Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 030540 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 140 AM EDT WED SEP 3 2014 .SYNOPSIS... A WEAK COLD FRONT TRACKS SOUTHEAST INTO OUR AREA OVERNIGHT...BEFORE STALLING ACROSS THE CAROLINAS AND WASHING OUT ON WEDNESDAY. HIGH PRESSURE SETS BACK UP OVER THE EAST BY FRIDAY WITH YET ANOTHER COLD FRONT MOVING TOWARD US THIS WEEKEND. && .NEAR TERM /THROUGH TODAY/... AS OF 100 AM EDT WEDNESDAY... WITH CONVECTION DIMINISHING...ADJUSTED POPS FOR EARLY THIS MORNING. MODIFIED TEMPERATURES FOR THE EARLY MORNING. MORE CHANGES LATER... AS OF 910 PM EDT TUESDAY... BAND OF DEEP CONVECTION CONTINUES TO PUSH EAST TOWARD THE BLUE RIDGE THIS EVENING AND DESPITE DECREASING INSTABILITY APPEARS PROGRESSION AIDED VIA OUTFLOW AND UPPER DYNAMICS. THIS MORE IN LINE WITH THE EARLIER NAM OUTPUT AND LATEST LOCAL WRF WHICH TEND TO PUSH MUCH OF THIS COVERAGE ACROSS MUCH OF THE CWA PAST MIDNIGHT. THIS SEEMS SUPPORTED BY LINGERING HIGHER CAPES JUST EAST OF THE BLUE RIDGE SO HAVE UPPED POPS FURTHER TO CATEGORICAL/LIKELYS OUT TO THE FOOTHILLS AND PUSHED CHANCES EAST ACROSS THE REMAINDER OF THE REGION. EVENING SOUNDINGS WERE ALSO QUITE UNSTABLE WITH HIGH DCAPES SO STILL AN ISOLATED SEVERE THREAT BETWEEN NOW AND MIDNIGHT WITH QUICK BURSTS OF RAINFALL RESULTING IN OVER AN INCH IN 30 MINUTES OR SO. SOME DOWNWARD ADJUSTS TO LOW TEMPS BUT OVERALL 60S TO LOW 70S GIVEN THE MUGGY AIR AROUND. UPDATED DISCUSSION AS OF 735 PM EDT TUESDAY... WITH THE NEXT ROUND OF CONVECTION RIDING UP THE DEVELOPING LINE JUST WEST OF THE CWA...WENT AHEAD AND RAISED POPS TO CATEGORICAL/HIGH LIKELYS FAR WEST FOR A FEW HOURS AND EXTENDED HIGHER CHANCES EAST ACROSS THE BLUE RIDGE. LINGERING INSTABILITY AND HIGH DCAPES STILL SUPPORT LOCALIZED MICROBURSTS WITH SLOW MOVING STORMS ABLE TO PRODUCE HEAVY RAIN IN A SHORT PERIOD. FEW OTHER CHANGES FOR NOW. PREVIOUS DISCUSSION AS OF 245 PM EDT TUESDAY... GOING TO SEE TWO AREAS OF CONVECTION THIS AFTERNOON INTO EARLY EVENING. ONE FIRING ACROSS THE BLUE RIDGE/FOOTHILLS FROM FLOYD SOUTH TO WILKES...AND OTHER MOVING INTO SE WV...ALLEGHANY HIGHLANDS. THE 12Z NAM IS DOING EXCELLENT ATTM WITH HAVING THIS...BUT AT 00Z THIS EVENING FIRES UP A LINE FROM THE SHENANDOAH VALLEY TO THE SOUTHWEST ACROSS THE MOUNTAINS OF FAR SW VA/SE KY. BY THIS TIME...LEANED TOWARD A SOLUTION CLOSER TO THE 12Z ECMWF/GFS...AND AT THE SAME TIME KEEP CONVECTION MOVING EAST INTO THE VA/NC PIEDMONT ALONG LEE TROUGH. UPSTREAM THE SHORTWAVE THAT IS OVER SRN OHIO AND ANOTHER OVER INDIANA WILL STAY MAINLY NORTH OF US BUT FRONTAL BOUNDARY WILL WORK SE THROUGH THE NIGHT. EXPECT TO SEE BEST THREAT OF SHOWERS AND STORMS ACROSS SE WV EARLY THIS EVENING...THEN TAPER POPS OVERNIGHT TO SLIGHT CHANCE...WITH LACK OF FORCING. LOWS TONIGHT KEEP THE PERSISTENT MUGGY TEMPS WE HAVE HAD...WITH MID 60S WEST TO LOWER 70S SOUTHEAST. WEDNESDAY...FRONT SHIFTS INTO NC AND WILL SEE MAIN FOCUS OF SHOWERS AND STORMS DO LIKEWISE...WHILE NORTH WINDS TRY TO DRY THINGS OUT OVER THE NRN CWA. HOWEVER 8H FRONT EDGES INTO THE NRN CWA ONLY...SO KEEPING MOST OF OUR REGION IN THE SOMEWHAT HUMID AIRMASS. FOR POPS WILL HAVE SLIGHT CHANCE SOUTH OF BLF-ROA-LYH LINE...MAINLY DRY NORTH...WITH THE SRN TIER OF THE CWA ACROSS THE NC/VA BORDER AND SOUTH IN THE LOW CHANCE. TEMPS WILL DROP A FEW DEGREES UP NORTH BUT STILL WARM ACROSS THE CWA...WITH LOWER 80S WEST...TO MID TO UPPER 80S EAST. && .SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... AS OF 330 PM EDT TUESDAY... STRONG LATE SEASON UPPER RIDGE OVER THE SOUTHERN CONUS REMAINS IN CONTROL THROUGH THE SHORT-TERM WHICH WILL MAINTAIN THE VERY WARM AND HUMID CONDITIONS ACROSS OUR AREA. A WEAK SURFACE RIDGE OVER PA WILL BE DRIFTING OFF THE COAST BY EARLY THURSDAY WITH THE WEAK FRONTAL BOUNDARY LOCATED ACROSS NC. THIS BOUNDARY MAY ACT AS THE FOCUS FOR SHOWER AND THUNDERSTORM ACTIVITY WHICH WILL REMAIN MAINLY SOUTH OF THE CWA ON THURSDAY WHERE BETTER CONVERGENCE AND DEEPER MOISTURE EXISTS. THE ACTIVE NORTHERN STREAM WILL REMAIN WELL POLEWARD OF OUR REGION IN THE SHORT TERM WITH SEVERAL STRONG IMPULSES TRACKING ACROSS SOUTHERN CANADA. THE FIRST OF THESE WILL DRAG A COLD FRONT DOWN FROM THE UPPER MIDWEST REACHING THE OHIO VALLEY BY LATE FRIDAY. SOME PRE-FRONTAL CONVECTION IS POSSIBLE FRIDAY AFTERNOON ACROSS OUR CWA BUT BETTER COVERAGE MORE LIKELY ON SATURDAY. TEMPS WILL CONTINUE TO BE REMAIN WELL ABOVE NORMAL BOTH THU AND FRI WITH HIGHS 5 TO 8F ABOVE EARLY SEPTEMBER CLIMATOLOGY...RUNNING MID 80S TO LOW 90S FOR HIGHS AND LOWS FROM NEAR 60 NW TO NEAR 70 SE. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 330 PM TUESDAY... SLOW-MOVING COLD FRONT APPROACHES DURING THE DAY SATURDAY WITH DECENT CHANCES FOR SHOWERS AND POSSIBLE THUNDERSTORMS BY AFTERNOON WITH THE HIGHEST POPS ACROSS THE MOUNTAINS. FRONT WILL CONTINUE TO DRIFT SLOWLY SOUTH THROUGH THE CAROLINAS ON SUNDAY AND LIKELY ACT AS FOCUS FOR RENEWED CONVECTION SUNDAY AFTERNOON...BUT WITH THE BEST COVERAGE SOUTH OF VA-NC BORDER. DRIER AND SOMEWHAT COOLER CONDITIONS LIKELY MON-TUE UNDER HIGH PRESSURE AS 850 MB TEMPS ARE KNOCKED BACK TO 12-14C RANGE..YIELDING AT LEAST NEAR NORMAL HIGHS/LOWS BEFORE RIDGE TRIES TO AMPLIFY AGAIN. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 139 AM EDT WEDNESDAY... SCATTERED SHOWERS WILL LINGER FOR A FEW HOURS THIS MORNING. ACROSS THE MOUNTAINS...CIGS/VSBYS WILL START TO LOWER IN FOG DEVELOPMENT DURING THE EARLY MORNING HOURS. OVERNIGHT THE ISSUE TURNS TOWARD FOG...AS LOW LVL MOISTURE WILL BE HIGH. QUESTION IS HOW MUCH CLEARING OCCURS AND IF IT RAINS NEAR A TERMINAL. THINK CONFIDENCE IN FOG OCCURRING IS HIGHER AT KLWB...KBCB AND KBLF...MAINLY MVFR TEMPO IFR. FOG GOES AWAY AFTER 14Z/10AM...WITH VFR EXPECTED INTO THE AFTERNOON BEFORE ADDED SHRA/TSRA START TO POP UP MAINLY ALONG THE KBLF-KDAN CORRIDOR AND POINTS SOUTH IN THE AFTERNOON. THINKING COVERAGE QUITE LESS THAN TUESDAY BUT ENOUGH TO INCLUDE A VCTS MENTION AT KDAN WHILE LEAVING OUT ELSW FOR NOW. MEDIUM CONFIDENCE IN CEILINGS...VISIBILITY AND WINDS DURING THE TAF PERIOD. EXTENDED AVIATION DISCUSSION... FRONT STALLS SOUTH OF US WEDNESDAY AND MODELS FAVOR CONVECTION SOUTH OF A DAN-TNB LINE. IN THE AFTERNOON. MAINLY VFR EXCEPT ANY LATE NIGHT FOG IN THE BCB/LWB AREA THU. FRONT WASHES OUT TO THE SOUTH OF THE AREA FRIDAY WITH MORE WIDELY SCATTERED DIURNAL NATURE SHOWERS AND STORMS...THEN PERHAPS BECOMING MORE WIDESPREAD SATURDAY INTO SUNDAY WITH PERIODIC MVFR IN MORE ORGANIZED COVERAGE AHEAD OF ANOTHER COLD FRONT ARRIVING FROM THE NORTHWEST LATE. OTRW WILL SEE A DAILY TREND OF EARLY MVFR/IFR IN FOG...FOLLOWED BY BRIEF VFR...THEN INCREASING AFTERNOON/EVENING CONVECTION WHEN MVFR TO LOCAL IFR WILL BE POSSIBLE. && .EQUIPMENT... AS OF 730 AM EDT FRIDAY ... THE VISIBILITY SENSOR AT KDAN...DANVILLE REGIONAL AIRPORT...WILL BE OUT OF SERVICE UNTIL FURTHER NOTICE. A PART HAS BEEN BACK-ORDERED. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/WP NEAR TERM...JH/KK/WP SHORT TERM...PC LONG TERM...PC AVIATION...JH/KK/RAB/WP EQUIPMENT...RAB

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