Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 210021 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 721 PM EST THU NOV 20 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD EAST ACROSS OUR REGION OVERNIGHT INTO FRIDAY AND SLIDE TO THE EAST BY SATURDAY NIGHT. AS THE HIGH MOVES FURTHER OFF THE COAST ON SUNDAY...A STRONG LOW PRESSURE SYSTEM WILL MOVE INTO THE WESTERN GREAT LAKES AND PUSH A WARM FRONT THROUGH THE AREA. THIS WILL BRING A GOOD CHANCE OF RAIN ON SUNDAY...BUT ALSO SOME WARMER AIR BEFORE ANOTHER COLD FRONT ARRIVES TUESDAY AND RETURNS TEMPERATURES TO MORE SEASONABLE LEVELS FOR THANKSGIVING. && .NEAR TERM /THROUGH FRIDAY/... AS OF 700 PM EST THURSDAY... QUICK UPDATE TO MATCH OBSERVATIONAL TRENDS. NO CHANGE IN FORECAST THINKING FOR THE OVERNIGHT. PREVIOUS VALID DISCUSSION... AS OF 230 PM EST THURSDAY... HIGH PRESSURE BUILDS IN WITH FLOW BECOMING NORTHWEST OVERNIGHT AS THE UPPER TROUGH AXIS PASSES OVERHEAD INTO FRIDAY MORNING. UPSLOPE WINDS IN THE WESTERN AREAS WILL RESULT IN SOME CLOUDS WITH POTENTIAL FOR FLURRIES AND SNOW SHOWERS. BECAUSE THERE IS VERY LITTLE MOISTURE AVAILABLE...DECREASED CLOUD COVER IN THE WEST AND TRIMMED BACK SNOW SHOWERS/FLURRIES TO JUST GREENBRIER VALLEY. WINDS TONIGHT LOOK TO STAY A BIT GUSTY ESPECIALLY FOR THE RIDGES. LOW TEMPERATURES TONIGHT WILL RANGE FROM TEENS IN THE NORTHWEST MOUNTAINS TO THE MID 20S IN THE PIEDMONT. HIGH PRESSURE WILL BE CENTERED OVER THE REGION FRIDAY. TEMPERATURES WILL BE 10 TO 15 DEGREES BELOW NORMAL WITH MAXIMUM READINGS FROM THE MID 20S IN THE NORTHWEST TO THE LOWER 40S IN THE PIEDMONT. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... AS OF 230 PM EST THURSDAY... ARCTIC HIGH PRESSURE WILL BUILD ACROSS THE REGION AGAIN FRIDAY NIGHT RESULTING IN CLEAR SKIES BUT VERY COLD TEMPS WITH LOWS IN THE MID/UPPER TEENS TO MID 20S. COLDEST TEMPS MAY ACTUALLY RESIDE OUT EAST WHERE THE CENTER OF THE RIDGE WILL BE OVERHEAD PROVIDING THE BEST RADIATIONAL COOLING SETUP. SHORTWAVE RIDGING INCREASES SATURDAY AHEAD OF THE DEVELOPING SOUTHERN STREAM LOW PRESSURE SYSTEM BACK ACROSS TX INCLUDING THE NORTHERN GULF COAST. THIS ALONG WITH THE SURFACE HIGH MOVING OFFSHORE SHOULD BRING BACK RETURN SW FLOW ALONG WITH STEADY WARMING ALOFT THAT WILL PUSH HIGHS WELL INTO THE 40S AND LOW 50S IN SPOT PENDING DEGREE OF WARM ADVECTION MID/HIGH CLOUDS. MOISTURE SLOWLY INCREASES FROM SW TO NE SATURDAY NIGHT WITH SOME INFLUX OF LOW LEVEL MOISTURE SOUTHERN BLUE RIDGE AS ISENTROPIC LIFT GETS GOING. HOWEVER THE MID LEVELS LOOK VERY DRY SO KEEPING POPS OUT SATURDAY NIGHT...BUT WARMER WITH LOWS 40S FAR WEST PER SOUTH/SE BREEZES AND MAINLY 30S ELSW. COMPLEX LOW PRESSURE SYSTEM WILL SWING NORTH UP ACROSS THE MID MISSISSIPPI VALLEY SUNDAY WHILE PUSHING A WARM FRONT NE INTO THE AREA SUNDAY AND TO THE NORTH LATE SUNDAY NIGHT. BROAD AREA OF LIFT ELONGATED NW-SE ALONG THIS AXIS TO QUICKLY PIVOT ACROSS MOSTLY SUNDAY AFTERNOON INTO SUNDAY EVENING AS MOST GUIDANCE HAS SLOWED DOWN THE ONSET QUITE A BIT. HOWEVER GIVEN THE STRENGTH OF THE UPPER JET AND INITIAL ISENTROPIC POTENTIAL PER SE FLOW...WILL CONTINUE TO GO A BIT FASTER WITH ARRIVAL BUT SLOW ENOUGH TO AVOID ANY PTYPE PROBLEMS AT THE START. SETUP ALSO STILL SUGGESTS THAT HEAVIEST RAIN COULD SPLIT WITH HEAVIEST SOUTHERN HALF AS BEST DYNAMICS PASS WELL TO THE NW AND INSTABILITY TO THE SOUTH/SE. THIS ALONG WITH ARRIVAL OF PRECIP INTO LOWER DEWPOINTS SUGGESTS A WEAK INDUCED WEDGE TO TAKE SHAPE WITH BEST SEVERE PARAMETERS INCLUDING STRONG WINDS PASSING OVERTOP THE WEAK COOL POOL SO SEVERE THREAT STILL APPEARS LOW. OTHER CONCERN REMAINS WITH STRONG SE WINDS ACROSS THE FAR SW JUST AHEAD OF THE PRECIP AS APPROACH OF THE RAIN TURNS THE FLOW MORE SE BEFORE THE INVERSION TRAPS THE HIGHER SPEEDS ALOFT. LATEST SOUNDINGS NOT OVERLY IMPRESSIVE IN MIXING DOWN STRONGER WINDS BUT WITH A 50-60 KT JET JUST ABOVE THE RIDGETOPS BUMPED UP SPEEDS AND MENTION IN THE HWO. OTRW POPS INCREASING QUICKLY FROM THE SW SUNDAY WITH HEAVIEST SUNDAY AFTERNOON INTO THE EVENING BEFORE DRY SLOTTING TAPERS TO CHANCE LATER SUNDAY NIGHT. QPF STILL ON THE ORDER OF AROUND A THIRD OF AN INCH NW TO ONE HALF TO AN INCH SOUTH. HIGHS SUNDAY A BIT BELOW MOS GIVEN WEDGE ONSET BUT STILL 40S TO LOW 50S MOST SPOTS WITH LITTLE FALL SUNDAY NIGHT. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 1230 PM EST THURSDAY... DEEP MOISTURE/LIFT ASSOCIATED WITH THE PASSING WARM FRONT FROM SUNDAY WILL HAVE PUSHED TO THE NE BY EARLY MONDAY AIDED BY A VERY STRONG JET ALOFT AND SUBSEQUENT DRY SLOT AHEAD OF THE LAGGING COLD FRONT. THIS SHOULD MAKE FOR REDUCED SHOWER CHANCES ON MONDAY EXCEPT PERHAPS THE FAR EAST WITH THE EXITING MOISTURE LOBE...AND WEST OF THE BLUE RIDGE LATE AS THE FRONT APPROACHES. WITH SUCH SHALLOW LEFTOVER MOISTURE AND WEDGING...DO EXPECT THE STRONG WINDS ALOFT TO MIX THINGS OUT ALLOWING FOR VERY WARM 85H READINGS TO MIX DOWN ACROSS THE REGION IN THE AFTERNOON. THIS SUPPORTS GOING AS LEAST AS WARM AS THE LATEST BLENDED MOS VALUES WHICH PUSHES MOST OF THE MOUNTAINS INTO THE 60S AND AROUND 70 OUT EAST. EARLIER CLEARING COULD MEAN SOME HIGHS CLOSE TO 70 NEAR THE BLUE RIDGE AND EVEN MID 70S PIEDMONT ON A GUSTY SW BREEZE. FRONT CROSSES THE REGION MONDAY NIGHT INTO TUESDAY WITH A FEW SHOWERS POSSIBLE WHILE MUCH OF THE COLD AIR LAGS THE BOUNDARY GIVEN THE STRONG SW FLOW ALOFT. AGAIN MAY BE VOID OF MUCH SHRA BUT LEAVING IN A LOW POP TO COVER ISOLATED COVERAGE BUT DECREASING BY TUESDAY AFTERNOON BEHIND THE BOUNDARY. SHOULD AGAIN BE PRETTY MILD MONDAY NIGHT PER LOWS IN THE 40S AND MOSTLY 50S TO AROUND 60 SE TUESDAY IF NOT WARMER ESPCLY IF THE FRONT SLOWS. COOLER AIR SHOULD FINALLY MAKE SOME INROADS WEDNESDAY INTO THURSDAY BUT TO WHAT DEGREE REMAINS IN QUESTION GIVEN QUITE DIFFERENT SCENARIOS IN DAYS 6-7 IN LATEST MODELS. COLDER GFS MORE PRONOUNCED IN DIGGING A DEEP 5H TROUGH OVER THE EAST WHILE THE ECMWF MORE ZONAL WITH MORE ENERGY SPILLING OVER THE RIDGE FARTHER TO THE WEST AND THE CMC IN BETWEEN. THIS SPELLS DIFFERENCES IN TEMPS BY 10-15 DEGREES INTO THANKSGIVING ALONG WITH ADDED UPSLOPE PRECIP VS JUST DRY WITH SEASONAL TEMPS. GIVEN TRENDS WITH MORE TROUGHING OVER THE EAST...GOING COOLER BUT A BIT ABOVE THE GFS WHILE KEEPING THINGS DRY BUT A GOOD 5-10 DEGREES BELOW NORMAL. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... AS OF 645 PM EST THURSDAY... OVERNIGHT...AS WINDS BECOME MORE NORTHWEST AND UPSLOPE FLOW IS ENHANCED...CIGS COULD 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. MAIN CONCERN THROUGH THE TAF VALID PERIOD WILL BE THE WIND. GUSTY WESTERLY WINDS EXPECTED THROUGH THE TAF VALID PERIOD AS THE GRADIENT TIGHTENS UP IN RESPONSE TO THE APPROACHING ARCTIC HIGH. 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. VFR CONDITIONS WILL PREVAILS FRIDAY AS HIGH PRESSURE SLIDES EAST ACROSS THE REGION. EXTENDED DISCUSSION... FRIDAY NIGHT 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 245 PM EST THURSDAY... 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...KK/MBS NEAR TERM...KK/PC SHORT TERM...JH LONG TERM...JH AVIATION...KK/PC EQUIPMENT...RAB

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