Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 011718 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 115 PM EDT SAT AUG 1 2015 .SYNOPSIS...A WEAK SURFACE FRONT WILL WAVER OVER EASTERN NORTH CAROLINA THROUGH SUNDAY WHILE WEAK HIGH PRESSURE WILL EXTEND INTO THE PIEDMONT. && .NEAR TERM /THROUGH SUNDAY NIGHT/... AS OF 1050 AM SATURDAY... LIGHT BUT PERSISTENT NLY LOW LEVEL FLOW HAS FILTERED LOWER DEWPOINTS INTO MOST OF THE PIEDMONT OF CENTRAL NC. THIS SLIGHTLY LESS HUMID AIR WILL WORK ITS WAY EAST AND ENCOMPASS SOME OF THE SANDHILLS AND COASTAL PLAIN THIS AFTERNOON. AN AREA OF HIGH PRESSURE AT 850MB (A BIT STRONGER THAN PREDICTED BY THE MODELS) EXTENDS WEST-TO-EAST ACROSS THE REGION THIS MORNING. ALOFT...DRY W-NW FLOW NOTED THANKS TO A BROAD UPPER TROUGH OVER THE EASTERN U.S. PRECIP WATER VALUES ARE BELOW NORMAL OVER MOST OF THE PIEDMONT (ABOUT HALF OF NORMAL) WHILE THE PRECIP WATER VALUES IN THE COASTAL PLAIN AND SANDHILLS ARE CLOSE TO NORMAL. THE RELATIVELY DRY AND STABLE (FOR SUMMER) AIR MASS WILL INHIBIT CONVECTIVE DEVELOPMENT THIS AFTERNOON FOR MOST OF THE REGION. THE EXCEPTION WILL BE THE FAR SE WHERE BETTER MOISTURE AND INSTABILITY MAY TRIGGER AN ISOLATED SHOWER OR STORM LATE THIS AFTERNOON-EARLY EVENING. WHILE IT WILL BE HOT THIS AFTERNOON WITH TEMPS IN THE 90-95 DEGREE RANGE...SFC DEWPOINTS IN THE 50S-LOWER 60S WILL HELP TO TAKE THE EDGE OFF THE HEAT. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 255 AM FRIDAY... LITTLE CHANGE TO THE FORECAST IN THE LONG TERM. THE UPPER LEVEL PATTERN REMAINS FAIRLY STAGNANT WITH UPPER RIDGE OVER THE SOUTHWEST CONUS AND EAST COAST UPPER TROUGH THAT WILL GRADUALLY RELAX THROUGH THE SHORT TERM. AN UPPER LOW AND REFLECTED SURFACE LOW WILL RESIDE NORTH OF THE GREAT LAKES BUT WILL BE OF LITTLE CONSEQUENCE TO THE AREA WHILE SEVERAL SHORTWAVE IMPULSES SKIRT THROUGH THE MID-ATLANTIC STATES...REMAINING MAINLY NORTH OF THE FORECAST AREA. ANY CONVECTION WILL BE DIURNALLY DRIVEN BUT MOISTURE AND PRECIPITABLE WATER VALUES ARE VERY LOW FOR THIS TIME OF YEAR...GENERALLY LESS THAN 1.5 INCHES. A SURFACE HIGH IN THE WESTERN ATLANTIC WILL BRING WEAK SOUTHWESTERLY RETURN FLOW OVER THE AREA. THIS WILL HELP HIGH TEMPERATURES WARM INTO THE MID 90S WITH SOME UPPER 90S POSSIBLE ACROSS THE SOUTH BY TUESDAY AFTERNOON. LOWS MAINLY IN THE UPPER 60S IN THE NW PIEDMONT TO LOWER 70S ELSEWHERE. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 255 AM SATURDAY... WEDNESDAY AND WEDNESDAY NIGHT: FORECAST BECOMES LESS CONFIDENT ON WEDNESDAY AS MODELS SHOW A SHORTWAVE WEST OF THE AREA THAT HELPS TO CAUSE A SOUTHWARD PUSH IN THE UPPER LEVEL PATTERN. THE EXACT LOCATION OF THE SHORTWAVE IS IN QUESTION WITH THE GFS DEVELOPING A STRONG WAVE IN THE OHIO VALLEY BUT THE ECMWF IS WEAKER WITH THE FEATURE AND MUCH FURTHER SOUTH...ACROSS THE TENNESSEE VALLEY. THUS THE ECMWF LENDS TO A LITTLE GREATER FORCING ACROSS CENTRAL NC FOR AFTERNOON CONVECTION ON WEDNESDAY. IN ADDITION...HIGH PRESSURE IN THE ATLANTIC IS CENTERED A LITTLE FURTHER SOUTH IN THE ECMWF AS WELL AND ALLOWS A SURFACE TROUGH ASSOCIATED WITH THE CANADIAN LOW TO BECOME MORE ACTIVE OVER THE AREA DURING THE AFTERNOON AND SERVE AS A CATALYST FOR CONVECTION. BEST CHANCES FOR ANY SHOWER AND THUNDERSTORM ACTIVITY WOULD BE ACROSS THE NORTH AND IN EASTERN COUNTIES. HIGHS IN THE MID 90S AND LOWS IN THE LOW 70S. THURSDAY AND FRIDAY: WITH UNCERTAINTIES ALREADY BUILT INTO WEDNESDAYS FORECAST...THURSDAY AND FRIDAY ONLY BECOMES MORE UNCERTAIN WITH REGARD TO THE EVOLUTION OF THE SHORTWAVE TO THE WEST...THE VERY LATEST RUN OF THE ECMWF HAS FALLEN MORE IN LINE WITH THE TIMING OF THE GFS FOR A THURSDAY NIGHT INTO FRIDAY PASSAGE OF THE SHORTWAVE...GFS SOLUTION STILL SLIGHTLY NORTHWARD OF THE ECMWF. REGARDLESS...MOISTURE INCREASES SIGNIFICANTLY BACK OVER 2 INCHES. THURSDAY AFTERNOON/EVENING WILL HAVE THE BEST CHANCE FOR CONVECTION WITH MODELS SHOWING ACTIVITY LINGERING THROUGH FRIDAY AFTERNOON AS WELL BEFORE THE WAVE FINALLY EXITS THE COAST OVERNIGHT FRIDAY NIGHT INTO SATURDAY MORNING. EXTRA CLOUDS AND PRECIPITATION WILL HELP TEMPERATURES DROP BACK AT LEAST INTO THE LOW 90S IF NOT UPPER 80S BY THE END OF THE WEEK. LOWS MAINLY IN THE LOWER 70S. && .AVIATION /18Z SATURDAY THROUGH WEDNESDAY/... AS OF 115 PM SATURDAY... HIGH CONFIDENCE OF VFR CONDITIONS ACROSS JUST ABOUT ALL OF CENTRAL NC FOR THE NEXT 24 HOURS. THE ONLY EXCEPTIONS WILL BE AN EXTREMELY SMALL CHANCE OF AN ISOLATED RAIN SHOWER THIS AFTERNOON IN THE SOUTHEASTERN COASTAL PLAIN (SOUTHEAST OF KGSB AND KFAY) AND A CHANCE OF SOME DAYBREAK STRATUS/FOG AT KFAY AND KRWI. THE RAIN CHANCES ARE SO SMALL TO PRECLUDE ANY MENTION OF RESTRICTIONS IN THE TAFS. THE THREAT OF MVFR/IFR STRATUS/FOG IS LIMITED WITH ONLY A SUBSET OF GUIDANCE INDICATING IT...MORE EMPHATICALLY AT KFAY. PROBABILITIES ARE LOW BUT STILL CONCERNED ABOUT THE OCCURRENCE...SO WILL INCLUDE A SHORT TEMPO GROUP TO COVER IT. OTHERWISE...SKIES WILL BE MAINLY CLEAR WITH JUST SOME VFR CUMULUS THIS AFTERNOON AT 4.5-6KFT AND PERHAPS SOME SCT FAIR WEATHER CUMULUS AND CIRRUS ON SUNDAY WITH VFR CONDITIONS. SURFACE WINDS WILL BE LIGHT THROUGH THE PERIOD...MAINLY FROM THE NORTHWEST TO NORTHEAST ALTHOUGH A PERIOD OF LIGHT SOUTHERLY WINDS IS POSSIBLE AT KFAY AND KRWI LATE TONIGHT AS THE SEA BREEZE BOUNDARY SHIFTS INLAND. LIGHT MAINLY NORTHERLY WINDS ARE EXPECTED AGAIN ON SUNDAY. LOOKING BEYOND 18Z SUN AFTERNOON... VFR CONDITIONS ARE EXPECTED TO DOMINATE THE WEATHER ACROSS CENTRAL NC THROUGH MID WEEK. SOME PATCHY MORNING STRATUS AND FOG IS POSSIBLE ON MONDAY AND TUESDAY MORNINGS. THE THREAT OF SHOWERS OR THUNDERSTORMS WILL BE VERY LOW THROUGH WEDNESDAY AND INCREASE SOMEWHAT ON THURSDAY. -BLAES && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...ELLIS LONG TERM...ELLIS AVIATION...BLAES

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