Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 271854 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 254 PM EDT WED AUG 27 2014 .SYNOPSIS...
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HIGH PRESSURE WILL EXTEND SOUTHWARD INTO THE REGION THROUGH THIS EVENING. A BACK DOOR COLD FRONT WILL SETTLE SOUTH INTO CENTRAL NC THU AND THU NIGHT.
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&& .NEAR TERM /THROUGH THURSDAY NIGHT/...
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AS OF 250 PM WEDNESDAY... SURFACE HIGH PRESSURE OVER THE AREA WILL BEGIN TO GET SHUNTED TO SOUTH AND WEST TONIGHT AS A BACKDOOR COLD FRONT APPROACHES THE AREA. NEVERTHELESS...ANOTHER PLEASANT NIGHT (AT LEAST FOR LATE AUGUST) IS EXPECTED AS TEMPS FALL INTO LOW TO MID 60S (MAYBE SOME UPPER 50S) UNDER MOSTLY CLEAR SKIES...LIGHT WINDS AND RELATIVELY DRY AIR. 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.
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&& .SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
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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.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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AS OF 250 PM WEDNESDAY... SUBTROPICAL RIDGE/BERMUDA HIGH PRESSURE OVER THE SOUTHEAST US WILL REMAIN A FORMIDABLE PLAYER INTO THE WEEKEND WITH WARM AIR ALOFT ACTING TO LARGELY SUPPRESS CONVECTION ON SATURDAY WITH A CONTINUATION OF ABOVE NORMAL TEMPERATURES INTO THE LOWER TO MID 90S SATURDAY AFTERNOON. BY SUNDAY...AS THE SUBTROPICAL RIDGE AXIS BEGINS TO SLIDE EASTWARD AND OUT OVER THE WESTERN ATLANTIC...RAIN CHANCES WILL BEGIN TO INCREASE ACROSS WESTERN PORTIONS OF THE STATE VIA RING OF FIRE CONVECTION PATTERN. RAIN CHANCES RETURN CWA WIDE MONDAY AND TUESDAY...UNDER WEAKENING HEIGHTS AND COOLING TEMPS ALOFT WITH SCATTERED DIURNAL CONVECTION FIRING ALONG A THERMAL TROUGH IN PLACE EAST OF THE MOUNTAINS. THE GFS REMAINS ON THE FAST SIDE OF MODEL GUIDANCE WITH BRINGING A COLD FRONT THROUGH THE AREA TUESDAY NIGHT/EARLY WEDNESDAY...WHILE THE EC IS NEARLY A FULL DAY BEHIND. FOR NOW WILL GO WITH THE SLOWER TIMING...KEEPING CHANCE POPS THROUGH WEDNESDAY. HIGHS EARLY NEXT WEEK IN THE UPPER 80S TO LOWER 90S.
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&& .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... AS OF 130 PM WEDNESDAY... VFR CONDITIONS ARE EXPECTED TO PERSIST THROUGH THE CURRENT TAF PERIOD. SOMEWHAT HIGHER NORTH/NORTHEASTERLY WINDS THIS AFTERNOON (STILL JUST AROUND 10 KNOTS AND MAINLY ACROSS THE EAST) WILL SUBSIDE THIS EVENING AND BECOMING LIGHT AND VARIABLE TO NEAR CALM. HOWEVER...THE LOW LEVEL FLOW WILL BECOME MORE NORTHWESTERLY TO WESTERLY OVERNIGHT AND THIS SHOULD PREVENT MUCH IN THE WAY OF FOG AND/OR STRATUS DEVELOPMENT TONIGHT. THEN...AN APPROACHING COLD FRONT MAY RESULT IN INCREASING MID/HIGH CLOUDS LATE THURSDAY MORNING/EARLY AFTERNOON...MOSTLY ACROSS THE NORTH. OUTLOOK...AS THE AFOREMENTIONED COLD FRONT SLIPS INTO AREA THURSDAY AFTERNOON...IT COULD TRIGGER A FEW SHOWERS OR THUNDERSTORMS (MAINLY ACROSS THE NORTHERN HALF OF THE FORECAST AREA). IN ADDITION...THE FRONT WILL LINGER ACROSS THE AREA INTO FRIDAY AND AGAIN COULD TRIGGER SOME ISOLATED SHOWERS/STORMS. THEN...PATCHY EARLY MORNING FOG DEVELOPMENT WILL INCREASE INTO THE WEEKEND AS THE LOW LEVEL FLOW BECOMES MORE SOUTHERLY...THUS INCREASING THE MOISTURE. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BSD/MWS NEAR TERM...KRD SHORT TERM...CBL LONG TERM...CBL AVIATION...KRD

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