Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 291133 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 733 AM EDT FRI AUG 29 2014 .SYNOPSIS...A SLOW MOVING BACK DOOR COLD FRONT WILL STALL OUT ACROSS CENTRAL NORTH CAROLINA TODAY. THE FRONT WILL GRADUALLY DISSIPATE OVER THE WEEKEND AS A LIGHT SOUTHERLY RETURN FLOW DEVELOPS ACROSS THE REGION. && .NEAR TERM /TODAY AND TONIGHT/...
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AS OF 730 AM FRIDAY... 7 AM UPDATE...THE NAM GUIDANCE BEST MATCHES THE LATEST OBSERVATIONAL DATA AS OF 11Z THIS MORNING...WITH LOW CEILINGS/CONVECTIVE OUTFLOW AND A NORTHEAST BREEZE ALONG AND NORTH OF HWY 64 INDICATING THE PROBABLE ONSET OF A HYBRID CAD WEDGE. AS A RESULT...WILL LOWER HIGH TEMPS AT LEAST SEVERAL DEGREES ALONG/NORTH OF HWY 64. PREVIOUS DISCUSSION REMAINS BELOW. -VINCENT OVERVIEW: AN UPPER LEVEL RIDGE CENTERED OVER THE SOUTHEAST STATES WILL EXTEND N/NE INTO THE MID-ATLANTIC TODAY/TONIGHT. A WEST-EAST ORIENTED BACK DOOR COLD FRONT LOCATED JUST SOUTH OF THE VA/NC BORDER AT 06Z THIS MORNING IS EXPECTED TO STALL OUT IN VICINITY OF THE HWY 64 CORRIDOR TODAY. BELOW AVERAGE CONFIDENCE IN THE FORECAST THROUGH TONIGHT. MODEL GUIDANCE CONTINUES TO VARY WITH THE PRECISE POSITION AND ORIENTATION OF THE STALLED FRONT TODAY...IN ADDITION TO THE PRECISE ORIENTATION OF THE LOW-LEVEL HEIGHT GRADIENT. AS A RESULT...POSSIBLE SOLUTIONS RANGE FROM A HYBRID COLD AIR DAMMING WEDGE AND ELEVATED CONVECTION DEVELOPING BETWEEN 12-18Z TODAY NORTH OF HWY 64 TO NO WEDGE DEVELOPMENT AND A SOMEWHAT TYPICAL POTENTIAL FOR ISOLD TO SCT SFC- BASED CONVECTION. GIVEN THE SUBTLE NATURE OF THE PATTERN IN PLACE AND THAT CONVECTION COULD LARGELY DICTATE THE EVOLUTION OF THE LOW- LEVEL PATTERN...WILL LEAVE THE FORECAST ROUGHLY AS-IS WITH A SLIGHT TO LOW CHANCE (20-30%) OF CONVECTION AND HIGHS RANGING FROM THE MID 80S NORTH TO LOWER 90S SOUTH. LOWS TONIGHT NEAR 70F.
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&& .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 220 AM FRIDAY... CENTRAL NC WILL REMAIN UNDER THE INFLUENCE OF AN UPPER LEVEL RIDGE SAT/SAT NIGHT AS THE CENTER OF THE RIDGE CURRENTLY OVER THE SOUTHEAST STATES SHIFTS SLIGHTLY EAST TOWARD THE COAST. THE LINGERING FRONTAL ZONE OVER PORTIONS OF CENTRAL NC SHOULD WASH OUT DURING THE DAY AS A LIGHT S/SE RETURN FLOW DEVELOPS ACROSS THE REGION. FORECAST SOUNDINGS SUGGEST MARGINAL DESTABILIZATION WITH 500- 1500 J/KG OF MLCAPE SAT AFTERNOON. GIVEN A PROTOTYPICAL SUMMERTIME `RIDGE` PATTERN...EXPECT ABOVE NORMAL TEMPS...IN THE LOWER 90S. MARGINAL INSTABILITY AND SEASONABLE MOISTURE (PWAT VALUES OF 1.50- 1.75") WOULD SUPPORT ISOLD CONVECTION ON SATURDAY...THOUGH FORCING FOR ASCENT WILL BE LIMITED TO THE SEABREEZE AND DIFFERENTIAL HEATING...PRIMARILY ALONG THE HIGHER TERRAIN IN WESTERN NC...AND IT IS POSSIBLE THAT NO CONVECTION WILL DEVELOP IN CENTRAL NC. WITH THE ABOVE IN MIND...WILL INDICATE A SLIGHT CHANCE OF CONVECTION DURING THE AFT AND EARLY EVE HOURS IN THE WESTERN PIEDMONT AND SE COASTAL PLAIN. EXPECT NEAR NORMAL LOWS SAT NIGHT IN THE UPPER 60S TO LOWER 70S. -VINCENT && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 245 AM FRIDAY... A RIDGE WILL BUILD OVER THE SOUTHEASTERN STATES EARLY TO MID WEEK. THIS WILL EXTEND OUR CURRENT MORE SUMMER-LIKE PATTERN ACROSS NC WELL INTO WEDNESDAY. THE CORE OF THE UPPER RIDGE IS FORECAST TO BE OVER THE NC/SC COAST SUNDAY. THE APPROACHING UPPER TROUGH FROM THE OHIO VALLEY WILL BE DEFLECTED TO OUR NORTH AND WEAKEN SUNDAY NIGHT AND MONDAY. EVEN WITH THE HEAT AND HUMIDITY WITH THE SOUTHERLY RETURN FLOW... ONLY ISOLATED AFTERNOON THUNDERSTORMS ARE EXPECTED. THE BEST CHANCE IS FORECAST OVER AND NEAR THE BLUE RIDGE WHERE INSTABILITY... MOISTURE... AND LIFT WILL BE HIGHEST. HIGHS SHOULD REACH THE 88-93 RANGE. THE CORE OF THE UPPER RIDGE IS FORECAST TO SHIFT SOUTHWEST WITH TIME TO OVER THE GULF COAST STATES TUE-WED. THIS WILL ALLOW A WEAK PIEDMONT TROUGH AT THE SURFACE WHICH MAY AID IN THE DEVELOPMENT OF SCATTERED THUNDERSTORMS DURING THE AFTERNOON AND EVENING EARLY TO MID WEEK. OTHERWISE... SIMPLY WARM AND HUMID WITH PARTLY CLOUDY SKIES. LOWS 69-74. HIGHS 88-93 NW TO SANDHILLS. FOR MID TO LATE WEEK... ANY SURFACE FRONT IS EXPECTED TO BE WEAK AND PROVIDE LITTLE IF ANY COOLING OR DRYING. HOWEVER... IT MAY ACT AS A CONTINUED FOCUS FOR SCATTERED MAINLY AFTERNOON THUNDERSTORMS WED- FRI. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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AS OF 730 AM FRIDAY... 24-HR TAF PERIOD: BELOW AVERAGE CONFIDENCE IN THE FORECAST THROUGH TONIGHT. THE NAM MODEL GUIDANCE BEST MATCHES THE LATEST OBS DATA... WHICH SUGGESTS THE NORTHERN TERMINALS (INT/GSO/RDU/RWI) WILL BE AFFECTED BY PERIODIC OR PERSISTENT IFR/MVFR CEILINGS THIS MORNING... WITH IMPROVEMENT TO MVFR DURING THE AFTERNOON. MVFR CEILINGS AND ISOLD CONVECTION WILL BE POSSIBLE THROUGH THE AFTERNOON AND EVENING HOURS. GIVEN THE LATEST TRENDS...A MORE PESSIMISTIC FORECAST MAY BE NECESSARY TONIGHT THROUGH SAT MORNING AT THE NORTHERN TERMINALS WHERE CONDITIONS MAY DETERIORATE TO IFR/LIFR OVERNIGHT BEFORE GRADUALLY IMPROVING TO VFR BY SAT AFTERNOON. LOOKING AHEAD: EXPECT A NEAR CLIMATOLOGICAL PATTERN THROUGH EARLY NEXT WEEK WITH A SLIGHT CHANCE OF AFTERNOON/EVENING CONVECTION AND A POTENTIAL FOR EARLY MORNING FOG/STRATUS. -VINCENT
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...PWB AVIATION...VINCENT

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