Area Forecast Discussion
Issued by NWS Blacksburg, VA

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498 FXUS61 KRNK 011744 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 144 PM EDT SUN MAY 1 2016 .SYNOPSIS... A COOL AIR WEDGE ERODES THIS AFTERNOON...AS SOUTHWEST FLOW INCREASES AHEAD OF A COLD FRONT. THIS FRONT WILL STALL TO OUR SOUTH MONDAY AS A WAVE OF LOW PRESSURE RIDES ALONG THE FRONT MONDAY INTO TUESDAY. 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 TONIGHT/... AS OF 1130 AM EDT SUNDAY... FORECAST UPDATED TO SHOW LESS COVERAGE OF SHOWERS AS WE ARE BETWEEN UPPER WAVES...WITH SOME SUBSIDENCE COMBINED WITH THE HEAVIER SHOWERS TO ERODE THE WEDGE A LITTLE FASTER OVER THE SOUTHWEST CWA. GETTING MORE SUNSHINE BREAKING OUT...SO THIS WILL ACT TO INCREASE INSTABILITY. HOWEVER...WILL HAVE TO AWAIT FOR THE NEXT SHORTWAVE OVER WRN KY LATE THIS MORNING TO SHIFT TO THE AREA BY THE END OF THE DAY. UNTIL THEN...COULD SEE SOME POP UP SHOWERS OR ISOLATED STORMS WITH INCREASING POPS IN THE WEST AFTER 4 PM. SVR THREAT STILL FAVORS KY/TN/OHIO INTO WV...AND MAY SEE SOME STRONGER STORMS MAKE IT TO FAR SW VA INTO SE WV BY 8PM. GIVEN MORE SUNSHINE...UPPED HIGHS A FEW DEGREES WITH MOST AREAS SEEING 70S. WEDGE MAY STICK AROUND LONGER FROM AMHERST TO KEYSVILLE VA...BUT EVEN THEN STRONG SUN ANGLE SHOULD ALLOW FOR SOME SUNSHINE AT TIMES LATER THIS AFTERNOON. PREVIOUS VALID DISCUSSION... THE AREA IS LEFT WITH SOUTHWEST FLOW ALOFT THANKS TO A PERSISTENT BROAD AREA OF LOW PRESSURE IN THE SOUTHWEST U.S. ADDITIONAL WEAK DISTURBANCES ARE EMBEDDED WITHIN THE UPPER FLOW...ONE WHICH WILL HELP PUSH A NEW COLD FRONT INTO THE REGION OVERNIGHT...WHICH WILL THEN STALL JUST TO OUR SOUTH BY MON. FEEL THAT WHATEVER IS LEFT OF THE WEDGE IN EASTERN SECTIONS WILL FINALLY ERODE OVERNIGHT INTO MONDAY MORNING...ALLOWING TEMPERATURES TO CONTINUE TO MODERATE WITH MINIMAL COOLING OVERNIGHT. AREAS EAST OF THE BLUE RIDGE MAY SEE MIN TEMPS MONDAY MORNING CLOSE TO MAX TEMPS THIS AFTERNOON. && .SHORT TERM /MONDAY 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 /18Z 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...RAB/WP SHORT TERM...PW LONG TERM...PW AVIATION...RAB/WP

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