Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 250438 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1138 PM EST TUE FEB 24 2015 .SYNOPSIS... AN AREA OF LOW PRESSURE WILL MOVE FROM THE GULF TOWARD THE CAROLINA COAST LATE WEDNESDAY INTO THURSDAY BRINGING MORE SNOWFALL FOR MUCH OF THE AREA...WITH THE HIGHEST AMOUNTS EXPECTED OVER THE SOUTHERN COUNTIES. HIGH PRESSURE WITH MORE COLD AIR WILL FOLLOW BEHIND THIS SYSTEM FOR LATE IN THE WEEK. && .NEAR TERM /THROUGH WEDNESDAY/...
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AS OF 1125 PM EST TUESDAY... WE ARE SEEING LESS CLOUD COVER NOW THAT DRIER AIR HAS PUSHED FURTHER IN FROM THE NORTH...BUT STILL SOME STRATUS/STRATOCU OVER THE MTN EMPIRE AND EAST OF THE MOUNTAINS IN NC. WILL SEE THESE WITHER AWAY OVERNIGHT WITH NEXT UPSTREAM CLOUDS ARRIVING TOWARD SE WV BY 4 AM WITH A FEW SNOW SHOWERS. NOT TOO MANY MAJOR MODIFICATIONS WERE NEEDED TO THE FORECAST OVERNIGHT. PREVIOUS VALID DISCUSSION... LOW TEMPERATURES WILL BE MILDER THAN THOSE OF THIS MORNING...BUT WE WILL STILL STAY ON THE LOW SIDE OF GUIDANCE...IF NOT SLIGHTLY LOWER THAN GUIDANCE. A MIX OF UPPER TEENS TO LOW 20S ARE FORECAST FOR THE MOUNTAINS WITH LOW TO MID 20S ACROSS THE PIEDMONT. ON WEDNESDAY...THE UPSLOPE SNOW SHOWERS WILL DECREASE IN COVERAGE AS 850 MB WINDS SLOW AND BECOME SOUTHERLY BY THE AFTERNOON. CLOUD COVER WILL INCREASE IN ADVANCE OF LOW PRESSURE MOVING THROUGH THE GULF COAST STATES. OVERRIDING PRECIPITATION FROM THIS SYSTEM MAY REACH THE FAR SOUTHWEST PART OF THE FORECAST AREA LATE IN THE DAY. WILL CONTINUE WITH A MENTION OF A SLIGHT CHANCE OF SNOW ACROSS THE NORTHERN MOUNTAINS OF NORTH CAROLINA AND NEIGHBORING FOOTHILLS. HIGH TEMPERATURES WILL RANGE FROM THE LOW TO MID 30S ACROSS THE MOUNTAINS AND UPPER 30S TO LOWER 40S ACROSS THE PIEDMONT.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
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AS OF 1125 PM EST TUESDAY... BASED ON THE TRENDS IN THE 21Z SREF/00Z NAM...REGARDING QPF AND THE MEAN OF THE SREF SHOWING A DEFINITE THREAT OF WARNING SNOW WENT AHEAD OF UPGRADED THE WATCH TO A WARNING FOR HEAVY SNOW FOR THE NC MTNS/FOOTHILLS...NORTH TO GRAYSON/CARROLL/PATRICK. THIS IS MAINLY DUE TO AN ARRIVAL TIME SHORTLY AFTER DUSK WED EVENING...WITH HEAVIER SNOW ARRIVING PRIOR TO MIDNIGHT. PER COORDINATION WITH OTHER OFFICES WILL LEAVE OUR EASTERN EXTENT OF THE WATCH WILL REMAIN IN A WATCH AS WELL AS SMYTH/WYTHE. THINK THE NC PIEDMONT AND SOUTHSIDE VA NORTHWEST TOWARD FLOYD/FRANKLIN/HENRY WILL LIKELY GET WARNING AMOUNTS BUT ITS TOO CLOSE. REST OF THE FORECAST WILL LIKELY BE IN ADVISORY LEVEL AMOUNTS. PREVIOUS DISCUSSION AT 645 PM... 18Z NAM/GFS...12Z ECMWF STILL ARE KEEPING A SHARP ENOUGH GRADIENT TO THE TOTAL QPF FOR THIS WINTER EVENT WED EVENING THROUGH THURSDAY SUCH THAT CONFIDENCE IS BORDERLINE ON WATCH VS WARNING IN SOUTHSIDE VA/NW NC. WILL TAKE A GANDER AT THE 21Z SREF THEN SOME 00Z MODELS BEFORE DECIDING ON WHETHER TO UPGRADE WATCH TO A WARNING. THE 15Z SREF DOES SHOW PROBABILITY OF 4" OR GREATER SNOWFALL BEING OVER 60 PERCENT OR MORE IN THE SOUTHSIDE VA PIEDMONT INTO THE NC PIEDMONT...WHICH IN 12 HRS FITS WARNING CRITERIA. FOR NOW WILL KEEP THE WATCH IN PLACE AS IS. PREVIOUS DISCUSSION AT 345 PM... WILL BE DEALING WITH IMPENDING SOUTHERN STREAM SYSTEM FROM LATE WEDNESDAY THROUGH A GOOD PART OF THURSDAY. PLENTY OF UNCERTAINTY EXISTS AMONG VARIOUS MODELS WITH SREF/NAM CONSIDERABLY MORE BULLISH ON QPF/SNOW THAN GLOBAL MODELS WHICH ARE CONSISTENTLY LESS AGGRESSIVE WITH THIS SYSTEM. ONE THING THAT DOES APPEAR CERTAIN IS P- TYPE WITH ALL THICKNESS PARAMETERS AND H85 TEMPS SUFFICIENTLY COLD FOR ALL SNOW EVEN ACROSS PIEDMONT. HENCE IT BECOMES A QPF FORECAST AND AT THIS POINT WE HAVE QPF RANGING FROM LESS THAN 0.10 INCHES NORTH OF ABOUT ROANOKE WITH INCREASING AMOUNTS SOUTHWARD REACHING ABOUT CLOSE TO 0.50 INCHES IN SOUTHERN PARTS OF OUR NORTH CAROLINA COUNTIES. THE TENDENCY OF THE LAST SEVERAL SYSTEMS TO SEE A LATE SHIFT NORTHWARD IN QPF HAS BEEN NOTED BY SEVERAL FORECASTERS AND THAT POTENTIAL CANNOT BE RULED OUT FOR THIS STORM. AT THIS POINT WILL GO WITH WINTER STORM WATCH INTO PARTS OF SOUTHERN VIRGINIA WHERE CURRENT FORECAST QPF/SNOW DOES NOT SUGGEST MEETING WINTER STORM CRITERIA BUT THIS ACCOUNTS FOR THE UNCERTAINTY OF A NORTHWARD SHIFT IN THE TRACK AND HIGHER SNOWFALL. FORECASTING CLOSE TO 6 INCHES OR POSSIBLY A LITTLE MORE IN FAR SOUTHERN COUNTIES...WITH HIGHEST OVER THE MOUNTAINS...DIMINISHING TO AROUND 3-5 INCHES ALONG THE NC/VA BORDER AND PERHAPS 2 TO 3 INCHES INTO THE NEW RIVER VALLEY AND INTO ROANOKE METRO AREA. SOME UPSLOPE CAN BE EXPECTED IN THE USUAL AREAS AS MORE COLD AIR MOVES IN BEHIND THIS LATEST WINTER STORM.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 355 PM EST TUESDAY... LOOKING TO FRIDAY MORNING...MAY SEE A FEW LINGERING SNOW SHOWERS ACROSS SOUTHEAST WEST VIRGINIA INTO THE NORTH CAROLINA HIGHLANDS AS ANOTHER SHOT OF ARCTIC HIGH PRESSURE BUILDS EAST FROM THE CENTRAL PLAINS...PUSHING TOWARD THE APPALACHIAN CHAIN THROUGH THE DAY. THE APPROACH OF THE HIGH WILL GRADUALLY CAUSE WINDS TO SHIFT NORTHEASTERLY...INCREASING THE FETCH OF COLD AIR FROM THE NORTH INTO OUR AREA. AS SUCH...DO NOT EXPECT AFTERNOON HIGHS ACROSS THE MOUNTAINS TO RISE ABOVE FREEZING...WHILE AREAS EAST OF THE BLUE RIDGE WILL ONLY REACH INTO THE LOW TO MID 30S. HIGH PRESSURE WILL REACH NEW ENGLAND FRIDAY EVENING...AND THEN BUILD SOUTH ACROSS THE MID ATLANTIC FRIDAY NIGHT. FRIDAY NIGHT WILL BE ESPECIALLY FRIGID DUE TO STRONG RADIATIONAL COOLING ASSOCIATED WITH MOSTLY CLEAR SKIES AND LIGHT WINDS...WITH OVERNIGHT LOWS RANGING FROM NEAR ZERO ACROSS SOUTHEAST WEST VIRGINIA...TO THE UPPER TEENS ACROSS THE SOUTHSIDE. FOR SATURDAY...HIGH PRESSURE WEDGED AGAINST THE EASTERN FACE OF THE APPALACHIANS WILL MAINTAIN CHILLY TEMPERATURES AREAWIDE...WITH AFTERNOON HIGHS RANGING FROM THE UPPER 20S NORTH TO THE MID 30S SOUTH. CLOUD COVER WILL INCREASE DURING THE EVENING HOWEVER...AS OUR NEXT UPPER LEVEL DISTURBANCE APPROACHES FROM THE WEST...SO EXPECT SATURDAY NIGHT LOWS TO HOLD IN THE TEENS AND LOW 20S. THE CHANCE FOR SNOW WILL INCREASE TOWARD DAWN SUNDAY AS A WEAK LOW PRESSURE SYSTEM PASSES UP THE ATLANTIC COAST...POTENTIALLY SPREADING PRECIPITATION AS FAR WEST AS THE NEW RIVER VALLEY. WITH COLD HIGH PRESSURE STILL IN PLACE ACROSS THE MID ATLANTIC...BELIEVE THE WEATHER MODELS ARE CALLING FOR TEMPERATURES THAT ARE FAR TOO WARM... AND THEREFORE WENT WITH HIGHS THAT ARE SEVERAL DEGREES COOLER. AS SUCH...DO NOT HAVE MUCH CONFIDENCE IN WHAT TYPE OF PRECIPITATION TO EXPECT...IF ANY. WILL JUST CONTINUE TO WATCH THE EVOLUTION OF THIS SYSTEM OVER THE NEXT DAY OR TWO. WITH THE PASSAGE OF THE COASTAL LOW PRESSURE SYSTEM...WINDS ACROSS OUR AREA WILL SHIFT WESTERLY AND DOWNSLOPE...WHICH WILL ALLOW FOR WARMER TEMPERATURES ON MONDAY. EARLY INDICATIONS ARE THAT HIGH TEMPERATURES NEXT MONDAY WILL BE THE WARMEST IN OVER A WEEK...WITH AFTERNOON TEMPERATURES RANGING FROM THE UPPER 40S ACROSS THE MOUNTAINS...TO THE MID 50S ACROSS THE SOUTHSIDE. RAIN CHANCES WILL INCREASE DURING THE AFTERNOON AS ANOTHER COLD FRONT APPROACHES FROM THE WEST. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 630 PM EST TUESDAY... MVFR CIGS WILL DIMINISH THIS EVENING OVER MOST OF THE AREA AS DRIER MOVES IN BEHIND STORM SYSTEM OFF THE COAST. LOOKING AT VFR THROUGH WEDNESDAY EXCEPT INCREASING MVFR CIGS TOWARD BLF LATER IN THE DAY AHEAD OF OUR NEXT WEATHER MAKER. THERE WILL BE A BRIEF PERIOD OF GUSTY WINDS OVERNIGHT...IN THE MTNS. NEXT STORM IS EXPECTED TO MOVE ACROSS THE DEEP SOUTH WEDNESDAY INTO THURSDAY. POTENTIAL FOR SUB- VFR CONDITIONS WILL EXIST ACROSS THE AREA WEDNESDAY NIGHT INTO THURSDAY ALONG WITH MEASURABLE SNOWFALL...HIGHER THREAT FOR SOUTHERN AREAS LIKE BCB-LYH-DAN...BUT THINK ALL TAF SITES WILL SEE SUB VFR CIGS. YET ANOTHER CLIPPER MAY CROSS THE AREA THURSDAY NIGHT INTO FRIDAY. WHILE LESS PROBABLE...THE WESTERN EXTENT OF A COASTAL SYSTEM COULD TEAM UP WITH THE CLIPPER AND BRING THE EASTERN PORTION OF THE FORECAST REGION A GREATER COVERAGE OF WINTRY PRECIPITATION FOR THE END OF THE WEEKEND. && .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY AFTERNOON FOR VAZ009-012-017-033-043-044-058-059. WINTER STORM WARNING FROM 7 PM WEDNESDAY TO 9 AM EST THURSDAY FOR VAZ015-016-032. NC...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY AFTERNOON FOR NCZ005-006. WINTER STORM WARNING FROM 7 PM WEDNESDAY TO 9 AM EST THURSDAY FOR NCZ001>004-018>020. WV...NONE.
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&& $$ SYNOPSIS...PC NEAR TERM...DS/WP SHORT TERM...PC/WP LONG TERM...NF AVIATION...DS/WP

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