Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 090519 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 119 AM EDT WED JUL 9 2014 .SYNOPSIS... A SLOW MOVING COLD FRONT WILL APPROACH FROM THE NORTHWEST OVERNIGHT AND WEDNESDAY...BEFORE CROSSING THROUGH THE AREA WEDNESDAY NIGHT. HIGH PRESSURE WILL FOLLOW THE FRONT FOR THURSDAY INTO SATURDAY. A MUCH STRONGER COLD FRONT WILL BE PASSING THROUGH THE REGION NEXT MONDAY AND TUESDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 833 PM EDT TUESDAY... KFCX 88D SHOWED COVERAGE AREA AND INTENSITY OF STORMS WEAKENING DURING THE PAST HOUR OR SO. THERE IS STILL SOME DEVELOPING OF CONVECTION ON THE EASTERN FRONT IN THE UNSTABLE AIR. SHAPED POPS TOWARDS A BLEND OF HIRESWARW...RNK WRFARW AND HRRR. WILL CONTINUE POPS IN THE WEST OVERNIGHT INTO WEDNESDAY MORNING. EXPECTING LITTLE PROGRESS IN THE EASTWARD MOVEMENT OF THE SURFACE COLD FRONT TONIGHT AND WEDNESDAY WITH BROAD SOUTHWEST FLOW PARALLEL TO THE BOUNDARY AND LIMITED MOVEMENT OF THE UPPER TROF. SHOWERS AND THUNDERSTORMS WILL DEVELOP AGAIN WEDNESDAY ALONG AND AHEAD OF THE FRONTAL BOUNDARIES. SOME OF THE THUNDERSTORMS WEDNESDAY COULD BE SEVERE WITH THE MAIN THREAT GUSTY WINDS. AS OF 601 PM EDT TUESDAY... UPDATED POPS FOR LATEST WSR-88D TRENDS FOR THUNDERSTORMS MOVING ACROSS THE MOUNTAINS AT THIS TIME. SOME OF THE THUNDERSTORMS ARE STRONG TO SEVERE WITH GUSTY WINDS THE MAIN THREAT.MODIFIED TEMPERATURES AND DEW POINTS FOR LATEST OBS AND SHAPED THIS EVENING INTO TONIGHT. AS OF 315 PM EDT TUESDAY... WATER VAPOR LOOP SHOWED THE FIRST OF TWO SHORT WAVES THAT WILL DEEPEN THE NORTHEAST TROF. THE SECOND WAVE CROSSES THE GREAT LAKES THEN INTO THE NORTHEAST WEDNESDAY NIGHT. LAST FEW RUNS OF THE LOCAL WRF AND HRRR WERE VERY CONSISTENT WITH THE TIMING OF A BAND OF THUNDERSTORMS MOVING IN FROM THE WEST...WHAT WAS CURRENTLY DEVELOPING FROM AROUND PITTSBURGH TO NORTHWEST OF CHARLESTON WV. STILL EXPECTING THIS TO REACH SOUTHEAST WEST VIRGINIA BETWEEN 20-22Z/4-6PM. GUSTY SOUTHWEST SURFACE WINDS AND LOW LEVEL MIXING HAS BROUGHT SURFACE DEW POINTS DOWN INTO THE UPPER 50S TO LOWER 60S...SO CAPES HAVE PEAKED AROUND 2000 J/KG. HOWEVER...AS INDICATED WITH A CLASSIC INVERTED V SOUNDING...DCAPE WAS A HIGH AS 1300 J/KG IN THE FAR SOUTHEAST COUNTY WARNING AREA. IF STORMS MANAGE TO GET INTO THIS ENVIRONMENT AND OVERCOME THE DOWNSLOPING EAST OF THE BLUE RIDGE THERE IS A POTENTIAL FOR STRONG TO DAMAGING WINDS. WITH THE REMOVAL OF HEATING...INTENSITY AND COVERAGE OF PRECIPITATION WILL DIMINISH...MAINLY AFTER 02Z/10PM. THE SOUTHERN END OF THE LINE OF STORMS...EXTENDING ACROSS THE TENNESSEE VALLEY MAY CONTINUE OVERNIGHT. HAVE KEPT A HIGHER PROBABILITY OF PRECIPITATION IN THE SOUTHWEST COUNTY WARNING AREA THROUGH WEDNESDAY MORNING. EXPECTING LITTLE PROGRESS IN THE EASTWARD MOVEMENT OF THE SURFACE COLD FRONT TONIGHT AND WEDNESDAY WITH BROAD SOUTHWEST FLOW PARALLEL TO THE BOUNDARY AND LIMITED MOVEMENT OF THE UPPER TROF. BEST PROBABILITY OF PRECIPITATION WEDNESDAY WILL BE IN THE AFTERNOON WITH AREAS OF SURFACE BASED IN STABILITY AND CONVERGENCE...PLUS ALONG ANY OUTFLOW PRODUCED BY THE THUNDERSTORMS THAT DEVELOP THIS AFTERNOON. NARROWING DOWN WHERE THIS WILL BE IS THE BIGGEST CHALLENGE. LOOKING FOR MUGGY CONDITIONS WILL DEW POINTS RISING BACK UP THROUGH THE 60S TONIGHT...ESPECIALLY WHERE IT RAINS. AMOUNT OF CLOUDS WILL DETERMINE HOW HOT TEMPERATURES WILL GET ON WEDNESDAY. WILL BE DEPENDENT ON WHERE IT IS RAINING IN THE MORNING. FOR NOW STAYED CLOSED TO THE MET GUIDANCE FOR MAXIMUM TEMPERATURES. && .SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... AS OF 310 PM EDT TUESDAY... WEAK COOL FRONT EXPECTED TO DRIFT SOUTHEAST THROUGH THE BLACKSBURG FORECAST AREA WEDNESDAY NIGHT. ACTUAL SURFACE REFLECTION WILL LIKELY BE DIFFICULT TO DEFINE CONSIDERING DIFFUSE NATURE OF FRONT...AND CONTAMINATION FROM COOL OUTFLOW BOUNDARIES GENERATED BY CONVECTIVE ACTIVITY PRECEDING IT. HOWEVER...UPPER TROF WILL REMAIN TO THE WEST...AND WITH SUBTLE BACKING OF LOW LEVEL FLOW EXPECTED AHEAD OF UPPER TROF...ALONG WITH GRADUAL COOLING ALOFT...SUPPORT FOR PRE- AND POST-FRONTAL PRECIPITATION MAY PERSIST WELL INTO THE EVENING...AND PERHAPS THOUGH MUCH OF THE NIGHT ACROSS SOUTHERN/SOUTHEASTERN AREAS. NORTHWESTERN AREAS SHOULD REMAIN DRY...OTHER THAN PERHAPS A LINGERING EARLY EVENING SHOWER. ALTHOUGH NORTHWESTERN AREAS EXPECTED TO REMAIN DRY ON THURSDAY...PROXIMITY OF OLD FRONTAL BOUNDARY LYING JUST TO THE SOUTH AND EAST...AND LIMITED ADDITIONAL MOVEMENT EAST OF UPPER TROF WARRANTS CONTINUED AT LEAST LOW THREAT FOR DIURNALLY DRIVEN SHOWERS OR THUNDERSTORMS ACROSS THE SOUTH AND SOUTHEAST PORTION OF THE FORECAST AREA DURING THE AFTERNOON INTO THE EVENING. UPPER TROF FINALLY EXPECTED TO MOVE OVER AND THEN JUST TO THE EAST OF THE FORECAST AREA ON FRIDAY...BUT PLACEMENT SUPPORTS AMPLIFICATION OF SURFACE RIDGE JUST TO OUR NORTHEAST WHICH ALLOWS LOW LEVEL FLOW TO VEER AROUND BY DAYS END INTO THE EAST. COMBINATION OF COOLER AIR ALOFT...PLENTY OF INSOLATION...AND LIGHT UPSLOPING AGAINST THE EASTERN FLANKS OF THE BLUE RIDGE MAY BE SUFFICIENT TO OVERCOME DEVELOPING CAP TO SUPPORT ISOLATED TO WIDELY SCATTERED CONVECTION ALONG AND EAST OF THE BLUE RIDGE BEFORE DIMINISHING WITH LOSS OF DAYTIME HEATING FRIDAY EVENING. POST FRONTAL TEMPERATURES WILL BE SLIGHTLY COOLER THAN THE PAST SEVERAL DAYS...MAINLY 70S TO AROUND 80 ACROSS THE HIGHER ELEVATIONS TO MAINLY 80S PIEDMONT...WITH 50S IN THE MOUNTAIN VALLEYS TO MAINLY 60S ACROSS THE PIEDMONT AT NIGHT. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 310 PM EDT TUESDAY... DAILY THREAT OF WIDELY SCATTERED TO SCATTERED DIURNALLY DRIVEN SHOWERS/THUNDERSTORMS APPEARS TO BE IN THE OFFING DURING THE LONG TERM PERIOD AS A SERIES OF WEAK SHORT WAVES IN RELATIVELY ZONAL FLOW FORECAST TO MOVE EAST THROUGH THE BLACKSBURG FORECAST AREA. FIRST WAVE EXPECTED ON SATURDAY...WITH SECOND WAVE ON SUNDAY...TO BE FOLLOWED BY MUCH MORE SUBSTANTIAL WAVE IN MONDAY/TUESDAY TIMEFRAME AS EASTERN CANADIAN UPPER LOW AMPLIFIES AND RETROGRESSES SOUTHWESTWARD INTO THE UPPER GREAT LAKES AREA. DEEPENING VERY BROAD UPPER TROF/CLOSED SYSTEM WILL SUPPORT A GOOD PUSH OF UNUSUALLY COOL AIR INTO THE MID APPALACHIAN AND MID ATLANTIC REGION BY THE END OF THE LONG TERM PERIOD...BUT WITH THE COOLEST PORTION OF THE AIRMASS TO ARRIVE JUST OUTSIDE OF THIS FORECAST PERIOD...ON WEDNESDAY. AT LEAST THROUGH MONDAY...EXPECT RELATIVELY SEASONAL TEMPERATURES WITH NO SIGNIFICANT DAY TO DAY CHANGES IN AIRMASS. HIGHS SHOULD RANGE FROM THE MID 70S TO LOWER 80S ACROSS THE HIGHER ELEVATIONS TO UPPER 80S TO LOWER 90S ACROSS THE PIEDMONT. OVERNIGHT LOWS SHOULD BE GENERALLY IN THE 60S...BUT WITH SOME UPPER 50S POSSIBLE ACROSS THE HIGHEST ELEVATIONS AND IN THE DEEPER MOUNTAIN VALLEYS. TEMPERATURES SHOULD BEGIN TRENDING DOWNWARD ABOUT 5F DAILY BEGINNING TUESDAY AS LEADING EDGE OF SUCCESSIVE WAVES OF COOLER AIR BEGIN TO IMPINGE UPON THE AREA. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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AS OF 100 AM EDT WEDNESDAY... COMMS ISSUES REMAIN AT KDAN DESPITE AN INTERMITTENT RETURN OF OBSERVATION DATA. AMD NOT SKED CONTINUED IN THE TAF. LINGERING CONVECTION CONTINUES ACROSS THE FAR SW ATTM WITH SOME OF THIS COVERAGE STARTING TO PUSH BACK INTO THE KBLF VICINITY. LATEST SHORT TERM MODELS VARY ON HOW FAR EAST TO ADVANCE ADDED SHRA OVERNIGHT WITH THE LATEST HRRR MOST AGGRESSIVE IN TAKING CLUSTERS OF SHRA/TSRA EAST OF THE BLUE RIDGE THROUGH DAWN. MOST OTHER SOLUTIONS KEEP THE MAJORITY ACROSS THE FAR WEST/SW WITH SHRA WEAKENING UPON HEADING EAST. GIVEN TRENDS APPEARS SOME OF THIS COVERAGE LIKELY TO REACH KBCB/KROA AND AFFECT KBLF AND PERHAPS KLWB MUCH OF THE OVERNIGHT. THIS LIKELY TO KEEP MVFR/OCNL IFR CONDITIONS IN THE SE WVA CORRIDOR WITH CIGS LOWERING HEADING EAST BUT STILL MAINLY VFR ELSW DESPITE SOME SHOWERS AROUND. APPEARS CLOUDS MAY LIMIT FOG BUT KEPT IN SPOTS WITH SHRA MOVING THROUGH AS VSBYS MAY DROP ONCE THE RAIN PASSES A TERMINAL OVERNIGHT. HOWEVER KEPT KLWB ABOVE LIFR FOR NOW GIVEN CURRENT CLOUDY TRENDS. FRONT WILL BE SLOWLY MOVING INTO THE AREA WEDNESDAY WITH A MIX OF MVFR TO VFR CIGS TO START THE MORNING BEFORE THINGS SLOWLY IMPROVE TO VFR MOST SPOTS BY MIDDAY. BEST CHANCE FOR MVFR/IFR THUNDERSTORMS ON WEDNESDAY WILL BE IN THE AFTERNOON IN CENTRAL AND EASTERN VIRGINIA AND NORTH CAROLINA WHERE THE INSTABILITY WILL COMBINE WITH OUTFLOW FROM PREVIOUS STORMS. HOWEVER CANT TOTALLY RULE OUT SHRA/TSRA DEVELOPING BY LATE MORNING BLUE RIDGE GIVEN MOISTURE AND ONSET OF HEATING. THUS GOING WITH A VCTS/VCSH FOR MOST SPOTS BY WEDNESDAY AFTERNOON WITH COVERAGE MORE ISOLATED OVER THE NW. DRY AIR ALOFT SHOULD START TO ARRIVE LATER IN THE AFTERNOON ALLOWING FOR LESS CONVECTION NW THIRD WHERE WILL CUT OUT PRECIP MENTION FROM KROA AND POINTS NW BY MID AFTERNOON WEDNESDAY. WINDS SHOULD BE LIGHTER AND MORE WESTERLY ON WEDNESDAY JUST AHEAD OF THE FRONT WITH A STEADY WEST/SW COMPONENT AT 5-15 KTS. EXTENDED AVIATION... THE COLD FRONT WILL FINALLY PUSH THROUGH THE REGION ON WEDNESDAY NIGHT BEFORE STALLING JUST TO THE SOUTH. THIS BOUNDARY WILL LINGER ACROSS SOUTHERN/EASTERN AREAS THROUGH THE END OF THE WEEK WITH IMPULSES RIDING ALONG IT. THIS WILL KEEP UNSETTLED CONDITIONS AT TAF SITES THROUGH THE END OF THE WEEK. EXPECT DIURNAL TRENDS FOR AFTERNOON CONVECTIVE PRECIPITATION WITH ASSOCIATED MVFR OR LOWER CONDITIONS... ESPECIALLY FOR KDAN/KLYH ON THURSDAY BUT LIKELY LESS CONVECTION ACROSS THE AREA ON FRIDAY AND PERHAPS SATURDAY AS WEAK HIGH PRESSURE SLIDES IN FROM THE NORTH. MOISTURE AND MORE WIDESPREAD SHRA/TSRA LIKELY TO RETURN FOR THE END OF THE WEEKEND AS THE FRONT RETURNS NORTH RESULTING IN PERIODS OF MVFR CONDITIONS. OTRW PATCHY FOG RESULTING IN LOCAL MVFR TO IFR CONDITIONS LIKELY DURING THE LATE NIGHTS AND EARLY MORNINGS ESPCLY VALLEY LOCATIONS AND WHERE EARLIER AFTERNOON RAINFALL OCCURRED.
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&& .EQUIPMENT... AS OF 315 PM EDT TUESDAY... COMMUNICATIONS OUTAGE CONTINUES WITH KDAN ASOS NOT TRANSMITTING. THE FAA IS AWARE OF THE OUTAGE AND WILL BE WORKING ON IT...BUT NO ESTIMATED TIME OF WHEN IT WILL BE WORKING AGAIN. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...AMS/KK SHORT TERM...WERT LONG TERM...AMS/WERT AVIATION...AMS/JH/KK EQUIPMENT...WP

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