Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 030735 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 335 AM EDT THU SEP 3 2015 .SYNOPSIS...
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HIGH PRESSURE ACROSS THE AREA WILL KEEP A HOT AND HUMID AIRMASS IN PLACE THROUGH THE END OF THE WEEK. A BACKDOOR COLD FRONT WILL CROSS THE REGION LATE FRIDAY NIGHT INTO SATURDAY...BRINGING BETTER CHANCES OF SHOWERS AND STORMS IN ADVANCE OF IT LATE FRIDAY INTO FRIDAY NIGHT. DRIER AND COOLER AIR WILL WORK ITS WAY INTO THE AREA FOR THE LATTER HALF OF THE WEEKEND INTO THE START OF NEXT WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 240 AM EDT THURSDAY... OVERALL PERSISTENCE FORECAST CONTINUES OVER THE NEXT 24 HOURS WITH YET ANOTHER HOT/HUMID AFTERNOON IN STORE TODAY UNDER SURFACE HIGH PRESSURE AND WARM 85H TEMPS. HOWEVER ENOUGH OF A WEAKNESS ALOFT IN THE WAKE OF THE UPPER WAVE FROM WEDNESDAY TO ELIMINATE ANY CAPPING THIS AFTERNOON ESPCLY GIVEN LOWER 5H HEIGHTS AND SLIGHTLY COOLER MID LEVEL TEMPS. THIS AGAIN SUPPORTS THE POTENTIAL FOR AT LEAST SCATTERED CONVECTIVE DEVELOPMENT ESPECIALLY BLUE RIDGE VICINITY AND POINTS WEST INTO EARLY THIS EVENING. LATEST MODEL SOLUTIONS MOSTLY IN LINE WITH THIS SCENARIO BUT DIFFER ON THE DEGREE OF COVERAGE AND WHERE ANY MORE ORGANIZED CLUSTERS MAY TAKE SHAPE. SPC WRF AGAIN SHOWING MORE WIDESPREAD MOUNTAIN TSRA WITH FOCUS ON RESIDUAL WEAK TROFFINESS SLIDING SE FROM THE OHIO VALLEY INTO WEAK LOW LEVEL CONVERGENCE AIDED BY OROGRAPHICS AND HIGH INSTABILITY. OTHER SOLUTIONS HAVE LESS WITH MORE SHOTGUN FLAVOR FARTHER WEST AND A BIT SLOWER TO INIT UNTIL MID OR LATE AFTERNOON. SINCE THE NCAR CAM PROGS SIMILAR TO THE SPC WRF WHICH WAS BEST YESTERDAY WENT WITH A BIT HIGHER POP COVERAGE OUT TO THE FOOTHILLS WITH PERHAPS A SWATH OF BEST COVERAGE NORTHERN BLUE RIDGE BACK TOWARD THE NEW RIVER...JUST SOUTH OF WHERE CONVECTION WAS ON WEDNESDAY. SEVERE THREAT AGAIN LIMITED BY LITTLE SHEAR BUT SLOW MOVEMENT AND UNIFORM BUT WEAK NORTHERLY FLOW ALOFT COULD SUPPORT A FEW STRONGER BANDS OR PULSE CLUSTERS LATE. HIGH TEMPS AGAIN LOOK TO TOP 90 IN THE EAST AND ESPECIALLY WHERE THE GROUND IS DRIER OVER THE SE. OTRW STAYED A BIT ON THE WARM SIDE OF MOS GIVEN HIGHS ABOVE GUIDANCE OF LATE. ANY CONVECTION SHOULD AGAIN FADE THIS EVENING BUT MAY TEND TO LINGER IN SPOTS OVER THE NORTH/EAST GIVEN APPROACH OF WEAK SHORTWAVE ENERGY FROM THE NW LATE. HOWEVER DID GO MOSTLY DRY AFTER MIDNIGHT WITH MORE FOG AROUND ALTHOUGH COVERAGE QUITE DEPENDENT UPON EARLIER RAINFALL. MUGGY LOWS AGAIN MOSTLY 60S TO AROUND 70.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY/... AS OF 315 PM EDT WEDNESDAY... 500 MB HEIGHTS CONTINUE TO RISE OVER THE NORTHEAST UNITED STATES THROUGH FRIDAY NIGHT. BUT AT THIS SAME TIME THE SHORT WAVE COMING OUT OF MINNESOTA TRACKS OVER THE GREAT LAKES WILL CONTRIBUTE TO AN ELONGATED REGION OVER LOWER HEIGHTS FROM THE GREAT LAKES TO THE CAROLINAS...BETWEEN TWO PARTS OF THE UPPER RIDGE BY FRIDAY. FRIDAY WILL STILL HAVE MAXIMUM TEMPERATURES ABOVE NORMAL BUT BY SATURDAY MORNING NORTHEAST WINDS BRINGS IN AN AIR MASS WITH 850 MB TEMPERATURES AROUND +14. THESE COOLER TEMPERATURES COMBINED WITH UPSLOPE CLOUDS ON EASTERN SLOPES WILL KEEP MAXIMUM TEMPERATURES AT OR JUST BELOW NORMAL ON SATURDAY. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... AS OF 100 PM EDT WEDNESDAY... A BULK OF THE UPPER RIDGE REMAINS OVER THE SOUTHERN PLAINS WHILE ANOTHER PIECE MOVES ACROSS THE NORTHEAST UNITED STATES. SUNDAY AND MONDAY MODELS STILL SHOWED RELATIVELY LOWER HEIGHT OVER THE SOUTHEAST UNITED STATES. DURING THE WEEK THE UPPER RIDGE FLATTENS AND BY WEDNESDAY...A DEEP TROF HAS PROGRESSED INTO THE CENTRAL UNITED STATES. DRY AIRMASS REMAINS OVER THE AREA SATURDAY NIGHT AND SUNDAY. MODELS BEGIN TO BRING LOW LEVEL MOISTURE BACK INTO THE REGION ON TUESDAY NIGHT AND WEDNESDAY. BY TUESDAY...AT THE SURFACE...THE PARENT HIGH MOVES FAR ENOUGH OFFSHORE THAT THE PART OF THE HIGH OVER THE CENTRAL APPALACHIANS WILL BE VERY WEAK. CHANGE IN UPPER PATTERN WILL SET UP DEEPER SOUTHWEST FLOW OVER THE REGION ON WEDNESDAY AHEAD OF THE APPROACHING UPPER TROF. BETTER COVERAGE OF PRE-FRONTAL SHOWERS AND THUNDERSTORMS WILL NOT BE UNTIL WEDNESDAY. WILL HAVE A MAINLY DRY FORECAST FOR SATURDAY NIGHT THROUGH TUESDAY IN ALL BUT THE FAR SOUTHWEST COUNTIES OF THE FORECAST AREA. TEMPERATURES WILL BE CLOSE TO NORMAL ON SATURDAY AND SUNDAY BUT WILL THEN GRADUALLY WARM THROUGH WEDNESDAY. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... AS OF 1258 AM EDT THURSDAY... EARLIER SHOWERS HAVE PUSHED TO THE SOUTH TONIGHT LEAVING MAINLY VFR CONDITIONS UNDER CLEAR SKIES IN PLACE. THIS WILL LEAD TO ANOTHER ROUND OF FOG/STRATUS ESPECIALLY IN THE VALLEYS WITH KLWB LIKELY TO FALL INTO LIFR...WITH A PERIOD OF IFR/MVFR POSSIBLE AT KBCB AND KLYH. ELSEWHERE EXPECTING FOG TO REMAIN SPOTTY WITH ONLY LIMITED MVFR COVERAGE BY DAYBREAK. THURSDAY...VFR CONDITIONS TO RETURN AGAIN BY MID MORNING...FOLLOWED BY INCREASING CU AND CB BUILD UPS ESPECIALLY OVER THE MOUNTAINS. HOWEVER...IN THE AFTERNOON...SHOWERS AND STORMS WILL AGAIN FIRE UP OVER MOUNTAINS AS OLD OUTFLOW AND PERHAPS A WEAK WAVE ALOFT ENHANCE LIFT A BIT. APPEARS KBLF/KLWB MORE IN LINE FOR SHOWERS OR STORMS...BUT STILL ONLY SCATTERED COVERAGE. THUS WILL INCLUDE A VCTS MENTION...AFTER 18Z/2PM WITH VCSH AT KBCB. OTHERWISE CIGS WILL MAINLY BE VFR 4-6KFT. EXTENDED AVIATION DISCUSSION... WILL SEE A WEAK FLOW PATTERN WITH AN UPPER TROUGH EXTENDING FROM EAST-WEST OVER OUR AREA FRIDAY INTO SUNDAY. THIS ALONG WITH HIGH PRESSURE TO THE NORTHEAST WILL CAUSE THE LOW LEVEL FLOW TO TURN MORE EASTERLY IN TIME. AS OF NOW...THE TERMINALS WILL BE VFR DURING THE DAY...WITH POSSIBLE MVFR OR WORSE WITH FOG AT NIGHT INTO FRIDAY NIGHT. THE EASTERLY FLOW EXPECTED BY SATURDAY WILL BRING LOWER CLOUDS IN AND POTENTIAL FOR MVFR CIGS AT LEAST FOR THE MOUNTAINS...AND LOW END VFR ROA/LYH/DAN. WITH THIS UPPER TROUGH THERE WILL BE DAILY THREAT OF SHOWERS...SO SUB VFR IN THESE IS POSSIBLE. BY SUNDAY-MONDAY THE WEAK TROUGH ALOFT MOVES OVER THE SOUTHEAST COAST WHILE UPPER RIDGING ELONGATES OVER THE MID ATLANTIC. WE WILL SEE SOME DRYING TAKE PLACE SO VFR SHOULD OCCUR SUNDAY-MONDAY WITH THE STILL A THREAT OF FOG AT NIGHT AT KBCB/KLWB. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...AMS LONG TERM...AMS AVIATION...JH/WP

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