Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 271855 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 255 PM EDT SAT JUN 27 2015 .SYNOPSIS...AN UNSEASONABLY STRONG COLD FRONT WILL CROSS THE MOUNTAINS THIS EVENING. THE FRONT WILL SLOWLY MOVE ACROSS THE CAROLINAS TONIGHT AND SUNDAY AND STALL NEAR THE COAST ON MONDAY. A COOLER AND DRIER AIR MASS WILL BUILD INTO THE REGION FOR LATE SUNDAY AND MONDAY BEFORE THE NEXT STORM SYSTEM APPROACHES ON TUESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1245 PM SATURDAY... ONLY A FEW ADJUSTMENTS TO THE PREVIOUS FORECAST ARE WARRANTED THIS MORNING. FAIRLY WIDESPREAD STRATUS WAS LOCATED ACROSS CENTRAL NC THIS MORNING WITH A FEW BREAK MAINLY CONFINED TO THE COASTAL PLAIN REGION. THESE CLOUDS HAVE LIMITED INSOLATION AND TEMPERATURES HAVE BEEN SLOW TO WARM. SOME THINNING HAS BEGUN DURING THE RECENT HOURS AND TEMPERATURES HAVE REACHES THE LOWER TO MID 80S ACROSS THE SOUTHERN PIEDMONT AND SANDHILLS. HAVE ADJUSTED THE HOURLY TEMPS TO SHOW A DELAYED RISE AND REDUCED MAX TEMPS DOWN A DEGREE OR SO...MAINLY ACROSS THE NORTH. AN AREA OF CONVECTION IS LOCATED ACROSS NORTHEAST NC WAS BEING DRIVEN BY A SHORTWAVE TROUGH AND THE NORTHEAST ADVANCEMENT OF THE 850MB FRONT. THIS AREA OF CONVECTION WILL CONTINUE TO LIFT NORTHEAST AND EXPAND ACROSS THE SOUTHEASTERN PIEDMONT AND COASTAL PLAIN. OTHER SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP ACROSS THE WESTERN PIEDMONT THIS AFTERNOON AND BECOME MORE NUMEROUS AS THE UNSEASONABLY STRONG DEEP UPPER TROUGH AND A PRE FRONTAL TROUGH APPROACH. THERE IS LITTLE CHANGE IN THE THINKING REGARDING THE POTENTIAL FOR SEVERE WEATHER THIS AFTERNOON AND EVENING. THE STRENGTHENING MID LEVEL FLOW WILL RESULT IN SUFFICIENT SHEAR TO SUPPORT ORGANIZED CONVECTION...ESPECIALLY ACROSS THE NORTHERN HALF OF THE CWA. INSTABILITY HAS BEEN RETARDED BY WIDESPREAD CLOUDINESS THIS MORNING BUT WE EXPECT THE SUN TO BREAK OUT AT TIMES AND PRODUCE MODERATE INSTABILITY WITH MLCAPE VALUES RANGING BETWEEN 1500-2500 J/KG. MID LEVEL LAPSE RATES ARE MARGINAL HOWEVER AND WILL RANGE (5.5-6.0 C/KM). THE SPC MAINTAINS THE ELEVATED SEVERE WEATHER THREAT TODAY WITH A PRIMARY THREAT OF DAMAGING WINDS RESULTING FROM TO DAMAGING WINDS GIVEN THE STRONG MID-LEVEL FLOW...MODERATE TO STRONG UPDRAFTS AND PRECIPITATION LOADING. HAIL IS ALSO A THREAT GIVEN THE POTENTIAL FOR SUSTAINED UPDRAFTS IN SUPERCELLS. THE TORNADO RISK IS SMALL BUT EXISTS GENERALLY CLOSE TO THE VA BORDER IN CLOSER VICINITY TO THE ENHANCED LOW LEVEL SHEAR NEAR A NORTHWARD ADVANCING WARM FRONT. A FLASH FLOOD WATCH REMAINS IN EFFECT THROUGH THIS EVENING ACROSS THE WEST AND THROUGH THE OVERNIGHT IN THE EAST. ANTICIPATING THE EVOLUTION OF THE CONVECTION AND REFINING MANY DETAILS IN THE DISTRIBUTION OF RAINFALL IS PROBLEMATIC. HOWEVER THERE IS STILL A SUFFICIENT POTENTIAL FOR HEAVY RAIN GIVEN PW VALUES OF 1.9 TO 2.0 INCHES. THIS COMBINED WITH THE CONVECTION LIKELY OCCURRING IN MULTIPLE ROUNDS WARRANTS MAINTAINING THE WATCH. -BLAES && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
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AS OF 250 PM SATURDAY... THE COLD FRONT IS EXPECTED TO BE OFFSHORE BY SUNDAY MORNING...THUS ALL PRECIP SHOULD BE EAST OF THE AREA TO START THE DAY. SKIES WILL GRADUALLY BE CLEARING THROUGHOUT THE DAY AS DRIER AIR FILTERS IN. THIS WILL RESULT IN PARTLY TO MOSTLY CLEAR SKIES FOR MUCH OF THE DAY. IN ADDITION...IT WILL FEEL NOTICEABLY COOLER AND DRIER (ESPECIALLY AFTER OUR RECENT HEAT WAVE)...WITH HIGHS REMAINING IN THE MID/UPPER 80S. A CLEAR AND (RELATIVELY) COOL NIGHT IS EXPECTED...WITH MIN TEMPS FALLING INTO THE UPPER 50S TO LOWER 60S.
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&& .LONG TERM /MONDAY THROUGH SATURDAY/...
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AS OF 250 PM SATURDAY... LONGWAVE TROUGHING WILL SET UP OVER THE EASTERN HALF OF THE CONUS THROUGH MUCH OF NEXT WEEK...BEFORE FLATTENING OUT SOME BY THE END OF THE WEEK. GIVEN THIS SET UP...ANY SHORT WAVE CROSSING THE REGION WILL BRING A CHANCE FOR (MOSTLY DIURNAL) SHOWERS/STORMS...ESPECIALLY FROM WEDNESDAY AND BEYOND AS THE PIEDMONT TROUGH BECOMES BETTER DEFINED. INCREASING POPS SLIGHTLY MORE BY THE END OF THE WEEK WILL BE THE APPROACH OF ANOTHER COLD FRONT...ALTHOUGH IT MAY NOT MAKE ALL THE WAY INTO NC...POSSIBLY STALLING OUT NEAR THE NC/VA BORDER. TEMPS WILL GRADUALLY MODERATE THROUGH THE PERIOD...WITH MOSTLY NEAR TO SLIGHTLY ABOVE NORMAL EXPECTED.
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&& .AVIATION /18Z SATURDAY THROUGH WEDNESDAY/... AS OF 230 PM SATURDAY... 24-HOUR TAF PERIOD...WIDESPREAD CUMULUS AND STRATO-CUMULUS ACROSS CENTRAL NC HAS RESULTED IN MVFR TO VFR CEILINGS WHICH WILL CONTINUE INTO THE EARLY OVERNIGHT HOURS. A CLUSTER OF THUNDERSTORMS ACROSS THE SOUTHERN PIEDMONT AND SANDHILLS WILL LIFT NORTH THIS AFTERNOON LIKELY IMPACTING THE TERMINALS AT KRDU AND KRWI DURING THE NEXT HOUR OR TWO. ADDITIONAL CONVECTION WILL DEVELOP IN CLUSTERS AND LINE SEGMENTS AND MOVE ACROSS CENTRAL NC DURING THE LATE AFTERNOON AND EVENING HOURS WITH PERIODS OF IFR CONDITIONS IN SHOWERS AND THUNDERSTORMS. THE CONVECTION WILL END FROM WEST TO EAST AS A COLD FRONT MOVES ACROSS THE STATE. ANY VISIBILITY OR CEILING RESTRICTIONS SHOULD END THE KINT AND KGSO TRIAD TERMINALS AT AROUND 03Z AND CLOSER TO 06Z AT THE KRWI AND KFAY TERMINALS. VFR CONDITIONS WITH A WEST TO NORTHWEST WIND ARE EXCEPTED FOR THE REMAINDER OF THE PERIOD INCLUDING SUNDAY. LOOKING AHEAD... VFR CONDITIONS ARE EXPECTED TO DOMINATE THROUGH EARLY NEXT WEEK AS A DRY AIRMASS ADVECTS INTO THE REGION. THE TREAT OF MAINLY AFTERNOON AND EVENING THUNDERSTORMS ARRIVES ON TUESDAY AND INCREASES ON WEDNESDAY. -BLAES && ..RAH WATCHES/WARNINGS/ADVISORIES... FLASH FLOOD WATCH THROUGH SUNDAY MORNING FOR NCZ009>011-026>028-041>043-077-078-085-086-088- 089. FLASH FLOOD WATCH THROUGH THIS EVENING FOR NCZ007-008-021>025- 038>040-073>076-083-084. && $$ SYNOPSIS...BLAES NEAR TERM...BLAES SHORT TERM...KRD LONG TERM...KRD AVIATION...BLAES

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