Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 022055 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 355 PM EST MON MAR 2 2015 .SYNOPSIS... A COLD FRONT WILL CONTINUE TO MOVE EAST AND OFF THE COAST THIS MORNING. HIGH PRESSURE WILL FOLLOW BEHIND THE FRONT...CROSSING THE OHIO VALLEY TONIGHT AND EXTENDING SOUTH INTO THE MID ATLANTIC REGION TONIGHT. A LOW PRESSURE SYSTEM OVER THE CENTRAL PLAINS ON TUESDAY WILL MOVE NORTHEAST AND WILL PUSH A STRONG COLD FRONT THROUGH OUR AREA ON WEDNESDAY NIGHT. && .NEAR TERM /THROUGH TUESDAY/... AS OF 930 AM EST MONDAY... A COLD FRONT MOVING EAST ACROSS THE REGION THIS MORNING. IN THE WAKE OF THE FRONT...HIGH PRESSURE WILL BUILD INTO OUR REGION THIS AFTERNOON INTO TONIGHT. WSR-88D SHOWED A FEW NARROW BANDS OF SNOW AND RAIN DIMINISHING THIS MORNING. MADE A QUICK UPDATE TO DIMINISH POPS THIS MORNING WITH DRY AIR PUNCH AND DOWNSLOPING EFFECT. LEANED POPS TOWARDS RNK WRF-ARW FOR NEXT COUPLE OF HOURS. MODIFIED TEMPERATURES FOR THIS MORNING INTO THIS AFTERNOON ACCORDING TO SFC OBS AND MODEL TRENDS. AS OF 500 AM EST MONDAY... A COLD FRONT COMES THROUGH THE MORNING AND WILL BE EAST OF THE FORECAST AREA BY NOON. MODELS HOLD A MAJORITY OF THE PRECIPITATION ALONG AND AHEAD OF THE FRONT IN THE FAR WESTERN COUNTY WARNING AREA THIS MORNING. PUSH OF DRIER AIR BEHIND THE FRONT WILL BE ENOUGH TO END CHANCE OF PRECIPITATION AND CLEAR OUR MUCH OF THE FOG AND CLOUD COVER THIS AFTERNOON. HIGH PRESSURE MOVES ACROSS THE OHIO VALLEY TODAY AND WEDGES DOWN THE EAST SLOPES OF THE APPALACHIANS TONIGHT. 850 MB WINDS BEHIND THE FRONT WILL BE 45 TO 55 KNOTS WITH PRESSURE RISES 5 TO 7 MB/6 HOURS THIS MORNING. WILL HAVE WINDS GUSTING JUST BELOW ADVISORY LEVEL...UP TO 50 MPH THIS MORNING. WINDS DIMINISH THIS AFTERNOON AND THE TURN TO THE EAST THEN SOUTHEAST TONIGHT AS THE WEDGE BECOMES ESTABLISHED. THE EAST TO SOUTHEAST WINDS WILL BRING LOW LEVEL MOISTURE BACK NORTH ALONG THE BLUE RIDGE AND EASTERN SLOPES OVERNIGHT. COLDER AIR COMES IN BEHIND THE FRONT TODAY...BUT WITH SHRINKING AREAL COVERAGE OF PRECIPITATION AND SOME SUN IN THE AFTERNOON...TEMPERATURES WILL HOLD STEADY OR SLOWLY RISE. AS WIND DROPS OFF THIS EVENING...TEMPERATURES WILL COOL BUT AS CLOUD FILL BACK IN LATE TONIGHT DROP IN TEMPERATURES WILL BE LIMITED. HAVE ADDED PATCHY DRIZZLE AND FREEZING DRIZZLE AFTER MIDNIGHT FOR THE TYPICAL UPSLOPE AREA ALONG AND EAST OF THE SOUTHERN BLUE RIDGE. BUFKIT SHOWED A WARM NOSE AROUND 3000 FT AGL AND SURFACE TEMPERATURES DROPPING BELOW FREEZING. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... AS OF 330 PM EST MONDAY... COMPLICATED SHORT TERM FORECAST WITH MULTIPLE CONCERNS. TO BEGIN TUESDAY NIGHT...ANY REMNANTS OF EARLIER WEDGE WILL BE LONG GONE TO THE NORTHEAST WITH THE AREA SOLIDLY IN THE WARM SECTOR. TEMPERATURES WILL BE WELL ABOVE FREEZING AND CONTINUING TO RISE DURING THE OVERNIGHT HOURS ON THE HEELS OF A STRONG SOUTHWESTERLY LLJ. CONSEQUENTLY...ANY ASSOCIATED WARM FRONTAL PRECIPITATION WILL ALSO HAVE LIFTED WELL NORTHEAST OF THE REGION. NOW...THE ATTENTION SHIFTS TO THE ARCTIC FRONT APPROACHING FROM THE WEST. A BROAD UPPER RIDGE ACROSS THE CENTRAL/EASTERN GULF...590+ DM AT THAT...WILL AMPLIFY INTO THE SOUTHEAST WHILE A DEEP UPPER TROUGH DIGS INTO THE SOUTHERN PLAINS. A SIGNIFICANT SURGE OF ARCTIC AIR WILL PLUNGE INITIALLY SOUTH INTO THE CENTRAL/SOUTH CENTRAL U.S. AS THE ASSOCIATED ARCTIC FRONT SLOWS ITS PUSH INTO THE MID- ATLANTIC/SOUTHEAST STATES THANKS TO THE AFOREMENTIONED UPPER RIDGE AND THE APPALACHIAN MOUNTAINS. THIS HOLDS THE HEAVIEST RAINFALL WEST OF OUR CWA THROUGH WEDNESDAY MUCH OF THE DAY WEDNESDAY...MAINLY ACROSS THE OH/TN VALLEYS. FINALLY...WEDNESDAY AFTERNOON/EVENING...THE FRONT WILL BEGIN A BETTER SOUTHEASTWARD PUSH AS SHORT WAVE ENERGY KICKS OUT OF THE CENTRAL PLAINS. WOULD EXPECT HEAVIER RAIN TO MOVE INTO THE WESTERN PARTS OF THE CWA BY 00Z WED...THEN BEGIN TO SPREAD EASTWARD OVERNIGHT. MEANWHILE...PART OF THE UPPER TROUGH LAGS BEHIND AND SURFACE LOW PRESSURE DEVELOPS ACROSS THE SOUTHEAST STATES IN RESPONSE. THIS WILL FURTHER DELAY THE PUSH OF THE PRECIPITATION INTO/THROUGH THE CWA...BUT PERHAPS NOT THE SHALLOW COLD ARCTIC AIR ONCE IT MANGES TO CROSS THE APPALACHIANS. QUITE A VARIETY OF SOLUTIONS PRESENTED BY THE MODELS AND WPC AS TO THE WINTER WEATHER THREAT THURSDAY GIVEN THAT THIS IS FAR FROM A NORMAL SYNOPTIC SITUATION FOR A SNOW EVENT IN THIS REGION. THE BIG QUESTION IS NOT WHETHER OR NOT THERE WILL BE PRECIPITATION...BUT HOW QUICKLY WILL THE COLD AIR SPREAD INTO THE REGION BEHIND THE FRONT...BEFORE THE HEAVIER PRECIPITATION MOVES OUT...AND HOW QUICKLY WILL THE COLD AIR BECOME DEEP ENOUGH TO CHANGE THE PRECIPITATION TO SNOW. AM INCLINED AT THIS POINT TO THROW OUT RAIN TO FREEZING RAIN SCENARIOS...NOT ONLY BECAUSE IT IS NOT CLIMATOLOGICALLY OR SYNOPTICALLY FAVORABLE IN THIS SITUATION...BUT THINKING IS THAT COLD AIR WILL BECOME DEEP ENOUGH QUICKLY ENOUGH TO CHANGE RAIN OVER TO SNOW...OTHER THAN A BRIEF PERIOD OF SLEET ALONG THE LEADING EDGE OF THE CHANGEOVER. FURTHERMORE...GROUND TEMPS WILL NOT SUPPORT FZRA AT THE CHANGEOVER TIME AS THE SOUNDING COLUMN COOLS ISOTHERMALLY. FINALLY...THIS IS YET AGAIN A SIGNIFICANT ARCTIC AIR MASS...SO ONCE IT ENTERS THE REGION...COOLING WILL BE QUICK...ESPECIALLY WEST OF I-81. FOR SNOW AMOUNTS...A PRELIMINARY ESTIMATE...FAIRLY CONSISTENT WITH WPC WWD...IS 4-5 INCHES NORTH...2-4 INCHES CENTRAL/WESTERN AREAS...1-2 INCHES VA PIEDMONT...LITTLE TO NONE NC PIEDMONT. SEE THE HYDROLOGY SECTION BELOW FOR FURTHER DETAILS ON THE FLOOD THREAT ASSOCIATED WITH COMBINED RAINFALL AND SNOW MELT. DID ADVERTISE A PERIOD OF MODERATE RAIN WEDNESDAY EVENING FROM WEST TO EAST...BUT HAVE REDUCED THE TIME PERIOD OF SUCH COMPARED TO PREVIOUS FORECAST PACKAGES. TEMPERATURE WISE...A LOT OF NON-DIURNAL TEMPERATURE TRENDS THROUGH THIS FORECAST PERIOD. TEMPERATURES CONTINUING TO RISE TUESDAY NIGHT/WEDNESDAY MORNING AND REMAINING MILD/ABOVE FREEZING UNTIL THE ARCTIC FRONT ARRIVES IN THE WEST WEDNESDAY NIGHT. THE PIEDMONT WILL LIKELY REMAIN ABOVE FREEZING FROM TUESDAY AFTERNOON UNTIL THURSDAY MORNING. LIKEWISE...A NON-DIURNAL COOLING TREND EXPECTED THROUGHOUT THE DAY THURSDAY AS ARCTIC AIR SPREADS INTO THE REGION. THE GFS IN PARTICULAR SHOW SFC TEMPS BELOW ZERO IN OUR WESTERN COUNTIES BY FRIDAY MORNING. GIVEN THAT IT IS EARLY MARCH AND THE 850MB TEMPS ARE ONLY AROUND -16C...AS COMPARED TO -26C A COUPLE OF WEEKS AGO...I FIND THIS SOMEWHAT EXTREME. NONETHELESS...IT IS A VERY COLD AIR MASS AND WELL BELOW NORMAL FOR THIS TIME OF YEAR. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 145 PM EST MONDAY... HIGH PRESSURE WILL BUILD OVER THE REGION ON FRIDAY...AND BE IN CONTROL OF OUR WEATHER PATTERN THROUGH AT LEAST SATURDAY NIGHT. THE HIGH WILL GRADUALLY BUILD INTO THE AREA FROM THE WEST...AND MAKE ITS WAY TO THE COAST BY SATURDAY. THIS WILL ALLOW FOR A TREND TOWARD MILDER CONDITIONS AS THE LOW LEVEL FLOW ACROSS THE AREA BECOMES GRADUALLY MORE SW-W...WHILE A SHORTWAVE RIDGE AND RISING 850 TEMPS TAKE PLACE. SUNDAY INTO MONDAY A GENEROUS AMOUNT OF VARIATIONS IN THE MODELS TAKE PLACE. WHILE BOTH THE GFS AND THE NAM EVENTUALLY COME INTO AGREEMENT OF A LONG WAVE TROUGH OVER THE EASTERN THIRD OF CONUS BY MONDAY OR TUESDAY OR NEXT WEEK...HOW THE SOLUTIONS COME TO BE THAT WAY HAVE NOTABLE DIFFERENCES. THE GFS IS MORE PROGRESSIVE IN ESTABLISHING THE TROUGH IN THE EAST BY SUNDAY...AND ANY SOUTHERN STREAM SYSTEMS EASILY BYPASS OUR REGION EXITING THE U.S. NEAR THE GA/FL BORDER. THE ECWMF IS NOT A QUICK TO ESTABLISH AN EAST COAST TROUGH...AND A SUCH...SOUTHERN STREAM SYSTEMS HAVE A BETTER OPPORTUNITY TO PROGRESS NORTHEAST THROUGH OUR REGION ON THE EAST SIDE OF AN APPROACHING SHORTWAVE TROUGH. OUR FORECAST FOR SUNDAY INTO MONDAY WILL BE A CONSENSUS OF THESE TWO...WITH IT RESEMBLING A WATERED DOWN VERSION OF THE ECWMF IN TERMS OF PRECIPITATION POTENTIAL ON SUNDAY AND SUNDAY NIGHT...AND ALSO STAYING ON MORE OF THE MILD SIDE THAN COLD IN REGARDS TO MONDAY. && .AVIATION /21Z MONDAY THROUGH SATURDAY/... AS OF 1237 PM EST MONDAY... THE COLD FRONT WILL CONTINUE TO PUSH EAST INTO THE ATLANTIC OCEAN THIS AFTERNOON INTO TONIGHT. SCT TO BKN MVFR CLOUDS ARE POSSIBLE THIS AFTERNOON INTO TONIGHT...MAINLY IN THE MOUNTAINS. HIGH PRESSURE WILL WEDGE DOWN THE EAST SLOPES OF THE APPALACHIANS TONIGHT. AS SURFACE AND LOW LEVEL WINDS TURN TO THE EAST AND SOUTHWEST...LOW LEVEL MOISTURE WILL RETURN NORTH ALONG THE SOUTHERN BLUE RIDGE. HIGH CONFIDENCE OF CEILINGS LOWERING TO MVFR AT KBCB AND KDAN AFTER 06Z/1AM. LIGHT RAIN...FREEZING RAIN AND SLEET WILL LIFT NORTHEAST ACROSS OUR REGION LATE TONIGHT INTO TUESDAY MORNING. GUSTY NORTHWEST WINDS WILL DIMINISH QUICKLY LATE THIS AFTERNOON AND EVENING AS HIGH PRESSURE BUILDS IN. A WINTRY MIXTURE TUESDAY MORNING WILL TRANSITION TO MAINLY RAIN TUESDAY AFTERNOON. MEDIUM CONFIDENCE IN CEILINGS...VISIBILITIES AND WINDS DURING THE PERIOD. EXTENDED FORECAST... ANOTHER LOW PRESSURE SYSTEM THAT WILL IMPACT ALL OF THE REGION WILL TRACK FROM THE CENTRAL PLAINS INTO NEW ENGLAND TUESDAY NIGHT INTO WEDNESDAY. THIS WILL RESULT IN SUB-VFR CONDITIONS WEDNESDAY AND THURSDAY WITH WIDESPREAD RAIN AHEAD OF THE FRONT ON WEDNESDAY AND WINTER PRECIPITATION BEHIND THE FRONT WEDNESDAY NIGHT AND THURSDAY. FRIDAY SHOULD SEE A RETURN TO HIGH PRESSURE AND VFR WEATHER. && .HYDROLOGY... AS OF 300 PM EST MONDAY LIKELY TO SEE SOME SUBSTANTIAL RISES ON AREA RIVERS AND STREAMS IN RESPONSE TO UPCOMING RAIN EVENT AND SNOWMELT IN THE MOUNTAINS...QUESTIONS REMAIN ABOUT HOW SUBSTANTIAL. SIGNIFICANT SNOW AMOUNTS ARE NOW CONFINED TO PARTS OF THE UPPER JAMES AND GREENBRIER RIVER BASINS WHERE THE LATEST AVAILABLE ESTIMATES FROM THE NATIONAL OPERATIONAL REMOTE SENSING CENTER SHOW ROUGHLY 1 TO 3 INCHES OF SNOW WATER EQUIVALENT WITH ISOLATED 4 INCHES IN THE HIGHEST ELEVATIONS OF THE GREENBRIER. IN THE OTHER MAJOR RIVER BASINS...NEW...ROANOKE/DAN AND TENNESSEE... MELTING OVER THE WEEKEND AND TODAY HAS REDUCED THE SNOW TO LESS THAN 1 INCH OF SNOW WATER AND IN MOST PLACES ZERO. THE OTHER ELEMENT OF COURSE IS THE QPF. 12Z MODELS (INCLUDING LATEST EC) HAVE NUDGED THE HEAVIEST QPF A LITTLE MORE TO THE WEST...REDUCING AMOUNTS IN THE JAMES AND GREENBRIER SOME. IT STILL APPEARS AS IF 1 TO 2 INCHES COULD FALL ACROSS THE WESTERN BASINS BY 12Z THURSDAY AND COMBINED WITH SNOWMELT THIS COULD PRODUCE AT LEAST MINOR RIVER FLOODING ALONG THE GREENBRIER AND POSSIBLY THE UPPER JAMES. GUIDANCE RECEIVED FROM OHRFC THIS MORNING SUGGESTED MINOR FLOOD STAGE AT ALDERSON WV ON THE GREENBRIER LIKELY BY EARLY THURSDAY WITH THE COMBINED SNOWMELT AND QPF. HOWEVER...GIVEN THE CONTINUED UNCERTAINTIES WILL HOLD OFF ON A FLOOD WATCH AT THIS POINT. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...WINTER WEATHER ADVISORY FROM 7 AM TO 1 PM EST TUESDAY FOR VAZ018>020-022>024-034-035-045>047. WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST TUESDAY FOR VAZ007-009-010-012-015-016. WINTER WEATHER ADVISORY FROM 4 AM TO 1 PM EST TUESDAY FOR VAZ011-013-014-017-032-033-043. NC...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST TUESDAY FOR NCZ001-002-018. WV...WINTER WEATHER ADVISORY FROM 7 AM TO 1 PM EST TUESDAY FOR WVZ507-508. WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST TUESDAY FOR WVZ042. WINTER WEATHER ADVISORY FROM 4 AM TO 1 PM EST TUESDAY FOR WVZ043-044. && $$ SYNOPSIS...RAB NEAR TERM...KK SHORT TERM...RAB LONG TERM...DS AVIATION...KK HYDROLOGY...PC

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