Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 251820 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 120 PM EST TUE NOV 25 2014 .SYNOPSIS... A COLD FRONT WILL MOVE EAST OF THE REGION TODAY. 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. && .NEAR TERM /THROUGH TONIGHT/... AS OF 105 PM EST TUESDAY... VERY MINOR UPDATE FOR MORE TEMPORARY CLEARING IN FAR WEST UNTIL LATE THIS AFTERNOON...WITH A COUPLE DEG MORE WARMING DUE TO MORE SUN BACK THERE. INCREASED GUSTS ON RIDGES A LITTEL FOR NEXT FEW HOURS UNTIL GRADIENT RELAXES DURING REST OF AFTERNOON. OTHERWISE NO CHANGES TO REST OF TODAY FORECAST. PREV DISCUSSION AS OF 1008 AM EST TUESDAY... AT THIS POINT NOT READY TO MAKE ANY CHANGES TO ANY HEADLINES FOR TONIGHT INTO WED UNTIL ALL THE 12Z GUIDANCE COMES IN GIVEN THERE IS STILL LARGE DEGREE OF UNCERTAINTY AND MUCH WILL DEPEND ON BOUNDARY LAYER TEMPERATURES AND EXACTLY WHERE HEAVIER BANDS OF PRECIP WILL SET UP FOR MORE EFFICIENT COOLING OF THE ENTIRE LAYER. FOR THE REST OF TODAY...COOLER AIRMASS BEHIND FRONT CONTINUES TO FILTER IN FROM THE WEST BUT NOT ESPECIALLY STRONG TEMPERATURE GRADIENT. DESPITE PLENTY OF HIGH CLOUDS...TEMPS IN EAST MAY STILL REACH INTO THE LOWER 60S. MAIN CHANGE WAS TO SLOW DOWN COOLING OFF OF TEMPS IN EAST THIS AFTERNOON. ALSO...WESTERN EDGE OF HIGH CLOUDS LIKELY TO TEMPORARILY SHIFT EAST SO THAT PARTS OF WESTERN FCST AREA BREAK OUT AND SEE A LITTLE MORE SUN FOR A WHILE TODAY...BEFORE CLOUDS MOVE BACK IN LATE TODAY AND TONIGHT AS UPPER WAVE APPROACHES FROM SOUTHWEST...SO MADE SOME ADJUSTMENTS TO SKY COVER MAINLY IN THE WEST. SHOULD REMAIN CLOUDY TO MOSTLY CLOUDY FROM BLUE RIDGE EAST TODAY. PREV DISCUSSION 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 ISENTROPIC 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. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... AS OF 430 AM EST TUESDAY... BY SUNRISE WEDNESDAY...AN INTENSIFYING LOW PRESSURE SYSTEM WILL BE GETTING READY TO PASS NORTH ACROSS THE NC OUTER BANKS. THIS SYSTEM WILL INFLUENCE WINDS ACROSS OUR AREA...SHIFTING THEM NORTHERLY TO DRAW COLDER AIR INTO THE CENTRAL APPALACHIANS FROM THE GREAT LAKES TO INTERACT WITH THE DEEP ATLANTIC MOISTURE THAT THE LOW IS RADIATING INTO THE MOUNTAINS. EXPECT TO START THE DAY WITH 850MB TEMPERATURES SLIGHTLY BELOW FREEZING...WHILE SURFACE TEMPERATURES ACROSS THE MOUNTAINS HOVER IN THE MID TO UPPER 30S. AS SUCH...BELIEVE THE BEST CHANCES FOR SNOWFALL ACCUMULATION WILL BE FOUND AT ELEVATIONS ABOVE 3000 FEET IN THE NORTH CAROLINA HIGHLANDS...AND ABOVE 2500 FEET IN THE COLDER AIR ACROSS SOUTHEAST WEST VIRGINIA. FOR THESE HIGHER COLDER LOCATIONS... HAVE MODERATE CONFIDENCE THAT WE CAN SEE 5+ INCHES OF SNOW WEDNESDAY MORNING INTO AFTERNOON...AND HAVE THEREFORE ISSUED A WINTER STORM WARNING FOR THESE HIGHER LOCATIONS. AT LOWER ELEVATIONS HOWEVER...FORECAST SNOWFALL ACCUMULATIONS ARE LESS CERTAIN. AIR TEMPERATURES IN THE MID TO UPPER 30S CAN RESULT IN A FLUCTUATION BETWEEN WHITE RAIN AND A WET SNOW THAT WILL GRADUALLY MELT AFTER CONTACT WITH THE SURFACE. WARM GROUND CONDITIONS WILL MEAN MOST ACCUMULATIONS WILL BE CONFINED TO GRASSY SURFACES AND ELEVATED OBJECTS...WHILE SNOW SHOULD MELT WITH CONTACT ON PAVEMENT. BELIEVE SNOWFALL AMOUNTS WILL VARY SIGNIFICANTLY OVER SHORT DISTANCES...AND WOULD NOT BE SURPRISED TO SEE SOME AREAS PICK UP A COUPLE INCHES QUICKLY WHERE A HEAVY BAND SETS UP. THE LOW WILL PASS EAST OF THE DELMARVA DURING EARLY AFTERNOON... ALLOWING COLDER AIR TO WORK ACROSS THE PIEDMONT. SURFACE TEMPERATURES ARE EXPECTED TO REMAIN WARM ENOUGH THROUGH THE DAY SOUTH OF HIGHWAY 460 TO KEEP PRECIPITATION AS RAIN...HOWEVER WILL LIKELY SEE A RAIN SNOW MIX FURTHER NORTH ACROSS THE PIEDMONT. MOISTURE WILL DECREASE QUICKLY FROM WEST TO EAST DURING MID AFTERNOON AS THE LOW PROGRESSES TOWARD NEW ENGLAND...WITH LINGERING SNOW SHOWERS ALL THAT REMAINS BY SUNSET. AFTER A BRIEF LULL IN PRECIPITATION ON WEDNESDAY EVENING...A SECOND LOW PRESSURE SYSTEM WILL ENTER THE CENTRAL APPALACHIANS FROM THE WEST...BRINGING ANOTHER ROUND OF SNOW SHOWERS TO OUR AREA FOR WEDNESDAY NIGHT. THE LOW WILL CARRY SNOW SHOWERS ACROSS THE PIEDMONT DURING EARLY THANKSGIVING MORNING BEFORE DAYTIME WARMING CAUSES PRECIPITATION TO CHANGE OVER TO RAIN. TEMPERATURES ACROSS THE MOUNTAINS WILL REMAIN COOLER...AND ARE EXPECTED TO SUPPORT A RAIN SNOW MIX THROUGH THE DAY. WILL THEN SEE UPSLOPE SNOW SHOWERS LINGER THROUGH THURSDAY NIGHT...BEFORE ENDING FRIDAY MORNING AS HIGH PRESSURE BUILDS INTO THE AREA. HIGH PRESSURE WILL PASS ACROSS THE AREA FRIDAY...AND WILL SHIFT SOUTHEAST FRIDAY NIGHT TO BRING A RETURN OF WARMER SOUTHWESTERLY WIND FLOW. && .LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 130 PM EST MONDAY... HIGH PRESSURE WILL KEEP THE REGION DRY 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. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... AS OF 110 PM EST TUESDAY... COLD FRONT HAS EXITED THE FCST AREA INTO THE CENTRAL PIEDMONT OF VA AND NC...WITH W TO NW WINDS MAINLY UNDER 10KTS EXCEPT FOR ALONG RIDGES. HIGH CLOUDS WILL CONTINUE CLEARING IN THE WEST THROUGH THE AFTERNOON..BUT WILL INCREASE AGAIN BY LATE AFTERNOON AND EARLY EVENING...LOWERING EVERYWHERE THROUGH THE EVENING IN ADVANCE OF NEXT SYSTEM MOVING IN FROM THE SOUTHWEST...WHICH WILL HAVE A SIGNIFICANT IMPACT ON MOST AIRPORTS. DEVELOPING LOW PRESSURE OFF THE SE COAST LATE TONIGHT WILL QUICKLY BRING DEEP MOISTURE BACK INTO THE REGION FROM THE SOUTH THIS EVENING WITH PRECIP OVERSPREADING THE AREA OVERNIGHT. MOST OF THIS WILL TAKE THE FORM OF RAIN TO START WITH AROUND 04/05Z THEN A CHANGE TO SNOW AT KBLF/KLWB/KBCB WITHIN A COUPLE HOURS OF ONSET. SOME ACCUMULATIONS CERTAINLY POSSIBLE AT THESE THREE AIRPORTS THROUGH MIDDAY WEDNESDAY...WITH PLOWABLE SNOW MOST LIKELY AT KBLF/KLWB...PERHAPS AT KBCB AS WELL. SNOW AMOUNTS REMAIN VERY TRICKY AND WILL VARY SIGNIFICANTLY ACROSS THE MOUNTAINS. FARTHER EAST...SOME MIX WITH SNOW AT KROA BEFORE LIKELY CHANGEOVER TO ALL SNOW AFTER DAYBREAK...BUT THIS LESS CERTAIN THAN AT THE HIGHER ELEVATIONS. VERY UNCLEAR HOW MUCH MAY ACCUMULATE AT KROA...BUT MOST LIKELY LESS THAN AN INCH. IT IS POSSIBLE THAT DEICING PROCEDURES WILL BE NEEDED FOR A FEW HOURS AT KROA WED MORNING. SNOW MAY MIX WITH RAIN AT KLYH AS WELL...BUT FOR BOTH KLYH AND KDAN DO NOT EXPECT ANY IMPACT FROM SNOW ON RUNWAY SURFACES AT THIS TIME. THIS SYSTEM SHOULD BRING WIDESPREAD MVFR TO ALL LOCATIONS BETWEEN MIDNIGHT AND 08Z WEDNESDAY...WITH AREAS OF IFR/LIFR IN SNOW FROM KBCB WEST DURING THE EARLY MORNING HOURS. THIS STORM SYSTEM SHOULD EXIT TO THE NE BY WEDNESDAY AFTERNOON ONLY TO BE FOLLOWED BY A FAST MOVING CLIPPER TYPE AREA OF LOW PRESSURE WEDNESDAY NIGHT INTO EARLY THURSDAY. THIS FEATURE AGAIN HAS THE POTENTIAL TO BRING WIDESPREAD SUB-VFR WEDNESDAY NIGHT WITH MVFR/IFR VSBY RESTRICTIONS IN LIGHT SNOW OVERNIGHT. LIGHT ACCUMULATIONS OF UP TO 2 INCHES ARE LIKELY AT KBLF/KLWB/KBCB...AND WITH A DUSTING TO AN INCH POSSIBLE FARTHER EAST BY THURSDAY MORNING. EXTENDED DISCUSSION... LOW CLOUDS AND SNOW SHOWERS/FLURRIES MAY PERSIST AT KBLF/KLWB INTO THURSDAY NIGHT WITH MVFR CIGS POSSIBLE. OTRW EXPECTING DOWNSLOPE DRYING TO BRING A RETURN TO VFR FROM THE BLUE RIDGE EAST AS HIGH PRESSURE STARTS TO BUILD IN AND DRIER AIR WINS OUT. THIS HIGH PRESSURE SYSTEM SHOULD BUILD ACROSS THE REGION AND TO THE EAST BY THE WEEKEND RESULTING IN MORE WIDESPREAD VFR TO END THE WEEK. BY LATE SUNDAY OR MONDAY...A WEAK FRONTAL BOUNDARY COULD SLIDE DOWN FROM THE NORTH BRINGING THE NEXT CHANCE FOR LIGHT PRECIP AND SUB-VFR CONDITIONS TO THE REGION...BUT ANY PRECIP LOOKS TO BE IN THE FORM OF RAIN. && .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... 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. && $$ SYNOPSIS...JH/KK NEAR TERM...JH/SK SHORT TERM...AMS/NF LONG TERM...DS AVIATION...JH/KK/SK EQUIPMENT...JH

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