Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 220551 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1250 AM EST SAT NOV 22 2014 .SYNOPSIS...
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HIGH PRESSURE REMAINS OVER THE REGION TODAY INTO TONIGHT. A STRONG LOW PRESSURE MOVING FROM THE SOUTHERN PLAINS INTO THE GREAT LAKES SUNDAY WILL SPREAD MOISTURE OVER THE REGION DURING THE DAY ON SUNDAY. ANOTHER COLD FRONT WILL MOVE EAST ACROSS MUCH OF THE AREA MONDAY...WITH LOW PRESSURE MOVING ALONG THE SOUTHEAST COAST TUESDAY INTO WEDNESDAY.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 940 PM FRIDAY... THE CENTER OF A STRONG (1035 MB) COLD HIGH PRESSURE WAS LOCATED OVER VIRGINIA THIS EVENING. THE HIGH PRESSURE IS FORECAST TO DRIFT DIRECTLY OVER NC BY 12Z/SAT. VERY DRY AND CLEAR AIR WAS IN PLACE WITH DEW POINTS IN THE 10-15 RANGE. WINDS HAD ALREADY DIED OFF TO NIL OVER THE NORTHERN AND WESTERN ZONES... AND WILL DO SO BY MIDNIGHT OR SLIGHTLY THEREAFTER. WITH 900 PM READINGS ALREADY IN THE LOWER 20S AT ROXBORO RANGING INTO THE MID 30S IN THE SOUTHEAST COASTAL PLAIN... EXPECT LOWS BY DAYBREAK TO FALL TO BETWEEN 15-20 NORTH TO LOWER 20S SOUTHEAST. CLEAR SKIES ARE EXPECTED. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 230 PM FRIDAY... LOW LEVEL THICKNESSES WILL RISE APPROX 30 METERS OR SO FROM TODAY... YIELDING HIGH TEMPERATURES ABOUT 3 DEGREES OR SO HIGHER...LOW TO MID 50S ACROSS THE AREA. WITH THE HIGH OVERHEAD...WINDS SHOULD REMAIN RELATIVELY LIGHT AROUND 5 KTS OR SO AND OUT OF THE SOUTH OR SOUTHWEST. THE HIGH WILL FLATTEN OUT AND SLOWLY DRIFT OFF THE NC COAST...ALLOWING A WARM FRONT TO MOVE INTO THE AREA FROM THE SOUTH OVERNIGHT AS WINDS BECOME MORE SOUTHEASTERLY TO EASTERLY BY 12Z SUNDAY. WITH THE MODELS HAVING SLOWED THE APPROACHING SYSTEM DOWN... ANY PRECIPITATION SHOULD HOLD OFF UNTIL AFTER 12Z. HOWEVER...THE HIGH CLOUDS THAT ARE EXPECTED TO BUILD IN ON SATURDAY WILL STICK AROUND OVERNIGHT AND AS LOW LEVEL MOISTURE INCREASES SO WILL THE CHANCE FOR LOW STRATUS TO DEVELOP TOWARD DAYBREAK SUNDAY. WITH THE INFLUX OF WARM MOIST AIR OVERNIGHT...EXPECT LOWS IN THE LOW TO MID 30S TO OCCUR WITHIN A COUPLE HOURS OF MIDNIGHT...BEFORE GRADUALLY INCREASING A FEW DEGREES BY SUNRISE. && .LONG TERM /SUNDAY THROUGH FRIDAY/... AS OF 230 PM FRIDAY... FOR DAYTIME SUNDAY...LITTLE CHANGE IN FORECAST THINKING FROM RECENT CYCLES...WITH THE PRIMARY FEATURE BEING A FAST-MOVING SOUTHERN STREAM S/W TROUGH THAT WILL MOVE FROM TX IN THE MORNING NE TO THE OH VALLEY BY EVENING. INCREASING SOUTHERLY FLOW AHEAD OF THIS VIGOROUS SYSTEM WILL TRANSPORT ABUNDANT MOISTURE NORTHWARD ACROSS OUR AREA AS NOTED IN FORECAST SOUNDINGS SHOWING PWAT INCREASING FROM AROUND 1/2 INCH AT DAWN TO 1.5 TO 1.75 INCHES (HIGHEST EAST) BY 11 PM PRIOR TO TROUGH PASSAGE. WITH INCREASING SW FLOW ABOVE A LINGERING SFC RIDGE...RESULTING ISENTROPIC LIFT WILL PRODUCE THICKENING/LOWERING CLOUDS AND LIGHT RAIN GRADUALLY DEVELOPING FROM SW TO NE AS THE DAY PROGRESSES. AS FOR TIMING THE ONSET OF LIGHT RAIN...RIGHT NOW LOOKS LIKE IT MAY BEGIN ACROSS OUR SOUTHERN/WESTERN ZONES BY EARLY TO MID AFTERNOON...THE TRIANGLE REGION BY MID-LATE AFTERNOON...THEN OUR NORTHERN/VA-BORDER ZONES BY SUNSET. TEMPS WILL CLIMB THROUGH THE 50S DURING THE DAYTIME...REMAINING COOLEST NW. DURING THE EVENING SUNDAY...RAIN WILL INCREASE IN COVERAGE AND INTENSITY AS THE MID-LEVEL TROUGH AXIS APPROACHES. AHEAD OF THE TROUGH AXIS...A SFC WARM FRONT IS PROGGED TO LIFT NORTH ACROSS OUR AREA SHORTY AFTER 00Z MONDAY. HOWEVER...WITH THE WARMEST BL AIR PROGGED TO REMAIN ACROSS THE EASTERN HALF OF THE STATE...EAST OF THE WEDGE FRONT...THE BEST INSTABILITY AND BEST CHANCE FOR CONVECTION RIGHT NOW IS EXPECTED TO REMAIN WELL EAST OF US-1. THIS BEARS CLOSE WATCHING THOUGH...AS BULK SHEAR VALUES WELL IN EXCESS OF 50KT AND FORMIDABLE LOW LEVEL HELICITY VALUES INVOF OF THE WARM FRONT WOULD PORTEND SEVERE CONVECTION IF THERE WAS ADEQUATE INSTABILITY. OTHERWISE...THE MID-LEVEL VORT AXIS LINKED TO THE AFOREMENTIONED TROUGH IS EXPECTED TO SWEEP ACROSS OUR AREA DURING THE EARLY OVERNIGHT HOURS...WITH SUBSIDENCE AND DRYING IN ITS WAKE AND THUS RAIN ENDING FROM W TO E. RAIN SHOULD BE OVER BY SUNRISE MONDAY. REGARDING TEMPS...WITH AN EVENING WARM FRONT PASSAGE...HIGH TEMPS ON SUNDAY WILL OCCUR AFTER SUNSET. TEMPS THEN STEADY IN THE UPPER 50S TO LOWER 60S...OR PERHAPS EVEN RISING A FEW DEGREES OVERNIGHT. DURING THE DAY MONDAY...THE TRAILING COLD FRONT WILL APPROACH FROM THE WEST. WITH THE BULK OF THE LINGERING MOISTURE REMAINING TO OUR EAST...LOOK FOR DRY WEATHER ACROSS CENTRAL NC ON MONDAY AND WARM PREFRONTAL TEMPS. HIGHS IN THE LOW-MID 70S. A DRY COLD FRONT PASSAGE IS EXPECTED LATE MONDAY EVENING OR AT NIGHT. THE FRONT WILL STALL ACROSS THE EASTERN CAROLINAS ON TUESDAY AS A DEEPENING UPPER TROUGH ACROSS THE MISS VALLEY GRADUALLY APPROACHES...AND SW FLOW AHEAD OF THIS TROUGH KEEPS THIS FRONT HELD UP ALONG THE COAST. AS THE AFOREMENTIONED UPPER TROUGH CONTINUES MOVING EAST...A SFC WAVE IS PROGGED TO DEVELOP ALONG THE FRONT LATE ON TUESDAY...AND MODELS HAVE RECENTLY TRENDED TOWARD A SOLUTION THAT ROTATES SOME MOISTURE AND PERHAPS SOME LIGHT COOL RAIN BACK ACROSS THE EASTERN HALF OF THE STATE TUESDAY NIGHT INTO EARLY WEDNESDAY. TEMPS TUESDAY AND WEDNESDAY...IN THE WAKE OF THE COLD FRONT...WILL BE COOLER WITH READINGS CLOSE TO...OR A FEW DEGREES BELOW NORMAL. LOOKING AHEAD TO THANKSGIVING...YET ANOTHER SHORT WAVE WILL DROP INTO THE LONGWAVE TROUGH THAT WILL BE POSITIONED ACROSS THE EAST. BOTH GFS AND ECMWF HAVE TRENDED DEEPER WITH THIS SHORT WAVE...AND EVEN SUGGEST A MID-LEVEL SHORT WAVE MAY TRY TO CLOSE OFF OVER THE MID-ATLANTIC OR CAROLINAS. WHILE THIS PATTERN MAY RAISE SOME CONCERN ...ITS WORTH NOTING THAT THIS IS 6 DAYS AWAYS AND SOLUTIONS ARE LIKELY TO CHANGE...AND SYSTEMS LIKE THIS THAT APPROACH US FROM NW IN THIS FASHION ARE OFTEN MOISTURE-LIMITED...AT LEAST ACROSS OUR AREA. WORTH WATCHING THOUGH. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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AS OF 1250 AM SATURDAY... FOR THE 06Z VALID TAF PERIOD...VFR CONDITIONS CONTINUE. LIGHT WINDS THIS MORNING GRADUALLY VEER WITH A SLIGHT INCREASE IN WIND SPEEDS AFTER SUNRISE...WITH SUSTAINED VALUES EXPECTED TO BE UNDER 10KT. SURFACE WINDS UNDER HIGH PRESSURE BECOME LIGHT OR CALM AGAIN THIS EVENING BACKING SLIGHTLY. BEYOND THE 06Z VALID TAF PERIOD...CONDITIONS DETERIORATE SUNDAY AND AS AREAS OF RAIN MOVE IN TO CENTRAL NORTH CAROLINA NUMEROUS AREAS OF SUB-VFR...LIKELY IFR...CONDITIONS DEVELOP DURING THE DAY CONTINUING AT LEAST INTO SUNDAY EVENING. WINDS OFF OF THE SURFACE WILL ALSO INCREASE SUNDAY AND REACH OR EVEN EXCEED 50KT BY 2000FT WHICH COULD MAKE LOW-LEVEL WIND SHEAR A PROBLEM BY LATE IN THE DAY INTO THE OVERNIGHT HOURS. IMPROVING AVIATION CONDITIONS ARE POSSIBLE MONDAY AND WHILE SOUTHWEST WINDS OFF THE SURFACE WILL NOT BE AS STRONG...A GUSTY CHARACTER TO THE SURFACE WINDS CONTINUES. AS LOW PRESSURE MOVES ALONG THE SOUTHEAST COAST TUESDAY INTO WEDNESDAY...UNCERTAINTY INCREASES IN TERMS OF THE POTENTIAL FOR A RETURN TO A PERIOD OF SUB- VFR CONDITIONS AND PRECIPITATION...ESPECIALLY EAST OF THE TRIAD. THE NAM MODEL RETURNS THESE CONDITIONS MUCH FASTER TUESDAY...WHILE THE GFS AND ECMWF ARE SLOWER...MORE OVERNIGHT TUESDAY INTO WEDNESDAY. THE CURRENT THINKING IS TOWARD THE SLOWER SOLUTIONS.
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&& .CLIMATE... RECORD LOW: GSO RDUFAY SAT 11/22 - 13 IN 1914 21 IN 2008 20 IN 2000 && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DJF NEAR TERM...PWB SHORT TERM...KC LONG TERM...NP AVIATION...DJF CLIMATE...RAH

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