Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 280654 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 255 AM EDT THU AUG 28 2014 .SYNOPSIS...WEAK HIGH PRESSURE WILL REMAIN CENTERED OVER THE SOUTHERN APPALACHIANS AHEAD OF A COLD FRONT THAT WILL SETTLE SOUTH INTO CENTRAL NC LATE THU AND THU NIGHT. && .NEAR TERM /THROUGH THURSDAY NIGHT/... AS OF 1010 PM WEDNESDAY... HIGH PRESSURE OVER THE REGION CONTINUES TO WEAKEN AND GIVE WAY TO A COLD FRONT APPROACHING FROM THE NORTH AND WEST. STARTING TO SEE SOME LOW-LEVEL MOISTURE ADVECTION AHEAD OF THE FRONT ACROSS VIRGINIA...BUT THE FEW AREAS OF SHOWERS ALONG THE FRONT...WHICH STRETCHES ACROSS KY/WV/PA...ARE EXPECTED TO DIMINISH AS THEY CROSS THE MOUNTAINS OVERNIGHT. NOT A LOT OF HIGH CLOUDS AHEAD OUT AHEAD OF THE FRONTAL ZONE...SO IT LOOKS LIKE MOST AREAS SHOULD REMAIN MOSTLY CLEAR WITH LIGHT WEST-NORTHWESTERLY AS HURRICANE CRISTOBAL PASSES WELL OFFSHORE. MAY SEE SOME RURAL AREAS IN THE UPPER 50S...BUT WITH DEWPOINTS BEGINNING TO CREEP UP FROM THE NORTH...SHOULD SEE MORE LOWER 60S THAN NIGHTS PAST. THE COLD FRONT WILL SLIP INTO THE NORTHERN PORTIONS OF THE AREA THURSDAY AFTERNOON. MODELS DO INDICATE SOME MOISTURE POOLING ALONG THE FRONT...HOWEVER OVERALL MOISTURE CONTENT IS EXPECTED TO REMAIN RATHER LOW AS THE LOW LEVEL FLOW TAKES ON A WESTERLY COMPONENT. THIS NEVERTHELESS...GIVEN THE SLIGHTLY INCREASED MOISTURE AND CONVERGENCE ALONG THE FRONT...THERE COULD BE SOME ISOLATED CONVECTION THAT DEVELOPS DURING THE AFTERNOON HOURS...MAINLY ACROSS THE NORTHERN HALF OF THE FORECAST AREA. THE SEVERE THREAT IS RATHER MINIMAL GIVEN THAT DEEP LAYER SHEAR VALUES ARE PROGGED TO STAY AROUND OR BELOW 20 KNOTS. HOWEVER... THE NAM CONTINUES TO SHOW MORE IN THE WAY OF INSTABILITY (ALTHOUGH IT STILL SEEMS OVERDONE GIVEN THE LOWER DEWPOINTS WITHIN THE WESTERLY FLOW). NEVERTHELESS...THE GFS DOES SHOW SOME INSTABILITY AND IF A STORM IS ABLE TO GROW DEEP ENOUGH... IT COULD PRODUCE A STRONG WIND GUST GIVEN THE DRY SUB-CLOUD LAYER. LOW LEVEL THICKNESS VALUES ARE PROGGED TO INCREASE ANOTHER 10-15M ON THURSDAY...WHICH SHOULD TRANSLATE INTO HIGHS SURGING INTO THE LOW TO MID 90S (ESPECIALLY WITH THE DRY DOWNSLOPE WESTERLY FLOW). THE FRONT IS EXPECTED TO STALL ACROSS THE NORTHERN PORTIONS OF THE FORECAST THURSDAY NIGHT. THERE COULD BE AN ISOLATED SHOWER OR TWO OVERNIGHT...BUT CHANCES ARE RATHER LOW. MORE IN THE WAY OF CLOUDS AND MOISTURE SHOULD RESULT IN MILDER OVERNIGHT LOW (RELATIVE TO PREVIOUS NIGHTS)...WITH MOSTLY UPPER 60S TO NEAR 70 DEGREES EXPECTED. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 250 PM WEDNESDAY... SUBTROPICAL RIDGE WILL STRENGTHEN OVER THE REGION ON FRIDAY. DIABATIC HEATING FROM STRONG INSOLATION WILL EVENTUALLY WASH OUT THE STALLED FRONTAL ZONE INVOF THE NC/VA BORDER...BUT NOT BEFORE SERVING AS A FOCUS FOR ISOLATED/SLIGHT CHANCE CONVECTION FRIDAY AFTERNOON. LOW-LEVEL THICKNESSES AND H8 (1430M AND 18-19C RESPECTIVELY)ARE PROGGED TO BE ON PAR TO THURSDAY. HIGHS IN THE LOWER 90S. LOWS IN THE UPPER 60S TO LOWER 70S. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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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.
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&& .AVIATION /06Z THURSDAY THROUGH MONDAY/... AS OF 135 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 LATE TODAY/TONIGHT...OR ROUGHLY FROM 21Z THIS AFT THROUGH 06Z FRI MORNING...WITH THE BEST CHANCE ALONG OR JUST SOUTH OF THE VIRGINIA BORDER...INCLUDING 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...MWS NEAR TERM...KRD/BLS SHORT TERM...CBL LONG TERM...PWB AVIATION...VINCENT

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