Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 110315 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1115 PM EDT THU JUL 10 2014 .SYNOPSIS... WEAK HIGH PRESSURE WILL SPILL SOUTH INTO THE REGION FRIDAY AND SATURDAY. DEEPER MOISTURE WILL RETURN LATER IN THE WEEKEND AND EARLY NEXT WEEK AHEAD OF A MUCH STRONGER COLD FRONT THAT WILL BE PASSING THROUGH THE REGION BY NEXT TUESDAY. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... AS OF 1105 PM EDT THURSDAY... FRONTAL BOUNDARY SITUATED FROM NRN VA SOUTHWEST INTO THE UPPER TN VALLEY ALONG WITH SOME UPPER SUPPORT ALLOWING FOR ISOLATES/SCATTERED SHRA/TSRA FROM THE ALLEGHANY HIGHLANDS EAST TO THE LYH CORRIDOR. HIGHRES WRF FROM OUR OFFICE SHOWS THAT AREAS EAST OF ROA TO CONTINUE TO SEE SOME COVERAGE THROUGH THE NEXT FEW HOURS WHILE 00Z NAM KEEPS THE EAST ISOLATED AS WELL. FORECAST WILL FOLLOW SOME BLEND OF THIS WITH TRENDS THE NEXT COUPLE HOURS BASED ON RADAR AND MESOANALYSIS FAVORING THE BUCKINGHAM TO FRANKLIN COUNTY CORRIDOR TO SEE AT LEAST 20 POPS. CANNOT RULE OUT SOME ISOLATED SHRA FURTHER WEST AHEAD OF THE SHORTWAVE. THINK THE THUNDERSTORM THREAT WILL DIMINISH AFTER 2-3 AM OUT EAST. UNTIL THEN SOME HEAVY RAINERS DUE TO WEAK FLOW IN THE LOW LVLS. FORECAST TEMPS STILL ON TRACK WITH UPPER 60S SOUTHEAST TO AROUND 60 WEST. DEWPOINTS STILL TRYING TO FALL INTO THE 50S ON THE WRN FRINGES...HIGHER ELEVATIONS LIKE BLF/HSP HAVE DIPPED INTO THE MID 50S...BUT THINK THE DRY AIR WILL BE SLOW TO MOVE EAST TONIGHT. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/... AS OF 400 PM EDT THURSDAY... FRIDAY THE SFC FRONT WILL BE WELL TO OUR SOUTHEAST WITH MUCH DRIER AIR FILTERING IN BEHIND IT...ESPECIALLY ALOFT. SFC DEW PTS WILL BE A LITTLE SLOWER TO DRY OUT BUT WITH GOOD MIXING DOWN OF DRY AIR ALOFT THEY SHOULD FALL MORE RAPIDLY BY THE AFTERNOON. GIVEN THIS MORE OBVIOUS PUSH OF DRIER AIR BEHIND THE FRONT NOW...HAVE LOWERED POPS AND RAISED TEMPS SLIGHTLY GIVEN TRENDS IN GUIDANCE. FCST SOUNDINGS SUGGEST IT WILL BE HARD TO GET MUCH SFC BASED CAPE EXCEPT FOR OVER HIGHER TERRAIN...AND MAINLY MTNS OF NW NC AND VA BLUE RIDGE SOUTH OF ROA. KEEPING A SLIGHT CHC POP UP ELSEWHERE INCLUDINGPIEDMONT WHICH IS A LITTLE CLOSER TO FRONTAL BOUNDARY AND SLIGHTLY DEEPER MSTR...BUT WE MAY BE ABLE TO DROP THIS TOO AND KEEP ANY CONVECTION LIMITED TO MTNS...AND ISOLATED. REALLY NOT SEEING ANY CHC FOR SEVERE THRESHOLDS WITH ANY OF THESE STORMS GIVEN LIMITED INSTABILITY AND VERY WEAK SHEAR. REST OF THE WEEKEND THE RIDGE DOMINATES WITH SLOWLY INCREASING TEMPERATURES AND SLOW RETURN TO MOISTURE AGAIN AS EASTERLY FLOW SHIFTS SLOWLY BACK TO SOUTHWEST BEHIND RIDGE...ESPECIALLY BY SUNDAY. STILL...HAVE TRENDED LOWER ON POPS GIVEN RELATIVELY DRY ATMOSPHERE...KEEPING IT DRY IN PIEDMONT BUT SOME AREAS OF CHC POPS IN MOUNTAINS. AGAIN NOT SEEING ENOUGH INSTABILITY OR ANY FORCING FOR MUCH IN THE WAY OF SEVERE THREAT. STORMS WILL BE FAIRLY WIDELY SCATTERED. SUNDAY THE MOISTURE RETURN IS A LITTLE MORE PRONOUNCED...AND STORMS WILL BE A LITTLE MORE WIDESPREAD BUT STILL CHC CATEGORY WITH NO FORCING. NAM SHOWING INCREASING SW WINDS WHILE GFS AND ECMWF SUGGEST A LITTLE MORE WESTERLY COMPONENT SO SOME QUESTION ABOUT HOW FAR EAST STORMS MAY DEVELOP OR SHIFT TO LATER IN THE DAY. MUCH MORE ORGANIZED AND POSSIBLY SEVERE STORMS WELL UPSTREAM CLOSER TO NEXT FRONTAL BOUNDARY SHOULD REMAIN WELL TO THE WEST THROUGH THE NIGHT...ESPECIALLY WITH WESTERLY WINDS AT RIDGE TOP LEVEL. SEASONAL TEMPS OVER THE WEEKEND WITH HIGHS IN THE MID 80S WEST TO LOWER 90S EAST. COULD BE EVEN MID 90S SUNDAY IN PIEDMONT IF DOWNSLOPE IS A LITTLE STRONGER AND CLOUDS STAY AWAY. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 1230 PM EDT THURSDAY... MONDAY A LOW PRESSURE SYSTEM WILL BE CENTERED OVER JAMES BAY WITH A HIGH PRESSURE SYSTEM TO OUR SOUTH ACROSS THE FL PANHANDLE. A COLD FRONT WILL STRETCH THROUGH THE OHIO VALLEY TO OUR WEST. WITH THIS SETUP...MONDAY WILL BE WARM AND HUMID WITH PLENTY OF INSTABILITY TO SET OFF SOME AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS. WAVES OF UPPER LEVEL ENERGY ASSOCIATION WITH AN UPPER LEVEL TROF AND ASSOCIATED CUT OFF LOW OVER THE NORTHERN GREAT LAKES WILL BRING ADDITIONAL SHOWERS AND THUNDERSTORMS AHEAD OF THE FRONT ON TUESDAY. TIMING DIFFERENCES REMAIN ON WHEN EXACTLY THE COLD FRONT WILL CROSS OUR REGION...HOWEVER IT WILL HAPPEN EITHER LATE TUESDAY OR EARLY WEDNESDAY. BEHIND THE COLD FRONT...HIGH PRESSURE BUILDS IN AND A NOTICEABLE DROP IN HUMIDITY WILL BE FELT AS DEWPTS CRASH INTO THE 40S AND 50S. HIGH TEMPS WEDNESDAY AND THURSDAY WILL BE SEVERAL DEGREES BELOW NORMAL. THIS MEANS MID TO UPPER 70S ACROSS THE MOUNTAINS AND LOW 80S EAST OF THE BLUE RIDGE. DEPENDING ON CLOUD COVER...WOULD NOT BE SURPRISED TO SEE A FEW MOUNTAIN LOCATIONS DROP INTO THE MID TO UPPER 40S FOR NIGHT TIME LOWS ESPECIALLY ON THURSDAY. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... AS OF 745 PM EDT THURSDAY... APPEARS THAT UPPER TROUGH WILL FINALLY SHIFT FAR ENOUGH EAST TO REMOVE MOST CONVECTION FROM THE CWA FRI. FOR THIS EVENING...ISOLATED SHRA/TSRA CONTINUE TO DEVELOP ALONG AND EAST OF WIND SHIFT LINE ACROSS EASTERN WV FROM EKN-BKW. TOO ISOLD TO INCLUDE IN ANY TAF SITES AT THIS TIME. THE POSSIBLE EXCEPTION WOULD BE KDAN...WHERE ISOLD SHRA/TSRA FROM NC PIEDMONT MAY COME NEAR AS THEY MOVE NE. MAIN CONCERN THROUGH THE TAF VALID PERIOD WILL BE POTENTIAL FOR OVERNIGHT FOG AND LOW CLOUDS. AIR MASS...ESPECIALLY WEST OF THE BLUE RIDGE...SLIGHTLY DRIER THAN THIS TIME YESTERDAY AND LESS RAIN AT MOST SITES WITH THE EXCEPTION OF KDAN TODAY. STILL FEEL T/TD SPREAD LOW ENOUGH AND AIR MOIST ENOUGH FOR POTENTIAL IFR-LIFR BR/FG KLYH AND KDAN...WITH LESS POTENTIAL FOR KBCB FURTHER WEST. NOT EXPECTING ANY FOG DEVELOPMENT AT KROA OR KBLF. HAVE BACKED OFF FOG DEVELOPMENT AT KLWB SINCE DEWPOINTS DOWN INTO THE MID 50S AND MAX-T THIS AFTERNOON IN THE MID 80S SUGGESTS FOG DEVELOPMENT LESS LIKELY WITH CROSSOVER TEMPERATURE OF 53-54F. WINDS CHAOTIC AND LIGHT...BUT HIGH PRESSURE ALONG MID-ATLANTIC COAST SUGGESTS WINDS ESE-SE 3-5KTS THROUGH MUCH OF THE TAF VALID PERIOD...WITH SOME TENDENCY TO TRANSITION MORE SE-SSE FRI AFTERNOON. OVERALL...OUTSIDE MORNING FOG/CLOUDS...EXPECT VFR CIGS AND VSBYS. MEDIUM TO HIGH CONFIDENCE IN CIGS THROUGHOUT THE TAF VALID PERIOD. MEDIUM CONFIDENCE IN VBSYS 06Z-13Z...OTHERWISE HIGH CONFIDENCE IN VFR VSBYS. MEDIUM CONFIDENCE IN WIND DIR THROUGH THE TAF VALID PERIOD...HIGH CONFIDENCE IN WIND SPD THROUGH THE TAF VALID PERIOD. EXTENDED AVIATION DISCUSSION... CONTINUED LOW PROBABILITY OF SHRA/TSRA SAT...AS WEAK HIGH PRESSURE SLIDES IN FROM THE NORTH WITH A RELATIVE DRY AIR MASS. MOISTURE AND MORE WIDESPREAD SHRA/TSRA LIKELY TO RETURN FOR THE END OF THE WEEKEND AND EARLY NEXT WEEK AS A BROAD UPPER TROUGH DIGS INTO THE GREAT LAKES REGION AND RESULTANT CYCLONIC FLOW RESULTING IN INCREASINGLY UNSTABLE/UNSETTLED CONDITIONS ACROSS THE REGION. PATCHY LATE NIGHT/EARLY MORNING FOG WILL RESULT IN LOCAL MVFR TO IFR CONDITIONS DURING THE LATE NIGHTS AND EARLY MORNINGS...ESPECIALLY IN VALLEY LOCATIONS AND WHERE EARLIER AFTERNOON RAINFALL OCCURRED. && .HYDROLOGY... AS OF 1000 AM EDT THURSDAY... US DROUGHT MONITOR ISSUED THIS MORNING...JULY 10 2014...SHOWS EXPANSION OF D0...ABNORMALLY DRY CATEGORY...ACROSS MUCH OF NEW RIVER VALLEY AND OVER PARTS OF THE VA AND NC PIEDMONT...CENTERED AROUND DANVILLE. PULASKI COUNTY VA APPEARS TO BE NEAR THE EPICENTER OF THE DEVELOPING CONDITIONS OVER THE NEW RIVER VALLEY WITH MUCH OF THAT COUNTY RECEIVING LESS THAN 50 PERCENT OF NORMAL RAINFALL SINCE EARLY MAY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/SK NEAR TERM...PC/WP SHORT TERM...RCS LONG TERM...CF AVIATION...RAB HYDROLOGY...PC

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