Forecast Discussions mentioning any of "HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 08/31/12


AREA FORECAST DISCUSSION
NWS DENVER/BOULDER CO
1023 AM MDT THU AUG 30 2012 .UPDATE...RED FLAG WARNING FOR THE EASTERN PLAINS STILL ON TRACK...ESPECIALLY WITH THE POOR OVERNIGHT HUMIDITY RECOVERIES. SOME SPOTS IN EASTERN ADAMS AND ARAPAHOE COUNTIES AS WELL AS INTO WASHINGTON AND LOGAN COUNTIES SAW HUMIDITIES RECOVER ONLY INTO THE LOW 20 PERCENT RANGE. SOUTHERLY WINDS ARE BEGINNING TO INCREASE AND MAY CAUSE CRITERIA TO BE REACH A LITTLE BEFORE NOON WHEN THE WARNING BEGINS. CONVECTION OVER THE HIGH TERRAIN ALREADY GETTING STARTED. CAPE VALUES CURRENTLY SHOWN TO BE AROUND 150 TO 200 J/KG BY THE RUC13 MODEL. PRECIPITABLE WATER VALUES ABOUT 0.5-0.1 INCHES LESS THAN THIS TIME YESTERDAY. STILL EXPECT SOME LIGHT RAIN WITH GUSTY WINDS FROM THESE STORMS...AND THESE SHOULD MAINLY STAY OVER THE MOUNTAINS WITH JUST A SLIGHT CHANCE OF THEM MOVING OFF LATER THIS AFTERNOON OVER THE NORTHERN I25 CORRIDOR. && .AVIATION...NO BIG CHANGES EXPECTED FOR THE 18Z TAF PACKAGE. STILL EXPECT TSTM ACTIVITY TO STAY OVER THE HIGHER TERRAIN TO THE WEST OF THE AIRPORTS TODAY...SO WILL KEEP OUT ANY MENTION OF VCTS IN THE 18Z TAF PACKAGE. SOUTHERLY WINDS BEGINNING TO SHOW IN RADAR VELOCITY TO THE EAST OF KDEN...EXPECT THESE TO REACH THE AIRPORTS WITHIN A COUPLE HOURS. SOUTHEASTERLY WINDS THIS AFTERNOON WILL RETURN TO DRAINAGE THIS EVENING THEN ANOTHER DAY OF SOUTHERLY WINDS TOMORROW. VFR CONDITIONS FOR THE NEXT 24-36 HOURS UNDER A MAINLY DRY AIRMASS. && .PREV DISCUSSION... /ISSUED 333 AM MDT THU AUG 30 2012/ SHORT TERM...THE UPPER LEVEL RIDGE WILL WEAKEN SOME TODAY HOWEVER THAT WILL NOT CHANGE THE OVERALL PTRN MUCH. SOME SUBTROPICAL MOISTURE WILL CONTINUE TO AFFECT THE MTNS WITH SCT AFTN AND EARLY EVENING TSTMS WHILE THE FOOTHILLS AND HIGHER VALLEYS SEE WDLY SCT TSTMS. OVER NERN CO IT WILL REMAIN DRY EXCEPT NR THE FOOTHILLS AND ALONG THE WY-CO BORDER WHERE A FEW STORMS WILL BE POSSIBLE. HIGHS THIS AFTN WILL BE SIMILAR TO WED WITH RECORD HIGHS POSSIBLE ONCE AGAIN. MEANWHILE GUSTY SOUTH WINDS COMBINED WITH LOW HUMIDITY WILL CREATE HIGH FIRE DANGER OVER MOST OF THE PLAINS. LONG TERM...NO BIG CHANGES IN FORECAST REASONING THIS TIME AROUND. THE MAIN IDEA REMAINS THAT THE UPPER RIDGE OVER THE STATE TODAY WILL FLATTEN AND EXPAND ACROSS THE SOUTHERN HALF OF THE COUNTRY OVER THE WEEKEND AS TROPICAL STORM ISAAC MOVES UP THE MISSISSIPPI VALLEY THEN EASTWARD OVER THE OHIO VALLEY. WEAK FLOW ALOFT OVER COLORADO WILL BECOME MORE WESTERLY OVER TIME. MID-LEVEL MOISTURE WILL LINGER OVER THE STATE TO FUEL AFTERNOON SHOWERS OVER THE MOUNTAINS EACH AFTERNOON. AT LOWER LEVELS TEMPERATURES WILL BE GRADUALLY COOLING THROUGH THE WEEKEND AS THICKNESS VALUES DECREASE. TEMPERATURES WILL STILL BE WELL ABOVE NORMAL FOR EARLY SEPTEMBER THOUGH. AS TEMPERATURES SLOWLY MODERATE AND WINDS DECREASE...THE THREAT OF DANGEROUS FIRE WEATHER CONDITIONS WILL ALSO DECREASE. NO ADDITIONAL FIRE WEATHER HIGHLIGHTS ARE EXPECTED AT THIS TIME. AFTER ABOUT SUNDAY THE GFS AND ECMWF BEGIN SHOWING DIFFERENCES IN HOW MUCH MOISTURE AND PRECIPITATION WILL OCCUR OVER THE FORECAST AREA. THE GFS IS THE MOISTER MODEL...DRAWING MOISTURE OVER THE STATE FROM THE REMAINS OF PACIFIC HURRICANE ILEANA WHICH IS CURRENTLY SOUTH OF BAJA CALIFORNIA. THE ECMWF HANDLES ILEANA DIFFERENTLY FROM THE GFS BY TAKING THE HURRICANE ON A MORE WESTERLY TRACK. THEREFORE THE ECMWF HAS LESS MOISTURE ACROSS THE SOUTHWESTERN U.S. FROM SUNDAY ONWARDS. A COMPROMISE SOLUTION BETWEEN THESE TWO MODELS WOULD THEREFORE HAVE A SLIGHT CHANCE OF SHOWERS CONTINUING OVER OUR MOUNTAINS THROUGH THE FIRST HALF OF NEXT WEEK. THE IDEA OF AFTERNOON SHOWERS PRIMARILY OVER THE MOUNTAINS HAS BEEN WORKING WELL FOR US FOR THE MOST OF THE PAST COUPLE WEEKS. WHY SHOULD WE DEVIATE FROM THAT NOW? AVIATION...ANY TSTM ACTIVITY SHOULD STAY TO THE WEST OF THE AIRPORT THIS AFTN INTO THE EARLY EVENING HOURS. MEANWHILE SO FAR THE RAP AND HRRR KEEP WINDS SLY THIS MORNING AND THEN SSE BY EARLY AFTN. SOME WIND GUSTS TO 20-25 MPH MAY DEVELOP AFTER 21Z AND LAST THRU 01Z OR SO. OVERNIGHT WINDS SHOULD REMAIN SLY. HYDROLOGY...SOME WIDELY SCATTERED THUNDERSTORMS WILL BE POSSIBLE IN THE BURN AREAS HOWEVER RAINFALL AMOUNTS SHOULD BE BELOW ONE QUARTER INCH. && .BOU WATCHES/WARNINGS/ADVISORIES... RED FLAG WARNING FROM NOON TODAY TO 8 PM MDT THIS EVENING FOR COZ242-244>251. && $$ SHORT TERM...RPK LONG TERM....DANKERS UPDATE/AVIATION...KRIEDERMAN
AREA FORECAST DISCUSSION
NWS DENVER CO
333 AM MDT THU AUG 30 2012 .SHORT TERM...THE UPPER LEVEL RIDGE WILL WEAKEN SOME TODAY HOWEVER THAT WILL NOT CHANGE THE OVERALL PTRN MUCH. SOME SUPTROPICAL MOISTURE WILL CONTINUE TO AFFECT THE MTNS WITH SCT AFTN AND EARLY EVENING TSTMS WHILE THE FOOTHILLS AND HIGHER VALLEYS SEE WDLY SCT TSTMS. OVER NERN CO IT WILL REMAIN DRY EXCEPT NR THE FOOTHILLS AND ALONG THE WY-CO BORDER WHERE A FEW STORMS WILL BE POSSIBLE. HIGHS THIS AFTN WILL BE SIMILAR TO WED WITH RECORD HIGHS POSSIBLE ONCE AGAIN. MEANWHILE GUSTY SOUTH WINDS COMBINED WITH LOW HUMIDITY WILL CREATE HIGH FIRE DANGER OVER MOST OF THE PLAINS. .LONG TERM...NO BIG CHANGES IN FORECAST REASONING THIS TIME AROUND. THE MAIN IDEA REMAINS THAT THE UPPER RIDGE OVER THE STATE TODAY WILL FLATTEN AND EXPAND ACROSS THE SOUTHERN HALF OF THE COUNTRY OVER THE WEEKEND AS TROPICAL STORM ISAAC MOVES UP THE MISSISSIPPI VALLEY THEN EASTWARD OVER THE OHIO VALLEY. WEAK FLOW ALOFT OVER COLORADO WILL BECOME MORE WESTERLY OVER TIME. MID-LEVEL MOISTURE WILL LINGER OVER THE STATE TO FUEL AFTERNOON SHOWERS OVER THE MOUNTAINS EACH AFTERNOON. AT LOWER LEVELS TEMPERATURES WILL BE GRADUALLY COOLING THROUGH THE WEEKEND AS THICKNESS VALUES DECREASE. TEMPERATURES WILL STILL BE WELL ABOVE NORMAL FOR EARLY SEPTEMBER THOUGH. AS TEMPERATURES SLOWLY MODERATE AND WINDS DECREASE...THE THREAT OF DANGEROUS FIRE WEATHER CONDITIONS WILL ALSO DECREASE. NO ADDITIONAL FIRE WEATHER HIGHLIGHTS ARE EXPECTED AT THIS TIME. AFTER ABOUT SUNDAY THE GFS AND ECMWF BEGIN SHOWING DIFFERENCES IN HOW MUCH MOISTURE AND PRECIPITATION WILL OCCUR OVER THE FORECAST AREA. THE GFS IS THE MOISTER MODEL...DRAWING MOISTURE OVER THE STATE FROM THE REMAINS OF PACIFIC HURRICANE ILEANA WHICH IS CURRENTLY SOUTH OF BAJA CALIFORNIA. THE ECMWF HANDLES ILEANA DIFFERENTLY FROM THE GFS BY TAKING THE HURRICANE ON A MORE WESTERLY TRACK. THEREFORE THE ECMWF HAS LESS MOISTURE ACROSS THE SOUTHWESTERN U.S. FROM SUNDAY ONWARDS. A COMPROMISE SOLUTION BETWEEN THESE TWO MODELS WOULD THEREFORE HAVE A SLIGHT CHANCE OF SHOWERS CONTINUING OVER OUR MOUNTAINS THROUGH THE FIRST HALF OF NEXT WEEK. THE IDEA OF AFTERNOON SHOWERS PRIMARILY OVER THE MOUNTAINS HAS BEEN WORKING WELL FOR US FOR THE MOST OF THE PAST COUPLE WEEKS. WHY SHOULD WE DEVIATE FROM THAT NOW? && .AVIATION...ANY TSTM ACTIVITY SHOULD STAY TO THE WEST OF THE AIRPORT THIS AFTN INTO THE EARLY EVENING HOURS. MEANWHILE SO FAR THE RAP AND HRRR KEEP WINDS SLY THIS MORNING AND THEN SSE BY EARLY AFTN. SOME WIND GUSTS TO 20-25 MPH MAY DEVELOP AFTER 21Z AND LAST THRU 01Z OR SO. OVERNIGHT WINDS SHOULD REMAIN SLY. && .HYDROLOGY...SOME WIDELY SCATTERED THUNDERSTORMS WILL BE POSSIBLE IN THE BURN AREAS HOWEVER RAINFALL AMOUNTS SHOULD BE BELOW ONE QUARTER INCH. && .BOU WATCHES/WARNINGS/ADVISORIES... RED FLAG WARNING FROM NOON TODAY TO 8 PM MDT THIS EVENING FOR COZ242-244>251. && $$ SHORT TERM...RPK LONG TERM....DANKERS AVIATION...RJK
AREA FORECAST DISCUSSION
NWS MELBOURNE FL
337 AM EDT FRI AUG 31 2012 .DISCUSSION... ...RIP CURRENT THREAT INCREASING OVER THE HOLIDAY WEEKEND... TODAY/TONIGHT... TWO DISTINCT H100-H70 ANTICYCLONIC GYRES...ONE OVER THE CAROLINAS AND ONE JUST E OF THE NRN BAHAMAS...WILL MERGE OVER THE SERN SEABOARD TODAY AND GENERATE A DEEP N/NERLY FLOW ACRS THE FL PENINSULA. NE FLOW REGIMES TYPICALLY ARE QUITE STABLE FOR CENTRAL FL AS THEY TEND TO PUSH DRY/STABLE CONTINENTAL AIR INTO THE REGION. THE 00Z SOUNDINGS CONTINUE TO SHOW PLENTIFUL MOISTURE ACRS THE STATE WITH PWAT VALUES BTWN 1.8"-2.0". HOWEVER...THE KTBW/KMFL/KEYW SOUNDINGS ALL SHOW THE MOISTURE IS MORE OR LESS EVENLY DISTRIBUTED THRU THE COLUMN...NOT CONCENTRATED IN THE LOW/MID LVLS IN A MANNER THAT WOULD SUPPORT PRECIP. LATEST RAP ANALYSIS ALSO SHOWS UPSTREAM MEAN RH VALUES THRU THE H100-H70 LYR ARE LARGELY AOB 70PCT. FURTHERMORE...RAP ANALYSIS SHOWS H70 TEMPS ARND 10C...H50 TEMPS AROUND -5.5C...RESULTING IN MID LVL LAPSE RATES AOB 5.5C/KM. ALOFT...A THIN BAND OF WEAK H85-H50 VORTICITY IS NOTED OVER THE NECK OF THE PENINSULA BUT IS EMBEDDED IN VERY WEAK FLOW...WHILE THE H30-H20 WIND PATTERN IS WEAKLY CONVERGENT. SAT PICS SHOW UPR LVL CLOUD DECK IS NOT AS ROBUST AS A FEW HRS AGO...BUT ANY UPR LVL DEBRIS CLOUDS THAT PUSH INTO CENTRAL FL WOULD ONLY FURTHER "DAMPEN" PRECIP CHANCES. THE AIRMASS IS CONDITIONALLY UNSTABLE...BUT JUST BARELY. WITH H100-H70 DRY AIR ADVECTION TAKING PLACE...MID LVL THERMAL RIDGING... AND WEAK DYNAMIC SUPPORT...STORM COVERAGE TODAY WILL BE PRIMARILY DEPENDENT ON MESOSCALE BOUNDARY COLLISIONS TO FORCE VERTICAL MOTION. HOWEVER...WITH A NE FLOW REGIME IN PLACE...MOST OF THESE WILL OCCUR OVER THE W PENINSULA. WILL MENTION A SLGT CHC OF TSRAS OVER THE INTERIOR COUNTIES AS THINNING UPR LVL CLOUDS MAY ALLOW A FEW SPOTS TO REACH THEIR CONVECTIVE TEMPS...BUT EVEN THIS IS GENEROUS GIVEN THE TORPID NATURE OF THIS AIRMASS. THE DEEPENING ONSHORE FLOW WILL KEEP MAX TEMPS NEAR AVG (U80S/L90S)...MIN TEMPS ABV AVG (M70S). HOLIDAY WEEKEND... RIDGING ALOFT AND NORTHEAST UPPER LEVEL WINDS ARE INDICATED ALONG WITH DEEP LAYER DRYING SO HAVE GONE WITH A DRY FORECAST...ESPECIALLY SINCE MOS POPS ARE 10 PERCENT OR LESS. AT THE SURFACE...HIGH PRESSURE RIDGE TO OUR NORTH WILL PROVIDE AN ONSHORE FLOW. THIS WILL KEEP COASTAL HIGH TEMPS IN THE UPPER 80S WITH MAINLY LOWER 90S ACROSS THE INTERIOR. WILL HAVE TO WATCH FOR A SMALL LONG PERIOD SWELL FROM DISTANT TROPICAL CYCLONE KIRK AFFECTING THE BEACHES AND LEADING TO DANGEROUS RIP CURRENTS BY SUNDAY. SWELLS FROM LESLIE MAY ARRIVE AS EARLY AS MON. TUE-FRI...MID-UPPER LEVEL LOW IS FORECAST TO PUSH SLOWLY WEST ACROSS THE NORTHERN BAHAMAS THEN LIFT OUT TO THE NORTH AS NORTHERN STREAM TROUGH DIGS OVER THE EASTERN HALF OF THE COUNTRY. THIS RUN HAS THE LOW MOVING CLOSER TO THE AREA AND THE SUBSIDENCE OUT AHEAD OF IT PERSISTING LONGER. MOS POPS ONLY REACH 20 PERCENT ON TUE...30 PERCENT WED-THU...40 PERCENT FRI AND WILL LARGELY FOLLOW THESE NUMBERS. AT THE SURFACE...THE FLOW REGIME WILL GRADUALLY TRANSITION FROM LIGHT ONSHORE TO LIGHT OFFSHORE BY LATE WEEK. VERY LITTLE CHANCE IN HIGH TEMPS INDICATE. LONG PERIOD SWELLS FROM DISTANT TROPICAL CYCLONE LESLIE WILL CONTINUE THE THREAT FROM DANGEROUS RIP CURRENTS THROUGH AT LEAST MID WEEK. && .AVIATION... THRU 31/12Z...LCL MVFR CIGS/VSBYS IN BR N OF KGIF-KDAB...OTHERWISE VFR ALL SITES THRU 01/00Z...CIGS AOA FL120. && .MARINE... TODAY/TONIGHT...BROAD SFC/LOW LVL RIDGE CENTERED OVER THE SE COAST WILL GENERATE A LIGHT TO GENTLE ERLY BREEZE ACRS THE LCL ATLC. SEAS AOB 2FT. NO TSTM ACTIVITY ANTICIPATED AS NERLY FLOW ALOFT WILL FOCUS WHAT FEW STORMS FORM THAT DO FORM OVER W FL. WEEKEND...HIGH PRESSURE RIDGE TO OUR NORTH WILL PROVIDE A NORTHEAST TO EAST WIND FLOW. THE GFS SHOWS A WEAK INVERTED TROUGH TRANSITING THE COASTAL WATERS SAT NIGHT INTO SUN WITH POSSIBLE 10-15 KNOTS FLOW...BUT OTHERWISE SPEEDS SHOULD BE AROUND 10 KNOTS. THE INVERTED TROUGH MAY BRING A FEW SHOWERS...BUT HAVE NOT INCLUDED IN THE FORECAST YET. SWELLS FROM DISTANT TROPICAL CYCLONE KIRK MAY IMPACT THE WATERS BY SUNDAY. MON-TUE...THE HIGH PRESSURE RIDGE WILL SLOWLY PUSH OFFSHORE WITH MAINLY EAST WINDS 10 KNOTS OR LESS. SMALL FORERUNNER SWELLS FROM DISTANT TROPICAL CYCLONE LESLIE WILL ARRIVE LATE MON AND CONTINUE THROUGH MID WEEK WITH GRADUALLY INCREASING HEIGHTS. NAVIGATION THROUGH INLETS DURING THE OUTGOING TIDE WILL BECOME HAZARDOUS. && .PRELIMINARY POINT TEMPS/POPS... DAB 88 74 89 71 / 10 0 10 10 MCO 92 75 92 72 / 20 0 10 10 MLB 89 77 87 75 / 10 0 10 10 VRB 88 76 88 73 / 10 0 10 10 LEE 92 74 93 72 / 20 0 10 10 SFB 93 75 91 72 / 20 0 10 10 ORL 92 75 92 73 / 20 0 10 10 FPR 88 76 88 73 / 10 10 10 10 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...NONE. && $$ SHORT TERM/AVIATION...BRAGAW LONG TERM....LASCODY
AREA FORECAST DISCUSSION...UPDATE FOR AVIATION
NWS PEACHTREE CITY GA
141 AM EDT THU AUG 30 2012 .UPDATE... /ISSUED AT 1102 AM EDT THU AUG 30 2012/ MORNING SOUNDING SHOWS DEEP TROPICAL MOISTURE IN-PLACE WITH 2.17 PW`S AND A MODERATELY STABLE MOIST ADIABATIC PROFILE. THE HRRR AND NAM MODELS SHOW WIDESPREAD CONVECTION DEVELOPING ACROSS MUCH OF THE FORECAST AREA TODAY. AS A RESULT... EXPECTING SCATTERED TO OCCASIONALLY NUMEROUS SHOWERS TO SPREAD UP FROM THE SW DURING DAYTIME HEATING... WITH THE HIGHER POPS WARRANTED FROM CARROLLTON TO ATLANTA DOWN TO MACON AND COLUMBUS AREAS. CLOUDS AND MAINLY SHOWERS WILL HOLD TEMPS AND INSTABILITIES DOWN TO MODEST LEVELS... SO WILL SHOW MAINLY SHOWERS TODAY... WITH ONLY AN ISOLATED THUNDER THREAT THROUGH THE AFTERNOON WHERE THE HIGHER POPS ARE SHOWN. WILL UPDATE ZONES TO REFLECT THESE NEW EXPECTATIONS. OTHERWISE... THE REST OF FORECAST LOOKS ON TRACK AT THIS TIME. && .PREV DISCUSSION... /ISSUED 431 AM EDT THU AUG 30 2012/ SHORT TERM /TODAY THROUGH FRIDAY/... CONCERN THIS FCST IS TIMING OF SHRA THIS MORNING AND LIKELIHOOD OF TSRA THIS AFTERNOON. MODELS IN PRETTY GOOD AGREEMENT THAT WARM/MOIST ADVECTION ASSOCIATED WITH H8 SOUTHERLY FLOW EAST OF ISAAC AND LOW/MID LEVEL DEFORMATION ZONE OVER NORTH GA WILL COMMENCE THIS MORNING. RECENT HRRR RUNS DO A NICE JOB PORTRAYING STRATIFORM PRECIP DEVELOPING OVER MIDDLE GA EARLY THIS MORNING AND IS SIMILAR TO LARGER SCALE MODELS SUCH AS THE NAM...GFS AND SREF. HAVE UPDATED GRIDS TO SHOW A LITTLE HIGHER POP IN THE MORNING. IN THE AFTERNOON ..SHOULD SEE A BRIEF LULL FOLLOWED BY ADDITIONAL SHRA/TSRA AFTER 2PM. AMOUNT AND INTENSITY OF TSRA DEPENDS ON HOW MUCH INSOLATION WE CAN GET. GOT A LITTLE MORE TSRA THAN EXPECTED YESTERDAY AND A FEW CELLS APPROACHED SVR...HOWEVER EXPECT COOLER TEMPS AND MORE CLOUDS THIS AFTERNOON THAN YESTERDAY RESULTING IN CAPE ONLY AT MOST 1000 J/KG. PRECIP SHOULD END QUICKLY THIS EVENING AS WAA PATTERN DISSIPATES AND SOLAR INSOLATION ENDS. NOT AS FAVORABLE A PATTERN FOR PRECIP FRIDAY BUT STILL HAVE SLT CHC BECOMING CHC SHRA/TSRA IN THE AFTERNOON. MOISTURE FROM ISAAC WILL BE DIFFICULT TO FULLY CLEAR OUT ANYTIME SOON. AS UPPER RIDGE BUILDS AROUND THE SOUTHEAST CONUS...TEMPS SHOULD WARM CONSIDERABLY INTO THE UPPER 80S AND LOWER 90S BUT ABUNDANT MOISTURE WILL HELP KEEP CLOUDS AND AFTERNOON CONVECTION GOING. SNELSON LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... MODELS IN GOOD AGREEMENT ON TAKING ISAAC NORTHWEST AND LOOPING IT BACK ACROSS THE OHIO AND TENNESSEE VALLEYS BY SUNDAY. BEYOND THAT TIME...NOT SO CLEAR WHERE THE REMNANTS OF ISAAC WIND UP. ECMWF WANTS TO HOLD THE TROUGH ACROSS TENNESSEE AND ALABAMA AREA...WHILE THE GFS PUSHES THE REMNANT TROUGH EASTWARD. IN GENERAL THERE SEEMS TO BE NO CHANGE IN AIR MASS FOR THE CWA THROUGH THE PERIOD. HAVE CONTINUED WITH MOSTLY CHANCE POPS...REDUCING TO SLIGHT CHANCE BY THE END OF THE FORECAST WHERE THE GFS HINTED AT SOME POSSIBLE DRYING. TEMPERATURES DEPEND ON AMOUNT OF CLOUDS AND RAIN...SO HAVE TWEAKED THEM DOWN A BIT TO MID 80S TO LOW 90S. 41 && .AVIATION... 18Z UPDATE... MVFR CIGS ARE EXPECTED TO PERSIST THROUGH AT LEAST 20-21Z TODAY AS PATCHY -RA/SPOTTY -SHRA`S CONTINUE TO DEVELOP AND MOVE ACROSS THE TAF SITES THIS AFTN-EVNG. EXPECT THE GREATER TSRA THREAT TO REMAIN OVER AL... SO WILL ONLY SHOW -RA/-SHRA THRU 02Z... THEN VCSH THRU 06-07Z TNGT. IFR CIGS SHOULD SETTLE BACK IN OVER THE TAF SITES BY 07-09Z TNGT WITH A SLOW IMPROVEMENT TO MVFR BY 15-16Z...THEN VFR BY 19-20Z FRI. THINKING ONLY LOW SCATTERED CONVECTIVE CONVERGE ON FRI... SO WILL ONLY SHOW VCSH BEGINNING AT 16Z FRI FOR NOW. WINDS WILL FROM THE SSE AROUND 10KTS THIS AFTN... DIMINISHING TO AROUND 4-6KTS AND BECOMING MORE ESE THIS EVENING...THEN SE AROUND 8-10KTS ON FRI. //ATL CONFIDENCE...18Z UPDATE... MODERATE CONFIDENCE ON TIMING/LOCATION OF SHRA THIS AFTN-EVNG. HIGH CONFIDENCE ON ALL OTHER ELEMENTS. 39 && .PRELIMINARY POINT TEMPS/POPS... ATHENS 84 70 88 70 / 50 20 30 20 ATLANTA 83 71 85 73 / 60 40 30 20 BLAIRSVILLE 81 66 82 67 / 40 20 40 20 CARTERSVILLE 85 71 85 70 / 50 30 30 20 COLUMBUS 87 73 89 73 / 60 30 30 20 GAINESVILLE 84 71 86 71 / 50 20 30 20 MACON 86 72 89 72 / 60 40 30 20 ROME 87 71 88 70 / 50 30 40 20 PEACHTREE CITY 84 71 86 70 / 60 40 40 20 VIDALIA 88 73 89 73 / 40 40 30 20 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...SNELSON LONG TERM....41 AVIATION...SNELSON
AREA FORECAST DISCUSSION...UPDATE
NWS PEACHTREE CITY GA
1102 AM EDT THU AUG 30 2012 .UPDATE... MORNING SOUNDING SHOWS DEEP TROPICAL MOISTURE IN-PLACE WITH 2.17 PW`S AND A MODERATELY STABLE MOIST ADIABATIC PROFILE. THE HRRR AND NAM MODELS SHOW WIDESPREAD CONVECTION DEVELOPING ACROSS MUCH OF THE FORECAST AREA TODAY. AS A RESULT... EXPECTING SCATTERED TO OCCASIONALLY NUMEROUS SHOWERS TO SPREAD UP FROM THE SW DURING DAYTIME HEATING... WITH THE HIGHER POPS WARRANTED FROM CARROLLTON TO ATLANTA DOWN TO MACON AND COLUMBUS AREAS. CLOUDS AND MAINLY SHOWERS WILL HOLD TEMPS AND INSTABILITIES DOWN TO MODEST LEVELS... SO WILL SHOW MAINLY SHOWERS TODAY... WITH ONLY AN ISOLATED THUNDER THREAT THROUGH THE AFTERNOON WHERE THE HIGHER POPS ARE SHOWN. WILL UPDATE ZONES TO REFLECT THESE NEW EXPECTATIONS. OTHERWISE... THE REST OF FORECAST LOOKS ON TRACK AT THIS TIME. && .PREV DISCUSSION... /ISSUED 431 AM EDT THU AUG 30 2012/ SHORT TERM /TODAY THROUGH FRIDAY/... CONCERN THIS FCST IS TIMING OF SHRA THIS MORNING AND LIKELIHOOD OF TSRA THIS AFTERNOON. MODELS IN PRETTY GOOD AGREEMENT THAT WARM/MOIST ADVECTION ASSOCIATED WITH H8 SOUTHERLY FLOW EAST OF ISAAC AND LOW/MID LEVEL DEFORMATION ZONE OVER NORTH GA WILL COMMENCE THIS MORNING. RECENT HRRR RUNS DO A NICE JOB PORTRAYING STRATIFORM PRECIP DEVELOPING OVER MIDDLE GA EARLY THIS MORNING AND IS SIMILAR TO LARGER SCALE MODELS SUCH AS THE NAM...GFS AND SREF. HAVE UPDATED GRIDS TO SHOW A LITTLE HIGHER POP IN THE MORNING. IN THE AFTERNOON ..SHOULD SEE A BRIEF LULL FOLLOWED BY ADDITIONAL SHRA/TSRA AFTER 2PM. AMOUNT AND INTENSITY OF TSRA DEPENDS ON HOW MUCH INSOLATION WE CAN GET. GOT A LITTLE MORE TSRA THAN EXPECTED YESTERDAY AND A FEW CELLS APPROACHED SVR...HOWEVER EXPECT COOLER TEMPS AND MORE CLOUDS THIS AFTERNOON THAN YESTERDAY RESULTING IN CAPE ONLY AT MOST 1000 J/KG. PRECIP SHOULD END QUICKLY THIS EVENING AS WAA PATTERN DISSIPATES AND SOLAR INSOLATION ENDS. NOT AS FAVORABLE A PATTERN FOR PRECIP FRIDAY BUT STILL HAVE SLT CHC BECOMING CHC SHRA/TSRA IN THE AFTERNOON. MOISTURE FROM ISAAC WILL BE DIFFICULT TO FULLY CLEAR OUT ANYTIME SOON. AS UPPER RIDGE BUILDS AROUND THE SOUTHEAST CONUS...TEMPS SHOULD WARM CONSIDERABLY INTO THE UPPER 80S AND LOWER 90S BUT ABUNDANT MOISTURE WILL HELP KEEP CLOUDS AND AFTERNOON CONVECTION GOING. SNELSON LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... MODELS IN GOOD AGREEMENT ON TAKING ISAAC NORTHWEST AND LOOPING IT BACK ACROSS THE OHIO AND TENNESSEE VALLEYS BY SUNDAY. BEYOND THAT TIME...NOT SO CLEAR WHERE THE REMNANTS OF ISAAC WIND UP. ECMWF WANTS TO HOLD THE TROUGH ACROSS TENNESSEE AND ALABAMA AREA...WHILE THE GFS PUSHES THE REMNANT TROUGH EASTWARD. IN GENERAL THERE SEEMS TO BE NO CHANGE IN AIR MASS FOR THE CWA THROUGH THE PERIOD. HAVE CONTINUED WITH MOSTLY CHANCE POPS...REDUCING TO SLIGHT CHANCE BY THE END OF THE FORECAST WHERE THE GFS HINTED AT SOME POSSIBLE DRYING. TEMPERATURES DEPEND ON AMOUNT OF CLOUDS AND RAIN...SO HAVE TWEAKED THEM DOWN A BIT TO MID 80S TO LOW 90S. 41 && .AVIATION... 12Z UPDATE... IFR CIGS AT MOST LOCATIONS WILL LIFT TO MVFR AROUND 14Z. HAVE REMOVED RA THIS MORNING IN FAVOR OF VCSH AFTER 16Z AND PREVAILING SHRA 19Z-00Z. ALSO DROPPED TSRA IN FCST DUE TO INSUFFICIENT PROBABILITY THIS AFTERNOON. IF WE SEE MORE BREAKS IN THE CLOUDS TODAY THAN EXPECTED...WILL HAVE TO UPDATE THIS. EAST SFC WINDS THROUGH AT LEAST 12Z FRI. //ATL CONFIDENCE...12Z UPDATE... MODERATE CONFIDENCE ON TSRA LIKELIHOOD AND TIMING/LIKELIHOOD OF SHRA TODAY. HIGH CONFIDENCE ON ALL OTHER ELEMENTS. SNELSON && .PRELIMINARY POINT TEMPS/POPS... ATHENS 84 70 88 70 / 50 20 30 20 ATLANTA 83 71 85 73 / 60 40 30 20 BLAIRSVILLE 81 66 82 67 / 40 20 40 20 CARTERSVILLE 85 71 85 70 / 50 30 30 20 COLUMBUS 87 73 89 73 / 60 30 30 20 GAINESVILLE 84 71 86 71 / 50 20 30 20 MACON 86 72 89 72 / 60 40 30 20 ROME 87 71 88 70 / 50 30 40 20 PEACHTREE CITY 84 71 86 70 / 60 40 40 20 VIDALIA 88 73 89 73 / 40 40 30 20 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...SNELSON LONG TERM....41 AVIATION...SNELSON
AREA FORECAST DISCUSSION
NWS PEACHTREE CITY GA
742 AM EDT THU AUG 30 2012 .UPDATE... QUICK UPDATE TO DECREASE POPS FOR THE MORNING HOURS. 06Z MODEL RUNS HINTING AT LACK OF LIFT UNTIL AFTER 15Z WHEN NEARLY ALL MODELS INDICATING DECENT QPF /0.10-0.25 INCH/ BY 18Z IN NORTH GA. ALSO DROPPED TSRA PROBS TO CHC WITH 50-70 POPS FOR SHRA THIS AFTERNOON. REST OF FCST LOOKS GOOD. SNELSON && .PREV DISCUSSION... /ISSUED 431 AM EDT THU AUG 30 2012/ SHORT TERM /TODAY THROUGH FRIDAY/... CONCERN THIS FCST IS TIMING OF SHRA THIS MORNING AND LIKELIHOOD OF TSRA THIS AFTERNOON. MODELS IN PRETTY GOOD AGREEMENT THAT WARM/MOIST ADVECTION ASSOCIATED WITH H8 SOUTHERLY FLOW EAST OF ISAAC AND LOW/MID LEVEL DEFORMATION ZONE OVER NORTH GA WILL COMMENCE THIS MORNING. RECENT HRRR RUNS DO A NICE JOB PORTRAYING STRATIFORM PRECIP DEVELOPING OVER MIDDLE GA EARLY THIS MORNING AND IS SIMILAR TO LARGER SCALE MODELS SUCH AS THE NAM...GFS AND SREF. HAVE UPDATED GRIDS TO SHOW A LITTLE HIGHER POP IN THE MORNING. IN THE AFTERNOON ..SHOULD SEE A BRIEF LULL FOLLOWED BY ADDITIONAL SHRA/TSRA AFTER 2PM. AMOUNT AND INTENSITY OF TSRA DEPENDS ON HOW MUCH INSOLATION WE CAN GET. GOT A LITTLE MORE TSRA THAN EXPECTED YESTERDAY AND A FEW CELLS APPROACHED SVR...HOWEVER EXPECT COOLER TEMPS AND MORE CLOUDS THIS AFTERNOON THAN YESTERDAY RESULTING IN CAPE ONLY AT MOST 1000 J/KG. PRECIP SHOULD END QUICKLY THIS EVENING AS WAA PATTERN DISSIPATES AND SOLAR INSOLATION ENDS. NOT AS FAVORABLE A PATTERN FOR PRECIP FRIDAY BUT STILL HAVE SLT CHC BECOMING CHC SHRA/TSRA IN THE AFTERNOON. MOISTURE FROM ISAAC WILL BE DIFFICULT TO FULLY CLEAR OUT ANYTIME SOON. AS UPPER RIDGE BUILDS AROUND THE SOUTHEAST CONUS...TEMPS SHOULD WARM CONSIDERABLY INTO THE UPPER 80S AND LOWER 90S BUT ABUNDANT MOISTURE WILL HELP KEEP CLOUDS AND AFTERNOON CONVECTION GOING. SNELSON LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... MODELS IN GOOD AGREEMENT ON TAKING ISAAC NORTHWEST AND LOOPING IT BACK ACROSS THE OHIO AND TENNESSEE VALLEYS BY SUNDAY. BEYOND THAT TIME...NOT SO CLEAR WHERE THE REMNANTS OF ISAAC WIND UP. ECMWF WANTS TO HOLD THE TROUGH ACROSS TENNESSEE AND ALABAMA AREA...WHILE THE GFS PUSHES THE REMNANT TROUGH EASTWARD. IN GENERAL THERE SEEMS TO BE NO CHANGE IN AIR MASS FOR THE CWA THROUGH THE PERIOD. HAVE CONTINUED WITH MOSTLY CHANCE POPS...REDUCING TO SLIGHT CHANCE BY THE END OF THE FORECAST WHERE THE GFS HINTED AT SOME POSSIBLE DRYING. TEMPERATURES DEPEND ON AMOUNT OF CLOUDS AND RAIN...SO HAVE TWEAKED THEM DOWN A BIT TO MID 80S TO LOW 90S. 41 && .AVIATION... 12Z UPDATE... IFR CIGS AT MOST LOCATIONS WILL LIFT TO MVFR AROUND 14Z. HAVE REMOVED RA THIS MORNING IN FAVOR OF VCSH AFTER 16Z AND PREVAILING SHRA 19Z-00Z. ALSO DROPPED TSRA IN FCST DUE TO INSUFFICIENT PROBABILITY THIS AFTERNOON. IF WE SEE MORE BREAKS IN THE CLOUDS TODAY THAN EXPECTED...WILL HAVE TO UPDATE THIS. EAST SFC WINDS THROUGH AT LEAST 12Z FRI. //ATL CONFIDENCE...12Z UPDATE... MODERATE CONFIDENCE ON TSRA LIKELIHOOD AND TIMING/LIKELIHOOD OF SHRA TODAY. HIGH CONFIDENCE ON ALL OTHER ELEMENTS. SNELSON && .PRELIMINARY POINT TEMPS/POPS... ATHENS 84 70 88 70 / 50 20 30 20 ATLANTA 83 71 85 73 / 60 40 30 20 BLAIRSVILLE 81 66 82 67 / 40 20 40 20 CARTERSVILLE 85 71 85 70 / 50 30 30 20 COLUMBUS 87 73 89 73 / 60 30 30 20 GAINESVILLE 84 71 86 71 / 50 20 30 20 MACON 86 72 89 72 / 60 40 30 20 ROME 87 71 88 70 / 50 30 40 20 PEACHTREE CITY 84 71 86 70 / 60 40 40 20 VIDALIA 88 73 89 73 / 40 40 30 20 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...SNELSON LONG TERM....41 AVIATION...SNELSON
AREA FORECAST DISCUSSION
NWS PEACHTREE CITY GA
431 AM EDT THU AUG 30 2012 .SHORT TERM /TODAY THROUGH FRIDAY/... CONCERN THIS FCST IS TIMING OF SHRA THIS MORNING AND LIKELIHOOD OF TSRA THIS AFTERNOON. MODELS IN PRETTY GOOD AGREEMENT THAT WARM/MOIST ADVECTION ASSOCIATED WITH H8 SOUTHERLY FLOW EAST OF ISAAC AND LOW/MID LEVEL DEFORMATION ZONE OVER NORTH GA WILL COMMENCE THIS MORNING. RECENT HRRR RUNS DO A NICE JOB PORTRAYING STRATIFORM PRECIP DEVELOPING OVER MIDDLE GA EARLY THIS MORNING AND IS SIMILAR TO LARGER SCALE MODELS SUCH AS THE NAM...GFS AND SREF. HAVE UPDATED GRIDS TO SHOW A LITTLE HIGHER POP IN THE MORNING. IN THE AFTERNOON ...SHOULD SEE A BRIEF LULL FOLLOWED BY ADDITIONAL SHRA/TSRA AFTER 2PM. AMOUNT AND INTENSITY OF TSRA DEPENDS ON HOW MUCH INSOLATION WE CAN GET. GOT A LITTLE MORE TSRA THAN EXPECTED YESTERDAY AND A FEW CELLS APPROACHED SVR...HOWEVER EXPECT COOLER TEMPS AND MORE CLOUDS THIS AFTERNOON THAN YESTERDAY RESULTING IN CAPE ONLY AT MOST 1000 J/KG. PRECIP SHOULD END QUICKLY THIS EVENING AS WAA PATTERN DISSIPATES AND SOLAR INSOLATION ENDS. NOT AS FAVORABLE A PATTERN FOR PRECIP FRIDAY BUT STILL HAVE SLT CHC BECOMING CHC SHRA/TSRA IN THE AFTERNOON. MOISTURE FROM ISAAC WILL BE DIFFICULT TO FULLY CLEAR OUT ANYTIME SOON. AS UPPER RIDGE BUILDS AROUND THE SOUTHEAST CONUS...TEMPS SHOULD WARM CONSIDERABLY INTO THE UPPER 80S AND LOWER 90S BUT ABUNDANT MOISTURE WILL HELP KEEP CLOUDS AND AFTERNOON CONVECTION GOING. SNELSON .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... MODELS IN GOOD AGREEMENT ON TAKING ISAAC NORTHWEST AND LOOPING IT BACK ACROSS THE OHIO AND TENNESSEE VALLEYS BY SUNDAY. BEYOND THAT TIME...NOT SO CLEAR WHERE THE REMNANTS OF ISAAC WIND UP. ECMWF WANTS TO HOLD THE TROUGH ACROSS TENNESSEE AND ALABAMA AREA...WHILE THE GFS PUSHES THE REMNANT TROUGH EASTWARD. IN GENERAL THERE SEEMS TO BE NO CHANGE IN AIR MASS FOR THE CWA THROUGH THE PERIOD. HAVE CONTINUED WITH MOSTLY CHANCE POPS...REDUCING TO SLIGHT CHANCE BY THE END OF THE FORECAST WHERE THE GFS HINTED AT SOME POSSIBLE DRYING. TEMPERATURES DEPEND ON AMOUNT OF CLOUDS AND RAIN...SO HAVE TWEAKED THEM DOWN A BIT TO MID 80S TO LOW 90S. 41 && AVIATION... 06Z UPDATE... PRIMARY CONCERN IS IFR CIGS THIS MORNING AND SHRA/TSRA THIS AFTERNOON. DEWPOINT DEPRESSIONS PRETTY LOW IFR CIGS HAVE FORMED ALREADY IN SEVERAL LOCATIONS INCLUDING KATL. HAVE CONTINUED THIS IN FCST THRU 14Z. SHRA LIKELY THIS AFTERNOON DUE TO RICH MOISTURE AND UPWARD MOTION. TSRA NOT AS LIKELY AS YESTERDAY DUE TO LESS INSTABILITY. HAVE CONTINUED PROB30 FOR TSRA 19Z-00Z BUT MAY REMOVE THIS IN LATER UPDATES IF DATA CONTINUES TO SHOW LIMITED POTENTIAL FOR TSRA. EAST SFC WINDS THROUGH THE FORECAST TO CONTINUE. //ATL CONFIDENCE...06Z UPDATE... MODERATE CONFIDENCE ON TSRA LIKELIHOOD. HIGH CONFIDENCE ON ALL OTHER ELEMENTS. SNELSON && .PRELIMINARY POINT TEMPS/POPS... ATHENS 84 70 88 70 / 60 20 30 20 ATLANTA 83 71 85 73 / 60 40 30 20 BLAIRSVILLE 81 66 82 67 / 40 20 40 20 CARTERSVILLE 85 71 85 70 / 60 40 30 20 COLUMBUS 87 73 89 73 / 60 30 30 20 GAINESVILLE 84 71 86 71 / 60 20 30 20 MACON 86 72 89 72 / 60 40 30 20 ROME 87 71 88 70 / 60 30 40 20 PEACHTREE CITY 84 71 86 70 / 60 40 40 20 VIDALIA 88 73 89 73 / 40 50 30 20 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...SNELSON LONG TERM....41 AVIATION...SNELSON
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
513 PM CDT FRI AUG 31 2012 .DISCUSSION... 349 PM CDT MAIN FORECAST CONCERNS THIS FORECAST PERIOD REVOLVE AROUND PRECIP CHANCES AND TRENDS...POSSIBLE HEAVY AT TIMES...THIS WEEKEND INTO THE START OF NEXT WEEK AS REMNANTS OF TROPICAL STORM ISAAC WORK ITS WAY NORTH ACROSS THE REGION. IN THE NEAR TERM...LATEST SATELLITE IMAGERY DEPICTING EXPANSIVE AREA OF MID AND HIGH LEVEL CLOUD COVER CONTINUING TO SPREAD NORTHWARD ACROSS MUCH OF THE REGION AS THIS SYSTEM SLOWLY MOVES NORTH. DESPITE AN INCREASE IN CLOUD COVER TODAY...MOSTLY SUNNY TO PARTLY CLOUDY SKIES HAVE BEEN OBSERVED WITH TEMPERATURES RISING TO THE LOWER 90S ACROSS NORTHERN ILLINOIS AND MID TO UPPER 80S ACROSS AREAS SOUTH OF INTERSTATE 80. DESPITE LATEST RADAR IMAGERY SHOWING SOME WEAK RETURNS FROM THE OUTER BANDS OF THIS SYSTEM ACROSS AREAS FROM PONTIAC IN ILLINOIS EAST TO FOWLER IN INDIANA...MOST OF THIS IS NOT REACHING THE GROUND. SOME DRIER AIR IS HELPING WITH THIS BUT WITH A VERY MOIST AIRMASS ON ITS WAY...IT SHOULDNT TAKE MUCH LONGER THIS EVENING BEFORE IT STARTS REACHING THE GROUND. OUTSIDE OF THIS SYSTEM TO THE SOUTH...A COLD FRONT HAS BEEN DROPPING SOUTH THROUGH PORTIONS OF WISCONSIN TODAY. ALTHOUGH...EXPECT THIS FRONT TO LOSE ITS SOUTHWARD MOMENTUM THIS EVENING AND THEN BECOME MORE DIFFUSE AS THE SYSTEM TO THE SOUTH MOVES INTO THE AREA. DESPITE THIS FRONT ACROSS THE REGION...ANY VERTICAL DEVELOPMENT HAS BEEN LIMITED AND IS EXPECTED TO REMAIN THIS WAY AS A MORE SUBSIDENT LARGE SCALE ENVIRONMENT REMAINS OVER THIS BOUNDARY. SHIFTING TOWARD MAIN FOCUS OF THIS FORECAST PERIOD...REMNANTS OF TROPICAL STORM ISAAC CONTINUE TO SLOWLY SHIFT NORTH THROUGH MISSOURI THIS AFTERNOON. THIS SYSTEM IS MARKED WITH A VERY MOIST ENVIRONMENT...OR A TROPICAL ENVIRONMENT. COPIOUS AMOUNTS OF MOISTURE WITH 12Z SOUNDINGS ACROSS MISSOURI INDICATING PWATS AROUND 2.4 INCHES THIS MORNING...AND LATEST RUC ANALYSIS SHOWING THIS AXIS OF HIGHER PWATS EXTENDING FROM THE ST. LOUIS AREA BACK SOUTH THROUGH MISSOURI INTO ARKANSAS. WITH A SLOW MOVEMENT OF THIS SYSTEM TONIGHT...THIS AXIS OF HIGHEST MOISTURE WILL ALSO SHIFT SLOWLY. NONETHELESS...THESE OUTWARD BANDS OF THIS SYSTEM AND HIGHER MOISTURE CONTENT AIR WILL LIFT NORTH OVERNIGHT. THIS SHOULD HELP BRING SHOWERS ACROSS THE SOUTHERN CWA PRIMARILY FOR AREAS ALONG AND SOUTH OF A LINE FROM PONTIAC IN ILLINOIS TO RENSSELAER IN INDIANA. HEAVIER DOWNPOURS ARE NOT EXPECTED TONIGHT AS WELL AS ANY THUNDER. DESPITE SOME INSTABILITY IN PLACE...THESE INITIAL SHOWERS WILL BE WEAKLY FORCED. ITS NOT UNTIL SATURDAY THROUGH THE REMAINDER OF THE WEEKEND THAT THE MAIN AXIS OF HIGHEST MOISTURE AND RAINFALL WILL REACH THE CWA. WITH BETTER FORCING WITH THIS SYSTEM SHIFTING NORTH AND SREF GUIDANCE INDICATING THAT THE AXIS OF HIGHER PWATS/MUCH HIGHER DEWPOINT AIR WILL REACH THE SOUTHERN CWA...THE POTENTIAL FOR HEAVIER RAIN WILL INCREASE. DESPITE SOME MODEL VARIABILITY WITH THE OVERALL EVOLUTION OF THIS SYSTEM...CONFIDENCE IS HIGH FOR AREAS ALONG AND SOUTH OF INTERSTATE 80 TO RECEIVE THE HIGHEST AMOUNTS OF RAIN THIS WEEKEND. WHERE CONFIDENCE IS LOWER AT THIS TIME IS IN REGARDS TO HOW FAR NORTH THIS RAIN WILL WORK ITS WAY NORTH. AS A FAIRLY TIGHT GRADIENT IS EXPECTED WITH THIS PRECIP SHIELD THIS WEEKEND...HAVE TRIED TO CONVEY THIS AS BEST AS POSSIBLE IN THE GRIDS. IF THIS SYSTEM WERE TO SHIFT NORTHWARD THAN PREVIOUSLY THOUGHT...THEN THIS AXIS OF RAINFALL WOULD OF COURSE SHIFT NORTH ACROSS THE CWA. AT THIS POINT IT APPEARS THAT A DRASTIC CUTOFF IN PRECIP SHOULD OCCUR AROUND THE I88 CORRIDOR. IN ALL AREAS ACROSS OUR CWA ARE EXPECTED TO RECEIVE A LARGE AMOUNT OF RAINFALL THROUGH SUNDAY NIGHT...WITH THE POTENTIAL FOR AMOUNTS OF 4 TO 5 INCHES OR GREATER ALONG AND SOUTH OF A LINE FROM THE PONTIAC AREA TO THE RENSSELAER AREA. MOVING NORTH OF THIS LINE...RAINFALL AMOUNTS ARE EXPECTED TO TAPER FROM AROUND 3 TO 4 INCHES TO AROUND 1 INCH JUST NORTH OF THE INTERSTATE 80 CORRIDOR. EXPECTED AMOUNTS ALONG THE INTERSTATE 88 CORRIDOR WILL ROUGHLY RANGE FROM THREE QUARTERS OF AN INCH UP TO ONE INCH...WITH THE POTENTIAL FOR LITTLE OR NO RAIN IN THE COUNTIES BORDERING WISCONSIN...GENERALLY UNDER A QUARTER INCH. NO HEADLINES AT THIS TIME BUT WILL CONTINUE THE ESF TODAY. RODRIGUEZ && .HYDROLOGY... 427 PM CDT EXPECTED RAINFALL AND POTENTIAL FOR HEAVY RAINFALL...POTENTIALLY FOR PERIODS OF TIME...ACROSS PORTIONS OF THE CWA STILL ON TRACK LATE TONIGHT THROUGH THE END OF THE WEEKEND. LATEST OBSERVATIONAL DATA STILL INDICATING A GOOD SWATH OF MOISTURE JUST SOUTH OF THE CWA THIS AFTERNOON...WITH LATEST GUIDANCE INDICATING THIS HIGHER MOISTURE CONTENT AIR TO CONTINUE SPREADING NORTHWARD TONIGHT INTO SATURDAY. AS THIS SLUG OF MOISTURE MOVES ACROSS THE CWA EARLY SATURDAY...IT WILL THEN LINGERING THROUGH THE REMAINDER OF THE WEEKEND. ALTHOUGH...LATEST GUIDANCE CONTINUES TO INDICATE THAT THE HIGHEST RAIN RATES/RAINFALL SHOULD STAY ACROSS THE SOUTHERN CWA WHICH SEEMS TO BE ON TRACK. THE POTENTIAL FOR RAINFALL AMOUNTS OF 4 TO 5 INCHES OR GREATER ALONG AND SOUTH OF A LINE FROM THE PONTIAC AREA TO THE RENSSELAER AREA SEEM TO BE ON TRACK FOR THIS WEEKEND. MOVING NORTH OF THIS LINE...RAINFALL AMOUNTS ARE EXPECTED TO TAPER FROM AROUND 3 TO 4 INCHES TO AROUND 1 INCH JUST NORTH OF THE INTERSTATE 80 CORRIDOR. EXPECTED AMOUNTS ALONG THE INTERSTATE 88 CORRIDOR WILL ROUGHLY RANGE FROM THREE QUARTERS OF AN INCH UP TO ONE INCH...WITH THE POTENTIAL FOR LITTLE OR NO RAIN IN THE COUNTIES BORDERING WISCONSIN...GENERALLY UNDER A QUARTER INCH. DESPITE THE EXPECTED HIGHER RAINFALL THIS WEEKEND...ONLY MINOR RISES IN AREAS RIVERS ARE EXPECTED WITH NO MAJOR PROBLEMS EXPECTED AT THIS TIME. A WORST CASE SCENARIO AT THIS TIME BASED ON CURRENT FORECASTS WOULD BE FOR RIVERS THAT RECEIVE THESE HIGHER AMOUNTS TO RISE TO MINOR OR JUST ABOVE MODERATE STAGES. ALTHOUGH WOULD LIKE TO REITERATE SOME UNCERTAINTY WITH THIS SYSTEMS OVERALL EVOLUTION...THAT EXTENDS INTO THE POTENTIAL RISES. WITH THIS IN MIND...THIS SITUATION NEEDS TO CONTINUE TO BE CLOSELY MONITORED THIS WEEKEND AS IT WOULD NOT BE OUT OF THE QUESTION FOR LOCALIZED AREAS OF HIGHER AMOUNTS AND THUS POSSIBLE HIGHER RISES. SOMETHING ELSE TO KEEP IN MIND THIS WEEKEND IS THE OVERALL SOIL CONDITIONS ACROSS THE AREA. WITH A DRY/HARD SOIL IN PLACE...IT WOULD NOT TAKE MUCH TIME FOR HIGH RAINFALL RATES TO QUICKLY TURN INTO RUNOFF. ONCE AGAIN...HAVE NOT ISSUED ANY FLOOD HEADLINES AT THIS TIME. ALTHOUGH...CONTINUE TO MONITOR LATEST UPDATES THIS WEEKEND AS THIS COMPLEX SYSTEM UNFOLDS ACROSS THE REGION. RODRIGUEZ && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 22Z... * TIMING WIND SHIFT FROM SW TO NE AS FRONTAL BOUNDARY SAGS SOUTH ACROSS THE TERMINALS. * TIMING ONSET OF RAINFALL SAT. BEACHLER //DISCUSSION...UPDATED 18Z... MODERATE SW-WSW LOW LEVEL FLOW HAS BEEN MIXING DOWN TO THE SURFACE WITH THE SKC CONDITIONS ALLOWING MAXIMUM HEATING THROUGH MIDDAY RESULTING IN SOME GUSTS IN THE 15-20KT RANGE THIS MORNING. OUTER EDGE OF CLOUD SHIELD OF THE T.D. CENTERED OVER SW MO HAVE SPREAD TO THE WI BORDER BY EARLY AFTERNOON WITH THICKER CIRRUS STRATUS TO SPREAD ACROSS THE LOCAL AREA DURING THE MID TO LATE AFTERNOON. WITH THICKENING HIGH CLOUDS ADDITIONAL INSOLATION WILL BE DECREASING THIS AFTERNOON...AND AS THE COLD FRONT ACROSS SOUTHERN WI CONTINUES TO CREEP SOUTHWARD THE SURFACE PRESSURE GRADIENT SLACKENS DURING THE AFTERNOON. WITH DECREASE IN BOTH SURFACE HEATING AND IN SURFACE PRESSURE GRADIENT SW-WSW WINDS WILL LOSE ANY MARGINAL GUSTS AND SETTLE TO SUSTAINED 10-12KT TIL DUSK. THE COLD FRONT IS SHOWN BY MODELS TO CROSS INTO FAR NORTHERN IL LATE THIS AFTERNOON AND EARLY THIS EVENING RESULTING IN A WIND SHIFT TO OUT OF THE NE-E AT 6-10KT. MODELS OFFERING SIMILAR SOLUTIONS ON LARGE SCALE BUT DIFFERENCES IN TIMING AND TRACK OF THE LOW OUT OF CENTRAL MO TO TO W CENTRAL IL SAT AND SAT NIGHT STILL LEAVES QUESTIONS ABOUT HOW FAR N THE RAIN WILL SPREAD AND HOW SOON IT WILL ARRIVE IN THE LOCAL AREA. TREND OF MODELS HAS BEEN SLOWER AND A BIT FURTHER S OF PREVIOUS FORECAST TRACKS. THIS DELAYS ARRIVAL OF ONSET OF RA AND KEEPS HEAVIER RAIN S OF ORD AND MDW. LOWER DEW POINT AIR BEHIND THE SLUGGISH COLD FRONT WILL BE ADVECTED OVER THE LOCAL TERMINALS ON NE-E LOW LEVEL WINDS BECOMING MODERATE TONIGHT BETWEEN HIGH PRESSURE BUILDING INTO THE UPPER GREAT LAKES AND THE LOW RIDGE BETWEEN THE MO LOW. SLIGHTLY MORE SOUTHWARD TRACK OF THE LOW AS IT MOVES INTO CENTRAL IL SUN AND INFLUX OF LOWER LOW LEVEL POINTS IS EXPECTED TO DELAY AND SIGNIFICANT THREAT OF SHRA/RA TIL LATER MORNING-EARLY AFTERNOON ON SAT...THEN PERSISTING THROUGH THE DAY. WITH HEAVER RAIN OCCURRING TO THE S OF THE TERMINALS AND THE FEED LOW DRIER LOW LEVEL AIR EXPECT VFR CONDITIONS TO PREVAIL LOCALLY THOUGH MAY BE AREAS MVFR BY MID-LATE SAT AFTERNOON. TRS //ORD AND MDW CONFIDENCE...UPDATED 22Z... * HIGH CONFIDENCE IN WIND SPEED. * MEDIUM/HIGH CONFIDENCE IN WIND SHIFT FROM SW TO NE. * MODERATE CONFIDENCE IN TIMING OF THE COLD FRONT PASSAGE THIS EVENING AND THE ACCOMPANYING WIND SHIFT. * HIGH CONFIDENCE IN VFR AND DRY CONDITIONS THROUGH THE NIGHT AND EARLY SAT MORNING. * MODERATE CONFIDENCE IN PREVAILING VFR CONTINUING FROM MID SAT MORNING ON WITH ONLY AREAS/OCCASIONAL MVFR. BEACHLER //OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z... SATURDAY NIGHT... SUNDAY...CHC OF RA/SHRA. MVFR/IFR POSSIBLE. MONDAY...SLGT CHC SHRA/TSRA. MVFR POSSIBLE. TUESDAY...VFR. WEDNESDAY...VFR. THURSDAY...CHC SHRA/TSRA. OTHERWISE VFR. RATZER && .MARINE... 351 PM CDT A COLD FRONT IS SLOWLY SINKING SOUTH ALONG LAKE MICHIGAN AND IS CURRENTLY LOCATED FROM THE WI/IL STATE LINE THROUGH MUSKEGON. THE FRONT WILL REACH SOUTHERN LAKE MICHIGAN THIS EVENING WITH WINDS TURNING NORTH TO NORTHEAST AND GUSTING TO AROUND 20 KT. WINDS WILL DIMINISH TO 10 TO 15 KT BEHIND THE FRONT AND VEER TO THE EAST BY SATURDAY MORNING OVER THE SOUTHERN HALF OF THE LAKE. WINDS WILL BE EAST ALONG THE ENTIRE LAKE BY SATURDAY NIGHT. THE PERSISTENT EASTERLY FLOW WILL RESULT IN LOCALLY HIGHER WAVES ALONG THE SOUTHERN WI AND IL COAST LINE OF 5 TO 8 FT BY SUNDAY AFTERNOON. WAVES IN THE IL NEARSHORE ZONES LOOK LIKE THEY WILL STAY JUST BELOW SMALL CRAFT ADVISORY CRITERIA...THEREFORE WILL REFRAIN FROM ISSUING A SCY NOW. HOWEVER...THE HIGHER WAVES AND ONSHORE FLOW ALONG THE IL NEARSHORE ZONES DO POSE AN INCREASED RIP CURRENT RISK. THE RISK ALSO IS INCREASED BY THE FACT THERE WILL PROBABLY BE AN ABOVE AVERAGE NUMBER OF SWIMMERS AT THE BEACH THIS HOLIDAY WEEKEND. ISSUED A RIP CURRENT STATEMENT FOR THE IL SIDE OF THE LAKE SATURDAY MORNING THROUGH SUNDAY EVENING. HIGH PRESSURE SPREADS ACROSS THE WESTERN GREAT LAKES TONIGHT. MEANWHILE LOW PRESSURE THAT WAS FORMALLY HURRICANE ISAAC IS MOVING NORTHWARD. THE PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS WILL TIGHTEN OVER SOUTHERN LAKE MICHIGAN. THEREFORE EAST WINDS WILL BE STRONGER OVER THE SOUTHERN HALF OF THE LAKE. THE LOW WILL ENTER SOUTH CENTRAL IL LATE SATURDAY AFTERNOON AND THEN TURN EASTWARD PASSING SOUTH OF LAKE MICHIGAN. HIGH PRESSURE MOVES OVER THE LAKE MONDAY NIGHT WITH WINDS WEAKENING ACROSS THE LAKE. ANOTHER TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST MID NEXT WEEK BUT CONFIDENCE IS LOW ON THE EXACT TIMING OF THIS SYSTEM DUE TO GUIDANCE INCONSISTENCIES. JEE && .LOT WATCHES/WARNINGS/ADVISORIES... IL...HIGH RIP CURRENT RISK...ILZ006-ILZ014...10 AM SATURDAY TO 7 PM SUNDAY. IN...NONE. LM...NONE. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
429 PM CDT FRI AUG 31 2012 .DISCUSSION... 349 PM CDT MAIN FORECAST CONCERNS THIS FORECAST PERIOD REVOLVE AROUND PRECIP CHANCES AND TRENDS...POSSIBLE HEAVY AT TIMES...THIS WEEKEND INTO THE START OF NEXT WEEK AS REMNANTS OF TROPICAL STORM ISAAC WORK ITS WAY NORTH ACROSS THE REGION. IN THE NEAR TERM...LATEST SATELLITE IMAGERY DEPICTING EXPANSIVE AREA OF MID AND HIGH LEVEL CLOUD COVER CONTINUING TO SPREAD NORTHWARD ACROSS MUCH OF THE REGION AS THIS SYSTEM SLOWLY MOVES NORTH. DESPITE AN INCREASE IN CLOUD COVER TODAY...MOSTLY SUNNY TO PARTLY CLOUDY SKIES HAVE BEEN OBSERVED WITH TEMPERATURES RISING TO THE LOWER 90S ACROSS NORTHERN ILLINOIS AND MID TO UPPER 80S ACROSS AREAS SOUTH OF INTERSTATE 80. DESPITE LATEST RADAR IMAGERY SHOWING SOME WEAK RETURNS FROM THE OUTER BANDS OF THIS SYSTEM ACROSS AREAS FROM PONTIAC IN ILLINOIS EAST TO FOWLER IN INDIANA...MOST OF THIS IS NOT REACHING THE GROUND. SOME DRIER AIR IS HELPING WITH THIS BUT WITH A VERY MOIST AIRMASS ON ITS WAY...IT SHOULDNT TAKE MUCH LONGER THIS EVENING BEFORE IT STARTS REACHING THE GROUND. OUTSIDE OF THIS SYSTEM TO THE SOUTH...A COLD FRONT HAS BEEN DROPPING SOUTH THROUGH PORTIONS OF WISCONSIN TODAY. ALTHOUGH...EXPECT THIS FRONT TO LOSE ITS SOUTHWARD MOMENTUM THIS EVENING AND THEN BECOME MORE DIFFUSE AS THE SYSTEM TO THE SOUTH MOVES INTO THE AREA. DESPITE THIS FRONT ACROSS THE REGION...ANY VERTICAL DEVELOPMENT HAS BEEN LIMITED AND IS EXPECTED TO REMAIN THIS WAY AS A MORE SUBSIDENT LARGE SCALE ENVIRONMENT REMAINS OVER THIS BOUNDARY. SHIFTING TOWARD MAIN FOCUS OF THIS FORECAST PERIOD...REMNANTS OF TROPICAL STORM ISAAC CONTINUE TO SLOWLY SHIFT NORTH THROUGH MISSOURI THIS AFTERNOON. THIS SYSTEM IS MARKED WITH A VERY MOIST ENVIRONMENT...OR A TROPICAL ENVIRONMENT. COPIOUS AMOUNTS OF MOISTURE WITH 12Z SOUNDINGS ACROSS MISSOURI INDICATING PWATS AROUND 2.4 INCHES THIS MORNING...AND LATEST RUC ANALYSIS SHOWING THIS AXIS OF HIGHER PWATS EXTENDING FROM THE ST. LOUIS AREA BACK SOUTH THROUGH MISSOURI INTO ARKANSAS. WITH A SLOW MOVEMENT OF THIS SYSTEM TONIGHT...THIS AXIS OF HIGHEST MOISTURE WILL ALSO SHIFT SLOWLY. NONETHELESS...THESE OUTWARD BANDS OF THIS SYSTEM AND HIGHER MOISTURE CONTENT AIR WILL LIFT NORTH OVERNIGHT. THIS SHOULD HELP BRING SHOWERS ACROSS THE SOUTHERN CWA PRIMARILY FOR AREAS ALONG AND SOUTH OF A LINE FROM PONTIAC IN ILLINOIS TO RENSSELAER IN INDIANA. HEAVIER DOWNPOURS ARE NOT EXPECTED TONIGHT AS WELL AS ANY THUNDER. DESPITE SOME INSTABILITY IN PLACE...THESE INITIAL SHOWERS WILL BE WEAKLY FORCED. ITS NOT UNTIL SATURDAY THROUGH THE REMAINDER OF THE WEEKEND THAT THE MAIN AXIS OF HIGHEST MOISTURE AND RAINFALL WILL REACH THE CWA. WITH BETTER FORCING WITH THIS SYSTEM SHIFTING NORTH AND SREF GUIDANCE INDICATING THAT THE AXIS OF HIGHER PWATS/MUCH HIGHER DEWPOINT AIR WILL REACH THE SOUTHERN CWA...THE POTENTIAL FOR HEAVIER RAIN WILL INCREASE. DESPITE SOME MODEL VARIABILITY WITH THE OVERALL EVOLUTION OF THIS SYSTEM...CONFIDENCE IS HIGH FOR AREAS ALONG AND SOUTH OF INTERSTATE 80 TO RECEIVE THE HIGHEST AMOUNTS OF RAIN THIS WEEKEND. WHERE CONFIDENCE IS LOWER AT THIS TIME IS IN REGARDS TO HOW FAR NORTH THIS RAIN WILL WORK ITS WAY NORTH. AS A FAIRLY TIGHT GRADIENT IS EXPECTED WITH THIS PRECIP SHIELD THIS WEEKEND...HAVE TRIED TO CONVEY THIS AS BEST AS POSSIBLE IN THE GRIDS. IF THIS SYSTEM WERE TO SHIFT NORTHWARD THAN PREVIOUSLY THOUGHT...THEN THIS AXIS OF RAINFALL WOULD OF COURSE SHIFT NORTH ACROSS THE CWA. AT THIS POINT IT APPEARS THAT A DRASTIC CUTOFF IN PRECIP SHOULD OCCUR AROUND THE I88 CORRIDOR. IN ALL AREAS ACROSS OUR CWA ARE EXPECTED TO RECEIVE A LARGE AMOUNT OF RAINFALL THROUGH SUNDAY NIGHT...WITH THE POTENTIAL FOR AMOUNTS OF 4 TO 5 INCHES OR GREATER ALONG AND SOUTH OF A LINE FROM THE PONTIAC AREA TO THE RENSSELAER AREA. MOVING NORTH OF THIS LINE...RAINFALL AMOUNTS ARE EXPECTED TO TAPER FROM AROUND 3 TO 4 INCHES TO AROUND 1 INCH JUST NORTH OF THE INTERSTATE 80 CORRIDOR. EXPECTED AMOUNTS ALONG THE INTERSTATE 88 CORRIDOR WILL ROUGHLY RANGE FROM THREE QUARTERS OF AN INCH UP TO ONE INCH...WITH THE POTENTIAL FOR LITTLE OR NO RAIN IN THE COUNTIES BORDERING WISCONSIN...GENERALLY UNDER A QUARTER INCH. NO HEADLINES AT THIS TIME BUT WILL CONTINUE THE ESF TODAY. RODRIGUEZ && .HYDROLOGY... 427 PM CDT EXPECTED RAINFALL AND POTENTIAL FOR HEAVY RAINFALL...POTENTIALLY FOR PERIODS OF TIME...ACROSS PORTIONS OF THE CWA STILL ON TRACK LATE TONIGHT THROUGH THE END OF THE WEEKEND. LATEST OBSERVATIONAL DATA STILL INDICATING A GOOD SWATH OF MOISTURE JUST SOUTH OF THE CWA THIS AFTERNOON...WITH LATEST GUIDANCE INDICATING THIS HIGHER MOISTURE CONTENT AIR TO CONTINUE SPREADING NORTHWARD TONIGHT INTO SATURDAY. AS THIS SLUG OF MOISTURE MOVES ACROSS THE CWA EARLY SATURDAY...IT WILL THEN LINGERING THROUGH THE REMAINDER OF THE WEEKEND. ALTHOUGH...LATEST GUIDANCE CONTINUES TO INDICATE THAT THE HIGHEST RAIN RATES/RAINFALL SHOULD STAY ACROSS THE SOUTHERN CWA WHICH SEEMS TO BE ON TRACK. THE POTENTIAL FOR RAINFALL AMOUNTS OF 4 TO 5 INCHES OR GREATER ALONG AND SOUTH OF A LINE FROM THE PONTIAC AREA TO THE RENSSELAER AREA SEEM TO BE ON TRACK FOR THIS WEEKEND. MOVING NORTH OF THIS LINE...RAINFALL AMOUNTS ARE EXPECTED TO TAPER FROM AROUND 3 TO 4 INCHES TO AROUND 1 INCH JUST NORTH OF THE INTERSTATE 80 CORRIDOR. EXPECTED AMOUNTS ALONG THE INTERSTATE 88 CORRIDOR WILL ROUGHLY RANGE FROM THREE QUARTERS OF AN INCH UP TO ONE INCH...WITH THE POTENTIAL FOR LITTLE OR NO RAIN IN THE COUNTIES BORDERING WISCONSIN...GENERALLY UNDER A QUARTER INCH. DESPITE THE EXPECTED HIGHER RAINFALL THIS WEEKEND...ONLY MINOR RISES IN AREAS RIVERS ARE EXPECTED WITH NO MAJOR PROBLEMS EXPECTED AT THIS TIME. A WORST CASE SCENARIO AT THIS TIME BASED ON CURRENT FORECASTS WOULD BE FOR RIVERS THAT RECEIVE THESE HIGHER AMOUNTS TO RISE TO MINOR OR JUST ABOVE MODERATE STAGES. ALTHOUGH WOULD LIKE TO REITERATE SOME UNCERTAINTY WITH THIS SYSTEMS OVERALL EVOLUTION...THAT EXTENDS INTO THE POTENTIAL RISES. WITH THIS IN MIND...THIS SITUATION NEEDS TO CONTINUE TO BE CLOSELY MONITORED THIS WEEKEND AS IT WOULD NOT BE OUT OF THE QUESTION FOR LOCALIZED AREAS OF HIGHER AMOUNTS AND THUS POSSIBLE HIGHER RISES. SOMETHING ELSE TO KEEP IN MIND THIS WEEKEND IS THE OVERALL SOIL CONDITIONS ACROSS THE AREA. WITH A DRY/HARD SOIL IN PLACE...IT WOULD NOT TAKE MUCH TIME FOR HIGH RAINFALL RATES TO QUICKLY TURN INTO RUNOFF. ONCE AGAIN...HAVE NOT ISSUED ANY FLOOD HEADLINES AT THIS TIME. ALTHOUGH...CONTINUE TO MONITOR LATEST UPDATES THIS WEEKEND AS THIS COMPLEX SYSTEM UNFOLDS ACROSS THE REGION. RODRIGUEZ && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 20Z... * TIMING WIND SHIFT FROM WSW TO NE WITH COLD FRONT SINKING FROM SE AND FAR SW WI DOWN ACROSS THE LOCAL AREA TOWARD EVENING. * TIMING ONSET AND NORTHWARD EXTEND OF SHOWERS/RAIN ASSOCIATED WITH T.D. ISAAC ON SAT. TRS //DISCUSSION...UPDATED 18Z... MODERATE SW-WSW LOW LEVEL FLOW HAS BEEN MIXING DOWN TO THE SURFACE WITH THE SKC CONDITIONS ALLOWING MAXIMUM HEATING THROUGH MIDDAY RESULTING IN SOME GUSTS IN THE 15-20KT RANGE THIS MORNING. OUTER EDGE OF CLOUD SHIELD OF THE T.D. CENTERED OVER SW MO HAVE SPREAD TO THE WI BORDER BY EARLY AFTERNOON WITH THICKER CIRRUS STRATUS TO SPREAD ACROSS THE LOCAL AREA DURING THE MID TO LATE AFTERNOON. WITH THICKENING HIGH CLOUDS ADDITIONAL INSOLATION WILL BE DECREASING THIS AFTERNOON...AND AS THE COLD FRONT ACROSS SOUTHERN WI CONTINUES TO CREEP SOUTHWARD THE SURFACE PRESSURE GRADIENT SLACKENS DURING THE AFTERNOON. WITH DECREASE IN BOTH SURFACE HEATING AND IN SURFACE PRESSURE GRADIENT SW-WSW WINDS WILL LOSE ANY MARGINAL GUSTS AND SETTLE TO SUSTAINED 10-12KT TIL DUSK. THE COLD FRONT IS SHOWN BY MODELS TO CROSS INTO FAR NORTHERN IL LATE THIS AFTERNOON AND EARLY THIS EVENING RESULTING IN A WIND SHIFT TO OUT OF THE NE-E AT 6-10KT. MODELS OFFERING SIMILAR SOLUTIONS ON LARGE SCALE BUT DIFFERENCES IN TIMING AND TRACK OF THE LOW OUT OF CENTRAL MO TO TO W CENTRAL IL SAT AND SAT NIGHT STILL LEAVES QUESTIONS ABOUT HOW FAR N THE RAIN WILL SPREAD AND HOW SOON IT WILL ARRIVE IN THE LOCAL AREA. TREND OF MODELS HAS BEEN SLOWER AND A BIT FURTHER S OF PREVIOUS FORECAST TRACKS. THIS DELAYS ARRIVAL OF ONSET OF RA AND KEEPS HEAVIER RAIN S OF ORD AND MDW. LOWER DEW POINT AIR BEHIND THE SLUGGISH COLD FRONT WILL BE ADVECTED OVER THE LOCAL TERMINALS ON NE-E LOW LEVEL WINDS BECOMING MODERATE TONIGHT BETWEEN HIGH PRESSURE BUILDING INTO THE UPPER GREAT LAKES AND THE LOW RIDGE BETWEEN THE MO LOW. SLIGHTLY MORE SOUTHWARD TRACK OF THE LOW AS IT MOVES INTO CENTRAL IL SUN AND INFLUX OF LOWER LOW LEVEL POINTS IS EXPECTED TO DELAY AND SIGNIFICANT THREAT OF SHRA/RA TIL LATER MORNING-EARLY AFTERNOON ON SAT...THEN PERSISTING THROUGH THE DAY. WITH HEAVER RAIN OCCURRING TO THE S OF THE TERMINALS AND THE FEED LOW DRIER LOW LEVEL AIR EXPECT VFR CONDITIONS TO PREVAIL LOCALLY THOUGH MAY BE AREAS MVFR BY MID-LATE SAT AFTERNOON. TRS //ORD AND MDW CONFIDENCE...UPDATED 20Z... * HIGH CONFIDENCE IN WIND TRENDS. * MODERATE CONFIDENCE IN TIMING OF THE COLD FRONT PASSAGE THIS EVENING AND THE ACCOMPANYING WIND SHIFT. * HIGH CONFIDENCE IN VFR AND DRY CONDITIONS THROUGH THE NIGHT AND EARLY SAT MORNING. * MODERATE CONFIDENCE IN PREVAILING VFR CONTINUING FROM MID SAT MORNING ON WITH ONLY AREAS/OCCASIONAL MVFR. TRS //OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z... SATURDAY NIGHT... SUNDAY...CHC OF RA/SHRA. MVFR/IFR POSSIBLE. MONDAY...SLGT CHC SHRA/TSRA. MVFR POSSIBLE. TUESDAY...VFR. WEDNESDAY...VFR. THURSDAY...CHC SHRA/TSRA. OTHERWISE VFR. RATZER && .MARINE... 351 PM CDT A COLD FRONT IS SLOWLY SINKING SOUTH ALONG LAKE MICHIGAN AND IS CURRENTLY LOCATED FROM THE WI/IL STATE LINE THROUGH MUSKEGON. THE FRONT WILL REACH SOUTHERN LAKE MICHIGAN THIS EVENING WITH WINDS TURNING NORTH TO NORTHEAST AND GUSTING TO AROUND 20 KT. WINDS WILL DIMINISH TO 10 TO 15 KT BEHIND THE FRONT AND VEER TO THE EAST BY SATURDAY MORNING OVER THE SOUTHERN HALF OF THE LAKE. WINDS WILL BE EAST ALONG THE ENTIRE LAKE BY SATURDAY NIGHT. THE PERSISTENT EASTERLY FLOW WILL RESULT IN LOCALLY HIGHER WAVES ALONG THE SOUTHERN WI AND IL COAST LINE OF 5 TO 8 FT BY SUNDAY AFTERNOON. WAVES IN THE IL NEARSHORE ZONES LOOK LIKE THEY WILL STAY JUST BELOW SMALL CRAFT ADVISORY CRITERIA...THEREFORE WILL REFRAIN FROM ISSUING A SCY NOW. HOWEVER...THE HIGHER WAVES AND ONSHORE FLOW ALONG THE IL NEARSHORE ZONES DO POSE AN INCREASED RIP CURRENT RISK. THE RISK ALSO IS INCREASED BY THE FACT THERE WILL PROBABLY BE AN ABOVE AVERAGE NUMBER OF SWIMMERS AT THE BEACH THIS HOLIDAY WEEKEND. ISSUED A RIP CURRENT STATEMENT FOR THE IL SIDE OF THE LAKE SATURDAY MORNING THROUGH SUNDAY EVENING. HIGH PRESSURE SPREADS ACROSS THE WESTERN GREAT LAKES TONIGHT. MEANWHILE LOW PRESSURE THAT WAS FORMALLY HURRICANE ISAAC IS MOVING NORTHWARD. THE PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS WILL TIGHTEN OVER SOUTHERN LAKE MICHIGAN. THEREFORE EAST WINDS WILL BE STRONGER OVER THE SOUTHERN HALF OF THE LAKE. THE LOW WILL ENTER SOUTH CENTRAL IL LATE SATURDAY AFTERNOON AND THEN TURN EASTWARD PASSING SOUTH OF LAKE MICHIGAN. HIGH PRESSURE MOVES OVER THE LAKE MONDAY NIGHT WITH WINDS WEAKENING ACROSS THE LAKE. ANOTHER TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST MID NEXT WEEK BUT CONFIDENCE IS LOW ON THE EXACT TIMING OF THIS SYSTEM DUE TO GUIDANCE INCONSISTENCIES. JEE && .LOT WATCHES/WARNINGS/ADVISORIES... IL...HIGH RIP CURRENT RISK...ILZ006-ILZ014...10 AM SATURDAY TO 7 PM SUNDAY. IN...NONE. LM...NONE. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
353 PM CDT FRI AUG 31 2012 .DISCUSSION... 349 PM CDT MAIN FORECAST CONCERNS THIS FORECAST PERIOD REVOLVE AROUND PRECIP CHANCES AND TRENDS...POSSIBLE HEAVY AT TIMES...THIS WEEKEND INTO THE START OF NEXT WEEK AS REMNANTS OF TROPICAL STORM ISAAC WORK ITS WAY NORTH ACROSS THE REGION. IN THE NEAR TERM...LATEST SATELLITE IMAGERY DEPICTING EXPANSIVE AREA OF MID AND HIGH LEVEL CLOUD COVER CONTINUING TO SPREAD NORTHWARD ACROSS MUCH OF THE REGION AS THIS SYSTEM SLOWLY MOVES NORTH. DESPITE AN INCREASE IN CLOUD COVER TODAY...MOSTLY SUNNY TO PARTLY CLOUDY SKIES HAVE BEEN OBSERVED WITH TEMPERATURES RISING TO THE LOWER 90S ACROSS NORTHERN ILLINOIS AND MID TO UPPER 80S ACROSS AREAS SOUTH OF INTERSTATE 80. DESPITE LATEST RADAR IMAGERY SHOWING SOME WEAK RETURNS FROM THE OUTER BANDS OF THIS SYSTEM ACROSS AREAS FROM PONTIAC IN ILLINOIS EAST TO FOWLER IN INDIANA...MOST OF THIS IS NOT REACHING THE GROUND. SOME DRIER AIR IS HELPING WITH THIS BUT WITH A VERY MOIST AIRMASS ON ITS WAY...IT SHOULDNT TAKE MUCH LONGER THIS EVENING BEFORE IT STARTS REACHING THE GROUND. OUTSIDE OF THIS SYSTEM TO THE SOUTH...A COLD FRONT HAS BEEN DROPPING SOUTH THROUGH PORTIONS OF WISCONSIN TODAY. ALTHOUGH...EXPECT THIS FRONT TO LOSE ITS SOUTHWARD MOMENTUM THIS EVENING AND THEN BECOME MORE DIFFUSE AS THE SYSTEM TO THE SOUTH MOVES INTO THE AREA. DESPITE THIS FRONT ACROSS THE REGION...ANY VERTICAL DEVELOPMENT HAS BEEN LIMITED AND IS EXPECTED TO REMAIN THIS WAY AS A MORE SUBSIDENT LARGE SCALE ENVIRONMENT REMAINS OVER THIS BOUNDARY. SHIFTING TOWARD MAIN FOCUS OF THIS FORECAST PERIOD...REMNANTS OF TROPICAL STORM ISAAC CONTINUE TO SLOWLY SHIFT NORTH THROUGH MISSOURI THIS AFTERNOON. THIS SYSTEM IS MARKED WITH A VERY MOIST ENVIRONMENT...OR A TROPICAL ENVIRONMENT. COPIOUS AMOUNTS OF MOISTURE WITH 12Z SOUNDINGS ACROSS MISSOURI INDICATING PWATS AROUND 2.4 INCHES THIS MORNING...AND LATEST RUC ANALYSIS SHOWING THIS AXIS OF HIGHER PWATS EXTENDING FROM THE ST. LOUIS AREA BACK SOUTH THROUGH MISSOURI INTO ARKANSAS. WITH A SLOW MOVEMENT OF THIS SYSTEM TONIGHT...THIS AXIS OF HIGHEST MOISTURE WILL ALSO SHIFT SLOWLY. NONETHELESS...THESE OUTWARD BANDS OF THIS SYSTEM AND HIGHER MOISTURE CONTENT AIR WILL LIFT NORTH OVERNIGHT. THIS SHOULD HELP BRING SHOWERS ACROSS THE SOUTHERN CWA PRIMARILY FOR AREAS ALONG AND SOUTH OF A LINE FROM PONTIAC IN ILLINOIS TO RENSSELAER IN INDIANA. HEAVIER DOWNPOURS ARE NOT EXPECTED TONIGHT AS WELL AS ANY THUNDER. DESPITE SOME INSTABILITY IN PLACE...THESE INITIAL SHOWERS WILL BE WEAKLY FORCED. ITS NOT UNTIL SATURDAY THROUGH THE REMAINDER OF THE WEEKEND THAT THE MAIN AXIS OF HIGHEST MOISTURE AND RAINFALL WILL REACH THE CWA. WITH BETTER FORCING WITH THIS SYSTEM SHIFTING NORTH AND SREF GUIDANCE INDICATING THAT THE AXIS OF HIGHER PWATS/MUCH HIGHER DEWPOINT AIR WILL REACH THE SOUTHERN CWA...THE POTENTIAL FOR HEAVIER RAIN WILL INCREASE. DESPITE SOME MODEL VARIABILITY WITH THE OVERALL EVOLUTION OF THIS SYSTEM...CONFIDENCE IS HIGH FOR AREAS ALONG AND SOUTH OF INTERSTATE 80 TO RECEIVE THE HIGHEST AMOUNTS OF RAIN THIS WEEKEND. WHERE CONFIDENCE IS LOWER AT THIS TIME IS IN REGARDS TO HOW FAR NORTH THIS RAIN WILL WORK ITS WAY NORTH. AS A FAIRLY TIGHT GRADIENT IS EXPECTED WITH THIS PRECIP SHIELD THIS WEEKEND...HAVE TRIED TO CONVEY THIS AS BEST AS POSSIBLE IN THE GRIDS. IF THIS SYSTEM WERE TO SHIFT NORTHWARD THAN PREVIOUSLY THOUGHT...THEN THIS AXIS OF RAINFALL WOULD OF COURSE SHIFT NORTH ACROSS THE CWA. AT THIS POINT IT APPEARS THAT A DRASTIC CUTOFF IN PRECIP SHOULD OCCUR AROUND THE I88 CORRIDOR. IN ALL AREAS ACROSS OUR CWA ARE EXPECTED TO RECEIVE A LARGE AMOUNT OF RAINFALL THROUGH SUNDAY NIGHT...WITH THE POTENTIAL FOR AMOUNTS OF 4 TO 5 INCHES OR GREATER ALONG AND SOUTH OF A LINE FROM THE PONTIAC AREA TO THE RENSSELAER AREA. MOVING NORTH OF THIS LINE...RAINFALL AMOUNTS ARE EXPECTED TO TAPER FROM AROUND 3 TO 4 INCHES TO AROUND 1 INCH JUST NORTH OF THE INTERSTATE 80 CORRIDOR. EXPECTED AMOUNTS ALONG THE INTERSTATE 88 CORRIDOR WILL ROUGHLY RANGE FROM THREE QUARTERS OF AN INCH UP TO ONE INCH...WITH THE POTENTIAL FOR LITTLE OR NO RAIN IN THE COUNTIES BORDERING WISCONSIN...GENERALLY UNDER A QUARTER INCH. NO HEADLINES AT THIS TIME BUT WILL CONTINUE THE ESF TODAY. RODRIGUEZ && .HYDROLOGY... 441 AM CDT NOT MUCH HAS CHANGED WITH THE TRACK OF THE REMNANTS OF TROPICAL CYCLONE ISAAC. THE SYSTEM IS EXPECTED TO TRACK FROM ITS CURRENT POSITION ACROSS WEST CENTRAL ARKANSAS...NORTHWARD TO CENTRAL MISSOURI BY EARLY SATURDAY...AND THEN TRANSITION TO THE EAST ALONG THE INTERSTATE 70 CORRIDOR THIS WEEKEND. DUE TO THE TROPICAL NATURE OF THE STORM SYSTEM...A VERY HIGH AMOUNT OF ATMOSPHERIC MOISTURE WILL ACCOMPANY THE SYSTEM. BECAUSE OF THIS...IT APPEARS LIKELY THAT PERIODS OF HEAVY RAINFALL WILL OCCUR ACROSS CENTRAL ILLINOIS AND PORTIONS OF NORTHWESTERN INDIANA ON SATURDAY THROUGH SUNDAY. THE LATEST FORECAST TOTAL RAINFALL AMOUNTS CALLS FOR BETWEEN THREE TO SIX INCHES ACROSS THE FAR SOUTHERN COUNTIES OF THE CWA...LIVINGSTON/FORD/IROQUOIS/BENTON...WITH AMOUNTS DROPPING OFF RAPIDLY TO THE NORTH. IT IS POSSIBLE THAT LOCATIONS NEAR THE WISCONSIN BORDER MAY SEE VERY LITTLE RAINFALL. THE RIVER BASINS MOSTLY LIKELY TO SEE THE GREATEST IMPACT WILL BE THE KANKAKEE...IROQUOIS AND VERMILION RIVERS AND SMALLER RIVERS AND CREEKS DRAINING INTO THEM. GIVEN THE SLOW MOVEMENT TO THE SYSTEM AND THE COPIOUS AMOUNTS OF DEEP LAYER MOISTURE LIKELY TO BE PRESENT...WIDESPREAD RAINFALL AMOUNTS OF 2 INCHES PER SIX HOUR PERIOD IS POSSIBLE...AND LOCALLY HIGHER AMOUNTS ARE CERTAINLY NOT OUT OF THE QUESTION. THIS AREA WILL NEED TO BE UNDER CONSIDERATION FOR AN AREAL FLOOD WARNING FOR LOCATIONS NORTH OF THE HEAVY RAINFALL AXIS...NORTHWARD TO THE I-88 CORRIDOR...1 TO 2 INCHES OF TOTAL RAINFALL IS POSSIBLE AND THE MORE FLASHY BASINS OF THE SOUTHERN PORTIONS OF THE CHICAGO METRO AREA COULD SEE FLOODING PROBLEMS AS WELL. KREIN/KJB && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 20Z... * TIMING WIND SHIFT FROM WSW TO NE WITH COLD FRONT SINKING FROM SE AND FAR SW WI DOWN ACROSS THE LOCAL AREA TOWARD EVENING. * TIMING ONSET AND NORTHWARD EXTEND OF SHOWERS/RAIN ASSOCIATED WITH T.D. ISAAC ON SAT. TRS //DISCUSSION...UPDATED 18Z... MODERATE SW-WSW LOW LEVEL FLOW HAS BEEN MIXING DOWN TO THE SURFACE WITH THE SKC CONDITIONS ALLOWING MAXIMUM HEATING THROUGH MIDDAY RESULTING IN SOME GUSTS IN THE 15-20KT RANGE THIS MORNING. OUTER EDGE OF CLOUD SHIELD OF THE T.D. CENTERED OVER SW MO HAVE SPREAD TO THE WI BORDER BY EARLY AFTERNOON WITH THICKER CIRRUS STRATUS TO SPREAD ACROSS THE LOCAL AREA DURING THE MID TO LATE AFTERNOON. WITH THICKENING HIGH CLOUDS ADDITIONAL INSOLATION WILL BE DECREASING THIS AFTERNOON...AND AS THE COLD FRONT ACROSS SOUTHERN WI CONTINUES TO CREEP SOUTHWARD THE SURFACE PRESSURE GRADIENT SLACKENS DURING THE AFTERNOON. WITH DECREASE IN BOTH SURFACE HEATING AND IN SURFACE PRESSURE GRADIENT SW-WSW WINDS WILL LOSE ANY MARGINAL GUSTS AND SETTLE TO SUSTAINED 10-12KT TIL DUSK. THE COLD FRONT IS SHOWN BY MODELS TO CROSS INTO FAR NORTHERN IL LATE THIS AFTERNOON AND EARLY THIS EVENING RESULTING IN A WIND SHIFT TO OUT OF THE NE-E AT 6-10KT. MODELS OFFERING SIMILAR SOLUTIONS ON LARGE SCALE BUT DIFFERENCES IN TIMING AND TRACK OF THE LOW OUT OF CENTRAL MO TO TO W CENTRAL IL SAT AND SAT NIGHT STILL LEAVES QUESTIONS ABOUT HOW FAR N THE RAIN WILL SPREAD AND HOW SOON IT WILL ARRIVE IN THE LOCAL AREA. TREND OF MODELS HAS BEEN SLOWER AND A BIT FURTHER S OF PREVIOUS FORECAST TRACKS. THIS DELAYS ARRIVAL OF ONSET OF RA AND KEEPS HEAVIER RAIN S OF ORD AND MDW. LOWER DEW POINT AIR BEHIND THE SLUGGISH COLD FRONT WILL BE ADVECTED OVER THE LOCAL TERMINALS ON NE-E LOW LEVEL WINDS BECOMING MODERATE TONIGHT BETWEEN HIGH PRESSURE BUILDING INTO THE UPPER GREAT LAKES AND THE LOW RIDGE BETWEEN THE MO LOW. SLIGHTLY MORE SOUTHWARD TRACK OF THE LOW AS IT MOVES INTO CENTRAL IL SUN AND INFLUX OF LOWER LOW LEVEL POINTS IS EXPECTED TO DELAY AND SIGNIFICANT THREAT OF SHRA/RA TIL LATER MORNING-EARLY AFTERNOON ON SAT...THEN PERSISTING THROUGH THE DAY. WITH HEAVER RAIN OCCURRING TO THE S OF THE TERMINALS AND THE FEED LOW DRIER LOW LEVEL AIR EXPECT VFR CONDITIONS TO PREVAIL LOCALLY THOUGH MAY BE AREAS MVFR BY MID-LATE SAT AFTERNOON. TRS //ORD AND MDW CONFIDENCE...UPDATED 20Z... * HIGH CONFIDENCE IN WIND TRENDS. * MODERATE CONFIDENCE IN TIMING OF THE COLD FRONT PASSAGE THIS EVENING AND THE ACCOMPANYING WIND SHIFT. * HIGH CONFIDENCE IN VFR AND DRY CONDITIONS THROUGH THE NIGHT AND EARLY SAT MORNING. * MODERATE CONFIDENCE IN PREVAILING VFR CONTINUING FROM MID SAT MORNING ON WITH ONLY AREAS/OCCASIONAL MVFR. TRS //OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z... SATURDAY NIGHT... SUNDAY...CHC OF RA/SHRA. MVFR/IFR POSSIBLE. MONDAY...SLGT CHC SHRA/TSRA. MVFR POSSIBLE. TUESDAY...VFR. WEDNESDAY...VFR. THURSDAY...CHC SHRA/TSRA. OTHERWISE VFR. RATZER && .MARINE... 351 PM CDT A COLD FRONT IS SLOWLY SINKING SOUTH ALONG LAKE MICHIGAN AND IS CURRENTLY LOCATED FROM THE WI/IL STATE LINE THROUGH MUSKEGON. THE FRONT WILL REACH SOUTHERN LAKE MICHIGAN THIS EVENING WITH WINDS TURNING NORTH TO NORTHEAST AND GUSTING TO AROUND 20 KT. WINDS WILL DIMINISH TO 10 TO 15 KT BEHIND THE FRONT AND VEER TO THE EAST BY SATURDAY MORNING OVER THE SOUTHERN HALF OF THE LAKE. WINDS WILL BE EAST ALONG THE ENTIRE LAKE BY SATURDAY NIGHT. THE PERSISTENT EASTERLY FLOW WILL RESULT IN LOCALLY HIGHER WAVES ALONG THE SOUTHERN WI AND IL COAST LINE OF 5 TO 8 FT BY SUNDAY AFTERNOON. WAVES IN THE IL NEARSHORE ZONES LOOK LIKE THEY WILL STAY JUST BELOW SMALL CRAFT ADVISORY CRITERIA...THEREFORE WILL REFRAIN FROM ISSUING A SCY NOW. HOWEVER...THE HIGHER WAVES AND ONSHORE FLOW ALONG THE IL NEARSHORE ZONES DO POSE AN INCREASED RIP CURRENT RISK. THE RISK ALSO IS INCREASED BY THE FACT THERE WILL PROBABLY BE AN ABOVE AVERAGE NUMBER OF SWIMMERS AT THE BEACH THIS HOLIDAY WEEKEND. ISSUED A RIP CURRENT STATEMENT FOR THE IL SIDE OF THE LAKE SATURDAY MORNING THROUGH SUNDAY EVENING. HIGH PRESSURE SPREADS ACROSS THE WESTERN GREAT LAKES TONIGHT. MEANWHILE LOW PRESSURE THAT WAS FORMALLY HURRICANE ISAAC IS MOVING NORTHWARD. THE PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS WILL TIGHTEN OVER SOUTHERN LAKE MICHIGAN. THEREFORE EAST WINDS WILL BE STRONGER OVER THE SOUTHERN HALF OF THE LAKE. THE LOW WILL ENTER SOUTH CENTRAL IL LATE SATURDAY AFTERNOON AND THEN TURN EASTWARD PASSING SOUTH OF LAKE MICHIGAN. HIGH PRESSURE MOVES OVER THE LAKE MONDAY NIGHT WITH WINDS WEAKENING ACROSS THE LAKE. ANOTHER TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST MID NEXT WEEK BUT CONFIDENCE IS LOW ON THE EXACT TIMING OF THIS SYSTEM DUE TO GUIDANCE INCONSISTENCIES. JEE && .LOT WATCHES/WARNINGS/ADVISORIES... IL...HIGH RIP CURRENT RISK...ILZ006-ILZ014...10 AM SATURDAY TO 7 PM SUNDAY. IN...NONE. LM...NONE. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
351 PM CDT FRI AUG 31 2012 .DISCUSSION... 349 PM CDT MAIN FORECAST CONCERNS THIS FORECAST PERIOD REVOLVE AROUND PRECIP CHANCES AND TRENDS...POSSIBLE HEAVY AT TIMES...THIS WEEKEND INTO THE START OF NEXT WEEK AS REMNANTS OF TROPICAL STORM ISAAC WORK ITS WAY NORTH ACROSS THE REGION. IN THE NEAR TERM...LATEST SATELLITE IMAGERY DEPICTING EXPANSIVE AREA OF MID AND HIGH LEVEL CLOUD COVER CONTINUING TO SPREAD NORTHWARD ACROSS MUCH OF THE REGION AS THIS SYSTEM SLOWLY MOVES NORTH. DESPITE AN INCREASE IN CLOUD COVER TODAY...MOSTLY SUNNY TO PARTLY CLOUDY SKIES HAVE BEEN OBSERVED WITH TEMPERATURES RISING TO THE LOWER 90S ACROSS NORTHERN ILLINOIS AND MID TO UPPER 80S ACROSS AREAS SOUTH OF INTERSTATE 80. DESPITE LATEST RADAR IMAGERY SHOWING SOME WEAK RETURNS FROM THE OUTER BANDS OF THIS SYSTEM ACROSS AREAS FROM PONTIAC IN ILLINOIS EAST TO FOWLER IN INDIANA...MOST OF THIS IS NOT REACHING THE GROUND. SOME DRIER AIR IS HELPING WITH THIS BUT WITH A VERY MOIST AIRMASS ON ITS WAY...IT SHOULDNT TAKE MUCH LONGER THIS EVENING BEFORE IT STARTS REACHING THE GROUND. OUTSIDE OF THIS SYSTEM TO THE SOUTH...A COLD FRONT HAS BEEN DROPPING SOUTH THROUGH PORTIONS OF WISCONSIN TODAY. ALTHOUGH...EXPECT THIS FRONT TO LOSE ITS SOUTHWARD MOMENTUM THIS EVENING AND THEN BECOME MORE DIFFUSE AS THE SYSTEM TO THE SOUTH MOVES INTO THE AREA. DESPITE THIS FRONT ACROSS THE REGION...ANY VERTICAL DEVELOPMENT HAS BEEN LIMITED AND IS EXPECTED TO REMAIN THIS WAY AS A MORE SUBSIDENT LARGE SCALE ENVIRONMENT REMAINS OVER THIS BOUNDARY. SHIFTING TOWARD MAIN FOCUS OF THIS FORECAST PERIOD...REMNANTS OF TROPICAL STORM ISAAC CONTINUE TO SLOWLY SHIFT NORTH THROUGH MISSOURI THIS AFTERNOON. THIS SYSTEM IS MARKED WITH A VERY MOIST ENVIRONMENT...OR A TROPICAL ENVIRONMENT. COPIOUS AMOUNTS OF MOISTURE WITH 12Z SOUNDINGS ACROSS MISSOURI INDICATING PWATS AROUND 2.4 INCHES THIS MORNING...AND LATEST RUC ANALYSIS SHOWING THIS AXIS OF HIGHER PWATS EXTENDING FROM THE ST. LOUIS AREA BACK SOUTH THROUGH MISSOURI INTO ARKANSAS. WITH A SLOW MOVEMENT OF THIS SYSTEM TONIGHT...THIS AXIS OF HIGHEST MOISTURE WILL ALSO SHIFT SLOWLY. NONETHELESS...THESE OUTWARD BANDS OF THIS SYSTEM AND HIGHER MOISTURE CONTENT AIR WILL LIFT NORTH OVERNIGHT. THIS SHOULD HELP BRING SHOWERS ACROSS THE SOUTHERN CWA PRIMARILY FOR AREAS ALONG AND SOUTH OF A LINE FROM PONTIAC IN ILLINOIS TO RENSSELAER IN INDIANA. HEAVIER DOWNPOURS ARE NOT EXPECTED TONIGHT AS WELL AS ANY THUNDER. DESPITE SOME INSTABILITY IN PLACE...THESE INITIAL SHOWERS WILL BE WEAKLY FORCED. ITS NOT UNTIL SATURDAY THROUGH THE REMAINDER OF THE WEEKEND THAT THE MAIN AXIS OF HIGHEST MOISTURE AND RAINFALL WILL REACH THE CWA. WITH BETTER FORCING WITH THIS SYSTEM SHIFTING NORTH AND SREF GUIDANCE INDICATING THAT THE AXIS OF HIGHER PWATS/MUCH HIGHER DEWPOINT AIR WILL REACH THE SOUTHERN CWA...THE POTENTIAL FOR HEAVIER RAIN WILL INCREASE. DESPITE SOME MODEL VARIABILITY WITH THE OVERALL EVOLUTION OF THIS SYSTEM...CONFIDENCE IS HIGH FOR AREAS ALONG AND SOUTH OF INTERSTATE 80 TO RECEIVE THE HIGHEST AMOUNTS OF RAIN THIS WEEKEND. WHERE CONFIDENCE IS LOWER AT THIS TIME IS IN REGARDS TO HOW FAR NORTH THIS RAIN WILL WORK ITS WAY NORTH. AS A FAIRLY TIGHT GRADIENT IS EXPECTED WITH THIS PRECIP SHIELD THIS WEEKEND...HAVE TRIED TO CONVEY THIS AS BEST AS POSSIBLE IN THE GRIDS. IF THIS SYSTEM WERE TO SHIFT NORTHWARD THAN PREVIOUSLY THOUGHT...THEN THIS AXIS OF RAINFALL WOULD OF COURSE SHIFT NORTH ACROSS THE CWA. AT THIS POINT IT APPEARS THAT A DRASTIC CUTOFF IN PRECIP SHOULD OCCUR AROUND THE I88 CORRIDOR. IN ALL AREAS ACROSS OUR CWA ARE EXPECTED TO RECEIVE A LARGE AMOUNT OF RAINFALL THROUGH SUNDAY NIGHT...WITH THE POTENTIAL FOR AMOUNTS OF 4 TO 5 INCHES OR GREATER ALONG AND SOUTH OF A LINE FROM THE PONTIAC AREA TO THE RENSSELAER AREA. MOVING NORTH OF THIS LINE...RAINFALL AMOUNTS ARE EXPECTED TO TAPER FROM AROUND 3 TO 4 INCHES TO AROUND 1 INCH JUST NORTH OF THE INTERSTATE 80 CORRIDOR. EXPECTED AMOUNTS ALONG THE INTERSTATE 88 CORRIDOR WILL ROUGHLY RANGE FROM THREE QUARTERS OF AN INCH UP TO ONE INCH...WITH THE POTENTIAL FOR LITTLE OR NO RAIN IN THE COUNTIES BORDERING WISCONSIN...GENERALLY UNDER A QUARTER INCH. NO HEADLINES AT THIS TIME BUT WILL CONTINUE THE ESF TODAY. RODRIGUEZ && .HYDROLOGY... 441 AM CDT NOT MUCH HAS CHANGED WITH THE TRACK OF THE REMNANTS OF TROPICAL CYCLONE ISAAC. THE SYSTEM IS EXPECTED TO TRACK FROM ITS CURRENT POSITION ACROSS WEST CENTRAL ARKANSAS...NORTHWARD TO CENTRAL MISSOURI BY EARLY SATURDAY...AND THEN TRANSITION TO THE EAST ALONG THE INTERSTATE 70 CORRIDOR THIS WEEKEND. DUE TO THE TROPICAL NATURE OF THE STORM SYSTEM...A VERY HIGH AMOUNT OF ATMOSPHERIC MOISTURE WILL ACCOMPANY THE SYSTEM. BECAUSE OF THIS...IT APPEARS LIKELY THAT PERIODS OF HEAVY RAINFALL WILL OCCUR ACROSS CENTRAL ILLINOIS AND PORTIONS OF NORTHWESTERN INDIANA ON SATURDAY THROUGH SUNDAY. THE LATEST FORECAST TOTAL RAINFALL AMOUNTS CALLS FOR BETWEEN THREE TO SIX INCHES ACROSS THE FAR SOUTHERN COUNTIES OF THE CWA...LIVINGSTON/FORD/IROQUOIS/BENTON...WITH AMOUNTS DROPPING OFF RAPIDLY TO THE NORTH. IT IS POSSIBLE THAT LOCATIONS NEAR THE WISCONSIN BORDER MAY SEE VERY LITTLE RAINFALL. THE RIVER BASINS MOSTLY LIKELY TO SEE THE GREATEST IMPACT WILL BE THE KANKAKEE...IROQUOIS AND VERMILION RIVERS AND SMALLER RIVERS AND CREEKS DRAINING INTO THEM. GIVEN THE SLOW MOVEMENT TO THE SYSTEM AND THE COPIOUS AMOUNTS OF DEEP LAYER MOISTURE LIKELY TO BE PRESENT...WIDESPREAD RAINFALL AMOUNTS OF 2 INCHES PER SIX HOUR PERIOD IS POSSIBLE...AND LOCALLY HIGHER AMOUNTS ARE CERTAINLY NOT OUT OF THE QUESTION. THIS AREA WILL NEED TO BE UNDER CONSIDERATION FOR AN AREAL FLOOD WARNING FOR LOCATIONS NORTH OF THE HEAVY RAINFALL AXIS...NORTHWARD TO THE I-88 CORRIDOR...1 TO 2 INCHES OF TOTAL RAINFALL IS POSSIBLE AND THE MORE FLASHY BASINS OF THE SOUTHERN PORTIONS OF THE CHICAGO METRO AREA COULD SEE FLOODING PROBLEMS AS WELL. KREIN/KJB && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 20Z... * TIMING WIND SHIFT FROM WSW TO NE WITH COLD FRONT SINKING FROM SE AND FAR SW WI DOWN ACROSS THE LOCAL AREA TOWARD EVENING. * TIMING ONSET AND NORTHWARD EXTEND OF SHOWERS/RAIN ASSOCIATED WITH T.D. ISAAC ON SAT. TRS //DISCUSSION...UPDATED 18Z... MODERATE SW-WSW LOW LEVEL FLOW HAS BEEN MIXING DOWN TO THE SURFACE WITH THE SKC CONDITIONS ALLOWING MAXIMUM HEATING THROUGH MIDDAY RESULTING IN SOME GUSTS IN THE 15-20KT RANGE THIS MORNING. OUTER EDGE OF CLOUD SHIELD OF THE T.D. CENTERED OVER SW MO HAVE SPREAD TO THE WI BORDER BY EARLY AFTERNOON WITH THICKER CIRRUS STRATUS TO SPREAD ACROSS THE LOCAL AREA DURING THE MID TO LATE AFTERNOON. WITH THICKENING HIGH CLOUDS ADDITIONAL INSOLATION WILL BE DECREASING THIS AFTERNOON...AND AS THE COLD FRONT ACROSS SOUTHERN WI CONTINUES TO CREEP SOUTHWARD THE SURFACE PRESSURE GRADIENT SLACKENS DURING THE AFTERNOON. WITH DECREASE IN BOTH SURFACE HEATING AND IN SURFACE PRESSURE GRADIENT SW-WSW WINDS WILL LOSE ANY MARGINAL GUSTS AND SETTLE TO SUSTAINED 10-12KT TIL DUSK. THE COLD FRONT IS SHOWN BY MODELS TO CROSS INTO FAR NORTHERN IL LATE THIS AFTERNOON AND EARLY THIS EVENING RESULTING IN A WIND SHIFT TO OUT OF THE NE-E AT 6-10KT. MODELS OFFERING SIMILAR SOLUTIONS ON LARGE SCALE BUT DIFFERENCES IN TIMING AND TRACK OF THE LOW OUT OF CENTRAL MO TO TO W CENTRAL IL SAT AND SAT NIGHT STILL LEAVES QUESTIONS ABOUT HOW FAR N THE RAIN WILL SPREAD AND HOW SOON IT WILL ARRIVE IN THE LOCAL AREA. TREND OF MODELS HAS BEEN SLOWER AND A BIT FURTHER S OF PREVIOUS FORECAST TRACKS. THIS DELAYS ARRIVAL OF ONSET OF RA AND KEEPS HEAVIER RAIN S OF ORD AND MDW. LOWER DEW POINT AIR BEHIND THE SLUGGISH COLD FRONT WILL BE ADVECTED OVER THE LOCAL TERMINALS ON NE-E LOW LEVEL WINDS BECOMING MODERATE TONIGHT BETWEEN HIGH PRESSURE BUILDING INTO THE UPPER GREAT LAKES AND THE LOW RIDGE BETWEEN THE MO LOW. SLIGHTLY MORE SOUTHWARD TRACK OF THE LOW AS IT MOVES INTO CENTRAL IL SUN AND INFLUX OF LOWER LOW LEVEL POINTS IS EXPECTED TO DELAY AND SIGNIFICANT THREAT OF SHRA/RA TIL LATER MORNING-EARLY AFTERNOON ON SAT...THEN PERSISTING THROUGH THE DAY. WITH HEAVER RAIN OCCURRING TO THE S OF THE TERMINALS AND THE FEED LOW DRIER LOW LEVEL AIR EXPECT VFR CONDITIONS TO PREVAIL LOCALLY THOUGH MAY BE AREAS MVFR BY MID-LATE SAT AFTERNOON. TRS //ORD AND MDW CONFIDENCE...UPDATED 20Z... * HIGH CONFIDENCE IN WIND TRENDS. * MODERATE CONFIDENCE IN TIMING OF THE COLD FRONT PASSAGE THIS EVENING AND THE ACCOMPANYING WIND SHIFT. * HIGH CONFIDENCE IN VFR AND DRY CONDITIONS THROUGH THE NIGHT AND EARLY SAT MORNING. * MODERATE CONFIDENCE IN PREVAILING VFR CONTINUING FROM MID SAT MORNING ON WITH ONLY AREAS/OCCASIONAL MVFR. TRS //OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z... SATURDAY NIGHT... SUNDAY...CHC OF RA/SHRA. MVFR/IFR POSSIBLE. MONDAY...SLGT CHC SHRA/TSRA. MVFR POSSIBLE. TUESDAY...VFR. WEDNESDAY...VFR. THURSDAY...CHC SHRA/TSRA. OTHERWISE VFR. RATZER && .MARINE... 246 AM CDT MARINE FORECAST CONCERNS INCLUDE A PERIOD OF GUSTY SOUTHWEST WINDS THIS MORNING AHEAD OF A COLD FRONT WHICH WILL SAG SOUTH ACROSS LAKE MICHIGAN TODAY...AND A PERIOD OF MODEST EAST-NORTHEAST WINDS THIS THE WEEKEND AS THE SURFACE LOW PRESSURE CIRCULATION ASSOCIATED WITH TROPICAL DEPRESSION ISAAC MOVES SLOWLY SOUTH OF THE GREAT LAKES. LOW PRESSURE WAS LOCATED OVER EASTERN QUEBEC EARLY THIS MORNING...WITH A COLD FRONT TRAILING SOUTHWESTWARD ACROSS THE NORTHERN LAKES AND INTO CENTRAL WISCONSIN. THIS COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY AS THE EASTERN CANADIAN LOW CONTINUES TO MOVE AWAY. SOUTHWEST WINDS AHEAD OF THE FRONT HAVE BEEN FAIRLY GUST PARTICULARLY OVER THE NORTHERN END OF LAKE MICHIGAN...WITH SOME GUSTS AROUND 30 KTS NOTED ALONG THE EASTERN SHORE NORTH OF MANISTEE AND AROUND CHARLEVOIX. THESE STRONGER WINDS SHOULD DIMINISH THIS MORNING...AS THE LOW LEVEL JET ASSOCIATED WITH A PASSING UPPER DISTURBANCE PULLS OF TO THE EAST. WINDS WILL VEER TO THE NORTH BEHIND THE FRONT TODAY AND TO NORTH-NORTHEAST TONIGHT...AS THE FRONT CONTINUES TO DRIFT TO THE SOUTH AND HIGH PRESSURE SPREADS ACROSS THE NORTHERN LAKES. THE HIGH WILL DRIFT SOUTHEAST ACROSS THE NORTHERN/EASTERN LAKES SATURDAY AND SUNDAY...WHILE THE AREA OF SURFACE LOW PRESSURE FROM TROPICAL DEPRESSION ISAAC SLOWLY LIFTS ACROSS THE LOWER MISSOURI VALLEY THROUGH TONIGHT...THEN TURNS EAST AND DRIFTS ACROSS SOUTH CENTRAL IL/IND AS IT FILLS DURING THE REMAINDER OF THE WEEKEND. FORECAST MODEL GUIDANCE CONTINUES TO EXHIBIT DIFFERENCES IN THE EXACT AND STRENGTH OF ISAAC DURING THIS PERIOD...THOUGH THE PASSAGE OF THIS LOW SOUTH OF THE LAKES SHOULD RESULT IN A PERIOD OF ENHANCED EASTERLY FLOW PARTICULARLY ON THE SOUTHERN HALF OF LAKE MICHIGAN ESPECIALLY LATE TONIGHT INTO SUNDAY. EAST WINDS TOPPING OUT IN THE 20-25 KT RANGE DURING THIS PERIOD MAY NECESSITATE SMALL CRAFT ADVISORIES ALONG THE WESTERN SHORE OF SOUTHERN LAKE MICHIGAN OVER THE WEEKEND...BEFORE THE LOW WEAKENS AND LOOSENS THE GRADIENT ACROSS THE LAKE BY MONDAY. RATZER && .LOT WATCHES/WARNINGS/ADVISORIES... IL...HIGH RIP CURRENT RISK...ILZ006-ILZ014...10 AM SATURDAY TO 7 PM SUNDAY. IN...NONE. LM...NONE. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1112 AM CDT FRI AUG 31 2012 .DISCUSSION... 340 AM CDT THE MAIN FORECAST CONCERNS CONTINUE TO CENTER ON THE HEAVY RAINFALL POTENTIAL ACROSS PORTIONS OF THE AREA THIS WEEKEND AS THE REMNANTS OF HURRICANE ISSAC MOVE ACROSS THE CENTRAL MISSISSIPPI VALLEY. I HAVE FOLLOWED CLOSER TO THE 00 UTC ECMWF...GFS AND UKMET FOR THIS FORECAST PERIOD AS THEY HAVE A DECENT HANDLE ON TRACKING THE REMNANTS UP ACROSS EAST CENTRAL MISSOURI EASTWARD ACROSS CENTRAL ILLINOIS. THE NAM SOLUTION WAS REJECTED AS IT IS DOING A POOR JOB WITH THE SYSTEM. NO BIG CHANGES TO THE PREVIOUS THINKING. THE CENTER OF THE STORM IS NOW LOCATED ACROSS WEST CENTRAL ARKANSAS. IT WILL SLOWLY LIFT NORTHWARD ACROSS SOUTHWESTERN MISSOURI LATER THIS AFTERNOON AND THEN THE SYSTEM IS EXPECTED TO BEGIN TO MOVE MORE EASTERLY LATER TONIGHT AS IT BECOMES INFLUENCED BY THE WESTERLIES. IT STILL APPEARS THE CENTER OF THE SYSTEM WILL PASS SOMEWHERE AROUND OR JUST NORTH OF THE ST LOUIS AREA AND TRANSVERSE THE CENTRAL SECTIONS OF ILLINOIS. ULTIMATELY THIS WILL RESULT IN THE HEAVIEST RAINFALL ACROSS MY SOUTHERN COUNTIES...SOUTH OF INTERSTATE 80. IT APPEARS THERE WILL BE A VERY SHARPE GRADIENT ACROSS NORTHERN ILLINOIS SOMEWHERE AROUND THE I 88 CORRIDOR. THE NORTHERN SUBURBS OF CHICAGO MAY ONLY GET MINOR AMOUNTS UP TO A QUARTER INCH...WHILE THE SOUTHERN BURBS GET MORE THAN AN INCH. BY FAR THE HEAVIEST AMOUNTS LOOK TO BE ACROSS MY SOUTHERN COUNTIES FROM SOUTHERN LA SALLE EASTWARD THROUGH KANKAKEE AND POINTS SOUTH. IN THESE AREAS 3 TO 6 INCHES ARE POSSIBLE...WITH LOCALLY HIGH AMOUNTS POSSIBLE. DUE TO THE EXPECTED RAINFALL...I LOWER TEMPERATURES INTO THE 70S FOR HIGHS...MANY SOUTH FOR SATURDAY AND SUNDAY. THE HEAVY RAIN THREAT WILL END FROM WEST TO EAST ON LATER ON SUNDAY AS THE SYSTEM MOVE EAST AND RAPIDLY WEAKENS. IN THE EXTENDED PERIOD OVERALL CONFIDENCE IS LOW AS IT APPEARS THE WESTERLIES WILL BECOME ACTIVE ACROSS NORTH AMERICA. THIS WILL LIKELY DRIVE A COUPLE OF POTENT MID/UPPER TROUGHS ACROSS SOUTHERN CANADA. THE GUIDANCE SUGGESTS THAT A TROUGH WILL TRY TO DIG ACROSS THE NORTH CENTRAL CONUS BY MID TO LATE WEEK. HOWEVER...THERE IS A SIGNIFICANT AMOUNT OF SPREAD AMONGST THE MODEL ENSEMBLES...INDICATING LARGE TIMING UNCERTAINTIES. IT DOES APPEAR THERE WILL BE A CHANCE OF THUNDERSTORMS SOMETIME EITHER WEDNESDAY NIGHT OR THURSDAY AS A COLD FRONT DROPS ACROSS THE AREA. TEMPERATURES DURING THE PERIOD WILL LIKELY BE NEAR AVERAGE EARLY ON IN THE WEEK...THEN TRENDING TO BELOW AVERAGE AS A COOL AIR MASS LOOKS TO SET UP ACROSS THE REGION BEHIND THIS COLD FRONT. KJB && .HYDROLOGY... 441 AM CDT NOT MUCH HAS CHANGED WITH THE TRACK OF THE REMNANTS OF TROPICAL CYCLONE ISAAC. THE SYSTEM IS EXPECTED TO TRACK FROM ITS CURRENT POSITION ACROSS WEST CENTRAL ARKANSAS...NORTHWARD TO CENTRAL MISSOURI BY EARLY SATURDAY...AND THEN TRANSITION TO THE EAST ALONG THE INTERSTATE 70 CORRIDOR THIS WEEKEND. DUE TO THE TROPICAL NATURE OF THE STORM SYSTEM...A VERY HIGH AMOUNT OF ATMOSPHERIC MOISTURE WILL ACCOMPANY THE SYSTEM. BECAUSE OF THIS...IT APPEARS LIKELY THAT PERIODS OF HEAVY RAINFALL WILL OCCUR ACROSS CENTRAL ILLINOIS AND PORTIONS OF NORTHWESTERN INDIANA ON SATURDAY THROUGH SUNDAY. THE LATEST FORECAST TOTAL RAINFALL AMOUNTS CALLS FOR BETWEEN THREE TO SIX INCHES ACROSS THE FAR SOUTHERN COUNTIES OF THE CWA...LIVINGSTON/FORD/IROQUOIS/BENTON...WITH AMOUNTS DROPPING OFF RAPIDLY TO THE NORTH. IT IS POSSIBLE THAT LOCATIONS NEAR THE WISCONSIN BORDER MAY SEE VERY LITTLE RAINFALL. THE RIVER BASINS MOSTLY LIKELY TO SEE THE GREATEST IMPACT WILL BE THE KANKAKEE...IROQUOIS AND VERMILLION RIVERS AND SMALLER RIVERS AND CREEKS DRAINING INTO THEM. GIVEN THE SLOW MOVEMENT TO THE SYSTEM AND THE COPIOUS AMOUNTS OF DEEP LAYER MOISTURE LIKELY TO BE PRESENT...WIDESPREAD RAINFALL AMOUNTS OF 2 INCHES PER SIX HOUR PERIOD IS POSSIBLE...AND LOCALLY HIGHER AMOUNTS ARE CERTAINLY NOT OUT OF THE QUESTION. THIS AREA WILL NEED TO BE UNDER CONSIDERATION FOR AN AREAL FLOOD WARNING FOR LOCATIONS NORTH OF THE HEAVY RAINFALL AXIS...NORTHWARD TO THE I-88 CORRIDOR...1 TO 2 INCHES OF TOTAL RAINFALL IS POSSIBLE AND THE MORE FLASHY BASINS OF THE SOUTHERN PORTIONS OF THE CHICAGO METRO AREA COULD SEE FLOODING PROBLEMS AS WELL. KREIN/KJB && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 16Z... * MARGINAL GUSTINESS OF 15-20 KT TIL THICK CIRRUS STRATUS OVERSPREADS AROUND NOON. * TIMING WIND SHIFT FROM WSW TO NE WITH COLD FRONT SINKING FROM SE AND FAR SW WI DOWN ACROSS AREA TOWARD EVENING. * SMALL POTENTIAL FOR SHRA/ISOLD TS FAR SOUTHERN WI INTO NE AND FAR N CENTRAL IL BORDER MID-LATE AFTERNOON. * POTENTIAL FOR SHOWERS ASSOCIATED WITH TD ISAAC MAINLY BEYOND 12Z SATURDAY. TRS //DISCUSSION...UPDATED 14Z... ONLY VERY MINOR TWEAKS MADE TO 14Z TAFOR. SSW-SW LOW LEVEL WINDS ADVECTING MID-UPPER 60S SURFACE DEW POINTS OVER THE AREA AT MID MORNING WITH UPPER 60-LOWER 70S ACROSS CENTRAL IL. WITH CONTINUED HEATING DURING THE LATE MORNING THE LOW LEVEL MOISTURE ADVECTION WILL BE OFFSET BY DEEPENING OF MIXING IN THE BOUNDARY LAYER. EXPECT DEW POINTS TO BE IN THE MID-UPPER 60S DURING THE AFTERNOON. THIS GIVES CONVECTIVE TEMPERATURES IN THE UPPER 80S WHICH IS FORECAST TO REACH AROUND NOON. THOUGH NOT OPERATIONALLY SIGNIFICANT DID INCLUDE A FORECAST STARTING AT 17Z INCLUDING HIGHER BASED CU DEVELOPING. MODELS SHOW LOW LEVEL CONVERGENCE ALONG THE WI COLD FRONT DROPPING TOWARD THE IL BORDER THIS AFTERNOON...AS WELL AS IN NE ALONG A LAKE BREEZE BOUNDARY PUSHING INLAND. FORECAST SOUNDINGS FROM THE 12Z RUC13 SHOW MINIMAL CIN OVER CHI AREA DURING THE LATER AFTERNOON ALONG WITH DECENT CAPE VALUES. LOW LEVEL WARMING AND CONVERGENCE WOULD FAVOR ISOLD TO SCT TS DEVELOPMENT ALONG THE COLD FRONT AND LAKE BREEZE MID-LATE AFTERNOON...WHILE SUBSIDENCE INN THE MID AND UPPER LEVELS ON THE PERIPHERY OF ISSAC REMNANTS SPREAD OVER THE LOCAL AREA. THIS WITH INCREASING CLOUDS CUTTING SURFACE HEATING DURING THE LATER AFTERNOON WOULD DISCOURAGE AN TS DEVELOPMENT. THREAT TOO LOW AT THIS TIME TO INCLUDE ANY MENTION IN TAFOR THOUGH LOW COVERAGE NOT TS LATE AFTERNOON NOT TOTALLY OUT OF THE QUESTION. TRS PREVIOUS DISCUSSION...UPDATED 12Z... LITTLE CHANGE IN AVIATION FORECAST THINKING FROM 06Z ISSUANCE. MAIN FOCUS REMAINS ON TIMING OF WEAK COLD FRONT AND WIND SHIFT FROM WEST-SOUTHWEST TO NORTHEAST TOWARD EVENING...THEN INCREASING HIGH CLOUDS THIS AFTERNOON AND EVENTUAL PRECIP POTENTIAL SATURDAY AS THE REMAINS OF TROPICAL DEPRESSION ISAAC MOVE SLOWLY INTO IL/IND. THE COLD FRONT...WHICH WAS FROM EAST CENTRAL WI TO NORTH CENTRAL IA AT 11Z...WILL CONTINUE TO MOVE SLOWLY SOUTH TOWARD THE TERMINALS TODAY. VAD WIND PROFILES INDICATE THE PRESENCE OF A 35 KT SPEED MAX ABOVE THE BOUNDARY LAYER AT AROUND 1000 FT AGL THIS MORNING WHICH WILL RESULT IN A PERIOD OF MARGINAL LLWS FOR THE NEXT HOUR OR TWO UNTIL THE BOUNDARY LAYER BECOMES MORE DEEPLY MIXED. WITH MIXING...SOUTHWEST WINDS WILL BECOME A BIT BREEZY BY MID-MORNING WITH GUSTS APPROACHING 20 KTS. THE GRADIENT SHOULD WEAKEN THIS AFTERNOON AS THE COLD FRONTAL TROUGH APPROACHES HOWEVER...ALLOWING WINDS TO DECREASE A BIT. TIMING OF THE FRONTAL PASSAGE AND A WIND SHIFT FROM WEST-SOUTHWEST TO NORTHEAST STILL APPEARS TO BE ON TRACK FOR THE 23-01Z PERIOD ACROSS THE TERMINALS...WITH WINDS REMAINING NORTHEAST AROUND 10 KTS OVERNIGHT. ATTENTION THEN TURNS TO THE REMAINS OF ISAAC...WHICH LIFT SLOWLY ACROSS THE MISSOURI VALLEY TODAY...THEN DRIFT EAST ACROSS CENTRAL IL/IND SAT. THIS SYSTEM SHOULD PRODUCE JUST INCREASING HIGH/MID CLOUDS ACROSS THE AREA LATER TODAY AND TONIGHT...WITH GUIDANCE INDICATING RAIN SHOWERS MOVING INTO THE TERMINALS GENERALLY AFTER 12Z SATURDAY MORNING. ALL MODELS INDICATE A SHARP NORTHERN CUTOFF TO THE PRECIP...WITH THAT CUTOFF LIKELY SOMEWHERE OVER NORTHERN IL. AT THIS DISTANCE HAVE INDICATED A VICINITY SHOWER MENTION FOR ORD IN THE FINAL HOURS OF THE 30 HR FORECAST...WITH ROOM FOR FURTHER DEFINITION IN SUBSEQUENT FORECASTS. WITH THE LOW PRESSURE CENTER MOVING INTO IL...THE PRESSURE GRADIENT LOOKS TO TIGHTEN ENOUGH FOR WINDS TO COME UP INTO THE 10-15 KT RANGE SATURDAY MORNING. RATZER //ORD AND MDW CONFIDENCE...UPDATED 16Z... * HIGH CONFIDENCE IN WIND TRENDS PRIOR TO WIND SHIFT TOWARD EVENING. * MEDIUM CONFIDENCE IN WIND SHIFT TIMING WITH COLD FRONT. * MEDIUM CONFIDENCE IN SHOWERS REMAINING S OF ORD/MDW THROUGH 12Z SAT. TRS //OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z... SATURDAY NIGHT... SUNDAY...CHC OF RA/SHRA. MVFR/IFR POSSIBLE. MONDAY...SLGT CHC SHRA/TSRA. MVFR POSSIBLE. TUESDAY...VFR. WEDNESDAY...VFR. THURSDAY...CHC SHRA/TSRA. OTHERWISE VFR. RATZER && .MARINE... 246 AM CDT MARINE FORECAST CONCERNS INCLUDE A PERIOD OF GUSTY SOUTHWEST WINDS THIS MORNING AHEAD OF A COLD FRONT WHICH WILL SAG SOUTH ACROSS LAKE MICHIGAN TODAY...AND A PERIOD OF MODEST EAST-NORTHEAST WINDS THIS THE WEEKEND AS THE SURFACE LOW PRESSURE CIRCULATION ASSOCIATED WITH TROPICAL DEPRESSION ISAAC MOVES SLOWLY SOUTH OF THE GREAT LAKES. LOW PRESSURE WAS LOCATED OVER EASTERN QUEBEC EARLY THIS MORNING...WITH A COLD FRONT TRAILING SOUTHWESTWARD ACROSS THE NORTHERN LAKES AND INTO CENTRAL WISCONSIN. THIS COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY AS THE EASTERN CANADIAN LOW CONTINUES TO MOVE AWAY. SOUTHWEST WINDS AHEAD OF THE FRONT HAVE BEEN FAIRLY GUST PARTICULARLY OVER THE NORTHERN END OF LAKE MICHIGAN...WITH SOME GUSTS AROUND 30 KTS NOTED ALONG THE EASTERN SHORE NORTH OF MANISTEE AND AROUND CHARLEVOIX. THESE STRONGER WINDS SHOULD DIMINISH THIS MORNING...AS THE LOW LEVEL JET ASSOCIATED WITH A PASSING UPPER DISTURBANCE PULLS OF TO THE EAST. WINDS WILL VEER TO THE NORTH BEHIND THE FRONT TODAY AND TO NORTH-NORTHEAST TONIGHT...AS THE FRONT CONTINUES TO DRIFT TO THE SOUTH AND HIGH PRESSURE SPREADS ACROSS THE NORTHERN LAKES. THE HIGH WILL DRIFT SOUTHEAST ACROSS THE NORTHERN/EASTERN LAKES SATURDAY AND SUNDAY...WHILE THE AREA OF SURFACE LOW PRESSURE FROM TROPICAL DEPRESSION ISAAC SLOWLY LIFTS ACROSS THE LOWER MISSOURI VALLEY THROUGH TONIGHT...THEN TURNS EAST AND DRIFTS ACROSS SOUTH CENTRAL IL/IND AS IT FILLS DURING THE REMAINDER OF THE WEEKEND. FORECAST MODEL GUIDANCE CONTINUES TO EXHIBIT DIFFERENCES IN THE EXACT AND STRENGTH OF ISAAC DURING THIS PERIOD...THOUGH THE PASSAGE OF THIS LOW SOUTH OF THE LAKES SHOULD RESULT IN A PERIOD OF ENHANCED EASTERLY FLOW PARTICULARLY ON THE SOUTHERN HALF OF LAKE MICHIGAN ESPECIALLY LATE TONIGHT INTO SUNDAY. EAST WINDS TOPPING OUT IN THE 20-25 KT RANGE DURING THIS PERIOD MAY NECESSITATE SMALL CRAFT ADVISORIES ALONG THE WESTERN SHORE OF SOUTHERN LAKE MICHIGAN OVER THE WEEKEND...BEFORE THE LOW WEAKENS AND LOOSENS THE GRADIENT ACROSS THE LAKE BY MONDAY. RATZER && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1007 AM CDT FRI AUG 31 2012 .DISCUSSION... 340 AM CDT THE MAIN FORECAST CONCERNS CONTINUE TO CENTER ON THE HEAVY RAINFALL POTENTIAL ACROSS PORTIONS OF THE AREA THIS WEEKEND AS THE REMNANTS OF HURRICANE ISSAC MOVE ACROSS THE CENTRAL MISSISSIPPI VALLEY. I HAVE FOLLOWED CLOSER TO THE 00 UTC ECMWF...GFS AND UKMET FOR THIS FORECAST PERIOD AS THEY HAVE A DECENT HANDLE ON TRACKING THE REMNANTS UP ACROSS EAST CENTRAL MISSOURI EASTWARD ACROSS CENTRAL ILLINOIS. THE NAM SOLUTION WAS REJECTED AS IT IS DOING A POOR JOB WITH THE SYSTEM. NO BIG CHANGES TO THE PREVIOUS THINKING. THE CENTER OF THE STORM IS NOW LOCATED ACROSS WEST CENTRAL ARKANSAS. IT WILL SLOWLY LIFT NORTHWARD ACROSS SOUTHWESTERN MISSOURI LATER THIS AFTERNOON AND THEN THE SYSTEM IS EXPECTED TO BEGIN TO MOVE MORE EASTERLY LATER TONIGHT AS IT BECOMES INFLUENCED BY THE WESTERLIES. IT STILL APPEARS THE CENTER OF THE SYSTEM WILL PASS SOMEWHERE AROUND OR JUST NORTH OF THE ST LOUIS AREA AND TRANSVERSE THE CENTRAL SECTIONS OF ILLINOIS. ULTIMATELY THIS WILL RESULT IN THE HEAVIEST RAINFALL ACROSS MY SOUTHERN COUNTIES...SOUTH OF INTERSTATE 80. IT APPEARS THERE WILL BE A VERY SHARPE GRADIENT ACROSS NORTHERN ILLINOIS SOMEWHERE AROUND THE I 88 CORRIDOR. THE NORTHERN SUBURBS OF CHICAGO MAY ONLY GET MINOR AMOUNTS UP TO A QUARTER INCH...WHILE THE SOUTHERN BURBS GET MORE THAN AN INCH. BY FAR THE HEAVIEST AMOUNTS LOOK TO BE ACROSS MY SOUTHERN COUNTIES FROM SOUTHERN LA SALLE EASTWARD THROUGH KANKAKEE AND POINTS SOUTH. IN THESE AREAS 3 TO 6 INCHES ARE POSSIBLE...WITH LOCALLY HIGH AMOUNTS POSSIBLE. DUE TO THE EXPECTED RAINFALL...I LOWER TEMPERATURES INTO THE 70S FOR HIGHS...MANY SOUTH FOR SATURDAY AND SUNDAY. THE HEAVY RAIN THREAT WILL END FROM WEST TO EAST ON LATER ON SUNDAY AS THE SYSTEM MOVE EAST AND RAPIDLY WEAKENS. IN THE EXTENDED PERIOD OVERALL CONFIDENCE IS LOW AS IT APPEARS THE WESTERLIES WILL BECOME ACTIVE ACROSS NORTH AMERICA. THIS WILL LIKELY DRIVE A COUPLE OF POTENT MID/UPPER TROUGHS ACROSS SOUTHERN CANADA. THE GUIDANCE SUGGESTS THAT A TROUGH WILL TRY TO DIG ACROSS THE NORTH CENTRAL CONUS BY MID TO LATE WEEK. HOWEVER...THERE IS A SIGNIFICANT AMOUNT OF SPREAD AMONGST THE MODEL ENSEMBLES...INDICATING LARGE TIMING UNCERTAINTIES. IT DOES APPEAR THERE WILL BE A CHANCE OF THUNDERSTORMS SOMETIME EITHER WEDNESDAY NIGHT OR THURSDAY AS A COLD FRONT DROPS ACROSS THE AREA. TEMPERATURES DURING THE PERIOD WILL LIKELY BE NEAR AVERAGE EARLY ON IN THE WEEK...THEN TRENDING TO BELOW AVERAGE AS A COOL AIR MASS LOOKS TO SET UP ACROSS THE REGION BEHIND THIS COLD FRONT. KJB && .HYDROLOGY... 441 AM CDT NOT MUCH HAS CHANGED WITH THE TRACK OF THE REMNANTS OF TROPICAL CYCLONE ISAAC. THE SYSTEM IS EXPECTED TO TRACK FROM ITS CURRENT POSITION ACROSS WEST CENTRAL ARKANSAS...NORTHWARD TO CENTRAL MISSOURI BY EARLY SATURDAY...AND THEN TRANSITION TO THE EAST ALONG THE INTERSTATE 70 CORRIDOR THIS WEEKEND. DUE TO THE TROPICAL NATURE OF THE STORM SYSTEM...A VERY HIGH AMOUNT OF ATMOSPHERIC MOISTURE WILL ACCOMPANY THE SYSTEM. BECAUSE OF THIS...IT APPEARS LIKELY THAT PERIODS OF HEAVY RAINFALL WILL OCCUR ACROSS CENTRAL ILLINOIS AND PORTIONS OF NORTHWESTERN INDIANA ON SATURDAY THROUGH SUNDAY. THE LATEST FORECASTED TOTAL RAINFALL AMOUNTS CALLS FOR BETWEEN THREE TO SIX INCHES ACROSS THE FAR SOUTHERN COUNTIES OF THE CWA...LIVINGSTON/FORD/IROQUOIS/BENTON...WITH AMOUNTS DROPPING OFF RAPIDLY TO THE NORTH. IT IS POSSIBLE THAT LOCATIONS NEAR THE WISCONSIN BORDER MAY SEE VERY LITTLE RAINFALL. THE RIVER BASINS MOSTLY LIKELY TO SEE THE GREATEST IMPACT WILL BE THE KANKAKEE...IROQUOIS AND VERMILLION RIVERS AND SMALLER RIVERS AND CREEKS DRAINING INTO THEM. GIVEN THE SLOW MOVEMENT TO THE SYSTEM AND THE COPIOUS AMOUNTS OF DEEP LAYER MOISTURE LIKELY TO BE PRESENT...WIDESPREAD RAINFALL AMOUNTS OF 2 INCHES PER SIX HOUR PERIOD IS POSSIBLE...AND LOCALLY HIGHER AMOUNTS ARE CERTAINLY NOT OUT OF THE QUESTION. THIS AREA WILL NEED TO BE UNDER CONSIDERATION FOR AN AREAL FLOOD WARNING FOR LOCATIONS NORTH OF THE HEAVY RAINFALL AXIS...NORTHWARD TO THE I-88 CORRIDOR...1 TO 2 INCHES OF TOTAL RAINFALL IS POSSIBLE AND THE MORE FLASHY BASINS OF THE SOUTHERN PORTIONS OF THE CHICAGO METRO AREA COULD SEE FLOODING PROBLEMS AS WELL. KREIN/KJB && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 12Z... *MARGINAL GUSTINESS AS BOUNDARY LAYER DEEPENS WITH HEATING... MIXING DOWN 15-20 KT TO THE SURFACE. * TIMING WIND SHIFT FROM WSW TO NE WITH COLD FRONT SINKING FROM N CENTRAL AND SW WI DOWN ACROSS AREA TOWARD EVENING. * SMALL POTENTIAL FOR SHRA/ISOLD TS FAR SOUTHERN WI INTO NE AND FAR N CENTRAL IL BORDER MID-LATE AFTERNOON. * POTENTIAL FOR SHOWERS ASSOCIATED WITH TD ISAAC MAINLY BEYOND 12Z SATURDAY. RATZER //DISCUSSION...UPDATED 14Z... ONLY VERY MINOR TWEAKS MADE TO 14Z TAFOR. SSW-SW LOW LEVEL WINDS ADVECTING MID-UPPER 60S SURFACE DEW POINTS OVER THE AREA AT MID MORNING WITH UPPER 60-LOWER 70S ACROSS CENTRAL IL. WITH CONTINUED HEATING DURING THE LATE MORNING THE LOW LEVEL MOISTURE ADVECTION WILL BE OFFSET BY DEEPENING OF MIXING IN THE BOUNDARY LAYER. EXPECT DEW POINTS TO BE IN THE MID-UPPER 60S DURING THE AFTERNOON. THIS GIVES CONVECTIVE TEMPERATURES IN THE UPPER 80S WHICH IS FORECAST TO REACH AROUND NOON. THOUGH NOT OPERATIONALLY SIGNIFICANT DID INCLUDE A FORECAST STARTING AT 17Z INCLUDING HIGHER BASED CU DEVELOPING. MODELS SHOW LOW LEVEL CONVERGENCE ALONG THE WI COLD FRONT DROPPING TOWARD THE IL BORDER THIS AFTERNOON...AS WELL AS IN NE ALONG A LAKE BREEZE BOUNDARY PUSHING INLAND. FORECAST SOUNDINGS FROM THE 12Z RUC13 SHOW MINIMAL CIN OVER CHI AREA DURING THE LATER AFTERNOON ALONG WITH DECENT CAPE VALUES. LOW LEVEL WARMING AND CONVERGENCE WOULD FAVOR ISOLD TO SCT TS DEVELOPMENT ALONG THE COLD FRONT AND LAKE BREEZE MID-LATE AFTERNOON...WHILE SUBSIDENCE INN THE MID AND UPPER LEVELS ON THE PERIPHERY OF ISSAC REMNANTS SPREAD OVER THE LOCAL AREA. THIS WITH INCREASING CLOUDS CUTTING SURFACE HEATING DURING THE LATER AFTERNOON WOULD DISCOURAGE AN TS DEVELOPMENT. THREAT TOO LOW AT THIS TIME TO INCLUDE ANY MENTION IN TAFOR THOUGH LOW COVERAGE NOT TS LATE AFTERNOON NOT TOTALLY OUT OF THE QUESTION. TRS PREVIOUS DISCUSSION...UPDATED 12Z... LITTLE CHANGE IN AVIATION FORECAST THINKING FROM 06Z ISSUANCE. MAIN FOCUS REMAINS ON TIMING OF WEAK COLD FRONT AND WIND SHIFT FROM WEST-SOUTHWEST TO NORTHEAST TOWARD EVENING...THEN INCREASING HIGH CLOUDS THIS AFTERNOON AND EVENTUAL PRECIP POTENTIAL SATURDAY AS THE REMAINS OF TROPICAL DEPRESSION ISAAC MOVE SLOWLY INTO IL/IND. THE COLD FRONT...WHICH WAS FROM EAST CENTRAL WI TO NORTH CENTRAL IA AT 11Z...WILL CONTINUE TO MOVE SLOWLY SOUTH TOWARD THE TERMINALS TODAY. VAD WIND PROFILES INDICATE THE PRESENCE OF A 35 KT SPEED MAX ABOVE THE BOUNDARY LAYER AT AROUND 1000 FT AGL THIS MORNING WHICH WILL RESULT IN A PERIOD OF MARGINAL LLWS FOR THE NEXT HOUR OR TWO UNTIL THE BOUNDARY LAYER BECOMES MORE DEEPLY MIXED. WITH MIXING...SOUTHWEST WINDS WILL BECOME A BIT BREEZY BY MID-MORNING WITH GUSTS APPROACHING 20 KTS. THE GRADIENT SHOULD WEAKEN THIS AFTERNOON AS THE COLD FRONTAL TROUGH APPROACHES HOWEVER...ALLOWING WINDS TO DECREASE A BIT. TIMING OF THE FRONTAL PASSAGE AND A WIND SHIFT FROM WEST-SOUTHWEST TO NORTHEAST STILL APPEARS TO BE ON TRACK FOR THE 23-01Z PERIOD ACROSS THE TERMINALS...WITH WINDS REMAINING NORTHEAST AROUND 10 KTS OVERNIGHT. ATTENTION THEN TURNS TO THE REMAINS OF ISAAC...WHICH LIFT SLOWLY ACROSS THE MISSOURI VALLEY TODAY...THEN DRIFT EAST ACROSS CENTRAL IL/IND SAT. THIS SYSTEM SHOULD PRODUCE JUST INCREASING HIGH/MID CLOUDS ACROSS THE AREA LATER TODAY AND TONIGHT...WITH GUIDANCE INDICATING RAIN SHOWERS MOVING INTO THE TERMINALS GENERALLY AFTER 12Z SATURDAY MORNING. ALL MODELS INDICATE A SHARP NORTHERN CUTOFF TO THE PRECIP...WITH THAT CUTOFF LIKELY SOMEWHERE OVER NORTHERN IL. AT THIS DISTANCE HAVE INDICATED A VICINITY SHOWER MENTION FOR ORD IN THE FINAL HOURS OF THE 30 HR FORECAST...WITH ROOM FOR FURTHER DEFINITION IN SUBSEQUENT FORECASTS. WITH THE LOW PRESSURE CENTER MOVING INTO IL...THE PRESSURE GRADIENT LOOKS TO TIGHTEN ENOUGH FOR WINDS TO COME UP INTO THE 10-15 KT RANGE SATURDAY MORNING. RATZER //ORD AND MDW CONFIDENCE...UPDATED 12Z... * HIGH CONFIDENCE IN WIND TRENDS PRIOR TO WIND SHIFT TOWARD EVENING. * MEDIUM CONFIDENCE IN WIND SHIFT TIMING WITH COLD FRONT. * MEDIUM CONFIDENCE IN SHOWERS REMAINING S OF ORD/MDW THROUGH 12Z SAT. TRS //OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z... SATURDAY NIGHT... SUNDAY...CHC OF RA/SHRA. MVFR/IFR POSSIBLE. MONDAY...SLGT CHC SHRA/TSRA. MVFR POSSIBLE. TUESDAY...VFR. WEDNESDAY...VFR. THURSDAY...CHC SHRA/TSRA. OTHERWISE VFR. RATZER && .MARINE... 246 AM CDT MARINE FORECAST CONCERNS INCLUDE A PERIOD OF GUSTY SOUTHWEST WINDS THIS MORNING AHEAD OF A COLD FRONT WHICH WILL SAG SOUTH ACROSS LAKE MICHIGAN TODAY...AND A PERIOD OF MODEST EAST-NORTHEAST WINDS THIS THE WEEKEND AS THE SURFACE LOW PRESSURE CIRCULATION ASSOCIATED WITH TROPICAL DEPRESSION ISAAC MOVES SLOWLY SOUTH OF THE GREAT LAKES. LOW PRESSURE WAS LOCATED OVER EASTERN QUEBEC EARLY THIS MORNING...WITH A COLD FRONT TRAILING SOUTHWESTWARD ACROSS THE NORTHERN LAKES AND INTO CENTRAL WISCONSIN. THIS COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY AS THE EASTERN CANADIAN LOW CONTINUES TO MOVE AWAY. SOUTHWEST WINDS AHEAD OF THE FRONT HAVE BEEN FAIRLY GUST PARTICULARLY OVER THE NORTHERN END OF LAKE MICHIGAN...WITH SOME GUSTS AROUND 30 KTS NOTED ALONG THE EASTERN SHORE NORTH OF MANISTEE AND AROUND CHARLEVOIX. THESE STRONGER WINDS SHOULD DIMINISH THIS MORNING...AS THE LOW LEVEL JET ASSOCIATED WITH A PASSING UPPER DISTURBANCE PULLS OF TO THE EAST. WINDS WILL VEER TO THE NORTH BEHIND THE FRONT TODAY AND TO NORTH-NORTHEAST TONIGHT...AS THE FRONT CONTINUES TO DRIFT TO THE SOUTH AND HIGH PRESSURE SPREADS ACROSS THE NORTHERN LAKES. THE HIGH WILL DRIFT SOUTHEAST ACROSS THE NORTHERN/EASTERN LAKES SATURDAY AND SUNDAY...WHILE THE AREA OF SURFACE LOW PRESSURE FROM TROPICAL DEPRESSION ISAAC SLOWLY LIFTS ACROSS THE LOWER MISSOURI VALLEY THROUGH TONIGHT...THEN TURNS EAST AND DRIFTS ACROSS SOUTH CENTRAL IL/IND AS IT FILLS DURING THE REMAINDER OF THE WEEKEND. FORECAST MODEL GUIDANCE CONTINUES TO EXHIBIT DIFFERENCES IN THE EXACT AND STRENGTH OF ISAAC DURING THIS PERIOD...THOUGH THE PASSAGE OF THIS LOW SOUTH OF THE LAKES SHOULD RESULT IN A PERIOD OF ENHANCED EASTERLY FLOW PARTICULARLY ON THE SOUTHERN HALF OF LAKE MICHIGAN ESPECIALLY LATE TONIGHT INTO SUNDAY. EAST WINDS TOPPING OUT IN THE 20-25 KT RANGE DURING THIS PERIOD MAY NECESSITATE SMALL CRAFT ADVISORIES ALONG THE WESTERN SHORE OF SOUTHERN LAKE MICHIGAN OVER THE WEEKEND...BEFORE THE LOW WEAKENS AND LOOSENS THE GRADIENT ACROSS THE LAKE BY MONDAY. RATZER && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$
AREA FORECAST DISCUSSION
NWS INDIANAPOLIS IN
1245 PM EDT FRI AUG 31 2012 .UPDATE... THE AVIATION SECTION HAS BEEN UPDATED BELOW. && .SYNOPSIS... ISSUED AT 234 AM EDT FRI AUG 31 2012 THE REMNANTS OF HURRICANE ISAAC WILL BE THE MAIN WEATHER FEATURE OVER THE NEXT SEVERAL DAYS. HIGH CLOUDS ARE EXPECTED TO ARRIVE TODAY AS THE REMNANTS MOVE FROM ARKANSAS INTO SOUTHERN MISSOURI. RAIN SHOWERS...ALONG WITH SOME HEAVY RAIN IS EXPECTED TO ARRIVE ON SATURDAY AFTERNOON AND SUNDAY AS THE REMNANTS BEGIN TO PUSH NORTHEAST INTO ILLINOIS. SCATTERED RAIN SHOWERS ARE EXPECTED TO LINGER ACROSS CENTRAL INDIANA ON MONDAY AS THE REMNANTS SLOWLY WEAKEN AND SLOWLY MEANDER EASTWARD INTO THE OHIO VALLEY. AS THE REMNANTS DEPART AS LOW PRESSURE ON TUESDAY NIGHT...HIGH PRESSURE WILL BUILD ACROSS INDIANA BRINGING DRY WEATHER FOR THE MIDDLE OF THE NEXT WORK WEEK. ANOTHER COLD FRONT WILL APPROACH OUR REGION THURSDAY AS A STRONG UPPER TROUGH DIGS INTO THE UPPER MIDWEST. && .NEAR TERM /REST OF TODAY/... ISSUED AT 1020 AM AM EDT FRI AUG 31 2012 VISIBLE SATELLITE SHOWS AN EXTENSIVE AREA OF MID CLOUDS WERE SPREADING NORTHEAST ACROSS OUR REGION. SOME OF THIS MAY THIN OUT THIS AFTERNOON...SO WILL GO PARTLY CLOUDY MOST SECTIONS TODAY. THE BIGGEST QUESTION WILL BE WHAT TO DO WITH TEMPERATURES. BOTH THE NAM AND 12Z RUC STILL INDICATE TEMPERATURES IN THE LOWER 90S THIS AFTERNOON. THIS SEEMS A BIT WARM GIVEN THAT THEY WERE SEVERAL DEGREES TOO WARM YESTERDAY WITH FULL SUNSHINE. WILL RAISE TEMPERATURES JUST A TAD TODAY GIVEN THAT CLOUDS MAY THIN OUT AND MODELS ARE RUNNING SO WARM. IN REGARDS TO PRECIP RADAR SHOWS A BAND OF MOSTLY VIRGA SPREADING NORTH ACROSS OUR STATE. RAPID REFRESH SHOWS A 2ND BAND OF SHOWERS AND THUNDERSTORMS WILL BE ALONG OUR WESTERN BORDER BY LATE AFTERNOON. WILL RAISE POPS A LITTLE ALONG OUR WEST AND ADD SLIGHT CHANCE POPS OVER MOST OF OUR FAR SOUTH THIS AFTERNOON. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... ISSUED AT 234 AM EDT FRI AUG 31 2012 MODELS ARE PRETTY CLOSE WITH THE HANDLING OF THE REMNANTS...BUT AS WE APPROACH SUNDAY AFTERNOON THE NAM SOLUTION OF KEEPING THE LOW CENTERED OVER MISSOURI DOESN/T MAKE MUCH SENSE...AS WELL AS THE LACK OF EASTERN PROPAGATION. THUS WILL USE A BLEND INITIALLY BUT TREND TOWARD THE GFS BY SUNDAY AND SUNDAY NIGHT. TWO FEATURES ARE GOING TO COME TOGETHER TO HELP PRODUCE RAIN ACROSS CENTRAL INDIANA THIS PERIOD. THE APPROACHING REMNANTS OF ISAAC COMBINING WITH A FRONTAL BOUNDARY OVER THE UPPER MIDWEST WHICH IS EXPECTED TO SAG SOUTHWARD AND HELP PROVIDE AN EXTRA LIFT MECHANISM ON SATURDAY AND SUNDAY. CLOUDS WILL BE EXPECTED TO INCREASE BY TONIGHT AND A FEW SHOWERS COULD REACH THE AREA AS BANDS OF PRECIP CONTINUE TO SWIRL AROUND THE LOW WHICH IS EXPECTED TO DRIFT INTO MISSOURI. GIVEN THE CURRENT STRUCTURE OF THE SYSTEM...AND AS DRY AIR CONTINUES TO INFILTRATE THE SYSTEM AS IT APPROACHES...A FEW SHOWERS CANNOT BE RULED OUT REACHING CENTRAL INDIANA OVERNIGHT...PARTICULARLY ACROSS THE WEST WHERE PROXIMITY IS BEST. WILL KEEP SOME PRECIP CHANCES FOR TONIGHT IN TO FORECAST PARTICULAR ACROSS THE WEST. WITH THE ARRIVAL OF A VERY MOIST AIR MASS WILL TREND LOWS HIGHER THAN MAVMOS. AS THE FRONTAL BOUNDARY SAGS SOUTHWARD AND BEGINS TO INTERACT WITH THE REMNANTS OF ISAAC ON SATURDAY AFTERNOON...MORE WIDESPREAD RAIN SHOWERS ARE EXPECTED TO DEVELOP. LOW LEVEL Q VECTORS DISPLAY STRONG CONVERGENCE ACROSS THE AREA BY SATURDAY AFTERNOON AND EVENING AS FORECAST SOUNDINGS REVEAL DEEP MOISTURE PRESENT. WILL STICK WITH NEAR CATEGORICAL POPS FOR SATURDAY...WITH BEST CHANCES STARTING THIS AFTERNOON...ALTHOUGH CONFIDENCE REGARDING PRECISE TIMING ON THE START OF RAINFALL REMAINS LOW DUE TO THE SLOW ARRIVAL OF THE APPROACHING SYSTEM. WILL ALSO TREND HIGH TEMPS COOLER THAN MAVMOS. GFS AND NAM Q VECTORS CONTINUE TO SUGGEST STRONG LOWER LEVEL CONVERGENCE ON SATURDAY NIGHT AND ON SUNDAY AND THE FRONTAL BOUNDARY FROM THE NORTH STALLS OVER THE REGION. FORECAST SOUNDINGS CONTINUE TO SHOW DEEP MOISTURE AVAILABLE WITH THE LINGERING TROPICAL REMNANTS. WILL CONTINUE TO KEEP HIGH POPS ONGOING ON SATURDAY AND SUNDAY...WITH LOW TEMPS WARMER THAN GUIDANCE AND HIGH TEMPS COOLER DUE TO EXPECTED CLOUDS AND RAIN. LOWER LEVEL PRESSURE GRADIENT APPEARS TO GET WEAKER AS THE SYSTEM ARRIVES...AND ALTHOUGH SOME GUSTY WINDS CANNOT BE RULED OUT...ANY GUSTS SHOULD BE LESS THAN PREVIOUSLY EXPECTED. WITH THE SLOW PROGRESSION OF THE SYSTEM...AS THE GFS DEPICTS THE LOW PRESSURE CENTER ONLY REACHING WESTERN INDIANA BY SUNDAY NIGHT WILL NEED TO CONTINUE WITH SOME POPS ON SUNDAY NIGHT. ALTHOUGH BEST FORCING WILL REMAIN WELL SOUTHEAST OF THE LOW...OVER SOUTHEAST INDIANA AND KENTUCKY AS THE FRONTAL BOUNDARY IS EXPECTED TO SAG SOUTHWARD TOWARD THE OHIO RIVER THEN. FORECAST SOUNDINGS CONTINUE TO INDICATE DEEP MOISTURE AVAILABLE...BUT WITH MORE LIMITED FORCING. WILL TREND LOWS WARMER THAN GUIDANCE GIVEN THE CLOUDS AND MOIST...TROPICAL AIR MASS THAT WILL BE PLACE. SUMMING UP...BEST CHANCES FOR HEAVY RAINS CONTINUE TO APPEAR TO BE SATURDAY THROUGH SUNDAY...AND THIS PERIOD WILL ALSO BE THE PERIOD THAT HAS THE BEST CHANCES FOR FLOODING. && .LONG TERM /MONDAY THROUGH THURSDAY/... ISSUED AT 234 AM EDT FRI AUG 31 2012 ENSEMBLE DATA INDICATE REMNANTS OF TROPICAL CYCLONE ISAAC MAY STILL BE IN THE PROCESS OF PASSING ACROSS THE AREA ON MONDAY. OTHERWISE...THE DATA INDICATE THE JET STREAM WILL BE GRADUALLY SINKING SOUTH WITH TIME AS A SERIES OF DISTURBANCES MOVE EAST SOUTHEAST ACROSS THE UPPER GREAT LAKES. LOOKS LIKE A RATHER UNSETTLED EXTENDED PERIOD...WITH THE POTENTIAL FOR A COUPLE OF FRONTAL PASSAGES IN ADDITION TO WHAT IS LEFT OF ISAAC. AT THIS POINT...THE ENSEMBLES SUGGEST A PRECIPITATION THREAT PRETTY MUCH EVERY DAY EXCEPT FOR THE TUESDAY NIGHT AND WEDNESDAY TIME FRAME. WILL GO WITH POPS ON MONDAY...TUESDAY...AND THURSDAY...AND KEEP WEDNESDAY DRY. && .AVIATION /DISCUSSION FOR THE 311800Z TAFS/... ISSUED AT 1245 PM EDT FRI AUG 31 2012 CONDITIONS WILL DETERIORATE TO MVFR TONIGHT AND REMAIN SO FOR MUCH OF SATURDAY. CONFIDENCE IS BELOW AVERAGE WITH FORECAST DUE TO CONTINUING UNCERTAINTY IN TIMING AND PATH OF ISAAC REMNANTS AND UNCERTAINTIES IN WHERE HEAVIER RAIN WILL DEVELOP. THROUGH 00Z OR SO ONLY EXPECT SCATTERED LOW CLOUDS AND BROKEN MID CLOUDS. THERE WILL BE SOME LIGHT SHOWER ACTIVITY...BUT MOST OF THE SHOWERS WILL BE CONFINED TO AREAS NEAR KHUF AND KLAF. VISIBILITIES WILL BE MAINLY VFR IN THE SHOWERS...BUT BRIEF MVFR IS NOT OUT OF THE QUESTION. OTHERWISE EXPECT MVFR CLOUDS TO MOVE IN OVERNIGHT AS MOISTURE CONTINUES TO INCREASE AHEAD OF REMNANTS OF ISAAC. RAIN WILL GRADUALLY BECOME MORE WIDESPREAD...ESPECIALLY ACROSS THE WESTERN SITES. HEAVIER RAIN SHOULDN/T ARRIVE UNTIL AFTER THE TAF PERIOD. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...PUMA NEAR TERM...JH SHORT TERM...PUMA LONG TERM....JAS AVIATION...50
AREA FORECAST DISCUSSION
NWS INDIANAPOLIS IN
1030 AM EDT FRI AUG 31 2012 .UPDATE... THE AVIATION SECTION HAS BEEN UPDATED BELOW. && .SYNOPSIS... ISSUED AT 234 AM EDT FRI AUG 31 2012 THE REMNANTS OF HURRICANE ISAAC WILL BE THE MAIN WEATHER FEATURE OVER THE NEXT SEVERAL DAYS. HIGH CLOUDS ARE EXPECTED TO ARRIVE TODAY AS THE REMNANTS MOVE FROM ARKANSAS INTO SOUTHERN MISSOURI. RAIN SHOWERS...ALONG WITH SOME HEAVY RAIN IS EXPECTED TO ARRIVE ON SATURDAY AFTERNOON AND SUNDAY AS THE REMNANTS BEGIN TO PUSH NORTHEAST INTO ILLINOIS. SCATTERED RAIN SHOWERS ARE EXPECTED TO LINGER ACROSS CENTRAL INDIANA ON MONDAY AS THE REMNANTS SLOWLY WEAKEN AND SLOWLY MEANDER EASTWARD INTO THE OHIO VALLEY. AS THE REMNANTS DEPART AS LOW PRESSURE ON TUESDAY NIGHT...HIGH PRESSURE WILL BUILD ACROSS INDIANA BRINGING DRY WEATHER FOR THE MIDDLE OF THE NEXT WORK WEEK. ANOTHER COLD FRONT WILL APPROACH OUR REGION THURSDAY AS A STRONG UPPER TROUGH DIGS INTO THE UPPER MIDWEST. && .NEAR TERM /REST OF TODAY/... ISSUED AT 1020 AM AM EDT FRI AUG 31 2012 VISIBLE SATELLITE SHOWS AN EXTENSIVE AREA OF MID CLOUDS WERE SPREADING NORTHEAST ACROSS OUR REGION. SOME OF THIS MAY THIN OUT THIS AFTERNOON...SO WILL GO PARTLY CLOUDY MOST SECTIONS TODAY. THE BIGGEST QUESTION WILL BE WHAT TO DO WITH TEMPERATURES. BOTH THE NAM AND 12Z RUC STILL INDICATE TEMPERATURES IN THE LOWER 90S THIS AFTERNOON. THIS SEEMS A BIT WARM GIVEN THAT THEY WERE SEVERAL DEGREES TOO WARM YESTERDAY WITH FULL SUNSHINE. WILL RAISE TEMPERATURES JUST A TAD TODAY GIVEN THAT CLOUDS MAY THIN OUT AND MODELS ARE RUNNING SO WARM. IN REGARDS TO PRECIP RADAR SHOWS A BAND OF MOSTLY VIRGA SPREADING NORTH ACROSS OUR STATE. RAPID REFRESH SHOWS A 2ND BAND OF SHOWERS AND THUNDERSTORMS WILL BE ALONG OUR WESTERN BORDER BY LATE AFTERNOON. WILL RAISE POPS A LITTLE ALONG OUR WEST AND ADD SLIGHT CHANCE POPS OVER MOST OF OUR FAR SOUTH THIS AFTERNOON. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... ISSUED AT 234 AM EDT FRI AUG 31 2012 MODELS ARE PRETTY CLOSE WITH THE HANDLING OF THE REMNANTS...BUT AS WE APPROACH SUNDAY AFTERNOON THE NAM SOLUTION OF KEEPING THE LOW CENTERED OVER MISSOURI DOESN/T MAKE MUCH SENSE...AS WELL AS THE LACK OF EASTERN PROPAGATION. THUS WILL USE A BLEND INITIALLY BUT TREND TOWARD THE GFS BY SUNDAY AND SUNDAY NIGHT. TWO FEATURES ARE GOING TO COME TOGETHER TO HELP PRODUCE RAIN ACROSS CENTRAL INDIANA THIS PERIOD. THE APPROACHING REMNANTS OF ISAAC COMBINING WITH A FRONTAL BOUNDARY OVER THE UPPER MIDWEST WHICH IS EXPECTED TO SAG SOUTHWARD AND HELP PROVIDE AN EXTRA LIFT MECHANISM ON SATURDAY AND SUNDAY. CLOUDS WILL BE EXPECTED TO INCREASE BY TONIGHT AND A FEW SHOWERS COULD REACH THE AREA AS BANDS OF PRECIP CONTINUE TO SWIRL AROUND THE LOW WHICH IS EXPECTED TO DRIFT INTO MISSOURI. GIVEN THE CURRENT STRUCTURE OF THE SYSTEM...AND AS DRY AIR CONTINUES TO INFILTRATE THE SYSTEM AS IT APPROACHES...A FEW SHOWERS CANNOT BE RULED OUT REACHING CENTRAL INDIANA OVERNIGHT...PARTICULARLY ACROSS THE WEST WHERE PROXIMITY IS BEST. WILL KEEP SOME PRECIP CHANCES FOR TONIGHT IN TO FORECAST PARTICULAR ACROSS THE WEST. WITH THE ARRIVAL OF A VERY MOIST AIR MASS WILL TREND LOWS HIGHER THAN MAVMOS. AS THE FRONTAL BOUNDARY SAGS SOUTHWARD AND BEGINS TO INTERACT WITH THE REMNANTS OF ISAAC ON SATURDAY AFTERNOON...MORE WIDESPREAD RAIN SHOWERS ARE EXPECTED TO DEVELOP. LOW LEVEL Q VECTORS DISPLAY STRONG CONVERGENCE ACROSS THE AREA BY SATURDAY AFTERNOON AND EVENING AS FORECAST SOUNDINGS REVEAL DEEP MOISTURE PRESENT. WILL STICK WITH NEAR CATEGORICAL POPS FOR SATURDAY...WITH BEST CHANCES STARTING THIS AFTERNOON...ALTHOUGH CONFIDENCE REGARDING PRECISE TIMING ON THE START OF RAINFALL REMAINS LOW DUE TO THE SLOW ARRIVAL OF THE APPROACHING SYSTEM. WILL ALSO TREND HIGH TEMPS COOLER THAN MAVMOS. GFS AND NAM Q VECTORS CONTINUE TO SUGGEST STRONG LOWER LEVEL CONVERGENCE ON SATURDAY NIGHT AND ON SUNDAY AND THE FRONTAL BOUNDARY FROM THE NORTH STALLS OVER THE REGION. FORECAST SOUNDINGS CONTINUE TO SHOW DEEP MOISTURE AVAILABLE WITH THE LINGERING TROPICAL REMNANTS. WILL CONTINUE TO KEEP HIGH POPS ONGOING ON SATURDAY AND SUNDAY...WITH LOW TEMPS WARMER THAN GUIDANCE AND HIGH TEMPS COOLER DUE TO EXPECTED CLOUDS AND RAIN. LOWER LEVEL PRESSURE GRADIENT APPEARS TO GET WEAKER AS THE SYSTEM ARRIVES...AND ALTHOUGH SOME GUSTY WINDS CANNOT BE RULED OUT...ANY GUSTS SHOULD BE LESS THAN PREVIOUSLY EXPECTED. WITH THE SLOW PROGRESSION OF THE SYSTEM...AS THE GFS DEPICTS THE LOW PRESSURE CENTER ONLY REACHING WESTERN INDIANA BY SUNDAY NIGHT WILL NEED TO CONTINUE WITH SOME POPS ON SUNDAY NIGHT. ALTHOUGH BEST FORCING WILL REMAIN WELL SOUTHEAST OF THE LOW...OVER SOUTHEAST INDIANA AND KENTUCKY AS THE FRONTAL BOUNDARY IS EXPECTED TO SAG SOUTHWARD TOWARD THE OHIO RIVER THEN. FORECAST SOUNDINGS CONTINUE TO INDICATE DEEP MOISTURE AVAILABLE...BUT WITH MORE LIMITED FORCING. WILL TREND LOWS WARMER THAN GUIDANCE GIVEN THE CLOUDS AND MOIST...TROPICAL AIR MASS THAT WILL BE PLACE. SUMMING UP...BEST CHANCES FOR HEAVY RAINS CONTINUE TO APPEAR TO BE SATURDAY THROUGH SUNDAY...AND THIS PERIOD WILL ALSO BE THE PERIOD THAT HAS THE BEST CHANCES FOR FLOODING. && .LONG TERM /MONDAY THROUGH THURSDAY/... ISSUED AT 234 AM EDT FRI AUG 31 2012 ENSEMBLE DATA INDICATE REMNANTS OF TROPICAL CYCLONE ISAAC MAY STILL BE IN THE PROCESS OF PASSING ACROSS THE AREA ON MONDAY. OTHERWISE...THE DATA INDICATE THE JET STREAM WILL BE GRADUALLY SINKING SOUTH WITH TIME AS A SERIES OF DISTURBANCES MOVE EAST SOUTHEAST ACROSS THE UPPER GREAT LAKES. LOOKS LIKE A RATHER UNSETTLED EXTENDED PERIOD...WITH THE POTENTIAL FOR A COUPLE OF FRONTAL PASSAGES IN ADDITION TO WHAT IS LEFT OF ISAAC. AT THIS POINT...THE ENSEMBLES SUGGEST A PRECIPITATION THREAT PRETTY MUCH EVERY DAY EXCEPT FOR THE TUESDAY NIGHT AND WEDNESDAY TIME FRAME. WILL GO WITH POPS ON MONDAY...TUESDAY...AND THURSDAY...AND KEEP WEDNESDAY DRY. && .AVIATION /DISCUSSION FOR THE 311430Z TAF UPDATE/... ISSUED AT 1030 AM EDT FRI AUG 31 2012 KIND TAF LOOKS GOOD. ONLY MINOR CHANGE TO WIND DIRECTION MADE. THERE COULD BE SOME SPRINKLES/LIGHT SHOWERS BY AFTERNOON...BUT THESE WILL NOT LOWER VISIBILITY BELOW VFR. PREVIOUS DISCUSSION FOLLOWS... CLOUD COVER WILL BE INCREASING TODAY...BUT CEILINGS SHOULD REMAIN WELL ABOVE 050 THROUGH 010000Z. SOME DIURNAL CLOUD COVER BASED AROUND 030 POSSIBLE AFTER 311500Z. SOME LOW POTENTIAL FOR WIDELY SCATTERED CONVECTION BY THE MID AFTERNOON HOURS...ESPECIALLY OVER THE MORE SOUTHERN TAF SITES...AS A VORTICITY LOBE SWINGS INTO THE AREA FROM THE SOUTH AND CONVECTIVE TEMPERATURES ARE WITHIN REACH. HOWEVER...CHANCES FOR A DIRECT IMPACT AT A PARTICULAR TAF SITE TOO LOW TO MENTION AT THIS POINT. NO PROLONGED VISIBILITY RESTRICTIONS...SURFACE WINDS GENERALLY UNDER 12 KTS THROUGH 010000Z. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...PUMA NEAR TERM...JH SHORT TERM...PUMA LONG TERM....JAS AVIATION...JAS/50
AREA FORECAST DISCUSSION
NWS INDIANAPOLIS IN
1020 AM EDT FRI AUG 31 2012 .UPDATE... NEAR TERM SECTION FOR THE REST OF TODAY HAS BEEN UDPATED BELOW. && .SYNOPSIS... ISSUED AT 234 AM EDT FRI AUG 31 2012 THE REMNANTS OF HURRICANE ISAAC WILL BE THE MAIN WEATHER FEATURE OVER THE NEXT SEVERAL DAYS. HIGH CLOUDS ARE EXPECTED TO ARRIVE TODAY AS THE REMNANTS MOVE FROM ARKANSAS INTO SOUTHERN MISSOURI. RAIN SHOWERS...ALONG WITH SOME HEAVY RAIN IS EXPECTED TO ARRIVE ON SATURDAY AFTERNOON AND SUNDAY AS THE REMNANTS BEGIN TO PUSH NORTHEAST INTO ILLINOIS. SCATTERED RAIN SHOWERS ARE EXPECTED TO LINGER ACROSS CENTRAL INDIANA ON MONDAY AS THE REMNANTS SLOWLY WEAKEN AND SLOWLY MEANDER EASTWARD INTO THE OHIO VALLEY. AS THE REMNANTS DEPART AS LOW PRESSURE ON TUESDAY NIGHT...HIGH PRESSURE WILL BUILD ACROSS INDIANA BRINGING DRY WEATHER FOR THE MIDDLE OF THE NEXT WORK WEEK. ANOTHER COLD FRONT WILL APPROACH OUR REGION THURSDAY AS A STRONG UPPER TROUGH DIGS INTO THE UPPER MIDWEST. && .NEAR TERM /REST OF TODAY/... ISSUED AT 1020 AM AM EDT FRI AUG 31 2012 VISIBLE SATELLITE SHOWS AN EXTENSIVE AREA OF MID CLOUDS WERE SPREADING NORTHEAST ACROSS OUR REGION. SOME OF THIS MAY THIN OUT THIS AFTERNOON...SO WILL GO PARTLY CLOUDY MOST SECTIONS TODAY. THE BIGGEST QUESTION WILL BE WHAT TO DO WITH TEMPERATURES. BOTH THE NAM AND 12Z RUC STILL INDICATE TEMPERATURES IN THE LOWER 90S THIS AFTERNOON. THIS SEEMS A BIT WARM GIVEN THAT THEY WERE SEVERAL DEGREES TOO WARM YESTERDAY WITH FULL SUNSHINE. WILL RAISE TEMPERATURES JUST A TAD TODAY GIVEN THAT CLOUDS MAY THIN OUT AND MODELS ARE RUNNING SO WARM. IN REGARDS TO PRECIP RADAR SHOWS A BAND OF MOSTLY VIRGA SPREADING NORTH ACROSS OUR STATE. RAPID REFRESH SHOWS A 2ND BAND OF SHOWERS AND THUNDERSTORMS WILL BE ALONG OUR WESTERN BORDER BY LATE AFTERNOON. WILL RAISE POPS A LITTLE ALONG OUR WEST AND ADD SLIGHT CHANCE POPS OVER MOST OF OUR FAR SOUTH THIS AFTERNOON. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... ISSUED AT 234 AM EDT FRI AUG 31 2012 MODELS ARE PRETTY CLOSE WITH THE HANDLING OF THE REMNANTS...BUT AS WE APPROACH SUNDAY AFTERNOON THE NAM SOLUTION OF KEEPING THE LOW CENTERED OVER MISSOURI DOESN/T MAKE MUCH SENSE...AS WELL AS THE LACK OF EASTERN PROPAGATION. THUS WILL USE A BLEND INITIALLY BUT TREND TOWARD THE GFS BY SUNDAY AND SUNDAY NIGHT. TWO FEATURES ARE GOING TO COME TOGETHER TO HELP PRODUCE RAIN ACROSS CENTRAL INDIANA THIS PERIOD. THE APPROACHING REMNANTS OF ISAAC COMBINING WITH A FRONTAL BOUNDARY OVER THE UPPER MIDWEST WHICH IS EXPECTED TO SAG SOUTHWARD AND HELP PROVIDE AN EXTRA LIFT MECHANISM ON SATURDAY AND SUNDAY. CLOUDS WILL BE EXPECTED TO INCREASE BY TONIGHT AND A FEW SHOWERS COULD REACH THE AREA AS BANDS OF PRECIP CONTINUE TO SWIRL AROUND THE LOW WHICH IS EXPECTED TO DRIFT INTO MISSOURI. GIVEN THE CURRENT STRUCTURE OF THE SYSTEM...AND AS DRY AIR CONTINUES TO INFILTRATE THE SYSTEM AS IT APPROACHES...A FEW SHOWERS CANNOT BE RULED OUT REACHING CENTRAL INDIANA OVERNIGHT...PARTICULARLY ACROSS THE WEST WHERE PROXIMITY IS BEST. WILL KEEP SOME PRECIP CHANCES FOR TONIGHT IN TO FORECAST PARTICULAR ACROSS THE WEST. WITH THE ARRIVAL OF A VERY MOIST AIR MASS WILL TREND LOWS HIGHER THAN MAVMOS. AS THE FRONTAL BOUNDARY SAGS SOUTHWARD AND BEGINS TO INTERACT WITH THE REMNANTS OF ISAAC ON SATURDAY AFTERNOON...MORE WIDESPREAD RAIN SHOWERS ARE EXPECTED TO DEVELOP. LOW LEVEL Q VECTORS DISPLAY STRONG CONVERGENCE ACROSS THE AREA BY SATURDAY AFTERNOON AND EVENING AS FORECAST SOUNDINGS REVEAL DEEP MOISTURE PRESENT. WILL STICK WITH NEAR CATEGORICAL POPS FOR SATURDAY...WITH BEST CHANCES STARTING THIS AFTERNOON...ALTHOUGH CONFIDENCE REGARDING PRECISE TIMING ON THE START OF RAINFALL REMAINS LOW DUE TO THE SLOW ARRIVAL OF THE APPROACHING SYSTEM. WILL ALSO TREND HIGH TEMPS COOLER THAN MAVMOS. GFS AND NAM Q VECTORS CONTINUE TO SUGGEST STRONG LOWER LEVEL CONVERGENCE ON SATURDAY NIGHT AND ON SUNDAY AND THE FRONTAL BOUNDARY FROM THE NORTH STALLS OVER THE REGION. FORECAST SOUNDINGS CONTINUE TO SHOW DEEP MOISTURE AVAILABLE WITH THE LINGERING TROPICAL REMNANTS. WILL CONTINUE TO KEEP HIGH POPS ONGOING ON SATURDAY AND SUNDAY...WITH LOW TEMPS WARMER THAN GUIDANCE AND HIGH TEMPS COOLER DUE TO EXPECTED CLOUDS AND RAIN. LOWER LEVEL PRESSURE GRADIENT APPEARS TO GET WEAKER AS THE SYSTEM ARRIVES...AND ALTHOUGH SOME GUSTY WINDS CANNOT BE RULED OUT...ANY GUSTS SHOULD BE LESS THAN PREVIOUSLY EXPECTED. WITH THE SLOW PROGRESSION OF THE SYSTEM...AS THE GFS DEPICTS THE LOW PRESSURE CENTER ONLY REACHING WESTERN INDIANA BY SUNDAY NIGHT WILL NEED TO CONTINUE WITH SOME POPS ON SUNDAY NIGHT. ALTHOUGH BEST FORCING WILL REMAIN WELL SOUTHEAST OF THE LOW...OVER SOUTHEAST INDIANA AND KENTUCKY AS THE FRONTAL BOUNDARY IS EXPECTED TO SAG SOUTHWARD TOWARD THE OHIO RIVER THEN. FORECAST SOUNDINGS CONTINUE TO INDICATE DEEP MOISTURE AVAILABLE...BUT WITH MORE LIMITED FORCING. WILL TREND LOWS WARMER THAN GUIDANCE GIVEN THE CLOUDS AND MOIST...TROPICAL AIR MASS THAT WILL BE PLACE. SUMMING UP...BEST CHANCES FOR HEAVY RAINS CONTINUE TO APPEAR TO BE SATURDAY THROUGH SUNDAY...AND THIS PERIOD WILL ALSO BE THE PERIOD THAT HAS THE BEST CHANCES FOR FLOODING. && .LONG TERM /MONDAY THROUGH THURSDAY/... ISSUED AT 234 AM EDT FRI AUG 31 2012 ENSEMBLE DATA INDICATE REMNANTS OF TROPICAL CYCLONE ISAAC MAY STILL BE IN THE PROCESS OF PASSING ACROSS THE AREA ON MONDAY. OTHERWISE...THE DATA INDICATE THE JET STREAM WILL BE GRADUALLY SINKING SOUTH WITH TIME AS A SERIES OF DISTURBANCES MOVE EAST SOUTHEAST ACROSS THE UPPER GREAT LAKES. LOOKS LIKE A RATHER UNSETTLED EXTENDED PERIOD...WITH THE POTENTIAL FOR A COUPLE OF FRONTAL PASSAGES IN ADDITION TO WHAT IS LEFT OF ISAAC. AT THIS POINT...THE ENSEMBLES SUGGEST A PRECIPITATION THREAT PRETTY MUCH EVERY DAY EXCEPT FOR THE TUESDAY NIGHT AND WEDNESDAY TIME FRAME. WILL GO WITH POPS ON MONDAY...TUESDAY...AND THURSDAY...AND KEEP WEDNESDAY DRY. && .AVIATION /DISCUSSION FOR THE 311200Z TAFS/... ISSUED AT 632 AM EDT FRI AUG 31 2012 CLOUD COVER WILL BE INCREASING TODAY...BUT CEILINGS SHOULD REMAIN WELL ABOVE 050 THROUGH 010000Z. SOME DIURNAL CLOUD COVER BASED AROUND 030 POSSIBLE AFTER 311500Z. SOME LOW POTENTIAL FOR WIDELY SCATTERED CONVECTION BY THE MID AFTERNOON HOURS...ESPECIALLY OVER THE MORE SOUTHERN TAF SITES...AS A VORTICITY LOBE SWINGS INTO THE AREA FROM THE SOUTH AND CONVECTIVE TEMPERATURES ARE WITHIN REACH. HOWEVER...CHANCES FOR A DIRECT IMPACT AT A PARTICULAR TAF SITE TOO LOW TO MENTION AT THIS POINT. NO PROLONGED VISIBILITY RESTRICTIONS...SURFACE WINDS GENERALLY UNDER 12 KTS THROUGH 010000Z. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...PUMA NEAR TERM...JH SHORT TERM...PUMA LONG TERM....JAS AVIATION...JAS
AREA FORECAST DISCUSSION...UPDATED
NWS JACKSON KY
225 PM EDT THU AUG 30 2012 .UPDATE... ISSUED AT 225 PM EDT THU AUG 30 2012 DID AN UPDATE TO THE GRIDS TO INCREASE THE DEWPOINTS...SKY COVER AND POPS IN THE SOUTH AS THE TROPICAL MOISTURE IS STARTING TO SEEP IN AND PROMOTE THE START OF CONVECTION. THE LATEST HRRR SUPPORTS THIS IDEA AS WELL. ACCORDINGLY...AN UPDATE TO THE GRIDS...WEB PAGES...AND ZONES IS FORTHCOMING. UPDATE ISSUED AT 955 AM EDT THU AUG 30 2012 13Z SFC ANALYSIS SHOWS HIGH PRESSURE OFF TO THE NORTHEAST OF KENTUCKY...BUT STILL EXERTING ENOUGH INFLUENCE TO KEEP THE CLOUDS AND WEATHER AT BAY FOR ONE MORE DAY. THIS IS BEING STARKLY DEMONSTRATED ON SATELLITE CURRENTLY AS THE LEADING HIGH CLOUDS FROM ISAAC HAVE SEEMINGLY HIT A WALL RIGHT ALONG OUR BORDER WITH TENNESSEE. THE EARLIER PATCHY VALLEY FOG HAS LIFTED AND DISSIPATED THROUGH THE AREA SO NOTHING STANDS IN THE WAY OF A SUNNY AND PLEASANT DAY FOR ALL BUT PARTS OF OUR TENNESSEE BORDER COUNTIES. HAVE UPDATED THE GRIDS TO REFLECT THE LATEST THOUGHTS ON SKY COVER THROUGH THE DAY AND FOR ADJUSTMENTS TO THE T AND TD ONES BASED ON THE LATEST OBS AND TRENDS. UPDATES HAVE BEEN SENT TO THE NDFD AND WEB SERVERS. HAVE ALSO UPDATED THE ZONES...MAINLY TO REMOVE THE MENTION OF MORNING FOG. UPDATE ISSUED AT 712 AM EDT THU AUG 30 2012 ISSUED A MORNING UPDATE TO FRESHEN UP THE GRIDS AND SEND THEM OFF TO NDFD. SOME 5 TO 7 KFT CLOUD LAYERS HAVE EDGED INTO THE AREA SOUTH OF THE HAL ROGERS PARKWAY SO UPDATED CLOUD COVER. OTHERWISE...FORECAST IS ON TRACK AND A NEW ZFP WILL NOT BE NEEDED. && .SHORT TERM...(TODAY THROUGH FRIDAY) ISSUED AT 345 AM EDT THU AUG 30 2012 MAIN CONCERNS DURING THE SHORT TERM WILL REVOLVE AROUND THE INITIAL IMPACTS OF ISAAC INTO THE OHIO VALLEY. AS OF 07Z CLEAR SKIES RESIDE OVER EASTERN KENTUCKY WITH CIRRUS ASSOCIATED WITH ISAAC SKIRTING THE TN BORDER. OTHERWISE CLEAR SKIES HAS ALLOWED A DECENT RIDGE VALLEY SPLIT ACROSS THE AREA AS WELL AS SOME VALLEY FOG...BUT CONFINED TO THE DEEPER RIVER VALLEYS SO WILL MENTION THAT THIS MORNING. AN INCREASE OF CLOUD COVER INTO THE AREA WILL KEEP MORNING LOWS IN THE UPPER 60S AND LOW 70S ACROSS THE SOUTHERN CWA FOR TONIGHT AS WELL AS LIMITING ANY FOG CHANCES. FOR FRIDAY...WITH SHORT TERM MODEL TRENDS IN THE NAM AND GFS SHOWING PRECIP MOVING INTO EASTERN KENTUCKY A BIT EARLIER...WILL ACCOUNT FOR THE INCREASED CLOUD COVER AND LOWER HIGHS ON FRIDAY A FEW DEGREES FROM TODAY AND BRING IN CLOUD COVER AND POPS A BIT FASTER. WILL STICK TO SLIGHT AND LOW CHANCE AS CURRENT TRENDS OF ISAAC MIGHT NOT GIVE THE FASTER APPROACH THAT THE MODELS PORTRAY. .LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY) ISSUED AT 345 AM EDT THU AUG 30 2012 THE MODELS START OUT IN GOOD AGREEMENT THROUGH SUNDAY MORNING AS THEY TRY TO PREDICT WHERE THE REMNANTS OF ISAAC WILL BE GOING. THE PROBLEM IS THAT THE STORM WILL BE MOVING UP AGAINST A FAIRLY STRONG AREA OF HIGH PRESSURE AND THE STEERING CURRENTS WILL BE FAIRLY WEAK. THIS TYPE OF SITUATION TENDS TO CHALLENGING FOR THE MODELS TO HANDLE AND EXPLAINS WHY THERE HAS BEEN SO MUCH RUN TO RUN INCONSISTENCIES WITH THE MODELS. THE MODELS DO SEEM TO BE GETTING A BIT MORE CONSISTENT...SO CONFIDENCE IS BEGINNING TO INCREASE. BY SUNDAY MORNING THE UPPER LOW WILL BE OVER SOUTHERN ILLINOIS. THE ECMWF THEN HAS THE LOW SLOW UP AND START TO DRIFT SLOW TO THE SOUTHWEST INTO KENTUCKY. THE ECMWF THEN HAS THE LOW AND UPPER TROUGH LINGER OVER KENTUCKY WHICH WILL HELP TO KEEP THE WEATHER UNSETTLED INTO TUESDAY. THIS SHOULD HELP TO SPREAD SOME RAIN ACROSS THE BLUEGRASS. THROUGH TUESDAY MOST LOCATIONS SHOULD BE SEEING BETWEEN 0.5 - 2 INCHES OF RAIN. SINCE IT IS CONVECTIVE IN NATURE...THE AMOUNTS CAN BE QUITE VARIABLE. THE BLENDED MODEL TEMPERATURES LOOKED REALLY GOOD AND ONLY HAD TO MAKE MINOR ADJUSTMENTS TO THE FORECAST. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON) ISSUED AT 225 PM EDT THU AUG 30 2012 EXPECT MAINLY VFR CONDITIONS TO CONTINUE THROUGH THE TAF PERIOD WITH THE EXCEPTION OF SOME LOWER...MVFR...CLOUDS THIS AFTERNOON AND AGAIN DURING THE DAY FRIDAY. THE INCREASE IN MOISTURE OVER THE SOUTHERN PARTS OF THE FORECAST AREA SHOULD BE ENOUGH TO TRIGGER ISOLATED TO SCATTERED CONVECTION BY LATE MORNING FRIDAY. TO ACCOUNT FOR THIS IN THE TAFS HAVE ADDED A VCTS AND BKN040CB STARTING AT BETWEEN 12 AND 14Z. LIGHT AND VARIABLE WINDS THROUGH THE NIGHT WILL START TO PICK UP FROM THE SOUTHWEST AT BETWEEN 5 AND 10 KTS DURING THE MORNING FRIDAY. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...SHALLENBERGER LONG TERM....JJ AVIATION...GREIF
AREA FORECAST DISCUSSION
NWS GRAY ME
1152 AM EDT FRI AUG 31 2012 .SYNOPSIS... A COLD FRONT WILL DROP SOUTH FROM CANADA TODAY AND WILL PUSH OFFSHORE THIS EVENING. HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST TONIGHT AND SATURDAY AND WILL SHIFT OFFSHORE ON SUNDAY. HIGH PRESSURE WILL REMAIN ANCHORED OFF THE COAST MONDAY. A COLD FRONT WILL APPROACH FROM THE WEST MONDAY NIGHT AND WILL PUSH EAST THROUGH NEW ENGLAND ON TUESDAY. A WEAK RIDGE OF HIGH PRESSURE WILL BUILD IN FROM THE WEST ON WEDNESDAY AND WILL HOLD OVER THE AREA ON THURSDAY. && .NEAR TERM /THROUGH TONIGHT/... ---1600Z UPDATE--- CLOUD COVER CONTINUES TO CAUSE ISSUES WITH FORECAST PACKAGE. SHOWERS AND THUNDERSTORMS MOVING ACROSS NORTHERN VERMONT WILL LIKELY HOLD TOGETHER LONG ENOUGH TO CROSS NEW HAMPSHIRE AND SOUTHERN MAINE. WITH LITTLE IN THE WAY OF POSSIBLE SUNSHINE...WILL CUT MAX TEMPERATURES SIGNIFICANTLY FOR TODAY. THIS IS ESPECIALLY TRUE OVER THE NORTHERN HALF OF THE CWA WHERE TEMPERATURES HAVE YET TO MAKE IT OUT OF THE 60S. WITH LACK OF SURFACE HEATING...WILL ALSO REDUCE THE THREAT OF SEVERE THUNDERSTORMS OVER THE MOUNTAINS. WILL TAKE OUT ENHANCED WORDING FOR THIS AFTERNOON. ---1400Z UPDATE--- SIGNIFICANT CLOUD COVER OVER THE COASTAL PLAIN THIS MORNING NOT BEING CAPTURED WELL BY THE FORECAST. MODELS ALSO NOT DOING A VERY GOOD JOB OF HANDLING THIS. THE RUC13 IS PROBABLY DOING THE BEST JOB OF HANDLING THE CLOUD COVER. NOT SURE IT WILL HAVE MUCH IMPACT ON HIGH TEMPERATURES FOR TODAY. UPDATED THE FORECAST TO ACCOUNT FOR THE ADDITIONAL CLOUD COVER. ---1230Z UPDATE--- INTERESTING DAY SHAPING UP FOR NORTHERN NEW ENGLAND. MOST OF THE MODELS ARE INDICATING A LATE AFTERNOON SEVERE WEATHER EVENT. HOWEVER...THE LATEST RUN OF THE HRRR IS TRYING TO BRING SOME CONVECTION INTO THE MOUNTAINS DURING THE LATE MORNING HOURS. WHEN COMPARED WITH CURRENT RADAR TRENDS...THIS SCENARIO LOOKS PROBABLE. THIS WILL THEN RAISE THE QUESTION ABOUT HOW WORKED OVER THE AIRMASS WILL BE AS THE FRONTAL BOUNDARY APPROACHES LATER TODAY. AS IT LOOKS NOW...WE MAY SEE SOME WEAK CONVECTION OVER THE MOUNTAINS TODAY BUT THE CELLS WILL BE TOO FAR AWAY FROM THE UPPER LEVEL SUPPORT TO REACH SEVERE LIMITS. HOWEVER...THERE SHOULD STILL BE PLENTY OF TIME THIS AFTERNOON FOR THE AIRMASS TO RECOVER ITS INSTABILITY AS TEMPERATURES RAPIDLY CLIMB. STILL LOOKS LIKE A CHANCE FOR SOME ISOLATED SEVERE THUNDERSTORMS THIS AFTERNOON...ESPECIALLY OVER THE MOUNTAINS. WILL UPDATE THE FORECAST TO ADJUST POPS THIS MORNING AND TWEAK TEMPERATURES A BIT. COLD FRONT DROPPING SOUTH FROM CANADA TODAY WILL BRING INCREASING CLOUDS AND A CHANCE OF SHOWERS AND THUNDERSTORMS TO THE REGION...MAINLY DURING THE AFTERNOON. FAIR AMOUNT OF SHEAR SETTING UP ACROSS THE REGION EARLY THIS MORNING AND THIS WILL INCREASE THROUGH EARLY AFTERNOON. ALTHOUGH CAPES WON`T BE TOO IMPRESSIVE STRONG DYNAMICS MAY SUPPORT A FEW SUPER CELLS ACROSS NORTHERN SECTIONS DURING THE MID TO LATE AFTERNOON. MAIN THREAT WITH THESE STORMS WOULD BE DAMAGING WINDS AND LARGE HAIL. WILL INCLUDED ENHANCED WORDING IN THE ZONES HIGHLIGHTING THESE CONCERNS. FARTHER SOUTH WILL SEE INCREASING HIGH CLOUDS AND A CHANCE OF AFTERNOON AND EVENING SHOWERS OR THUNDERSTORMS. TEMPERATURES SHOULD TAKE A PRETTY GOOD JUMP THIS MORNING AS MIXING GETS GOING. STRONG SOUTHWEST FLOW AHEAD OF THE FRONT ALREADY PUSHING TEMPS INTO THE LOWER TO MID 70S IN MONTREAL AT 2 AM. 850 TEMPS GOOD ENOUGH FOR LOWER 90S IN SOUTHERN NEW HAMPSHIRE INTO SOUTHWEST MAINE. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... COLD FRONT WILL PUSH OFFSHORE BY LATE THIS EVENING AND EXPECT CLEARING SKIES AS HIGH PRESSURE BUILDS IN FROM THE NORTHWEST. LOOKING FOR LOWS NEAR 50 IN THE NORTH AND MID 50S TO LOWER 60S IN THE SOUTH. BEAUTIFUL WEATHER FOR SATURDAY AS HIGH PRESSURE BUILDS IN FROM THE WEST. LOOKING FOR ABUNDANT SUN AND SEASONABLE TEMPERATURES THROUGHOUT THE FORECAST AREA. && .LONG TERM /SUNDAY THROUGH THURSDAY/... SFC HIGH PRES BUILDS IN SATURDAY NGT THEN MOVES E ON SUNDAY PROVIDING FAIR WX...THOUGH THE MODELS DRIVE A SHORT WAVE TROF SE THRU THE UPR LVL RIDGE OVER NEW ENGLAND ON SUNDAY. THIS WILL BRING SOME CLOUDINESS AND MAYBE ISOLD SHRA THOUGH NOT MUCH MOISTURE OR SFC SYSTEM TO SUPPORT MUCH, IF ANY, PRCP ON SUNDAY. THE UPR LVL AND SFC RIDGE BECOME RE-ESTABLISHED OVER THE NE SUNDAY NGT AND MONDAY WITH MORE FAIR WX. AN UPR LVL SHORT WAVE TROF MOVES E MONDAY NGT AND TUESDAY AS MOISTURE INCREASES...GIVING US A CHC OF PRCP. ANOTHER WEAK UPR LVL IMPULSE AND A SFC FNT CONT THE CHC OF PRCP TUESDAY NGT INTO WEDNESDAY. HIGH PRES AND FAIR WX RETURNS LATE WEDNESDAY INTO THURSDAY THOUGH ANOTHER UPR LVL TROF AND SFC SYSTEM MOVING IN FROM THE W COULD PRODUCE A CHC OF PRCP LATE THURSDAY. GENERALLY USED GFS40...HPC QPF AND BLEND OF MAV/MET MOS FOR SATURDAY NGT AND SUNDAY. FOR REST OF THE LONG TERM FCST USED GMOS...EXCEPT USED A BLEND OF GFS40, HPC GUIDANCE AND MEX MOS GUIDANCE FOR MAX AND MIN TEMPS. && .AVIATION /16Z FRIDAY THROUGH TUESDAY/... SHORT TERM...VFR TODAY THROUGH SATURDAY. SOME ISOLATED MVFR/IFR CEILINGS/VSBY THIS AFTERNOON IN SCATTERED THUNDERSTORMS. LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...MOSTLY VFR WX THOUGH SLGT CHC MVFR WITH -SHRA SUNDAY AND CHC OF MVFR WITH SHRA MONDAY NGT AND TUESDAY. && .MARINE... SHORT TERM...INCREASING SOUTHWEST TO WEST FLOW WILL BRING GUSTS OF 25 TO 30 KT ON THE WATERS THIS MORNING THROUGH THIS EVENING WITH SEAS BUILDING 4 TO 6 FT. HAVE ISSUED SCA FROM MID MORNING THROUGH THIS EVENING. LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...WEAK FLOW SATURDAY NGT THRU SUNDAY NGT. SOUTHERLY ONSHORE FLOW INCREASE MONDAY AND TUESDAY BUT LIKELY TO STAY BELOW SCA LEVELS. SEAS BELOW SCA LEVELS SATURDAY NGT THRU SUNDAY NGT THEN THEY BUILD WITH THE INCREASING ONSHORE FLOW MONDAY THRU TUESDAY...POSSIBLY REACHING SCA LEVELS ON TUESDAY. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ150-152- 154. && $$ POHL
AREA FORECAST DISCUSSION
NWS GRAY ME
1009 AM EDT FRI AUG 31 2012 .SYNOPSIS... A COLD FRONT WILL DROP SOUTH FROM CANADA TODAY AND WILL PUSH OFFSHORE THIS EVENING. HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST TONIGHT AND SATURDAY AND WILL SHIFT OFFSHORE ON SUNDAY. HIGH PRESSURE WILL REMAIN ANCHORED OFF THE COAST MONDAY. A COLD FRONT WILL APPROACH FROM THE WEST MONDAY NIGHT AND WILL PUSH EAST THROUGH NEW ENGLAND ON TUESDAY. A WEAK RIDGE OF HIGH PRESSURE WILL BUILD IN FROM THE WEST ON WEDNESDAY AND WILL HOLD OVER THE AREA ON THURSDAY. && .NEAR TERM /THROUGH TONIGHT/... ---1400Z UPDATE--- SIGNIFICANT CLOUD COVER OVER THE COASTAL PLAIN THIS MORNING NOT BEING CAPTURED WELL BY THE FORECAST. MODELS ALSO NOT DOING A VERY GOOD JOB OF HANDLING THIS. THE RUC13 IS PROBABLY DOING THE BEST JOB OF HANDLING THE CLOUD COVER. NOT SURE IT WILL HAVE MUCH IMPACT ON HIGH TEMPERATURES FOR TODAY. UPDATED THE FORECAST TO ACCOUNT FOR THE ADDITIONAL CLOUD COVER. ---1230Z UPDATE--- INTERESTING DAY SHAPING UP FOR NORTHERN NEW ENGLAND. MOST OF THE MODELS ARE INDICATING A LATE AFTERNOON SEVERE WEATHER EVENT. HOWEVER...THE LATEST RUN OF THE HRRR IS TRYING TO BRING SOME CONVECTION INTO THE MOUNTAINS DURING THE LATE MORNING HOURS. WHEN COMPARED WITH CURRENT RADAR TRENDS...THIS SCENARIO LOOKS PROBABLE. THIS WILL THEN RAISE THE QUESTION ABOUT HOW WORKED OVER THE AIRMASS WILL BE AS THE FRONTAL BOUNDARY APPROACHES LATER TODAY. AS IT LOOKS NOW...WE MAY SEE SOME WEAK CONVECTION OVER THE MOUNTAINS TODAY BUT THE CELLS WILL BE TOO FAR AWAY FROM THE UPPER LEVEL SUPPORT TO REACH SEVERE LIMITS. HOWEVER...THERE SHOULD STILL BE PLENTY OF TIME THIS AFTERNOON FOR THE AIRMASS TO RECOVER ITS INSTABILITY AS TEMPERATURES RAPIDLY CLIMB. STILL LOOKS LIKE A CHANCE FOR SOME ISOLATED SEVERE THUNDERSTORMS THIS AFTERNOON...ESPECIALLY OVER THE MOUNTAINS. WILL UPDATE THE FORECAST TO ADJUST POPS THIS MORNING AND TWEAK TEMPERATURES A BIT. COLD FRONT DROPPING SOUTH FROM CANADA TODAY WILL BRING INCREASING CLOUDS AND A CHANCE OF SHOWERS AND THUNDERSTORMS TO THE REGION...MAINLY DURING THE AFTERNOON. FAIR AMOUNT OF SHEAR SETTING UP ACROSS THE REGION EARLY THIS MORNING AND THIS WILL INCREASE THROUGH EARLY AFTERNOON. ALTHOUGH CAPES WON`T BE TOO IMPRESSIVE STRONG DYNAMICS MAY SUPPORT A FEW SUPER CELLS ACROSS NORTHERN SECTIONS DURING THE MID TO LATE AFTERNOON. MAIN THREAT WITH THESE STORMS WOULD BE DAMAGING WINDS AND LARGE HAIL. WILL INCLUDED ENHANCED WORDING IN THE ZONES HIGHLIGHTING THESE CONCERNS. FARTHER SOUTH WILL SEE INCREASING HIGH CLOUDS AND A CHANCE OF AFTERNOON AND EVENING SHOWERS OR THUNDERSTORMS. TEMPERATURES SHOULD TAKE A PRETTY GOOD JUMP THIS MORNING AS MIXING GETS GOING. STRONG SOUTHWEST FLOW AHEAD OF THE FRONT ALREADY PUSHING TEMPS INTO THE LOWER TO MID 70S IN MONTREAL AT 2 AM. 850 TEMPS GOOD ENOUGH FOR LOWER 90S IN SOUTHERN NEW HAMPSHIRE INTO SOUTHWEST MAINE. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... COLD FRONT WILL PUSH OFFSHORE BY LATE THIS EVENING AND EXPECT CLEARING SKIES AS HIGH PRESSURE BUILDS IN FROM THE NORTHWEST. LOOKING FOR LOWS NEAR 50 IN THE NORTH AND MID 50S TO LOWER 60S IN THE SOUTH. BEAUTIFUL WEATHER FOR SATURDAY AS HIGH PRESSURE BUILDS IN FROM THE WEST. LOOKING FOR ABUNDANT SUN AND SEASONABLE TEMPERATURES THROUGHOUT THE FORECAST AREA. && .LONG TERM /SUNDAY THROUGH THURSDAY/... SFC HIGH PRES BUILDS IN SATURDAY NGT THEN MOVES E ON SUNDAY PROVIDING FAIR WX...THOUGH THE MODELS DRIVE A SHORT WAVE TROF SE THRU THE UPR LVL RIDGE OVER NEW ENGLAND ON SUNDAY. THIS WILL BRING SOME CLOUDINESS AND MAYBE ISOLD SHRA THOUGH NOT MUCH MOISTURE OR SFC SYSTEM TO SUPPORT MUCH, IF ANY, PRCP ON SUNDAY. THE UPR LVL AND SFC RIDGE BECOME RE-ESTABLISHED OVER THE NE SUNDAY NGT AND MONDAY WITH MORE FAIR WX. AN UPR LVL SHORT WAVE TROF MOVES E MONDAY NGT AND TUESDAY AS MOISTURE INCREASES...GIVING US A CHC OF PRCP. ANOTHER WEAK UPR LVL IMPULSE AND A SFC FNT CONT THE CHC OF PRCP TUESDAY NGT INTO WEDNESDAY. HIGH PRES AND FAIR WX RETURNS LATE WEDNESDAY INTO THURSDAY THOUGH ANOTHER UPR LVL TROF AND SFC SYSTEM MOVING IN FROM THE W COULD PRODUCE A CHC OF PRCP LATE THURSDAY. GENERALLY USED GFS40...HPC QPF AND BLEND OF MAV/MET MOS FOR SATURDAY NGT AND SUNDAY. FOR REST OF THE LONG TERM FCST USED GMOS...EXCEPT USED A BLEND OF GFS40, HPC GUIDANCE AND MEX MOS GUIDANCE FOR MAX AND MIN TEMPS. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... SHORT TERM...VFR TODAY THROUGH SATURDAY. SOME ISOLATED MVFR/IFR CEILINGS/VSBY THIS AFTERNOON IN SCATTERED THUNDERSTORMS. LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...MOSTLY VFR WX THOUGH SLGT CHC MVFR WITH -SHRA SUNDAY AND CHC OF MVFR WITH SHRA MONDAY NGT AND TUESDAY. && .MARINE... SHORT TERM...INCREASING SOUTHWEST TO WEST FLOW WILL BRING GUSTS OF 25 TO 30 KT ON THE WATERS THIS MORNING THROUGH THIS EVENING WITH SEAS BUILDING 4 TO 6 FT. HAVE ISSUED SCA FROM MID MORNING THROUGH THIS EVENING. LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...WEAK FLOW SATURDAY NGT THRU SUNDAY NGT. SOUTHERLY ONSHORE FLOW INCREASE MONDAY AND TUESDAY BUT LIKELY TO STAY BELOW SCA LEVELS. SEAS BELOW SCA LEVELS SATURDAY NGT THRU SUNDAY NGT THEN THEY BUILD WITH THE INCREASING ONSHORE FLOW MONDAY THRU TUESDAY...POSSIBLY REACHING SCA LEVELS ON TUESDAY. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ150-152- 154. && $$ SYNOPSIS... NEAR TERM... SHORT TERM... LONG TERM... AVIATION... MARINE...
AREA FORECAST DISCUSSION
NWS GRAY ME
819 AM EDT FRI AUG 31 2012 .SYNOPSIS... A COLD FRONT WILL DROP SOUTH FROM CANADA TODAY AND WILL PUSH OFFSHORE THIS EVENING. HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST TONIGHT AND SATURDAY AND WILL SHIFT OFFSHORE ON SUNDAY. HIGH PRESSURE WILL REMAIN ANCHORED OFF THE COAST MONDAY. A COLD FRONT WILL APPROACH FROM THE WEST MONDAY NIGHT AND WILL PUSH EAST THROUGH NEW ENGLAND ON TUESDAY. A WEAK RIDGE OF HIGH PRESSURE WILL BUILD IN FROM THE WEST ON WEDNESDAY AND WILL HOLD OVER THE AREA ON THURSDAY. && .NEAR TERM /THROUGH TONIGHT/... ---1230Z UPDATE--- INTERESTING DAY SHAPING UP FOR NORTHERN NEW ENGLAND. MOST OF THE MODELS ARE INDICATING A LATE AFTERNOON SEVERE WEATHER EVENT. HOWEVER...THE LATEST RUN OF THE HRRR IS TRYING TO BRING SOME CONVECTION INTO THE MOUNTAINS DURING THE LATE MORNING HOURS. WHEN COMPARED WITH CURRENT RADAR TRENDS...THIS SCENARIO LOOKS PROBABLE. THIS WILL THEN RAISE THE QUESTION ABOUT HOW WORKED OVER THE AIRMASS WILL BE AS THE FRONTAL BOUNDARY APPROACHES LATER TODAY. AS IT LOOKS NOW...WE MAY SEE SOME WEAK CONVECTION OVER THE MOUNTAINS TODAY BUT THE CELLS WILL BE TOO FAR AWAY FROM THE UPPER LEVEL SUPPORT TO REACH SEVERE LIMITS. HOWEVER...THERE SHOULD STILL BE PLENTY OF TIME THIS AFTERNOON FOR THE AIRMASS TO RECOVER ITS INSTABILITY AS TEMPERATURES RAPIDLY CLIMB. STILL LOOKS LIKE A CHANCE FOR SOME ISOLATED SEVERE THUNDERSTORMS THIS AFTERNOON...ESPECIALLY OVER THE MOUNTAINS. WILL UPDATE THE FORECAST TO ADJUST POPS THIS MORNING AND TWEAK TEMPERATURES A BIT. COLD FRONT DROPPING SOUTH FROM CANADA TODAY WILL BRING INCREASING CLOUDS AND A CHANCE OF SHOWERS AND THUNDERSTORMS TO THE REGION...MAINLY DURING THE AFTERNOON. FAIR AMOUNT OF SHEAR SETTING UP ACROSS THE REGION EARLY THIS MORNING AND THIS WILL INCREASE THROUGH EARLY AFTERNOON. ALTHOUGH CAPES WON`T BE TOO IMPRESSIVE STRONG DYNAMICS MAY SUPPORT A FEW SUPER CELLS ACROSS NORTHERN SECTIONS DURING THE MID TO LATE AFTERNOON. MAIN THREAT WITH THESE STORMS WOULD BE DAMAGING WINDS AND LARGE HAIL. WILL INCLUDED ENHANCED WORDING IN THE ZONES HIGHLIGHTING THESE CONCERNS. FARTHER SOUTH WILL SEE INCREASING HIGH CLOUDS AND A CHANCE OF AFTERNOON AND EVENING SHOWERS OR THUNDERSTORMS. TEMPERATURES SHOULD TAKE A PRETTY GOOD JUMP THIS MORNING AS MIXING GETS GOING. STRONG SOUTHWEST FLOW AHEAD OF THE FRONT ALREADY PUSHING TEMPS INTO THE LOWER TO MID 70S IN MONTREAL AT 2 AM. 850 TEMPS GOOD ENOUGH FOR LOWER 90S IN SOUTHERN NEW HAMPSHIRE INTO SOUTHWEST MAINE. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... COLD FRONT WILL PUSH OFFSHORE BY LATE THIS EVENING AND EXPECT CLEARING SKIES AS HIGH PRESSURE BUILDS IN FROM THE NORTHWEST. LOOKING FOR LOWS NEAR 50 IN THE NORTH AND MID 50S TO LOWER 60S IN THE SOUTH. BEAUTIFUL WEATHER FOR SATURDAY AS HIGH PRESSURE BUILDS IN FROM THE WEST. LOOKING FOR ABUNDANT SUN AND SEASONABLE TEMPERATURES THROUGHOUT THE FORECAST AREA. && .LONG TERM /SUNDAY THROUGH THURSDAY/... SFC HIGH PRES BUILDS IN SATURDAY NGT THEN MOVES E ON SUNDAY PROVIDING FAIR WX...THOUGH THE MODELS DRIVE A SHORT WAVE TROF SE THRU THE UPR LVL RIDGE OVER NEW ENGLAND ON SUNDAY. THIS WILL BRING SOME CLOUDINESS AND MAYBE ISOLD SHRA THOUGH NOT MUCH MOISTURE OR SFC SYSTEM TO SUPPORT MUCH, IF ANY, PRCP ON SUNDAY. THE UPR LVL AND SFC RIDGE BECOME RE-ESTABLISHED OVER THE NE SUNDAY NGT AND MONDAY WITH MORE FAIR WX. AN UPR LVL SHORT WAVE TROF MOVES E MONDAY NGT AND TUESDAY AS MOISTURE INCREASES...GIVING US A CHC OF PRCP. ANOTHER WEAK UPR LVL IMPULSE AND A SFC FNT CONT THE CHC OF PRCP TUESDAY NGT INTO WEDNESDAY. HIGH PRES AND FAIR WX RETURNS LATE WEDNESDAY INTO THURSDAY THOUGH ANOTHER UPR LVL TROF AND SFC SYSTEM MOVING IN FROM THE W COULD PRODUCE A CHC OF PRCP LATE THURSDAY. GENERALLY USED GFS40...HPC QPF AND BLEND OF MAV/MET MOS FOR SATURDAY NGT AND SUNDAY. FOR REST OF THE LONG TERM FCST USED GMOS...EXCEPT USED A BLEND OF GFS40, HPC GUIDANCE AND MEX MOS GUIDANCE FOR MAX AND MIN TEMPS. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... SHORT TERM...VFR TODAY THROUGH SATURDAY. SOME ISOLATED MVFR/IFR CEILINGS/VSBY THIS AFTERNOON IN SCATTERED THUNDERSTORMS. LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...MOSTLY VFR WX THOUGH SLGT CHC MVFR WITH -SHRA SUNDAY AND CHC OF MVFR WITH SHRA MONDAY NGT AND TUESDAY. && .MARINE... SHORT TERM...INCREASING SOUTHWEST TO WEST FLOW WILL BRING GUSTS OF 25 TO 30 KT ON THE WATERS THIS MORNING THROUGH THIS EVENING WITH SEAS BUILDING 4 TO 6 FT. HAVE ISSUED SCA FROM MID MORNING THROUGH THIS EVENING. LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...WEAK FLOW SATURDAY NGT THRU SUNDAY NGT. SOUTHERLY ONSHORE FLOW INCREASE MONDAY AND TUESDAY BUT LIKELY TO STAY BELOW SCA LEVELS. SEAS BELOW SCA LEVELS SATURDAY NGT THRU SUNDAY NGT THEN THEY BUILD WITH THE INCREASING ONSHORE FLOW MONDAY THRU TUESDAY...POSSIBLY REACHING SCA LEVELS ON TUESDAY. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ150-152- 154. && $$ POHL
AREA FORECAST DISCUSSION
NWS CARIBOU ME
101 AM EDT FRI AUG 31 2012 .SYNOPSIS... LOW PRESSURE WILL TRACK NORTH OF MAINE OVERNIGHT THROUGH FRIDAY...DRAWING A COLD FRONT ACROSS THE REGION FRIDAY. HIGH PRESSURE WILL BUILD ACROSS THE REGION THROUGH THE WEEKEND.&& .NEAR TERM /THROUGH TODAY/... 1230 AM UPDATE: UPDATED POPS AND WX GRIDS TO MENTION SCT SHWRS ACROSS ALL OF NRN AROOSTOOK COUNTY (ZONES 1 AND 2) FOR THE REMAINDER OF THE NGT. ALTHOUGH HRRR RAPID UPDATE MODEL DATA DOES NOT INDICATE TSTMS CURRENTLY IN THE ST LAWRENCE VLY AREA OF QB NEAR ALMA AND BAGOTTSVILLE MAKING IT INTO OUR FA BEFORE DISSIPATING...WE DO MENTION ISOLD TSTMS CAPABLE OF PRODUCING GUSTY WINDS TIL ABOUT DAYBREAK. MOST OF THIS ACTIVITY SHOULD MOVE OUT OF NRN AREAS BY 12Z. WE ALSO WENT AHEAD AND DERIVED THE POP DISTRIBUTION FOR SHWRS/TSTMS FOR FRI DAY AND EVE...INCLUDING ENHANCED WORDING FOR HAIL AND CNVCTV WINDS AND QPF WITH TSTMS FRI AFTN INTO ERLY EVE ASSOCIATED WITH AN ADVANCING COLD FRONT...BUT MORE DETAILS ON THIS WITH THE NEXT FCST UPDATE. PREV UPDATE: LOW PRESSURE WILL BEGIN TO TRACK NORTH OF MAINE OVERNIGHT...WITH HIGH PRESSURE TO THE SOUTH. THE LOW WILL DRAW A COLD FRONT TOWARD THE REGION LATE TONIGHT. PARTLY/MOSTLY CLOUDY SKIES WILL EXIST ACROSS NORTHERN AREAS OVERNIGHT ALONG WITH A CHANCE OF SHOWERS. MOSTLY CLEAR SKIES ARE EXPECTED DOWNEAST OVERNIGHT. OVERNIGHT LOW TEMPERATURES WILL GENERALLY RANGE FROM THE UPPER 50S TO THE LOWER 60S ACROSS THE FORECAST AREA. HAVE UPDATED THE FORECAST TO ADJUST FOR CURRENT CONDITIONS ALONG WITH EXPECTED OVERNIGHT CLOUD COVER/SHOWER CHANCES/TEMPERATURES. HAVE SLIGHTLY INCREASED SHOWER CHANCES ACROSS NORTHERN AREAS OVERNIGHT. ORGNL DISC: THE LOW MOVING NORTH OF MAINE FRIDAY WILL PULL A COLD FRONT ACROSS THE AREA. FORECAST CAPES AHEAD OF THE FRONT RANGE FROM AROUND 1500 J/KG ON THE NAM TO 500 J/KG ON THE GFS. THE SHEARING ENVIRONMENT IS VERY STRONG WITH WINDS INCREASING FROM AROUND 15KT ON THE SURFACE TO ALMOST 40 KT AT 5000 FT. THE SHEAR COULD MAKE IT DIFFICULT FOR CONVECTION TO DEVELOP. HOWEVER...CONVECTION THAT DOES DEVELOP COULD RESULT IN STRONG GUSTY AND POSSIBLY DAMAGING WINDS DUE TO THE STRONG WINDS ALOFT THAT COULD CARRY MOMENTUM TO THE SURFACE IN ANY DOWNDRAFTS. THE FRONT WILL REACH THE DOWNEAST REGION LATE FRIDAY AS COOLER AIR BEGINS TO FILTER INTO THE NORTH. && .SHORT TERM /TONIGHT THROUGH SUNDAY/... COOLER, DRIER AIR TO MOVE IN FRIDAY NIGHT AS A COLD FRONT PASSES THROUGH THE AREA FROM NORTHWEST TO SOUTHEAST. WEAK UPPER LEVEL RIDGE AND A SURFACE HIGH PRESSURE OVERHEAD ON SATURDAY WILL LEAD TO A VERY PLEASANT DAY. HIGH PRESSURE OVERHEAD SATURDAY NIGHT WILL ALLOW FOR TEMPERATURES TO DROP EASILY INTO THE 40S FOR MOST AREAS, WITH SOME 30S IN PROTECTED VALLEYS OF NORTHERN MAINE. A WEAK UPPER LEVEL TROUGH WILL PASS THROUGH DURING THE DAY SUNDAY, IGNITING ISOLATED TO SCATTERED SHOWERS MAINLY DURING THE AFTERNOON. MODELS ARE IN GOOD AGREEMENT FRIDAY NIGHT THROUGH SUNDAY. PRIMARY CHANGE TO PREVIOUS FORECAST WAS TO INTRODUCE 20 TO 40 PERCENT POPS FOR SUNDAY. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... HIGH PRESSURE BUILDS IN FOR MONDAY BUT IS QUICKLY REPLACED BY UPPER LEVEL SOUTHWEST FLOW AND MOIST LOW LEVEL SOUTHERLY FLOW TUESDAY AND WEDNESDAY. SOME OF THE MOISTURE MOVING INTO THE AREA WILL BE FROM THE REMNANTS OF ISAAC. A GOOD CHANCE OF SOME RAIN DURING THIS PERIOD. MODEL AGREEMENT FALLS APART FROM LATE WEDNESDAY ONWARD ON WHETHER WE DRY OUT OR REMAIN WET. WENT WITH A MIDDLE OF THE ROAD APPROACH FOR NOW. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... NEAR TERM: GENERALLY VFR CONDITIONS ARE EXPECTED ACROSS THE REGION OVERNIGHT...THOUGH OCCASIONAL MVFR CONDITIONS COULD OCCUR ACROSS NORTHERN AREAS LATE. OCCASIONAL MVFR/IFR CONDITIONS COULD OCCUR WITH ANY SHOWERS AND THUNDERSTORMS FRIDAY. GUSTY WINDS WILL ALSO OCCUR ACROSS THE REGION FRIDAY...WITH STRONGER WINDS POSSIBLE WITH ANY THUNDERSTORMS. SHORT TERM: GENERALLY VFR CONDITIONS EXPECTED FRIDAY NIGHT THROUGH MONDAY. MVFR CONDITIONS ARE POSSIBLE TUESDAY. && .MARINE... NEAR TERM: WINDS/SEAS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY LEVELS OVERNIGHT. SMALL CRAFT ADVISORY LEVEL WINDS/SEAS ARE THEN POSSIBLE FRIDAY. SHORT TERM: WINDS WILL SHIFT FROM SOUTHWEST TO NORTH FRIDAY NIGHT AS A COLD FRONT PASSES THROUGH. WINDS AND SEAS WILL BE AT OR JUST BELOW SMALL CRAFT LEVELS FRIDAY NIGHT, BUT CONDITIONS CALM DOWN FOR SATURDAY AND SUNDAY WITH HIGH PRESSURE OVERHEAD. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...NONE. MARINE...NONE. && $$ NEAR TERM...VJN SHORT TERM...FOISY LONG TERM...FOISY AVIATION...VJN MARINE...VJN/FOISY
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
406 PM EDT FRI AUG 31 2012 .SHORT TERM...(THIS EVENING THROUGH SATURDAY) ISSUED AT 401 PM EDT FRI AUG 31 2012 WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A TROF OVER THE PACIFIC NW...RIDGING DOWNSTREAM OVER THE NRN PLAINS/SCNTRL CANADA AND A TROF OVER SE CANADA/NEW ENGLAND. THE UPSTREAM RIDGE IS CURRENTLY GAINING AMPLITUDE. WITH THE RIDGE CONTINUING TO BUILD THRU SAT AS IT SHIFTS E TOWARD THE UPPER LAKES...THE SHORT TERM PORTION OF THE FCST WILL BE TRANQUIL. THERE IS AN AREA OF MID/HIGH CLOUDS OVER THE DAKOTAS... AND THE CLOUDS HAVE SOME SUPPORT FROM THE RIGHT ENTRANCE OF UPPER JET ALONG THE U.S./CANADA BORDER THRU THE UPPER LAKES. SINCE THE UPPER JET SUPPORT BREAKS DOWN TONIGHT...CLOUDS SHOULD TEND TO DISSIPATE AND PROBABLY WON`T BE MUCH OF A FACTOR HERE. UNDER MAINLY CLR SKIES...WINDS WILL DROP OFF TO CALM/NEAR CALM AS SFC HIGH PRES OVER NW MN SETTLES OVER THE UPPER GREAT LAKES TONIGHT. COMBINED WITH A DRY COLUMN (PRECIPITABLE WATER 50-60PCT OF NORMAL)...TONIGHT WILL BE A STRONG RADIATIONAL COOLING NIGHT. OPTED TO GO AT OR BLO THE LOWEST GUIDANCE OVER THE INTERIOR...ESPECIALLY THE W SINCE WINDS THERE WILL FALL TO CALM AROUND SUNSET. EXPECT MINS AS LOW AS THE UPPER 30S IN THE TRADITIONAL COLD SPOTS. DIMINISHING SOIL MOISTURE DUE TO RECENT DRY SPELL WILL ALSO AID COOLING POTENTIAL TONIGHT. TYPICAL FOR THIS TIME OF YEAR...LENGTHENING NIGHTS AND WARM WATER IN SWAMPS/STREAMS/RIVERS/LAKES MAY LEAD TO SOME GROUND FOG. UNDER MOSTLY SUNNY SKIES...THE FIRST DAY OF METEOROLOGICAL AUTUMN WILL BE A NICE ONE. ALTHOUGH TEMPS WILL BE ABOVE NORMAL...LOW DWPTS WILL MAKE FOR A COMFORTABLE DAY. MIXING TOWARD 800MB ON FCST SOUNDINGS YIELDS MAX TEMPS AROUND 80F INTO THE LWR 80S IN THE INTERIOR. WITH SFC HIGH SETTING UP OVER LAKE SUPERIOR...LAKESIDE LOCATIONS WILL HOLD TO THE LOW/MID 70S. WEAKER LAKE BREEZE OFF LAKE MI WILL PROVIDE LIMITED COOLING. AFTN DWPTS WILL LIKELY FALL TOWARD THE LWR 40S IN THE INTERIOR BASED ON MIXING DEPTH. ALTHOUGH RH WILL BOTTOM OUT AS LOW AS THE 25-30PCT RANGE...LIGHT WINDS WILL HELP TO EASE FIRE WX CONCERNS. .LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY) ISSUED AT 401 PM EDT FRI AUG 31 2012 SATURDAY NIGHT... THE APEX OF THE SFC TO 500MB RIDGE WILL BE NEAR THE CWA AT 00Z SUNDAY...WITH THE REMNANTS OF ISAAC ACROSS MO. LOOK FOR THE SFC HIGH TO SHIFT E TO THE ONTARIO/QUEBEC BORDER AND LOWER GREAT LAKES OVERNIGHT...WITH A WEAK RETURN OF SSE FLOW WITH SOME MOISTENING OF THE ATMOSPHERE THANKS TO WINDS PUSHING N AROUND WHAT IS LEFT OF ISAAC. PW VALUES STARTING OFF AROUND 0.5IN EAST /55 PERCENT OF NORMAL/ JUMPING TO VALUES RIGHT AROUND NORMAL FOR THIS TIME OF YEAR BY 12Z SUNDAY...OR 0.75 TO 1IN. SUNDAY THROUGH SUNDAY NIGHT... SLIGHT SW FLOW BEGINS ALOFT BEGINS SUNDAY...AND BECOMES MORE ZONAL MONDAY AS THE 500MB LOW TRANSITIONING ACROSS CENTRAL/S CANADA PUSHES ACROSS SASKATCHEWAN AND MANITOBA. THERE ARE SIGNIFICANT DISCREPANCIES WRT THE 31/06Z GFS AND 31/00Z ECMWF...WITH THE 31/00Z CANADIAN LOOKING TO BE A CLOSE BLEND OF THE 2. THE 12Z RUNS OF THE GFS AND ECMWF ARE MOVING CLOSER TO A SIMILAR SOLUTION WITH THE CANADIAN TRACKING LOW. THE RESULT WILL BE AN INCREASE IN MOISTURE...WITH THE SFC LOW OVER N SASKATCHEWAN AT 18Z SUNDAY...AND THE COLD FRONT EXTENDING THROUGH THE DAKOTAS AND CENTRAL PLAINS. EXPECT INCREASED S WINDS SUNDAY NIGHT IN ADVANCE OF THE COLD FRONT...WITH A CHANCE OF TSRA WEST BY DAYBREAK MONDAY. MONDAY THROUGH TUESDAY... THE SFC COLD FRONT SET UP OVER FAR W LAKE SUPERIOR AT 12Z MONDAY /OR EVEN ACROSS THE KEWEENAW PENINUSLA ACCORDING TO THE 31/00Z ECMWF/...WILL PUSH JUST E OR RIGHT ACROSS THE FAR E END OF THE CWA BY 00Z TUESDAY. SO FOR MEMORIAL DAY...A CHANCE OF TSRA WILL CONTINUE TO TRACK E...WITH IMPROVING CONDITIONS W BY EARLY AFTERNOON. I ATTEMPTED TO KEEP THE BEST CHANCE OF THUNDER RIGHT ALONG AND JUST AHEAD OF THE FRONT. MONDAY NIGHT STILL LOOKS TO BE MAINLY DRY AS HIGH PRESSURE PUSHES IN FROM THE SSW...AS TEMPS FALL INTO THE MID 50S INTERIOR W. TUESDAY NIGHT THROUGH FRIDAY... UNSETTLED WEATHER AND A RETURN TO NEAR NORMAL TEMPS WILL LIKELY BE THE NORM FROM TUESDAY NIGHT THROUGH FRIDAY AS A SERIES OF DISTURBANCES PUSH OVER OR JUST NORTH OF THE CWA. GIVEN THE FCST DISCREPANCIES FROM THE VARIOUS MODELS...WILL NOT BE TERRIBLY SPECIFIC WITH TIMING AS LOW PRESSURE SYSTEMS PUSH NEAR OR JUST N OF LAKE SUPERIOR. WINDS WEDNESDAY WILL LIKELY BE HIGHER THAN FORECAST. THE MAIN DILEMMA HERE STEMS FROM AN AVERAGING OF MODEL GUIDANCE DIRECTIONS...NW OFF THE GFS AND S OFF THE ECMWF. THE 12Z RUNS GIVE GETTER CONFIDENCE IN A MORE NW FLOW SOLUTION...SIMILAR TO THE 06Z RUN OF THE GFS. THIS WILL NEED TO BE LOOKED AT A BIT CLOSER OVER THE NEXT COUPLE OF RUNS...TO MAKE SURE THIS TREND CONTINUES. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON) ISSUED AT 125 PM EDT FRI AUG 31 2012 VFR CONDITIONS WILL BE THE RULE AT KIWD/KCMX/KSAW AS DRY HIGH PRESSURE BUILDS OVER THE REGION THRU SAT. && .MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE) ISSUED AT 401 PM EDT FRI AUG 31 2012 AS SFC HIGH PRES SETTLES OVER LAKE SUPERIOR TONIGHT AND SAT...WINDS WILL MOSTLY BE UNDER 15KT. AS THE HIGH SHIFTS TO THE E SAT NIGHT/SUN AND A COLD FRONT APPROACHES FROM THE W...SOUTHEASTERLY WINDS WILL GRADUALLY INCREASE...REACHING 10-20KT. SOUTHERLY WINDS MAY GUST UP TO AROUND 25KT SUN NIGHT/EARLY MON JUST AHEAD OF THE FRONT. THE STRONGER WINDS WILL BE OBSERVED ON THE HIGHER OBS PLATFORMS. PRES GRADIENT THEN SLACKENS WITH PASSING COLD FRONT MON...RESULTING IN WINDS DIMINISHING BACK TO UNDER 15KT MON INTO TUE. THE LIGHTER WINDS WILL THEN PERSIST INTO WED. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... NONE. LAKE SUPERIOR... NONE. LAKE MICHIGAN... NONE. && $$ SHORT TERM...ROLFSON LONG TERM...KF AVIATION...ROLFSON MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
717 AM EDT FRI AUG 31 2012 .SYNOPSIS... ISSUED AT 352 AM EDT FRI AUG 31 2012 A WEAK COLD FRONT WILL DROP SOUTH THROUGH THE AREA TODAY. TEMPERATURES AHEAD OF THE FRONT WILL CLIMB WELL INTO THE 80S AND APPROACH 90 IN SOME LOCATIONS. TEMPERATURES FOR THE WEEKEND INTO NEXT WEEK WILL REMAIN ABOVE NORMAL. CHANCES FOR RAIN WILL GENERALLY BE LIMITED TO THE SOUTHERN PORTION OF THE STATE AS THE TROPICAL SYSTEM MOVES TO THE OHIO VALLEY. && .SHORT TERM...(TODAY THROUGH SUNDAY) ISSUED AT 352 AM EDT FRI AUG 31 2012 FORECAST CONCERNS ARE SOMEWHAT LIMITED THIS MORNING AND MAINLY DEAL WITH THE COLD FRONT PASSING THROUGH TODAY AND CHANCES FOR RAIN AS THE TROPICAL LOW MOVES NORTH. THE FORECAST HASN/T CHANGED MUCH AND CONFIDENCE IS REASONABLY HIGH THAT WE/RE NOT GOING TO SEE MUCH PCPN FOR THE NEXT FEW DAYS. LATEST IR LOOP SHOWS A BAND OF CLOUDS FROM SOUTH DAKOTA NEWD INTO SRN ONTARIO. THIS MARKS THE WEAK COLD FRONT THAT WILL MOVE SOUTH TODAY. TEMPS AHEAD OF THE FRONT WILL CLIMB TO NEAR 90 DEGREES SOUTH OF I-94 THIS AFTERNOON. MODERATE INSTABILITY WILL BE PRESENT TOO. HOWEVER...DUE TO THE LACK OF APPRECIABLE MOISTURE CONFIDENCE IS LOW THAT WE/LL SEE ANY RAIN ALONG THE FRONT. CAN/T RULE IT OUT COMPLETELY BUT CHANCES ARE LOW ENOUGH THAT WE HAVE DRY GRIDS TODAY...WHICH IS A CONTINUATION OF THE CURRENT FORECAST. HIGH PRESSURE WILL BUILD INTO THE REGION AND FUNNEL DRY AIR INTO THE REGION. THIS HIGH WILL KEEP THE TROPICAL SYSTEM FROM MOVING NORTH INTO THE GREAT LAKES. AS IT FUNNELS DRY AIR SWWD FROM ONTARIO...WE/LL LIKELY SEE A SHARP PCPN GRADIENT FROM SRN LWR MI INTO NRN INDIANA. WE/RE NOT GOING TO SEE MUCH IF ANY RAIN FROM THIS SYSTEM. WE RAIN FALLS IN THE CWA WILL LIKELY BE SOUTH OF I-94 SATURDAY NIGHT INTO SUNDAY. .LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY) ISSUED AT 352 AM EDT FRI AUG 31 2012 THE PRIMARY WEATHER ISSUES FOR THIS COMING WEEK ARE RELATED TO THE POTENTIAL FOR CONVECTION WITH THE COLD FRONT MONDAY AND THEN AGAIN THURSDAY. IT WOULD NOW SEEMS A STRONG STORM COMING OFF THE KAMCHATKA PENINSULA MONDAY BECOMES THE DOMINATE UPPER LEVEL WAVE FEATURE IN THE NORTHERN HEMISPHERE. IT DEVELOPS A DEEP BUT NONE THE LESS PROGRESSIVE UPPER TROUGH WITH A 160 KNOT JET CORE WHICH IS STILL DIGGING INTO THE WEST SIDE OF THAT TROUGH TUESDAY MORNING. THAT SYSTEM PICKS UP REMNANT LOW FROM A FORMER WEST PACIFIC TYPHOON. THIS COMBINED SYSTEM REACHES THE DATELINE BY WEDNESDAY. THIS OF COURSE BUILDS A LARGE UPPER RIDGE IN FRONT OF IT. THAT IS OVER THE WEST COAST OF NORTH AMERICA FROM CALIFORNIA TO CENTRAL ALASKA IN THE WEDNESDAY TIME FRAME. THIS THEN SETS THE STAGE FOR SOME SIGNIFICANT DOWN STREAM WEATHER CHANGES THAT IMPACT SOUTHWEST MICHIGAN (THINK FALL LIKE WEATHER). THIS ACTUALLY HAS BEEN A RATHER STABLE FEATURE OF THE MODELS OVER THE PAST FEW DAYS. BY THE WAY THIS ALSO GOES ALONG WITH THE MJO PHASE PROGRESSION (WHICH SUGGESTS WARM INTO MID WEEK HERE THEN COOLER). MY DISCUSSION FROM YESTERDAY TALKED ABOUT A SYSTEM OFF BRITISH COLUMBIA COAST POSSIBLY PHASING WITH A SYSTEM NOW OVER WESTERN ALASKA. ALL OF THAT IS FORCED BY THE SYSTEM FROM NORTHERN RUSSIA DIGGING THE DEEP TROUGH WEST OF THE DATELINE. SO WHAT DOES THIS MEAN FOR SOUTHWEST MICHIGAN WEATHER? IT MEANS WE GET TWO COLD FRONTS THIS WEEK. BOTH OF WHICH MAY HAVE CONVECTION WITH THEM. THE LEAD SYSTEM TRIES TO COME THROUGH MONDAY BUT THE TRAILING SYSTEM IS STRONGER AND DEEPER SO IT BOOTS THE LEAD SYSTEM OUT OF THE WAY. THAT MEANS THE COLD FRONT WILL WEAKEN AS IT COMES THROUGH AND IN SO DOING WILL NOT BE PULLING DOWN MUCH COOL AIR BEHIND IT FOR TUESDAY AND WEDNESDAY. EVEN SO WE COULD GET INTO THE JET ENTRANCE REGION LIFT AREA MONDAY AFTERNOON OR EVENING. THAT WOULD HELP THE CAUSE FOR A FEW THUNDERSTORMS BUT MOISTURE IS LIMITED SO I KEPT THE POP LOW FOR THIS EVENT. THE BETTER EVENT WILL BE LATER IN THE WEEK AS THE SYSTEM FROM WESTERN ALASKA COMES INTO THE PICTURE. BY THEN THE WESTERN RIDGE WILL HAVE HAD A CHANCE TO REALLY BUILD WHICH IN TURN DEEPS THE DOWN STREAM TROUGH OVER THE GREAT LAKES. IT IS AT THIS TIME OUR CHANCE OF A SIGNIFICANT CONVECTIVE EVENT WOULD BE. GIVEN THE STRENGTH OF THE UP STREAM SYSTEM DRIVING THIS... I COULD SEE THIS SLOWING DOWN BY 12 TO 24 HOURS THROUGH. SO I HAVE LOW POPS FOR THURSDAY YET BUT I FEEL STRONGLY THIS SYSTEM LATE IN THE WEEK OVERALL WILL GIVE SOUTHWEST && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING) ISSUED AT 718 AM EDT FRI AUG 31 2012 BREEZY WITH VFR CONDITIONS INTO THIS AFTERNOON. VFR CONDITIONS EXPECTED TONIGHT. THE STRONG WINDS... WEST 40 KNOTS ARE SHOWING UP ON OUR VAD WIND PROFILE THIS MORNING BETWEEN 2000 AND 3000 FT AGL. WINDS ARE SOUTHWEST 5 TO 15 KNOTS BELOW 10000 FT AGL. SO THE LOW LEVEL WIND SHEAR WILL CONTINUE UNTIL THE BOUNDARY LAYER MIXES OUT BETWEEN 13Z AND 15Z. ONCE IT DOES THROUGH SURFACE WINDS WILL BE GUSTY FROM THE WEST... LIKE 15 KNOTS GUSTING TO 25 KNOTS. WINDS WILL BE STRONGER OVER FOR THE MORE EASTERN TAF SITES LIKE LANSING. SKIES SHOULD BE NEARLY CLEAR THROUGH EARLY AFTERNOON EVEN WITH THE FRONT DROPPING SOUTH INTO THE AREA BY MID AFTERNOON. THE AIR IS SO DRY ON THE RAP SOUNDINGS THAT THE LCL IS NEAR 12000 FT INTO LATE MORNING. I WOULD EXPECT SOME HIGH BASED MID CLOUDS BEHIND THE FRONT TONIGHT SO I BROUGHT IN A MID CLOUD DECK FOR THAT. WINDS WILL BECOME LIGHT FROM THE NORTH NORTHEAST AT THE SURFACE BEHIND THE COLD FRONT. && .MARINE... ISSUED AT 352 AM EDT FRI AUG 31 2012 SCA CONTINUES INTO THE AFTERNOON. WINDS WILL SLOWLY DIMINISH AND SCA CONDITIONS WILL SUBSIDE LATE IN THE DAY. && .HYDROLOGY... ISSUED AT 352AM EDT FRI AUG 31 2012 VERY LITTLE RAINFALL EXPECTED OVER THE WEEKEND. A QUARTER INCH OR LESS POSSIBLE SOUTH OF I-94 THROUGH SUNDAY. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...BEACH HAZARDS STATEMENT UNTIL 3 PM EDT THIS AFTERNOON FOR MIZ037- 043-050-056-064-071. LM...SMALL CRAFT ADVISORY UNTIL 3 PM EDT THIS AFTERNOON FOR LMZ844>849. && $$ SYNOPSIS...93 SHORT TERM...93 LONG TERM...WDM AVIATION...WDM HYDROLOGY...93 MARINE...93
AREA FORECAST DISCUSSION
NWS NORTH PLATTE NE
1208 AM CDT FRI AUG 31 2012 .AVIATION... VFR IS EXPECTED ALL AREAS OVERNIGHT THROUGH FRIDAY EVENING. NO TSTMS ARE FORECAST. SOUTH WINDS DEVELOP FRIDAY IN RESPONSE TO LOW PRESSURE DEVELOPING ACROSS THE NRN HIGH PLAINS. && .PREV DISCUSSION... /ISSUED 908 PM CDT THU AUG 30 2012/ UPDATE... DISCUSSION... WINDS HAVE DECREASED WELL BELOW 25 MPH AND RELATIVE HUMIDITY HAS RECOVERED TO OVER 20 PERCENT IN MOST AREAS. THE RED FLAG WARNING HAS BEEN CANCELLED. A FIRE WEATHER WATCH CONTINUES FOR FRIDAY. PREV DISCUSSION... /ISSUED 350 PM CDT THU AUG 30 2012/ SYNOPSIS... SURFACE ANALYSIS THIS AFTERNOON...AS A COLD FRONT EXTENDING FROM AROUND LEWELLEN...TO ARTHUR...TO DUNNING...TO EWING. NORTH OF THIS FEATURE...TEMPS RANGE FROM 80 AT VALENTINE...TO 94 AT O`NEILL. SOUTH OF THE FRONT...TEMPS WERE AROUND 100 DEGREES WITH RELATIVE HUMIDITIES RANGING FROM 5 TO 15 PERCENT. A MAJOR FIRE WAS BURNING ACROSS NORTHWESTERN SHERIDAN COUNTY THIS AFTERNOON AT THE METCALF STATE WILDLIFE MANAGEMENT AREA. EVACUATION ORDERS HAVE BEEN GIVEN FOR THIS AREA OF SHERIDAN COUNTY. ADDITIONAL DETAILS ARE IN OMAEVILBF. ALOFT AT H5...RIDGING HAS BEGUN TO TRANSITION EAST THIS MORNING...AS A TROUGH OF LOW PRESSURE BUILDS ALONG THE PACIFIC NW COAST. AT 12Z THIS MORNING...ISSAC WAS LOCATED NORTHWEST OF BATON ROUGE LA. DISCUSSION... SHORT RANGE...TONIGHT THROUGH SUNDAY...MAIN FORECAST CHALLENGE IS TEMPERATURES AND FIRE WEATHER CONCERNS OVER THE NEXT 24 TO 36 HRS. FOR TONIGHT...THE LATEST NAM SOLN STALLS THE COLD FRONT ALONG HIGHWAYS 92 AND 91 THIS EVENING...WHILE THE HIGH RES RUC PUSHES THIS FEATURE THROUGH NORTH PLATTE TO JUST SOUTH OF INTERSTATE 80. EVEN WITH A MORE AGGRESSIVE FRONTAL PUSH DEPICTED BY THE HI RES RUC...LOCATIONS AHEAD OF THE FRONT HAVE ALREADY TORCHED OUT THIS AFTERNOON WITH WIDESPREAD HIGHS WELL ABOVE THE CENTURY MARK AND RELATIVE HUMIDITIES AS LOW AS 5 PERCENT. AS SURFACE HIGH PRESSURE BUILDS EAST OF THE DAKOTAS OVERNIGHT...SRLY WINDS WILL BEGIN TO LIFT THE FRONT NORTH ON FRIDAY CONTINUES TO BE PROBLEMATIC AS THE LATEST NEAR TERM MODEL SOLUTIONS ARE MUCH FARTHER SOUTH WITH THIS FEATURE COMPARED TO YESTERDAY`S RUNS. THE LATEST MODEL RUNS PUSH THE FRONT NORTH TO THE BLACK HILLS AND NERN NEBRASKA FRIDAY MORNING...WHICH WILL LEAD TO ANOTHER TORCH OUT ACROSS A LARGE PORTION OF THE FORECAST AREA ON FRIDAY. WENT AHEAD AND TRENDED TEMPS UPWARD FOR FRIDAY...WHICH YIELDED HIGHS RANGING FROM THE MID 90S TO LOWER 100S. VERY DRY BOUNDARY LAYER AIR WILL REMAIN IN PLACE...WHICH WILL LEAD TO CRITICAL OR NEAR CRITICAL MINIMUM RH VALS FOR TOMORROW AFTERNOON. THE ONE QUESTION NOW IS THE WINDS AND HOW HARD THEY WILL BLOW FRIDAY. ATTM...THE BEST THREAT FOR GUSTS TO 25 MPH...IS ALONG AND WEST OF HIGHWAY 83 FROM VALENTINE TO NORTH PLATTE. FURTHER EAST...SLIGHTLY LIGHTER WINDS...WITH AN EASTERLY COMPONENT ARE EXPECTED WHICH WILL ALSO BEGIN TO LIFT SOME BL MOISTURE FROM THE REMNANTS OF ISAAC. WITH SOME DOUBT AS TO WHERE THE FRONT WILL STALL TOMORROW...WILL HOIST A FIRE WEATHER WATCH FOR TOMORROW AFTERNOON FOR ALL ZONES WITH THE EXCEPTION OF ZONE 209 WHERE WINDS WILL BE LIGHTER. FOR SATURDAY AND SUNDAY...FIRE THREAT IS EXPECTED TO DIMINISH SOMEWHAT FOR SATURDAY IN THE CENTRAL AND THE EAST. IT WILL BE WARM ONCE AGAIN WITH HIGHS IN THE LOWER TO MIDDLE 90S. HOWEVER...LOW LEVEL MOISTURE WILL INCREASE FRIDAY NIGHT AS ISAAC LIFTS INTO MISSOURI. FCSTED DEW POINTS SATURDAY AFTERNOON WILL RANGE FROM THE MID 40S IN THE WEST TO AROUND 60 IN THE EAST. WITH THE EXCEPTION OF THE WEST...SRLY WINDS WILL GENERALLY BE UNDER 15 MPH. EXTREME OR NEAR CRITICAL FIRE DANGER LOOKS POSSIBLE IN THE WEST AND WILL CONTINUE TO MONITOR. BY SUNDAY...A SURFACE TROUGH OF LOW PRESSURE WILL APPROACH WESTERN AND NORTH CENTRAL NEBRASKA. EAST OF THIS FEATURE...HOT TEMPERATURES IN THE 90S ARE LIKELY. ATTM ENOUGH RESIDUAL MOISTURE WILL BE IN PLACE...WHICH SHOULD KEEP CRITICAL FIRE CONDS IN CHECK. SOME WESTERN AREAS MAY BE UNDER THE GUN FOR FIRE DANGER SUNDAY...WITH HIGHS IN THE 90S AND MINIMUM DEW POINTS IN THE LOWER TO MID 40S. LONG RANGE...SUNDAY NIGHT THROUGH THURSDAY...SUNDAY NIGHT THROUGH THURSDAY. UPPER LEVEL RIDGE IS FORECASTED TO TRANSITION BACK TO THE DESERT SOUTHWEST DURING THE PERIOD...WITH THE UPPER FLOW OVER OUR AREA BECOMING WEST TO NORTHWEST ALOFT. SOME INCREASE IN MOISTURE IS EXPECTED BOTH AT THE SFC AND ALOFT...AND AT LEAST A SLIGHT CHANCE FOR SHOWERS AND THUNDERSTORMS ARE ANTICIPATED MONDAY THROUGH WEDNESDAY AS A SERIES OF DISTURBANCES EMBEDDED WITHIN THE FLOW CROSS THE AREA. TEMPERATURE WISE...AN OVERALL COOLING TREND BACK TO NEAR NORMAL IS EXPECTED. HIGHS WILL RANGE FROM THE UPPER 80S MONDAY AND TUESDAY...COOLING TO THE UPPER 70S TO MID 80S WEDNESDAY AND THURSDAY. FIRE WEATHER... A LARGE FIRE IS ONGOING ACROSS NORTHWESTERN SHERIDAN COUNTY AND AN EVACUATION ORDER HAS BEEN GIVEN FOR METCALF STATE WILDLIFE MANAGEMENT AREA. SEE OMAEVILBF FOR DETAILS. RH WILL BEGIN TO RECOVER TO 20 TO 30 PERCENT IN SOUTHERN AREAS AROUND 03Z THIS EVENING...SO THE ONGOING RED FLAG WARNING WILL CONTINUE FOR ALL ZONES EXCEPT NEZ208. ALL LOCATIONS IN THIS ZONE ARE NOW NORTH OF THE COLD FRONT...WITH RH`S CURRENTLY RUNNING FROM 30 TO 40 PERCENT. OVERNIGHT TONIGHT...THE COLD FRONT WILL LIFT NORTH AS A WARM FRONT...AS HIGH PRESSURE LIFTS INTO MINNESOTA. FOR FRIDAY...A WARM FRONT WILL BE ANCHORED FROM THE BLACK HILLS INTO NERN NEBRASKA...WHICH WILL ALLOW THE HEAT TO BUILD NORTH INTO WESTERN AND NORTH CENTRAL NEBRASKA FRIDAY AFTERNOON. GUSTY SRLY WINDS WILL DEVELOP ACROSS THE CENTRAL AND WESTERN SAND HILLS...AS WELL AS THE EASTERN NEBRASKA PANHANDLE AND SOUTHWESTERN NEBRASKA FRIDAY AFTERNOON AND MAY GUST AS HIGH AS 25 MPH. WITH FCST DEW POINTS IN THE 30S AND LOWER 40S FRIDAY AFTERNOON...MINIMUM RH`S OF AROUND 15 PERCENT ARE POSSIBLE. WILL BE HOISTING A FIRE WEATHER WATCH FOR FRIDAY AFTERNOON AND EVENING FOR ALL ZONES EXCEPT 209 FOR THE POSSIBILITY OF CRITICAL FIRE DANGER FRIDAY AFTERNOON. && .LBF WATCHES/WARNINGS/ADVISORIES...FIRE WEATHER WATCH FROM 10 AM CDT /9 AM MDT/ THIS MORNING THROUGH THIS EVENING FOR NEZ204-206-208-210-219. && $$ SHORT TERM/EXTENDED...BUTTLER/TAYLOR AVIATION...ROBERG
AREA FORECAST DISCUSSION...UPDATED
NWS NORTH PLATTE NE
908 PM CDT THU AUG 30 2012 .UPDATE... .DISCUSSION... WINDS HAVE DECREASED WELL BELOW 25 MPH AND RELATIVE HUMIDITY HAS RECOVERED TO OVER 20 PERCENT IN MOST AREAS. THE RED FLAG WARNING HAS BEEN CANCELLED. A FIRE WEATHER WATCH CONTINUES FOR FRIDAY. && .PREV DISCUSSION... /ISSUED 622 PM CDT THU AUG 30 2012/ UPDATE... AVIATION... VFR IS EXPECTED ALL AREAS OVERNIGHT AND FRIDAY. NO TSTMS ARE FORECAST. A COLD FRONT ACROSS NCNTL NEB THIS AFTN WILL DRIFT SOUTH INTO THE PLATTE VALLEY THIS EVENING AND THEN RETREAT NORTH FRIDAY AS A WARM FRONT. PREV DISCUSSION... /ISSUED 350 PM CDT THU AUG 30 2012/ SYNOPSIS... SURFACE ANALYSIS THIS AFTERNOON...AS A COLD FRONT EXTENDING FROM AROUND LEWELLEN...TO ARTHUR...TO DUNNING...TO EWING. NORTH OF THIS FEATURE...TEMPS RANGE FROM 80 AT VALENTINE...TO 94 AT O`NEILL. SOUTH OF THE FRONT...TEMPS WERE AROUND 100 DEGREES WITH RELATIVE HUMIDITIES RANGING FROM 5 TO 15 PERCENT. A MAJOR FIRE WAS BURNING ACROSS NORTHWESTERN SHERIDAN COUNTY THIS AFTERNOON AT THE METCALF STATE WILDLIFE MANAGEMENT AREA. EVACUATION ORDERS HAVE BEEN GIVEN FOR THIS AREA OF SHERIDAN COUNTY. ADDITIONAL DETAILS ARE IN OMAEVILBF. ALOFT AT H5...RIDGING HAS BEGUN TO TRANSITION EAST THIS MORNING...AS A TROUGH OF LOW PRESSURE BUILDS ALONG THE PACIFIC NW COAST. AT 12Z THIS MORNING...ISSAC WAS LOCATED NORTHWEST OF BATON ROUGE LA. DISCUSSION... SHORT RANGE...TONIGHT THROUGH SUNDAY...MAIN FORECAST CHALLENGE IS TEMPERATURES AND FIRE WEATHER CONCERNS OVER THE NEXT 24 TO 36 HRS. FOR TONIGHT...THE LATEST NAM SOLN STALLS THE COLD FRONT ALONG HIGHWAYS 92 AND 91 THIS EVENING...WHILE THE HIGH RES RUC PUSHES THIS FEATURE THROUGH NORTH PLATTE TO JUST SOUTH OF INTERSTATE 80. EVEN WITH A MORE AGGRESSIVE FRONTAL PUSH DEPICTED BY THE HI RES RUC...LOCATIONS AHEAD OF THE FRONT HAVE ALREADY TORCHED OUT THIS AFTERNOON WITH WIDESPREAD HIGHS WELL ABOVE THE CENTURY MARK AND RELATIVE HUMIDITIES AS LOW AS 5 PERCENT. AS SURFACE HIGH PRESSURE BUILDS EAST OF THE DAKOTAS OVERNIGHT...SRLY WINDS WILL BEGIN TO LIFT THE FRONT NORTH ON FRIDAY CONTINUES TO BE PROBLEMATIC AS THE LATEST NEAR TERM MODEL SOLUTIONS ARE MUCH FARTHER SOUTH WITH THIS FEATURE COMPARED TO YESTERDAY`S RUNS. THE LATEST MODEL RUNS PUSH THE FRONT NORTH TO THE BLACK HILLS AND NERN NEBRASKA FRIDAY MORNING...WHICH WILL LEAD TO ANOTHER TORCH OUT ACROSS A LARGE PORTION OF THE FORECAST AREA ON FRIDAY. WENT AHEAD AND TRENDED TEMPS UPWARD FOR FRIDAY...WHICH YIELDED HIGHS RANGING FROM THE MID 90S TO LOWER 100S. VERY DRY BOUNDARY LAYER AIR WILL REMAIN IN PLACE...WHICH WILL LEAD TO CRITICAL OR NEAR CRITICAL MINIMUM RH VALS FOR TOMORROW AFTERNOON. THE ONE QUESTION NOW IS THE WINDS AND HOW HARD THEY WILL BLOW FRIDAY. ATTM...THE BEST THREAT FOR GUSTS TO 25 MPH...IS ALONG AND WEST OF HIGHWAY 83 FROM VALENTINE TO NORTH PLATTE. FURTHER EAST...SLIGHTLY LIGHTER WINDS...WITH AN EASTERLY COMPONENT ARE EXPECTED WHICH WILL ALSO BEGIN TO LIFT SOME BL MOISTURE FROM THE REMNANTS OF ISAAC. WITH SOME DOUBT AS TO WHERE THE FRONT WILL STALL TOMORROW...WILL HOIST A FIRE WEATHER WATCH FOR TOMORROW AFTERNOON FOR ALL ZONES WITH THE EXCEPTION OF ZONE 209 WHERE WINDS WILL BE LIGHTER. FOR SATURDAY AND SUNDAY...FIRE THREAT IS EXPECTED TO DIMINISH SOMEWHAT FOR SATURDAY IN THE CENTRAL AND THE EAST. IT WILL BE WARM ONCE AGAIN WITH HIGHS IN THE LOWER TO MIDDLE 90S. HOWEVER...LOW LEVEL MOISTURE WILL INCREASE FRIDAY NIGHT AS ISAAC LIFTS INTO MISSOURI. FCSTED DEW POINTS SATURDAY AFTERNOON WILL RANGE FROM THE MID 40S IN THE WEST TO AROUND 60 IN THE EAST. WITH THE EXCEPTION OF THE WEST...SRLY WINDS WILL GENERALLY BE UNDER 15 MPH. EXTREME OR NEAR CRITICAL FIRE DANGER LOOKS POSSIBLE IN THE WEST AND WILL CONTINUE TO MONITOR. BY SUNDAY...A SURFACE TROUGH OF LOW PRESSURE WILL APPROACH WESTERN AND NORTH CENTRAL NEBRASKA. EAST OF THIS FEATURE...HOT TEMPERATURES IN THE 90S ARE LIKELY. ATTM ENOUGH RESIDUAL MOISTURE WILL BE IN PLACE...WHICH SHOULD KEEP CRITICAL FIRE CONDS IN CHECK. SOME WESTERN AREAS MAY BE UNDER THE GUN FOR FIRE DANGER SUNDAY...WITH HIGHS IN THE 90S AND MINIMUM DEW POINTS IN THE LOWER TO MID 40S. LONG RANGE...SUNDAY NIGHT THROUGH THURSDAY...SUNDAY NIGHT THROUGH THURSDAY. UPPER LEVEL RIDGE IS FORECASTED TO TRANSITION BACK TO THE DESERT SOUTHWEST DURING THE PERIOD...WITH THE UPPER FLOW OVER OUR AREA BECOMING WEST TO NORTHWEST ALOFT. SOME INCREASE IN MOISTURE IS EXPECTED BOTH AT THE SFC AND ALOFT...AND AT LEAST A SLIGHT CHANCE FOR SHOWERS AND THUNDERSTORMS ARE ANTICIPATED MONDAY THROUGH WEDNESDAY AS A SERIES OF DISTURBANCES EMBEDDED WITHIN THE FLOW CROSS THE AREA. TEMPERATURE WISE...AN OVERALL COOLING TREND BACK TO NEAR NORMAL IS EXPECTED. HIGHS WILL RANGE FROM THE UPPER 80S MONDAY AND TUESDAY...COOLING TO THE UPPER 70S TO MID 80S WEDNESDAY AND THURSDAY. AVIATION...A COLD FRONT WILL STALL FROM NEAR KBUB TO KSNY THIS AFTERNOON. TO THE NORTH OF THE FRONT...SFC WINDS WILL NE NORTH TO NORTHEAST AT 5 TO 15 KTS...WHILE SOUTHWEST WINDS WILL CONTINUE AT 10 TO 20 KTS TO THE SOUTH OF THE FRONT. BROKEN MID LEVEL CEILINGS AND FEW LIGHT RAIN SHOWERS ARE POSSIBLE TO THE NORTH OF THE FRONT THROUGH LATE THIS AFTERNOON. FIRE WEATHER... A LARGE FIRE IS ONGOING ACROSS NORTHWESTERN SHERIDAN COUNTY AND AN EVACUATION ORDER HAS BEEN GIVEN FOR METCALF STATE WILDLIFE MANAGEMENT AREA. SEE OMAEVILBF FOR DETAILS. RH WILL BEGIN TO RECOVER TO 20 TO 30 PERCENT IN SOUTHERN AREAS AROUND 03Z THIS EVENING...SO THE ONGOING RED FLAG WARNING WILL CONTINUE FOR ALL ZONES EXCEPT NEZ208. ALL LOCATIONS IN THIS ZONE ARE NOW NORTH OF THE COLD FRONT...WITH RH`S CURRENTLY RUNNING FROM 30 TO 40 PERCENT. OVERNIGHT TONIGHT...THE COLD FRONT WILL LIFT NORTH AS A WARM FRONT...AS HIGH PRESSURE LIFTS INTO MINNESOTA. FOR FRIDAY...A WARM FRONT WILL BE ANCHORED FROM THE BLACK HILLS INTO NERN NEBRASKA...WHICH WILL ALLOW THE HEAT TO BUILD NORTH INTO WESTERN AND NORTH CENTRAL NEBRASKA FRIDAY AFTERNOON. GUSTY SRLY WINDS WILL DEVELOP ACROSS THE CENTRAL AND WESTERN SAND HILLS...AS WELL AS THE EASTERN NEBRASKA PANHANDLE AND SOUTHWESTERN NEBRASKA FRIDAY AFTERNOON AND MAY GUST AS HIGH AS 25 MPH. WITH FCST DEW POINTS IN THE 30S AND LOWER 40S FRIDAY AFTERNOON...MINIMUM RH`S OF AROUND 15 PERCENT ARE POSSIBLE. WILL BE HOISTING A FIRE WEATHER WATCH FOR FRIDAY AFTERNOON AND EVENING FOR ALL ZONES EXCEPT 209 FOR THE POSSIBILITY OF CRITICAL FIRE DANGER FRIDAY AFTERNOON. && .LBF WATCHES/WARNINGS/ADVISORIES...FIRE WEATHER WATCH FROM FRIDAY MORNING THROUGH FRIDAY EVENING FOR NEZ204-206-208-210-219. && $$ SHORT TERM/EXTENDED...JACOBS AVIATION...CDC
AREA FORECAST DISCUSSION...UPDATED
NWS NORTH PLATTE NE
622 PM CDT THU AUG 30 2012 .UPDATE... .AVIATION... VFR IS EXPECTED ALL AREAS OVERNIGHT AND FRIDAY. NO TSTMS ARE FORECAST. A COLD FRONT ACROSS NCNTL NEB THIS AFTN WILL DRIFT SOUTH INTO THE PLATTE VALLEY THIS EVENING AND THEN RETREAT NORTH FRIDAY AS A WARM FRONT. && .PREV DISCUSSION... /ISSUED 350 PM CDT THU AUG 30 2012/ SYNOPSIS... SURFACE ANALYSIS THIS AFTERNOON...AS A COLD FRONT EXTENDING FROM AROUND LEWELLEN...TO ARTHUR...TO DUNNING...TO EWING. NORTH OF THIS FEATURE...TEMPS RANGE FROM 80 AT VALENTINE...TO 94 AT O`NEILL. SOUTH OF THE FRONT...TEMPS WERE AROUND 100 DEGREES WITH RELATIVE HUMIDITIES RANGING FROM 5 TO 15 PERCENT. A MAJOR FIRE WAS BURNING ACROSS NORTHWESTERN SHERIDAN COUNTY THIS AFTERNOON AT THE METCALF STATE WILDLIFE MANAGEMENT AREA. EVACUATION ORDERS HAVE BEEN GIVEN FOR THIS AREA OF SHERIDAN COUNTY. ADDITIONAL DETAILS ARE IN OMAEVILBF. ALOFT AT H5...RIDGING HAS BEGUN TO TRANSITION EAST THIS MORNING...AS A TROUGH OF LOW PRESSURE BUILDS ALONG THE PACIFIC NW COAST. AT 12Z THIS MORNING...ISSAC WAS LOCATED NORTHWEST OF BATON ROUGE LA. DISCUSSION... SHORT RANGE...TONIGHT THROUGH SUNDAY...MAIN FORECAST CHALLENGE IS TEMPERATURES AND FIRE WEATHER CONCERNS OVER THE NEXT 24 TO 36 HRS. FOR TONIGHT...THE LATEST NAM SOLN STALLS THE COLD FRONT ALONG HIGHWAYS 92 AND 91 THIS EVENING...WHILE THE HIGH RES RUC PUSHES THIS FEATURE THROUGH NORTH PLATTE TO JUST SOUTH OF INTERSTATE 80. EVEN WITH A MORE AGGRESSIVE FRONTAL PUSH DEPICTED BY THE HI RES RUC...LOCATIONS AHEAD OF THE FRONT HAVE ALREADY TORCHED OUT THIS AFTERNOON WITH WIDESPREAD HIGHS WELL ABOVE THE CENTURY MARK AND RELATIVE HUMIDITIES AS LOW AS 5 PERCENT. AS SURFACE HIGH PRESSURE BUILDS EAST OF THE DAKOTAS OVERNIGHT...SRLY WINDS WILL BEGIN TO LIFT THE FRONT NORTH ON FRIDAY CONTINUES TO BE PROBLEMATIC AS THE LATEST NEAR TERM MODEL SOLUTIONS ARE MUCH FARTHER SOUTH WITH THIS FEATURE COMPARED TO YESTERDAY`S RUNS. THE LATEST MODEL RUNS PUSH THE FRONT NORTH TO THE BLACK HILLS AND NERN NEBRASKA FRIDAY MORNING...WHICH WILL LEAD TO ANOTHER TORCH OUT ACROSS A LARGE PORTION OF THE FORECAST AREA ON FRIDAY. WENT AHEAD AND TRENDED TEMPS UPWARD FOR FRIDAY...WHICH YIELDED HIGHS RANGING FROM THE MID 90S TO LOWER 100S. VERY DRY BOUNDARY LAYER AIR WILL REMAIN IN PLACE...WHICH WILL LEAD TO CRITICAL OR NEAR CRITICAL MINIMUM RH VALS FOR TOMORROW AFTERNOON. THE ONE QUESTION NOW IS THE WINDS AND HOW HARD THEY WILL BLOW FRIDAY. ATTM...THE BEST THREAT FOR GUSTS TO 25 MPH...IS ALONG AND WEST OF HIGHWAY 83 FROM VALENTINE TO NORTH PLATTE. FURTHER EAST...SLIGHTLY LIGHTER WINDS...WITH AN EASTERLY COMPONENT ARE EXPECTED WHICH WILL ALSO BEGIN TO LIFT SOME BL MOISTURE FROM THE REMNANTS OF ISAAC. WITH SOME DOUBT AS TO WHERE THE FRONT WILL STALL TOMORROW...WILL HOIST A FIRE WEATHER WATCH FOR TOMORROW AFTERNOON FOR ALL ZONES WITH THE EXCEPTION OF ZONE 209 WHERE WINDS WILL BE LIGHTER. FOR SATURDAY AND SUNDAY...FIRE THREAT IS EXPECTED TO DIMINISH SOMEWHAT FOR SATURDAY IN THE CENTRAL AND THE EAST. IT WILL BE WARM ONCE AGAIN WITH HIGHS IN THE LOWER TO MIDDLE 90S. HOWEVER...LOW LEVEL MOISTURE WILL INCREASE FRIDAY NIGHT AS ISAAC LIFTS INTO MISSOURI. FCSTED DEW POINTS SATURDAY AFTERNOON WILL RANGE FROM THE MID 40S IN THE WEST TO AROUND 60 IN THE EAST. WITH THE EXCEPTION OF THE WEST...SRLY WINDS WILL GENERALLY BE UNDER 15 MPH. EXTREME OR NEAR CRITICAL FIRE DANGER LOOKS POSSIBLE IN THE WEST AND WILL CONTINUE TO MONITOR. BY SUNDAY...A SURFACE TROUGH OF LOW PRESSURE WILL APPROACH WESTERN AND NORTH CENTRAL NEBRASKA. EAST OF THIS FEATURE...HOT TEMPERATURES IN THE 90S ARE LIKELY. ATTM ENOUGH RESIDUAL MOISTURE WILL BE IN PLACE...WHICH SHOULD KEEP CRITICAL FIRE CONDS IN CHECK. SOME WESTERN AREAS MAY BE UNDER THE GUN FOR FIRE DANGER SUNDAY...WITH HIGHS IN THE 90S AND MINIMUM DEW POINTS IN THE LOWER TO MID 40S. LONG RANGE...SUNDAY NIGHT THROUGH THURSDAY...SUNDAY NIGHT THROUGH THURSDAY. UPPER LEVEL RIDGE IS FORECASTED TO TRANSITION BACK TO THE DESERT SOUTHWEST DURING THE PERIOD...WITH THE UPPER FLOW OVER OUR AREA BECOMING WEST TO NORTHWEST ALOFT. SOME INCREASE IN MOISTURE IS EXPECTED BOTH AT THE SFC AND ALOFT...AND AT LEAST A SLIGHT CHANCE FOR SHOWERS AND THUNDERSTORMS ARE ANTICIPATED MONDAY THROUGH WEDNESDAY AS A SERIES OF DISTURBANCES EMBEDDED WITHIN THE FLOW CROSS THE AREA. TEMPERATURE WISE...AN OVERALL COOLING TREND BACK TO NEAR NORMAL IS EXPECTED. HIGHS WILL RANGE FROM THE UPPER 80S MONDAY AND TUESDAY...COOLING TO THE UPPER 70S TO MID 80S WEDNESDAY AND THURSDAY. AVIATION...A COLD FRONT WILL STALL FROM NEAR KBUB TO KSNY THIS AFTERNOON. TO THE NORTH OF THE FRONT...SFC WINDS WILL NE NORTH TO NORTHEAST AT 5 TO 15 KTS...WHILE SOUTHWEST WINDS WILL CONTINUE AT 10 TO 20 KTS TO THE SOUTH OF THE FRONT. BROKEN MID LEVEL CEILINGS AND FEW LIGHT RAIN SHOWERS ARE POSSIBLE TO THE NORTH OF THE FRONT THROUGH LATE THIS AFTERNOON. FIRE WEATHER... A LARGE FIRE IS ONGOING ACROSS NORTHWESTERN SHERIDAN COUNTY AND AN EVACUATION ORDER HAS BEEN GIVEN FOR METCALF STATE WILDLIFE MANAGEMENT AREA. SEE OMAEVILBF FOR DETAILS. RH WILL BEGIN TO RECOVER TO 20 TO 30 PERCENT IN SOUTHERN AREAS AROUND 03Z THIS EVENING...SO THE ONGOING RED FLAG WARNING WILL CONTINUE FOR ALL ZONES EXCEPT NEZ208. ALL LOCATIONS IN THIS ZONE ARE NOW NORTH OF THE COLD FRONT...WITH RH`S CURRENTLY RUNNING FROM 30 TO 40 PERCENT. OVERNIGHT TONIGHT...THE COLD FRONT WILL LIFT NORTH AS A WARM FRONT...AS HIGH PRESSURE LIFTS INTO MINNESOTA. FOR FRIDAY...A WARM FRONT WILL BE ANCHORED FROM THE BLACK HILLS INTO NERN NEBRASKA...WHICH WILL ALLOW THE HEAT TO BUILD NORTH INTO WESTERN AND NORTH CENTRAL NEBRASKA FRIDAY AFTERNOON. GUSTY SRLY WINDS WILL DEVELOP ACROSS THE CENTRAL AND WESTERN SAND HILLS...AS WELL AS THE EASTERN NEBRASKA PANHANDLE AND SOUTHWESTERN NEBRASKA FRIDAY AFTERNOON AND MAY GUST AS HIGH AS 25 MPH. WITH FCST DEW POINTS IN THE 30S AND LOWER 40S FRIDAY AFTERNOON...MINIMUM RH`S OF AROUND 15 PERCENT ARE POSSIBLE. WILL BE HOISTING A FIRE WEATHER WATCH FOR FRIDAY AFTERNOON AND EVENING FOR ALL ZONES EXCEPT 209 FOR THE POSSIBILITY OF CRITICAL FIRE DANGER FRIDAY AFTERNOON. && .LBF WATCHES/WARNINGS/ADVISORIES...RED FLAG WARNING UNTIL 11 PM CDT /10 PM MDT/ THIS EVENING FOR NEZ204-206-209-210-219. FIRE WEATHER WATCH FROM FRIDAY MORNING THROUGH FRIDAY EVENING FOR NEZ204-206-208-210-219. && $$ SHORT TERM/EXTENDED...CDC AVIATION...CLB
AREA FORECAST DISCUSSION
NWS NORTH PLATTE NE
350 PM CDT THU AUG 30 2012 .SYNOPSIS... SURFACE ANALYSIS THIS AFTERNOON...AS A COLD FRONT EXTENDING FROM AROUND LEWELLEN...TO ARTHUR...TO DUNNING...TO EWING. NORTH OF THIS FEATURE...TEMPS RANGE FROM 80 AT VALENTINE...TO 94 AT O`NEILL. SOUTH OF THE FRONT...TEMPS WERE AROUND 100 DEGREES WITH RELATIVE HUMIDITIES RANGING FROM 5 TO 15 PERCENT. A MAJOR FIRE WAS BURNING ACROSS NORTHWESTERN SHERIDAN COUNTY THIS AFTERNOON AT THE METCALF STATE WILDLIFE MANAGEMENT AREA. EVACUATION ORDERS HAVE BEEN GIVEN FOR THIS AREA OF SHERIDAN COUNTY. ADDITIONAL DETAILS ARE IN OMAEVILBF. ALOFT AT H5...RIDGING HAS BEGUN TO TRANSITION EAST THIS MORNING...AS A TROUGH OF LOW PRESSURE BUILDS ALONG THE PACIFIC NW COAST. AT 12Z THIS MORNING...ISSAC WAS LOCATED NORTHWEST OF BATON ROUGE LA. && .DISCUSSION... SHORT RANGE...TONIGHT THROUGH SUNDAY...MAIN FORECAST CHALLENGE IS TEMPERATURES AND FIRE WEATHER CONCERNS OVER THE NEXT 24 TO 36 HRS. FOR TONIGHT...THE LATEST NAM SOLN STALLS THE COLD FRONT ALONG HIGHWAYS 92 AND 91 THIS EVENING...WHILE THE HIGH RES RUC PUSHES THIS FEATURE THROUGH NORTH PLATTE TO JUST SOUTH OF INTERSTATE 80. EVEN WITH A MORE AGGRESSIVE FRONTAL PUSH DEPICTED BY THE HI RES RUC...LOCATIONS AHEAD OF THE FRONT HAVE ALREADY TORCHED OUT THIS AFTERNOON WITH WIDESPREAD HIGHS WELL ABOVE THE CENTURY MARK AND RELATIVE HUMIDITIES AS LOW AS 5 PERCENT. AS SURFACE HIGH PRESSURE BUILDS EAST OF THE DAKOTAS OVERNIGHT...SRLY WINDS WILL BEGIN TO LIFT THE FRONT NORTH ON FRIDAY CONTINUES TO BE PROBLEMATIC AS THE LATEST NEAR TERM MODEL SOLUTIONS ARE MUCH FARTHER SOUTH WITH THIS FEATURE COMPARED TO YESTERDAY`S RUNS. THE LATEST MODEL RUNS PUSH THE FRONT NORTH TO THE BLACK HILLS AND NERN NEBRASKA FRIDAY MORNING...WHICH WILL LEAD TO ANOTHER TORCH OUT ACROSS A LARGE PORTION OF THE FORECAST AREA ON FRIDAY. WENT AHEAD AND TRENDED TEMPS UPWARD FOR FRIDAY...WHICH YIELDED HIGHS RANGING FROM THE MID 90S TO LOWER 100S. VERY DRY BOUNDARY LAYER AIR WILL REMAIN IN PLACE...WHICH WILL LEAD TO CRITICAL OR NEAR CRITICAL MINIMUM RH VALS FOR TOMORROW AFTERNOON. THE ONE QUESTION NOW IS THE WINDS AND HOW HARD THEY WILL BLOW FRIDAY. ATTM...THE BEST THREAT FOR GUSTS TO 25 MPH...IS ALONG AND WEST OF HIGHWAY 83 FROM VALENTINE TO NORTH PLATTE. FURTHER EAST...SLIGHTLY LIGHTER WINDS...WITH AN EASTERLY COMPONENT ARE EXPECTED WHICH WILL ALSO BEGIN TO LIFT SOME BL MOISTURE FROM THE REMNANTS OF ISAAC. WITH SOME DOUBT AS TO WHERE THE FRONT WILL STALL TOMORROW...WILL HOIST A FIRE WEATHER WATCH FOR TOMORROW AFTERNOON FOR ALL ZONES WITH THE EXCEPTION OF ZONE 209 WHERE WINDS WILL BE LIGHTER. FOR SATURDAY AND SUNDAY...FIRE THREAT IS EXPECTED TO DIMINISH SOMEWHAT FOR SATURDAY IN THE CENTRAL AND THE EAST. IT WILL BE WARM ONCE AGAIN WITH HIGHS IN THE LOWER TO MIDDLE 90S. HOWEVER...LOW LEVEL MOISTURE WILL INCREASE FRIDAY NIGHT AS ISAAC LIFTS INTO MISSOURI. FCSTED DEW POINTS SATURDAY AFTERNOON WILL RANGE FROM THE MID 40S IN THE WEST TO AROUND 60 IN THE EAST. WITH THE EXCEPTION OF THE WEST...SRLY WINDS WILL GENERALLY BE UNDER 15 MPH. EXTREME OR NEAR CRITICAL FIRE DANGER LOOKS POSSIBLE IN THE WEST AND WILL CONTINUE TO MONITOR. BY SUNDAY...A SURFACE TROUGH OF LOW PRESSURE WILL APPROACH WESTERN AND NORTH CENTRAL NEBRASKA. EAST OF THIS FEATURE...HOT TEMPERATURES IN THE 90S ARE LIKELY. ATTM ENOUGH RESIDUAL MOISTURE WILL BE IN PLACE...WHICH SHOULD KEEP CRITICAL FIRE CONDS IN CHECK. SOME WESTERN AREAS MAY BE UNDER THE GUN FOR FIRE DANGER SUNDAY...WITH HIGHS IN THE 90S AND MINIMUM DEW POINTS IN THE LOWER TO MID 40S. LONG RANGE...SUNDAY NIGHT THROUGH THURSDAY...SUNDAY NIGHT THROUGH THURSDAY. UPPER LEVEL RIDGE IS FORECASTED TO TRANSITION BACK TO THE DESERT SOUTHWEST DURING THE PERIOD...WITH THE UPPER FLOW OVER OUR AREA BECOMING WEST TO NORTHWEST ALOFT. SOME INCREASE IN MOISTURE IS EXPECTED BOTH AT THE SFC AND ALOFT...AND AT LEAST A SLIGHT CHANCE FOR SHOWERS AND THUNDERSTORMS ARE ANTICIPATED MONDAY THROUGH WEDNESDAY AS A SERIES OF DISTURBANCES EMBEDDED WITHIN THE FLOW CROSS THE AREA. TEMPERATURE WISE...AN OVERALL COOLING TREND BACK TO NEAR NORMAL IS EXPECTED. HIGHS WILL RANGE FROM THE UPPER 80S MONDAY AND TUESDAY...COOLING TO THE UPPER 70S TO MID 80S WEDNESDAY AND THURSDAY. && .AVIATION...A COLD FRONT WILL STALL FROM NEAR KBUB TO KSNY THIS AFTERNOON. TO THE NORTH OF THE FRONT...SFC WINDS WILL NE NORTH TO NORTHEAST AT 5 TO 15 KTS...WHILE SOUTHWEST WINDS WILL CONTINUE AT 10 TO 20 KTS TO THE SOUTH OF THE FRONT. BROKEN MID LEVEL CEILINGS AND FEW LIGHT RAIN SHOWERS ARE POSSIBLE TO THE NORTH OF THE FRONT THROUGH LATE THIS AFTERNOON. && .FIRE WEATHER... A LARGE FIRE IS ONGOING ACROSS NORTHWESTERN SHERIDAN COUNTY AND AN EVACUATION ORDER HAS BEEN GIVEN FOR METCALF STATE WILDLIFE MANAGEMENT AREA. SEE OMAEVILBF FOR DETAILS. RH WILL BEGIN TO RECOVER TO 20 TO 30 PERCENT IN SOUTHERN AREAS AROUND 03Z THIS EVENING...SO THE ONGOING RED FLAG WARNING WILL CONTINUE FOR ALL ZONES EXCEPT NEZ208. ALL LOCATIONS IN THIS ZONE ARE NOW NORTH OF THE COLD FRONT...WITH RH`S CURRENTLY RUNNING FROM 30 TO 40 PERCENT. OVERNIGHT TONIGHT...THE COLD FRONT WILL LIFT NORTH AS A WARM FRONT...AS HIGH PRESSURE LIFTS INTO MINNESOTA. FOR FRIDAY...A WARM FRONT WILL BE ANCHORED FROM THE BLACK HILLS INTO NERN NEBRASKA...WHICH WILL ALLOW THE HEAT TO BUILD NORTH INTO WESTERN AND NORTH CENTRAL NEBRASKA FRIDAY AFTERNOON. GUSTY SRLY WINDS WILL DEVELOP ACROSS THE CENTRAL AND WESTERN SAND HILLS...AS WELL AS THE EASTERN NEBRASKA PANHANDLE AND SOUTHWESTERN NEBRASKA FRIDAY AFTERNOON AND MAY GUST AS HIGH AS 25 MPH. WITH FCST DEW POINTS IN THE 30S AND LOWER 40S FRIDAY AFTERNOON...MINIMUM RH`S OF AROUND 15 PERCENT ARE POSSIBLE. WILL BE HOISTING A FIRE WEATHER WATCH FOR FRIDAY AFTERNOON AND EVENING FOR ALL ZONES EXCEPT 209 FOR THE POSSIBILITY OF CRITICAL FIRE DANGER FRIDAY AFTERNOON. && .LBF WATCHES/WARNINGS/ADVISORIES...RED FLAG WARNING THROUGH 11 PM CDT (10 PM MDT) TONIGHT FOR ZONES NEZ204-206-209-210-219. FIRE WEATHER WATCH FROM 10 AM CDT (9 AM MDT) THROUGH 11 PM CDT (10 PM MDT) FRIDAY FOR ZONES NEZ204-206-208-210-219. $$ SYNOPSIS...SHORT AND FIRE WEATHER...BUTTLER AVIATION AND LONG RANGE...TAYLOR
AREA FORECAST DISCUSSION
NWS BUFFALO NY
355 PM EDT FRI AUG 31 2012 .SYNOPSIS... A COLD FRONT WILL DROP SOUTH ACROSS THE AREA OVERNIGHT WITH NO MORE THAN ISOLATED SHOWERS AND THUNDERSTORMS ACROSS NORTHERN NEW YORK. HIGH PRESSURE WILL RETURN BEHIND THE FRONT WITH MORE SEASONABLE TEMPERATURES FOR THE WEEKEND. THE NEXT CHANCE FOR RAIN WILL BE EARLY NEXT WEEK WHEN THE REMNANTS OF ISSAC WILL POTENTIALLY IMPACT THE REGION. && .NEAR TERM /THROUGH SATURDAY/... SURFACE ANALYSIS ALONG WITH RADAR AND SATELLITE IMAGERY REVEAL A COLD FRONT ORIENTED EAST TO WEST ACROSS SOUTHERN QUEBEC AND ONTARIO PROVINCES JUST NORTH OF OTTAWA AT 19Z. KTYX NWS DOPPLER AND THE CANADIAN RADAR NEAR MONTREAL SHOW A BAND OF THUNDERSTORMS ORIENTED ALONG THE FRONT WITH ANOTHER AREA OF THUNDERSTORMS BETWEEN MONTREAL QUEBEC AND MASSENA NEW YORK. A TIGHT PRESSURE GRADIENT EXISTS ACROSS NEW YORK SOUTH OF THE FRONT AS IT SLOWLY SQUEEZES SOUTH TOWARD A SURFACE HIGH OVER THE MID ATLANTIC. THIS IS CREATING GUSTY SOUTHWEST WINDS ACROSS THE FORECAST AREA AVERAGING 20 TO 30 MPH. HIGH RESOLUTION MODEL DATA INCLUDING THE 17Z HRRR AND LATEST NMM/ARW WRF RUNS INDICATE INCREASING CONVECTION FORMING AHEAD OF AND ALONG THE FRONT INTO THE EARLY EVENING AS IT PRESSES FURTHER SOUTHWARD TOWARD NORTHERN NY. THE BIG QUESTION IS WHETHER ENOUGH LOW LEVEL MOISTURE WILL BE AVAILABLE ACROSS NORTHERN NY AND IF SURFACE INSTABILITY CAN OVERCOME THE MID LEVEL HEAT RIDGE BUILDING NORTH ACROSS CENTRAL NEW YORK. WHILE SURFACE MOISTURE IS LIMITED WITH DEWPOINT DEPRESSIONS OF AROUND 15F...SOME MID LEVEL MOISTURE IS AVAILABLE...SPC MESOANALYSIS DATA SHOWING 1.5 TO 1.8 INCHES OF PRECIPITABLE WATER EAST OF LAKE ONTARIO. MESOANALYSIS ALSO REVEALS A CAP IN PLACE ACROSS THE FORECAST AREA WITH THE ONLY UNCAPPED AREA WITH SOME CAPE BEING NEAR OTTAWA. WIND SHEAR HOWEVER IS HIGH WITH MESOANALYSIS INDICATING 0-6 KM SHEAR RUNNING GREATER THAN 50 KTS. IF SIGNIFICANT STORM UPDRAFTS CAN DEVELOP SOUTH INTO THE EASTERN LAKE ONTARIO REGION IT APPEARS THAT DAMAGING WINDS WOULD BE THE MAIN SEVERE WEATHER THREAT WITH THE STRONGEST CELLS. SPC HAS INCLUDED PARTS OF THE EASTERN LAKE ONTARIO REGION IN A SLIGHT RISK FOR SEVERE STORMS. TONIGHT...WIND GUSTS ARE FORECAST TO FALL OFF NEAR SUNSET WITH SUSTAINED WINDS OF AROUND 10 MPH FINALLY LOWERING WHEN THE SURFACE FRONT SHIFTS SOUTH OF THE AREA. COOLER TEMPERATURES WILL ADVECT INTO THE REGION WITH MAINLY CLEAR SKIES. OVERNIGHT LOWS FORECASTED A BIT WARMER BASED ON 12Z MODEL GUIDANCE AND HIGH TEMPS REACHED TODAY FALLING INTO THE 60S. NORTHERLY FLOW SETTING UP BEHIND THE FRONT MAY HOLD THE LAKE PLAIN AREAS A LITTLE WARMER. MOS GUIDANCE AND BUFKIT PROFILES INDICATE PATCHY FOG ALSO POSSIBLE TONIGHT MOST LIKELY IN SHELTERED AREAS AFTER THE WINDS FALL OFF. CLEAR SKIES SHOULD PROVIDE GREAT RADIATIONAL COOLING BUT WINDS WILL BE THE QUESTION. ON SATURDAY HIGH PRESSURE OVER MINNESOTA THIS EVENING WILL SHIFT EASTWARD AND BUILD IN BEHIND THE FRONT. EXPECT MAINLY CLEAR SKIES WITH LIGHT NORTHERLY WINDS AND SEASONABLE TEMPERATURES RUNNING IN THE UPPER 70S TO LOW 80S...A FINE LATE SUMMER DAY! && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... HIGH PRESSURE ACROSS THE UPPER LAKES SATURDAY EVENING WILL SHIFT TO NORTHERN NEW ENGLAND THROUGH SUNDAY NIGHT. IT STILL APPEARS THIS HIGH WILL KEEP MOISTURE ASSOCIATED WITH THE REMNANTS OF ISAAC TO OUR SOUTH AND WEST. EXPECT SUNDAY TO BE A QUITE PLEASANT DAY ACROSS WESTERN NEW YORK...WITH SEASONABLE TEMPERATURES IN THE UPPER 70S AND LOWER 80S. THERE WILL BE QUITE A BIT OF SUNSHINE ACROSS MOST OF THE REGION...WITH CLOUDS A BIT MORE PREVALENT IN THE SOUTHERN TIER. THERE MAY BE SCATTERED SHOWERS TO OUR SOUTH...BUT A PRETTY STRONG MODEL CONSENSUS KEEPS THIS OUT OF OUR REGION ON THE STRENGTH OF THE HIGH POSITIONED TO OUR NORTH. && .LONG TERM /MONDAY THROUGH FRIDAY/... 12Z MODEL CONSENSUS HAS SLOWED A BIT WITH THE APPROACH OF MOISTURE FROM THE TROPICAL REMNANTS OF ISAAC. PART OF THIS IS THAT MODEL GUIDANCE HAS BEEN TRENDING TOWARD A WEAKER SHORTWAVE EARLY NEXT WEEK...WHICH ALSO SLOWS AND WEAKENS THE APPROACH OF AN ASSOCIATED FRONTAL BOUNDARY. WHILE THE MAJORITY OF MODELS (GFS/EUROPEAN) BRING SHOWERS AND THUNDERSTORMS INTO WESTERN NEW YORK ON MONDAY...THE GGEM IS A LARGELY DRY FORECAST. WITH THIS TREND IN MIND...EXPECT THE STEADIEST RAINS TO COME DURING THE LATTER HALF OF MONDAY NIGHT THROUGH TUESDAY MORNING...WITH THIS AXIS LIKELY TO SHIFT INTO EASTERN PORTIONS OF THE CWA TUESDAY AFTERNOON. OUTSIDE OF THE SLIGHTLY SLOWER TIMING...OUR EXPECTATION OF RAINFALL AVERAGING AROUND AN INCH REMAINS THE SAME. MODEL GUIDANCE HAS BEEN INCONSISTENT ON QPF...WITH THE 12Z GFS IN PARTICULAR LIKELY OVERDONE IN A CONVECTIVE BULLSEYE IN WESTERN PORTIONS OF THE SOUTHERN TIER. THE GGEM/EUROPEAN ARE BOTH MUCH MORE IN LINE WITH PREVIOUS CONSENSUS...THOUGH IT SHOULD BE NOTED THAT LOCALLY HIGHER...AND LOWER...AMOUNTS ARE EXPECTED. IT IS SIMPLY TOO FAR OFF TO PIN SPECIFICS DOWN. WHILE RAINFALL AMOUNTS WILL VARY...AN INCH OF RAIN WOULD BE BENEFICIAL FOR AREAS IMPACTED BY THE DROUGHT. THE POTENTIAL FOR FLOODING REMAIN LOW FOR WESTERN NEW YORK...WITH THE ONLY REAL THREAT COMING FROM LOCALIZED OR SLOW MOVING CONVECTIVE CELLS. THE SHORTWAVE AND ASSOCIATED FRONTAL BOUNDARY WILL EXIT TO THE EAST TUESDAY NIGHT...WITH THE REGION LIKELY TO END UP BETWEEN SYSTEMS WEDNESDAY. THEN A DEEPER SHORTWAVE WILL APPROACH...WITH A BLEND OF THE GFS/EUROPEAN BRINGING THIS ACROSS WEDNESDAY NIGHT OR THURSDAY. THIS FRONT SUPPORTS CHANCE POPS FOR NOW. BOTH THE 12Z GFS/EUROPEAN EXIT THIS FRONT TO THE EAST...WITH DRY WEATHER LIKELY FOR FRIDAY. THE GFS IS QUITE A BIT COOLER THAN THE EUROPEAN...WITH OUR FORECAST A BLEND BETWEEN THE TWO. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... MAINLY VFR CONDITIONS EXPECTED THROUGH THE 18Z TAF CYCLE EXCEPT FOR SOME FOG DEVELOPING ACROSS THE SOUTHERN TIER WHICH MAY IMPACT KJHW. THIS EVENING A COLD FRONT LOCATED JUST NORTH OF THE NY/CANADIAN BORDER WILL DRIFT SOUTH ACROSS THE STATE. ONLY ISOLATED SHOWERS OR THUNDERSTORMS COULD DEVELOP ACROSS NORTHERN NEW YORK EARLY THIS AHEAD OF THE FRONT. WINDS WILL BE THE MAIN ISSUE EARLY THIS EVENING WITH GUSTS STILL RUNNING 25 TO 35 KTS AT 19Z. HIGHEST WIND ISSUES WILL BE ACROSS THE NIAGARA FRONTIER AS THE SOUTHWEST WINDS FUNNEL ALONG LAKE ERIE. WIND GUSTS WILL FALL OFF NEAR SUNSET WITH THE END OF MIXING. SUSTAINED WINDS WILL THEN FALL OFF INTO THE LATE EVENING AFTER THE COLD FRONT DROPS SOUTH. LATE TONIGHT MOS AND LAMP GUIDANCE INDICATE POTENTIAL FOR FOG AT KJHW. WHILE GUIDANCE IS GOING AS LOW AS LIFR OPTED TO KEEP VIS DOWN TO ONLY 2SM FOR NOW. THE ISSUE WHICH MAY PREVENT THIS WOULD BE WINDS REMAINING TOO HIGH LATE TONIGHT. VFR SATURDAY UNDER HIGH PRESSURE. OUTLOOK... SATURDAY THROUGH SUNDAY...VFR. MONDAY...LIKELY RAIN SHOWERS DETERIORATING TO MVFR. MONDAY NIGHT AND TUESDAY...MVFR/IFR IN RAIN SHOWERS LIKELY MONDAY NIGHT...AND POSSIBLY ON TUESDAY. && .MARINE... A COLD FRONT DROPPING SOUTHWARD FROM CANADA HAS TIGHTEN THE PRESSURE GRADIENT OVER THE LOWER GREAT LAKES REGION THIS AFTERNOON AND EVENING AS IT RUNS INTO A HIGH PRESSURE SYSTEM OVER THE MID-ATLANTIC. SOUTHWEST WINDS AND WAVES HAVE REACHED SMALL CRAFT ADVISORY CRITERIA TODAY AHEAD OF THE FRONT. SMALL CRAFTS REMAIN IN EFFECT FOR ALL MARINE ZONES EXCEPT THE LOWER NIAGARA AND ST. LAWRENCE RIVER. BEHIND THE FRONT...WINDS WILL SHIFT TO LIGHT NORTHERLY AND WAVE HEIGHTS WILL EVENTUALLY SUBSIDE OVER THE LAKES. HIGH PRESSURE WILL THEN BUILD ACROSS THE REGION SATURDAY...RESULTING IN FINE BOATING WEATHER FOR THE WEEKEND. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LEZ020. SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR LEZ040-041. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LOZ042-043. SMALL CRAFT ADVISORY UNTIL 1 AM EDT SATURDAY FOR LOZ045. SMALL CRAFT ADVISORY UNTIL 3 AM EDT SATURDAY FOR LOZ044. && $$ SYNOPSIS...SMITH NEAR TERM...SMITH SHORT TERM...APFFEL LONG TERM...APFFEL AVIATION...SMITH MARINE...APFFEL/SMITH
AREA FORECAST DISCUSSION
NWS RALEIGH NC
144 AM EDT FRI AUG 31 2012 .SYNOPSIS... AN UPPER LEVEL RIDGE WILL STRENGTHEN OVER THE AREA THROUGH SATURDAY... RESULTING IN ABOVE NORMAL TEMPERATURES. THE REMNANTS OF TROPICAL CYCLONE ISAAC WILL APPROACH THE AREA FROM THE WEST EARLY NEXT WEEK. && .NEAR TERM /THROUGH FRIDAY NIGHT/... AS OF 1010 PM THURSDAY... TONIGHT: SURFACE HIGH OFF THE NC COAST WILL YIELD A MOIST SSW RETURN FLOW OVER CENTRAL NC OVERNIGHT. SKIES HAVE CLEARED ACROSS MOST OF NC AS OF 02Z. LATEST RUC ANALYSIS SHOWS SURFACE RH OF 95 TO 100 PERCENT BETWEEN 06 AND 12Z AND SURFACE DEWPOINT DEPRESSIONS OF ONE OR LESS ACROSS MUCH OF THE AREA BY 09Z...INCREASING SIGNIFICANTLY AFTER 12Z. THE RUC FORECASTED SURFACE WINDS ARE AROUND 5 KTS AS A SURFACE TROUGH MOVES ACROSS NORTHERN VA...INCREASING THE PRESSURE GRADIENT ACROSS THE NORTH EARLY FRIDAY MORNING. IT IS LIKELY THAT FOG WILL DEVELOP ACROSS MUCH OF THE AREA BETWEEN 09Z AND 12Z...HOWEVER THERE IS STILL A BIT OF UNCERTAINTY...PARTICULARLY ACROSS THE NORTH WHERE THE WINDS MAY BE STRONG ENOUGH TO INHIBIT FOG DEVELOPING. HAVE KEPT AREAS OF FOG IN FOR THE PRE-DAWN HOURS GIVEN THE PERSISTENCE FROM THURSDAY MORNING...AND THE CLEAR SKIES...LIGHT WINDS AND ABUNDANT LOW LEVEL MOISTURE. THESE CONDITIONS SHOULD ALSO RESULT IN GOOD RADIATIONAL COOLING...YIELDING OVERNIGHT LOW TEMPS IN THE MID TO UPPER 60S. -KC THERE ARE A COUPLE OF POSSIBLE INHIBITING FACTORS FOR THE DEVELOPMENT OF DENSE FOG...HOWEVER. ONE IS THE TIGHTENING OF THE SURFACE PRESSURE GRADIENT AND LEE TROUGH DEVELOPMENT ACROSS NORTHERN NC...WHICH MAY PRODUCE SOME STIRRING OF SOUTHWESTERLY SURFACE WINDS OVER THE NORTHERN PIEDMONT AND RESULT IN VERY LOW STRATUS LAYER AND LIGHTER FOG...VERSUS A HIGHER LIKELIHOOD OF CALM AND DENSE FOG DEVELOPMENT DIRECTLY WITHIN THE RIDGE AXIS ACROSS SOUTHERN NC. THE OTHER POSSIBLE INHIBITING FACTOR IS THE POTENTIAL FOR A SCT-BKN STRATOCUMULUS CLOUD FIELD FROM A RIBBON OF H85 MOISTURE TO ADVECT IN AN ARC CYCLONICALLY FROM WESTERN TO NORTH CENTRAL TO EASTERN NC...AFFECTING MAINLY LOCALES NEAR THE VA BORDER IN THE RAH CWFA. FRI-FRI NIGHT: WARMER AND MAINLY DRY. A LOW LEVEL THERMAL RIDGE ON THE NORTHERN AND NORTHEASTERN PERIPHERY OF THE AFOREMENTIONED MID LEVEL RIDGE AND CHARACTERIZED BY TEMPERATURES ALREADY IN THE UPPER 90S TO LOWER 100S OVER NE AND IA AT 18Z...WILL ADVECT EASTWARD TO THE MIDDLE ATLANTIC STATES AND YIELD PROJECTED LOW LEVEL THICKNESSES NEAR 1430 METERS AT GSO BY 00Z/1ST. SUCH THICKNESSES SHOULD SUPPORT TEMPERATURES MAINLY IN THE 89 TO 94 DEGREE RANGE UNDER A MOSTLY SUNNY SKY. CONVECTIVE POTENTIAL WILL REMAIN QUITE LOW...AND HAS BEEN LEFT OUT OF THE FORECAST GIVEN THE SUBSIDENT AND CAPPING INFLUENCE OF THE RIDGE ALOFT...DESPITE SHALLOW LOW LEVEL CONVERGENCE AND BL MOISTURE GRADIENT INVOF THE PIEDMONT SURFACE TROUGH AXIS. CONTINUED MAINLY CLEAR...BUT MILDER WITH A SOUTHWESTERLY STIRRING WIND AS THE SURFACE TROUGH FURTHER STRENGTHENS...WITH LOWS WITHIN A COUPLE OF DEGREES OF 70. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 235 PM THURSDAY... FOR SATURDAY/SATURDAY NIGHT: BASED ON THE LATEST MODEL OUTPUT... THERE IS A RISING RISK FOR LATE AFTERNOON/EVENING STORMS SATURDAY. A MID LEVEL TROUGH AXIS SWINGING (WITH A SLIGHT POSITIVE TILT) THROUGH THE NORTHEAST STATES WILL HELP PUSH A BACKDOOR FRONT SOUTHWARD TOWARD (BUT NOT INTO) NC... WITH LEESIDE TROUGH DEVELOPMENT LIKELY OVER CENTRAL NC. AS FRIDAY`S MID LEVEL ANTICYCLONE CENTER GETS SUPPRESSED TO OUR SOUTH... MID LEVEL FLOW WILL STRENGTHEN FROM THE NORTHWEST. THE RESULTING INCREASE IN DEEP LAYER SHEAR (YET STILL MODEST AT JUST 15-20 KTS) ACCOMPANIED BY IMPROVING THERMODYNAMICS (1200-2000 J/KG OF MLCAPE) AND RISING PW TO 1.8-2.0 INCHES WILL SUPPORT A FEW AFTERNOON SHOWERS AND STORMS... INCLUDING THOSE EXPECTED TO DEVELOP OVER THE HIGHER TERRAIN AND DROP SOUTHEASTWARD INTO THE FORECAST AREA LATE IN THE DAY. LOW LEVEL THICKNESSES WILL BE ABOUT 15-25 METERS ABOVE NORMAL... WHILE 700 MB TEMPS RISE TO 11-12C... COMPARABLE TO UPSTREAM VALUES WHERE SURFACE TEMPS EARLY THIS AFTERNOON HAD ALREADY EXCEEDED 90. EXPECT HIGHS OF 90-94. WARM LOWS OF 69-73 WITH MOSTLY CLOUDY SKIES AS CONVECTIVE DEBRIS AND MID-HIGH CLOUDS STREAMING FROM ISAAC OVERSPREAD THE REGION. FOR SUNDAY/SUNDAY NIGHT: THIS IS ABOUT THE TIME WE SHOULD BEGIN TO FEEL THE DIRECT EFFECTS OF THE REMNANTS OF ISAAC. THE CENTER OF THE REMNANT SURFACE CYCLONE IS EXPECTED TO BE OVER SRN IL SUNDAY MORNING... DRIFTING INTO INDIANA BEFORE IT BEGINS TO GET ABSORBED INTO THE SURFACE FRONTAL SYSTEM APPROACHING FROM THE NW. MODELS SUPPORT HOLDING A WEAK FRONTAL ZONE ORIENTED ROUGHLY FROM KY ACROSS SW NC AND ALONG THE NC/SC BORDER... AND THIS MAY REMAIN A FOCUS FOR SCATTERED STORMS DEVELOPING WITH DAYTIME HEATING AND DESTABILIZATION (MLCAPE OF 1500-2400 J/KG)... AND WITH DEEP LAYER SHEAR INCHING UP A BIT TO 20-25 KTS. PW VALUES WILL STAY QUITE HIGH... CLOSE TO 2.0 INCHES... SO IT SHOULD NOT TAKE MUCH TO INDUCE CONVECTION. HAVE BUMPED UP POPS TO A 40-50 PERCENT CHANCE... MAINLY AFTERNOON THROUGH EVENING. HIGHS 85-89 WITH GENERALLY MOSTLY CLOUDY SKIES. LOWS 68-72 WITH LOWER RAIN CHANCES OVERNIGHT. -GIH && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 115 PM THURSDAY... FOR MONDAY/MONDAY NIGHT: MODELS AGREE ON ISAAC`S CORRESPONDING MID LEVEL SHORTWAVE TROUGH SLOWLY PASSING OVER KY/TN AS IT APPROACHES NC FROM THE WEST... ALTHOUGH MODEL SOLUTIONS VARY WITH RESPECT TO ITS SPEED AND AMPLITUDE. WITH A STRONG MID LEVEL RIDGE COVERING THE DESERT SOUTHWEST AND A FAST FLOW OVER THE NORTHERN PORTION OF THE CONUS... THIS WAVE SHOULD SLOWLY DEAMPLIFY AS POLAR SHORTWAVE ENERGY DROPS ESE THROUGH ONTARIO... BUT IT SHOULD REMAIN A DISTINCT AND TRACKABLE WAVE AS IT MOVES INTO THE SRN APPALACHIANS. THE GFS/ECMWF BOTH DEPICT WEAK NW-SE WARM FRONTOGENESIS OVER THE CAROLINAS AS THE WAVE APPROACHES... AND BOTH ALSO DEVELOP WIDESPREAD CONVECTION MONDAY AFTERNOON ACCOMPANYING THE MID LEVEL HEIGHT FALLS WITH CONFLUENT GULF- AND ATLANTIC-SOURCE SOUTHEAST AND SOUTHERLY LOW LEVEL FLOW. GIVEN THE IMPROVING DYNAMICS AND INSTABILITY... WILL HAVE GOOD CHANCES OF SHOWERS AND A FEW STORMS MONDAY AFTERNOON AND EVENING... DECREASING WITH LOSS OF HEATING OVERNIGHT. THICKNESSES POINT TO HIGHS IN THE MID 80S. IT`S WORTH NOTING THAT IF THE LOW LEVEL WARM FRONT SETS UP TO OUR SOUTH WITH NUMEROUS SHOWERS OVER CENTRAL NC WITHIN THE BIT MORE STABLE AIR... WE COULD SEE COOLER TEMPS THAN ARE CURRENTLY ANTICIPATED. FOR TUESDAY THROUGH THURSDAY: A MARKED DIVERGENCE IN MODEL SOLUTIONS BECOMES PROBLEMATIC FOR OUR DAY-TO-DAY FORECAST STARTING TUESDAY. ACCORDING TO THE 00Z/06Z GFS... THE WEAKENING MID LEVEL TROUGH IS EXPECTED TO HAVE SHIFTED SE OF THE CWA BY WEDNESDAY MORNING AS THE MEAN LONGWAVE TROUGH DIGS FROM JAMES BAY THROUGH THE ERN GREAT LAKES TO THE MIDATLANTIC COAST... AND AS A SURFACE COLD FRONT PUSHES SE THROUGH CENTRAL NC. BUT THERE ARE INDICATIONS THAT THE 00Z/06Z GFS MAY BE TOO AGGRESSIVE WITH ITS NORTHEAST-NOAM HEIGHT FALLS... AS THE 00Z ECMWF FAVORS DIGGING A TROUGH MUCH MORE WESTWARD INTO MT/ID BY LATE TUESDAY NIGHT. THE ECMWF (WHICH IS THE STRONGEST WITH ISAAC`S REMNANT MID LEVEL SHORTWAVE TROUGH) ALSO DEVELOPS A CLOSED LOW WELL OFF THE BAHAMAS ON SUNDAY AND THEN BRINGS THIS LOW WESTWARD AND NORTHWESTWARD TOWARD THE SOUTHEAST COAST BY LATE TUESDAY. IN TERMS OF SENSIBLE WEATHER... THIS RESULTS IN STORMY-EARLY-BUT-CLEARING WEATHER DURING THIS PERIOD ON THE GFS... AND MILD AND QUITE WET/STORMY (ALMOST TROPICAL-LIKE) ON THE ECMWF. THE ECMWF ENSEMBLE MEAN PROVIDES A MIDDLE-OF-THE-ROAD SOLUTION... GRADUALLY DEEPENING THE LONGWAVE TROUGH OVER THE UPPER MIDWEST AND WRN GREAT LAKES... A LITTLE WEST OF THE 00Z/06Z GFS BUT CLOSER IN LINE WITH THE NEW 12Z GFS. FAVORING THIS... EXPECT A GOOD CHANCE OF SHOWERS/STORMS THROUGH TUESDAY... DECREASING WEST BUT REMAINING FAIRLY HIGH IN THE EASTERN FORECAST AREA ON WEDNESDAY... AND A LOWER CHANCE ON THURSDAY AS THE SURFACE FRONT SHOULD BE EAST OF THE AREA WITH DRIER AIR FILTERING IN FROM THE NW. BUT CONFIDENCE IN THE DETAILS HERE IS RATHER LOW... AND THIS SCENARIO COULD CHANGE IN THE COMING DAYS AS THE FORECAST IS REFINED. LOW LEVEL THICKNESSES ARE UNLIKELY TO REACH HIGHLY ANOMALOUS VALUES... AS THEY SHOULD HOLD WITHIN 5-15 METERS ABOVE NORMAL. EXPECT HIGHS MOSTLY IN THE MID 80S WITH LOWS IN THE MID 60S TO NEAR 70. -GIH && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 140 AM FRIDAY... 24-HR TAF PERIOD: A CONTINUED MOIST BOUNDARY LAYER COUPLED WITH LIGHT AND VARIABLE TO CALM WINDS AND CURRENT CLEAR SKIES WILL LEAD TO ANOTHER MORNING OF LOW STRATUS AND FOG ACROSS CENTRAL NC. EXPECT THE WORST CONDITIONS TO BE ACROSS SOUTHERN AND POSSIBLY EASTERN PORTIONS OF THE AREA... WHERE IFR/LIFR CONDITIONS WILL BE POSSIBLE (KRWI/KFAY). FURTHER NORTH AND WEST... A DEVELOPING SURFACE TROUGH MAY PREVENT WINDS FROM GOING CALM. THIS WOULD LOWER THE PROBABILITY OF DENSE FOG... AND POSSIBLE FAVOR MORE STRATUS (ESPECIALLY AT KGSO/KINT). THUS... WILL CONTINUE TO GO WITH A COMBINATION OF STRATUS AN FOG AT THESE SITES (KGSO/KINT/KRDU)... WITH GENERALLY MVFR/IFR CONDITIONS DEVELOPING THIS MORNING IN THE PRE-DAWN HOURS. EXPECT AND LOW STRATUS AND OR FOG TO LIFT/DISSIPATE BY 15/16Z AT THE LATEST. VFR CONDITIONS ARE EXPECTED AFTER THE FOG AND STRATUS LIFT ALONG WITH CONTINUED DRY WEATHER... AS STRONG HIGH PRESSURE ALOFT BUILDS OVER THE AREA. LOOKING AHEAD: VFR CONDITIONS ARE EXPECTED TO RULE THROUGH SAT NIGHT IN ASSOCIATION WITH THE AFOREMENTIONED UPPER LEVEL RIDGE...THOUGH A SMALL CHANCE FOR SHOWERS/STORMS CANNOT BE RULED OUT SAT AFTERNOON/EVENING... BEST CHANCE AT KGSO/KINT. THE NEXT CHANCE FOR ADVERSE AVIATION CONDITIONS WILL BE LATE SUNDAY INTO MON/TUE AS THE REMNANTS OF TROPICAL CYCLONE ISAAC PROGRESS EAST TOWARD THE REGION. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BSD/JB NEAR TERM...KC/MWS/SEC SHORT TERM...HARTFIELD LONG TERM...HARTFIELD AVIATION...BSD/VINCENT
AREA FORECAST DISCUSSION
NWS RALEIGH NC
1013 PM EDT THU AUG 30 2012 .SYNOPSIS... AN UPPER LEVEL RIDGE WILL STRENGTHEN OVER THE CAROLINAS THROUGH SATURDAY...RESULTING IN ABOVE NORMAL TEMPERATURES. THE REMNANTS OF TROPICAL CYCLONE ISAAC WILL APPROACH THE AREA FROM THE WEST EARLY NEXT WEEK. && .NEAR TERM /THROUGH FRIDAY NIGHT/... AS OF 1010 PM THURSDAY... TONIGHT: SURFACE HIGH OFF THE NC COAST WILL YIELD A MOIST SSW RETURN FLOW OVER CENTRAL NC OVERNIGHT. SKIES HAVE CLEARED ACROSS MOST OF NC AS OF 02Z. LATEST RUC ANALYSIS SHOWS SURFACE RH OF 95 TO 100 PERCENT BETWEEN 06 AND 12Z AND SURFACE DEWPOINT DEPRESSIONS OF ONE OR LESS ACROSS MUCH OF THE AREA BY 09Z...INCREASING SIGNIFICANTLY AFTER 12Z. THE RUC FORECASTED SURFACE WINDS ARE AROUND 5 KTS AS A SURFACE TROUGH MOVES ACROSS NORTHERN VA...INCREASING THE PRESSURE GRADIENT ACROSS THE NORTH EARLY FRIDAY MORNING. IT IS LIKELY THAT FOG WILL DEVELOP ACROSS MUCH OF THE AREA BETWEEN 09Z AND 12Z...HOWEVER THERE IS STILL A BIT OF UNCERTAINTY...PARTICULARLY ACROSS THE NORTH WHERE THE WINDS MAY BE STRONG ENOUGH TO INHIBIT FOG DEVELOPING. HAVE KEPT AREAS OF FOG IN FOR THE PRE-DAWN HOURS GIVEN THE PERSISTENCE FROM THURSDAY MORNING...AND THE CLEAR SKIES...LIGHT WINDS AND ABUNDANT LOW LEVEL MOISTURE. THESE CONDITIONS SHOULD ALSO RESULT IN GOOD RADIATIONAL COOLING...YIELDING OVERNIGHT LOW TEMPS IN THE MID TO UPPER 60S. -KC THERE ARE A COUPLE OF POSSIBLE INHIBITING FACTORS FOR THE DEVELOPMENT OF DENSE FOG...HOWEVER. ONE IS THE TIGHTENING OF THE SURFACE PRESSURE GRADIENT AND LEE TROUGH DEVELOPMENT ACROSS NORTHERN NC...WHICH MAY PRODUCE SOME STIRRING OF SOUTHWESTERLY SURFACE WINDS OVER THE NORTHERN PIEDMONT AND RESULT IN VERY LOW STRATUS LAYER AND LIGHTER FOG...VERSUS A HIGHER LIKELIHOOD OF CALM AND DENSE FOG DEVELOPMENT DIRECTLY WITHIN THE RIDGE AXIS ACROSS SOUTHERN NC. THE OTHER POSSIBLE INHIBITING FACTOR IS THE POTENTIAL FOR A SCT-BKN STRATOCUMULUS CLOUD FIELD FROM A RIBBON OF H85 MOISTURE TO ADVECT IN AN ARC CYCLONICALLY FROM WESTERN TO NORTH CENTRAL TO EASTERN NC...AFFECTING MAINLY LOCALES NEAR THE VA BORDER IN THE RAH CWFA. FRI-FRI NIGHT: WARMER AND MAINLY DRY. A LOW LEVEL THERMAL RIDGE ON THE NORTHERN AND NORTHEASTERN PERIPHERY OF THE AFOREMENTIONED MID LEVEL RIDGE AND CHARACTERIZED BY TEMPERATURES ALREADY IN THE UPPER 90S TO LOWER 100S OVER NE AND IA AT 18Z...WILL ADVECT EASTWARD TO THE MIDDLE ATLANTIC STATES AND YIELD PROJECTED LOW LEVEL THICKNESSES NEAR 1430 METERS AT GSO BY 00Z/1ST. SUCH THICKNESSES SHOULD SUPPORT TEMPERATURES MAINLY IN THE 89 TO 94 DEGREE RANGE UNDER A MOSTLY SUNNY SKY. CONVECTIVE POTENTIAL WILL REMAIN QUITE LOW...AND HAS BEEN LEFT OUT OF THE FORECAST GIVEN THE SUBSIDENT AND CAPPING INFLUENCE OF THE RIDGE ALOFT...DESPITE SHALLOW LOW LEVEL CONVERGENCE AND BL MOISTURE GRADIENT INVOF THE PIEDMONT SURFACE TROUGH AXIS. CONTINUED MAINLY CLEAR...BUT MILDER WITH A SOUTHWESTERLY STIRRING WIND AS THE SURFACE TROUGH FURTHER STRENGTHENS...WITH LOWS WITHIN A COUPLE OF DEGREES OF 70. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 235 PM THURSDAY... FOR SATURDAY/SATURDAY NIGHT: BASED ON THE LATEST MODEL OUTPUT... THERE IS A RISING RISK FOR LATE AFTERNOON/EVENING STORMS SATURDAY. A MID LEVEL TROUGH AXIS SWINGING (WITH A SLIGHT POSITIVE TILT) THROUGH THE NORTHEAST STATES WILL HELP PUSH A BACKDOOR FRONT SOUTHWARD TOWARD (BUT NOT INTO) NC... WITH LEESIDE TROUGH DEVELOPMENT LIKELY OVER CENTRAL NC. AS FRIDAY`S MID LEVEL ANTICYCLONE CENTER GETS SUPPRESSED TO OUR SOUTH... MID LEVEL FLOW WILL STRENGTHEN FROM THE NORTHWEST. THE RESULTING INCREASE IN DEEP LAYER SHEAR (YET STILL MODEST AT JUST 15-20 KTS) ACCOMPANIED BY IMPROVING THERMODYNAMICS (1200-2000 J/KG OF MLCAPE) AND RISING PW TO 1.8-2.0 INCHES WILL SUPPORT A FEW AFTERNOON SHOWERS AND STORMS... INCLUDING THOSE EXPECTED TO DEVELOP OVER THE HIGHER TERRAIN AND DROP SOUTHEASTWARD INTO THE FORECAST AREA LATE IN THE DAY. LOW LEVEL THICKNESSES WILL BE ABOUT 15-25 METERS ABOVE NORMAL... WHILE 700 MB TEMPS RISE TO 11-12C... COMPARABLE TO UPSTREAM VALUES WHERE SURFACE TEMPS EARLY THIS AFTERNOON HAD ALREADY EXCEEDED 90. EXPECT HIGHS OF 90-94. WARM LOWS OF 69-73 WITH MOSTLY CLOUDY SKIES AS CONVECTIVE DEBRIS AND MID-HIGH CLOUDS STREAMING FROM ISAAC OVERSPREAD THE REGION. FOR SUNDAY/SUNDAY NIGHT: THIS IS ABOUT THE TIME WE SHOULD BEGIN TO FEEL THE DIRECT EFFECTS OF THE REMNANTS OF ISAAC. THE CENTER OF THE REMNANT SURFACE CYCLONE IS EXPECTED TO BE OVER SRN IL SUNDAY MORNING... DRIFTING INTO INDIANA BEFORE IT BEGINS TO GET ABSORBED INTO THE SURFACE FRONTAL SYSTEM APPROACHING FROM THE NW. MODELS SUPPORT HOLDING A WEAK FRONTAL ZONE ORIENTED ROUGHLY FROM KY ACROSS SW NC AND ALONG THE NC/SC BORDER... AND THIS MAY REMAIN A FOCUS FOR SCATTERED STORMS DEVELOPING WITH DAYTIME HEATING AND DESTABILIZATION (MLCAPE OF 1500-2400 J/KG)... AND WITH DEEP LAYER SHEAR INCHING UP A BIT TO 20-25 KTS. PW VALUES WILL STAY QUITE HIGH... CLOSE TO 2.0 INCHES... SO IT SHOULD NOT TAKE MUCH TO INDUCE CONVECTION. HAVE BUMPED UP POPS TO A 40-50 PERCENT CHANCE... MAINLY AFTERNOON THROUGH EVENING. HIGHS 85-89 WITH GENERALLY MOSTLY CLOUDY SKIES. LOWS 68-72 WITH LOWER RAIN CHANCES OVERNIGHT. -GIH && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 115 PM THURSDAY... FOR MONDAY/MONDAY NIGHT: MODELS AGREE ON ISAAC`S CORRESPONDING MID LEVEL SHORTWAVE TROUGH SLOWLY PASSING OVER KY/TN AS IT APPROACHES NC FROM THE WEST... ALTHOUGH MODEL SOLUTIONS VARY WITH RESPECT TO ITS SPEED AND AMPLITUDE. WITH A STRONG MID LEVEL RIDGE COVERING THE DESERT SOUTHWEST AND A FAST FLOW OVER THE NORTHERN PORTION OF THE CONUS... THIS WAVE SHOULD SLOWLY DEAMPLIFY AS POLAR SHORTWAVE ENERGY DROPS ESE THROUGH ONTARIO... BUT IT SHOULD REMAIN A DISTINCT AND TRACKABLE WAVE AS IT MOVES INTO THE SRN APPALACHIANS. THE GFS/ECMWF BOTH DEPICT WEAK NW-SE WARM FRONTOGENESIS OVER THE CAROLINAS AS THE WAVE APPROACHES... AND BOTH ALSO DEVELOP WIDESPREAD CONVECTION MONDAY AFTERNOON ACCOMPANYING THE MID LEVEL HEIGHT FALLS WITH CONFLUENT GULF- AND ATLANTIC-SOURCE SOUTHEAST AND SOUTHERLY LOW LEVEL FLOW. GIVEN THE IMPROVING DYNAMICS AND INSTABILITY... WILL HAVE GOOD CHANCES OF SHOWERS AND A FEW STORMS MONDAY AFTERNOON AND EVENING... DECREASING WITH LOSS OF HEATING OVERNIGHT. THICKNESSES POINT TO HIGHS IN THE MID 80S. IT`S WORTH NOTING THAT IF THE LOW LEVEL WARM FRONT SETS UP TO OUR SOUTH WITH NUMEROUS SHOWERS OVER CENTRAL NC WITHIN THE BIT MORE STABLE AIR... WE COULD SEE COOLER TEMPS THAN ARE CURRENTLY ANTICIPATED. FOR TUESDAY THROUGH THURSDAY: A MARKED DIVERGENCE IN MODEL SOLUTIONS BECOMES PROBLEMATIC FOR OUR DAY-TO-DAY FORECAST STARTING TUESDAY. ACCORDING TO THE 00Z/06Z GFS... THE WEAKENING MID LEVEL TROUGH IS EXPECTED TO HAVE SHIFTED SE OF THE CWA BY WEDNESDAY MORNING AS THE MEAN LONGWAVE TROUGH DIGS FROM JAMES BAY THROUGH THE ERN GREAT LAKES TO THE MIDATLANTIC COAST... AND AS A SURFACE COLD FRONT PUSHES SE THROUGH CENTRAL NC. BUT THERE ARE INDICATIONS THAT THE 00Z/06Z GFS MAY BE TOO AGGRESSIVE WITH ITS NORTHEAST-NOAM HEIGHT FALLS... AS THE 00Z ECMWF FAVORS DIGGING A TROUGH MUCH MORE WESTWARD INTO MT/ID BY LATE TUESDAY NIGHT. THE ECMWF (WHICH IS THE STRONGEST WITH ISAAC`S REMNANT MID LEVEL SHORTWAVE TROUGH) ALSO DEVELOPS A CLOSED LOW WELL OFF THE BAHAMAS ON SUNDAY AND THEN BRINGS THIS LOW WESTWARD AND NORTHWESTWARD TOWARD THE SOUTHEAST COAST BY LATE TUESDAY. IN TERMS OF SENSIBLE WEATHER... THIS RESULTS IN STORMY-EARLY-BUT-CLEARING WEATHER DURING THIS PERIOD ON THE GFS... AND MILD AND QUITE WET/STORMY (ALMOST TROPICAL-LIKE) ON THE ECMWF. THE ECMWF ENSEMBLE MEAN PROVIDES A MIDDLE-OF-THE-ROAD SOLUTION... GRADUALLY DEEPENING THE LONGWAVE TROUGH OVER THE UPPER MIDWEST AND WRN GREAT LAKES... A LITTLE WEST OF THE 00Z/06Z GFS BUT CLOSER IN LINE WITH THE NEW 12Z GFS. FAVORING THIS... EXPECT A GOOD CHANCE OF SHOWERS/STORMS THROUGH TUESDAY... DECREASING WEST BUT REMAINING FAIRLY HIGH IN THE EASTERN FORECAST AREA ON WEDNESDAY... AND A LOWER CHANCE ON THURSDAY AS THE SURFACE FRONT SHOULD BE EAST OF THE AREA WITH DRIER AIR FILTERING IN FROM THE NW. BUT CONFIDENCE IN THE DETAILS HERE IS RATHER LOW... AND THIS SCENARIO COULD CHANGE IN THE COMING DAYS AS THE FORECAST IS REFINED. LOW LEVEL THICKNESSES ARE UNLIKELY TO REACH HIGHLY ANOMALOUS VALUES... AS THEY SHOULD HOLD WITHIN 5-15 METERS ABOVE NORMAL. EXPECT HIGHS MOSTLY IN THE MID 80S WITH LOWS IN THE MID 60S TO NEAR 70. -GIH && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... AS OF 900 PM THURSDAY... 24-HR TAF PERIOD: VFR CONDITIONS THIS EVENING ARE EXPECTED TO DETERIORATE OVERNIGHT IN ASSOCIATION WITH WIDESPREAD FOG GIVEN CLEAR SKIES...CALM OR LIGHT WINDS...AND A MOIST BOUNDARY LAYER. THE PRESSURE GRADIENT IS EXPECTED TO TIGHTEN BETWEEN 06-12Z IN ASSOC/W A DEVELOPING LEE TROUGH...AND THIS MAY HELP TO MITIGATE THE POTENTIAL FOR DENSE FOG AT THE NORTHERN (INT/GSO/RDU) TAF SITES...THOUGH UNCERTAINTY PERSISTS...AND IT IS POSSIBLE THAT IFR/LIFR STRATUS MAY DEVELOP AT THE INT/GSO TERMINALS WHERE DEEPER MOISTURE IS PRESENT. FURTHER SOUTH...THE FAY/RWI TAF SITES ARE MOST LIKELY TO SEE DENSE FOG AND LIFR CONDITIONS...SIMILAR TO THIS MORNING...BETWEEN 07-12Z. FOG WILL LIFT/SCATTER OUT TO VFR BETWEEN 12-14Z GIVEN SUNNY SKIES AND STRONG INSOLATION AS AN UPPER LEVEL RIDGE STRENGTHENS OVER THE REGION. DRY/VFR CONDITIONS WILL RULE THE REMAINDER OF THE TAF PERIOD. LOOKING AHEAD: VFR CONDITIONS ARE EXPECTED TO RULE THROUGH SAT NIGHT IN ASSOCIATION WITH THE AFOREMENTIONED UPPER LEVEL RIDGE...THOUGH A SMALL CHANCE FOR SHOWERS/STORMS CANNOT BE RULED OUT SAT EVENING. THE NEXT CHANCE FOR ADVERSE AVIATION CONDITIONS WILL BE LATE SUNDAY INTO MON/TUE AS THE REMNANTS OF TROPICAL CYCLONE ISAAC PROGRESS EAST TOWARD THE REGION. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...JB NEAR TERM...KC/MWS/SEC SHORT TERM...HARTFIELD LONG TERM...HARTFIELD AVIATION...VINCENT
AREA FORECAST DISCUSSION
NWS NEWPORT/MOREHEAD CITY NC
929 AM EDT THU AUG 30 2012 .SYNOPSIS... HIGH PRESSURE WILL BUILD IN FROM THE NORTH TODAY AND EXTEND OVER THE AREA THROUGH SATURDAY. A COLD FRONT WILL APPROACH FROM THE NORTH SATURDAY NIGHT AND STALL OVER NORTHERN SECTIONS SUNDAY AND MONDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... AS OF 930 AM THURSDAY...MUCH DIFFERENT AIRMASS THIS MORNING AS OPPOSED TO RECENT DAYS AS PRECIPITABLE WATER HAS DROPPED FROM 2.4 INCHES YESTERDAY TO 1.4 INCHES TODAY. LATEST RAP MODEL KEEPS PRECIPITATION TO THE SOUTH OF OUR CWA WHICH IS IN AGREEMENT WITH CURRENT FORECAST AND NO CHANGES MADE TO POPS. NAM DOES INDICATE SOME WEAK 500 MB VORTICITY SWINGING ACROSS THE REGION AND CANNOT RULE OUT AN ISOLATED SHOWER OR TWO...BUT COVERAGE WILL BE LIMITED AND POPS CAN BE LEFT OUT OF THE FORECAST. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... AS OF 330 AM THURSDAY...RIDGING SFC AND ALOFT WILL PRODUCE FAIR CONDITIONS TONIGHT. MIN TEMPS RANGING FROM MID-UPR 60S INLAND TO LOW-MID 70S COAST. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... AS OF 250 AM THU...WILL CONTINUE DRY WEATHER FORECAST FRIDAY AND SATURDAY AS STRONG RIDGE BRIEFLY BUILDS OVER THE EASTERN US. SOME OF THE MODELS CONTINUE TO INDICATE ISOLATED CONVECTION SATURDAY BUT WITH LACK OF UPPER SUPPORT WILL MAINTAIN DRY FORECAST. A WEAK COLD FRONT WILL ATTEMPT TO DRIFT SOUTH INTO NORTHERN CWA LATE SATURDAY AND SATURDAY NIGHT THEN SHOULD DRIFT BACK NORTH INTO VA SUNDAY. SUNDAY INTO MONDAY THE REMNANTS OF ISSAC ALOFT WILL MOVE INTO THE LOWER LAKES AND BECOME ABSORBED INTO A UPPER TROUGH MOVING ACROSS SOUTHERN CANADA. RESULTING NW FLOW ALOFT OVER THE EASTERN US WILL ALLOW ANOTHER COLD FRONT TO SLOWLY SLIDE SOUTHEAST ACROSS THE REGION. THE MODELS DIFFER ON TIMING OF THIS FEATURE BUT THEY ALL TEND TO AGREE THAT MOISTURE AND LIFT WILL BE INCREASING ACROSS EASTERN NC SO WILL CONTINUE CHANCE POPS MONDAY THROUGH WEDNESDAY. EXPECT TEMPS NEAR OR SLIGHTLY ABOVE CLIMO THROUGH THE PERIOD...WITH HIGHS 85-90 DEG AND LOWS IN THE 70S. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... SHORT TERM /THROUGH 12Z FRIDAY/... AS OF 700 AM THURSDAY...CURRENT VSBYS AROUND 2SM AT KPGV..KOAJ AND KISO WILL IMPROVE TO FR BY 13Z. VFR PREVAILING ALL SITES REST OF DAY INTO EVENING WITH NO CONVECTIVE ACTIVITY EXPECTED. MOS GDNC INDICATING PERIOD OF IFR VSBYS AGAIN 09Z-12Z LATE TONIGHT...AND CONDITIONS MAY BE MORE CONDUCIVE WITH MOSTLY CLEAR SKIES. HOWEVER...GDNC HAS BEEN OVERDONE WITH DURATION OF IFR VSBYS PAST FEW DAYS AND WILL GO WITH PREVAILING MVFR 3SM FOR NOW. LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 250 AM THU...PREDOMINATE VFR CONDITIONS EXPECTED THROUGH THE WEEKEND...OUTSIDE OF ANY BRIEF MORNING FOG. MOISTURE WILL BEGIN TO INCREASE ACROSS THE AREA SUNDAY INTO MONDAY WITH PRECIP CHANCES INCREASING. SUB-VFR CONDITIONS WILL BE POSSIBLE SUN INTO MON AHEAD OF A SLOW MOVING COLD FRONT. && .MARINE... SHORT TERM /THROUGH TONIGHT/... AS OF 700 AM THURSDAY...GENERALLY E/SE WINDS AT 10 KNOTS OR LESS ACROSS THE COASTAL WATERS EXCEPT WINDS GUSTING CLOSE TO 15 KNOTS FROM CAPE LOOKOUT SOUTHWARD. SEAS ARE 2 TO 4 FEET WITH A 9 TO 11 SECOND SWELL COMPONENT. WINDS SHOULD BECOME MORE SOUTHERLY TODAY AND THEN BECOME S-SW OVERNIGHT WITH SPEEDS INCREASING TO 10-15 KT NORTHERN WATERS WITH TIGHTENING PRES GRAD. WW3 AND SWAN IN AGREEMENT ON SEAS REMAINING 2-3 FT DURING PERIOD. LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 250 AM THU...TYPICAL SUMMERTIME PATTERN RETURNS FRI WITH HIGH PRESSURE OVER THE AREA RESULTING IN SW WINDS AOB 15KT AND SEAS 2-3FT. MODELS IN GOOD AGREEMENT SHOWING SW SURGE FRIDAY EVENING...GENERALLY 10-20KT...AS PGRADIENT TIGHTENS BTWN HIGH PRESSURE OVER THE AREA AND LOW PRESSURE NEAR CANADA/NEWFOUNDLAND. A WEAK FRONTAL BOUNDARY WILL APPROACH THE NORTHERN WATERS AND ALBEMARLE SOUND LATE SATURDAY INTO SUNDAY...WITH FLOW LIKELY BECOMING MORE ELY SUN NORTH OF HATTERAS...STILL EXPECT SPEEDS BELOW 15KT. SUN INTO MON EXPECT S/SE FLOW. OVERALL SEAS WILL REMAIN 2-4FT THROUGH THE PERIOD. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...NONE. MARINE...NONE. && $$ SYNOPSIS...CTC NEAR TERM...JBM/CTC SHORT TERM...CTC LONG TERM...JME/CQD AVIATION...JBM/CQD MARINE...JBM/CTC/CQD/LEP
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
1037 PM EDT WED AUG 29 2012 .SYNOPSIS... A COLD FRONT WILL DROP INTO THE AREA TONIGHT. A GRADUAL DRYING AND WARMING TREND WILL BEGIN THURSDAY AND CONTINUE INTO THE WEEKEND AS HIGH PRESSURE BUILDS INTO THE AREA. A COLD FRONT WILL APPROACH FROM THE NORTH AND WEST EARLY NEXT WEEK BUT WILL REMAIN NORTH OF THE AREA THROUGH MID WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1030 PM WEDNESDAY...NO SIGNIFICANT CHANGES HAVE BEEN MADE TO ANY OF MY EARLIER THINKING. THE LATEST SEVERAL HRRR MODEL RUNS REMAIN INSISTENT THE CONVECTION ACROSS SOUTHEASTERN SOUTH CAROLINA WILL SPREAD INTO MUCH OF OUR EASTERN SOUTH CAROLINA COUNTIES AFTER MIDNIGHT...ALBEIT IN A WEAKENED STATE. THE 12Z MHX SOUNDING SHOWS 300 MB WIND SPEEDS HAVE INCREASED TO 55 KNOTS WHICH IS IN GOOD AGREEMENT WITH 18Z MODEL PROGS...AND CONFIRMS THE IDEA THAT UPPER LEVEL DYNAMICS WILL HELP SUSTAIN LATE NIGHT SHOWERS. PREVIOUS DISCUSSION FROM 730 PM FOLLOWS... A SURFACE COLD FRONT EXTENDS EAST TO WEST ACROSS SOUTH-CENTRAL NORTH CAROLINA APPROXIMATELY FROM NEW BERN THROUGH FAYETTEVILLE TO JUST NORTH OF CHARLOTTE. THIS BOUNDARY SEPARATES TROPICAL AIR TO THE SOUTH (MID 70S DEWPOINTS) FROM SOMEWHAT DRIER CONTINENTAL AIR (60S DEWPOINTS) TO THE NORTH. SURFACE TO 850 MB WINDS ARE VERY WEAK ON EITHER SIDE OF THE FRONT SO THERE IS NO LOW-LEVEL CONVERGENCE TO SPEAK OF. THE FRONT SHOULD DROP SOUTH OVERNIGHT AND WILL END UP IN THE MYRTLE BEACH/GEORGETOWN AREA LATE. THERE IS LITTLE PUSH OF WIND ON EITHER SIDE OF THE FRONT AND WE ARE ACTUALLY ANTICIPATING NEARLY CALM CONDITIONS OVERNIGHT. SEVERAL CLUSTERS OF SHOWERS AND THUNDERSTORMS HAVE PRODUCED HEAVY RAIN AND FLOODING LATE THIS AFTERNOON MAINLY ACROSS EASTERN SOUTH CAROLINA. THESE STORMS WERE DRIVEN BY PURE INSTABILITY WITH CAPE VALUES EARLIER NEAR 2000 J/KG BUT WITH NO MENTIONABLE SHEAR OR UPPER DISTURBANCES. MUCH OF THE EARLIER INSTABILITY HAS ALREADY BEEN DISSIPATED BY THE STORMS AND THE BOUNDARY LAYER IS BECOMING CAPPED TO SURFACE-BASED CONVECTION. ONCE THE CURRENT CONVECTIVE ACTIVITY MOVES OFF THE SOUTH CAROLINA COAST WE SHOULD HAVE A FEW HOURS OF GENERALLY DRY CONDITIONS LATE THIS EVENING. MODELS SHOW A RESURGENCE OF SHOWER ACTIVITY ACROSS EASTERN SOUTH CAROLINA AFTER MIDNIGHT AS SYNOPTIC LIFT INCREASES WITH A 300 MB JET STREAK DEVELOPING ACROSS EASTERN NORTH CAROLINA. THE RIGHT-ENTRANCE REGION OF THIS JET SHOULD PRODUCE ENOUGH LIFT FOR ELEVATED CONVECTION...MAINLY FROM MIDNIGHT THROUGH ABOUT 5-6 AM THURSDAY. SHOWER CHANCES ARE LESS ACROSS SOUTHEASTERN NORTH CAROLINA WITH A LESS FAVORABLE POSITIONING OF THE JET...BUT WE`RE STILL PAINTING 20-40 PERCENT CHANCES OF SHOWERS AFTER MIDNIGHT HERE. LOWS SHOULD FALL INTO THE LOWER 70S INLAND WITH MID 70S AT THE COAST...VERY SIMILAR TO LAST NIGHT. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 PM WEDNESDAY...THURSDAY WILL BE A DAY OF TRANSITION AS A SLOWLY MOVING COLD FRONT CONTINUES TO DRIFT SOUTH ACROSS THE CWA. ALTHOUGH TEMPS WILL NOT CHANGE MUCH WITH THIS BOUNDARY...DRIER AIR BUILDS IN BEHIND IT AND PRECIP CHANCES WILL FALL SLOWLY THROUGH THE DAY. BY THE END OF THE DAY...CONVECTIVE CHANCES SHOULD DECREASE SIGNIFICANTLY. FOR THE REMAINDER OF THE PERIOD...DRY WEATHER IS EXPECTED UNDER CLEAR TO PARTLY CLOUDY SKIES. DAYTIME HIGHS WILL GENERALLY REACH THE MIDDLE 80S THURSDAY AND MID 80S TO AROUND 90 FRIDAY. LOWS EACH NIGHT SHOULD FALL TO THE UPPER 60S TO LOWER 70S. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 3 PM WEDNESDAY...RIDGE SFC-ALOFT OVERHEAD ON SATURDAY WILL BE SHUNTED SOUTH AS THE REMNANTS OF ISAAC MAKE THEIR WAY FROM THE MID MISSISSIPPI RIVER VALLEY INTO THE MID-ATLANTIC REGION. SOUTHERLY LOW-LEVEL FLOW WILL DEVELOP BY LATE SATURDAY AND PERSIST THROUGH THE PERIOD. THIS WILL RESULT IN A WARM...MOIST AND UNSTABLE AIRMASS ACROSS THE AREA...FAVORABLE FOR SCATTERED CONVECTION. PRECIPITABLE WATERS WILL SURGE TO 2.25 INCHES BY SUNDAY AND REMAIN IN EXCESS OF TWO INCHES THROUGH TUESDAY. THEREFORE LOCALLY HEAVY DOWNPOURS WOULD BE EXPECTED IN ASSOCIATION WITH THE SHOWERS/TSTMS. MID-LEVEL TROUGH AXIS WILL MOVE OFFSHORE WEDNESDAY AND DRYING IN THE H7-H3 LAYER SHOULD RESULT IN LESSER COVERAGE OF CONVECTION. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... AS OF 00Z...VFR THROUGH THE VALID PERIOD...WITH EXCEPTION OF MVFR/IFR OVERNIGHT INTO THE MORNING HOURS. CURRENT RADAR DEPICTS SCATTERED HEAVY SHOWERS ALONG THE COAST...CREATING BRIEF MVFR TO KCRE/KMYR. AFTER THIS ACTIVITY MOVES OFFSHORE...THINGS WILL BE QUIET FOR A FEW HOURS BEFORE ANOTHER ROUND OF ISOLATED/SCATTERED SHRA IS POSSIBLE OVERNIGHT. WITH NEARLY CALM WINDS AND ABUNDANT MOISTURE ACROSS THE AREA...ANTICIPATE FOG DEVELOPMENT LATE OVERNIGHT INTO THE EARLY MORNING HOURS TO CREATE MVFR/IFR RESTRICTIONS DUE TO VISIBILITIES...AND POSSIBLY CIGS...ESPECIALLY INLAND. HOWEVER...OVERALL AFFECT OF FOG DEVELOPMENT WILL DEPEND ON OPACITY OF LINGERING CLOUD DEBRIS. AFTER DAYBREAK...FOG WILL DISSIPATE GIVING WAY TO VFR CONDITIONS ACROSS THE AREA. EAST WINDS WILL PREVAIL...SUSTAINED AOB 10 KTS...GRADUALLY SHIFTING TO THE SE AT THE COAST. EXTENDED OUTLOOK...VFR THROUGH SATURDAY. A CHANCE FOR SCATTERED CONVECTION SUNDAY AFTERNOON THROUGH MONDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1030 PM WEDNESDAY...LIGHT WINDS AND 2-3 FT SEAS SHOULD CONTINUE OVERNIGHT. SHOWERS SHOULD INCREASE IN COVERAGE ACROSS THE WATERS MAINLY SOUTH OF CAPE FEAR AFTER MIDNIGHT. PREVIOUS DISCUSSION FROM 730 PM FOLLOWS... A SLOW-MOVING COLD FRONT NEAR CAPE LOOKOUT AND SHOULD DROP SOUTH INTO THE CAPE FEAR/MYRTLE BEACH AREA OVERNIGHT...BUT WITH VERY LITTLE FANFARE. LIGHT GENERALLY SOUTH TO SOUTHWEST WINDS NOW WILL VEER TO THE WEST...THEN TO THE NORTH TO NORTHEAST LATE. WIND SPEEDS SHOULD REMAIN BELOW 10 KNOTS REGARDLESS. ONE WAVE OF SHOWERS AND EMBEDDED THUNDERSTORMS IS WORKING ITS WAY OFFSHORE CURRENTLY. THERE SHOULD BE A 3-4 HOUR LULL BEHIND THESE SHOWERS BEFORE A SECOND WAVE OF SHOWERS DEVELOPS ACROSS EASTERN SOUTH CAROLINA AND MOVES OFFSHORE AFTER MIDNIGHT. SEAS RANGE FROM 2-3 FT...AND THE BIGGEST CHANGE IN OUR FORECAST WAS TO REMOVE ANY 1-FOOT SEAS FROM THE NEARSHORE WATERS BASED ON OBSERVATIONS FROM THE OCEAN CREST PIER WAVE GAUGE AND AREA SURFCAMS. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 PM WEDNESDAY...EXPECT TO SEE E TO NE WINDS AROUND 10 KT THURSDAY MORNING GRADUALLY VEER TO THE SOUTH BY FRIDAY EVENING AND REMAIN AROUND 10 KT OR LESS WITH A WEAK GRADIENT IN PLACE. SEAS SHOULD REMAIN 3 FT OR LESS THROUGH THE PERIOD. LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 300 PM WEDNESDAY...A SURFACE RIDGE CENTERED SOUTHEAST OF CAPE FEAR SATURDAY WILL COMBINE WITH A TROUGH ACROSS THE SANDHILLS AND PEE DEE REGION TO PRODUCE SOUTHWESTERLY FLOW OVER THE WATERS. THE INLAND TROUGH WILL WEAKEN ON SUNDAY...AND AS A RESULT...FLOW WILL BACK MORE TOWARDS THE SOUTH. THE GRADIENT MAY TIGHTEN SLIGHTLY MONDAY AS THE FRONT GETS CLOSERS TO THE AREA. SPEEDS ARE EXPECTED TO REMAIN 15 KT OR LESS THROUGH THE PERIOD AS A RESULT OF A RELATIVELY BENIGN PRESSURE GRADIENT. && .TIDES/COASTAL FLOODING... INCREASING ASTRONOMICAL TIDES WILL BRING STANDING WATER TO PORTIONS OF DOWNTOWN WILMINGTON ALONG THE CAPE FEAR RIVER AT HIGH TIDE THIS EVENING...MAINLY BETWEEN 600 PM AND 900 PM. AS A RESULT A COASTAL FLOOD ADVISORY HAS BEEN ISSUED FOR INLAND NEW HANOVER COUNTY. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...COASTAL FLOOD ADVISORY FROM 6 PM TO 11 PM EDT THIS EVENING FOR NCZ107. MARINE...NONE. && $$ NEAR TERM...TRA SHORT TERM...31 LONG TERM...CRM AVIATION...MRR TIDES/COASTAL FLOODING...HAWKINS
AREA FORECAST DISCUSSION
NWS TULSA OK
621 AM CDT FRI AUG 31 2012 .AVIATION... CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM. FOR THE 12Z TAFS... REMNANTS OF TROPICAL SYSTEM ISAAC WILL CONTINUE MOVING NORTHWARD THROUGH WESTERN ARKANSAS TODAY. OUR ARKANSAS TAF SITES WILL LIKELY EXPERIENCE IFR CEILINGS WITH RAINFALL AND WINDS INTERMITTENTLY THROUGHOUT MUCH OF THE DAY. IT IS UNCERTAIN HOW FAR WEST THE EFFECTS OD ISAAC WILL BE FELT. OKLAHOMA TAF SITES MAY EXPERIENCE MVFR CEILINGS ALONG WITH RAIN AND SOME WINDS. && .PREV DISCUSSION... /ISSUED 348 AM CDT FRI AUG 31 2012/ DISCUSSION... REMAINS OF ISAAC ARE CURRENTLY ALONG THE MONTGOMERY/SCOTT COUNTY LINE IN SWRN AR...AND HAS SHOWN A NNW MOVEMENT OVER THE PAST SEVERAL HOURS. THE BULK OF THE RAINFALL HAS REMAINED E AND N OF THE CIRCULATION CENTER...ALTHOUGH HAVE RECENTLY SEEN A NARROW BAND FAR NERN OK. 06Z NAM SEEMS TO HAVE A REASONABLE HANDLE ON THE TRACK OF ISAAC...TAKING IT TO JUST E OF FORT SMITH EARLY THIS MORNING...THEN EVENTUALLY INTO SWRN MO EARLY THIS AFTERNOON. PERIODS OF SHOWERS AND ISOLATED THUNDERSTORMS ARE A GIVEN ACROSS NWRN AR...ALTHOUGH POP FORECAST IS QUITE A BIT TRICKIER FARTHER W INTO ERN OK. NAM AND HRRR BOTH SUGGEST THAT A FEW BANDS OF HEAVIER SHOWERS COULD EVENTUALLY WRAP BACK DEEPER INTO NERN OK...AND GIVEN THE RECENT TRENDS...HAVE OPTED TO MAINTAIN THE HIGH POPS FROM THE PREVIOUS FORECAST. ADDITIONAL RAINFALL AMOUNTS OF 1 TO 2 INCHES ARE POSSIBLE ACROSS NWRN AR...ALTHOUGH RECENT DROUGHT CONDITIONS SHOULD KEEP THE FLOODING POTENTIAL ON THE LOW END. SEVERE WEATHER THREAT APPEARS MINIMAL AS WELL...WITH THE BEST CHANCES TODAY JUST E OF OUR FORECAST AREA. WIND GUSTS HAVE GENERALLY REMAINED BELOW 30-35 MPH OVERNIGHT. WHILE AN ISOLATED 40 MPH GUST ISNT OUT OF THE QUESTION THIS MORNING...PLAN ON DROPPING THE WIND ADVISORY WITH THE 4 AM FORECAST PACKAGE. CIRCULATION CENTER WILL EVENTUALLY PULL NE OF THE REGION TONIGHT INTO SATURDAY...WITH POPS GENERALLY TAPERING OFF BY LATE IN THE DAY. MID-LEVEL RIDGING WILL BUILD BACK ACROSS THE SRN PLAINS THIS WEEKEND AND INTO EARLY NEXT WEEK. EXPECT AFTERNOON TEMPS TO WARM BACK ABOVE NORMALS...WITH READINGS PUSHING 100F IN SEVERAL SPOTS SUNDAY AND MONDAY. THE UPPER RIDGE FLATTENS A BIT BY MID-TO-LATE WEEK...PUTTING OUR AREA ALONG THE SRN EDGE OF THE WESTERLIES. WILL KEEP SHOWER/THUNDERSTORM CHANCES AROUND 20/30 PERCENT FOR NOW...ALTHOUGH THESE NUMBERS MAY GO UP IF GFS REMAINS CONSISTENT WITH POTENTIAL MCS SETUP WEDNESDAY NIGHT INTO THURSDAY. && .TSA WATCHES/WARNINGS/ADVISORIES... OK...NONE. AR...NONE. && $$ AVIATION...06
AREA FORECAST DISCUSSION
NWS TULSA OK
348 AM CDT FRI AUG 31 2012 .DISCUSSION... REMAINS OF ISAAC ARE CURRENTLY ALONG THE MONTGOMERY/SCOTT COUNTY LINE IN SWRN AR...AND HAS SHOWN A NNW MOVEMENT OVER THE PAST SEVERAL HOURS. THE BULK OF THE RAINFALL HAS REMAINED E AND N OF THE CIRCULATION CENTER...ALTHOUGH HAVE RECENTLY SEEN A NARROW BAND FAR NERN OK. 06Z NAM SEEMS TO HAVE A REASONABLE HANDLE ON THE TRACK OF ISAAC...TAKING IT TO JUST E OF FORT SMITH EARLY THIS MORNING...THEN EVENTUALLY INTO SWRN MO EARLY THIS AFTERNOON. PERIODS OF SHOWERS AND ISOLATED THUNDERSTORMS ARE A GIVEN ACROSS NWRN AR...ALTHOUGH POP FORECAST IS QUITE A BIT TRICKIER FARTHER W INTO ERN OK. NAM AND HRRR BOTH SUGGEST THAT A FEW BANDS OF HEAVIER SHOWERS COULD EVENTUALLY WRAP BACK DEEPER INTO NERN OK...AND GIVEN THE RECENT TRENDS...HAVE OPTED TO MAINTAIN THE HIGH POPS FROM THE PREVIOUS FORECAST. ADDITIONAL RAINFALL AMOUNTS OF 1 TO 2 INCHES ARE POSSIBLE ACROSS NWRN AR...ALTHOUGH RECENT DROUGHT CONDITIONS SHOULD KEEP THE FLOODING POTENTIAL ON THE LOW END. SEVERE WEATHER THREAT APPEARS MINIMAL AS WELL...WITH THE BEST CHANCES TODAY JUST E OF OUR FORECAST AREA. WIND GUSTS HAVE GENERALLY REMAINED BELOW 30-35 MPH OVERNIGHT. WHILE AN ISOLATED 40 MPH GUST ISNT OUT OF THE QUESTION THIS MORNING...PLAN ON DROPPING THE WIND ADVISORY WITH THE 4 AM FORECAST PACKAGE. CIRCULATION CENTER WILL EVENTUALLY PULL NE OF THE REGION TONIGHT INTO SATURDAY...WITH POPS GENERALLY TAPERING OFF BY LATE IN THE DAY. MID-LEVEL RIDGING WILL BUILD BACK ACROSS THE SRN PLAINS THIS WEEKEND AND INTO EARLY NEXT WEEK. EXPECT AFTERNOON TEMPS TO WARM BACK ABOVE NORMALS...WITH READINGS PUSHING 100F IN SEVERAL SPOTS SUNDAY AND MONDAY. THE UPPER RIDGE FLATTENS A BIT BY MID-TO-LATE WEEK...PUTTING OUR AREA ALONG THE SRN EDGE OF THE WESTERLIES. WILL KEEP SHOWER/THUNDERSTORM CHANCES AROUND 20/30 PERCENT FOR NOW...ALTHOUGH THESE NUMBERS MAY GO UP IF GFS REMAINS CONSISTENT WITH POTENTIAL MCS SETUP WEDNESDAY NIGHT INTO THURSDAY. && .PRELIMINARY POINT TEMPS/POPS... TUL 84 73 93 72 / 80 30 20 10 FSM 85 73 94 73 / 90 50 30 10 MLC 90 74 97 73 / 40 20 10 10 BVO 85 70 92 68 / 80 30 20 10 FYV 81 73 90 68 / 100 70 40 20 BYV 80 71 88 69 / 100 70 50 20 MKO 85 71 94 71 / 80 40 20 10 MIO 81 73 89 71 / 90 60 40 20 F10 88 73 95 74 / 40 20 10 10 HHW 93 74 95 74 / 20 20 10 10 && .TSA WATCHES/WARNINGS/ADVISORIES... OK...NONE. AR...NONE. && $$ SHORT TERM...06 LONG TERM....18
AREA FORECAST DISCUSSION...UPDATED
NWS ABERDEEN SD
1223 AM CDT FRI AUG 31 2012 .UPDATE... THE AVIATION DISCUSSION HAS BEEN UPDATED FOR THE 06Z TAF ISSUANCE. 00Z 300/500MB ANALYSIS INDICATED A LARGE UPPER RIDGE OVER THE CENTRAL CONUS WITH A TROUGH OF LOW PRESSURE OVER THE PAC NW. THE REMNANTS OF ISAAC WERE LIFTING NEWD THRU THE LOWER/MID MISSISSIPPI VALLEY. AT THE SFC...HIGH PRESSURE CENTERED OVER ND IS EXPECTED TO BUILD S/SEWD OVERNIGHT. SFC DEWPOINTS THIS EVENING ARE RANGING FROM THE LOWER 50S OVER NERN SD...DOWN TO THE MIDDLE 30S OVER CENTRAL AND WRN SD. TEMPERATURES EARLY THIS EVENING ARE DROPPING OFF PRETTY QUICKLY DUE TO THE DRY AIRMASS...AND MOSTLY CLEAR SKIES. HOWEVER...LATEST IR SATELLITE IMAGERY INDICATES A FAIRLY WIDESPREAD AREA OF MID LEVEL CLOUDINESS ADVECTING INTO THE AREA FROM THE SW IN THE RIGHT ENTRANCE REGION OF THE UPPER JET. IN FACT KVTN ACTUALLY REPORTED LIGHT RAIN/SPRINKLES...WHICH IS PRETTY AMAZING CONSIDERING THE VERY DRY AMS EVIDENT IN THE KLBF 00Z RAOB. ALSO INTERESTING TO NOTE THAT THE 22Z HRRR INDICATES A FEW SPRINKLES MOVING INTO THE FAR SW LATER TONIGHT. WILL LEAVE FORECAST DRY FOR NOW DUE TO VERY DRY AIR AT LOW LEVELS...BUT A FEW SPRINKLES/LIGHT SHOWERS ARE POSSIBLE. TOUGH CALL ON HOW LOW TO GO WITH LOW TEMPERATURES AS WELL. DECIDED TO DROP LOW TEMPERATURES A FEW DEGREES IN THE EAST...BEFORE THICKER CLOUD COVER MOVES IN AFTER 06Z. UPDATES OUT... && .PREVIOUS DISCUSSION... .SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT SPRINKLES AND DRY LIGHTNING CONTINUE FROM WEST CENTRAL MN SOUTHWEST INTO SOUTH CENTRAL SD THIS AFTERNOON BEHIND A TRAILING COLD FRONT. THIS ACTIVITY IS EXPECTED TO EXIT THE REGION OVER THE NEXT 2 TO 3 HRS. HIGH PRESSURE WILL BUILD IN OVERNIGHT BRINGING DRY CONDITIONS AND ABOVE AVERAGE TEMPERATURES THROUGH SATURDAY. A LLJ WILL DEVELOP OVER THE WESTERN CWA EARLY ON SATURDAY MORNING. DECIDED NOT TO MENTION POSSIBILITY OF PRECIP AT THIS POINT BECAUSE LOWER LEVELS WILL BE VERY DRY...AND BEST FORCING WILL BE IN ND. WINDS WILL INCREASE AHEAD OF THE LEE SIDE TROF FRIDAY AND SATURDAY. MAY NEED TO ISSUE FIRE WEATHER HEADLINES...ESPECIALLY ON SATURDAY. AS THE COLD FRONT MOVES OFF THE ROCKIES SAT EVENING...MODELS ARE BEGINNING TO DIVERGE FROM PREVIOUS SOLUTIONS. CURRENT RUNS TRACK THE BULK OF PRECIP OVER ND NOW ON SAT NIGHT. LEFT SOME ISOLATED POPS ACROSS WESTERN CORSON COUNTY SAT NIGHT BUT MAY NEED TO REMOVE THESE AS WELL IF MODELS CONTINUE THIS TREND. HIGHS WILL CLIMB BACK INTO THE 90S OVER THE WEEKEND...ABOUT 10 DEGREES ABOVE AVERAGE IN MOST LOCATIONS. .LONG TERM...SUNDAY THROUGH THURSDAY SUNDAY INTO SUNDAY EVENING MODELS ARE CONSISTENT IN SHOWING A WEAK SFC TROUGH PASSING THROUGH THE AREA...ALTHOUGH MOISTURE AVAILABLE FOR THIS FEATURE IS RATHER LIMITED. WILL CONTINUE WITH LOW POPS FOR THE EASTERN CWA SUNDAY INTO SUNDAY NIGHT. BY THE MIDDLE OF THE WEEK A MORE SIGNIFICANT SHORTWAVE MOVES ACROSS THE AREA AND THE INHERITED GUIDANCE POPS LOOKED OK FOR THIS POTENTIAL EVENT FOR THE TIME BEING. THERE ARE STILL TIMING AND PLACEMENT ISSUES WITH THE MIDDLE OF THE WEEK SYSTEM SO DID NOT STRAY TOO FAR FROM GUIDANCE AT THIS POINT. TEMPS LOOK TO STAY RATHER WARM THROUGH THE PERIOD WITH A SLIGHT COOL DOWN TOWARDS THE END OF NEXT WEEK PERHAPS. && .AVIATION... 06Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS VFR CONDITIONS WILL PREVAIL THE NEXT 24 HOURS. SATELLITE IMAGERY INDICATING INCREASING MID-LEVEL CLOUDS FROM THE SOUTHWEST...AND THIS BROKEN DECK OF CLOUDINESS IS EXPECTED TO PERSIST THROUGH MUCH OF FRIDAY. A FEW SPRINKLES ARE POSSIBLE OVERNIGHT BUT IMPACTS WILL BE MINIMAL. LIGHT NORTHEAST WINDS OVERNIGHT WILL BECOME E/SELY ON FRIDAY AS HIGH PRESSURE SLIDES EAST OF THE AREA. A TIGHTER SFC GRADIENT WILL RESULT IN BREEZY CONDITIONS AFTER 17Z AT KPIR/KMBG...WITH A FEW GUSTS AROUND 25 KTS. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ UPDATE...FOWLE SHORT TERM...WISE LONG TERM...TMT AVIATION...TDK WEATHER.GOV/ABERDEEN
AREA FORECAST DISCUSSION
NWS ABERDEEN SD
845 PM CDT THU AUG 30 2012 .UPDATE... 00Z 300/500MB ANALYSIS INDICATED A LARGE UPPER RIDGE OVER THE CENTRAL CONUS WITH A TROUGH OF LOW PRESSURE OVER THE PAC NW. THE REMNANTS OF ISAAC WERE LIFTING NWD THRU THE LOWER/MID MISSISSIPPI VALLEY. AT THE SFC...HIGH PRESSURE CENTERED OVER ND IS EXPECTED TO BUILD S/SEWD OVERNIGHT. SFC DEWPOINTS THIS EVENING ARE RANGING FROM THE LOWER 50S OVER NERN SD...DOWN TO THE MIDDLE 30S OVER CENTRAL AND WRN SD. TEMPERATURES EARLY THIS EVENING ARE DROPPING OFF PRETTY QUICKLY DUE TO THE DRY AIRMASS...AND MOSTLY CLEAR SKIES. HOWEVER...LATEST IR SATELLITE IMAGERY INDICATES A FAIRLY WIDESPREAD AREA OF MID LEVEL CLOUDINESS ADVECTING INTO THE AREA FROM THE SW IN THE RIGHT ENTRANCE REGION OF THE UPPER JET. IN FACT KVTN ACTUALLY REPORTED LIGHT RAIN/SPRINKLES...WHICH IS PRETTY AMAZING CONSIDERING THE VERY DRY AMS EVIDENT IN THE KLBF 00Z RAOB. ALSO INTERESTING TO NOTE THAT THE 22Z HRRR INDICATES A FEW SPRINKLES MOVING INTO THE FAR SW LATER TONIGHT. WILL LEAVE FORECAST DRY FOR NOW DUE TO VERY DRY AIR AT LOW LEVELS...BUT A FEW SPRINKLES/LIGHT SHOWERS ARE POSSIBLE. TOUGH CALL ON HOW LOW TO GO WITH LOW TEMPERATURES AS WELL. DECIDED TO DROP LOW TEMPERATURES A FEW DEGREES IN THE EAST...BEFORE THICKER CLOUD COVER MOVES IN AFTER 06Z. UPDATES OUT... FOWLE && .PREVIOUS DISCUSSION... .SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT SPRINKLES AND DRY LIGHTNING CONTINUE FROM WEST CENTRAL MN SOUTHWEST INTO SOUTH CENTRAL SD THIS AFTERNOON BEHIND A TRAILING COLD FRONT. THIS ACTIVITY IS EXPECTED TO EXIT THE REGION OVER THE NEXT 2 TO 3 HRS. HIGH PRESSURE WILL BUILD IN OVERNIGHT BRINGING DRY CONDITIONS AND ABOVE AVERAGE TEMPERATURES THROUGH SATURDAY. A LLJ WILL DEVELOP OVER THE WESTERN CWA EARLY ON SATURDAY MORNING. DECIDED NOT TO MENTION POSSIBILITY OF PRECIP AT THIS POINT BECAUSE LOWER LEVELS WILL BE VERY DRY...AND BEST FORCING WILL BE IN ND. WINDS WILL INCREASE AHEAD OF THE LEE SIDE TROF FRIDAY AND SATURDAY. MAY NEED TO ISSUE FIRE WEATHER HEADLINES...ESPECIALLY ON SATURDAY. AS THE COLD FRONT MOVES OFF THE ROCKIES SAT EVENING...MODELS ARE BEGINNING TO DIVERGE FROM PREVIOUS SOLUTIONS. CURRENT RUNS TRACK THE BULK OF PRECIP OVER ND NOW ON SAT NIGHT. LEFT SOME ISOLATED POPS ACROSS WESTERN CORSON COUNTY SAT NIGHT BUT MAY NEED TO REMOVE THESE AS WELL IF MODELS CONTINUE THIS TREND. HIGHS WILL CLIMB BACK INTO THE 90S OVER THE WEEKEND...ABOUT 10 DEGREES ABOVE AVERAGE IN MOST LOCATIONS. .LONG TERM...SUNDAY THROUGH THURSDAY SUNDAY INTO SUNDAY EVENING MODELS ARE CONSISTENT IN SHOWING A WEAK SFC TROUGH PASSING THROUGH THE AREA...ALTHOUGH MOISTURE AVAILABLE FOR THIS FEATURE IS RATHER LIMITED. WILL CONTINUE WITH LOW POPS FOR THE EASTERN CWA SUNDAY INTO SUNDAY NIGHT. BY THE MIDDLE OF THE WEEK A MORE SIGNIFICANT SHORTWAVE MOVES ACROSS THE AREA AND THE INHERITED GUIDANCE POPS LOOKED OK FOR THIS POTENTIAL EVENT FOR THE TIME BEING. THERE ARE STILL TIMING AND PLACEMENT ISSUES WITH THE MIDDLE OF THE WEEK SYSTEM SO DID NOT STRAY TOO FAR FROM GUIDANCE AT THIS POINT. TEMPS LOOK TO STAY RATHER WARM THROUGH THE PERIOD WITH A SLIGHT COOL DOWN TOWARDS THE END OF NEXT WEEK PERHAPS. && .AVIATION... 00Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS VFR CONDITIONS WILL PREVAIL THROUGH THE NEXT 24 HOURS. EXPECTING AN INCREASE IN MAINLY MID LEVEL CLOUDINESS OVERNIGHT...ALTHOUGH CIGS WILL BE AOA 12K FEET AGL. LIGHT NORTHEAST WINDS OVERNIGHT WILL BECOME E/SELY ON FRIDAY AS HIGH PRESSURE SLIDES EAST OF THE AREA. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ UPDATE...FOWLE SHORT TERM...WISE LONG TERM...TMT AVIATION...FOWLE WEATHER.GOV/ABERDEEN
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
1233 PM CDT THU AUG 30 2012 .DISCUSSION.../ISSUED AT 1048 AM CDT/ FORECAST FOR TODAY GENERALLY LOOKS IN GOOD SHAPE. LATEST HI RES NAM AND HRRR IN GOOD AGREEMENT ON FRONTAL TIMING...ADDING CONFIDENCE TO THIS AFTERNOONS FORECAST. FRONT IS CURRENTLY THROUGH HURON AND CHAMBERLAIN. THINKING IT PUSHES THROUGH MITCHELL SHORTLY...SIOUX FALLS AROUND 20Z...YANKTON AROUND 22Z AND NOT REACHING SIOUX CITY OR SPENCER UNTIL 0Z OR LATER. MID LEVEL CLOUDS AHEAD OF THE FRONT ARE DISSIPATING...SO NOT THINKING THEY WILL HAVE TOO BIG OF AN IMPACT ON HIGH TEMPERATURES. MADE SOME MINOR ADJUSTMENTS TO HIGHS...MAINLY DROPPED THEM A FEW DEGREES IN THE NORTHWEST BEHIND THE FRONT...AND WARMED THEM A BIT NEAR YANKTON. OUTFLOW FROM CONVECTION IN NORTHEAST SOUTH DAKOTA HAS PUSHED SOUTH INTO SOUTHWEST MINNESOTA. DESPITE THIS BEING A LOW LEVEL BOUNDARY...THE ATMOSPHERE IS UNSTABLE ENOUGH THAT IT HAS TRIGGERED CLOUDS TO FORM UP AT 15000 FEET. THESE CLOUDS WILL LIKELY HOLD TEMPERATURES DOWN SOME THERE...BUT THEY SHOULD ALSO TEND TO DISSIPATE INTO EARLY AFTERNOON. WINDS LIKELY TO BE GUSTING TO 30 MPH AHEAD OF THE FRONT THIS AFTERNOON OUT OF THE SOUTH...WITH GUSTS UP TO 20 MPH OUT OF THE NORTH BEHIND IT. FIRE WEATHER HEADLINES LOOK GOOD. RH VALUES EXPECTED TO DROP BELOW 20 PERCENT AHEAD OF THE FRONT. IN SOUTHWEST MINNESOTA...LOOKING LIKE ONLY THE SOUTHERN TIER OF COUNTIES ARE GOING TO REACH CRITERIA BEFORE THE FRONT PUSHES THROUGH. /CHENARD && .AVIATION.../FOR THE 18Z TAF ISSUANCE/ VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. A FEW LIGHT SHOWERS WILL BE POSSIBLE INTO EARLY THIS AFTERNOON FROM 9V9 THROUGH ATY. SOUTHWEST WINDS WILL GUST AROUND 30 FROM ABOUT SIOUX FALLS SOUTH AND EAST AHEAD OF AN INCOMING DRY COOL FRONT. WINDS WILL SHIFT TO THE NORTH BEHIND THE BOUNDARY...WITH GUSTS AROUND 20 MPH POSSIBLE. WINDS WILL CALM DOWN TONIGHT...AND WILL BE A BIT BREEZY TOMORROW OUT OF THE EAST NORTH OF THE BOUNDARY. FRONTAL TIMING LOOKS LIKE AROUND 20Z IN SIOUX FALLS. FRONT WILL WASH OUT BY THE TIME IT APPROACHES SIOUX CITY...THUS MAINLY LIGHT AND VARIABLE WINDS EXPECTED THERE FOR TONIGHT INTO TOMORROW MORNING. /CHENARD && .PREVIOUS DISCUSSION.../ISSUED AT 455 AM CDT/ FIRE WEATHER CONCERNS ONCE AGAIN AT FOREFRONT THIS MORNING...AFTER YESTERDAY WHICH FEATURED EXTREME CONDITIONS THROUGH THE MISSOURI RIVER VALLEY AND LOESS HILLS REGION. GENERAL DISCUSSION FOLLOWS... WITH DETAILS BELOW IN FIRE WEATHER SECTION. TAIL END OF WEAK WAVE BRUSHING THROUGH NORTHERN SOUTH DAKOTA AND DRIVING A FRONTAL BOUNDARY SOUTHWARD...AT 09Z ON A LINE FROM SOUTHEAST NORTH DAKOTA TO SOUTHWEST SOUTH DAKOTA. STRONG LOW LEVEL JET ESTABLISHED OVERNIGHT ACROSS THE AREA AHEAD OF THIS BOUNDARY... AS WARM FRONT ROCKETED NORTHWARD. HIGHER ELEVATIONS SITES IN SOUTH CENTRAL SOUTH DAKOTA HAVE STRUGGLED TO DROP BELOW THE MID 80S THUS FAR...AND WINDS ON AND DOWNSTREAM OF THE BUFFALO RIDGE NOW GUSTING TO 25 TO 35 KNOTS. LOW LEVEL DRY AIR ALREADY ESTABLISHED IN MIXY ENVIRONMENT...WITH 30S TO LOWER 40S DEWPOINTS IN THE WEST...AND A PARTIALLY DECOUPLED AIRSTREAM IN THE EAST STRUGGLING TO MAINTAIN NEAR 60 VALUES. NAM AGAIN IS THE FAST OUTLIER WITH BOUNDARY... SOMEWHAT SLOWER THAN YESTERDAY...AND PREFER A ECMWF/GFS BLEND FOR TIMING. THIS WOULD PUT FRONT THROUGH THE SIOUX FALLS AREA EARLY AFTERNOON...RATHER THAN MID MORNING. RESULT WILL BE ANOTHER SCORCHER ACROSS THE AREA WITH ADDITIONAL RECORD TEMPERATURES. WARMEST READINGS FOR TODAY SEEM TO BE FOCUSING ONTO THE LOWER MISSOURI VALLEY AROUND KSUX...EXTENDING TOWARD KCKP/KSPW AREAS...WHERE EXPECT 100 TO 105 DEGREE READINGS. MORE EXTENSIVE MID TO HIGH CLOUDS ACROSS THE WEST AND NORTH WILL PUT SOME CONTROL ON TEMPS...BUT WITH WAVE PUSHING PAST...SHOULD THIN OUT SOMEWHAT FOR THE AFTERNOON. EVEN THEN...WILL LIKELY STRUGGLE TO 90 DEGREES IN THE NORTHWEST...AND ACTUALLY FIND SOME TEMPS DROPPING BACK A BIT DURING THE AFTERNOON BASED ON MIXING POTENTIAL. FRONT WILL SLOW BUT CONTINUE TO PUSH THROUGH THE CWA THIS EVENING... WITH AN EASTERLY FLOW REGIME BECOMING ESTABLISHED ON FRIDAY. RIDGE WILL AGAIN STRENGTHEN A BIT BETWEEN WESTERLIES TO NORTH AND TROPICAL REMNANTS OF ISAAC TO THE SOUTH. SHOULD HAVE MORE SUNSHINE...BUT THE EXTREME WARMTH OF LAST COUPLE DAYS AND TODAY WILL BE REPLACED BY JUST YOUR TYPICAL ABOVE NORMAL READINGS. SATURDAY...REMNANTS OF ISAAC WILL TAKE A WIDE RIGHT PASS...BUT SOME LOW LEVEL TRAJECTORIES SUGGEST MAY BE ABLE TO BLEED OFF A SOMEWHAT ENHANCED DEWPOINT THROUGH THE EASTERN CWA...LIKELY RESULTS IN SOME FLAT CUMULUS DEVELOPMENT...AND SLIGHTLY COOLER TEMPERATURES. IN THE EXTENDED RANGE /SUNDAY THROUGH WEDNESDAY/ ECMWF HAS FLIPPED TO A MUCH WEAKER MONDAY WAVE...AND INSTEAD PUT ITS EGGS IN THE SECONDARY BASKET WITH IMPRESSIVELY SHARP TROUGH ON WEDNESDAY. GFS...WHILE AT ODDS WITH A FAIR POPULATION OF ITS OWN ENSEMBLES...SUGGESTS A STRONGER INITIAL TROUGH ON MONDAY AND DRIVES BOUNDARY WELL SOUTH THROUGH THE UPCOMING WEEK...SOMEWHAT COOLER... AND CERTAINLY DRY. WITH AS MUCH CONSTERNATION AS THE MODELS HAVE HAD WITH UPCOMING LARGER SCALE PATTERN...DID NOT ALTER EXTENDED AS MUCH AS MIGHT HAVE...OTHER THAN THE USUAL STRETCHING OF DIURNAL RANGES A BIT...AND HACKING OUT SOME OF THE SLIGHT CHANCE POPS RESULTING FROM THE BLENDING OF WIDELY VARYING SOLUTIONS. THROUGH SUNDAY...ENOUGH AGREEMENT TO SUGGEST NUDGING HIGHS UP A BIT THROUGH THE WEST/MID PORTIONS OF CWA AHEAD OF NEXT FRONTAL BOUNDARY. NOT A GREAT DEAL OF DEEPER FORCING DOWN TOWARD OUR END OF THE FRONT...SO KEPT POPS LIMITED TO LOWER CHANCE AND THROUGH THE NORTH/EAST AREAS FROM LATE AFTERNOON THROUGH EVENING HOURS. POTENTIALLY ENOUGH SHEAR AND WITH SOME INCREASED MOISTURE LINGERING...MAY GET 1000-1500 J/KG MLCAPE AND ENOUGH SHEAR TO HAVE A LIMITED SEVERE THREAT. /CHAPMAN && .FIRE WEATHER... WITH LITTLE QUESTION TO THE EXTENT OF DRY AIRMASS SITTING ACROSS THE AREA ALREADY THIS MORNING WITH MID 30S TO LOWER 40S DEWPOINTS ACROSS CENTRAL NEBRASKA AND A VASTLY DRY KLBF RAOB FROM LAST EVENING... SIGNIFICANT ISSUE FOR THE ISSUANCE OF RED FLAG WARNING IS PROGRESSION OF THE FRONTAL BOUNDARY AND MIXING OF WINDS AHEAD OF THIS BOUNDARY. PROFILER WINDS AT NLG SUPPORT STRONG PREFRONTAL LOW LEVEL JET... AND HAVE SEEN HIGHER ELEVATION SITES CONTINUE TO REPORT 20 TO 30 KNOTS GUSTS OVERNIGHT. THEREFORE...LITTLE DOUBT IN WINDS AS WEAK WAVE PASSING NORTH CONTINUES TO SUPPORT LOW LEVEL JET WITH A SLOW WEAKENING TREND THROUGH MIDDAY. THIS SHOULD BE BALANCED SOMEWHAT BY THE QUICK AND DEEPER MIXING. LOWEST HUMIDITY AREA OF LESS THAN 20 PERCENT IS GENERAL OUTLINE USED FOR ISSUANCE OF RED FLAG WARNING... WITH SUSTAINED WINDS PROBABLY OVERALL TECHNICALLY JUST A BIT UNDER FOR MOST...BUT ENOUGH FOR FREQUENT GUSTS AT OF ABOVE 25 KNOTS. FOR THE TWO ADDITIONS IN SOUTHEAST SOUTH DAKOTA AND SOUTHWEST MINNESOTA...IT IS REALLY ONLY THE SOUTHEAST PORTIONS OF THOSE AREAS OF GREATEST CONCERN. IT ALSO IS POSSIBLE THAT A COUPLE HOURS WILL APPROACH OR EXCEED CRITERIA RIGHT AROUND KFSD...BUT WITH MUCH LESS AREA IN THIS ZONE THAT MAY BE IMPACTED BEFORE WINDS DROP OFF ENOUGH...WILL KEEP CLEAR OF A RED FLAG WARNING FOR NOW. DID END THE NORTHERNMOST GROUPS A COUPLE HOURS EARLIER TO ACCOUNT FOR THE BOUNDARY AND EARLIER LOSS OF GRADIENT. /CHAPMAN && .FSD WATCHES/WARNINGS/ADVISORIES... IA...RED FLAG WARNING FROM NOON TODAY TO 8 PM CDT THIS EVENING FOR IAZ300-301. MN...RED FLAG WARNING FROM NOON TODAY TO 6 PM CDT THIS EVENING FOR MNZ900. NE...RED FLAG WARNING FROM NOON TODAY TO 8 PM CDT THIS EVENING FOR NEZ249. SD...RED FLAG WARNING FROM NOON TODAY TO 6 PM CDT THIS EVENING FOR SDZ258. $$
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
1048 AM CDT THU AUG 30 2012 .DISCUSSION.../ISSUED AT 1048 AM CDT/ FORECAST FOR TODAY GENERALLY LOOKS IN GOOD SHAPE. LATEST HI RES NAM AND HRRR IN GOOD AGREEMENT ON FRONTAL TIMING...ADDING CONFIDENCE TO THIS AFTERNOONS FORECAST. FRONT IS CURRENTLY THROUGH HURON AND CHAMBERLAIN. THINKING IT PUSHES THROUGH MITCHELL SHORTLY...SIOUX FALLS AROUND 20Z...YANKTON AROUND 22Z AND NOT REACHING SIOUX CITY OR SPENCER UNTIL 0Z OR LATER. MID LEVEL CLOUDS AHEAD OF THE FRONT ARE DISSIPATING...SO NOT THINKING THEY WILL HAVE TOO BIG OF AN IMPACT ON HIGH TEMPERATURES. MADE SOME MINOR ADJUSTMENTS TO HIGHS...MAINLY DROPPED THEM A FEW DEGREES IN THE NORTHWEST BEHIND THE FRONT...AND WARMED THEM A BIT NEAR YANKTON. OUTFLOW FROM CONVECTION IN NORTHEAST SOUTH DAKOTA HAS PUSHED SOUTH INTO SOUTHWEST MINNESOTA. DESPITE THIS BEING A LOW LEVEL BOUNDARY...THE ATMOSPHERE IS UNSTABLE ENOUGH THAT IT HAS TRIGGERED CLOUDS TO FORM UP AT 15000 FEET. THESE CLOUDS WILL LIKELY HOLD TEMPERATURES DOWN SOME THERE...BUT THEY SHOULD ALSO TEND TO DISSIPATE INTO EARLY AFTERNOON. WINDS LIKELY TO BE GUSTING TO 30 MPH AHEAD OF THE FRONT THIS AFTERNOON OUT OF THE SOUTH...WITH GUSTS UP TO 20 MPH OUT OF THE NORTH BEHIND IT. FIRE WEATHER HEADLINES LOOK GOOD. RH VALUES EXPECTED TO DROP BELOW 20 PERCENT AHEAD OF THE FRONT. IN SOUTHWEST MINNESOTA...LOOKING LIKE ONLY THE SOUTHERN TIER OF COUNTIES ARE GOING TO REACH CRITERIA BEFORE THE FRONT PUSHES THROUGH. /CHENARD .PREVIOUS DISCUSSION.../ISSUED AT 455 AM CDT/ FIRE WEATHER CONCERNS ONCE AGAIN AT FOREFRONT THIS MORNING...AFTER YESTERDAY WHICH FEATURED EXTREME CONDITIONS THROUGH THE MISSOURI RIVER VALLEY AND LOESS HILLS REGION. GENERAL DISCUSSION FOLLOWS... WITH DETAILS BELOW IN FIRE WEATHER SECTION. TAIL END OF WEAK WAVE BRUSHING THROUGH NORTHERN SOUTH DAKOTA AND DRIVING A FRONTAL BOUNDARY SOUTHWARD...AT 09Z ON A LINE FROM SOUTHEAST NORTH DAKOTA TO SOUTHWEST SOUTH DAKOTA. STRONG LOW LEVEL JET ESTABLISHED OVERNIGHT ACROSS THE AREA AHEAD OF THIS BOUNDARY... AS WARM FRONT ROCKETED NORTHWARD. HIGHER ELEVATIONS SITES IN SOUTH CENTRAL SOUTH DAKOTA HAVE STRUGGLED TO DROP BELOW THE MID 80S THUS FAR...AND WINDS ON AND DOWNSTREAM OF THE BUFFALO RIDGE NOW GUSTING TO 25 TO 35 KNOTS. LOW LEVEL DRY AIR ALREADY ESTABLISHED IN MIXY ENVIRONMENT...WITH 30S TO LOWER 40S DEWPOINTS IN THE WEST...AND A PARTIALLY DECOUPLED AIRSTREAM IN THE EAST STRUGGLING TO MAINTAIN NEAR 60 VALUES. NAM AGAIN IS THE FAST OUTLIER WITH BOUNDARY... SOMEWHAT SLOWER THAN YESTERDAY...AND PREFER A ECMWF/GFS BLEND FOR TIMING. THIS WOULD PUT FRONT THROUGH THE SIOUX FALLS AREA EARLY AFTERNOON...RATHER THAN MID MORNING. RESULT WILL BE ANOTHER SCORCHER ACROSS THE AREA WITH ADDITIONAL RECORD TEMPERATURES. WARMEST READINGS FOR TODAY SEEM TO BE FOCUSING ONTO THE LOWER MISSOURI VALLEY AROUND KSUX...EXTENDING TOWARD KCKP/KSPW AREAS...WHERE EXPECT 100 TO 105 DEGREE READINGS. MORE EXTENSIVE MID TO HIGH CLOUDS ACROSS THE WEST AND NORTH WILL PUT SOME CONTROL ON TEMPS...BUT WITH WAVE PUSHING PAST...SHOULD THIN OUT SOMEWHAT FOR THE AFTERNOON. EVEN THEN...WILL LIKELY STRUGGLE TO 90 DEGREES IN THE NORTHWEST...AND ACTUALLY FIND SOME TEMPS DROPPING BACK A BIT DURING THE AFTERNOON BASED ON MIXING POTENTIAL. FRONT WILL SLOW BUT CONTINUE TO PUSH THROUGH THE CWA THIS EVENING... WITH AN EASTERLY FLOW REGIME BECOMING ESTABLISHED ON FRIDAY. RIDGE WILL AGAIN STRENGTHEN A BIT BETWEEN WESTERLIES TO NORTH AND TROPICAL REMNANTS OF ISAAC TO THE SOUTH. SHOULD HAVE MORE SUNSHINE...BUT THE EXTREME WARMTH OF LAST COUPLE DAYS AND TODAY WILL BE REPLACED BY JUST YOUR TYPICAL ABOVE NORMAL READINGS. SATURDAY...REMNANTS OF ISAAC WILL TAKE A WIDE RIGHT PASS...BUT SOME LOW LEVEL TRAJECTORIES SUGGEST MAY BE ABLE TO BLEED OFF A SOMEWHAT ENHANCED DEWPOINT THROUGH THE EASTERN CWA...LIKELY RESULTS IN SOME FLAT CUMULUS DEVELOPMENT...AND SLIGHTLY COOLER TEMPERATURES. IN THE EXTENDED RANGE /SUNDAY THROUGH WEDNESDAY/ ECMWF HAS FLIPPED TO A MUCH WEAKER MONDAY WAVE...AND INSTEAD PUT ITS EGGS IN THE SECONDARY BASKET WITH IMPRESSIVELY SHARP TROUGH ON WEDNESDAY. GFS...WHILE AT ODDS WITH A FAIR POPULATION OF ITS OWN ENSEMBLES...SUGGESTS A STRONGER INITIAL TROUGH ON MONDAY AND DRIVES BOUNDARY WELL SOUTH THROUGH THE UPCOMING WEEK...SOMEWHAT COOLER... AND CERTAINLY DRY. WITH AS MUCH CONSTERNATION AS THE MODELS HAVE HAD WITH UPCOMING LARGER SCALE PATTERN...DID NOT ALTER EXTENDED AS MUCH AS MIGHT HAVE...OTHER THAN THE USUAL STRETCHING OF DIURNAL RANGES A BIT...AND HACKING OUT SOME OF THE SLIGHT CHANCE POPS RESULTING FROM THE BLENDING OF WIDELY VARYING SOLUTIONS. THROUGH SUNDAY...ENOUGH AGREEMENT TO SUGGEST NUDGING HIGHS UP A BIT THROUGH THE WEST/MID PORTIONS OF CWA AHEAD OF NEXT FRONTAL BOUNDARY. NOT A GREAT DEAL OF DEEPER FORCING DOWN TOWARD OUR END OF THE FRONT...SO KEPT POPS LIMITED TO LOWER CHANCE AND THROUGH THE NORTH/EAST AREAS FROM LATE AFTERNOON THROUGH EVENING HOURS. POTENTIALLY ENOUGH SHEAR AND WITH SOME INCREASED MOISTURE LINGERING...MAY GET 1000-1500 J/KG MLCAPE AND ENOUGH SHEAR TO HAVE A LIMITED SEVERE THREAT. /CHAPMAN && .AVIATION.../FOR THE 12Z TAF ISSUANCE/ VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. A FEW SHOWERS AND VERY ISOLATED THUNDERSTORMS WILL BE POSSIBLE THROUGH MID MORNING FROM ABOUT 9V9 THROUGH ATY. SOUTHWEST WINDS COULD GUST AS HIGH AS 30 KNOTS FROM ABOUT SIOUX FALLS SOUTH AND EAST AHEAD OF AN INCOMING DRY COOL FRONT. /08 && .FIRE WEATHER... WITH LITTLE QUESTION TO THE EXTENT OF DRY AIRMASS SITTING ACROSS THE AREA ALREADY THIS MORNING WITH MID 30S TO LOWER 40S DEWPOINTS ACROSS CENTRAL NEBRASKA AND A VASTLY DRY KLBF RAOB FROM LAST EVENING... SIGNIFICANT ISSUE FOR THE ISSUANCE OF RED FLAG WARNING IS PROGRESSION OF THE FRONTAL BOUNDARY AND MIXING OF WINDS AHEAD OF THIS BOUNDARY. PROFILER WINDS AT NLG SUPPORT STRONG PREFRONTAL LOW LEVEL JET... AND HAVE SEEN HIGHER ELEVATION SITES CONTINUE TO REPORT 20 TO 30 KNOTS GUSTS OVERNIGHT. THEREFORE...LITTLE DOUBT IN WINDS AS WEAK WAVE PASSING NORTH CONTINUES TO SUPPORT LOW LEVEL JET WITH A SLOW WEAKENING TREND THROUGH MIDDAY. THIS SHOULD BE BALANCED SOMEWHAT BY THE QUICK AND DEEPER MIXING. LOWEST HUMIDITY AREA OF LESS THAN 20 PERCENT IS GENERAL OUTLINE USED FOR ISSUANCE OF RED FLAG WARNING... WITH SUSTAINED WINDS PROBABLY OVERALL TECHNICALLY JUST A BIT UNDER FOR MOST...BUT ENOUGH FOR FREQUENT GUSTS AT OF ABOVE 25 KNOTS. FOR THE TWO ADDITIONS IN SOUTHEAST SOUTH DAKOTA AND SOUTHWEST MINNESOTA...IT IS REALLY ONLY THE SOUTHEAST PORTIONS OF THOSE AREAS OF GREATEST CONCERN. IT ALSO IS POSSIBLE THAT A COUPLE HOURS WILL APPROACH OR EXCEED CRITERIA RIGHT AROUND KFSD...BUT WITH MUCH LESS AREA IN THIS ZONE THAT MAY BE IMPACTED BEFORE WINDS DROP OFF ENOUGH...WILL KEEP CLEAR OF A RED FLAG WARNING FOR NOW. DID END THE NORTHERNMOST GROUPS A COUPLE HOURS EARLIER TO ACCOUNT FOR THE BOUNDARY AND EARLIER LOSS OF GRADIENT. /CHAPMAN && .FSD WATCHES/WARNINGS/ADVISORIES... IA...RED FLAG WARNING FROM NOON TODAY TO 8 PM CDT THIS EVENING FOR IAZ300-301. MN...RED FLAG WARNING FROM NOON TODAY TO 6 PM CDT THIS EVENING FOR MNZ900. NE...RED FLAG WARNING FROM NOON TODAY TO 8 PM CDT THIS EVENING FOR NEZ249. SD...RED FLAG WARNING FROM NOON TODAY TO 6 PM CDT THIS EVENING FOR SDZ258. $$
AREA FORECAST DISCUSSION
NWS HOUSTON/GALVESTON TX
1020 AM CDT THU AUG 30 2012 .DISCUSSION... ISAAC WAS LOCATED IN NORTH-CENTRAL LOUISIANA AT MID MORNING WITH SOME OF THE OUTER BANDS OF THE STORM MOVING ACROSS EAST TEXAS... JUST TO THE EAST OF THE HGX FORECAST AREA. THE NAM AND RAP MODELS BOTH BRING THE MORE MOIST AIRMASS INTO THE EASTERN COUNTIES OF THE FORECAST AREA THIS AFTERNOON. THIS IMPLIES THAT THE OUTER BANDS SHOULD MOVE ACROSS THESE AREAS. OTHERWISE...MOST OF SE TX WILL EXPERIENCE HOT AND MOSTLY SUNNY CONDITIONS. THE CONTINUED OFFSHORE WIND FLOW WILL KEEP THE WATER LEVELS LOW IN GALVESTON BAY WITH THE LOWEST LEVELS LIKELY IN THE NORTHERN PORTIONS OF THE BAY AND IN THE SHIP CHANNEL. IN PARTICULAR...MORGANS POINT HAS HAD WATER LEVELS DOWN ALMOST 2 FEET BELOW THE EXPECTED MEAN LOWER LOW WATER. FOR THE MOST PART...THE CURRENT FORECAST IS ON TRACK. ADJUSTED THE WINDS DOWNWARD A BIT AND DROPPED THE MARINE HAZARDS WITH THE EXCEPTION OF THE LOW WATER HAZARD IN GALVESTON BAY. 40 && .PRELIMINARY POINT TEMPS/POPS... COLLEGE STATION (CLL) 100 76 98 77 96 / 20 10 10 10 10 HOUSTON (IAH) 98 78 96 78 93 / 20 20 20 10 20 GALVESTON (GLS) 95 82 92 81 91 / 20 20 20 20 20 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ DISCUSSION...40 AVIATION/MARINE...47
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AREA FORECAST DISCUSSION
NWS LA CROSSE WI
632 PM CDT WED AUG 29 2012 .SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT 309 PM CDT WED AUG 29 2012 MAIN FORECAST CONCERNS THIS PACKAGE...HEAT AND FIRE WEATHER CONCERNS THU...ANY RAIN CHANCES FROM ISAAC SAT/SAT NIGHT. 18Z DATA ANALYSIS HAD A BROAD AREA OF LOW PRESSURE OVER THE NORTHERN PLAINS. GRADIENT OVER MN/IA/WI WAS TIGHTENING AHEAD OF THIS FEATURE WITH INCREASING SOUTHEAST TO SOUTHWEST WINDS OVER THE REGION. SOUTHWEST FLOW OVER NEB/WESTERN IA ALONG WITH DEEP MIXING WAS SPREADING DRIER AIR NORTHEAST INTO THE REGION...AND DEW POINTS WEST OF I-35 AND SOUTH OF I-90 WERE FALLING INTO THE LOWER 50S. OTHERWISE BROAD LOW LEVEL WARM ADVECTION AND PLENTY OF SUNSHINE WERE HELPING EARLY AFTERNOON TEMPS CLIMB INTO THE UPPER 70S AND 80S MOST OF THE UPPER MIDWEST. 29.12Z MODELS LOOK TO HAVE INITIALIZED WELL...BUT FOR GFS SOME 5F OR SO TOO HIGH WITH SFC DEW POINT OVER MUCH OF THE MID/UPPER MS VALLEY AND NORTHERN PLAINS. SOLUTIONS REASONABLY SIMILAR FOR THE UPPER MIDWEST TONIGHT INTO FRI NIGHT AS A COLD FRONT SINKS SOUTH INTO/ ACROSS THE AREA...AT LEAST WITH SFC AND 500MB FEATURES. PLENTY OF DIFFERENCES WITH SFC-925MB TEMPS/DEW POINTS ON THU. SOLUTIONS DIVERGE ON HOW FAR WEST/NORTH THE REMNANTS OF ISAAC END UP BY FRI AND BEYOND. DPROG/DT OF 500MB HGTS AT 29.12Z SHOWED MODEL RUNS OF 27.12Z AND 28.12Z VERIFIED REASONABLY WELL ACROSS NOAM. 27.12Z RUNS WERE SLOW WITH THE SHORTWAVE MOVING THRU THE PAC NORTHWEST WHILE A COMPROMISE/ CONSENSUS OF THE EARLIER RUNS WAS BEST WITH THE LOCATION OF ISAAC. MODEL CONSENSUS TIGHTENING/IMPROVING TONIGHT THRU FRI WITH REMNANTS OF ISAAC INTO THE MID MS VALLEY AND NEXT TROUGH ONTO THE WEST COAST. CONSENSUS BETTER FRI NIGHT INTO SAT NIGHT...BUT TIMING/PLACEMENT DIFFERENCES WITH WHATS LEFT OF ISAAC STILL ENOUGH TO HAVE SENSIBLE WEATHER IMPACTS HEADING INTO THE WEEKEND. CHECK OF OBS VS. MODEL DATA AT 18Z SHOWED ALL REASONABLE WITH THE LOCATION OF ISAAC AND LOW/TROUGHING IN THE NORTHERN PLAINS INTO UPPER MIDWEST. GFS REMAINED AS MUCH AS 10F TOO HIGH WITH SFC DEW POINTS OVER PARTS OF MN/IA/WI AND DAKOTAS. PER WV IMAGERY...NAM APPEARED TOO FAR WEST WITH THE MID LEVEL ISAAC CIRCULATION WHILE THE OTHER MODELS LOOKED QUITE GOOD. REASONS TO FAVOR EACH MODEL BUT NO ONE CLEAR FAVORITE. WITH THE TREND TOWARD A COMMON CONSENSUS...PREFERRED A MODEL/ ENSEMBLE BLEND. SHORT TERM FCST CONFIDENCE AVERAGE TO GOOD THIS CYCLE. IN THE SHORT TERM...QUIET TONIGHT WITH THE PRESSURE GRADIENT CONTINUING TO TIGHTEN. SOUTH/SOUTHWEST WINDS REMAIN IN THE 10-20 MPH RANGE TONIGHT...KEEPING THE BOUNDARY LAYER MIXED AND LOWS WELL ABOVE LATE AUG NORMALS. TIGHT GRADIENT REMAINS OVER THE AREA THU... WITH 925MB WINDS IN THE 30KT RANGE AND SOUNDINGS SHOWING MIXING TO AT LEAST 900MB. PLENTY OF DRY AIR IN THE SFC-850MB LAYER TO MIX/ ADVECT INTO THE AREA ON THE BRISK/STRONG SOUTHWEST LOW LEVEL FLOW. THU DEW POINTS EXPECTED TO FALL INTO THE UPPER 40S TO MID 50S. THIS ALONG WITH THE BRISK WINDS SETTING UP THE FIRE WEATHER CONCERNS. SEE FIRE WEATHER SECTION BELOW FOR MORE DETAILS. MODELS QUITE VARIABLE ON THE 925MB TEMPS/MOISTURE OVER THE AREA THU. WITH GFS TOO COOL/WET WITH SFC-925MB TEMPS/DEW POINTS TODAY AND ITS KNOW WET BIAS ON SFC DEW POINTS...ITS COOLER SOLUTION FOR THU DISCOUNTED. PREVIOUS FCST FOR THU HAD HIGH TEMPS IN THE 95 TO 100F RANGE WELL TRENDED BUT LOWERED DEW POINTS A BIT TO BETTER BLEND WITH NEIGHBORS AND REFLECT TRENDS IN WESTERN IA TODAY. WITH THE LOWER DEW POINTS... HEAT INDICES COME UP JUST SHORT OF ADVISORY CRITERIA. 15-25MPH AND GUSTY WINDS ON THU WILL AID THE COMFORT LEVEL OF THE THU AIRMASS AS WELL. THE 925-850MB THERMAL RIDGE IS QUICKLY PUSHED SOUTH OF THE AREA THU NIGHT/FRI AS A COLD FRONT DROPS SOUTH INTO AND ACROSS THE AREA. WITH A DEEP...DRY AIRMASS AND LITTLE IN THE WAY OF SFC THRU MID LEVEL FORCING FOR LIFT...LEFT THU NIGHT/FRI DRY. 925-850MB TEMPS DO REMAIN WELL ABOVE NORMAL BEHIND THE FRONT...AND SOME QUESTION AS TO HOW FAR SOUTH THE FRONT GETS ON FRI. FRI TO BE ANOTHER WARM DAY WITH HIGH TEMPS STILL AROUND 90 OR LOWER 90S OVER THE CENTRAL/SOUTH PARTS OF THE FCST AREA. IMPROVING MODEL CONSENSUS KEEPS THE DEEPER 850-700MB MOISTURE AND CIRCULATION FROM ISAAC SOUTH OF THE FCST AREA FRI NIGHT AND LEFT THIS PERIOD DRY ACROSS THE FAR SOUTH END OF THE FCST AREA. 29.12Z ECMWF/GFS/GEM MODEL CONSENSUS CLIPS THE SOUTHEAST END OF THE FCST AREA WITH THE REMNANT CIRCULATION OF ISAAC AND THE 850-700MB MOISTURE SAT/SAT NIGHT. STILL NOT A LOT OF CONFIDENCE WITH THIS GIVEN MODELS ARE DEALING WITH A RATHER TIGHT/SMALL 850-500MB CIRCULATION LIFTING NORTH THRU A MID LEVEL RIDGE AXIS. PLENTY OF ROOM FOR ERROR HERE AND CHANGES IN LATER MODEL RUNS. THUS LEFT ANY RAIN CHANCES ACROSS THE SOUTH END SAT/SAT NIGHT IN THE 20-30 PERCENT RANGE. WITH ANY PRECIP THESE PERIODS ON THE NORTH FRIDGE OF THE REMNANT CIRCULATION AND MUCAPE TRENDING TO BE MINIMAL...REMOVED TSRA MENTION FROM SAT/SAT NIGHT. .LONG TERM...SUNDAY THROUGH WEDNESDAY 309 PM CDT WED AUG 29 2012 29.00Z AND 29.12Z MEDIUM RANGE MODELS IN REASONABLE AGREEMENT SUN. HOWEVER OVERALL TREND APPEARS BIT SLOWER/STRONGER THAN PREVIOUS RUNS WITH REMNANTS OF ISAAC IN THE MID MS VALLEY AND STRONGER WITH TROUGHING INTO SOUTH-CENTRAL CAN. REASONABLE CONSENSUS MON THRU WED WITH BROAD LONGWAVE TROUGHING OVER CAN AND NORTHERN CONUS. HOWEVER PLENTY OF DETAIL DIFFERENCES WITH THE STRONGER...TRACKABLE FEATURES IN THIS FLOW. ECMWF DOES OFFER RATHER GOOD RUN-TO-RUN CONSISTENCY WITH ITS 28.00Z RUN IN THE MON-WED PERIOD. LONG-TERM FCST CONFIDENCE FOR RAIN CHANCES AVERAGE THIS CYCLE. CONFIDENCE FOR TEMPERATURES CLOSER TO BUT STILL ABOVE SEASONAL NORMALS IN THE DAY 4-7 PERIOD GOOD THIS CYCLE. LATEST MODEL CONSENSUS KEEPS REMNANTS OF ISAAC OVER CENTRAL IL SUN MORNING...CLOSE ENOUGH FOR A SMALL -SHRA CHANCE OVER THE SOUTHEAST END OF THE FCST AREA. CONSENSUS SHIFT OF THE MID LEVEL FLOW PATTERN TO THE BROAD TROUGH OVER CAN/NORTH-CENTRAL CONUS FOR MON-WED SENDS A SERIES OF FRONTS/TROUGHS ACROSS THE UPPER MIDWEST FOR THE FIRST HALF OF NEXT WEEK. SOMEWHAT BETTER MODEL AGREEMENT FOR ONE OF THESE TO PASS ON LABOR DAY /MON/...THEN WEAK HIGH PRESSURE TUE AND ANOTHER STRONGER TROUGH/FRONT TO MOVE IN WED. BUT AGAIN TIMING IS QUESTIONABLE MUCH BEYOND MON. RAIN CHANCES IN THE 20-40 PERCENT RANGE PER MODEL/ENSEMBLE CONSENSUS LOOK REASONABLE FOR MON AND WED. GIVEN POTENTIAL FRONT/TROUGH TIMING ISSUES...MODEL/ENSEMBLE CONSENSUS HIGHS/LOWS ABOUT 5F ABOVE NORMAL FOR MUCH OF DAYS 4-7 LOOKS GOOD. && .AVIATION...TONIGHT AND THURSDAY 632 PM CDT WED AUG 29 2012 MAIN CONCERN IS ON LOW LEVEL WIND SHEAR POTENTIAL TONIGHT AT BOTH TAF SITES. VFR CONDITIONS EXPECTED WITH MAINLY CLEAR SKIES THROUGH THE TAF PERIOD. 925MB JET STRENGTHENS OVERNIGHT WITH BOTH THE NAM AND RAP SHOWING 45 TO 50 KNOT WINDS ACROSS THE AREA. MAIN QUESTION WILL BE HOW MUCH DECOUPLING WILL OCCUR AT THE SURFACE. FEEL BETTER CHANCES ARE AT KLSE IN THE VALLEY AND THUS HAVE INCLUDED LLWS IN THE 00Z TAF. AT KRST...SOME CONCERN WITH SURFACE WINDS STAYING UP OR INCREASING THROUGH THE OVERNIGHT HOURS AS GRADIENT REMAINS TIGHT. KRST LOOKS TO BE BORDERLINE TO HIT LLWS CRITERIA AND THUS HAVE LEFT IT OUT FOR NOW AND WILL RE-EVAULATE FOR THE 06Z ISSUANCE. && .CLIMATE...THURSDAY 309 PM CDT WED AUG 29 2012 THURSDAY REMAINS ON TRACK TO BE THE HOTTEST DAY OF THE WEEK...AS THE CORE OF THE HOT AIRMASS SPREADS ACROSS SOUTHEAST MINNESOTA AND WESTERN WISCONSIN. WITH CURRENT RECORDS IN THE MIDDLE 90S AND FORECAST HIGHS IN THE UPPER 90S TO NEAR 100...MANY AREAS SHOULD COMFORTABLY ESTABLISH NEW RECORD HIGHS. BELOW ARE THE RECORD HIGH INFORMATION FOR ROCHESTER AND LA CROSSE. ROCHESTER MN AUGUST 30...96/1941 AUGUST 31...93/1960 LA CROSSE WI AUGUST 30...94/1969 AUGUST 31...95/1953 ALSO OF NOTE IS THE HISTORICAL RANKINGS FOR THE FREQUENCY OF 90 DEGREES AT LSE. THROUGH YESTERDAY AUG 28TH...LA CROSSE HAS SEEN 32 90 DEGREE DAYS AND THIS STANDS AT 10TH MOST OVERALL. IF THE CURRENT FORECAST FOR AT LEAST 90 OR HIGHER TODAY THROUGH FRIDAY VERIFIES...THIS WOULD PROPEL THE RANKING TO TIED FOR 3RD. && .FIRE WEATHER...THURSDAY 309 PM CDT WED AUG 29 2012 AHEAD OF AN APPROACHING COLD FRONT...THE COMBINATION OF A HOT/DRY AIRMASS AND STRONG SOUTHWESTERLY WINDS ARE LIKELY TO CREATE CRITICAL FIRE WEATHER CONDITIONS THURSDAY ACROSS PARTS OF THE AREA. HIGH TEMPERATURES ARE EXPECTED TO TOP OUT IN THE 95 TO 100 DEGREE RANGE AND AFTERNOON RELATIVE HUMIDITIES WILL FALL TO BETWEEN 20 AND 30 PERCENT. A TIGHT PRESSURE GRADIENT WILL RESULT IN SUSTAINED SOUTHWEST WINDS 15 TO 25 MPH WITH GUSTS UP TO 30 MPH POSSIBLE. AS SUCH...THE FIRE WEATHER WATCH HAS BEEN UPGRADED TO A RED FLAG WARNING FOR AREAS ACROSS SOUTHEAST MINNESOTA AND PARTS OF NORTHEAST IOWA WHERE WINDS WILL BE A BIT STRONGER AND CONCERN IS FOR DRYING CROPS AND FINE/GRASSY FUELS. ACROSS WESTERN INTO CENTRAL WISCONSIN...PER COORDINATION WITH WISCONSIN DNR...CURRENT FUEL MOISTURE LEVELS SUGGEST RED FLAG WARNING IS NOT WARRANTED BUT CONDITIONS REMAINS CRITICAL. THE COLD FRONT WILL SAG ACROSS MINNESOTA AND WISCONSIN LATE THURSDAY...AND WINDS WILL SLACKEN ALONG WITH RECOVERING RELATIVE HUMIDITIES. ON FRIDAY...WITH THE FRONTAL BOUNDARY LINGERING AROUND...IMPROVING CONDITIONS WILL BE SEEN HOWEVER HIGHS ARE EXPECTED TO STILL BE ABOVE NORMAL IN THE UPPER 80S TO LOWER 90S. PLEASE SEE MKERWFARX AND MKEFWFARX FOR DETAILS CONCERNING THE FIRE WEATHER FORECAST. && .ARX WATCHES/WARNINGS/ADVISORIES... 309 PM CDT WED AUG 29 2012 WI...NONE. MN...RED FLAG WARNING FROM NOON TO 8 PM CDT THURSDAY FOR MNZ079- 086>088-094>096. IA...RED FLAG WARNING FROM NOON TO 8 PM CDT THURSDAY FOR IAZ008- 009-018. && $$ SHORT TERM.....RRS LONG TERM......RRS AVIATION...RABERDING CLIMATE........ZT FIRE WEATHER...ZT