Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 042355 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 755 PM EDT SAT JUL 4 2015 .SYNOPSIS... LOW PRESSURE MOVING OFF THE MIDDLE ATLANTIC COAST WILL PUSH A COLD FRONT SOUTHWARD TONIGHT INTO SUNDAY. THIS WILL RESULT IN ROUNDS OF SHOWERS AND THUNDERSTORMS. THE UNSETTLED WEATHER WILL CONTINUE TO AFFECT THE REGION FOR THE NEXT SEVERAL DAYS...KEEPING A CHANCE OF SHOWERS AND THUNDERSTORMS IN THE FORECAST THROUGH THE FIRST PART OF NEXT WEEK...AS TEMPERATURES BEGIN A GRADUAL WARMING TREND. && .NEAR TERM /THROUGH SUNDAY/... AS OF 330 PM EDT SATURDAY... SEVERAL SHORTWAVES WILL ROTATE THROUGH THE UPPER TROF OVER EAST WITH SURFACE FRONT WAVERING AROUND THROUGH THE AREA. LOW PRESSURE WILL PUSH OFF THE MIDDLE ATLANTIC COAST WHICH SWINGS COLD FRONT SOUTH THIS AFTERNOON INTO TONIGHT. SOLAR HEATING HAS RESULTED IN ENOUGH INSTABILITY TO GENERATE SCATTERED SHOWERS AND THUNDERSTORMS. THE MOST UNSTABLE CAPES AND DEEP MOISTURE CONVERGENCE ON SPC HOURLY MESO ANALYSIS POINTING TO EAST OF THE MOUNTAINS. THE DAY ONE CONVECTIVE OUTLOOK CLIPS THE SOUTHEAST OF CWA WITH A MARGINAL THREAT WITH SLIGHT POTENTIAL ACROSS EASTERN NORTH CAROLINA. THE WINDOW FOR ANY STRONGER STORMS THIS AFTERNOON IS VERY SMALL. STORMS ARE MOVING THUS NOT ANTICIPATING ANY FLOODING ISSUE. THE BULK OF THE CONVECTION SHOULD TAPER OFF THIS EVENING INTO TONIGHT WITH JUST SOME LINGERING ISOLATED SHOWERS FOR THE OVERNIGHT. IT APPEARS THAT MANY LOCATIONS WILL BE ABLE TO GET OFF FIREWORKS DISPLAYS. LOWS TEMPERATURES TONIGHT WILL REMAIN MILD WITH READINGS FROM AROUND 60 IN THE NORTHWEST MOUNTAINS TO THE UPPER 60S IN THE PIEDMONT. THE WAVY FRONTAL BOUNDARY REMAIN ACROSS THE REGION ON SUNDAY. SHORTWAVES CONTINUE TO TRAVEL EAST ALONG THE UPPER TROUGH. SHOWERS AND THUNDERSTORMS WILL DEVELOP BY SUNDAY LATE MORNING AND BECOME NUMEROUS BY SUNDAY AFTERNOON. HIGH TEMPERATURES SUNDAY WILL RANGE FROM THE UPPER UPPER 60S IN THE MOUNTAINS TO THE MID 80S IN THE PIEDMONTS. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... AS OF 330 PM EDT SATURDAY... MODELS ARE IN AGREEMENT WITH RESPECT TO THE DEVELOPMENT OF A WEAK CLOSED UPPER LOW ACROSS THE SOUTHEAST STATES AND ITS SUBSEQUENT NORTHWARD DRIFT INTO THE FIRST PART OF NEXT WEEK. TAIL END OF LONG STANDING EASTERN U.S. TROUGH WILL BECOME CUTOFF ACROSS NORTHERN GA/AL/EASTERN TN FROM THE PARENT UPPER TROUGH...WHICH WILL SHEAR OUT ACROSS NEW ENGLAND AS A SHORT WAVE RIDGE DRIFTS INTO THE OH VALLEY. THE UPPER LOW WILL THEN DRIFT SLOWLY NORTHEAST INTO MON...FINALLY LIFTING NORTH OF THE REGION BY TUESDAY AS THE NEXT UPSTREAM TROUGH DIGS INTO THE GREAT LAKES REGION. AS THE LOW MOVES NORTH FROM GA IT TAKES ON A NEGATIVE TILT...WHICH WILL FURTHER ENHANCE OVERALL WEAK DYNAMICS/LIFT AND CERTAINLY PROLONG THE WET WEATHER PATTERN. ABUNDANT DEEP MOISTURE WILL REMAIN IN PLACE WITH PWATS IN THE 1.75 TO 2.0 INCH RANGE ACROSS MUCH OF THE CWA. EXTENSIVE TO NEAR SOLID CLOUD COVER WILL LIMIT HEATING...SO INSTABILITIES REMAIN MEAGER AND OVERALL DYNAMICS ARE WEAK. MODELS ARE IN GOOD AGREEMENT WITH A LARGE SWATH OF DEEP MOISTURE...ASSOCIATED WITH THE UPPER LOW AND OVERRUNNING EXISTING SURFACE FRONTAL BOUNDARY...TRACKING FROM GA/SC NORTHWARD INTO THE RNK CWA BY SUN AFTERNOON...DRIFTING INTO THE NORTHERN PARTS OF THE CWA MON...THEN FINALLY LIFTING NORTHEAST OF THE CWA BY TUE. THIS WILL SUPPORT HIGH PROBABILITY OF RAINFALL FROM SUNDAY THROUGH MONDAY ACROSS MUCH OF THE CWA...WITH A LIMITED DIURNAL SWING OF TEMPERATURE GIVEN THE UPPER LOW WILL ESSENTIALLY BE DRIFTING RIGHT ACROSS THE HEART OF THE CWA. THE PATH OF THE UPPER LOW SHOULD FOCUS THE HEAVIEST RAINFALL ACROSS THE WESTERN PART OF THE CWA...BLUE RIDGE AND WEST. WITH 3HR FFG VALUES AVERAGING IN THE 1.5 TO 2.5 INCH RANGE ACROSS MUCH OF THE CWA AND THE RECENT PROLONGED WET SPELL...WE WILL NEED TO MONITOR RAINFALL AMOUNTS CAREFULLY...HOWEVER...THE LACK OF ANY ORGANIZED OR STRONG CONVECTION...GIVEN THE MEAGER LAPSE RATES AND LACK OF INSTABILITY/DYNAMICS...SHOULD HOLD HOURLY RAINFALL AMOUNTS IN CHECK. WILL CONTINUE TO HIGHLIGHT THREAT OF POOR DRAINAGE FLOODING IN THE HWO...BUT POTENTIAL FOR FLASH FLOODING DOES NOT APPEAR TO BE A CONCERN ATTM. AS THE UPPER LOW DRIFTS NORTH OF THE AREA TUE...WE SHOULD SEE ENOUGH SUBSIDENCE AND DRYING TO FINALLY SQUELCH THE SHOWER THREAT PROVIDING A BREAK BEFORE NEW FRONTAL SYSTEM APPROACHES TUESDAY NIGHT OR WEDNESDAY. MAXIMUM TEMPERATURES SHOULD REMAIN BELOW NORMAL THROUGH MON...TRENDING CLOSER TO NORMAL VALUES TUESDAY WITH GREATER INSOLATION. MINIMUM TEMPERATURES WILL REMAIN ABOVE NORMAL WITH HIGH PWATS/DEWPOINTS. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 445 PM EDT SATURDAY... UNSETTLED WEATHER DESTINED TO CONTINUE. AFTER A VERY BRIEF RESPITE FROM WIDESPREAD PRECIPITATION TUESDAY...A NEW FRONTAL SYSTEM WILL DRIFT INTO THE REGION FROM THE WEST BY WEDNESDAY AND THEN BECOME ELONGATED WEST-EAST ACROSS THE REGION AND STALL FOR THE LATTER HALF OF THE WEEK. WITH SUBTROPICAL RIDGING TO OUR SOUTH AND FASTER WESTERLIES TO OUR NORTH...THIS WILL FAVOR ACTIVE BAROCLINIC ZONE WITH DAILY THREAT FOR SHOWERS/STORMS. PATTERN SUPPORTS SOME ORGANIZATION OF STORM ACTIVITY AND POTENTIAL FOR STRONG/SEVERE STORMS PER PRESENCE OF WITH ASSOCIATED UPPER LEVEL SHORT WAVE ENERGY THAT WILL BE PASSING THROUGH THE FASTER WESTERLIES TO OUR NORTH. THE UPPER FLOW ATTEMPTS TO TRANSITION BACK TO NORTHWEST FLOW TOWARD THE WEEKEND AS UPPER RIDING AMPLIFIES ACROSS THE WEST- CENTRAL CONUS. THIS COULD REDUCE THE POTENTIAL FOR PROLONGED CONVECTION/RAINFALL...BUT WILL NONETHELESS SUPPORT AN ACTIVE AND UNSETTLED WEATHER PATTERN. WITH ABOVE AVERAGE CLOUD COVER AND MOISTURE LEVELS CONTINUING...EXPECT NEAR TO SLIGHTLY BELOW NORMAL MAX TEMPERATURES AND WELL ABOVE NORMAL MINIMUM TEMPERATURES THROUGH THE WEEK. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... AS OF 740 PM EDT SATURDAY... CLUSTER OF THUNDERSTORMS ON THE NORTHEAST SIDE OF THE KDAN AIRPORT WILL BE MORE THAN 10 NM AWAY FROM THE AIRPORT BY THE 00Z START TIME OF THE TAF. NO OTHER SHOWERS OR THUNDERSTORMS CLOSE TO...OR EXPECTED AT THE OTHER (KLWB/KBLF/KBCB/KROA/KLYH) FOR THE REST OF THE EVENING. SURFACE LOW PRESSURE WAS OVER NORTHEAST VIRGINIA WITH A COLD FRONT EXTENDING FROM THE LOW INTO NORTHERN TENNESSEE. THIS BOUNDARY WILL MOVE SLOWLY EAST TONIGHT. EXPECTING IFR STRATUS NORTH AND WEST OF THE LOW OVERNIGHT...WITH THE HIGHEST CONFIDENCE OF CEILINGS BELOW 500 FT AT KLWB AND KBLF. LOCATIONS THAT HAD RAIN SATURDAY AFTERNOON AND EVENING WILL ALSO HAVE PATCHY FOG WITH OCCASIONAL MVFR TO LIFR VISIBILITIES. A CLOSED LOW OVER WESTERN TENNESSEE WILL MOVE NORTHEAST ON SUNDAY AND SPREAD SHOWERS AND THUNDERSTORMS INTO THE MID ATLANTIC REGION AFTER 12Z/8AM. LOWER CONFIDENCE ON THE ARRIVAL TIME OF THE RAIN AND WHEN THE BEST CHANCE FOR THUNDER WILL BE...BUT HIGH CONFIDENCE OF PRECIPITATION...ESPECIALLY OVER THE MOUNTAINS DURING THE DAY SUNDAY. EXTENDED AVIATION DISCUSSION... POOR AVIATION CONDITIONS TO CONTINUE INTO NEXT WEEK...BUT WINDOWS OF OPPORTUNITY FOR VFR CONDITIONS INCREASE TUE. UPPER LOW/TROUGH WILL MOVE INTO OHIO BY MONDAY. MEANWHILE...A COLD FRONT WILL APPROACH FROM THE OH VALLEY BY WED. THIS LEAVES A VERY UNSETTLED/WET PATTERN ACROSS THE REGION THROUGH THE PERIOD. EXPECT WIDESPREAD LATE NIGHT/EARLY MORNING LOW CLOUDS/FOG WITH IFR-LIFR CIGS/VSBYS. OVERALL...CONDITIONS SHOULD IMPROVE TO MVFR- VFR OUTSIDE SHRA/TSRA ACTIVITY DURING THE AFTERNOONS. AT THIS POINT...TUESDAY APPEARS TO OFFER THE BEST OPPORTUNITY FOR MORE WIDESPREAD VFR CONDITIONS. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...KK NEAR TERM...KK SHORT TERM...PM LONG TERM...PM/RAB AVIATION...AMS/KK

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