Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 300147 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 947 PM EDT WED OCT 29 2014 .SYNOPSIS... A COLD FRONT WILL PUSH OFFSHORE TONIGHT. HIGH PRESSURE WILL BUILD ACROSS THE REGION THURSDAY INTO THURSDAY NIGHT. A SHOT OF COLDER AIR WILL ARRIVE THIS WEEKEND...ASSOCIATED WITH A FAST MOVING CLIPPER SYSTEM FROM CANADA THAT WILL RESULT IN THE SPIN UP OF A STRONG AREA OF LOW PRESSURE IN THE UPPER LEVELS OF THE ATMOSPHERE AS IT REACHES THE MID ATLANTIC REGION SATURDAY. && .NEAR TERM /THROUGH THURSDAY/... AS OF 945 PM EDT WEDNESDAY... A STRAY SHOWER IS MOVING OVER GREENSBORO NORTH CAROLINA AT THIS HOUR...AND THE TREND ON RADAR INDICATES KEEPING POPS HIGHER OVER THE FAR SOUTHEASTERN PORTION OF THE CWA FOR THE NEXT TWO HOURS THAN PREVIOUSLY ADVERTISED. OTHERWISE...THE REST OF THE FORECAST APPEARS ON TRACK...WITH MINOR TWEAKS MADE TO TEMPERATURES AND DEWPOINTS. HIGH PRESSURE BUILDING OVERHEAD AFTER MIDNIGHT SHOULD ALLOW THE WINDS TO SLACKEN. THE 00Z RNK SOUNDING SHOWS PLENTY OF DRY AIR ALOFT...AS THE PRECIPITABLE WATER IS JUST 0.37 INCHES. PREVIOUS VALID DISCUSSION... UPDATED FORECAST REFLECTS REDUCING POPS IN THE EAST WITH ONLY ISOLATED SHOWERS REMAINING FROM FVX-DAN-SIF...ALONG THE BACK EDGE OF THE HIGHER THETA-E AIR. DRIER AIR CONTINUES TO TRACK EAST PER CHANCE IN THETA-E AND DEWPOINTS THIS AFTERNOON/EARLY EVENING. THINK THE SKIES WILL BE CLEARING A LITTLE FASTER AS WELL...SO LOWERED TEMPS SOME THIS EVENING AS LATEST TRENDS SHOW COOLER READINGS THAN EARLIER FORECAST. MOST OF THE SHOWERS WILL BE EAST OF THE CWA BY 9 PM. LOW LEVEL MOISTURE...MAINLY BELOW 850 MB...RETURNS TO THE UPSLOPE AREAS AFTER MIDNIGHT. HAVE ADDED MORE CLOUD COVER IN FOR THE FAR WEST THROUGH THURSDAY AFTERNOON. BUFKIT SOUNDINGS FOR BLF AND LWB SUGGEST IT MAY TAKE MOST OF THE DAY FOR THESE CLOUDS TO CLEAR. MODELS AND BUFKIT DATA SHOWED DRY AIR AT MID AND UPPER LEVELS AS WELL AS 850 MB TEMPERATURES DROPPING TO THE -2 TO +2 RANGE BY THURSDAY MORNING. EXPECT NORTHWEST UPSLOPE WINDS TONIGHT BUT AS SURFACE HIGH PRESSURE BUILDS IN FROM THE OHIO VALLEY BY MORNING WINDS WILL DIMINISH. STAYED ON COOLER SIDE OF GUIDANCE FOR MAXIMUM TEMPERATURES IN THE WEST WHERE MORE CLOUDS ARE EXPECTED ON THURSDAY. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... AS OF 407 PM EDT WEDNESDAY... OUR FIRST WINTER STORM OF THE SEASON MAY BE POSSIBLE FRIDAY NIGHT INTO SATURDAY. A DEEP UPPER LEVEL TROUGH DROPS SOUTH FROM THE WESTERN GREAT LAKES THURSDAY NIGHT...BECOMING A CLOSED LOW AS IT CROSSES THE OHIO RIVER NEAR CINCINNATI FRIDAY EVENING. THE LOW CENTER REACHES CHARLOTTE/COLUMBIA FRIDAY NIGHT INTO SATURDAY MORNING. A SECONDARY SURFACE CYCLOGENESIS OCCURS ALONG THE NORTH CAROLINA COAST SATURDAY INTO SATURDAY NIGHT. CLOUDS INCREASE THURSDAY NIGHT AS THE LOW PRESSURE CENTER APPROACHES FROM THE WEST. LOW TEMPERATURES THURSDAY NIGHT WILL RANGE FROM AROUND FREEZING IN THE MOUNTAIN VALLEYS TO THE UPPER 30S IN THE PIEDMONT. SHOWERS WILL ENTER OUR WESTERN SLOPES FRIDAY MORNING...AND SPREAD EAST AS A DEEP UPPER LEVEL TROUGH DROPS SOUTH FROM THE WESTERN GREAT LAKES. TEMPERATURES ARE WARM ENOUGH THAT PRECIPITATION STARTS AS RAIN. ALL MODELS ARE IN AGREEMENT THAT THIS SYSTEM WILL BRING THE COLDEST AIR WE HAVE SEEN THIS AUTUMN...AND THAT THE SYSTEM WILL PASS RAPIDLY ACROSS OUR AREA. RAIN SHOWERS WILL BECOME WIDESPREAD FRIDAY AFTERNOON. 850MB TEMPERATURES WILL GRADUALLY DROP THROUGH THE DAY AS THE UPPER LOW APPROACHES...WITH THE AIR BECOMING COLD ENOUGH FRIDAY EVENING INTO FRIDAY NIGHT TO RESULT IN A MIXTURE OF RAIN AND SNOW. THE HIGHEST ELEVATIONS WILL HAVE THE BEST CHANCE FOR SNOW AND EVENTUALLY CHANGE OVER TO ALL...SNOW ACROSS MUCH OF THE AREA BY EARLY SATURDAY. TOO EARLY FOR CONFIDENCE IN SNOW ACCUMULATIONS WITH WARM GROUND...UNCERTAINTY WITH SNOW RATES AND QUESTIONS IN ACTUAL TRACK OF THE LOW CENTER. AT THIS POINT LOOKS LIKE NORTHWEST SNOW EVENT WITH SNOW ADVISORY LEVEL ACCUMULATIONS POSSIBLE ALONG THE WESTERN SLOPES THE MOUNTAINS...THEN ANY SNOW TOTALS WILL DECREASE AS ONE HEADS EAST. LEANED TOWARDS THE GFS OVER THE NAM SOLUTION REGARDING SNOW TOTALS. BY EARLY SATURDAY AFTERNOON...THE UPPER LOW WILL PUSH OFF THE NORTH CAROLINA COAST...CAUSING PRECIPITATION TO FADE FROM EAST TO WEST OVER OUR AREA AS WINDS BECOME NORTHWESTERLY. WIND SPEEDS WILL INCREASE DRASTICALLY AS THE PRESSURE GRADIENT BETWEEN THE DEPARTING LOW AND HIGH PRESSURE APPROACHING FROM THE WEST INCREASES TO 10MB TO 12MB. THESE HEALTHY 6 HOUR PRESSURE RISES SHIFT EASTWARD SATURDAY NIGHT TOWARDS THE ATLANTIC COAST...THEN WIND SPEEDS WILL DECREASE AS THE PRESSURE GRADIENT BEGINS TO RELAX OVERNIGHT. WE WILL ALSO HAVE TO CONSIDER WIND HEADLINES FRIDAY NIGHT INTO SATURDAY NIGHT. SNOW SHOWERS WILL LINGER IN THE MOUNTAINS SATURDAY NIGHT...WITH SNOW SHOWERS FADING QUICKLY IN THE NORTHWESTERLY DOWNSLOPE FLOW EAST OF THE BLUE RIDGE. MOISTURE WILL BECOME INCREASINGLY SHALLOW THROUGH THE NIGHT ACROSS THE WESTERN RIDGES... SO ACTUALLY MAY SEE PRECIPITATION TRANSITION MORE TO LIGHT FREEZING DRIZZLE AS OPPOSED TO SNOW SHOWERS. TEMPERATURES BY SATURDAY WILL BE 10-15 DEGREES BELOW NORMAL ACROSS THE REGION. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 407 PM EDT WEDNESDAY... TEMPERATURES WILL MODERATE OVER THE FIRST FEW DAYS OF NEXT WEEK AS THE UPPER LOW MOVES AWAY FROM OUR AREA. HIGH PRESSURE WILL BUILD SOUTHEAST ACROSS OUR REGION SUNDAY. HIGH PRESSURE WILL PASS OVERHEAD ON SUNDAY NIGHT...SO TEMPERATURES STILL PRETTY CHILLY SUNDAY AND SUNDAY NIGHT. AS THE HIGH SHIFTS TOWARD THE CAROLINA COAST ON MONDAY...WINDS WILL SHIFT SOUTHWESTERLY... WHICH WILL BEGIN TO CARRY WARMER AIR FROM THE GULF OF MEXICO NORTHWARD ALONG THE APPALACHIAN CHAIN. THE HIGH CENTER WILL SLIDE OFF INTO THE ATLANTIC OCEAN ON MONDAY NIGHT AS A COLD FRONT APPROACHES FROM THE WEST. THE COLD FRONT WITH CONVECTION AHEAD AND ALONG IT WILL TRAVEL THROUGH OUR REGION ON WEDNESDAY. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... AS OF 714 PM EDT WEDNESDAY... CIGS WILL STAY VFR WITH MID DECK CLEARING THE LYH/DAN AREA BY MIDNIGHT-2AM EDT. THE 18Z NAM IS MOST AGGRESSIVE WITH CLOUDS IN THE WRN SLOPES LATE TONIGHT INTO THURSDAY...BUT LEANED TOWARD MORE OPTIMISTIC CMC/GFS SHOWING SCATTERED CLOUDS AROUND 2-4KFT FROM ROA-BCB WEST THURSDAY. CANNOT RULE OUT SOME BKN CIGS AT BLF IN THE MORNING BUT CONFIDENCE IS LOW AT THIS TIME FOR THIS. WITH SOME GROUND MOISTURE FROM THE SHOWERS...A POTENTIAL EXISTS FOR MVFR/IFR FOG AROUND 09Z AT BLF/LWB ERODING BY 12Z. CONFIDENCE IS MEDIUM ON CIGS/VSBYS. EXTENDED AVIATION DISCUSSION... MAINLY EXPECTING VFR INTO FRIDAY MORNING BEFORE A STRONG STORM SYSTEM MOVES IN FROM THE NORTHWEST. THIS SYSTEM WILL BRING A PROLONGED PERIOD OF POTENTIALLY IFR- LIFR CIGS AND PRECIPITATION...-SHSN OR -SN BLF/LWB AREA...WITH -RA ELSEWHERE. CONSIDERABLE UNCERTAINTY REGARDING THE TRACK OF THIS SYSTEM AND HOW MUCH PRECIP FALLS BUT LOOKS LIKE AVIATION ISSUES WILL ABOUND FROM THE CAROLINAS UP THE EAST COAST INTO THE MID ATLANTIC OVER THE WEEKEND. WINDS WILL ALSO BE STRONG AND GUSTY AS COLDER AIR FILTERS INTO THE SYSTEM AND AS LOW PRESSURE EVOLVES WITH TIME. VFR CONDITIONS ARE EXPECTED ON MONDAY. && .EQUIPMENT... THE AC UNITS FOR THE RADAR SHELTER ARE BAD. RADAR OPERATION WILL BE INTERMITTENT UNTIL SUCH TIME THE AC UNITS ARE FIXED. IF SHELTER TEMPERATURES RISE ABOVE CRITICAL LEVELS WE WILL PLACE THE RADAR INTO STANDBY TO AVOID DAMAGE TO THE TRANSMITTER. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...AMS/PW/WP SHORT TERM...KK LONG TERM...KK AVIATION...AMS/RCS/WP EQUIPMENT...PM

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