Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 200425
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1125 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 CLEARING 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 /04Z SATURDAY THROUGH WEDNESDAY/...
AS OF 1125 PM EST FRIDAY...

HIGH CLOUDINESS COVERED THE REGION THIS MORNING...WITH MOSTLY VFR
CONDITIONS OBSERVED. LOW CLOUDS WITH IFR CIGS IN SOUTHEAST WV
NORTH OF KLWB AND KBLF ARE FORECAST REMAIN NORTH THESE LOCATIONS
TONIGHT.

THE TIMING FOR THE ARRIVAL OF LIGHT SNOW CONTINUES TO BE DELAYED
AS A DEEP LAYER OF DRY AIR OVER OUR AREA WILL TAKE TIME TO
SATURATE. THE LIGHT SNOW IS EXPECTED BEGIN ALONG THE SOUTHERN
BLUE RIDGE BETWEEN 10Z-13Z AND SPREAD NORTHWARD IN OUR AREA. CIGS
WILL FALL...BUT NOT EXPECTED TO DROP INTO THE MVFR RANGE. LIGHT
SNOW/FLURRIES WITH LITTLE RESTRICTIONS TO VISIBILITY SHOULD ARRIVE
AT MOST SITES BETWEEN 12Z-15Z

THIS SYSTEM MOVES OUT FAIRLY QUICK WITH MOST PRECIPITATION ENDING
BY SATURDAY AFTERNOON. HOWEVER...A SHALLOW LAYER OF MOISTURE
BANKING UP AGAINST THE WESTERN SLOPES WILL KEEP CLOUDS...LOWERING
TO MVFR LEVELS...AT KBLF AND KLWB AND POSSIBILITY KBCB LATE
SATURDAY AFTERNOON THROUGH THE NIGHT. SOME PATCHY DRIZZLE/LIGHT
SNOW IS ALSO POSSIBLE 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...PH/WP


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