Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 230729 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 325 AM EDT WED JUL 23 2014 .SYNOPSIS...ATLANTIC HIGH PRESSURE WILL EXTEND WESTWARD OVER THE CAROLINAS TODAY. A COLD FRONT WILL APPROACH FROM THE NORTHWEST TONIGHT... THEN PUSH SOUTHEAST THROUGH NORTH CAROLINA THURSDAY AND THURSDAY NIGHT. WEAK HIGH PRESSURE WILL PUSH IN FROM THE NORTH ON FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 255 AM WEDNESDAY... FOR TODAY/TONIGHT: ISOLATED SHOWERS ON THE PERIPHERY OF THE ATLANTIC RIDGE OFF THE SOUTHEAST COAST HAVE ALL BUT DIED OFF THIS MORNING. PATCHY FOG AND STRATUS WILL HOLD UNTIL SOON AFTER DAYBREAK (PRIMARILY OVER THE ERN HALF OF THE CWA)... FOLLOWED BY A TREND TO PARTLY TO MOSTLY SKIES AS A LIGHT SW SURFACE BREEZE INDUCES MIXING AND DISPERSION OF THE LOW LEVEL MOISTURE. DEEP LAYER SHEAR REMAINS LOW TODAY (10-15 KTS) WITH MARGINAL INSTABILITY (MLCAPE PEAKING AT 500-1000 J/KG) WITH MODEST MID LEVEL LAPSE RATES OF 5.5-6.0 C/KM. DYNAMICALLY WE SHOULD BE IN A RELATIVE LULL ZONE TODAY WITH THE MID LEVEL RIDGE CENTERED OFF THE SE COAST CONTINUING TO NOSE WESTWARD OVER THE SOUTHEAST... WHILE ENERGY DIVES FROM THE UPPER MIDWEST SOUTHEASTWARD TOWARD THE WRN OH VALLEY... HELPING DIG THE TROUGH JUST TO OUR NW TONIGHT AS THE ASSOCIATED SURFACE FRONT APPROACHES. PW VALUES REMAIN ELEVATED (1.7-2.1)... SO STILL EXPECT SCATTERED SHOWER/STORM ACTIVITY TODAY... BUT THE LACK OF DEEP SHEAR AND CONVECTIVE FOCUS AND THE WEAK MID LEVEL FLOW WILL HAMPER STORM ORGANIZATION AND STRENGTH. BOTH THE TRADITIONAL AND CONVECTION- ALLOWING MODELS BEAR THIS OUT WITH LIMITED COVERAGE TODAY... ALONG WITH A SHIFT IN BEST LOW LEVEL MOISTURE TRANSPORT TO COASTAL SECTIONS. WILL KEEP POPS AT 25-35% TODAY... PEAKING DURING THE TYPICAL MID-LATE AFTERNOON... AND TAPERING DOWN IN THE MID-LATE EVENING AS THE BOUNDARY LAYER STABILIZES AND PW DIPS SLIGHTLY. HIGHS 89-93 WITH NEAR-NORMAL THICKNESSES AND SOME SUNSHINE. LOWS 69-74 UNDER PARTLY TO MOSTLY CLOUDY SKIES. -GIH && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... AS OF 315 AM WEDNESDAY... MUCH OF THE CWA SHOULD SEE SHOWERS/STORMS AT SOME POINT THU. THE MID LEVEL TROUGH DIGS JUST WEST OF THE FORECAST AREA EARLY THU... WITH PROJECTED HEIGHT FALLS OF 30-50 M OVER NC. THE ACCOMPANYING SURFACE FRONT IS EXPECTED TO REACH THE SPINE OF THE APPALACHIANS EARLY THU MORNING... THEN EASE SLOWLY EASTWARD INTO CENTRAL NC DURING THE AFTERNOON WITH SURFACE LOW PRESSURE FORMING ALONG THE FRONT AS DPVA ALOFT STRENGTHENS. THIS IMPROVING DYNAMIC FORCING FOR ASCENT WILL ATTEND STRENGTHENING MID LEVEL WINDS AND GREATER DEEP LAYER SHEAR OF 30-35 KTS. INSTABILITY COULD HOLD ON THE LOW SIDE HOWEVER... AS MODELS SHOW MUCAPE TOPPING OUT AT 1000-2000 J/KG OVER THE CENTRAL/ERN CWA... WHICH COULD BE A FUNCTION OF THE EARLY ARRIVAL OF THE DYNAMIC LIFT AS SUGGESTED BY TRADITIONAL MODELS (WHICH SHOW GOOD QPF COVERAGE OVER THE NRN/WRN CWA PRIOR TO 18Z) AS WELL AS THE HIGH- RES WRF-NMM/ARW AND THE (NAM-HEAVY) SREF PROBABILITIES. WILL BRING IN MID RANGE CHANCE POPS OVER THE NW CWA BY LATE MORNING... SPREADING EAST OVER THE REST OF THE CWA DURING THE AFTERNOON... BEFORE ENDING WNW TO ESE FROM LATE AFTERNOON THROUGH THE EVENING. DID KEEP A LOW CHANCE OF LINGERING SHOWERS OVER THE SOUTHEAST CWA THROUGH THE NIGHT GIVEN THAT THE FRONTAL ZONE COULD BECOME STALLED OUT THERE... AND THE INCOMING SURFACE HIGH PRESSURE WILL STILL BE CENTERED OVER IN/OH OVERNIGHT... NOT A FAVORABLE LOCATION FOR THE MORE DENSE AIR TO BE ABLE TO GET OVER THE MOUNTAINS. THE RISK OF A FEW SEVERE STORMS REMAINS... BOOSTED BY THE LARGE SCALE FORCING FOR ASCENT AND THE IMPROVING KINEMATICS... BUT IF THE CONVECTION COMES IN EARLIER IN THE DAY AS EXPECTED... THIS WILL CUT DOWN ON HEATING AND RESULTING INSTABILITY OVER ALL BUT THE FAR SE CWA. AND MARGINAL MID LEVEL LAPSE RATES (BARELY APPROACHING 6.0) SHOULD LIMIT THE LARGE HAIL THREAT. BUT WITH THE RELATIVE VIGOROUS NATURE OF THIS SYSTEM (FOR JULY) AND POSSIBLE MODERATE INSTABILITY... WILL CONTINUE THE MENTION OF AN ISOLATED SEVERE STORM OR TWO ESPECIALLY FROM THE TRIANGLE SOUTH AND EAST... HIGHLIGHTING DAMAGING WINDS AS THE PRIMARY THREAT. HIGHS 84 NW TO 93 SE. LOWS 64 NW TO 73 SE. -GIH && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 240 AM WEDNESDAY... FRIDAY AND FRIDAY NIGHT: THE SURFACE FRONT AND THE UPPER LEVEL TROUGH WILL MOVE EAST OF MUCH OF CENTRAL NC BY FRIDAY...WITH WINDS VEERING TO THE NORTHWEST AND COOL HIGH PRESSURE BUILDING IN. IT APPEARS THAT THE COOLEST AIR MAY ONLY MAKE IT INTO THE FAR NW ON FRIDAY AS WEAK LOW PRESSURE IS EXPECTED TO SIT ALONG THE CAROLINA COAST FRIDAY AND FRIDAY NIGHT. HIGHS ON FRIDAY IN THE MID TO UPPER 80 WITH LOWS IN THE MID 60S TO AROUND 70 DEGREES EXPECTED. GIVEN THE LINGERING SFC LOW ALONG THE COAST AND THE FRONT STALLING IN THAT GENERAL VICINITY...THERE WILL BE THE CHANCE FOR ADDITIONAL SHOWERS AND STORMS ON FRIDAY...MAINLY ACROSS THE SOUTHEAST. PWATS WILL DECREASE TO UNDER AN INCH FOR FRIDAY AS MID LEVEL DRY AIR IS ADVECTED INTO THE REGION. SATURDAY THROUGH TUESDAY: THERE MAY BE A LINGERING CHANCE FOR SOME CONVECTION IN THE EAST SATURDAY WITH A SURFACE TROUGH AND WARM SOUTHERLY FLOW SETTING UP ALONG THE CAROLINA COAST. OTHERWISE... EXPECT MAINLY DRY WEATHER FOR MUCH OF THE AREA AS THE UPPER LEVEL TROUGH SHIFTS OFFSHORE. HIGHS WILL BE GENERALLY IN THE UPPER 80S TO LOW 90S AND LOWS IN THE UPPER 60S TO LOW 70S. THE PIEDMONT TROUGH WILL REMAIN IN PLACE SUNDAY AND SUNDAY NIGHT AS ANOTHER FRONTAL SYSTEM APPROACHES FROM THE WEST. EXPECT INCREASING CHANCES FOR CONVECTION...DIURNAL IN NATURE...SUNDAY AND MONDAY AS THE FRONT APPROACHES. ALTHOUGH THE TIMING OF THIS SYSTEM IS STILL A BIT UNCERTAIN...AS IS THE MODEL FORECAST PRECIPITATION...EXPECT THE BEST CHANCE OF CONVECTION ON MONDAY. AS OF THE LATEST (00Z) GFS MODEL RUN...THE FRONT SHOULD MOVE THROUGH THE AREA MONDAY NIGHT...WITH COOLER AND DRIER CONDITIONS FOR TUESDAY. SUNDAY SHOULD BE THE WARMEST DAY...HIGHS IN THE LOW TO MID 80S AND LOWS IN THE LOW TO MID 70S. TEMPERATURES ON MONDAY WILL DEPEND ON THE TIMING OF THE FRONT AND ITS ASSOCIATED CONVECTION...BUT FOR NOW WILL FORECAST HIGHS A FEW DEGREES COOLER THAN SUNDAY...MID 80S TO AROUND 90 DEGREES. NOTICEABLE TEMPERATURE CHANGE MONDAY NIGHT AND TUESDAY...WITH LOWS IN THE MID 60S TO AROUND 70 DEGREES AND HIGHS IN THE LOW TO MID 80S. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 1250 AM WEDNESDAY... PATCHY SHOWERS NEAR FAY ARE EXPECTED TO SLOWLY MEANDER ABOUT BEFORE WEAKENING AND DISSIPATING OVER THE NEXT FEW HOURS. THESE COULD AFFECT FAY WITH A PERIOD OF MVFR VSBY... BUT THE REMAINDER OF THE CENTRAL NC TAF AIRFIELDS SHOULD STAY DRY THIS MORNING. OTHERWISE... CONFIDENCE IS LOWER THAN IN PAST MORNINGS BUT IT APPEARS THAT ALL SITES ARE LIKELY TO SEE A PERIOD OF MVFR VSBYS PRIOR TO 12Z... AND SUB-MVFR CONDITIONS ARE LESS LIKELY GIVEN THE SPARSITY OF RAINFALL YESTERDAY. MVFR TO HIGH-END IFR CIGS ARE EXPECTED TO DOMINATE AT RWI THROUGH 13Z... WITH ONLY BRIEF MVFR OR HIGH-END IFR CIGS AT RDU/RWI... AND VFR CIGS LIKELY HOLDING AT INT/GSO. VFR CONDITIONS ARE LIKELY FROM 14Z ON THROUGH THE DAY AS CIGS LIFT AND BREAK UP WITH MIXING... WITH SURFACE WINDS FROM THE SW AT 8-12 KTS. ANY SHOWERS/STORMS WILL BE ISOLATED OR IN SMALL CLUSTERS... AND THE CHANCE OF THEM AFFECTING TAF SITES IS TOO SMALL TO INCLUDE IN THE TAFS AT THIS TIME. VFR CONDITIONS SHOULD PREVAIL THROUGH 06Z EXCEPT AT RWI... WHICH MAY SEE MVFR VSBYS IN FOG AFTER 03Z. LOOKING BEYOND 06Z EARLY THU MORNING... EXCEPT FOR SOME LIGHT FOG AT RWI... VFR CONDITIONS SHOULD HOLD ELSEWHERE OVERNIGHT WITH A LIGHT BREEZE FROM THE SW. AN APPROACHING COLD FRONT WILL BRING NUMEROUS SHOWERS AND STORMS WITH SUB-VFR CONDITIONS STARTING LATE MORNING (15Z-18Z) AT INT/GSO BEFORE SPREADING EAST TO RDU DURING THE EARLY AFTERNOON AND TO RWI/FAY DURING THE MID-LATE AFTERNOON. THE FRONT MAY SLOW DOWN OVER COASTAL SECTIONS THU NIGHT/FRI... KEEPING A CHANCE OF SUB-VFR SHOWERS/STORMS FRI AFTERNOON... BUT OTHERWISE VFR CONDITIONS ARE EXPECTED FRI-SAT AS HIGH PRESSURE NOSES IN FROM THE NORTH. AN UPPER LEVEL DISTURBANCE WILL MOVE IN FROM THE NORTHWEST ON SUNDAY... POTENTIALLY BRINGING ANOTHER ROUND OF SHOWERS/STORMS. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS..HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...HARTFIELD LONG TERM...KC AVIATION...HARTFIELD

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