Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 010617 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 217 AM EDT FRI MAY 1 2015 .SYNOPSIS...
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AN UPPER LEVEL LOW WILL HEAD INTO NORTH CAROLINA TODAY. THIS UPPER LEVEL LOW SHOULD DEPART BY FRIDAY NIGHT...AND HIGH PRESSURE WILL ARRIVE TO BRING WARMER WEATHER FOR EARLY NEXT WEEK. THE CHANCE OF AFTERNOON SHOWERS AND THUNDERSTORMS WILL RETURN AS THE WEEK PROGRESSES.
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&& .NEAR TERM /THROUGH TODAY/...
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AS OF 200 AM EDT FRIDAY... FORECAST UPDATED TO CONCENTRATE HIGHER POPS FROM SRN WV...SOUTHEAST ACROSS THE NEW RIVER VALLEY INTO THE NW PIEDMONT OF NC...ALONG AXIS OF BEST SFC AND UPPER LEVEL FORCING AHEAD OF THE UPPER LOW. EXPECT THE SHOWERS TO PIVOT SW OVER THE MTNS AND TO THE NORTH OVER THE PIEDMONT AS EVIDENCED ON RADAR. AS THE LOW MOVES ACROSS NRN NC LATER THIS MORNING THE SHOWERS TO SHIFT FURTHER NORTHEAST TOWARD THE LYH/FVX AREA WITH SOME DRY SLOTTING DEVELOPING OVER THE NC MTNS/FOOTHILLS. AS SUCH KEPT SOME TREND OF OFFICIAL FORECAST THEN MADE SOME ADJUSTMENTS BASED ON LATEST HRRR/LOCAL WRF. OTHER ISSUE IS COLD AIR ALOFT. RADAR SHOWING BRIGHT BANDING OVER THE NRV INTO SRN WV...WITH EVIDENCE OF FZ LVL ABOUT 2000FT AGL. AS SUCH ADDED SOME SNOW MIXED IN ALONG THE HIGHER TERRAIN ABOVE 4KFT. PLACES LIKE MT ROGERS AND BEECH MTN COULD SEE A DUSTING TO AN MAYBE AN INCH. TEMP AT BEECH MTN AT 32F. PREVIOUS DISCUSSION FROM LATE THURSDAY EVENING... UPPER LOW CONTINUES TO DRIFT SOUTHEAST AND IN SO DOING...RAIN SHOWERS HAVE SPREAD BACK INTO THE REGION FROM THE NORTHWEST...GENERALLY PIVOTING ABOUT THE ROA/BCB REGION. ONE AREA OF RAIN PERSISTED FOR QUITE SOME TIME ACROSS NORTHERN PITTSYLVANIA/SOUTHERN CAMPBELL COUNTY WHERE DOPPLER RAINFALL ESTIMATES 1.5 TO 2.0 INCHES OF RAIN HAS FALLEN TODAY. CURRENT TREND ON POPS LOOKS GOOD. NOT SEEING ANY LIGHTNING ANY MORE AND WITH THE LOSS OF DAYTIME HEATING WOULD NOT EXPECT ANY FROM THIS POINT FORWARD. PREVIOUS GRIDS CAPTURED THE ENDING TIME OF THAT AS WELL. EARLIER ADJUSTMENT DOWNWARD OF TEMPERATURES HAS BEEN ON TRACK AND OTHER THAN A MINOR ADJUSTMENT DOWNWARD ACROSS THE PIEDMONT...TEMPERATURES APPEAR TO BE ON TRACK FOR THE REMAINDER OF THE NIGHT. SYNOPTIC SITUATION NOT PARTICULARLY SUPPORTIVE OF FOG...SO WILL NOT ADD ANY IN THE GRIDS AT THIS TIME. AS OF 730 PM EDT THURSDAY... SCATTERED RAIN SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE TO ROTATE AROUND THE UPPER LOW. MAIN AREA AT THIS MOMENT HAS SHIFTED OVER INTO THE NC PIEDMONT OUT OF OUR CWA...BUT A NEW AREA IS POISED TO MOVE INTO FAR SW VA. HRRR INDICATES ACTIVITY UP IN PA/NORTHERN VA/MD WILL SHIFT SOUTH OVERNIGHT ACROSS THE CWA FROM NORTH-SOUTH AS THE UPPER LOW MOVES ESE TOWARD THE COAST. THE PRECIPITATION RESULTED IN SOME SIGNIFICANT EVAPORATIVE COOLING IN THE WEST WITH TEMPERATURES DOWN IN THE 40S IN THE WESTERN COUNTIES. THUS...HAD TO LOWER TEMPERATURES IN THOSE AREAS A GOOD 10 DEGREES. HOWEVER...ADDITIONAL COOLING OVERNIGHT SHOULD BE LIMITED AS TEMPERATURES NEAR DEWPOINT. ONLY ADJUSTED OVERNIGHT MINS DOWN A COUPLE OF DEGREES. DID NOT ADJUST POPS MUCH AS HRRR SHOWS ACTIVITY CONTINUING MUCH OF THE NIGHT. WILL RE-EVALUATE POPS WITH LATER UPDATES. AS OF 405 PM EDT THURSDAY... AN UPPER LEVEL LOW CONTINUES TO HEAD CLOSER TO THE WESTERN PORTION OF THE CWA. CURRENTLY...SCATTERED SHOWERS AND THUNDERSTORMS ARE LINING UP OVER THE PIEDMONT. WEAK FLOW ALOFT IS CAUSING CONSIDERABLY SLOW STORM MOTIONS. DUE TO EARLIER SUNSHINE AND STEEPENING LAPSE RATES AS COOLER AIR ARRIVES ALOFT...SOME SMALL HAIL IS LIKELY IN THE STRONGER STORMS. WE HAVE ALREADY RECEIVED SEVERAL REPORTS OF PEA TO DIME SIZE HAIL THIS AFTERNOON...BUT NOTHING HAS REACHED SEVERE LIMITS. MEANWHILE...MORE SHOWERS AND THUNDERSTORMS ARE SPREADING OVER THE WESTERN MOUNTAINS. THIS ACTIVITY IS MUCH LESS ORGANIZED...BUT IT COULD PICK UP A LITTLE DURING THE NEXT SEVERAL HOURS. BY TONIGHT...THE UPPER LEVEL LOW WILL BE DIRECTLY OVERHEAD...WHICH WILL KEEP THE SHOWER ACTIVITY ONGOING THROUGHOUT THE NIGHT. HOWEVER...THUNDER CHANCES SHOULD DIMINISH AFTER MIDNIGHT. CLOUD COVER WILL BE WIDESPREAD...WHICH MEANS LOW TEMPERATURES COULD DROP NO FURTHER THAN THE 40S. ALTHOUGH MOISTURE WILL GRADUALLY SUBSIDE DURING FRIDAY...THE SHOWERS WILL LINGER INTO FRIDAY AFTERNOON. THE ACTIVITY SHOULD SPREAD EASTWARD INTO THE PIEDMONT...AND EVENTUALLY CLEAR THE CWA BY SUNSET. HIGHS ON FRIDAY MAY BE A LITTLE TRICKY IF THE CLOUD COVER TRIES TO SCATTER SOONER THAN ANTICIPATED BY THE MODELS. ONLY MID 50S TO LOWER 60S ARE EXPECTED FOR HIGHS...WHICH ARE A COUPLE DEGREES BELOW MOS GUIDANCE.
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&& .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... AS OF 215 PM EDT THURSDAY... SATURDAY NIGHT...SOME LINGERING SHOWERS WILL STILL BE POSSIBLE DURING THE EARLY EVENING HOURS FROM EARLIER CONVECTION SATURDAY AFTERNOON. THE GREATEST CONCENTRATION WILL BE ACROSS THE MOUNTAINS...ALONG AND NORTH OF ROUTE 460. ON SATURDAY...ONE LAST SHORTWAVE TROUGH WILL SPIRAL AROUND THE WEST SIDE OF THE DEPARTING UPPER LOW. ANTICIPATED ISOLATED TO SCATTERED SHOWERS TO DEVELOP DURING THE PEAK HEATING OF THE AFTERNOON ACROSS THE EASTERN HALF OF THE REGION. INSTABILITY AT THIS TIME APPEARS TOO WEAK TO INCLUDE MENTION OF ISOLATED STORMS. SATURDAY NIGHT INTO SUNDAY...AN UPPER RIDGE WILL START TO BUILD JUST WEST OF THE REGION. THIS WILL BE THE START OF THE TREND OF MILDER CONDITIONS AND A MUCH LOWER PROBABILITY OF PRECIPITATION. AT BEST...ISOLATED SHOWERS MAY OCCUR SUNDAY AFTERNOON ACROSS THE NORTHERN MOUNTAINS OF NORTH CAROLINA. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 1230 PM EDT THURSDAY... UPPER LEVEL RIDGING WILL CONTINUE ACROSS THE REGION DURING THE MAJORITY OF THIS PORTION OF THE FORECAST. AN UPPER LOW MOVING EASTWARD THROUGH CANADA WILL WEAKEN THE RIDGE A BIT WEDNESDAY INTO THURSDAY...SHIFTING A BACKDOOR FRONT TOWARD OUR REGION. WHILE ALL OF THIS IS OCCURRING...AN ELONGATED TROUGH/UPPER LOW WILL BE DEVELOPING ACROSS THE CENTRAL PART OF THE COUNTRY. WE ARE ANTICIPATING PROGRESSIVELY MILDER TEMPERATURES EACH DAY WITHIN THIS REGIME. FOR PRECIPITATION...THE CENTER OF THE SURFACE HIGH WILL JUST BE SHIFTING EAST OF THE AREA ON MONDAY. THIS WILL LIMIT THE DEGREE OF RETURN MOISTURE INTO THE AREA TO THE NORTHERN MOUNTAINS OF NORTH CAROLINA. IT IS HERE WHERE ISOLATED SHOWERS WILL BE FORECAST FOR THE AFTERNOON. FROM TUESDAY INTO THURSDAY...COVERAGE OF SHOWERS AND STORMS WILL BE INCREASING...ESPECIALLY IN THE WEST...WITH THE APPROACH...AND POTENTIAL ARRIVAL...OF THE BACKDOOR FRONT. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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AS OF 200 AM EDT FRIDAY... SHOWERS WILL BE MORE NUMEROUS OVERNIGHT INTO FRIDAY AS UPPER LOW MOVES FROM THE MTNS OF SW VA INTO THE NC PIEDMONT. AXIS OF MODERATE TO HEAVY SHOWER SHOULD AFFECT BLF-BCB-DAN THIS MORNING THEN LIFT NE TO ROA/LYH AND POSSIBLY LWB THROUGH THE MORNING. NOT GOING TO GET CUTE WITH THE INS AND OUTS OF LIGHT TO MODERATE RAIN AND KEEP IT MOSTLY LIGHT. FREEZING LEVEL IS ABOUT 4-5KFT MSL...SO MAY HAVE TO DEAL WITH ICING. THE TERMINALS SHOULD GO TO SUB VFR IF NOT ALREADY THERE AS LOW LVLS MOISTEN UP. KEEPING SOME FOG IN AS WELL ACROSS THE MTNS LATER THIS MORNING. MODELS SHOWING INCREASE IN CIGS TOWARD MID TO LATE MORNING AND WILL TREND THAT WAY...WHICH WE ALREADY HAD IN THE PREVIOUS TAFS. THE RAIN SHOWER SWING EAST THROUGH THE DAY AND SHOULD BE GONE FRIDAY AFTERNOON...WITH ALL SITES TURNING TO VFR...THOUGH NW FLOW IS GOING TO PERSIST INTO THE MTNS...SO BLF APPEARS THEY MAY KEEP MVFR CIGS THRU THE END OF THIS TAF PERIOD. CONFIDENCE IS FAIRLY HIGH FOR WINDS/CIGS AND MEDIUM ON RAINFALL INTENSITY AND VSBYS. A SIGNIFICANT WEATHER PATTERN CHANCE WILL TAKE PLACE THIS WEEKEND...AS HIGH PRESSURE BUILDS OVERHEAD. OTHER THAN POSSIBLE EARLY MORNING MVFR FOG IN THE USUAL RIVER VALLEY LOCATIONS...VFR CONDITIONS SHOULD PERSIST THROUGH THIS WEEKEND INTO EARLY NEXT WEEK. A WARMER AND MOISTER AIR MASS COULD ALLOW FOR A FEW SHOWERS TO POP UP DURING MONDAY AFTERNOON. A GREATER CHANCE OF SHOWERS...WITH A FEW ISOLATED THUNDERSTORMS IN THE WESTERN MOUNTAINS...ARE POSSIBLE FOR TUESDAY.
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&& .EQUIPMENT...
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AS OF 150 AM EDT FRIDAY... PART FOR THE UPPER AIR ARRIVED LATE FRIDAY EVENING AND TECHNICIANS WILL WORK ON GETTING THIS FIXED TO HAVE A 12Z UPPER AIR RUN TODAY.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PW NEAR TERM...PW/WP SHORT TERM...DS/RAB LONG TERM...DS AVIATION...KK/PW/WP EQUIPMENT...WP

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