Area Forecast Discussion
Issued by NWS Blacksburg, VA

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498 FXUS61 KRNK 050824 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 324 AM EST FRI FEB 5 2016 .SYNOPSIS...
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STRONG UPPER DISTURBANCE PASSES EAST OF US THIS MORNING. HIGH PRESSURE BUILDS INTO THE AREA FROM THE SOUTHWEST TONIGHT...AND STAYS IN THE GENERAL AREA THROUGH SATURDAY. A STORM SYSTEM MOVES WELL SOUTH OF US SATURDAY NIGHT INTO SUNDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 304 AM EST FRIDAY... LIGHT SNOW...SOME SLEET/SNOW GRAINS BEING REPORTED FROM EAST OF ROANOKE SOUTH TO MOUNT AIRY AND PILOT MTN NC THIS MORNING...AND AS FAR EAST AS DANVILLE. DEFORMATION ZONE WITH 700 MB FRONTOGENESIS SHOWING UP FAIRLY WELL OVER THE PIEDMONT EARLY THIS MORNING...WITH TROUGH TAKING ON NEGATIVE TILT AND MAIN SHORTWAVE PUSHING INTO SC/NC. THIS WAVE WILL WORK EAST OF US BY MID MORNING WITH PRECIP MOVING OUT OF THE AREA. TEMPS WHERE THERE HAS BEEN SNOW HAVE BEEN IN THE MID TO UPPER 30S...SO OVERALL ANTICIPATING ONLY A COATING ON GRASSY SFCS/METAL OBJECTS IN THE EAST THIS MORNING. FURTHER WEST TEMPS COLDER AND UPSLOPE FLOW WILL LEAD TO AN INCH OR SO OVER THE HIGHER TERRAIN FROM SE WV INTO NW NC...BUT WITH THE 8H FLOW BECOMING MORE ANTICYCLONIC APPEARS THE MOISTURE SHOULD DWINDLE TOWARD 12Z...SO A SHORT-LIVED NW FLOW EVENT...NOT HEADLINE WORTHY BUT SHOULD BE ENOUGH TO COAT ROADS IN THE HIGHER ELEVATIONS. THE WINDS WILL BE THE OTHER ISSUE THIS MORNING. SEEMS ITS A MARGINAL EVENT GIVEN THE 8H FLOW TURNING MORE NNW...THOUGH THIS TYPE OF FLOW IF THE LOW LVL JET IS STRONG ENOUGH CAN CAUSE MORE ISSUES ON THE ERN SLOPE/DOWNSLOPE SIDE OF THE BLUE RIDGE...SUCH AS FANCY GAP ON I-77. SINCE GUIDANCE AND LOCAL STUDY SUGGESTS A MARGINAL WIND EVENT AT BEST WITH GREATEST PRESSURE RISES STAYING SOUTH OF US AN 8H JET ONLY REACHING NEAR 40 KTS...WILL LET THE WIND ADVISORY RUN AS IS. REST OF THE DAY WILL BECOME SUNNY BUT STAY SOMEWHAT BRISK...THOUGH WINDS SUBSIDE AFTER MIDDAY. HIGH TEMPS WILL JUST UNDER SEASONABLE NORMS WITH MID 40S EAST TO LOWER TO MID 30S WEST. TONIGHT...THE UPPER FLOW SWINGS BACK TO MORE WSW. ATTM...EXPECTING MOSTLY CLEAR SKIES...THOUGH THINK THE 00Z NAMDNG SHOWING MORE COVERAGE IN HIGH CLOUDS BEARS WATCHING. IF THIS OCCURS...TEMPS WILL NOT BE AS COLD TONIGHT. FOR NOW WILL LEAN TOWARD A PARTLY CLOUDY FORECAST AFTER MIDNIGHT. LOW TEMPS WILL RANGE FROM UPPER TEENS IN THE VALLEYS WITH 20 TO 25 OVER MOST OF THE REGION.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
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AS OF 237 AM EST FRIDAY... DRY HIGH PRESSURE WILL DRIFT OFF THE EAST COAST AS AN UPPER LEVEL TROUGH CROSSES OVER THE SOUTHERN OHIO AND TENNESSEE VALLEYS SATURDAY AFTERNOON. TEMPERATURES SATURDAY WILL BE CLOSE TO NORMAL WITH LOWER 40S WEST TO NEAR 50F EAST. THIS TROUGH MAY BECOME A CLOSED LOW OVER THE SOUTHERN APPALACHIANS SATURDAY NIGHT...GENERATING A SURFACE WAVE OFF THE EAST COAST OF FLORIDA. MODELS ARE KEEPING ALL THE PRECIPITATION WITH THE SURFACE LOW AND ONLY AN INCREASE IN CLOUDS FOR THE FORECAST AREA. WITH SOME MOISTURE AND LIFT...THERE COULD BE A FEW SPRINKLES OR FLURRIES ALONG THE TN/VA AND VA/NC BORDER SATURDAY NIGHT. DURING THE DAY SUNDAY...THIS SYSTEM BECOMES OCCLUDED OVER BERMUDA...LEAVING THE REGION UNDER MOSTLY SUNNY SKIES WITH TEMPERATURES FROM THE MID 40S TO MID 50S. UNDER GOOD RADIATIONAL COOLING SUNDAY EVENING...TEMPERATURES WILL QUICKLY DROP INTO THE 30S. THIS WILL SET THE STAGE FOR SOME LIGHT SNOW TO ENTER THE MOUNTAINS EARLY MONDAY MORNING AS A COLD FRONT APPROACHES THE REGION.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 245 PM EST THURSDAY... THE LONG WAVE TROF OVER THE EAST CONTINUES TO DEEPEN MONDAY...WITH A CLOSED UPPER LOW WITHIN THIS TROF OVER THE OHIO VALLEY ON TUESDAY. BY TUESDAY NIGHT...500 MB HEIGHTS WILL BE DOWN AROUND 522 DECAMETERS AND 850 MB TEMPERATURES AROUND -12C. BY MONDAY MORNING THE COASTAL LOW IS WELL NORTHEAST OF THE DELMARVA PENINSULA WITH ANOTHER LOW OVER THE GREAT LAKES AND MID ATLANTIC REGION. A COLD FRONT WILL CROSS THROUGH THE FORECAST AREA ON MONDAY...WITH A RE-ENFORCEMENT OF COLDER AIR ON TUESDAY. UPSLOPE FLOW AND PERSISTENT LOW LEVEL MOISTURE WILL RESULT IN A PROLONGED PERIOD OF SNOW SHOWERS IN THE FAVORED MOUNTAIN AREAS MONDAY NIGHT THROUGH WEDNESDAY NIGHT. WENT ON THE COOLER SIDE OF GUIDANCE ON MONDAY WITH CLOUDS AND PRECIPITATION EXPECTED. ECMWF AND GFS ARE DIFFERENT WITH HOW FAST THE TROF LIFTS OUT AND THE COLDER AIR MASS MODERATES ON WEDNESDAY AND THURSDAY. WEDNESDAY NIGHT THURSDAY WILL BE DRY WITH UNDER SURFACE HIGH PRESSURE. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... AS OF 1150 PM EST THURSDAY... INITIAL CONCERN WILL BE FOCUSED AROUND A COASTAL LOW PRESSURE AREA DEVELOPING ALONG THE SC/NC COAST OVERNIGHT IN RESPONSE TO A VIGOROUS NEGATIVELY TILTED UPPER TROUGH LIFTING OUT OF THE SOUTHEAST STATES. WHILE THE BULK OF THE ASSOCIATED PRECIPITATION WILL REMAIN EAST OF THE CWA...OVER THE NEXT 4-8 HOURS...POTENTIAL FOR LOW-LEVEL MOISTURE AND LIGHT PRECIPITATION TO BE PULLED BACK INTO THE PIEDMONT. MORE IMPORTANTLY...A DEFORMATION ZONE IS NOW DEVELOPING NEAR KROA THAT WILL ALSO BRING LIGHT -RA AND/OR -RASN TO AREAS BACK TOWARD THE BLUE RIDGE...INCLUDING KROA. KROA IS OBSERVING -RASN MIX AT THIS HOUR. TO THE WEST...UPSLOPE CLOUDS HAVE ALREADY COMMENCED AND UPSLOPE -SHSN CAN BE EXPECTED AFT 06Z AS LOW PRESSURE INTENSIFIES ALONG THE COAST AND THE NORTHWEST FLOW INTENSIFIES. ANY REDUCTIONS TO VISIBILITY WILL BE BRIEF...IF AT ALL...AND HIGH END MVFR AT WORST. BY 12Z...ANY COASTAL LOW ASSOCIATED PRECIPITATION WILL BE MOVING RAPIDLY AWAY FROM THE CWA AND UPSLOPE WILL BE WINDING DOWN FAIRLY QUICKLY. UPSLOPE CLOUDS WILL PERSIST ALONG THE ALLEGHANY FRONT UNTIL EARLY AFTERNOON...THEN SCATTER OUT. FURTHER EAST...EXPECT CLEARING EAST OF THE BLUE RIDGE BY LATE MORNING/EARLY AFTERNOON. AFT LATE AFTERNOON...JUST SCT250. WINDS WILL BE AN INCREASING CONCERN THROUGH THE TAF VALID PERIOD AS THE COASTAL LOW INTENSIFIES. EXPECT N-NNW 7-10KTS INCREASING TO 12-15KTS WITH GUSTS 25-30KTS AFT 08Z THROUGH LATE AFTERNOON FRIDAY. WINDS WILL BECOME MORE NORTHWEST AS THE LOW MOVES FURTHER UP THE COAST. WIND GUSTS HIGHER THAN 40KTS WILL BE POSSIBLE ACROSS THE HIGHER ELEVATIONS OF THE WESTERN MOUNTAINS. WINDS WILL DIMINISH QUICKLY TOWARD SUNSET FRIDAY EVENING...BECOMING NW 3-7KTS BY 00Z. MEDIUM CONFIDENCE IN CIGS AND VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID PERIOD. EXTENDED DISCUSSION... ANOTHER SYSTEM MOVING ACROSS THE SOUTHEAST APPEARS TO STAY JUST SOUTH OF US SUNDAY WITH POSSIBLE LIGHT PRECIP AND MVFR CIGS EDGING TOWARD THE VA/NC BORDER SUNDAY AFTERNOON. AN ARCTIC FRONT/CLIPPER PUSHES IN MONDAY AND WILL BRING SOME SNOW TO PORTIONS OF THE AREA...MAINLY THINKING KBLF/KLWB AND EAST TOWARD KROA/KLYH. SHOULD SEE SOME MVFR TO AT TIMES IFR CIGS/VSBYS IN WV AND POTENTIALLY TO KBCB/KROA/KLYH MONDAY. LINGERING NW FLOW WILL SUPPORT A CONTINUATION OF MVFR CIGS OVER THE MOUNTAINS MONDAY NIGHT INTO TUESDAY WITH PERIODIC SUB-VFR IN SNOW SHOWERS. EXPECT CIGS EAST OF THE MOUNTAINS TO RETURN TO MAINLY VFR BY MONDAY NIGHT INTO TUESDAY. && .HYDROLOGY...
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AS OF 323 AM EST FRIDAY... MINOR FLOODING CONTINUES ALONG THE LOWER ROANOKE RIVER AROUND RANDOLPH AND ACROSS THE DAN RIVER BASIN FROM PACES DOWNSTREAM TO SOUTH BOSTON. THESE RIVERS ARE CRESTING OR HAVE CRESTED AND WILL BE DROPPING BELOW FLOOD STAGE THROUGH THIS EVENING. SEE THE LATEST WBCFLSRNK PRODUCT FOR ADDED DETAILS.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...WIND ADVISORY UNTIL 10 AM EST THIS MORNING FOR VAZ015. NC...WIND ADVISORY UNTIL 10 AM EST THIS MORNING FOR NCZ001-002-018. WV...NONE. && $$ SYNOPSIS...WP NEAR TERM...WP SHORT TERM...RCS LONG TERM...AMS AVIATION...JH/RAB/RCS/WP HYDROLOGY...WP

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