Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 212357 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 757 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 305 PM TUESDAY... REMAINDER OF THE AFTERNOON-EARLY EVENING...A COLD FRONT WILL CROSS THE TRIAD REGION BY 22Z...THE EASTERN PIEDMONT AND SANDHILLS BY 00Z...AND EXIT THE COASTAL PLAIN BY 02Z. PER MESO-ANALYSIS PLOTS...AIR MASS STILL RELATIVELY DRY AND STABLE. HOWEVER LATEST RAP AND HRR MODEL GUIDANCE SUGGESTING ENOUGH MOISTURE AND CONVERGENCE ALONG AND BEHIND THE FRONT TO TRIGGER A FEW SHOWERS ACROSS THE FAR NE PIEDMONT AND THE NORTHERN COASTAL PLAIN. SOME OF THESE WRF MODELS ARE NAM BASED WHICH IS WETTER MORE AGGRESSIVE WITH SHOWER DEVELOPMENT. THUS...BELIEVE A 1:3 CHANCE OF A SHOWER IN THE VICINITY OF ROANOKE RAPIDS IS A WORST CASE SCENARIO. MARGINALLY BLUSTERY CONDITIONS EXPECTED BEHIND THE FRONT WITH A N0NW WIND GUSTING UP TO 20KTS WELL INTO THE NIGHT. OTHERWISE NEAR TERM MODEL GUIDANCE IN GOOD AGREEMENT IN THE DEVELOPMENT/MOVEMENT OF AN UPPER LEVEL LOW ACROSS THE NORTHERN MID ATLANTIC LATE TONIGHT-EARLY WED. THE CIRCULATION AROUND THIS DEVELOPING SYSTEM SHOULD MAINTAIN VARYING CLOUDINESS NEAR THE VIRGINIA BORDER UNTIL LATE TONIGHT WITH PARTIAL CLEARING TOWARD MORNING. 850MB THERMAL TROUGH POSITIONED TO OUR NW TONIGHT WITH BETTER LOW LEVEL CAA EXPECTED TO COMMENCE BY DAYBREAK. MOS GUIDANCE IN GENERAL AGREEMENT RANGING IN THE MID 40S OVER THE WEST TO THE UPPER 40S/AROUND 50 EAST. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... AS OF 307 PM TUESDAY... WEDNESDAY... AN UPPER LEVEL FLOW OVER THE NORTHERN MID ATLANTIC WILL MAINTAIN A STRONG CYCLONIC FLOW OVER CENTRAL NC. PERTURBATIONS WITHIN THIS FLOW IN CONJUNCTION WITH AVAILABLE MOISTURE WILL CAUSE PERIODS OF CLOUDINESS...MAINLY ACROSS THE NE HALF THROUGH EARLY WEDNESDAY EVENING. STEEP MID LEVEL LAPSE RATES (7-7.5 DEG C/KM) COUPLED WITH AFTERNOON HEATING MAY TRIGGER AN ISOLATED SHOWER OR TWO...MAINLY IN VICINITY OF ROANOKE RAPIDS/WARRENTON AND TARBORO. FARTHER SOUTH AND EAST...AIR MASS APPEARS TOO DRY TO SUPPORT ANYTHING MORE THAN A FEW CLOUDS. N-NW WINDS WILL REMAIN A LITTLE BLUSTERY WITH GUSTS AROUND 25 MPH POSSIBLE. LOW LEVEL CAA MORE PRONOUNCED WITH THERMAL TROUGH OVER THE REGION. AFTERNOON TEMPS WILL STRUGGLE TO REACH THE LOWER 60S IN THE NW WITH MID-UPPER 60S COMMON ELSEWHERE. WEDNESDAY NIGHT...UPPER LEVEL LOW BEGINS TO PULL OUT WEDNESDAY NIGHT. MID LEVEL SUBSIDENCE IN ITS WAKE WILL RID ARE AREA OF ANY LINGERING SHOWERS AND CLOUDINESS. LOW LEVEL MIXING WILL PERSIST...AIDING TO MAINTAIN OVERNIGHT TEMPS. OF SFC WINDS WERE TO DECOUPLE (MAINLY WESTERN-SOUTHERN PIEDMONT)...COULD SEE MIN TEMPS AS LOW AS THE MID 30S AT A FEW SPOTS. FOR NOW WILL BOTTOM OUT TEMPS IN THE UPPER 30S IN THE WESTERN-SOUTHERN PIEDMONT WITH IN TEMPS IN THE LOW-MID 40S ELSEWHERE. && .LONG TERM /THURSDAY THROUGH TUESDAY/... AS OF 3 PM TUESDAY... THURSDAY THROUGH FRIDAY NIGHT: WEAK SHORTWAVE RIDING WILL BRIEFLY APPROACH/BUILD OVER THE AREA ON THURSDAY INTO THURSDAY NIGHT AS THE DEEP MID LEVEL LOW SLOWLY CONTINUES TO LIFT OFF TO THE NORTHEAST. THIS WILL YIELD MOSTLY SUNNY/SUNNY SKIES-CLEAR/MOSTLY CLEAR SKIES. HOWEVER... WITH THE DEPARTING SYSTEM... WE MAY SEE SUSTAINED NORTHWESTERLY WINDS IN THE 10 TO 15 MPH RANGE... WITH SOME GUSTS OF AROUND 20 MPH OR SO DURING THE DAYLIGHT HOURS OF THURSDAY. AFTERNOON LOW LEVEL THICKNES VALUES AREA EXPECTED TO BE IN THE 1350S TO 1360S. THUS... GIVEN FULL SUN IS EXPECTED ALONG WITH SOMEWHAT OF A DOWNSLOPE FLOW WILL GO WITH HIGH TEMPS RANGING FROM THE MID TO UPPER 60S. LOWS THURSDAY NIGHT WITH CLEAR/MOSTLY CLEAR SKIES AND A WEAKENING WIND ARE EXPECTED TO BE IN THE LOWER TO MID 40S... WITH A FEW UPPER 30S NOT OUT OF THE QUESTION IN THE USUAL RURAL COLD SPOTS. ONE LAST S/W DISTURBANCE IS FORECAST TO TRACK SOUTHEASTWARD FROM THE NORTHERN PLAINS/UPPER MIDWEST ON THURSDAY AND MOVE ACROSS CENTRAL NC ON FRIDAY INTO FRIDAY NIGHT. THE ECMWF CONTINUES TO BE MUCH STRONGER WITH THIS FEATURE THAN THE GFS AND NAM. HOWEVER... WITH SUCH A DRY AIRMASS IN PLACE PRECEDING THE FEATURE AND LACK OF ANY REAL MOISTURE RETURN IN ADVANCE OF IT MODELS DO NOT SHOW ANY PRECIP BEING GENERATED ACROSS CENTRAL NC AS IT ACROSS THE AREA. THUS... WILL JUST SHOW AN INCREASE IN CLOUD COVER ON FRIDAY. HOW STRONG THE SYSTEM ENDS UP BEING WILL HAVE AN AFFECT ON HIGH TEMPS THOUGH (WITH CLOUD COVER BEING THE VARIABLE IN QUESTION). FOR NOW WILL JUST SHOW PARTLY SUNNY SKIES ON FRIDAY... WITH HIGH TEMPS IN THE UPPER 60S TO NEAR 70 SOUTH. LOWS FRIDAY NIGHT WITH CLEARING SKIES ARE EXPECTED TO BE IN THE 40S. SATURDAY THROUGH TUESDAY: QUITE WEATHER IS EXPECTED TO CONTINUE FOR THE UPCOMING WEEKEND AND INTO NEXT WEEK. MID LEVEL RIDGING IS FORECAST TO BUILD OVER THE AREA FROM THE CENTRAL U.S. BY EARLY NEXT WEEK... YIELDING A WARMING TREND. EXPECT TEMPS WILL BE NEAR NORMAL TEMPS TO START THE PERIOD... INCREASING TO HIGH TEMPS A CATEGORY OR TWO ABOVE NORMAL BY EARLY NEXT WEEK. THIS YIELDS HIGH TEMPS THIS WEEKEND AROUND 70/LOWER 70S... WITH TEMPS WARMING TO THE LOWER TO MID 70S BY MONDAY AND TUESDAY... WITH POSSIBLY SOME UPPER 70S BY TUESDAY. GIVEN THE PATTERN CHANCE TO RIDING ALOFT... SKIES ARE EXPECTED TO GENERALLY BE MOSTLY SUNNY/MOSTLY CLEAR FOR THIS ENTIRE PERIOD. THIS SHOULD YIELD A NICE DIURNAL TEMP RANGE... GIVEN THE DRY CONDITIONS AND RATHER LIGHT WINDS EXPECT FROM SUNDAY ONWARD. LOWS ARE EXPECTED TO BE IN THE 40S... TO AROUND 50 ACROSS OUR FAR SOUTHEAST BY EARLY NEXT WEEK. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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AS OF 750 PM TUESDAY... VFR CONDITIONS WILL PERSIST THROUGH THE CURRENT TAF PERIOD. A COLD FRONT IS MAKING ITS WAY THROUGH THE FORECAST AREA THIS EVENING AND WILL CLEAR THE REGION IN THE NEXT COUPLE OF HOURS. SOME CLOUDS WILL ACCOMPANY THE FRONT...BUT WILL REMAIN IN THE VFR RANGE. WINDS WILL BECOME NORTH/NORTHWESTERLY BEHIND THE FRONT AND ADDITIONALLY THERE COULD BE A BRIEF PERIOD OF GUSTINESS. A COUPLE OF SHOWERS WERE NOTED NEAR THE VA BORDER AND THIS IS WHERE THE ISOLATED COVERAGE IS EXPECTED TO REMAIN...ALTHOUGH CANNOT COMPLETELY RULE OUT A SHOWER OR TWO IN CENTRAL NC...ESPECIALLY ACROSS THE NORTHEAST. THEN...WINDS ARE EXPECTED TO INCREASE WEDNESDAY MORNING...WITH GUSTS UP TO 25 MPH POSSIBLE. ALSO...AN UPPER LEVEL LOW OVER THE NORTHERN MID ATLANTIC MAY CAUSE PERIODS OF CLOUDINESS WITH CEILINGS 3500-5000FT...MAINLY IN VICINITY OF KRDU AND KRWI DUE TO THE PROXIMITY OF THE LOW. THIS FEATURE MAY ALSO RESULT IN A SHOWER OR TWO...MOST LIKELY ACROSS THE NORTHEAST (IN THE VICINITY OF KRWI)...BUT ESPECIALLY CLOSER TO THE VIRGINIA BORDER. OUTLOOK...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...WSS LONG TERM...BSD AVIATION...KRD/WSS

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