Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 130152 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 952 PM EDT SAT JUL 12 2014 .SYNOPSIS... HIGH PRESSURE WILL GIVE WAY TO RETURN SOUTHWEST FLOW AND INCREASING MOISTURE THROUGH SUNDAY. THEN A STRONG COLD FRONT APPROACHES FROM THE WEST ON MONDAY AND CROSS THE REGION ON TUESDAY. COOL HIGH PRESSURE FOLLOWS THE FRONT FOR THE LATTER HALF OF NEXT WEEK. && .NEAR TERM /THROUGH SUNDAY/...
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AS OF 930 PM EDT SATURDAY... PATCHY FOG OVERNIGHT...MAINLY IN THE MOUNTAIN VALLEYS WHERE SOME ISOLATED SHOWERS OCCURRED LATE SATURDAY AFTERNOON. OTHER THAN THAT...ANTICIPATE A QUIET OVERNIGHT...WITH NEAR NORMAL TEMPERATURES. EVENING RNK SOUNDING REVEALED MODEST CAPE...1100 J/KG...ENOUGH TO DRIVE SHOWER ACTIVITY VCNTY OF THE LATE DAY WIND CONVERGENCE ALONG THE MOUNTAINS. DID NOT HAVE ANY SEVERE REPORTS. BEST COVERAGE WAS OVER THE NC HIGH COUNTRY...AND OVER THE HIGHER RIDGES JUST NORTHWEST OF ROANOKE. PRETTY DESCENT STORM OCCURRED IN EASTERN CRAIG COUNTY VA...EAST OF NEW CASTLE. THIS STORM DEPOSITED A HEALTHY 1.50 INCH OF RAIN...A NARROW CORE...MOST OF THIS FALLING IN THE NATIONAL FOREST. THIS SAME STORM CELL HAD THE HIGHEST CONCENTRATION OF CLOUD TO GROUND LIGHTNING OF ALL THE STORMS THAT OCCURRED IN THE CWA TODAY. OF THE OFFICIAL REPORTING STATIONS...WE MEASURED 0.11 IN THE GAGE HERE AT THE NWS OFFICE IN BLACKSBURG...A 10 MINUTE THUNDERSHOWER. THERE WAS NO CLOUD TO GROUND LIGHTNING OBSERVED WITH THIS SHOWER...BUT WE DID HEAR SOME IN-CLOUD RUMBLINGS. THUNDERSTORMS ASSOCIATED WITH AN UPPER LEVEL TROUGH OVER THE UPPER MIDWEST WILL RESULT IN AN ADVANCING AREA OF CIRRUS CLOUDS...THIS DEBRIS CLOUDINESS MOVING DOWNSTREAM AND POTENTIALLY IMPACTING OUR CWA LATE TONIGHT. THE RESULT WILL BE THE POTENTIAL FOR LESS NET RADIATIONAL COOLING WHICH MAY REDUCE THE AMOUNT OF FOG DEVELOPMENT. LOW TEMPERATURES TONIGHT WILL BE JUST SLIGHTLY HIGHER THAN THOSE REALIZED SATURDAY MORNING THANKS TO THE POTENTIAL FOR MORE CLOUD COVER. ON SUNDAY...WE EXPECT GREATER COVERAGE OF SHOWERS AND STORMS AS COMPARED TO WHAT IS OCCURRING TODAY. WHILE DAYTIME HEATING WILL HELP FUEL CONVECTION...AN ADDED FEATURE WILL BE INCREASED JET DYNAMICS ALOFT WITH THE APPROACH OF AN UPPER TROUGH. WE STILL EXPECT THE GREATEST COVERAGE ACROSS THE MOUNTAINS...HOWEVER...ISOLATED CONVECTION WILL BE POSSIBLE EVEN ACROSS THE PIEDMONT. HIGH TEMPERATURES SUNDAY IN THE WEST MAY BE SLIGHTLY COOLER THAN THOSE REALIZED TODAY THANKS TO A GREATER POTENTIAL FOR PRECIPITATION AND MORE CLOUD COVER. ACROSS THE PIEDMONT...READINGS MAY BE SLIGHTLY HIGHER THAN THOSE OF TODAY.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... AS OF 355 PM EDT SATURDAY... ANY SCATTERED CONVECTION WILL DISSIPATE IN THE EVENING...ALTHOUGH LEFT A SMALL AREA OF SLIGHT CHC POPS IN NW NC MTNS AREA DUE TO SOME WEAK CONVERGENCE AND LIGHT PRECIP SUGGESTED BY NAM. WHILE THERE IS LIKELY TO BE A BREAK IN THE FAR WEST BETWEEN DYING EVENING SHOWERS AND WHEN CHANCES INCREASE AGAIN TOWARD MORNING WITH LEFT-OVER ACTIVITY TRYING TO REACH WESTERN SLOPES FROM OVERNGIHT CONVECTION FAR TO THE WEST...KEPT A LOW CHC POP GOING IN FAR WEST...INCREASING TO MID CHC TOWARD MORNING SINCE CONFIDENCE IS LOW IN TERMS OF EXCATLY WHEN SOME OF THIS MIGHT ARRIVE. MOST LIKELY IT WILL NOT BE UNTIL AFTER 12Z MONDAY MORNING...BUT NAM SUGGESTING FASTER TIMING IF ENOUGH OF A COLD POOL DEVELOPS WITH AN ORGANIZED LINE WELL UPSTREAM OVERNIGHT...THE DYING REMNANTS COULD SNEAK IN EARLIER. CERTAINLY NOT CONFIDENT ENOUGH TO DROP POPS ENTIRELY FOR THE OVERNIGHT BACK ON WESTERN SLOPES. LOWS SUNDAY NIGHT WILL BE BIT MILDER IN THE WEST GIVEN ARRIVAL OF CLOUDS OVERNIGHT AHEAD OF CONVECTION...AND GOING ON WARM SIDE OF GUIDANCE THERE...AND WITH COOLER GUIDANCE IN EAST WHERE SKIES WILL BE PARTLY TO MOSTLY CLEAR. RIGHT NOW AHVE BLF AND DAN WITH SAME LOW TEMP...AND WOULD NOT BE SURPRISED IF BLF IS WARMER. MONDAY THE FRONT APPROACHES FROM THE WEST WITH INCREASING SHEAR AND MOISTURE...BUT BIG QUESTION IS INSTABILITY AND AMOUNT OF ANY DRY AIR TO AID IN DOWNBURST PRODUCTION. MUCH DEPENDS ALSO ON HOW MUCH LINGERING SHOWER ACTIVITY CAN GET INTO THE WEST IN THE MORNING...WHICH WOULD REDUCE INSTABILITY FURTHER. SOME CONVERGENCE IN LEE TROUGH DEVELOPS LATER IN THE DAY TOO...AND WITH FCST SOUNDINGS SUGGESTING BETTER MIXING AND DIFFERENCE IN TEMP AND DEW PT OUT THERE...WONDERING NOW IF THE BETTER SEVERE POTENTIAL WILL BE ALONG AND EAST OF THE BLUE RIDGE VS. IN THE MOUNTAINS. WITH SFC FRONT STILL TO THE WEST THOUGH...AND HEATING AHEAD OF IT COULD STILL CAUSE SOME TROUBLE...SO AT THIS POINT DONT WANT TO TRY AND DIFFERENTIATE SEVERE THREAT BETWEEN WEST AND EAST...BUT AM LEANING TOWARD A MINIMAL THREAT OVERALL...WITH A LITTLE BETTER POTENTIAL IN THE EAST. WILL NOT KNOW MUCH MORE UNTIL WE GET A BETTER HANDLE ON WHAT COULD BE LINGERING MONDAY MORNING AND HOW MUCH HEATING WILL OCCUR TO HELP INCREASE INSTABILITY BEYOND WHAT MODELS ARE SUGGESTING NOW. BUMPED UP HIGHS A BIT IN EAST WITH THE IDEA OF MORE SUNSHINE EARLY...AND GUDIANCE STILL GOING WITH SOME MID 90S. MUCH BIGGER DIFFERENCE IN DAYTIME HIGHS FROM WEST TO EAST MONDAY COMPARED TO LAST COUPLE OF DAYS. DECREASED THUNER POTENTIAL LATE OVERNIGHT MONDAY NIGHT BUT NOT ELIMINATING ENTIRELY...WITH MID CHC POPS GIVEN PLENTY OF MOISTURE AND FRONTAL BOUNDARY MOVING INTO WEST. BY DAYTIME...MODELS SUGGESTING A MUCH STRONGER LEE TROUGH DEVELOPING AND IDEA THAT THE SFC FRONT WILL EVENTUALLY JUMP INTO THIS POSITION BY LATE IN THE DAY. INITIALLY...THERE COULD BE SOME ACTIVITY ALONG WEAKENING SFC BOUNDARY ACROSS WEST...BUT INSTABILITY IS VERY MINIMAL. AGAIN...BETTER IN EAST. ANY SEVERE CHANCES SHOULD BE ACROSS EAST...AND DEPENDING ON WHERE THE BOUNDARY IS BY MID AFTERNOON...IT COULD ACTUALLY BE JUST SOUTHEAST OF THE FCST AREA. COOLER WITH HIGHS DUE TO EXTENSIVE CLOUD COVER AND SCATTERED TO NUMEROUS SHOWERS/THUNDERSTORMS. SOME COOLER AND SLIGHTLY DRIER AIR TO BEGIN PUSHING IN FROM WEST OVERNIGHT TUES NIGHT...BUT TRENDS ARE TO SLOW THIS MOISTURE BOUNDRY DOWN A BIT...AND STILL THINK THERE COULD BE LINGERING SHOWERS IN THE EAST MUCH OF THE NIGHT WITH SLOWLY MOVING BOUNDARY...BUT LEFT IT NO HIGHER THAN CHC POPS IN FAR EAST BY EVENING. WE HAVE BEEN RUNNING MUCH COOLER THAN GUIDANCE FOR OVERNIGHT LOWS...AND THIS MAY BE THE CASE IN FAR WEST...BUT NOT SO SURE ABOUT EAST WITH LINGERING SHOWERS AND UNCERTAINTY IN HOW FAR EAST BOUNDARY WILL BE...SO BUMPED UP LOWS A BIT IN THE EAST. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 1230 PM EDT SATURDAY... BY 12Z WEDNESDAY MORNING THE COLD FRONT WILL BE ACROSS EASTERN VA. HIGH PRESSURE BUILDS IN BRINGING DRIER AND MUCH COOLER CONDITIONS. AS THE HIGH SHIFTS TO THE EAST TOWARDS THE NE STATES BY THE END OF THE WEEK OUR WIND DIRECTION WILL GRADUALLY SHIFT FROM NW TO AN E/SE FLOW. THERE WILL BE A NOTICEABLE DROP IN HUMIDITY BEHIND THE FRONT AS DEWPTS CRASH INTO THE 40S AND 50S. 850MB TEMPS WILL RANGE FROM +11-15C WHICH WILL COORDINATE TO SURFACE TEMPS 5-10F BELOW NORMAL. HIGHER ELEVATIONS OF THE MOUNTAINS MAY NOT MAKE IT OUT OF THE 60S ON WEDNESDAY AND THURSDAY...WHILE EVEN LOWER LYING AREAS WILL ONLY RANGE FROM THE LOW 70S TO NEAR 80 EAST OF THE BLUE RIDGE. NIGHT TIME LOWS WILL ALSO BE 5-10F BELOW NORMAL. WHILE ITS TOO SOON TO TALK ABOUT ANY POTENTIAL RECORD LOWS...SEVERAL OF THEM MAY BE WITHIN REACH SHOULD WE GET SUFFICIENT RADIATIONAL COOLING. AT THE END OF THE PERIOD...THE GFS CONTINUES TO HINT AT A SHORTWAVE DISTURBANCE PIVOTING TOWARDS THE REGION FROM THE SOUTHERN PLAINS FOR FRIDAY AND SATURDAY. THE FLOW BECOMES MORE SOUTHERLY AND MOISTURE INCREASES AHEAD OF THE DISTURBANCE. PLACED A BROAD AREA OF LOW CHANCE POPS ACROSS THE AREA FOR THOSE TWO DAYS. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... AS OF 135 PM EDT SATURDAY... ISOLATED TO SCATTERED SHOWERS ARE EXPECTED TO CONTINUE TO DEVELOP ALONG AND WEST OF THE CREST OF THE BLUE RIDGE THROUGH THE REMAINDER OF THE AFTERNOON. WHILE NO TAF SITE IS CARRYING WX IN EITHER A PREVAILING AND TEMPORARY GROUP WITHIN THE TAFS...KROA AND KBCB ARE THE MOST LIKELY TAF LOCATIONS TO POTENTIALLY HAVE SHOWERS OR STORMS NEAR THEM THIS AFTERNOON. WILL UPDATE ACCORDINGLY AS NEED BE. ANY CONVECTION WILL BE MAINLY SUNSHINE DRIVEN TODAY...SO ANY ACTIVITY SHOULD QUICKLY DISSIPATE AROUND SUNSET. THROUGH THE NIGHT...MOST AREA WILL REMAIN VFR. HOWEVER...ANY LOCATIONS THAT RECEIVES RAIN TODAY WILL HAVE A INCREASED CHANCE OF SOME MVFR FOG AND/OR CEILINGS FOR ABOUT A FOUR HOUR PERIOD TONIGHT ENDING AROUND 12Z/8AM SUNDAY. SUNDAY WILL BE COMPARABLE TODAY WITH MAINLY VFR CONDITIONS...BUT POTENTIALLY HAVE GREATER COVERAGE OF SHOWERS AND STORMS WITH A SLIGHTLY EARLY START TIME. TODAY AND TOMORROW...ANY HEAVY CELLS COULD POTENTIALLY CAUSED SOME VERY BRIEF AND LOCALIZED SUB-VFR CONDITIONS. EXTENDED AVIATION DISCUSSION... SUNDAY AFTERNOON...COVERAGE OF SHOWERS AND STORMS WILL CONTINUE TO INCREASE COMPARED TO THE CONDITIONS JUST PRIOR TO 18Z/2PM. THE ACTIVITY WILL AGAIN BE MAINLY SUNSHINE DRIVEN...SO ANTICIPATE THE ACTIVITY TO DISSIPATE AROUND SUNSET. MONDAY NIGHT THROUGH TUESDAY NIGHT...A BETTER CHANCE OF SHOWER AND THUNDERSTORM ACTIVITY...ALONG WITH THE POTENTIAL FOR A GREATER COVERAGE OF SUB-VFR CONDITIONS WILL EXIST THANKS TO AN UPPER LEVEL LOW/TROUGH AND ITS ASSOCIATED DYANAMICS PROGRESSING EASTWARD THROUGH THE GREAT LAKES REGION AND THEN INTO NEW ENGLAND. ITS ASSOCIATED SURFACE FEATURES WILL OFFER A COLD FRONTAL PASSAGE TUESDAY AFTERNOON OR EVENING ALONG WITH A SLIGHT CHANCE OF SEVERE WEATHER AS OFFERED BY THE STORM PREDICTION CENTER. HIGH PRESSURE WILL TRY TO WORK ITS WAY INTO THE AREA WEDNESDAY INTO THURSDAY. THERE IS SOME QUESTION AS TO JUST HOW FAR SOUTH OF THE AREA THE COLD FRONT WILL MAKE IT BEFORE THE REGION IS ON THE WEST SIDE OF THE HIGH...AND THUS WE RETURN TO A SOUTHERLY FLOW OF MOISTURE INTO THE AREA. EITHER WAY...LOW LEVEL MOISTURE WILL LIKELY NOT COMPLETELY DRY OUT...AND THE POTENTIAL FOR OVERNIGHT IFR/MVFR FOG IS PROMISING...ESPECIALLY FOR AREAS THAT RECEIVE THE MOST RAINFALL MONDAY INTO TUESDAY. BY FRIDAY...MOST GUIDANCE IS IN AGREEMENT THAT A WAVE WILL MOVE ALONG THE STALLED FRONT AND BRING ANOTHER SUBSTANTIAL ROUND OF SHOWERS AND STORMS TO THE AREA. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS/SK NEAR TERM...DS/PM SHORT TERM...SK LONG TERM...CF AVIATION...PM

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