Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 290716 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 316 AM EDT WED OCT 29 2014 .SYNOPSIS... A COLD FRONT WILL MOVE EAST TONIGHT...PASSING THROUGH THE MID ATLANTIC REGION WEDNESDAY. TEMPERATURES RETURN TO MORE SEASONABLE LEVELS AFTER THE PASSAGE OF THE COLD FRONT ON WEDNESDAY. A LINE OF SHOWERS PERHAPS A THUNDERSTORM WILL ACCOMPANY THE FRONTAL PASSAGE...RAIN AMOUNTS OF A QUARTER INCH OR LESS. && .NEAR TERM /THROUGH TODAY/... AS OF 935 PM EDT TUESDAY... HAVE MADE SOME NOTABLE ADJUSTMENTS FOR THE DISTRIBUTION OF PRECIPITATION ACROSS PORTIONS OF THE REGION THROUGH THE REMAINDER OF THE OVERNIGHT HOURS...AND INTO THE MORNING HOURS OF WEDNESDAY. LATEST MESOSCALE MODELS OFFER A SOLUTION THAT STRUGGLES TO BRING PRECIPITATION EASTWARD INTO AND THROUGH THE FORECAST AREA WITH A GENEROUS COVERAGE OF DRY AIR IN PLACE ACROSS THE REGION. RATHER THAN ALLOWING FOR SOME COVERAGE EAST OF THE CREST OF THE BLUE RIDGE BY THE FORENOON WEDNESDAY...HAVE LIMITED COVERAGE WEST OF THE BLUE RIDGE...WITH ISOLATED COVERAGE AT BEST NEAR THE CREST BY 900 AM WEDNESDAY. THE GREATEST FOCUS FOR SHOWERS WILL CONTINUE TO BE NEAR A BLUEFIELD TO LEWISBURG WV LINE STARTING LATER TONIGHT AND CONTINUING IN WEDNESDAY MORNING. AS OF 645 PM EDT TUESDAY... EARLY EVENING UPDATE WILL REFLECT MAINLY A SMALL TWEAK IN THE TIMING OF THE ARRIVAL OF SHOWERS IN THE WEST. LATEST PROJECTIONS BASED UP TRENDS ON REGIONAL RADARS IS FOR THE LEADING EDGE TO BE NEAR A BLUEFIELD TO LEWISBURG WEST VIRGINIA LINE AROUND 800 OR 900 PM. HAVE ALSO ADJUSTED HOURLY TEMPERATURES...DEW POINTS AND WIND SPEED AND DIRECTION BASED UPON THE LATEST OBSERVATIONS AND EXPECTED TRENDS THROUGH THE EVENING HOURS. NO OTHER MAJOR ADJUSTMENTS AT THIS TIME. AS OF 300 PM EDT TUESDAY... RIDGING ALOFT ALONG THE EAST COAST WILL MOVE EAST TONIGHT INTO WEDNESDAY. SFC COLD FRONT LOCATED TO OUR WEST FROM THE GREAT LAKE REGION SOUTHWARD TO TEXAS THIS AFTERNOON WILL MOVE EAST TONIGHT INTO THE WESTERN MOUNTAINS. INITIALLY SHAPED POPS THIS AFTERNOON TOWARDS A BLEND OF THE RNK WRFARW...HRRR AND NAM...THEN TOWARDS THE GFS WEDNESDAY. LEANED TONIGHT LOW TEMPERATURES TOWARDS THE ADJMAV WITH READINGS FROM THE UPPER 40S IN THE MOUNTAINS TO THE MID 50S IN THE PIEDMONT. COLD FRONT IS EXPECTED TO SWEEP RAPIDLY EAST THROUGH THE AREA ON WEDNESDAY...PRECEDED AND ACCOMPANIED BY A BAND OF PRE- AND POST FRONTAL CONVECTION. EXPECT THE HIGHEST THREAT FOR MEASURABLE PRECIPITATION TO OCCUR ACROSS THE WESTERN FLANKS OF THE APPALACHIANS THROUGH EARLY AFTERNOON...WITH AREAS LIKELY TO BECOME INCREASINGLY MORE SCATTERED IN NATURE EAST OF THE BLUE RIDGE AS BAND TRANSITIONS INTO A DOWNSLOPING ENVIRONMENT DURING THE AFTERNOON. UNDER PLENTY OF CLOUDS...HIGH TEMPERATURES WEDNESDAY WILL RANGE FROM THE MID 50S IN THE MOUNTAINS TO THE MID 70S IN THE PIEDMONT. && .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/... AS OF 300 PM EDT TUESDAY... A WEAK COLD FRONT WILL MOVE EAST OF THE AREA WEDNESDAY NIGHT...FOLLOWED BY A CHILLY AREA OF HIGH PRESSURE THURSDAY. COLD AIR BEHIND THIS FRONT WILL KNOCK THURSDAY AFTERNOON HIGHS BACK DOWN BELOW NORMAL BY 5F-10F. THURSDAY AFTERNOON HIGHS WILL RANGE FROM THE MID 50S WEST TO LOWER 60S EAST. A BROAD UPPER LEVEL TROUGH MOVES EAST OF THE MISSISSIPPI VALLEY AND WILL RESIDE OVER THE EAST COAST THURSDAY NIGHT. THIS TROUGH WILL KEEP COOL AIR OVER THE AREA INTO FRIDAY. CLOUDS STREAMING INTO THE REGION WITH THIS TROUGH MAY KEEP TEMPERATURES EAST OF THE BLUE RIDGE FROM DROPPING DOWN INTO THE 30S. SINCE RADIATIONAL COOLING IS NOT IDEAL...FROST POTENTIAL OUTSIDE OF DEEPER MOUNTAIN VALLEYS IS NOT LIKELY. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 100 PM EDT TUESDAY... LATEST 12Z GFS IS STARTING TO COME INTO AGREEMENT WITH THE PREVIOUS RUN OF THE ECMWF. A DEEP UPPER LEVEL TROUGH DIGS ACROSS THE EASTERN UNITED STATES ON FRIDAY AND SATURDAY. THERE ARE SIGNIFICANT DIFFERENCES IN 850MB TEMPS WITH THE 12Z GFS RUNNING MUCH WARMER THAN PREVIOUS RUNS. FOR NOW KEEPING THINGS MORE ALIGNED WITH WPC AND PREVIOUS MODEL RUNS. RAIN SHOWERS WILL ARRIVE FRIDAY EVENING ACROSS THE WEST AND SPILL OVER TO THE REST OF THE CWA ON SATURDAY. EXPECT A TRANSITION TO SNOW SHOWERS IN THE HIGHER ELEVATIONS OF THE MOUNTAINS EARLY SATURDAY...WITH SCATTERED SNOW SHOWERS CONTINUING IN THE FAVORED UPSLOPE REGIONS OF SOUTHEAST WV INTO EARLY SUNDAY BEFORE TAPERING OFF. DEPENDING ON WHEN THE TRANSITION TO SNOW TAKES PLACE AND HOW MUCH AVAILABLE MOISTURE REMAINS WILL DICTATE IF THERE ARE ANY SNOWFALL ACCUMULATIONS ACROSS THE HIGHER ELEVATIONS. SURFACE TEMPS WILL BE WELL BELOW NORMAL THIS WEEKEND. LOW TEMPS WILL BE IN THE UPPER 20S TO LOWER 30S ACROSS THE MOUNTAINS WITH MID 30S EAST OF THE BLUE RIDGE. HIGH TEMPS ON SATURDAY WILL HOLD IN THE 40S IN MOST LOCATIONS...AND ADDING JUST A FEW DEGREES TO THAT ON SUNDAY. AS HIGH PRESSURE BUILDS IN AND SLOWLY MOVES EAST OF THE AREA EARLY NEXT WEEK...THE FLOW WILL BECOME MORE SOUTHERLY AND TEMPERATURES WILL MODERATE CLOSER TO NORMAL. ALSO THIS WEEKEND...PRESSURE RISES...STRONG COLD AIR ADVECTION AND A 45-55KT CROSS BARRIER LOW LEVEL JET WILL BRING WINDY AND GUSTY CONDITIONS TO THE MOUNTAINS STARTING LATE FRIDAY NIGHT THROUGH SATURDAY BEFORE TAPERING OFF ON SUNDAY AS HIGH PRESSURE TAKES HOLD. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
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AS OF 300 PM EDT WEDNESDAY... COLD FRONT WILL MOVE FROM WEST TO EAST ACROSS THE FORECAST AREA TODAY. MAIN CONCERN THROUGH THE TAF VALID PERIOD WILL BE PASSAGE OF THIS FRONT AND ASSOCIATED -SHRA ACTIVITY. MODELS IN GENERAL CONSENSUS THAT MUCH OF THIS ACTIVITY WILL PASS THROUGH THE MOUNTAINS THIS MORNING...THEN EAST OF THE MOUNTAINS THIS AFTERNOON. THERE ARE SOME DISCREPANCIES BETWEEN OBSERVED TIMING AND MODEL TIMING...BUT ONLY BY A FEW HOURS. AT ANY RATE...LOOK FOR A PERIOD...ABOUT A 4-8 HOUR WINDOW OF TIME...WHERE -SHRA AND LOWERING CIGS WILL OCCUR BEFORE THE FRONT CLEARS THE AREA AND CONDITIONS IMPROVE. PRIOR TO THE FRONTAL PASSAGE...SFC WINDS WILL BE PRETTY LIGHT...OUT OF THE SOUTHWEST AT 3-7KTS. FRONTAL PASSAGE WILL BRING A WIND SHIFT TO THE NORTHWEST...SPEEDS INCREASING INTO THE 6 TO 10 KT RANGE WITH GUSTS OF 15 TO 20KTS. STRONGEST WINDS WILL OCCUR VCNTY OF THE RIDGE CRESTS AND JUST LEE OF THE BLUE RIDGE VCNTY OF KBCB AND KROA. EXTENDED AVIATION DISCUSSION... VFR CONDITIONS TO RETURN TO ALL SITES THURSDAY. A DEEP LOW PRESSURE AREA IS THEN SLATED TO DIVE SOUTHWARD INTO THE REGION OVER THE WEEKEND PROVIDING A LONGER PERIOD OF POTENTIALLY IFR-LIFR CIGS AND PRECIPITATION...POTENTIALLY EVEN -SHSN OR -SN BLF/LWB AREA...WITH -RA ELSEWHERE. CONSIDERABLE UNCERTAINTY REGARDING THIS NEXT EVENT AT THIS POINT BECAUSE OF MODEL FLIP-FLOPS FROM RUN-TO- RUN. WINDS WILL ALSO BE QUITE STRONG AS CANADIAN AIR FILTERS INTO THE SYSTEM AND ANY POTENTIAL COASTAL LOW DEVELOPMENT ALSO EVOLVES WITH TIME. OVERALL...VERY POOR AVIATION CONDITIONS EXPECTED FRI- SUN.
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&& .EQUIPMENT...
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THE AC UNITS FOR THE RADAR SHELTER ARE BAD. RADAR OPERATION WILL BE INTERMITTENT UNTIL SUCH TIME THE AC UNITS ARE FIXED. IF SHELTER TEMPERATURES RISE ABOVE CRITICAL LEVELS WE WILL BE FORCED TO PLACE THE RADAR INTO STANDBY TO AVOID DAMAGE TO THE TRANSMITTER.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...KK NEAR TERM...DS/KK SHORT TERM...RCS LONG TERM...CF AVIATION...PM EQUIPMENT...PM

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