Area Forecast Discussion
Issued by NWS Blacksburg, VA

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094 FXUS61 KRNK 072043 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 343 PM EST SUN FEB 7 2016 .SYNOPSIS...
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DEEP LOW PRESSURE OFF THE CAROLINAS WILL CONTINUE TO SHIFT SLOWLY NORTHEAST AND AWAY FROM THE REGION OVERNIGHT INTO EARLY MONDAY. ANOTHER AREA OF UPPER LEVEL LOW PRESSURE ACROSS THE GREAT LAKES WILL SWING A STRONG COLD FRONT ACROSS THE MID ATLANTIC MONDAY...FOLLOWED BY A SECONDARY SURGE OF ARCTIC AIR TUESDAY INTO WEDNESDAY. WEAK IMPULSES COMBINED WITH NORTHWEST FLOW AND DEEP MOISTURE WILL THEN RESULT IN A PROLONGED SNOW SHOWER EVENT ESPECIALLY OVER THE MOUNTAINS INTO MIDWEEK.
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&& .NEAR TERM /THROUGH MONDAY/...
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AS OF 245 PM EST SUNDAY... DEEP LOW PRESSURE OFF THE CAROLINAS HAS CONTINUED TO FAN A DEFORMATION MID/HIGH CLOUD CANOPY ACROSS THE REGION THIS AFTERNOON BUT FINALLY SEEING SIGNS OF THINNING WITH DRY AIR WORKING IN FROM THE NORTH. EXPECT AS THE SYSTEM CONTINUES TO WRAP UP WILL SEE THIS AXIS OF CLOUDS FINALLY SHIFT EAST...EXITING THE EASTERN ZONES LATER THIS EVENING PER LATEST GFS CLOUD FORECAST. THIS SHOULD ALLOW FOR A BRIEF PERIOD OF SUBSIDENCE CLEARING BETWEEN THE EXITING OFFSHORE SURFACE LOW AND THE NEXT UPSTREAM UPPER TROUGH FOR MUCH OF THE NIGHT. THUS WENT BELOW MOS TEMPS GIVEN A PERIOD OF CLEAR SKIES AND DIMINISHING WINDS LATE BEFORE CLOUDS ARRIVE ACROSS THE FAR WEST LATE. STRONG UPPER LOW ACROSS THE GREAT LAKES PIVOTS EAST MONDAY ALLOWING AN ASSOCIATED COLD FRONT TO WORK EAST INTO THE REGION MONDAY AFTERNOON. THIS WILL BRING AN AXIS OF LIFT INTO THE WEST BY MIDDAY MONDAY WITH THIS PRE-FRONTAL BAND OF MOISTURE POSSIBLY WORKING ACROSS THE CWA BY THE END OF THE DAY. CONCERNS REMAIN WITH TIMING AND THE DEGREE OF BOUNDARY LAYER WARMING THAT COULD OCCUR...AND JUST HOW MUCH QPF WILL BE ABLE TO BE GENERATED AS MOISTURE WORKS INTO LEFTOVER SUBSIDENCE BEHIND THE OFFSHORE LOW. LATEST GFS REMAINS THE WETTEST WITH OVER A QUARTER INCH LIQUID OVER THE NORTH/WEST WHILE THE NAM QUITE DRY AND THE SREF/12Z EC IN THE MIDDLE. SINCE THERE IS SOME GOOD BACKING AHEAD OF THE BOUNDARY...AND A RATHER STRONG BUT BRIEF PERIOD OF LIFT...THINK THERE COULD BE A DECENT BAND OF SNOW OVER THE WESTERN THIRD IF ARRIVAL IS AS FAST AS THE GFS. ELSEWHERE MAY SEE PRECIP START AS A BRIEF PERIOD OF RAIN CLOSER TO THE BLUE RIDGE...WITH MOSTLY LIQUID HEADING EAST EXCLUDING THE HIGHER ELEVATIONS SUCH AS THE SOUTHERN SHENANDOAH VALLEY CTYS AND SKYLINE DRIVE WHERE MORE SNOW POSSIBLE UP TOP. THEREFORE TRENDING POPS WITH A BAND OF LIKELY/CATEGORICAL WORKING EAST...REACHING THE BLUE RIDGE AROUND MIDDAY...AND THE PIEDMONT MID/LATE AFTERNOON. PROVIDED TOO MUCH WARMING DOESN`T OCCUR AND THE BAND STAYS TOGETHER CROSSING THE HIGHER ELEVATIONS...EXPECT A RANGE FROM 1-3 INCHES FAR WEST TO UP TO AN INCH OUT TO PARTS OF THE BLUE RIDGE AND LITTLE ELSEWHERE. GIVEN AMOUNTS BASICALLY NEAR ADVISORY LEVELS...WILL GO AHEAD AND INCLUDE A SECOND PERIOD ADVISORY FOR THE FAR WESTERN SLOPE COUNTIES FOR MONDAY FOR NOW. HIGH TEMPS TRICKY WITH POTENTIAL TO RISE WELL INTO THE 40S OR WARMER EAST GIVEN WARM ADVECTION...WHILE PERHAPS GETTING STUCK IN THE LOW/MID 30S FAR WEST IF PRECIP IS FASTER. THIS SUPPORTS RUNNING WITH A BLEND WHILE NUDGING VALUES CLOSER TO THE WARMER MOS OUT EAST.
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
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AS OF 340 PM EST SUNDAY... MODELS SHOWING NEXT SURGES OF COLDER AIR COMING IN ON MONDAY NIGHT...THEN AGAIN ON WEDNESDAY NIGHT. PERSISTENT NORTHWEST WINDS FROM THE SURFACE THROUGH AROUND 700 MB...THEREFORE RESULTING GIN SNOW SHOWERS. THERE MAY BE OCCASIONAL LULLS IN THE SNOW SHOWERS...BUT ANTICIPATE MORE TIME WITH PRECIPITATION THAN WITHOUT. MORE QUESTIONABLE IS WHEN AND HOW FAR EAST BANDS OF SNOW SHOWERS MAY DEVELOP DURING THIS TIME FRAME. WITH GOOD COLD AIR ADVECTION AND FORECAST SOUNDINGS SHOWING PRIME ICE CRYSTAL GROWTH...WILL TREND TOWARD AT LEAST SOME PROBABILITY OF SNOW SHOWERS OR FLURRIES NEARLY AS FAR EAST AS THE BLUE RIDGE. APPEARS THAT DEEPER MOISTURE WILL ERODE FROM SOUTH TO NORTH ON WEDNESDAY AND WEDNESDAY NIGHT...WITH THE SNOW SHOWERS ENDING FIRST IN THE NORTHWEST NORTH CAROLINA MOUNTAINS AND EVENTUALLY IN SOUTHEAST WEST VIRGINIA. ALSO ENHANCING THE AVAILABLE MOISTURE...HYSPLIT TRAJECTORIES OFF THE GFS SHOWED BETWEEN AIR 2000 AND 300 FEET AGL MAY BE PICKING UP SOME MOISTURE FROM LAKE MICHIGAN. ISSUED A WINTER STORM WATCH FOR SEVERAL COUNTIES IN THE FAR WESTERN COUNTY WARNING AREA...SINCE TOTAL SNOWFALL FROM MONDAY NIGHT THROUGH WEDNESDAY NIGHT WILL BE ENOUGH TO IMPACT TRAVEL. PLUS...ENOUGH COLD AIR...COMBINED WITH MODERATE WINDS...TO RESULT IN HAZARDOUS WIND CHILL VALUES. HIGHEST SNOW AMOUNTS WILL BE ON THE HIGHER WEST FACING SLOPES AND COLDEST WIND CHILLS WILL BE AT HIGHER ELEVATIONS WEDNESDAY NIGHT. STAYED AS COLD OR SLIGHTLY COLDER THAN GUIDANCE THROUGH WEDNESDAY NIGHT.
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&& .LONG TERM /THURSDAY THROUGH SUNDAY/...
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AS OF 250 PM EST SUNDAY... CLOSED 500 MB LOW REMAINS OVER SOUTHEAST CANADA BUT HEIGHTS RISE OVER THE REGION. LONG WAVE TROUGH REMAINS OVER THE EAST THROUGH SUNDAY WITH MODELS SHOWING DIFFERENCE IN TIMING AND INTENSITY OF SHORT WAVES EMBEDDED WITHIN THE TROUGH. SURFACE HIGH PRESSURE WILL BE CENTERED OVER THE FORECAST AREA ON FRIDAY MORNING. MORE ARCTIC AIR COMES IN SATURDAY AND SUNDAY. BOTH GFS AND ECMWF ARE SHOWING VARIATIONS OF A 1040 MB HIGH BUILDING WELL INTO THE OHIO VALLEY AND MID ATLANTIC REGION DURING THAT TIME FRAME. SNOW SHOWERS WILL BE ENDING IN THE NORTHWEST COUNTY WARNING AREA. WILL HAVE A LOW PROBABILITY OF SNOW IN THE FORECAST FOR FRIDAY OR SATURDAY THAT IS ASSOCIATION WITH A SOMEWHAT STRONGER SHORT WAVE TRACKING THROUGH THE BASE OF THE UPPER TROF. BUT AT THAT TIME FRAME...LOCATION AND TIMING ARE LIKELY TO CHANGE.
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&& .AVIATION /21Z SUNDAY THROUGH FRIDAY/... AS OF 1212 PM EST SUNDAY... MID AND HIGH LEVEL CANOPY ASSOCIATED WITH THE STORM SYSTEM OFF THE CAROLINAS WILL LINGER OVER MUCH OF THE REGION THIS AFTERNOON BEFORE FINALLY SHIFTING EAST THIS EVENING. HOWEVER STILL EXPECTING CIGS TO REMAIN VFR WITH MOST BASES ABOVE 10K FEET. WINDS WILL BE GUSTY AS THE SYSTEM DEEPENS OFFSHORE WITH NORTHERLY WINDS INCREASING TO 10-20 KTS AT TIMES. SHOULD GET IN BETWEEN THE EXITING OFFSHORE LOW TONIGHT AND THE NEXT UPSTREAM COLD FRONT WITH THE NEXT SURGE OF MOISTURE EXPECTED TO ARRIVE MONDAY. THIS SHOULD PROVIDE FOR A PERIOD OF CLEAR SKIES OVERNIGHT BEFORE ANOTHER ROUND OF MID DECK ARRIVES OVER THE WEST AFTER MIDNIGHT. AXIS OF DEEPER MOISTURE SHOULD BE NEARING KBLF/KLWB BY 12Z/7AM MONDAY WITH PERHAPS THE ONSET OF MVFR VSBYS SHORTLY THEREAFTER PENDING TIMING OF THE PRECIP. HOWEVER THINK CIGS WILL REMAIN VFR UNTIL AFTER DAYBREAK WITH MOSTLY MID/HIGH CLOUDS TO THE EAST. LOBE OF DEEPER MOISTURE WITH AN ASSOCIATED PERIOD OF SNOW/RAIN LOOKS TO CROSS THE REGION FROM WEST TO EAST AHEAD OF AN INITIAL COLD FRONT DURING MONDAY. THIS SHOULD CAUSE CIGS TO LOWER TO MVFR/IFR SE WEST VA SITES AND MVFR OUT TO THE BLUE RIDGE AROUND MIDDAY. EXPECT TO SEE MVFR TO IFR VSBYS IN SNOW ALSO AT KBLF/KLWB DURING THE MORNING WITH THIS PRECIP AND LOWER VSBYS SPREADING OUT TOWARD KBCB/KROA BY MIDDAY. SOME LIGHT RAIN ALSO POSSIBLE IN THE EAST MAINLY AFTER THE VALID TAF PERIOD ON MONDAY BUT EXPECT A BREAK FROM SUB-VFR ALONG/WEST OF THE BLUE RIDGE TO VFR CIGS OUT EAST IN THE AFTERNOON. EXTENDED DISCUSSION... SUB-VFR SHOULD BECOME MORE CONFINED TO THE WESTERN SLOPES MONDAY NIGHT INTO MIDWEEK WITH PROLONGED MVFR/IFR CONDITIONS AT KBLF/KLWB IN SNOW SHOWERS THROUGH AT LEAST WEDNESDAY NIGHT AS ARCTIC AIR ARRIVES. POTENTIAL ALSO FOR PERIODS OF MVFR AT KBCB/KROA AS IMPULSES ROTATE ACROSS THE MOUNTAINS AND BANDS DEVELOP DURING THE OVERNIGHT HOURS. ACCUMULATING SNOW IS LIKELY IN THE MOUNTAINS WEST OF THE BLUE RIDGE. FLURRIES MAY ALSO OCCUR AS FAR EAST AS THE PIEDMONT WHERE INTERVALS OF VFR TO MVFR CIGS COULD ALSO OCCUR. CONDITIONS SHOULD BRIEFLY RETURN TO MAINLY VFR THURSDAY/THURSDAY NIGHT AS WEAK HIGH PRESSURE BUILDS IN AND MOISTURE DECREASES. && .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...WINTER STORM WATCH FROM MONDAY EVENING THROUGH THURSDAY MORNING FOR VAZ007-009>012-015-019-020. WINTER WEATHER ADVISORY FROM 7 AM TO 6 PM EST MONDAY FOR VAZ007-009-015. NC...WINTER STORM WATCH FROM MONDAY EVENING THROUGH THURSDAY MORNING FOR NCZ001-018. WINTER WEATHER ADVISORY FROM 7 AM TO 6 PM EST MONDAY FOR NCZ001-018. WV...WINTER STORM WATCH FROM MONDAY EVENING THROUGH THURSDAY MORNING FOR WVZ042>044-507-508. WINTER WEATHER ADVISORY FROM 7 AM TO 6 PM EST MONDAY FOR WVZ042-043-508.
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&& $$ SYNOPSIS...JH/PM NEAR TERM...JH SHORT TERM...AMS LONG TERM...AMS AVIATION...JH/PM

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