Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 032345 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 645 PM EST TUE MAR 3 2015 .SYNOPSIS... A WARM FRONT WILL LIFT NORTH THROUGH THE REGION THIS EVENING INTO TONIGHT AS A COLD FRONT APPROACHES FROM THE WEST. LOW PRESSURE OVER THE CENTRAL PLAINS WILL TRACK INTO SOUTHEAST CANADA AND WILL PUSH A COLD FRONT INTO THE REGION ON WEDNESDAY. COLDER AIR BEHIND THE FRONT WILL ALLOW FOR A TRANSITION FROM RAIN TO SNOW WEDNESDAY NIGHT AND THURSDAY. && .NEAR TERM /THROUGH WEDNESDAY/... AS OF 300 PM EST TUESDAY... TEMPERATURES WILL CONTINUE TO SLOWLY RISE THIS AFTERNOON INTO TONIGHT. KFCX WSR-88D SHOWED THAT THE HEAVIEST PRECIPITATION HAS MOVED EAST OF OUR AREA THIS AFTERNOON WITH ANOTHER ROUND OF RAIN TO OUR NORTHWEST SLIDING EAST. MOSTLY LIGHT RAIN...DRIZZLE AND FOG EXPECTED THIS EVENING INTO TONIGHT...WITH A STRONG LOW LEVEL JET PUSHES UP TEMPERATURES AND DEW POINTS. PLAYED POPS HIGHEST IN THE NORTHWEST TO THE LIGHTEST IN THE SOUTHEAST. USED A NON-DIURNAL CURVE FOR TEMPERATURES THIS EVENING INTO TONIGHT. LOW TEMPERATURES OVERNIGHT WILL RANGE MID 30S IN THE NORTHEAST TO NEAR 50 DEGREES IN THE WEST. AFTER MIDNIGHT...THE COLD FRONT APPROACHES AND THE PROBABILITY OF MODERATE RAIN IN THE NORTHWEST COUNTY WARNING AREA INCREASES. WEDNESDAY MORNING STARTS WITH A COLD FRONT SITUATED ACROSS THE NORTHWEST PORTIONS OF FORECAST AREA FROM THE ALLEGHANY HIGHLANDS THROUGH THE MOUNTAIN EMPIRE. STRONG MOISTURE FLOW INTO THE AREA ON A 50KT TO 60KT SOUTHWESTERLY LOW LEVEL JET WILL PUSH PRECIPITABLE WATER VALUES TO 1.0-1.1 INCHES IN THE WEST...AND AS HIGH AS 1.4 INCHES FURTHER EAST...ALL SIGNIFICANTLY ABOVE NORMAL FOR EARLY MARCH. DURING THE MORNING...RAIN WILL BE WIDESPREAD WEST OF THE BLUE RIDGE...ALTHOUGH THE STRONGEST LIFT/HEAVIEST RAINFALL PROGGED TO BE WEST OF THE CONTINENTAL DIVIDE...JUST SCRAPPING SOUTHEAST WEST VIRGINIA...PARTICULARLY THE WEST FACING SLOPES. FURTHER EAST...WILL LIKELY SEE A BAND OF HEAVY RAIN JUST AHEAD OF THE FRONT AS IT SLOWLY DRIFTS EAST THROUGH THE DAY. THE NAM...GFS AND ECMWF...DEVELOP A WAVE OF LOW PRESSURE ALONG THE FRONTAL BOUNDARY WEDNESDAY AFTERNOON INTO WEDNESDAY EVENING SLOWING ITS PROGRESSES SOUTH. HIGH TEMPERATURES ON WEDNESDAY WILL BE QUITE MILD WITH READINGS FROM THE UPPER 40S IN THE NORTHWEST TO THE LOWER TO MID 60S IN THE PIEDMONT. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/... AS OF 230 PM TUESDAY... ISSUE THIS PERIOD WILL BE WITH HOW QUICK COLDER AIR ARRIVES IN TIMING WITH PRECIP. 12Z MODELS CONTINUE TO FAVOR SLOWER ARRIVAL OF FRONT BUT EDGE COLDER AIR INTO THE MOUNTAINS OF WV BY WEDNESDAY EVENING. AT THE SAME TIME...LOW PRESSURE ALONG THE FRONT MOVING NE WILL AID IN A WARM NOSE PUNCHING BACK WEST TO CHANGE ANY SNOW TO SLEET BEFORE THE ARCTIC AIR PLUNGES SE AS THE LOW MOVES BY THURSDAY MORNING. QPF IS THE ISSUE AND STILL APPEARS THE CORRIDOR OF HIGHER QPF WILL STRETCH FROM ERN KY THROUGH NORTHERN VA WITH SECONDARY MAX IN THE PIEDMONT WITH SFC LOW INFLUENCE. WITH WINTRY PRECIP...WENT CLOSER TO THE 12Z GFS WITH A BLEND OF ECMWF ON TEMPS. WITH THIS IN MIND CONFIDENCE IS 50/50 THAT OUR EXTREME NRN CWA FROM GREENBRIER TO AMHERST WILL FLIRT WITH WARNING LEVEL SNOW/SLEET BY THURSDAY AFTERNOON...AND IN COLLABORATION WITH WFO STERLING AND WFO CHARLESTON ISSUE A WINTER STORM WATCH FROM GREENBRIER TO AMHERST. EXPECT THE HIGHER TOTALS TO OCCUR IN THE MOUNTAINS OF WRN GREENBRIER...NE GREENBRIER INTO THE ALLEGHANYS OF BATH...TO THE BLUE RIDGE MTNS OF AMHERST. OVERALL AMOUNTS SHOULD BE IN THE 2 TO 6 INCH RANGE...THOUGH SOME HIGHER AMOUNTS WILL BE POSSIBLE ESPECIALLY IF THE COLDER AIR SURGES SWD QUICKER WITH PRECIP IN PLACE. THIS WATCH RUNS FROM MIDNIGHT WED NIGHT THROUGH 7PM THURSDAY. FURTHER SOUTH EXPECT RAIN TO WINTRY MIX THROUGH THURSDAY. COULD SEE A WINTER ADVISORY GOING UP FOR THE REST OF THE CWA FOR THURSDAY...EXCEPT PERHAPS THE NC FOOTHILLS/PIEDMONT INTO SRN VA. TEMPS WED NIGHT WILL SLOWLY FALL...AND MAY STAY STEADY OUT EAST AHEAD OF THE FRONT. TEMPS WILL THEN DROP ACROSS MOST OF THE CWA THURSDAY WITH COLD AIR ADVECTION TAKING SHAPE. 8H TEMPS FALL FROM +6C IN THE PIEDMONT/-6C IN THE WV MTNS AT 12Z THU TO ZERO EAST TO -12C WEST BY 00Z FRI. SO THE LOWS THURSDAY MORNING WILL BE THE HIGHS THURSDAY FOR SOME OF OUR MTN COUNTIES...WITH TEMPS FALLING TO 20 BY DUSK THURSDAY. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... AS OF 215 PM EST TUESDAY... THURSDAY EVENING...THE BULK OF THE PRECIPITATION ASSOCIATED WITH THE EXITING FRONT WILL HAVE EXITED THE REGION...OR JUST BE ON THE EASTERN FRINGES. ALSO...ACROSS SOUTHEAST WEST VIRGINIA...NORTHWEST FLOW UPSLOPE SCATTERED SNOW SHOWER WILL BE POSSIBLE THROUGH THE EVENING HOURS. BY MIDNIGHT...THE LOW LEVEL FLOW WEAKENS AND VEERS MORE NORTHERLY...MUCH LESS CONDUCIVE FOR ADDITIONAL UPSLOPE SNOW SHOWERS. MUCH COLDER AIR WILL ADVECT INTO THE AREA IN THE WAKE OF THE FRONT. OVERNIGHT LOW TEMPERATURES ARE EXPECTED TO RANGE FROM AROUND ZERO TO PLUS FIVE OVER SOUTHEAST WEST VIRGINIA AND PLUS FIVE TO LOWER TEENS OVER THE MOUNTAINS OF SOUTHWEST VIRGINIA AND NORTHWEST NORTH CAROLINA. ACROSS THE PIEDMONT...LOWS WILL BE IN THE TEENS. WINDS WILL BE ON THE LIGHT SIDE BY LATE THURSDAY NIGHT INTO EARLY FRIDAY MORNING...BUT WITH THE LOW TEMPERATURES WIND CHILL VALUES WILL FLIRT WITH THE ADVISORY THRESHOLD OF FIVE BELOW ZERO ACROSS THE HIGHER TERRAIN IN AREAS ALONG AND NORTH OF INTERSTATE 64. FRIDAY AND SATURDAY...HIGH PRESSURE BUILDS OVER THE REGION...WITH ITS CENTER SHIFTING EAST OF THE AREA BY SATURDAY NIGHT. THE RESULT WILL BE A DRY FORECAST...WITH MODERATING TEMPERATURES. AFTER HIGHS ON FRIDAY IN THE UPPER 20S TO MID 30S ACROSS THE FORECAST AREA...HIGHS ON SATURDAY WILL RANGE MORE IN THE 40S WEST TO LOWER 50S EAST. THERE HAS BEEN CONSIDERABLE VARIATION IN THE MODEL GUIDANCE DURING THE SUNDAY THROUGH TUESDAY TIME PERIOD. WHILE EACH IS FAIRLY CONSISTENT THAT A LONG WAVE TROUGH WILL DEVELOP ACROSS THE EASTERN THIRD OF CONUS...THERE HAVE BEEN INCONSISTENCIES AS TO WHETHER OR NOT...AND WHEN...AND WHAT TRACK A SOUTHERN STREAM SYSTEM MAY GET PICKED UP ON THE EAST SIDE OF THIS TROUGH AND PROGRESS NORTHEAST ACROSS OUR AREA. THE GFS HAS NOT BEEN FAVORABLE OF THIS OCCURRENCE. THE ECMWF WAS OPTIMISTIC ON AN ARRIVAL A SOUTHERN SYSTEM ON MONDAY IN YESTERDAYS SOLUTION. TODAYS SOLUTION PLACES THAT EVENT ABOUT 24 HOURS LATER ON TUESDAY. OUR FORECAST TODAY WILL REFLECT TEMPERATURES CONTINUING TO MODERATE THROUGH MONDAY...WITH THE THINKING THAT THE DEVELOPING TROUGH AXIS WILL REMAIN TO OUR WEST...AND WE WILL CONTINUE IN WARM AIR ADVECTION AT THE SURFACE. IT WILL ALSO REFLECT THE POTENTIAL FOR SOME ISOLATED TO SCATTERED UPSLOPE SNOW SHOWERS ACROSS SOUTHEAST WEST VIRGINIA WHERE 850 MB FLOW WILL BE MORE W-NW. IT WILL ALSO ALLOW FOR A SLIGHT CHANCE OF A SOUTHERN STREAM SYSTEM IMPACTING THE AREA ON TUESDAY WITH RAIN OR FREEZING RAIN. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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AS OF 630 PM EST TUESDAY... LIGHT RAIN WILL PROGRESSIVELY INCREASE ACROSS THE REGION FROM THE WEST TO THE EAST AS THE NIGHT PROGRESSES. CIGS CURRENTLY ARE MAINLY IN THE MVFR RANGE WITH VSBYS VFR. THE TREND WILL BE FOR CIGS TO LOWER INTO THE LIFR RANGE WITH VSBYS IFR DURING THE NIGHT. LOW LEVEL WIND SHEAR WILL BE LIKELY...NOW THROUGH ROUGHLY 13Z/8AM ON THURSDAY COINCIDENT WITH THE SOUTHWEST FLOW ASSOCIATED WITH THE APPROACH AND PASSAGE OF THE WARM FRONT. THE ARRIVAL AND PASSAGE OF THE COLD FRONT WILL DISCONTINUE THE SHEAR...OR AT LEAST MAKE IT TOO WEAK TO INCLUDE IN THE TAFS AT THAT POINT. A WAVE OF LOW PRESSURE WILL RIDE ALONG THE COLD FRONT TOMORROW AND PROVIDE FOR WIDESPREAD RAINFALL AND IFR/MVFR CIGS AND VSBYS. LOW LEVEL WINDS WILL SHIFT NORTHWEST BEHIND THE FRONT. IT SHOULD REACH ALL OUR TAF SITES BUT KDAN BY 00Z TOMORROW...BUT IT WILL BE ON ITS WESTERN DOORSTEP AT THAT TIME. MEDIUM CONFIDENCE ON CEILINGS...VISIBILITIES AND WINDS DURING THE TAF PERIOD. AS OF 1230 PM EST TUESDAY... EXTENDED FORECAST... WINTER PRECIPITATION IS LIKELY BEHIND THE FRONT WEDNESDAY NIGHT AND THURSDAY. AT THIS TIME THE MOST LIKELY PRECIPITATION TYPES ARE SNOW AND SLEET. FRIDAY AND SATURDAY WILL SEE A RETURN TO HIGH PRESSURE AND VFR WEATHER.
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&& .HYDROLOGY... AS OF 300 PM EST TUESDAY... FLOODING THREAT APPEARS TO STAY JUST WEST AND NORTH OF OUR CWA AS MODELS HAVE 1.5" OR MORE IN 12 HRS PROJECTED HERE. PLUS ARRIVAL OF COLDER AIR WITH BRUNT OF QPF MAY LIMIT RAINFALL BEFORE IT CHANGES TO SLEET THEN SNOW. RIVER FORECAST CENTERS AS OF THIS MORNING WERE FORECASTING A RISE TO JUST BELOW FLOOD STAGE AT ALDERSON IN GREENBRIER COUNTY...TAKING INTO ACCOUNT GUIDANCE FROM LAST NIGHT. WITH LESS QPF THIS MAY BE BACKED OFF. GIVEN SNOW MELT AND TIMING OF COLDER AIR TO CHANGEOVER THERE SHOULD ONLY BE RISES ON RIVERS AND STREAMS...BUT THE THREAT OF FLOODING IS NOT ENOUGH TO WARRANT A FLOOD WATCH AT THIS TIME. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING FOR VAZ020-024-035. NC...NONE. WV...WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING FOR WVZ507-508. && $$ SYNOPSIS...KK NEAR TERM...KK SHORT TERM...WP LONG TERM...DS AVIATION...AMS/DS/KK HYDROLOGY...WP

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