Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 261759 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 159 PM EDT TUE APR 26 2016 .SYNOPSIS... FRONT WITH WAVES OF LOW PRESSURE EXTENDED FROM NEW JERSEY TO MISSOURI THIS MORNING. THIS FRONT WILL DRIFT SOUTH THEN STALL OVER THE MID ATLANTIC REGION ON WEDNESDAY. ANOTHER LOW PRESSURE SYSTEM WILL TRACK FROM THE MID MISSISSIPPI VALLEY TO THE EAST COAST ON THURSDAY AND FRIDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... AS OF 1255 PM EDT TUESDAY... INITIAL BAND OF SHOWERS AND ISOLATED THUNDERSTORMS DISSIPATED BEFORE REACHING INTO THE NRN PORTION ON OUR FCST AREA...HOWEVER AN OUTFLOW BOUNDARY IN ITS WAKE OVER CENTRAL WV IS NOW STARTING TO FIRE...AND NEW RUNS OF HI RES WRF...ESPECIALLY ARW CORE...SEEM TO HAVE THIS IDEA...ALTHOUGH MAYBE NOT DEVELOPING QUITE FAST ENOUGH. HRRR ALSO NOT AS QUICK TO DEVELOP THIS...SO BY THE TIME IT DOES AROUND 20 UTC OR SO IT MAY BE A LITTLE TOO FAR NORTH WITH IT. THIS ALL MAKES FOR TRICKY TIMING OF WHEN THE BROKEN LINE OF CONVECTION MAY REACH GREENBRIER COUNTY...BUT WITH MANY MODELS STILL PRETTY SLOW ON THIS INTO THE EVENING...HAVE MADE SLIGHT ADJUSTMENTS FOR ITS ARRIVAL AROUND 20 OR 21 UTC...AND THEN NOT TO THE U.S. 460 LINE UNTIL 00 UTC OR LATER. ALSO LESS AND LESS CHANCE OF MUCH OF ANYTHING GETTING GOING IN THE MOUNTAINS SOUTH OF THIS GIVEN DRI AIR ALOFT AND FAIRLY EXTENSIVE CUMULUS FIELD EARLY...SO LOWERED POPS TO SLIGHT CHC EXCEPT FOR VERY HIGHEST MTNS WITH LOW CHC POP. SO FAR SFC-BASED CAPE PRETTY LIMITED LARGELY THANKS TO EARLIER CONVECTION AND RESIDUAL CLOUD COVER AND EARLY START TO CU FIELD. THIS COULD LIMIT SEVERE POTENTIAL...ALONG WITH LATER ARRIVAL TIME NOW MAINLY INTO THE EVENING. AN ISOLATED STRONG STORM...PRIMARILY WIND THREAT...STILL POSSIBLE. PREV DISCUSSION AS OF 1015 AM EDT TUESDAY... AREA OF CONVECTION TO THE SOUTH OF THE FRONTAL BOUNDARY CONTINUES TO DRIFT SOUTHEASTWARD THROUGH NRN WEST VIRGINIA...AND MAY BRUSH THE FAR NRN PORTION OF OUR FCST AREA BETWEEN 11AM AND NOON BEFORE DISSIPATING. HOWEVER THIS SHOULD LEAVE AN OUTFLOW BOUNDARY TO AID IN THE DEVELOPMENT OF MORE CONVECTION BY MID TO LATE AFTERNOON. FARTHER SOUTH IT LOOKS LIKE SOME WEAK SUBSIDENCE WILL PREVENT MORE THAN ISOLATED SHWRS OR THUNDERSTORMS TO FORM...AND THESE WOULD BE CONFINED TO MTNS...BUT BEST CHANCES WILL BE LATE AFTERNOON INTO EARLY EVENING MAINLY NORTH OF U.S. 460. ONE OR TWO OF THE CONVECTIVE RESOLVING MODELS DO SUGGESTS A BROKEN LINE WILL MAKE IT DOWN TO AT LEAST THE NORTH CAROLINA BORDER BY LATE EVENING...BUT AM SKEPTICAL OF THESE ARE WILL AWAIT 12Z UPDATES TO SOME OF THESE BEFORE REFINING FORECAST FURTHER. FOR NOW HAVE REDUCED POPS FARTHER SOUTH AND SLOWED DOWN TIMING OF ARRIVAL OF THES SCATTERED STORMS. STILL EXPECTING SOME ISOLATED SEVERE THREAT NORTH OF 460 AND MAINLY WEST OF BLUE RIDGE...WITH WIND DAMAGE BEING MOST LIKELY CONCERN GIVEN DRY AIR ALOFT TO SUPPORT DOWNDRAFTS AND MODEST LOW LEVEL WIND SHEAR TO ALLOW FOR SOME DEGREE OF ORGANIZATION. CANNOT RULE OUT A HAIL THREAT BUT INSTABILITY IS NOT ESPECIALLY HIGH AND WARM BOUNDARY LAYER TEMPS WILL HELP WITH MELTING. PREV DISCUSSION AS OF 355 AM EDT TUESDAY... LOW PRESSURE OVER MICHIGAN WILL MOVE EAST ALONG A FRONT INTO EASTERN PENNSYLVANIA TODAY. THEN THE FRONT WILL MOVE SOUTH INTO THE MID ATLANTIC REGION LATE TODAY INTO TONIGHT. THE SURFACE BOUNDARY REACHES THE FORECAST AREA AFTER 00Z/8PM...WHILE THE 850MB FRONT STAYS WELL TO THE NORTH. STARTING OUT WITH LITTLE CLOUD COVER THIS MORNING SO TEMPERATURES WILL WARM QUICKLY AFTER SUNRISE. WITH SURFACE DEW POINTS IN THE 50S...CONVECTIVE AVAILABLE POTENTIAL ENERGY WAS FORECAST TO BE AROUND 1500 J/KG THIS AFTERNOON AHEAD OF THE FRONT. SOME GUIDANCE SUGGESTED POOLING OF DEW POINTS IN THE LOWER 60S JUST AHEAD OF THE BOUNDARY WHICH WOULD RESULT IN EVEN LARGER CAPE. 00Z NAM AS WELL AS THE RAP AND LOCAL WRF HAVE A BULK OF THE PRECIPITATION THAT WILL BE AHEAD OF THE FRONT REACHING THE NORTHERN COUNTY WARNING AREA JUST AFTER 18Z/2PM. BETTER COVERAGE OF SHOWERS AND THUNDERSTORMS MAY NOT PROGRESS SOUTH...REACHING THE VIRGINIA/NORTH CAROLINA BORDER UNTIL AROUND 00Z/8PM. BETTER VORTICITY ADVECTION AND JET SUPPORT REACH THE FORECAST AREA TONIGHT SO HAVE INCREASED THE PROBABILITY OF PRECIPITATION FOR TONIGHT. GUIDANCE WAS TOO COOL FOR MAXIMUM TEMPERATURES ON MONDAY. HAVE GONE CLOSER TO WARMER GUIDANCE AND PERSISTENCE FROM MONDAY FOR MAXIMUM TEMPERATURES TODAY. CLOUDS AND MILD DEW POINTS WILL KEEP TEMPERATURES FROM DROPPING MUCH OVERNIGHT. HAVE RAISED MINIMUM TEMPERATURES SLIGHTLY ACROSS THE PIEDMONT TONIGHT. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/... AS OF 330 AM EDT TUESDAY... THE UPPER LEVEL PATTERN WILL REMAIN UNSETTLED AS THE WESTERN TROF SPLINTERS INTO PIECES WITH SEVERAL BITS OF SHORT WAVE ENERGY MOVING IN OUR DIRECTION INTERSPERSED WITH PERIODS OF GENERALLY FLAT RIDGING. AND WITHOUT SOLID UPPER LEVEL SUPPORT TO MOVE IT ALONG...THE FRONTAL ZONE AT THE SURFACE WILL SIMPLY LINGER OVER THE REGION THROUGH THE END OF THE WEEK. AMPLE CONVERGENCE AND INSTABILITY IN THE FRONTAL ZONE WILL KEEP UP WITH A CHANCE OF SHOWERS AND THUNDERSTORMS EACH DAY. BY FRIDAY IT APPEARS THAT A SHORT WAVE REMNANT OF THE WESTERN TROF WILL SWING BY TO OUR NORTH AND HELP PUSH THE FRONTAL BOUNDARY FURTHER TO THE SOUTH AND ALLOW A WEDGE OF HIGH PRESSURE TO BUILD DOWN EAST OF THE APPALACHIANS. HOWEVER ANY IMPROVEMENT IN OUR WEATHER LOOK TO BE MARGINAL SINCE CLOUDS AND SOME LIGHT PRECIPITATION WILL ACCOMPANY THE WEDGE. TEMPERATURES WILL GENERALLY BE A BIT ABOVE NORMAL THROUGH THE END OF THE WEEK WITH HIGHS IN THE MID 70S TO AROUND 80 EAST OF THE BLUE RIDGE...AND IN THE LOW TO MID 70S WEST. && .LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 245 PM EDT MONDAY... WEAK UPPER RIDGING THROUGH SATURDAY WILL KEEP PRECIP CHANCES CONFINED TO ISOLATED/WIDELY SCATTERED IN COVERAGE. AT THE SFC...12Z ECMWF KEEPS WEDGE IN PLACE THROUGH SATURDAY. WHILE TEMPS WERE BROUGHT DOWN A COUPLE OF DEGREES DURING THIS TIME...THESE FORECAST VALUES STILL MAY BE TOO WARM. HOWEVER...BETTER CHANCES FOR MORE WIDESPREAD PRECIPITATION ARRIVE LATER SUNDAY INTO MONDAY...DEPENDING ON THE ARRIVAL OF AN OPENING UPPER LOW MOVING THROUGH THE OHIO VALLEY. AS IT TYPICAL FOR THE LONG RANGE MODELS...THERE IS DISAGREEMENT IN THE TIMING AND TRACK OF THIS SYSTEM...BUT INDIVIDUAL GEFS ENSEMBLE MEMBERS SUGGEST THE BEST CHANCES FOR PRECIPITATION WILL BE LATE SUNDAY INTO EARLY MONDAY...AND THIS IS THE TIME PERIOD WHERE THE POPS ARE HIGHEST. TEMPS ARE EXPECTED TO BE BELOW NORMAL EARLY WITH THE WEDGE IN PLACE TO NEAR NORMAL LATER IN THE LONG TERM PERIOD. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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AS OF 200 PM EDT TUESDAY... COLD FRONT REMAINS JUST SOUTH OF THE GREAT LAKES IN NORTHERN OHIO BUT A BAND OF SHOWERS AND THUNDERSTORMS WELL TO THE SOUTH OF THIS HAS DEVELOPED ACROSS CENTRAL WEST VIRGINIA...BUT WILL BE SLOW TO MOVE SOUTHWARD. BEFORE THIS ARRIVES...VFR CONDITIONS WILL PREVAIL...BUT ANY STORMS COULD PRODUCE BRIEF MVFR CONDITIONS AS WELL AS GUSTY NORTHWEST WINDS. EXPECTED ARRIVAL TIME AT KLWB AROUND 22 UTC...THEN KBLF...KBCB...KROA...KLYH AROUND 00 UTC PLUS OR MINUS AN HOUR...THEN LESS CERTAIN THAT THESE WILL EVER GET TO KDAN BUT LEANING TOWARD THEY EVENTUALLY WILL BUT MORE AROUND 02 UTC AND MAY NOT EVEN BE THUNDER AT THAT POINT BUT SOME GUSTY NW WINDS STILL POSSIBLE. LESS LIKELY TO SEE SUB VFR CONDITIONS AT KDAN AS WELL. THUNDER THREAT WILL DIMINISH BY MIDNIGHT BUT SOME SHOWERS COULD LINGER...ESPECIALLY AT WESTERN TAF SITES...AND SOME IFR CONDITIONS MAY EVENTUALLY BE POSSIBLY AT KLWB AND KBLF...ESPECIALLY IF SHOWERS MOVE AWAY FOR A FEW HOURS. DID NOT INCLUDE ANY PREVAILING IFR CONDITIONS...BUT MOST CONCERNED ABOUT KLWB LATE TONIGHT. IF SHOWERS MOVE OUT COULD EASILY GET IFR FOG. AN UPPER LEVEL WAVE AND MORE ORGANIZED AREA OF THUNDERSTORMS WILL APPROACH THE WEST BY MORNING AND RECENT GUIDANCE IS SUGGESTING THAT THIS COULD MAINTAIN THROUGH THE FCST AREA DURING THE MORNING WEDNESDAY...ALTHOUGH NOT CLIMATOLOGICALLY FAVORED. BEST CHANCES FOR SHOWERS AND SOME EMBEDDED THUNDERSTORMS WOULD BE IN THE WEST...AND INCLUDED THOSE WITH MVFR CONDITIONS AT KBLF...KLWB...AND KBCB...ALTHOUGH NOT ESPECIALLY HIGH CONFIDENCE. AS FAR AS WINDS...WEST TO SOUTHWEST TODAY...GUSTING TO 15 KTS OR SO REMAINDER OF AFTERNOON...THEN BECOMING LIGHTER TONIGHT EXCEPT FRO NEAR ANY STORMS...WHICH COULD BRING THEM TO NORTHWEST OR NORTH GUSTING BRIEFLY TO 25 OR 30 KTS. MORE VARIABLE OVERNIGHT...PERHAPS BACK TO WEST. BY EARLY WED BACK DOOR FRONTAL BOUNDARY MAY ARRIVE AT KLYH FOR A NORTHEAST WIND FOR MUCH OF THE DAY. THIS MAY NOT GET TO ANY OTHER TAF SITES UNTIL LATE IN DAY OR OVERNIGHT. EXTENDED AVIATION DISCUSSION... THIS BACK DOOR FRONT WILL SLOWLY PUSH THROUGH WEDNESDAY NIGHT AND THEN REMAIN STALLED OR SLOWLY DRIFT BACK NORTH ON THURSDAY...BEFORE A STRONGER COLD FRONT ENTERS FROM THE WEST TO PUSH THE WEAKER FRONT OFFSHORE LATE THURSDAY. DURING THIS TIME...SCATTERED SHOWERS WITH A FEW AFTERNOON THUNDERSTORMS APPEAR LIKELY. THE GREATEST CHANCE OF RAIN AND MVFR/IFR CONDITIONS WILL ACCOMPANY THE STRONGER COLD FRONT ON THURSDAY. SOME CLEARING SHOULD TAKE PLACE DURING FRIDAY...ALTHOUGH A FEW MOUNTAIN SHOWERS AND MVFR CLOUDS ARE POSSIBLE.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...AMS/SK SHORT TERM...PH LONG TERM...PH AVIATION...AMS/DS/SK

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