Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 212352 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 652 PM EST FRI NOV 21 2014 .SYNOPSIS...
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ARCTIC HIGH PRESSURE WILL REMAIN ACROSS MUCH OF THE REGION TONIGHT BEFORE SLIDING OFFSHORE SATURDAY INTO SATURDAY NIGHT. A COMPLEX STORM SYSTEM WILL APPROACH THE REGION FROM THE SOUTHWEST SUNDAY...MOVING THROUGH THE REGION SUNDAY NIGHT AND EARLY MONDAY BRINGING WIDESPREAD RAINFALL. UNSEASONABLY WARM CONDITIONS ARE EXPECTED MONDAY IN THE WAKE OF THIS SYSTEM BEFORE A COLD FRONT MOVES THROUGH TUESDAY...RETURNING TEMPERATURES TO BELOW NORMAL FOR THE REST OF NEXT WEEK.
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&& .NEAR TERM /THROUGH SATURDAY/... AS 200 PM EST FRIDAY... HIGH PRESSURE WILL DRIFT EAST TONIGHT INTO SATURDAY. RADIATIONAL COOLING CONDITIONS EXPECTED OVERNIGHT UNDER THE ARCTIC HIGH WITH CLEAR SKIES AND CALM WINDS. WHILE IN THE WEST ACROSS THE HIGHER ELEVATIONS...850 MB WARM ADVECTION IS EXPECTED WITH TEMPERATURES CLIMBING TO AROUND PLUS 5C BY 12Z SATURDAY. LOW TEMPERATURES OVERNIGHT WILL RANGE FROM AROUND 10 DEGREES IN THE COLDER MOUNTAIN VALLEYS TO THE MID 20S ACROSS THE RIDGETOPS. HIGH PRESSURE SLIDES OFF TO OUR EAST ON SATURDAY. UNDER BRIGHT SUNSHINE HIGH TEMPERATURES SATURDAY WILL RANGE FROM THE LOWER 40S IN THE MOUNTAINS TO THE LOWER 50S IN THE PIEDMONT. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... AS OF 145 PM EST FRIDAY... RIDGING BOTH SURFACE AND ALOFT EXTENDING INLAND ACROSS THE SE STATES WILL WEAKEN SATURDAY NIGHT AHEAD OF THE COMPLEX/LARGE STORM SYSTEM THAT WILL TAKE SHAPE FROM TX EAST ALONG THE GULF COAST STATES. NEW MODELS CONTINUE TO SLOW DOWN THE NORTHWARD ADVANCE OF DEEPER MOISTURE WITH THIS SYSTEM SATURDAY NIGHT AS PIECES OF CONVECTION FROM THE UPPER LOW WELL TO THE SW AND OVER THE SE WITH THE COASTAL FRONT TEND TO INHIBIT TRANSPORT. HOWEVER FORECAST SOUNDINGS DO INDICATE PERHAPS ENOUGH ISENTROPIC LIFT/UPSLOPE AND LOW LEVEL MOISTURE TO POSSIBLY DEVELOP SOME LIGHT RAIN ALONG THE NW N CAROLINA MOUNTAINS SO KEPT A VERY LOW POP LATE ALTHOUGH APPEARS LITTLE MORE THAN DRIZZLE AT THIS POINT. DO EXPECT TEMPS TO RISE GIVEN THE STRONG WARM ADVECTION SETUP SO REMOVED ALL FROZEN PRECIP MENTION AT THE ONSET DESPITE SOME COLD AIR LIKELY TRAPPED IN THE DEEPER VALLEYS. ELSW INCREASING CLOUDS BUT STILL DRY OVERNIGHT WITH LOWS MAINLY 30S BEFORE EDGING UP LATE. SIMILAR TO PREVIOUS...GUIDANCE QUICKLY EJECTS THE PARENT LOW WITH THE SOUTHERN STREAM SHORTWAVE TROUGH WELL TO THE WEST SUNDAY...WITH A JET DRIVEN BAND OF DEEPER LIFT SWINGING TOWARD THE REGION FROM THE SW ESPCLY DURING THE AFTERNOON...AND ACROSS MOST SPOTS BY MIDNIGHT. THIS AHEAD OF A SURFACE WARM FRONT THAT WILL GET SLOWED UP BY PRECIP INTO A VERY DRY BOUNDARY LAYER...WHICH SHOULD LIKELY DELAY THE ONSET FARTHER NORTH...BUT ALSO CREATE A WEAK INSITU WEDGE LATER IN THE DAY. HOWEVER TIMING REMAINS IFFY GIVEN CONSENSUS OF GOING EVEN SLOWER AND POTENTIAL FOR SOME SPLITTING OF THE HEAVIER RAIN PER STRONG DYNAMICS WELL TO THE NW AND CONVECTION ALONG THE COASTAL FRONT OVER THE EASTERN CAROLINAS. FOR NOW APPEARS EVEN WITH THAT SCENARIO THAT THE DEEP SOUTH/SE FLOW WILL BE ENOUGH TO OVERCOME TO SOME DEGREE SO CONTINUING THE TREND OF LIKELY/CAT POPS SLIDING NE SUNDAY AFTERNOON...JUST A COUPLE HOURS SLOWER SIMILAR TO THE GFS. BRIEF PERIOD OF 50 KNOT WINDS AT 85H CROSSING THE MTN EMPIRE REGION SUNDAY AFTERNOON REMAINS A CONCERN FOR AT LEAST ADVISORY WINDS ON THE RIDGES SO KEEPING MENTION IN THE HWO FOR A FEW COUNTIES OUT WEST. KEPT HIGHS A BIT BELOW THE MAV MOS AS THE COOL MET MOS VALUES LOOK TOO COOL GIVEN THE SLOWER NATURE TO PRECIP ARRIVAL INTO THE DRY AIR...AND THE DEGREE OF WARMING ABOVE. BEST UPWARD MOTION AS SEEN VIA MODEL DIFFLUENCE FIELDS LIKELY TO OCCUR SUNDAY EVENING AS THE AXIS OF DEEP MOISTURE ACCELERATES A BIT WITH A BAND OF HEAVIER RAIN POSSIBLY SWEEPING ACROSS ESPCLY SOUTHERN/EASTERN SECTIONS. HOWEVER DESPITE STRONG WINDS ALOFT AND FORECAST HIGH HELICITY...MOST OF THIS TO STAY ABOVE THE LOW LEVEL INVERSION...AND GIVEN LACK OF MUCH INSTABILITY WILL TAKE A FASTER SURFACE WARM FRONTAL PASSAGE OVER THE SE TO COINCIDE WITH THE BETTER SHEAR WHICH DOESNT LOOK TO HAPPEN AT THIS POINT. OTRW RUNNING WITH OVERALL CAT POPS DURING THE EVENING...THEN QUICKLY CUTTING BACK TO CHANCE OR LESS OVERNIGHT AS THE UPPER JET RIDES A VERY PRONOUNCED DRY SLOT ALOFT INTO THE AREA LATE. LOW TEMPS SHOULD REMAIN MILD AND COULD RISE SOME LATE AS THE FLOW TURNS MORE SW FROM ABOVE. ASSOCIATED COLD FRONT TRAILING THE PARENT LOW TO THE NORTH WILL SLIDE TOWARD THE REGION A BIT FASTER FROM THE WEST MONDAY...WITH THE LAGGING COLD ADVECTION SPILLING IN MONDAY NIGHT. MOISTURE AHEAD OF THE FRONT WILL REMAIN VERY SHALLOW BUT MAY BE ENOUGH TO KEEP TEMPS FROM ZOOMING MONDAY AFTERNOON ESPCLY EAST...AND OVER THE FAR WEST WHERE MORE OF A SHOWER THREAT COULD OCCUR. LATEST MOS REMAINS VERY WARM PER SUCH MILD 85H TEMPS THAT LOOK TO PUNCH TO THE SURFACE ON GOOD MIXING BEFORE THINGS COOL ALOFT LATER ON. SINCE TREND IN THIS SETUP IS USUALLY FOR THE FRONT TO BE SLOWER CROSSING THE RIDGES AND IN LINE WITH THE 12Z ECMWF...STAYED ON THE WARM SIDE WITH 60S WEST AND SOME LOW 70S EAST. POPS IFFY BUT INCLUDED A 20/30 POPS MOST SPOTS WITH SKIES BECOMING PC MONDAY...THEN MOSTLY ISOLATED RAIN/SNOW SHOWERS WESTERN SLOPES MONDAY NIGHT AS COLDER AIR OOZES IN. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 130 PM EST FRIDAY... TUESDAY INTO WEDNESDAY...AN UPPER LOW IS PROGGED TO PROGRESS FROM NEAR JAMES BAY NORTHEAST TOWARDS GREENLAND. THE SYSTEMS TRAILING COLD FRONT IS EXPECTED TO PROGRESS EASTWARD TO NEAR THE EAST COAT OF THE U.S. MODEL GUIDANCE OFFERS VARIOUS SOLUTIONS REGARDING A WAVE OF LOW PRESSURE THAT IS PROGGED TO HEAD NORTH ALONG THIS FRONT...FROM THE GULF COAST STATES TO THE MID-ATLANTIC SEABOARD BY MIDDAY WEDNESDAY. ENOUGH SOLUTIONS OFFER THE POTENTIAL THAT THIS WAVE WILL HELP BUCKLE THE FRONT AND ITS ASSOCIATED MOISTURE WESTWARD...SO THAT PRECIPITATION RETURNS TO AT LEAST THE EASTERN PARTS OF THE REGION...IF NOT ALSO CENTRAL PORTIONS. OUR LATEST FORECAST FOR WEDNESDAY WILL REFLECT THIS POTENTIAL...WITH THE GREATEST CHANCE FOR PRECIPITATION OVER THE EASTERN PARTS OF THE REGION ON WEDNESDAY. ENOUGH COLDER AIR WILL HAVE MADE ITS WAY INTO THE REGION FOR SOME TYPE OF WINTRY PRECIPITATION. GIVEN THE MODEL VARIATIONS...FOR SIMPLICITY SAKE...WILL ONLY OFFER A RAIN VERSUS SNOW FORECAST AT THIS TIME. BY WEDNESDAY NIGHT INTO THURSDAY...THIS COASTAL WAVE WILL BE NEAR THE CANADIAN MARITIMES AND NO LONGER BE A FACTOR IN OUR FORECAST. WHAT WILL BECOME A FACTOR IS YET ANOTHER DEEPENING UPPER LOW THURSDAY INTO FRIDAY. GUIDANCE IS OFFERING THIS ONE TO TAKE A FARTHER SOUTH TRACK THAN ITS PREDECESSOR...DEEPEN MORE...AND FUNNEL A STRONGER SURGE OF COLDER AIR INTO OUR REGION. AFTER AN INITIAL ROUND OF ISENTROPIC LIFT ASSOCIATED PRECIPITATION ON THURSDAY...ITS ASSOCIATED COLD FRONT WILL SWEEP THROUGH THE AREA THURSDAY NIGHT. IN ITS WAKE...UPSLOPE SNOW SHOWERS AND GUSTY NORTHWEST WINDS ARE ANTICIPATED IN THE PREFERRED AREAS OF SOUTHEAST WEST VIRGINIA THURSDAY NIGHT INTO FRIDAY. TEMPERATURES THROUGH THE PERIOD WILL TREND LOWER EACH DAY...WITH THE BIGGEST DROP BEING THURSDAY INTO FRIDAY. TUESDAY IS EXPECTED TO BE THE ONLY DAY ABOVE NORMAL WITH THE REST OF THE PERIOD BELOW NORMAL. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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AS OF 650 PM EST FRIDAY... HIGH PRESSURE WILL PROVIDE OUR REGION WITH VFR CONDITIONS TONIGHT AND SATURDAY. WINDS WILL BE LIGHT AND VARIABLE OVERNIGHT AS THE HIGH PASSES ACROSS THE MID ATLANTIC STATES. THE HIGH CENTER WILL PUSH OFF THE COAST SATURDAY NIGHT INTO SUNDAY WHICH WILL BRING SURFACE WINDS AROUND TO THE SOUTHWEST. HIGH CONFIDENCE IN CEILINGS...VISIBILITIES AND WINDS THROUGH THE TAF PERIOD. EXTENDED DISCUSSION... THE NEXT SIGNIFICANT WEATHER WILL ARRIVE ON SUNDAY WITH RAIN AND MVFR OR LOWER CIGS...ESPECIALLY SUNDAY AFTERNOON/NIGHT. ALSO...STRENGTHENING LOW LEVEL WINDS LATER ON SUNDAY MAY LEAD TO LLWS...ESPECIALLY THE BLF AREA. 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. FOR THE REMAINDER OF NEXT WEEK...EXPECT PERIODS OF MVFR CIGS ACROSS EASTERN WV/FAR SW VA...BUT MOSTLY VFR ELSEWHERE WITH A COLDER NW FLOW.
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&& .EQUIPMENT... AS OF 215 PM EST FRIDAY... THE VISIBILITY SENSOR AT KLYH...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...JH/RAB NEAR TERM...KK SHORT TERM...JH LONG TERM...DS AVIATION...AMS/KK EQUIPMENT...RAB

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