Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 201205 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 705 AM EST THU NOV 20 2014 .SYNOPSIS... ASIDE FROM A FEW FLURRIES AND SNOW SHOWERS WEST OF THE BLUE RIDGE...HIGH PRESSURE BUILDING IN FROM THE WEST WILL BRING QUIET BUT BREEZY CONDITIONS...WITH CONTINUED BELOW NORMAL TEMPERATURES...THROUGH THE END OF THE WORKWEEK AND INTO THE FIRST PART OF THE WEEKEND. AS THE HIGH SLIPS OFF TO OUR EAST ON SUNDAY...A STRONG LOW PRESSURE SYSTEM WILL MOVE UP THE MISSISSIPPI VALLEY AND PUSH A WARM FRONT THROUGH THE AREA. THIS WILL BRING A GOOD CHANCE OF RAIN TO OUR FORECAST ON SUNDAY...BUT ALSO SOME WARMER TEMPERATURES AS WE HEAD INTO NEXT WEEK. HOWEVER...THE WARM UP WILL BE SHORT LIVED AS COLD HIGH PRESSURE BUILDS IN AGAIN FROM THE WEST. && .NEAR TERM /THROUGH TONIGHT/... AS OF 355 AM EST THURSDAY... SFC LOW MOVING THROUGH THE GREAT LAKES WILL BE PUSHING A WEAK COLD FRONT THROUGH THE REGION THIS MORNING. THIS WILL EVENTUALLY SHIFT WINDS AROUND TO A WND DIRECTION. THERE MAY BE SOME UPSLOPE FLURRIES/SNOW SHOWERS FOR THE FAR WESTERN SLOPES IN WV BUT WOULD LIKE TO SEE FLOW MORE NEWLY AND A BIT MORE MOISTURE THAN IS CURRENTLY AVAILABLE TO GET ANYTHING APPRECIABLE. SOME CLOUDS MAY ALSO SPILL EWE PAST THE RIDGE SINCE DOWNSLOPE WILL NOT BE MAXIMIZED. IN ANY EVENT...OVERALL FLAVOR OF THE DAY WILL BE FAIR EAST OF THE RIDGE...IMPROVING TO THE WEST AS THE DAY WEARS ON...AND BECOMING WINDY EVERYWHERE AS DIURNAL MIXING TAPS SOME OF THE BRISK LOW LEVEL WINDS. TEMPS WILL CONTINUE TO MODERATE AND...WHILE STILL REMAINING WELL BELOW NORMAL...LOCATIONS EAST OF THE RIDGE SHOULD RISE ABOVE 50F FOR THE FIRST TIME IN A WHILE. HIGH PRESSURE PUSHES IN FROM THE NORTHWEST TONIGHT. THIS WILL BRING WINDS AROUND TO A MORE NEWLY DIRECTION AND GET UPSLOPE FLURRIES/SNOW SHOWERS GOING AGAIN FOR THE FAR WESTERN SLOPES. MAYBE A DUSTING FOR THE HIGHER ELEVATIONS. MODEL SOUNDINGS ALSO INDICATE A PERIOD OF BETTER DOWNWARD MOMENTUM TRANSFER TONIGHT SO WINDS LOOK TO STAY A BIT GUSTY ESPECIALLY FOR THE RIDGES. && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/... AS OF 345 AM EST THURSDAY... THE FINAL ARCTIC HIGH IN THE SERIES OF FOUR OVER THE PAST WEEK WILL BE CENTERED OVER THE REGION EARLY FRI. ONE MORE FINAL COLD DAY WITH TEMPERATURES WELL BELOW NORMAL...ON THE ORDER OF 10 TO 15 DEGREES BELOW NORMAL...NOTHING LIKE THE COLD TEMPERATURES YESTERDAY AND THE DAY BEFORE. CANNOT COMPLETELY RULE OUT A FEW LINGERING SNOW FLURRIES ALONG UPSLOPE AREAS OF THE ALLEGHANYS IN WESTERN GREENBRIER...BUT OTHERWISE...A DRY AND BECOMING MOSTLY SUNNY DAY. A MODEL BLEND YIELDED A VERY REASONABLE SOLUTION FOR TEMPERATURES. FOR SATURDAY...THE REMNANT ARCTIC SFC HIGH WILL MOVE ELSE-SE OF THE REGION UNDER INCREASINGLY CONFLUENT FLOW ALOFT ACROSS THE MID- ATLANTIC REGION IN RESPONSE TO A VIGOROUS SOUTHERN STREAM SHORT WAVE COMING OUT OF THE SW U.S. THE HIGH WILL INITIALLY INTENSIFY AND SHIFT TO THE SE OF THE REGION BY SAT EVENING. WHILE CERTAINLY NOT A FAVORABLE POSITION FOR A CLASSIC WEDGE...IT WILL THEN MOVE EAST OFFSHORE SUN INTO A MORE TYPICAL IN-SIT WEDGE POSITION. A SHORT WAVE RIDGE WILL BUILD OVER THE REGION BRIEFLY SATURDAY AS THE INCREASINGLY VIGOROUS SOUTHERN STREAM SHORT WAVE DIGS INTO TX/LAW AND TAKES ON A SIGNIFICANT NEGATIVE TILT. CLOUDS WILL BE ON THE INCREASE SATURDAY...BUT THE CWA WILL REMAIN PRECIPITATION FREE WITH A VERY DRY AIR MASS TO START RESIDING OVER THE REGION. THIS WILL ALLOW FOR ONE MORE COLD MORNING BEFORE A NOTABLE WARMING TREND BEGINS SATURDAY AFTERNOON AS SFC WINDS COME AROUND TO THE SOUTH. FOR SUN THE STRONGLY NEGATIVE TILTED SHORT WAVE ROTATES QUICKLY THROUGH THE REGION. THE CONCERNS THAT ARISE WITH THIS SYSTEM ARE WINTER WEATHER THREAT...SEVERE WEATHER THREAT...AND RAINFALL AMOUNTS. FOR THE WINTER WEATHER THREAT...THIS APPEARS TO ESSENTIALLY BE NIL. CLOUDS INCREASE ENOUGH IN SOUTHWEST PARTS OF THE CWA TO PREVENT MUCH RADIATIONAL COOLING. IN ADDITION...A STRONG 60KT+ LAW TRAVERSES THE AREA BRINGING WARM/GULF AIR TO NORMALLY COLDER HIGHER ELEVATIONS EVEN SOONER. THE GREENBRIER VALLEY AND SOUTHERN SHENANDOAH VALLEY WILL SEE TEMPERATURES JUST BELOW FREEZING EARLY SUN. THUS...IF PRECIPITATION CAN REACH THESE AREAS...THERE MAY BE A FEW BRIEF POCKETS OF FREEZING RAIN EARLY SUN MORNING...BUT SIGNIFICANT PRECIPITATION IS NOT EXPECTED IN THESE AREAS UNTIL LATE MORNING OR AFTERNOON WHEN TEMPERATURES WILL BE WELL ABOVE FREEZING. OTHERWISE...AS NOTED...THE WINTER WEATHER THREAT WITH THIS SYSTEM IS NEAR ZERO. FOR THE SEVERE WEATHER THREAT...THE DYNAMICS ARE CERTAINLY THERE. HOWEVER...THERE IS STRONG ENOUGH EVIDENCE OF THE IN-SIT WEDGE AND A STABLE...COOLER AIR MASS...ALSO ANTECEDENT DRY AIR MASS/30-DEGREE DEWPOINTS...TO PRECLUDE MUCH THREAT OF SEVERE. NO THUNDER WAS INHERITED IN THE GRIDS AND NONE WAS ADDED WITH THIS PACKAGE. THE MAIN CONCERN WOULD BE STRONG SOUTHEAST GRADIENT WINDS THAT AFFECT THE HIGHER ELEVATIONS OF SE WV/SW VA IN THE TYPICALLY FAVORED LOCATIONS...E.G...TAZEWELL...MERCER...SMYTH COUNTY REGION. RAINFALL ALSO DOES NOT APPEAR TO BE A SIGNIFICANT CONCERN. THE PERIOD OF ANY MODERATE TO HEAVY RAINFALL SHOULD BE LIMITED TO THE 12Z-18Z PERIOD SUN IN THE SOUTHWEST PART OF THE CWA AND 18Z-00Z IN THE NORTHEAST PART OF THE CWA. CURRENTLY ADVERTISED RAINFALL FOR SUN IS 1/3RD INCH NORTH TO 2/3RD INCH SOUTH. THIS IS CONSISTENT WITH PCS LATEST DECREASE IN RAINFALL ACROSS THE REGION FROM LESS THAN AN INCH NORTH TO AROUND AN INCH NC/VA PIEDMONT COUNTIES. OVERALL...IT APPEARS THAT THERE COULD BE A SPLIT IN THE HEAVIER PRECIPITATION ASSOCIATED WITH THE LARGE SCALE SYNOPTIC SYSTEM...ONE AREA OF HEAVIER RAINFALL ACROSS THE OH VALLEY WITH THE MAIN SFC LOW TRACK...AND ANOTHER TO THE SOUTHEAST OF THE REGION CLOSER TO THE COAST...ALTHOUGH SOME ENHANCEMENT OF RAINFALL ALONG SOUTHEAST FACING SLOPES OF THE BLUE RIDGE SEEMS PROBABLE WITH INCREASING SOUTHEAST SFC WINDS. HAVE KEPT TEMPERATURES ON THE COLD SIDE OF GUIDANCE SUN WITH A WEDGE IN PLACE AND SIGNIFICANT LIKELY AS THE PRECIPITATION OVERSPREADS THE ANTECEDENT DRY AIR MASS. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... AS OF 420 AM EST THURSDAY... MON WILL BRING THE WARMEST TEMPERATURES THE CWA HAS SEEN IN OVER A WEEK...WITH 50S POSSIBLE IN THE MOUNTAINS TO AROUND 70 TOWARD DANVILLE/CASWELL AREA AS THE AREA MOVES INTO A DRY SLOT BETWEEN A BAROCLINIC ZONE...NOW SHIFTED CLEARLY OFF THE EAST COAST...AND THE MAIN UPPER TROUGH/COLD FRONT...STILL WELL TO THE WEST OF THE REGION. SCT SHOWERS APPEAR POSSIBLE WITHIN THE LARGE WARM SECTOR ACROSS THE REGION...BUT MODELS ARE INCONSISTENT ON PLACEMENT OF THE BETTER PRECIPITATION. COVERAGE LOOKS SPOTTY ON ALL MODELS...SO HAVE JUST ADVERTISED MOSTLY CHANCE POPS FOR NOW. IF ANY THUNDER WERE TO OCCUR...MONDAY WOULD BE THE DAY FOR IT...BUT MID-LEVEL WARMING AND LACK OF FOCUSED DYNAMICS SHOULD INHIBIT MUCH IF ANY...THUS IT HAS NOT BEEN ADVERTISED AT THIS POINT. THE MAIN COLD FRONT BEGINNING A LONG TERM COOLING TREND AGAIN WILL MOVE THROUGH THE REGION MON NIGHT/EARLY TUE. AN INCREASE IN FRONTAL ASSOCIATED SHOWERS APPEARS LIKELY WITHIN THIS TIME FRAME AS THE MAIN UPPER TROUGH LAGS BACK TO THE WEST. COLDER AIR WILL BEGIN TO FILTER INTO THE REGION THEN THROUGH MID-WEEK. IT SHOULD THEN BE COLD ENOUGH BY WED NIGHT FOR SNOW SHOWERS IN THE USUAL UPSLOPE AREAS OF THE ALLEGHANYS AS A CLIPPER SYSTEM COMES THROUGH. ANOTHER LARGE ARCTIC HIGH APPEARS DESTINED FOR THE REGION FOR THANKSGIVING TOWARD THE WEEKEND. HOWEVER...THE ECMWF AND GFS DIVERGE SIGNIFICANTLY TOWARD THE END OF THE WEEK WITH THE ECMWF INDICATING MUCH MORE POTENTIAL FOR A WESTERN U.S. TROUGH/EASTERN U.S. RIDGE RS. THE GFS WITH A DEEP EASTERN U.S. TROUGH. THE 00Z ECMWF CONTINUED THE MARKED DISCREPANCY IN THE LATER PORTIONS OF THE EXTENDED. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... AS OF 650 AM EST THURSDAY... ANOTHER ARCTIC SURGE...ALBEIT LESS SIGNIFICANT THAN THE LAST...HEADED TOWARD THE REGION TODAY. ASSOCIATED CLOUD COVER BANKED UP AGAINST THE WESTERN SLOPES AND SPILLING INTO THE NEW RIVER VALLEY EXPECTED TO CONTINUE THROUGH MUCH OF THE DAY. OVERNIGHT...AS WINDS BECOME MORE NORTHWEST AND UPSLOPE FLOW IS ENHANCED...CIGS WILL LIKELY LOWER TO MVFR ALONG UPSLOPE AREAS OF THE ALLEGHANYS. THE NEW RIVER VALLEY AREA AND THE ALLEGHANY HIGHLANDS WILL SEE SCT MVFR LEVEL CLOUDS...OCCASIONALLY BKN. EAST OF THE BLUE RIDGE IT SHOULD REMAIN VFR THROUGHOUT THE TAF VALID PERIOD. A FEW -SHSN OR FLURRIES WILL BE POSSIBLE AFTER MIDNIGHT INTO THE EARLY MORNING HOURS ALONG UPSLOPE AREAS OF THE ALLEGHANYS...BUT NO VISIBILITY RESTRICTIONS ARE EXPECTED. WINDS MAIN CONCERN THROUGH THE TAF VALID PERIOD WILL BE THE WIND. GUSTY WSW-WND WINDS EXPECTED THROUGH THE TAF VALID PERIOD AS THE GRADIENT TIGHTENS UP IN RESPONSE TO THE APPROACHING ARCTIC HIGH. SPEEDS INCREASING TO 1O TO 15KTS WITH GUSTS TO 25KTS POSSIBLE THROUGH THE LATE MORNING AND AFTERNOON. MEDIUM TO HIGH CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD. HIGH CONFIDENCE IN VSBY THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID PERIOD. EXTENDED DISCUSSION... FRIDAY THROUGH SATURDAY WILL AGAIN BE VFR...WITH HIGH PRESSURE IN THE REGION. A MORE SIGNIFICANT SYSTEM WILL APPROACH THE AREA WITH RAIN AND SUB-VFR CONDITIONS SUNDAY INTO SUNDAY NIGHT. MAY SEE A BRIEF RETURN TO VFR DURING MONDAY OUTSIDE OF THE MOUNTAINS AS A DRY SLOT DEVELOPS BETWEEN THE EXITING FRONT FROM SUNDAY AND THE NEXT UPSTREAM COLD FRONT. && .EQUIPMENT... AS OF 355 AM EST WEDNESDAY... THE VISIBILITY SENSOR AT CLAY...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...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...OBS NEAR TERM...OBS SHORT TERM...RAB LONG TERM...OF/RAB AVIATION...OBS/PC EQUIPMENT...RAB

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