Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 312349 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 649 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 640 PM EST SATURDAY... CURRENT FORECAST ON TRACK WITH INCREASING HIGH CLOUDS THIS EVENING WITH MORE MID DECK ROLLING IN AFTER MIDNIGHT. ONLY MINOR TWEAKS TO THE TEMPS/SKY THRU THIS EVENING WERE MADE. PREVIOUS DISCUSSION ISSUED AT 4 PM... 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 CONFINED 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 /00Z SUNDAY THROUGH THURSDAY/... AS OF 635 PM EST SATURDAY... HIGH THEN MID CLOUDS WILL INCREASE OVER THE AREA TONIGHT...WITH VFR CONDITIONS PREVAILING ALONG WITH LIGHT WINDS. SUNDAY...SOUTHERLY FLOW WILL INCREASE AHEAD OF A COLD FRONT. STILL LOOKING AT MAINLY VFR CIGS AROUND 5-15KFT...BUT COULD START TO SEE SOME MVFR CIGS AND LIGHT RAIN HEADING TOWARD BLF/LWB BY 00Z MON. EXTENDED DISCUSSION... THIS STORM SYSTEM OVER THE CENTRAL U.S. WILL TRACK INTO OHIO SUNDAY NIGHT AND OFF THE MID ATLANTIC COAST MONDAY AFTERNOON...SWING A COLD FRONT THROUGH. 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. 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/WP SHORT TERM...RCS LONG TERM...NF AVIATION...AMS/WP

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