Area Forecast Discussion
Issued by NWS Blacksburg, VA

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127 FXUS61 KRNK 262009 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 409 PM EDT TUE APR 26 2016 .SYNOPSIS... A FRONTAL BOUNDARY FROM CENTRAL ILLINOIS EXTENDING EASTWARD THROUGH CENTRAL NEW JERSY THIS AFTERNOON WILL SLOWLY PUSH SOUTHWARD AND INTO THE CENTRAL APPALACHIAN REGION TONIGHT AND INTO WEDNESDAY AS WAVES OF LOW PRESSURE TRACK ALONG IT. ONE WAVE WILL MOVE ACROSS WEDNESDAY MORNING FROM THE WEST...AND A MORE SIGNIFICANT WAVE WILL TRACK JUST NORTHWEST OF OUR AREA ON THURSDAY...BRINGING ADDITIONAL MOISTURE BACK ACROSS THE SURFACE BOUNDARY STILL DRAPED OVER THE REGION. && .NEAR TERM /THROUGH WEDNESDAY/... AS OF 405 PM EDT TUESDAY... SFC FRONTAL BOUNDARY REMAINS WELL TO THE NORTH OVER CENTRAL OHIO AND PA...WITH SCATTERED CONVECTION DEVELOPING ALONG IT AND ALSO A LITTLE SOUTH NEAR AN OUTFLOW BOUNDARY. INSTABILITY OVER THE CENTRAL APPALACHIANS REMAINS RELATIVELY LOW THANKS TO QUICK DEVELOPMENT OF BROKEN CUMULUS FIELD EARLIER TODAY. ALSO DRY AIR ALOFT LIKELY SURPRESSING DEEPER CONVECTIVE DEVELOPMENT IN OUR MTNS. SCATTERED CONVECTION MAY DRIFT IN TO PARTS OF SOUTHEAST WV BETWEEN 5 AND 6PM...BUT NOT EXPECTING MOST OF THE ACTIVITY TO MOVE IN GENERALLY NORTH OF U.S. 460 UNTIL AFTER 6PM...AND BY THAT TIME INSTABILITY BEGINNING TO WEAKEN EVEN MORE. STILL...ISOLATED DEEPER UPDRAFTS THAT MAY STILL DEVELOP OR MOVE IN CAN TAP SOME DRIER AIR ALOFT AND RESULT IN VERY GUST DOWNDRAFT GIVEN DCAPE VALUES IN THE 700-900 J/KG RANGE. BELIEVE SEVERE THREAT THIS EVENING IS VERY MINIMAL...IF ANY...BUT STILL WORTH KEEPING AN EYE ON THROUGH THE LATE EVENING HOURS NORTH OF U.S. 460. UNCERTAINTY REGARDING IMPACTS OF SIGNIFICANT WAVE APPROACHING FROM THE WEST TOWARD MORNING...IN ASSOCIATE WITH MESOSCALE CONVECTIVE SYSTEM CROSS MISSISSIPPI RIVER NEAR ST LOUIS THIS AFTERNOON. MODELS EACH HANDLE THIS A BIT DIFFERENTLY...WITH MOST BRINGING IT AT LEAST INTO ERN KY...BUT MANY BRINGING LINGERING SHOWERS AND STORMS INTO MOUNTAINS DURING THE MORNING HOURS. AT THE SAME TIME...THE SFC BOUNDARY TO THE NORTH BEGINS TO BACK DOOR FROM THE NORTHEAST THROUGH THE LYNCHBURG AREA DURING THE DAY WEDNESDAY...AND REMNANTS OF THIS WAVE FROM THE WEST COULD INTERSECT THIS IN THE EAST EITHER ALLOWING CONVECTION TO CONTINUE...OR REDEVELOPING IN THE PIEDMONT. DECIDED TO JUST MAINTAIN LOW LIKELY TO HIGH CHANCE POPS MOST OF THE DAY TOMORROW...WITH CHC THUNDER PRETTY MUCH ALL DAY. MIDNIGHT SHIFT CAN REASSESS AS THIS WAVE FROM THE WEST APPROACHES AND WE MAY NEED TO REMOVE THUNDER CHANCES DURING THE MORNING...AND RE- INTRODUCE LATER IN AFTERNOON. BUT IN GENERAL MOST LOCATIONS STAND A GOOD CHANCE OF SEE A PERIOD OF SHOWERS AND MAYBE A THUNDER STORM AS WELL. SEVERE CHANCES APPEAR MINIMAL...AND WILL DEPEND ON HEATING...BUT NOT A ZERO THREAT. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... AS OF 230 PM EDT TUESDAY... A FRONTAL BOUNDARY WILL REMAIN STALLED AROUND OR JUST SOUTH OF THE VA/NC BORDER WEDNESDAY NIGHT INTO THURSDAY. DISTURBANCES FROM THE MIDDLE MISSISSIPPI VALLEY WILL PINWHEEL EASTWARD FROM A PARENT UPPER TROUGH LOCATED OVER THE UPPER MISSISSIPPI VALLEY. THESE FEATURES WILL RIDE ALONG THE BOUNDARY BRINGING EXTRA ENERGY TO THE REGION TO SUPPORT BETTER ORGANIZATION OF SHOWERS/STORMS. ONE SUCH FEATURE IS PROGGED TO ARRIVE THURSDAY MORNING IN THE WEST AND TRANSLATE ACROSS THE REGION DURING THE COURSE OF THE DAY. NOTABLE SURFACE BASED INSTABILITY AND WEAK LOW LEVEL SHEAR WILL BE SUFFICIENT FOR SOME STORMS TO BE ON THE STRONG SIDE. NORTHEAST PARTS OF THE AREA ARE EXPECTED TO EXPERIENCE THE LEAST COVERAGE OF STORMS. HERE...A NOSING RIDGE OF HIGH PRESSURE WILL HELP TO KEEP AT LEAST SURFACE BASED CONVECTION AT BAY. BY THURSDAY EVENING...A COLD FRONT ASSOCIATED WITH THE PARENT UPPER LOW WILL BE REACHING THE WESTERN PART OF THE AREA...AND MOVE TROUGH THE REGION THURSDAY NIGHT. LOOK FOR A CONTINUATION OF SHOWERS INTO THE OVERNIGHT HOURS...WITH ISOLATED STORMS STILL POSSIBLE IN THE EVENING. BY FRIDAY...THE UPPER LEVEL TROUGH AXIS WILL CROSS THE REGION. THE BEST DYNAMICS ARE PROGGED TO STAY NORTH OF THE AREA. HOWEVER...ENOUGH INSTABILITY IS EXPECTED TO REACH A LEAST THE NORTHERN HALF THE AREA FOR THE FOCUS FOR SHOWERS...AND A FEW STORMS...TO BE THERE. ALSO...DAYTIME HEATING IN THE EAST WILL COINCIDE WITH THE PASSAGE OF THE TROUGH...SO EXPECT ISOLATED TO SCATTERED COVERAGE OF SHOWERS AND ISOLATED STORMS IN THE EAST AS WELL. TEMPERATURES DURING THIS PORTION OF THE FORECAST WILL AVERAGE A FEW DEGREES ABOVE NORMAL. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... AS OF 310 PM EDT TUESDAY... FRIDAY NIGHT...ANTICIPATE SOME LINGERING ISOLATED SHOWERS AS THE UPPER TROUGH AXIS DEPARTS THE REGION. THE FOCUS FOR ANY ACTIVITY WILL BE IN THE NORTHEAST PART OF THE FORECAST AREA. OVER THE WEEKEND...UPPER RIDGING WILL TAKE PLACE ACROSS THE REGION AS ANOTHER LOW WITH ASSOCIATED FRONTAL FEATURES DEVELOPS IN THE CENTRAL PORTION OF THE COUNTRY. THIS FEATURES WILL ADVECT MOISTURE AND BITS OF SHORTWAVE ENERGY TOWARDS THE REGION. WHILE IT WILL INITIALLY BE DAMPENED BY THE RIDGE...BY THE END OF THE WEEKEND...THE RIDGE WILL HAVE BEEN DISPLACED BY ZONAL FLOW...AND BY MONDAY...LOW/TROUGH SYSTEM PROGRESSING THROUGH THE REGION. ANTICIPATE INCREASING CHANCES OF SHOWERS DURING THE WEEKEND...WITH THE GREATEST COVERAGE IN THE WEST. ISOLATED THUNDERSTORMS ARE POSSIBLE WITH THE BEST CHANCES OF THESE IN THE WEST AND SOUTH. BY LATE SUNDAY NIGHT INTO MONDAY...MODERATE RAIN SHOWERS ARE LIKELY WITH ISOLATED STORMS AS THE UPPER SYSTEM PASSES THE REGION. ANOTHER SYSTEM ON THE HEELS OF THE MONDAY ACTIVITY IS PROGGED TO SWING THROUGH THE AREA ON TUESDAY...HELPING TO MAINTAIN OUR CHANCES OF SCATTERED SHOWERS. TEMPERATURES DURING THIS PORTION OF THE FORECAST WILL AVERAGE FIVE DEGREES ABOVE NORMAL THROUGH MONDAY. ON TUESDAY...NEAR NORMAL TEMPERATURES ARE FORECAST. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... 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. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS/SK NEAR TERM...SK SHORT TERM...DS LONG TERM...DS AVIATION...AMS/DS/SK

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