Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 050916 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 516 AM EDT SUN JUL 5 2015 .SYNOPSIS...
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AN UPPER LOW WILL DRIFT SLOWLY FROM EAST TENNESSEE TODAY TOWARD WESTERN PENNSYLVANIA BY LATE MONDAY BRINGING WIDESPREAD RAIN AND A FEW THUNDERSTORMS TO THE AREA TODAY THROUGH MONDAY. A COLD FRONT WILL MOVE INTO THE REGION FROM THE OHIO VALLEY BY WEDNESDAY...THEN STALL AND LIFT BACK NORTH AS A WARM FRONT LATE IN THE WEEK AS HIGH PRESSURE ALOFT BUILDS ACROSS THE SOUTHEAST STATES. SCATTERED SHOWERS AND THUNDERSTORMS WILL ACCOMPANY THE FRONT. BELOW NORMAL TEMPERATURES EARLY IN THE WEEK WILL TREND TO ABOVE NORMAL TEMPERATURES BY THE END OF THE WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 515 AM EDT SUNDAY... A CLOSED LOW WILL BE SPLITTING OFF FROM THE MEAN TROF AND SLOWLY MOVING OVER THE REGION TODAY AND TONIGHT. THIS WILL SET THE AREA UP FOR SOME WIDESPREAD RAINFALL WITH UPPER DIFFLUENCE AND DEEP E/SE FLOW WITH GOOD MOISTURE TRANSPORT GENERATING PRECIPITABLE WATER VALUES APPROACHING TWO INCHES. THANKFULLY ANTECEDENT CONDITIONS ARE NOT AS WET AS THEY COULD HAVE BEEN AND THE MOST VULNERABLE AREAS TO HYDRO CONCERNS ARE FROM THE MOUNTAIN EMPIRE REGION UP THROUGH SOUTHEAST WEST VIRGINIA...SO A FLASH FLOOD WATCH HAS BEEN POSTED FOR THOSE COUNTIES FROM LATE THIS MORNING THROUGH TONIGHT. AS THE LOW SPINS SLOWLY TO OUR WEST...WE WILL SEE A BIT OF A DRY SOT WORK IN FROM THE SOUTHWEST. SEVERAL MODELS ARE QUITE AGGRESSIVE WITH SHUTTING DOWN THE PRECIPITATION QUICKLY BUT WITH A CLOSED LOW AND DECENT SYNOPTIC SUPPORT IN PLACE WILL SHADE THINGS TOWARD THE SLOWER/WETTER SOLUTIONS. WITH A GOOD AMOUNT OF CLOUD COVER EXPECTED WE SHOULD SEE TEMPERATURES TODAY JUST A FEW DEGREES COOLER THAN YESTERDAY WITH LOW/MID 80S EAST TO LOW/MID 70S WEST. LOWS TONIGHT WILL GENERALLY BE 65 TO 70 EAST...WITH 60 TO 65 WEST.
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&& .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
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AS OF 430 AM EDT SUNDAY... CLOSED UPPER LOW WILL BE NEAR THE VA/WV/KY BORDER INTERSECTION AT 12Z MON...DRIFTING NORTH-NORTHEAST INTO WESTERN PA BY EVENING. THE WARM ADVECTION AND HEAVIEST PART OF THE RAINFALL SHOULD BE LIFTING TOWARD THE I-64 CORRIDOR AT THE START OF THIS PERIOD...THEN INTO NORTHERN VA/WV BY AFTERNOON/EVENING. AS IT DOES SO...A BAROCLINIC ZONE WILL DEVELOP ON THE WEST SIDE OF THE UPPER LOW. SOMEWHAT OF A DRY SLOT IS EVIDENT WORKING ITS WAY INTO THE PIEDMONT AND AREAS EAST OF THE BLUE RIDGE BY AFTERNOON. WIDESPREAD RAIN SHOWERS DURING THE MORNING SHOULD FOCUS MORE TOWARD THE NORTHERN AND WESTERN PART OF THE CWA BY AFTERNOON INTO THE EARLY EVENING...BEFORE TAPERING OFF IN THESE AREAS AFTER SUNSET. THE HEAVIEST RAIN DURING THE DAY SHOULD FALL ROUGHLY NEAR THE I-77 AND I-64 CORRIDORS WITH THE COMBINED EFFECT OF WARM ADVECTION RAINFALL EARLY IN THE EVENT...TRANSITIONING TO DEFORMATION RAINFALL WEST DURING THE AFTERNOON. AFTERNOON PRECIPITATION SHOULD BE LIMITED TO A FEW SPOTTY SHOWERS ACROSS AREAS EAST OF THE BLUE RIDGE WITH AN ANTICIPATED DRY SLOT IN THAT REGION. WILL HOLD ONTO LIKELY POPS ACROSS WEST MUCH OF THE DAY...WITH POPS DECREASING INTO THE SLIGHT CHANCE CATEGORY NC COUNTIES BY EVENING. QPF AFT 12Z SHOULD RANGE FROM 3/4 INCH IN THE WEST AND NORTHWEST TO 1/4 INCH IN THE SOUTHEAST PART OF THE CWA. THIS RAINFALL SHOULD NOT BE ENOUGH TO EXACERBATE ANY FLOODING PROBLEMS...BUT LATER SHIFTS WILL NEED TO EVALUATE IF THE FLASH FLOOD WATCH WILL NEED TO CONTINUE BEYOND THE CURRENT 10Z MON EXPIRATION. BY MONDAY NIGHT...THE UPPER LOW WILL HAVE MOVED FAR ENOUGH NORTH AWAY FROM THE AREA...AS WELL AS SHEARING OUT...THAT ANY ASSOCIATED RAINFALL ACROSS OUR REGION SHOULD HAVE ENDED. LOW CLOUDS AND PATCHY DRIZZLE MAY LINGER ACROSS THE MOUNTAINS...BUT NO APPRECIABLE RAINFALL IS EXPECTED. FOR TUESDAY...PROGRESSIVE FLOW ACROSS THE NORTHERN STATES WILL QUICKLY PUSH A NEW FRONTAL ZONE AND ASSOCIATED WEAK UPPER TROUGH INTO THE REGION FROM THE WEST. LINEAR ORIENTED...POTENTIALLY STRONG CONVECTION...APPEARS LIKELY WITH THIS SYSTEM. THIS ACTIVITY WILL LIKELY REACH WESTERN WV/FAR SOUTHWEST VA AND THEN DIMINISH AS IT ATTEMPTS TO CROSS THE MOUNTAINS DURING THE LESS FAVORABLE EVENING HOURS. THIS AGREES WELL WITH THE MARGINAL RISK SPC HAS ADVERTISED ON DAY 3 ENDING JUST SHY OF OUR WESTERN BORDER. OTHERWISE...MUCH OF THE DAY TUESDAY SHOULD OFFER A MINIMUM OF PRECIPITATION ACTIVITY ACROSS THE CWA...ESPECIALLY EAST OF THE BLUE RIDGE. HAVE GENERALLY ADVERTISED ONLY SLIGHT CHANCE POPS FOR AREAS EAST OF THE BLUE RIDGE WITH A WARM...MOIST ATMOSPHERE IN PLACE...BUT DYNAMICS WILL BE LIMITED AT BEST. WEDNESDAY HAS BECOME MORE PROBLEMATIC TODAY AMONG THE MODELS THAN INDICATED YESTERDAY AS A RESULT OF INCREASED SUBTROPICAL RIDGING ACROSS THE SOUTHEAST STATES. THIS ALLOWS THE TUESDAY FRONT TO DRIFT INTO THE CWA AND THEN LIFT BACK NORTH. IT SHOULD LINGER LONG ENOUGH IN THE REGION WEDNESDAY TO SERVE AS A FOCUS FOR SCATTERED IF NOT NUMEROUS CONVECTION DURING AFTERNOON HEATING. TEMPERATURES SHOULD REMAIN BELOW NORMAL WEST OF THE BLUE RIDGE MONDAY WITH WIDESPREAD CLOUDS AND RAIN. HOWEVER...EAST OF THE BLUE RIDGE SOME INSOLATION IS EXPECTED DURING THE AFTERNOON AND WE SHOULD SEE MAXIMUM TEMPERATURES CLOSER TO NORMAL IN THOSE AREAS. MAXIMUM TEMPERATURES FINALLY REACH ABOVE NORMAL LEVELS IN MUCH OF THE CWA TUESDAY WITH INCREASED AMOUNTS OF SUNSHINE AND SOUTHWEST SURFACE FLOW. WESTERN AREAS WILL SEE MAXIMUM TEMPERATURES CLOSER TO NORMAL AGAIN WEDNESDAY WITH CLOUDS AND PRECIPITATION. MINIMUM TEMPERATURES WILL AVERAGE WELL ABOVE NORMAL THROUGH MUCH OF THE PERIOD...THANKS TO CONTINUED HIGH MOISTURE CONTENT AND DEWPOINTS.
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&& .LONG TERM /THURSDAY THROUGH SATURDAY/...
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AS OF 500 AM EDT SUNDAY... EXTENDED PERIOD TRENDING WARMER...BUT STILL SOMEWHAT UNSETTLED. MODELS...TO VARYING DEGREES...ADVERTISING AN INTENSIFYING UPPER RIDGE ACROSS THE SOUTHEAST STATES INTO THE MID-ATLANTIC. THE GFS/CANADIAN ARE STRONGEST WITH THE UPPER RIDGE...THE ECMWF IS THE WEAKEST...KEEPING A MORE ACTIVE WESTERLY FLOW ACROSS THE REGION. AT ANY RATE...INSTABILITY WILL BE GREATER THAN IN RECENT DAYS. AT THIS POINT...IT APPEARS THAT THURSDAY SHOULD OFFER THE BEST CHANCE FOR WIDESPREAD CONVECTION...BUT CONDITIONS SHOULD BECOME MORE UNFAVORABLE FOR WIDESPREAD ORGANIZED CONVECTION THROUGH THE END OF THE WEEK INTO THE WEEKEND WITH UPPER RIDGING TAKING HOLD OF THE REGION FROM THE SOUTH. THIS SHOULD PUSH THE MORE ACTIVE BAROCLINIC ZONE INTO OH/PA/MD/NJ. WILL NEED TO WATCH LATER TRENDS OF THE MODELS TO MAKE SURE THIS TREND CONTINUES...AS OPPOSED TO SHIFTING THE BAROCLINIC ZONE FURTHER SOUTH AND WITH NORTHWEST FLOW ALOFT...SHOULD THE UPPER RIDGE DRIFT FURTHER WEST AND REMAIN LESS AMPLIFIED THAN CURRENTLY INDICATED. WITH THE UPPER RIDGING...WE WILL HAVE TO START TALKING ABOUT HIGHS IN THE 90S AGAIN ACROSS THE PIEDMONT. HUMIDITY LEVELS WILL BE HIGH WITH DEWPOINTS NEAR 70...SO WILL NEED TO WATCH APPARENT TEMPERATURES IN THOSE AREAS TOWARD MID-WEEK. NEEDLESS TO SAY...TEMPERATURES APPEAR DESTINED TO ABOVE NORMAL LEVELS THROUGH MUCH OF THE PERIOD.
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&& .AVIATION /09Z SUNDAY THROUGH THURSDAY/... AS OF 154 AM EDT SUNDAY... ONE AREA OF SHOWERS/EMBEDDED THUNDER WAS DIRECTLY UPSTREAM FROM KDAN SO HAVE GONE PESSIMISTIC THERE FOR THE INITIAL ONE TO TWO HOUR PERIOD. THIS AREA OF PRECIPITATION IS CURRENTLY WEAKENING SO WILL AMEND AS NEEDED. AVIATION CONDITIONS WILL BE QUITE POOR TODAY AS A CLOSED LOW DEVELOPS ALOFT STAYS JUST TO OUR WEST THROUGH THE PERIOD...WHILE A SURFACE LOW SLIDES INTO THE WESTERN PORTION OF OUR AREA ALONG THE OLD LINGERING FRONTAL BOUNDARY THAT HAS BEEN WAVERING ABOUT FOR THE PAST SEVERAL DAYS. THIS WILL ESTABLISH A DEEP AND PERSISTENT E/SE WIND FLOW WITH EXCELLENT MOISTURE TRANSPORT INTO THE TAF SITES. EXPECT MVFR/IFR CONDITIONS TO MOVE IN FROM THE WEST OVERNIGHT BEFORE BOUNCING BACK UP TO AOA VFR BY LATE MORNING/EARLY AFTERNOON. PRECIPITATION CHANCES WILL BE INCREASING THROUGHOUT THE MORNING WITH THE WORST CONDITIONS HOLDING OFF UNTIL THE AFTERNOON WHEN THERE WILL ALSO BE SOME EMBEDDED THUNDER. THERE ARE INDICATIONS FOR SPOTTY IMPROVEMENT LATE IN THE PERIOD BUT DO NOT HAVE ENOUGH CONFIDENCE IN EXACTLY WHERE/WHEN SO WILL STAY PESSIMISTIC THROUGH THE END OF THE VALID PERIOD. 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...
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VA...FLASH FLOOD WATCH FROM 11 AM EDT THIS MORNING THROUGH LATE TONIGHT FOR VAZ007-009-010-012. NC...NONE. WV...FLASH FLOOD WATCH FROM 11 AM EDT THIS MORNING THROUGH LATE TONIGHT FOR WVZ042-043-507-508.
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&& $$ SYNOPSIS...MBS NEAR TERM...AMS/MBS SHORT TERM...RAB LONG TERM...PM/RAB AVIATION...AMS/MBS

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