Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 221652 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1252 PM EDT TUE JUL 22 2014 .SYNOPSIS...
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UPPER TROUGH OVER THE GULF COAST STATES SHIFTS WEST THROUGH WEDNESDAY LEAVING A RESIDUAL WEAK BOUNDARY AND LOW LEVEL MOISTURE OVER THE AREA INTO MID WEEK. A COLD FRONT WILL BE ARRIVING THURSDAY FROM THE NORTHWEST...THEN EXITING BY THURSDAY NIGHT. HIGH PRESSURE BUILDS IN ON FRIDAY.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 930 AM EDT TUESDAY... NOT A LOT OF CHANGE WITH THE RESIDUAL LOW LEVEL WEDGE STILL OVER THE REGION ANCHORED BY A WEAK BUBBLE HIGH SEEN ALONG THE BLUE RIDGE THIS MORNING. MORNING SOUNDINGS CONTINUE TO REVEAL QUITE A DIFFERENCE IN MOISTURE DEPTH FROM SOUTH TO NORTH AS WELL AS PWATS WITH GSO JUST BELOW 2 INCHES. FARTHER NORTH AT RNK SEEING LESS PWAT ALONG WITH A LINGERING MID LEVEL CAP INCLUDING LOTS OF DRY AIR ABOVE 7H. MAIN FOCUS CONTINUES WITH THE WEAK BOUNDARY TO THE SOUTH ALONG WITH OLD OUTFLOW THAT LIKELY RESIDES BETWEEN WHERE THE HEAVIER RAIN WAS ACROSS THE FAR SOUTH LATE YDA AND SOUTH OF THE DRIER AIR ALOFT ESPCLY NORTH OF HIWAY 460. ALSO EXPECT WEAK SOUTH/SE FLOW TO AID LOW LEVEL CONVERGENCE ALONG THE SOUTHERN BLUE RIDGE SO UPPED POPS TO LOW LIKELYS FAR SOUTH/SW THIS AFTERNOON FOR MAINLY SLOW MOVING HEAVY RAIN PRODUCING SHRA/TSRA DESPITE WEAK FORECAST INSTABILITY. APPEARS BEST HEATING AND CAPES ABOVE 1000 J/KG WILL OCCUR OVER THE FAR WEST/NW WHERE MAY POP A BAND OR TWO OF CONVECTION ON THE EDGE OF THE EASTERN CLOUD SHIELD. OTRW KEEPING SCATTERED POPS WITH CONTINUED HEAVY RAIN MENTION IN THE HWO WITH ONLY A LOW SEVERE THREAT UNLESS CELLS CAN PUNCH INTO THE DRIER AIR FARTHER NORTH. WARMER HIGH TEMPS BASED ON SEEING SOME BREAKS DEVELOP IN THE LOW CLOUDS AS APPEARS MAY TAKE UNTIL LATER IN THE DAY TO SEE MORE SUN SO BUMPED DOWN LOWS A LITTLE SOUTH- EAST. PREVIOUS VALID DISCUSSION AS OF 330 AM EDT TUESDAY... GOING TO SEE HIGH PRESSURE AT THE SFC WEAKEN TODAY INTO TONIGHT AS IT PUSHES SOUTH OVER THE SOUTHERN APPALACHIANS. UPPER LEVEL TROUGH IS GOING TO RETROGRADE TOWARD THE LOUISIANA COAST BY TONIGHT AS WELL...AS A NORTHERN STREAM TROUGH STARTS TO DIG SOUTHEAST INTO THE GREAT LAKES...WITH UPPER RIDGING EXTENDING WWD FROM THE SOUTHEAST COAST. FOR US...THE MODELS CONTINUE TO ADVERTISE DIURNALLY DRIVEN CONVECTION...WITH NO REAL FOCUS ASIDE FROM DIFFERENTIAL HEATING AND SOME LOW LVL UPSLOPE CONVERGENCE IN THE SRN MTNS. BETTER LIFT EXPECTED TO STAY WEST OF THE APPALACHIANS THIS AFTERNOON. PWATS REMAIN HIGH GIVEN WEAK FLOW...THE SLOW MOVING STORMS COULD PRODUCE WELL OVER AN INCH OF RAIN IN A SHORT AMOUNT OF TIME. THUNDERSTORM THREAT WILL BE THERE...BUT SOUNDING SUGGEST NO ROBUST CAPE...SO NOT REALLY SEEING ANY STRONG/SVR STORM THREAT AT THIS TIME. TONIGHT...THE SHOWERS AND ISOLATED STORMS WEAKEN/DISSIPATE BY MIDNIGHT. ISOLATED SHOWERS MAY LINGER OVERNIGHT...GIVEN PLENTIFUL MOISTURE IN THE LOW LVLS INTERACTING WITH ANY OUTFLOW BOUNDARIES. STILL LOOKS LIKE A LITTLE MORE SUN ESPECIALLY IN THE WEST TODAY WITH SKIES STAYING PARTLY SUNNY-OVC EAST OF THE BLUE RIDGE. HIGHS TODAY WILL BE SIMILAR TO A FEW DEGREES WARMER THAN MONDAY...DEPENDING ON EXTENT OF SUN. WILL BE REALLY HUMID...WHICH WITH HIGHS IN THE MID TO UPPER 80S OUT EAST SHOULD DRIVE HEAT INDICES INTO THE LOWER TO MID 90S. TONIGHTS LOWS REMAIN MUGGY/WARM WITH MID 60S TO AROUND 70. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... AS OF 345 AM EDT TUESDAY... WILL START WEDNESDAY MORNING OFF WITH ONLY ISOLATED SHOWER ACTIVITY UNDER LIGHT SOUTHWEST TO WESTERLY WIND FLOW AS A SURFACE TROUGH DEVELOPS EAST OF THE BLUE RIDGE. COVERAGE OF SHOWERS AND THUNDERSTORMS WILL INCREASE DURING THE AFTERNOON HOWEVER AS A COLD FRONT APPROACHES FROM THE OHIO RIVER VALLEY. BEST INSTABILITY WILL BE FOUND ACROSS THE MOUNTAINS...WHERE CAPES WILL REACH INTO THE 1500- 2000 J/KG RANGE BY EARLY EVENING AS AFTERNOON HIGHS REACH INTO THE MID 80S WEST TO THE LOW 90S EAST. BELIEVE SHOWERS AND STORMS WILL DEVELOP ACROSS THE MOUNTAINS BY EARLY AFTERNOON AS PULSE HIT AND MISS ACTIVITY...POSSIBLY MERGING INTO MORE ORGANIZED LINE SEGMENTS ACROSS THE PIEDMONT DURING THE EVENING. WITH STRONG HEATING AND ABUNDANT DRY AIR IN THE MID LEVELS...EXPECT A FEW STORMS TO BECOME SEVERE DURING LATE AFTERNOON AND EVENING...PRODUCING STRONG WINDS AS THE MAIN THREAT...IN ADDITION TO HAIL AND LOCALLY HEAVY RAIN. STORMS WILL WEAK DURING LATE EVENING...BUT EXPECT WE WILL STILL HAVE SHOWERS PASSING ACROSS THE AREA WEDNESDAY NIGHT AS THE COLD FRONT ARRIVES ON OUR DOORSTEP. MODELS ARE IN DECENT AGREEMENT THAT THE COLD FRONT WILL ENTER OUR SOUTHEAST WEST VIRGINIA COUNTIES LATE MORNING/EARLY AFTERNOON ON THURSDAY...AND CONTINUE EAST THROUGH THE DAY. HOWEVER...WITH AN UPPER LEVEL TROUGH SHIFTING EAST OF OUR AREA AND INCREASED CLOUD COVER TO LIMIT HEATING...ATMOSPHERIC INSTABILITY WILL NOT BE AS INTENSE. EXPECT MORE IN THE WAY OF SHOWER ACTIVITY ON THURSDAY WITH ONLY WIDELY SCATTERED THUNDERSTORMS IN THE MIX...MAINLY ACROSS THE PIEDMONT. HIGHS WILL REACH INTO THE UPPER 70S ACROSS THE MOUNTAINS...WHILE WE MAY TOUCH 90 ACROSS THE SOUTHSIDE BEFORE THE COLD FRONT MOVES ACROSS. WEAK HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT...AND WILL BE IN CONTROL OF OUR WEATHER PATTERN FOR FRIDAY. AS SUCH...EXPECT A LIGHT NORTHERLY FLOW THAT WILL CARRY DRIER AIR INTO THE REGION FROM THE GREAT LAKES. AFTERNOON HIGHS WILL VARY FROM THE MID 70S WEST TO THE MID 80S EAST. MAY SEE THUNDERSTORMS RETURN TO THE AREA LATE FRIDAY NIGHT AS WINDS ALOFT SHIFT NORTHWESTERLY...ALLOWING UPPER LEVEL DISTURBANCES TO APPROACH THE AREA FROM THE MIDWEST. && .LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 445 PM EDT MONDAY... FOR THE WEEKEND AND INTO EARLY NEXT WEEK...THE AREA REMAINS VULNERABLE TO NW FLOW DISTURBANCES TRACKING AROUND THE LARGE WESTERN/CENTRAL CONUS UPPER RIDGE. THERE ARE SEVERAL SUCH STRONG DISTURBANCES NOTED IN THE MODELS DURING THIS TIME FRAME...THE MOST NOTABLE ON SUN...THAT COULD BRING THUNDERSTORMS BACK INTO THE AREA. HAVE RETAINED EXISTING CHC POPS THAT WERE ADVERTISED WITH EARLIER FORECAST PACKAGES...BUT CLEARLY THESE COULD POTENTIALLY BECOME LIKELY AT SOME POINT AS THE DEVELOPMENT OF AN UPSTREAM MCS BECOMES MORE APPARENT. BY EARLY THE FOLLOWING WEEK...MODELS IN GOOD AGREEMENT ON THE UPPER TROUGH REAMPLIFYING ACROSS THE EASTERN CONUS...WHICH SHOULD KEEP CONDITIONS UNSETTLED WITH NEAR TO SLIGHTLY BELOW NORMAL TEMPERATURES WHILE THE EXTREME HEAT REMAINS WELL TO OUR WEST AND WELL AWAY FROM OUR PART OF THE COUNTRY. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/...
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AS OF 1230 PM EDT TUESDAY... HEATING OF LOW LEVEL MOISTURE HAS RESULTED IN AN EXPANSIVE CU FIELD ACROSS THE REGION THIS AFTERNOON WITH BASES EXPECTED TO RISE TO MOSTLY VFR LEVELS IN THE NEXT COUPLE OF HOURS. HOWEVER SPOTTY CONVECTION DEVELOPING CLOSE TO KDAN MAY KEEP THEM MORE IN THE HIGH END MVFR LEVEL RANGE AS WELL AS KLYH WHERE PERIODS OF MVFR LIKELY. SOME ADDED SHRA OR TSRA MAY POP ALONG THE BLUE RIDGE BY MID OR LATE AFTERNOON SO LEAVING IN A VCSH/VCTS MENTION MAINLY WHERE ALREADY ONGOING WHICH EXCLUDES KBLF/KLYH FOR NOW. OTRW LOOKING AT OVERALL CLOUD BASES OF 3-5K FT THIS AFTERNOON/EARLY EVENING WITH SE WINDS LESS THAN 10 KTS. MOST CONVECTION WEAKENS/SUBSIDES SHORTLY AFTER SUNSET WITH ONLY ISOLATED SHRA/TSRA PERHAPS LINGERING MOUNTAINS BEFORE MIDNIGHT. FOG FORMATION LIKELY LATE EVENING INTO OVERNIGHT BUT GIVEN LESS OF A LOW LEVEL WEDGE AND LIGHT WEST WINDS NOT EXPECTING THE OVERALL MORE WIDESPREAD IFR/LIFR CONDITIONS SEEN THE LAST FEW NIGHTS. THINK THE VALLEY LOCATIONS SUCH AS KBCB AND KLWB HAVE THE BEST CHANCE OF SEEING IFR/LIFR CONDITIONS WITH IFR TO MVFR AT KLYH/KDAN BY EARLY WEDNESDAY MORNING. LOW LEVEL FLOW TURNS MORE WESTERLY AHEAD OF AN UPSTREAM COLD FRONT ON WEDNESDAY WHICH SHOULD ALLOW LOW CLOUDS/FOG TO SCOUR OUT A BIT SOONER WEDNESDAY MORNING. THUS EXPECTING A RETURN TO VFR AT ALL LOCATIONS BY MID OR LATE MORNING WEDNESDAY. HOWEVER HEATING WILL AGAIN LEAD TO ADDED SHRA/TSRA DEVELOPMENT ESPCLY ALONG THE SOUTHERN BLUE RIDGE DURING THE AFTERNOON AND ACROSS THE SE WEST VA SITES BY EARLY EVENING. THIS MAY RESULT IN INCREASING PERIODIC MVFR CONDITIONS OVER THE MOUNTAINS BUT MOSTLY VFR OUT EAST. EXTENDED AVIATION DISCUSSION... NEXT NORTHERN STREAM UPPER TROUGH AND ITS ASSOCIATED COLD FRONT WILL APPROACH WEDNESDAY NIGHT AND WORK THROUGH THE REGION ON THURSDAY. THIS WILL BRING THE BEST CHANCES OF MORE WIDESPREAD SHOWERS TO THE MOUNTAINS AND PERHAPS SOME DEEPER CONVECTION EAST OF THE BLUE RIDGE PENDING TIMING OF THE BOUNDARY THURSDAY AFTERNOON. AIRMASS WILL DRY OUT BEHIND THE FRONT GOING INTO FRIDAY- SATURDAY. OVERALL EXPECT SUB VFR AT TIMES THURSDAY WITH SHRA/TSRA AND MAYBE SOME FOG THU NIGHT...FOLLOWED BY VFR FRI- SAT OUTSIDE OF ANY VALLEY FOG AT KLWB/KBCB EACH MORNING.
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&& .EQUIPMENT...
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AS OF 1215 PM EDT TUESDAY... KFCX RADAR REMAINS DOWN. HOWEVER TECHNICIANS ARE CURRENTLY WORKING ON THE PROBLEM AND AT THE MOMENT ARE EXPECTING A RETURN TO SERVICE THIS AFTERNOON.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/WP NEAR TERM...JH/WP SHORT TERM...NF LONG TERM...PM/RAB AVIATION...JH/WP EQUIPMENT...WP

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