Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 231730 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1230 PM 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/... AS OF 1030 AM EST FRIDAY... SO FAR THINGS ARE ON TRACK WITH VERY COMPLEX PTYPE FORECAST UNDERWAY. PRECIPITATION SHIELD FROM DEVELOPING LOW PRESSURE MOVING OUT OF THE GULF HAS SPREAD INTO THE SOUTHWESTERN THIRD OF THE AREA THIS MORNING WITH MANY REPORTS OF SLEET. WITH WARMER AIR MOVING IN ALOFT AND SURFACE TEMPS ABOVE FREEZING LOCATIONS EAST OF THE BLUE RIDGE STILL LOOK GOOD FOR A LIQUID EVENT. FROM THE BLUE RIDGE WEST IS MOST PROBLEMATIC AS ANY AND ALL PTYPES CAN BE EXPECTED. THERE WILL BE SUBSTANTIAL MELTING OF ANY SNOW THAT DOES FALL SINCE TEMPS WILL BE BORDERLINE AND THIS WILL TEMPER ACCUMULATIONS. THAT BEING SAID...LATEST SET OF GRIDS WILL INDICATE A BIT MORE SNOW AFTER LOOKING AT MORNING SOUNDINGS /NO RNK SOUNDING DUE TO SOFTWARE FAILURE/ AND LATEST TEMP TRENDS. PRECIP SHIELD WILL OVERSPREAD THE ENTIRE REGION DURING THE AFTERNOON AND A DRY SLOT WILL START TO WORK IN FROM THE WEST AS WE HEAD INTO THIS EVENING. PREVIOUS AFD... 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. && .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/... 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. && .AVIATION /17Z FRIDAY THROUGH TUESDAY/...
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AS OF 1230 PM EST FRIDAY... IFR/LIFR CONDITIONS SETTING IN ALL SITES FOR THIS EVENING WITH SIGNIFICANT IMPROVEMENT HOLDING OFF UNTIL SATURDAY MORNING. COMPLICATED PTYPE SCENARIO UNDERWAY ACROSS THE REGION FOR THE EARLY PORTION OF THE TAF PERIOD. FOR KLYH AND KDAN...EXPECTING WARMER AIR MOVING IN ALOFT TO CHANGE PCPN OVER TO ALL RAIN IN THE NEAR FUTURE. WHILE THERE MAY BE SOME MIXED PCPN EARLY ON BELIEVE THIS WILL BE QUITE EPHEMERAL SO WILL JUST GO WITH LIQUID AS EXPECTING THIS TO BECOME THE DOMINANT PTYPE. KBCB AND KROA WILL SEE SOME COLDER AIR NEAR THE SURFACE HOLD ON A BIT LONGER FOR A DECENT AMOUNT OF SLEET MIXING IN EARLY. WITH TIME WE WILL START TO LOSE DENDRITIC GROWTH IN THE CLOUDY LAYER AS THE DRY SLOT MOVES IN THIS EVENING. THIS WILL TRANSITION PCPN OVER TO SOME SNIZZLE OR FREEZING DRIZZLE AT KBCB WITH JUST A PLAIN DRIZZLE AT KROA. KBLF WILL BE WARMING TO MOSTLY RAIN THEN TO DRIZZLE...BUT KLWB WILL SEE THE MOST FROZEN/FREEZING PCPN AS THE COLDER AIR STAYS AROUND LONGER. AS THE LOW STARTS TO PULL AWAY ON SATURDAY...WINDS WILL PICK UP FROM THE NW AND TRAILING BAND OF SYNOPTIC PCPN WILL SWING THROUGH THE AREA WITH UPSLOPE LOCATIONS FROM THE BLUE RIDGE WEST TRANSITIONING BACK TO SNOW SHOWERS AND STAYING IN PCPN THROUGH THE LATTER PORTION OF THE TAF PERIOD. EXTENDED AVIATION DISCUSSION... 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...
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VA...WINTER WEATHER ADVISORY UNTIL 10 AM EST SATURDAY FOR VAZ018>020-022>024-034-035. WINTER WEATHER ADVISORY UNTIL 10 AM EST SATURDAY FOR VAZ010>017. NC...WINTER WEATHER ADVISORY UNTIL 10 AM EST SATURDAY FOR NCZ001- 002-018. WV...WINTER WEATHER ADVISORY UNTIL 10 AM EST SATURDAY FOR WVZ043- 044-507-508. WINTER WEATHER ADVISORY UNTIL 10 AM EST SATURDAY FOR WVZ042.
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&& $$ SYNOPSIS...RAB NEAR TERM...AMS/MBS/RAB SHORT TERM...RCS LONG TERM...PH AVIATION...MBS/RAB

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