Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221102 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 700 AM EDT TUE APR 22 2014 .SYNOPSIS...
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A COLD FRONT WILL APPROACH FROM THE WEST TODAY... AND CROSS THE REGION THIS EVENING. HIGH PRESSURE WILL THEN BUILD IN FROM THE NORTHWEST WEDNESDAY THROUGH THURSDAY. ANOTHER COLD FRONT WILL APPROACH FROM THE WEST ON FRIDAY.
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&& .NEAR TERM /THROUGH WEDNESDAY NIGHT/... 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 && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 310 AM TUESDAY... HIGH PRESSURE BUILDING SOUTH FROM THE GREAT LAKES WILL BECOME CENTERED OFF THE CAROLINA COAST BY THURSDAY...WHILE A SHORTWAVE RIDGE SHIFTS OVERHEAD. RETURN FLOW WILL DEVELOP LATE IN THE DAY...MAINLY ACROSS THE WEST...AND RESULTING HIGHS WILL RANGE FROM MID 70S WEST TO AROUND 70 IN THE EAST UNDER MOSTLY CLEAR SKIES. RETURN FLOW WILL THEN RAMP UP THURSDAY NIGHT AND EARLY FRIDAY AS AN UPPER TROUGH AXIS AND SURFACE COLD FRONT MOVE INTO THE TENNESSEE/OHIO VALLEY REGION. GFS FORECAST SOUNDINGS ARE MUCH MORE BULLISH THAN NAM SOUNDINGS WITH STRATUS DEVELOPMENT LATE THURSDAY NIGHT...FOCUSING LOW CLOUDS MAINLY ACROSS THE WEST. MODELS ALSO HINT AT A FEW SHOWERS OVER THE WESTERN PIEDMONT FRIDAY MORNING AS THE UPPER TROUGH AND ASSOCIATED DCVA MOVE OUT AHEAD OF THE MAIN FRONTAL ZONE. BY THE TIME THE FRONT MOVES INTO CENTRAL NC FRIDAY AFTERNOON/EVENING IT WILL BE RATHER WEAK AND THE MID-LEVEL FLOW WILL BE WESTERLY. LOW-LEVEL MOISTURE RETURN WILL BE BETTER AHEAD OF THIS FRONT WTH DEWOINTS POTENTIALLY IN THE UPPER 50S AND LOWER 60S...AND SO SOME DESTABILIZATION IS LIKELY FRIDAY AFTERNOON. DEEP LAYER SHEAR WILL BE MARGINALLY STRONG...UP TO 35KT...AND WHILE A FEW STRONG STORMS ARE POSSIBLE...THE BEST SHEAR AND INSTABILITY MAY NOT LINE UP FOR MUCH SEVERE THREAT. HIGHS WILL BE IN THE MID AND UPPER 70S. LOWS FRIDAY NIGHT MID TO UPPER 50S. && .LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 310 AM TUESDAY... THE COLD FRONT WILL MOVE THROUGH THE AREA FRIDAY EVENING AND THEN ESSENTIALLY WASH OUT AS SOUTHWESTERLY FLOW REDEVELOPS ON SATURDAY AHEAD OF A STRONGER SECONDARY FRONTAL ZONE MOVES INTO THE MID ATLANTIC STATES. MODELS SHOW CENTRAL NC REMAINING MOSTLY WITHIN THE WARM SECTOR THROUGH THE WEEKEND...WITH THE FRONT HOLDING JUST TO OUR NORTH. THERE ARE RATHER LARGE MODEL DIFFERENCES REGARDING PRECIP DEVELOPING ALONG THE FRONT AS A COUPLE OF SHORTWAVES ROTATE ACROSS THE GRAT LAKES REGION. A MORE SIGNIFICANT STORM SYSTEM IS FORECAST TO DEVELOP OVER THE SOUTH/CENTRAL PLAINS ON SUNDAY...WHICH SHOULD EVENTUALLY SPREAD BETTER PRECIP CHANCES ACROSS OUR REGION BY MONDAY INTO TUESDAY. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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AS OF 700 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 12Z 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
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...SMITH LONG TERM...SMITH AVIATION...HARTFIELD

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