Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281435 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1035 AM 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 /12Z THURSDAY THROUGH MONDAY/... AS OF 715 AM THURSDAY... 24-HR TAF PERIOD: VFR CONDITIONS AND CALM OR LIGHT AND VARIABLE WINDS WILL PREVAIL THROUGH THE MAJORITY OF THE TAF PERIOD. THE ONLY POSSIBLE EXCEPTION WILL BE A POTENTIAL FOR ISOLD TO SCT CONVECTION AT THE LEADING EDGE OF A BACKDOOR COLD FRONT MOVING SOUTH/SE INTO THE REGION THIS AFT/EVE INTO TONIGHT...OR ROUGHLY FROM 21Z THIS AFT THROUGH 06Z FRI MORNING...WITH THE BEST CHANCE FROM THE VA BORDER SOUTH TO THE INT/GSO/RDU/RWI TERMINALS. LOOKING AHEAD: THE FRONT WILL STALL AND SLOWLY BEGIN TO DISSIPATE OVER THE REGION FRI/FRI NIGHT. CONFIDENCE REMAINS BELOW NORMAL IN THIS PERIOD...AND IT IS POSSIBLE THAT VFR CONDITIONS PREVAIL EVERYWHERE FRI/FRI NIGHT...OR THAT SUB-VFR CONDITIONS ASSOC/W LOW CEILINGS AND ISOLD ELEVATED CONVECTION COULD BE PRESENT LATE FRI/FRI NIGHT. OTHERWISE...CLIMATOLOGICAL CONDITIONS APPEAR LIKELY SAT THROUGH EARLY NEXT WEEK...I.E. A POTENTIAL FOR ISOLD AFT/EVE CONVECTION AND EARLY MORNING FOG/STRATUS. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...KC SHORT TERM...VINCENT LONG TERM...PWB AVIATION...VINCENT

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