Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 221450 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 950 AM EST SAT NOV 22 2014 .SYNOPSIS... HIGH PRESSURE WILL BRING ONE MORE DAY OF FAIR WEATHER TO THE REGION AS WE START THE WEEKEND. THEN...A STORM SYSTEM MOVING NORTHWARD THROUGH THE MISSISSIPPI VALLEY WILL PUSH A WARM FRONT INTO THE APPALACHIANS AND CENTRAL MID ATLANTIC REGION...BRINGING WET AND WINDY CONDITIONS TO THE AREA BY SUNDAY AFTERNOON. UNSEASONABLY WARM CONDITIONS ARE EXPECTED MONDAY IN THE WAKE OF THIS SYSTEM BEFORE A COLD FRONT MOVES THROUGH TUESDAY...RETURNING TEMPERATURES TO BELOW NORMAL FOR THE REST OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 950 AM EST SATURDAY... HIGH PRESSURE OVER OUR REGION THIS MORNING WILL SLIDE EAST THIS AFTERNOON INTO TONIGHT. AN UPPER AIR DISTURBANCE WILL ROTATE EASTWARD TO OUR NORTH AROUND THE HIGH CENTER. THE HRRR...NAM AND HIRESW-ARW KEEP MOISTURE/PRECIPITATION TO THE NORTH OF OUR FORECAST AREA WITH THIS FEATURE. INCREASED CLOUD COVER IN THE NORTHWEST FOR HIGH LEVEL MOISTURE FOR THIS MORNING INTO THIS AFTERNOON. HOWEVER...SIGNIFICANT CLOUDS AND MOISTURE WILL BE HOLDING OFF UNTIL TONIGHT AS DEEP SOUTHWEST FLOW SETS UP IN THE BOUNDARY LAYER AHEAD OF APPROACHING WARM FRONT. MADE SOME MINOR CHANGES IN TEMPERATURES AND DEW POINTS FOR THIS MORNING INTO THIS AFTERNOON. WILL HOLD WITH CURRENT FORECAST HIGH TEMPERATURES FOR NOW...BUT WILL MONITOR FOR ANY CHANGES LATER THIS MORNING. ENJOY YOUR SATURDAY ! AS OF 330 AM EST SATURDAY... ONE MORE QUIET DAY ON TAP AS HIGH PRESSURE OVER THE REGION SLIDES OFF TO OUR EAST TODAY. LOW CLOUDS TO OUR WEST LOOK TO ROTATE AROUND THE BACK SIDE OF THE HIGH...WHICH WILL KEEP THEM JUST WEST AND NORTH OF THE FORECAST AREA. HOWEVER THERE WILL BE SOME HIGH CLOUDS OVERSPREADING FROM THE SOUTHWEST...RESULTING IN A FAIR WEATHER DAY WITH FILTERED SUNSHINE. SIGNIFICANT CLOUDS AND MOISTURE WILL BE HOLDING OFF UNTIL LATE TONIGHT AS DEEP SWLY FLOW SETS UP IN THE BOUNDARY LAYER AHEAD OF APPROACHING WARM FRONT...AND CLOUDS MOVE IN EN MASSE FROM THE SOUTHWEST. AND WITH THE CLOUDS COMES THE INCREASING CHANCE OF RAIN...ENTERING THE FORECAST FROM THE NORTH CAROLINA MOUNTAINS BY DAYBREAK SUNDAY. WINDS WILL BE LIGHT THROUGH TONIGHT...BUT WILL BE RAMPING UP QUICKLY AS WE HEAD INTO SUNDAY MORNING.
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&& .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... AS OF 400 AM EST SATURDAY... THE PRIMARY FOCUS THROUGH THE SHORT TERM WILL BE ON A VIGOROUS SOUTHERN STREAM SHORT WAVE SLATED TO TRAVERSE THE REGION FROM SOUTHWEST TO NORTHEAST SUN AFTERNOON/SUN NIGHT. THE SHORT WAVE WILL EJECT IN ADVANCE OF A BROADER TROUGH PROGGED TO DEVELOP THROUGH THE CENTRAL U.S. SUN-MON. AS THE BROAD UPPER TROUGH BEGINS TO DEVELOP SUN...THE LEADING SHORT WAVE WILL TAKE ON A STRONG NEGATIVE TILT AND ROTATE OUT OF THE ARKLATEX/MID-SOUTH REGION TOWARD THE OH VALLEY SUN EVENING/OVERNIGHT. THE ANTECEDENT AIR MASS ACROSS THE RNK CWA WILL BE DRY/COOL FROM THE REMNANT ARCTIC HIGH HAVING DRIFTED OFFSHORE IN A FAVORABLE IN-SITU WEDGE POSITION. A WARM FRONT WILL APPROACH THE REGION FROM THE SOUTH SUN AFTERNOON WITH WIDESPREAD RAIN OVERRUNNING THE WARM FRONT IN AN AREA OF SUBSTANTIAL ISENTROPIC LIFT. AS USUAL WITH THESE TYPE OF SITUATIONS...THE WEDGE LEADS TO A STABLE ENVIRONMENT AS THE MAIN DYNAMICS PASS THROUGH THE REGION AND THIS IS NO EXCEPTION. CONCERNS ARISE...HOWEVER...AS A 70-80KT LLJ TRAVERSES THE AREA IN ASSOCIATION WITH THE WARM FRONT/UPPER TROUGH SUN AFTERNOON/EARLY EVENING. SPC HAS PUSHED THE GENERAL THUNDER AREA UP TOWARD THE BLUE RIDGE...AND A MARGINAL SEVERE RISK APPROACHING THE FAR SE COUNTIES...NAMELY HALIFAX/CASWELL. FEEL THAT THIS WILL BE ANOTHER SITUATION WHERE THE COOL BOUNDARY LAYER WILL REMAIN DECOUPLED FROM THE STRONGER WINDS ALOFT ACROSS THE PIEDMONT COUNTIES. MODEL ADVERTISED INSTABILITY AND BUFKIT SOUNDINGS SHOWING NEAR ZERO INSTABILITY...POSITIVE LIS...AND ZERO CAPE...BUT SUBSTANTIAL SHEAR WITH STRONGLY CURVED HODOGRAPHS AND 30+KTS LOW-LEVEL SHEAR ACROSS MUCH OF THE REGION. A TYPICAL HIGH SHEAR/LOW CAPE ENVIRONMENT. HOWEVER...WITH CAPE NEAR ZERO...DO NOT FEEL THERE WILL BE ENOUGH SUPPORT FOR TSRA AT THIS POINT AND HAVE CONTINUED TO LEAVE IT OUT OF THE GRIDS IN COORDINATION WITH OUR NEIGHBORS. THE GREATER CONCERN THROUGH THE SUN TIME FRAME WILL BE AS THE STRONG LLJ TRAVERSES THE HIGHER TERRAIN OF NW NC/SW VA/SE WV. THIS IS FAIRLY CLASSICAL SETUP FOR STRONG TO HIGH WINDS IN THE SMYTH/TAZEWELL/MERCER COUNTY REGION. CURRENT ADVERTISED WIND SPEEDS DO NOT SUPPORT A HIGH WIND WATCH AT THIS POINT WITH SUSTAINED WINDS AROUND 22KTS AND GUSTS TO AROUND 38KTS. A WIND ADVISORY SEEMS QUITE PROBABLE THOUGH AS WE MOVE CLOSER TO THE EVENT. WHILE A BRIEF PERIOD OF MODERATE RAINFALL CAN BE EXPECTED SUN AFTERNOON INTO THE EVENING HOURS...MAINLY IN THE 18Z-06Z TIME FRAME...OVERALL QPF REMAIN MOSTLY 1 INCH OR LESS FOR THE ENTIRE CWA. THE HEAVIEST RAINFALL SHOULD FALL ACROSS UPSLOPE SOUTHEAST FACING SLOPES OF THE BLUE RIDGE WITH A STRONG S-SE WIND THROUGH THE BULK OF THE RAIN EVENT. MONDAY...THE WARM FRONT MOVES TO THE NORTH AND A VERY DEEP 966MB SFC LOW PRESSURE AREA CRANKS UP ACROSS THE GREAT LAKES AS THE VIGOROUS NEGATIVELY TILTED SHORT WAVE MOVES INTO THAT REGION AND PHASES WITH THE PARENT UPPER TROUGH MOVING SLOWLY EAST. THIS WILL RESULT IN A STRONG SW SFC AND BOUNDARY LOW FLOW ACROSS OUR REGION. THE CWA WILL BE SOLIDLY IN THE WARM SECTOR FOR SURE. TEMPERATURES MAY ACTUALLY BEGIN TO RISE OVERNIGHT SUN NIGHT WITH STRONG LOW-LEVEL WAA. WITH 850MB TEMPS +10C TO EVEN +12C ACROSS PARTS OF THE CWA AND THE STRONG SW FLOW...HIGH TEMPERATURES WILL BE UNSEASONABLY WARM IN THE 60S WEST OF THE BLUE RIDGE TO THE 70S EAST OF THE BLUE RIDGE...WITH EVEN 50S IN THE WESTERN MOUNTAINS. COMPARED TO THE BITTER COLD OF THE PAST WEEK...IT WILL FEEL LIKE SUMMER. CANNOT COMPLETELY RULE OUT A PASSING SHOWER IN THE SUMMERLIKE AIR MASS...BUT OTHER THAN THE STRONG LOW-LEVEL FLOW...THE SOUNDINGS SHOW A STRONG MID-LEVEL CAP...SO SHOWERS WOULD MOSTLY LIKELY BE CONFINED TO PASSING MDT CU CAPABLE OF A SPRINKLE...WHICH IS NOT LIKELY. WE BEGIN TO RETURN TO REALITY TUESDAY AS THE BROAD UPPER TROUGH CONTINUES TO SHIFT INTO THE EASTERN U.S. IN RESPONSE TO A BUILDING SW U.S. UPPER RIDGE. COOLER AIR WILL FILTER INTO THE REGION FROM THE WEST WITH A GRADUAL COOL DOWN EXPECTED THROUGH THE THANKSGIVING WEEK. MAX/MIN TEMPERATURES TUE SHOULD BE A GOOD 20-30 DEGREES COOLER THAN MON...BUT NOTHING CLOSE TO OUR RECENT COLD TEMPERATURES. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 445 AM EST SATURDAY... WEDNESDAY...THE CENTER OF THE UPPER LOW IS PROGGED TO PROGRESS FROM NEAR JAMES BAY NORTHEAST TOWARDS GREENLAND. THE SYSTEMS TRAILING COLD FRONT IS EXPECTED TO PROGRESS EASTWARD TO NEAR THE EAST COAT OF THE U.S. MODEL GUIDANCE CONTINUE TO OFFER VARIOUS SOLUTIONS REGARDING A WAVE OF LOW PRESSURE THAT IS PROGGED TO HEAD NORTH ALONG THIS FRONT...FROM THE GULF COAST STATES TO THE MID- ATLANTIC SEABOARD BY MIDDAY WEDNESDAY. GENERAL CONSENSUS IS NOW THAT THIS WILL OCCUR...WITH THE ECMWF PULLING THE MOISTURE FARTHEST BACK INLAND AND TO THE WEST...WHILE THE CANADIAN IS THE DRIEST. THE GFS SEEMS TO BE A REASONABLE COMPROMISE AT THIS POINT. AT ANY RATE...ENOUGH CONFIDENCE THAT THIS WILL BUCKLE THE FRONT FROM TUE...AT THAT POINT LYING ALONG THE COASTAL AREAS...AND ALLOW THE ASSOCIATED MOISTURE TO SPREAD BACK INTO THE PIEDMONT AT A MINIMUM...POSSIBLY AS FAR WEST WED AS THE ALLEGHANY FRONT. THUS...HAVE CONTINUED TO INCREASE POPS FOR WED ACROSS MOST OF THE CWA...APPROACHING LIKELY VALUES IN FAR EASTERN AREAS. ENOUGH COLDER AIR WILL HAVE MADE ITS WAY INTO THE REGION FOR SOME TYPE OF WINTRY PRECIPITATION IN WESTERN AREAS. HOWEVER...THE WESTERN AREAS ARE THE AREAS LEAST LIKELY TO RECEIVE PCPN WITH THIS EVENT...SO ANY WINTER PCPN...PRIMARILY SNOW...WOULD BE MINOR AT BEST AND DOES NOT APPEAR TO AROUSE ANY WINTER WEATHER CONCERNS AT THIS POINT. FOR AREAS EAST OF THE BLUE RIDGE...THE PRECIPITATION SHOULD REMAIN IN THE FORM OF RAIN THROUGHOUT THE EVENT. BY WEDNESDAY NIGHT INTO THURSDAY...THIS COASTAL WAVE WILL BE NEAR THE CANADIAN MARITIMES AND NO LONGER BE A FACTOR IN OUR FORECAST. WHAT WILL BECOME A FACTOR IS YET ANOTHER DEEPENING UPPER LOW THURSDAY INTO FRIDAY. GUIDANCE IS OFFERING THIS ONE TO TAKE A FARTHER SOUTH TRACK THAN ITS PREDECESSOR...DEEPEN MORE...AND FUNNEL A STRONGER SURGE OF COLDER AIR INTO OUR REGION. AFTER AN INITIAL ROUND OF ISENTROPIC LIFT ASSOCIATED PRECIPITATION ON THURSDAY...ITS ASSOCIATED COLD FRONT WILL SWEEP THROUGH THE AREA THURSDAY NIGHT. IN ITS WAKE...UPSLOPE SNOW SHOWERS AND GUSTY NORTHWEST WINDS ARE ANTICIPATED IN THE PREFERRED AREAS OF SOUTHEAST WEST VIRGINIA THURSDAY NIGHT INTO FRIDAY. TEMPERATURES THROUGH THE PERIOD WILL TREND LOWER EACH DAY...WITH THE BIGGEST DROP BEING THURSDAY INTO FRIDAY...WITH SLIGHTLY BELOW TO BELOW NORMAL TEMPERATURES EXPECTED THROUGH THE REMAINDER OF THE THANKSGIVING WEEK. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... AS OF 630 AM EST SATURDAY... HIGH CONFIDENCE IN VFR CONDITIONS AT ALL TAF SITES THIS PERIOD. ESSENTIALLY A NIL WEATHER FORECAST THIS TAF PACKAGE AS CENTER OF HIGH PRESSURE STARTS THE PERIOD OVER THE REGION AND SLOWLY SLIDES OFF TO OUR EAST. LOW CLOUDS UPSTREAM ARE FORECAST TO ROTATE AROUND THE BACK SIDE OF THE HIGH TO OUR WEST AND NORTH. MAYBE A FEW PUFFS OF CU AT KLWB OR KBLF THIS AFTERNOON BUT DO NOT FEEL IT WARRANTS ANY MENTION IN THE TAF. BUT MODEL UPPER LEVEL RH FIELDS CORRELATE WELL WITH CIRRUS SEEN STREAMING IN OUR DIRECTION ON CURRENT SATELLITE LOOP SO IT LOOKS LIKE A HIGH CIG OF BKN CIRRUS WILL PREVENT SKC FOR SKY CONDITION. WINDS WILL BE LIGHT AT ALL SITES THROUGH THE FORECAST PERIOD...BUT KBLF WILL SEE WINDS BACK FROM SW TO SLY AND STAY UP A BIT TONIGHT AS THE INFLUENCE OF APPROACHING LOW PRESSURE AND WARM FRONT START TO BE FELT. TOWARDS THE END OF THE TAF PERIOD MOISTURE WILL START TO ENCROACH FROM THE SOUTH. WILL NOT INCLUDE ANY LOW CLOUDS WITH THIS ISSUANCE BUT KDAN AND POSSIBLY KBCB AND KBLF MAY HAVE MVFR CIGS ON THEIR DOORSTEP BY 12Z SUNDAY. EXTENDED DISCUSSION... THE NEXT SIGNIFICANT WEATHER WILL ARRIVE ON SUNDAY WITH WINDY CONDITIONS DEVELOPING DURING THE MORNING...AND RAIN WITH MVFR TO IFR CONDITIONS SUNDAY AFTERNOON AND NIGHT. ALSO...STRENGTHENING LOW LEVEL WINDS LATER ON SUNDAY MAY LEAD TO LLWS...ESPECIALLY THE BLF AREA. A BRIEF RETURN TO VFR DURING MONDAY OUTSIDE OF THE MOUNTAINS AS A DRY SLOT DEVELOPS BETWEEN THE EXITING FRONT FROM SUNDAY AND THE NEXT UPSTREAM COLD FRONT. MONDAY INTO TUESDAY LOOK TO FEATURE QUITE A BIT OF WIND. FOR THE REMAINDER OF NEXT WEEK...EXPECT PERIODS OF MVFR CIGS ACROSS EASTERN WV/FAR SW VA...BUT MOSTLY VFR ELSEWHERE WITH A COLDER NW FLOW. && .EQUIPMENT... AS OF 215 PM EST FRIDAY... THE VISIBILITY SENSOR AT KLYH...LYNCHBURG AIRPORT...WILL BE OUT OF SERVICE UNTIL PARTS ARRIVE TO REPLACE THE SENSOR. UNTIL THEN THE VISIBILITY WILL ONLY BE REPORTED WHEN THE CONTROL TOWER IS STAFFED. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...MBS NEAR TERM...KK/MBS SHORT TERM...RAB LONG TERM...DS/RAB AVIATION...KK/MBS EQUIPMENT...RAB

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