Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 291743 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 143 PM EDT WED JUL 29 2015 .SYNOPSIS... UPPER RIDGE WILL STAY CENTERED OVER THE SOUTHERN U.S. TODAY INTO TONIGHT. A FRONT WILL SLIDE ACROSS OUR REGION THURSDAY...STALLING ALONG THE SOUTHEAST COAST FRIDAY INTO SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1029 AM EDT WEDNESDAY... MADE SOME MINOR ADJUSTMENTS IN TEMPERATURES...CLOUD COVER AND POPS FOR THIS MORNING INTO THIS AFTERNOON. EXTENSIVE LOW CLOUDS AND FOG THIS MORNING MAY DELAYED THE ONSET OF THUNDERSTORMS FOR THIS AFTERNOON. KFCX 88D SHOWED SOME ISOLATED SHOWERS PUSHING INTO THE WESTERN MOUNTAINS THIS MORNING. STEERING FLOW IS FASTER TODAY...BUT MOISTURE IS DEEPER. RNK 12Z MORNING SOUNDING SHOWED A WESTERLY FLOW AND A PWAT AROUND 1.60 INCH. THUS THE THREAT FOR LOCALLY HEAVY RAIN CONTINUES THIS AFTERNOON. MORE CHANGES LATER THIS AFTERNOON. AS OF 345 AM EDT WEDNESDAY... RIDGE ALOFT REMAINS ANCHORED FROM THE DESERT SOUTHWEST INTO THE LOWER MS VALLEY AND ELONGATED TOWARD THE SOUTHERN APPALACHIANS. FOR OUR AREA WILL SEE A COUPLE OF WEAK VORTS MOVE ESE ALONG THE NE SIDE OF THIS RIDGE THIS AFTERNOON INTO THE EVENING. AM BANKING ON ASCENT FROM DIFFERENTIAL HEATING...LEFTOVER BOUNDARIES AND WEAK UPPER LEVEL DISTURBANCES FOR THUNDERSTORMS TO FIRE UP THIS AFTERNOON IN THE MOUNTAINS FIRST...THEN DRIFTING TO THE ESE TO THE PIEDMONT. THE WIND FLOW STAYS WEAK AT 5-15 KTS...SO A FEW STORMS WILL HAVE THE POTENTIAL FOR HEAVY RAINERS LIKE TUESDAY. WILL MAINTAIN WORDING IN THE HWO FOR LOCALIZED FLOODING THREAT. EXPECT THE HUMIDITY TO STAY ELEVATED TODAY KEEPING IT FEELING LIKE THE TYPICAL DOG DAYS OF SUMMER. HIGH TEMPS WILL RUN FROM THE LOWER TO MID 80S WEST TO UPPER 80S/AROUND 90 EAST. ANOTHER WEAK WAVE MAY ACROSS US BY 12Z THURSDAY THOUGH THINK ATTM WILL SEE LIMITED SHOWERS OVERNIGHT. WILL SEE LINGERING CONVECTION IN THE EVENING BEFORE THINGS FADE AROUND MIDNIGHT. LOWS WILL RANGE FROM THE UPPER 60S TO LOWER 70S FOR MOST OF THE REGION. && .SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/... AS OF 415 AM EDT WEDNESDAY... SOME SUBTLE SYNOPTIC CHANGES WILL LEAD TO AN END OF THE DAILY THUNDERSTORM REGIME THIS PERIOD AND ALSO BRING A PERIOD OF RESPITE FROM THE HIGHER DEWPOINTS/RELATIVE HUMIDITY LEVELS. THE CHANGES WILL BE THE RESULT OF A DEEP UPPER LOW TRACKING EASTWARD ACROSS CENTRAL INTO EASTERN CANADA...FORCING THE STRONG SUBTROPICAL RIDGE...WHICH HAS BEEN ANCHORED ACROSS THE SOUTHERN PLAINS FOR THE PAST SEVERAL DAYS...TO RETROGRADE INTO THE DESERT SOUTHWEST. THE COLD FRONT THAT WILL BRING THE CHANGE IN AIR MASS TO THE REGION WILL BE ON OUR WESTERN DOORSTEP AT 12Z THU. AS WITH THE PAST SEVERAL EVENTS...THERE WILL LIKELY BE AN AREA OF SHOWERS AND ISOLATED THUNDERSTORMS ALONG AND NEAR THE FRONT AT DAYBREAK THU. THIS ACTIVITY WILL BE IN A DIMINISHING/DECAYING STATE...BUT WILL LIKELY REDEVELOP FAIRLY QUICKLY...DEPENDING ON DOWNSTREAM CLOUD DEBRIS AND SUBSEQUENT MORNING HEATING...AS THE ASSOCIATED OUTFLOW BOUNDARY MOVES TOWARD THE BLUE RIDGE. INSTABILITY IS MEAGER FOR LATE JULY AND DYNAMICS ARE WEAK...BUT STRONG HEATING AND PWATS NEARING 2.00 INCHES EAST OF THE BLUE RIDGE SHOULD YIELD SOME FAIRLY ROBUST STORMS...ALSO WITH LOCALLY HEAVY RAINFALL. SPC HAS CONTINUED TO OUTLOOK AREAS MAINLY EAST OF THE BLUE RIDGE FOR A MARGINAL RISK OF SEVERE ON THU. CONVECTION SHOULD BE DIMINISHING AND MOVING EAST OF THE AREA FAIRLY QUICKLY THU NIGHT. SOME ACTIVITY WILL LIKELY LINGER ACROSS THE CHARLOTTE TO HALIFAX COUNTY AREA OF THE PIEDMONT TOWARD MIDNIGHT...BUT AFTER THAT IT SHOULD ALL SHIFT EAST OF THE CWA. FOR THE REST OF THE PERIOD...THE FRONT IS STILL PROGGED BY MOST OF THE SYNOPTIC-SCALE MODELS TO BE PUSHED WELL SOUTH OF THE CWA AS THE UPPER FLOW AMPLIFIES...WITH A STRONG UPPER RIDGE WESTERN U.S. AND A DEEPENING TROUGH EASTERN U.S. THUS...THE FRONT SHOULD MOVE TO NEAR CENTRAL GA/CENTRAL SC AND TOWARD THE CENTRAL NC COAST BEFORE STALLING. THERE ARE STILL INDICATIONS THAT THE TAIL END OF THE TROUGH WILL BECOME CUTOFF ACROSS SOUTH GA/FL PANHANDLE...WITH AN ELONGATED TROUGH AXIS STUCK ALONG THE SOUTHEAST TO THE NC COASTLINE INTO EARLY NEXT WEEK. WAVES OF CONVECTION WILL LIKELY RIDE ALONG AND NEAR THIS BOUNDARY...BUT ALL OF THIS IS EXPECTED TO REMAIN WELL SOUTH OF OUR AREA. COOLING BEHIND THE FRONT WILL BE NOMINAL AT BEST...LIKELY ON A FEW DEGREES. 850MB TEMPS ARE NOT EXPECTED TO DROP MUCH BELOW +20C THROUGH THE PERIOD. MORE IMPORTANTLY...MOST OF THE MODELS ARE IN AGREEMENT THAT DEWPOINTS WILL FALL INTO THE 50S ACROSS THE MOUNTAINS AND 60S ACROSS THE PIEDMONT...BUT WILL HOVER NEAR 70 IN THE DANVILLE AREA. THIS WILL BE SOMEWHAT REFRESHING...BUT THE LATE JULY/EARLY AUGUST SUN WILL STILL FEEL QUITE WARM IN THE DAYTIME. EXPECT MIN TEMPS CLOSER TO NORMAL...WITH MAX TEMPS STILL LIKELY AVERAGING ABOVE NORMAL THROUGH MUCH OF THE PERIOD. && .LONG TERM /SUNDAY THROUGH TUESDAY/... AS OF 430 AM EDT WEDNESDAY... AS NOTED ABOVE...MODELS HAVE FINALLY COME INTO GOOD AGREEMENT IN KEEPING ANY CUTOFF UPPER LOW/WEAKNESS/PSEUDO-TROPICAL DEVELOPMENT ALONG THE SOUTHEAST U.S. COAST WELL SOUTH OF OUR REGION...EVENTUALLY BEING PUSHED OUT TO SEA OFF THE SC/NC COAST. SOME MODELS...ESPECIALLY THE ECMWF...TRY TO PUSH MOISTURE INTO THE FAR SOUTHEAST PART OF THE CWA OVER THE WEEKEND...BUT MOST MODELS SUGGEST THAT ANY PRECIPITATION WILL REMAIN FURTHER SOUTHEAST. HAVE HEDGED ON THE FAR SOUTHEAST CORNER WITH SOME LOW POPS...BUT HAVE GENERALLY KEPT IT RAIN FREE ELSEWHERE. NORTHWEST FLOW ALOFT WILL DOMINATE THE REGION AS THE UPPER TROUGH REMAINS IN PLACE ACROSS THE EASTERN CANADIAN PROVINCES. EVENTUALLY...A SERIES OF NORTHWEST FLOW DISTURBANCES APPEAR DESTINED TO END THE DRIER CONDITIONS EXPECTED FRI-SUN. THE FIRST OF THESE DISTURBANCES IS SLATED TO SKIRT THE NORTHERN PART OF THE CWA SUN NIGHT/MON. THERE IS ENOUGH INSTABILITY AND MOISTURE AT THAT POINT TO SUPPORT ISOLD SHRA/TSRA ACROSS THE MOUNTAINS AND I-64 CORRIDOR...SO ADDED SOME LOW POPS. THE NEXT SUCH DISTURBANCE SHOULD ARRIVE TOWARD THE MID PART OF NEXT WEEK. OVERALL...THE PATTERN IS GENERALLY DRY...WITH NO WIDESPREAD SYNOPTIC OR MEANINGFUL RAINFALL EVENTS INDICATED FOR THE PERIOD. TEMPERATURES WILL BE MOSTLY NEAR NORMAL THROUGH THE PERIOD...LOWS 60S WEST TO AROUND 70 EAST...WITH HIGHS 70S MOUNTAINS AND 80S ELSEWHERE...CREEPING CLOSER TO 90 PIEDMONT AS 850MB TEMPS HOVER MOSTLY IN THE +15C TO +20C RANGE THROUGH MOST OF THE PERIOD. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... AS OF 143 PM EDT WEDNESDAY... SCT TO BKN MVFR CLOUDS WILL PREVAIL THIS AFTERNOON INTO TONIGHT WITH POCKETS OF IFR/LIFR IN CONVECTION AND LOW CLOUDS. THE GREAT VARIABILITY IN CONDITIONS WILL HINDER AVIATION OPERATIONS THIS AFTERNOON INTO TONIGHT. THE COMBINATION OF LINGER SFC BOUNDARIES AND INSTABILITY WILL RESULT IN SCATTERED DIURNAL SHOWERS AND THUNDERSTORMS INTO TONIGHT. TAF SITES OF LWB...BLF AND BCB HAVE THE BEST CHANCE OF HAVING CONVECTION THIS AFTERNOON. STORMS WILL FADE WITH LOSS OF HEATING THIS EVENING INTO TONIGHT WITH FOG FORMING THURSDAY MORNING. A COLD FRONTAL BOUNDARY WILL BE APPROACHING LATE TONIGHT/EARLY THURSDAY. WE WILL HAVE TO WATCH FOR CONVECTION MOVING INTO OUR WESTERN MOUNTAINS EARLY THURSDAY MORNING. THE COLD FRONT WILL MOVE EAST ACROSS THE REGION THURSDAY INTO THURSDAY NIGHT. THE FRONT WILL SERVE AS A TRIGGER FOR MORE ENHANCED CHANCE OF WIDESPREAD MVFR/IFR SHOWERS AND THUNDERSTORMS THURSDAY AFTERNOON INTO EVENING. SOME OF THE STRONGER STORMS COULD CONTAINS GUSTY WINDS ESPECIALLY EAST OF THE MOUNTAINS. MEDIUM CONFIDENCE IN CEILINGS...VISIBILITIES AND WINDS DURING THE TAF PERIOD. EXTENDED AVIATION FORECAST... THIS FRONT SHOULD PUSH SOUTH OF THE AREA AND ALLOW FOR DRIER AND MOSTLY VFR CONDITIONS FRIDAY THROUGH SUNDAY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...WP NEAR TERM...KK/WP SHORT TERM...RAB LONG TERM...KK/RAB AVIATION...KK/RAB

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