Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 250939 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 439 AM EST TUE NOV 25 2014 .SYNOPSIS...
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A COLD FRONT WILL MOVE EAST OF THE REGION THIS MORNING. NORTHWEST FLOW BEHIND THE FRONT WILL RESULT IN COLDER TEMPERATURES TONIGHT INTO WEDNESDAY. A STORM SYSTEM MOVING UP ALONG THE CAROLINA COAST WILL BRING THE NEXT ROUND OF PRECIPITATION FOR LATE TONIGHT THROUGH MUCH OF WEDNESDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 235 AM EST TUESDAY... SURFACE COLD FRONT SLOWLY WORKING OFF THE BLUE RIDGE ATTM BUT WILL STILL TAKE A WHILE TO CLEAR THE PIEDMONT EARLY THIS MORNING GIVEN LACK OF MUCH PUSH IN THE PARALLEL FLOW ALOFT. PIPELINE OF SHOWERS STREAMING NORTH THROUGH THE EASTERN CAROLINAS WITH THE UPPER JET COULD BRUSH THE FAR SE EARLY ON OTRW EXPECTING GRADUAL LOW LEVEL DRYING TODAY AS LOWER DEWPOINT AIR OOZES SE. HOWEVER WILL REMAIN ON THE MILD SIDE GIVEN THE LAGGING 85H BOUNDARY THAT LIKELY WILL KEEP THE MAIN TEMP GRADIENT ALOFT BACK OVER THE WEST THROUGH MUCH OF THE DAY. MODELS ALSO SUGGEST PERIODIC ROUNDS OF HIGH CLOUDS WITH WEAK RIPPLES ALOFT RIDING THROUGH WITH ONLY A GRADUAL SHIFT TO THE EAST WITH THE CANOPY BEFORE IT STALLS AND STARTS TO SHIFT BACK WEST LATER ON IN RESPONSE TO BACKING ALOFT. BUMPED HIGHS UP A CAT OR SO MOST SECTIONS GIVEN THE WARM START AND ESPCLY EAST WHERE ONLY SLOW COOLING ALOFT WILL OCCUR ALLOWING READINGS TO LIKELY GO BACK ABOVE 60 AND EVEN AROUND 50 OR BETTER WEST. THINGS START TO UNFOLD TONIGHT IN REGARDS TO THE NEXT ROUND OF WINTRY WEATHER AS ENERGY OVER THE SW STATES HEADS EAST CAUSING A MORE SUBSTANTIAL AREA OF SURFACE LOW PRESSURE TO DEVELOP OVER THE NE GULF THIS EVENING. THIS SYSTEM WILL ZIP NE TO SOMEWHERE ALONG OR JUST EAST OF THE NORTH CAROLINA COAST LATE. STRONG JET ALOFT COMBO WITH A QUICK RETURN OF INSENTROPIC LIFT LIKELY TO GET PRECIP DEVELOPING NORTH INTO THE AREA AS SOON AS LATE EVENING...WITH CATEGORICAL COVERAGE OVER THE CWA BY DAYBREAK. THIS SUPPORTED BY SLIGHTLY FASTER MODEL SOLUTIONS WHICH MAKES FOR A VERY TRICKY PTYPE SCENARIO GIVEN MOISTURE INTO WARMER AIR A BIT SOONER AS SEEN BY SLIGHTLY HIGHER THICKNESS VALUES WEST OVERNIGHT. LATEST GFS AND 00Z EC HAVE ALSO TRENDED WARMER WHILE THE NAM REMAINS COLDER AND THE CMC IN BETWEEN BUT WITH LESS QPF. THUS HAVE DELAYED THE SWITCH TO SNOW BELOW THE HIGHEST ELEVATIONS UNTIL THE EARLY MORNING HOURS WHEN THE DEVELOPING DEFORMATION BAND LIKELY TO USE DYNAMICS TO COOL THE COLUMN FROM RIDGETOP TO VALLEY BOTTOMS BY DAWN. THIS COULD PRODUCE A QUICK 1-3 INCHES FROM THE MOUNTAINS OF NW N CAROLINA ACROSS MT ROGERS TO BLF...LWB AND HSP BEFORE SUNRISE. PRECIP PENDING RATE OF FALL...SHOULD TRANSITION TO MORE ELEVATION DRIVEN WET SNOW HEADING OUT TOWARD THE NEW RIVER VALLEY AS WELL VERY LATE WHERE SOME SLEET MAY MIX IN BUT A CLOSE CALL TO ACCUMULATION ESPCLY SOUTH OF I-81 GIVEN LATEST PROFILE/THICKNESS TRENDS. ELSW KEEPING IT MOSTLY RAIN WITH SOME HIGHER PEAKS FROM BENT MTN TO THE PEAKS OF OTTER AND THE SKYLINE DRIVE SEEING SPOTS CHANGE TO SNOW AS WELL. KEPT LOWS CLOSER TO THE LATEST COLDER MET MOS GIVEN MORE EVAPORATIVE POTENTIAL.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 335 PM EST MONDAY... TWO STRONG SHORT WAVES COME THROUGH THE LONG WAVE TROF OVER THE EASTERN UNITED STATES THIS TIME FRAME. THE FIRST CROSSES THE FORECAST AREA FROM THE SOUTHERN STREAM ON WEDNESDAY AND THE NEXT FROM THE NORTHERN STREAM ON WEDNESDAY NIGHT. IN ADDITION TO THE POSITIVE VORTICITY ADVECTION ON WEDNESDAY THERE WILL ALSO BE GOOD Q-VECTOR FORCING AND UPPER DIFFLUENCE. WILL BE INCREASING PROBABILITY OF PRECIPITATION FOR LATE TUESDAY NIGHT INTO WEDNESDAY NIGHT ACROSS THE SOUTHERN COUNTY WARNING AREA. MODELS HAVE COME INTO BETTER AGREEMENT AND HAVE TRENDED WEST WITH TRACK OF THE 850MB AND SURFACE LOWS. 12Z NAM IS COLDER WITH THE TEMPERATURE PROFILE ON TUESDAY NIGHT AND WEDNESDAY THAN 12Z GFS. AT THIS TIME WILL BE TAKING A BLEND. LOWEST LAYERS DROP BELOW FREEZING IN THE WEST LATE TUESDAY NIGHT WITH BUFKIT WAS SHOWING PERIODS OF ISOTHERMAL TEMPERATURES. PRECIPITATION TYPE WILL ALSO BE DEPENDENT ON INTENSITY AND RATES. TEMPERATURES WEDNESDAY WILL BE NEARLY STEADY AND 10 TO 15 DEGREES BELOW NORMAL. SOME OF COOLING IS EXPECTED AS THE TEMPERATURE DROPS TOWARD WET BULB VALUES...BUT EVEN SO...ONLY HIGHER ELEVATIONS OF THE BLUE RIDGE AND AREAS WEST WILL HAVE SURFACE TEMPERATURES COLD ENOUGH FOR SNOW ACCUMULATION. COMBINING THE PRECIPITATION AMOUNTS AND SNOWFALL FROM THE TUESDAY NIGHT AND WEDNESDAY SYSTEM WITH THE SNOWFALL FROM THE CLIPPER ON WEDNESDAY NIGHT MAY PUSH SNOWFALL TOTALS IN SOME LOCATIONS ABOVE WARNING CRITERIA. CHALLENGING TO SAY AT THIS POINT HOW WIDESPREAD THIS WILL BE AND HOW MUCH OF A GAP THERE WILL BE FROM THE TIME THE COASTAL LOW PRECIPITATION EXITS TO THE TIME THE SNOW WITH THE CLIPPER COMES THROUGH. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 130 PM EST MONDAY... HIGH PRESSURE WILL KEEP THE REGION DRY ON FRIDAY AND THROUGH THE START OF THE UPCOMING WEEKEND. BY SUNDAY...AND TO A SLIGHTLY BETTER DEGREE ON MONDAY...THE CENTER OF THE HIGH WILL SHIFT TO THE COAST...AND A COLD FRONT WILL BECOME STALLED OVER THE OHIO VALLEY. THIS WILL SET THE REGION UP FOR A SOUTHWEST FLOW...WARM AIR ADVECTION PATTERN. LIFT WITHIN THE VICINITY OF THE STALLED FRONT WILL ALLOW FOR LIGHT PRECIPITATION TO SLOWLY INCREASE IN COVERAGE FROM NORTHWEST TO SOUTHEAST AS WE HEAD FROM SUNDAY INTO MONDAY. THERE MAY BE A PRECIPITATION TYPE ISSUE THESE TWO DAYS WHERE SURFACE TEMPERATURES ARE BELOW OR HOVER AROUND THE FREEZING MARK DURING THE LATE OVERNIGHT AND EARLY MORNING HOURS AND A STRONG WARM NOSE EXISTS ALOFT. AT THIS TIME...WILL HAVE A RAIN VERSUS FREEZING RAIN FORECAST...WITH VERY LITTLE IN THE WAY OF FREEZING RAIN COVERAGE AND ALSO IN TIME DURATION. TEMPERATURES THROUGH THIS PERIOD WILL TREND MILDER EACH DAY SO THAT BY MONDAY UPPER 50S TO LOWER 60S WILL BE COMMON ACROSS THE REGION FOR HIGH TEMPERATURES. THIS CONTRASTS TO HIGHS IN THE MID 30S TO NEAR 40 ACROSS THE MOUNTAINS AND LOW TO MID 40S ACROSS THE PIEDMONT ON FRIDAY. && .AVIATION /10Z TUESDAY THROUGH SATURDAY/... AS OF 1235 AM EST TUESDAY... SURFACE COLD FRONT IS CURRENTLY MOVING ACROSS THE MOUNTAINS...BUT FORWARD SPEED HAS BEEN SLOWING WITH TIME PER WIND FLOW ALOFT BECOMING PARALLEL WITH FRONT. THIS FRONT IS EXPECTED TO MOVE EAST OF THE MOUNTAINS DURING THE OVERNIGHT...THEN TO ALONG THE COAST TUESDAY AFTERNOON. WINDS BEHIND THE FRONT WILL SHIFT TO THE WEST INITIALLY...THEN TREND MORE NORTHERLY WITH TIME DURING THE DAY TUESDAY AS HIGH PRESSURE BUILDS INTO THE FORECAST AREA FROM THE NORTHWEST. CLOUD BASES THROUGH THE 24 HR TAF PERIOD ARE EXPECTED BE VFR EXCEPT ACROSS THE FAR SOUTHEAST AROUND KDAN WHERE A PERIOD OF MVFR IN LOWER STRATO-CU COULD OCCUR THROUGH DAYBREAK TUESDAY. MEDIUM TO HIGH FCST CONFIDENCE DURING THE TAF PERIOD. EXTENDED DISCUSSION... A DEVELOPING STORM SYSTEM IS EXPECTED TO MOVE UP THE SOUTHEAST COAST BY EARLY WEDNESDAY WHICH MAY BRING WINTRY PRECIP TO THE AREA ALONG WITH SUB VFR AT ALL SITES. LOOKS LIKE FLIGHTS WILL BE IMPACTED GREATLY ACROSS THE MID ATLANTIC INTO THE NORTHEAST WITH THIS SYSTEM WITH WITH WIDESPREAD PRECIPITATION. FOR THE CENTRAL APPALACHIANS BEST CHC FOR SUB VFR WILL OCCUR WED INTO EARLY THANKSGIVING BEFORE HIGH PRESSURE WORKS IN FROM THE WEST. WESTERN SLOPES...VCNTY OF BLF/LWB...MAY KEEP LOWER CIGS UNTIL FRIDAY AFTERNOON. && .EQUIPMENT... AS OF 330 AM EST MONDAY... THE VISIBILITY SENSOR AT KLYH...LYNCHBURG AIRPORT...WILL BE OUT OF SERVICE UNTIL PARTS ARRIVE TO REPLACE THE SENSOR. UNTIL THEN THE VISIBILITY WILL ONLY BE REPORTED WHEN THE CONTROL TOWER IS STAFFED. && .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 4 PM EST WEDNESDAY FOR VAZ007-009>013-015-018. WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO MIDNIGHT EST WEDNESDAY NIGHT FOR VAZ019-024-035. WINTER STORM WARNING FROM 9 PM THIS EVENING TO 4 PM EST WEDNESDAY FOR VAZ015. WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO MIDNIGHT EST WEDNESDAY NIGHT FOR VAZ020. WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO MIDNIGHT EST WEDNESDAY NIGHT FOR VAZ020. NC...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 4 PM EST WEDNESDAY FOR NCZ001-002-018. WINTER STORM WARNING FROM 9 PM THIS EVENING TO 4 PM EST WEDNESDAY FOR NCZ001-018. WV...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 4 PM EST WEDNESDAY FOR WVZ042>044. WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO MIDNIGHT EST WEDNESDAY NIGHT FOR WVZ507. WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO MIDNIGHT EST WEDNESDAY NIGHT FOR WVZ508. WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO MIDNIGHT EST WEDNESDAY NIGHT FOR WVZ508.
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&& $$ SYNOPSIS...JH/KK NEAR TERM...JH SHORT TERM...AMS LONG TERM...DS AVIATION...JH/KK/WP EQUIPMENT...JH

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