Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 220650 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 250 AM EDT TUE APR 22 2014 .SYNOPSIS...A WARM SOUTHWEST FLOW WILL BRING ABOVE NORMAL TEMPERATURES TODAY. A COLD FRONT WILL MOVE SLOWLY EASTWARD ACROSS OUR REGION THIS EVENING... THEN HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST WEDNESDAY THROUGH THURSDAY. ANOTHER COLD FRONT WILL APPROACH FROM THE WEST ON FRIDAY. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/...
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AS OF 250 AM TUESDAY... FOR TODAY/TONIGHT: CURRENT FORECAST CONTINUES TO MATCH WELL WITH EXTRAPOLATED UPSTREAM CONDITIONS AND THE LATEST MODEL GUIDANCE. THE COLD FRONT NOW SWINGING THROUGH THE GREAT LAKES/OH VALLEY AND LOWER MISS VALLEY AND ITS ASSOCIATED MID LEVEL TROUGH WILL PROGRESS EASTWARD INTO NC TODAY... BEFORE SWEEPING SOUTHEAST THROUGH NC THIS EVENING. AHEAD OF THE FRONT... WSW SURFACE WINDS AND MAINLY WESTERLY 850-700 MB WINDS WILL MINIMIZE THE POTENTIAL FOR MOISTURE RETURN INTO THE AREA... EXEMPLIFIED BY PRECIP WATER PROGS SHOWING A NARROW TIME WINDOW OF VALUES JUST ABOVE 1.0 INCH... JUST SLIGHTLY ABOVE THE NORMAL FOR THIS TIME OF YEAR. EXPECT A VEIL OF MID AND HIGH CLOUDS THIS MORNING ACCOMPANYING THE APPROACHING WEAK SOUTHERN PORTION OF THE MID LEVEL TROUGH... WITH LOWER CLOUDS (YET STILL FAIRLY HIGH) BASED AROUND 6-7K FEET MOVING IN TOWARD THE AFTERNOON WITH PERSISTENT WEAK DPVA ALOFT AND THE ARRIVAL OF SOMEWHAT BETTER MOISTURE. LATEST MODEL RUNS ARE FAIRLY CONSISTENT IN BRINGING SCATTERED SHOWERS AND A FEW STORMS INTO THE WRN CWA AROUND 18Z... SHIFTING ESE THEN EXITING THE SE CWA BY 01Z-02Z. COVERAGE AND INTENSITY OF THIS CONVECTION WILL BE GREATLY LIMITED BY THE SUBPAR TO ABSENT DYNAMIC FORCING FOR ASCENT AT ALL LEVELS AS WELL AS THE MARGINAL MOISTURE. DEEP LAYER SHEAR IS ALSO UNIMPRESSIVE... JUST AROUND 20-25 KTS... AND FORECAST MUCAPE PEAKS AT 500-800 J/KG... AND THIS MAY BE OVERDONE DUE TO MODEL OVERESTIMATION OF SURFACE DEW POINTS (PARTICULARLY ON THE GFS)... WHICH SHOULD PEAK IN THE 50S AT BEST. AS SUCH... WILL KEEP CONVECTION COVERAGE AT JUST 30-40%. WHILE THE DEEP LAYER SHEAR AND INSTABILITY ARE BOTH MARGINAL... THE NAM DEPICTS A DRY SUBCLOUD LAYER SUGGESTING ENHANCED WIND GUSTS WITH ANY CONVECTION... AND SUCH AN ISOLATED OCCURRENCE CANNOT BE RULED OUT. EXPECT COOLING/CLEARING OVERNIGHT BEHIND THE FRONT AS HIGH PRESSURE STARTS TO BUILD IN FROM THE NW. WARM THICKNESSES AND STATISTICAL GUIDANCE SUPPORT HIGHS TODAY 77-84. LOWS TONIGHT FROM 46 NW TO 55 SE. FOR WED/WED NIGHT: A PLEASANT AND SLIGHTLY COOL DAY WITH LOW HUMIDITY. THE DRY AND STABLE COLUMN WITH DEEP NORTHWEST FLOW AS HIGH PRESSURE BUILDS IN FROM THE NW SHOULD YIELD GENERALLY CLEAR SKIES WED INTO WED NIGHT. LOW LEVEL THICKNESSES DROP TO AROUND 25-30 M BELOW NORMAL... SUGGESTING HIGHS ONLY IN THE UPPER 60S TO LOWER 70S FACTORING IN THE ABUNDANT SUNSHINE. BELOW-NORMAL LOWS WED NIGHT 40- 47... WITH INCREASING (BUT STILL THIN AND LOW IN COVERAGE) MID CLOUDS OVERNIGHT AS MID LEVEL ENERGY RIDES ATOP THE WEAK SHORTWAVE RIDGE TO OUR WEST. -GIH
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&& .SHORT TERM //...
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AS OF 1258 PM MONDAY... TO BE UPDATED.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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AS OF 245 PM MONDAY... THU: DRY CONDITIONS WILL RULE IN THIS PERIOD DUE TO SYNOPTIC SUBSIDENCE ASSOC/W RISING HEIGHTS ATTENDANT AN UPPER LEVEL RIDGE BUILDING EAST FROM THE CENTRAL CONUS TO THE EASTERN SEABOARD. EXPECT TEMPS SEVERAL DEGREES BELOW NORMAL FOR THIS TIME OF YEAR...RANGING FROM THE LOWER TO MID 70S ON THU IN ASSOC/W SFC HIGH PRESSURE BUILDING INTO THE REGION FROM THE NORTH. FRI/FRI NIGHT: LOW-LEVEL MOISTURE ADVECTION WILL STRENGTHEN ACROSS THE CAROLINAS ON FRIDAY AS UPPER LEVEL RIDGING GIVES WAY TO BROAD CYCLONIC FLOW ALOFT OVER THE REGION. MARGINAL DIURNAL DESTABILIZATION (500-1000 J/KG MLCAPE) APPEARS LIKELY GIVEN RELATIVELY STEEP MID-LEVEL LAPSE RATES (~7 C/KM) ATOP AN INCREASINGLY MOIST BOUNDARY LAYER (CHARACTERIZED BY SFC DEWPOINTS AT OR SLIGHTLY ABOVE 60F). ALTHOUGH DEEP LAYER SHEAR WILL BE MORE THAN SUFFICIENT FOR ORGANIZED CONVECTION...DEAMPLIFYING SHORTWAVE ENERGY IS PROGGED TO TRACK ACROSS THE NORTHERN MID-ATLANTIC AND THE BEST FORCING /DCVA/ IS EXPECTED TO REMAIN FAR REMOVED FROM CENTRAL NC. AS A RESULT...UNCERTAINTY PERSISTS WITH REGARD TO WHETHER OR NOT DEEP CONVECTION (I.E. THUNDERSTORMS) WILL EVEN DEVELOP. WITH THE ABOVE IN MIND...WILL KEEP PRECIP CHANCES IN THE 30-40% RANGE. HIGHS FRI UPPER 70S TO LOWER 80S...LOWS FRI NIGHT MID/UPPER 50S. SAT-MON: UNCERTAINTY INCREASES DRAMATICALLY THIS WEEKEND INTO EARLY NEXT WEEK WITH REGARD TO THE EVOLUTION OF THE UPPER LEVEL PATTERN OVER THE EASTERN CONUS. THE 12Z ECMWF INDICATES A HIGHER THETA-E AIRMASS IN PLACE ACROSS THE CAROLINAS WITH AN OCCASIONAL CHANCE FOR CONVECTION...ESP SUN/MON...WHILE THE GFS INDICATES A COOLER/DRIER AIRMASS WITH LITTLE CHANCE FOR PRECIPITATION. AT THIS TIME WILL CONTINUE TO INDICATE A DRY FORECAST WITH NEAR NORMAL MAX/MIN TEMPERATURES. -VINCENT
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&& .AVIATION /06Z TUESDAY THROUGH SATURDAY/... AS OF 105 AM TUESDAY... VFR CONDITIONS ARE LIKELY TO DOMINATE AT ALL CENTRAL NC TAF SITES TODAY AND TONIGHT. A COLD FRONT APPROACHING SLOW FROM THE WNW TODAY WILL CROSS THE AREA THIS EVENING... CAUSING THE WARM SURFACE WINDS FROM THE SOUTHWEST TO SHIFT TO WEST THEN NORTHWEST LATE TONIGHT AS A SECONDARY FRONT DROPS SE THROUGH THE AREA. SCATTERED SHOWERS AND ISOLATED STORMS ARE EXPECTED ALONG AND AHEAD OF THIS FRONT... AFFECTING INT/GSO MAINLY 18Z-22Z TODAY... RDU 20Z-00Z... AND FAY/RWI MAINLY 21Z-01Z. CLOUD BASES ARE EXPECTED TO REMAIN VFR... AND THE DRY SUBCLOUD LAYER WILL LIMIT PRECIP AMOUNTS AND WILL KEEP VSBYS MOSTLY VFR... ALTHOUGH BRIEF MVFR VSBYS IN SHOWERS OR STORM REMAINS POSSIBLE. ENHANCED VARIABLE WIND GUSTS ARE POSSIBLE IN AND NEAR SHOWERS/STORMS. SCT CLOUDS BASED ABOVE 3500 FT ARE EXPECTED POST- FRONT TOWARD THE END OF THE TAF PERIOD. LOOKING BEYOND 06Z EARLY WEDNESDAY MORNING... HIGH CONFIDENCE IN VFR CONDITIONS IN CENTRAL NC THROUGH THU WITH HIGH PRESSURE BUILDING IN FROM THE NW. AN APPROACHING STORM SYSTEM FROM THE WEST WILL BRING A CHANCE FOR MVFR OR IFR CONDITIONS WITHIN SCATTERED SHOWERS/STORMS STARTING FRI MORNING. THIS SYSTEM WEAKENS LATE FRI AND HIGH PRESSURE SHOULD THEN RETURN FOR SAT... BRINGING A RETURN TO VFR CONDITIONS FRI NIGHT/SAT. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...BADGETT LONG TERM...VINCENT AVIATION...HARTFIELD

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