Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 260837 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 337 AM EST WED NOV 26 2014 .SYNOPSIS...
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LOW PRESSURE WILL MOVE NORTHEAST AND DEEPEN ALONG THE CAROLINA COAST THIS MORNING BEFORE PASSING EAST OF THE VIRGINIA CAPES THIS AFTERNOON. A CLIPPER TYPE LOW PRESSURE SYSTEM WILL MOVE SOUTHEAST TOWARD THE REGION LATER TODAY AND WILL CROSS THE MID ATLANTIC STATES LATER TONIGHT. HIGH PRESSURE WILL COVER THE REGION THURSDAY NIGHT AND FRIDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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AS OF 220 AM EST WEDNESDAY... PRECIP CONTINUING TO OVERSPREAD THE REGION EARLY THIS MORNING WITH SURFACE LOW PRESSURE TRACKING QUICKLY NNE ALONG THE SOUTH CAROLINA COAST SIMILAR TO THE LATEST GFS/EC INITS. HOWEVER PRECIP GIVEN SUCH A WARM BOUNDARY LAYER AND LACK OF HIGHER RATES...HAS BEEN SLOW TO TRANSITION TO SNOW EXCEPT ON THE HIGHER PEAKS FROM BEECH MTN UP TO MT ROGERS ATTM. LATEST REGIONAL RADAR TRENDS SHOW HEAVIER PRECIP TO THE SOUTH AND EXPECT THIS AXIS TO PIVOT INTO THE REGION TOWARD DAYBREAK BEFORE QUICKLY SLIDING EAST BY MIDDAY AS THE SURFACE LOW TRACKS TO NEAR VA BEACH AROUND 18Z. ALTHOUGH GUIDANCE IN GENERAL AGREEMENT ON HEAVIER QPF ESPCLY BLUE RIDGE EAST...STILL LOTS OF UNCERTAINTY IN REGARDS TO PTYPE AS THE NAM REMAINS QUITE COLD WITH MORE WIDESPREAD SNOW PER LOW PRESSURE SLIGHTLY FARTHER EAST...WHILE THE GFS/EC STAYING WARMER THROUGH 12Z BEFORE PIVOTING IN COLDER THICKNESS AS THE COASTAL STARTS TO WIND UP THIS MORNING. THIS TIMING AND HEIGHT OF THE SNOW LEVEL CRITICAL TO SEEING 3-6 INCHES IN SPOTS ON THE RIDGES AND LITTLE OR NO ACCUMULATION IN OTHERS AS THE BEST FRONTOGENETIC FORCING LOOKS TO SET UP ALONG THE BLUE RIDGE THIS MORNING. APPEARS BEST LIFT...DYNAMIC COOLING AND COLD ADVECTION TO ALL COINCIDE BETWEEN ABOUT 10-15Z ACROSS THE WESTERN HALF JUST AHEAD OF THE MAIN SHORTWAVE ALOFT AND WITHIN A BELT OF MORE LOW LEVEL NORTHERLY FLOW BEHIND THE SURFACE LOW. THIS IS WHEN AN INCH/HOUR TYPE SNOWFALL RATES POSSIBLE AS GUIDANCE INDICATES SOME CSI BANDING ESPCLY AS BEST LIFT DEVELOPS WITHIN THE DENDRITIC GROWTH ZONE AND SNOW LEVELS CHASE DOWN THE RIDGES ABOVE 2500 FEET AND INTO THE VALLEYS. HOWEVER THIS LOOKING MORE AND MORE UNCERTAIN GIVEN THE WARM BOUNDARY LAYER BUT STILL A CLOSE CALL. OTRW WILL CONTINUE TO FOLLOW A MORE BLENDED/CONSENSUS APPROACH AND KEEP AMOUNTS GENERALLY CLOSE TO GOING VALUES FOR NOW. ONLY EXCEPTIONS TO LOWER AT THE ONSET SW...AND BY AFTERNOON GIVEN EXITING MOISTURE. FARTHER EAST...DEGREE OF ACCUMULATION INTO THE NEW RIVER VALLEY AND POINTS NE DEPENDENT UPON GETTING SNOW ON THE GROUND PRIOR TO THE DAYLIGHT HOURS AND RATE OF FALL. THUS FEW CHANGES TO GOING HEADLINES FOR NOW ALTHOUGH SOME ADJUSTS MAY BE NEEDED ONCE THINGS START TO CHANGEOVER FROM WEST TO EAST PRIOR TO 12Z. SHOULD SEE POPS QUICKLY TAPER FROM SW TO NE BY 21Z/4PM WITH SOME REDEVELOPMENT OF RAIN/SNOW SHOWERS OVER THE WEST AS THE FLOW TURNS MORE NW LATE. HIGH TEMPS IFFY WITH READINGS TO FALL WITH PRECIP EARLY...THEN PERHAPS REBOUND A BIT MORE THIS AFTERNOON AS MOISTURE EXITS SO BUMPED UP HIGHS A NOTCH ESPCLY GIVEN CURRENT WARMER READINGS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... AS OF 340 PM EST TUESDAY... CLIPPER CURRENTLY ENTERING MONTANA WILL BE IN THE TENNESSEE VALLEY BY WEDNESDAY NIGHT. MODELS WEAKEN THIS FEATURE AS IT CROSSES THE SOUTHERN APPALACHIANS BUT SOUTHERN BLUE RIDGE AND WESTERN MOUNTAINS WILL STILL HAVE ADDITIONAL LIGHT SNOW ACCUMULATIONS WITH THIS LOW. PRECIPITATION WILL EXTENDED WELL EAST OF THE BLUE RIDGE BUT ANY SNOWFALL AMOUNTS THAT FAR EAST WILL REMAIN LIGHT. WILL STAY JUST BELOW GUIDANCE FOR LOWS ON WEDNESDAY NIGHT SINCE THERE WILL BE NEW SNOW ON THE GROUND. BLEND OF MET/MAV GUIDANCE WAS REASONABLE FOR HIGHS ON THURSDAY AND LOWS ON THURSDAY NIGHT. UPSLOPE SNOW SHOWERS IN THE MOUNTAINS TAPER OFF THURSDAY NIGHT. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 145 PM EST TUESDAY... GUSTY NORTHWEST FLOW IN THE WAKE OF THE DEPARTING SYSTEM WILL CONTINUE THROUGH THE MORNING HOURS...BEFORE BACKING SOUTHWEST BY THE AFTERNOON. THE RESULT WILL BE SOME LINGERING ISOLATED UPSLOPE SNOW SHOWERS OR FLURRIES ACROSS THE MOUNTAINS DURING THE MORNING...WITH DECREASING CLOUD COVER AND THE ONSET OF SOME MODERATING TEMPERATURES BY THE AFTERNOON. DEPENDING UPON HOW MUCH SNOW ACTUALLY FALLS TONIGHT AND WEDNESDAY...THERE STILL MAY ENOUGH OF A SNOWPACK AROUND TO INFLUENCE BOTH THE FRIDAY HIGH AND THE FRIDAY NIGHT LOW. HAVE GONE WITH SLIGHTLY COOLER READINGS BOTH OF THESE TIME PERIODS WHERE WE CURRENT ANTICIPATE THE GREATEST SNOWFALL. BY LATE FRIDAY AFTERNOON AND INTO THE EVENING...THE CENTER OF SURFACE HIGH PRESSURE WILL MOVE ACROSS AND THEN EAST OF OF THE REGION. THIS WILL HELP SET THE STAGE FOR A SOUTHWEST FLOW...WARM AIR ADVECTION PATTERN TO TAKE US INTO AND THROUGH THE WEEKEND. CONCURRENTLY...A COLD FRONT WILL HEAD SOUTH...AND THEN STALL ALONG THE OHIO RIVER VALLEY. INCREASING MOISTURE WITHIN THE SOUTHWEST FLOW...AND THE PROXIMITY OF THE BAROCLINIC ZONE...WILL ALLOW FOR SMALL CHANCES OF LIGHT PRECIPITATION TO GRADUALLY WORK THEIR WAY INTO THE AREA FROM THE NORTHWEST SATURDAY NIGHT INTO SUNDAY. BY SUNDAY AFTERNOON...PRECIPITATION CHANCES WILL RANGE FROM ROUGHLY 20 TO 40 PERCENT ACROSS THE MOUNTAINS...WITH DRY WEATHER STILL EXPECTED EAST OF THE CREST OF THE BLUE RIDGE. THE BOUNDARY WILL START TO SAG SOUTH INTO THE REGION BY MONDAY...WITH PRECIPITATION CHANCES LIKEWISE SPREADING INTO MORE OF THE REGION. BY TUESDAY...GUIDANCE HAS NOTABLE DIFFERENCES AS TO THE PROGRESSION OF THE FRONT. WILL LEAN ON THE SIDE OF CONSENSUS WITH A SLIGHT CHANCE STILL OVER THE AREA. THE PRECIPITATION TYPE IS EXPECTED TO BE MAINLY RAIN. THE EXCEPTION MAY BE SOME PARTS OF THE FAR NORTHWEST AND NORTH PARTS OF THE FORECASTS AREA EARLY SATURDAY MORNING...AND THEN AGAIN LATE SATURDAY NIGHT INTO EARLY SUNDAY MORNING. THERE MAY BE SOME ISOLATED SPOTS THAT HAVE SURFACE TEMPERATURES BELOW FREEZING. WITH A STRONG WARM NOSE ALOFT...PRECIPITATION IS EXPECTED TO BE RAIN. A FEW ISOLATED SPOTS COULD SEE FREEZING RAIN FOR A SHORT DURATION. TEMPERATURES SHOULD GRADUALLY MODERATE THROUGH MONDAY WITH READINGS SOME 10 TO 15 DEGREES ABOVE NORMAL BY THAT TIME. TEMPERATURES WILL COOL TO NEAR NORMAL READINGS BEHIND THE FRONT ON TUESDAY. && .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/... AS OF 1230 AM EST WEDNESDAY... DEVELOPING LOW PRESSURE OFF THE SE COAST OVERNIGHT WILL CONTINUE TO SPREAD DEEP MOISTURE BACK INTO THE REGION FROM THE SOUTH THROUGH EARLY WEDNESDAY WITH RAPID DETERIORATING FLIGHT CONDITIONS ANTICIPATED FROM SOUTH TO NORTH ACROSS THE MID ATLANTIC AFTER MIDNIGHT. THIS STORM SYSTEM WILL PRODUCE MAINLY RAIN EAST OF THE BLUE RIDGE...WITH SNOW ALONG AND WEST OF THE BLUE RIDGE. EVENING RNK SOUNDING PROFILE INDICATED ABOVE FREEZING TEMPERATURES THROUGH ABOUT 9KFT AGL. THIS LAYER IS EXPECTED TO COOL RAPIDLY WITH ONSET OF PRECIPITATION AFTER MIDNIGHT WITH THE FREEZING LEVEL DROPPING TO WITHIN 1-3KFT OF THE SURFACE BEFORE DAYBREAK WEDNESDAY. FOR THE MOUNTAIN TERMINALS WHICH INCLUDE KBLF/KLWB/KBCB ONSET OF PRECIPITATION IS EXPECTED BETWEEN 1AM AND 3AM. INITIAL P-TYPE WILL BE RAIN BUT THEN CHANGE TO SNOW BEFORE DAYBREAK AS THE FREEZING LEVEL DROPS TO WITHIN 1KFT OF THE SURFACE. SOME ACCUMULATIONS LIKELY AT THESE THREE AIRPORTS THROUGH MIDDAY WEDNESDAY...WITH PLOWABLE SNOW MOST LIKELY AT KBLF/KLWB...PERHAPS AT KBCB. BETWEEN 8AM AND NOON...SNOWFALL RATES OF AN INCH AN HOUR ARE POSSIBLE. FARTHER EAST...CLOSER TO THE BLUE RIDGE VCNTY OF KROA...RAIN IS ALSO EXPECTED AT THE ONSET...THEN MIXING WITH AND POSSIBLY CHANGING TO SNOW BEFORE ENDING. FREEZING LEVEL AT KROA IS EXPECTED TO DROP TO WITHIN 2KFT OF THE SURFACE...CERTAINLY ALLOWING FOR ACCUMULATING SNOW ON THE SURROUNDING RIDGES...BUT LESS CONFIDENT ON MUCH IN THE WAY OF ACCUMULATION AT THE AIRPORT DUE TO THE WARMER VALLEY TEMPERATURES. IN SPITE OF THE WARM GROUND TEMPERATURES...IT IS STILL POSSIBLE THAT DE-ICING 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...WITH PRIMARILY RAIN OCCURRING AT BOTH KLYH AND KDAN...THE FREEZING LEVEL ONLY DROPPING TO WITHIN 3KFT OF THE SURFACE. DEVELOPMENT OF WIDESPREAD MVFR CONDITIONS IS ANTICIPATED AT ALL LOCATIONS BY 09Z/3AM WEDNESDAY...WITH AREAS OF IFR/LIFR IN SNOW FROM KBCB WEST FROM ABOUT 10Z/5AM - 16Z/NOON. THIS STORM SYSTEM IS EXPECTED TO MOVE RAPIDLY NORTHEAST IMPACTING NUMEROUS FLIGHT TERMINALS EAST OF THE APPALACHIAN MOUNTAINS AND ALONG THE NEW ENGLAND COAST. FOR THE LOCAL REGION...THIS STORM SYSTEM SHOULD EXIT THE AREA BY MID/LATE WEDNESDAY AFTERNOON 18-21Z...ONLY TO BE FOLLOWED BY A FAST MOVING CLIPPER TYPE AREA OF LOW PRESSURE...UPPER LEVEL DISTURBANCE...WEDNESDAY NIGHT INTO EARLY THURSDAY. THIS SECOND WEATHER FEATURE 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. && .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR VAZ007-009>018. WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR VAZ019- 020-024-035. WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST THURSDAY FOR VAZ007-009-015. WINTER STORM WARNING UNTIL 4 PM EST THIS AFTERNOON FOR VAZ015. WINTER STORM WARNING UNTIL MIDNIGHT EST TONIGHT FOR VAZ020. NC...WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR NCZ001-002-018. WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST THURSDAY FOR NCZ001-018. WINTER STORM WARNING UNTIL 4 PM EST THIS AFTERNOON FOR NCZ001- 018. WV...WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR WVZ042>044. WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR WVZ507. WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST THURSDAY FOR WVZ508. WINTER STORM WARNING UNTIL MIDNIGHT EST TONIGHT FOR WVZ508.
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&& $$ SYNOPSIS...AMS/JH NEAR TERM...JH SHORT TERM...AMS/NF LONG TERM...DS AVIATION...JH/PM

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