Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 191835 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 235 PM EDT SUN OCT 19 2014 .SYNOPSIS....HIGH PRESSURE WILL SETTLE OVER NC AND VA TONIGHT. THE HIGH WILL DRIFT OFFSHORE MON...AHEAD OF AN UPPER LEVEL TROUGH THAT WILL MOVE INTO OUR REGION MON NIGHT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 235 PM SUNDAY... AN AREA OF HIGH PRESSURE AT THE SURFACE WILL SETTLE OVER CENTRAL NC TONIGHT. THE DRY AIR ASSOCIATED WITH THIS WEATHER SYSTEM ALONG WITH A LIGHT/CALM WIND REGIME WILL CAUSE TEMPERATURES TO PLUMMET INTO THE 40S AFTER SUNSET THEN GRADUALLY LOWER INTO THE UPPER 30S TO AROUND 40 OVERNIGHT. THE NORMALLY COLDER LOCATIONS MAY DIP INTO THE MID 30S. PATCHY FROST IS POSSIBLE WHERE TEMPS DROP BELOW 37 DEGREES. AT THIS TIME EXPECT THE FROST TO BE VERY PATCHY AND LIGHT...LIMITED TO ROOFTOPS AND ON THE TOPS OF CARS. EXPECT TO SEE AN INCREASE IN HIGH CLOUDS FROM THE WEST BY MIDNIGHT AS A WEAKENING UPPER LEVEL DISTURBANCE APPROACHES. CURRENT CIRRUS SHIELD ASSOCIATED WITH THIS SYSTEM NOT OVERLY IMPRESSIVE...LEAVING ONE TO WONDER IF THE GFS/ECMWF ARE TOO WET WITH THEIR RH DEPICTION ALOFT LATER TONIGHT. THUS PLAN TO FORECAST TEMPS ON THE COOL SIDE OF GUIDANCE IN ANTICIPATION THAT THE HIGH CLOUDS WILL BE THIN AND PATCHY. IF THE GFS/ECMWF END UP VERIFYING...THEN MIN TEMPS MAY BE 2- 4 DEGREES WARMER THAN FORECAST AND LIGHT PATCHY FROST WILL BE OF LITTLE CONCERN. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... AS OF 235 PM SUNDAY... MONDAY...SFC HIGH WILL DRIFT EAST...COMMENCING AIR MASS MODIFICATION. LOW LEVEL RETURN EXPECTED TO BE SWLY BY AFTERNOON WITH OCCASIONAL GUSTS AROUND 15 KTS PROBABLE. LOW LEVEL THICKNESSES REBOUND ABOUT 10M FROM LEVELS OCCURRING THIS AFTERNOON. THIS YIELDS MAX TEMPS 2-3 DEGREES WARMER THAN TODAY. FACTORING IN ADDITIONAL WARMING FROM THE LOW LEVEL SW FLOW SUPPORT MAX TEMPS NEAR 70 TO THE LOWER 70S. MONDAY NIGHT...L/W TROUGH OVER THE EASTERN U.S. UNDERGOES AMPLIFICATION THANKS TO A S/W CROSSING THE GREAT LAKES INTO SOUTHERN NEW ENGLAND. THE TAILE ND OF THIS S/W WILL CROSS CENTRAL NC MONDAY NIGHT...GENERATING AREAS OF MID-HIGH LEVEL CLOUDINESS. WARM AIR ADVECTION IN THE 8000-15000FT LAYER MAY PRODUCE ENOUGH LIFT TO INITIATE SOME PRECIP BUT THE SUB CLOUD LAYER STILL QUITE DRY. THUS...EXPECT NOTHING WORSE THAN A FEW SPRINKLES...MAINLY ACROSS THE NORTH HALF...AS THIS SYSTEM CROSSES OUR REGION. VARIABLE CLOUDINESS AND A MODIFYING AIR MASS WILL RESULT IN MIN TEMPS SEVERAL DEGREES WARMER COMPARED TO TONIGHT. MIN TEMPS IN THE 40S TO AROUND 50. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 315 AM SUNDAY... SHORTWAVE ENERGY CURRENTLY OVER THE CANADIAN ROCKIES WILL DIVE THROUGH THE MIDWEST AND CROSS THE AREA EARLY TUESDAY...IMMEDIATELY FOLLOWED BY ANOTHER WAVE...AND ITS ASSOCIATED COLD FRONT...DIGGING THROUGH THE DEEPENING LONGWAVE TROUGH TUESDAY EVENING. DURING THE DAY...A WEST-SOUTHWESTERLY WIND AND LIMITED CLOUD COVER AHEAD OF THE COLD FRONT WILL ALLOW TEMPS TO WARM BACK INTO THE UPPER 60S AND LOWER 70S. AS THE COLD FRONT MOVES THROUGH TUESDAY EVENING...A SHOT OF STRONG DCVA WILL HAVE TO OVERCOME LIMITED MOISTURE...PW BELOW 0.75"...IN ORDER TO TO SQUEAK OUT A FEW ISOLATED...LIGHT SHOWERS...MAINLY ACROSS THE FAR NORTHERN COASTAL PLAIN WHERE MOISTURE PROFILES ARE SLIGHTLY MORE CONDUCIVE FOR PRECIP. HOWEVER...MODELS ARE ONLY GENERATING A HUNDREDTH OR TWO OF QPF IN SPOTS...SO SLIGHT CHANCE POPS CONTINUE TO BE THE BEST BET. BEHIND THE FRONT...A NORTHWESTERLY WIND WILL PERSIST THROUGH MOST OF THE WEEK AS THE UPPER TROUGH CLOSES OFF INTO AN UPPER LOW OVER THE MID-ATLANTIC COAST. MODELS HAVE HINTED AT A FEW SHOWERS ON WEDNESDAY AFTERNOON AS THE CORE OF THE COLD AIR ALOFT AND SOME VERY WEAK INSTABILITY DEVELOPS. HOWEVER...MOISTURE WILL STILL EB SEVERELY LACKING AND JUST ENHANCE CLOUD COVER SEEMS MORE LIKELY. THICKNESSES ARE FORECAST TO BRIEFLY TOUCH 1340M ON WEDNESDAY MORNING...THEN CLIMB BACK TOWARD NORMAL VALUES AROUND 1360M BY THE END OF THE WEEK AS THE UPPER BEGINS TO DRIFT NORTHEAST AWAY FROM THE REGION. THUS...HIGHS WILL BE COOLEST WEDNESDAY IN THE LOW TO MID 60S AND TREND BACK INTO THE UPPER 60S TO LOWER 70S. THERE ARE SIGNIFICANT MODEL DIFFERENCES BY NEXT WEEKEND AS ENERGY CROSSING THE CENTRAL US IS FORCED INTO THE DEEP SOUTH AND THEN EITHER MOVES EAST ACROSS THE SOUTHEAST US (GFS SOLUTION) OR CUTS OFF OVER THE GULF COAST (ECMWF SOLUTION). WPC HAS A STRONG PREFERENCE FOR THE ECMWF AND ITS ENSEMBLE MEAN. EITHER WAY THE FORECAST WILL REMAIN DRY AND NEAR NORMAL THROUGH THE END OF THE EXTENDED PERIOD. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... AS OF 135 PM SUNDAY... A DRY AND STABLE AIR MASS OVER CENTRAL NC WILL RESULT IN VFR CONDITIONS THROUGH TUESDAY. AN AREA OF HIGH PRESSURE WILL SETTLE OVERHEAD TONIGHT THEN DRIFT EAST ON MONDAY. RETURN SLY FLOW WILL BEGIN TO ADVECT LOW LEVEL MOISTURE INTO OUR REGION...RESULTING IN SCATTERED CUMULUS...MAINLY IN VICINITY OF KFAY. THRE IS A GOOD CHANCE THAT VFR CONDITIONS WILL PREVAIL TUESDAY THROUGH FRIDAY. A SERIES OF S/W ROTATING AROUND A CLOSED UPPER LEVEL LOW OVER THE NORTHERN MID ATLANTIC WILL CAUSE PERIODS OF CLOUDINESS OVER CENTRAL NC TUESDAY THROUGH WEDNESDAY NIGHT. HOWEVER CLOUD BASES SHOULD REMAIN ABOVE MVFR CRITERIA. THE UPPER LEVEL LOW WILL LIFT GRADUALLY NEWD THU INTO FRIDAY...ALLOWING HIGH PRESSURE TO BUILD INTO OUR REGION. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS/MWS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...BLS AVIATION...WSS

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