Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 211712 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 115 PM EDT TUE OCT 21 2014 .SYNOPSIS....A COLD FRONT WILL CROSS CENTRAL NC LATE THIS AFTERNOON AND THIS EVENING. AN UPPER LEVEL LOW WILL SETTLE SOUTHEAST ACROSS THE MIDDLE ATLANTIC REGION TONIGHT...AND LINGER OVER THE REGION THROUGH WEDNESDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1100 AM TUESDAY... A COLD FRONT CROSSING THE OH AND TN VALLEYS LATE THIS MORNING WILL CROSS CENTRAL NC LATE THIS AFTERNOON AND TONIGHT. STEADY SW FLOW AHEAD OF THIS FEATURE ALONG WITH AMPLE SUNSHINE WILL PUSH TEMPERATURES INTO THE LOW-MID 70S NORTH...AND MID-UPPER 70S SOUTH. AS THE FRONT GETS CLOSER...MAY SEE AN INCREASE IN CLOUDINESS...MAINLY ACROSS THE NORTH HALF. WHILE MOISTURE IS LIMITED (AS PER 12Z GSO SOUNDING)...ENOUGH LIFT GENERATED BY THE FRONT AND ATTENDANT S/W MAY CAUSE A STRAY SHOWER OR A FEW SPRINKLES ACROSS THE FAR NORTHERN-NE COUNTIES LATE THIS AFTERNOON THROUGH THIS EVENING. NW WINDS BEHIND THE FRONT WILL BE BLUSTERY AT TIMES AS LOW LEVEL COLD AIR ADVECTION COMMENCES. MIN TEMPS MID 40S WEST TO UPEPR 40S EAST-SE. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... AS OF 340 AM TUESDAY... THE UPPER LOW WILL DRIFT ACROSS THE CHESAPEAKE BAY AND DELMARVA ON WED...THEN LIFT SLOWLY UP THE MIDDLE ATLANTIC COAST WED NIGHT AND BEYOND. ASSOCIATED SURFACE COASTAL LOW PRESSURE WILL DEEPEN BY ABOUT 10 MB (FROM JUST UNDER 1010 MB TO JUST UNDER 1000 MB) FROM 12Z WED TO 12Z THU...AS IT TOO LIFTS UP THE MIDDLE ATLANTIC COAST. THE COLDEST TEMPERATURES/STEEPEST LAPSE RATES ALOFT ASSOCIATED WITH THE UPPER LOW...THE FORMER IN EXCESS OF MINUS 20 C AND THE LATTER BETWEEN 6.5-7 C/KM...WILL CONSEQUENTLY BRUSH THE NORTHEAST PIEDMONT AND NORTHERN-CENTRAL COASTAL PLAIN...AND RESULT IN A CHANCE OF "INSTABILITY" SHOWERS OR SPRINKLES WITH DIURNAL HEATING. IT WILL OTHERWISE BE COOLER AND BREEZY...WITH NORTHWESTERLY DAYTIME WIND GUSTS UP TO 25 MPH OWING TO THE DEEPENING COASTAL LOW...AND HIGHS IN THE 60S. CLEARING AND SIMILARLY COOLER WED NIGHT...WITH LOWS MOSTLY IN THE LOWER TO MIDDLE 40S. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 320 AM TUESDAY... DEEP NORTHWESTERLY FLOW WILL CONTINUE ON THURSDAY BETWEEN THE UPPER LOW DRIFTING NORTHEAST ALONG THE NEW ENGLAND COAST AND A SHORTWAVE RIDGE OVER THE MISSISSIPPI RIVER VALLEY. LOW-LEVEL THICKNESSES ARE FORECAST TO BE AROUND 1335M THURSDAY MORNING...AND FULL INSOLATION DURING THE AFTERNOON SUPPORTS HIGHS IN THE 63-68 RANGE. THE ALREADY LOW AMPLITUDE RIDGE WILL BREAK DOWN ON THURSDAY NIGHT INTO FRIDAY AS ANOTHER WAVE DIVES DOWN THE BACKSIDE OF THE DEPARTING UPPER LOW AND CROSSES NC FRIDAY NIGHT. WE SHOULD SEE SOME HIGH CLOUDS SPREAD ACROSS THE AREA LATE THURSDAY NIGHT AND FRIDAY AS AN UPPER JET STRENGTHENS OVER THE SOUTHEAST AHEAD OF THE TROUGH...THOUGH ITS NOT CLEAR HOW THICK THE CLOUD COVER WILL BE. HAVE NUDGED THURSDAY NIGHT LOWS UP A COUPLE DEGREES INTO THE MID 40S. HIGHS FRIDAY IN THE MID/UPPER 60S. MODELS HAVE TRENDED TOWARD A MUCH MORE COMPACT AND CLOSED OFF WAVE WITH A STRONG SHOT OF DCVA FRIDAY NIGHT...BUT WITH NO QPF EAST OF THE MOUNTAINS AS IT ENCOUNTERS A VERY DRY AIRMASS OVER CENTRAL NC. THE PROGRESSIVE NATURE OF THE TROUGH LOOKS LIKE IT WILL ALSO KEEP A POTENTIAL (SUB)TROPICAL SYSTEM AND ASSOCIATED MOISTURE IN THE CARIBBEAN WELL TO OUR SOUTH. THUS THE FORECAST WILL BE DRY THROUGH THE PERIOD. ONCE THE TROUGH PASSES...THE ECMWF AND GFS ROUGHLY AGREE THAT UPPER RIDGING WILL BUILD ACROSS THE SOUTHERN US...WITH THICKNESSES CLIMBING BACK TOWARD 1370M...WHICH IS SLIGHTLY ABOVE NORMAL. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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AS OF 115 PM TUESDAY... A COLD FRONT WILL CROSS CENTRAL NC LATE THIS AFTERNOON THROUGH EARLY THIS EVENING. THE FRONTAL PASSAGE WILL BE NOTED BY THE SURFACE WINDS VEERING FROM THE WEST-SW TO THE N-NW WITH SUSTAINED WINDS 8-12KTS AND GUSTS AROUND 20KTS. A LOW END VFR CEILING 3500-5000FT MAY ALSO ACCOMPANY THE FRONT BETWEEN 20Z-02Z...MAINLY ACROSS THE NORTHERN COUNTIES IN VICINITY OF THE TRIAD TERMINALS AS WELL AS KRDU AND KRWI. ENOUGH LIFT MAY OCCUR TO PRODUCE A SHOWER OR TWO BUT CONFIDENCE THAT A SHOWER WILL OCCUR IN VICINITY OF A TERMINAL IS TOO LOW TO MENTION IN THE AERODROME FORECAST AT THIS TIME. SKIES ARE EXPECTED TO TEMPORARILY CLEAR AFTER 04Z. FOR WEDNESDAY...BLUSTERY N-NW WINDS WILL PERSIST WITH GUSTS 18-23KTS HIGHLY PROBABLE. THE CLOSE PROXIMITY OF AN UPPER LEVEL LOW OVER THE NORTHERN MID ATLANTIC WILL CAUSE PERIODS OF CLOUDINESS WITH CEILINGS 3500-5000FT IN VICINITY OF KRDU AND KRWI. A SHOWER OR TWO MAY OCCUR IN VICINITY OF KRWI...BUT MORE SO NEAR THE VIRGINIA BORDER. A HIGH PROBABILITY OF VFR CONDITIONS WILL PERSIST THURSDAY THROUGH SUNDAY. THE UPPER LEVEL LOW IS PROJECTED TO LIFT TO THE NE THURSDAY AND THURSDAY NIGHT. THIS WILL ALLOW AN AREA OF HIGH PRESSURE TO BUILD THEN SETTLE OVER CENTRAL NC THROUGH THE WEEKEND.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...MWS LONG TERM...BLS AVIATION...WSS

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