Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 201740 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 140 PM EDT MON OCT 20 2014 .SYNOPSIS... A DEEPENING TROUGH OF LOW PRESSURE WILL APPROACH THE AREA TODAY AND CROSS THE REGION TONIGHT INTO TUESDAY...AND THEN STALL AND TRANSITION INTO AN UPPER LOW PRESSURE SYSTEM ACROSS THE MID-ATLANTIC REGION BY WEDNESDAY. FOR OUR REGION THIS SERIES OF EVENTS WILL RESULT IN INCREASED CHANCES OF SHOWERS...ESPECIALLY ACROSS THE MOUNTAINS AND GUSTY NORTHWEST WINDS. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 135 PM EDT MONDAY... HAVE MADE SOME ADJUSTMENTS TO THE FORECAST THAT IMPACT THE FORECAST FOR THIS AFTERNOON INTO THE EARLY EVENING. FIRST...PLENTY OF SUNSHINE THIS AFTERNOON OVER MUCH OF THE REGION IS ALLOWING THE TEMPERATURE TO REACH TO WITHIN A DEGREE OR TWO OF FORECAST HIGH TEMPERATURES ALREADY. CLOUDS ARE APPROACHING FROM THE WEST...BUT THEY WILL NOT ARRIVE BEFORE THE IMPACT OF THE SUNSHINE HELPS TEMPERATURES CLIMB AT LEAST ANOTHER 3 TO 5 DEGREES. AS SUCH...HAVE INCREASED FORECAST HIGHS BY ROUGHLY THIS MUCH ACROSS MOST OF THE REGION. SECONDLY...THE APPROACHING LIGHT PRECIPITATION CURRENTLY IN SOUTHERN WEST VIRGINIA IS ON TRACK TO ENTER THE REGION AS CURRENTLY FORECAST. HOWEVER...BOTH THE HRRR AND RNK WRK ARW SOLUTIONS...AND CURRENT REGIONAL RADAR TRENDS...SUGGEST A BIT MORE OF A BREAK BETWEEN THIS FIRST WAVE...AND THE SECOND ONE THAT IS EXPECTED TO ARRIVE THIS EVENING. AS SUCH...HAVE ATTEMPTED TO DEPICT THIS PATTERN WITHIN THE HOURLY NDFD POP AND WEATHER GRIDS DURING THIS TIME FRAME. NO OTHER SIGNIFICANT CHANCES AT THIS TIME. AS OF 1045 AM EDT MONDAY... ALL FROST/FREEZE PRODUCTS HAVE EXPIRED AND VISIBLE SATELLITE IMAGERY IS SHOWING A GOOD AMOUNT OF SUNSHINE ACROSS THE REGION THIS MORNING. HOWEVER...UPSTREAM RADARS SHOW A BAND OF PCPN APPROACHING FROM THE WEST ASSOCIATED WITH A SHORT WAVE ROTATING AROUND THE UPPER TROF MOVING THROUGH THE EASTERN US. MESO MODELS SEEM TO HAVE A GOOD GRASP OF THE SITUATION AND BASED ON THIS...WILL BUMP TIMING OF POPS UP A COUPLE OF HOURS TO REFLECT EXPECTED TRENDS. OTHER PARAMETERS ARE ON TRACK WITH CURRENT GRID SET SO WILL FRESHEN WITH CURRENT DATA AND MAKE ONLY MINOR TREND ADJUSTMENTS. .PREVIOUS AFD... TEMPERATURES WILL RISE QUICKLY MELTING AWAY ANY FROST AFTER SUNRISE. SOUTHWEST WINDS WILL START TO INCREASE AROUND NOON...AND BE NEAR 10 MPH AT MOST LOCATIONS BY THE AFTERNOON. HIGH LEVEL CLOUD COVER WILL BE ON THE INCREASE INTO THIS AFTERNOON FROM WEST TO EAST ACROSS THE REGION WITH THE APPROACH OF THE UPPER TROUGH. LEANED HIGH TEMPERATURES THIS AFTERNOON CLOSE TO THE ADJMETBC WITH READINGS FROM THE MID 50S IN THE NORTHWEST MOUNTAINS TO THE UPPER 60S IN THE PIEDMONT. SCATTERED SHOWERS TONIGHT ESPECIALLY ACROSS THE MOUNTAINS AS ANOTHER WEAK UPPER LEVEL DISTURBANCE PASSES ALONG THE APPALACHIAN CHAIN IN ADVANCE OF OUR NEXT COLD FRONT. THE SOUTHWESTERLY WIND FLOW AND INCREASED CLOUD COVER WILL MAKE FOR WARMER OVERNIGHT TEMPERATURES WITH LOWS GENERALLY IN THE 40S IN MOST LOCATIONS...ALTHOUGH A FEW OF THE HIGHER RIDGES MAY REMAIN IN THE LOWER 50S.
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&& .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... AS OF 415 AM EDT MONDAY... FOCUS THROUGH THE ENTIRE SHORT TERM WILL BE ON A SLOW MOVING CLOSED UPPER LOW THAT AT THE BEGINNING OF THE PERIOD WILL BE ACROSS THE WESTERN GREAT LAKES...MEANDERING TOWARD THE MID- ATLANTIC REGION WED-THU. AFTER SEVERAL DAYS OF MODEL RUNS TAKING THE CENTER OF THIS SYSTEM FURTHER NORTH...THE LATEST MODEL RUNS HAVE TRENDED FURTHER SOUTH ONCE AGAIN...BUT REMAINING FAR ENOUGH EAST THAT IT WILL STILL LEAVE THE CWA ON THE DRIER SOUTHWEST SIDE OF THE SYSTEM. THE PRIMARY...LEADING WAVE AND ASSOCIATED LIGHT PRECIPITATION WILL TRACK FROM NW TO SE ACROSS THE REGION TONIGHT...THEN TUE INTO EARLY WED...THE UPPER LOW WILL DIVE TO ITS SOUTHERN MOST POSITION...TOWARD EAST CENTRAL VA. IN SO DOING...THE NEXT LOBE OF PVA WILL WILL TRACK FROM NORTH TO SOUTH ACROSS THE REGION AND RESULT IN A SLIGHT UPTICK IN RAIN SHOWER COVERAGE. OTHERWISE...MUCH OF THE PERIOD WILL BE CHARACTERIZED BY CYCLONIC FLOW...ABUNDANT CLOUD COVER...SCT -SHRA...MAINLY MOUNTAINS AND AREAS NORTH OF U.S. 460. THE BEST OVERALL COVERAGE OF PRECIPITATION THROUGH THE PERIOD SHOULD COME WITH THIS AFOREMENTIONED LOBE OF PVA AS THE UPPER LOW ROTATES TO A POSITION JUST OFF THE DELMARVA BY WED EVENING. TOTAL QPF THROUGH THE PERIOD WILL RANGE FROM ABOUT 1/3 INCH NORTHERN GREENBRIER COUNTY TO TRACE AMOUNTS AT BEST ACROSS MOST OF THE NC AND VA PIEDMONT COUNTIES. THE MAJORITY OF THE CWA WILL SEE LESS THAN 1/10 INCH OF PRECIPITATION THROUGH THE ENTIRE EVENT. SLOW IMPROVEMENT CAN BE EXPECTED THU AS THE UPPER LOW ROTATES BACK TOWARD NEW ENGLAND...ALLOWING DRIER AIR FROM THE MIDWEST TO BEGIN TO SPREAD INTO WESTERN AREAS. TEMPERATURES WILL BE QUITE COOL THROUGH THE PERIOD WITH ABUNDANT CLOUD COVER AND 850MB TEMPS HOVERING IN THE LOW SINGLE DIGIT CENTIGRADE RANGE. THERE IS A POCKET OF NEAR 0C 850MB TEMPS ON THE BACK SIDE OF THE UPPER LOW THAT SETTLES DOWN OVER THE WESTERN PART OF THE CWA EARLY THU...BUT THE CHANCE OF PCPN AT THAT TIME IN THAT REGION IS NEAR ZERO...SO NO CONCERNS WITH WINTER PRECIPITATION THROUGHOUT THIS EVENT...EVEN AT HIGHER ELEVATIONS. WE MAY NEED TO ENTERTAIN FROST/FREEZE ADVISORIES LATE IN THE WEEK ONCE AGAIN...BUT AGAIN APPEARS TO BE A MARGINAL SITUATION. USED A MODEL BLEND OF MAX/MIN TEMPS THROUGHOUT THE PERIOD. MAX TEMPS WILL BE ABOUT 10 DEGREES BELOW NORMAL THROUGH MUCH OF THE PERIOD...WITH MIN TEMPS NEAR NORMAL. && .LONG TERM /FRIDAY THROUGH SUNDAY/... AS OF 445 AM EDT MONDAY... THE CLOSED UPPER LOW WILL FINALLY LIFT AWAY FROM THE REGION FRI- SAT AS A BROAD UPPER RIDGE BUILDS FROM THE CENTRAL U.S. INTO THE EASTERN U.S. THIS UPPER RIDGE WILL EFFECTIVELY SHUT OFF ALL GULF MOISTURE FROM THE REGION FOR SEVERAL DAYS AS WELL AS LOCKING ANY REALLY COLD AIR WELL NORTH OF THE CANADIAN BORDER. A WEAK...DRY UPPER DISTURBANCE WILL TRACK FROM NW TO SE ACROSS THE REGION FRI-SAT...WHICH AT THIS POINT APPEARS TO DO LITTLE MORE THAN BRING A FEW MID/HIGH CLOUDS. HIGH PRESSURE AT THE SURFACE AND ALOFT WILL THEN DOMINATE FOR THE WEEKEND. THIS WILL PROVIDE MOSTLY SUNNY CONDITIONS FOR A CHANGE ALONG WITH SEASONAL TEMPERATURES...LOWS IN THE 40S AND HIGHS IN THE 60S WEST AND 70S EAST. SHOULD BE A BEAUTIFUL WEEKEND FOR THE ENTIRE REGION. && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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AS OF 100 PM EDT MONDAY... TAF PERIOD WILL START OFF GOOD ENOUGH WITH VFR FOR ALL SITES. HOWEVER...RADAR SHOWS A BAND OF PCPN HEADING IN FROM THE WEST ASSOCIATED WITH SHORT WAVE ENERGY ROTATING THROUGH THE UPPER TROF MOVING INTO THE ERN US. SITES MOST AFFECTED BY THE PCPN WILL BE FROM THE BLUE RIDGE WEST. UPSTREAM LOCATIONS ALSO DO NOT SHOW VERY LOW CIGS WITH THIS PCPN. WILL TIME THE BAND OF PCPN WEST TO EAST EARLY IN THE PERIOD AND KEEP CIGS VFR WITH A TEMPO TO MVFR FOR VSBY WITH SHOWERS FROM THE RIDGE WEST. LOW LEVEL MOISTURE LAGS A BIT SO CIGS LOOK TO STAY UP THROUGH EARLY TONIGHT. FLOW IS A BIT LAZY IN SWINGING AROUND TO A GOOD NWLY UPSLOPE DIRECTION AND THIS LOOKS TO PREVENT KBLF FROM HAVING A SOLID IFR CIG SET IN. SHOULD BE ENOUGH CLOUDS AND ENOUGH OF A LIGHT WIND TO KEEP THINGS MIXED AND PREVENT SIGNIFICANT OBVIS FROM SETTING UP. ADDITIONAL SHORT WAVE ENERGY WILL SWING THROUGH THE REGION OVERNIGHT...BUT THE BEST SHOT LOOKS TO HOLD OFF UNTIL VERY LATE IN THE TAF PERIOD WHEN DIURNAL HEATING AND A BETTER NW UPSLOPE FETCH WILL HELP GET SHOWERS AND LOWER CIGS GOING WEST OF THE RIDGE. WINDS MAY BE A BIT GUSTY EARLY IN THE PERIOD...THEN AGAIN VERY LATE IN THE PERIOD. EXTENDED AVIATION DISCUSSION... AN UPPER LEVEL TROUGH WILL CROSS THE AREA TUESDAY MORNING AND DEEPEN INTO A NEARLY STATIONARY CLOSED LOW OVER THE MID-ATLANTIC REGION BY WEDNESDAY. THE SYSTEM WILL MAKE SLOW MOVEMENT NORTHEAST THROUGH THURSDAY. FOR OUR REGION...THE MAIN IMPACT WITH BE A PERSISTENT NORTHWEST GUSTY WIND AND SCATTERED RAIN SHOWERS THAT WILL IMPACT PRIMARILY THE PREFERRED UPSLOPE REGION OF SOUTHEAST WEST VIRGINIA. MVFR CLOUDS WILL ALSO BE COMMON ACROSS THE MOUNTAINS DURING THIS TIME PERIOD...BUT FROM ROA TO LYH TO DAN CONDITIONS ARE LIKELY TO REMAIN VFR THROUGH THIS PERIOD. THE PERSISTENT TROUGH WITH NORTHWEST FLOW AND LOW-LEVEL UPSLOPE CLOUDS IN WEST WILL LIKELY BE REPLACED BY AN UPPER LEVEL RIDGE BY FRIDAY OR SATURDAY...FOR DRY AND WARM CONDITIONS.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...KK NEAR TERM...DS/KK/MBS SHORT TERM...RAB LONG TERM...NF/RAB AVIATION...MBS

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