Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 171154 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 654 AM EST MON NOV 17 2014 .SYNOPSIS... A STRONG COLD FRONT SWINGS ACROSS THE AREA TODAY. ARCTIC AIR WILL FOLLOW TONIGHT WITH HIGH PRESSURE MOVING INTO THE MID MISSISSIPPI VALLEY. EXPECT A PERIOD OF SNOW SHOWERS...WINDS AND COLD WIND CHILLS LATE TONIGHT INTO TUESDAY MORNING AS A RESULT. HIGH PRESSURE BUILDS ACROSS THE SOUTHEAST INTO WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 630 AM EST MONDAY... RADAR STARTING TO FILL IN OVER THE MTNS THIS MORNING. FORECAST ON TRACK...SO NO MAJOR CHANGES WITH UPDATE...EXCEPT WITH WARMER TEMPS IN THE FAR SW VA AREA. PREVIOUS DISCUSSION... EARLIER RUN OF THE HRRR HAD A GREAT HANDLE ON THE RAIN MOVING IN FROM THE SOUTHWEST. FOLLOWED ITS SOLUTION THROUGH THE MORNING...BLENDING IN THE 00Z GFS/NAM. LOOKS LIKE A SLAM DUNK FOR EVERYONE SEEING RAIN TODAY...THOUGH AMOUNTS MAY BE LESS THAN EARLIER THOUGHT AS DID NOT SEE AS MUCH FALL SUNDAY. STILL A GOOD ONE HALF TO THREE QUARTERS OF AN INCH WILL OCCUR TODAY. THIS FRONT LOCATED ACROSS THE CENTRAL APPALACHIANS SOUTHWEST INTO ALABAMA WILL SLIDE EAST ACROSS THE AREA TODAY...WITH A COUPLE WAVES OF LOW PRESSURE ALONG IT. THE MAIN FORECAST ISSUE WILL BE THE COLDER AIR ARRIVING BEHIND THE FRONT. THE 00Z NAM DEPICTED THE COLDER AIR BETTER AT 06Z AT 8H THAN THE GFS/ECMWF...SO LEANED TOWARD IT TEMP FORECAST. SHOULD SEE DEEP MOISTURE EDGE EAST EARLY THIS AFTERNOON IN THE MTNS WHILE THE COLDER AIR STARTS TURNING RESIDUAL SHOWERS OVER TO SNOW LATER IN THE AFTERNOON. BY DUSK MOST OF THE EASTERN HALF OF THE CWA WILL BE DRYING OUT AS WINDS TURN WNW. TEMPS DESPITE THE RAIN...OR REALLY AS A RESULT OF THE RAIN BRINGING DOWN THE WARMER TEMPS ALOFT MAY BRING READINGS INTO THE 50S BEFORE THE COLD AIR ARRIVES IN THE PIEDMONT THIS AFTERNOON. IN THE MTNS HIGHS SHOULD BE OCCURRING BY MIDDAY THEN DROPPING IN THE LATE AFTERNOON. FORECAST SOUNDINGS IN THE MTNS SHOW MOISTURE BECOMING SHALLOW FAST...WITH THE FAVORABLE SNOW GROWTH TEMPS ALOFT NOT BEING REALIZED UNTIL LATE EVENING...SO COULD BE SOME PATCHY FREEZING DRIZZLE ISSUES...AND WILL ADVERTISE THIS IN THE MTNS OF THE FAR WEST THIS EVENING. THIS HERE LIES THE PROBLEM...WHERE IT RAINS...COMBINED WITH ARCTIC AIR ARRIVING AND SNIZZLE(SNOW AND FREEZING DRIZZLE) FOLLOWING...ROADS WILL BECOME SLICK IN THE HIGHER ELEVATIONS BY LATE DUSK. AFTER COLLABORATING WITH NEIGHBORING OFFICES...IT WAS DECIDED TO GO WITH A WINTER WX ADVISORY FOR THE NC MTNS INTO THE GRAYSON HIGHLANDS...BUT TO DELAY ANY HEADLINES...IF THEY ARE NEEDED FURTHER NORTH INTO THE MTN EMPIRE OF SW VA AND SE WV MTNS. STILL THINK THE TEMPS FALLING FAST LATE TONIGHT MAY REQUIRE AT LEAST A SPECIAL WX STATEMENT. THE SNOWFALL ACCUMULATION WILL BE LIGHT GIVEN THE LIMITED MOISTURE BUT 1 TO 3 INCHES IN THE WESTERN SLOPES ARE POSSIBLE INTO TUESDAY MORNING. IN ADDITION...THE WINDS WILL BE GUSTING OVER 40 MPH WITH 6 HR PRESSURE RISES OF 5-7MB EXPECTED BEHIND THE FRONT THIS EVENING INTO TUESDAY MORNING. THIS WAS ADDED TO THE WINTER WX ADVISORY IN THE NC MTNS. CLOUDS MAY PREVENT IDEAL MIXING OF THE STRONGER WINDS ALOFT...BUT WHERE IT THE CLOUD/CLEARING LINE IS ALONG/NEAR THE BLUE RIDGE...THINK AN OCCASIONAL 50 MPH GUST WILL BE REALIZED. OUTSIDE THE WINTER WX ADVISORY FOR ELEVATIONS ABOVE 3000 FT...HIGHLIGHT WEATHER IN THE HAZARDOUS WEATHER OUTLOOK. WILL TAKE A LOOK AT MORE DATA COMING IN AND FURTHER COORDINATING WITH OTHER WFO OFFICES TO SEE IF MORE HEADLINES ARE NEEDED. FOR TONIGHT...TEMPS WILL DROP INTO THE TEENS MOUNTAINS...SOME SINGLE DIGITS HIGHEST ELEVATIONS...WITH 20S IN THE EAST. WIND CHILLS BY DAWN TUESDAY WILL RANGE FROM 5 ABOVE TO 5 BELOW IN THE MOUNTAINS...TO THE TEENS IN THE EAST.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... AS OF 315 AM EST MONDAY... COLD FRONT PUSHES OUT INTO THE ATLANTIC OCEAN TUESDAY AS THE 1033 SURFACE HIGH PRESSURE IN TEXAS BUILDS NORTHWARD INTO OUR REGION. THE AXIS OF THE UPPER TROF CROSS OUR AREA TUESDAY INTO TUESDAY NIGHT. GUSTY NORTHWEST WINDS WILL CONTINUE TUESDAY AS A TIGHT PRESSURE GRADIENT WILL REMAIN OVER THE REGION THROUGH TUESDAY. THE GFS...NAM AND HIRESW-ARW SHOWED UPSLOPE SNOW SHOWERS AND SNOW FLURRIES CONTINUE IN THE WESTERN MOUNTAINS. ADDITIONAL LIGHT ACCUMULATIONS MAY BE POSSIBLE IN THE NORTHWEST UPSLOPE FAVORED LOCATIONS. HIGH TEMPERATURES TUESDAY WILL RANGE FROM THE UPPER TEENS IN THE NORTHWEST MOUNTAINS TO THE MID 30S IN THE PIEDMONT. HIGH PRESSURE CONTINUES TRAVEL EASTWARD TUESDAY NIGHT. TUESDAY NIGHT WILL BE A VERY COLD NIGHT WITH TEMPERATURES ACROSS THE AREA RANGING FROM THE SINGLE DIGITS IN THE HIGHER ELEVATIONS TO THE UPPER TEENS ACROSS THE PIEDMONT. WINDS WILL DECREASE TUESDAY NIGHT...BUT WIND CHILLS WILL BE COLD WITH SINGLE DIGITS IN THE WEST TO TEENS IN THE EAST. A WARM FRONT WILL PASS OVER THE REGION WEDNESDAY...AS A COLD FRONT DROPS SOUTH INTO THE OHIO VALLEY. WEDNESDAY AFTERNOON HIGH TEMPERATURES WILL AVERAGE 20F COLDER THAN NORMAL WITH READINGS FROM THE LOWER 30S IN THE MOUNTAINS TO THE LOWER 40S IN THE PIEDMONT. COLD FRONT APPROACHES FROM THE WEST WEDNESDAY NIGHT. ALLOWED FOR ISOLATED SNOW SHOWERS ACROSS THE NORTH. LOW TEMPERATURES WEDNESDAY NIGHT WILL GENERALLY BE FROM AROUND 20 DEGREES TO THE MID 20S. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... AS OF 400 PM EST SUNDAY... SURGE OF ARCTIC AIR TO INVADE THE REGION INTO THURSDAY. THIS WAS NOT ADVERTISED A FEW RUNS BACK...BUT GIVEN GENERAL CONSENSUS AMONG THE MODELS AND A PREVAILING MEAN DEEP MERIDIONAL TROUGH ACROSS THE EASTERN HALF OF THE U.S...THIS APPEARS TO BE A REASONABLE SOLUTION AND THUS WILL LEAN IN THIS DIRECTION. HOWEVER...IN TERMS OF INTENSITY...THIS FINAL ARCTIC SURGE WILL NOT EVEN COME CLOSE TO THE ONE EARLIER IN THE WEEK. MOISTURE IS LIMITED...BUT SLIGHT CHC TO LOW CHC POPS FOR UPSLOPE -SHSN ACROSS THE USUAL WESTERN UPSLOPE AREAS OF THE ALLEGHANYS SEEMS REASONABLE AND HAVE BEEN INCLUDED...WITH NO MENTION OF POPS EAST OF THE ALLEGHANY FRONT. THE PARENT ARCTIC HIGH WILL SETTLE OVER THE REGION EARLY SATURDAY...SO BELOW NORMAL TEMPERATURES SHOULD REMAIN IN PLACE THROUGH SAT MORNING. MODEL TEMPS IN REASONABLE AGREEMENT THROUGH FRI...BUT FEEL THE GFS MOS IS TOO QUICK TO SPREAD WARMER RETURN FLOW INTO THE REGION SAT...SO LEANED TOWARD THE COLDER ECMWF MOS. BIGGER QUESTIONS REMAIN FOR THE REMAINDER OF THE EXTENDED PERIODS. AS THE ARCTIC HIGH RETREATS TOWARD THE COAST SAT...THE LONG AWAITED RETURN TO A LESS AMPLIFIED FLOW PATTERN BEGINS TO EVOLVE. THE EASTERN U.S. TROUGH IS REPLACED BY A SHORT WAVE RIDGE AS BROAD MEAN TROUGHING RELOCATES TO THE WESTERN/CENTRAL U.S. THE MAIN CONCERN FOR THE WEEKEND IS THE TIMING AND ASSOCIATED WARMING/MOISTENING WITH A STRONG NEGATIVELY TITLED HIGHLY PROGRESSIVE SHORT WAVE PROGGED TO EJECT OUT OF THE BASE OF THE MEAN TROUGH INTO THE SOUTHEAST STATES SAT NIGHT-SUN. 12Z ECMWF IN EXCELLENT AGREEMENT WITH 12Z GFS IN BRINGING THIS SYSTEM THROUGH OUR REGION SUN AFTERNOON. SUPERBLEND POPS WERE LIKELY TO CATEGORICAL SUN NIGHT-MON. GIVEN THE ASSOCIATED PVA...AND AMOUNT OF MOIST/WARM ADVECTION INTO THE REGION...THIS SEEMED REASONABLE. HOWEVER...NEIGHBORING OFFICES WERE NOT ON BOARD WITH THESE HIGH VALUES THIS FAR OUT...SO STOPPED AT A MORE REASONABLE 50 PERCENT VALUE FOR NOW. GIVEN RECENT MODEL RUN-TO-RUN VARIATION...THAT SEEMED REASONABLE FOR SURE. A SIGNIFICANT WARM UP WILL ENSUE SAT- SUN...BUT AS NOTED ABOVE...PERHAPS NOT TO THE DEGREE ADVERTISED BY THE MEX MOS. THUS...HAVE USED A MODEL BLEND FOR SAT- SUN. AN EVEN MORE SIGNIFICANT NEGATIVELY TILTED UPPER TROUGH APPEARS ON TRACK FOR THE REGION INTO MON. ECMWF/GFS SHOWING SOME INCREDIBLY WARM/MOIST AIR FOR THIS TIME OF YEAR SPREADING INTO THE REGION FROM THE SOUTH BY MON MORNING ON THE HEELS A STRONG LOW-LEVEL SOUTHERLY JET WITH DEWPOINTS APPROACHING 60 DEGREES BY MON AFTERNOON ACROSS THE PIEDMONT AND SOUTHSIDE. PROGGED LIFTED INDICES AND CAPES ALONG WITH EVIDENT SHEAR SUGGEST SOME -TSRA MAY NEED TO BE CONSIDERED BY MON AFTERNOON ACROSS THE PIEDMONT. TO SAY THE LEAST...EARLY NEXT WEEK WILL BE IN SHARP CONTRAST TO THE WEATHER EXPECTED THIS WEEK WITH TEMPERATURES ACTUALLY ABOVE SEASONAL NORMALS...ESPECIALLY IF LOWS ARE ONLY IN THE 50S MON MORNING WITH HIGHS IN THE 60S. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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AS OF 640 AM EST MONDAY... RAINFALL INCREASING OVER THE AREA THIS MORNING AND SHOULD SPREAD EAST THRU LATE MORNING. AIRPORTS WILL FLUCTUATE IN THE CIGS/VSBYS WITH MODERATE TO AT TIMES HEAVY RAIN BRING CIGS UP AND VSBYS DOWN WHILE LIGHTER RAINS ALLOW CIGS TO DROP TO IFR/LIFR. STRONG LLJ TO INCREASE AT THE TAF START TIME THEN LIFT OUT BY MIDDAY. INVERSION AT THE SFC WILL ALLOW FOR LIGHT WINDS...SUCH THAT LOW LVL WIND SHEAR WILL OCCUR AS 2KFT AGL WILL START RUNNING INTO THE 30-45 KT JET. LOOK FOR THE RAIN TO DIMINISH IN THE MTNS BY EARLY AFTERNOON WITH COLDER AIR WORKING IN BY 21-00Z...WITH UPSLOPE SNOW SHOWERS GETTING GOING. FURTHER EAST THE RAIN SHIELD SHOULD EXIT ROA/BCB BY 19-21Z...LYH/DAN 22Z. WINDS WILL PICK UP FROM THE WNW AND GUST TO 30 TO 40 MPH IN THE MTNS TONIGHT. CIGS WILL STAY MVFR IN THE MTNS TONIGHT AND VFR EAST. ARCTIC BLAST OF AIR MAY LEAD TO WATER FREEZING ON RUNWAYS/AIRPLANES THIS EVENING...THOUGH WINDS MAY LEAD TO QUICKER EVAPORATION OF THE WET SFCS. EXTENDED DISCUSSION... EXPECT MAINLY VFR WEATHER TUESDAY-THURSDAY. NEXT SYSTEM APPEARS TO ARRIVE FRIDAY WITH MVFR CIGS IN THE MTNS.
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&& .CLIMATE... AS OF 315 PM EST SUNDAY... RECORD COOLEST HIGHS...TUESDAY NOV 18TH BLACKSBURG VA...30 IN 2008 BLUEFIELD WV....27 IN 2008 DANVILLE VA.....38 IN 1959 ROANOKE VA......33 IN 1951 LEWISBURG WV....30 IN 2008 LYNCHBURG VA....32 IN 1924 && .EQUIPMENT... AS OF 120 AM EST MONDAY... KFCX RADAR DOWN DUE TO TRANSMITTER FAULT. TECHNICIANS WILL WORK ON RESTORING THIS BY NOON TODAY. THE VISIBILITY SENSOR AT KLYH...LYNCHBURG AIRPORT...WILL BE OUT OF SERVICE UNTIL MONDAY WHEN TECHNICIANS WILL 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 4 PM THIS AFTERNOON TO 6 AM EST TUESDAY FOR VAZ015. NC...WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM EST TUESDAY FOR NCZ001-018. WV...NONE. && $$ SYNOPSIS...WP NEAR TERM...WP SHORT TERM...KK LONG TERM...RAB AVIATION...WP CLIMATE...RCS EQUIPMENT...WERT/WP

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