Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 221641 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1241 PM EDT TUE APR 22 2014 .SYNOPSIS... A COLD FRONT WILL CROSS THE REGION THIS AFTERNOON ACCOMPANIED BY SCATTERED SHOWERS AND POSSIBLY A FEW THUNDERSTORMS. HIGH PRESSURE OVER THE MIDWEST WILL BUILD EASTWARD BY WEDNESDAY BRINGING A DRY...WINDY AND COOLER DAY. THE NEXT CHANCE FOR PRECIPITATION IS NOT UNTIL FRIDAY AS ANOTHER FRONT APPROACHES. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 945 AM EDT TUESDAY... COLD FRONT REMAINS WELL WEST OF THE MOUNTAINS THIS MORNING WITH A PRECEDING BAND OF SHOWERS ON THE WESTERN FRINGE OF THE CWA DENOTED BY A SLIGHTLY ENHANCED BAND OF CLOUDS OFF VIS PICS. THIS PRE- FRONTAL BAND LOOKS TO BE THE MAIN FOCUS OF ANY ADDITIONAL CONVECTION THROUGH THE AFTERNOON ESPCLY AS IT CROSSES THE BLUE RIDGE AFTER MIDDAY. LATEST GUIDANCE SHOWS BRIEF LOW LEVEL BACKING FROM THE SRN BLUE RIDGE EAST ALONG WITH SOME WEAK INSTABILITY AND A SLIGHTLY HIGHER AXIS OF 85H THETA-E SNEAKING INTO THE FOOTHILLS/PIEDMONT. HOWEVER CURRENT INCREASE IN CLOUDS FROM THE WEST LIKELY TO LIMIT CAPE AS WELL AS THE DEEP WESTERLY FLOW SEEN OFF MORNING SOUNDINGS. LATEST HRRR AND THE LOCAL RNK-WRF REMAIN MORE AGGRESSIVE IN DEVELOPING AT LEAST SOME SCTD SHRA/ISOLD TSRA ALONG THE BLUE RIDGE INTO NW NC AFTER 18Z/2PM AS A FAINT IMPULSE NOW OVER ERN TN SHEARS EAST. HOWEVER LOW LEVEL MOISTURE ALSO REMAINS LIMITED PER CURRENT DEWPOINTS SO ONLY HOLDING ONTO LIKELY POPS FOR NOW TO SEE HOW THINGS UNFOLD WITH BEST QPF OVER THE SW AND LEAST OVER THE NORTH. OTRW TRIMMING POPS BACK A BIT SOONER FAR WEST WHILE ADJUSTING TIMING CENTRAL/EAST. LEFT TEMPS CLOSE TO CURRENT VALUES EXCEPT LOWERING SOME NW PER CURRENT CLDNS AND LIGHT SHOWERS. PREVIOUS DISCUSSION AS OF 355 AM EDT TUESDAY... EARLY MORNING REGIONAL RADAR LOOPS SHOWS SCATTERED SHOWERS ACROSS PORTIONS OF OHIO AND WEST VIRGINIA BUT THESE ARE SO FAR DRYING UP AS THEY MOVE EAST INTO DRIER AIR MASS ACROSS OUR REGION. THE COLD FRONT REMAINS ON TRACK TO CROSS THE MOUNTAINS BY THIS AFTERNOON WITH SHOWERS AND POSSIBLY A FEW THUNDERSTORMS AHEAD OF AND ALONG IT. FORECAST SEVERE WEATHER PARAMETERS CONTINUE TO REMAIN MODEST WITH SREF MEMBERS AND OTHER MODELS SHOWING MEAN MLCAPES GENERALLY IN 400-600 J/KG RANGE...0-6 KM BULK SHEAR LESS THAN 30 KTS AT TIME OF MAXIMUM HEATING AND MID-LEVEL LAPSE RATES LESS THAN 7C. SPC DAY 1 OUTLOOK HAS THE REGION WELL WITHIN A SEE TEXT OR MARGINAL CHANCE OF SEVERE THIS AFTERNOON NOTING THE WEAK FORCING EXPECTED. BEST CHANCES FOR ISOLATED STRONG THUNDERSTORMS WOULD BE IN FAR EAST IF EARLY SOLAR HEATING IS ABLE TO BEAT THE INCOMING CLOUD COVER FOR A FEW HOURS AND GENERATE SOME INSTABILITY. DRY AIR WHICH HAS BEEN HOLDING TOUGH ALL NIGHT WILL BE FINALLY DISPLACED BY MODEST NORTHWARD SURGE OF MOISTURE AHEAD OF FRONT WITH FORECAST PWATS BRIEFLY REACHING 1 INCH IN THE AFTERNOON. HOWEVER QPF ALSO EXPECTED TO BE LIMITED WITH RELATIVELY DISORGANIZED NATURE OF THE CONVECTION AND STEADY EASTWARD MOVEMENT OF THE FRONT. GENERALLY EXPECTING TOTAL AMOUNTS FROM 0.10 TO 0.25 INCHES. WINDS SHIFT INTO WEST QUICKLY BEHIND FRONT AND SHARPLY COOLER AIR MOVES IN OVERNIGHT WITH UPPER 30S IN THE FAR NW TO LOW 50S IN THE EAST BY WED MORNING.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 300 AM EDT TUESDAY... SURFACE HIGH PRESSURE WILL TRACK ACROSS THE OHIO VALLEY WEDNESDAY AND BE OVERHEAD WEDNESDAY NIGHT. THE SURFACE HIGH SLIDES OFF THE SOUTHEAST COAST THURSDAY WITH A RETURN OF SOUTHERLY FLOW BY THE AFTERNOON. CLOUDS WILL BEGIN TO STREAM INTO THE REGION THURSDAY NIGHT AS THE NEXT FRONT APPROACHES THE REGION. THE PRESSURE GRADIENT REMAINS TIGHT WITH PRESSURE RISES CONTINUING ALONG WITH A 40-50KT CROSS-BARRIER JET OVER THE FORECAST AREA WEDNESDAY MORNING. BREEZY AND GUSTY CONDITIONS ARE EXPECTED INTO EARLY WEDNESDAY AFTERNOON. AS THE HIGH MOVES CLOSER TO THE REGION...THE WINDS WILL DIMINISH BY THE EVENING...BECOMING CALM WEDNESDAY NIGHT. FOLLOWING THE FRONTAL PASSAGE TUESDAY...WEDNESDAY TEMPERATURES WILL BE AROUND 5F COOLER THAN NORMAL. WITH THE HIGH OVERHEAD WEDNESDAY NIGHT...RADIATIONAL COOLING WILL DROP MOUNTAIN VALLEY TEMPERATURES INTO THE 30S WITH PATCHY FROST POSSIBLE. TEMPERATURES IN THE EAST MAY DROP TO 40F WEDNESDAY NIGHT WITH NO FROST EXPECTED. TEMPERATURES REBOUND QUICKLY TO NORMAL LEVELS THURSDAY WITH RANGES FROM THE UPPER 60S TO LOWER 70S. THURSDAY NIGHT WILL HAVE MILD TEMPERATURES IN THE 50S AHEAD OF THE NEXT FRONT. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 300 PM EDT MONDAY... DESPITE AN INCREASE IN CLOUDS AND A CHANCE FOR SHOWERS AND STORMS ASSOCIATED WITH A COLD FRONT FRIDAY...STRONG WARM AIR ADVECTION WITH A DEEP SOUTHWEST/WEST FLOW...SHOULD CONTINUE THE TREND FOR MODERATING TEMPS. THE PATTERN FRIDAY APPEARS VERY SIMILAR TO TUESDAY`S...WITH A FAST MOVING COLD FRONT MOVING INTO THE WEST EARLY ON FRIDAY AND EXITING DURING THE AFTERNOON. ONCE AGAIN...LOW LEVEL MOISTURE AND INSTABILITY WILL BE RACING NORTH TO INTERCEPT THE FRONT IN THE FAR EASTERN PORTION OF THE FORECAST AREA. THIS WILL BE WHERE THE BEST CHANCE FOR THUNDERSTORMS WILL TAKE PLACE. WHILE THE FRONT PASSES THROUGH FRIDAY AFTERNOON...THE STRONG COLD AIR ADVECTION IS DELAYED UNTIL LATER SATURDAY...SO ANOTHER WARM DAY IS ANTICIPATED EAST OF THE BLUE RIDGE. AFTER SATURDAY THERE ARE CONSIDERABLE DIFFERENCES IN THE LONG RANGE MODELS WITH THE GFS...CANADIAN AND GFS ENSEMBLES ALL KEEPING A SFC FRONT TO OUR SOUTH WITH A DRY NORTHWEST FLOW. MEANWHILE...THE 00Z/21 ECMWF KEEPS OUR AREA IN THE WARM SECTOR WITH A MOIST SOUTHERLY FLOW. THE GFS HAS SHOWN MORE RUN TO RUN CONSISTENCY AND THE LATEST GLOBAL WIND OSCILLATION (GWO) PLOT FAVORS AN EASTERN U.S. TROF. THEREFORE...NUDGED TEMPS DOWN A FEW DEGREES AND KEPT AREA FREE OF PRECIPITATION THROUGH THE WEEKEND. A QUICK LOOK AT THE 12Z ECMWF SHOWS A TREND TOWARD THIS COOLER SOLUTION. AS A SFC WARM FRONT BEGINS TO LIFT NORTH AND LOW LEVEL MOISTURE RETURNS...SCATTERED SHOWERS POSSIBLE IN THE MOUNTAINS. CONFIDENCE ON THE LOCATION OF THE WARM FRONT AND CHANCES FOR PRECIP ARE LOW. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/...
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AS OF 1220 PM EDT TUESDAY... BROKEN PRE-FRONTAL BAND OF -SHRA CONTINUES TO SHIFT SE ACROSS THE WEST EARLY THIS AFTERNOON WITH MOST RAINFALL REMAINING SOUTH/WEST OF THE TAF SITES. THIS SHOULD KEEP OVERALL VFR CONDITIONS GOING FOR A WHILE LONGER AS WESTERLY WINDS TEND TO ERODE THE EASTWARD PUSH OF THE PRECIP. HOWEVER EXPECT A GRADUAL INCREASE IN BOTH COVERAGE/INTENSITY OVER THE SW SECTIONS THIS AFTERNOON WITH AN EVENTUAL JUMP OUT EAST OF THE BLUE RIDGE BY 19Z/3PM. OTRW BEST CHANCE OF MVFR CIGS/VSBYS WILL BE AT BLF/LWB WITH LOWERING CIGS UNDER UPSLOPE FLOW AND LIGHTER SHOWERS. BAND OF ISOLATED TO SCATTERED SHRA/TSRA POSSIBLE ALONG THE LYH-DAN CORRIDOR THIS AFTERNOON WHERE A PERIOD OF MVFR CONDITIONS ALSO POSSIBLE BUT LOW CONFIDENCE AT THIS POINT. COULD SEE BRIEF STRONG WINDS IN ANY THUNDERSTORMS THAT DO DEVELOP. THE FRONT WILL EXIT THE REGION THIS EVENING...RESULTING IN A RETURN TO VFR WEATHER AND GUSTY NW WINDS OVERNIGHT INTO WEDNESDAY. ONLY EXCEPTTION IS THE POTENTIAL OF SOME MVFR CIGS AND SPOTTY -SHRA LINGERING OVER THE FAR WESTERN UPSLOPE SITES IN SE WEST VA. PERIODS OF STRONGER WINDS WILL OCCUR BEHIND THE FRONT OVERNIGHT WITH GUSTS TO 30 KTS POSSIBLE...AND AGAIN WITH STRONG MIXING WEDNESDAY. EXTENDED AVIATION DISCUSSION... HIGH PRESSURE WILL THEN BUILD INTO AND OVER THE REGION ON THURSDAY...WITH WIDESPREAD VFR LIKELY. ANOTHER FAST MOVING COLD FRONT WILL ARRIVE ON FRIDAY...WITH A BRIEF PERIOD OF MVFR RESTRICTIONS POSSIBLE AS SHOWERS/ISOLATED STORMS MOVE EAST WITH THE FRONT THROUGH THE AREA. STRONG HIGH PRESSURE BUILDS IN FRIDAY NIGHT INTO SATURDAY WITH VFR EXPECTED UNDER GUSTY NORTHWEST WINDS.
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&& .FIRE WEATHER...
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AS OF 945 AM EDT TUESDAY... COLD FRONT WILL CROSS THE REGION THIS AFTERNOON WITH MODEST RAINFALL RANGING FROM LESS THAN 0.10 INCHES IN THE PIEDMONT UP TO AROUND 0.25 INCHES IN THE SOUTHWEST MOUNTAINS AND PERHAPS NORTH CAROLINA FOOTHILLS. STRONG NW WINDS WILL FOLLOW THE FRONT ON WEDNESDAY WITH GUSTS TO 25 TO 35 MPH POSSIBLE ALONG WITH ANOTHER QUICK DROP IN HUMIDITY WEDNESDAY AFTERNOON. THIS MAY LEAD TO ENHANCED FIRE DANGER ESPECIALLY IF LESS WETTING RAINFALL IS REALIZED WITH THE FRONTAL PASSAGE THIS AFTERNOON/EVENING. A FIRE WEATHER WATCH MAY BE NEEDED FOR PARTS OF THE AREA ON WEDNESDAY. THE NEXT BEST OPPORTUNITY FOR PRESCRIBED BURNS WHERE GOOD DRYING CONDITIONS WILL EXIST...AND WHERE TRANSPORT WINDS WILL BE MORE FAVORABLE DUE TO BETTER TRANSPORT AND CONSISTENCY OF DIRECTION WILL OCCUR ON THURSDAY AT THIS POINT.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PC NEAR TERM...JH/PC SHORT TERM...RCS LONG TERM...PH AVIATION...JH/KK/PC FIRE WEATHER...JH/KK

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