Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 291722 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 120 PM EDT MON SEP 29 2014 .SYNOPSIS...AN UPPER LEVEL DISTURBANCE WILL CROSS THE CAROLINAS TODAY...THEN MOVE OFFSHORE TONIGHT. WEAK HIGH PRESSURE WILL EXTEND SOUTHWARD INTO THE REGION ON TUESDAY AND WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1200 PM MONDAY... OVERVIEW: A SHORTWAVE OVER THE TN VALLEY WILL PROGRESS EAST OF THE MOUNTAINS TODAY...MOVING OFFSHORE THE CAROLINA/MID-ATLANTIC COAST LATE TONIGHT. WEAK HIGH PRESSURE WILL PERSIST OVER CENTRAL NC THROUGH TONIGHT AS A WEAK LOW PRESSURE SYSTEM (ATTENDANT THE APPROACHING SHORTWAVE) DEVELOPS ALONG A BAROCLINIC ZONE OFFSHORE THE SOUTHEAST COAST. PRECIPITATION: FORCING FOR ASCENT TODAY WILL BE CONFINED TO DPVA...H5 WARM ADVECTION...AND DIFFLUENT FLOW ALOFT ATTENDANT THE APPROACHING SHORTWAVE. IN THE ABSENCE OF ANY LOW-LEVEL FORCING OR MOISTURE ADVECTION...FORCING ASSOC/W THE SHORTWAVE WILL BE SUFFICIENT TO MAINTAIN BROKEN/OVERCAST MID-LEVEL CEILINGS THROUGHOUT THE DAY...BUT LITTLE MORE THAN SPRINKLES GIVEN A RELATIVELY DRY AIRMASS IN THE LOWEST 10 KFT PER 12Z GSO/MHX RAOB DATA. MARGINAL ELEVATED DESTABILIZATION (LESS THAN 100 J/KG) ASSOC/W MID-LEVEL WARM ADVECTION MAY BE SUFFICIENT FOR OCCASIONAL ELEVATED SHOWER ACTIVITY THIS AFTERNOON ALONG/EAST OF THE HWY 1 CORRIDOR...PER LATEST RAP/NAM FCST SOUNDINGS. WILL INDICATE A 40-60% CHANCE OF SPRINKLES OR LIGHT SHOWERS THROUGH SUNSET...DECREASING/ENDING FROM WEST-EAST BETWEEN 00- 06Z AS THE SHORTWAVE PROGRESSES TOWARD THE COAST AND SUBSIDENCE ENSUES OVER WESTERN/CENTRAL NC. TEMPERATURES: OVERCAST MID-LEVEL CEILINGS WILL REDUCE INSOLATION THIS AFTERNOON...WHILE SPRINKLES AND ELEVATED SHOWERS FOSTER THE DEVELOPMENT OF AN IN-SITU TYPE CAD WEDGE. AS A RESULT...HIGHS TODAY ARE SOMEWHAT CHALLENGING. GIVEN THE LATEST TRENDS...EXPECT HIGHS RANGING FROM THE UPPER 60S TO LOWER 70S OVER MOST OF CENTRAL NC... COOLEST IN THE N/NW PIEDMONT. -VINCENT && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 1200 PM MONDAY... WITH A MOIST/STAGNANT SURFACE AIRMASS IN PLACE...CLEARING ASSOC/W SUBSIDENCE IN THE WAKE OF THE SHORTWAVE TONIGHT IS EXPECTED TO FOSTER THE DEVELOPMENT OF DENSE FOG AND/OR OVERCAST LOW CEILINGS BY 07-10Z TUESDAY MORNING. WITH LITTLE IN THE WAY OF ADVECTION OR MIXING...FOG AND/OR LOW CEILINGS WILL BE RELATIVELY SLOW TO LIFT AND COULD PERSIST FOR MUCH OF THE MORNING. HOWEVER...MODEL GUIDANCE SUGGESTS DIURNAL HEATING/BUOYANT MIXING SHOULD BE SUFFICIENT FOR CLOUD COVER TO LIFT/SCATTER BY ~15Z...WITH MOSTLY SUNNY SKIES DURING THE AFTERNOON. AS A RESULT...EXPECT HIGHS REBOUNDING INTO THE UPPER 70S TO 80-81F. SHORTWAVE ENERGY DIGGING INTO THE UPPER GREAT LAKES TODAY WILL PROGRESS ACROSS THE MID-ATLANTIC NEAR OR JUST NORTH OF THE MASON DIXON LINE TUE NIGHT. UPPER LEVEL FORCING (AND ANY POTENTIAL FOR PRECIPITATION) ASSOC/W THIS FEATURE IS EXPECTED TO REMAIN WELL NORTH OF CENTRAL NC...THOUGH A PERIOD OF CLOUD COVER WILL BE POSSIBLE ~06Z WED IN THE N/NW PIEDMONT. EXPECT LOWS IN THE UPPER 50S. -VINCENT && .LONG TERM /WEDNESDAY THROUGH MONDAY/... AS OF 120 PM MONDAY... FAIR WEATHER IS EXPECTED WEDNESDAY AND THURSDAY AS SFC HIGH PRESSURE...ALONG WITH SHORT WAVE RIDGING ALOFT...SET UP OVER THE AREA. FORECAST SOUNDINGS ARE FAIRLY DRY...ALTHOUGH SUGGEST SOME AFTERNOON SHALLOW CU BENEATH THE MID-LEVEL INVERSION. LOW LEVEL THICKNESS AROUND 1395 SUGGESTS HIGHS A FEW DEGREES ABOVE NORMAL... HIGHS AROUND 80 AND LOWS AROUND 60. THE NEXT WEATHER-MAKER FOR US WILL BE A COLD FRONT THAT`S NOW PROGGED TO SWEEP ACROSS THE STATE LATE ON FRIDAY. FORECAST SOUNDINGS SHOW THE HIGH CLOUDS THICKENING AHEAD OF IT THURSDAY NIGHT...THEN RAPID MID AND LOW LEVEL MOISTURE INCREASE DURING THE AFTERNOON FRIDAY AS SW FLOW IN THE BL INCREASES AHEAD OF THE FRONT. THE END RESULT NOWS LOOKS LIKE A BAND OF SHOWERS JUST AHEAD OF THE FRONT WILL QUICKLY MOVE ACROSS CENTRAL NC PERHAPS DURING THE LATE AFTERNOON AND EVENING HOURS FRIDAY. AS FOR INTENSITY...MOST OF THE PRECIP SHOULD BE OF SHOWER VARIETY...BUT FORECAST SOUNDINGS DO SHOW SOME SKINNY CAPE AND THE POTENTIAL FOR AN ISOLATED THUNDERSTORM... BUT MORE NOTABLY 30-40 KTS OF BULK SHEAR...SO WILL NEED TO KEEP AN EYE ON INSTABILITY TRENDS WITH FUTURE MODELS RUNS. OF COURSE THE TIMING OF THIS WILL BE FINE-TUNED AS WE GET A LITTLE CLOSER...SO IF YOU HAVE OUTDOOR EVENTS FRIDAY AFTERNOON AND/OR EVENING...YOU`LL DEFINITELY WANT TO CHECK BACK LATER THIS WEEK FOR AN UPDATE. NOW LOOKS LIKE THE FRONT WILL BE WELL OFF THE COAST BY SATURDAY MORNING...WITH A COOLING AND DRYING TREND IN ITS WAKE FOR THIS WEEKEND. A LITTLE BREEZY ON SATURDAY IN THE TIGHT PRES GRADIENT AS THE HIGH`S BUILDING IN...BUT OVERALL SHOULD SEE DECENT AMOUNT OF SUNSHINE BOTH DAYS. TEMPS WILL FALL BACK CLOSER TO - OR PERHAPS A LITTLE BELOW- NORMAL BEHIND THE FRONT...HIGHS IN THE MID 70S AND LOWS IN THE MID 50S. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... AS OF 1200 PM MONDAY... 24-HR TAF PERIOD: AN APPROACHING UPPER LEVEL DISTURBANCE WILL RESULT IN OVERCAST MID-LEVEL CEILINGS (8-12 KFT) AND OCCASIONAL SPRINKLES OR LIGHT SHOWERS THIS AFTERNOON. A BRIEF PERIOD OF MVFR CONDITIONS CANNOT BE RULED OUT...HOWEVER...VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH MIDNIGHT. MID-LEVEL CEILINGS WILL CLEAR OUT OVERNIGHT AS THE SHORTWAVE EXITS TO THE EAST...AND FCST SOUNDINGS STRONGLY SUGGEST THAT DENSE FOG OR LIFR/VLIFR CEILINGS WILL DEVELOP BY ~08Z IN ASSOC/W CALM WINDS AND AN AIRMASS THAT IS ALREADY NEARLY SATURATED...PARTICULARLY AT THE RDU/FAY/RWI TERMINALS. IMPROVEMENT MAY BE SLOW TO OCCUR TUE MORNING GIVEN SUCH A STAGNANT LOW-LEVEL PATTERN...AND VFR CONDITIONS APPEAR UNLIKELY TO RETURN PRIOR TO ~14Z. LOOKING AHEAD: VFR CONDITIONS ARE EXPECTED TO PREVAIL TUE/WED AS WEAK HIGH PRESSURE EXTENDS INTO THE REGION FROM THE NORTH. MVFR/IFR CEILINGS MAY DEVELOP EARLY THURSDAY MORNING AS HIGH PRESSURE BEGINS TO SHIFT OFF THE EASTERN SEABOARD. OTHERWISE...THE NEXT CHANCE FOR ADVERSE AVIATION CONDITIONS WILL BE FRI INTO FRI NIGHT AS A STRONG COLD FRONT CROSSES THE CAROLINAS. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...NP AVIATION...VINCENT

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