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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
356 PM EST SAT JAN 31 2015

.SYNOPSIS...

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE SOUTHEAST AND 
OFFSHORE BY MORNING. LOW PRESSURE WAS DEVELOPING OVER THE CENTRAL 
ROCKIES AND WILL TRACK INTO THE OHIO VALLEY SUNDAY NIGHT THEN OFF 
THE NEW JERSEY COAST ON MONDAY. THIS SYSTEM WILL PUSH A COLD FRONT 
THROUGH OUR REGION ON SUNDAY NIGHT...WHICH WILL BE FOLLOWED BY HIGH 
PRESSURE FOR MONDAY AND TUESDAY. 

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 350 PM EST SATURDAY...

12Z SOUNDINGS IN THE AREA SHOWED A LAYER OF VERY DRY AIR AROUND 2500 
FEET ABOVE GROUND LEVEL. THIS DRIER AIR HAD MIXED DOWN TO THE 
SURFACE AND RESULTED IN LOW RELATIVE HUMIDITY THIS AFTERNOON. 
SURFACE WINDS WERE OUT OF THE WEST AND WIND SPEEDS WILL CONTINUE TO 
DIMINISH AS THE WIND DIRECTION BACKS TO THE SOUTH OVERNIGHT WITH HIGH 
PRESSURE OVER THE MID ATLANTIC REGION MOVING OFF THE SOUTHEAST COAST 
TONIGHT. 

THE LEADING EDGE OF A LARGE AREA OF CLOUD COVER WAS JUST TO THE WEST 
OF THE FORECAST AREA THIS AFTERNOON. IT WILL BE A RACE BETWEEN 
FALLING TEMPERATURES AT SUNSET AND THIN CIRRUS LOWERING AND 
THICKENING DURING THE EVENING. THE LONGER THE FORECAST AREA STAYS 
RELATIVELY CLOUD FREE...THE MORE TEMPERATURES WILL DROP TOWARD THE 
VERY LOW DEW POINTS. ONCE THE CLOUDS COME IN THE DROP IN TEMPERATURE 
WILL BE MORE LIMITED. HOWEVER...BUFKIT INDICATED WINDS WILL BECOME 
LIGHT AND VARIABLE JUST BEFORE SUNRISE WHICH IS ALSO FAVORABLE FOR 
LOWER TEMPERATURES. CONSIDERING ALL THESE FACTORS...HAVE GONE WITH 
COLDER MAV GUIDANCE FOR OVERNIGHT LOWS. 

AS THE LOW PRESSURE SYSTEM MOVE INTO THE OHIO VALLEY LATE 
TONIGHT...THERE WILL BE SOME WARM ADVECTION AND A BAND OF HIGHER 
RELATIVE HUMIDITY ABOVE THE DRIER SURFACE LAYER. THE ATMOSPHERE WILL 
MOISTEN FROM THE TOP DOWN BUT LOWEST LAYERS MAY STILL BE TOO DRY FOR 
PRECIPITATION TO REACH THE GROUND. HAVE LEFT A LOW PROBABILITY OF 
PRECIPITATION IN THE FAR NORTHERN COUNTY WARNING AREA LATE TONIGHT 
AND EARLY MONDAY. BUFKIT SHOWED A WEAK WARM NOSE SO THE MOST LIKELY 
PRECIPITATION TYPE WILL BE SNOW AND/OR SLEET. 

HAVE SLOWED DOWN THE PRECIPITATION EXPECTED AHEAD OF THE COLD FRONT 
ON SUNDAY. TIMING ON THE GUIDANCE DOES NOT HAVE ANY PRECIPITATION IN 
THE FORECAST AREA BEFORE 21Z/4PM. WITH ALL THE CLOUD COVER ON MONDAY 
HAVE STAYED WITH COOLER MET GUIDANCE FOR AFTERNOON HIGHS.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
AS OF 345 PM EST SATURDAY...

AN UPPER LEVEL TROUGH COMING ACROSS THE MISSISSIPPI VALLEY AND INTO 
THE OHIO VALLEY WILL PUSH A SURFACE WAVE OVER THE SOUTHERN OHIO 
VALLEY SUNDAY EVENING...NEAR PITTSBURGH EARLY MONDAY MORNING...THEN 
OFF THE MID ATLANTIC COAST BY NOON. THIS NORTHEAST TRACK ACROSS THE 
OHIO VALLEY WILL KEEP THE AREA IN THE WARM SECTOR THROUGH MUCH OF 
SUNDAY NIGHT INTO MONDAY MORNING. STRONG WARM AIR ADVECTION WILL 
SEND 85H TEMPERATURES TO NEAR 8C...KEEPING PTYPE AS RAIN FOR MUCH OF 
THE AREA INTO EARLY MONDAY MORNING. THE COLD FRONT WILL TRACK OVER 
THE MOUNTAINS BY SUNRISE MONDAY WITH HIGHER ELEVATIONS CHANGING OVER 
TO SNOW. BY NOON...THE FRONT IS EAST OF THE PIEDMONT AND MOUNTAIN 
TEMPERATURES BEGIN TO CRASH THROUGH THE DAY. AS COLDER AIR FILTERS 
INTO THE REGION IN THE AFTERNOON...MOISTURE WILL BECOME SHALLOW WITH 
ANY SNOW ACCUMULATIONS CONFIDED TO WESTERN SLOPES OF SOUTHEASTERN 
WEST VIRGINIA TO NORTHWESTERN NORTH CAROLINA MOUNTAINS. 
ACCUMULATIONS ALONG WESTERN SLOPES WILL RANGE FROM 1-3 INCHES ACROSS 
WESTERN GREENBRIER TO UP TO TWO INCHES ACROSS HIGHER ELEVATIONS OF 
NORTHWESTERN NORTH CAROLINA. IF SNOW BANDS ARE ABLE TO SETUP MONDAY 
AFTERNOON...THE NEW RIVER VALLEY AND ALLEGHANY HIGHLANDS COULD SEE A 
STRIP OF AN INCH BUT IN GENERAL...LESS THAN A HALF OF AN INCH. HIGH 
PRESSURE BUILDS OVER THE OHIO VALLEY BY MONDAY EVENING...THEREFORE 
SNOW SHOWERS AND FLURRIES WILL NOT LAST LONG PAST SUNSET.

STRONG PRESSURE RISES (8-12MB/6HRS) BEHIND THE FRONT WILL BRING 
WINDY AND GUSTY CONDITIONS TO THE AREA MONDAY AFTERNOON INTO MONDAY 
NIGHT. COUPLE THESE PRESSURE RISES WITH STRONG COLD AIR ADVECTION 
AND A 50KT OR HIGHER NORTHWESTERLY LOW LEVEL JET COULD BRING HIGH 
WIND WARNINGS TO COUNTIES ALONG AND WEST OF THE BLUE 
RIDGE...ADVISORIES ELSEWHERE. ONE HITCH IN THIS STRONG WIND EVENT IS 
CLOUD COVER. IF CLOUDS REMAIN THICK ENOUGH ONCE WE GO INTO UPSLOPE 
SNOW SHOWERS...THESE WINDS WILL NOT BE ABLE TO MIX DOWN. WITH THIS 
IN MIND AND BEING A 4TH-5TH PERIOD EVENT...WILL HIGHLIGHT WIND 
POTENTIAL IN HAZARDOUS WEATHER OUTLOOK. 

ONCE EVERY THING BLOWS THROUGH MONDAY NIGHT...HIGH PRESSURE TAKES 
RESIDENCE OVER THE AREA FOR A COUPLE OF DAYS. WARMEST TEMPERATURES 
LIKELY SUNDAY NIGHT INTO MONDAY MORNING...THEN DROP 30F OR SO MONDAY 
NIGHT INTO TUESDAY MORNING. AIR TEMPERATURES TUESDAY MORNING RANGING 
BETWEEN 5F-15F ABOVE ACROSS THE WEST TO THE LOWER 20S EAST. WE 
EXPECT MONDAY'S HIGH WINDS TO DROP OFF BY TUESDAY MORNING WITH
WIND CHILLS ACROSS THE MOUNTAINS REMAINING ABOVE ZERO.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 300 PM EST SATURDAY...

EXPECT TO START WEDNESDAY WITH SOUTHWESTERLY WINDS ESTABLISHED 
ACROSS OUR AREA AS WEAK UPPER LEVEL RIDGING SETS UP AHEAD OF AN 
APPROACHING UPPER LEVEL TROUGH AND ASSOCIATED COLD FRONT. DESPITE 
INCREASING CLOUDS DURING THE AFTERNOON...WE CAN LOOK FORWARD TO A 
MILD DAY AS AFTERNOON TEMPERATURES CLIMB INTO THE MID/UPPER 40S 
ACROSS THE MOUNTAINS...AND REACH TO THE LOW/MID 50S EAST OF THE BLUE 
RIDGE. 

WEATHER FORECAST MODELS HAVE NOT CHANGED MUCH TODAY CONCERNING THE 
APPROACH OF THE UPPER TROUGH AND ITS SUPPORT OF DEVELOPMENT OF A LOW 
PRESSURE SYSTEM ALONG THE SOUTHEAST COAST WEDNESDAY NIGHT. AS 
SUCH...EXPECT THE COLD FRONT APPROACHING FROM THE NORTHWEST TO PUSH 
RAPIDLY ACROSS OUR AREA LATE WEDNESDAY EVENING...FOLLOWED BY HIGH 
PRESSURE PASSING ACROSS THE GREAT LAKES INTO NEW ENGLAND...WITH THE 
HIGH THEN BUILDING SOUTHWARD ACROSS THE MID ATLANTIC TO WEDGE 
AGAINST THE EASTERN FACE OF THE APPALACHIANS BY THURSDAY AFTERNOON. 
MEANWHILE...THE LOW ALONG THE SOUTHEAST COAST WILL GRADUALLY DEEPEN 
AND DRIFT NORTHWARD...RADIATING MOISTURE INLAND ACROSS THE SOUTHEAST 
STATES INTO THE MID ATLANTIC. 

THE BIG QUESTION IS TO WHAT DEGREE THAT THE COASTAL LOW WILL AFFECT 
OUR WEATHER FOR THURSDAY. THE GFS FORECAST MODEL IS MOST AGGRESSIVE 
IN PUSHING MOISTURE ACROSS OUR AREA...WITH THE CANADIAN MODEL 
SIMILAR BUT NOT QUITE AS AGGRESSIVE. ON THE OTHER END OF THE 
SPECTRUM IS THE ECMWF MODEL WHICH DOES NOT DEVELOP THE COASTAL LOW 
AS DEEPLY AND THEREFORE KEEPS OUR AREA DRY IN THE WAKE OF THE COLD 
FRONT. RIGHT NOW...AM LEANING TOWARD THE GFS/CANADIAN SOLUTION... 
WHICH WILL BRING LIGHT WINTRY PRECIPITATION TO OUR AREA FOR 
THURSDAY INTO THURSDAY NIGHT. ALL MODELS AGREE THAT ATMOSPHERIC 
TEMPERATURES WILL BE COLD ENOUGH FOR ALMOST EXCLUSIVELY SNOW FOR OUR 
ENTIRE AREA. BECAUSE OF THE WIDE RANGE IN PRECIPITATION AMOUNTS 
WITHIN THE MODELS...HAVE NO CONFIDENCE AT THIS POINT IN THE AMOUNT 
OF SNOW WE WOULD RECEIVE...BUT NONE OF THE MODELS TODAY ARE CALLING 
FOR ACCUMULATIONS THAT WOULD CONSTITUTE A WINTER STORM ANYWHERE IN 
OUR AREA.

MOISTURE WILL DECREASE LATE THURSDAY NIGHT AS THE LOW CONTINUES 
NORTHWARD OFF THE COAST. COOL HIGH PRESSURE WILL PASS ACROSS THE 
APPALACHIAN CHAIN ON FRIDAY...RESULTING IN MOSTLY CLEAR SKIES AND 
LIGHT WINDS. TEMPERATURES IN THE AFTERNOON WILL REMAIN IN THE 30S 
AREAWIDE.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
AS OF 1255 PM EST SATURDAY...

VFR THIS AFTERNOON THROUGH SUNDAY AFTERNOON. HIGH THIN CLOUDS THIS
AFTERNOON WILL THICKEN AND CEILINGS WILL LOWER TONIGHT AND SUNDAY
MORNING. HIGH CONFIDENCE THAT CEILINGS WILL REMAIN ABOVE 5000 FEET
THROUGH 4AM SUNDAY.  

THERE IS SOME POTENTIAL FOR SOME VERY LIGHT SNOW TO OCCUR OVER
SOUTHEAST WEST VIRGINIA AND NORTHERN VIRGINIA LATE TONIGHT.
PROBABILITY WAS TOO LOW TO INCLUDE AT KLWB BUT JUST TO THE NORTH
THERE MAY BE LIGHT SNOW AFTER 09Z/4AM.

A DEVELOPING STORM SYSTEM OVER THE CENTRAL U.S. WILL MOVE EAST ON
SUNDAY...THE SURFACE LOW TRACKING ALONG I-70 FROM STL 12Z/7AM
SUNDAY TO NEAR HGR BY 12Z/7AM MONDAY. THIS TRACK KEEPS THE
FORECAST AREA ON THE WARM SIDE OF THE SYSTEM ON SUNDAY NIGHT. HIGH
CONFIDENCE OF WIDESPREAD RAIN AND MVFR OR LOWER CEILINGS. TIMING
ON THE MODELS IS SLIGHTLY SLOWER THAN BEFORE. DO NOT EXPECT RAIN
TO REACH KBLF AND KLWB BEFORE 21Z/4PM ON SUNDAY.

A COLD FRONT WILL CROSS THROUGH THE AREA ON SUNDAY NIGHT TURNING
WINDS TO THE WEST THEN NORTHWEST. AHEAD OF THE FRONT...A STRONG
SOUTHWEST LOW LEVEL JET DEVELOPS AFTER 00Z/7PM ON SUNDAY NIGHT.
LLWS IS POSSIBLE...ESPECIALLY AT KROA/KLYH AND KDAN.

EXTENDED DISCUSSION...
MONDAY...AFTER RAIN AND MVFR CONDITIONS IN THE MORNING...CEILINGS
WILL LIFT IN THE AFTERNOON. EXPECT GUSTY WINDS BEHIND THIS SYSTEM
WITH GUSTS OF 25 TO 40 KNOTS AT HIGHER ELEVATIONS.

TUESDAY AND WEDNESDAY...HIGH PRESSURE PASSES OVERHEAD WITH VFR WX.

THURSDAY...LOW PRESSURE MOVING ACROSS THE SOUTHEAST U.S. MAY
BRING SUB-VFR CONDITIONS AND PRECIPITATION...POSSIBLY SNOW TO THE
REGION.

&&

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

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS
SHORT TERM...RCS
LONG TERM...NF
AVIATION...PM

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