Area Forecast Discussion
Issued by NWS Blacksburg, VA

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718 FXUS61 KRNK 082050 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 350 PM EST MON FEB 8 2016 .SYNOPSIS... A STRONG CYCLONE IN THE UPPER LEVELS OF THE ATMOSPHERE WILL SINK SOUTH ACROSS THE GREAT LAKES AND INTO THE OHIO VALLEY TODAY. THE AREA OF LOW PRESSURE WILL CUTOFF AND REMAIN NEARLY STATIONARY FOR THE NEXT THREE DAYS...TEMPERATURES FALLING AFTER TODAY AND REMAINING BELOW FREEZING THROUGH MUCH OF THE UPCOMING WEEK. THE LEADING EDGE OF THIS AIRMASS WILL ARRIVE IN THE FORM OF A COLD FRONT...THIS FRONT CROSSING THE MOUNTAINS THIS AFTERNOON... ASSOCIATED WITH RAIN AND SNOW SHOWERS. THE COLDEST OF THE AIR WILL NOT ARRIVE UNTIL TUESDAY. WEAK UPPER LEVEL IMPULSES WILL MOVE ACROSS THE MOUNTAINS DURING THE WEEK RESULTING IN A PROLONGED SNOW SHOWER EVENT ESPECIALLY OVER THE MOUNTAINS THROUGH MIDWEEK. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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AS OF 315 PM EST MONDAY... TODAY`S PRECIPITATION DID NOT START UNTIL LATE IN THE MORNING...WHICH ALLOWED TEMPERATURES TO PEAK IN THE UPPER 30S TO LOWERS 40S WEST OF THE BLUE RIDGE TO THE UPPER 40S TO LOWER 50S EAST. WARM AIR ADVECTION AHEAD OF A COLD FRONT BROUGHT SOME SNOW TO HIGHER ELEVATIONS AND WHITE RAIN TO THE VALLEYS THIS AFTERNOON. THIS PRECIPITATION LOWERED TEMPERATURES ACROSS THE MOUNTAINS DURING THE AFTERNOON BY 5F OR SO. BECAUSE THE WARM BOUNDARY IS SO SHALLOW...SNOW WAS ABLE TO MAKE IT TO THE GROUND EVEN...THOUGH TEMPERATURES WERE ABOVE FREEZING. THE FIRST COLD FRONT...LOCATED ACROSS THE OHIO AND TENNESSEE VALLEYS...WILL MOVE ACROSS THE MOUNTAINS EARLY THIS EVENING...THEN ACROSS THE PIEDMONT BY MIDNIGHT. THIS FRONT MAY BE A FEW HOURS SLOWER TO CLEAR THE AREA...AS A SURFACE REFLECTION DEVELOPS ALONG THE FRONT TRACKING ACROSS THE PIEDMONT THIS EVENING. PRECIPITATION WITH THE FRONT WILL REMAIN LIGHT WITH SNOW OR WHITE RAIN ACROSS THE MOUNTAINS AND A COLD RAIN IN THE EAST. A SECOND COLD FRONT WITH ARCTIC AIR WILL APPROACH THE AREA EARLY TUESDAY MORNING. PRECIPITATION AHEAD AND BEHIND THIS FRONT WILL BE ALL SNOW WITH ACCUMULATIONS PRIMARILY ALONG WESTERN SLOPES. WESTERN SLOPES OF GREENBRIER AND SUMMERS COUNTY COULD SEE 2-3 INCHES THIS AFTERNOON INTO TONIGHT. WESTERN SLOPES FROM THE BLUEFIELD-RICHLAND AREA TO THE GRAYSON HIGHLANDS AND NORTHWEST NORTH CAROLINA HIGH COUNTY COULD HAVE 1-2 INCHES...POSSIBLE 3-4 INCHES ABOVE 4000 FT. FOR HEADLINES...WE WILL CONTINUE THE WINTER WEATHER ADVISORY FOR THE FIRST FRONT THROUGH 6PM THIS EVENING FOR OUR WESTERN COUNTIES. WE WILL ALLOW THIS ADVISORY TO EXPIRE. WE WILL THEN UPGRADE THE CURRENT WINTER STORM WATCH TO A WINTER STORM WARNING FOR WESTERN SLOPES OF GREENBRIER COUNTY SOUTH INTO SUMMERS AND MERCER COUNTY. OTHER COUNTIES IN THE WATCH WILL BE CHANGED TO A WINTER WEATHER ADVISORY FROM THE ALLEGHANY HIGHLANDS TO THE MOUNTAIN EMPIRE AND NORTHWEST NORTH CAROLINA HIGH COUNTY. AT THIS TIME...NO OTHER COUNTIES WILL HAVE HEADLINES TO INCLUDED THE NEW RIVER AND ROANOKE VALLEYS...WHO MAY SEE SOME SNOW TONIGHT INTO TUESDAY WITH ONLY LIGHT ACCUMULATIONS.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY NIGHT/...
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AS OF 330 PM EST MONDAY... DEEP UPPER LOW OVER THE OHIO VALLEY TUESDAY AND WEDNESDAY. SHORT WAVE OVER THE FORECAST AREA TUESDAY MORNING ALONG WITH MUCH COLDER TEMPERATURES ALOFT...IN THE RANGE OF -30 TO -36 WILL PROVIDE SOME LIFT AND RELATIVE INSTABILITY. THIS SHOULD EXTEND SNOW SHOWERS WELL EAST OF THE BLUE RIDGE ON TUESDAY...ESPECIALLY NORTH OF ROANOKE. 850 MB TEMPERATURES WILL CONTINUE TO DROP...REACHING -18 TO -20 BY 12Z/7AM THURSDAY. MODELS ARE SIMILAR IN OVERALL SYNOPTIC PATTERN BUT SUBTLE DIFFERENCES SHOW UP IN SPEED AND LOCATION OF SHORT WAVED EMBEDDED IN THE LARGE UPPER TROF. ENOUGH COLD AIR COMING IN THAT WESTERN SLOPE LOCATIONS AND AREAS WITH SNOW SHOWERS WILL HAVE STEADY OR EVEN SLIGHTLY FALLING TEMPERATURES DURING THE DAY WEDNESDAY. EXPECTING SNOW TO LIQUID RATIOS OF 25:1 BY WEDNESDAY NIGHT. ENOUGH DRY AIR AND DOWNSLOPING ON WEDNESDAY AND THURSDAY TO HAVE SOME CLEARING EAST OF THE BLUE RIDGE.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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AS OF 250 PM EST MONDAY... EASTERN UPPER TROF GETS RE-ENFORCED FRIDAY NIGHT AND SATURDAY...THEN TROF AXIS MOVES OF THE COAST ON SUNDAY. BOTH THE ECMWF AND GFS BRING A CLIPPER ACROSS THE CENTRAL UNITED STATES MONDAY THEN INTO THE MID ATLANTIC REGION BY TUESDAY. WPC SUGGESTED THE TRACK OFF THE ECMWF MAY BE TOO FAR SOUTH. SOME 850 MB WARM AIR ADVECTION AND LOW LEVEL CONVERGENCE ALONG THE LEADING EDGE OF THE NEXT SURGE OF ARCTIC AIR. BEST LIFT LOOKS TO BE ON FRIDAY WITH SOME UPPER DIFFLUENCE. SNOW SHOULD BE MORE WIDESPREAD THAN JUST UPSLOPE. THEN GUSTY WINDS AND VERY LOW WIND CHILL VALUES ON FRIDAY NIGHT THROUGH SATURDAY NIGHT WITH NORTHWEST 850 MB WINDS APPROACHING 50 KNOTS. WIND CHILLS WILL AGAIN BE IN ADVISORY CRITERIA...BETWEEN -5 TO -19 IN THE MOUNTAINS ON SATURDAY NIGHT. A ROUGHLY 1045 MB SURFACE HIGH WILL BUILD INTO THE AREA FRIDAY NIGHT AND SATURDAY. THIS FEATURE WILL BE CENTERED OVER THE MID ATLANTIC REGION MONDAY MORNING. WINDS WILL DIMINISH ENOUGH WITH THE APPROACH OF THIS HIGH...AND WITH THE ASSOCIATED DRY AIR...TO END UPSLOPE SNOW SHOWERS IN THE MOUNTAINS SUNDAY.
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&& .AVIATION /21Z MONDAY THROUGH SATURDAY/...
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AS OF 700 AM EST MONDAY... PREFRONTAL PRECIPITATION BRINGING LIGHT SNOW TO THE MOUNTAIN EARLY THIS AFTERNOON. SOME LOCATIONS UNDER STRONGER BANDS WILL HAVE VISIBILITIES TEMPORARY DROPPING TO VLIFR. WARMER AIR TO ENTER THIS AFTERNOON AND WILL LIKELY CHANGE SNOW OVER TO RAIN. THE FIRST FRONT WILL MOVE EAST THIS EVENING...THEN AN ARCTIC FRONT COMES ACROSS TONIGHT. MVFR SNOW SHOWERS WILL BE COMMON AT BLF/LWB AND MVFR CEILING TO BCB/ROA FOR THE NEXT SEVERAL DAYS. WINDS WILL REMAIN LIGHT...LESS THAN 6KT AHEAD OF THE APPROACHING FRONT...THEN BECOME WESTERLY AND INCREASE IN MAGNITUDE AFTER ARCTIC FRONT CLEAR THE AREA TUESDAY MORNING. EXTENDED DISCUSSION... SUB-VFR SHOULD BECOME MORE CONFINED TO THE MOUNTAINS AND WESTERN SLOPES TONIGHT INTO MIDWEEK WITH PROLONGED MVFR/IFR CONDITIONS AT KBLF/KLWB IN SNOW SHOWERS THROUGH AT LEAST WEDNESDAY NIGHT AS ARCTIC AIR ARRIVES. POTENTIAL ALSO FOR PERIODS OF MVFR AT KBCB/KROA AS IMPULSES ROTATE ACROSS THE MOUNTAINS AND BANDS OF SNOW DEVELOP DURING THE OVERNIGHT HOURS. ACCUMULATING SNOW IS LIKELY IN THE MOUNTAINS WEST OF THE BLUE RIDGE. FLURRIES MAY ALSO OCCUR AS FAR EAST AS THE PIEDMONT WHERE INTERVALS OF VFR TO MVFR CIGS COULD ALSO OCCUR. CONDITIONS SHOULD BRIEFLY RETURN TO MAINLY VFR THURSDAY/THURSDAY NIGHT AS WEAK HIGH PRESSURE BUILDS IN AND MOISTURE DECREASES.
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&& .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR VAZ010>012- 019-020. WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR VAZ007-009- 015. NC...WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR NCZ001-018. WV...WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR WVZ044-507. WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR WVZ042-043. WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR WVZ043-508. WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR WVZ508.
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&& $$ SYNOPSIS...RCS NEAR TERM...RCS SHORT TERM...AMS LONG TERM...AMS AVIATION...RCS

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