Area Forecast Discussion
Issued by NWS Blacksburg, VA

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182 FXUS61 KRNK 012008 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 408 PM EDT SUN MAY 1 2016 .SYNOPSIS... A SLOW MOVING FRONT WILL HEAD INTO THE MOUNTAINS MONDAY...STALLING ACROSS THE BLUE RIDGE MONDAY NIGHT...THEN FINALLY SLIDING SOUTHEAST BY MIDWEEK. FOR WEDNESDAY THROUGH FRIDAY...AN UPPER LOW WILL DRIFT SOUTHWARD INTO THE REGION FROM THE GREAT LAKES...KEEPING AN UNSETTLED AND UNSEASONABLY COOL PATTERN THROUGHOUT THE REGION. && .NEAR TERM /THROUGH MONDAY/... AS OF 320 PM EDT SUNDAY... FEW SHOWERS THIS AFTERNOON BETWEEN UPPER WAVES. LOOKING FURTHER WEST...ENVIRONMENT INCREASINGLY UNSTABLE OVER KY IN ASSOCIATION WITH UPPER SHORTWAVE AND STEEPER LAPSE RATES. AS WE HEAD TOWARD EVENING THIS WAVE IS GOING TO NOSE EAST TOWARD THE CENTRAL APPALACHIANS BY LATE AFTERNOON INTO THE EVENING. THINKING IS THE SAME AS EARLIER...IN THAT SHOWERS AND STORMS WILL INCREASE AGAIN BY EARLY EVENING OVER THE MOUNTAINS...WITH A SCT/BKN LINE OF CONVECTION POSSIBLY SHIFTING EAST/SOUTHEAST FROM SE WV TO THE PIEDMONT THIS EVENING. SVR PARAMETERS FAVOR STRONGER STORMS IN WV/KY/FAR SW VA...BUT WEAKEN FURTHER EAST...BUT CANNOT RULE OUT STRONGER STORMS TO THE BLUE RIDGE THIS EVENING. ORIENTATION OF THE CONVECTION AND SPEED OF MOVEMENT SHOULD PREVENT A FLASH FLOOD THREAT...THOUGH LOCALIZED FLOODING IS POSSIBLE...GIVEN THE 1 INCH+ WE HAD EARLIER TODAY IN PORTIONS OF THE REGION. STILL NOT ENOUGH FOR A FLOOD WATCH. FOR LATE TONIGHT...SHOWERS WANE AND WILL SEE CONTINUED SW ALOFT. CANNOT RULE OUT A FEW SHOWERS AT TIMES ESPECIALLY GIVEN HIGHER MOISTURE IN THE LOW LVLS. FOG PARAMETERS ALSO FAVOR GOOD COVERAGE OF FOG ACROSS THE RIVER VALLEYS AND WHERE IT RAINS THIS EVENING...DEPENDENT ON HOW MUCH CLEARING TAKES PLACE BEHIND THE CONVECTION. MONDAY...WE WILL SEE THE COLD FRONT MOVE FROM THE EASTERN OHIO VALLEY SOUTHWEST TO MIDDLE TN IN THE MORNING...SLOWLY EAST TO THE CENTRAL APPALACHIANS TO CUMBERLAND PLATEAU BY AFTERNOON. EXPECTING TO SEE A FEW SHOWERS OR STORMS ACROSS THE MOUNTAINS IN THE MORNING. CLOUD COVER WILL BE INCREASING ALOFT BUT WILL STILL SEE SOME SUNSHINE AT TIMES AND THIS SHOULD LEAD TO MUCAPES OF 1500-2500 J/KG BY MID AFTERNOON. MODELS ARE IN SOMEWHAT AGREEMENT THAT THE 2ND OF THE UPPER SHORTWAVES WILL PASS ACROSS THE CENTRAL AND SOUTHERN APPALACHIANS DURING THE LATE AFTERNOON LEADING TO MORE ROBUST CONVECTION. THE STORM PREDICTION CENTER HAS MARGINAL RISK FOR MOST OF THE AREA. IF THE FRONT MOVES QUICKER THEN CLOUD COVER WILL HINDER LOW LVL INSTABILITY. THE BEST SHEAR LOOKS TO SITUATE ITSELF FROM FAR SW VA/SE KY NORTHWARD INTO THE MD/PA AREA...SO THIS COULD LEAD TO MORE OF A WIND THREAT IN OUR FAR WRN CWA...WITH MARGINALLY STRONG TO SEVERE STORMS EAST. BETTER LOW LVL AND UPPER LEVEL SUPPORT DOES NOT REALLY GET GOING UNTIL AFTER 21Z/5PM OVER THE MOUNTAINS SO COULD BE ANOTHER LATE AFTERNOON INTO EVENING EVENT. WITH NO WEDGE MONDAY AND DEPENDING ON SKY COVER...TEMPS SHOULD WARM INTO THE 70S IN THE MOUNTAINS...TO LOWER 80S EAST. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... AS OF 530 AM EDT SUNDAY... THE COLD FRONT SHOULD PUSH EASTWARD OVER THE MID ATLANTIC ON MONDAY...AND BRING ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS. SPC HIGHLIGHTS THE CWA FOR A MARGINAL RISK OF SEVERE WEATHER...AND THE MODEL SOUNDINGS APPEAR FAVORABLE FOR CONVECTIVE DEVELOPMENT. HIGHS FOR MONDAY REACH THE LOWER 70S TO THE LOWER 80S...WHICH WILL ALLOW CAPE VALUES TO EXCEED 1000 J/KG BY THE AFTERNOON IN THE PIEDMONT. IF ANY STRONGER STORMS MATERIALIZE AHEAD OF THE COLD FRONT...LARGE HAIL AND DAMAGING WINDS WOULD BE THE MAIN THREATS. THIS FRONT IS PROJECTED TO WEAKEN AND STALL DURING MONDAY NIGHT INTO TUESDAY...BUT HOW FAR SOUTH IT CAN REACH BEFORE IT BECOMES STATIONARY REMAINS A LITTLE QUESTIONABLE. REGARDLESS...IT WILL KEEP SCATTERED SHOWERS IN THE FORECAST THROUGHOUT THIS TIME. SEVERAL MORE WAVES OF LOW PRESSURE RIDE NORTHWARD ALONG THE STALLED FRONTAL BOUNDARY DURING TUESDAY AND WEDNESDAY. WHILE THE CHANCE OF SHOWERS SHOULD LINGER THROUGH THESE TWO DAYS...THE THREAT OF THUNDERSTORMS APPEARS LIMITED TO MAINLY NORTHWEST NORTH CAROLINA ON TUESDAY AFTERNOON DUE TO LINGERING INSTABILITY AND THE PROXIMITY OF THE STALLED FRONT. HIGH TEMPERATURES ON TUESDAY SHOULD DIP FIVE TO TEN DEGREES LOWER THAN ON MONDAY. THE CHANCE OF THUNDERSTORMS DIMINISHES ON TUESDAY NIGHT...AS THE WAVES OF LOW PRESSURE SUCCESSFULLY PUSH THE FRONTAL BOUNDARY TOWARD THE COAST BY WEDNESDAY. THAT SITUATION SHOULD KEEP JUST A CHANCE OF SHOWERS THROUGH WEDNESDAY...WITH HIGHS NEARLY THE SAME COMPARED TO TUESDAY. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... AS OF 545 AM EDT SUNDAY... AS THE COLD FRONT FINALLY GAINS ENOUGH ENERGY TO LIFT OFFSHORE ON WEDNESDAY NIGHT...A DEEP UPPER LEVEL TROUGH WILL MIGRATE FROM THE HUDSON BAY IN CANADA TOWARD THE GREAT LAKES. THE TROUGH SHOULD REACH THE APPALACHIAN MOUNTAINS BY THURSDAY...AND EVENTUALLY CUT OFF OVERHEAD. MEANWHILE...ANOTHER CLOSED UPPER LEVEL LOW WILL ALSO CUT OFF OVER THE ROCKY MOUNTAINS. IN BETWEEN THESE TWO LOWS...A STRONG UPPER LEVEL RIDGE WILL RESIDE OVER THE PLAINS. THIS ATMOSPHERIC PATTERN CREATES ANOTHER OMEGA BLOCK OVER THE UNITED STATES SIMILAR TO WHAT WAS WITNESSED BACK IN MID APRIL...WHICH BOTH THE LATEST ECMWF AND GFS MODELS DEPICT IN REASONABLY GOOD AGREEMENT. UNLIKE THE LAST OMEGA BLOCK WHERE THE MID ATLANTIC ENJOYED UNSEASONABLY WARM AND DRY CONDITIONS UNDER THE UPPER LEVEL RIDGE...JUST THE OPPOSITE WILL OCCUR DUE TO BEING UNDER THE UPPER LEVEL LOW...WITH COOL AND WET CONDITIONS EXPECTED THROUGH THE END OF THIS WORK WEEK. HIGHS WILL ONLY REACH THE 50S AND 60S BY THURSDAY AND FRIDAY. ON SATURDAY...THE OMEGA BLOCK GRADUALLY WEAKENS...WHILE UPPER LEVEL RIDGING SLOWLY BEGINS OVERHEAD. IT APPEARS THAT WARMER AND DRIER CONDITIONS COULD ARRIVE TOWARD THE END OF THIS WEEKEND. && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... AS OF 137 PM EDT SUNDAY... FORECAST REFLECTS A BLEND OF THE LATEST RAP/NAM MODELS. SHOULD SEE ALL SITES BECOME VFR THIS AFTERNOON AS CLOUDS ERODE AND SW FLOW DIMINISHES THE WEDGE. AS WE HEAD TOWARD LATE AFTERNOON WILL BE SEEING ANOTHER UPPER IMPULSE MOVING FROM KY INTO THE CENTRAL APPALACHIANS AND SHENANDOAH VALLEY. UNTIL THEN...ISOLATED SHOWERS/STORMS MAY POP...BUT LOOKS LIKE BEST THREAT WILL NOT BE UNTIL AFTER 21Z ACROSS BLF/LWB THEN POSSIBLY ROA/BCB BY 00Z. STILL MODELS ARE SHOWING SCT/BKN COVERAGE SO FOR POINTS LIKE LYH/ROA WILL ONLY PUT IN VCSH FOR NOW...THOUGH THUNDERSTORMS CANNOT BE RULED OUT. ONCE THIS IMPULSE MOVES EAST BY MIDNIGHT...A BREAK IN THE SHOWERS SHOULD OCCUR OVERNIGHT. QUESTION WILL BE LOW LVL MOISTURE LEADING TO LOWER CIGS AND/OR VSBYS. NOT SEEING ANY RETURN TO WEDGE AS FLOW STAYS SW AT THE SFC. KEPT CLOSE TO THE PREVIOUS FORECAST AND KEPT TEMPO IN AT LWB/BCB...BUT ALL SITES COULD SINK TO IFR OR WORSE DURING THE 06-13Z TIME FRAME. AS SW FLOW KICKS IN MONDAY MORNING A TRANSITION TO SCT/BKN VFR CIGS TO TAKE PLACE AT ALL SITES...WITH SHOWERS AND STORMS EXPECTED IN THE AFTERNOON. EXTENDED AVIATION DISCUSSION... FRONTAL BOUNDARY WILL STALL OVERHEAD BY MONDAY. MORE WAVES OF LOW PRESSURE WILL MOVE ALONG THE STALLED BOUNDARY FROM TUESDAY THROUGH THURSDAY...WHICH SHOULD HELP PUSH THE BOUNDARY OFFSHORE. A DEEP UPPER LEVEL TROUGH IS PROJECTED TO DIVE SOUTHWARD OVER THE APPALACHIAN MOUNTAINS BY WEDNESDAY INTO THURSDAY. OVERALL...FLYING CONDITIONS APPEAR RATHER POOR THROUGH MOST OF THIS WEEK DUE TO THE LIKELIHOOD OF LOW CLOUDS...PERIODS OF RAIN...AND PATCHY FOG. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...RAB/WP NEAR TERM...WP SHORT TERM...PW LONG TERM...PW AVIATION...RAB/WP

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