Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 280500 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1200 AM EST WED JAN 28 2015 .SYNOPSIS... AN UPPER LEVEL DISTURBANCE WILL DROP SOUTHEAST ACROSS THE REGION TONIGHT BRINGING CONTINUED GUSTY WINDS ALONG WITH SOME MOUNTAIN SNOW SHOWERS OR FLURRIES. HIGH PRESSURE BUILDS IN ON WEDNESDAY...FOLLOWED BY ANOTHER CLIPPER AREA OF LOW PRESSURE FOR THURSDAY. COLD HIGH PRESSURE SHOULD AGAIN FOLLOW THIS SYSTEM WITH ANOTHER ROUND OF COLDER AIR INCLUDING STRONG NORTHWEST WINDS AND MOUNTAIN SNOW SHOWERS FOR THE END OF THE WEEK. && .NEAR TERM /THROUGH WEDNESDAY/...
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AS OF 1155 PM EST TUESDAY... CURRENT TEMPERATURES RUNNING 1-3 DEGREES COOLER IN MANY AREAS THAN ADVERTISED...SO LOWERED AND ADJUSTED MIN TEMPS MORE IN LINE WITH ECMWF MOS MINS...WHICH WERE THE COLDEST AMONG THE THREE MODELS AND APPEARED TO BE ON TRACK. SNOW FLURRIES HAVE BEEN FAIRLY PERSISTENT FROM LWB DOWN TO BCB IN CONJUNCTION WITH NW-SE UPPER DISTURBANCE ON BACK SIDE OF DEEP NE U.S. UPPER TROUGH. RETAINED ADVERTISED POPS/-SHSN ACROSS EASTERN WV...BUT ADDED SNOW FLURRIES INTO THE ALLEGHANY HIGHLANDS...NEW RIVER VALLEY...AND DOWN INTO NORTHWEST NC...COINCIDENT WITH ONGOING LOW CLOUDS...JUST WEST OF THE BLUE RIDGE. SKY CONDITION LOOKED GOOD...SO DID NOT MAKE ANY CHANGES TO THAT. AS OF 710 PM EST TUESDAY... SHORT WAVE ENERGY AND MOISTURE WILL ROTATE AROUND THE BACK SIDE OF BROAD UPPER LOW DRIVING THE BIG NOR EASTER OFF THE NEW ENGLAND COAST AND MOVE THROUGH OUR REGION TONIGHT. LATEST FOG PRODUCT SATELLITE IMAGES SHOW CLOUDS CORRESPONDING WITH THESE FEATURES MOVING IN FROM THE NORTHWEST THIS EVENING. ALL OF THIS IS CAPTURED NICELY BY THE MODELS AND POPS VERIFY NICELY WITH LIGHT UPSTREAM RADAR RETURNS AND LATEST SFC OB FROM KLWB WITH INDICATES 10SM IN LIGHT SNOW. EXPECT SNOW SHOWERS TO ENHANCE A BIT AS THEY ENCOUNTER TERRAIN WITH ACCUMULATIONS OF LESS THAN AN INCH FOR WESTERN GREENBRIER COUNTY. PERHAPS TRACE AMOUNTS DOWN THE FAR WESTERN SLOPES FURTHER SOUTH INTO TAZEWELL COUNTY. A FEW STRAY FLURRIES MAY ALSO BE ENCOUNTERED THROUGH THE NEW RIVER VALLEY/MOUNTAIN EMPIRE REGION BUT POPS NOT HIGH ENOUGH TO WARRANT A MENTION. A GOOD NUMBER OF OBSERVATION SITES SHOWING WIND GUSTS IN THE 20KT TO 30KT RANGE. DESCENDING INVERSION WILL SQUEEZE THE LOW LEVEL FLOW AND CONTINUE THESE GUSTY CONDITIONS WITH GUSTS NEAR 40KT POSSIBLE FOR SOME OF THE RIDGES...ESPECIALLY FROM THE GRAYSON HIGHLANDS AND ALONG THE BLUE RIDGE FROM FLOYD COUNTY SOUTH INTO THE NORTH CAROLINA MOUNTAINS THROUGH ABOUT MIDNIGHT...THEN WINDS WILL SLACKEN TOWARD DAYBREAK. TEMPERATURES CONTINUE TO FALL WITH READINGS ALREADY IN THE LOWER TEENS FOR THE HIGH SPOTS OF WESTERN GREENBRIER. CLOUDS MOVING IN WILL HELP KEEP TEMPS FROM FALLING MUCH FARTHER BUT AREAS FURTHER SOUTH AND EAST OF THE BLUE RIDGE WILL STILL LOSE ANOTHER 10F TO 15F BY MORNING. PREVIOUS AFD... HIGH PRESSURE FINALLY SLIDES IN FROM THE NW WEDNESDAY UNDER BUILDING 5H HEIGHTS ALLOWING FOR SUNNY SKIES AND DIMINISHING WINDS. WITH VERY DRY AIR IN PLACE AND GRADUAL 85H WARMING...EXPECT HIGHS TO BE CLOSER TO THE WARMER MAV MOS ESPECIALLY EAST WHERE SOME MID/UPPER 40S LIKELY...WITH MID 30S TO AROUND 40 WEST.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... AS OF 330 PM EST TUESDAY... THINGS TO REMAIN VERY PROGRESSIVE FOR THE MIDDLE OF THE WEEK WITH THE UPPER RIDGE CROSSING THE AREA WEDNESDAY NIGHT AHEAD OF THE NEXT FAST MOVING CLIPPER APPROACHING FROM THE UPPER MIDWEST. EXPECT INCREASING WARM ADVECTION ALOFT AHEAD OF THIS SYSTEM TO SPREAD A MID/HIGH CLOUD CANOPY IN FROM THE NW ALONG THE UPPER JET ESPECIALLY MOUNTAINS OVERNIGHT BUT DRY. SURFACE HIGH SLIDING EAST IN COMBINATION WITH CLOUDS SHOULD ACT TO HOLD TEMPS UP OUTSIDE THE DEEPER VALLEYS WITH LOWS MOSTLY IN THE 20S INCLUDING A FEW TEENS NW PENDING CLOUD COVERAGE. CENTER OF THE LOW PRESSURE SYSTEM PROGGED TO PASS WELL TO THE NORTH LATER THURSDAY WHILE SWINGING ANOTHER FAST MOVING COLD FRONT INTO THE REGION THURSDAY AFTERNOON. GIVEN BEST DYNAMICS AND LIFT HEADING BY TO THE NORTH...EXPECT MOISTURE TO BE LIMITED UNDER ONLY BRIEF/WEAK RETURN LOW LEVEL FLOW SO PRECIP CHANCES LOOK IFFY OUTSIDE THE MOUNTAINS. HOWEVER DOES APPEAR THAT A BAND OF SNOW/RAIN WILL ARRIVE OVER THE FAR WEST BY MIDDAY AND THEN PERHAPS CLIP THE NORTHERN BLUE RIDGE UPON ATTEMPTING TO CROSS THE RIDGES UNDER A QUICKLY VEERING WESTERLY FLOW. PTYPE LIKELY TO START AS LIGHT SNOW MOUNTAINS BEFORE SWITCHING TO MORE LIQUID NATURE AS BOTH 85H AND BOUNDARY LAYER WARMING TAKE OVER. THUS KEEPING A NARROW SWATH OF LIKELY POPS NW THURSDAY WITH CHANCES ELSEWHERE WEST...BUT MAINLY SLIGHT POPS SOUTH AS WELL AS THE EASTERN THIRD. SNOWFALL AMOUNTS OF PERHAPS AN INCH OR SO WESTERN GREENBRIER WITH OVERALL QPF OF LESS THAN A TENTH OF AN INCH...MAINLY WEST. EXPECTING HIGH TEMPS TO GET A BOOST THURSDAY AFTERNOON GIVEN THE SLOWING FRONT AND PERHAPS MORE SUN OUT EAST WHERE COULD SEE VALUES AROUND 50. THINK ONLY THE FAR NW AND HIGHER ELEVATIONS TO REMAIN IN THE 30S...PENDING TIMING OF CLOUDS AND ANY PRECIP. HOWEVER COULD SEE MOST PUSH INTO THE 40S...AS USUALLY WARMER JUST SOUTH OF THESE CLIPPERS PASSING WAY NORTH WITH MODELS TOO WET...AND TOO COLD SO STAYED ABOVE MOS FOR HIGHS. COLD FRONT FROM THE CLIPPER SCOOTING BY TO OUR NORTH WILL MOVE THROUGH THE REGION EARLY THURSDAY NIGHT...USHERING IN MUCH COLDER AIR FOR THE END OF THE WORKWEEK AND INTO THE WEEKEND. THIS WILL SET UP WHAT LOOKS TO BE PRETTY DECENT NW FLOW SNOW SHOWERS WEST OF THE BLUE RIDGE. ACCUMULATIONS FOR THE FAR WESTERN SLOPES LOOK TO BE AN INCH OR TWO...BUT WESTERN GREENBRIER COUNTY SHOULD PICK UP A TOTAL OF AROUND 5 INCHES BEFORE THINGS START TO WIND DOWN FRIDAY MORNING INTO FRIDAY AFTERNOON. IF LATER MODEL RUNS ARE AS ROBUST WITH THE QPF AND SNOW THIS WILL REQUIRE A WINTER WEATHER ADVISORY AT LEAST FOR WESTERN GREENBRIER THURSDAY NIGHT/FRIDAY MORNING. THE OTHER BIG STORY WILL BE THE VERY STRONG WINDS DEVELOPING THURSDAY NIGHT AND CONTINUING INTO FRIDAY. THE LOW LEVEL FLOW WILL VEER AROUND FROM WEST TOP NORTHWEST AND INCREASE TO 50KTS OR MORE PER THE LATEST GFS. NAM SOUNDINGS ON BUFKIT SHOW THE INVERSION LOWERING TO AROUND 850MB BY FRIDAY MORNING WITH 50KT WINDS RIGHT AT THE TOP OF THE SHALLOW MIXED LAYER BELOW THE INVERSION. IF THIS SCENARIO PLAYS OT AS CURRENTLY ADVERTISED BY THE MODELS IT WILL PRODUCE WIND GUSTS AROUND 50MPH...POSSIBLY HIGHER. WE WILL BE KEEPING A CLOSE EYE ON THIS IN LATER MODEL RUNS TO SEE IF A HIGH WIND WATCH IS NECESSARY FOR THE THURSDAY NIGHT/FRIDAY TIME FRAME. WITH THE COMBINED WIND AND COLD WILL ALSO BE LOOKING AT SOME WIND CHILL VALUES IN THE TEENS TO SINGLE DIGITS WEST OF THE BLUE RIDGE. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 330 PM EST TUESDAY... BELOW NORMAL TEMPERATURES TRENDING TO MUCH BELOW THROUGH THE EXTENDED...ALONG WITH POSSIBILITY OF MORE STRONG NORTHWEST WINDS SUNDAY NIGHT THROUGH MONDAY. UPPER LEVEL PATTERN FOR THE EXTENDED WILL BE SPLIT FLOW WITH A DOMINANT NORTHERN STREAM TROF IN THE EAST AND RIDGE FOR THE PAC NW. THERE IS ENOUGH GENERAL AGREEMENT BETWEEN THE GFS AND ECMWF MEMBERS...WHICH ARE SUPPORTED BY NAEFS ANOMALIES...TO BUY OFF ON THIS WHICH WILL BE A COLD SOLUTION. SATURDAY LOOKS LIKE FAIR WEATHER UNDER COLD HIGH PRESSURE. NEXT SYSTEM DEVELOPS TO OUR WEST AND TRACKS INTO NEW ENGLAND WITH A TRAILING COLD FRONT SWEEPING THROUGH THE REGION SUNDAY NIGHT. WILL NOT SPLIT HAIRS ABOUT PTYPE THIS FAR OUT BUT THE GENERAL TRACK TO OUR WEST AND NORTH WILL KEEP US ON THE WARM SIDE OF THE STORM. POSSIBLE HYBRID WEDGE IN PLACE AT THE ONSET MAY HELP COOL THINGS FOR WINTRY MIX AT ONSET GOING TO RAIN FOR THE BULK OF SUNDAY THEN BACK TO WINTRY AS PCPN TAPERS OFF...THOUGH TYPICAL NW FLOW UPSLOPE SNOW SHOWERS WEST OF THE BLUE RIDGE BECOME ESTABLISHED IN THE COLD AIR BEHIND THE COLD FRONT. MAY ALSO BE LOOKING AT ANOTHER STRONG NW WIND EVENT AS WE GO THROUGH SUNDAY NIGHT AND INTO MONDAY BUT THERE IS PLENTY OF TIME TO WATCH THIS AND SEE HOW LATER MODEL RUNS HANDLE THE EVOLUTION OF LOW LEVEL WINDS. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 1145 PM EST TUESDAY... DEEP COASTAL LOW NORTHEAST U.S. AND ASSOCIATED UPPER TROUGH/CYCLONIC FLOW STILL DOMINATING THE WEATHER ACROSS THE REGION. A COUPLE OF EMBEDDED NORTHWEST FLOW SHORT WAVES AND UPSLOPE FLOW CONTINUING TO ENHANCE CLOUDS ACROSS THE ALLEGHANYS...WITH CLOUDS OCCASIONALLY SPILLING OVER INTO THE NEW RIVER/ROANOKE VALLEY. THIS SHOULD BE THE TREND THROUGH THE NIGHT AS THESE SYSTEMS TRACK SOUTHEAST. LYH/DAN SHOULD REMAIN MOSTLY SKC...WITH SCT-BKN VFR CLOUDS AT ROA...SCT-BKN MVFR CLOUDS FOR BCB...AND BKN-OVC IFR CIGS FOR LWB/BLF. THE UPPER SHORT WAVE TRACKING THROUGH WV/ALONG WITH UPSLOPE MAY SUPPORT OCCASIONAL -SN MAINLY FOR LWB FOR A FEW MORE HOURS. LWB HAS BEEN REPORTING AN MVFR VSBY FOR SEVERAL HOURS...WHICH SEEMS HARD TO BELIEVE GIVEN RADAR COVERAGE...BUT POSSIBLE SINCE RADAR OVERSHOOTING VERY LOW TOPPED ECHOES. WILL INCLUDE A TEMPO MVFR GROUP FOR A FEW HOURS AT BEGINNING OF TAF VALID PERIOD...THEN EXPECT AS UPPER SUPPORT/UPSLOPE DIMINISHES...VFR VSBYS SHOULD PREVAIL. VFR VISIBILITIES ARE EXPECTED ELSEWHERE THROUGH THE TAF VALID PERIOD. VFR CIGS SHOULD RETURN TO EASTERN WV MID-LATE MORNING WED AS WELL AS HIGH PRESSURE BUILDS IN FROM THE WEST. EXPECT VFR CIGS AT ALL TAF SITES AFT 15Z WED MORNING. WINDS WILL CONTINUE TO BE AN ISSUE FOR A FEW MORE HOURS. NW WINDS 10-13KTS WITH GUSTS 18-23KTS PERSIST WEST OF THE BLUE RIDGE...AND LIKELY WILL THROUGH THE NIGHT. MODELS SHOW AN ENHANCEMENT AREA TO THE WINDS NEAR ROANOKE/FLOYD COUNTIES THROUGH THE NIGHTTIME. EVEN DAN HAS BEEN SEEING LOW END GUSTS FOR THE PAST FEW HOURS. WINDS WILL VEER TO THE NNW THROUGH THE DAY WED AND DECREASE TO 5-7KTS BY EVENING...BECOMING CALM/LIGHT AND VARIABLE MOST SITES BY 23Z. MEDIUM TO HIGH CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD. HIGH CONFIDENCE IN VSBYS THROUGH THE TAF VALID PERIOD...EXCEPT MEDIUM TO HIGH CONFIDENCE AT LWB. HIGH CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID PERIOD. EXTENDED DISCUSSION... ANOTHER CLIPPER SYSTEM ARRIVES ON THURSDAY...BRINGING A CHANCE OF SUB-VFR CIGS AND VSBYS...WITH A CHANCE FOR -SHRA...-SHSN IN THE MOUNTAINS. MVFR CIGS LIKELY TO LINGER OVER THE MOUNTAINS THURSDAY NIGHT INTO FRIDAY IN THE WAKE OF THIS SYSTEM WITH STRONG NW WINDS ALSO PERSISTING INTO FRIDAY EVENING. ANOTHER AREA OF HIGH PRESSURE SHIFTS EAST INTO THE AREA SATURDAY WITH VFR EXPECTED INTO SATURDAY NIGHT. THE NEXT LOW PRESSURE SYSTEM HEADING OUT OF THE SW STATES WILL BRING A RETURN OF CLOUDS AND SOME PRECIPITATION ON SUNDAY WITH WIDESPREAD MVFR TO IFR LIKELY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...JH/MBS/RAB SHORT TERM...JH/MBS LONG TERM...MBS AVIATION...JH/RAB

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