Issued by NWS Blacksburg, VA
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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --000 FXUS61 KRNK 131803 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 103 PM EST FRI FEB 13 2009 .SYNOPSIS... HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE REGION BY TONIGHT. GUSTY WEST WINDS WILL GRADUALLY DIMINISH THIS AFTERNOON. A FAST MOVING LOW PRESSURE SYSTEM WILL PASS ACROSS THE CAROLINAS ON SATURDAY...BRINGING A CHANCE FOR SOME LIGHT PRECIPITATION. && .NEAR TERM /THROUGH TONIGHT/... WINDS HAVE DIMINISHED SOMEWHAT...BUT WITH A NEARLY ZONAL AND SLIGHTLY CONFLUENT FLOW ALOFT ACROSS THE REGION TODAY...THE PRESSURE GRADIENT WILL REMAIN FAIRLY STRONG. GUSTY WEST TO NORTHWEST WINDS WILL CONTINUE THROUGH MUCH OF THE DAY...STRONGEST ON THE HIGHER RIDGES ALONG THE BLUE RIDGE AND INTO THE FOOTHILLS. THOUGH IT LOOKS LIKE WINDS WILL REMAIN BELOW ADVISORY CRITERIA...WIND GUSTS... ESPECIALLY THROUGH THE MORNING...WILL BE AROUND 40 MPH. WITH THE ZONAL FLOW TODAY...THERE IS ONLY WEAK COLD ADVECTION AT THE MOST. NEARLY FULL SUN IS EXPECTED TODAY. ONLY EXCEPTION MAY BE THE NW PIEDMONT OF NC AND SOUTHSIDE VA WHERE MODELS INDICATE MTN WAVE CIRROSTRATUS MAY BE FAIRLY THICK. THICKNESSES SUPPORT HIGHS FROM THE LOWER AND MID 50S IN THE MTNS...TO THE LOWER AND MID 60S IN THE NW NC PIEDMONT. TONIGHT SHOULD START OFF FAIRLY CLEAR...AND WITH SFC HIGH PRESSURE FINALLY MOVG OVERHEAD...I EXPECT ALL BUT THE RIDGES TO DECOUPLE EARLY IN THE EVENING. THUS TEMPS SHOULD DROP OFF FAST IN THE EVENING. THE SHORT WAVE CURRENTLY OVER NM/KS SHOULD MOVE RAPIDLY EASTWARD IN THE ZONAL FLOW ALOFT...AND TEMPS SHOULD LEVEL OFF OVERNIGHT AS OVERRUNNING CLOUDS AHEAD OF THE SHORT WAVE MOVE IN. I HAVE LEANED TOWARD THE COLDER MET MOS LOWS...WITH VALLEYS A FEW DEGREES COLDER THAN GUIDANCE. MODELS HAVE SLOWED DOWN THE ARRIVAL OF OVERRUNNING PRECIP UNTIL AFTER 12Z SATURDAY. SINCE WE ALREADY HAD CHC POPS AFTER MIDNIGHT...AND I EXPECT THE SHORT WAVE TO MOVE RAPIDLY EASTWARD...I HAVE NOT REMOVED POPS COMPLETELY IN THE SWRN CWA...BUT DID CUT THEM BACK. IF PRECIP MOVES IN BEFORE DAYBREAK...THEN EVAPORATIONAL COOLING WOULD BE ENOUGH TO PRODUCE SOME SLEET BASED ON MODEL TEMP PROFILES. HOWEVER...QPF WOULD BE VERY LIGHT...AND GROUND TEMPS WILL BE WARM...SO I DO NOT FORESEE ANY ROAD PROBLEMS IF IT OCCURS. && .SHORT TERM /SATURDAY THROUGH MONDAY/... NO SIGNIFICANT CHANGES WERE MADE TO THE FORECAST ON SATURDAY...WITH SOUTHERN STREAM ENERGY MAINTAINING THE HIGHEST THREAT OF OVERRUNNING PRECIPITATION ACROSS THE SOUTHERN AND SOUTHWESTERN PORTION OF THE BLACKSBURG FORECAST AREA. UPPER FLOW REMAINS RELATIVELY ZONAL...AND WITH LIMITED DYNAMICS AND RATHER LACKLUSTER UPWARD VERTICAL MOTIONS FIELDS DUE TO WEAK ISENTROPIC LIFT...ANY PRECIPITATION THAT THE AREA EXPERIENCES WILL LIKELY BE LIGHT...GENERALLY A TRACE TO NO MORE THAN ONE TENTH OF AN INCH. LOWER ATMOSPHERIC THERMAL PROFILES ARE STILL SOMEWHAT PROBLEMATIC FOR PRECIPITATION TYPE...WITH A THREAT OF MIXED PRECIPITATION UNTIL MID TO LATE MORNING WHEN THE BOUNDARY LAYER TEMPERATURES HAVE WARMED UP A BIT...AND AS THE WARM ADVECTION LAYER DEEPENS. HOWEVER...THIS WILL BE A MARGINAL EVENT...AND WITH A WARM GROUND...NO SIGNIFICANT ICING OR ACCUMULATIONS OF SLEET OR FREEZING RAIN ARE EXPECTED. REGARDLESS...IN-SITU DEEPENING WEDGE OF COOL AIR AND ABUNDANT CLOUD COVER SHOULD KEEP MOST AREAS WELL BELOW GUIDANCE...AND THIS ALREADY REFLECTED WELL IN CURRENT SET OF GRIDS. AS THE SOUTHERN STREAM WAVE PASSES BY TO THE EAST BY SATURDAY AFTERNOON...ANY LINGERING PRECIPITATION SHOULD END. HOWEVER...INCREASING COOL AIR ADVECTION AND UPSLOPING ON SATURDAY NIGHT MAY ALLOW FOR THE REDEVELOPMENT OF SOME SHOWERY WIDELY SCATTERED PRECIPITATION ACROSS THE FAVORED AREAS WEST OF THE BLUE RIDGE. APPROACH OF ANOTHER SHORT WAVE WILL BRING ANOTHER INCREASE IN THE THREAT FOR PRECIPITATION LATER SUNDAY INTO MONDAY MORNING...BEFORE THIS SYSTEM PASSES OFF TO THE SOUTH AND EAST. A CONTINUATION OF SLOW COOL ADVECTION AS HIGH PRESSURE TRIES TO BUILD IN FROM THE NORTH AND WEST MAY ALLOW FOR A CHANGEOVER TO SNOW...EVEN INTO THE NORTHWESTERN NORTH CAROLINA PIEDMONT LATER SUNDAY NIGHT INTO MONDAY MORNING BEFORE TRANSITIONING BACK OVER TO A MAINLY UPSLOPE SNOW SHOWER EVENT WEST OF THE BLUE RIDGE BY MONDAY AFTERNOON. WITH THE PASSAGE OF THIS FINAL WAVE...DOWNSLOPING WINDS SHOULD ALLOW FOR SKIES TO CLEAR EAST OF THE BLUE RIDGE. EVEN ACROSS THE WEST...ANY UPSLOPING SNOW SHOWERS AND ASSOCIATED CLOUDS SHOULD DISSIPATE BY LATE MONDAY AFTERNOON AS SURFACE HIGH PRESSURE RAPIDLY BUILDS EAST INTO THE MID ATLANTIC REGION. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... MODEL FORECASTS OF AREA OF LOW PRESSURE PASSING OFF THE COAST SUNDAY INTO MONDAY MORNING HAVE BEEN FLIP FLOPPING NORTH AND SOUTH THE PAST COUPLE OF DAYS. ALTHOUGH NOT PERFECTLY CONSISTENT...THE ECMWF HAS SHOWN THE SMALLEST AMOUNT OF NORTHERLY SHIFT OVER THE PAST DAY OR SO...THUS USED IT AS A GUIDE. HIGH PRESSURE OVER THE MIDDLE ATLANTIC SHOULD RESULT IN A COLD NIGHT FOR THE NW HALF OF THE CWA MONDAY NIGHT. ANOTHER...STRONGER AREA OF LOW PRESSURE THEN CUTS THROUGH THE OHIO VALLEY...WITH POSSIBLE DEVELOPMENT ALONG THE COAST. ATTM...NOT MUCH COLD AIR WITH THIS SYSTEM...ALTHOUGH THE WEDGE MAY BE SUFFICIENT ENOUGH FOR FZRA ALONG THE MOST FAVORED SPOTS...NORTH CENTRAL CWA AND MAYBE EVEN FLOYD COUNTY WEDNESDAY MORNING...BUT STILL A LOT OF UNCERTAINTY. RIGHT NOW...LOOKS MOSTLY LIKE A RAIN EVENT AND HELD THE CHC TO HIGH CHC POPS WITH THE ENTIRE LONG RANGE SUITE INDICATING QPF WED AND WED NIGHT. THURS AND THURS NIGHT COULD FEATURE A PROLONGED UPSLOPE SNOW EVENT IN SE WEST VA TOO. WITH SOME HIGH LATITUDE BLOCKING ALREADY IN PLACE IN SE CANADA AND NEAR GREENLAND...THIS STORM COULD CHG THE PATTERN TOWARDS EASTERN TROUGHINESS AND MORE WINTERLIKE TEMPS. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...-- Changed Discussion --MAIN AVIATION CONCERN FOR THIS AFTERNOON WILL BE SFC WINDS. THERE IS STILL A TIGHT PRESSURE GRADIENT ACROSS THE REGION...WITH WIND GUSTS OF 20-30 KTS. THESE STRONG WINDS WILL GRADUALLY DIMINISH DURING THE AFTERNOON...SUBSIDING COMPLETELY AFTER SUNSET. SURFACE HIGH PRESSURE WILL FINALLY BUILD INTO THE MID ATLANTIC REGION BY TONIGHT. NO CEILING OR VSBY RESTRICTIONS ARE EXPECTED THROUGH EARLY SATURDAY. HOWEVER...THE FIRST IN A SERIES OF WEATHER DISTURBANCES FROM THE SOUTH AND WEST WILL BRING A THREAT OF LIGHT PRECIPITATION TO THE AREA TOWARD DAYBREAK SATURDAY...AND THEN LASTING THROUGH THE DAY. THIS MAY BRING A PERIOD OF MVFR VISIBILITIES AND CIGS. HIGHER ELEVATIONS MAY SEE SOME SLEET OR SNOW...WHILE DEEPER VALLEY LOCATIONS MAY SEE SOME FREEZING RAIN SATURDAY MORNING. THESE SYSTEMS MAY BE FOLLOWED BY SOME ADDITIONAL MVFR RESTRICTIONS DUE TO UPSLOPE WINDS FROM THE WEST ACROSS THE SOUTHEAST WEST VIRGINIA...INCLUDING BLF AND LWB SATURDAY NIGHT INTO SUNDAY. POINTS EAST OF THE BLUE RIDGE SHOULD RETURN TO VFR WEATHER DURING THIS PERIOD. ANOTHER DISTURBANCE MAY BRING MORE LIGHT PRECIPITATION TO THE AREA SUNDAY NIGHT AND MONDAY...WITH THE THREAT OF MVFR CIGS AND VSBYS. VFR CONDITIONS ARE EXPECTED MONDAY NIGHT AND TUESDAY.-- End Changed Discussion --&& .FIRE WEATHER...-- Changed Discussion --VERY DRY AFTERNOON ANTICIPATED WITH HUMIDITY MINIMUMS NEAR 20 PERCENT ALONG AND EAST OF THE BLUE RIDGE. WINDS WILL BE MORE SUBDUED...BUT WE STILL EXPECT SOME GUSTS OF 25 TO 30 MPH DURING THE AFTERNOON WHEN HUMIDITIES ARE THE LOWEST. THE EXPECTED WIND CONDITIONS ARE NOT QUITE UP TO RED FLAG CRITERIA...EXCEPT FOR MAYBE THE HIGHEST ELEVATIONS. HAVE COORDINATED THIS WITH THE USFS AND IN AGREEMENT THE BEST COARSE OF ACTION IS A FIRE DANGER STATEMENT HIGHLIGHTING THE DANGER.-- End Changed Discussion --&& .EQUIPMENT...-- Changed Discussion --THE HINTON WV NOAA WEATHER RADIO IS WORKING IN A DEGRADED MODE... 300 WATTS AS OPPOSED TO 1000 WATTS. THE COMMERCIAL POWER IS OUT DUE TO THE WIND DAMAGE IN THE AREA AND IT MAY TAKE SEVERAL DAYS TO RESTORE. IN THE MEAN TIME WE ARE RUNNING OFF OF A GENERATOR...BUT AT A REDUCED POWER. THE BLUEFIELD ASOS IS ALSO NOT REPORTING DUE TO A POWER OUTAGE AT THE AIRPORT. NOTHING CAN BE DONE ABOUT THIS UNTIL COMMERCIAL POWER IS RESTORED...EARLIEST ESTIMATE ON WHEN IT WILL BE BACK IN SERVICE IS SOMETIME SATURDAY.-- End Changed Discussion --&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JJ NEAR TERM...JJ SHORT TERM...DS/WERT LONG TERM...KM AVIATION...PM FIRE WEATHER...PM EQUIPMENT...PM
