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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
938 PM EST FRI DEC 19 2014

.SYNOPSIS...
HIGH PRESSURE BUILDS SOUTHEAST ACROSS THE AREA RESULTING IN
OVERALL DRY WEATHER INTO EARLY TONIGHT. A WEAK AREA OF LOW
PRESSURE WILL DEVELOP ALONG THE GULF COAST STATES LATE TONIGHT AND
MOVE EAST OVER THE SOUTHEAST STATES ON SATURDAY. THIS SYSTEM WILL
BRING A PERIOD OF LIGHT WINTRY PRECIPITATION TO MAINLY SOUTHERN
AND WESTERN AREAS SATURDAY. ANOTHER LOW DEVELOPS ACROSS THE
SOUTHEAST SUNDAY NIGHT MOVING UP THE COAST TO THE TIDEWATER OF
VIRGINIA BY MONDAY AFTERNOON.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 945 PM EST FRIDAY...

MOSAIC OF NWS DOPPLER RADARS INDICATES LEADING EDGE OF PRECIP
EXPANDING INTO SOUTHEAST TN...AND CENTRAL GA. HOWEVER...SFC OBS
SUGGEST MOST OF THE LEADING RADAR RETURNS ARE NOT REACHING THE
GROUND...AS SFC OBS SHOW PRECIP REPORTED IN ALABAMA.

HRRR...RUC/RAP...AND HI-RES ARW MODELS ALL ARE IN THE BALLPARK ON
WHERE PRECIP IS FALLING AT 02Z...AND NONE OF THESE MODELS BRING
LIGHT PRECIP INTO OUR FORECAST AREA UNTIL AFTER 09Z. COMBINE THIS
WITH THE FACT THAT THE OOZ SOUNDINGS FROM RNK AND GSO SHOW A
TREMENDOUS DRY LAYER (PWATS 0.25 AND 0.31 RESPECTFULLY) BELOW
400MB...AND CHANCES FOR MEANINGFUL MEASURABLE PRECIP WITH THIS
SYSTEM ARE DIMINISHING.

AS A RESULT...DELAYED THE ARRIVAL OF PRECIP FROM THE
SOUTHWEST. REDUCED POPS...ESPECIALLY NORTH OF 460...AND LOWERED
QPF/SNOWFALL AMOUNTS. HIGH CLOUDINESS IS GRADUALLY OVERSPREADING
THE REGION...BUT POCKETS OF CLEARNING HAVE ALLOWED TEMPS IN SOME
AREAS LIKE DAN AND HSP TO FALL FASTER THAN ANTICIPATED. THEREFORE
LOWERED TEMPS A FEW DEGREES...BUT TEMP FALL SHOULD SLOW AS CLOUDS
THICKEN.

TEMPS WILL NOT RISE TOO MUCH SATURDAY WITH PRECIP AROUND...THINKING 
MID TO UPPER 30S MOUNTAINS...TO LOWER 40S EAST.

MOISTURE BEGINS TO LIFT OUT BY MID-LATE AFTERNOON SUCH THAT
PRECIP SHOULD TAPER OFF.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 320 PM EST FRIDAY...

500 MB PATTERN SATURDAY NIGHT AND SUNDAY HAD SLIGHTLY RISING HEIGHTS 
AND WEAK RIDGING. THEN HIGHER AMPLITUDE LONG WAVE TROF BEGINS 
DIGGING IN THE CENTRAL UNITED STATES. WPC IS FAVORING THE TIMING OFF 
THE ECMWF FOR THE NEXT SOUTHERN STREAM SHORT WAVE WHICH CROSSES THE 
FORECAST AREA ON MONDAY. WILL KEEP HIGHEST PROBABILITY OF 
PRECIPITATION ON MONDAY. 

850 MB TEMPERATURES RISE ABOVE ZERO ON SUNDAY. BY MONDAY STRONGER 
SURFACE WEDGE WILL BE IN PLACE AS LOW PRESSURE DEVELOPS OFF THE 
CAROLINA COAST. BY MONDAY MORNING...WARM NOSE ABOVE WEDGE REACHES 
TEMPERATURES WARM ENOUGH TO MELT ANY FROZEN PRECIPITATION. POCKET OF 
STRONGER WIND SPEEDS AT 850 MB WILL ENHANCE UPSLOPE ON EASTERN SIDE 
OF THE BLUE RIDGE ON MONDAY. BUFKIT SOUNDINGS SHOWED THE POTENTIAL 
FOR FREEZING RAIN AT LEWISBURG AND HOT SPRINGS. AMOUNT OF 
PRECIPITATION THAT FAR NORTHWEST OF THE STORM WAS STILL UNCERTAIN. 
HIGHEST AMOUNTS WILL BE CLOSER TO THE COAST. 

WILL STAY CLOSE TO GUIDANCE FOR TEMPERATURES SATURDAY NIGHT THROUGH 
SUNDAY NIGHT. MONDAY WILL HAVE LITTLE TO NO TEMPERATURE RISE SINCE 
REGION WILL BE IN A WELL ESTABLISHED RIDGE WITH PRECIPITATION AND 
PLENTY OF CLOUDS.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 240 PM EST FRIDAY...

WEAK CAD EVENT WITH OVERRUNNING PRECIPITATION WILL CONTINUE MONDAY 
NIGHT INTO TUESDAY. LIGHT RAIN...POSSIBLY WITH A FEW POCKETS OF 
SLEET OR FREEZING RAIN EXPECTED. WITH CLOUDS AND PRECIPITATION KEPT 
LOW TEMPERATURES COOLER THAN MOS WITH READINGS FROM AROUND FREEZING 
TO THE UPPER 30S IN THE SOUTHEAST. 

A DEEP LONGITUDINAL TROUGH DEVELOPS FROM GREAT LAKES SOUTH TO THE 
GULF OF MEXICO ON TUESDAY WITH INCREASING SOUTHERLY LOW LEVEL FLOW 
ACROSS OUR REGION...ACCOMPANIED BY INCREASING MOISTURE ADVECTION. 
TEMPERATURES WILL WARM TUESDAY AHEAD OF THE COLD FRONT WITH HIGHS 
FROM THE MID 40S IN THE MOUNTAINS TO THE LOWER 50S IN THE PIEDMONT.

MODEL CONSENSUS OF GFS AND ECMWF IS THAT A SYNOPTIC UPPER TROUGH 
OVER THE MISSISSIPPI VALLEY WILL AMPLIFY TUESDAY AND THEN EJECT 
NEGATIVELY TILTED THROUGH THE SOUTHEAST U. S. TUESDAY NIGHT INTO 
WEDNESDAY. WITH THE POSITION OF THE ASSOCIATED SURFACE OCCLUDED 
FRONT AND THE TRIPLE POINT PASSING SOMEWHERE NEAR OR JUST SOUTH OF 
OUR REGION....THERE IS THE POTENTIAL FOR OUR REGION TO HAVE ACTIVE 
WEATHER LATE TUESDAY NIGHT INTO WEDNESDAY WITH PLENTY OF 
SHOWERS...PERHAPS VERY GUSTY WINDS AND A FEW THUNDERSTORMS. LOOKS 
LIKE THE AXIS OF BETTER INSTABILITY MAY BE A LITTLE FURTHER SOUTH ON 
THE 12Z MODEL RUN. 

COLD AIR PUSHES INTO THE REGION TUESDAY NIGHT INTO WEDNESDAY
ALLOWING FOR SOME RAIN AND SNOW SHOWERS. IF ENOUGH COLD AIR
ARRIVES QUICKLY...THERE COULD BE SOME ACCUMULATING SNOW IN THE
WESTERN MOUNTAINS. LOW TEMPERATURES TUESDAY NIGHT WILL RANGE FROM
THE LOWER 30S IN THE MOUNTAINS TO THE LOWER 40S IN THE SOUTHEAST.

A COLD FRONT WILL MOVE EAST ACROSS OUR REGION WEDNESDAY INTO 
WEDNESDAY NIGHT.  HIGHS ON WEDNESDAY WILL WARM INTO THE LOWER 40S IN 
THE WEST TO THE LOWER 50S IN THE EAST. RAIN AND SNOW SHOWERS WILL 
CHANGEOVER TO SNOW SHOWERS AND SNOW FLURRIES IN THE WEST WEDNESDAY 
NIGHT. LOW TEMPERATURES WEDNESDAY NIGHT WILL DROP INTO THE MID 20S 
IN THE MOUNTAINS TO THE LOWER 30S IN THE PIEDMONT. WEST TO NORTHWEST 
UPPER FLOW WILL CONTINUE INTO THURSDAY WITH HIGHS FROM THE UPPER 20S 
IN THE MOUNTAINS TO AROUND 50 IN PIEDMONT. WINDS WILL BE QUITE 
STRONG ON THURSDAY AS A 50 TO 55 KNOT 850MB JET PIVOTS ACROSS THE 
REGION. THE UPPER FLOW SHIFTS TO THE SOUTHWEST THURSDAY NIGHT INTO 
FRIDAY AS TROF CURVES OUT IN THE CENTRAL US WITH SFC INFLECTION OF 
LOW PRESSURE DEVELOPING OVER THE TENNESSEE VALLEY BY FRIDAY MORNING. 
MOISTURE SLOWLY RETURN FRIDAY NIGHT INTO SATURDAY AS THE HIGH CENTER 
SLIDE OFF THE COAST.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
AS OF 650 PM EST FRIDAY...

VFR CONDITIONS EXPECTED THIS EVENING INTO TONIGHT. HIGH CLOUDS
INCREASE THIS EVENING...THEN LOWER TO A MID DECK AROUND MIDNIGHT.
A LIGHT SNOW EVENT ON TAP SATURDAY FOR OUR REGION. LIGHT SNOW WILL
BEGIN ALONG THE SOUTHERN BLUE RIDGE BETWEEN 4-7 AM AND SPREAD
NORTHWARD IN OUR AREA. SOME LIGHT SNOW/FLURRIES EXPECTED AT ALL
SITES BEFORE 18Z...WITH HIGHEST IMPACT FOR AVIATION LOOKING TO
STAY SOUTH OF A TRI-FVX LINE...SO WENT WITH MVFR VSBYS/CIGS AT DAN
AROUND 15Z...WITH POSSIBLE MVFR CIGS AT BLF. THIS SYSTEM MOVES OUT
FAIRLY QUICK WITH PRECIPITATION ENDING SATURDAY AFTERNOON INTO
SATURDAY EVENING. 

MEDIUM CONFIDENCE ON VISIBILITIES...WINDS AND CEILINGS DURING THE
TAF PERIOD. 

EXTENDED DISCUSSION...

ONCE THIS FEATURE EXITS WILL SEE THE NEXT WAVE ALONG THE COAST
BRING ANOTHER ROUND OF SUB-VFR CONDITIONS FOR LATER SUNDAY NIGHT
INTO MONDAY. RAIN WILL BE THE PRIMARY PRECIPITATION TYPE WITH 
THE POTENTIAL FOR POCKETS OF FREEZING RAIN LATE SUNDAY NIGHT INTO
MONDAY MORNING ACROSS COLDER NORTHERN PORTIONS OF FORECAST AREA WHICH
MIGHT IMPACT LWB IF TEMPERATURES ARE COLD ENOUGH.

RAIN WILL IMPACT AREAS ALONG AND EAST OF THE BLUE RIDGE...WITH
YET ANOTHER SYSTEM SLATED FOR LATE TUESDAY INTO WEDNESDAY AHEAD OF
A STRONG COLD FRONT. THESE SYSTEMS ARE EXPECTED TO BRING A PERIOD
MAINLY RAIN BUT COULD BE SOME WINTRY WX AS WELL ESPECIALLY IN THE
MOUNTAINS WITH THE SUNDAY NIGHT/MONDAY EVENT. EXPECT POTENTIAL LOW
LEVEL WIND SHEAR AS WELL AND POOR FLYING WEATHER FOR EARLY NEXT
WEEK. RAIN AND SNOW SHOWERS WILL CONTINUE INTO WEDNESDAY. GUSTY
NORTHWEST WINDS ARE POSSIBLE WEDNESDAY INTO THURSDAY. MOUNTAIN
SNOW SHOWERS AND SNOW FLURRIES EXPECTED WEDNESDAY NIGHT INTO
CHRISTMAS.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.

&&

$$
SYNOPSIS...JH/WP
NEAR TERM...PH/WP
SHORT TERM...AMS
LONG TERM...KK
AVIATION...JH/KK/WP

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