Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281722 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 122 PM EDT THU AUG 28 2014 .SYNOPSIS...A BACK DOOR COLD FRONT WILL TRACK SOUTHWARD FROM VIRGINIA INTO NORTH CAROLINA THROUGH TONIGHT...THEN STALL OUT ACROSS THE REGION THROUGH FRIDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1035 AM THURSDAY... UPPER AIR ANALYSES FROM 12Z TODAY SHOW HIGH PRESSURE CENTERED OVER THE MISSISSIPPI RIVER VALLEY WITH THE RIDGE AXIS SANDWICHED BETWEEN A LOW OVER NE AND A LOW WELL TO THE NE OF NEW ENGLAND. THE H85 FRONT EXTENDS FROM APPROX NYC WSW THROUGH OH AND INTO IA. EXPECT THE HIGH TO DRIFT EAST TODAY...WITH THE RIDGE DAMPENING AND THE FRONT SLOWLY SLIDING SOUTH TOWARD THE NC/VA BORDER. A WEAK DISTURBANCE AT H5 TRAVERSING THE RIDGE OVER VA ALONG THE FRONT MAY HELP GENERATE SOME ISOLATED SHOWER ACTIVITY LATER THE AFT AND EVE. AT THE SURFACE...THE BACKDOOR COLD FRONT WILL APPROACH THE AREA THROUGH THIS EVENING... STALLING AROUND THE NC/VA BORDER OVERNIGHT. AS LOW-MID LEVEL MOISTURE IS ADVECTED IN AHEAD OF THE FRONT WILL SEE DEWPOINTS INCREASE ACROSS THE NORTH AND PW`S INCREASING FROM ABOUT 1.50" TO 1.75" THIS EVENING. THE FORECAST INSTABILITY DIFFERS BETWEEN THE NAM AND GFS...WITH THE NAM FORECASTING MLCAPE OF 1000-1500 J/KG WHILE THE GFS ONLY HAS AROUND 500 J/KG. MOST OF THE HI-RES CONVECTION ALLOWING MODELS ARE GENERATING SOME SHOWERS AROUND 21Z THIS AFTERNOON...MAINLY ACROSS THE NORTHERN HALF OF THE REGION...DRIFTING SOUTH THROUGH THE EVENING. WILL CONTINUE TO INDICATE THE CHANCE FOR CONVECTION LATER TODAY AND TONIGHT...BUT COVERAGE IS NOT EXPECTED TO BE GREAT. HIGHS TODAY IN THE LOW TO MID 90S EXPECTED...WITH LOWS TONIGHT AROUND 70 DEGREES. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 315 AM THURSDAY... RIDGING ALOFT WILL PRECLUDE MUCH IN THE WAY OF UPPER LEVEL FORCING FRI/FRI NIGHT...HOWEVER...THE FRONTAL ZONE STALLING OVER THE REGION WILL INTRODUCE A LARGE DEGREE OF UNCERTAINTY WITH REGARD TO TEMPERATURES AND PRECIP CHANCES...INCLUDING A POTENTIAL FOR WEAK HYBRID CAD AND ELEVATED CONVECTION. AT THIS TIME WILL MAKE LITTLE CHANGE TO THE PREVIOUS FORECAST...THOUGH ADDITIONAL MODIFICATIONS MAY BE NEEDED PER FURTHER MODEL/DATA ANALYSIS THIS MORNING. THE MOST LIKELY CHANGES WOULD BE A DROP IN HIGH TEMPS ACROSS THE N/NW PIEDMONT AND AT LEAST A LOW CHANCE (20%) OF CONVECTION IN MOST LOCATIONS...POSSIBLY EVEN FRI NIGHT WHEN FCST SOUNDINGS SUGGEST A WEAK NOCTURNAL WARM ADVECTION REGIME IN THE PRESENCE OF PLENTIFUL LOW-LEVEL MOISTURE AND ELEVATED INSTABILITY. -VINCENT && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 255 AM THURSDAY... UPPER RIDGING IS EXPECTED TO RESIDE OVER THE SOUTHEASTERN STATES SAT- MON... THEN BUILD WESTWARD INTO THE SOUTHERN PLAINS NEXT WEEK. GUIDANCE WAS FASTER THIS RUN WITH THE HEIGHT FALLS AND THE ATTENDANT SURFACE COLD FRONT NOW SLATED INTO THE REGION FROM THE NORTHWEST ON WEDNESDAY AFTERNOON AND EVENING. HIGHLIGHTS IN THE LONG TERM WILL BE INCREASING HEAT...HUMIDITY... AND THE CHANCES OF SHOWERS AND THUNDERSTORMS. THIS PATTERN WILL LIKELY LAST THROUGH MID-WEEK WHEN A COLD FRONT IS NOW SLATED TO ARRIVE WED PM. THE FRONT SHOULD SETTLE SOUTH OF THE STATE THURSDAY ALLOWING FOR COOLING FROM THE NE AGAIN THU-FRI. UNTIL THEN... EXPECT PARTLY SUNNY TO PARTLY CLOUDY SKIES THIS WEEKEND. A CHANCE OF PM THUNDERSTORMS ESPECIALLY BY SUNDAY. HIGHS RETURN TO NEAR NORMAL (86-92) BOTH SAT-SUN. LOWS 65-70. MON-WED... A CHANCE OF MAINLY AFTERNOON AND EVENING THUNDERSTORMS EACH DAY... WITH THE BEST CHANCE EXPECTED WEDNESDAY. HIGHS 86-92. LOWS IN THE UPPER 60S TO MID 70S. TEMPS WILL COOL BACK INTO THE LOWER TO MID 80S BY THURSDAY WITH THE NE FLOW LEVEL FLOW. ALSO... THE CHANCE OF THUNDERSTORMS WILL SHIFT WITH THE FRONT INTO FAR SE NC AND SC. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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AS OF 120 PM THURSDAY... 24-HOUR TAF PERIOD: EXPECT VFR CONDITIONS FOR THE REMAINDER OF TODAY...WITH A SLIGHT CHANCE FOR SOME ISOLATED CONVECTION ACROSS THE NORTH (KINT/KGSO/KRDU/KRWI) BETWEEN 21Z TODAY AND 06Z FRIDAY AS A BACKDOOR COLD FRONT APPROACHES FROM THE NORTH. WITH THE COVERAGE AND CONFIDENCE BEING LIMITED...WILL NOT INCLUDE IN TAFS BUT MAY NEED TO AMEND SHOULD SHOWERS DEVELOP OVER THE NEXT SEVERAL HOURS. THE INCREASING MOISTURE AHEAD/SOUTH OF THE FRONT...MAINLY ACROSS THE NORTHERN HALF OF THE AREA...COULD RESULT IN SOME LOW STRATUS DEVELOPING BETWEEN 10Z AND 12Z FRIDAY MORNING...WITH CIGS OF 500- 1500 FT POSSIBLE. WITH THE FRONT STALLING ALONG THE NC/VA BORDER FRIDAY...CLOUDS COULD REMAIN BROKEN TO SCATTERED AROUND 3 KFT THROUGH THE DAY AT THE AFOREMENTIONED TERMINALS. FOR NOW WILL KEEP CIGS SCATTERED BUT THERE IS THE CHANCE FOR THE NORTHERN TERMINALS TO HAVE HIGH END MVFR TO LOW END VFR CIGS THROUGH THE REMAINDER OF THE 24 HOUR TAF PERIOD. THE CHANCE FOR ISOLATED CONVECTION IN THE VICINITY OF THE FRONT WILL ALSO BE PRESENT...BUT AGAIN CONFIDENCE IS STILL LOW AT THIS TIME. LOOKING AHEAD: CONFIDENCE REMAINS BELOW NORMAL IN THIS PERIOD. EXPECT THE FRONT TO SLOWLY LIFT NNE AWAY FROM THE REGION FRIDAY NIGHT...WITH AN INCREASE IN SOUTHERLY RETURN FLOW INTO THE REGION... INCREASING LOW TO MID LEVEL MOISTURE THROUGH THE WEEKEND. THIS WILL YIELD INCREASED CHANCES FOR LOW CEILINGS IN THE PRE-DAWN HOURS THROUGH EARLY NEXT WEEK. FOR NOW EXPECT SATURDAY TO BE DRY...WITH INCREASING CHANCES FOR CONVECTION...MAINLY IN THE AFT/EVE...SUNDAY NIGHT THROUGH TUESDAY.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...KC SHORT TERM...VINCENT LONG TERM...PWB AVIATION...KC

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