Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 231158 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 658 AM EST FRI JAN 23 2015 .SYNOPSIS... AN AREA OF LOW PRESSURE WILL MOVE NORTHEAST FROM THE GULF OF MEXICO TOWARD THE MID-ATLANTIC COAST THROUGH SATURDAY BRINGING A VARIETY OF SNOW...SLEET...AND FREEZING RAIN TO AREAS WEST OF THE BLUE RIDGE AND RAIN TO THE EAST. GUSTY WINDS AND SNOW SHOWERS ARE EXPECTED IN THE MOUNTAINS SATURDAY AS THE DEEP AREA OF LOW PRESSURE MOVES NORTHEAST ALONG THE COAST. AN ALBERTA CLIPPER WILL BRING ANOTHER CHANCE OF SNOW AND COLDER TEMPERATURES TO THE AREA BY EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 500 AM EST FRIDAY... FOCUS WILL BE WELL ADVERTISED AREA OF LOW PRESSURE MOVING NORTHEAST FROM THE GULF OF MEXICO DURING THE PERIOD FORMING MAJOR COASTAL LOW PRESSURE AREA OFF THE DELMARVA BY SATURDAY AFTERNOON. FORECAST REMAINS ON TRACK WITH RESPECT TO TIMING AS EARLIER EXPECTED...ALTHOUGH THERE CONTINUE TO BE QUESTIONS REGARDING THE DEGREE OF THE COLD AIR. MODEL SOUNDINGS HAVE TRENDED WARMER ONCE AGAIN...LEADING TO A TREND TOWARD MORE SLEET/FREEZING RAIN/RAIN AND LESS SNOW. THERE IS A PRONOUNCED WARM NOSE IN THE 850-700MB LAYER BY AFTERNOON/EVENING...EVEN ON THE NORMALLY COLDER GFS. HOWEVER...SFC TEMPS HAVE ALSO TRENDED WARMER...AND WITH THE PRECIPITATION STILL WELL BACK IN GA/SC AT THIS HOUR AND LIKELY NOT REACHING EVEN THE SOUTHWEST PART OF OUR CWA UNTIL MID OR LATE MORNING...SFC TEMPS SHOULD BE ABOVE FREEZING IN MOST AREAS BY THAT TIME. THUS...COOLING TO FREEZING...WILL BE HINGED ON THE INTENSITY OF THE DEVELOPING IN-SITU WEDGE SUPPORTED BY A WEAK HIGH TO OUR NORTH ACROSS PA. USING LATEST TEMPERATURE TRENDS AND THE TOP DOWN APPROACH ONCE AGAIN...HAS RESULTED IN AN INCREASED AMOUNT OF RAIN/FREEZING RAIN...ESPECIALLY THE I-64 CORRIDOR...AND LESS SNOW. I STILL FEEL FAIRLY CONFIDENT THAT THE LOWER ATMOSPHERE WILL ATTEMPT TO GO ISOTHERMAL FAIRLY QUICKLY AND CHANGE ANY INITIAL FREEZING RAIN TO SLEET FOR A WHILE SHORTLY AFTER ONSET. OTHER CONCERNS THAT COULD LIMIT WINTER PRECIPITATION ARE POTENTIAL FOR CONVECTIVE COMPLEX TO DEVELOP OFF THE GA/SC/NC COAST...REDUCING MOISTURE INFLUX UP OUR WAY...AND A DRY SLOT PROGGED TO MOVE IN BY EVENING. THE BULK OF THE QPF COMES THROUGH THE SW HALF OF THE CWA IN THE 18Z-00Z TIME FRAME AND IN THE NE HALF IN THE 00Z-06Z TIME FRAME. WE MAY SEE A TRANSITION TO DRIZZLE/FREEZING DRIZZLE THROUGH THE EVENING HOURS WEST OF THE BLUE RIDGE. THE GOOD NEWS IS THAT THE WARMER TREND REDUCES TO NEARZERO THE THREAT OF ANY ICING AT ALL EAST OF THE BLUE RIDGE ACROSS THE PIEDMONT. FOR TEMPERATURES...SHOW MAX TEMPS MID-LATE MORNING BEFORE THE PRECIPITATION BEGINS...THEN DROPPING INTO THE LOW 30S WEST TO MID 30S EAST DURING THE EARLY AFTERNOON AS PRECIPITATION OVERSPREADS THE REGION FROM SOUTHWEST TO NORTHEAST...THEN REMAINING NEAR STEADY FOR SEVERAL HOURS UNTIL THE AIR MASS BEGINS TO TOTALLY SATURATE AND WARM. ON THE BACK SIDE OF THE SURFACE LOW...WE ARE STILL EXPECTING A DEFORMATION ZONE TO TRACK INTO THE REGION FROM THE WEST. MOST OF THE PRECIPITATION WITH THIS WILL BE SNOW AND LARGELY OCCURRING AFTER 12Z SAT...MAINLY WEST OF THE BLUE RIDGE...WITH SOME LIGHT RAIN SHOWERS POSSIBLE EAST OF THE BLUE RIDGE. ALL ADVERTISED AMOUNTS OF WINTER PRECIPITATION REMAIN WITHIN ADVISORY CRITERIA AT THIS TIME. ONE CHANGE TO THE PREVIOUS ADVISORY CONFIGURATION WERE TO REMOVE SMYTH AND TAZEWELL COUNTIES AS ICE ACCUMULATIONS THAT FAR WEST...OUT OF THE IN-SITU WEDGE AREA...WILL BE LITTLE TO NONE AS SFC TEMPS REMAIN LARGELY AT-OR- ABOVE FREEZING. THE ONLY OTHER CHANGE WAS TO HAVE AN EARLIER START TIME TO THE NORTHERN PART OF THE ADVISORY AS REQUESTED BY RLX AND IN CONCERT WITH FASTER TRENDS AMONG THE GFS/ECMWF ESPECIALLY.
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&& .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/... AS OF 320 AM EST FRIDAY... THE UPPER LEVEL PORTION AND DEFORMATION ZONE OF FRIDAYS SYSTEM WILL TRACK ACROSS THE FORECAST AREA SATURDAY MORNING...EXITING THE PIEDMONT BY EARLY AFTERNOON. TEMPERATURES AND THICKNESS LEVELS CONTINUE TO LOWER ACROSS THE MOUNTAINS...THEREFORE WILL KEEP PRECIPITATION AS SNOW. COLD AIR DOES NOT ARRIVE IN THE EAST UNTIL MOISTURE IS EXITING IN THE AFTERNOON...SO WILL KEEP PRECIPITATION AS A COLD RAIN. DEFORMATION ZONES ARE NOTORIOUS FOR PRODUCING MORE SNOW THAN MODELS ADVERTISE...ESPECIALLY IF WE ARE UNDER THE PIVOT POINT. IN THIS CASE...THE UPPER LEVEL TROUGH IS OPEN AND SHOULD TRACK THE DEFORMATION ZONE FAIRLY QUICKLY TO THE EAST-NORTHEAST SATURDAY. WILL CONTINUE TO KEEP AN ADDITIONAL INCH OF SNOW IN THE WEST SATURDAY MORNING...LIKELY TO MELT THROUGH THE DAY AS THE SUN POKES OUT DURING THE AFTERNOON. TEMPERATURES MAY WARM SOME IN THE WEST SATURDAY WITH HIGHS POSSIBLY REACHING THE MID TO UPPER 30S. WITH THE DELAY OF COLD AIR REACHING THE EAST IN THE AFTERNOON...TEMPERATURES COULD WARM INTO THE 40S. ALSO DURING THE AFTERNOON...PRESSURE RISING BEHIND THE DEPARTING TROUGH WILL BRING BREEZY AND GUSTY CONDITIONS TO THE AREA. THESE BREEZY CONDITIONS AND WESTERN UPSLOPE SNOW SHOWERS WILL LINGER ACROSS THE MOUNTAINS SATURDAY NIGHT. AN ADDITIONAL HALF INCH OF SNOW POSSIBLE ALONG WESTERN SLOPES OF WESTERN GREENBRIER. ON SUNDAY...MODELS ARE DROPPING A DISTURBANCE OUT OF THE GREAT LAKES AND INTO THE OHIO VALLEY. A WARM FRONT WILL MODERATE TEMPERATURES TO NEAR NORMAL LEVELS SUNDAY AFTERNOON...ONLY TO DROP AGAIN BEHIND THE COLD FRONT SUNDAY NIGHT INTO MONDAY. TIMING THE COLD FRONT IS A LITTLE TRICKY WITH THE 00Z ECM HAVING A CLOSED LOW SLOWING THE DISTURBANCE DOWN. THE 00Z GFS IS MORE PROGRESSIVE WITH AN OPEN TROUGH. TEMPERATURES COLD ENOUGH ALOFT TO HAVE ALL SNOW FOR HIGHER ELEVATIONS WITH A COUPLE OF INCHES ON THE GROUND BY SUNRISE MONDAY MORNING. LOWER ELEVATIONS NOT AS CLEAR WITH P-TYPE AS MODELS LOW LEVEL THICKNESSES ONLY LOWERING TO 1300M-1310M. PRECIPITATION WILL MOVE EAST OF THE BLUE RIDGE AS WINDS BACK TO THE SOUTHWEST...UNFORTUNATELY TEMPERATURES WILL BE WARM ENOUGH FOR JUST A COLD RAIN. WINDS BEHIND THE COLD FRONT WILL BE BREEZY WITH STRONG PRESSURE RISES BUT LACKING A LONG LASTING LOW LEVEL JET. WINDS COULD BE A CONCERN BEHIND THE WARM FRONT AND AHEAD OF THE COLD FRONT SUNDAY IN THE BLUEFIELD-RICHLANDS AREA. WITH AN APPROACHING 40 KT SOUTHWESTERLY JET AND WARM AIR ADVECTION...ADVISORY LEVEL WINDS COULD MIX DOWN IN EXTREME SOUTHWEST VIRGINIA. && .LONG TERM /TUESDAY THROUGH THURSDAY/...
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AS OF 330 PM EST THURSDAY... THE LONG RANGE MODELS ARE IN GENERAL AGREEMENT THAT A HIGH AMPLITUDE UPPER TROF DEVELOPS ACROSS THE EASTERN U.S. EARLY IN THE WEEK KEEPING COLDER THAN NORMAL TEMPS IN PLACE...BEFORE LIFTING OUT LATE WEDNESDAY ALLOWING TEMPS TO MODERATE. A WEAK NORTHERN STREAM SYSTEM ZIPS THROUGH THE GREAT LAKES THURSDAY...BUT WITH MINIMAL MOISTURE IN PLACE ONLY SOME LIGHT UPSLOPE PRECIP IS EXPECTED. THERE ARE STILL DIFFERENCES WITH REGARD TO THE TIMING AND STRENGTH OF A SYSTEM THAT MOVES THROUGH EARLY MONDAY...WITH THE GFS DEEPER AND SLOWER COMPARED TO THE 12Z ECMWF AND CANADIAN MODELS. FORECAST SOUNDINGS SUGGEST THIS SHOULD BE RAIN OR SNOW EVENT WITH THE ABSENCE OF A WARM NOSE ALOFT AND FORECAST LOW LEVEL TEMPS KEEP PRECIP MAINLY LIQUID (EXCEPT A FEW HOURS IN THE MORNING) EAST OF THE BLUE RIDGE. MINOR SNOW ACCUMULATIONS ARE POSSIBLE IN THE MOUNTAINS...AND WILL CONTINUE TO HIGHLIGHT THIS THREAT IN THE HWO. UPSLOPE SNOW SHOWERS MAY CONTINUE THROUGH TUESDAY WITH COLD AIR ADVECTION AND WEAK SHORTWAVES RIDING DOWN THE WEST SIDE OF THE UPPER TROF...BUT EXACT TIMING OF PRECIP UNCLEAR. LOW LEVEL WINDS BACK AROUND EARLY WEDNESDAY BRINGING AN END THE UPSLOPE SNOW SHOWERS WITH TEMPERATURES MODERATING THROUGH THURSDAY.
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&& .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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AS OF 645 AM EST FRIDAY... DEEPENING LOW PRESSURE AREA FROM THE GULF WILL TRACK TO OFF THE MID-ATLANTIC COAST BY SATURDAY AFTERNOON. THIS WILL BRING POOR AVIATION CONDITIONS TO THE REGION TODAY IN THE FORM OF RAIN...SNOW...SLEET...AND FREEZING RAIN...WITH THE WINTER PRECIPITATION WEST OF THE BLUE RIDGE...WITH JUST RAIN TO THE EAST. A DEFORMATION ZONE ON THE BACK SIDE WILL PROLONG THE POOR AVIATION CONDITIONS INTO SATURDAY. WHILE CIGS ARE STILL VFR AT THIS WRITING...THEY WILL QUICKLY TRANSITION TO MVFR AND IFR AS THE PRECIPITATION SHIELD SPREADS INTO THE REGION FROM THE SOUTHWEST IN THE 14Z-18Z TIME FRAME. SFC TEMPS NEAR FREEZING AND BL TEMPS WARMING AOA FREEZING WILL RESULT IN A COMPLEX PRECIP TYPE WEST OF THE BLUE RIDGE...WITH SNOW/SLEET AT THE ONSET...TRANSITIONING TO FZRA/SLEET LATER IN THE AFTERNOON AND EVENING. THEN CHANGING BACK TO SNOW WEST OF THE BLUE RIDGE LATE AFT 06Z AS COLDER AIR AND THE DEFORMATION ZONE MOVE INTO THE AREA AND THE COASTAL LOW MOVES TOWARD THE DELMARVA. MUCH OF THIS PERIOD WILL FEATURE IFR OR WORSE CIGS AND VSBYS. WINDS WILL BECOME E-SE THIS MORNING AT SPEEDS OF 5-7KTS...THEN BECOME NE DURING THE AFTERNOON AT MOST SITES IN THE 7-9KT RANGE...THEN BACK FURTHER TO NNE-NNW AFT 06Z FROM WEST TO EAST AT THE SAME SPEEDS. SOME LOW END GUSTS ARE POSSIBLE EAST OF THE BLUE RIDGE AS THE COASTAL LOW NEARS THE NC/VA COAST. MEDIUM CONFIDENCE IN CIGS AND VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND SPEED/DIRECTION THROUGH THE TAF VALID PERIOD. EXTENDED AVIATION DISCUSSION... THE STORM MOVES UP THE EAST COAST SATURDAY AND SATURDAY NIGHT. MVFR CEILINGS WILL REMAIN IN KBLF AND KLWB AS WELL AS THE REST OF THE AFOREMENTIONED DEFORMATION ZONE WILL PROLONG SNOW WEST OF THE BLUE RIDGE INTO SATURDAY MORNING...TRANSITIONING TO SNOW SHOWERS IN FAVORED UPSLOPE AREAS ON THE WEST FLANK OF THE APPALACHIANS BY AFTERNOON/EVENING. GUSTY NORTHWEST WINDS ARE EXPECTED THROUGHOUT THE REGION SATURDAY AND SATURDAY NIGHT. WIND GUSTS AROUND 30 KNOTS ARE POSSIBLE...ESPECIALLY AT HIGHER ELEVATIONS IN THE WEST. SUNDAY THROUGH TUESDAY....PERSISTENT UPSLOPE CLOUDS AND POSSIBLE SUB VFR CIGS AT BLF/LWB ALONG WITH PERIODS OF SNOW SHOWERS. AN ALBERTA CLIPPER WILL BRING MORE A MORE WIDESPREAD CHANCE OF SNOW TO THE ENTIRE REGION LATE SUNDAY INTO MONDAY. GENERALLY MVFR TO VFR CONDITIONS ALONG AND EAST OF THE BLUE RIDGE WITH A CHANCE OF RAIN OR SNOW THERE CONFINED TO MONDAY.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...WINTER WEATHER ADVISORY FROM 2 PM THIS AFTERNOON TO 10 AM EST SATURDAY FOR VAZ018>020-022>024-034-035. WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 10 AM EST SATURDAY FOR VAZ010>017. NC...WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 10 AM EST SATURDAY FOR NCZ001-002-018. WV...WINTER WEATHER ADVISORY FROM 2 PM THIS AFTERNOON TO 10 AM EST SATURDAY FOR WVZ043-044-507-508. WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 10 AM EST SATURDAY FOR WVZ042. && $$ SYNOPSIS...RAB NEAR TERM...AMS/RAB SHORT TERM...RCS LONG TERM...PH AVIATION...RAB

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