Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 241751 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 151 PM EDT SUN APR 24 2016 .SYNOPSIS... HIGH PRESSURE ACROSS THE REGION WILL SLIDE SOUTHEAST TO THE COAST LATER TODAY AND TONIGHT...THEN OFFSHORE THE CAROLINAS MONDAY. THE NEXT COLD FRONT WILL DROP SOUTH INTO THE AREA ON TUESDAY AND THEN LINGER RESULTING IN UNSETTLED WEATHER THROUGH MIDWEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 130 PM EDT SUNDAY... TRANQUIL WEATHER EXPECTED TO CONTINUE THROUGH THE PERIOD AS HIGH PRESSURE ALONG THE EASTERN SEABOARD SLOWLY SHIFTS EAST THROUGH THE PERIOD. LIGHT SOUTHEAST WINDS WILL COME AROUND TO SOUTHWEST THROUGH THE PERIOD...THEN INCREASE AFTER DAYBREAK MONDAY. CLEAR SKIES EXPECTED UNTIL OVERNIGHT WHEN SOME CIRRUS WILL START TO SPREAD IN FROM THE WEST. GFS REMAINS TOO AGGRESSIVE IN TRYING TO BRING RETURN MOISTURE NORTHWARD THROUGH THE APPALACHIANS OVERNIGHT INTO MONDAY. NAM/CANADIAN/ECMWF MUCH DRIER AND MORE PLAUSIBLE. NONETHELESS...EXPECT RH VALUES TO INCREASE ON THE HEELS OF INCREASING SSW SURFACE FLOW MONDAY...ALLOWING FOR SCT CU DEVELOPMENT BY LATE MORNING...POSSIBLY BROKEN BY THE AFTERNOON. ONLY THE GFS HINTS AT ANY QPF/SPRINKLES WITH THIS MOISTURE THROUGH THE APPALACHIANS. FOR THIS AFTERNOON...TEMPERATURES RUNNING A LITTLE WARMER THAN FORECAST. OTHERWISE...ALL PARAMETERS ARE WITHIN TOLERANCE. ALTHOUGH RH VALUES ARE DROPPING INTO THE 30 PERCENT RANGE THIS AFTERNOON...WINDS ARE WELL BELOW ANY CRITICAL FIRE WEATHER CRITERIA. AS OF 230 AM EDT SUNDAY... MAINLY A TEMPERATURE FORECAST THROUGH TONIGHT UNDER SHORTWAVE RIDGING WHILE SURFACE HIGH PRESSURE TRAVERSES FROM THE MID ATLANTIC COAST TODAY TO OVER EASTERN NORTH CAROLINA LATER TONIGHT. THIS WILL KEEP SUBSIDENCE IN PLACE AS THE FLOW TURNS FROM MORE OF A LIGHT AND VARIABLE...MAINLY NORTHERLY COMPONENT TODAY UNDER THE RIDGE AXIS...TO A SOUTH AND EVENTUALLY SW TRAJECTORY ALOFT OVERNIGHT WITH THE RETURN FLOW REGIME. THIS SUPPORTS KEEPING IT MAINLY SUNNY TODAY AFTER EARLY FOG/PATCHY FROST MOUNTAIN VALLEYS...AND CLEAR OVERNIGHT WITH POSSIBLE HIGH CLOUDS WEST LATE AHEAD OF MUCH WARMER 85H AIR INVADING FROM THE WEST. WARMEST AIR ALOFT WILL REMAIN OVER THE WEST TODAY AS THE RESIDUAL 85H COOL POOL LINGERS OUT EAST WITH BETTER RETURN FLOW WARM ADVECTION DEVELOPING WEST OF THE BLUE RIDGE LATER THIS AFTERNOON. LATEST PROGGED THICKNESS VALUES SHOW LITTLE CHANGE FROM SATURDAY IN THE EAST WITH LATE DAY RISES FAR WEST UNDER INCREASING SW FLOW ALOFT. MOS ALSO REMAINS A BIT WARMER FAR WEST/SW WHERE STAYING WITH LOW/MID 70S WHILE COOLER PIEDMONT GIVEN COOLER AIR ALOFT AND LINGERING NORTH/NE FLOW UNTIL LATER TODAY. HOWEVER THINK HEATING OF DRY AIR LIKELY TO EVEN THINGS OUT SO ALSO TRENDING TOWARD 70-75 EAST WITH WARMER VALUES CLOSER TO THE BLUE RIDGE.
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&& .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 AM EDT SUNDAY... WEAK HIGH PRESSURE REMAINS ALONG THE EAST COAST MONDAY. MEANWHILE...LOW PRESSURE WITH ASSOCIATED WARM FRONT EXTENDING EASTWARD INTO SOUTHERN NEW ENGLAND AND COLD FRONT TRAILING SOUTH WILL MOVE SLOWLY EAST MONDAY INTO MONDAY NIGHT. HIGH TEMPERATURES ON MONDAY WILL RANGE FROM THE LOWER 70S IN THE MOUNTAINS TO THE LOWER 80S IN THE PIEDMONT. A WEAK UPPER AIR DISTURBANCE MAY TRIGGER AN ISOLATED SHOWER IN THE MOUNTAINS MONDAY AFTERNOON. HOWEVER...MOST AREAS WILL REMAIN DRY. THE QUIET MILD WEATHER WILL CONTINUE MONDAY NIGHT WITH LOW TEMPERATURES VARYING FROM THE MID 50S IN THE WEST TO NEAR 60 DEGREES IN THE EAST. THERE WILL BE LITTLE FRONTAL MOVEMENT UNTIL TUESDAY WHEN A NORTHERN STREAM SHORTWAVE MOVES SOUTHEAST THROUGH NEW ENGLAND...FORCING THE BACKDOOR FRONT SOUTHWARD. ON TUESDAY...THE FRONTAL ZONE/BAROCLINIC ZONE WILL SHIFT SOUTHWARD INTO THE REGION...REACHING THE CWA DURING THE AFTERNOON/EVENING. JUST HOW FAR SOUTH DOES THE FRONT TRAVEL IS THE FORECAST QUESTION. THERE REMAINS CONSIDERABLE DIFFERENCES BETWEEN THE VARIOUS MODELS AS TO THE TIME OF ARRIVAL OF THE FRONT AND THE DEGREE OF ASSOCIATED INSTABILITY/CONVECTION. THE GFS CONTINUES TO BE THE FASTEST AND MOST UNSTABLE SOLUTION WITH A MORE ROBUST CONVECTION AND QPF. THE ECMWF AND NAM ARE SLOWER THAN THE GFS...AND ALSO INDICATE NOTABLY LESS INSTABILITY AND MOISTURE. USED A COMPROMISED SOLUTION WITH THE FRONT REACHING THE AREA TUESDAY EVENING AND THEN STALLING. HIGH TEMPERATURES TUESDAY WILL CLIMB INTO THE MID 60S IN THE NORTHWEST MOUNTAINS TO THE MID 80S IN THE PIEDMONT. THERE IS ENOUGH INSTABILITY TO MENTION THUNDERSTORMS...BUT BEST FORCING REMAINS TO THE NORTH WITH LIMITED SHEAR. THUS...NOT EXPECTING STRONG OR SEVERE THUNDERSTORMS. LOW TEMPERATURES TUESDAY NIGHT WILL GENERALLY FROM THE LOWER 50S TO AROUND 60 DEGREES. UNSETTLED WEATHER WILL CONTINUE WEDNESDAY WITH FRONTAL BOUNDARY SLOWING OR STALLING...BEFORE RETURNING NORTHWARD LATER IN THE WEEK AS A WARM FRONT. HIGHS ON WEDNESDAY WILL FEATURE THE MID 60S IN THE MOUNTAINS TO AROUND 80 DEGREES IN THE PIEDMONT. LOOK FOR LOW TEMPERATURES WEDNESDAY NIGHT INTO THURSDAY MORNING TO DROP INTO THE MID 50S IN THE WEST TO THE UPPER 50S IN THE EAST. && .LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 300 AM EDT SUNDAY... UNSETTLED WEATHER EXPECTED THROUGH THE PERIOD WITH ALMOST MULTIPLE DAILY CHANCES FOR SHOWERS/THUNDERSTORMS AS A STALLED FRONTAL BOUNDARY LINGERS ACROSS THE REGION. ALBEIT SCATTERED...THE RAINFALL WILL BE WELCOME TO ALLEVIATE THE DRY/CRITICAL FIRE WEATHER CONDITIONS. BUT...NO WIDESPREAD GENERAL SOAKING RAIN IS FORESEEN THROUGH THE PERIOD...MAINLY SCATTERED CONVECTION. AS NOTED ABOVE...THERE ARE DIFFERENCES AMONG THE MODELS AS TO WHERE THE BOUNDARY WILL STALL...BUT IN ANY EVENT...IT WILL RETURN OR BE LOCATED OVER THE REGION IN THE THU- SAT TIME FRAME. IN ADDITION...THE NEXT IN THE SERIES OF STRONGER CENTRAL U.S. UPPER TROUGHS/SHORT WAVES WILL BE SHEARING OUT AND HEADING EASTWARD BY FRIDAY...WHICH WILL SERVE TO ENHANCE FOR CHANCES FOR SHOWERS AND THUNDERSTORMS. THERE IS ENOUGH INSTABILITY PRESENT AND GIVEN THE TIME OF YEAR TO SUPPORT MENTION OF THUNDER MOST AFTERNOON/EVENINGS THROUGH THE PERIOD. TEMPERATURES WILL CONTINUE TO BE ABOVE NORMAL THROUGH THE PERIOD WITH SW-WSW FLOW ALOFT AND UPPER RIDGING JUST TO OUR SOUTHEAST...AGAIN WITH NO APPRECIABLE CHANGE IN AIR MASS. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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AS OF 145 PM EDT SUNDAY... VFR CONDITIONS EXPECTED TO CONTINUE THROUGH MOST OF THE TAF VALID PERIOD AS HIGH PRESSURE EXTENDING NORTH-SOUTH ALONG THE EASTERN SEABOARD SLOWLY DRIFTS EAST THROUGH THE PERIOD. LIGHT SOUTHEAST WINDS WILL COME AROUND TO THE SOUTHWEST BY MONDAY MORNING AND INCREASE AFT 14Z MONDAY. SOME LOW END GUSTS POSSIBLE MONDAY AFTERNOON. THESE S-SW WINDS WILL ALSO ALLOW LOW-LEVEL MOISTURE FROM THE GULF TO GRADUALLY CREEP N-NE DURING THE DAY MONDAY ALLOWING FOR SCT TO POTENTIALLY BKN CU IN THE 045-060 RANGE BY 18Z MON. OTHERWISE...ONLY SOME AREAS OF CIRRUS EXPECTED MAINLY ACROSS THE NORTHERN PARTS OF THE CWA. FRONTAL BOUNDARY NEAR THE U.S./CANADIAN BORDER WILL REMAIN WELL NORTH OF THE REGION THROUGH MONDAY...THEN BEGIN A SLOW SOUTHWARD MOVEMENT INTO NORTHERN VA/WV BY TUESDAY AFTERNOON...THEN INTO OUR REGION BY WED. THE ONLY EXCEPTION TO VFR CONDITIONS THROUGH THE PERIOD WOULD BE PATCHY MORNING FOG IN THE VALLEYS...MAINLY AFFECTING KLWB AND KBCB AS IT DID THIS MORNING. HOWEVER...WITH A WARMER AIR MASS IN PLACE TONIGHT AND SLIGHTLY STRONGER WINDS...AM NOT ANTICIPATING DEVELOPMENT OF LIFR CONDITIONS AS WE SAW THIS MORNING. IFR-MVFR AT WORST...CONFINED TO THE 08Z-13Z TIME FRAME. HIGH CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND DIR/SPD THROUGH THE TAF VALID PERIOD. EXTENDED AVIATION DISCUSSION... VFR CONDITIONS EXPECTED TO CONTINUE MONDAY INTO MUCH OF TUESDAY...OUTSIDE ANY PATCHY LATE NIGHT/EARLY MORNING FOG. A WEAK BACKDOOR COLD FRONT WILL DRIFT INTO NORTHERN VA/WV BY TUESDAY AFTERNOON...THEN SLOWLY SOUTHWARD INTO SOUTHERN VA/NORTHERN NC BY WED AFTERNOON...THEN STALL AWAITING A STRONGER FRONT FOR THU ARRIVING FROM THE WEST. SCT SHOWERS/THUNDERSTORMS ARE EXPECTED TO ACCOMPANY THE FRONT. HOW FAR SOUTH THESE GET TUESDAY IS IN QUESTION AND MOST MODELS SUGGEST THAT THEY WILL NOT MOVE SOUTH OF THE I-64 CORRIDOR UNTIL AT LEAST AFT 00Z WED. MORE LIKELY SEE REDEVELOPMENT OF SHRA/TSRA WED AFTERNOON NEAR THE LINGERING BOUNDARY. BRIEF PERIOD OF MVFR-IFR CIGS/VSBYS POSSIBLE IN THUNDERSTORMS...BUT OVERALL THE PERIOD APPEARS TO BE VFR OUTSIDE THIS AND ANY EARLY MORNING FOG...WHICH MAY BE ON THE INCREASE AS LOW-LEVEL MOISTURE ALSO INCREASES THROUGH THE PERIOD. BEST CHANCE FOR WIDESPREAD SHRA/TSRA AND SUB-VFR CONDITIONS WOULD BE THURSDAY.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...JH/RAB SHORT TERM...KK LONG TERM...KK/RAB AVIATION...JH/RAB

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