Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 231024
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
524 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/...
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 NEA
ZERO 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.

&&

.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 .

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 /10Z FRIDAY THROUGH TUESDAY/...
AS OF 1140 PM EST THURSDAY...

EVOLVING LORE PRESSURE SYSTEM WILL MOVE FROM THE GULF OF MEXICO
TONIGHT...TO THE FLORIDA PANHANDLE ON FRIDAY...TO THE CAROLINA
COAST ON SATURDAY MORNING. A LARGE AREA OF PRECIPITATION WILL
SPREAD INTO SOUTHERN VIRGINIA FRIDAY. MODELS WERE IN GOOD
AGREEMENT WITH THE TIMING. HIGH CONFIDENCE THAT KROA/KDAN/KBCB
AND KBLF WILL NOT HAVE PRECIPITATION...OR EVEN MVFR CEILINGS
BEFORE 12Z/7AM.

CEILINGS WILL LOWER QUICKLY TO MVFR THEN IFR AFTER 12Z/7AM WITH
RAIN...SLEET OR SNOW BY 18Z. LOW CONFIDENCE ON PRECIPITATION TYPE
SINCE MODELS HAVE BEEN TRENDING WARMER EACH RUN. HAVE A FEW HOURS
OF VFR CEILINGS AT KLWB EARLY FRIDAY MORNING BUT CONFIDENCE IS
LOW. HAVE ADDED FREEZING RAIN AND SNOW IN FOR KBLF/KLWB AND KBCB
AFTER 00Z/7PM BASED ON LATEST BUFKIT FORECAST SOUNDINGS.

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 FAVORED UPSLOPE AREAS ON THE WEST FLANK OF THE APPALACHIANS.
SNOW SHOWERS ARE ALSO EXPECTED BUT LOWER CONFIDENCE THAT SNOW WILL
PERSIST PAST SATURDAY EVENING. GUSTY NORTHWEST WINDS ARE EXPECTED
THROUGHOUT THE REGION SATURDAY AND SATURDAY NIGHT. WIND GUSTS
AROUND 30 KNOTS ARE POSSIBLE...ESPECIALLY AT HIGHER ELEVATIONS.

SUNDAY THROUGH TUESDAY....PERSISTENT UPSLOPE CLOUDS AND POSSIBLE
SUB VFR CIGS AT BLF/LWB ALONG WITH PERIODS OF SNOW SHOWERS. VFR
CONDITIONS ALONG AND EAST OF THE BLUE RIDGE.

&&

.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...AMS/MBS


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