Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 121701 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1201 PM EST FRI FEB 12 2016 .SYNOPSIS... AN UPPER LEVEL DISTURBANCE WILL PASS JUST SOUTH OF THE REGION THIS AFTERNOON BRINGING PERIODS OF LIGHT SNOW OR SNOW SHOWERS ESPECIALLY ACROSS THE MOUNTAINS. A SURGE OF ARCTIC AIR FOLLOWS THIS SYSTEM OVERNIGHT RESULTING IN VERY WINDY CONDITIONS AND BITTERLY COLD TEMPERATURES...ALONG WITH SOME ADDED SNOW SHOWERS FOR THE FAR WESTERN SLOPES OF THE APPALACHIANS INTO SATURDAY. BY MONDAY ANOTHER WINTER STORM SYSTEM WILL BEGIN TO AFFECT THE REGION WITH THE POTENTIAL FOR SNOW AND MIXED PRECIPITATION THROUGH THE FIRST PART OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 945 AM EST FRIDAY... COLUMN CONTINUING TO SLOWLY MOISTEN AS AXIS OF ISENTROPIC LIFT SPILLS EAST AHEAD OF THE STRONG UPPER SHORTWAVE SEEN ON WATER VAPOR PASSING TO THE SOUTH. LATEST SHORT TERM GUIDANCE CONTINUES TO VARY ON JUST HOW FAR EAST ANY OF THESE BANDS WILL MAKE IT WITH SOME PRIMARILY CONFINED TO THE WESTERN SLOPES...WHILE OTHERS INCLUDING THE WRF-ARW AND TO SOME DEGREE THE HRRR SPILL LIGHT SNOW EAST TO THE BLUE RIDGE AND POINTS EAST. ALTHOUGH THIS LOOKS OVERDONE...PERIOD OF BACKING ALOFT MAY BE ENOUGH TO HELP PUSH LIGHT SNOW FARTHER EAST THAN TYPICAL DOWNSLOPING WOULD ALLOW ESPCLY WITH THE UPSTREAM TRAILING CHANNELED VORT AXIS SEEN BACK IN KY. THUS BUMPED UP AMOUNTS A BIT ACROSS THE FAR SW PER CURRENT TRAJECTORY OF SNOW TO THE WEST AND HEADING OUT EAST OF THE BLUE RIDGE FOR AT LEAST A COATING. APPEARS LEAST AMOUNT OF SNOW MAY OCCUR OVER THE NORTH AS THE TRANSFER OF ENERGY FROM THE MOUNTAINS TO THE COASTAL DUCKS FARTHER SOUTH THROUGH THE AFTERNOON. STILL GOING HEADLINES ON TRACK FOR AN INCH OR SO TODAY OUT WEST AND COMBINED UPSLOPE OVERNIGHT SO NO CHANGES THERE OTHER THAN TO TWEAK AMOUNTS. ALSO MADE SOME SLIGHT UPWARD ADJUSTS TO TEMPS MAINLY EAST WHERE COULD SURGE UP AS A FEW BREAKS DEVELOP AHEAD OF ANY PRECIP THAT ATTEMPTS TO HEAD EAST OF THE RIDGES. THINK MOST PTYPE EVEN OUT THERE TO BE SNOW GIVEN COLDNESS ALOFT SO RUNNING WITH MOSTLY SNOW/SNOW SHOWERS. WILL NEED TO TAKE A LOOK AT THE WINDS OVERNIGHT INTO SATURDAY MORNING BEHIND THE PASSING ARCTIC FRONT AS COULD SEE WARNING CRITERIA SW BUT WILL AWAIT 12Z GUIDANCE BEFORE UPDATING. PREVIOUS DISCUSSION AS OF 400 AM EST FRIDAY... THE MAIN WEATHER PLAYERS FOR OUR REGION TODAY AND TONIGHT WILL BE AN UPPER LEVEL SHORT WAVE BRINGING SOME LIGHT SNOW TO THE FAR WESTERN PORTION OF THE AREA BEFORE A STRONG COLD FRONT MOVES THROUGH AND SETS OFF ANOTHER ROUND OF UPSLOPE SNOW SHOWERS WEST OF THE BLUE RIDGE. BELIEVE THE MOUNTAIN EMPIRE REGION WILL SEE AN INCH OR LESS OF SNOW BEFORE THE UPSLOPE REALLY KICKS IN AND PROVIDES ADDITIONAL ACCUMULATIONS ALONG THE FAR WESTERN SLOPES THROUGH TONIGHT. THE AIR MOVING IN BEHIND THE FRONT IS QUITE COLD INDEED AND WILL CREATE SOME VERY STEEP LOW LEVEL LAPSE RATES AND EVEN A BIT OF CAPE...WHICH MAY BRING US ANOTHER CHANCE FOR A PERIOD OF THUNDERSNOW EARLY TONIGHT. MESO MODELS ALSO INDICATE A DECENT UPSTREAM CONTRIBUTION TO THE MOISTURE FROM THE GREAT LAKES. BELIEVE THESE FACTORS WILL COMBINE TO GENERATE SNOW ACCUMULATIONS GENERALLY IN THE 2 TO 4 INCH RANGE FOR THE WESTERN SLOPES WITH SOME LOCALLY HIGHER AMOUNTS POSSIBLE SO WILL ISSUE AN ADVISORY FOR THIS AREA FROM THIS AFTERNOON THROUGH TONIGHT. LOW LEVEL WINDS WILL ALSO START TO INCREASE TONIGHT AND GOOD MOMENTUM TRANSFER IN THE BOUNDARY LAYER WILL ALLOW FOR QUITE A BIT OF WIND OVERNIGHT WITH GUSTS OVER 40 MPH EXPECTED ESPECIALLY OVER THE HIGHER TERRAIN. THIS WILL COMBINE WITH TEMPERATURES WEST OF THE BLUE RIDGE FALLING INTO THE SINGLE DIGITS TO GENERATE WIND CHILL VALUES OF 5 TO 15 BELOW ZERO...WITH READINGS TO 25 BELOW FOR WESTERN GREENBRIER COUNTY IN WEST VIRGINIA. WINDS WILL GRADUALLY SUBSIDE ON SATURDAY BUT THE COMBINATION OF WIND AND VERY COLD TEMPERATURES WILL CONTINUE TO GENERATE VERY LOW WIND CHILL VALUES THROUGH SUNDAY MORNING. A WIND CHILL ADVISORY WILL BE ISSUED FOR THE AREA ALONG AND WEST OF THE BLUE RIDGE FROM TONIGHT THROUGH SUNDAY MORNING WITH A WIND CHILL WARNING FOR WESTERN GREENBRIER. CONDITIONS EAST OF THE RIDGE WILL NOT BE QUITE AS SEVERE AS LOWS TONIGHT REACH THE 15 TO 20 DEGREE RANGE WITH WIND CHILL VALUES INTO THE SINGLE DIGITS.
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&& .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/... AS OF 430 AM EST FRIDAY... COLDEST AIR OF THE SEASON STILL SLATED TO BE SPREADING INTO THE REGION FOR SATURDAY...WITH TEMPERATURES BOTTOMING OUT SUNDAY MORNING. THE MODELS HAVE BACKED OFF THE INTENSITY OF THE COLD AIR MASS JUST SLIGHTLY WITH EACH SUCCEEDING RUN...NOW STOPPING AROUND -22C ACROSS THE FAR NORTHERN PORTION OF THE CWA. SIMILAR EVENTS THE PAST TWO YEARS HAVE SEEN READINGS CLOSER TO -25/-26C...SO FEEL CONFIDENT THAT MORNING LOW TEMPERATURES SUNDAY MORNING WILL FALL A COUPLE OF DEGREES SHY OF WHAT WE SAW THE LAST COUPLE OF YEARS WITH SIMILAR ARCTIC OUTBREAKS. ALSO...SNOW COVER IS LIMITED EAST OF THE ALLEGHANY FRONT AND THE MOUNTAINS OF SW VA/NW NC...SO THAT WILL ALSO NOT HELP DRIVE TEMPERATURES TO THE LEVELS WE SAW AROUND THIS TIME LAST YEAR. NONETHELESS...IT WILL BE BITTERLY COLD AND VERY WINDY...PROMPTING A CONTINUATION OF THE WIND CHILL ADVISORIES WEST OF THE BLUE RIDGE AND THE WARNING FOR WESTERN GREENBRIER. WINDS WILL BEGIN TO DIMINISH LATE IN THE DAY AND SATURDAY NIGHT...BUT WITH TEMPERATURES FALLING INTO THE SINGLE DIGITS AND NEAR 0 TO -5F AT THE HIGHER ELEVATIONS...THE ADVISORIES/WARNINGS ARE WARRANTED TO CONTINUE INTO SUNDAY MORNING AS IT WILL TAKE VERY LITTLE FOR WIND CHILLS TO MEET CRITERIA WITH TEMPS THAT LOW. UPSLOPE SNOW SHOWERS SHOULD BE WINDING DOWN SATURDAY MORNING FAIRLY QUICKLY AS THE VERY DRY ARCTIC AIR MASS SPREADS INTO THE REGION. WILL KEEP SLIGHT CHANCE TO LOW CHANCE POPS FOR SNOW SHOWERS GOING THROUGH MID-DAY...THEN END THEM...ALBEIT SOME FLURRIES COULD CONTINUE INTO THE AFTERNOON AS ARCTIC COLD- ADVECTION SQUEAKS OUT ANY REMAINING MOISTURE. WINDS WILL BE STRONG AND GUSTY THROUGHOUT THE DAY...BUT LIKELY DROP BELOW ADVISORY CRITERIA IN THE WEST DURING THE AFTERNOON...ALTHOUGH THAT IS LUMPED INTO THE WSW. THE ARCTIC HIGH SETTLES OVER THE REGION SUNDAY MORNING WITH...AS NOTED ABOVE...BITTERLY COLD TEMPERATURES...BUT WINDS TRENDING TOWARD CALM. BY AFTERNOON...THE ARCTIC HIGH HAS ALREADY SHIFTED TOWARD THE VA/MD COAST WITH RETURN FLOW EVIDENT ESPECIALLY IN SOUTHWEST VA. A NORTHERN STREAM SHORT WAVE QUICKLY MOVES TOWARD THE REGION BY SUNDAY AFTERNOON...WITH INCREASING MOISTURE FROM TOP DOWN. THE ANTECEDENT AIR MASS WILL CLEARLY BE VERY DRY AND COLD AND NOT SURE HOW QUICKLY THE AIR MASS WILL SATURATE TO ALLOW GENERATED PRECIPITATION ALOFT TO REACH THE GROUND. INDICATIONS ARE THAT THIS SHOULD BEGIN TO TAKE PLACE AFTER SUNSET IN THE WEST AND CLOSER TO MIDNIGHT IN THE EAST. THUS...WILL LEAVE THE DAYTIME HOURS OF SUNDAY DRY WITH POPS BELOW 15 PERCENT. ALL PRECIPITATION SUNDAY NIGHT WILL BE SNOW ACROSS THE ENTIRE CWA AS THE SOUNDINGS REMAIN BELOW FREEZING AT ALL LEVELS. AS WE MOVE INTO MONDAY...THE SITUATION BECOMES INCREASINGLY COMPLICATED. THE NORTHERN STREAM SHORT WAVE WILL MOVE NORTHEAST OF THE REGION EARLY MONDAY...WHILE A STRONGER SOUTHERN STREAM SHORT WAVE DEEPENS INTO THE MID-SOUTH. DEEP SURFACE LOW PRESSURE WILL THEN DEVELOP IN RESPONSE TO THIS SECOND SOUTHERN STREAM SHORT WAVE ACROSS THE MID-SOUTH...MOVING TOWARD THE EASTERN TN VALLEY BY MONDAY EVENING. ALL OF THE MODELS HAVE TAKEN A SLIGHT WEST JOG WITH THE SURFACE LOW PRESSURE...RESULTING IN THE POTENTIAL FOR WARMER AIR FROM THE SOUTH AND SOUTHEAST TO ENCROACH ON THE REGION. NONETHELESS...THE ANTECEDENT AIR MASS WILL BE VERY COLD AND MODELS OFTEN ADVERTISE A WARMUP TOO QUICKLY WITH THIS TYPE OF SITUATION. A WARM FRONT WILL LIE ACROSS THE REGION MONDAY NIGHT...THEN BEGIN TO LIFT NORTHWARD EARLY TUE. THIS IS WHEN THE P-TYPE ISSUES WILL BEGIN WITH A TRANSITION FROM SNOW TO SLEET TO FREEZING RAIN AND PERHAPS EVEN RAIN IN PARTS OF THE PIEDMONT. THIS ENTIRE PERIOD WILL EVENTUALLY HAVE TO BE HANDLED BY TOP-DOWN OR SIMILAR P-TYPE PROCEDURES...BUT GIVEN IT IS STILL OUT IN THE DAY 4 AND BEYOND PERIOD....WILL STICK WITH A RAIN/SNOW MIXTURE FOR NOW. ALTHOUGH SNOW/SLEET/ICE AMOUNTS STILL HIGHLY IN QUESTION...IT STILL APPEARS QUITE CERTAIN THAT WINTER STORM CRITERIA WILL LIKELY BE MET ACROSS MUCH OF THE CWA IN THE SUN NIGHT THROUGH EARLY TUE TIME FRAME...WITH STILL THE POTENTIAL FOR SIGNIFICANT SNOWFALL ACCUMULATIONS IN THE WESTERN MOUNTAINS. THUS...WILL CONTINUE TO HIGHLIGHT THIS POTENTIAL IN THE HWO. A WINTER STORM WATCH FOR THIS PERIOD WILL LIKELY NEED TO FOLLOW ON THE HEELS OF THE CURRENT WINTER WEATHER ADVISORIES. && .LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 100 PM EST THURSDAY... A DEEPENING SURFACE LOW...REMAINING MOSTLY INLAND...WILL TRACK ACROSS THE CWA TUE...MOVING TOWARD THE NORTHERN MID-ATLANTIC BY EVENING. SIGNIFICANT WINTER WEATHER WILL LIKELY CONTINUE FOR MUCH OF THE CWA...BUT POTENTIALLY TRANSITIONING TO RAIN ACROSS THE PIEDMONT. BUFKIT SHOWS CONSIDERABLE VERTICAL MOTION IN THE SNOW GROWTH ZONE EARLY TUESDAY...SO THERE COULD BE A BURST OF HEAVY SNOW/SLEET BEFORE THE DRY SLOT SPREADS INTO THE REGION FROM THE SOUTHWEST AND SHUTS OFF THE HEAVIER PRECIPITATION...WHICH SHOULD OCCUR BY MIDDAY TUE. BY EVENING...COLDER AIR BEGINS TO FILTER BACK INTO THE WESTERN AREAS AND UPSLOPE SNOW SHOWERS COMMENCE ONCE AGAIN. IN THE WAKE OF THE STRONG SYNOPTIC SYSTEM TUESDAY...ANOTHER CLIPPER IS EVIDENT IN CONTINUED NORTHWEST FLOW ALOFT. OVERALL WARMING OF ANY SIGNIFICANCE LOOKS LIMITED DURING THIS PERIOD. ALTHOUGH PREVIOUS RUNS OF THE GFS SHOWED SUBSTANTIAL WARMING DURING THIS TIME FRAME...THAT IS NOT EVIDENT TODAY. MEXMOS KEEPS WESTERN AREAS MOSTLY AT OR BELOW FREEZING THROUGH MIDWEEK...WITH ONLY LIMITED WARMING DURING THE LATER HALF OF THE WEEK. THE CLIPPER TUE NIGHT/WED...COULD BRING ADDITIONAL MINOR SNOW ACCUMULATIONS TO THE WESTERN PARTS OF THE CWA BEFORE MOVING NORTHEAST OF THE REGION. OUTSIDE OF UPSLOPE SNOW SHOWERS...THAT SHOULD BE THE LAST OF ANY SYNOPTIC-SCALE INDUCED PRECIPITATION FOR THIS PERIOD. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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AS OF 1150 AM EST FRIDAY... LOWER CIGS AND ASSOCIATED LIGHT SNOW BANDS WILL CONTINUE TO HEAD EAST CROSSING THE BLUE RIDGE BY EARLY AFTERNOON. THIS WILL RESULT IN PERIODS OF MVFR/IFR OVER THE WESTERN SITES AND BRIEF MVFR ESPCLY AROUND KDAN BY MID AFTERNOON. ONCE THE WINDS TURN MORE NORTHWEST SHOULD SEE CONDITIONS IMPROVE OVER THE EAST AND RETURN TO VFR BY EARLY EVENING IF NOT SOONER. HOWEVER FOR KBCB/KBLF/KLWB THE NWLY WINDS WILL BE UPSLOPE AND THIS WILL KEEP SNOW SHOWERS AT THESE LOCATIONS WITH MVFR/IFR CIGS/VSBYS INTO THIS EVENING AT KBCB...CONTINUING OVERNIGHT AT KBLF/KLWB. BEHIND THE FRONT ALL SITES WILL SEE SIGNIFICANT WIND GUSTS AS A WELL MIXED BOUNDARY LAYER ALLOWS FOR EFFICIENT MOMENTUM TRANSFER OF INCREASING LOW LEVEL FLOW. EXPECT G40-45KT AT KROA WITH GUSTS AOA 35KT FOR KBCB/KBLF OVERNIGHT. A GRADUAL RETURN TO VFR APPEARS LIKELY ON SATURDAY ALTHOUGH KBLF/KLWB LIKELY TO KEEP MVFR IN SNOW SHOWERS AROUND UNTIL LATE IN THE DAY. WINDS WILL REMAIN STRONG ON SATURDAY WITH GUSTS TO 30-40 KTS LIKELY UNTIL HIGH PRESSURE BUILDS IN DURING THE AFTERNOON. EXTENDED DISCUSSION... THE NEXT LOW PRESSURE SYSTEM WILL ARRIVE ON SUNDAY NIGHT. CONFIDENCE IS HIGH THAT POOR FLYING WEATHER WILL TAKE PLACE DURING MONDAY AND TUESDAY. THIS SYSTEM WILL LIKELY BRING WINTRY PRECIPITATION TO MUCH OF THE AREA...BUT FURTHER UPDATES FROM THE LONGER RANGE MODELS MAY IMPACT THE DETAILS ON PRECIPITATION TYPE AND STORM TRACK. ANOTHER WEAK CLIPPER AREA OF LOW PRESSURE MAY KEEP MVFR CONDITIONS ACROSS THE MOUNTAINS TUESDAY NIGHT INTO WEDNESDAY WITH MAINLY VFR EAST OF THE BLUE RIDGE.
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&& .CLIMATE... COLDEST AIR OF THE SEASON ARRIVES THIS WEEKEND. SEVERAL RECORD LOW MAX TEMPERATURES AND LOW TEMPERATURES ARE POSSIBLE. BELOW ARE THE CURRENT RECORDS FOR SATURDAY 2/13 AND SUNDAY 2/14. SATURDAY 02/13/2016 SITE MINT YEAR LOMAX YEAR KBLF 4 1988 19 1988 KDAN 11 1955 32 1981 KLYH 5 1979 9 1899 KROA 8 1917 18 1914 KRNK -4 1969 14 1955 SUNDAY 02/14/2016 SITE MINT YEAR LOMAX YEAR KBLF 5 1971 16 1960 KDAN 15 1986 32 1986 KLYH 4 1899 24 1905 KROA 10 1943 26 1986 KRNK -2 1969 24 1986 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...WIND CHILL ADVISORY FROM 11 PM THIS EVENING TO 10 AM EST SUNDAY FOR VAZ007-009>020-022>024-032>035. WINTER WEATHER ADVISORY UNTIL 7 AM EST SATURDAY FOR VAZ007-009- 015. NC...WIND CHILL ADVISORY FROM 11 PM THIS EVENING TO 10 AM EST SUNDAY FOR NCZ001-002-018. WINTER WEATHER ADVISORY UNTIL 7 AM EST SATURDAY FOR NCZ001-018. WV...WIND CHILL ADVISORY FROM 11 PM THIS EVENING TO 10 AM EST SUNDAY FOR WVZ042>044-507. WINTER WEATHER ADVISORY UNTIL 7 AM EST SATURDAY FOR WVZ042-043- 508. WIND CHILL WARNING FROM 11 PM THIS EVENING TO 10 AM EST SUNDAY FOR WVZ508. && $$ SYNOPSIS...JH/MBS NEAR TERM...JH/MBS SHORT TERM...RAB LONG TERM...AMS/RAB AVIATION...JH/MBS/WP CLIMATE...CF

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