Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 290553 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 153 AM EDT FRI APR 29 2016 .SYNOPSIS... A COMPLEX LOW PRESSURE SYSTEM WILL MOVE EAST ACROSS THE REGION TONIGHT WITH A WEAK COLD FRONT CROSSING THROUGH OUR AREA FRIDAY MORNING. WEAK HIGH PRESSURE FOLLOWS THE FRONT FRIDAY INTO FRIDAY NIGHT BRINGING A PERIOD OF DRIER WEATHER. LOW PRESSURE WILL TRACK UP ALONG THE FRONT LATER SATURDAY INTO SUNDAY RESULTING IN ADDED SHOWERS OVER THE WEEKEND. && .NEAR TERM /THROUGH TODAY/... AS OF 930 PM EDT THURSDAY... GIVEN DECREASING TRENDS IN CONVECTION OVER THE WEST WENT AHEAD AND DROPPED THE REMAINDER OF THE GOING SEVERE WATCH. HOWEVER GIVEN LINGERING INSTABILITY...CANT TOTALLY RULE OUT A HEAVIER SHOWER OR STORM ACROSS THE NEW RIVER/ROA VALLEY SECTIONS IN THE NEXT HOUR OR TWO WHERE HAVE SEEN NO RAIN TODAY. OTRW WILL STILL HAVE TO WAIT FOR THE RESIDUAL FRONT/WAVE TO THE WEST TO CLEAR THE REGION LATER TONIGHT BEFORE REMOVING ALL POPS. STILL APPEARS PER THE LATEST HRRR AND SUBSEQUENT SHORT TERM MODELS THAT WILL SEE MOST COVERAGE FADE AFTER MIDNIGHT AS THE FLOW TURNS MORE WESTERLY OVER THE MOUNTAINS WHILE THE WEDGE LINGERS IN THE EAST. THEREFORE WILL TAPER POPS FROM WEST TO EAST OVER THE NEXT FEW HOURS WITH JUST ABOUT ALL SHOWERS GONE OUT EAST BEFORE DAYBREAK. MAY NUDGE LOW TEMPS DOWN A BIT WITHIN THE WEDGE OTRW MOSTLY 50S TO AROUND 60 OVERNIGHT. PREVIOUS UPDATE AS OF 845 PM EDT THURSDAY... QUICK UPDATE TO DROP THE WATCH ACROSS THE NW NC COUNTIES GIVEN DEEPER CONVECTION ACTUALLY FARTHER NORTH AND UPSTREAM IN WEST VA THAT WILL LIKELY ONLY AFFECT WESTERN VA. ALSO MOST AREAS OVER NW NC HAVE BEEN WORKED OVER SO NOT EXPECTING MUCH ADDED CONVECTION DOWN THAT WAY. LEFT THE REMAINDER OF THE WATCH IN PLACE GIVEN CONVECTION OVERTOP THE WEDGE UP NORTH AND LINGERING INSTABILITY SOUTHERN SECTIONS. OTRW FEW ADDED CHANGES FOR NOW. PREVIOUS AFTERNOON DISCUSSION... FORECAST ISSUE THIS AFTERNOON WILL BE COVERAGE OF SHOWERS AND STORMS. WEDGE HAS HELD ALL DAY FROM CHARLOTTE COUNTY NORTHWEST TO BEDFORD/AMHERST. VIS SAT LOOP SHOWS MINOR EROSION OF THE WEDGE AND WITH 1018 MB HIGH OVER SRN PA WILL SEE LITTLE NE MOVEMENT OF THE EROSION. CONVECTION OVER THE ALLEGHANYS WILL WORK EWD INTO THE WEDGE BUT ONLY ELEVATED CONVECTION EXPECTED...SO SVR THREAT ALMOST NIL FOR LYH TODAY. FURTHER SOUTHWEST SUNSHINE MOST OF THE DAY HAS ALLOWED MUCAPES TO EXCEED 2000 J/KG FROM THE NC PIEDMONT AND FOOTHILLS...NORTHWEST TO THE SRN BLUE RIDGE OF VA. THIS SEEMS TO BE THE AREA TO WATCH CONCERNING SVR THREAT. EFFECTIVE SHEAR IS 40-45KTS IN THIS AREA. UPPER FLOW IS MAINLY WEST-EAST...AND FAIRLY QUICK. THIS COULD BE A LIMITING FACTOR ON SOME VERTICAL DEVELOPMENT ESPECIALLY IN CLUSTERS...AS SHEAR MAY TEAR INTO THE TCU. ANY CELLS THAT CAN OVERCOME THIS WILL BE CAPABLE OF GETTING SEVERE WITH DAMAGING WINDS AND HAIL. LOW PRESSURE SITUATED FROM INDIANA TO THE NC MTNS WILL BE MOVING SLOWLY EAST TO THE PIEDMONT BY MIDNIGHT. THIS WILL KEEP THE CONVERGENCE ZONE AS SUCH IN OUR CWA FOR A FEW HOURS...SO LOOKING AT HIGH CHANCE POPS ESPECIALLY IN THE BLUE RIDGE AND POINTS EAST THROUGH EARLY EVENING. HOWEVER...BETTER SUPPORT STARTS TO LIFT NORTHEAST DURING THIS TIME...AS DRY SLOT WORKS IN FROM THE SOUTHWEST. SHOULD SEE THINGS CLEAR AND DRY OUT LATE TONIGHT...EXCEPT EAST OF THE BLUE RIDGE WHERE SOME LINGERING LOW LVL MOISTURE REMAINS. SHOULD SEE SOME GOOD SUBSIDENCE BEHIND SYSTEM FRIDAY WITH MOSTLY SUNNY SKIES BY AFTERNOON...AFTER SOME MORNING LOW CLOUDS EAST. HIGHS WILL RANGE FROM THE LOWER 80S SOUTHSIDE VA INTO NC PIEDMONT...TO MID TO UPPER 70S ELSEWHERE...WITH SOME 60S POSSIBLE INTO THE BLUE RIDGE AND EAST TO BUCKINGHAM IF IT DOES NOT CLEAR OUT. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... AS OF 324 PM EDT THURSDAY... THE UNSETTLED WEATHER WILL CONTINUE FOR THE END OF THE MONTH INTO EARLY MAY. HIGH PRESSURE OVER CENTRAL CANADA WILL BUILD SOUTH DOWN INTO THE EASTERN UNITED STATES AND WEDGE DOWN THE EASTERN SEABOARD. THIS WILL RESULT IN COOLER WEATHER WITH SLIGHT CHANCE OF LIGHT RAIN AND DRIZZLE TO THE AREA FRIDAY NIGHT INTO SATURDAY. LOW TEMPERATURES FRIDAY NIGHT WILL RANGE FROM THE MID 40S IN THE NORTHWEST MOUNTAINS TO THE MID 50S IN THE PIEDMONT. THE FRONTAL BOUNDARY WILL LIFT NORTH ON SATURDAY AS A WARM FRONT...WITH SCATTERED SHOWERS AND A FEW DIURNAL THUNDERSTORMS MAINLY IN THE WESTERN MOUNTAINS. HIGH TEMPERATURES ON SATURDAY WILL VARY FROM AROUND 60 DEGREES IN THE NORTH TO THE LOWER 70S IN THE SOUTH. ISENTROPIC LIFT OVER THE HIGH PRESSURE WEDGE WILL BRING WIDESPREAD PRECIPITATION TO THE REGION SATURDAY NIGHT. LOW TEMPERATURES SATURDAY NIGHT WILL GENERALLY BE IN THE LOWER 50S TO NEAR 60 DEGREES. SEVERAL WAVES OF LOW PRESSURE WILL LIFT NORTHEAST ALONG THE FRONTAL BOUNDARY PRODUCING ROUNDS OF SHOWERS AND EMBEDDED THUNDERSTORMS. HIGH TEMPERATURES SUNDAY WILL WARM INTO THE MID 60S IN THE WEST TO THE MID 70S IN THE EAST. CLOUDS AND SHOWERS WILL LINGER SUNDAY NIGHT AS LOW PRESSURE PUSHES OFF THE EAST. THE GFS AND ECMWF ARE SHOWING SOME DRIER AIR IN THE MIDDLE BETWEEN THE MAIN AREA OF RAIN AND SHOWERS ASSOCIATED WITH SHORTWAVE IN THE WESTERN MOUNTAINS. LOW TEMPERATURES SUNDAY NIGHT INTO MONDAY MORNING WILL DROP INTO THE LOWER 50S IN THE MOUNTAINS TO AROUND 60 DEGREES IN THE PIEDMONT. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 324 PM EDT THURSDAY... LOW PRESSURE LOCATED OVER NORTHERN WEST VIRGINIA WITH A TRAILING COLD FRONT IN THE MOUNTAINS MONDAY MORNING WILL TRAVEL EAST MONDAY AFTERNOON INTO MONDAY NIGHT. THE COMBINATION OF A SHORTWAVE...WARM MOIST AIR AND ISENTROPIC LIFT WILL KEEP A CHANCE FOR RAIN AND LOW CLOUDS IN THE REGION MONDAY MORNING. THEN...A STRONG NORTHERN STREAM TROUGH WILL ERODE THE WEDGE AND KICK THE RAIN EAST AND OFF SHORE MONDAY AFTERNOON. THE EROSION OF THE WEDGE IS ALWAYS A FORECAST CHALLENGE AND MAY BE SLOWER THAN EXPECTED ON MODELS. IF WEDGES ERODES AS FORECASTED HIGHS ON MONDAY WILL BE WARMER THAN SUNDAY WITH READINGS FROM NEAR 60 DEGREES IN THE NORTHWEST MOUNTAINS TO THE MID AND UPPER 70S IN THE PIEDMONT. DRIER AIR PUSHES IN MONDAY NIGHT INTO TUESDAY. LOW TEMPERATURES MONDAY NIGHT WILL DROP INTO THE MID 40S IN THE MOUNTAINS TO THE LOWER 50S IN THE PIEDMONT. A WAVY FRONTAL BOUNDARY STALL TO OUR SOUTH ON TUESDAY INTO TUESDAY NIGHT. HIGH TEMPERATURES WILL VARY FROM THE UPPER 50S IN THE MOUNTAINS TO THE LOWER 70S IN THE PIEDMONT. LEANED TOWARDS GFS WITH HIGH PRESSURE BUILDING IN FROM THE NORTH TUESDAY NIGHT...AND DRIER AIR OVER THE WET ECMWF. LOW TEMPERATURES TUESDAY NIGHT WILL DROP INTO THE MID 40S IN THE WEST TO THE LOWER 50S IN THE EAST. HARD TO JUDGE HOW FAR NORTH MOISTURE ADVECTED WITH A DISTURBANCE THAT MOVES ACROSS THE SOUTHEASTERN STATES MIDWEEK INTO THURSDAY. FOLLOWED THE SUPERBLEND WITH COOLING TREND AND ISOLATED TO SCATTERED SHOWERS WEDNESDAY INTO THURSDAY. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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AS OF 145 AM EDT FRIDAY... SATELLITE PICTURES SHOWED IFR CLOUDS EXPANDING WEST AND SOUTH OVER SOUTHWEST VIRGINIA AND NORTHERN NORTH CAROLINA. AT THE 06Z START OF THE TAF FORECAST PERIOD KBCB WAS ON THE WESTERN EDGE OF THE LOW CLOUD SHIELD. HIGH CONFIDENCE THAT CONDITIONS AT KROA/KLYH/KDAN WILL REMAIN IFR UNTIL AFTER SUNRISE. EXPECT CLOUDS TO ERODE FROM SOUTHWEST TO NORTHEAST IN THE MORNING...HOWEVER...KLYH MAY NOT IMPROVE TO VFR UNTIL AROUND 18Z/2PM. FOG WITH MVFR TO LIFR VISIBILITIES WILL DEVELOP EARLY THIS MORNING...ESPECIALLY WEST OF THE BLUE RIDGE WHERE THE SKY WAS MOSTLY CLEAR AND WHERE THERE WAS RAIN ON THURSDAY. THIS FOG WILL ALSO DISSIPATE DURING THE MORNING. WITH SOME MID AND HIGH LEVEL CLOUDS SPREADING ACROSS THE AREA TONIGHT...CONDITIONS WILL BE VFR AFTER 00Z/8PM. EXTENDED AVIATION DISCUSSION... MORE WIDESPREAD SHOWERS WITH MVFR INCLUDING LOCALLY IFR CONDITIONS RETURN SATURDAY AFTERNOON AND PERSIST INTO SUNDAY NIGHT AS LOW PRESSURE TRACKS UP THE RESIDUAL STALLED FRONT RESULTING IN WIDESPREAD RAINFALL...AND SUB VFR CONDITIONS. A WEAK COLD SHOULD CROSS THE REGION MONDAY BRINGING IMPROVING FLYING CONDITIONS BY AFTERNOON AND VFR CONDITIONS MONDAY NIGHT INTO TUESDAY.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS/JH/WP NEAR TERM...JH/WP SHORT TERM...KK LONG TERM...KK AVIATION...AMS/JH

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