Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 242024 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 424 PM EDT TUE MAR 24 2015 .SYNOPSIS... HIGH PRESSURE WILL REMAIN WEDGED ALONG THE EASTERN SLOPES OF THE APPALACHIANS TONIGHT. A WARM FRONT WILL LIFT SLOWLY NORTH INTO THE AREA LATE WEDNESDAY AHEAD OF A STRONG COLD FRONT APPROACHING FROM THE WEST. THE FRONT WILL CROSS THE REGION LATE THURSDAY... BRINGING MORE WIDESPREAD SHOWERS AND POSSIBLY A FEW THUNDERSTORMS. && .NEAR TERM /THROUGH WEDNESDAY/... AS OF 330 PM EDT TUESDAY... HIGH PRESSURE REMAINS WEDGE AGAINST THE EASTERN FACE OF THE APPALACHIANS THIS AFTERNOON...MAINTAINING AN EAST TO SOUTHEASTERLY WIND FLOW GENERALLY EAST OF INTERSTATE 77. THE HIGH PRESSURE WEDGE IS SHALLOW HOWEVER AND IS LESS INFLUENTIAL WEST OF THE INTERSTATE... WHERE WARMER SOUTHWESTERLY WIND FLOW HAS BEEN DOMINANT. THIS EVENING...AN UPPER LEVEL DISTURBANCE WILL APPROACH FROM THE WEST...BRINGING INCREASING RAIN CHANCES TO THE AREA GENERALLY NORTH OF HIGHWAY 460 THROUGH SUNSET...AND FURTHER SOUTH AFTERWARD. THESE DISTURBANCES ARE EXPECTED TO REMAIN WEAK...AND DO NOT HAVE VERY MUCH MOISTURE TO WORK WITH...SO DO NOT SEE MORE THAN A TENTH OF AN INCH FOR A GIVEN AREA THROUGH THE NIGHT. HOWEVER...THE SPOTTY RAINFALL AND COOLER AIR IN THE WAKE OF THE DISTURBANCE WILL ACT TO ENHANCE THE HIGH PRESSURE WEDGE...RESULTING IN AN INCREASE IN CLOUD COVER THAT WILL PERSIST WELL INTO THE DAY ON WEDNESDAY. EXPECT OVERNIGHT TEMPERATURES TO RANGE FROM THE MID TO UPPER 30S NORTH OF INTERSTATE 64...PLACES THAT ARE DEEPEST IN THE WEDGE... TO THE MID TO UPPER 40S ACROSS THE MOUNTAIN EMPIRE WHERE SOUTHWESTERLY FLOW WILL BE MOST INFLUENTIAL. MAY SEE A COUPLE POCKETS OF LIGHT FREEZING RAIN FOR A FEW HOURS TOWARD DAWN ALONG THE HIGHER RIDGES NORTH OF INTERSTATE 64...BUT ICING WILL BE VERY LIGHT...IF ANY...AND WILL BE CONFINED TO ELEVATED OBJECT AS THE GROUND IS TOO WARM. WHILE WINDS WILL SHIFT MORE SOUTHERLY ON WEDNESDAY AS HIGH PRESSURE PUSHES OFFSHORE...BELIEVE THE COOL AIR HUGGING THE SURFACE EAST OF THE BLUE RIDGE WILL STILL HOLD IN PLACE... ESPECIALLY WITH A TRAIN OF UPPER LEVEL DISTURBANCES TRIGGERING PERIODS OF SPOTTY LIGHT RAIN THROUGH THE DAY. THEREFORE...LOOKING FOR AFTERNOON HIGHS TO HOLD IN THE LOW/MID 50S EAST OF THE BLUE RIDGE...WHILE THE WARMEST TEMPERATURES WILL BE FOUND WEST OF INTERSTATE 77...REACHING THE MID/UPPER 60S ACROSS WESTERN TAZEWELL COUNTY. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... AS OF 345 PM EDT TUESDAY... REMNANT WEDGE CONTINUES TO ERODE WEDNESDAY NIGHT/EARLY THURSDAY IN ADVANCE OF A DEEPENING FULL-LATITUDE UPPER TROUGH LOCATED IN THE CENTRAL U.S. AT THE BEGINNING OF THE FORECAST PERIOD. A WEAK WARM FRONT AND ASSOCIATED ISENTROPIC LIFT IS EVIDENT EARLY THU. ALL OF THE MODELS BROADBRUSH MUCH OF THE FORECAST AREA AND SURROUNDING AREAS WITH LOW QPF...GENERALLY 0.10 INCH OR LESS THROUGH 18Z THU. THROUGH THIS TIME FRAME...ALL OF THE APPRECIABLE FORCING REMAINS WEST OF THE ALLEGHANY FRONT...ACTUALLY EVEN FURTHER WEST ACROSS OH/KY/TN AREA. WITH LIMITED FORCING...DO NOT EXPECT MUCH MORE THAN A FEW SPRINKLES OR HUNDREDTHS OF AN INCH WITHIN THIS TIME FRAME. THROUGH THE DAY THURSDAY...MUCH OF THE FORECAST AREA MOVES INTO A SUBSTANTIAL WARM SECTOR WITH TEMPERATURES SOARING INTO THE 60S AND 70S AS 850MB TEMPS CLIMB TO NEAR +12C. SUPERBLEND TEMPERATURES REMAIN A LITTLE ON THE LOW SIDE...SO AS YESTERDAY BUMPED THEM UP A COUPLE OF DEGREES FOR BETTER AGREEMENT WITH NEIGHBORS AND IN LIGHT OF AT LEAST PARTLY SUNNY SKIES ALLOWING FOR SOME INSOLATION...ESPECIALLY EAST OF THE ALLEGHANYS. TIMING OF THE ARRIVAL OF THE FRONT AND BETTER FORCING HAS SLOWED ABOUT 6 HOURS FROM WHAT WAS INDICATED YESTERDAY. HOWEVER...THE BEST DYNAMIC FORCING ACROSS THE AREA REMAINS IN THE MORNING HOURS ACROSS THE REGION...THEN LIFTS RAPIDLY NORTHWARD INTO NEW ENGLAND. THUS...THE BEST DYNAMICS ARE REMOVED FROM THE BEST THERMODYNAMICS IN THE AFTERNOON/EARLY EVENING. MODEST CAPES ARE FORECAST...GENERALLY LESS THAN 1000 J/KG ON MOST MODELS...AND ONLY IN A NARROW WINDOW FROM AROUND 18Z-21Z. THE ACTUAL FRONT DOES NOT ARRIVE UNTIL AFT 00Z IN THE WEST. THERE REMAINS SUPPORT FOR THUNDER...BUT EVEN LESS SUPPORT THAN YESTERDAY FROM MY VIEWPOINT FOR ANYTHING SEVERE. THERE IS NO LLF EVIDENT IN COINCIDENCE WITH THE BEST THERMODYNAMICS...SO WILL CONTINUE NOT TO MENTION SEVERE IN THE HWO AT THIS TIME. FOR FRIDAY...AS NOTED ABOVE...THE COLD FRONT AND THE COLD AIR IS ABOUT 6 HOURS SLOWER TO REACH THE FORECAST AREA THAN THOUGHT YESTERDAY. THIS WILL DELAY THE POSSIBILITY OF COMBINING FREEZING TEMPERATURES WITH LINGERING PRECIPITATION. THUS...WHILE THE THREAT FOR UPSLOPE SNOW SHOWERS CONTINUES ACROSS THE ALLEGHANYS EARLY FRIDAY...THE THREAT FURTHER EAST APPEARS VERY LIMITED AT THIS POINT. MINOR ACCUMULATIONS OF SNOW...1/2 INCH OR LESS...ARE DEPICTED IN THE GRIDS FOR WESTERN GREENBRIER BY EARLY FRIDAY FROM UPSLOPE -SHSN. A FEW FLURRIES COULD REACH AREAS AS FAR EAST AS BATH...MONTGOMERY...WATAUGA COUNTIES BEFORE THE MOISTURE EXITS THE REGION FRIDAY MORNING. SIGNIFICANTLY COLDER TEMPERATURES EXPECTED FRIDAY AS 850MB TEMPS BEGIN THE PLUNGE TOWARD -15C READINGS BY EARLY SAT...BUT AGAIN...SLIGHTLY LESS IMPACT/SLOWER TO ARRIVE THAN EXPECTED YESTERDAY. WINDS BEHIND THE FRONT FRIDAY WILL BE QUITE SIGNIFICANT AND MAY EVENTUALLY WARRANT A WIND ADVISORY. WIND CHILLS FRIDAY NIGHT SHOULD REMAIN ABOVE CRITERIA. THE COMBINATION OF THE WIND AND FALLING/COLDER TEMPERATURES WILL BE A RUDE AWAKENING THAT WINTER IS NOT YET FINISHED...COMPARED TO RECENT MILD/WARM DAYS. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 345 PM EDT TUESDAY... BEGINNING VERY COLD WITH TEMPERATURES WELL BELOW NORMAL. THE PARENT ARCTIC/CANADIAN HIGHS SETTLES OVER THE REGION SATURDAY WITH TEMPERATURES ABOUT THE LOWEST WE HAVE SEEN SINCE AROUND MARCH 6TH. TEMPERATURES WILL BOTTOM OUT SOME 15 TO 20 DEGREES BELOW NORMAL SATURDAY MORNING WITH WIND AND SUNDAY MORNING FROM RADIATIONAL COOLING. SATURDAY MAX TEMPERATURES WILL STRUGGLE TO REACH 32F IN THE WESTERN MOUNTAINS...30S BULK OF THE CWA...40S PIEDMONT. AN ALBERTA CLIPPER SLATED TO ROTATE THROUGH THE BOTTOM OF THE DEEP EASTERN U.S. UPPER TROUGH SATURDAY REMAINS OF INTEREST AS NOW THE CANADIAN HAS COME ON BOARD WITH THE GFS IN ADVERTISING A SMALL DISTURBANCE ROTATING THROUGH THE BOTTOM OF THE TROUGH SATURDAY. THE TRACK OF THIS SYSTEM HAS VARIED FROM RUN-TO-RUN ON THE GFS FROM GA/SC TO OVER OUR REGION. THE LATEST RUNS OF THE GFS/CANADIAN FOCUS MORE ON EAST TN/WESTERN NC...CLIPPING THE SOUTHWEST PART OF OUR CWA. THE ECMWF IS BEGINNING TO HINT AT THIS SYSTEM AS WELL...BUT NOT TO THE DEGREE OF THE GFS/CANADIAN. THERE WILL ALSO BE UPSLOPE POTENTIAL WITH THE CLIPPER AS WELL. THE TWO SYSTEMS COMBINED COMPELS ME TO CONTINUE TO ADVERTISE LOW CHANCE POPS ACROSS THE ALLEGHANYS AND THROUGH SW VA/NW NC INTO SAT...ENDING BY AFTERNOON. A SLIGHT REINFORCING SHOT OF COLD AIR IS EXPECTED SUNDAY...BUT NOT AS SIGNIFICANT AS THE FRI-SAT EVENT. BEYOND THAT...THE FLOW BECOMES MORE ZONAL WITH A SHORT WAVE...VARYING FROM VERY STRONG ON THE GFS TO VERY WEAK ON THE ECMWF TRACKING INTO THE REGION TOWARD THE VERY END OF THE FORECAST PERIOD. HAVE LOW CHANCE TO CHANCE POPS WITH THIS SYSTEM IN THE WEST MONDAY...NOT TO THE DEGREE THE GFS WOULD ADVERTISE AT THIS POINT. WILL EVALUATE THUNDER POTENTIAL WITH LATER MODELS...BUT HAVE NOT INCLUDED AS OF YET. && .AVIATION /19Z TUESDAY THROUGH SUNDAY/... AS OF 230 PM EDT TUESDAY... HIGH PRESSURE REMAINS SITUATED OVER THE DELMARVA THIS AFTERNOON... MAINTAINING A LIGHT EAST TO SOUTHEASTERLY FLOW GENERALLY EAST OF THE INTERSTATE 77 CORRIDOR. FURTHER WEST...OBSERVING SOUTHWESTERLY WIND FLOW WHERE HIGH PRESSURE IS LESS INFLUENTIAL. SATELLITE INDICATES A CU FIELD WEST OF THE BLUE RIDGE WITH VFR BASES GENERALLY IN THE 5KFT TO 7KFT. RADAR INDICATES A FEW SHOWERS ASSOCIATED WITH AN APPROACHING UPPER LEVEL DISTURBANCE PASSING EAST ACROSS WEST VIRGINIA. THIS EVENING...CLOUD COVER WILL CONTINUE TO INCREASE AS THE DISTURBANCE APPROACHES. MAY SEE A FEW SHOWERS ACROSS THE MOUNTAINS BEFORE SUNSET...BUT MORE WIDESPREAD LIGHT RAIN WILL ENTER THE AREA BETWEEN SUNSET AND MIDNIGHT. WHILE RAINFALL IS EXPECTED TO BE LIGHT AND RESULT IN ONLY SPORADIC/MODEST REDUCTIONS IN VISIBILITY... DO EXPECT THE ADDED MOISTURE TO ENHANCE THE HIGH PRESSURE WEDGED AGAINST THE MOUNTAINS...RESULTING IN LOWERING CEILINGS THROUGH THE NIGHT. EXPECT VFR CONDITIONS TO PERSIST MOST LOCATIONS THROUGH 05Z/06Z...BEFORE CEILINGS BEGIN TO LOWER TO MVFR...AND EVENTUALLY IFR TOWARD DAWN WEDNESDAY FOR SPOTS ACROSS THE MOUNTAINS. DRIER AIR HUGGING THE SURFACE EAST OF THE BLUE RIDGE SHOULD KEEP CEILINGS TO LOW END MVFR. A TRAIN OF WEAK DISTURBANCES WILL CONTINUE TO PUSH ACROSS THE AREA ON WEDNESDAY...KEEPING THE HIGH PRESSURE WEDGE LOCKED IN...WITH SOUTH TO SOUTHEASTERLY WIND FLOW AND ONLY A GRADUAL IMPROVEMENT OF CEILINGS INTO THE AFTERNOON. SOUTHWEST WINDS ARE EXPECTED TO INCREASE AHEAD OF AN APPROACHING COLD FRONT LATE WEDNESDAY NIGHT...ALLOWING FOR IMPROVEMENT TO VFR INTO THURSDAY. THIS COLD FRONT IS EXPECTED TO MOVE INTO OUR AREA THURSDAY EVENING...WITH SHOWERS AND THE POTENTIAL FOR A FEW THUNDERSTORMS. DO SEE SOME POTENTIAL FOR FRONTAL SLOWDOWN AHEAD OF ANOTHER DISTURBANCE APPROACHING FROM THE WEST FRIDAY...RESULTING IN LINGERING RAIN/MOUNTAIN SNOW SHOWERS AND SUB VFR CEILINGS OVER THE WEST. VFR RETURNS TO AREAS EAST OF THE BLUE RIDGE SATURDAY WHILE UPSLOPE DRIVEN MVFR LOW CLOUDS LIKELY PERSIST MOUNTAINS UNDER CONTINUED GUSTY NORTHWEST WINDS. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...NF NEAR TERM...NF SHORT TERM...RAB LONG TERM...AMS/RAB AVIATION...JH/NF

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