Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 031826 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 226 PM EDT MON AUG 3 2015 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OVER THE AREA TODAY PROVIDING MAINLY DRY WEATHER. A COLD FRONT DROPS SOUTHEAST INTO THE REGION BY TUESDAY BEFORE STALLING OUT MIDWEEK. LOW PRESSURE WILL RIDE ALONG THE FRONT BRINGING A BETTER CHANCE FOR MORE WIDESPREAD SHOWERS AND STORMS THURSDAY INTO FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1230 PM EDT MONDAY... ADJUSTED THE CLOUD COVER TO REFLECT CURRENT TRENDS AND REMOVED THE LOW CHANCE POPS THAT WERE IN FOR THE NEXT FEW HOURS. ALL OTHER NEAR TERM FORECAST DETAILS FROM PREVIOUS DISCUSSION REMAIN INTACT. AS OF 500 AM EDT MONDAY... FORECAST AREA REMAINS UNDER INFLUENCE OF DRY AIR COURTESY OF HIGH PRESSURE CENTERED OVER THE REGION. THIS DOME OF FAIR WEATHER IS GRADUALLY FADING PER DEEPER MOISTURE OVER THE SOUTHEAST STATES OOZING NORTH...AND A COLD FRONT DROPPING SOUTHEAST THROUGH THE GREAT LAKES. SOUTHWEST FLOW AHEAD OF THE APPROACHING FRONT WILL BEGIN TO DRAW HIGHER DEWPOINTS INTO THE REGION...BUT LACK OF FORCING WILL KEEP POPS AT A MINIMUM. MAIN THREAT FOR SHOWERS/STORMS WILL BE OVER THE OHIO VALLEY ALONG THE APPROACHING FRONT. THIS ACTIVITY MAY REACH OUR FAR NORTHWESTERN CWA...WV COUNTIES...TOWARD SUNSET. MODELS INSIST THAT ACTIVITY WILL DRY UP AS IT TRIES TO CROSS THE MOUNTAINS LATE THIS EVENING AND OVERNIGHT. OTHER ISOLATED SHOWERS MAY DEVELOP WITHIN THE LEE TROF OVER THE SOUTHEAST CWA...PIEDMONT COUNTIES...THIS AFTERNOON...BUT COVERAGE LESS THAN 30 PERCENT. OVERALL IT LOOKS LIKE A MOSTLY SUNNY...VERY WARM AND MAINLY DRY AFTERNOON. 85H TEMPS OF +20 DEG C SHOULD PROMOTE SURFACE TEMPERATURES WELL INTO THE 80S ACROSS THE MOUNTAIN VALLEYS...AND INTO THE LOWER 90S ALONG AND EAST OF THE BLUE RIDGE. ELEVATIONS ABOVE 3500 FEET SHOULD REMAIN MAINLY IN THE 70S. && .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... AS OF 430 AM EDT MONDAY... UPPER LEVEL TROUGHING WILL GRADUALLY BECOME LESS PRONOUNCED OVER THE NORTHEAST THROUGH MID WEEK...ALLOWING WINDS ALOFT TO BECOME GENERALLY WEST TO EAST ACROSS THE MID ATLANTIC...THEREBY OPENING OUR AREA TO THE APPROACH OF DISTURBANCES FROM THE CENTRAL PLAINS AND MIDWEST. ONE DISTURBANCE PASSING NEAR THE OHIO RIVER EARLY TUESDAY WILL HELP PUSH A COLD FRONT SOUTHWARD ACROSS OUR AREA DURING THE DAY. WITH ONLY MODEST MOISTURE RETURNING AHEAD OF THE BOUNDARY...BELIEVE THAT SHOWER AND THUNDERSTORM ACTIVITY DEVELOPING WITH AFTERNOON HEATING WILL BE WIDELY SCATTERED...WITH BETTER CHANCES FOUND SOUTH OF HIGHWAY 460. THE COLD FRONT WILL CLEAR OUR AREA TO THE SOUTH LATE TUESDAY NIGHT...WITH POST FRONTAL NORTHWESTERLY WINDFLOW HELPING TO DIMINISH ANY LINGERING SHOWER ACTIVITY. HIGH PRESSURE BUILDING IN BEHIND THE FRONT WILL MAKE FOR DRY CONDITIONS MOST AREAS FOR WEDNESDAY...WITH PERHAPS A FEW PULSE VARIETY SHOWERS/ISOLATED STORMS DEVELOPING DURING THE AFTERNOON AND EVENING. AGAIN...BETTER RAIN CHANCES WILL BE FOUND SOUTH OF HIGHWAY 460...ESPECIALLY IN THE HIGHLANDS OF NORTH CAROLINA WHERE CONVERGENCE ALONG THE RIDGETOPS MAY TRIGGER BETTER SLIGHTLY COVERAGE OF CONVECTION IN THE DEEPER MOISTURE. A LOW PRESSURE SYSTEM WILL APPROACH FROM THE PLAINS WEDNESDAY NIGHT. MODELS ARE IN DECENT AGREEMENT THAT WAVES OF ENERGY RIDING AHEAD OF THE LOW WILL PASS ACROSS OUR AREA...AND SUPPORT SCATTERED SHOWERS THROUGH THE NIGHT AS THE FRONTAL BOUNDARY BEGINS TO LIFT BACK TO THE NORTH AS A WARM FRONT TOWARD DAYBREAK THURSDAY. THE LOW WILL PUSH UP THE OHIO RIVER VALLEY ON THURSDAY. EXPECT TO START THE DAY WITH ONLY SPOTTY RAIN ACTIVITY...HOWEVER SHOWER AND THUNDERSTORM CHANCES WILL INCREASE DURING THE EVENING AS THE LOW APPROACHES THE APPALACHIAN CHAIN. THE LOW WILL PASS JUST NORTH OF OUR AREA THURSDAY NIGHT...DRAGGING ANOTHER COLD FRONT INTO THE MOUNTAINS BEFORE DAWN. OF NOTE IS THE SIGNIFICANT DIFFERENCE BETWEEN MODELS IN THE INTENSITY OF THE LOW AS IT PASSES OUR AREA. THE GFS MODEL IS FAR WEAKER THAN THE ECMWF/CANADIAN MODELS IN ITS DEPICTION OF THE LOW...WITH THE STRONGER SOLUTIONS INDICATING A THREAT FOR SEVERE WEATHER DURING THE NIGHT. RIGHT NOW...BELIEVE THE ECMWF/ CANADIAN SOLUTIONS ARE A LITTLE TOO STRONG GIVEN THE TIME OF YEAR AND LACK OF UPPER LEVEL SUPPORT...SO FOR NOW WILL STICK CLOSER TO THE WEAKER GFS SOLUTION AND SIMPLY CONTINUE TO WATCH THE EVOLUTION OF THIS SYSTEM IN FUTURE MODEL RUNS. && .LONG TERM /FRIDAY THROUGH SUNDAY/... AS OF 1245 PM EDT SUNDAY... TRANSITION TO MORE ZONAL FLOW ALOFT WILL OCCUR EARLY IN THE PERIOD AS THE REGION GETS CAUGHT UNDER THE SURFACE-850 MB BAROCLINIC ZONE AND WITHIN A NEARBY FRONTAL ZONE STRETCHED BACK INTO THE MIDWEST. STRONGER ENERGY ALOFT DROPPING OVER THE CENTRAL STATES UPPER RIDGE WILL THEN START TO DIG OUT ANOTHER RATHER STRONG 5H TROUGH TO THE NW FRIDAY...WITH AN ASSOCIATED SURFACE WAVE HELPING TO DRIVE THE NEXT COLD FRONT THROUGH THE REGION BY FRIDAY EVENING. SIMILAR TO THE LAST WEEK OR TWO...APPEARS ANOTHER SURGE OF MUCH DRIER/COOLER AIR LIKELY BEHIND THE FRONT NEXT WEEKEND AS YET ANOTHER 5H TROUGH CARVES ITSELF OUT ACROSS THE EAST. GUIDANCE EVEN COOLER ALOFT WITH THIS SYSTEM GIVEN PROGGED 850 MB TEMPS AS COOL AS +12C MOUNTAINS BUT MAY BE TOO COOL THAT FAR OUT. HOWEVER STILL ENOUGH TO DROP HIGHS BACK IN THE 70S MOUNTAINS AND ONLY LOW/MID 80S OUT EAST AS HIGH PRESSURE BUILDS/WEDGES IN FROM THE NORTH. RESIDUAL POPS A BIT TRICKY TOWARD DAYS 6/7 BUT SHOULD BE DRIER WITH PERHAPS SOME LEFTOVER UPSLOPE SHOWERS WEST SATURDAY AND ONLY ISOLATED FAR SOUTHWEST ON SUNDAY. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... AS OF 115 PM EDT MONDAY... THERE ARE A LOT OF SUBTLE FEATURES TO CONSIDER THAT MAKE FOR SOME UNCERTAINTY WITH THIS TAF PACKAGE. THE REGION IS CURRENTLY BETWEEN SYSTEMS AS A COLD FRONT APPROACHES FROM THE NORTHWEST WITH A TROF/BOUNDARY TO OUR EAST. RADAR SHOES THAT STORMS HAVE FIRED ALONG THE TROF/BOUNDARY EAST OF THE AREA AND BELIEVE ANY REDEVELOPMENT FURTHER WEST WILL BE ISOLATED AND NOT WORTH A VCTS MENTION...AND MESO MODELS INDICATE ANY ACTIVITY APPROACHING FROM THE NORTHWEST WILL NOT ARRIVE UNTIL AFTER 00Z. THIS WILL YIELD VFR TAFS THROUGH THE EARLY PART OF THE PERIOD. THERE IS SOME DISCREPANCY IN THE MESO MODELS AS TO WHEN ACTIVITY WILL ARRIVE FROM THE NORTHWEST. BELIEVE THE MOST LIKELY TIMING IS FOR ACTIVITY TO ARRIVE NO EARLIER THAN 06Z AND BE DIMINISHING AS IT APPROACHES. WILL INTRODUCE AN MVFR CIG AT KBLF/KLWB BUT KEEP VFR CLOUDS ELSEWHERE. THE ANTICIPATED CLOUDS/PRECIPITATION WILL COMPLICATE THE FOG FORECAST TONIGHT. TO THE EAST CONDITIONS SHOULD FAVOR RADIATIONAL COOLING AND SOME THIN FOG DEVELOPMENT. FOG AND STRATUS WAS NOT TOO FAR OFF TO THE SOUTHEAST THIS MORNING AND INDICATIONS ARE THAT KDAN WILL GET INTO SOME MVFR FOG AND SOME SCATTERED LOW CLOUDS TOWARD DAYBREAK. CLOUD COVER WILL INHIBIT RADIATIONAL COOLING WEST OF THE RIDGE BUT THE EXACT AMOUNT OF CLOUDS AND PRECIPITATION WILL PLAY A BIG ROLE IN FOG POTENTIAL. CURRENTLY FEEL CONDITIONS WILL NOT FAVOR FOG AND WILL OMIT FROM TAFS THIS PACKAGE. IF UPSTREAM CLOUDS/PRECIPITATION ARE LESS THAN ANTICIPATED EARLY TONIGHT THIS WILL TIP THE SCALES IN FAVOR OF FOG AND IT MAY BECOME NECESSARY TO ADD MVFR CONDITIONS AT KBLF/KBCB WITH SOME IFR/LIFR AT KLWB. THE FRONTAL BOUNDARY WILL BE MOVING THROUGH THE REGION TOMORROW AND EXPECT SOME SHOWER/THUNDERSTORM ACTIVITY TO DEVELOP LATE IN THE TAF PERIOD...BUT DUE TO UNCERTAINTY IN TIMING AND LOCATION WILL NOT INCLUDE ANY MENTION OF TS/SHRA WITH THIS PACKAGE. EXPECT WINDS TO BE WESTERLY WITH SOME LOW LEVEL GUSTS POSSIBLE... ESPECIALLY TOMORROW AS WINDS BECOME MORE NWLY WITH THE FRONTAL PASSAGE. EXTENDED AVIATION FORECAST... MOSTLY VFR OUTSIDE OF ANY DEEP CONVECTION THROUGH THE PERIOD. A FRONT WILL STALL ACROSS THE MID ATLANTIC FOR MID WEEK WHICH COULD BRING A BIT MORE COVERAGE OF SHOWERS/THUNDERSTORMS LATER WEDNESDAY AND A BETTER CHANCE THURSDAY. THE THREAT OF SUB-VFR REMAINS LOW UNTIL THURSDAY...EXCEPT FOR THE TYPICAL FOG POTENTIAL AT KLWB/KBCB EACH MORNING BETWEEN 09-13Z. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...CF/PM SHORT TERM...NF LONG TERM...JH AVIATION...MBS/PM

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