Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 311358 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 958 AM EDT MON AUG 31 2015 .SYNOPSIS... AN UPPER LEVEL DISTURBANCE PASSING ACROSS THE CAROLINAS WILL MAINTAIN SHOWER ACTIVITY ACROSS THE AREA THROUGH LATE MORNING... WITH ADDITIONAL SHOWERS THEN DEVELOPING WITH DAYTIME HEATING. UPPER LEVEL HIGH PRESSURE WILL THEN STRENGTHEN AND KEEP US IN A RATHER STAGNANT PATTERN...MAINTAINING A CHANCE FOR AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS THROUGH THE MIDDLE OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 100 AM EDT MONDAY... THE CURRENT FORECAST IS ON TRACK SO ONLY SOME MINOR ADJUSTMENTS WERE MADE TO REFLECT THE MOST RECENT RADAR TRENDS AS THE BULK OF PRECIPITATION ASSOCIATED WITH THE SHORT WAVE PULLING THROUGH THE REGION IS HEADED OFF TO OUR EAST...LEAVING SPOTTY SHOWERS AND A CHANCE FOR SOME DIURNAL CONVECTION THIS AFTERNOON. PREVIOUS AFD... THE DISTURBANCE TRIGGERING OUR SPOTTY RAINFALL WILL PROGRESS EAST THROUGH LATE MORNING...WITH SHOWER ACTIVITY BECOMING ISOLATED TO WIDELY SCATTERED BY LUNCHTIME. HOWEVER...WE CAN EXPECT SPOTTY SHOWERS TO REDEVELOP DURING THE AFTERNOON AS WE APPROACH MAXIMUM DAYTIME HEATING. BETTER CHANCES FOR SHOWER ACTIVITY WILL BE FOUND ACROSS THE MOUNTAINS...WHERE CONVERGENCE ALONG THE RIDGETOPS WILL PROVIDE ADDED LIFT. RAINFALL AMOUNTS WILL REMAIN LIGHT...PERHAPS ONE TO TWO TENTHS OF AN INCH IN SPOTS. SKIES WILL REMAIN CLOUDY TO MOSTLY CLOUDY...WHICH WILL LIMIT AFTERNOON HIGHS TO THE UPPER 70S FOR THE MOUNTAINS...AND THE LOW 80S FOR THE PIEDMONT. WITH THE UPPER LEVEL DISTURBANCE OUT OF OUR AREA BY MONDAY EVENING... EXPECT SHOWERS TO END AND CLOUD COVER TO DECREASE. WE WILL HANG ON TO THE MUGGY AIRMASS HOWEVER...WHICH WILL MAKE FOR ANOTHER WARM NIGHT WHERE TEMPERATURES HOLD IN THE LOW TO MID 60S AREAWIDE. THE DECREASE IN CLOUDS...COUPLED BY LIGHT WINDS...WILL ALSO SUPPORT ANOTHER ROUND OF PATCHY FOG.
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&& .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... AS OF 400 AM EDT MONDAY... SEVERAL WEAK SYNOPTIC FEATURES TO NOTE ACROSS THE REGION TUESDAY...ALL UNDERLYING A BROAD SUBTROPICAL UPPER RIDGE EXTENDING FROM THE SOUTH CENTRAL U.S. INTO THE NORTHEAST U.S. REMNANTS OF FORMER T.S. ERIKA WILL BE LOCATED OFF THE NC/VA COAST AND TRACKING SOUTHEAST AROUND THE EASTERN PERIPHERY OF THE UPPER RIDGE. MEANWHILE...A VERY WEAK AREA OF LOW PRESSURE ALOFT WILL PERSIST FROM EASTERN TX INTO THE OH VALLEY. OVERALL...THERE IS LITTLE IN THE WAY OF A FOCUSING MECHANISM FOR PRECIPITATION AND ANY CONVECTION SHOULD BE THE RESULT OF DIFFERENTIAL HEATING AND LINGERING TROPICAL MOISTURE ACROSS THE MOUNTAINS...MAINLY ACROSS THE ALLEGHANYS OF EASTERN WV/WESTERN VA...AND THE BLUE RIDGE OF NORTHWEST NC. FOR WEDNESDAY...THE PATTERN BECOMES SOMEWHAT MORE INTERESTING. A WEAK SHORT WAVE...ORIGINALLY EMANATING FROM LOW PRESSURE IN THE PACIFIC NORTHWEST...WILL TRACK AROUND THE NORTHERN PERIPHERY OF THE UPPER LOW...RESULTING IN A TEMPORARY SUPPRESSING OF THE UPPER RIDGE TO THE SOUTH. THE WEAK UPPER TROUGH WILL SLIDE SE-SSE INTO NORTHERN VA DURING PEAK DIURNAL HEATING. WITH RESIDUAL TROPICAL MOISTURE IN PLACE...THERE SHOULD BE AN INCREASE IN AFTERNOON/EVENING CONVECTION AS COMPARED TO TUESDAY. CERTAINLY...ORGANIZATION AND COVERAGE SHOULD BE BETTER THAN TUESDAY...BUT WITH WEAK DYNAMICS...STILL PRUDENT TO KEEP POPS IN THE LOW-MID CHANCE RANGE AT THIS POINT. THE WEAK UPPER TROUGH WILL SAG FURTHER SOUTH TO SOUTH-SOUTHWEST THURSDAY AS A VERY HIGH AMPLITUDE RIDGE BUILDS TOWARD HUDSON BAY. THE UPPER RIDGE WILL BE THE UNDERLYING SYNOPTIC FEATURE FOR THE ENTIRE EASTERN U.S. THE BEST THREAT FOR CONVECTION WILL FOLLOW THE SOUTHWARD SHIFT OF THE WEAK UPPER TROUGH...MAINLY ACROSS SOUTHWEST VA/NORTHWEST NC...SOUTHSIDE VA...AND THE NC PIEDMONT BY AFTERNOON. WITH VERY WEAK DYNAMICS...CONVECTION WILL AGAIN BE THE RESULT OF DAYTIME INSTABILITY AND DIFFERENTIAL HEATING. POPS HAVE ONCE AGAIN BEEN HELD MOSTLY IN THE 20-30 PERCENT RANGE. UNDER THE UPPER RIDGE...850MB TEMPS WILL HOVER IN THE +18C TO +20C RANGE MUCH OF THE PERIOD. THE HOTTEST AIR WILL REMAIN TO OUR NORTH...HOWEVER. DEWPOINTS WILL HOVER AROUND 60F MOUNTAINS TO THE UPPER 60S PIEDMONT. THIS WILL RESULT IN A CONTINUATION OF ABOVE NORMAL TEMPERATURES THROUGH THE PERIOD...ESPECIALLY MIN TEMPS. OVERALL EXPECT MIN TEMPS TO AVERAGE 10 DEGREES ABOVE NORMAL...WITH MAX TEMPS 5 TO 7 DEGREES ABOVE NORMAL THROUGH THE PERIOD. USED A MODEL BLEND FOR MAX/MIN TEMPS THROUGH THE PERIOD AS THE GFS CONTINUES TO BE TOO WARM...AS IT HAS MOST OF THE SUMMER. THIS WILL RESULT IN MAX TEMPS MOSTLY IN THE 80S...WITH 70S IN THE MOUNTAINS AND A FEW SPOTS NEAR 90 ACROSS THE PIEDMONT. && .LONG TERM /FRIDAY THROUGH SUNDAY/... AS OF 415 AM EDT MONDAY... A LATE SUMMER...HIGH AMPLITUDE UPPER RIDGE REMAINS OVER THE NORTHEAST U.S. INTO SOUTHEAST CANADA AT THE BEGINNING OF THE PERIOD WITH A FAIRLY DEEP TROUGH IN THE NORTHWEST U.S. THIS PATTERN WILL REMAIN IN PLACE THROUGH THE WEEKEND...THEN STILL APPEARS DESTINED TO BREAK DOWN EARLY NEXT WEEK AS THE AFOREMENTIONED NORTHWEST U.S. UPPER TROUGH BEGINS TO TRACK EASTWARD. CONSEQUENTLY...UPPER HEIGHTS AND 850MB TEMPS REMAIN WELL ABOVE NORMAL FOR EARLY SEPTEMBER AS SUMMER HANGS ON. HOWEVER...MODELS CONTINUE TO INDICATE DEVELOPMENT OF A BACKDOOR COLD FRONT DURING THE LATER HALF OF THE WEEK AS A LARGE 1030MB SFC HIGH DEVELOPS UNDERNEATH THE NORTHEAST U.S. UPPER RIDGE. THIS SURFACE HIGH BUILDS SOUTHWEST INTO THE WEEKEND...PUSHING THE ASSOCIATED BACKDOOR COLD FRONT INTO THE REGION THURSDAY...BEFORE IT STALLS ACROSS THE SOUTH- SOUTHWEST PART OF THE CWA. THIS FEATURE...COMBINED WITH RESIDUAL ANTECEDENT TROPICAL MOISTURE...SHOULD SERVE TO RESULT IN AN ENHANCEMENT OF DIURNAL CONVECTION. HOWEVER...WITH EXTREMELY WEAK DYNAMICS ALOFT UNDERNEATH THE MAMMOTH UPPER RIDGE...CONVECTION WILL LARGELY BE DRIVEN BY LOW-LEVEL CONVERGENCE ATTEMPTING TO OVERCOME LARGE SCALE SUBSIDENCE. IT MAY END UP BEING MORE OF A LIGHT SHOWER SITUATION WITH ABUNDANT CLOUD COVER BANKED UP ALONG THE EASTERN SLOPES OF THE ALLEGHANYS. THE BEST COVERAGE OF PRECIPITATION SHOULD BE ACROSS THE NORTHERN PARTS OF THE CWA FRI...SHIFTING TO THE SOUTHWEST PART OF THE CWA SAT-SUN. DESPITE THE UPPER RIDGE...THE CLOUD COVER AND INCREASING NORTHEAST SFC WINDS WILL RESULT IN A TREND TOWARD COOLER TEMPERATURES DURING THIS PERIOD...ESPECIALLY MAX TEMPS AND MOST NOTABLY ACROSS THE NORTH AND EAST PARTS OF THE CWA. MAX TEMPS WILL DROP BACK FROM THE MID AND UPPER 80S THU TO THE 70S BY THE WEEKEND. MIN TEMPS WILL BE HARDER PRESSED TO DROP HOWEVER WITH LOWS STILL MOSTLY IN THE 60S. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... AS OF 745 AM EDT MONDAY... RADAR INDICATES THAT THE MAJORITY OF HEAVIER RAIN ASSOCIATED WITH AN UPPER LEVEL DISTURBANCE PASSING ACROSS THE CAROLINAS IS NOW EAST OF THE TAF SITES THIS MORNING...LEAVING ONLY SPOTTY LIGHT RAIN/SPRINKLES ACROSS THE FORECAST AREA. CEILINGS ACROSS THE AREA ARE MOSTLY MID LEVEL...WITH BASES RANGING FROM 5KFT TO 8KFT. VISIBILITIES ACROSS THE AREA ARE RANGING FROM 3SM TO 5SM...BUT EXPECT THESE VISIBILITIES TO IMPROVE AS HEATING INCREASES...AFTER 31/14Z. EXPECT VFR CONDITIONS TO PERSIST THROUGH THE DAY...WITH GENERALLY LIGHT AND VARIABLE WINDS. LIGHT SHOWERS/SPRINKLES WILL PERSIST THROUGH THE AFTERNOON...WITH COVERAGE INCREASING SLIGHTLY ACROSS THE MOUNTAINS DURING AROUND MAXIMUM DAYTIME HEATING. CANNOT RULE OUT AN ISOLATED THUNDERSTORM...HOWEVER INSTABILITY APPEARS TO BE STRICTLY LIMITED. SHOWER ACTIVITY WILL DIMINISH AND SKIES WILL SCATTER TOWARD SUNSET...AND EXPECT TO ENTER THE NIGHT RAIN-FREE. WITH PARTLY CLOUDY SKIES AND LIGHT WINDS OVERNIGHT...EXPECT PATCHY FOG TO DEVELOP ACROSS MOST OF THE FORECAST REGION. HAVE ENTERED MVFR/IFR VISIBILITIES FOR MOST OF THE TAF SITES...BEGINNING AS EARLY AS 01/06Z. EXTENDED AVIATION DISCUSSION... THE FORECAST AREA WILL REMAIN IN A WEAKLY FORCED SYNOPTIC ENVIRONMENT THROUGH MIDWEEK...WITH CHANCES FOR DIURNAL CONVECTION MAINLY FROM THE BLUE RIDGE WEST...AND SOME MVFR/IFR FOG/STRATUS DEVELOPMENT AT NIGHT...ESPECIALLY AT KBCB AND KLWB. && .EQUIPMENT... AS OF 400 AM EDT MONDAY... THE DEW POINT READING AT KJFZ...RICHLANDS VA AWOS...IS INCORRECT. AT THIS TIME WE DO NOT KNOW WHEN THIS SENSOR WILL BE REPAIRED. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...NF NEAR TERM...MBS/NF SHORT TERM...RAB LONG TERM...AMS/RAB AVIATION...NF/WP EQUIPMENT...JM

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