Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 301908 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 304 PM EDT TUE JUN 30 2015 .SYNOPSIS...AN INCREASINGLY ACTIVE CYCLONIC FLOW ALOFT WILL PREVAIL OVER THE REGION THROUGH THE END OF THE WORK WEEK. && .NEAR TERM /TODAY AND TONIGHT/...
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AS OF 300 PM TUESDAY... THE WESTERN HALF OF THE CWA CONTINUES TO BE UNDER A SLIGHT RISK FOR SEVERE THUNDERSTORMS WITH DAMAGING WINDS THE MOST LIKELY THREAT. THE SPC HAS ISSUED A MESOSCALE DISCUSSION FOR CENTRAL NC AND INDICATES THAT A SEVERE THUNDERSTORM WATCH IS POSSIBLE LATER THIS AFTERNOON/EVENING BUT IT IS UNCLEAR AT THIS TIME HOW CONVECTION ENTERING UPSTATE SOUTH CAROLINA WILL EVOLVE. SEVERE STORMS ARE CURRENTLY ONGOING IN THIS AREA WITH SEVERAL REPORTS OF WIND DAMAGE ALREADY. WITH A ROBUST SHORTWAVE SUPPLYING THE VORTICITY AND UPPER DIVERGENCE BEING HELPED BY AN EXITING JET TO THE NORTHEAST...EFFECTIVE SHEAR IN THE AREA OF CONVECTION HAS BEEN AROUND 30-35 KTS WITH MULTI CELLULAR CONVECTION STARTING TO EVOLVE INTO LINE SEGMENTS AS OF LAST HOUR. THIS AMOUNT OF SHEAR IS EXPECTED TO BE MAINTAINED OVER THE NEXT SEVERAL HOURS BEFORE WEAKENING SLIGHTLY AROUND 00Z. A LOT OF THIS SHEAR IS WELL OFF THE DECK AND LOW LEVEL SHEAR AND HELICITY VALUES ARE FAIRLY LOW DURING THE TIME OF CONVECTION LIMITING THE TORNADO THREAT. ON THE INSTABILITY SIDE OF THINGS...CONVECTION WILL BE MOVING INTO AN AREA OF 1000-1500 J/KG OF MIXED LAYER CAPE AND BRINGING WITH IT AN AREA OF 1200-1400 J/KG OF DCAPE. LOW LEVEL LAPSE RATES AT THIS TIME ARE VERY HIGH WITH A MODERATE 6 DEG/KM OR SO IN THE MID-LEVELS. WITH CURRENT CONVECTION ALREADY ORGANIZING IT IS NOT HARD TO ENVISION IT HANGING TOGETHER AS THE VORT MAX MAKES ITS WAY UP THE PIEDMONT TROUGH. WHILE DIURNAL TIMING MAY NOT YIELD QUITE AS GOOD OF AN ENVIRONMENT AS THE STORMS ARE CURRENTLY IN...CONFIDENCE IS FAIRLY GOOD THAT AT LEAST SOME ACTIVITY WILL MOVE INTO THE CWA FROM THE SOUTHWEST AND PROPAGATE ACROSS THE CWA EXITING SOMETIME AFTER 5Z OR SO ON WEDNESDAY MORNING. EXPECT THE BEST CHANCE FOR STRONGER CONVECTION ACROSS THE SOUTHWEST PIEDMONT AND INTO THE WESTERN SANDHILLS BEFORE STARTING TO WEAKEN AS IT HEADS NORTHEAST. CONVECTION IS POSSIBLE IN THE TRIAD AS WELL AS ANOTHER LINE OF STORMS IS BEGINNING TO POP UP ALONG THE FOOTHILLS. ALL OF THIS ACTIVITY SHOULD TRANSLATE EASTWARD. WHILE THE TRIANGLE MAY NOT GET THE BRUNT OF THE ACTIVITY...STRONG STORMS ARE CERTAINLY POSSIBLE IN THIS AREA AS WELL BUT MIGHT BE ON THE NORTHERN FRINGE OF THE STRONGER ACTIVITY. OVERNIGHT TONIGHT SKIES SHOULD BEGIN TO CLEAR OUT WITH AN OUTSIDE CHANCE OF SOME FOG/LOW STRATUS EXISTS IN THE EAST WITH LOWS MID 60S TO LOWER 70S.
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&& .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
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AS OF 300 PM TUESDAY... ON WEDNESDAY THE UPPER LEVEL TROUGH OVER THE EASTERN CONUS RELAXES A LITTLE AND A STRONG SURFACE LOW EXITS THE GREAT LAKES REGION TO THE NORTHEAST AND MOVES INTO SOUTHERN ONTARIO. WITH A GAP IN THE MOISTURE BEHIND THIS SYSTEM AND AHEAD OF WHAT WILL BE A STRING OF APPROACHING SHORTWAVES FROM THE MIDWEST...LOOK FOR A RELATIVELY DRY DAY ON WEDNESDAY WITH AN ISOLATED DIURNAL SHOWER OR THUNDERSTORM POSSIBLE BUT OTHERWISE DRY. WITH THE BERMUDA HIGH FORCED OFF THE COAST AND CENTRAL NC SITTING AT THE BASE OF THE UPPER TROUGH...TEMPERATURES WILL STAY FAIRLY REASONABLE FOR THIS TIME OF YEAR WITH HIGHS IN THE UPPER 80S NW TO LOW 90S SE. FORECAST SOUNDINGS DO NOT INDICATE MUCH CHANCE FOR FOG OR LOW STRATUS THURSDAY MORNING BUT A BROKEN LOW CEILING IS NOT OUT OF THE QUESTION IN THE EAST BUT CONFIDENCE IN THAT HAPPENING IS VERY LOW AT THIS TIME.
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/... AS OF 300 PM TUESDAY... THE GENERAL OVERALL PATTERN WILL BE DOMINATED BY GENERAL TROUGHINESS IN THE UPPER LEVELS OVER THE EASTERN U.S. WITH A FEW SHORTWAVE DISTURBANCES PROGRESSING THROUGH THE AREA. AT THE SURFACE...A WARM FRONT WILL LIFT NORTH THROUGH NC THURSDAY NIGHT INTO FRIDAY. EXPECT GENERAL LOW PRESSURE TO LINGER OVER THE SOUTHEAST U.S. AND HIGH PRESSURE STUCK OVER THE EASTERN GREAT LAKES AND NEW ENGLAND THEREAFTER. SMALL VARIATIONS IN THIS PATTERN WILL HAVE BIG IMPACTS ON THE CHANCES...TIMING...AND LOCATION OF CONVECTION...THUS CONFIDENCE IS NOT TERRIBLY HIGH IN THAT RESPECT. GENERALLY THOUGH... EXPECT THE USUAL HIGHEST CHANCES IN THE AFT/EVE AND LOWEST OVERNIGHT/EARLY MORNING. TEMPERATURE WISE: WITH THE EXCEPTION OF FRIDAY (WHICH FOR NOW APPEARS TO BE THE COOLEST DAY)...HIGHS WILL GENERALLY BE IN THE UPPER 80S TO LOW 90S THROUGH THE PERIOD...WITH OVERNIGHT LOWS STEADY IN THE UPPER 60S TO LOW 70S TO SLIGHTLY INCREASING EARLY NEXT WEEK. && .AVIATION /18Z TUESDAY THROUGH MONDAY/... AS OF 200 PM TUESDAY... 24 HOUR TAF PERIOD: VFR CONDITIONS PREVAILING ACROSS THE CWA THIS AFTERNOON WITH STRATOCUMULUS STARTING TO ENCROACH FROM THE WEST AS A SHORTWAVE APPROACHES FROM THE SOUTHWEST. WINDS WILL BE VARIABLE AT TIMES THIS AFTERNOON BUT GENERALLY 5-10 KTS AND WITH A SOUTHWESTERLY COMPONENT. SOME WIND GUSTS OF AROUND 15-20 KTS WILL CONTINUE THROUGH SUNSET BEFORE DISSIPATING. A LINE OF CONVECTION MOVING INTO UPSTATE SOUTH CAROLINA WILL CONTINUE TO DEVELOP TO THE NORTHEAST AND TRACK ACROSS THE AREA THIS EVENING. WHILE THERE IS GREAT UNCERTAINTY WHETHER OR NOT STRONGER STORMS WILL AFFECT THE TRIAD AIRPORTS TIMING FOR AT LEAST SOME SHOWERS IN THIS AREA WILL BE BETWEEN 21Z AND 00Z. A RAGGED LINE OF STORMS COULD PROGRESS EASTWARD THROUGH THE EVENING AFFECTING KRDU AND KFAY AROUND 00Z AND PROGRESSING EASTWARD OUT OF THE CWA BY 5Z AT THE LATEST. SOME SEVERE STORMS ARE POSSIBLE IN THIS LINE WITH DAMAGING WINDS THE MOST LIKELY THREAT. AFTER STORMS EXIT TO THE EAST...EXPECT SOME GENERAL CLEARING WITH SOME FOG/LOW STRATUS POSSIBLE...ESPECIALLY AT THE EASTERN 3 TERMINALS. THIS WILL DISSIPATE AT OR SHORTLY AFTER SUNRISE AND CONDITIONS WILL RETURN TO VFR. WE CAN EXPECT MOSTLY CLEAR SKIES AND SOUTHWESTERLY WINDS THROUGH THE END OF THE TAF PERIOD. LONG TERM: CENTRAL NC IS SETTING UP TO BE IN A FAIRLY ACTIVE AND UNSETTLED PATTERN FOR THE NEXT SEVERAL DAYS WITH PERIODS OF ADVERSE CONDITIONS POSSIBLE THROUGH EARLY NEXT WEEK. && ..RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...ELLIS SHORT TERM...ELLIS LONG TERM...RAH AVIATION...ELLIS

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