS DOWN INTO THE 50S THROUGH AT LEAST WED AND WINDS DROPPING OFF EACH NIGHT...EXPECT MORE IDEAL RADIATIONAL COOLING LEADING TO OVERNIGHT LOWS AROUND 60 WITH UPPER 50S INLAND. ACTUALLY TEMPS WILL BE CLOSE TO NORMAL AND WILL CREEP UPWARD THROUGH MID WEEK AS H5 HEIGHTS RISE BACK UP WITH RIDGE BUILDING IN THE SOUTHEAST. BY WED MOISTURE INCREASES ENOUGH IN THE LOW LEVELS AS WINDS SHIFT AROUND TO THE NE TO PRODUCE SOME CU AROUND. OVERALL EXPECT SUNNY AND DRY WEATHER THROUGH THE WEEK. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 06Z...TSRA ACROSS THE PEE DEE REGION OF SC WILL SLIP SOUTHEAST AND AWAY FROM FLORENCE OVER THE NEXT SEVERAL HOURS...BUT MAY BRUSH BY MYR. BIGGER STORY WILL BE THE EXPANSION OF LOW CEILINGS AT OR BELOW 600 FT AGL. THESE IFR CONDITIONS HAVE ALREADY DEVELOPED AT LBT AND MAY EXPAND TO ILM AND FLO OVER THE NEXT SEVERAL HOURS AS A WEAK CONVECTIVE OUTFLOW BOUNDARY SINKS SOUTH ACROSS THE AREA. AFTER DAYBREAK...ANY LINGERING FOG WILL QUICKLY DISSIPATE GIVING WAY TO VFR ACROSS THE AREA. AS A SFC TROUGH CONTINUES TO PROGRESS ACROSS THE AREA...EXPECT ISOLATED SHRA/TSRA DURING THE AFTERNOON HOURS ALONG THE COAST...WHILE THE INLAND SITES ARE EXPECTED TO REMAIN QUIET WITH VFR THROUGH THE REMAINDER OF THE PERIOD. BY THE AFTERNOON...SOUTHWEST WINDS WILL BECOME SOUTH...INCREASING TO AOB 12 KTS. INTO THE EVENING HOURS...ACTIVITY WILL DIMINISH ALLOWING VFR TO PREVAIL WITH DECREASING WINDS AND CLEARING SKIES. EXTENDED OUTLOOK...SCATTERED SHRA/TSRA THROUGH SUNDAY...WITH A CHANCE OF EARLY MORNING LIFR/IFR CONDITIONS IN BR INLAND...AND MVFR AT THE COAST. VFR MONDAY AND TUESDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 300 AM FRIDAY...A WEAK UPPER LEVEL DISTURBANCE AND SURFACE TROUGH ALONG THE CAROLINA COAST IS RESPONSIBLE FOR SEVERAL WAVES OF SHOWERS AND THUNDERSTORMS AFFECTING THE NC OFFSHORE WATER THIS MORNING. SCATTERED SHOWERS AND STORMS SHOULD DIMINISH IN COVERAGE THROUGH THE EARLY MORNING HOURS AS THIS DISTURBANCE PUSHES OFFSHORE AND WEAKENS FURTHER. GENERALLY OFFSHORE WINDS EARLY THIS MORNING WILL TURN LIGHT AND VARIABLE LATER THIS MORNING...AND THEN SOUTHERLY DRIVEN PRIMARILY BY THE SEABREEZE THIS AFTERNOON. A STRONG COLD FRONT APPROACHING FROM THE WEST WILL CREATE SLOWLY INCREASING SOUTHWEST WINDS TONIGHT. SWELL FROM HURRICANE LESLIE HAS SHORTENED TO AROUND 10 SECONDS IN PERIOD AND SHOULD CONTINUE THROUGH THE WEEKEND. ADDITIONAL SHORT PERIOD WIND WAVES WILL ADD VERY LITTLE EXTRA TO THE TOTAL SEA STATE...AND WE`RE EXPECTING 2-4 FT ACROSS THE SOUTH CAROLINA COASTAL WATERS...AND 3-4 FT FOR THE NC COASTAL WATERS. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY...SOUTHWEST FLOW WILL INCREASE THROUGH SATURDAY AHEAD OF APPROACHING COLD FRONT. SOUTHWEST WINDS UP AROUND 15 KTS WILL VEER AROUND BECOMING OFF SHORE THROUGH SUNDAY MORNING AS COLD FRONT MOVES THROUGH. THESE SOUTHWEST WINDS WILL COMBINE WITH CONTINUED LONG PERIOD E-SE SWELLS TO PRODUCE SEAS IN THE 3 TO 5 FT RANGE MOST PLACES THROUGH SATURDAY. THERE WILL BE SOME 6 FTERS IN OUTER WATERS. AS COLD FRONT MOVES FURTHER OFF SHORE THROUGH SUNDAY...WINDS WILL VEER AROUND TO THE NORTH AROUND 10 TO 15 KTS AS HIGH PRESSURE BUILDS IN FROM THE N-NW. LONG TERM /MONDAY THROUGH TUESDAY/... AS OF 300 AM FRIDAY...NORTHERLY WINDS WILL CONTINUE TO MIX WITH LONGER PERIOD SWELLS FROM LESLIE TO PRODUCE SEAS IN THE 2 TO 4 FT RANGE MOST WATERS. THE COOL NIGHTS WILL KEEP A WELL MIXED ATMOSPHERE AS COOL AIR RIDES OVER THE WARM WATERS. THIS COULD PRODUCE NORTHERLY WINDS UP TO 20 KTS OVERNIGHT. EXPECT SEAS CLOSER TO 5 FT IN OUTER WATERS AND MAY SEE SEAS UP NEAR OR SLIGHTLY ABOVE SCA EARLY MON IN NORTHERLY SURGE BEHIND FRONT. THE WINDS WILL GRADUALLY SHIFT AROUND BECOMING NE TO E AS HIGH PRESSURE BUILDS SOUTH AND EAST THROUGH MID WEEK. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...TRA SHORT TERM...RGZ LONG TERM...RGZ AVIATION...TRA/SGL
AREA FORECAST DISCUSSION
NWS RALEIGH NC
339 AM EDT FRI SEP 7 2012 .SYNOPSIS... A WEAK SURFACE TROUGH WILL STALL OVER THE EASTERN CAROLINAS TODAY. A DEEPENING LOW PRESSURE SYSTEM OVER THE GREAT LAKES WILL PUSH A STRONG COLD FRONT THROUGH THE CAROLINAS SATURDAY AFTERNOON AND EVENING. COOLER AND DRIER CONDITIONS WILL PREVAIL IN THE WAKE OF THE FRONT SUNDAY THROUGH EARLY NEXT WEEK AS HIGH PRESSURE BUILDS INTO THE REGION. && .NEAR TERM /TODAY AND TONIGHT/... AS OF 330 AM FRIDAY... OVERVIEW: AN H5 SHORTWAVE CENTERED NEAR THE HWY 1 CORRIDOR AT 06Z THIS MORNING IS EXPECTED TO TRACK SLOWLY EAST TOWARD THE CAROLINA COAST THIS AFTERNOON BEFORE FURTHER WEAKENING AND SHIFTING OFFSHORE THIS EVENING/TONIGHT. A SFC-H85 TROUGH ATTENDANT THE SHORTWAVE IS PROGGED TO STALL OUT OVER THE COASTAL PLAIN TODAY...THEN DISSIPATE TONIGHT AS HEIGHT FALLS OVERSPREAD THE AREA FROM WEST-EAST IN ADVANCE OF AN AMPLIFYING UPPER LEVEL TROUGH AND ASSOCIATED SURFACE COLD FRONT PROGRESSING INTO THE OH VALLEY. PRECIPITATION CHANCES: MOISTURE THROUGHOUT THE COLUMN WILL VARY WIDELY ACROSS THE AREA TODAY...BETWEEN A DRY AIRMASS (PWAT VALUES ~1.00") OVER THE MOUNTAINS AND A VERY MOIST AIRMASS (PWAT VALUES ~2.00") OVER THE COASTAL CAROLINAS WHERE THE AFOREMENTIONED SFC-H85 TROUGH IS PROGGED TO STALL OUT. THE LATEST GFS/RAP MODEL GUIDANCE INDICATES THE DRIER AIRMASS TO THE NORTH AND WEST ADVECTING INTO CENTRAL NC THROUGHOUT THE MORNING...WITH PWAT VALUES FALLING TO 1.00-1.25" OVER THE BULK OF THE AREA...EXCEPT THE SOUTHEAST COASTAL PLAIN WHERE PWAT VALUES MAY LINGER NEAR ~1.75". THE LATEST 00Z NAM APPEARS TO BE AN OUTLIER...INDICATING DEEPER MOISTURE LINGERING MUCH FURTHER WEST (TO THE TRIANGLE/HWY 1 CORRIDOR) THAN EITHER THE 00Z GFS OR 06Z RAP. GIVEN THAT THE GFS HAS SUPPORT FROM THE MOST RECENT RAP MODEL RUN... THE NAM WILL BE DISREGARD AT THIS TIME. ANTICIPATE THAT INSTABILITY WILL GENERALLY BE CONFINED TO AREAS SOUTH AND EAST OF THE TRIANGLE DURING PEAK HEATING...WITH MLCAPE VALUES RANGING FROM 1000-1500 J/KG IN THE SOUTHEAST COASTAL PLAIN...PRIMARILY IN CUMBERLAND/SAMPSON/ WAYNE COUNTIES. SOME UNCERTAINTY IS PRESENT...AND THE INSTABILITY AXIS COULD BE SLIGHTLY FURTHER TO THE EAST OR WEST...DEPENDING ON THE LOCATION OF THE SFC-H85 TROUGH. FORCING FOR ASCENT TODAY WILL PRIMARILY BE ASSOCIATED WITH LOW-LEVEL CONVERGENCE IN VICINITY OF THE SEABREEZE AND THE SFC-H85 TROUGH OVER THE COASTAL CAROLINAS. SHORTWAVE ENERGY PROGRESSING INTO ILLINOIS AT 06Z WILL PROGRESS EAST THROUGH THE MID-ATLANTIC THIS AFTERNOON...RESULTING IN WEAK DPVA OVER NORTHERN PORTIONS OF THE STATE. WITH THE ABOVE IN MIND...WILL INDICATE A 20-30% CHANCE OF SHOWERS/STORMS IN THE SOUTHEAST COASTAL PLAIN CLOSER TO THE BEST MOISTURE/INSTABILITY AND LOW-LEVEL FORCING DURING PEAK HEATING. ANTICIPATE THAT THE DRIER /MORE STABLE/ AIRMASS IN PLACE OVER NORTHERN PORTIONS OF THE AREA WILL PRECLUDE A CHANCE FOR CONVECTION WITH THE AFOREMENTIONED SHORTWAVE ENERGY. WILL KEEP THE FORECAST DRY OVERNIGHT. TEMPERATURES: GIVEN LESS CLOUD COVER AND 1000-850 MB THICKNESSES SIMILAR TO PREVIOUS DAYS...EXPECT HIGHS IN THE UPPER 80S TO 90-91F. LOWS TONIGHT IN THE UPPER 60S TO LOWER 70S...WARMEST WHERE A LIGHT SOUTHERLY BREEZE IS PRESENT AS THE MSLP GRADIENT BEGINS TO TIGHTEN FROM THE WEST PRIOR TO SUNRISE. -VINCENT && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 303 AM FRIDAY... ...SLIGHT CHANCE OF SEVERE THUNDERSTORMS SATURDAY AFTERNOON AND EARLY EVENING... THE BIG PATTERN CHANGE THAT HAS BEEN ADVERTISED FOR DAYS WILL START WITH A BANG SATURDAY AFTERNOON. A POSITIVELY TILTED MID-UPPER TROUGH IS FORECAST TO AMPLIFY AS IT DIVES SE ACROSS THE CENTRAL APPALACHIANS AND MID-ATLANTIC STATES SATURDAY AFTERNOON. THE ASSOCIATED COLD FRONT WILL PUSH INTO THE REGION DURING PEAK HEATING. THE THE MOST FAVORABLE WINDS ALOFT FOR ORGANIZED SEVERE STORMS MAY REMAIN JUST TO OUR NORTH. HOWEVER... STRONG SURFACE HEATING IS EXPECTED TO DESTABILIZE THE BOUNDARY LAYER BY EARLY AFTERNOON OUT AHEAD OF A PRE-FRONTAL TROUGH/REMNANT CONVECTIVE OUTFLOW BOUNDARY. THIS BOUNDARY SHOULD BEGIN TO ARRIVE DURING PEAK HEATING FOR MUCH OF CENTRAL NORTH CAROLINA. WITH STRONG HEATING... TEMPERATURES SHOULD REACH AROUND 90 BY EARLY AFTERNOON THROUGHOUT MOST OF THE REGION. THIS WILL COMBINE WITH DEW POINTS FORECAST TO BE IN THE LOWER 70S TO PRODUCE FAVORABLE PARAMETERS FOR MULTICELL STORM CLUSTERS. A FEW OF THESE STORMS MAY BECOME SEVERE WITH THE MAIN THREAT BEING DAMAGING WET DOWNBURSTS. THE MULTICELL CLUSTERS MAY EVOLVE INTO A LINE BY LATE AFTERNOON AGAIN FAVORING ISOLATED DAMAGING WIND GUSTS ALONG LEWP/BOWING SEGMENTS. THERE MAY BE A FINAL LINE OF CONVECTION WITH THE MAIN COLD FRONT LATER IN THE DAY OR EVENING. REGARDLESS... SATURDAY AFTERNOON AND EVENING IS EXPECTED TO BE ACTIVE ONCE AGAIN. IN ADDITION TO THE SLIGHT CHANCE OF SEVERE STORMS... FREQUENT CG LIGHTNING AND LOCALLY HEAVY RAIN IS AGAIN EXPECTED WITH THE STORMS. EARLY MORNING STRATUS WILL GIVE WAY TO PARTLY SUNNY SKIES. WE WILL CARRY LIKELY POP FOR SHOWERS AND THUNDERSTORMS IN THE AFTERNOON AND EVENING. HIGHS 90-93 EXCEPT UPPER 80S NW. THE STORMS WILL GRADUALLY END SATURDAY EVENING NW... AND ELSEWHERE OVERNIGHT WITH THE ACTUAL COLD FRONTAL PASSAGE. GOOD DRY/COOL AIR ADVECTION WILL ARRIVE MAINLY BETWEEN 06Z-12Z. THIS LATE CAA ARRIVAL COMBINED WITH LINGER CLOUDS SHOULD KEEP LOWS MILD AND LIKELY ABOVE GUIDANCE. WE WILL CARRY 60-65 MOST AREAS. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 303 AM FRIDAY... A LONG AWAITED BREATHER FROM ALL THE VERY WARM/HUMID/THUNDERY WEATHER WILL BEGIN SUNDAY. A REFRESHING BREEZE WILL COMBINE WITH AMPLE SUNSHINE TO BRING A SPRING-LIKE FEEL. HIGHS OF 78-83 EXPECTED (WITH DEW POINTS IN THE 40S NW AND LOWER 50S SE). A NORTHERLY BREEZE AT 10-15 MPH WILL MAKE IT FEEL APRIL-FRESH AT TIMES. MONDAY THROUGH THURSDAY... EXPECT DRY AND SEASONABLY COOL CONDITIONS MONDAY AND TUESDAY... WITH MODERATING DAYTIME TEMPS WED AND THUR. MOSTLY CLEAR/MOSTLY SUNNY WITH LOWS IN THE 50S EACH DAY. HIGHS 75 TO 80 MON-TUE... WARMING INTO THE LOWER TO MID 80S BY THURSDAY. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 155 AM FRIDAY... 24-HR TAF PERIOD: IFR TO VLIFR CEILINGS AND VISBYS ARE PRESENT OVER PORTIONS OF THE NORTHERN PIEDMONT (INCLUDING RDU/RWI) AS OF 06Z. GIVEN A VERY MOIST LOW-LEVEL AIRMASS...LIGHT/CALM WINDS...AND A DRIER MID-LEVEL AIRMASS PROGRESSING INTO THE AREA FROM THE NORTHWEST...EXPECT THAT ALL TAF SITES WILL SEE CONDITIONS DETERIORATE INTO THE IFR TO VLIFR RANGE BETWEEN 06-12Z THIS MORNING. FOG AND LOW CEILINGS ARE EXPECTED TO LIFT AND SCATTER TO VFR BETWEEN 12-15Z AT INT/GSO/RDU. CONDITIONS SHOULD BE SLOWER TO IMPROVE AT THE FAY/RWI TERMINALS WHERE MOISTURE IS DEEPER AND MVFR CEILINGS MAY PERSIST THROUGH ~18Z. ISOLATED SHOWERS AND STORMS WILL BE POSSIBLE DURING THE AFTERNOON...THOUGH CHANCES WILL MOST LIKELY BE LIMITED TO THE FAY TERMINAL. OTHERWISE...EXPECT VFR CONDITIONS TO PREVAIL THIS AFTERNOON THROUGH 06Z TONIGHT. LOW-LEVEL SOUTHERLY FLOW WILL STRENGTHEN PRIOR TO SUNRISE SATURDAY IN ADVANCE OF AN APPROACHING COLD FRONT...AND IT IS POSSIBLE THAT MVFR/IFR CEILINGS MAY DEVELOP BETWEEN 09-12Z SAT. LOOKING AHEAD: A STRONG COLD FRONT WILL TRACK EAST INTO CENTRAL NC SATURDAY AFT/EVE. A LINE OF SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ALONG AND AHEAD OF THE FRONT. RAIN MAY LINGER INTO SATURDAY NIGHT AND EARLY SUNDAY MORNING IN THE WAKE OF THE FRONTAL PASSAGE...PRIMARILY AT THE FAY/RWI TERMINALS. VFR CONDITIONS WILL RULE IN THE WAKE OF THE COLD FRONT SUNDAY THROUGH EARLY NEXT WEEK AS COOL AND DRY HIGH PRESSURE BUILDS INTO THE CAROLINAS. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM....VINCENT SHORT TERM...BADGETT LONG TERM...BADGETT AVIATION...VINCENT
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
148 AM EDT FRI SEP 7 2012 .SYNOPSIS... A WEAK DISTURBANCE WILL BRING A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS TO NORTHERN PORTIONS OF THE AREA TODAY. HIGH PRESSURE WILL WORK INTO THE AREA TONIGHT AND REMAIN ACROSS THE AREA THROUGH FRIDAY MORNING. A LOW PRESSURE SYSTEM...AND A STRONG COLD FRONT...WILL BRING PRECIPITATION BACK TO THE AREA FROM FRIDAY AFTERNOON THROUGH SATURDAY MORNING. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... ISOLATED SHOWERS AND THUNDERSTORMS CONTINUE NEAR A WEAK FRONTAL BOUNDARY ACROSS THE NORTHERN PORTIONS OF THE FORECAST AREA. HAVE EXTENDED SLIGHT CHANCE POPS UNTIL MIDNIGHT FOR PORTIONS OF THE AREA. THE LATEST HRRR INDICATES THAT SOME OF THIS ACTIVITY MAY TRY TO REDEVELOP FARTHER SOUTH...LIKELY OUTFLOW INITIATED...WHERE THE BETTER ELEVATED INSTABILITY IS LOCATED. HOWEVER...KEPT THESE ZONES DRY FOR NOW. IN THE SOUTH...SURFACE DEWPOINTS IN THE UPPER 60S WILL ALLOW FOR SOME FOG TO DEVELOP...BUT NOT LIKELY AS WIDESPREAD AS THE PAST TWO NIGHTS. HAVE LIMITED THE MENTION OF FOG IN THE ZONES MAINLY TO VALLEY LOCATIONS ACROSS THE SOUTHERN HALF OF THE FORECAST AREA. ACROSS THE NORTH...SLIGHTLY DRIER CONDITIONS AND A MORE CLOUDY START TO THE OVERNIGHT PERIOD SHOULD LIMIT FOG DEVELOPMENT. MINIMUM TEMPERATURES WERE NOT ADJUSTED ON THIS UPDATE AS EVENTUAL LATE NIGHT CLEARING ACROSS THE NORTH WILL ALLOW FOR TEMPERATURES TO DROP INTO THE LOW 60S. SOUTH OF THE FRONT...TEMPERATURES WILL REMAIN IN THE UPPER 60S. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/... SURFACE LOW PRESSURE IS EXPECTED TO DEVELOP OVER NORTHERN ILLINOIS ON FRIDAY AFTERNOON. THIS LOW WILL MOVE QUICKLY TO THE ENE AS IT DEEPENS...AND ROUNDS THE FRONT EDGE OF A VERY SHARP MID LEVEL TROUGH OVER THE GREAT LAKES. A STRONG COLD FRONT WILL TRAIL SOUTHWEST FROM THIS LOW PRESSURE CENTER...MOVING EAST THROUGH THE OHIO VALLEY THROUGH SATURDAY MORNING. FRONTAL TIMING IS IN DECENT AGREEMENT BETWEEN THE MODELS...ALTHOUGH BY THE END OF ITS PASSAGE...THE SURFACE LOW POSITION AND STRENGTH ARE HANDLED SLIGHTLY DIFFERENTLY. DESPITE THE DIFFERING POSITIONS OF THE SURFACE LOW (WHICH WILL NOT DIRECTLY IMPACT THE ILN CWA)...THE RIBBON OF DEEP MOISTURE AND EXPECTED PRECIPITATION SEEM TO BE WITHIN 3 HOURS OF EACH OTHER EVEN BY SATURDAY AFTERNOON. THIS HAS LED TO A VERY DETERMINISTIC POP/WX FORECAST...WITH A 100 PERCENT CHANCE OF TS/RA THAT SPREAD ACROSS THE ENTIRE FORECAST AREA. FORCING WILL NOT BE IN QUESTION WITH THIS SYSTEM...WITH PLENTY OF SUPPORT FROM THE COLD FRONT AND UPPER TROUGH. THE POTENTIAL FOR HAZARDOUS WEATHER WITH THIS SYSTEM IS THE PRIMARY CONCERN OF THE SHORT TERM FORECAST. THE FRONT WILL BE MOVING INTO AN ENVIRONMENT WITH 30-40 KNOTS OF 0-6KM SHEAR...AND 15-25 KNOTS IN THE LOWEST KILOMETER OR TWO. MLCAPE DURING PEAK HEATING WILL BE IN THE 1500-2000 J/KG RANGE. GIVEN THE STRONG FORCING...THESE PARAMETERS CERTAINLY SUPPORT A SEVERE WEATHER THREAT. THE BIGGEST NEGATIVE FOR SEVERE POTENTIAL IS THE TIMING...SINCE MUCH OF THE ACTIVITY IS EXPECTED TO TAKE PLACE AFTER 00Z. THERE IS NO BIG PUSH OF MOISTURE IN THE BOUNDARY LAYER...WITH THE HIGHEST DEWPOINTS BEING RELEGATED TO A RIBBON ALONG AND NEAR THE FRONT. WANING INSTABILITY AFTER SUNSET (A FACTOR PARTIALLY CONNECTED TO THE ABOVE) WILL LIMIT THE STRENGTH OF THE CONVECTION. IN ADDITION...THE FRONT IS EXPECTED TO BE FORWARD PROPAGATING AT AROUND 30 MPH...NOT FAST ENOUGH TO KEEP UP WITH THE MOVEMENT OF INDIVIDUAL STORM CELLS OR LINES (OR THEIR OUTFLOW BOUNDARIES). THE END RESULT IS THAT A LINE (OR BROKEN LINE) OF STRONG TO SEVERE CONVECTION IS EXPECTED TO MOVE INTO THE ILN CWA LATE TOMORROW AFTERNOON. THE GREATER THREAT IS IN THE WESTERN HALF OF THE CWA...WITH A PROJECTED WEAKENING TREND IN THE CONVECTION DURING THE EVENING AND OVERNIGHT HOURS. DAMAGING WINDS WILL BE THE PRIMARY THREAT...WITH SOME LARGE HAIL ALSO POSSIBLE. THE LOW LEVEL SHEAR WILL SUPPORT SOME POSSIBILITY OF TORNADOES BEFORE THE BOUNDARY LAYER BEGINS TO DECOUPLE...THOUGH THIS THREAT WOULD LIKELY BE TIED TO THE EVOLUTION OF THE INDIVIDUAL QLCS ELEMENTS WITHIN THE CONVECTION. HEAVY RAIN IS ALSO A POSSIBILITY. ALTHOUGH WIDESPREAD QPF TOTALS WILL PROBABLY BE IN THE 0.75-1.25 INCH RANGE...PWATS NEAR TWO INCHES AND MOISTURE TRANSPORT THAT PARALLELS THE FRONT WILL RESULT IN SOME POSSIBILITY OF TRAINING AND POTENTIAL LOCALIZED FLOODING. THE FRONT DOES SLOW DOWN SOMEWHAT AS IT MOVES INTO THE UPPER OHIO VALLEY...AS ITS ORIENTATION BECOMES MORE SSW/NNE AND THE SURFACE LOW ALSO GAINS MORE OF A NORTHERLY COMPONENT TO ITS MOTION. EVEN STILL...THE SYSTEM IS LARGELY A PROGRESSIVE ONE. THIS FORECAST PACKAGE WILL BE SLIGHTLY AGGRESSIVE IN CLEARING POPS OUT BEHIND THE FRONT...WITH THE EXPECTATION THAT MOST OF THE WESTERN HALF OF THE CWA WILL HAVE A DRY SATURDAY. HOWEVER...SOME LOW LEVEL MOISTURE BEHIND THE FRONT WILL KEEP CLOUDS AROUND FOR A WHILE. ESPECIALLY GIVEN THE COLD ADVECTION PROVIDED BY THE FRONT...A SIGNIFICANT COOL DOWN IS EXPECTED...WITH HIGHS ONLY REACHING THE LOWER 70S. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... SHORT WAVE ENERGY WILL ROTATE DOWN ACROSS THE GREAT LAKES SATURDAY NIGHT INTO SUNDAY. MOISTURE IS PRETTY LIMITED...BUT THE COMBINATION OF THIS AND SOME DAYTIME HEATING...MAY BE ENOUGH TO SQUEEZE OUT A FEW SHOWERS OR SPRINKLES ACROSS OUR NORTH SUNDAY AFTERNOON. OTHERWISE...RIDGING AT THE SURFACE AND ALOFT WILL BUILD INTO THE AREA THROUGH TUESDAY BEFORE SHIFTING OFF TO THE EAST THROUGH THE END OF THE LONG TERM PERIOD. THIS WILL PROVIDE DRY CONDITIONS AND MAINLY CLEAR SKIES THROUGH AT LEAST MID WEEK. AS THE SURFACE HIGH SLIDES OVERHEAD...CLEAR SKIES AND LIGHT WINDS WILL LEAD TO SOME SEASONABLY COOL NIGHTS. EXPECT OVERNIGHT LOWS TO DIP DOWN INTO THE 40S IN SOME OF THE OUTLYING AREAS THROUGH THE FIRST PART OF THE WEEK WITH DAYTIME HIGHS GENERALLY IN THE 70S. WE WILL THEN SEE A GRADUAL MODERATION IN TEMPS WEDNESDAY INTO THURSDAY AS THE HIGH BEGINS TO PUSH OFF TO THE EAST AND WE GET INTO RETURN FLOW. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... TIMING OF THE INITIAL LINE OF SHOWERS AND THUNDERSTORMS APPEARS TO KEEP BEING PUSHED BACK WITH EACH MODEL AND SUCCESSIVE RUN. DO NOT EXPECT ANY WX AT TAF SITES THROUGH 0Z...EVEN THOUGH SOME WARM SECTOR SHOWERS AHEAD OF THE FRONT WILL LIKELY OCCUR. PREVAILING RAINFALL WILL BE AT A MAXIMUM IN THE 4-8Z TIME FRAME AND TRAIL OFF AFTER THIS. WIND SHIFT WITH FROPA MAY SEE SOME GUSTS APPROACHING 30KTS...BUT THIS IS BEYOND THE FIRST 24 HOURS COVERED IN TAFS. .OUTLOOK...MVFR CIGS AND VSBYS ARE POSSIBLE IN SHOWERS SATURDAY MORNING. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HATZOS NEAR TERM...LATTO SHORT TERM...HATZOS LONG TERM...JGL AVIATION...FRANKS
AREA FORECAST DISCUSSION
NWS NORMAN OK
437 AM CDT FRI SEP 7 2012 .DISCUSSION... BIG CHANGES WILL BE SEEN THIS AFTERNOON AND EVENING...BUT BEFORE THE FRONT ARRIVES IT WILL BE QUITE HOT WITH FAIRLY SUBSTANTIAL PRE-FRONTAL THERMAL RIDGE IN PLACE. FIRST PERIOD OF FORECAST WILL CLOSELY RESEMBLE WRF SOLUTIONS OF THE PAST COUPLE OF RUNS. HOTTER AHEAD OF FRONT AND MORE SUBSTANTIAL CAA/WIND BEHIND IT. WE WILL ISSUE A WIND ADVISORY FOR THIS AFTERNOON AND EVENING. FREQUENT GUSTS AROUND 45 MPH NOT OUT OF THE QUESTION FOR AT LEAST 2 TO 4 HOURS AFTER FROPA COINCIDING WITH STRONG CAA. SOME OF THE WINDIER SPOTS OF W/SW OKLAHOMA COULD SEE SOME GUSTS IN EXCESS OF 50 MPH. AS FAR AS THE CHANGE IN TEMPERATURE GOES...WE EXPECT TEMPS TO FALL 20 TO 30 DEGREES IN JUST A FEW HOURS AFTER FRONTAL PASSAGE... ESPECIALLY ACROSS CENTRAL AND SOUTHERN PORTIONS OF OKLAHOMA AND NORTH TEXAS WHERE TEMPS EXPECTED TO APPROACH OR EXCEED 100 AHEAD OF FRONT. AS FAR AS POPS GO...COULD SEE SOME ISOLATED SHOWERS OR STORMS ACROSS NORTH-CENTRAL AND PERHAPS CENTRAL OKLAHOMA EARLY THIS MORNING...WITH THE HRRR BEING THE MOST AGGRESSIVE WITH THIS POTENTIAL. SCATTERED STORMS MAY FORM ALONG FRONT THIS AFTERNOON BUT BEST CHANCES FOR RAIN APPEAR TO BE THIS EVENING BEHIND THE FRONT AS MAIN MID-LEVEL TROUGH AXIS MOVES INTO THE REGION. SEASONABLY COOL WEEKEND IN STORE BEFORE TEMPS BEGIN TO INCREASE AHEAD OF NEXT FRONTAL BOUNDARY WHICH MEDIUM RANGE MODELS WANT TO BRING TOWARD THE END OF NEXT WEEK. && .PRELIMINARY POINT TEMPS/POPS... OKLAHOMA CITY OK 99 57 83 54 / 30 40 0 0 HOBART OK 99 55 85 54 / 20 30 0 0 WICHITA FALLS TX 104 59 86 56 / 20 30 0 0 GAGE OK 88 53 83 49 / 20 10 0 0 PONCA CITY OK 93 53 82 54 / 40 20 0 0 DURANT OK 102 60 84 53 / 10 30 0 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 10 PM CDT THIS EVENING FOR OKZ007-008-012-013-016>026-033>036. WIND ADVISORY FROM NOON TODAY TO 6 PM CDT THIS EVENING FOR OKZ004>006-009>011-014-015. WIND ADVISORY FROM 6 PM TO 10 PM CDT THIS EVENING FOR OKZ027>031- 037>040-044-045. TX...WIND ADVISORY FROM 6 PM TO 10 PM CDT THIS EVENING FOR TXZ083>090. && $$ 06/11
AREA FORECAST DISCUSSION...UPDATED
NWS MILWAUKEE/SULLIVAN WI
1133 PM CDT THU SEP 6 2012 .UPDATE... LIGHT PRECIPITATION FALLING FROM 10K TO 12K-FOOT CLOUD DECK NORTH OF CWA WITH BRIEF 10SM LIGHT RAIN ON OBS. CONVECTION IN NW IOWA ON NOSE OF 850 MB JET WILL BE MOVING TOWARD SRN WISCONSIN AS WEAK 850MB RIDGE AXIS SHIFTS EAST. HRRR AND ARW IN AGREEMENT WITH 12Z ECMWF AND TAKE THIS COMPLEX SOUTH INTO NRN IL...WITH 07/00Z NAM BRINGING LIGHT QPF AMOUNTS INTO WRN CWA BETWEEN 09Z AND 12Z FRI BUT BULK OF PCPN OVER NRN IL. 00Z RUC AT 12Z FRI...AND NMM BRING PRECIP INTO THE SOUTH HALF OF CWA...WITH NMM DROPPING 0.25 TO 0.50 INCH OF RAIN BY 15Z FRI. ALL MODELS SHOW A BRIEF BREAK IN THE LATE MORNING/EARLY AFTERNOON THEN FIRE PCPN BACK UP WITH DYNAMICS WITH PASSAGE OF WAVE. && .AVIATION/06Z TAFS/... KENW HAS MVFR/PATCHY IFR FOG WITH SKIES STILL CLEAR AND LIGHT WIND. WILL KEEP VFR CONDITIONS OVER REMINDER OF TAF SITES AS HIGH TO MID-LEVEL CLOUDS FILL IN AND LOWER WITH GRADUAL SATURATION. SHOULD SEE SOME IMPROVEMENT IN VSBYS AT KENW WITH CLOUD BLANKET. GIVEN CURRENT RADAR OBSERVATIONS AND MODEL TRENDS WILL HOLD PCPN OFF AT KMSN UNTIL 09Z...AND THEN SPREAD IT EAST TO REACH EASTERN TAF SITES BETWEEN 12Z AND 15Z. SOME EASING OF PCPN...IF NOT A PERIOD OF DRY WEATHER IN THE LATE MORNING/EARLY AFTERNOON...THEN PRECIPITATION FIRES UP AHEAD OF STRONG WAVE FOR LATE AFTERNOON AND EVENING HOURS WITH MVFR CIGS AND VSBYS. CONDITIONS WILL IMPROVE WITH PASSAGE OF 500 MB TROUGH AXIS...WITH PCPN ENDING AROUND 00Z SATURDAY AT KMSN...BETWEEN 00Z AND 03Z AT KUES...AND BY 06Z AT KMKE AND KENW. && .PREV DISCUSSION... /ISSUED 438 PM CDT THU SEP 6 2012/ SHORT TERM... TONIGHT AND FRIDAY...FORECAST CONFIDENCE MEDIUM MAIN FORECAST ISSUE IS THE TIMING...PLACEMENT...AND COVERAGE OF PRECIP MOVING IN TONIGHT. IT LOOKS LIKE TWO AREAS OF RAIN WILL FORM...ONE CLOSER TO THE 500 MB VORT MAX AND ONE WITH AN AREA OF FRONTOGENESIS THAT WILL MOVE MAINLY TO OUR SOUTHWEST. PRECIPITABLE WATER VALUES ARE ALMOST AT PLUS 2 STANDARD DEVIATIONS IN THE SOUTH...SO IT LOOKS LIKE QPF WILL BE THE HIGHEST THERE. MEANWHILE...VALUES IN THE NORTH AREN/T BAD EITHER... BUT ARE CLOSER TO THE 75TH PERCENTILE. ALSO WORTH NOTING...UPPER DIVERGENCE LOOKS THE BEST OVER THE FAR SOUTHERN AREA. HAVE UPPED POPS ACROSS THOUGH CWA TO CATEGORICAL BASED ON THE STRENGTH OF THE VORT MAX AND THE 250 MB JET. ALTHOUGH...THE JET ISN/T QUITE AS BEEFY ON THE NEW NAM AS BEFORE...THERE IS GOOD AGREEMENT AMONG THE MESO MODELS THAT EVERYWHERE WILL SEE RAIN...JUST SOME AREAS JUST WON/T GET AS MUCH. HIGH TEMPERATURES COULD STRUGGLE TOMORROW WITH CLOUD COVER AND PRECIP...ALTHOUGH THERE COULD BE SOME CLEARING IN THE NORTHWEST IN THE AFTERNOON THAT WOULD HELP A BIT. FRIDAY NIGHT THROUGH SUNDAY...FORECAST CONFIDENCE MEDIUM TO HIGH LGT RAIN COULD LINGER INTO FRI EVENING OVER SE WI AS THE UPPER TROUGH AXIS WILL PASS THROUGH DURING THE EVENING. OVERALL THOUGH...COLD AND DRY ADVECTION WILL BE UNDERWAY SO KEPT POPS RELATIVELY LOW. NWLY FLOW AND COLD ADVECTION TO WEAKEN ON SAT WHILE A JET STREAK AND SHORTWAVE TROUGH WILL DIVE SWD FROM CANADA INTO LAKE HURON AND THE ERN GREAT LAKES. BELIEVE THIS FEATURE WILL REMAIN FAR ENOUGH EAST TO MAINTAIN PARTLY CLOUDY SKIES AND DRY CONDITIONS BASED ON A CONSENSUS OF MODELS. THE ECMWF IS FARTHER WEST OVER WI AND MI WITH THESE FEATURES BUT IS AN OUTLIER. 500 HTS CONTINUE TO RISE SAT NT AND SUN WITH SFC HIGH PRESSURE SETTLING OVER THE CENTRAL USA INCLUDING WI. WITH DRY AIR OVER THE REGION...GOOD MIXING IS EXPECTED THIS WEEKEND AND 925-850 MB TEMPS SUGGEST HIGH TEMPS IN THE LOWER 70S FOR SAT AND LOWER TO MID 70S FOR SUN. LONG TERM...MONDAY THROUGH THURSDAY...FORECAST CONFIDENCE MEDIUM A STRONG POLAR TROUGH AND ASSOCIATED CYCLOGENESIS WILL PROGRESS EWD ACROSS SRN CANADA NEXT WEEK. THIS WILL BRING BREEZY SSWLY WINDS AND WARM ADVECTION FOR MON AND TUE. TEMPS WILL RISE INTO THE 80S FOR TUE. THE SRN PERIPHERY OF THE COLD FRONT WILL BE WEAK AND POSSIBLY STALL OVER SRN WI OR THE VICINITY FOR WED AND THU. WILL KEEP FROPA DRY FOR NOW BUT THIS COULD CHANGE IN LATER FORECASTS IF LOW LEVEL MOISTURE CAN ARRIVE FROM THE SOUTH. AVIATION/00Z TAFS/...THE APPROACH OF A SURFACE FRONT AND MID LEVEL TROUGH...ALONG WITH THE DEVELOPMENT OF AN UPPER JET...WILL BRING LOW CLOUDS AND PRECIP TO THE AREA FROM MIDNIGHT TONIGHT THROUGH THE MAJORITY OF THE REST OF THE PERIOD. EXPECTING TO SEE LOW CLOUDS AND PRECIP BUILD INTO AREAS WEST OF MADISON AFTER MIDNIGHT...THEN SPREAD EASTWARD DURING THE MORNING HOURS...AND DIMINISH WEST TO EAST FRIDAY EVENING. LOOKING LIKE WE WILL SEE MVFR/IFR CONDITIONS DEVELOP IN MADISON DURING THE FIRST PART OF THE MORNING...THEN IN EASTERN LOCATIONS BY MID MORNING. MARINE... BRISK NORTH WINDS AND INCREASING WAVES MAY BRING SMALL CRAFT ADVISORY CONDITIONS FRIDAY NIGHT AS A TIGHT PRESSURE GRADIENT DEVELOPS BETWEEN DEPARTING LOW PRESSURE TO THE EAST AND HIGH PRESSURE OVER THE GREAT PLAINS. && .MKX WATCHES/WARNINGS/ADVISORIES... WI...NONE. LM...NONE. && $$ UPDATE...REM TONIGHT/FRIDAY AND AVIATION/MARINE...MEB FRIDAY NIGHT THROUGH THURSDAY...GEHRING
AREA FORECAST DISCUSSION...UPDATED
NWS PHOENIX AZ
540 AM MST FRI SEP 7 2012 .UPDATE... UPDATED AVIATION AND FIRE WEATHER SECTIONS. && .SYNOPSIS... A VERY MOIST AND UNSTABLE MONSOON AIRMASS WILL CONTINUE TO COVER THE REGION THROUGH EARLY NEXT WEEK...AND LEAD TO A CHANCE OF MAINLY AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS EACH DAY. THUNDERSTORM COVERAGE AND INTENSITY WILL VARY FROM DAY TO DAY...WITH SOMEWHAT BETTER CHANCES EXPECTED OVER THE WEEKEND AND INTO NEXT MONDAY. HIGH TEMPERATURES WILL REMAIN NEAR OR SLIGHTLY BELOW SEASONAL NORMALS EACH DAY GIVEN THE HIGH MOISTURE CONTENT IN THE ATMOSPHERE. && .DISCUSSION... COMPLICATED WEATHER PATTERN ESTABLISHING ITSELF ACROSS THE REGION THIS MORNING FOLLOWING A SOMEWHAT ACTIVE DAY ON THURSDAY. PORTIONS OF SOUTHERN ARIZONA DID VERY WELL PRECIP-WISE YESTERDAY WHILE THE MAJORITY OF THE PHOENIX METRO ONLY SAW DUST...A FEW HUNDREDTHS HERE AND THERE...A FEW TENTHS IN THE FAR NW VALLEY. WATER VAPOR AND RADAR IMAGERY AT 09Z REVEAL REMNANT CONVECTION ACROSS EASTERN ARIZONA AND A DEVELOPING MCV ACROSS SOUTHERN GILA COUNTY. WHILE STORMS DO NOT APPEAR STRONG AT THIS TIME...ACARS SOUNDINGS CONTINUE TO REVEAL 300-400 J/KG OF UNCAPPED CAPE ABOVE 750MB...MOST LIKELY THE REASON THESE STORMS REFUSE TO DIE OFF 9 HRS AFTER SUNSET. ALSO SOME HINT OF SOME DEVELOPING CONVECTION ACROSS CENTRAL PIMA COUNTY ALTHOUGH THAT PORTION OF THE STATE WAS WORKED OVER PRETTY HEAVILY ON THURSDAY. A FEW SPOT CHECKS ACROSS THE REGION REVEAL THE 00Z NAM HAS INITIALIZED THE TEMP/MOISTURE/WIND FIELDS BETTER THAN THE GFS AND EURO.../GFS LOOKS ENTIRELY TOO DRY AT NEARLY ALL SITES/ THUS THE FORECAST FOR THE FIRST 24 HOURS WILL BE HEAVILY WEIGHTED TOWARD THE NAM SOLUTION. THE NAM SHOWS LINGERING CONVECTION ACROSS PORTIONS OF SE AZ THIS MORNING...GRADUALLY TRANSITIONING TO A MORE TYPICAL MONSOON ORIENTATION ALONG THE RIM LATER THIS AFTERNOON. ABUNDANT MOISTURE WITH MIXING RATIOS AROUND 12 G/KG AND MLCAPES AOA 1000 J/KG ARE ONLY PART OF THE EQUATION NATURALLY...BIG QUESTION IS WHETHER THE REMNANT MCV WILL ALLOW FOR ANY STORMS TO MOVE OFF THE RIM AND INTO THE VALLEY LATER TODAY. AT THIS POINT IT LOOKS TO BE A SLIGHTLY-MORE-ACTIVE-THAN-USUAL DAY AND POPS WERE DRAWN APPROX 10 PERCENT ABOVE CLIMO GIVEN THE PRESENCE OF THE MCV IN THE AREA. ONE CONCERN WORTH MENTIONING IS LINGERING CLOUD COVER AS IT WILL TAKE A FEW HOURS TO SCOUR OUT ALL THE MID AND HIGH MOISTURE AND MAY NOT BE MOSTLY SUNNY UNTIL LATE MORNING. THE WEEKEND LOOKS TO BE PARTICULARLY ACTIVE AND THE MODELS HAVE BEEN HINTING AT THIS FOR THE PAST FEW DAYS. A FEW 700-300MB INVERTED TROUGHS ARE EXPECTED TO MOVE THROUGH THE REGION THIS WEEKEND...AND SHOULD INTERACT WITH A LARGER MORE WELL DEFINED 200-300MB PVD /PRESENTLY OVER BAJA CALIFORNIA/. INTERESTINGLY ENOUGH...THE USUALLY ACTIVE PORTIONS NORTH AND EAST OF PHOENIX MAY SEE A BIT OF A BREAK AT TIMES THIS WEEKEND AS THE GREATEST MOISTURE AND INSTABILITY ORIENT INTO A LAS VEGAS TO NOGALES AXIS. ALL GUIDANCE PRETTY MUCH AGREES THAT SOUTHERN GILA COUNTY MAY SEE LITTLE TO NO INSTABILITY SATURDAY AND SUNDAY. NOT SAYING THESE AREAS WILL BE DRY ALTOGETHER...BUT I REFINED THE POPS TO BETTER REFLECT THE AXIS OF MOISTURE/INSTABILITY. POPS WERE INCREASED ACROSS THE PHOENIX METRO AS WELL BUT AS USUAL...THERE IS JUST ENOUGH UNCERTAINTY IN THE GUIDANCE TO PRECLUDE ME FROM GOING MUCH ABOVE 40-50 PERCENT. WILL STORMS FORM OVER SOUTHERN ARIZONA AND MOVE NORTHWARD OR WILL STORMS FORM OVER NORTHERN MARICOPA COUNTY AND MISS PHOENIX ALTOGETHER...THESE ARE MY MAIN QUESTIONS THIS MORNING. HOPE TO GAIN SOME CLARITY FROM THE HI-RES WRF MODELS LATER TODAY. SIMILAR CONVECTIVE DEVELOPMENT IS EXPECTED ON SUNDAY WITH THE BEST CHANCES FROM PHOENIX WESTWARD TO THE COASTAL MOUNTAINS OF CALIFORNIA. WESTERLY FLOW ALOFT BEGINS TO TAKE SHAPE ON MONDAY AS THE UPPER LEVEL PVD MOVES THROUGH SOUTHERN ARIZONA INTO NEW MEXICO. MOISTURE SHOULD WORK ITS WAY BACK INTO EASTERN ARIZONA AND ALL LOCATIONS SHOULD SEE A DECENT CHANCE OF SHOWERS AND THUNDERSTORMS. MONDAY COULD BE THE BEST CHANCE AREA-WIDE FOR PRECIP GIVEN FAVORABLE UPPER LEVEL SUPPORT AND POPS WERE INCREASED INTO THE 40-50 PERCENT RANGE TO REFLECT THIS. FOLLOWING THE TROUGH...A GRADUAL DECREASE IN MOISTURE AND INSTABILITY WILL GREATLY REDUCE THE AMOUNT OF STORMS FROM TUESDAY ONWARD. COULD SEE A FEW RENEGADE STORMS EAST OF PHOENIX ON TUESDAY WHERE SOME MOISTURE AND INSTABILITY WILL RESIDE /PER THE SLOWER ECMWF SOLUTION/ BUT WESTERLY FLOW WILL STEER THESE STORMS AWAY FROM THE DESERTS. 1000-700MB MOISTURE DROPS ALL THE WAY DOWN TO AROUND 6 G/KG ON WEDNESDAY WITH BARELY ANY INSTABILITY TO SPEAK OF ANYWHERE IN THE STATE. MAY STRUGGLE TO EVEN GET AFTERNOON CU LATE NEXT WEEK AND POPS WERE REDUCED WELL BELOW CLIMO FOR THE END OF THE FORECAST PERIOD. WITH ELEVATED MOISTURE...TEMPS SHOULD STAY AOB NORMAL THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. TEMPS WILL CLIMB SLIGHTLY FROM THE MIDDLE OF NEXT WEEK ONWARD IN RESPONSE TO DECREASING MOISTURE BUT STILL IN THE BALLPARK OF NORMAL FOR MID SEPTEMBER. && .AVIATION... SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL... A WEAK WEATHER DISTURBANCE ALONG WITH ABUNDANT MOISTURE OVER THE SOUTHERN HALF OF ARIZONA WILL LEAD TO SHOWER AND THUNDERSTORM ACTIVITY IN SOMETHING OF A RANDOM PATTERN THIS MORNING. SHWRS/TSTMS WILL BE POSSIBLE ANYWHERE DESPITE THE LACK OF SURFACE HEATING. THUS THE VCSH/VCTS IN THE PHOENIX AREA TAFS. NAM MODEL SEEMS TO BE DOING A BETTER JOB EARLY THIS MORNING THAN THE GFS AND IT INDICATES MORE SHOWER ACTIVITY THIS MORNING THAN LATER THIS AFTERNOON. 09Z RUC INDICATES THIS AS WELL. WITH ALL THE MOISTURE AND CLOUDINESS...OPTIMAL INSTABILITY MAY NOT BE REALIZED. THIS...ALONG WITH UNCERTAINTIES IN TIMING AND LOCATION OF PRECIP IS WHY TEMPO SHRA/TSRA WAS WITHHELD FROM THE TAFS. ANY TSTMS THAT MOVE OVER AN AIRFIELD WILL BE ABLE TO REDUCE VSBYS AT OR BELOW 6SM IN HEAVY RAIN. SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH... NAM AND RUC INDICATE THAT THE LOWER COLORADO RIVER VALLEY WILL HAVE A BETTER CHANCE AT PRECIP THIS AFTERNOON THAN THE IMPERIAL VALLEY. A LOT OF UNCERTAINTIES REMAIN REGARDING INSTABILITY AND THUS THE OCCURRENCE OF CONVECTIVE SHOWERS. ANTICIPATE THAT LA PAZ COUNTY WILL BE ACTIVE ENOUGH LATER TODAY TO PRODUCE STORMS IN THE VICINITY OF KBLH. CANT RULE OUT STORM POSSIBILITIES FOR KIPL BUT TOO LOW AT THIS TIME TO REFLECT IN THE TAFS. SIGNIFICANTLY REDUCED VISIBILITIES IN HEAVY RAIN WILL BE POSSIBLE WITH THE STRONGER SHOWERS. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... SUNDAY THROUGH THURSDAY... LINGERING MOISTURE WILL MAINTAIN AN ELEVATED CHANCE OF THUNDERSTORMS FOR EARLY NEXT WEEK. DEEPER WESTERLY FLOW WILL LEAD TO A DOWNTREND IN ATMOSPHERIC MOISTURE BEGINNING TUESDAY. THUS...HUMIDITIES AND STORM CHANCES WILL DECLINE FROM WEST TO EAST. THERE WILL BE ONLY A SLIGHT CHANCE OF THUNDERSTORMS LEFT OVER THE HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA ON WEDNESDAY AND THURSDAY. MINIMUM HUMIDITIES WILL DROP INTO THE UPPER TEENS OVER SOUTHEAST CALIFORNIA BY THURSDAY. APART FROM THUNDERSTORM OUTFLOWS...NO STRONG WINDS ARE ANTICIPATED. AFTERNOON WINDS ARE EXPECTED TO FAVOR SOUTHWEST AND WESTERLY DIRECTIONS FOR MOST AREAS BEGINNING TUESDAY. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX DISCUSSION...LEINS AVIATION...AJ FIRE WEATHER...AJ
AREA FORECAST DISCUSSION...UPDATED
NWS NORTH PLATTE NE
637 AM CDT FRI SEP 7 2012 .UPDATE... .AVIATION... VFR IS EXPECTED MOST AREAS TODAY AND TONIGHT. LIGHT RAIN AND LOCALLY MVFR CIGS OVC025 MAY BE DEVELOPING BENEATH SOME OF THE STRONGER RADAR RETURNS. GIVEN THE COUPLED JET STRUCTURE FOCUSED ALONG AND NORTH OF NEBRASKA HIGHWAY 2...THE RAPID UPDATE MODELS...HRRR AND RAP MAINTAIN THIS FEATURE ACROSS NRN NEB THIS MORNING AND PERHAPS UNTIL 21Z. THEREAFTER THE DISTURBANCE SHOULD MOVE EAST WITH VFR BECOMING ABSOLUTE THROUGH 12Z SATURDAY MORNING. OTHERWISE THE PREDOMINATE CIGS SHOULD OPERATE AS OVC070. && .PREV DISCUSSION... /ISSUED 352 AM CDT FRI SEP 7 2012/ DISCUSSION... PRIMARY FORECAST ISSUES TODAY INCLUDE TEMPERATURES TODAY AND TONIGHT AS WELL AS THE LIGHT RAIN FOR TODAY. THEN GOING ON THROUGH THE NEXT WEEK...WARMING CONDITIONS AND BREEZY WINDS RETURN WHICH AGAIN BRINGS FIRE CONCERNS BACK TO THE FOREFRONT. THEN INTO THE MIDDLE PART OF NEXT WEEK...FORECAST ISSUES INVOLVE A DECENT COOLING TREND AND CHANCES FOR RAIN. AT 07.07Z WATER VAPOR IMAGERY SHOWED A SHORTWAVE TROUGH EXTENDING FROM THE UPPER LOW OVER SOUTHERN HUDSON BAY THROUGH NORTH DAKOTA AND INTO MONTANA AND IDAHO. BROAD RIDGING REMAINED OVER THE DESERT SOUTHWEST INTO TEXAS AND THE LOWER MISSISSIPPI RIVER VALLEY...WHILE RIDGING WAS ALSO OBSERVED OVER THE PACIFIC NORTHWEST. AT THE SURFACE..THE COLD FRONT HAD PUSHED SOUTHEAST THROUGH THE FORECAST AREA THURSDAY EVENING AND BY 07Z WAS INTO KANSAS AND EASTERN NEBRASKA. WINDS VARIED BEHIND THE FRONT WITH SOME LOCATIONS REMAINING MIXED WITH BREEZY CONDITIONS STILL...WHILE OTHERS HAD DECOUPLED WITH LIGHT WINDS BEING OBSERVED. RADAR DID SEE ONGOING ACTIVITY EARLY THIS MORNING WITH A DECENT BAND OF RAIN JUST NORTH OF THE NEBRASKA/SOUTH DAKOTA BORDER. THIS BANDING FEATURE WAS OCCURRING WITH FRONTOGENESIS ABOVE 600MB. RADAR IS INDICATING RAINFALL UP TO A HALF INCH UNDER THIS BAND...BUT WITH ALL CEILINGS ACROSS THE AREA AT OR ABOVE 8K FEET...THOSE VALUES ARE WAY OVERDONE. CUSTER SD DID PICK UP 0.08 INCHES EARLIER SO THINKING EVEN IN THE HIGHER REFLECTIVITY AREAS...A FEW TENTHS IS PROBABLY THE HIGHEST AMOUNTS. WILL HAVE TO WAIT UNTIL THE SHOWERS GET OVER A MEASURING STATION THOUGH TO GET GROUND TRUTH. SHORT TERM...TODAY THROUGH SUNDAY NIGHT FRONTOGENESIS SIGNAL SHIFTS SOUTH...WITH A SECONDARY BAND LOOKING TO TAKE OVER TO THE SOUTH OVER THE SANDHILLS. THIS SIGNAL DOES DECREASE IN STRENGTH AS THE MORNING PROGRESSES AND BY THIS AFTERNOON...VERY LITTLE FORCING REMAINS OVER THE FORECAST AREA. DID INCREASE PRECIPITATION OVER THE MORNING HOURS DUE TO HIGHER COVERAGE...HOWEVER WITH THE DRY BOUNDARY LAYER THAT NEEDS TO BE PENETRATED...DON/T THINK MUCH OF THE RAIN WILL MAKE IT TO THE SURFACE. SO BASICALLY LOOKING FOR HIGHER COVERAGE OF LIGHT QPF...UP TO A TENTH OF AN INCH AT MOST. CLOUDS WILL SHIFT OUT OF THE MAJORITY OF THE FORECAST AREA BY MID AFTERNOON. TEMPERATURES TODAY WILL BE MUCH COOLER THAN YESTERDAY /15 TO 20 DEGREES MOST PLACES/ AS COLDER AIR MOVES SOUTH BEHIND THE SYSTEM. FOR EXAMPLE...07.00Z UPPER AIR DATA SHOWS A DIFFERENCE OF 27C ANT KLBF...WITH 18C AT KUNR AND 10C OVER THE UPPER AIR SITES IN MONTANA. EVEN AFTER THE STRONG PUSH OF COLDER AIR...WITH CLOUDS MOVING OUT ALLOWING GOOD SUNSHINE IN THE AFTERNOON...AND A RAPIDLY DRYING BOUNDARY LAYER WILL ALLOW FOR TEMPERATURES TO WARM INTO THE UPPER 70S AT SOME LOCATIONS. LOWS TONIGHT STAY A HOT TOPIC...WITH THE COLDEST NIGHT OF THE SEASON POSSIBLE. MODEL SOLUTIONS SHOWING THE SURFACE HIGH CENTERED TO THE WEST OF THE FORECAST AREA...INDICATING WINDS WILL STAY LIGHT RATHER THAN COMPLETELY DROPPING OFF. WOULD LIKE TO SEE THE HIGH DIRECTLY OVERHEAD FOR WIDESPREAD LOWS IN THE 30S. MADE MINIMAL CHANGES TO THE FORECAST LOWS...WITH MOST AREAS EXPECTED IN THE LOW 40S...WITH UPPER 30S IN VALLEYS AND OTHER FAVORED DRAINAGE LOCATIONS. IF THE PLACEMENT OF THE HIGH CHANGES...THESE VALUES WILL NEED TO BE REVISITED IN THE NEXT FORECAST PACKAGE. NORTHERLY FLOW WILL BE IN PLACE SATURDAY...HOWEVER GRADUAL WARMING ALOFT THROUGH THE DAY WILL ALLOW FOR TEMPERATURES TO WARM DECENTLY AS DEEP MIXING IS EXPECTED. WENT ON THE HIGH SIDE OF GUIDANCE AS HAS BEEN THE WAY TO GO LATELY. THIS WOULD BRING HIGHS TO NEAR OR SLIGHTLY ABOVE NORMAL FOR THE FORECAST AREA. ANOTHER QUITE COOL NIGHT IS IN STORE FOR SATURDAY NIGHT AS THE SURFACE HIGH SHIFTS INTO EASTERN NEBRASKA...WITH A COOLER AIRMASS CONTINUING TO SIT OVER THE REGION. DON/T THINK IT WILL BE AS COLD AS FRIDAY NIGHT AS THE AIRMASS SHOULD HAVE WARMED SLIGHTLY...BUT LOWS IN THE 40S CERTAINLY LOOKS LIKELY IN PLACES...ESPECIALLY IN CENTRAL AND EASTERN NEBRASKA WHICH WILL SIT UNDER THE RIDGE. SOUTHERLY FLOW WILL RETURN IN FULL FORCE SUNDAY WITH WARMING TEMPERATURES AND BREEZY WINDS. DEWPOINTS WILL STILL BE QUITE DRY THOUGH AS LITTLE MOISTURE RETURN IS EXPECTED. 850MB WINDS LOOK TO RETURN INTO THE 20S ACROSS THE ENTIRE AREA BY SUNDAY AFTERNOON...SO HIGHS IN THE UPPER 80S AND LOW 90S LOOKS APPROPRIATE. LONG TERM...MONDAY THROUGH THURSDAY HAVE BEEN WATCHING MONDAY FOR THE PAST SEVERAL DAYS AND IT CONTINUES TO LOOK LIKE IT WILL BE AN ANOMALOUSLY WARM DAY WITH HIGHS LIKELY IN THE 90S ACROSS THE ENTIRE FORECAST AREA. WITH CONFIDENCE BUILDING IN THIS OUTCOME...DID RAISE HIGHS ANOTHER COUPLE DEGREES WITH MID 90S IN PARTS OF THE FORECAST AREA. THERE IS SUGGESTION FROM SOME MODEL OUTPUT OF UPPER 90S...BUT DIDN/T GO THAT WARM YET. LOW PRESSURE WILL BE OFF TO THE WEST...BUT LONGER RANGE MODELS ARE NOT SHOWING A STRONG EASTWARD PUSH OF THE DRYLINE MONDAY. THIS BEING SAID...DEWPOINTS IN THE UPPER 30S AND 40S WILL STILL COMBINE WITH TEMPERATURES IN THE 90S TO DROP RELATIVE HUMIDITY DOWN TO NEAR 15 PERCENT. ALSO...WIND SIGNALS ARE NOT LOOKING FOR STRONG WINDS...BUT BREEZY CONDITIONS WITH GUSTS AT 20 TO 30 AT TIMES ARE VERY POSSIBLE. FIRE WEATHER WILL BE OF HIGH CONCERN ON MONDAY DUE TO THESE CONDITIONS. MODEL SOLUTIONS BEGIN TO DIVERGE AFTER MONDAY SO CONFIDENCE IN THE LATTER PART OF THE FORECAST DOES GO DOWN. THAT BEING SAID...THERE IS AGREEMENT IN A SYSTEM MOVING ACROSS THE CENTRAL PLAINS TO BRING RAIN TO A GOOD PORTION OF THE AREA. THE CONTINUED ISSUE WILL BE HOW MUCH MOISTURE THERE WILL BE IN THE AREA...IF ENOUGH WILL RETURN MONDAY AND TUESDAY TO ALLOW FOR SOME WIDESPREAD RAINS. DID INCLUDE CHANCES FOR RAIN THE THE MIDDLE AND LATE PARTS OF NEXT WEEK...BUT WITH LOW CONFIDENCE LIMITED THESE CHANCES TO SLIGHT CHANCES AND ONLY TO THE SOUTHERN COUNTIES. ALSO...A GOOD COOLDOWN IS BEING INDICATED FOR THE SECOND HALF OF NEXT WEEK. COULD SEE SEVERAL CONSECUTIVE DAYS OF HIGHS IN THE 70S AND LOW 80S. AVIATION... VFR IS EXPECTED ALL AREAS THROUGH TODAY AND TONIGHT. A MIDLEVEL DISTURBANCE WILL TRAVERSE THE AREA TODAY REDUCING CIGS TO BKN-OVC070-100 IN PERIODS OF LIGHT RAIN. CLEAR SKIES ARE EXPECTED TONIGHT. FIRE WEATHER... ANOTHER SIGNIFICANT LOW PRESSURE SYSTEM WILL MOVE THROUGH THE NRN PLAINS THIS WEEKEND AND MONDAY BEFORE A COLD FRONT MOVES THROUGH TUESDAY. OPPORTUNITIES FOR HIGH OR EXTREME FIRE DANGER DEVELOP SATURDAY...SUNDAY AND MONDAY AS THIS LOW DEEPENS ACROSS THE NRN PLAINS. THE UNCERTAINTY IN THE FIRE WEATHER THREAT RESIDES IN THE WIND GUST FORECASTS WHICH ARE LIMITED TO JUST TWO MODELS...THE NAMDNG AND GFS MOSGUIDE DATA. WIND PROFILES SUGGEST CRITICAL FIRE DANGER SHOULD BE CLOSELY MONITORED ACROSS NCNTL NEB EAST OF HIGHWAY 83 SATURDAY...WRN AND NRN NEB SUNDAY AND ALL ZONES MONDAY. THE NAMDNG DATA SHOWS WIND GUSTS BELOW CRITERIA WHILE THE GFS MOSGUIDE INDICATES GUSTS EXCEEDING CRITERIA. LATER FORECASTS WILL MONITOR THIS SITUATION. && .LBF WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM/EXTENDED...CDC AVIATION...CDC
AREA FORECAST DISCUSSION
NWS BUFFALO NY
1046 AM EDT FRI SEP 7 2012 .SYNOPSIS... EXPECT A FAIR AMOUNT OF SUNSHINE TODAY ALONG WITH ABOVE NORMAL TEMPERATURES AND SCATTERED AFTERNOON SHOWERS AND THUNDERSTORMS POSSIBLE. CLOUD COVER WILL INCREASE TONIGHT AND THE WEATHER WILL TURN MORE UNSETTLED BY SATURDAY MORNING AS A RAPIDLY DEVELOPING LOW TRACKS ACROSS THE GREAT LAKES BRINGING HEAVY RAIN AND GUSTY WINDS TO THE REGION ON SATURDAY. A COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL SWEEP ACROSS THE REGION LATE ON SATURDAY USHERING IN MUCH COOLER TEMPERATURES FOR THE LATTER HALF OF THE WEEKEND AND BEGINNING OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... A STALLED FRONT TO THE WEST WILL LEAVE WESTERN NEW YORK ON THE WARM AND MUGGY SIDE OF THE BOUNDARY. HIGHS SHOULD BE SIMILAR TO A TAD WARMER THAN YESTERDAY. A BLEND OF THE BIAS CORRECTED SREF...LAV GUIDANCE...AND THE 12Z BUFFALO SUGGEST HIGHS WILL BE IN THE LOWER TO MID 80S TODAY. THE MOIST AND UNSTABLE AIRMASS IN PLACE ACROSS THE REGION WILL ONCE AGAIN CREATE THE POTENTIAL FOR THE DEVELOPMENT OF ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON WITH THE MOST LIKELY FOCUS FOR SAID ACTIVITY BEING ACROSS THE GENESEE VALLY AND FINGER LAKES...AWAY FROM THE STABILIZING INFLUENCE OF THE LAKES. WITH NO DISTINCT LARGE-SCALE FOCUS FOR CONVECTION...EXPECT LAKE BREEZE BOUNDARIES WILL BE THE MAIN FOCUS FOR ANY CONVECTION WHICH DEVELOPS. FEEL THE HRRR HAS THE RIGHT IDEA IN THIS...THOUGH IT MAY BE OFF SLIGHTLY ON THE POSITION OF THE BOUNDARIES. SEVERE WEATHER POTENTIAL IS MINIMAL GIVEN FAIRLY WEAK WINDS BELOW 850MB...HOWEVER A STRONG PULSE THUNDERSTORM CANNOT BE RULED OUT. ANY SHOWERS OR THUNDERSTORMS SHOULD HOLD OFF UNTIL MID- AFTERNOON. THE FOCUS OF ANY LINGERING SHOWER AND THUNDERSTORM ACTIVITY SHOULD SHIFT NORTH TOWARDS CANADA THIS EVENING AS THE STATIONARY FRONT LIFTS NORTH AS A WARM FRONT AHEAD OF A RAPIDLY DEVELOPING LOW PRESSURE SYSTEM MOVING OUT OF THE MIDWEST INTO THE LOWER GREAT LAKES. STRENGTHENING SOUTHERLY FLOW AHEAD OF THIS LOW WILL ADVECT EVEN WARMER AIR INTO THE REGION WITH 850MB TEMPS SURGING TO +16 TO +18C...RESULTING IN A SULTRY LATE SUMMER NIGHT ACROSS THE REGION WITH LOWS ONLY DIPPING INTO THE UPPER 60S ALONG THE LAKE PLAINS WITH MID 60S ACROSS HIGHER ELEVATIONS INLAND. THE CHANCE FOR SHOWERS AND THUNDERSTORMS WILL ONCE AGAIN INCREASE ACROSS THE NIAGARA FRONTIER AFTER MIDNIGHT AHEAD OF THE APPROACHING COLD FRONT. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AT THE START OF THE PERIOD ON SATURDAY A VERY DYNAMIC AND MOISTURE LADEN SYSTEM WILL BRING ANOTHER ROUND OF WIDESPREAD RAINFALL TO THE REGION. VERY STRONG DYNAMICS WILL COME INTO PLAY WITH STRONG HEIGHT FALLS AND DPVA AND STRONG UPPER LEVEL DIVERGENCE IN THE RIGHT ENTRANCE REGION OF A 120+ KNOT UPPER LEVEL JET. THE FRONTAL WAVE WILL ALSO INDUCE A STRONG DIFFERENTIAL THERMAL ADVECTION PATTERN AND FORCE A STRONG RIBBON OF FRONTOGENESIS ALONG THE COLD FRONT. THE SYSTEM WILL CAPTURE A PLUME OF DEEPER MOISTURE AS IT ROUNDS THE BASE OF THE TROUGH...WITH PWAT RISING TO 1.5 TO 1.75 INCHES. THE QUALITY OF FORCING AND MOISTURE COMING INTO PLAY WILL BRING ANOTHER PERIOD OF MODERATE OR EVEN HEAVY RAINFALL TO THE REGION...WITH QPF POTENTIAL OF AROUND AN INCH POSSIBLE...WITH LOCALLY HIGHER AMOUNTS WHERE EMBEDDED CONVECTION TRAINS. NAM/SREF/CMC MODELS ARE SHOWING A SLIGHTLY SLOWER SCENARIO WITH THE PREFRONTAL CONVECTION TO ARRIVE DURING THE DAY ON SATURDAY RATHER THAN EARLIER ARRIVAL DURING LATE FRIDAY NIGHT AS DEPICTED BY GFS. WILL CONTINUE WITH THE 100 PERCENT POP GRIDS BUT HAVE A LITTLE MORE RESOLUTION ALONG AND IN ADVANCE OF THE FRONTAL BOUNDARY. WHILE SATURDAY WILL BE A WET DAY ACROSS THE REGION...LATE SATURDAY AND AT LEAST THE FIRST HALF OF SATURDAY NIGHT COULD BE QUITE WINDY AS WELL. THIS WILL ESPECIALLY BE THE CASE OVER THE FAR WESTERN COUNTIES AND IN PARTICULAR...THE CORRIDOR FROM BUFFALO AND THE LAKE ERIE SHORE TO ROCHESTER. EXPECT TO SEE A RISE IN WINDS AND GUSTS IMMEDIATELY FOLLOWING FROPA...AND ESPECIALLY FROM THE NIAGARA FRONTIER TO THE LOWER GENESEE VALLEY...AFFECTING THE BUF/IAG/ROC METRO AREAS. HAVE BACKED OFF A BIT ON THE INTENSITY OF THE WINDS AS MODELS ARE NOT EXPLICITLY DEPICTING ADVISORY CRITERIA SURFACE WINDS BUT THERE WILL REMAIN THE RISK OF HIGHER TURBULENT GUSTS WITHIN THE BRISK GRADIENT WINDS DURING LATE SATURDAY AFTERNOON AND EVENING. LATER SATURDAY NIGHT AND SUNDAY ANOTHER STRONG SHORTWAVE WILL ROUND THE BASE OF THE TROUGH WITH 850MB TEMPS BOTTOMING OUT AROUND +4C. MOISTURE WILL BE LIMITED...BUT COLD AIR ALOFT AND SOME ADDITION OF MOISTURE FROM THE LAKES WILL PRODUCE SCATTERED SHOWERS. SUNDAY MORNING MOST OF THE SHOWERS MAY BE PURELY LAKE EFFECT SOUTHEAST OF THE LAKES. BY AFTERNOON THE GREATER INSTABILITY SHOULD FOCUS ACROSS THE LAND WITH LESS ACTIVITY OVER THE LAKES. SUNDAY NIGHT ALL OF THIS WILL GRADUALLY END AS SURFACE HIGH PRESSURE AND DRIER AIR BUILD INTO THE GREAT LAKES. THE COOLEST TEMPERATURES OF THIS EARLY FALL SEASON WILL ARRIVE OVER THE WEEKEND. TEMPS MAY BRIEFLY TOUCH THE LOWER 70S SATURDAY MORNING ESPECIALLY ACROSS CENTRAL NY BEFORE THE RAIN ARRIVES. BY SUNDAY HIGHS WILL ONLY BE IN THE UPPER 60S AT LOWER ELEVATIONS AND LOW TO MID 60S ACROSS HIGHER TERRAIN. && .LONG TERM /MONDAY THROUGH THURSDAY/... HIGH PRESSURE WILL BUILD INTO THE OHIO VALLEY AND GREAT LAKES MONDAY WITH A RETURN TO SUNSHINE. TEMPERATURES WILL STILL BE COOL HOWEVER WITH A CHILLY AIRMASS IN PLACE. EXPECT HIGHS IN THE UPPER 60S ACROSS LOWER ELEVATIONS AND LOW TO MID 60S AT HIGHER TERRAIN. MONDAY NIGHT SHOULD BE THE COOLEST NIGHT OF THE STRETCH AS HIGH PRESSURE SETTLES DIRECTLY OVERHEAD WITH IDEAL RADIATIONAL COOLING CONDITIONS. EXPECT LOWER 50S ON THE LAKE PLAINS AND PLENTY OF 40S INLAND...WITH A FEW OF THE COOLER SOUTHERN TIER VALLEYS AND TUG HILL REGION DIPPING INTO THE UPPER 30S. TUESDAY THROUGH WEDNESDAY HIGH PRESSURE WILL SLIDE TO THE EAST COAST AND THE PATTERN WILL REMAIN PROGRESSIVE...WITH THE WESTERN RIDGE FLATTENING AND HEADING EAST. THIS WILL BRING A STEADY WARM-UP WITH HIGHS BACK INTO THE 70S...AND POSSIBLY NEAR 80 BY WEDNESDAY. DRY WEATHER WILL CONTINUE THROUGH THE PERIOD WITH PLENTY OF SUNSHINE. BY THURSDAY THE NEW 12Z ECMWF LEANS A WEAK COLD FRONT INTO THE LOWER LAKES...BUT THE 12Z GFS IS MUCH SLOWER WITH THIS FRONT KEEPING IT WELL TO OUR WEST. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... VFR CONDITIONS WILL THEN PREVAIL THROUGH THE TAF PERIOD. THERE IS A POSSIBILITY OF SHOWERS AND THUNDERSTORMS DEVELOPING THIS AFTERNOON WITH THE FOCUS BEING ACROSS THE GENESEE VALLEY AND FINGER LAKES. ANY CONVECTION THIS AFTERNOON SHOULD WEAKEN AND/OR LIFT NORTH THIS EVENING AS THE STALLED OUT FRONTAL BOUNDARY AIDING THE DEVELOPMENT OF THESE SHRA/TSRA LIFTS NORTH INTO CANADA AS A WARM FRONT. THE MAIN FOCUS WILL THEN SHIFT TO THE RAPIDLY DEVELOPING LOW PRESSURE SYSTEM THAT IS FORECAST TO TRACK ACROSS THE LOWER GREAT LAKES FRIDAY NIGHT AND SATURDAY BRINGING WIDESPREAD HEAVY RAIN WITH WIDESPREAD MVFR/IFR CONDITIONS AND STRONG WINDS. THE LEADING EDGE OF THIS FRONTAL BAND IS EXPECTED TO BEGIN TO EDGE INTO THE NIAGARA FRONTIER AND WESTERN SOUTHERN TIER AFTER 09Z SATURDAY MORNING WITH CONDITIONS CONTINUING TO DETERIORATE THROUGH THE MORNING ON SATURDAY...NEAR AND AFTER THE END OF THE CURRENT TAF PERIOD. IN ADDITION...THE ARRIVAL OF A 35-40KT LOW LEVEL JET MAY POSE LLWS ISSUES AFTER 09Z HOWEVER THIS WILL BE DEPENDENT ON HOW STRONG THE NOCTURNAL INVERSION SETS UP TONIGHT. OUTLOOK... SATURDAY...MVFR/IFR IN RAIN AND SCATTERED THUNDERSTORMS. SUNDAY...VFR/MVFR WITH A CHANCE OF SHOWERS. MONDAY THROUGH WEDNESDAY...VFR. && .MARINE... LIGHT WINDS AND WAVES WILL PREVAIL ON THE LAKES TODAY AND THIS EVENING AS HIGH PRESSURE SLOWLY RETREATS TOWARDS THE EAST COAST. CONDITIONS ON THE LAKES WILL DETERIORATE FROM WEST TO EAST LATER TONIGHT AS A RAPIDLY DEVELOPING LOW PRESSURE SYSTEM TRACKS FROM THE MIDWEST ACROSS THE LOWER GREAT LAKES. SOUTHERLY WINDS WILL FRESHEN AHEAD OF THIS LOW LATE FRIDAY NIGHT/EARLY SATURDAY MORNING AND WILL TRANSITION TO STRONGER WEST/SOUTHWESTERLY WINDS LATER ON SATURDAY AS A COLD FRONT SWEEPS ACROSS THE LAKES. A BRIEF PERIOD OF GALES MAY BE POSSIBLE IMMEDIATELY IN THE WAKE OF THE FRONT...HOWEVER THERE IS STILL SOME UNCERTAINTY AS TO WHERE EXACTLY THE STRONGEST WINDS WILL LINE UP WITH RELATION TO THE LAKES. SIGNIFICANTLY COLDER AIR WILL FILTER INTO THE REGION BEHIND THE COLD FRONT...BRINGING AN INCREASED POTENTIAL FOR WATERSPOUTS FOR THE LATTER HALF OF THE WEEKEND INTO THE EARLY PART OF NEXT WEEK. IN ADDITION A PROLONGED PERIOD OF BRISK WESTERLY WINDS WILL LIKELY MEAN AN EXTENDED PERIOD OF SMALL CRAFT ADVISORY CONDITIONS ON THE LAKES. && .CLIMATE... AN EARLY WARM SPRING AND CONTINUED WARMTH THROUGH THE SUMMER HAS LED TO MANY DAYS THAT HAVE REACHED 80F ACROSS WESTERN AND NORTH CENTRAL NEW YORK. BELOW IS A LIST OF THE NUMBER OF DAYS IN THE CALENDAR YEAR THAT HAVE REACHED 80 DEGREES OR GREATER. THE 2012 TOTAL WILL INCREASE AS WE REACH ADDITIONAL 80F DAYS THROUGH THE EARLY FALL. BUFFALO (SINCE 1871) 1 83 1949 2 82 1959 3 77 1991 77 2012 (THROUGH THU 9/6) 5 76 1955 6 75 1947 75 1983 75 2005 9 73 2011 ROCHESTER (SINCE 1871) 1 91 1959 2 86 2007 3 83 2002 83 1973 83 1949 83 1947 7 82 2012 (THROUGH THU 9/6) 8 81 1991 9 80 2005 80 1921 ... 21 75 2011 WATERTOWN (SINCE 1949) 1 75 1949 2 73 1959 3 69 2012 (THROUGH THU 9/6) 4 68 1955 5 67 1973 ... 9 60 2011 && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...NONE. && $$ SYNOPSIS...WOOD NEAR TERM...APFFEL/WOOD SHORT TERM...WCH LONG TERM...HITCHCOCK AVIATION...APFFEL/WOOD MARINE...WOOD CLIMATE...THOMAS/JJR
AREA FORECAST DISCUSSION
NWS BUFFALO NY
941 AM EDT FRI SEP 7 2012 .SYNOPSIS... EXPECT A FAIR AMOUNT OF SUNSHINE TODAY ALONG WITH ABOVE NORMAL TEMPERATURES AND SCATTERED AFTERNOON SHOWERS AND THUNDERSTORMS POSSIBLE. CLOUD COVER WILL INCREASE TONIGHT AND THE WEATHER WILL TURN MORE UNSETTLED BY SATURDAY MORNING AS A RAPIDLY DEVELOPING LOW TRACKS ACROSS THE GREAT LAKES BRINGING HEAVY RAIN AND GUSTY WINDS TO THE REGION ON SATURDAY. A COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL SWEEP ACROSS THE REGION LATE ON SATURDAY USHERING IN MUCH COOLER TEMPERATURES FOR THE LATTER HALF OF THE WEEKEND AND BEGINNING OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... ANY LINGERING FOG WILL BURN OFF QUICKLY...GIVING WAY TO MOSTLY SUNNY SKIES BY LATE MORNING. A STALLED FRONT TO THE WEST WILL LEAVE WESTERN NEW YORK ON THE WARM AND MUGGY SIDE OF THE BOUNDARY. HIGHS SHOULD BE SIMILAR TO A TAD WARMER THAN YESTERDAY. A BLEND OF THE BIAS CORRECTED SREF...LAV GUIDANCE...AND THE 12Z BUFFALO SUGGEST HIGHS WILL BE IN THE LOWER TO MID 80S TODAY. THE MOIST AND UNSTABLE AIRMASS IN PLACE ACROSS THE REGION WILL ONCE AGAIN CREATE THE POTENTIAL FOR THE DEVELOPMENT OF ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON WITH THE MOST LIKELY FOCUS FOR SAID ACTIVITY BEING ACROSS THE GENESEE VALLY AND FINGER LAKES...AWAY FROM THE STABILIZING INFLUENCE OF THE LAKES. WITH NO DISTINCT LARGE-SCALE FOCUS FOR CONVECTION...EXPECT LAKE BREEZE BOUNDARIES WILL BE THE MAIN FOCUS FOR ANY CONVECTION WHICH DEVELOPS. FEEL THE HRRR HAS THE RIGHT IDEA IN THIS...THOUGH IT MAY BE OFF SLIGHTLY ON THE POSITION OF THE BOUNDARIES. SEVERE WEATHER POTENTIAL IS MINIMAL GIVEN FAIRLY WEAK WINDS BELOW 850MB...HOWEVER A STRONG PULSE THUNDERSTORM CANNOT BE RULED OUT. ANY SHOWERS OR THUNDERSTORMS SHOULD HOLD OFF UNTIL MID- AFTERNOON. THE FOCUS OF ANY LINGERING SHOWER AND THUNDERSTORM ACTIVITY SHOULD SHIFT NORTH TOWARDS CANADA THIS EVENING AS THE STATIONARY FRONT LIFTS NORTH AS A WARM FRONT AHEAD OF A RAPIDLY DEVELOPING LOW PRESSURE SYSTEM MOVING OUT OF THE MIDWEST INTO THE LOWER GREAT LAKES. STRENGTHENING SOUTHERLY FLOW AHEAD OF THIS LOW WILL ADVECT EVEN WARMER AIR INTO THE REGION WITH 850MB TEMPS SURGING TO +16 TO +18C...RESULTING IN A SULTRY LATE SUMMER NIGHT ACROSS THE REGION WITH LOWS ONLY DIPPING INTO THE UPPER 60S ALONG THE LAKE PLAINS WITH MID 60S ACROSS HIGHER ELEVATIONS INLAND. THE CHANCE FOR SHOWERS AND THUNDERSTORMS WILL ONCE AGAIN INCREASE ACROSS THE NIAGARA FRONTIER AFTER MIDNIGHT AHEAD OF THE APPROACHING COLD FRONT. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AT THE START OF THE PERIOD ON SATURDAY A VERY DYNAMIC AND MOISTURE LADEN SYSTEM WILL BRING ANOTHER ROUND OF WIDESPREAD RAINFALL TO THE REGION. VERY STRONG DYNAMICS WILL COME INTO PLAY WITH STRONG HEIGHT FALLS AND DPVA AND STRONG UPPER LEVEL DIVERGENCE IN THE RIGHT ENTRANCE REGION OF A 120+ KNOT UPPER LEVEL JET. THE FRONTAL WAVE WILL ALSO INDUCE A STRONG DIFFERENTIAL THERMAL ADVECTION PATTERN AND FORCE A STRONG RIBBON OF FRONTOGENESIS ALONG THE COLD FRONT. THE SYSTEM WILL CAPTURE A PLUME OF DEEPER MOISTURE AS IT ROUNDS THE BASE OF THE TROUGH...WITH PWAT RISING TO 1.5 TO 1.75 INCHES. THE QUALITY OF FORCING AND MOISTURE COMING INTO PLAY WILL BRING ANOTHER PERIOD OF MODERATE OR EVEN HEAVY RAINFALL TO THE REGION...WITH QPF POTENTIAL OF AROUND AN INCH POSSIBLE...WITH LOCALLY HIGHER AMOUNTS WHERE EMBEDDED CONVECTION TRAINS. NAM/SREF/CMC MODELS ARE SHOWING A SLIGHTLY SLOWER SCENARIO WITH THE PREFRONTAL CONVECTION TO ARRIVE DURING THE DAY ON SATURDAY RATHER THAN EARLIER ARRIVAL DURING LATE FRIDAY NIGHT AS DEPICTED BY GFS. WILL CONTINUE WITH THE 100 PERCENT POP GRIDS BUT HAVE A LITTLE MORE RESOLUTION ALONG AND IN ADVANCE OF THE FRONTAL BOUNDARY. WHILE SATURDAY WILL BE A WET DAY ACROSS THE REGION...LATE SATURDAY AND AT LEAST THE FIRST HALF OF SATURDAY NIGHT COULD BE QUITE WINDY AS WELL. THIS WILL ESPECIALLY BE THE CASE OVER THE FAR WESTERN COUNTIES AND IN PARTICULAR...THE CORRIDOR FROM BUFFALO AND THE LAKE ERIE SHORE TO ROCHESTER. EXPECT TO SEE A RISE IN WINDS AND GUSTS IMMEDIATELY FOLLOWING FROPA...AND ESPECIALLY FROM THE NIAGARA FRONTIER TO THE LOWER GENESEE VALLEY...AFFECTING THE BUF/IAG/ROC METRO AREAS. HAVE BACKED OFF A BIT ON THE INTENSITY OF THE WINDS AS MODELS ARE NOT EXPLICITLY DEPICTING ADVISORY CRITERIA SURFACE WINDS BUT THERE WILL REMAIN THE RISK OF HIGHER TURBULENT GUSTS WITHIN THE BRISK GRADIENT WINDS DURING LATE SATURDAY AFTERNOON AND EVENING. LATER SATURDAY NIGHT AND SUNDAY ANOTHER STRONG SHORTWAVE WILL ROUND THE BASE OF THE TROUGH WITH 850MB TEMPS BOTTOMING OUT AROUND +4C. MOISTURE WILL BE LIMITED...BUT COLD AIR ALOFT AND SOME ADDITION OF MOISTURE FROM THE LAKES WILL PRODUCE SCATTERED SHOWERS. SUNDAY MORNING MOST OF THE SHOWERS MAY BE PURELY LAKE EFFECT SOUTHEAST OF THE LAKES. BY AFTERNOON THE GREATER INSTABILITY SHOULD FOCUS ACROSS THE LAND WITH LESS ACTIVITY OVER THE LAKES. SUNDAY NIGHT ALL OF THIS WILL GRADUALLY END AS SURFACE HIGH PRESSURE AND DRIER AIR BUILD INTO THE GREAT LAKES. THE COOLEST TEMPERATURES OF THIS EARLY FALL SEASON WILL ARRIVE OVER THE WEEKEND. TEMPS MAY BRIEFLY TOUCH THE LOWER 70S SATURDAY MORNING ESPECIALLY ACROSS CENTRAL NY BEFORE THE RAIN ARRIVES. BY SUNDAY HIGHS WILL ONLY BE IN THE UPPER 60S AT LOWER ELEVATIONS AND LOW TO MID 60S ACROSS HIGHER TERRAIN. && .LONG TERM /MONDAY THROUGH THURSDAY/... HIGH PRESSURE WILL BUILD INTO THE OHIO VALLEY AND GREAT LAKES MONDAY WITH A RETURN TO SUNSHINE. TEMPERATURES WILL STILL BE COOL HOWEVER WITH A CHILLY AIRMASS IN PLACE. EXPECT HIGHS IN THE UPPER 60S ACROSS LOWER ELEVATIONS AND LOW TO MID 60S AT HIGHER TERRAIN. MONDAY NIGHT SHOULD BE THE COOLEST NIGHT OF THE STRETCH AS HIGH PRESSURE SETTLES DIRECTLY OVERHEAD WITH IDEAL RADIATIONAL COOLING CONDITIONS. EXPECT LOWER 50S ON THE LAKE PLAINS AND PLENTY OF 40S INLAND...WITH A FEW OF THE COOLER SOUTHERN TIER VALLEYS AND TUG HILL REGION DIPPING INTO THE UPPER 30S. TUESDAY THROUGH WEDNESDAY HIGH PRESSURE WILL SLIDE TO THE EAST COAST AND THE PATTERN WILL REMAIN PROGRESSIVE...WITH THE WESTERN RIDGE FLATTENING AND HEADING EAST. THIS WILL BRING A STEADY WARM-UP WITH HIGHS BACK INTO THE 70S...AND POSSIBLY NEAR 80 BY WEDNESDAY. DRY WEATHER WILL CONTINUE THROUGH THE PERIOD WITH PLENTY OF SUNSHINE. BY THURSDAY THE NEW 12Z ECMWF LEANS A WEAK COLD FRONT INTO THE LOWER LAKES...BUT THE 12Z GFS IS MUCH SLOWER WITH THIS FRONT KEEPING IT WELL TO OUR WEST. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... LOCALIZED FOG ACROSS THE SOUTHERN TIER AND NIAGARA FRONTIER WILL DISSIPATE OVER THE NEXT COUPLE OF HOURS AS SUNSHINE AND VFR CONDITIONS TAKE HOLD ACROSS THE REGION. VFR CONDITIONS WILL THEN PREVAIL THROUGH THE REST OF THE TAF PERIOD. THERE IS A POSSIBILITY OF SHOWERS AND THUNDERSTORMS DEVELOPING THIS AFTERNOON WITH THE FOCUS BEING ACROSS THE GENESEE VALLEY AND FINGER LAKES. ANY CONVECTION THIS AFTERNOON SHOULD WEAKEN AND/OR LIFT NORTH THIS EVENING AS THE STALLED OUT FRONTAL BOUNDARY AIDING THE DEVELOPMENT OF THESE SHRA/TSRA LIFTS NORTH INTO CANADA AS A WARM FRONT. THE MAIN FOCUS WILL THEN SHIFT TO THE RAPIDLY DEVELOPING LOW PRESSURE SYSTEM THAT IS FORECAST TO TRACK ACROSS THE LOWER GREAT LAKES FRIDAY NIGHT AND SATURDAY BRINGING WIDESPREAD HEAVY RAIN WITH WIDESPREAD MVFR/IFR CONDITIONS AND STRONG WINDS. THE LEADING EDGE OF THIS FRONTAL BAND IS EXPECTED TO BEGIN TO EDGE INTO THE NIAGARA FRONTIER AND WESTERN SOUTHERN TIER AFTER 09Z SATURDAY MORNING WITH CONDITIONS CONTINUING TO DETERIORATE THROUGH THE MORNING ON SATURDAY...NEAR AND AFTER THE END OF THE CURRENT TAF PERIOD. IN ADDITION...THE ARRIVAL OF A 35-40KT LOW LEVEL JET MAY POSE LLWS ISSUES AFTER 09Z HOWEVER THIS WILL BE DEPENDENT ON HOW STRONG THE NOCTURNAL INVERSION SETS UP TONIGHT. OUTLOOK... SATURDAY...MVFR/IFR IN RAIN AND SCATTERED THUNDERSTORMS. SUNDAY...VFR/MVFR WITH A CHANCE OF SHOWERS. MONDAY THROUGH WEDNESDAY...VFR. && .MARINE... LIGHT WINDS AND WAVES WILL PREVAIL ON THE LAKES TODAY AND THIS EVENING AS HIGH PRESSURE SLOWLY RETREATS TOWARDS THE EAST COAST. CONDITIONS ON THE LAKES WILL DETERIORATE FROM WEST TO EAST LATER TONIGHT AS A RAPIDLY DEVELOPING LOW PRESSURE SYSTEM TRACKS FROM THE MIDWEST ACROSS THE LOWER GREAT LAKES. SOUTHERLY WINDS WILL FRESHEN AHEAD OF THIS LOW LATE FRIDAY NIGHT/EARLY SATURDAY MORNING AND WILL TRANSITION TO STRONGER WEST/SOUTHWESTERLY WINDS LATER ON SATURDAY AS A COLD FRONT SWEEPS ACROSS THE LAKES. A BRIEF PERIOD OF GALES MAY BE POSSIBLE IMMEDIATELY IN THE WAKE OF THE FRONT...HOWEVER THERE IS STILL SOME UNCERTAINTY AS TO WHERE EXACTLY THE STRONGEST WINDS WILL LINE UP WITH RELATION TO THE LAKES. SIGNIFICANTLY COLDER AIR WILL FILTER INTO THE REGION BEHIND THE COLD FRONT...BRINGING AN INCREASED POTENTIAL FOR WATERSPOUTS FOR THE LATTER HALF OF THE WEEKEND INTO THE EARLY PART OF NEXT WEEK. IN ADDITION A PROLONGED PERIOD OF BRISK WESTERLY WINDS WILL LIKELY MEAN AN EXTENDED PERIOD OF SMALL CRAFT ADVISORY CONDITIONS ON THE LAKES. && .CLIMATE... AN EARLY WARM SPRING AND CONTINUED WARMTH THROUGH THE SUMMER HAS LED TO MANY DAYS THAT HAVE REACHED 80F ACROSS WESTERN AND NORTH CENTRAL NEW YORK. BELOW IS A LIST OF THE NUMBER OF DAYS IN THE CALENDAR YEAR THAT HAVE REACHED 80 DEGREES OR GREATER. THE 2012 TOTAL WILL INCREASE AS WE REACH ADDITIONAL 80F DAYS THROUGH THE EARLY FALL. BUFFALO (SINCE 1871) 1 83 1949 2 82 1959 3 77 1991 77 2012 (THROUGH THU 9/6) 5 76 1955 6 75 1947 75 1983 75 2005 9 73 2011 ROCHESTER (SINCE 1871) 1 91 1959 2 86 2007 3 83 2002 83 1973 83 1949 83 1947 7 82 2012 (THROUGH THU 9/6) 8 81 1991 9 80 2005 80 1921 ... 21 75 2011 WATERTOWN (SINCE 1949) 1 75 1949 2 73 1959 3 69 2012 (THROUGH THU 9/6) 4 68 1955 5 67 1973 ... 9 60 2011 && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...NONE. && $$ SYNOPSIS...WOOD NEAR TERM...APFFEL/WOOD SHORT TERM...WCH LONG TERM...HITCHCOCK AVIATION...WOOD MARINE...WOOD CLIMATE...THOMAS/JJR
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
1030 AM EDT FRI SEP 7 2012 .SYNOPSIS... LONG PERIOD SWELLS FROM HURRICANE LESLIE WILL IMPACT THE BEACHES THROUGH THE WEEKEND...INCREASING THE RISK FOR STRONG AND FREQUENT RIP CURRENTS AND LARGER THAN NORMAL BREAKERS. A WEAK RIDGE OF HIGH PRESSURE WILL REMAIN ALONG THE COAST AS A TROUGH OF LOW PRESSURE SLOWLY APPROACHES THE CAROLINAS FROM THE WEST TODAY. A STRONGER FRONTAL SYSTEM WILL USHER IN FALL-LIKE WEATHER SUNDAY...WITH DRIER AND COOLER HIGH PRESSURE BUILDING IN THROUGH NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... THE EXITING SHORTWAVE CLEARLY VISIBLE IN WV IMAGERY SUGGESTS THAT DOWNWARD VERTICAL MOTION SHOULD BE IN PLACE AT THE MID LEVELS THROUGH MOST OF THE DAY. THIS WILL ACT TO SUPPRESS ALL BUT THE MOST ISOLATED ACTIVITY ALONG THE SEABREEZE. INLAND LOCATIONS HAVE FAIRLY EXTENSIVE CLOUD COVER AND MAY HAVE A TOUGH TIME SEEING ANY CONVECTION UNLESS THE CLOUDS THIN. BOTH OF THESE ARE BACKED BY THE LATEST RUN OF THE HRRR. NO CHANGES TO THE PREVIOUS FORECAST ARE ANTICIPATED. AS OF 630 AM FRIDAY...NO CHANGES HAVE BEEN MADE WITH RESPECT TO ANTICIPATED COVERAGE OF AFTERNOON SHOWERS AND THUNDERSTORMS. CURRENT RADAR LOOPS SHOW A CLUSTER OF SHOWERS IN GEORGETOWN COUNTY AND PERHAPS HINTS OF ADDITIONAL DEVELOPMENT UPSTREAM THE SANTEE RIVER ACROSS WILLIAMSBURG COUNTY. 06Z MODELS WERE SLIGHTLY COOLER WITH AFTERNOON HIGHS SO A FEW SPOTS HAVE BEEN DROPPED BY A DEGREE. CHANGES WERE ALL MINOR. PREVIOUS DISCUSSION FROM 330 AM FOLLOWS... A WEAK 500 MB DISTURBANCE AND SURFACE TROUGH/OUTFLOW BOUNDARY HAVE BEEN MAINTAINING SCATTERED CONVECTION THROUGH THE EARLY MORNING HOURS. ACTIVITY HAS BEEN MOST PREVALENT IN THE SC PEE DEE REGION WHERE RADAR ESTIMATES UP TO 4.50 INCHES OF RAIN EXIST ACROSS PORTIONS OF FLORENCE...MARION AND WILLIAMSBURG COUNTIES. THERMODYNAMICALLY THIS CONVECTION IS ELEVATED...ROOTED IN A LAYER 4000-7000 FT ABOVE THE GROUND. AS THE UPPER DISTURBANCES WEAKENS AND PRESSES OFFSHORE IN THE NEXT COUPLE OF HOURS THE CONVECTION SHOULD WEAKEN AS WELL. THE 04Z HRRR DID NOT INITIALIZE WELL...BUT EARLIER RUNS (PARTICULARLY THE 01Z RUN) MODEL THE CURRENTLY OBSERVED PATTERNS ON RADAR WELL. LOW STRATUS CLOUDS ARE FILLING IN NORTH OF THE RAIN AREA AND MAY SPREAD DOWN AS FAR SOUTH AS FLORENCE...MARION...WHITEVILLE AND WILMINGTON BY DAYBREAK. AFTER PROVIDING A GLOOMY SUNRISE THESE CLOUDS SHOULD BURN OFF BY 10:00 AM WITH AN EXPANSIVE CUMULUS FIELD DEVELOPING IN ITS PLACE. TRIGGERS FOR AFTERNOON CONVECTION SHOULD INCLUDE A WELL-DEFINED SEABREEZE...THE REMNANT OUTFLOW BOUNDARY FROM THE EARLY MORNING CONVECTION ACROSS SOUTH CAROLINA...AND A DIFFERENTIAL HEATING BOUNDARY AROUND THE EDGE OF THE MORNING LOW STRATUS DECK. DESPITE NO SUPPORT FROM THE UPPER LEVELS AND A FORECAST STORM CELL MOTION OF LESS THAN 5 MPH...I`M STILL INCLUDING 20 POPS INLAND AND 30 POPS NEAR THE COAST FOR THIS AFTERNOON GIVEN ALL THE SURFACE BOUNDARIES AND WIDESPREAD 1500 J/KG SURFACE-BASED CAPE EXPECTED. ANY LINGERING CONVECTION SHOULD DIE AWAY QUICKLY THIS EVENING AS THE BOUNDARY LAYER COOLS. THE ATMOSPHERE WILL BEGIN TO RESPOND TO AN APPROACHING UPPER LEVEL TROUGH THAT WILL DRIVE A STRONG COLD FRONT THROUGH THE CAROLINAS THIS WEEKEND. DEEP-LAYER FLOW THAT IS ESSENTIALLY LIGHT AND VARIABLE THIS AFTERNOON WILL TURN SOUTHWEST AND STEADILY INCREASE THROUGH THE NIGHT. SURFACE WINDS WILL NOT INCREASE APPRECIABLY GIVEN THE STABLE LOW-LEVEL THERMAL PROFILES AT NIGHT...BUT WINDS 1000 FT AGL AND HIGHER WILL PICK UP SPEED AFTER MIDNIGHT. HIGHS TODAY SHOULD REACH 90 OR SO INLAND...WITH UPPER 80S NEAR THE COAST AND MID 80S ON THE BEACHES. LOWS TONIGHT WILL FALL INTO THE LOWER TO MID 70S. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY...STRONG COLD FRONT WILL APPROACH THE AREA SATURDAY MOVING THROUGH BY SUNDAY. LOCAL AREA WILL BE IN WARM SECTOR ON SAT WITH DEEP LAYER MOISTURE MAKING ITS WAY IN A SW FLOW LATER IN THE DAY AS MOISTURE POOLS AHEAD OF FRONT. GFS ACTUAL SHOWS SOME DRIER AIR IN PLACE IN THE MID LEVELS INITIALLY THROUGH THE AFTERNOON AND THEN PCP WATER VALUES SHOOT UP OVER 2 INCHES THROUGH SAT EVENING. EXPECT BEST LIFT AND MOISTURE THROUGH THE LATE EVENING AND OVERNIGHT AS MID TO UPPER TROUGH PUSHES COLD FRONT THROUGH. POTENTIAL FOR STRONG TO SEVERE STORMS ESPECIALLY JUST AHEAD OF FRONT. THE FRONT WILL MAKE IT THROUGH AFTER THE BEST HEATING OF THE DAY AND THIS MAY WORK IN OUR FAVOR LIMITING MORE WIDESPREAD STORMS. THE SFC FRONT SHOULD MAKE IT OFF SHORE BY SUN MORNING BUT WINDS IN THE LOW TO MID LEVELS WILL TAKE A LITTLE WHILE LONGER TO VEER AROUND. PCP WATER VALUES WILL DROP OUT THROUGH SUNDAY DOWN LESS THAN 1.5 INCHES BY SUN AFTN AND DROPPING EVEN FURTHER TO LESS THAN AN INCH BY END OF THE PERIOD. OVERALL EXPECT MORE LOCALIZED CONVECTION THROUGH SAT AFTN WITH MORE WIDESPREAD ACTIVITY WITH APPROACH OF FRONT LATE SAT INTO EARLY SUNDAY. THEN CLEARING THROUGH SUNDAY BEHIND FRONT AS PLENTY OF DRY AIR MAKES IT WAY IN. SAT WILL BE THE LAST DAY OF VERY WARM TEMPS AS 850 TEMPS REMAIN UP NEAR 18 C BUT AS COOLER AIR ADVECTS IN ON SUNDAY...850 TEMPS WILL FALL THROUGH THE DAY REACHING DOWN TO 10 C BY MON MORNING. MAX TEMPS ON SAT WILL BE UP AROUND 90 OR SO WHILE SUNDAY THE TEMPS WILL BE BETWEEN 80 AND 85 MOST PLACES WHILE DEWPOINT TEMPS DROP ABOUT 10 DEGREES DOWN TO 60. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 300 AM FRIDAY...FALL LIKE WEATHER WILL EXIST THROUGH MUCH OF NEXT WEEK AS COOL AND DRY HIGH PRESSURE BUILDS DOWN OVER THE SOUTHEAST. BRIGHT SEPTEMBER SUN WILL PRODUCE MAX TEMPS BETWEEN 80 AND 85 MOST PLACES BUT THE VERY DRY AIR MASS WILL PRODUCE SOME LARGE DIURNAL SWINGS. WITH DEWPOINT TEMPS DOWN INTO THE 50S THROUGH AT LEAST WED AND WINDS DROPPING OFF EACH NIGHT...EXPECT MORE IDEAL RADIATIONAL COOLING LEADING TO OVERNIGHT LOWS AROUND 60 WITH UPPER 50S INLAND. ACTUALLY TEMPS WILL BE CLOSE TO NORMAL AND WILL CREEP UPWARD THROUGH MID WEEK AS H5 HEIGHTS RISE BACK UP WITH RIDGE BUILDING IN THE SOUTHEAST. BY WED MOISTURE INCREASES ENOUGH IN THE LOW LEVELS AS WINDS SHIFT AROUND TO THE NE TO PRODUCE SOME CU AROUND. OVERALL EXPECT SUNNY AND DRY WEATHER THROUGH THE WEEK. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... AS OF 12Z...THE CONVECTION HAS NOW EXITED THE COAST...ALONG WITH THE DEEP MOISTURE. ORIGINALLY THOUGHT WE WOULD SEE BOUTS OF STRATUS FOR THE FIRST COUPLE OF HOURS THIS MORNING...HOWEVER IT SEEMS MOST OF IT HAS NOW DISSIPATED. MODELS INDICATE THERE WILL BE ENOUGH MOISTURE ALONG THE IMMEDIATE COAST TO KICK OFF SCATTERED CONVECTION. BEST CHANCE WILL BE AROUND MAX HEATING...WITH MOST OF THE ACTIVITY ENDING BY 22Z. WINDS WILL BE VARIABLE THIS MORNING WITH THE LIGHT GRADIENT...BECOMING PREDOMINATELY EAST SOUTHEAST WITH THE RESULTANT THIS AFTERNOON. EXTENDED OUTLOOK...SCATTERED SHRA/TSRA THROUGH SUNDAY...WITH A CHANCE OF EARLY MORNING LIFR/IFR CONDITIONS IN BR INLAND...AND MVFR AT THE COAST. VFR MONDAY AND TUESDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1030 AM FRIDAY...NO CHANGES NEEDED TO THE MARINE FORECAST. PREVIOUS DISCUSSION FROM 330 AM FOLLOWS... A WEAK UPPER LEVEL DISTURBANCE AND SURFACE TROUGH ALONG THE CAROLINA COAST IS RESPONSIBLE FOR SEVERAL WAVES OF SHOWERS AND THUNDERSTORMS AFFECTING THE NC OFFSHORE WATER THIS MORNING. SCATTERED SHOWERS AND STORMS SHOULD DIMINISH IN COVERAGE THROUGH THE EARLY MORNING HOURS AS THIS DISTURBANCE PUSHES OFFSHORE AND WEAKENS FURTHER. GENERALLY OFFSHORE WINDS EARLY THIS MORNING WILL TURN LIGHT AND VARIABLE LATER THIS MORNING...AND THEN SOUTHERLY DRIVEN PRIMARILY BY THE SEABREEZE THIS AFTERNOON. A STRONG COLD FRONT APPROACHING FROM THE WEST WILL CREATE SLOWLY INCREASING SOUTHWEST WINDS TONIGHT. SWELL FROM HURRICANE LESLIE HAS SHORTENED TO AROUND 10 SECONDS IN PERIOD AND SHOULD CONTINUE THROUGH THE WEEKEND. ADDITIONAL SHORT PERIOD WIND WAVES WILL ADD VERY LITTLE EXTRA TO THE TOTAL SEA STATE...AND WE`RE EXPECTING 2-4 FT ACROSS THE SOUTH CAROLINA COASTAL WATERS...AND 3-4 FT FOR THE NC COASTAL WATERS. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY...SOUTHWEST FLOW WILL INCREASE THROUGH SATURDAY AHEAD OF APPROACHING COLD FRONT. SOUTHWEST WINDS UP AROUND 15 KTS WILL VEER AROUND BECOMING OFF SHORE THROUGH SUNDAY MORNING AS COLD FRONT MOVES THROUGH. THESE SOUTHWEST WINDS WILL COMBINE WITH CONTINUED LONG PERIOD E-SE SWELLS TO PRODUCE SEAS IN THE 3 TO 5 FT RANGE MOST PLACES THROUGH SATURDAY. THERE WILL BE SOME 6 FTERS IN OUTER WATERS. AS COLD FRONT MOVES FURTHER OFF SHORE THROUGH SUNDAY...WINDS WILL VEER AROUND TO THE NORTH AROUND 10 TO 15 KTS AS HIGH PRESSURE BUILDS IN FROM THE N-NW. LONG TERM /MONDAY THROUGH TUESDAY/... AS OF 300 AM FRIDAY...NORTHERLY WINDS WILL CONTINUE TO MIX WITH LONGER PERIOD SWELLS FROM LESLIE TO PRODUCE SEAS IN THE 2 TO 4 FT RANGE MOST WATERS. THE COOL NIGHTS WILL KEEP A WELL MIXED ATMOSPHERE AS COOL AIR RIDES OVER THE WARM WATERS. THIS COULD PRODUCE NORTHERLY WINDS UP TO 20 KTS OVERNIGHT. EXPECT SEAS CLOSER TO 5 FT IN OUTER WATERS AND MAY SEE SEAS UP NEAR OR SLIGHTLY ABOVE SCA EARLY MON IN NORTHERLY SURGE BEHIND FRONT. THE WINDS WILL GRADUALLY SHIFT AROUND BECOMING NE TO E AS HIGH PRESSURE BUILDS SOUTH AND EAST THROUGH MID WEEK. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...MBB SHORT TERM...RGZ LONG TERM...RGZ AVIATION...43
AREA FORECAST DISCUSSION
NWS RALEIGH NC
731 AM EDT FRI SEP 7 2012 .SYNOPSIS... A WEAK SURFACE TROUGH WILL STALL OVER THE EASTERN CAROLINAS TODAY. A DEEPENING LOW PRESSURE SYSTEM OVER THE GREAT LAKES WILL PUSH A STRONG COLD FRONT THROUGH THE CAROLINAS SATURDAY AFTERNOON AND EVENING. COOLER AND DRIER CONDITIONS WILL PREVAIL IN THE WAKE OF THE FRONT SUNDAY THROUGH EARLY NEXT WEEK AS HIGH PRESSURE BUILDS INTO THE REGION. && .NEAR TERM /TODAY AND TONIGHT/... AS OF 330 AM FRIDAY... OVERVIEW: AN H5 SHORTWAVE CENTERED NEAR THE HWY 1 CORRIDOR AT 06Z THIS MORNING IS EXPECTED TO TRACK SLOWLY EAST TOWARD THE CAROLINA COAST THIS AFTERNOON BEFORE FURTHER WEAKENING AND SHIFTING OFFSHORE THIS EVENING/TONIGHT. A SFC-H85 TROUGH ATTENDANT THE SHORTWAVE IS PROGGED TO STALL OUT OVER THE COASTAL PLAIN TODAY...THEN DISSIPATE TONIGHT AS HEIGHT FALLS OVERSPREAD THE AREA FROM WEST-EAST IN ADVANCE OF AN AMPLIFYING UPPER LEVEL TROUGH AND ASSOCIATED SURFACE COLD FRONT PROGRESSING INTO THE OH VALLEY. PRECIPITATION CHANCES: MOISTURE THROUGHOUT THE COLUMN WILL VARY WIDELY ACROSS THE AREA TODAY...BETWEEN A DRY AIRMASS (PWAT VALUES ~1.00") OVER THE MOUNTAINS AND A VERY MOIST AIRMASS (PWAT VALUES ~2.00") OVER THE COASTAL CAROLINAS WHERE THE AFOREMENTIONED SFC-H85 TROUGH IS PROGGED TO STALL OUT. THE LATEST GFS/RAP MODEL GUIDANCE INDICATES THE DRIER AIRMASS TO THE NORTH AND WEST ADVECTING INTO CENTRAL NC THROUGHOUT THE MORNING...WITH PWAT VALUES FALLING TO 1.00-1.25" OVER THE BULK OF THE AREA...EXCEPT THE SOUTHEAST COASTAL PLAIN WHERE PWAT VALUES MAY LINGER NEAR ~1.75". THE LATEST 00Z NAM APPEARS TO BE AN OUTLIER...INDICATING DEEPER MOISTURE LINGERING MUCH FURTHER WEST (TO THE TRIANGLE/HWY 1 CORRIDOR) THAN EITHER THE 00Z GFS OR 06Z RAP. GIVEN THAT THE GFS HAS SUPPORT FROM THE MOST RECENT RAP MODEL RUN... THE NAM WILL BE DISREGARD AT THIS TIME. ANTICIPATE THAT INSTABILITY WILL GENERALLY BE CONFINED TO AREAS SOUTH AND EAST OF THE TRIANGLE DURING PEAK HEATING...WITH MLCAPE VALUES RANGING FROM 500-1500 J/KG IN THE SOUTHEAST COASTAL PLAIN...PRIMARILY IN CUMBERLAND/SAMPSON/ WAYNE COUNTIES. SOME UNCERTAINTY IS PRESENT...AND THE INSTABILITY AXIS COULD BE SLIGHTLY FURTHER TO THE EAST OR WEST...DEPENDING ON THE LOCATION OF THE SFC-H85 TROUGH. FORCING FOR ASCENT TODAY WILL PRIMARILY BE ASSOCIATED WITH LOW-LEVEL CONVERGENCE IN VICINITY OF THE SEABREEZE AND THE SFC-H85 TROUGH OVER THE COASTAL CAROLINAS. SHORTWAVE ENERGY PROGRESSING INTO ILLINOIS AT 06Z WILL PROGRESS EAST THROUGH THE MID-ATLANTIC THIS AFTERNOON...RESULTING IN WEAK DPVA OVER NORTHERN PORTIONS OF THE STATE. WITH THE ABOVE IN MIND...WILL INDICATE A 20-30% CHANCE OF SHOWERS/STORMS IN THE SOUTHEAST COASTAL PLAIN CLOSER TO THE BEST MOISTURE/INSTABILITY AND LOW-LEVEL FORCING DURING PEAK HEATING. ANTICIPATE THAT THE DRIER /MORE STABLE/ AIRMASS IN PLACE OVER NORTHERN PORTIONS OF THE AREA WILL PRECLUDE A CHANCE FOR CONVECTION WITH THE AFOREMENTIONED SHORTWAVE ENERGY. WILL KEEP THE FORECAST DRY OVERNIGHT. TEMPERATURES: GIVEN LESS CLOUD COVER AND 1000-850 MB THICKNESSES SIMILAR TO PREVIOUS DAYS...EXPECT HIGHS IN THE UPPER 80S TO 90-91F. LOWS TONIGHT IN THE UPPER 60S TO LOWER 70S...WARMEST WHERE A LIGHT SOUTHERLY BREEZE IS PRESENT AS THE MSLP GRADIENT BEGINS TO TIGHTEN FROM THE WEST PRIOR TO SUNRISE. HAZARDOUS WEATHER: CONVECTION ALLOWING MODELS DEVELOP ISOLD CONVECTION OVER THE FAR SOUTHEAST COASTAL PLAIN THIS AFTERNOON...IN ASSOC/W THE LINGERING SFC-H85 TROUGH AND/OR THE SEABREEZE. DEEP-LAYER SHEAR WILL BE NEGLIGIBLE TODAY (< 15 KT IN SOUTHEAST NC)...AND DESTABILIZATION IS EXPECTED TO YIELD RELATIVELY MARGINAL INSTABILITY WITH MLCAPE VALUES IN THE 500-1500 J/KG RANGE...SO ANY CONVECTION THAT DEVELOPS WILL BE UNORGANIZED AND SHORT-LIVED. HOWEVER...THE ADVECTION OF A DRIER MID-LEVEL AIRMASS INTO THE AREA WILL RESULT IN A MARKED INCREASE IN DCAPE THIS AFTERNOON...EVEN IN THE SOUTHEAST COASTAL PLAIN...WHERE VIRTUALLY ALL MODEL GUIDANCE INDICATE VALUES IN THE 1000-1500 J/KG RANGE. WITH THIS IN MIND...AN ISOLD UPDRAFT INTERACTING WITH OR ENHANCED BY OUTFLOW IN THE PRESENCE OF RELATIVELY HIGH DCAPE COULD YIELD A BRIEF/ISOLD INSTANCE OF DAMAGING WIND...PRIMARILY IN CUMBERLAND/SAMPSON/WAYNE COUNTIES...THOUGH THE PROBABILITY IS TOO LOW TO MENTION IN THE HAZARDOUS WEATHER OUTLOOK. -VINCENT && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 303 AM FRIDAY... ...SLIGHT CHANCE OF SEVERE THUNDERSTORMS SATURDAY AFTERNOON AND EARLY EVENING... THE BIG PATTERN CHANGE THAT HAS BEEN ADVERTISED FOR DAYS WILL START WITH A BANG SATURDAY AFTERNOON. A POSITIVELY TILTED MID-UPPER TROUGH IS FORECAST TO AMPLIFY AS IT DIVES SE ACROSS THE CENTRAL APPALACHIANS AND MID-ATLANTIC STATES SATURDAY AFTERNOON. THE ASSOCIATED COLD FRONT WILL PUSH INTO THE REGION DURING PEAK HEATING. THE THE MOST FAVORABLE WINDS ALOFT FOR ORGANIZED SEVERE STORMS MAY REMAIN JUST TO OUR NORTH. HOWEVER... STRONG SURFACE HEATING IS EXPECTED TO DESTABILIZE THE BOUNDARY LAYER BY EARLY AFTERNOON OUT AHEAD OF A PRE-FRONTAL TROUGH/REMNANT CONVECTIVE OUTFLOW BOUNDARY. THIS BOUNDARY SHOULD BEGIN TO ARRIVE DURING PEAK HEATING FOR MUCH OF CENTRAL NORTH CAROLINA. WITH STRONG HEATING... TEMPERATURES SHOULD REACH AROUND 90 BY EARLY AFTERNOON THROUGHOUT MOST OF THE REGION. THIS WILL COMBINE WITH DEW POINTS FORECAST TO BE IN THE LOWER 70S TO PRODUCE FAVORABLE PARAMETERS FOR MULTICELL STORM CLUSTERS. A FEW OF THESE STORMS MAY BECOME SEVERE WITH THE MAIN THREAT BEING DAMAGING WET DOWNBURSTS. THE MULTICELL CLUSTERS MAY EVOLVE INTO A LINE BY LATE AFTERNOON AGAIN FAVORING ISOLATED DAMAGING WIND GUSTS ALONG LEWP/BOWING SEGMENTS. THERE MAY BE A FINAL LINE OF CONVECTION WITH THE MAIN COLD FRONT LATER IN THE DAY OR EVENING. REGARDLESS... SATURDAY AFTERNOON AND EVENING IS EXPECTED TO BE ACTIVE ONCE AGAIN. IN ADDITION TO THE SLIGHT CHANCE OF SEVERE STORMS... FREQUENT CG LIGHTNING AND LOCALLY HEAVY RAIN IS AGAIN EXPECTED WITH THE STORMS. EARLY MORNING STRATUS WILL GIVE WAY TO PARTLY SUNNY SKIES. WE WILL CARRY LIKELY POP FOR SHOWERS AND THUNDERSTORMS IN THE AFTERNOON AND EVENING. HIGHS 90-93 EXCEPT UPPER 80S NW. THE STORMS WILL GRADUALLY END SATURDAY EVENING NW... AND ELSEWHERE OVERNIGHT WITH THE ACTUAL COLD FRONTAL PASSAGE. GOOD DRY/COOL AIR ADVECTION WILL ARRIVE MAINLY BETWEEN 06Z-12Z. THIS LATE CAA ARRIVAL COMBINED WITH LINGER CLOUDS SHOULD KEEP LOWS MILD AND LIKELY ABOVE GUIDANCE. WE WILL CARRY 60-65 MOST AREAS. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 303 AM FRIDAY... A LONG AWAITED BREATHER FROM ALL THE VERY WARM/HUMID/THUNDERY WEATHER WILL BEGIN SUNDAY. A REFRESHING BREEZE WILL COMBINE WITH AMPLE SUNSHINE TO BRING A SPRING-LIKE FEEL. HIGHS OF 78-83 EXPECTED (WITH DEW POINTS IN THE 40S NW AND LOWER 50S SE). A NORTHERLY BREEZE AT 10-15 MPH WILL MAKE IT FEEL APRIL-FRESH AT TIMES. MONDAY THROUGH THURSDAY... EXPECT DRY AND SEASONABLY COOL CONDITIONS MONDAY AND TUESDAY... WITH MODERATING DAYTIME TEMPS WED AND THUR. MOSTLY CLEAR/MOSTLY SUNNY WITH LOWS IN THE 50S EACH DAY. HIGHS 75 TO 80 MON-TUE... WARMING INTO THE LOWER TO MID 80S BY THURSDAY. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... AS OF 730 AM FRIDAY... 24-HR TAF PERIOD: MVFR TO VLIFR CONDITIONS ARE PRESENT OVER CENTRAL NC AS OF 11Z. FOG AND LOW CEILINGS ARE EXPECTED TO LIFT AND SCATTER TO VFR BETWEEN 12-15Z AT INT/GSO/RDU. CONDITIONS SHOULD BE SLOWER TO IMPROVE AT THE FAY/RWI TERMINALS WHERE MOISTURE IS DEEPER AND MVFR CEILINGS MAY PERSIST THROUGH ~18Z...ESPECIALLY AT FAY. ISOLATED SHOWERS AND STORMS WILL BE POSSIBLE DURING THE AFTERNOON...THOUGH CHANCES WILL MOST LIKELY BE LIMITED TO THE FAY TERMINAL. OTHERWISE...EXPECT VFR CONDITIONS TO PREVAIL THIS AFTERNOON INTO TONIGHT. LOW-LEVEL SOUTHERLY FLOW WILL STRENGTHEN PRIOR TO SUNRISE SATURDAY IN ADVANCE OF AN APPROACHING COLD FRONT...AND IT IS POSSIBLE THAT IFR/LIFR CEILINGS MAY DEVELOP BETWEEN 09-12Z SAT. LOOKING AHEAD: A STRONG COLD FRONT WILL TRACK EAST INTO CENTRAL NC SATURDAY AFTERNOON. A LINE OF SHOWERS AND THUNDERSTORMS ARE EXPECTED ALONG AND AHEAD OF THE FRONT. RAIN MAY LINGER INTO SATURDAY NIGHT AND EARLY SUNDAY MORNING IN THE WAKE OF THE FRONTAL PASSAGE AT THE FAY/RWI TERMINALS. VFR CONDITIONS WILL RULE IN THE WAKE OF THE COLD FRONT SUNDAY THROUGH EARLY NEXT WEEK AS COOL AND DRY HIGH PRESSURE BUILDS INTO THE CAROLINAS. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM....VINCENT SHORT TERM...BADGETT LONG TERM...BADGETT AVIATION...VINCENT
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
705 AM EDT FRI SEP 7 2012 .SYNOPSIS... LONG PERIOD SWELLS FROM HURRICANE LESLIE WILL IMPACT THE BEACHES THROUGH THE WEEKEND...INCREASING THE RISK FOR STRONG AND FREQUENT RIP CURRENTS AND LARGER THAN NORMAL BREAKERS. A WEAK RIDGE OF HIGH PRESSURE WILL REMAIN ALONG THE COAST AS A TROUGH OF LOW PRESSURE SLOWLY APPROACHES THE CAROLINAS FROM THE WEST TODAY. A STRONGER FRONTAL SYSTEM WILL USHER IN FALL-LIKE WEATHER SUNDAY...WITH DRIER AND COOLER HIGH PRESSURE BUILDING IN THROUGH NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 630 AM FRIDAY...NO CHANGES HAVE BEEN MADE WITH RESPECT TO ANTICIPATED COVERAGE OF AFTERNOON SHOWERS AND THUNDERSTORMS. CURRENT RADAR LOOPS SHOW A CLUSTER OF SHOWERS IN GEORGETOWN COUNTY AND PERHAPS HINTS OF ADDITIONAL DEVELOPMENT UPSTREAM THE SANTEE RIVER ACROSS WILLIAMSBURG COUNTY. 06Z MODELS WERE SLIGHTLY COOLER WITH AFTERNOON HIGHS SO A FEW SPOTS HAVE BEEN DROPPED BY A DEGREE. CHANGES WERE ALL MINOR. PREVIOUS DISCUSSION FROM 330 AM FOLLOWS... A WEAK 500 MB DISTURBANCE AND SURFACE TROUGH/OUTFLOW BOUNDARY HAVE BEEN MAINTAINING SCATTERED CONVECTION THROUGH THE EARLY MORNING HOURS. ACTIVITY HAS BEEN MOST PREVALENT IN THE SC PEE DEE REGION WHERE RADAR ESTIMATES UP TO 4.50 INCHES OF RAIN EXIST ACROSS PORTIONS OF FLORENCE...MARION AND WILLIAMSBURG COUNTIES. THERMODYNAMICALLY THIS CONVECTION IS ELEVATED...ROOTED IN A LAYER 4000-7000 FT ABOVE THE GROUND. AS THE UPPER DISTURBANCES WEAKENS AND PRESSES OFFSHORE IN THE NEXT COUPLE OF HOURS THE CONVECTION SHOULD WEAKEN AS WELL. THE 04Z HRRR DID NOT INITIALIZE WELL...BUT EARLIER RUNS (PARTICULARLY THE 01Z RUN) MODEL THE CURRENTLY OBSERVED PATTERNS ON RADAR WELL. LOW STRATUS CLOUDS ARE FILLING IN NORTH OF THE RAIN AREA AND MAY SPREAD DOWN AS FAR SOUTH AS FLORENCE...MARION...WHITEVILLE AND WILMINGTON BY DAYBREAK. AFTER PROVIDING A GLOOMY SUNRISE THESE CLOUDS SHOULD BURN OFF BY 10:00 AM WITH AN EXPANSIVE CUMULUS FIELD DEVELOPING IN ITS PLACE. TRIGGERS FOR AFTERNOON CONVECTION SHOULD INCLUDE A WELL-DEFINED SEABREEZE...THE REMNANT OUTFLOW BOUNDARY FROM THE EARLY MORNING CONVECTION ACROSS SOUTH CAROLINA...AND A DIFFERENTIAL HEATING BOUNDARY AROUND THE EDGE OF THE MORNING LOW STRATUS DECK. DESPITE NO SUPPORT FROM THE UPPER LEVELS AND A FORECAST STORM CELL MOTION OF LESS THAN 5 MPH...I`M STILL INCLUDING 20 POPS INLAND AND 30 POPS NEAR THE COAST FOR THIS AFTERNOON GIVEN ALL THE SURFACE BOUNDARIES AND WIDESPREAD 1500 J/KG SURFACE-BASED CAPE EXPECTED. ANY LINGERING CONVECTION SHOULD DIE AWAY QUICKLY THIS EVENING AS THE BOUNDARY LAYER COOLS. THE ATMOSPHERE WILL BEGIN TO RESPOND TO AN APPROACHING UPPER LEVEL TROUGH THAT WILL DRIVE A STRONG COLD FRONT THROUGH THE CAROLINAS THIS WEEKEND. DEEP-LAYER FLOW THAT IS ESSENTIALLY LIGHT AND VARIABLE THIS AFTERNOON WILL TURN SOUTHWEST AND STEADILY INCREASE THROUGH THE NIGHT. SURFACE WINDS WILL NOT INCREASE APPRECIABLY GIVEN THE STABLE LOW-LEVEL THERMAL PROFILES AT NIGHT...BUT WINDS 1000 FT AGL AND HIGHER WILL PICK UP SPEED AFTER MIDNIGHT. HIGHS TODAY SHOULD REACH 90 OR SO INLAND...WITH UPPER 80S NEAR THE COAST AND MID 80S ON THE BEACHES. LOWS TONIGHT WILL FALL INTO THE LOWER TO MID 70S. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY...STRONG COLD FRONT WILL APPROACH THE AREA SATURDAY MOVING THROUGH BY SUNDAY. LOCAL AREA WILL BE IN WARM SECTOR ON SAT WITH DEEP LAYER MOISTURE MAKING ITS WAY IN A SW FLOW LATER IN THE DAY AS MOISTURE POOLS AHEAD OF FRONT. GFS ACTUAL SHOWS SOME DRIER AIR IN PLACE IN THE MID LEVELS INITIALLY THROUGH THE AFTERNOON AND THEN PCP WATER VALUES SHOOT UP OVER 2 INCHES THROUGH SAT EVENING. EXPECT BEST LIFT AND MOISTURE THROUGH THE LATE EVENING AND OVERNIGHT AS MID TO UPPER TROUGH PUSHES COLD FRONT THROUGH. POTENTIAL FOR STRONG TO SEVERE STORMS ESPECIALLY JUST AHEAD OF FRONT. THE FRONT WILL MAKE IT THROUGH AFTER THE BEST HEATING OF THE DAY AND THIS MAY WORK IN OUR FAVOR LIMITING MORE WIDESPREAD STORMS. THE SFC FRONT SHOULD MAKE IT OFF SHORE BY SUN MORNING BUT WINDS IN THE LOW TO MID LEVELS WILL TAKE A LITTLE WHILE LONGER TO VEER AROUND. PCP WATER VALUES WILL DROP OUT THROUGH SUNDAY DOWN LESS THAN 1.5 INCHES BY SUN AFTN AND DROPPING EVEN FURTHER TO LESS THAN AN INCH BY END OF THE PERIOD. OVERALL EXPECT MORE LOCALIZED CONVECTION THROUGH SAT AFTN WITH MORE WIDESPREAD ACTIVITY WITH APPROACH OF FRONT LATE SAT INTO EARLY SUNDAY. THEN CLEARING THROUGH SUNDAY BEHIND FRONT AS PLENTY OF DRY AIR MAKES IT WAY IN. SAT WILL BE THE LAST DAY OF VERY WARM TEMPS AS 850 TEMPS REMAIN UP NEAR 18 C BUT AS COOLER AIR ADVECTS IN ON SUNDAY...850 TEMPS WILL FALL THROUGH THE DAY REACHING DOWN TO 10 C BY MON MORNING. MAX TEMPS ON SAT WILL BE UP AROUND 90 OR SO WHILE SUNDAY THE TEMPS WILL BE BETWEEN 80 AND 85 MOST PLACES WHILE DEWPOINT TEMPS DROP ABOUT 10 DEGREES DOWN TO 60. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 300 AM FRIDAY...FALL LIKE WEATHER WILL EXIST THROUGH MUCH OF NEXT WEEK AS COOL AND DRY HIGH PRESSURE BUILDS DOWN OVER THE SOUTHEAST. BRIGHT SEPTEMBER SUN WILL PRODUCE MAX TEMPS BETWEEN 80 AND 85 MOST PLACES BUT THE VERY DRY AIR MASS WILL PRODUCE SOME LARGE DIURNAL SWINGS. WITH DEWPOINT TEMPS DOWN INTO THE 50S THROUGH AT LEAST WED AND WINDS DROPPING OFF EACH NIGHT...EXPECT MORE IDEAL RADIATIONAL COOLING LEADING TO OVERNIGHT LOWS AROUND 60 WITH UPPER 50S INLAND. ACTUALLY TEMPS WILL BE CLOSE TO NORMAL AND WILL CREEP UPWARD THROUGH MID WEEK AS H5 HEIGHTS RISE BACK UP WITH RIDGE BUILDING IN THE SOUTHEAST. BY WED MOISTURE INCREASES ENOUGH IN THE LOW LEVELS AS WINDS SHIFT AROUND TO THE NE TO PRODUCE SOME CU AROUND. OVERALL EXPECT SUNNY AND DRY WEATHER THROUGH THE WEEK. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... AS OF 12Z...THE CONVECTION HAS NOW EXITED THE COAST...ALONG WITH THE DEEP MOISTURE. ORIGINALLY THOUGHT WE WOULD SEE BOUTS OF STRATUS FOR THE FIRST COUPLE OF HOURS THIS MORNING...HOWEVER IT SEEMS MOST OF IT HAS NOW DISSIPATED. MODELS INDICATE THERE WILL BE ENOUGH MOISTURE ALONG THE IMMEDIATE COAST TO KICK OFF SCATTERED CONVECTION. BEST CHANCE WILL BE AROUND MAX HEATING...WITH MOST OF THE ACTIVITY ENDING BY 22Z. WINDS WILL BE A BIT SQUIRLY THIS MORNING WITH THE LIGHT GRADIENT...BECOMING PREDOMINATELY EAST SOUTHEAST WITH THE RESULTANT THIS AFTERNOON. EXTENDED OUTLOOK...SCATTERED SHRA/TSRA THROUGH SUNDAY...WITH A CHANCE OF EARLY MORNING LIFR/IFR CONDITIONS IN BR INLAND...AND MVFR AT THE COAST. VFR MONDAY AND TUESDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 630 AM FRIDAY...NO CHANGES NEEDED TO THE MARINE FORECAST. PREVIOUS DISCUSSION FROM 330 AM FOLLOWS... A WEAK UPPER LEVEL DISTURBANCE AND SURFACE TROUGH ALONG THE CAROLINA COAST IS RESPONSIBLE FOR SEVERAL WAVES OF SHOWERS AND THUNDERSTORMS AFFECTING THE NC OFFSHORE WATER THIS MORNING. SCATTERED SHOWERS AND STORMS SHOULD DIMINISH IN COVERAGE THROUGH THE EARLY MORNING HOURS AS THIS DISTURBANCE PUSHES OFFSHORE AND WEAKENS FURTHER. GENERALLY OFFSHORE WINDS EARLY THIS MORNING WILL TURN LIGHT AND VARIABLE LATER THIS MORNING...AND THEN SOUTHERLY DRIVEN PRIMARILY BY THE SEABREEZE THIS AFTERNOON. A STRONG COLD FRONT APPROACHING FROM THE WEST WILL CREATE SLOWLY INCREASING SOUTHWEST WINDS TONIGHT. SWELL FROM HURRICANE LESLIE HAS SHORTENED TO AROUND 10 SECONDS IN PERIOD AND SHOULD CONTINUE THROUGH THE WEEKEND. ADDITIONAL SHORT PERIOD WIND WAVES WILL ADD VERY LITTLE EXTRA TO THE TOTAL SEA STATE...AND WE`RE EXPECTING 2-4 FT ACROSS THE SOUTH CAROLINA COASTAL WATERS...AND 3-4 FT FOR THE NC COASTAL WATERS. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY...SOUTHWEST FLOW WILL INCREASE THROUGH SATURDAY AHEAD OF APPROACHING COLD FRONT. SOUTHWEST WINDS UP AROUND 15 KTS WILL VEER AROUND BECOMING OFF SHORE THROUGH SUNDAY MORNING AS COLD FRONT MOVES THROUGH. THESE SOUTHWEST WINDS WILL COMBINE WITH CONTINUED LONG PERIOD E-SE SWELLS TO PRODUCE SEAS IN THE 3 TO 5 FT RANGE MOST PLACES THROUGH SATURDAY. THERE WILL BE SOME 6 FTERS IN OUTER WATERS. AS COLD FRONT MOVES FURTHER OFF SHORE THROUGH SUNDAY...WINDS WILL VEER AROUND TO THE NORTH AROUND 10 TO 15 KTS AS HIGH PRESSURE BUILDS IN FROM THE N-NW. LONG TERM /MONDAY THROUGH TUESDAY/... AS OF 300 AM FRIDAY...NORTHERLY WINDS WILL CONTINUE TO MIX WITH LONGER PERIOD SWELLS FROM LESLIE TO PRODUCE SEAS IN THE 2 TO 4 FT RANGE MOST WATERS. THE COOL NIGHTS WILL KEEP A WELL MIXED ATMOSPHERE AS COOL AIR RIDES OVER THE WARM WATERS. THIS COULD PRODUCE NORTHERLY WINDS UP TO 20 KTS OVERNIGHT. EXPECT SEAS CLOSER TO 5 FT IN OUTER WATERS AND MAY SEE SEAS UP NEAR OR SLIGHTLY ABOVE SCA EARLY MON IN NORTHERLY SURGE BEHIND FRONT. THE WINDS WILL GRADUALLY SHIFT AROUND BECOMING NE TO E AS HIGH PRESSURE BUILDS SOUTH AND EAST THROUGH MID WEEK. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...TRA SHORT TERM...RGZ LONG TERM...RGZ AVIATION...43
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
640 AM EDT FRI SEP 7 2012 .SYNOPSIS... LONG PERIOD SWELLS FROM HURRICANE LESLIE WILL IMPACT THE BEACHES THROUGH THE WEEKEND...INCREASING THE RISK FOR STRONG AND FREQUENT RIP CURRENTS AND LARGER THAN NORMAL BREAKERS. A WEAK RIDGE OF HIGH PRESSURE WILL REMAIN ALONG THE COAST AS A TROUGH OF LOW PRESSURE SLOWLY APPROACHES THE CAROLINAS FROM THE WEST TODAY. A STRONGER FRONTAL SYSTEM WILL USHER IN FALL-LIKE WEATHER SUNDAY...WITH DRIER AND COOLER HIGH PRESSURE BUILDING IN THROUGH NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 630 AM FRIDAY...NO CHANGES HAVE BEEN MADE WITH RESPECT TO ANTICIPATED COVERAGE OF AFTERNOON SHOWERS AND THUNDERSTORMS. CURRENT RADAR LOOPS SHOW A CLUSTER OF SHOWERS IN GEORGETOWN COUNTY AND PERHAPS HINTS OF ADDITIONAL DEVELOPMENT UPSTREAM THE SANTEE RIVER ACROSS WILLIAMSBURG COUNTY. 06Z MODELS WERE SLIGHTLY COOLER WITH AFTERNOON HIGHS SO A FEW SPOTS HAVE BEEN DROPPED BY A DEGREE. CHANGES WERE ALL MINOR. PREVIOUS DISCUSSION FROM 330 AM FOLLOWS... A WEAK 500 MB DISTURBANCE AND SURFACE TROUGH/OUTFLOW BOUNDARY HAVE BEEN MAINTAINING SCATTERED CONVECTION THROUGH THE EARLY MORNING HOURS. ACTIVITY HAS BEEN MOST PREVALENT IN THE SC PEE DEE REGION WHERE RADAR ESTIMATES UP TO 4.50 INCHES OF RAIN EXIST ACROSS PORTIONS OF FLORENCE...MARION AND WILLIAMSBURG COUNTIES. THERMODYNAMICALLY THIS CONVECTION IS ELEVATED...ROOTED IN A LAYER 4000-7000 FT ABOVE THE GROUND. AS THE UPPER DISTURBANCES WEAKENS AND PRESSES OFFSHORE IN THE NEXT COUPLE OF HOURS THE CONVECTION SHOULD WEAKEN AS WELL. THE 04Z HRRR DID NOT INITIALIZE WELL...BUT EARLIER RUNS (PARTICULARLY THE 01Z RUN) MODEL THE CURRENTLY OBSERVED PATTERNS ON RADAR WELL. LOW STRATUS CLOUDS ARE FILLING IN NORTH OF THE RAIN AREA AND MAY SPREAD DOWN AS FAR SOUTH AS FLORENCE...MARION...WHITEVILLE AND WILMINGTON BY DAYBREAK. AFTER PROVIDING A GLOOMY SUNRISE THESE CLOUDS SHOULD BURN OFF BY 10:00 AM WITH AN EXPANSIVE CUMULUS FIELD DEVELOPING IN ITS PLACE. TRIGGERS FOR AFTERNOON CONVECTION SHOULD INCLUDE A WELL-DEFINED SEABREEZE...THE REMNANT OUTFLOW BOUNDARY FROM THE EARLY MORNING CONVECTION ACROSS SOUTH CAROLINA...AND A DIFFERENTIAL HEATING BOUNDARY AROUND THE EDGE OF THE MORNING LOW STRATUS DECK. DESPITE NO SUPPORT FROM THE UPPER LEVELS AND A FORECAST STORM CELL MOTION OF LESS THAN 5 MPH...I`M STILL INCLUDING 20 POPS INLAND AND 30 POPS NEAR THE COAST FOR THIS AFTERNOON GIVEN ALL THE SURFACE BOUNDARIES AND WIDESPREAD 1500 J/KG SURFACE-BASED CAPE EXPECTED. ANY LINGERING CONVECTION SHOULD DIE AWAY QUICKLY THIS EVENING AS THE BOUNDARY LAYER COOLS. THE ATMOSPHERE WILL BEGIN TO RESPOND TO AN APPROACHING UPPER LEVEL TROUGH THAT WILL DRIVE A STRONG COLD FRONT THROUGH THE CAROLINAS THIS WEEKEND. DEEP-LAYER FLOW THAT IS ESSENTIALLY LIGHT AND VARIABLE THIS AFTERNOON WILL TURN SOUTHWEST AND STEADILY INCREASE THROUGH THE NIGHT. SURFACE WINDS WILL NOT INCREASE APPRECIABLY GIVEN THE STABLE LOW-LEVEL THERMAL PROFILES AT NIGHT...BUT WINDS 1000 FT AGL AND HIGHER WILL PICK UP SPEED AFTER MIDNIGHT. HIGHS TODAY SHOULD REACH 90 OR SO INLAND...WITH UPPER 80S NEAR THE COAST AND MID 80S ON THE BEACHES. LOWS TONIGHT WILL FALL INTO THE LOWER TO MID 70S. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY...STRONG COLD FRONT WILL APPROACH THE AREA SATURDAY MOVING THROUGH BY SUNDAY. LOCAL AREA WILL BE IN WARM SECTOR ON SAT WITH DEEP LAYER MOISTURE MAKING ITS WAY IN A SW FLOW LATER IN THE DAY AS MOISTURE POOLS AHEAD OF FRONT. GFS ACTUAL SHOWS SOME DRIER AIR IN PLACE IN THE MID LEVELS INITIALLY THROUGH THE AFTERNOON AND THEN PCP WATER VALUES SHOOT UP OVER 2 INCHES THROUGH SAT EVENING. EXPECT BEST LIFT AND MOISTURE THROUGH THE LATE EVENING AND OVERNIGHT AS MID TO UPPER TROUGH PUSHES COLD FRONT THROUGH. POTENTIAL FOR STRONG TO SEVERE STORMS ESPECIALLY JUST AHEAD OF FRONT. THE FRONT WILL MAKE IT THROUGH AFTER THE BEST HEATING OF THE DAY AND THIS MAY WORK IN OUR FAVOR LIMITING MORE WIDESPREAD STORMS. THE SFC FRONT SHOULD MAKE IT OFF SHORE BY SUN MORNING BUT WINDS IN THE LOW TO MID LEVELS WILL TAKE A LITTLE WHILE LONGER TO VEER AROUND. PCP WATER VALUES WILL DROP OUT THROUGH SUNDAY DOWN LESS THAN 1.5 INCHES BY SUN AFTN AND DROPPING EVEN FURTHER TO LESS THAN AN INCH BY END OF THE PERIOD. OVERALL EXPECT MORE LOCALIZED CONVECTION THROUGH SAT AFTN WITH MORE WIDESPREAD ACTIVITY WITH APPROACH OF FRONT LATE SAT INTO EARLY SUNDAY. THEN CLEARING THROUGH SUNDAY BEHIND FRONT AS PLENTY OF DRY AIR MAKES IT WAY IN. SAT WILL BE THE LAST DAY OF VERY WARM TEMPS AS 850 TEMPS REMAIN UP NEAR 18 C BUT AS COOLER AIR ADVECTS IN ON SUNDAY...850 TEMPS WILL FALL THROUGH THE DAY REACHING DOWN TO 10 C BY MON MORNING. MAX TEMPS ON SAT WILL BE UP AROUND 90 OR SO WHILE SUNDAY THE TEMPS WILL BE BETWEEN 80 AND 85 MOST PLACES WHILE DEWPOINT TEMPS DROP ABOUT 10 DEGREES DOWN TO 60. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 300 AM FRIDAY...FALL LIKE WEATHER WILL EXIST THROUGH MUCH OF NEXT WEEK AS COOL AND DRY HIGH PRESSURE BUILDS DOWN OVER THE SOUTHEAST. BRIGHT SEPTEMBER SUN WILL PRODUCE MAX TEMPS BETWEEN 80 AND 85 MOST PLACES BUT THE VERY DRY AIR MASS WILL PRODUCE SOME LARGE DIURNAL SWINGS. WITH DEWPOINT TEMPS DOWN INTO THE 50S THROUGH AT LEAST WED AND WINDS DROPPING OFF EACH NIGHT...EXPECT MORE IDEAL RADIATIONAL COOLING LEADING TO OVERNIGHT LOWS AROUND 60 WITH UPPER 50S INLAND. ACTUALLY TEMPS WILL BE CLOSE TO NORMAL AND WILL CREEP UPWARD THROUGH MID WEEK AS H5 HEIGHTS RISE BACK UP WITH RIDGE BUILDING IN THE SOUTHEAST. BY WED MOISTURE INCREASES ENOUGH IN THE LOW LEVELS AS WINDS SHIFT AROUND TO THE NE TO PRODUCE SOME CU AROUND. OVERALL EXPECT SUNNY AND DRY WEATHER THROUGH THE WEEK. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 06Z...TSRA ACROSS THE PEE DEE REGION OF SC WILL SLIP SOUTHEAST AND AWAY FROM FLORENCE OVER THE NEXT SEVERAL HOURS...BUT MAY BRUSH BY MYR. BIGGER STORY WILL BE THE EXPANSION OF LOW CEILINGS AT OR BELOW 600 FT AGL. THESE IFR CONDITIONS HAVE ALREADY DEVELOPED AT LBT AND MAY EXPAND TO ILM AND FLO OVER THE NEXT SEVERAL HOURS AS A WEAK CONVECTIVE OUTFLOW BOUNDARY SINKS SOUTH ACROSS THE AREA. AFTER DAYBREAK...ANY LINGERING FOG WILL QUICKLY DISSIPATE GIVING WAY TO VFR ACROSS THE AREA. AS A SFC TROUGH CONTINUES TO PROGRESS ACROSS THE AREA...EXPECT ISOLATED SHRA/TSRA DURING THE AFTERNOON HOURS ALONG THE COAST...WHILE THE INLAND SITES ARE EXPECTED TO REMAIN QUIET WITH VFR THROUGH THE REMAINDER OF THE PERIOD. BY THE AFTERNOON...SOUTHWEST WINDS WILL BECOME SOUTH...INCREASING TO AOB 12 KTS. INTO THE EVENING HOURS...ACTIVITY WILL DIMINISH ALLOWING VFR TO PREVAIL WITH DECREASING WINDS AND CLEARING SKIES. EXTENDED OUTLOOK...SCATTERED SHRA/TSRA THROUGH SUNDAY...WITH A CHANCE OF EARLY MORNING LIFR/IFR CONDITIONS IN BR INLAND...AND MVFR AT THE COAST. VFR MONDAY AND TUESDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 630 AM FRIDAY...NO CHANGES NEEDED TO THE MARINE FORECAST. PREVIOUS DISCUSSION FROM 330 AM FOLLOWS... A WEAK UPPER LEVEL DISTURBANCE AND SURFACE TROUGH ALONG THE CAROLINA COAST IS RESPONSIBLE FOR SEVERAL WAVES OF SHOWERS AND THUNDERSTORMS AFFECTING THE NC OFFSHORE WATER THIS MORNING. SCATTERED SHOWERS AND STORMS SHOULD DIMINISH IN COVERAGE THROUGH THE EARLY MORNING HOURS AS THIS DISTURBANCE PUSHES OFFSHORE AND WEAKENS FURTHER. GENERALLY OFFSHORE WINDS EARLY THIS MORNING WILL TURN LIGHT AND VARIABLE LATER THIS MORNING...AND THEN SOUTHERLY DRIVEN PRIMARILY BY THE SEABREEZE THIS AFTERNOON. A STRONG COLD FRONT APPROACHING FROM THE WEST WILL CREATE SLOWLY INCREASING SOUTHWEST WINDS TONIGHT. SWELL FROM HURRICANE LESLIE HAS SHORTENED TO AROUND 10 SECONDS IN PERIOD AND SHOULD CONTINUE THROUGH THE WEEKEND. ADDITIONAL SHORT PERIOD WIND WAVES WILL ADD VERY LITTLE EXTRA TO THE TOTAL SEA STATE...AND WE`RE EXPECTING 2-4 FT ACROSS THE SOUTH CAROLINA COASTAL WATERS...AND 3-4 FT FOR THE NC COASTAL WATERS. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY...SOUTHWEST FLOW WILL INCREASE THROUGH SATURDAY AHEAD OF APPROACHING COLD FRONT. SOUTHWEST WINDS UP AROUND 15 KTS WILL VEER AROUND BECOMING OFF SHORE THROUGH SUNDAY MORNING AS COLD FRONT MOVES THROUGH. THESE SOUTHWEST WINDS WILL COMBINE WITH CONTINUED LONG PERIOD E-SE SWELLS TO PRODUCE SEAS IN THE 3 TO 5 FT RANGE MOST PLACES THROUGH SATURDAY. THERE WILL BE SOME 6 FTERS IN OUTER WATERS. AS COLD FRONT MOVES FURTHER OFF SHORE THROUGH SUNDAY...WINDS WILL VEER AROUND TO THE NORTH AROUND 10 TO 15 KTS AS HIGH PRESSURE BUILDS IN FROM THE N-NW. LONG TERM /MONDAY THROUGH TUESDAY/... AS OF 300 AM FRIDAY...NORTHERLY WINDS WILL CONTINUE TO MIX WITH LONGER PERIOD SWELLS FROM LESLIE TO PRODUCE SEAS IN THE 2 TO 4 FT RANGE MOST WATERS. THE COOL NIGHTS WILL KEEP A WELL MIXED ATMOSPHERE AS COOL AIR RIDES OVER THE WARM WATERS. THIS COULD PRODUCE NORTHERLY WINDS UP TO 20 KTS OVERNIGHT. EXPECT SEAS CLOSER TO 5 FT IN OUTER WATERS AND MAY SEE SEAS UP NEAR OR SLIGHTLY ABOVE SCA EARLY MON IN NORTHERLY SURGE BEHIND FRONT. THE WINDS WILL GRADUALLY SHIFT AROUND BECOMING NE TO E AS HIGH PRESSURE BUILDS SOUTH AND EAST THROUGH MID WEEK. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...TRA SHORT TERM...RGZ LONG TERM...RGZ AVIATION...TRA/SGL
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
647 AM EDT FRI SEP 7 2012 .SYNOPSIS... HIGH PRESSURE TODAY PROVIDING HOT AND MOSTLY DRY WEATHER. STRONG COLD FRONT SATURDAY. HIGH PRESSURE SUNDAY INTO EARLY NEXT WEEK BRINGING MUCH COOLER WEATHER. && .NEAR TERM /THROUGH TONIGHT/... 630 AM UPDATE...NO SIGNIFICANT CHANGES MADE TO FORECAST. HOWEVER THERE IS AT LEAST SOME GROWING POTENTIAL FOR A FEW ISOLATED SHOWERS/STORMS ACROSS THE FAR NW ZONES DURING THE LATE AFTERNOON/EARLY EVE IN SE OHIO WHERE A BIT MORE LLVL MOISTURE WILL RESIDE AROUND THE 850MB LEVEL UNCAPPED PER LATEST NAM AND RUC SOUNDINGS. WILL PASS THIS ALONG TO DAYSHIFT FOR MONITORING. PREVIOUS DISCUSSION... PRIMARY CONCERN FOR THIS FORECAST PERIOD CONTINUES TO BE THE APPROACHING COLD FRONT DURING THE OVERNIGHT HOURS. TODAY...SOME EARLY MORNING CLOUDS MAINLY ACROSS THE NORTHERN AND EASTERN ZONES SHOULD DISSIPATE. FORECAST AREA WILL TRANSITION FROM A ZONAL FLOW TO SOUTHWESTERLY FLOW AS VIGOROUS UPPER LEVEL TROUGH DIVES SOUTHEASTWARD ACROSS THE WESTERN GREAT LAKES REGION. BEST FLOW REMAINS WELL TO THE WEST OF THE FORECAST AREA PRIOR TO 00Z SAT. BOTH FINER RESOLUTION NAM/GFS DEPICT AN AREA OF INCREASED 850-700MB MOISTURE OVER THE HIGHER TERRAIN OF RANDOLPH/POCAHONTAS COUNTIES ALONG WITH SFC CONVERGENCE IN THOSE AREAS. AM SOMEWHAT SUSPICIOUS OF THIS DEPICTION BUT WILL GO AHEAD AND INTRODUCE SLIGHT POPS FOR A FEW HOURS ACROSS THOSE FAR EASTERN COUNTIES MAINLY BETWEEN 19Z-00Z DURING MAX HEATING. INHERITED MAX TEMPS AROUND 90 DEGREES STILL LOOK GOOD AND HAVE ONLY MADE MINOR ADJUSTMENTS. DURING THE EVENING AND OVERNIGHT HOURS THE TROUGH AND COLD FRONT CONTINUE MOVING TOWARDS THE FORECAST AREA. BOTH THE LATEST NAM AND GFS SLOW THE SYSTEM/S PROGRESSION AS WELL AS DEEPEN THE LOW ITSELF...WITH THE AXIS PROGGED TO BE ROUGHLY ACROSS NW INDIANA AND THE SFC COLD FRONT JUST NEARING/ENTERING THE FAR NW ZONES BY 12Z. WILL SLOW THE ONSET OF POPS DOWN BY A FEW HOURS BUT WITH GOOD DEPTH OF LLVL MOISTURE INCREASING RAPIDLY ACROSS THE WESTERN ZONES BY 09Z AND A VORT MAX PROGGED TO LOCATED ACROSS CENTRAL KY BY 06Z MOVING NE-WARD...STILL THINK SHOWERS AND THUNDERSTORMS A GOOD BET BY 09Z MAINLY ALONG AND WEST OF THE OHIO RIVER...WITH PERHAPS A SMALL GAP BETWEEN THIS AREA OF PRECIP AND THE PRECIP ASSOC WITH THE FRONT ITSELF. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... STRONG UPPER TROUGH AND ASSOCIATED COLD FRONT WILL SWEEP ACROSS THE AREA SATURDAY. MODELS ARE IN PRETTY GOOD AGREEMENT WITH THE TIMING OF THIS FRONT. THE NAM SEEMS A LITTLE BIT FASTER CONTRARY TO THE ECMWF/GFS/CMC MODELS. ADJUSTED PREVIOUS CATEGORICAL POPS AND WINDS DELAYING THE WIND SHIFT AND ONSET OF PCPN ABOUT 3 HOURS. STRONG H5 VORTICITY ADVECTION PROVIDE STRONG OMEGA AT H5-H7 LAYER...AS WELL AS DESCENT UPPER LEVEL JET DIVERGENCE WORKING OVER PWATS AROUND 2 INCHES AND A H7-H85 THETA-E RIDGE. THEREFORE...PREVIOUS FORECAST HAD A GOOD HANDLE ON CATEGORICAL POPS AND MINOR ADJUSTMENTS WERE REQUIRED. DRIER AIR BEHIND THE FRONT WILL BRING COOLER TEMPS SATURDAY NIGHT...AND PUSH PCPN OVER THE EASTERN MOUNTAINS BY 00Z SUNDAY. HOWEVER...KEPT LOW CHANCE POPS FOR LINGERING STRATIFORM PCPN THRU AT LEAST 06 SUNDAY OVER THE MOUNTAINS. ANOTHER BUT UPPER LEVEL TROUGH MOVES THRU ON SUNDAY...WITH LESS MOISTURE AVAILABLE. THERE COULD BE ENOUGH MOISTURE TO PRODUCE FEW SHOWERS OR STORMS MAINLY ACROSS THE NORTHERN PORTIONS OF WV. THEREFORE...ADDED LOW CHANCE POPS FOR NOW. AT LEAST EXPECT CLOUDS MOVING THROUGH WITH FEW SHOWERS. WITH CLOUDS...AND THEN THE COOLER AIRMASS BEHIND THE COLD FRONT...KEPT AFTERNOON HIGHS IN THE 60S AND 70S THIS WEEKEND. FRIDAY NIGHT WILL BE WARM AS CLOUDS AND MOISTURE INCREASE...WITH A MUCH COOLER NIGHT SATURDAY INTO SUNDAY. && .LONG TERM /MONDAY THROUGH THURSDAY/... OVERALL A DRY PATTERN EXPECTED FOR THE LONG TERM...WITH UPPER LEVEL RIDGE BUILDING OVER THE SOUTHERN PLAINS...AND SLIDING EAST INTO THE SE UNITED STATES BY MID WEEK. BOTH GFS AND ECMWF SHOWING AN UPPER LOW MOVING TOWARDS HUDSON BAY LATE NEXT WEEK. ECMWF A BIT FASTER...BUT ALSO KEEPS THE ENERGY FARTHER NORTH...WHILE GFS DOES NOT SHOW THE TROUGH IMPACTING FORECAST AREA UNTIL AFTER LONG TERM PERIOD...SO WILL KEEP THINGS DRY ALL WEEK. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... EARLY MORNING FOG AND LOW STRATUS WILL BURN OFF/SCATTER SHORTLY AFTER SUNRISE. VFR CONDITIONS WILL PREVAIL FOR MUCH OF THE REMAINDER OF VALID PERIOD WITH SURFACE FLOW OUT OF THE SOUTHWEST. DURING THE EVENING HOURS PREDOMINATELY HIGH AND MID LEVEL CLOUDS WILL INCREASE IN ADVANCE OF AN APPROACHING COLD FRONT...WITH AN INCREASING CHANCE OF SHOWERS AND THUNDERSTORMS NEAR THE END OF THE PERIOD MAINLY BETWEEN 09Z-12Z ALONG AND WEST OF THE OHIO RIVER...WITH POTENTIAL REDUCTION IN VIS IN STRONGER SHOWERS/STORMS. ABUNDANT CLOUD COVER AND STRONGER WINDS AT AND ABOVE SURFACE SHOULD PRECLUDE WIDESPREAD FOG DEVELOPMENT. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z SATURDAY... FORECAST CONFIDENCE: HIGH. ALTERNATE SCENARIOS: DISSIPATION OF FOG AND LOW STRATUS MAY VARY BY AN HOUR OR TWO. 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 11 12 13 14 15 16 17 18 19 20 21 22 EDT 1HRLY 07 08 09 10 11 12 13 14 15 16 17 18 CRW CONSISTENCY L L M H H H H H H H H H HTS CONSISTENCY L L M H H H H H H H H H BKW CONSISTENCY L H H H H H H H H H H H EKN CONSISTENCY L L H H H H H H H H H H PKB CONSISTENCY L L H H H H H H H H H H CKB CONSISTENCY L L M H H H H H H H H H AFTER 12Z SATURDAY... IFR POSSIBLE IN SHOWERS AND THUNDERSTORMS SATURDAY. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...ARJ/50 NEAR TERM...50 SHORT TERM...ARJ LONG TERM...MZ AVIATION...50
AREA FORECAST DISCUSSION
NWS NORMAN OK
633 AM CDT FRI SEP 7 2012 .AVIATION... 07/12Z TAFS...VFR CONDITIONS EXPECTED. SCATTERED TSRA COULD AFFECT MAINLY KPNC DOWN TOWARD KOKC ALONG AND BEHIND STRONG FRONT THAT WILL SURGE SOUTHWARD TODAY. VERY LITTLE IF ANY COLD FRONT TIMING CHANGES MADE FROM PREVIOUS FORECAST CYCLE. OUTSIDE OF POSSIBILITY FOR TSRA FOR A FEW HOURS LATE THIS AFTERNOON AND THIS EVENING... MAIN IMPACTS TO TERMINALS WILL BE STRONG NORTHERLY WIND WITH GUSTS AOA 40KT SEVERAL HOURS FOLLOWING FROPA. && .PREV DISCUSSION... /ISSUED 437 AM CDT FRI SEP 7 2012/ DISCUSSION... BIG CHANGES WILL BE SEEN THIS AFTERNOON AND EVENING...BUT BEFORE THE FRONT ARRIVES IT WILL BE QUITE HOT WITH FAIRLY SUBSTANTIAL PRE-FRONTAL THERMAL RIDGE IN PLACE. FIRST PERIOD OF FORECAST WILL CLOSELY RESEMBLE WRF SOLUTIONS OF THE PAST COUPLE OF RUNS. HOTTER AHEAD OF FRONT AND MORE SUBSTANTIAL CAA/WIND BEHIND IT. WE WILL ISSUE A WIND ADVISORY FOR THIS AFTERNOON AND EVENING. FREQUENT GUSTS AROUND 45 MPH NOT OUT OF THE QUESTION FOR AT LEAST 2 TO 4 HOURS AFTER FROPA COINCIDING WITH STRONG CAA. SOME OF THE WINDIER SPOTS OF W/SW OKLAHOMA COULD SEE SOME GUSTS IN EXCESS OF 50 MPH. AS FAR AS THE CHANGE IN TEMPERATURE GOES...WE EXPECT TEMPS TO FALL 20 TO 30 DEGREES IN JUST A FEW HOURS AFTER FRONTAL PASSAGE... ESPECIALLY ACROSS CENTRAL AND SOUTHERN PORTIONS OF OKLAHOMA AND NORTH TEXAS WHERE TEMPS EXPECTED TO APPROACH OR EXCEED 100 AHEAD OF FRONT. AS FAR AS POPS GO...COULD SEE SOME ISOLATED SHOWERS OR STORMS ACROSS NORTH-CENTRAL AND PERHAPS CENTRAL OKLAHOMA EARLY THIS MORNING...WITH THE HRRR BEING THE MOST AGGRESSIVE WITH THIS POTENTIAL. SCATTERED STORMS MAY FORM ALONG FRONT THIS AFTERNOON BUT BEST CHANCES FOR RAIN APPEAR TO BE THIS EVENING BEHIND THE FRONT AS MAIN MID-LEVEL TROUGH AXIS MOVES INTO THE REGION. SEASONABLY COOL WEEKEND IN STORE BEFORE TEMPS BEGIN TO INCREASE AHEAD OF NEXT FRONTAL BOUNDARY WHICH MEDIUM RANGE MODELS WANT TO BRING TOWARD THE END OF NEXT WEEK. && .PRELIMINARY POINT TEMPS/POPS... OKLAHOMA CITY OK 99 57 83 54 / 30 40 0 0 HOBART OK 99 55 85 54 / 20 30 0 0 WICHITA FALLS TX 104 59 86 56 / 20 30 0 0 GAGE OK 88 53 83 49 / 20 10 0 0 PONCA CITY OK 93 53 82 54 / 40 20 0 0 DURANT OK 102 60 84 53 / 10 30 0 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 10 PM CDT THIS EVENING FOR OKZ007-008-012-013-016>026-033>036. WIND ADVISORY FROM NOON TODAY TO 6 PM CDT THIS EVENING FOR OKZ004>006-009>011-014-015. WIND ADVISORY FROM 6 PM TO 10 PM CDT THIS EVENING FOR OKZ027>031- 037>040-044-045. TX...WIND ADVISORY FROM 6 PM TO 10 PM CDT THIS EVENING FOR TXZ083>090. && $$ 06/11/11
AREA FORECAST DISCUSSION
NWS LUBBOCK TX
954 AM CDT FRI SEP 7 2012 .UPDATE... LATEST OBSERVED TRENDS WITH THE FRONT SHOW IT IS MOVING A BIT QUICKER THAN PREVIOUSLY ANTICIPATED WITH THE FRONT MOVING SOUTHWARD AT A SPEED OF ABOUT 33KT. RAP ANALYSIS INDICATES IMPRESSIVE 8 MB PER THREE HOUR PRESSURE RISES IN SOUTHEASTERN COLORADO. SUSTAINED WINDS BEHIND THE FRONT WERE OBSERVED TO BE AROUND 25KT OR SO WITH GUSTS UP TO 40 KT. HAVE UPDATED THE FORECAST FOR A FASTER FRONTAL MOVEMENT AND TO ADD BLOWING DUST FOR THE REST OF THE MORNING IN THE SOUTHWESTERN PANHANDLE AND NORTHERN SOUTH PLAINS. && PREV DISCUSSION... /ISSUED 255 AM CDT FRI SEP 7 2012/ SHORT TERM... A BROAD UA TROUGH ACROSS THE NORTHERN ROCKIES/NORTHERN PLAINS...IS PROGGED TO TRANSLATE SSE ACROSS THE CENTRAL PLAINS THIS AFTERNOON/EVENING...WHICH WILL AID TO SHIFT THE CENTER OF THE UA RIDGE WEST OF THE SOUTHERN PLAINS. THE TROUGH/S ASSOCIATED FROPA WHICH WAS LOCATED ACROSS CENTRAL COLORADO AND NORTHERN KANSAS PER 07Z METARS...IS EXPECTED TO ENTER THE NWRN ZONES AOA 18Z AND THROUGH THE REMAINDER OF THE CWA BY 00Z. WHAT NEEDS TO BE CONSIDERED WITH THIS LATE SUMMER FRONTAL INTRUSION ARE /1/ PRECIPITATION CHANCES AND /2/ THE STRENGTH OF THE FRONT. BEST LARGE SCALE ASCENT IS FAVORED TO BE NORTH OF THE REGION...HOWEVER FORECAST SOLUTIONS EXHIBITED PRECIP COMMENCING BETWEEN 21-00Z ACROSS PORTIONS OF THE NRN AND CNTRL ZONES...THANKS TO ADEQUATE FRONTOGENETICAL FORCING. THE PRECIP WILL SHIFT TO THE CNTRL AND SRN ZONES THIS EVENING AND TONIGHT...WITH LINGERING PRECIP ACROSS SRN ZONES EARLY TOMORROW MORNING /NEAREST TO BEST MOISTURE AXIS/. IT IS INTERESTING TO NOTE MODEL RUNS SHOWING THE PRECIP IN A RATHER NARROW CORRIDOR VERSUS WIDESPREAD CONVECTION. THIS IS LIKELY DUE TO THE TOP-DOWN MOISTENING THAT WILL HAVE TO OCCUR GIVEN INITIAL DRY LOW LEVELS...QUICKLY FOLLOWED BY A SFC RIDGING FILTERING IN A MUCH DRIER AND COOLER AIRMASS FROM NORTH TO SOUTH. AS SUCH...CLOUD BASES WILL BE RELATIVELY HIGH BUT INVERTED-V SOUNDING PROFILES SUGGESTS THUNDERSTORM WIND GUSTS OF 40-50 MPH NOT OUT OF THE QUESTION. THE OTHER CONCERN IS HOW STRONG THIS NORTH TO NORTHEASTERLY FROPA WILL BE. THE 1020 MB SFC RIDGE DRIVING THIS FRONT WILL PROMOTE A TIGHTENED PRESSURE GRADIENT AND THUS PROGGED PRESSURE RISES OF 6-9 MB PER THREE HOURS /HIGHEST PRESSURE RISES EXPECTED TO BE ACROSS ERN LOCALES/. MIXING TO 850 MB...FORECAST SOLUTIONS SHOW WIND SPEEDS OF 40-50 MPH AT THAT SAID LEVEL...WHICH CORRESPONDS TO 20-30 MPH AT THE SFC...WHICH IS NEARING WIND ADVISORY SPEED CRITERIA /31-39 MPH/. AS SUCH...SOME LOCALES ON THE CAPROCK COULD SEE AREAS OF BLOWING DUST. IT IS QUITE POSSIBLE THAT A FEW LOCALES MAY CERTAINLY EQUATE THE SPEED CRITERIA OF THE WIND ADVISORY BUT CONFIDENCE IS NOT HIGH FOR THIS TO OCCUR FOR AN HOUR OR LONGER /SECOND HALF OF THE WIND ADVISORY CRITERIA/...GIVEN THE RELATIVELY QUICK DECLINATION IN PRESSURE RISES. THE DAY SHIFT WILL HAVE TO KEEP AN EYE ON THE STRENGTH OF THE FRONT AS IT NEARS DRAWS...ESPECIALLY IF IT APPROACHES THE AIRPORT WEATHER WARNING CRITERIA /SFC WINDS OF 30 KTS OR GREATER/. WILL THEREFORE MAINTAIN A MENTION IN THE HAZARDOUS WEATHER OUTLOOK ATTM. FURTHERMORE...THE STRENGTH OF THE COLD FRONT COMBINED WITH THE ASSOCIATED CLOUD COVER WILL CREATE A TEMP-GRADIENT FROM NW /LOWER 80S/ TO SE /LOWER TRIPLE DIGITS/. LONG TERM... A COOL AND DRY AIR MASS WILL SPREAD ACROSS THE FCST AREA SATURDAY WITH POTENTIAL FOR A FEW LINGERING SHOWERS ACROSS THE SWRN ZONES EARLY IN THE DAY. RETURN FLOW AND A WARMING TREND THEN QUICKLY SET UP SUNDAY AS UPPER LEVEL RIDGING BEGINS TO BUILD EWD ONCE AGAIN. THEN THROUGH THE COURSE OF NEXT WEEK WILL SEE A VERY SLOWLY PROGRESSIVE PATTERN WITH THE UPPER RIDGE CONTINUE TO MOVE EWD... FLATTENING UPPER LEVEL FLOW ACROSS THE SRN PLAINS...AND THE APPROACH OF A LOW AMPLITUDE SHORT WAVE TROUGH FROM THE WEST TOWARD THE MIDDLE OF THE WEEK. CONTINUOUS SOUTHERLY FLOW EARLY IN THE WEEK WILL EVENTUALLY DRAW SOME LOW LEVEL MOISTURE NWD...BUT WHETHER IT AND FORCING ASSOCIATED WITH THE AFOREMENTIONED TROUGH WILL BE ENOUGH TO GENERATE SOME PRECIP BY ABOUT WEDNESDAY OR THURSDAY REMAINS UNCERTAIN. GFS DEPICTS BETTER RAIN CHANCES VERY LATE IN THE FCST PERIOD TOWARD THE END OF THE WEEK WITH THE PASSAGE OF THE NEXT COLD FRONT. ECMWF NOT YET IN AGREEMENT...SO TIME WILL TELL IF THIS WILL PAN OUT. FOR NOW WILL MAINTAIN A DRY FCST FOR THE UPCOMING WEEK. HIGH TEMPS TO RETURN TO THE UPPER 80S AND 90S FOR MUCH OF THE WEEK...BUT ATTM IT APPEARS REACHING THE CENTURY MARK AGAIN IN ANY PART OF THE FCST AREA IS UNLIKELY. && .PRELIMINARY POINT TEMPS/POPS... FRIONA 83 54 76 48 83 / 20 20 0 0 0 TULIA 84 55 76 49 83 / 20 20 0 0 0 PLAINVIEW 86 56 76 49 85 / 20 30 0 0 0 LEVELLAND 88 56 76 48 82 / 20 30 10 0 0 LUBBOCK 88 57 77 51 85 / 20 30 10 0 0 DENVER CITY 95 58 75 50 82 / 20 40 20 0 0 BROWNFIELD 95 57 76 52 83 / 20 40 20 0 0 CHILDRESS 93 59 80 55 88 / 20 30 0 0 0 SPUR 98 60 79 52 85 / 20 30 10 0 0 ASPERMONT 100 62 80 57 87 / 20 30 10 0 0 && .LUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 01
AREA FORECAST DISCUSSION
NWS TUCSON AZ
255 PM MST FRI SEP 7 2012 .SYNOPSIS...ABUNDANT MOISTURE WILL RESULT IN MAINLY AFTERNOON AND EVENING THUNDERSTORMS THROUGH WEDNESDAY. HEAVY RAINFALL WILL OCCUR WITH THE STRONGER THUNDERSTORMS. THEREAFTER...A DRYING TREND IS EXPECTED FOR THE LATTER PART OF NEXT WEEK. && .DISCUSSION...SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ONGOING EAST AND SOUTH OF TUCSON. MEANWHILE...ISOLATED SHOWERS OCCURRING ACROSS FAR WRN PIMA COUNTY. OPTED TO EXPAND THE TIME OF THE FLASH FLOOD WATCH FOR ALL OF SE AZ UNTIL 10 PM MST THIS EVENING. THE 07/18Z RUC HRRR PROGS PRECIP TO CONTINUE EAST OF TUCSON THRU THIS EVENING. MEANWHILE...GENERALLY PRECIP-FREE CONDITIONS TO OCCUR FROM TUCSON WWD. THUS...CONFIDENCE IS NOT HIGH REGARDING THE FORECAST DETAIL INTO THIS EVENING. IF THE RUC HRRR SOLUTIONS IS CLOSE TO REALITY...THE OFFICIAL FORECAST IS DEFINITELY OVERDONE REGARDING PRECIP CHANCES THIS EVENING. SAT-TUE... 07/12Z GFS/ECMWF WERE SIMILAR WITH MOVING UPPER LOW FROM OVER SE AZ THIS AFTERNOON WESTWARD TO NRN BAJA CALIFORNIA BY MIDDAY SUN. UPPER LOW IS PROGGED TO REMAIN QUASI-STATIONARY OVER NRN BAJA CALIFORNIA MON...THEN SYSTEM IS PROGGED TO EJECT EWD ACROSS CENTRAL AZ TUE. MOISTURE TO REMAIN SUFFICIENT FOR SCATTERED MAINLY AFTERNOON AND EVENING SHOWERS/TSTMS THIS WEEKEND AND EARLY NEXT WEEK. SHOWERS/ TSTMS MAY BE ENHANCED PARTICULARLY TUE AS SYSTEM EJECTS EWD AND JUST NORTH OF THE AREA. OPTED TO INCREASE POPS TUE TO REFLECT THIS NOTION. WED-FRI... MARKEDLY DRIER REGIME PROGGED VIA THE GFS/ECMWF WITH THE BULK OF DEEPER MOISTURE TO MOVE EAST OF THE AREA. FOR WED...A SLIGHT CHANCE OF AFTERNOON/EVENING SHOWERS/TSTMS MOST SECTIONS. THUR AND FRI... A SLIGHT CHANCE OF AFTERNOON/EVENING SHOWERS/TSTMS GENERALLY EAST AND SOUTH OF TUCSON WITH PRECIP-FREE CONDITIONS ELSEWHERE. HIGH TEMPS SAT-WED TO AVERAGE A FEW DEGS BELOW NORMAL. NEAR NORMAL DAYTIME TEMPS FORECAST TO OCCUR THUR-FRI. && .AVIATION...SCT TO NUMEROUS TSRA/SHRA THRU THIS EVENING THEN PRECIP DECREASING IN COVERAGE LATE TONIGHT. SCT -TSRA/-SHRA TO OCCUR SATURDAY AFTERNOON. OTHERWISE...VFR CONDITIONS AND SURFACE WIND MOSTLY LESS THAN 10 KTS THRU SATURDAY AFTERNOON OR 09/00Z. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS. && .FIRE WEATHER...SCATTERED THUNDERSTORMS WILL OCCUR THROUGH TUESDAY FOLLOWED BY A GRADUAL DECREASE IN THUNDERSTORMS DURING THE LATTER PART OF THE UPCOMING WEEK. && .CLIMATE...07/12Z KTWC TOTAL PRECIP WATER VALUE OF 1.99 INCHES IS THE HIGHEST RECORDED VALUE FOR SEPTEMBER BASED ON UPPER AIR DATA RECORDS SINCE 1951. THE YEARLY TIME SERIES PLOT MAY BE FOUND AT (ALL LOWERCASE EXCEPT FOR TWC): HTTP://WWW.CRH.NOAA.GOV/UNR/INCLUDE/PW.PHP?SID=TWC && .TWC WATCHES/WARNINGS/ADVISORIES... FLASH FLOOD WATCH UNTIL 10 PM MST THIS EVENING FOR AZZ501>515. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/TUCSON
AREA FORECAST DISCUSSION
NWS PHOENIX AZ
1010 AM MST FRI SEP 7 2012 .SYNOPSIS... A VERY MOIST AND UNSTABLE MONSOON AIRMASS WILL CONTINUE TO COVER THE REGION THROUGH EARLY NEXT WEEK...AND LEAD TO A CHANCE OF MAINLY AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS EACH DAY. THUNDERSTORM COVERAGE AND INTENSITY WILL VARY FROM DAY TO DAY...WITH SOMEWHAT BETTER CHANCES EXPECTED OVER THE WEEKEND AND INTO NEXT MONDAY. HIGH TEMPERATURES WILL REMAIN NEAR OR SLIGHTLY BELOW SEASONAL NORMALS EACH DAY GIVEN THE HIGH MOISTURE CONTENT IN THE ATMOSPHERE. && ...AREAS OF FLASH FLOODING EXPECTED IN THE PHOENIX METRO AREA... .DISCUSSION... WELL-DEFINED LOW PRESSURE SYSTEM ACROSS SOUTHERN AZ IS PRODUCING A CONSIDERABLE AMOUNT OF UPWARD VERTICAL MOTION ACROSS EAST-CENTRAL AZ. LEFTOVER CAPE FROM YESTERDAY HAS FINALLY BEEN REALIZED AND WIDESPREAD SHOWERS AND THUNDERSTORMS ERUPTED ACROSS EASTERN GILA COUNTY EARLY THIS MORNING. LATEST PSR SOUNDING CAME IN WITH 2.1 INCHES OF PRECIPITABLE WATER AND THE FOCUS REMAINS ON HEAVY RAIN/FLOODING. NORTHEASTERLY FLOW HAS STRENGTHENED BETWEEN THE VORT MAX TO THE SOUTH AND HIGH PRESSURE NEAR SAN DIEGO...WHICH HAS HELPED TO STEER THE ACTIVITY INTO THE PHOENIX METRO AREA. RAINFALL RATES HAVE BEEN EXTREMELY HIGH SO FAR ACROSS EAST MESA...GILBERT AND CHANDLER...AND ADDITIONAL FLOODING IS ANTICIPATED ACROSS PORTIONS OF THE VALLEY THIS AFTERNOON. HIGHEST RAINFALL TOTALS SO FAR HAVE BEEN 2.40 INCHES AT SAGUARO LAKE AND 2.36 INCHES IN MESA. ADJUSTMENTS TO THE FORECAST WERE ALREADY MADE THIS MORNING TO INCREASE POP/QPF/SKY. ADDITIONAL UPDATES TO LOWER TEMPERATURES ARE FORTHCOMING. && .PREVIOUS DISCUSSION... THE WEEKEND LOOKS TO BE PARTICULARLY ACTIVE AND THE MODELS HAVE BEEN HINTING AT THIS FOR THE PAST FEW DAYS. A FEW 700-300MB INVERTED TROUGHS ARE EXPECTED TO MOVE THROUGH THE REGION THIS WEEKEND...AND SHOULD INTERACT WITH A LARGER MORE WELL DEFINED 200-300MB PVD /PRESENTLY OVER BAJA CALIFORNIA/. INTERESTINGLY ENOUGH...THE USUALLY ACTIVE PORTIONS NORTH AND EAST OF PHOENIX MAY SEE A BIT OF A BREAK AT TIMES THIS WEEKEND AS THE GREATEST MOISTURE AND INSTABILITY ORIENT INTO A LAS VEGAS TO NOGALES AXIS. ALL GUIDANCE PRETTY MUCH AGREES THAT SOUTHERN GILA COUNTY MAY SEE LITTLE TO NO INSTABILITY SATURDAY AND SUNDAY. NOT SAYING THESE AREAS WILL BE DRY ALTOGETHER...BUT I REFINED THE POPS TO BETTER REFLECT THE AXIS OF MOISTURE/INSTABILITY. POPS WERE INCREASED ACROSS THE PHOENIX METRO AS WELL BUT AS USUAL...THERE IS JUST ENOUGH UNCERTAINTY IN THE GUIDANCE TO PRECLUDE ME FROM GOING MUCH ABOVE 40-50 PERCENT. WILL STORMS FORM OVER SOUTHERN ARIZONA AND MOVE NORTHWARD OR WILL STORMS FORM OVER NORTHERN MARICOPA COUNTY AND MISS PHOENIX ALTOGETHER...THESE ARE MY MAIN QUESTIONS THIS MORNING. HOPE TO GAIN SOME CLARITY FROM THE HI-RES WRF MODELS LATER TODAY. SIMILAR CONVECTIVE DEVELOPMENT IS EXPECTED ON SUNDAY WITH THE BEST CHANCES FROM PHOENIX WESTWARD TO THE COASTAL MOUNTAINS OF CALIFORNIA. WESTERLY FLOW ALOFT BEGINS TO TAKE SHAPE ON MONDAY AS THE UPPER LEVEL PVD MOVES THROUGH SOUTHERN ARIZONA INTO NEW MEXICO. MOISTURE SHOULD WORK ITS WAY BACK INTO EASTERN ARIZONA AND ALL LOCATIONS SHOULD SEE A DECENT CHANCE OF SHOWERS AND THUNDERSTORMS. MONDAY COULD BE THE BEST CHANCE AREA-WIDE FOR PRECIP GIVEN FAVORABLE UPPER LEVEL SUPPORT AND POPS WERE INCREASED INTO THE 40-50 PERCENT RANGE TO REFLECT THIS. FOLLOWING THE TROUGH...A GRADUAL DECREASE IN MOISTURE AND INSTABILITY WILL GREATLY REDUCE THE AMOUNT OF STORMS FROM TUESDAY ONWARD. COULD SEE A FEW RENEGADE STORMS EAST OF PHOENIX ON TUESDAY WHERE SOME MOISTURE AND INSTABILITY WILL RESIDE /PER THE SLOWER ECMWF SOLUTION/ BUT WESTERLY FLOW WILL STEER THESE STORMS AWAY FROM THE DESERTS. 1000-700MB MOISTURE DROPS ALL THE WAY DOWN TO AROUND 6 G/KG ON WEDNESDAY WITH BARELY ANY INSTABILITY TO SPEAK OF ANYWHERE IN THE STATE. MAY STRUGGLE TO EVEN GET AFTERNOON CU LATE NEXT WEEK AND POPS WERE REDUCED WELL BELOW CLIMO FOR THE END OF THE FORECAST PERIOD. WITH ELEVATED MOISTURE...TEMPS SHOULD STAY AOB NORMAL THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. TEMPS WILL CLIMB SLIGHTLY FROM THE MIDDLE OF NEXT WEEK ONWARD IN RESPONSE TO DECREASING MOISTURE BUT STILL IN THE BALLPARK OF NORMAL FOR MID SEPTEMBER. && .AVIATION... SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL... A WEAK WEATHER DISTURBANCE ALONG WITH ABUNDANT MOISTURE OVER THE SOUTHERN HALF OF ARIZONA WILL LEAD TO SHOWER AND THUNDERSTORM ACTIVITY IN SOMETHING OF A RANDOM PATTERN THIS MORNING. SHWRS/TSTMS WILL BE POSSIBLE ANYWHERE DESPITE THE LACK OF SURFACE HEATING. THUS THE VCSH/VCTS IN THE PHOENIX AREA TAFS. NAM MODEL SEEMS TO BE DOING A BETTER JOB EARLY THIS MORNING THAN THE GFS AND IT INDICATES MORE SHOWER ACTIVITY THIS MORNING THAN LATER THIS AFTERNOON. 09Z RUC INDICATES THIS AS WELL. WITH ALL THE MOISTURE AND CLOUDINESS...OPTIMAL INSTABILITY MAY NOT BE REALIZED. THIS...ALONG WITH UNCERTAINTIES IN TIMING AND LOCATION OF PRECIP IS WHY TEMPO SHRA/TSRA WAS WITHHELD FROM THE TAFS. ANY TSTMS THAT MOVE OVER AN AIRFIELD WILL BE ABLE TO REDUCE VSBYS AT OR BELOW 6SM IN HEAVY RAIN. SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH... NAM AND RUC INDICATE THAT THE LOWER COLORADO RIVER VALLEY WILL HAVE A BETTER CHANCE AT PRECIP THIS AFTERNOON THAN THE IMPERIAL VALLEY. A LOT OF UNCERTAINTIES REMAIN REGARDING INSTABILITY AND THUS THE OCCURRENCE OF CONVECTIVE SHOWERS. ANTICIPATE THAT LA PAZ COUNTY WILL BE ACTIVE ENOUGH LATER TODAY TO PRODUCE STORMS IN THE VICINITY OF KBLH. CANT RULE OUT STORM POSSIBILITIES FOR KIPL BUT TOO LOW AT THIS TIME TO REFLECT IN THE TAFS. SIGNIFICANTLY REDUCED VISIBILITIES IN HEAVY RAIN WILL BE POSSIBLE WITH THE STRONGER SHOWERS. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... SUNDAY THROUGH THURSDAY... LINGERING MOISTURE WILL MAINTAIN AN ELEVATED CHANCE OF THUNDERSTORMS FOR EARLY NEXT WEEK. DEEPER WESTERLY FLOW WILL LEAD TO A DOWNTREND IN ATMOSPHERIC MOISTURE BEGINNING TUESDAY. THUS...HUMIDITIES AND STORM CHANCES WILL DECLINE FROM WEST TO EAST. THERE WILL BE ONLY A SLIGHT CHANCE OF THUNDERSTORMS LEFT OVER THE HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA ON WEDNESDAY AND THURSDAY. MINIMUM HUMIDITIES WILL DROP INTO THE UPPER TEENS OVER SOUTHEAST CALIFORNIA BY THURSDAY. APART FROM THUNDERSTORM OUTFLOWS...NO STRONG WINDS ARE ANTICIPATED. AFTERNOON WINDS ARE EXPECTED TO FAVOR SOUTHWEST AND WESTERLY DIRECTIONS FOR MOST AREAS BEGINNING TUESDAY. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX DISCUSSION...HIRSCH PREVIOUS DISCUSSION...LEINS AVIATION...AJ FIRE WEATHER...AJ
AREA FORECAST DISCUSSION
NWS TUCSON AZ
950 AM MST FRI SEP 7 2012 .SYNOPSIS...ABUNDANT MOISTURE WILL RESULT IN MAINLY AFTERNOON AND EVENING THUNDERSTORMS INTO EARLY NEXT WEEK. EXPECT HEAVY RAINFALL WITH THE STRONGER THUNDERSTORMS. && .DISCUSSION...SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ONGOING ACROSS SOUTH CENTRAL PINAL COUNTY AND WRN/CENTRAL PIMA COUNTY WEST OF TUCSON AT THIS TIME. ELSEWHERE...PRECIP-FREE CONDITIONS THUS FAR. HOWEVER...07/12Z UNIV OF AZ WRF-NAM AND 07/12Z-13Z RUC HRRR WERE VERY SIMILAR WITH PROGGED PRECIP INTO THIS EVENING. IN ESSENCE...PRECIP TO DECREASE IN COVERAGE AND INTENSITY WEST OF TUCSON DURING THE NEXT FEW HOURS FOLLOWED BY MOSTLY DRY CONDITIONS THIS AFTERNOON AND THIS EVENING. EAST OF TUCSON...PRECIP TO DEVELOP IN THE NEXT COUPLE OF HOURS...THEN SCT-NMRS SHOWERS/TSTMS ACROSS GREENLEE/GRAHAM/COCHISE COUNTIES THIS AFTERNOON INTO THIS EVENING. SEEMS REASONABLE...PARTICULARLY THE PRECIP FOR ERN SECTIONS...GIVEN THE ABUNDANT AVAILABLE MOISTURE AND APPROACHING CYCLONIC CIRCULATION SYSTEM AS PER WATER VAPOR IMAGERY MOVING WWD INTO NERN SONORA. THUS...HAVE EXPANDED THE FLASH FLOOD WATCH TO INCLUDE ALL OF SE AZ UNTIL 8 PM MST THIS EVENING. IF THE AFOREMENTIONED SOLUTIONS COME CLOSE TO REALITY...WILL LIKELY CANCEL THE FLASH FLOOD WATCH EARLY THIS AFTERNOON FOR LOCALES WEST OF TUCSON AND MAINTAIN THE FLASH FLOOD WATCH FROM TUCSON EWD. PLEASE REFER TO THE PREVIOUS DISCUSSION SECTION BELOW FOR ADDITIONAL FORECAST DETAIL. ALSO...PLEASE REFER TO THE CLIMATE SECTION BELOW FOR DETAIL REGARDING THE 07/12Z KTWC SOUNDING. && .PREV DISCUSSION...DEBRIS CLOUD WITH EMBEDDED SHOWERS THIS MORNING...EXPECT THAT TO CONTINUE TO SLOWLY THIN THROUGH THE MORNING HOURS WITH PARTIAL CLEARING BY LATE MORNING. ABUNDANT MOISTURE WITH PRECIPITABLE WATER VALUES IN THE 1.75 TO 2 INCH RANGE...SOMETHING ON THE ORDER OF 200 PERCENT OF CLIMO. INITIAL IMPULSE THAT HELPED ORGANIZE CONVECTION LIFTING NORTHWEST OF THE AREA THIS MORNING BUT WATER VAPOR IMAGERY INDICATING ANOTHER EASTERLY IMPULSE SHIFTING ACROSS NORTHWEST CHIHUAHUA INTO NORTHEAST SONORA. NAM12 AND ECMWF GRAB THIS FEATURE AND KICK OFF ANOTHER BUSY DAY WITH A FOCUS THROUGH PIMA...SANTA CRUZ AND SOUTHERN COCHISE COUNTIES. MAY NEED A FLASH FLOOD WATCH TODAY AND THOSE AREAS WOULD BE A FIRST GUESS FOR A STARTING POINT. LARGER SCALE WEAKNESS IN THE FLOW SHIFTS TOWARD SOUTHWEST ARIZONA WITH AN EMPHASIS TO WESTERN AREAS OVER THE WEEKEND. HIGHER LATITUDE FLOW SHOULD MANAGE TO GRAB THIS FEATURE AND DRAG IT BACK EASTWARD MONDAY OR TUESDAY FOR ANOTHER BIG KICK TO THE THUNDERSTORM FORECAST. ULTIMATELY THE UPSTREAM FOR THAT WESTERLY FLOW WILL DRY OUT SOONER OR LATER...WITH A DOWNTURN IN THUNDERSTORMS COVERAGE EXPECTED BY THE SECOND HALF OF NEXT WEEK. && .AVIATION...SCT TO NUMEROUS TSRA/SHRA WEST AND NW OF KTUS BECOMING ISOLD-SCT TSRA/SHRA THIS AFTERNOON INTO THIS EVENING. EAST OF KTUS... PRECIP DEVELOPING LATE THIS MORNING AND BECOMING SCT TO NUMEROUS TSRA/SHRA THIS AFTERNOON INTO THIS EVENING. PRECIP DECREASING AREA WIDE LATE TONIGHT ALTHOUGH SCT -TSRA/-SHRA CONTINUING. OTHERWISE... VFR CONDITIONS AND GENERALLY LIGHT WINDS THRU SATURDAY MORNING OR 08/12Z. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS. && .FIRE WEATHER...AN UPPER LEVEL DISTURBANCE ACROSS THE AREA WILL BRING WETTING RAINFALL TO MOST OF SOUTHEAST ARIZONA INTO EARLY NEXT WEEK. WINDS WILL INCREASE ACROSS MOST OF ZONE 148 AND SOUTHERN HALF OF ZONE 146 SATURDAY AS THE SYSTEM BEGINS TO EXIT THE REGION TO THE WEST. OTHERWISE...LIGHT DIURNAL WIND TRENDS ARE EXPECTED INTO EARLY NEXT WEEK. && .CLIMATE...07/12Z KTWC TOTAL PRECIP WATER VALUE OF 1.99 INCHES IS THE HIGHEST RECORDED VALUE BASED ON UPPER AIR DATA RECORDS SINCE 1951. THE YEARLY TIME SERIES PLOT MAY BE FOUND AT (ALL LOWERCASE EXCEPT FOR TWC): HTTP://WWW.CRH.NOAA.GOV/UNR/INCLUDE/PW.PHP?SID=TWC && .TWC WATCHES/WARNINGS/ADVISORIES... FLASH FLOOD WATCH UNTIL 8 PM MST THIS EVENING FOR AZZ501>515. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/TUCSON
AREA FORECAST DISCUSSION
NWS TAUNTON MA
153 PM EDT FRI SEP 7 2012 .SYNOPSIS... A DIFFUSE FRONTAL BOUNDARY ACROSS THE REGION WILL LIFT BACK NORTHWARD DURING THE COURSE OF TODAY INTO TONIGHT AS A WARM FRONT. A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS IS POSSIBLE ALONG THE FRONT...OTHERWISE REMAINING DRY AND HUMID INTO SATURDAY. SHOWERS AND THUNDERSTORMS ARE LIKELY SATURDAY NIGHT AS A STRONG COLD FRONT MOVES ACROSS THE REGION. MUCH COOLER AND DRIER WEATHER WILL FOLLOW EARLY NEXT WEEK...THEN A SLOW WARMING TREND TOWARD THE LATTER HALF OF THE WEEK. HURRICANE LESLIE WILL TRACK SEVERAL HUNDRED MILES EAST OF NEW ENGLAND BUT BRING DANGEROUS SURF TO THE SOUTHERN NEW ENGLAND COAST THIS WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 200 PM UPDATE... FORECAST CONTINUES TO STAY ON TRACK. HAVE PUSHED BACK POPS TIL AFTER 18Z PER LATEST HRRR MODEL RUN. OTHERWISE CU FIELD IS SLOWLY DEVELOPING ALONG THE SOUTH SHORE SEA BREEZE. WITH MODEST INSTABILITY MAY SEE AN ISOLATED CONVECTION...AM NOT EXPECTING ANYTHING WIDESPREAD. LIMITING FACTOR WOULD BE CELL UPDRAFT...WITH A VERY DRY AIR ALOFT...EXPECT CELLS TO REMAIN LOW TOPPED. GOOD AMOUNT OF LOW LEVEL MOISTURE PER LATEST DEWPOINT OBSERVATION SO THE POTENTIAL IS THERE. WILL HAVE TO MONITOR RADAR AND LATEST CONDITIONS. OTHERWISE MADE SOME MINOR UPDATES TO THE FORECAST TO ACCOUNT FOR CURRENT TRENDS. TEMPS CONTINUE TO BE ON THE RISE...AND WIT THE SEA BREEZES PUSHING INWARD...ALONG THE COAST MAY BE A TAD COOLER. OVERALL A DECENT DAY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... TONIGHT... LOOKING AT A QUIET NIGHT WITH STRONG SLY FLOW KEEPING SFC TEMPS NEAR-STABLE AND MILD IN AND AROUND THE MID-UPR 60S. THE ABUNDANCE OF LOW-LVL MOISTURE BELOW THE NOCTURNAL INVERSION WILL LIKELY RESULT IN A MIX OF PATCHY FOG AND LOW-LYING STRATUS. AS ALLUDED TO BY THE PREV FCSTR...IT/S PLAUSIBLE TO SEE TROPICAL MOISTURE STREAMING NWD FROM LESLIE TOWARDS THE S SHORELINE OF NEW ENGLAND. LATEST MDL GUIDANCE SUGGESTS IT SHOULD REMAIN WELL OFFSHORE PRIOR TO SATURDAY MORNING. SATURDAY... THERE ARE SOME SUBTLE DIFFERENCES IN THE 07/0Z FCST GUIDANCE WORTH NOTING...SUCH AS THE STRENGTH AND POSITION OF THE SFC LOW PRES CENTER AND ATTENDANT STRENGTH OF THE LLJ ALONG AND AHEAD OF THE TRAILING SFC COLD FRNT. NEVERTHELESS...THERE IS BETTER AGREEMENT AMONGST THE GUIDANCE ON THE TIMING OF THE SYS FOR THE LATE PD INTO SATURDAY NIGHT. THRU THE DAY...STRONG ONSHORE SLY FLOW /SUSTAINED AROUND 10-15 MPH WITH GUSTS UP TO 25 MPH/ SHOULD ADVECT TROPICAL AIR NWD WITH LOW 70 DWPTS. LOOKING TO BE A MILD AND SULTRY DAY. WAA PREVAILING BETWEEN H925-85 MAY ACT TO CAP THE LOWER ATMOS... RESULTING IN MOISTURE POOLING WITHIN THE BOUNDARY LYR AND DEVELOPMENT OF LOW-LVL STRATUS. ANTICIPATING PARTLY SUNNY CONDITIONS WITH THE POSSIBILITY THAT LOW-LVLS WILL MIX OUT ALLOWING FOR ENTRAINMENT OF DRIER AIR ALOFT /ABOVE H85/. LOWERING HEIGHTS ACROSS THE RGN COMBINED WITH OROGRAPHIC LIFT AND LOW-LVL MOISTURE CONVERGENCE OF THE ONSHORE TROPICAL AIRMASS MAY RESULT IN SCTD LIGHT SHOWER ACTIVITY PRIOR TO THE MAIN SHOW. WILL LEAN MORESO TOWARDS THE 06/21Z SREF POPS. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... HIGHLIGHTS... * SHOWERS AND THUNDERSTORMS SAT NIGHT...IMPROVING CONDITIONS SUNDAY * DRY AND MUCH COOLER EARLY NEXT WEEK FOLLOWED BY A WARMING TREND OVERVIEW... MODELS HAVE COME INTO BETTER AGREEMENT ON TIMING OF COLD FRONT AND ASSOCD SHOWERS/TSTMS SAT NIGHT WITH GRADUAL IMPROVING CONDITIONS SUNDAY. AN EXTENDED PERIOD OF DRY WEATHER IS EXPECTED FOR MUCH OF NEXT WEEK WITH BELOW NORMAL TEMPS TO START THE WEEK FOLLOWED BY A GRADUAL MODERATING TREND. ECMWF IS SLOWER THAN GFS LIFTING THE MID LEVEL TROF AWAY FROM NEW ENG...BUT THE MAIN EFFECT OF THIS DIFFERENCE WILL BE HOW QUICKLY WARMER AIR RETURNS TO SNE. SAT NIGHT INTO SUNDAY... COLD FRONT WILL BE MOVING ACROSS SNE SAT NIGHT REACHING THE CAPE AND ISLANDS AROUND 12Z SUN. FAVORABLE JET DYNAMICS WITH LOW LEVEL JET COLLOCATED WITH RIGHT ENTRANCE REGION OF UPPER JET WHICH WILL RESULT IN AN AREA OF ENHANCED OMEGA MOVING ACROSS THE REGION SAT NIGHT. THIS COMBINED WITH HIGH PWAT AIRMASS AND ELEVATED INSTABILITY WILL BRING A PERIOD OF SHOWERS AND SCT THUNDERSTORMS. FRONT IS PROGRESSIVE SO WE DONT EXPECT EXCESSIVE RAINFALL BUT BRIEF HEAVY DOWNPOURS ARE POSSIBLE. NAM IS MORE ROBUST WITH THE LOW LEVEL JET AND OMEGA RESULTING IN GREATER QPF...BUT IS AN OUTLIER COMPARED TO GFS/ECMWF. GIVEN THAT MAIN THRUST OF SHORTWAVE ENERGY IS LIFTING TO THE N SAT NIGHT WE LEANED TOWARD THE GFS/ECMWF. FRONT WILL BE MOVING TO THE E ON SUNDAY. SHOWERS ARE LIKELY EARLY SUNDAY...MAINLY ACROSS E NEW ENG AND COULD LINGER INTO THE AFTERNOON CAPE/ISLANDS IF SLOWER ECMWF IS CORRECT. WE LEANED TOWARD SLIGHTLY FASTER GFS WHICH SUGGESTS PARTIAL CLEARING MOVING IN FROM WEST TO EAST. MONDAY THROUGH THURSDAY... THIS PERIOD WILL BE DOMINATED BY HIGH PRESSURE RESULTING IN AN EXTENDED PERIOD OF DRY WEATHER. IT WILL BE A COOL START TO THE WEEK WITH BELOW NORMAL TEMPS EXPECTED...THEN A MODERATING TREND TOWARD THE LATTER HALF OF THE WEEK AS MID LEVEL RIDGE BUILDS IN FROM THE WEST WITH RISING HEIGHTS. GFS IS PROBABLY TOO QUICK LIFTING THE MID LEVEL TROF OUT SO WARMER AIRMASS WILL LIKELY BE DELAYED TIL WED OR THU. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT MODERATE...30 PERCENT TO 60 PERCENT HIGH...GREATER THAN 60 PERCENT OVERVIEW...MODERATE CONFIDENCE. DIURNAL CU WILL CONTINUE TO DEVELOP UNDER LGT AND VRB FLOW. WINDS WILL TURN MORE SLY LATE INTO THE DAY AND OVRNGT. SEA BREEZE SHLD DISSIPATE BY SUNSET. VSBYS AND LOW-STRATUS SHOULD REAPPEAR DURING THE OVRNGT PD AND CONTINUE INTO SATURDAY. UNCERTAIN ON TIMING OF DISSIPATION. WINDS WILL BE GUSTING AT AROUND 20 KTS ALONG AND AHEAD OF AN APPROACHING COLD FRNT FOR SAT NIGHT. SHRA/TSRA WILL INCREASE LATE SAT INTO THE OVERNIGHT PERIOD. KBOS TAF...MODERATE CONFIDENCE. VFR TODAY WITH SEA-BREEZES INTO THE MIDDAY PD RESULTING IN MOSTLY CLEAR TO SCT CONDITIONS. SLY FLOW OVRNGT WITH PSBL LOW-LVL STRATUS REAPPEARING INTO SATURDAY MORNING. TSRA/SHRA LOOKS LIKELY SAT NIGHT. KBDL TAF...MODERATE CONFIDENCE. VRB WINDS BECOMING SLY THIS AFTERNOON. LOW CONFIDENCE ON SHRA/TSRA TODAY...BUT CAN/T RULE OUT THE POSSIBILITY. SOUTHERLY FLOW OVERNIGHT WITH LOW-STRATUS TONIGHT INTO SATURDAY. TSRA/SHRA CONDITIONS LATE SATURDAY...LOWERING TO MVFR/IFR. OUTLOOK...SATURDAY NIGHT THROUGH TUESDAY... SATURDAY NIGHT INTO SUNDAY... MODERATE TO HIGH CONFIDENCE IN A PERIOD OF MVFR/IFR SAT NIGHT AS SHOWERS MOVE ACROSS THE REGION WITH AREAS OF STRATUS AND PATCHY FOG. SHOWERS AND LOWER CONDITIONS MAY PERSIST INTO EARLY SUNDAY...MAINLY E NEW ENG BUT IMPROVING CONDITIONS TO VFR EXPECTED FROM WEST TO EAST. MONDAY INTO TUESDAY...VFR. HIGH CONFIDENCE. && .MARINE... OVERVIEW...MODERATE TO HIGH CONFIDENCE. FCST GUIDANCE SUGGESTS A SLIGHT DECREASE IN SWELLS THROUGH THE FORECAST PERIOD INTO THE EARLY PART OF NEXT WEEKEND WITH A CONSISTENT WAVE PERIOD AROUND 12 SECONDS. WAVE HEIGHTS REMAIN FAIRLY STABLE...ONLY TO RESURGE WITH INCREASING SLY FLOW AHEAD OF AN AREA OF LOW PRES APPROACHING THE WATERS INTO THE WEEKEND...AND THE CLOSE PROXIMITY PASSAGE OF LESLIE. WHILE THERE MAY BE THE SLGT CHC OF SHOWERS AND THUNDERSTORMS DURING THE PD /ESPECIALLY LATER CLOSER TO SATURDAY NIGHT/ A MORE SIGNIFICANT IMPACT MAY BE PATCHY FOG DURING THE OVRNGT HRS. OUTLOOK...SATURDAY NIGHT THROUGH TUESDAY... MODERATE TO HIGH CONFIDENCE... A PERIOD OF SCA PREFRONTAL S/SW GUSTS EXPECTED SAT NIGHT AS LOW LEVEL JET MOVES ACROSS THE REGION. A TEMPORARY DECREASE IN WINDS SUNDAY...THEN NW WIND GUSTS MAY APPROACH 25 KT AT TIMES LATE SUN NIGHT INTO TUESDAY. INCREASING SE SWELL FROM LESLIE EXPECTED THIS WEEKEND INTO EARLY NEXT WEEK RESULTING IN HAZARDOUS SEA CONDITIONS THROUGH MUCH OF THE PERIOD. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 3 PM EDT SATURDAY FOR ANZ235-237-254>256. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 8 PM THIS EVENING TO 3 PM EDT SATURDAY FOR ANZ250. && $$ SYNOPSIS...KJC/SIPPRELL NEAR TERM...DUNTEN SHORT TERM...SIPPRELL LONG TERM...KJC AVIATION...KJC/DUNTEN MARINE...KJC/SIPPRELL
AREA FORECAST DISCUSSION
NWS GOODLAND KS
231 PM MDT FRI SEP 7 2012 .SHORT TERM...(THIS AFTERNOON THROUGH TONIGHT) ISSUED AT 210 PM MDT FRI SEP 7 2012 LATEST WV IMAGERY AND RUC H5 ANALYSIS SHOW POSITIVELY TILTED TROUGH OVER NORTHERN GREAT LAKES WITH AXIS EXTENDING SOUTHWEST ACROSS CENTRAL NEBRASKA. LARGE SCALE SUBSIDE IS CURRENTLY BUILDING INTO TRI-STATE AREA AS THIS TROUGH SHIFTS EAST. AT THE SURFACE HIGH PRESSURE BUILDING INTO THE CWA FROM THE NORTHWEST. ISOLATED LIGHT SHOWERS/SPRINKLES WILL REMAIN POSSIBLE ACROSS THE NW THIS AFTERNOON ASSOCIATED WITH COLD POOL ALOFT AND STEEPENING LAPSE RATES. WE ALSO HAVE SOME WEAK H85-H7 FRONTOGENESIS LINGERING JUST TO THE NORTHWEST OF THE CWA...RESPONSIBLE FOR CURRENT SHOWER ACTIVITY OUTSIDE OF CWA. DO NOT ANTICIPATE ANY PRECIP LINGERING PAST SUNSET WHEN DIURNAL HEATING COMES TO AN END. COOLER AIR MASS ALREADY IN PLACE AFTER FRONTAL PASSAGE LAST NIGHT...WITH H85 TEMPS BASED ON THIS MORNINGS 12Z SOUNDING IN THE 12-14C RANGE. WITH CALM WINDS AND CLEARING SKIES I EXPECT OVERNIGHT TEMPS TO DROP TO THE LOW TO MID 40S ACROSS THE AREA. IF WE WERE TO SEE LOWER TD VALUES ADVECT INTO THE CWA...THEN WE COULD BREAK A FEW LOW TEMPERATURE RECORDS TONIGHT...WITH VALUES IN THE UPPER 30S. PREVIOUS GUIDANCE WAS BRINGING MUCH LOWER TD VALUES INTO THE AREA TONIGHT. HOWEVER...BASED ON UPSTREAM TRENDS AND CURRENT GUIDANCE TD VALUES SHOULD REMAIN 40F OR HIGHER...WHICH WILL LIMIT COOLING POTENTIAL. .LONG TERM...(SATURDAY THROUGH FRIDAY) ISSUED AT 226 PM MDT FRI SEP 7 2012 SATURDAY THROUGH SUNDAY NIGHT WILL REMAIN DRY AS THE UPPER LEVEL RIDGE CURRENTLY OVER THE SOUTHERN CONUS BUILDS NORTHWARD OVER THE GREAT BASIN AND EXPANDS EAST INTO THE PLAINS. SUNDAY AFTERNOON AND SUNDAY NIGHT THE RIDGE WILL FLATTEN OUT AS A SHORT WAVE TROUGH MOVES ACROSS IT. THE SHORT WAVE TROUGH WILL MOVE INTO THE AREA SUNDAY NIGHT. HOWEVER AM ONLY EXPECTING SOME CLOUDS TO DEVELOP WITH THE TROUGH DUE TO THE SHALLOW MOIST LAYER TO WORK WITH BETWEEN 500-600MB. TUESDAY THROUGH FRIDAY WILL HAVE CHANCES FOR PRECIPITATION ALMOST EVERY DAY. TUESDAY AN UPPER LEVEL SHORT WAVE TROUGH AND ASSOCIATED SURFACE TROUGH MOVE ACROSS THE AREA PROVIDING AN OPPORTUNITY FOR SOME LOCATIONS TO RECEIVE RAINFALL. TUESDAY NIGHT INTO WEDNESDAY ANOTHER UPPER LEVEL SHORT WAVE TROUGH FOLLOWS A COLD FRONT THROUGH THE AREA...OFFERING A SHOT FOR MORE WIDE SPREAD RAINFALL. THE NEXT BEST CHANCE FOR WIDE SPREAD RAINFALL COMES WEDNESDAY NIGHT THROUGH THURSDAY NIGHT AS AN UPPER LEVEL LONG WAVE TROUGH MOVES ACROSS THE PLAINS. THERE MAY BE SOME LINGERING STORM ACTIVITY ON FRIDAY AS THE TROUGH DEPARTS THE AREA. HIGH TEMPERATURES WILL BE WARMEST ON MONDAY AND TUESDAY AHEAD OF THE COLD FRONT...ROUGHLY 10 DEGREES ABOVE NORMAL. FROM WEDNESDAY THROUGH FRIDAY HIGH TEMPERATURES WILL BE ALMOST 10 DEGREES BELOW NORMAL. LOW TEMPERATURES FOR THE PERIOD WILL BE NEAR NORMAL. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON) ISSUED AT 1117 AM MDT FRI SEP 7 2012 VFR CONDITIONS WILL PREVAIL AT BOTH KGLD AND KMCK TERMINALS THROUGH THE PERIOD. GUSTY NORTH WINDS WILL CONTINUE THROUGH AROUND SUNSET AT BOTH TERMINALS...WITH GUSTS 20-25KT EXPECTED. VARIABLE WINDS LESS THAN 10KT ARE THEN EXPECTED TO PREVAIL THROUGH THE REMAINING TAF PERIOD AS SURFACE HIGH PRESSURE MOVES INTO THE REGION. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...DR LONG TERM...JTL AVIATION...DR
AREA FORECAST DISCUSSION
NWS GOODLAND KS
211 PM MDT FRI SEP 7 2012 .SHORT TERM...(THIS AFTERNOON THROUGH TONIGHT) ISSUED AT 210 PM MDT FRI SEP 7 2012 LATEST WV IMAGERY AND RUC H5 ANALYSIS SHOW POSITIVELY TILTED TROUGH OVER NORTHERN GREAT LAKES WITH AXIS EXTENDING SOUTHWEST ACROSS CENTRAL NEBRASKA. LARGE SCALE SUBSIDE IS CURRENTLY BUILDING INTO TRI-STATE AREA AS THIS TROUGH SHIFTS EAST. AT THE SURFACE HIGH PRESSURE BUILDING INTO THE CWA FROM THE NORTHWEST. ISOLATED LIGHT SHOWERS/SPRINKLES WILL REMAIN POSSIBLE ACROSS THE NW THIS AFTERNOON ASSOCIATED WITH COLD POOL ALOFT AND STEEPENING LAPSE RATES. WE ALSO HAVE SOME WEAK H85-H7 FRONTOGENESIS LINGERING JUST TO THE NORTHWEST OF THE CWA...RESPONSIBLE FOR CURRENT SHOWER ACTIVITY OUTSIDE OF CWA. DO NOT ANTICIPATE ANY PRECIP LINGERING PAST SUNSET WHEN DIURNAL HEATING COMES TO AN END. COOLER AIRMASS ALREADY IN PLACE AFTER FRONTAL PASSAGE LAST NIGHT...WITH H85 TEMPS BASED ON THIS MORNINGS 12Z SOUNDING IN THE 12-14C RANGE. WITH CALM WINDS AND CLEARING SKIES I EXPECT OVERNIGHT TEMPS TO DROP TO THE LOW TO MID 40S ACROSS THE AREA. IF WE WERE TO SEE LOWER TD VALUES ADVECT INTO THE CWA...THEN WE COULD BREAK A FEW LOW TEMPERATURE RECORDS TONIGHT...WITH VALUES IN THE UPPER 30S. PREVIOUS GUIDANCE WAS BRINGING MUCH LOWER TD VALUES INTO THE AREA TONIGHT. HOWEVER...BASED ON UPSTREAM TRENDS AND CURRENT GUIDANCE TD VALUES SHOULD REMAIN 40F OR HIGHER...WHICH WILL LIMIT COOLING POTENTIAL. .LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY) ISSUED AT 230 AM MDT FRI SEP 7 2012 SATURDAY NIGHT-SUNDAY NIGHT...H5 RIDGE WILL AMPLIFY DURING THE PERIOD BEFORE BEGINNING TO FLATTEN BY SUNDAY NIGHT. WITH DRY AIR MASS IN PLACE ACROSS THE AREA AND LOW LEVEL FLOW NOT REALLY FAVORABLE FOR ANY MEANINGFUL MOISTURE RETURN SEE NO REASON WHY DRY CONDITIONS WILL NOT CONTINUE TO PREVAIL THROUGH THE PERIOD. TEMPERATURES WILL WARM THROUGH THE PERIOD WITH LOWS WARMING SEVERAL DEGREES FROM THE PREVIOUS DAY ON SATURDAY AND AGAIN ON SUNDAY. HIGH TEMPERATURES WILL ALSO WARM THROUGH THE PERIOD WITH MID 80S TO LOW 90S POSSIBLE BY SUNDAY. WARMER TEMPERATURES WILL RETURN BY EARLY NEXT WEEK AS THE SURFACE HIGH SLIDES EAST INTO THE MISSISSIPPI AND OHIO RIVER VALLEYS AND A BROAD RIDGE BUILDS INTO THE CENTRAL PORTION OF THE COUNTRY. THE RIDGE WILL CONTINUE TO SHIFT EASTWARD TOWARDS THE ATLANTIC COAST AS A VIGOROUS TROUGH SWINGS ACROSS THE CANADIAN AND NORTH CENTRAL PLAINS. THE ATTENDANT COLD FRONT WILL MOVE ACROSS THE REGION TUESDAY AFTERNOON AND EVENING WITH THE CHANCE OF SCATTERED THUNDERSTORMS DEVELOPING AS IT MOVES THROUGH. THERE IS A CHANCE THAT A FEW SHOWERS MAY LINGER INTO WEDNESDAY MORNING. ANOTHER CHANCE FOR SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE LATE WEDNESDAY AFTERNOON AS A SHORTWAVE TROUGH MOVING THROUGH THE FLOW IMPACTS THE AREA. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON) ISSUED AT 1117 AM MDT FRI SEP 7 2012 VFR CONDITIONS WILL PREVAIL AT BOTH KGLD AND KMCK TERMINALS THROUGH THE PERIOD. GUSTY NORTH WINDS WILL CONTINUE THROUGH AROUND SUNSET AT BOTH TERMINALS...WITH GUSTS 20-25KT EXPECTED. VARIABLE WINDS LESS THAN 10KT ARE THEN EXPECTED TO PREVAIL THROUGH THE REMAINING TAF PERIOD AS SURFACE HIGH PRESSURE MOVES INTO THE REGION. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...DR LONG TERM...JRM/PMM AVIATION...DR
AREA FORECAST DISCUSSION
NWS PADUCAH KY
1248 PM CDT FRI SEP 7 2012 .NEAR TERM...(THIS AFTERNOON AND TONIGHT) ISSUED AT 1248 PM CDT FRI SEP 7 2012 SOME OF THE DISCUSSION BELOW IS FROM AN UPDATE AT 1141 AM. UPDATED SKY FORECAST...AS IT WAS TOO PESSIMISTIC. NAM TEMPS ALSO QUITE A WAYS OFF. SIDED WITH WARMER GFS MOS NUMBERS AND BLENDED THEM WITH OUR EXISTING NUMBERS. CONVECTION HAS BEEN WEAK OVER SOUTHERN ILLINOIS THIS MORNING. THERE IS NEWLY DEVELOPED CONVECTION ALONG A BOUNDARY JUST NORTH OF OUR CWFA...BUT IT APPEARS TO BE HEADING OFF TO THE EAST. HERE IS THE LATEST THINKING ON THE SEVERE WEATHER / THUNDERSTORM SCENARIO THIS AFTERNOON AND EVENING. FIRST...LOOKING AS VISIBLE IMAGERY...AND H5 ANALYSIS...HARD TO SAY WHAT THE FOCUS WILL BE EARLY ON. THAT MEANS OUR CONFIDENCE IN THE MESO SCALE MODELS IS LOW AT BEST. HINTS OF ELEVATED INSTABILITY PER ACCAS AND ENHANCED CLOUDS ON VISIBLE...BUT VERY WEAK FORCING ACROSS THE AREA. THE HRRR SUGGESTS THAT SUPPORT AND ASSOC CONVECTION SOUTH OF JOPLIN COULD ORGANIZE WITH TIME AND HEAD EAST ACROSS SOUTHERN MISSOURI...MAYBE EVEN REACHING WESTERN KENTUCKY BY EARLY EVENING. THIS MAY NOT BE TOO UNREASONABLE...GIVEN THE MODELS GENERATE DECENT INSTABILITY INTO SOUTHERN AND SOUTHEAST MISSOURI THIS AFTERNOON. WILL MONITOR THIS. THEN OF COURSE YOU HAVE THE FRONT COMING IN FROM THE NORTHWEST WHICH THE HRRR HAS FROM ECNTRL IL TO NEAR KSTL INTO SW MISSOURI AROUND 00Z. CONVECTION IS LINED OUT ALONG THE FRONT AS WELL...ALONG AND JUST BEHIND IT. WE HAVE NEW POP GRIDS...TAILORED TOWARD THE POSSIBILITY OF CONVECTION COMING IN FROM THE WEST INTO SOUTHEAST MISSOURI...AND IN FROM THE NORTHWEST WITH THE FRONT. BEST WE CAN DO GIVEN THE LOWER CONFIDENCE IN THE MESOSCALE MODELS. AS FAR AS SEVERE TYPE. NOT MUCH DIFFERENCE IN AIRMASS. MAIN DIFFERENCE SYNOPTICALLY IS A STRONG FRONT MOVING INTO THE AREA...AND ANY ADDITIONAL MESOSCALE BOUNDARIES AHEAD OF IT CONVECTION CAN ACT UPON. GIVEN THE DEGREE OF FORECAST POTENTIAL INSTABILITY AND AMOUNT OF LOW LEVEL MOISTURE...SEVERE WINDS SEEMS TO BE THE MAIN HAZARD...ESPECIALLY SHOULD ANY CLUSTERS BECOME SELF SUSTAINING AND ORGANIZED. FREEZING LEVELS ARE SLIGHTLY LOWER...SO A MARGINAL SEVERE HAIL THREAT IS IN PLAY. TORNADIC POSSIBILITY SHOULD BE LOW GIVEN LACK OF SUBSTANTIAL WIND FIELDS. CANNOT RULE OUT THE PESKY SPIN UPS WHERE NEAR STORM RELATIVE FLOW ENVIRONMENT MAY SEE ENHANCED SHEAR. TONIGHT...BEST CHANCE POPS FROM 03Z THROUGH 09Z AS THE FRONT MOVES STEADILY FROM NW TO SE ACROSS THE AREA. WIDESPREAD COVERAGE EXPECTED SO BUMPED UP POPS TO NEAR 100 PERCENT...WITH SOME AREAS LIKELY RECEIVING 1-2 INCHES OF RAINFALL. ENDING PRECIPITATION WILL FOLLOW ESPECIALLY FROM SOUTHERN ILLINOIS INTO SOUTHEAST MISSOURI. STAY TUNED...PROBABILITY OF A WATCH OF SOME KIND IS LIKELY HIGH GIVEN SPC/S SEVERE WEATHER PROBABILITIES. .SHORT/LONG TERM...(SATURDAY THROUGH FRIDAY) ISSUED AT 1248 PM CDT FRI SEP 7 2012 THIS PERIOD WILL START WITH THE MEAN TROUGH ALONG AND JUST EAST OF THE WFO PAH FORECAST AREA. THIS WILL ALLOW COLD AIR ADVECTION TO CONTINUE THROUGH THE DAYTIME HOURS SATURDAY...WITH THE GRADIENT WEAKENING SATURDAY NIGHT. BELOW NORMAL TEMPERATURES /10-15 DEGREES BELOW NORMAL/ CAN BE EXPECTED SATURDAY...SLOWLY MODERATING INTO EARLY NEXT WEEK AS LOW AMPLITUDE RIDGING PUSHES ACROSS THE CENTRAL UNITED STATES. THIS RIDGE WILL TAKE MOST OF THE WEEK TO PUSH EAST OF THE WFO PAH FORECAST AREA...SO THERE WILL BE A SLOW BUT GRADUAL RISE IN DAILY TEMPERATURES INTO THE MIDDLE 80S...PRIMARILY DOMINATED BY DIURNAL TRENDS...MAINLY SUNSHINE...GIVEN MINIMAL CLOUD COVER EXPECTED THROUGH NEXT WEEK. THE GFS ATTEMPTS TO MOVE A FRONT CLOSE THE THE NORTHWEST SECTIONS OF THE WFO PAH FORECAST AREA BY LATE NEXT FRIDAY. GIVEN THE UNCERTAINTY DUE TO THE TIMING OF THIS SYSTEM...WILL KEEP THE FORECAST DRY THROUGH ALL OF NEXT WEEK. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY) ISSUED AT 1141 AM CDT FRI SEP 7 2012 CONFIDENCE IN CONVECTION IS LOW THROUGH LATE AFTERNOON. HOWEVER CONFIDENCE INCREASES LATE AFTERNOON INTO FIRST PART OF TONIGHT AS A STRONG COLD FRONT PUSHES SOUTH ACROSS THE REGION. WILL NOT DEVIATE MUCH FROM CURRENT TAFS AND INDICATE DECENT PROBABILITIES FOR CONVECTION AFTER 21-23Z...EVEN BEHIND THE FRONT...AS THE MODELS INDICATE POST FRONTAL CONVECTION LIKELY AS WELL. BEST CHANCE TIME FRAME FOR BROAD SCALE COVERAGE IS 03Z-09Z. BY 12Z...THE AREA SHOULD BE CLEAR OF CONVECTION. CHANCE OF STRONG TO SEVERE STORMS IS STILL IN PLAY AS WELL THIS AFTERNOON AND EVENING. DAMAGING WINDS APPEAR TO BE THE MAIN HAZARD. VISIBILITY RESTRICTIONS DUE TO HEAVY RAIN LIKELY AT THE TAF SITES AT SOME POINT ALONG WITH LOW END MVFR TO IFR CONDITIONS. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...NONE. MO...NONE. IN...NONE. KY...NONE. && $$ NEAR TERM/AVIATION...NOLES SHORT/LONG TERM....SMITH
AREA FORECAST DISCUSSION
NWS PADUCAH KY
1141 AM CDT FRI SEP 7 2012 .UPDATE... ISSUED AT 1141 AM CDT FRI SEP 7 2012 UPDATED TO INCLUDE NEAR TERM DISCUSSION SECTION. UPDATED THE AVIATION SECTION. && .NEAR TERM...(REST OF TODAY) ISSUED AT 1141 AM CDT FRI SEP 7 2012 UPDATED SKY FORECAST...AS IT WAS TOO PESSIMISTIC. NAM TEMPS ALSO QUITE A WAYS OFF. SIDED WITH WARMER GFS MOS NUMBERS AND BLENDED THEM WITH OUR EXISTING NUMBERS. CONVECTION HAS BEEN WEAK OVER SOUTHERN ILLINOIS THIS MORNING. THERE IS NEWLY DEVELOPED CONVECTION ALONG A BOUNDARY JUST NORTH OF OUR CWFA...BUT IT APPEARS TO BE HEADING OFF TO THE EAST. HERE IS THE LATEST THINKING ON THE SEVERE WEATHER / THUNDERSTORM SCENARIO THIS AFTERNOON AND EVENING. FIRST...LOOKING AS VISIBLE IMAGERY...AND H5 ANALYSIS...HARD TO SAY WHAT THE FOCUS WILL BE EARLY ON. THAT MEANS OUR CONFIDENCE IN THE MESO SCALE MODELS IS LOW AT BEST. HINTS OF ELEVATED INSTABILITY PER ACCAS AND ENHANCED CLOUDS ON VISIBLE...BUT VERY WEAK FORCING ACROSS THE AREA. THE HRRR SUGGESTS THAT SUPPORT AND ASSOC CONVECTION SOUTH OF JOPLIN COULD ORGANIZE WITH TIME AND HEAD EAST ACROSS SOUTHERN MISSOURI...MAYBE EVEN REACHING WESTERN KENTUCKY BY EARLY EVENING. THIS MAY NOT BE TOO UNREASONABLE...GIVEN THE MODELS GENERATE DECENT INSTABILITY INTO SOUTHERN AND SOUTHEAST MISSOURI THIS AFTERNOON. WILL MONITOR THIS. THEN OF COURSE YOU HAVE THE FRONT COMING IN FROM THE NORTHWEST WHICH THE HRRR HAS FROM ECNTRL IL TO NEAR KSTL INTO SW MISSOURI AROUND 00Z. CONVECTION IS LINED OUT ALONG THE FRONT AS WELL...ALONG AND JUST BEHIND IT. WE HAVE NEW POP GRIDS...TAILORED TOWARD THE POSSIBILITY OF CONVECTION COMING IN FROM THE WEST INTO SOUTHEAST MISSOURI...AND IN FROM THE NORTHWEST WITH THE FRONT. BEST WE CAN DO GIVEN THE LOWER CONFIDENCE IN THE MESOSCALE MODELS. AS FAR AS SEVERE TYPE. NOT MUCH DIFFERENCE IN AIRMASS. MAIN DIFFERENCE SYNOPTICALLY IS A STRONG FRONT MOVING INTO THE AREA...AND ANY ADDITIONAL MESOSCALE BOUNDARIES AHEAD OF IT CONVECTION CAN ACT UPON. GIVEN THE DEGREE OF FORECAST POTENTIAL INSTABILITY AND AMOUNT OF LOW LEVEL MOISTURE...SEVERE WINDS SEEMS TO BE THE MAIN HAZARD...ESPECIALLY SHOULD ANY CLUSTERS BECOME SELF SUSTAINING AND ORGANIZED. FREEZING LEVELS ARE SLIGHTLY LOWER...SO A MARGINAL SEVERE HAIL THREAT IS IN PLAY. TORNADIC POSSIBILITY SHOULD BE LOW GIVEN LACK OF SUBSTANTIAL WIND FIELDS. CANNOT RULE OUT THE PESKY SPIN UPS WHERE NEAR STORM RELATIVE FLOW ENVIRONMENT MAY SEE ENHANCED SHEAR. STAY TUNED...PROBABILITY OF A WATCH OF SOME KIND IS LIKELY HIGH GIVEN SPC/S SEVERE WEATHER PROBABILITIES. && .SHORT TERM...(TONIGHT THROUGH SUNDAY NIGHT) ISSUED AT 149 AM CDT FRI SEP 7 2012 RISK WILL SUBSIDE BY 06Z AS LOSS OF DIURNAL FUEL SAPS SURFACE BASED INSTABILITY AND PCPN BECOMES MORE POST FRONTAL. POPS PEAK AT THIS STAGE WITH FROPA AND JUST BEHIND IT. HEALTHY PW`S MEAN ANOTHER SUBSTANTIAL RAIN FOR THE AREA WITH CATEGORICAL POPS AND MEAN AVERAGE QPF OF AROUND 2 INCHES. LOCALLY HIGHER AMOUNTS WILL BE POSSIBLE. THE 00Z MODELS TODAY SUPPORT WHAT THEY DID YESTERDAY...WHICH IS USHER THE FRONT/PCPN THRU AND END IT BY 12Z. WE`VE LEANED THE FORECAST AGAIN IN THIS DIRECTION WITH JUST A SLIGHT SPILLOVER SMALL EARLY AM POP IN THE SE ONLY SATURDAY. AFTER THAT IT`S DISTINCTLY DRIER/COOLER AIR WORKING IN BEHIND THE FRONT TO MAKE FOR A PLEASANT WEEKEND WITH LIGHT NORTHERLIES. .LONG TERM...(MONDAY THROUGH THURSDAY) ISSUED AT 149 AM CDT FRI SEP 7 2012 GFS AND ECMWF CONTINUE TO SHOW HIGH PRESSURE OVER THE EASTERN U.S. THROUGH MID WEEK...WITH THE CENTER OF THE HIGH SLIDING EAST OF THE PAH FORECAST AREA MONDAY NIGHT INTO TUESDAY. VERY DRY AND UNSEASONABLY COOL AIR WILL REMAIN OVER THE REGION MONDAY DUE TO NORTH TO NORTHEAST WINDS...WITH TEMPERATURES 5 TO 10 DEGREES BELOW SEASONAL NORMALS. A RETURN OF SOUTHERLY FLOW TUESDAY WILL LEAD TO A WARM UP AND INCREASING DEW POINTS TUESDAY THROUGH THURSDAY...WITH TEMPERATURES BACK TO SEASONAL READINGS FOR WEDNESDAY AND THURSDAY. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY) ISSUED AT 1141 AM CDT FRI SEP 7 2012 CONFIDENCE IN CONVECTION IS LOW THROUGH LATE AFTERNOON. HOWEVER CONFIDENCE INCREASES LATE AFTERNOON INTO FIRST PART OF TONIGHT AS A STRONG COLD FRONT PUSHES SOUTH ACROSS THE REGION. WILL NOT DEVIATE MUCH FROM CURRENT TAFS AND INDICATE DECENT PROBABILITIES FOR CONVECTION AFTER 21-23Z...EVEN BEHIND THE FRONT...AS THE MODELS INDICATE POST FRONTAL CONVECTION LIKELY AS WELL. BEST CHANCE TIME FRAME FOR BROAD SCALE COVERAGE IS 03Z-09Z. BY 12Z...THE AREA SHOULD BE CLEAR OF CONVECTION. CHANCE OF STRONG TO SEVERE STORMS IS STILL IN PLAY AS WELL THIS AFTERNOON AND EVENING. DAMAGING WINDS APPEAR TO BE THE MAIN HAZARD. VISIBILITY RESTRICTIONS DUE TO HEAVY RAIN LIKELY AT THE TAF SITES AT SOME POINT ALONG WITH LOW END MVFR TO IFR CONDITIONS. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...NONE. MO...NONE. IN...NONE. KY...NONE. && $$ UPDATE/NEAR TERM/AVIATION...NOLES
AREA FORECAST DISCUSSION
NWS BUFFALO NY
354 PM EDT FRI SEP 7 2012 .SYNOPSIS... RAPIDLY DEVELOPING LOW PRESSURE WILL TRACK ACROSS THE GREAT LAKES SATURDAY WHICH WILL BRING HEAVY RAINS AND GUSTY WINDS TO WESTERN NEW YORK. A COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL SWEEP ACROSS THE REGION LATE ON SATURDAY USHERING IN MUCH COOLER TEMPERATURES FOR THE LATTER HALF OF THE WEEKEND AND BEGINNING OF NEXT WEEK. && .NEAR TERM /THROUGH SATURDAY/... THE GREATEST FORECAST CONCERN IS THE POTENTIAL FOR DAMAGING WINDS ON SATURDAY. THE GREATEST THREAT IS EAST OF WAYNE/ONTARIO COUNTIES...AS A STRONG FRONTAL BOUNDARY HAS THE POTENTIAL OF SPARKING A LINE OF THUNDERSTORMS CAPABLE OF BRINGING STRONG WINDS ALOFT DOWN TO THE SURFACE. HOWEVER...DEPENDING ON HOW QUICKLY THE LOW DEEPENS...THIS THREAT MAY EXTEND WEST AND INCLUDE THE BUFFALO AND ROCHESTER METRO AREAS. FOR THE DETAILS... THROUGH THIS EVENING...EXPECT MOST AREAS WILL STAY DRY...DESPITE THE HIGH CLOUDS. THERE WILL BE SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE SOUTHERN TIER...BUT FEEL MUCH OF THE 12Z GUIDANCE (NAM/GFS) ARE OVERDONE IN QPF WITH COURSE MODEL GRIDS SPREADING SHOWERS INTO WESTERN NEW YORK. THE HRRR HAS THE RIGHT IDEA...BUT APPEARS OVERDONE LATE AFTERNOON...ESPECIALLY TO THE NORTH NEAR LAKE ONTARIO. LEAN TOWARD THE DRIER RGEM...WITH SCATTERED SHOWERS AND THUNDERSTORMS IN THE SOUTHERN TIER TO TAPER OFF...PROVIDING A PERIOD OF DRY WEATHER FOR MOST OF THE EVENING. THINGS WILL GET MUCH MORE ACTIVE AFTER THIS...AS LOW PRESSURE DEVELOPS RAPIDLY ACROSS THE EASTERN LAKES LATE TONIGHT...LIFTING TO THE QUEBEC/ONTARIO BORDER SATURDAY AFTERNOON. THE RAPIDLY DEEPENING LOW WILL PUSH A STRONG COLD FRONT ACROSS THE REGION. CONSIDERING THE TIMEFRAME...MODEL AGREEMENT IS VERY POOR...WITH THE 12Z NAM/RGEM SIGNIFICANTLY SLOWER THAN THE 12Z GFS...WITH THE UKMET/EUROPEAN SOMEWHERE IN THE MIDDLE. THE RUC/HRRR TREND ON THE FASTER SIDE OF GUIDANCE...LEAVING TIMING SOMEWHAT UNCERTAIN. GIVEN THIS...FORECAST IS A BLEND BETWEEN THE TWO...WITH A LATE MORNING FRONTAL PASSAGE EXPECTED IN BUFFALO...EARLY AFTERNOON IN ROCHESTER...AND MID-AFTERNOON IN WATERTOWN. BECAUSE OF MODEL UNCERTAINTY...CAN SEE THIS TURNING OUT A COUPLE HOURS FASTER OR SLOWER DEPENDING ON HOW THINGS VERIFY. THIS PRESENTS A COUPLE OF WIND CONCERNS FOR THE REGION. THE MAJOR ONE IS THE POTENTIAL FOR CONVECTION WITH THE FRONT...WHICH COULD TRANSPORT WINDS DOWN TO THE SURFACE. FEEL THIS THREAT IS LESS FURTHER TO THE WEST AS THE LOW IS DEVELOPING...AND THE FRONT LESS DEFINED. AS THE LOW DEEPENS...A LINE OF THUNDERSTORMS WILL LIKELY DEVELOP...AND BECOME MORE ORGANIZED SATURDAY AFTERNOON. DRIVING THIS WILL BE A STRONG SHORTWAVE...WHICH WILL RACE AND CATCH UP TO THE SURFACE FRONT. WITH MODEL CONSENSUS AGREEING ON A PRE-FRONTAL WIND FIELD OF 50 TO 60 KTS AT 850 MB...FEEL THIS POSES A SIGNIFICANT SEVERE WEATHER THREAT. INSTABILITY WILL BE MODEST AHEAD OF THE FRONT...BUT GIVEN THE STRONG DYNAMIC LIFT...EXPECT EVEN MODEST INSTABILITY WILL BE ENOUGH...WITH ANY DAYTIME HEATING A BONUS. FOLLOWING THIS...SPC HAS PLACED MUCH OF CENTRAL NEW YORK IN A MODERATE RISK FOR SEVERE WEATHER...WITH STRONG WINDS THE MAIN CONCERN. A SECONDARY CONCERN IS SIMPLY THE GRADIENT WINDS WITH THE FRONT. THE TRACK OF THE LOW IS FAIRLY FAVORABLE FOR PRODUCING STRONG WINDS...BUT THE LOW IS A BIT LATE TO DEVELOP. THIS SOMEWHAT MITIGATES THE THREAT FOR DAMAGING WINDS WEST OF ROCHESTER...THOUGH HIGHER TERRAIN AND THE LAKE ERIE SHORELINE ARE STILL VULNERABLE. GUSTY WINDS ARE LIKELY EAST OF LAKE ONTARIO ON SATURDAY...WITH GUSTS LIKELY TO EXCEED 40 MPH EVEN WITHOUT CONVECTION. STRONGEST WINDS WILL BE IN THE BLACK RIVER VALLEY AND FORT DRUM. ANOTHER THING TO WATCH IS BECAUSE TREES STILL HAVE LEAVES...THEY WILL BE MORE SUSCEPTIBLE TO DAMAGE IN GUSTY WINDS. OTHERWISE...EXPECT STEADY SHOWERS WITH EMBEDDED THUNDERSTORMS TO ENTER WESTERN NEW YORK AROUND OR SHORTLY AFTER MIDNIGHT. THIS LINE WILL WORK FROM WEST TO EAST THROUGH SATURDAY MORNING...EXITING TO THE EAST OF THE CWA SATURDAY AFTERNOON OR EVENING. CONSENSUS QPFS BRING BETWEEN .50 AND 1.00 INCHES OF RAIN. THE HIGHER AMOUNT ARE WEST OF ROCHESTER...WHERE THE FRONT SHOULD BE MOVING A BIT SLOWER. SLOWER MOVING CELLS ARE POSSIBLE LATE TONIGHT IN BUFFALO AND WESTERN PORTIONS OF THE SOUTHERN TIER...WITH LOCALIZED FLOODING POSSIBLE. AS THE FRONT ACCELERATES TO THE EAST ON SATURDAY AFTERNOON...RAINFALL AMOUNTS SHOULD DIMINISH. OTHERWISE...TEMPERATURES WILL START OFF IN THE 80S LATE AFTERNOON...BUT DROP RAPIDLY BEHIND THE FRONT. EXPECT SATURDAY TO START OFF WARM...BUT TO COOL THROUGH THE DAYLIGHT HOURS. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... BY EARLY SATURDAY EVENING...ALL GUIDANCE IS IN GOOD AGREEMENT THAT THE SURFACE COLD FRONT AND ACCOMPANYING POTENTIAL SQUALL LINE WILL EITHER HAVE EXITED OR WILL BE IN THE PROCESS OF EXITING OUR FAR EASTERN ZONES. IN ITS WAKE...AN AREA OF LIMITED WRAPAROUND MOISTURE WILL PIVOT ACROSS THE AREA SATURDAY EVENING...WHILE A BRISK WESTERLY FLOW OF MUCH COOLER AIR OVERSPREADS OUR REGION...WITH 850 MB TEMPS FALLING TO A MUCH MORE AUTUMNAL +6C DURING THE COURSE OF THE NIGHT. WITH SUCH COOL AIR ALOFT AND SOME CONTRIBUTION FROM THE LAKES LIKELY AS A RESULT...FEEL THAT MOST AREAS SHOULD SEE SOME SCATTERED SHOWERS FOR A TIME SUNDAY EVENING...BEFORE FURTHER SYNOPTIC-SCALE DRYING LEADS TO THE DEMISE OF THIS ACTIVITY OVERNIGHT. THE EXCEPTIONS TO THIS WILL BE IN AREAS MORE IMMEDIATELY DOWNWIND OF THE LAKES...WHERE CONTINUED LAKE-DRIVEN INSTABILITY WILL KEEP SHOWER CHANCES ONGOING THROUGH THE NIGHT. THIS SAID...THE RELATIVELY SHALLOW MOISTURE FIELD THAT WILL BE IN PLACE PRECLUDES GOING WITH ANYTHING MORE THAN MID-HIGH CHANCE POPS EVEN IN THESE AREAS. ON SUNDAY...THE CORE OF THE LARGE-SCALE UPPER TROUGH WILL SETTLE ACROSS THE REGION. WITH DAYTIME HEATING...THE AREA OF BEST INSTABILITY WILL TRANSITION FROM LAKE TO LAND...WITH ANY SCATTERED LAKE EFFECT SHOWERS TRANSITIONING TO MORE GENERAL DIURNALLY-DRIVEN SHOWERS THAT WILL ALSO CONCENTRATED MORE OVER LAND. THIS SAID... THESE WILL AGAIN ONLY BE WORTH SOME LOW CHANCE POPS GIVEN THE VERY LIMITED AMOUNTS OF MOISTURE THAT WILL AGAIN BE IN PLACE. SUNDAY NIGHT...ANY DIURNALLY-DRIVEN SCATTERED SHOWERS SHOULD END RATHER QUICKLY WITH THE LOSS OF HEATING SUNDAY EVENING. ANY WEAK LAKE-DRIVEN SHOWERS ONGOING EAST-SOUTHEAST OF THE LAKES SUNDAY EVENING WILL ALSO TEND TO SHIFT SOUTHWARD AND FALL APART WITH TIME AS THE FLOW TURNS MORE NORTHWESTERLY AND SURFACE RIDGING/EVEN DRIER AIR BUILDS EAST FROM THE CENTRAL GREAT LAKES. BY MONDAY MORNING... EXPECT ONLY SOME LEFTOVER LAKE EFFECT CLOUDS AND PERHAPS AN ISOLATED SHOWER OR TWO SOUTHEAST OF LAKE ONTARIO. ANY SUCH ACTIVITY WILL THEN BE QUICKLY SQUELCHED BY THE ADVANCING RIDGE AND DIURNAL INFLUENCES MONDAY MORNING...WITH DRY AND FAIR WEATHER THEN EXPECTED THROUGH THE REMAINDER OF THE SHORT TERM PERIOD. WITH REGARD TO TEMPS...THE MUCH COOLER AIRMASS ARRIVING SATURDAY NIGHT WILL PERSIST THROUGH SUNDAY AND MONDAY...WHILE PROVIDING US WITH THE COOLEST TEMPERATURES SO FAR OF THIS VERY YOUNG METEOROLOGICAL FALL SEASON. LOOK FOR LOWS IN THE LOWER HALF OF THE 50S SATURDAY NIGHT...WITH 850 MB TEMPS OF +6C TO +8C ONLY SUPPORTING HIGHS IN THE MID 60S TO LOWER 70S ON SUNDAY...WITH THE COOLER READINGS FOUND ACROSS THE HIGHER TERRAIN. SIMILAR HIGH TEMPS CAN BE EXPECTED ON MONDAY...WHILE LOWS SUNDAY NIGHT AND MONDAY NIGHT WILL LIKELY DIP INTO THE 45 TO 50 RANGE...WITH SOME LOWER 40S FOUND ACROSS INTERIOR PORTIONS OF THE SOUTHERN TIER AND NORTH COUNTRY. && .LONG TERM /TUESDAY THROUGH FRIDAY/... THE FIRST HALF OF THE EXTENDED PERIOD WILL FEATURE CONTINUED DRY WEATHER AND RETURN TO WARMER TEMPERATURES AS SURFACE RIDGING SLIDES EAST TO THE ATLANTIC COAST...WHILE UPPER LEVEL RIDGING OVER THE PLAINS STATES FLATTENS AND PUSHES EAST INTO THE GREAT LAKES. A BLEND OF THE GFS AND ECMWF SUGGESTS 850 MB TEMPS RECOVERING TO +7C TO +9C ON TUESDAY AND TO THE +12C TO +14C RANGE ON WEDNESDAY...WHICH SHOULD SUPPORT HIGHS RECOVERING BACK INTO THE LOWER 70S ON TUESDAY...AND THE UPPER 70S/NEAR 80 ON WEDNESDAY. AFTER THAT...THE AXIS OF THE UPPER RIDGE SHOULD CONTINUE TO FLATTEN AND SLIDE EAST OFF THE ATLANTIC COAST AS THE NEXT BROAD UPPER LEVEL TROUGH GRADUALLY DIGS SOUTHEAST INTO THE GREAT LAKES. THIS SAID... THE MEDIUM RANGE GUIDANCE CONTINUES TO DIFFER ON THE RATE AT WHICH THIS PROCESS OCCURS...WITH THE GFS SWINGING AN ASSOCIATED WEAK COLD FRONT INTO THE AREA ON FRIDAY...AND THE ECMWF REMAINING ABOUT 18-24 HOURS FASTER...ALTHOUGH THIS LATTER MODEL ALSO SPITS OUT MUCH LESS IN THE WAY OF PRECIP. GIVEN THE ABOVE FACTORS AND WHAT SHOULD BE A TENDENCY FOR THIS FRONT TO SLOW DOWN AS IT BECOMES ORIENTED INCREASING PARALLEL TO THE LARGE-SCALE UPPER LEVEL FLOW...WILL KEEP THURSDAY DRY FOR NOW...THEN INTRODUCE SOME VERY LOW-END CHANCE POPS FOR FRIDAY. IN ADVANCE OF THE BOUNDARY...850 MB TEMPS OF +12C TO +14C SHOULD PERSIST... SUPPORTING HIGHS IN THE UPPER 70S TO AROUND 80 ON BOTH THURSDAY AND FRIDAY. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... THROUGH 06Z TONIGHT...EXPECT MAINLY VFR CONDITIONS. THE MAIN CONCERN FOR AVIATION FROM 18Z FRI THROUGH 06Z SAT WILL BE SCATTERED THUNDERSTORMS...WHICH WILL MAINLY BE ACROSS THE SOUTHERN TIER THIS AFTERNOON. THUNDERSTORMS MAY IMPACT JHW...WITH THE CHANCE FOR THUNDERSTORMS ELSEWHERE TOO SMALL TO WARRANT A MENTION IN THE TAFS. AFTER THIS...DEEPENING LOW PRESSURE WILL PUSH A STRONG FRONTAL BOUNDARY ACROSS THE REGION SATURDAY MORNING. WINDS ALOFT WILL INCREASE AHEAD OF THE FRONT. THIS MAY RESULT IN LLWS AT SOME LOCATIONS...WHERE THESE WINDS DON/T MIX DOWN. THERE WILL ALSO BE SHOWERS AND THUNDERSTORMS WITH THE FRONT...WHICH MAY LOWER VSBY AND CIGS IN BRIEF PERIODS OF HEAVY RAIN. ANOTHER CONCERN WILL BE STRONG WINDS WITH THUNDERSTORMS ALONG THE FRONT. THIS COULD HAVE A BRIEF BUT SIGNIFICANT IMPACT ON TAF SITES. THE FRONT WILL PUSH EASTWARD SATURDAY AFTERNOON...EXITING EAST OF ART BY 00Z SUN. OUTLOOK... SATURDAY NIGHT AND SUNDAY...VFR/MVFR WITH A CHANCE OF SHOWERS. MONDAY THROUGH THURSDAY...MAINLY VFR. PATCHY VALLEY FOG POSSIBLE EARLY EACH MORNING. && .MARINE... OPTED TO HOIST GALES ON BOTH OF THE LAKES. FEEL FAIRLY CONFIDENT LAKE ONTARIO WILL REACH GALE CRITERIA ALONG AND BEHIND THE FRONT ON SATURDAY. LAKE ERIE WILL BE A BIT MORE MARGINAL...BUT GIVEN THE GOOD POTENTIAL FOR A BRIEF PERIOD OF GALE CRITERIA GUSTS WITH THE FRONT...HAVE OPTED TO ISSUE THE GALES FOR LAKE ERIE AS WELL. FOR NOW...WENT WITH SMALL CRAFT ADVISORIES ON THE RIVERS...WHERE MIXING WILL NOT BE AS GOOD. SIGNIFICANTLY COLDER AIR WILL FILTER INTO THE REGION BEHIND THE COLD FRONT...BRINGING AN INCREASED POTENTIAL FOR WATERSPOUTS FOR THE LATTER HALF OF THE WEEKEND INTO THE EARLY PART OF NEXT WEEK. IN ADDITION A PROLONGED PERIOD OF BRISK WESTERLY WINDS WILL LIKELY MEAN AN EXTENDED PERIOD OF SMALL CRAFT ADVISORY CONDITIONS ON THE LAKES. && .CLIMATE... AN EARLY WARM SPRING AND CONTINUED WARMTH THROUGH THE SUMMER HAS LED TO MANY DAYS THAT HAVE REACHED 80F ACROSS WESTERN AND NORTH CENTRAL NEW YORK. BELOW IS A LIST OF THE NUMBER OF DAYS IN THE CALENDAR YEAR THAT HAVE REACHED 80 DEGREES OR GREATER. THE 2012 TOTAL WILL INCREASE AS WE REACH ADDITIONAL 80F DAYS THROUGH THE EARLY FALL. BUFFALO (SINCE 1871) 1 83 1949 2 82 1959 3 78 2012 (THROUGH FRI 9/7) 4 77 1991 5 76 1955 6 75 1947 75 1983 75 2005 9 73 2011 ROCHESTER (SINCE 1871) 1 91 1959 2 86 2007 3 83 2012 (THROUGH FRI 9/7) 83 2002 83 1973 83 1949 83 1947 8 81 1991 9 80 2005 80 1921 ... 21 75 2011 WATERTOWN (SINCE 1949) 1 75 1949 2 73 1959 3 70 2012 (THROUGH FRI 9/7) 4 68 1955 5 67 1973 ... 9 60 2011 && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...SMALL CRAFT ADVISORY FROM 8 AM TO 8 PM EDT SATURDAY FOR LEZ020. GALE WARNING FROM 8 AM TO 8 PM EDT SATURDAY FOR LEZ040-041. SMALL CRAFT ADVISORY FROM 8 AM TO 8 PM EDT SATURDAY FOR LOZ030. GALE WARNING FROM 11 AM TO 11 PM EDT SATURDAY FOR LOZ042>045-062>065. SMALL CRAFT ADVISORY FROM 11 AM TO 11 PM EDT SATURDAY FOR SLZ022-024. && $$ SYNOPSIS...APFFEL NEAR TERM...APFFEL/WOOD SHORT TERM...JJR LONG TERM...JJR AVIATION...APFFEL MARINE...APFFEL/JJR CLIMATE...THOMAS/JJR
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
130 PM EDT FRI SEP 7 2012 .SYNOPSIS... LONG PERIOD SWELLS FROM HURRICANE LESLIE WILL IMPACT THE BEACHES THROUGH THE WEEKEND...INCREASING THE RISK FOR STRONG AND FREQUENT RIP CURRENTS AND LARGER THAN NORMAL BREAKERS. A WEAK RIDGE OF HIGH PRESSURE WILL REMAIN ALONG THE COAST AS A TROUGH OF LOW PRESSURE SLOWLY APPROACHES THE CAROLINAS FROM THE WEST TODAY. A STRONGER FRONTAL SYSTEM WILL USHER IN FALL-LIKE WEATHER SUNDAY...WITH DRIER AND COOLER HIGH PRESSURE BUILDING IN THROUGH NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... THE EXITING SHORTWAVE CLEARLY VISIBLE IN WV IMAGERY SUGGESTS THAT DOWNWARD VERTICAL MOTION SHOULD BE IN PLACE AT THE MID LEVELS THROUGH MOST OF THE DAY. THIS WILL ACT TO SUPPRESS ALL BUT THE MOST ISOLATED ACTIVITY ALONG THE SEABREEZE. INLAND LOCATIONS HAVE FAIRLY EXTENSIVE CLOUD COVER AND MAY HAVE A TOUGH TIME SEEING ANY CONVECTION UNLESS THE CLOUDS THIN. BOTH OF THESE ARE BACKED BY THE LATEST RUN OF THE HRRR. NO CHANGES TO THE PREVIOUS FORECAST ARE ANTICIPATED. AS OF 630 AM FRIDAY...NO CHANGES HAVE BEEN MADE WITH RESPECT TO ANTICIPATED COVERAGE OF AFTERNOON SHOWERS AND THUNDERSTORMS. CURRENT RADAR LOOPS SHOW A CLUSTER OF SHOWERS IN GEORGETOWN COUNTY AND PERHAPS HINTS OF ADDITIONAL DEVELOPMENT UPSTREAM THE SANTEE RIVER ACROSS WILLIAMSBURG COUNTY. 06Z MODELS WERE SLIGHTLY COOLER WITH AFTERNOON HIGHS SO A FEW SPOTS HAVE BEEN DROPPED BY A DEGREE. CHANGES WERE ALL MINOR. PREVIOUS DISCUSSION FROM 330 AM FOLLOWS... A WEAK 500 MB DISTURBANCE AND SURFACE TROUGH/OUTFLOW BOUNDARY HAVE BEEN MAINTAINING SCATTERED CONVECTION THROUGH THE EARLY MORNING HOURS. ACTIVITY HAS BEEN MOST PREVALENT IN THE SC PEE DEE REGION WHERE RADAR ESTIMATES UP TO 4.50 INCHES OF RAIN EXIST ACROSS PORTIONS OF FLORENCE...MARION AND WILLIAMSBURG COUNTIES. THERMODYNAMICALLY THIS CONVECTION IS ELEVATED...ROOTED IN A LAYER 4000-7000 FT ABOVE THE GROUND. AS THE UPPER DISTURBANCES WEAKENS AND PRESSES OFFSHORE IN THE NEXT COUPLE OF HOURS THE CONVECTION SHOULD WEAKEN AS WELL. THE 04Z HRRR DID NOT INITIALIZE WELL...BUT EARLIER RUNS (PARTICULARLY THE 01Z RUN) MODEL THE CURRENTLY OBSERVED PATTERNS ON RADAR WELL. LOW STRATUS CLOUDS ARE FILLING IN NORTH OF THE RAIN AREA AND MAY SPREAD DOWN AS FAR SOUTH AS FLORENCE...MARION...WHITEVILLE AND WILMINGTON BY DAYBREAK. AFTER PROVIDING A GLOOMY SUNRISE THESE CLOUDS SHOULD BURN OFF BY 10:00 AM WITH AN EXPANSIVE CUMULUS FIELD DEVELOPING IN ITS PLACE. TRIGGERS FOR AFTERNOON CONVECTION SHOULD INCLUDE A WELL-DEFINED SEABREEZE...THE REMNANT OUTFLOW BOUNDARY FROM THE EARLY MORNING CONVECTION ACROSS SOUTH CAROLINA...AND A DIFFERENTIAL HEATING BOUNDARY AROUND THE EDGE OF THE MORNING LOW STRATUS DECK. DESPITE NO SUPPORT FROM THE UPPER LEVELS AND A FORECAST STORM CELL MOTION OF LESS THAN 5 MPH...I`M STILL INCLUDING 20 POPS INLAND AND 30 POPS NEAR THE COAST FOR THIS AFTERNOON GIVEN ALL THE SURFACE BOUNDARIES AND WIDESPREAD 1500 J/KG SURFACE-BASED CAPE EXPECTED. ANY LINGERING CONVECTION SHOULD DIE AWAY QUICKLY THIS EVENING AS THE BOUNDARY LAYER COOLS. THE ATMOSPHERE WILL BEGIN TO RESPOND TO AN APPROACHING UPPER LEVEL TROUGH THAT WILL DRIVE A STRONG COLD FRONT THROUGH THE CAROLINAS THIS WEEKEND. DEEP-LAYER FLOW THAT IS ESSENTIALLY LIGHT AND VARIABLE THIS AFTERNOON WILL TURN SOUTHWEST AND STEADILY INCREASE THROUGH THE NIGHT. SURFACE WINDS WILL NOT INCREASE APPRECIABLY GIVEN THE STABLE LOW-LEVEL THERMAL PROFILES AT NIGHT...BUT WINDS 1000 FT AGL AND HIGHER WILL PICK UP SPEED AFTER MIDNIGHT. HIGHS TODAY SHOULD REACH 90 OR SO INLAND...WITH UPPER 80S NEAR THE COAST AND MID 80S ON THE BEACHES. LOWS TONIGHT WILL FALL INTO THE LOWER TO MID 70S. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY...STRONG COLD FRONT WILL APPROACH THE AREA SATURDAY MOVING THROUGH BY SUNDAY. LOCAL AREA WILL BE IN WARM SECTOR ON SAT WITH DEEP LAYER MOISTURE MAKING ITS WAY IN A SW FLOW LATER IN THE DAY AS MOISTURE POOLS AHEAD OF FRONT. GFS ACTUAL SHOWS SOME DRIER AIR IN PLACE IN THE MID LEVELS INITIALLY THROUGH THE AFTERNOON AND THEN PCP WATER VALUES SHOOT UP OVER 2 INCHES THROUGH SAT EVENING. EXPECT BEST LIFT AND MOISTURE THROUGH THE LATE EVENING AND OVERNIGHT AS MID TO UPPER TROUGH PUSHES COLD FRONT THROUGH. POTENTIAL FOR STRONG TO SEVERE STORMS ESPECIALLY JUST AHEAD OF FRONT. THE FRONT WILL MAKE IT THROUGH AFTER THE BEST HEATING OF THE DAY AND THIS MAY WORK IN OUR FAVOR LIMITING MORE WIDESPREAD STORMS. THE SFC FRONT SHOULD MAKE IT OFF SHORE BY SUN MORNING BUT WINDS IN THE LOW TO MID LEVELS WILL TAKE A LITTLE WHILE LONGER TO VEER AROUND. PCP WATER VALUES WILL DROP OUT THROUGH SUNDAY DOWN LESS THAN 1.5 INCHES BY SUN AFTN AND DROPPING EVEN FURTHER TO LESS THAN AN INCH BY END OF THE PERIOD. OVERALL EXPECT MORE LOCALIZED CONVECTION THROUGH SAT AFTN WITH MORE WIDESPREAD ACTIVITY WITH APPROACH OF FRONT LATE SAT INTO EARLY SUNDAY. THEN CLEARING THROUGH SUNDAY BEHIND FRONT AS PLENTY OF DRY AIR MAKES IT WAY IN. SAT WILL BE THE LAST DAY OF VERY WARM TEMPS AS 850 TEMPS REMAIN UP NEAR 18 C BUT AS COOLER AIR ADVECTS IN ON SUNDAY...850 TEMPS WILL FALL THROUGH THE DAY REACHING DOWN TO 10 C BY MON MORNING. MAX TEMPS ON SAT WILL BE UP AROUND 90 OR SO WHILE SUNDAY THE TEMPS WILL BE BETWEEN 80 AND 85 MOST PLACES WHILE DEWPOINT TEMPS DROP ABOUT 10 DEGREES DOWN TO 60. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 300 AM FRIDAY...FALL LIKE WEATHER WILL EXIST THROUGH MUCH OF NEXT WEEK AS COOL AND DRY HIGH PRESSURE BUILDS DOWN OVER THE SOUTHEAST. BRIGHT SEPTEMBER SUN WILL PRODUCE MAX TEMPS BETWEEN 80 AND 85 MOST PLACES BUT THE VERY DRY AIR MASS WILL PRODUCE SOME LARGE DIURNAL SWINGS. WITH DEWPOINT TEMPS DOWN INTO THE 50S THROUGH AT LEAST WED AND WINDS DROPPING OFF EACH NIGHT...EXPECT MORE IDEAL RADIATIONAL COOLING LEADING TO OVERNIGHT LOWS AROUND 60 WITH UPPER 50S INLAND. ACTUALLY TEMPS WILL BE CLOSE TO NORMAL AND WILL CREEP UPWARD THROUGH MID WEEK AS H5 HEIGHTS RISE BACK UP WITH RIDGE BUILDING IN THE SOUTHEAST. BY WED MOISTURE INCREASES ENOUGH IN THE LOW LEVELS AS WINDS SHIFT AROUND TO THE NE TO PRODUCE SOME CU AROUND. OVERALL EXPECT SUNNY AND DRY WEATHER THROUGH THE WEEK. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... AS OF 18Z...STILL LOOKING FOR ISOLATED CONVECTION THIS AFTERNOON...MAINLY ALONG THE COAST. BEST CHANCE WILL BE AROUND MAX HEATING...WITH MOST OF THE ACTIVITY ENDING BY 22Z. WINDS WILL BE VARIABLE THIS MORNING WITH THE LIGHT GRADIENT...BECOMING PREDOMINATELY EAST SOUTHEAST WITH THE RESULTANT THIS AFTERNOON. TONIGHT...THINK WE COULD SEE SOME STRATUS...PROBABLY THE INLAND TERMINALS. SATURDAY...FRONTAL BOUNDARY WILL APPROACH FROM THE WEST. NO EFFECTS FOR THE TAF PERIOD...SAVE AN INCREASING SOUTHWEST WIND. EXTENDED OUTLOOK...SCATTERED SHRA/TSRA THROUGH SUNDAY...WITH A CHANCE OF EARLY MORNING LIFR/IFR CONDITIONS IN BR INLAND...AND MVFR AT THE COAST. VFR MONDAY THROUGH WEDNESDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1030 AM FRIDAY...NO CHANGES NEEDED TO THE MARINE FORECAST. PREVIOUS DISCUSSION FROM 330 AM FOLLOWS... A WEAK UPPER LEVEL DISTURBANCE AND SURFACE TROUGH ALONG THE CAROLINA COAST IS RESPONSIBLE FOR SEVERAL WAVES OF SHOWERS AND THUNDERSTORMS AFFECTING THE NC OFFSHORE WATER THIS MORNING. SCATTERED SHOWERS AND STORMS SHOULD DIMINISH IN COVERAGE THROUGH THE EARLY MORNING HOURS AS THIS DISTURBANCE PUSHES OFFSHORE AND WEAKENS FURTHER. GENERALLY OFFSHORE WINDS EARLY THIS MORNING WILL TURN LIGHT AND VARIABLE LATER THIS MORNING...AND THEN SOUTHERLY DRIVEN PRIMARILY BY THE SEABREEZE THIS AFTERNOON. A STRONG COLD FRONT APPROACHING FROM THE WEST WILL CREATE SLOWLY INCREASING SOUTHWEST WINDS TONIGHT. SWELL FROM HURRICANE LESLIE HAS SHORTENED TO AROUND 10 SECONDS IN PERIOD AND SHOULD CONTINUE THROUGH THE WEEKEND. ADDITIONAL SHORT PERIOD WIND WAVES WILL ADD VERY LITTLE EXTRA TO THE TOTAL SEA STATE...AND WE`RE EXPECTING 2-4 FT ACROSS THE SOUTH CAROLINA COASTAL WATERS...AND 3-4 FT FOR THE NC COASTAL WATERS. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY...SOUTHWEST FLOW WILL INCREASE THROUGH SATURDAY AHEAD OF APPROACHING COLD FRONT. SOUTHWEST WINDS UP AROUND 15 KTS WILL VEER AROUND BECOMING OFF SHORE THROUGH SUNDAY MORNING AS COLD FRONT MOVES THROUGH. THESE SOUTHWEST WINDS WILL COMBINE WITH CONTINUED LONG PERIOD E-SE SWELLS TO PRODUCE SEAS IN THE 3 TO 5 FT RANGE MOST PLACES THROUGH SATURDAY. THERE WILL BE SOME 6 FTERS IN OUTER WATERS. AS COLD FRONT MOVES FURTHER OFF SHORE THROUGH SUNDAY...WINDS WILL VEER AROUND TO THE NORTH AROUND 10 TO 15 KTS AS HIGH PRESSURE BUILDS IN FROM THE N-NW. LONG TERM /MONDAY THROUGH TUESDAY/... AS OF 300 AM FRIDAY...NORTHERLY WINDS WILL CONTINUE TO MIX WITH LONGER PERIOD SWELLS FROM LESLIE TO PRODUCE SEAS IN THE 2 TO 4 FT RANGE MOST WATERS. THE COOL NIGHTS WILL KEEP A WELL MIXED ATMOSPHERE AS COOL AIR RIDES OVER THE WARM WATERS. THIS COULD PRODUCE NORTHERLY WINDS UP TO 20 KTS OVERNIGHT. EXPECT SEAS CLOSER TO 5 FT IN OUTER WATERS AND MAY SEE SEAS UP NEAR OR SLIGHTLY ABOVE SCA EARLY MON IN NORTHERLY SURGE BEHIND FRONT. THE WINDS WILL GRADUALLY SHIFT AROUND BECOMING NE TO E AS HIGH PRESSURE BUILDS SOUTH AND EAST THROUGH MID WEEK. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ NEAR TERM...MBB SHORT TERM...RGZ LONG TERM...RGZ AVIATION...43
AREA FORECAST DISCUSSION
NWS TULSA OK
320 PM CDT FRI SEP 7 2012 .DISCUSSION... CHANGES ARE A COMING. THE SURFACE COLD FRONT...WHICH WAS HELD UP FOR A TIME TODAY AS A WEAK LOW PRESSURE RIPPLED ON BY...IS NOW ON THE MOVE. WIND GUSTS ARE TOPPING 50 MPH BEHIND THE FRONT...DUE TO THE TIGHT PRESSURE GRADIENT AND ISALLOBARIC FORCING. AS THIS FRONT MOVES SOUTH THE POTENTIAL FOR STRONG WIND GUSTS IN EXCESS OF 40 MPH WILL LIKELY CONTINUE...MAINLY ACROSS NORTHEAST OK. WILL LET THE ONGOING WIND ADVISORY CONTINUE THRU 03Z AND LET THE EVENING SHIFT ADJUST IF NEED BE. AHEAD OF THE FRONT...TEMPS HAVE SOARED ONCE THE MID CLOUDS CLEARED OUT ENOUGH TO ALLOW FOR SOME INSOLATION. BRISTOW MESONET HAS HIT 108 DEGREES. MUCH OF EASTERN OK IN FACT IS ABOVE 100 DEGREES THIS HOUR. WILL LET THE HEAT HEADLINES CONTINUE THROUGH 00Z...AND WE WILL FINALLY BE ABLE TO SHELVE THIS FOR AWHILE BY TONIGHT. PRECIP CHANCES WILL BE A CHALLENGE...ESPECIALLY FOR WESTERN SECTIONS. THE HRRR SUGGESTS THAT CONVECTION WILL GRADUALLY INCREASE IN COVERAGE IN THE VICINITY OF THE FRONT THIS AFTERNOON...EVENTUALLY ORGANIZING INTO LINE SEGMENTS OR CLUSTERS AS THEY MOVE INTO FAR EASTERN OK AND WESTERN AR THIS EVENING. THE LATEST ECMWF ALSO SUGGESTS A BAND OF POST FRONTAL CONVECTION WILL DEVELOP LATER ON TONIGHT...AS STRONG MID LVL COLD FRONTOGENESIS AND QG FORCING FOR ASCENT INCREASES AS THE MAIN SHORTWAVE APPROACHES. I HAVE ADJUSTED POPS UPWARD ACROSS NORTHEAST OK IN ANTICIPATION OF THIS. GIVEN THE INSTABILITY AND GRADUALLY INCREASING SHEAR WITH TIME...SEVERE WIND AND HAIL ARE A GOOD POSSIBILITY...ESPECIALLY IF AN ORGANIZED LINE SEGMENT OR CLUSTER CAN GET GOING IN THE HOT WARM SECTOR. PRECIP CHANCES WILL QUICKLY SHIFT SOUTHEAST AFTER 06Z AND SHOULD BE DONE BY 12Z WITH SKIES CLEARING OUT. SHOULD BE A VERY NICE WEEKEND WITH HIGHS IN THE 80S AND LOWS IN THE 50S...EVEN UPPER 40S BY SUNDAY MORNING OVER PARTS OF NW AR. A BACK DOOR FRONT WILL ATTEMPT TO KEEP THE WARMING TREND IN CHECK OVER NE OK AND NW AR SUNDAY AFTERNOON. TEMPS WILL WARM BACK INTO THE 90S EARLY NEXT WEEK WITH SHORTWAVE RIDGING OVERHEAD. A FRONTAL BOUNDARY WILL EVENTUALLY PUSH INTO THE REGION BY FRIDAY OF NEXT WEEK...AND THERE IS REASONABLE ENOUGH AGREEMENT BETWEEN THE MEDIUM RANGE MODELS TO INSERT A SLIGHT CHANCE FOR THE TAIL END OF THE FORECAST. LACY && .PRELIMINARY POINT TEMPS/POPS... TUL 55 80 53 88 / 60 0 0 0 FSM 61 81 54 88 / 60 0 0 0 MLC 60 81 54 89 / 40 0 0 0 BVO 54 81 51 88 / 50 0 0 0 FYV 55 76 48 84 / 80 0 0 0 BYV 54 75 49 81 / 80 0 0 0 MKO 57 80 53 86 / 60 0 0 0 MIO 55 78 53 82 / 70 0 0 0 F10 58 80 56 87 / 50 0 0 0 HHW 63 82 55 87 / 30 0 0 0 && .TSA WATCHES/WARNINGS/ADVISORIES... OK...EXCESSIVE HEAT WARNING UNTIL 7 PM FRIDAY FOR OKZ053. HEAT ADVISORY UNTIL 7 PM FRIDAY FOR OKZ049-OKZ060-OKZ064-OKZ065- OKZ066-OKZ067-OKZ068-OKZ070-OKZ071-OKZ072-OKZ073-OKZ074- OKZ075-OKZ076. WIND ADVISORY UNTIL 10 PM FRIDAY FOR OKZ054-OKZ055-OKZ056-OKZ057- OKZ058-OKZ059-OKZ060-OKZ061-OKZ062-OKZ063-OKZ064-OKZ065- OKZ066-OKZ067. AR...HEAT ADVISORY UNTIL 7 PM FRIDAY FOR ARZ019-ARZ020. EXCESSIVE HEAT WARNING UNTIL 7 PM FRIDAY FOR ARZ029. && $$ LONG TERM....30
AREA FORECAST DISCUSSION
NWS NORMAN OK
1234 PM CDT FRI SEP 7 2012 .AVIATION... 18Z TAFS... STRONG COLD FRONT WILL CONTINUE TO MOVE ACROSS THE REGION WITH GUSTY WINDS BEHIND THE FRONT. ISOLATED/SCATTERED SHOWERS/STORMS WILL BE POSSIBLE MAINLY ALONG AND BEHIND THE FRONT THIS AFTERNOON AND TONIGHT. CHANCES ARE TOO LOW AT TIMES FOR MENTION IN TAFS. CEILINGS WILL BE MOSTLY VFR... BUT LOW VFR. && .PREV DISCUSSION... /ISSUED 633 AM CDT FRI SEP 7 2012/ AVIATION... 07/12Z TAFS...VFR CONDITIONS EXPECTED. SCATTERED TSRA COULD AFFECT MAINLY KPNC DOWN TOWARD KOKC ALONG AND BEHIND STRONG FRONT THAT WILL SURGE SOUTHWARD TODAY. VERY LITTLE IF ANY COLD FRONT TIMING CHANGES MADE FROM PREVIOUS FORECAST CYCLE. OUTSIDE OF POSSIBILITY FOR TSRA FOR A FEW HOURS LATE THIS AFTERNOON AND THIS EVENING... MAIN IMPACTS TO TERMINALS WILL BE STRONG NORTHERLY WIND WITH GUSTS AOA 40KT SEVERAL HOURS FOLLOWING FROPA. PREV DISCUSSION... /ISSUED 437 AM CDT FRI SEP 7 2012/ DISCUSSION... BIG CHANGES WILL BE SEEN THIS AFTERNOON AND EVENING...BUT BEFORE THE FRONT ARRIVES IT WILL BE QUITE HOT WITH FAIRLY SUBSTANTIAL PRE-FRONTAL THERMAL RIDGE IN PLACE. FIRST PERIOD OF FORECAST WILL CLOSELY RESEMBLE WRF SOLUTIONS OF THE PAST COUPLE OF RUNS. HOTTER AHEAD OF FRONT AND MORE SUBSTANTIAL CAA/WIND BEHIND IT. WE WILL ISSUE A WIND ADVISORY FOR THIS AFTERNOON AND EVENING. FREQUENT GUSTS AROUND 45 MPH NOT OUT OF THE QUESTION FOR AT LEAST 2 TO 4 HOURS AFTER FROPA COINCIDING WITH STRONG CAA. SOME OF THE WINDIER SPOTS OF W/SW OKLAHOMA COULD SEE SOME GUSTS IN EXCESS OF 50 MPH. AS FAR AS THE CHANGE IN TEMPERATURE GOES...WE EXPECT TEMPS TO FALL 20 TO 30 DEGREES IN JUST A FEW HOURS AFTER FRONTAL PASSAGE... ESPECIALLY ACROSS CENTRAL AND SOUTHERN PORTIONS OF OKLAHOMA AND NORTH TEXAS WHERE TEMPS EXPECTED TO APPROACH OR EXCEED 100 AHEAD OF FRONT. AS FAR AS POPS GO...COULD SEE SOME ISOLATED SHOWERS OR STORMS ACROSS NORTH-CENTRAL AND PERHAPS CENTRAL OKLAHOMA EARLY THIS MORNING...WITH THE HRRR BEING THE MOST AGGRESSIVE WITH THIS POTENTIAL. SCATTERED STORMS MAY FORM ALONG FRONT THIS AFTERNOON BUT BEST CHANCES FOR RAIN APPEAR TO BE THIS EVENING BEHIND THE FRONT AS MAIN MID-LEVEL TROUGH AXIS MOVES INTO THE REGION. SEASONABLY COOL WEEKEND IN STORE BEFORE TEMPS BEGIN TO INCREASE AHEAD OF NEXT FRONTAL BOUNDARY WHICH MEDIUM RANGE MODELS WANT TO BRING TOWARD THE END OF NEXT WEEK. && .PRELIMINARY POINT TEMPS/POPS... OKLAHOMA CITY OK 99 57 83 54 / 30 40 0 0 HOBART OK 99 55 85 54 / 20 30 0 0 WICHITA FALLS TX 104 59 86 56 / 20 30 0 0 GAGE OK 88 53 83 49 / 20 10 0 0 PONCA CITY OK 93 53 82 54 / 40 20 0 0 DURANT OK 102 60 84 53 / 10 30 0 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 10 PM CDT THIS EVENING FOR OKZ007-008-012-013-016>026-033>036. WIND ADVISORY UNTIL 6 PM CDT THIS EVENING FOR OKZ004>006-009>011- 014-015. WIND ADVISORY FROM 6 PM TO 10 PM CDT THIS EVENING FOR OKZ027>031- 037>040-044-045. TX...WIND ADVISORY FROM 6 PM TO 10 PM CDT THIS EVENING FOR TXZ083>090. && $$ 26/25/25
AREA FORECAST DISCUSSION
NWS LUBBOCK TX
1219 PM CDT FRI SEP 7 2012 .AVIATION... STRONG COLD FRONT STILL PLOWING THROUGH THE REGION EARLY THIS AFTERNOON IS EXPECTED TO MOVE THROUGH THE TAF SITES WITH THE NEXT HOUR OR TWO. WINDS WILL SHARPLY TURN TO THE NORTH AND BECOME SUSTAINED AROUND 20-25KT WITH GUSTS UP TO 35KT. THESE WINDS ARE EXPECTED TO PERSIST THROUGH MUCH OF THE AFTERNOON BEFORE SLOWLY DECREASING THIS EVENING. THERE IS AN OUTSIDE CHANCE OF LIGHT RAIN SHOWERS IMMEDIATELY BEHIND THE FRONT WITHIN AN AREA OF MID LEVEL CLOUDS. HOWEVER...A BETTER CHANCE FOR THUNDER WILL EXIST THIS EVENING AT KLBB. && .PREV DISCUSSION... /ISSUED 954 AM CDT FRI SEP 7 2012/ UPDATE... LATEST OBSERVED TRENDS WITH THE FRONT SHOW IT IS MOVING A BIT QUICKER THAN PREVIOUSLY ANTICIPATED WITH THE FRONT MOVING SOUTHWARD AT A SPEED OF ABOUT 33KT. RAP ANALYSIS INDICATES IMPRESSIVE 8 MB PER THREE HOUR PRESSURE RISES IN SOUTHEASTERN COLORADO. SUSTAINED WINDS BEHIND THE FRONT WERE OBSERVED TO BE AROUND 25KT OR SO WITH GUSTS UP TO 40 KT. HAVE UPDATED THE FORECAST FOR A FASTER FRONTAL MOVEMENT AND TO ADD BLOWING DUST FOR THE REST OF THE MORNING IN THE SOUTHWESTERN PANHANDLE AND NORTHERN SOUTH PLAINS. PREV DISCUSSION... /ISSUED 255 AM CDT FRI SEP 7 2012/ SHORT TERM... A BROAD UA TROUGH ACROSS THE NORTHERN ROCKIES/NORTHERN PLAINS...IS PROGGED TO TRANSLATE SSE ACROSS THE CENTRAL PLAINS THIS AFTERNOON/EVENING...WHICH WILL AID TO SHIFT THE CENTER OF THE UA RIDGE WEST OF THE SOUTHERN PLAINS. THE TROUGH/S ASSOCIATED FROPA WHICH WAS LOCATED ACROSS CENTRAL COLORADO AND NORTHERN KANSAS PER 07Z METARS...IS EXPECTED TO ENTER THE NWRN ZONES AOA 18Z AND THROUGH THE REMAINDER OF THE CWA BY 00Z. WHAT NEEDS TO BE CONSIDERED WITH THIS LATE SUMMER FRONTAL INTRUSION ARE /1/ PRECIPITATION CHANCES AND /2/ THE STRENGTH OF THE FRONT. BEST LARGE SCALE ASCENT IS FAVORED TO BE NORTH OF THE REGION...HOWEVER FORECAST SOLUTIONS EXHIBITED PRECIP COMMENCING BETWEEN 21-00Z ACROSS PORTIONS OF THE NRN AND CNTRL ZONES...THANKS TO ADEQUATE FRONTOGENETICAL FORCING. THE PRECIP WILL SHIFT TO THE CNTRL AND SRN ZONES THIS EVENING AND TONIGHT...WITH LINGERING PRECIP ACROSS SRN ZONES EARLY TOMORROW MORNING /NEAREST TO BEST MOISTURE AXIS/. IT IS INTERESTING TO NOTE MODEL RUNS SHOWING THE PRECIP IN A RATHER NARROW CORRIDOR VERSUS WIDESPREAD CONVECTION. THIS IS LIKELY DUE TO THE TOP-DOWN MOISTENING THAT WILL HAVE TO OCCUR GIVEN INITIAL DRY LOW LEVELS...QUICKLY FOLLOWED BY A SFC RIDGING FILTERING IN A MUCH DRIER AND COOLER AIRMASS FROM NORTH TO SOUTH. AS SUCH...CLOUD BASES WILL BE RELATIVELY HIGH BUT INVERTED-V SOUNDING PROFILES SUGGESTS THUNDERSTORM WIND GUSTS OF 40-50 MPH NOT OUT OF THE QUESTION. THE OTHER CONCERN IS HOW STRONG THIS NORTH TO NORTHEASTERLY FROPA WILL BE. THE 1020 MB SFC RIDGE DRIVING THIS FRONT WILL PROMOTE A TIGHTENED PRESSURE GRADIENT AND THUS PROGGED PRESSURE RISES OF 6-9 MB PER THREE HOURS /HIGHEST PRESSURE RISES EXPECTED TO BE ACROSS ERN LOCALES/. MIXING TO 850 MB...FORECAST SOLUTIONS SHOW WIND SPEEDS OF 40-50 MPH AT THAT SAID LEVEL...WHICH CORRESPONDS TO 20-30 MPH AT THE SFC...WHICH IS NEARING WIND ADVISORY SPEED CRITERIA /31-39 MPH/. AS SUCH...SOME LOCALES ON THE CAPROCK COULD SEE AREAS OF BLOWING DUST. IT IS QUITE POSSIBLE THAT A FEW LOCALES MAY CERTAINLY EQUATE THE SPEED CRITERIA OF THE WIND ADVISORY BUT CONFIDENCE IS NOT HIGH FOR THIS TO OCCUR FOR AN HOUR OR LONGER /SECOND HALF OF THE WIND ADVISORY CRITERIA/...GIVEN THE RELATIVELY QUICK DECLINATION IN PRESSURE RISES. THE DAY SHIFT WILL HAVE TO KEEP AN EYE ON THE STRENGTH OF THE FRONT AS IT NEARS DRAWS...ESPECIALLY IF IT APPROACHES THE AIRPORT WEATHER WARNING CRITERIA /SFC WINDS OF 30 KTS OR GREATER/. WILL THEREFORE MAINTAIN A MENTION IN THE HAZARDOUS WEATHER OUTLOOK ATTM. FURTHERMORE...THE STRENGTH OF THE COLD FRONT COMBINED WITH THE ASSOCIATED CLOUD COVER WILL CREATE A TEMP-GRADIENT FROM NW /LOWER 80S/ TO SE /LOWER TRIPLE DIGITS/. LONG TERM... A COOL AND DRY AIR MASS WILL SPREAD ACROSS THE FCST AREA SATURDAY WITH POTENTIAL FOR A FEW LINGERING SHOWERS ACROSS THE SWRN ZONES EARLY IN THE DAY. RETURN FLOW AND A WARMING TREND THEN QUICKLY SET UP SUNDAY AS UPPER LEVEL RIDGING BEGINS TO BUILD EWD ONCE AGAIN. THEN THROUGH THE COURSE OF NEXT WEEK WILL SEE A VERY SLOWLY PROGRESSIVE PATTERN WITH THE UPPER RIDGE CONTINUE TO MOVE EWD... FLATTENING UPPER LEVEL FLOW ACROSS THE SRN PLAINS...AND THE APPROACH OF A LOW AMPLITUDE SHORT WAVE TROUGH FROM THE WEST TOWARD THE MIDDLE OF THE WEEK. CONTINUOUS SOUTHERLY FLOW EARLY IN THE WEEK WILL EVENTUALLY DRAW SOME LOW LEVEL MOISTURE NWD...BUT WHETHER IT AND FORCING ASSOCIATED WITH THE AFOREMENTIONED TROUGH WILL BE ENOUGH TO GENERATE SOME PRECIP BY ABOUT WEDNESDAY OR THURSDAY REMAINS UNCERTAIN. GFS DEPICTS BETTER RAIN CHANCES VERY LATE IN THE FCST PERIOD TOWARD THE END OF THE WEEK WITH THE PASSAGE OF THE NEXT COLD FRONT. ECMWF NOT YET IN AGREEMENT...SO TIME WILL TELL IF THIS WILL PAN OUT. FOR NOW WILL MAINTAIN A DRY FCST FOR THE UPCOMING WEEK. HIGH TEMPS TO RETURN TO THE UPPER 80S AND 90S FOR MUCH OF THE WEEK...BUT ATTM IT APPEARS REACHING THE CENTURY MARK AGAIN IN ANY PART OF THE FCST AREA IS UNLIKELY. && .PRELIMINARY POINT TEMPS/POPS... FRIONA 54 76 48 83 53 / 20 0 0 0 0 TULIA 55 76 49 83 54 / 20 0 0 0 0 PLAINVIEW 56 76 49 85 54 / 30 0 0 0 0 LEVELLAND 56 76 48 82 55 / 30 10 0 0 0 LUBBOCK 57 77 51 85 55 / 30 10 0 0 0 DENVER CITY 58 75 50 82 56 / 40 20 0 0 0 BROWNFIELD 57 76 52 83 57 / 40 20 0 0 0 CHILDRESS 59 80 55 88 57 / 30 0 0 0 0 SPUR 60 79 52 85 56 / 30 10 0 0 0 ASPERMONT 62 80 57 87 57 / 30 10 0 0 0 && .LUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 01
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
248 PM CDT FRI SEP 7 2012 .SHORT TERM...TONIGHT THROUGH MONDAY 248 PM CDT FRI SEP 7 2012 MAIN FORECAST CONCERNS ARE ON TEMPERATURES THROUGH THE WEEKEND AND RAIN CHANCES SATURDAY AFTERNOON INTO SATURDAY EVENING. LATEST WATER VAPOR IMAGERY SHOWED AN ELONGATED UPPER TROUGH EXTENDING FROM JAMES BAY SOUTHWEST THROUGH MINNESOTA AND ACROSS SOUTH DAKOTA. THE TROUGH WAS MOVING SOUTH ACROSS THE UPPER MISSISSIPPI RIVER VALLEY. MUCH COOLER AIR WILL MOVE INTO THE REGION TONIGHT IN THE WAKE OF A SECONDARY COLD FRONT PUSHING THROUGH THE REGION. SKIES WILL RANGE FROM PARTLY CLOUDY TO MOSTLY CLEAR BY LATE THIS EVENING AS SUBSIDENCE SLIDES OVER THE AREA IN THE WAKE OF THE DEPARTING TROUGH. PLAN ON LOW TEMPERATURES IN THE 40S WITH LOW LYING AREAS SUCH AS DIAMOND LAKE...BLACK RIVER FALLS....AND SPARTA FALLING INTO THE UPPER 30S. THE FORECAST AREA WILL BE IN A TIGHT PRESSURE GRADIENT THROUGH THE OVERNIGHT HOURS WITH SURFACE HIGH PRESSURE CENTERED OF THE DAKOTAS AND THE SURFACE TROUGH MOVING ACROSS THE EASTERN GREAT LAKES. NORTHWEST WINDS ARE EXPECTED TO SUBSIDE LATE THIS EVENING. WINDS ALOFT SHOULD HELP TO PROMOTE MIXING AND LIMIT FOG DEVELOPMENT. HOWEVER...SHOULD SEE SOME FOG IN THE LOW LYING AREAS THAT DECOUPLE GIVEN THE RECENT RAINFALL AND CLOUDS OVER THE REGION THROUGH MUCH OF THE DAYTIME HOURS. WOULD EXPECT THE FOG TO BE SHALLOW AND PATCHY WITH VISIBILITIES POSSIBLY REDUCED TO AROUND 1/2 MILE OR LESS IF IT DEVELOPS. ANOTHER TROUGH IS EXPECTED TO DIVE INTO THE REGION ON SATURDAY FROM MANITOBA/ONTARIO. THE TROUGH WILL MOVE INTO THE FORECAST AREA SATURDAY AFTERNOON. SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS NORTH CENTRAL INTO CENTRAL WISCONSIN DURING THE AFTERNOON HOURS. SCATTERED TO ISOLATED SHOWERS AND EXPECTED ACROSS WEST CENTRAL INTO PORTIONS OF SOUTHWEST WISCONSIN. SOUNDINGS ARE SHOWING VERY DRY AIR NEAR THE SURFACE...ESPECIALLY ALONG AND WEST OF THE MISSISSIPPI RIVER. DECIDED KEEP LOCATIONS WEST OF THE MISSISSIPPI RIVER DRY WHERE CLOUDS WILL BE ON THE INCREASE DURING THE AFTERNOON HOURS BUT NOT EXPECTING ANY SHOWERS THAT FAR WEST. PLAN ON HIGHS ON SATURDAY BEING REACHED IN THE LATE MORNING HOURS BEFORE CLOUDS SPREAD INTO THE REGION. LOOK FOR HIGHS TO RANGE FROM THE MID 60S ACROSS NORTHERN WISCONSIN TO THE MID 70S OVER NORTHEAST IOWA. THE TROUGH WILL SLIDE EAST OF THE REGION LATE SATURDAY NIGHT INTO SUNDAY AS SURFACE HIGH PRESSURE BUILDS IN TO THE REGION. LOOK FOR DECREASING CLOUDS LATE SUNDAY EVENING WITH SKIES BECOMING MOSTLY CLEAR DURING THE OVERNIGHT HOURS. THE HIGH WILL DOMINATE THE WEATHER ON SUNDAY WITH MOSTLY SUNNY SKIES ACROSS THE REGION. LOOK FOR HIGHS TO RANGE FROM THE UPPER 60S ACROSS NORTHERN WISCONSIN TO THE LOWER 70S OVER NORTHEAST IOWA. THE SYNOPTIC SET UP LOOKS VERY FAVORABLE FOR VALLEY FOG LATE SUNDAY NIGHT INTO EARLY SUNDAY MORNING. HIGH PRESSURE OVERHEAD....CLEAR SKIES...CALM TO LIGHT WINDS FROM THE SURFACE THROUGH 6 KFT. DECIDED TO ADD AREAS OF FOG TO THE RIVER VALLEYS LATE SUNDAY NIGHT THROUGH EARLY MONDAY MORNING. THE SURFACE HIGH WILL SLIDE EAST LATE ON MONDAY AS AN UPPER LEVEL RIDGE MOVE INTO THE REGION. SOUTHERLY FLOW WILL INCREASE ACROSS THE AREA AS A SURFACE TROUGH DEVELOPS OVER THE HIGH PLAINS. THE SOUTHERLY FLOW WILL USHER IN WARMER TEMPERATES WITH HIGHS IN THE 70S TO AROUND 80. .LONG TERM...TUESDAY THROUGH FRIDAY 248 PM CDT FRI SEP 7 2012 07.12 MEDIUM RANGE MODELS ARE IN REASONABLE AGREEMENT THROUGH THE EXTENDED PERIOD. HAVE WARMED HIGHS A FEW DEGREES ON TUESDAY OVER THE PREVIOUS FORECAST GIVEN THE STRONG SOUTHWEST FLOW AT NEAR THE SURFACE AND THE UPPER RIDGE OVERHEAD. IN ADDITION...ECMWF 850MB TEMPERATURE STANDARDIZED ANOMALIES ARE AROUND PLUS 1.5. FLOW ALOFT WILL TURN SOUTHWEST TUESDAY NIGHT INTO WEDNESDAY AS A TROUGH MOVES INTO THE NORTHERN PLAINS AND EDGES EAST INTO THE UPPER MISSISSIPPI RIVER VALLEY. THE TROUGH WILL INTERACT WITH A FRONTAL BOUNDARY GRADUALLY MOVING FROM NORTHWEST TO SOUTHEAST ACROSS THE FORECAST AREA. PLAN ON CHANCES FOR SHOWERS AND THUNDERSTORMS FROM TUESDAY NIGHT THROUGH EARLY THURSDAY AS THE FRONT SLOWLY DRIFTS ACROSS THE AREA. COOLER AIR WILL RETURN BEHIND THE FRONT WITH HIGHS ON WEDNESDAY FALLING BACK INTO THE LOWER 70S BEHIND THE FRONT...ACROSS SOUTHEAST MINNESOTA INTO NORTH CENTRAL WISCONSIN. HIGHS WILL BE IN THE 70S TO LOWER 80S ACROSS PORTIONS OF NORTHEAST IOWA INTO FAR SOUTHWEST WISCONSIN BEFORE THE FRONT MOVES THROUGH. SHOWER AND THUNDERSTORMS CHANCES WILL FINALLY SHIFT SOUTH OF THE AREA ON FRIDAY AS HIGH PRESSURE BUILDS IN. && .AVIATION...THROUGH 18Z SATURDAY 1221 PM CDT FRI SEP 7 2012 UPPER TROUGH WILL ROTATE ACROSS THE AREA THIS AFTERNOON. FRONTOGENETICALLY FORCED SHOWERS NOW MOVING THROUGH SOUTHEAST MINNESOTA INTO WESTERN WISCONSIN. MAIN BAND SHOULD BE SOUTH OF THE THE TAF SITES BY 18Z. HOWEVER...COULD SEE SOME REDEVELOPMENT BEHIND THIS BAND BETWEEN 18Z-20Z AND NOTED ON THE 07/12 ARXLAPS AND 07.13Z HRRR...WILL KEEP VCSH AT BOTH SITES THROUGH 20Z. CEILINGS EXPECTED TO REMAIN IN THE VFR CATEGORY WITH BASES 4K-6K FEET...ANY MVFR CEILINGS WITH SHOWERS WILL BE SHORT LIVED. SUBSIDENCE IN THE WAKE OF THE TROUGH WILL OVERSPREAD THE AREA THIS EVENING WITH CLEARING SKIES. BOTH THE 07.12Z NAM AND 07.15Z RAP BUFKIT SOUNDINGS DO SHOW WINDS TO REMAIN RATHER STRONG JUST ABOVE THE SURFACE THROUGH THE OVERNIGHT HOURS. THUS DESPITE CLEARING SKIES AND THE RECENT RAIN NOT EXPECTING ANY FOG FORMATION AT EITHER TAF SITE. DECENT MIXING LATER SATURDAY MORNING AND PRESSURE GRADIENT TO REMAIN STRONG DID ADD SOME GUST TO NEAR 20 KNOTS AT BOTH KLSE AND KRST AFTER 16Z. && .ARX WATCHES/WARNINGS/ADVISORIES... 248 PM CDT FRI SEP 7 2012 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...WETENKAMP LONG TERM...WETENKAMP AVIATION...RABERDING
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1221 PM CDT FRI SEP 7 2012 .SHORT TERM...TODAY THROUGH SUNDAY NIGHT 327 AM CDT FRI SEP 7 2012 MAIN FORECAST CONCERNS THIS PACKAGE...SHRA/TSRA CHANCES TODAY... SHRA CHANCES WITH SECONDARY FRONTAL/SHORTWAVE PASSAGE SAT... TEMPERATURES THRU THE PERIOD. 06Z DATA ANALYSIS HAD LOW PRESSURE OVER JAMES BAY WITH A TROUGH SOUTHWEST TO A LOW NEAR KOMA. 850-700MB MOISTURE TRANSPORT/THETA-E CONVERGENCE AND WARM ADVECTION AHEAD OF THE KOMA LOW PRODUCING SHRA/TSRA OVER MUCH OF CENTRAL/NORTHERN IA. FURTHER NORTH...SOME 850-700MB WARM ADVECTION AND FN-CONVERGENCE ALONG WITH INCREASING PV ADVECTION ALOFT PRODUCING SHRA OVER MUCH OF NORTHERN WI INTO CENTRAL MN. WITH ALL THE CLOUD COVER AND BROAD LOW LEVEL WARM ADVECTION...EARLY MORNING TEMPS GENERALLY ON THE MILD SIDE FOR EARLY SEPT. NO BIG ERRORS NOTED WITH 07.00Z MODEL INITIALIZATIONS. SOLUTIONS RATHER SIMILAR FOR TODAY THRU SUN NIGHT BUT FOR SOME DIFFERENCES WITH SHRA CHANCES ON SAT...RELATED TO TRACK OF A SECONDARY SHORTWAVE DROPPING OUT OF CANADA. DPROG/DT OF 500MB HGTS AT 07.00Z SHOWED THE MODEL RUNS OF 05.00Z AND 6.00Z VERIFIED VERY WELL ACROSS NOAM/EASTERN PAC. TREND FAVORS A TIGHTER COMPROMISE OF THE EARLIER RUNS ON MOST FEATURES...BUT STRONGER OF EARLIER RUNS ON THE SHORTWAVE DROPPING SOUTH NEAR LK WINNIPEG EARLY THIS MORNING. BETTER CONSENSUS THRU TODAY/TONIGHT AS THE LK WINNIPEG SHORTWAVE/TROUGH DROPS SOUTH ACROSS THE REGION...TOWARD A COMPROMISE OF THE EARLIER RUNS. TREND IS A BIT STRONGER WITH THE NEXT SHORTWAVE DROPPING SOUTHEAST ACROSS MAN/WESTERN ONT. CONSENSUS CONTINUES TO IMPROVE AS THIS SHORTWAVE PASSES SAT/SAT NIGHT AND STRONG TROUGHING DEVELOPS OVER THE EASTERN CONUS. GOOD CONSENSUS FOR THE PATTERN TO BE PROGRESSIVE AND RIDGING ALOFT TO BUILD INTO THE NORTH-CENTRAL CONUS SUN/SUN NIGHT. CHECK OF OBS VS. MODEL DATA AT 06Z SHOWED ALL REASONABLE WITH THE SFC MASS FIELDS ACROSS THE NORTH-CENTRAL CONUS. PER WV IMAGERY NAM/GFS/ECMWF LOOKED BETTER WITH THE LK WINNIPEG SHORTWAVE...GEM LOOKED TO FAR EAST. GEM DID LOOK GOOD WITH THE SHORTWAVE OVER NORTHERN BC...MODELS ALL GENERALLY GOOD WITH THE 00- 06Z SHRA/RAIN OVER NORTH-CENTRAL MN/NORTHERN WI WHILE MOST WERE TOO FAR SOUTH WITH THE SHRA/TSRA OVER IA. NO CLEAR FAVORITE AND WITH A TREND TOWARD A TIGHTER COMPROMISE...PREFERRED A MODEL/ENSEMBLE BLEND THIS CYCLE. SHORT TERM FCST CONFIDENCE GENERALLY GOOD THIS CYCLE. IN THE SHORT TERM...MAIN FORCING/LIFT TODAY WILL COME FROM PV ADVECTION AS THE LK WINNIPEG SHORTWAVE DROPS SOUTH-SOUTHEAST ACROSS THE REGION AND 850-500MB FN CONVERGENCE WITH THE MID LEVEL TROUGH. THIS FORCING/LIFT WILL EVENTUALLY INTERACT WITH THE DEEPER MOISTURE SPREADING NORTHEAST ACROSS IA INTO SOUTHERN WI...WITH SHRA EXPECTED TO BECOME MORE WIDESPREAD AS THE LIFT MOVES SOUTH/EAST ACROSS THE AREA. INSTABILITY REMAINS LIMITED AND MAINLY CONFINED TO THE SOUTH END OF THE FCST AREA THIS MORNING. LIMITED TSRA MENTION AS ISOLATED OVER THE SOUTHEAST 1/4 OF THE FCST AREA THIS MORNING. CONTINUED HIGHEST RAIN CHANCES OVER THE SOUTH/EAST 2/3 OF THE FCST AREA THIS MORNING AND RAISED THESE A BIT OVER THE SOUTHEAST END WHERE THE DEEPER MOISTURE WILL RESIDE. ONCE THE SHORTWAVE/TROUGH AXIS PASSES...LIFT SHUTS OFF VERY QUICKLY WITH SUBSIDENCE/DRYING SPREADING SOUTHEAST ACROSS THE FCST AREA DURING THE AFTERNOON. LIMITED SHRA CHANCES AFTER 18Z TO 20-40 PERCENT AND MAINLY OVER THE SOUTHEAST HALF OF THE FCST AREA. SUBSIDENCE/DRYING/LOW LEVEL COLD ADVECTION CONTINUE TO SPREAD SOUTHEAST ACROSS THE UPPER MIDWEST TONIGHT. A SEASONABLY COOL NIGHT TONIGHT WITH MOSTLY CLEAR SKIES...LIGHT WINDS AND 850-700MB COOL POOL OVER THE AREA. 925-700MB WARM ADVECTION QUICKLY RETURNS SAT...AHEAD OF THE NEXT SHORTWAVE/TROUGH AND SFC COLD FRONT. MOISTURE LIMITED AHEAD OF THIS TROUGH/FRONT WITH PW VALUES OF 0.5 TO 0.75 INCH. ON THE PLUS SIDE IS RATHER STRONG 500-300 PV ADVECTION FOR LIFT AHEAD OF THE SHORTWAVE. QUESTION IS WHERE WILL THE SHORTWAVE TRACK. GEM/ECMWF A COUPLE OF THE FURTHER WEST SOLUTIONS WITH THE TRACK OF THE SHORTWAVE...AND STRONGER LIFT/SATURATION OVER THE NORTHEAST END OF THE FCST AREA SAT AFTERNOON/EVENING. WITH THE TREND TOWARD STRONGER AS THIS FEATURE DROPS ACROSS THE REGION...CONTINUED A SLIGHT CHANCE OF SHRA MAINLY ALONG/NORTHEAST OF I-94 SAT AFTERNOON/EVENING. DRY..QUIET WEATHER RETURNS FOR LATER SAT NIGHT INTO MON NIGHT AS HGTS ALOFT GRADUALLY RISE AND CANADIAN HIGH PRESSURE DRIFTS SOUTHEAST ACROSS THE UPPER MIDWEST. CENTER OF THE HIGH MOVES OVER THE AREA SUN NIGHT. DEPENDING ON HOW DRY THE AIRMASS IS OVER THE AREA SUN/SUN NIGHT...THERE MAY BE VALLEY FOG POTENTIAL LATE SUN NIGHT INTO MON MORNING. SYNOPTIC SET-UP WILL BE FAVORABLE WITH STRONG DECOUPLING DURING THE EVENING...HOWEVER MODELS TRENDING TOWARD A RATHER DRY AIRMASS OVER THE AREA SUN NIGHT AND LEFT ANY FOG MENTION OUT OF THE GRIDS FOR NOW. TRENDED TOWARD A BLEND OF THE NUMERICAL TEMP GUIDANCE FOR HIGHS/LOWS TODAY THRU SUN NIGHT...WITH TEMPS A CATEGORY OR TWO BELOW NORMAL. .LONG TERM...MONDAY THROUGH THURSDAY 327 AM CDT FRI SEP 7 2012 MEDIUM RANGE MODEL RUNS OF 07.00Z IN GOOD AGREEMENT MON/TUE AS THE MID LEVEL RIDGE AXIS MOVES EAST ACROSS THE UPPER MIDWEST. LOWER LEVEL WARM ADVECTION INCREASES MON/TUE AS THE SFC HIGH MOVES INTO THE OH VALLEY...TROUGHING DEVELOPS IN THE CENTRAL/NORTHERN PLAINS AND THE PRESSURE GRADIENT TIGHTENS OVER THE REGION. TEMPS MON/TUE RETURN TO NEAR/ABOVE NORMAL AS THE 850-700MB THERMAL RIDGE AHEAD OF THE TROUGHING BUILDS INTO THE AREA. MODEL CONSENSUS REMAINS REASONABLE WED/THU AS THE NEXT TROUGH MOVES EAST ALONG THE US/CAN BORDER. THIS TROUGH PUSHES A COLD FRONT INTO/ACROSS THE AREA CENTERED ON WED. QUESTION WILL BE EXTENT OF MOISTURE DRAWN NORTHWARD AHEAD OF THIS FEATURE WITH AUTUMN PROGRESSING...CROPS/VEGETATION SOME 2-3 WEEKS AHEAD OF NORMAL...MATURING AND SHUTTING DOWN WITH EVAPO-TRANSPIRATION WANING. SHRA/TSRA CHANCES IN THE 20-30 PERCENT RANGE FOR WED INTO THU REASONABLE FOR NOW. WITH MORE CLOUDS AND PASSAGE OF THE COLD FRONT...TEMPS CLOSER TO NORMAL FOR WED/THU LOOK WELL TRENDED AT THIS TIME. && .AVIATION...THROUGH 18Z SATURDAY 1221 PM CDT FRI SEP 7 2012 UPPER TROUGH WILL ROTATE ACROSS THE AREA THIS AFTERNOON. FRONTOGENETICALLY FORCED SHOWERS NOW MOVING THROUGH SOUTHEAST MINNESOTA INTO WESTERN WISCONSIN. MAIN BAND SHOULD BE SOUTH OF THE THE TAF SITES BY 18Z. HOWEVER...COULD SEE SOME REDEVELOPMENT BEHIND THIS BAND BETWEEN 18Z-20Z AND NOTED ON THE 07/12 ARXLAPS AND 07.13Z HRRR...WILL KEEP VCSH AT BOTH SITES THROUGH 20Z. CEILINGS EXPECTED TO REMAIN IN THE VFR CATEGORY WITH BASES 4K-6K FEET...ANY MVFR CEILINGS WITH SHOWERS WILL BE SHORT LIVED. SUBSIDENCE IN THE WAKE OF THE TROUGH WILL OVERSPREAD THE AREA THIS EVENING WITH CLEARING SKIES. BOTH THE 07.12Z NAM AND 07.15Z RAP BUFKIT SOUNDINGS DO SHOW WINDS TO REMAIN RATHER STRONG JUST ABOVE THE SURFACE THROUGH THE OVERNIGHT HOURS. THUS DESPITE CLEARING SKIES AND THE RECENT RAIN NOT EXPECTING ANY FOG FORMATION AT EITHER TAF SITE. DECENT MIXING LATER SATURDAY MORNING AND PRESSURE GRADIENT TO REMAIN STRONG DID ADD SOME GUST TO NEAR 20 KNOTS AT BOTH KLSE AND KRST AFTER 16Z. && .ARX WATCHES/WARNINGS/ADVISORIES... 327 AM CDT FRI SEP 7 2012 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...RRS LONG TERM....RRS AVIATION...RABERDING