Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 291126 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 726 AM EDT FRI MAY 29 2015 .SYNOPSIS... HIGH PRESSURE OFFSHORE WILL MAINTAIN A MOIST SOUTHERLY FLOW ACROSS THE REGION TODAY INTO THE WEEKEND. A COLD FRONT WILL APPROACH FROM THE NORTHWEST LATE IN THE WEEKEND BEFORE DIPPING SOUTH OF THE AREA EARLY NEXT WEEK RESULTING IN MORE WIDESPREAD SHOWERS AND STORMS LATER SUNDAY INTO MONDAY. COOLER AND DRIER CONDITIONS WILL THEN BUILD IN FROM THE NORTH BY THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 220 AM EDT FRIDAY... OVERALL PERSISTENCE FORECAST LOOKS IN ORDER TODAY WITH CONTINUED MOISTURE FEED ON SE FLOW BETWEEN HIGH PRESSURE WELL OFFSHORE AND THE NEXT UPPER TROUGH WELL TO THE WEST. FOCUS AGAIN OTHER THAN FOR OROGRAPHICS AND RESIDUAL OUTFLOW LOOKS WEAK WITH ONLY A FAINT BOUNDARY ACROSS THE NORTH TO HELP WITH ADDED FORCING THIS AFTERNOON. HOWEVER MOST LATEST SHORT TERM GUIDANCE SHOWS A BIT FASTER DEVELOPMENT MAINLY ACROSS THE NW AND BLUE RIDGE BY EARLY AFTERNOON...WITH BEST COVERAGE PROGGED OVER THE VA HIGHLANDS INTO THE GREENBRIER VALLEY WHERE CLOSER TO THE RESIDUAL FRONT. IN ADDITION...GOOD POOLING OF HIGHER 85H THETA-E PROGGED ALONG THE EASTERN SLOPES OF THE BLUE RIDGE GIVEN SE FLOW...BUT MORE DRYING SE AS WEAK SUBSIDENCE TOWARD THE COAST WORKS TO THE NW. THUS WILL BUMP UP TO A PERIOD OF LIKELY POPS WEST-NW BY MID AFTERNOON GIVEN COMBO OF MOISTURE...WEAK CONVERGENCE AND PROGGED CAPES OF 1-2K J/KG LATER ON. OTRW MAINLY MID TO HIGH CHANCE POPS ELSEWHERE...EXCEPT ONLY ISOLATED COVERAGE FAR SE. WEAK STEERING AGAIN UNDER HIGH PWATS SUGGESTS MORE HEAVY RAIN POTENTIAL WITH PERHAPS A BIT HIGHER CHANCE OF A FEW STRONGER PULSE NATURE CELLS PER SOME DRYING ALOFT SEEN ON FORECAST RAOBS. KEPT TEMPS CLOSER TO THE WARMER MET MOS EAST WHERE EXPECT LESS CONVECTION AFTER EARLY ISOLATED SHRA FADE...WHILE TRENDING A LITTLE MORE TOWARD THE MAV VALUES BLUE RIDGE...AND POINTS NORTH GIVEN SE FLOW AND ANTICIPATED BETTER SHOWER COVERAGE. MODELS SUGGEST SWATH OF DEEPER MOISTURE TO PUSH NW THIS EVENING AS BETTER CONVERGENCE DEVELOPS WELL WEST OF THE MOUNTAINS AHEAD OF THE NEXT COLD FRONT. THIS SHOULD ALLOW AN AREA OF WEAK SINKING MOTION TO ADVECT OVER MOST OF THE REGION ESPCLY AFTER MIDNIGHT BRINGING AN END TO ANY EVENING CONVECTION MAINLY NW. HOWEVER PENDING AFTERNOON COVERAGE...WILL LEAVE IN SOME DECENT CHANCE POPS MOUNTAINS TO INIT THIS EVENING BEFORE CUTTING BACK TO JUST PC INCLUDING SOME PATCHY FOG LATE. LOWS MOSTLY IN THE 60S BUT LIKELY NOT QUITE AS MUGGY GIVEN SOME SLIGHT DECREASE IN DEWPOINTS OVERNIGHT AS DEEP MOISTURE EXITS. && .SHORT TERM /SATURDAY THROUGH MONDAY/...
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AS OF 230 AM EDT FRIDAY THE UPPER RIDGE ACROSS THE EASTERN U.S. EARLY SATURDAY GRADUALLY FLATTENS BY EARLY NEXT WEEK AS SHORTWAVE ENERGY MOVES INTO THE NORTHERN GREAT LAKES. FOR SATURDAY...CONVECTION SHOULD BE DIURNALLY DRIVEN...BUT COVERAGE IS EXPECTED TO BE LESS AS DRY AIR SEEN ACROSS SOUTH GEORGIA AND N. FLORIDA LIFTS NORTH INTO OUR AREA AROUND THE LARGE ATLANTIC HIGH. AS A RESULT...PWAT VALUES ARE EXPECTED TO BE SLIGHTLY LOWER. THIS SLIGHTLY DRIER AIRMASS COMBINED WITH WARMING 850MB TEMPS IN ADVANCE OF AN APPROACHING SFC FRONT SHOULD ALLOW TEMPS TO BE A COUPLE OF DEGREES WARMER THAN FRIDAY. ON SUNDAY...HIGHER PWAT AIR SURGES BACK INTO THE REGION IN ADVANCE OF A COLD FRONT. MEDIUM RANGE MODELS DIFFER ON THE FORECAST LOCATION OF THE FRONT...WITH THE NAM MUCH SLOWER COMPARED TO THE GFS AND 12Z ECMWF. INCREASING FORCING ASSOCIATED WITH THIS BOUNDARY WILL BRING INCREASED COVERAGE IN PRECIP TO THE REGION...AND MORE ORGANIZED STORMS. THEREFORE PUSHED POPS INTO HIGH CHANCE TO NEAR LIKELY ON SUNDAY. TEMPS COULD AGAIN BE VERY WARM WITH WARMING AHEAD OF THE LOW LEVEL BOUNDARY AND 850MB THERMAL RIDGE OVER THE REGION...ESPECIALLY IN THE EAST WHERE CLOUD COVER IS EXPECTED TO BE LESS. BUMPED UP TEMPS A COUPLE OF DEGREES FOR HIGHS. IF THE LATEST GFS VERIFIES...HIGH PRESSURE WEDGING SOUTH WILL PUSH THE COLD FRONT SOUTH OF OUR AREA MONDAY...LEAVING BEST CONVERGENCE AND CHANCES FOR PRECIP TO THE SOUTH ALONG WITH COOLER TEMPS. FOR NOW...LEANED TOWARD THE ECMWF WHICH KEEPS THE BOUNDARY IN OUR AREA AND LEAVING THE SOUTHERN HALF OF OUR AREA IN THE WARM SECTOR. EVEN WITH THE MORE AGGRESSIVE GFS...PRECIP COVERAGE SHOULD BE FAIRLY WIDESPREAD WITH WEAK OVERRUNNING...AND A WAVE OF LOW PRESSURE MOVING ALONG THE BOUNDARY THROUGH OUR AREA.
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&& .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... AS OF 330 PM EDT THURSDAY... MODELS HAVE CLUSTERED AROUND A BASIC SOLUTION OF BUILDING A DECENT SUMMER WEDGE BUILDS ON OVER THE FORECAST AREA MONDAY NIGHT INTO WEDNESDAY. WILL TRIM BACK MAXIMUM TEMPERATURES A CATEGORY OR TWO BUT AMOUNT OF HEATING WILL DEPEND ON AMOUNT OF CLOUDS. PLUS THE WEDGE WILL BE SHALLOW. THE BOUNDARY AT 850 NEVER MAKES IT SOUTH THROUGH THE REGION AND WITHOUT A BIG CHANGE IN AIRMASS...MOIST DEW POINTS WILL LIMIT HOW COOL IT GETS AT NIGHT AND SO EACH DAY WILL BE STARTING WITH MILD TEMPERATURES. THE EAST TO SOUTHEAST SURFACE WINDS WILL PROVIDE SOME UPSLOPE COMPONENT FOR INCREASED PROBABILITY OF PRECIPITATION ALONG THE BLUE RIDGE THROUGH TUESDAY NIGHT. BY WEDNESDAY AND THURSDAY AREA WILL BE UNDER RIDGING ALOFT WITH LOW LEVEL FLOW GENERALLY OUT OF THE SOUTHEAST. SURFACE BOUNDARY AND WEDGE TRICKY TO DISTINGUISH BY DAY 7. WILL HAVE DRY WX ON THURSDAY. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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AS OF 650 AM EDT FRIDAY... FOG REMAINS QUITE SPOTTY ACROSS THE REGION WITH VARYING DEGREES OF LOWER VSBYS RANGING FROM MVFR/IFR IN SPOTS NEAR THE TAF SITES TO UNLIMITED VSBY UNDER MID DECK IN OTHERS. MAY STILL SEE FOG DRIFT ACROSS ANY OF THE VALLEY LOCATIONS DURING THE NEXT HOUR OR TWO RESULTING IN BRIEF IFR/LIFR VSBY BEFORE THE FOG QUICKLY BURNS OFF BY MID MORNING IF NOT SOONER. THIS TO BE FOLLOWED BY ANOTHER ROUND OF DIURNALLY-DRIVEN CONVECTION BY OR SHORTLY AFTER NOON IN THE MOUNTAINS AND FOOTHILLS...PERHAPS A COUPLE-FEW HOURS LATER OUT ACROSS THE PIEDMONT TERMINAL FORECAST SITES. SINCE APPEARS BASED ON LATEST GUIDANCE THAT THE WEST WILL HAVE THE BEST SHOT AT SEEING THE MORE WIDESPREAD CONVECTION...KEPT A PREVAILING MVFR SHRA GROUP WITH VCTS MENTION AT BOTH KBLF/KLWB THIS AFTERNOON...AND LEFT IN VCTS AT ALL SITES EXCEPT FOR KDAN WHERE THINK CHANCES ARE LESS WITHIN THE SE FLOW. A FEW SHRA/TSRA MAY LINGER ALONG THE KBLF-KLWB CORRIDOR THIS EVENING BEFORE MOISTURE DECREASES OVERNIGHT. THIS MAY RESULT IN SOME LINGERING MVFR IN SHRA OVER THE WEST THIS EVENING BEFORE ALL BRIEFLY RETURN TO VFR IN SCTD/BKN STRATO-CU AND MID DECK. ONCE THE SHOWERS END AND SKIES CLEAR A BIT EXPECTING ANOTHER ROUND OF FOG ESPCLY IN THE VALLEYS AND WHERE EARLIER RAINFALL OCCURRED. THIS SUPPORTS MORE WIDESPREAD IFR/LIFR ACROSS THE WESTERN VALLEYS WITH ONLY PATCHY COVERAGE IN THE EAST INCLUDING KROA. EXTENDED AVIATION DISCUSSION... THROUGH THE UPCOMING WEEKEND...A MOIST UNSTABLE AIR MASS WILL REMAIN IN PLACE ACROSS THE REGION WITH ONLY WEAK FORCING. THIS WILL RESULT IN MAINLY SLOW MOVING DIURNALLY DRIVE DEEP CONVECTION DURING THE AFTERNOON AND EVENING HOURS FOLLOWED BY STABLE CONDITIONS AT NIGHT. A FRONTAL SYSTEM WILL APPROACH FROM THE NORTH DURING THE WEEKEND...BUT WILL LIKELY REMAIN WELL NORTH OF THE FORECAST AREA THROUGH SUNDAY. THUS...NO CHANGE IN AIR MASS IS EXPECTED THROUGH THE PERIOD. THIS BOUNDARY SHOULD FINALLY SINK SOUTH INTO THE REGION EARLY NEXT WEEK RESULTING IN MORE WIDESPREAD CONVECTION POSSIBLY AS EARLY AS SUNDAY EVENING...FOLLOWED BY ADDITIONAL ROUNDS OF SHRA/TSRA INTO AT LEAST MONDAY NIGHT BEFORE PERHAPS THE BOUNDARY SINKS TO THE SOUTH. THIS SHOULD MAKE FOR MORE FREQUENT PERIODS OF SUB-VFR FROM LATER SUNDAY INTO MONDAY NIGHT WITH LOWER CIGS/VSBY REDUCTIONS DUE TO SHOWERS/STORMS DURING THE DAY...AND IN FOG OVERNIGHT INTO THE EARLY MORNING HOURS EACH DAY. MAY SEE ENOUGH DRYING TO BRING AN END TO SHOWERS ON TUESDAY WHILE LOWER MVFR/IFR CIGS LIKELY SLOW TO IMPROVE WITH EASTERLY FLOW AND WEDGING IN PLACE.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...PH LONG TERM...AMS AVIATION...JH/MBS/WERT

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