Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 012354 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 754 PM EDT FRI MAY 1 2015 .SYNOPSIS... AN UPPER LEVEL LOW PRESSURE SYSTEM WILL PROGRESS EASTWARD...OUT OF THE REGION TONIGHT. HIGH PRESSURE WILL BUILD INTO THE REGION THIS WEEKEND AND BE POSITIONED ACROSS OUR REGION INTO MUCH OF NEXT WEEK. OUR NEXT BEST CHANCE OF PRECIPITATION WILL COME DURING THE MIDDLE OF NEXT WEEK WHEN A BACKDOOR COLD FRONT APPROACHES OUR AREA. && .NEAR TERM /THROUGH SATURDAY/...
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AS OF 555 PM EDT FRIDAY... ADJUSTED TEMPERATURES DOWN IN RAIN COOLED LOCATIONS AND BLEND LAMP TEMPERATURES INTO THE OVERNIGHT. MODIFIED POPS AND WEATHER WITH LATEST WSR-88D TRENDS AND SHAPED POPS THIS EVENING INTO TONIGHT TOWARDS A BLEND OF THE HRRR AND THE RNK WRFARW. AS THE UPPER LOW PUSHES EAST...AREAL COVERAGE OF CONVECTION WILL DIMINISH AND EXIT THE REGION. PATCHES OF FOG WILL DEVELOP ESPECIALLY WHERE IT RAIN THIS AFTERNOON AND THIS EVENING AND CONTINUE INTO THE OVERNIGHT. HELD ON TO THE THE OVERNIGHT LOW TEMPERATURES FROM AROUND 40 DEGREES IN THE NORTHWEST MOUNTAINS TO THE UPPER 40S IN THE PIEDMONT. AS OF 300 PM EDT FRIDAY... AN AREA OF SHOWERS WITH A FEW THUNDERSTORMS CONTINUES TO EXPAND IN COVERAGE BETWEEN ROUGHLY HOT SPRINGS AND BLACKSBURG VA. THE PRECIPITATION WAS EXPANDING TOWARDS THE S-SW. HEADING INTO THIS EVENING...THE REGION OF PRECIPITATION WILL GRADUALLY MAKE PROGRESS EASTWARD...IN PACE WITH THE PROGRESSION OF THE RESPONSIBLE UPPER LEVEL LOW PRESSURE SYSTEM. COVERAGE WILL START TO DECREASE AT SUNSET...WITH THE LAST SHOWERS EXITING THE AREA OR DISSIPATING AROUND 11PM BETWEEN DANVILLE AND LYNCHBURG. CLOUD COVER WILL BE ON THE DECREASE THE REMAINDER OF THE NIGHT. PATCHY LIGHT RIVER VALLEY FOG WILL BE POSSIBLE...AND ALSO IN VALLEYS THAT RECEIVED PRECIPITATION THIS AFTERNOON OR EVENING. LOW TEMPERATURES WILL RANGE FROM AROUND 40 TO THE MID 40S ACROSS THE MOUNTAINS...WITH MID 40S TO UPPER 40S ACROSS THE PIEDMONT. ON SATURDAY...HIGH PRESSURE WILL START TO WORK ITS WAY INTO THE REGION FROM THE WEST. ONE LATE SHORTWAVE TROUGH ROUNDING THE BACKSIDE OF THE DEPARTING UPPER LOW IS EXPECTED TO MOVE SOUTH THROUGH CENTRAL VIRGINIA AND NORTH CAROLINA TOMORROW AFTERNOON. THIS FEATURE PASSING AT THE TIME OF PEAK HEATING MAY HELP TO GENERATE SOME ISOLATED SHOWERS...GENERALLY ALONG AND EAST OF A LEXINGTON VA TO REIDSVILLE NORTH CAROLINA LINE. THANKS TO BUILDING HEIGHTS AND LESS CLOUD COVER...ANTICIPATE A MILDER DAY ON SATURDAY AS COMPARED TO TODAY. HIGHS ACROSS THE MOUNTAINS WILL RANGE FROM THE MID 60S TO NEAR 70 DEGREES...WITH LOW TO MID 70S ACROSS THE PIEDMONT.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... AS OF 315 PM EDT FRIDAY... 500 MB HEIGHTS GRADUALLY RISE SATURDAY NIGHT AND SUNDAY AS THE PATTERN BECOMES MORE ZONAL. BUFKIT DATA FOR SUNDAY IN THE SOUTHWEST COUNTY WARNING AREA SHOWED A LARGE ENOUGH LOW LEVEL LAPSE RATE AND A LAYER OF MOISTURE THAT WOULD SUPPORT SHOWERS ISOLATED THUNDERSTORMS. HOWEVER...THERE WILL ONLY BE MINIMAL LIFT FROM ANY VORTICITY SO COVERAGE WILL BE CONFINED TO AREAS WITH THE BEST HEATING AND INSTABILITY. AIR MASS WARMS THROUGH THE PERIOD AND WILL BE CLOSE TO +10 TO +12 VALUES AT 850 MB BY THE END OF THE DAY ON MONDAY. THIS WILL PUT MAXIMUM TEMPERATURES JUST ABOVE NORMAL MONDAY. HIGH PRESSURE WILL BE OVER THE AREA SATURDAY NIGHT AND SUNDAY. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... AS OF 125 PM EDT FRIDAY... LONG WAVE PATTERN ADVERTISED BY MODELS SHOWED TROFING IN THE WESTERN UNITED STATES AND A BROAD SOUTHEAST U.S. RIDGE. A SURFACE COLD FRONT THE THE NORTHERN STREAM WILL BE OVER THE GREAT LAKES ON MONDAY AND WILL PUSH SOUTH AS A BACKDOOR FRONT OVER THE MID ATLANTIC REGION TUESDAY AND WEDNESDAY. QUESTIONABLE HOW FAR SOUTH THIS BOUNDARY GETS HEADING INTO A LARGE RIDGE OVER THE SOUTHEAST. BEST PROBABILITY OF PRECIPITATION WILL BE IN THE VICINITY OF THIS BOUNDARY. OTHERWISE THE CHANCE WILL BE LIMITED TO AIRMASS TYPE THUNDERSTORMS...MAINLY IN THE MOUNTAINS EACH AFTERNOON AND EVENING. MAXIMUM/MINIMUM TEMPERATURES WILL REMAIN 5 TO 15 DEGREES ABOVE NORMAL TUESDAY THROUGH FRIDAY. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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AS OF 745 PM EDT FRIDAY... IMPROVING AVIATION CONDITIONS EXPECTED THIS TAF VALID PERIOD. PESKY UPPER LOW CENTERED NEAR ORF WILL DRIFT FURTHER OUT TO SEA OVERNIGHT AND SATURDAY. A BROAD RIDGE OF HIGH PRESSURE WILL BUILD EAST FROM THE OH/TN VALLEY FOR THE WEEKEND. HOWEVER...THE LAST FEW LOBES OF PVA WILL ROTATE AROUND THE BACK SIDE OF THE UPPER LOW AND WILL CONTINUE TO SUPPORT A FEW SHOWERS MAINLY EAST OF THE BLUE RIDGE OVERNIGHT. NOT TOTALLY CONVINCED THAT THERE MIGHT NOT BE ONE OR TWO SHOWER ACROSS THE FAR EASTERN PIEDMONT SATURDAY AFTERNOON DURING MAX HEATING AS THE LAST VESTIGES OF THE UPPER LOW LINGER IN THAT REGION...BUT WITH THE POSSIBLE EXCEPTION OF LYH...THIS SHOULD REMAIN EAST OF THE TAF VALID SITES. CIGS/VSBYS ARE VFR AT THE CURRENT TIME...EXCEPT FOR KDAN...WHERE AN AREA OF SHRA...WITH SOME +SHRA...WILL DRIFT THROUGH OVER THE NEXT HOUR. ONE CONCERN OVERNIGHT IS FOG POTENTIAL...AND THEN LOW CLOUDS ACROSS EASTERN WV. WITH MOIST GROUND FROM RAINFALL THIS AFTERNOON...AM CONCERNED THAT FOG WILL GROUND FOG WILL DEVELOP IN SOME AREAS OVERNIGHT...INCLUDING LYH/DAN/LWB/BCB. LESS CONVINCED THAT SUCH WILL OCCUR AT ROA. BUFKIT SHOWS GOOD POTENTIAL FOR FOG DEVELOPMENT AT LYH AND DAN. NEGATING EFFECT WOULD BE A LIGHT NW BREEZE...BUT DO NOT FEEL THIS WILL BE ENOUGH TO PRECLUDE FOG DEVELOPMENT ACROSS THE PIEDMONT. HAVE LOWERED VISIBILITIES TO IFR IN BR AT LYH/BCB/LWB IN THE 08Z-12Z TIME FRAME. AFTER 14Z SAT...EXPECT VFR CONDITIONS AREA WIDE...WITH JUST SOME BKN LOW END VFR CIGS ACROSS THE PIEDMONT DURING PEAK HEATING. WINDS LIGHT AND MOSTLY NW THROUGH THE TAF VALID PERIOD ON THE BACK SIDE OF THE UPPER LOW...BUT SOME VARIABLE WINDS THIS EVENING. AT ANY RATE...SPEEDS MOSTLY 7KTS OR LESS THROUGH THE TAF VALID PERIOD. MEDIUM CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD. MEDIUM CONFIDENCE IN VSBYS THROUGH 14Z...THEN HIGH CONFIDENCE IN VFR VSBYS AT ALL TAF SITES. MEDIUM CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID PERIOD. NOTE...THE VISIBILITY SENSOR AT THE ASOS AT KBLF CONTINUES TO MALFUNCTION. WILL CONTINUE WITH AMD NOT SKED APPENDED TO ITS TAF. EXTENDED AVIATION DISCUSSION... OTHER THAN SOME PATCHY LATE NIGHT/EARLY MORNING RIVER VALLEY FOG IN THE TYPICAL LOCATIONS...VFR CONDITIONS ARE EXPECTED THROUGH MONDAY NIGHT. SCATTERED AFTERNOON SHOWERS COULD AFFECT THE MOUNTAINS TUE...BUT MORE LIKELY WED-THU AS A BACK DOOR FRONT DRIFTS TOWARD THE REGION. HIGH PRESSURE ALOFT WILL NOT PROVIDE MUCH IN THE WAY OF ANY SYNOPTIC-SCALE FORCING THROUGH THE PERIOD THOUGH.
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&& .EQUIPMENT... AS OF 330 PM EDT FRIDAY... THE VISIBILITY SENSOR AT THE BLUEFIELD...KBLF...ASOS MAY ALTERNATE BETWEEN AVAILABLE AND UNAVAILABLE UNTIL SUCH TIME APPROPRIATE CORRECTIVE MEASURES CAN BE COMPLETED. THE NOAA WEATHER RADIO AT ROANOKE VIRGINIA...WXL60...WHICH BROADCASTS AT A FREQUENCY OF 162.475 MHZ...IS BACK ON THE AIR. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...DS NEAR TERM...DS/KK SHORT TERM...AMS/RAB LONG TERM...AMS AVIATION...DS EQUIPMENT...DS

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