Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 130812
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
412 AM EDT SUN JUL 13 2014

.SYNOPSIS...
HIGH PRESSURE WILL GIVE WAY TO RETURN SOUTHWEST FLOW AND
INCREASING MOISTURE TODAY. 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 TONIGHT/...
AS OF 400 AM EDT SUNDAY...

CLOUD COVER SHOWN BY SATELLITE PICTURES OVER THE OHIO VALLEY AND
CIRRUS FROM THE THUNDERSTORMS OVER INDIANA AND ILLINOIS WILL MOVE
INTO THE FORECAST AREA THIS MORNING. TEMPERATURES WERE ALREADY
MILD...IN THE MID 60S TO LOWER 70S SO EVEN WITH ONLY OCCASIONAL
BREAKS IN THE CLOUDS...MAXIMUM TEMPERATURES WILL CLIMB INTO THE
LOWER 80S TO LOWER 90S.

BUFKIT FORECAST SOUNDINGS SHOWED NARROW CAPE...POSSIBLY UP TO 800
J/KG WITH ENOUGH OF A WARM LAYER ABOVE 600 MB TO CAP SOME OF THE
DEVELOPMENT OF THUNDERSTORMS. EXPECT COVERAGE OF THUNDERSTORMS TO
BE SIMILAR TO SATURDAY...MAINLY ALONG AND JUST EAST OF THE BLUE
RIDGE...ESPECIALLY SOUTH OF ROANOKE WHERE THE LOW LEVEL
CONVERGENCE IS THE BEST THIS AFTERNOON.

MODELS WERE SHOWING DIFFERENT SOLUTIONS TO HOW MUCH THE UPSTREAM
SHOWERS AND THUNDERSTORMS WILL IMPACT THE NORTHWEST COUNTY WARNING
AREA OVERNIGHT. AXIS OF HEAVIEST PRECIPITATION AND BEST
PRECIPITATION POTENTIAL PLACEMENT LOOKS LIKE IT WILL EXTENDED
FROM SOUTHWEST PENNSYLVANIA TO SOUTHEAST MISSOURI...STAYING JUST
NORTHWEST OF THE FORECAST AREA. HAVE HELD PROBABILITY TO CHANCE
RANGE FOR TONIGHT.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 320 AM EDT SUNDAY...

THE UPPER TROUGH WILL AMPLIFY AND SHIFT SOUTHEAST THE GREAT LAKES
AND OHIO VALLEY REGIONS. THE MAIN COLD FRONT WILL APPROACH FROM THE
WEST ON MONDAY WITH INCREASING SHEAR AND MOISTURE. SWODY2 HAS PLACED
OUR AREA IN A SLIGHT RISK FOR WELL-ORGANIZED MULTICELLS/LINE
SEGMENTS CAPABLE OF DAMAGING WINDS AND SOME HAIL. MONDAY MORNING
SHOWERS AND THUNDERSTORMS WITH ASSOCIATED CLOUD COVER MAY BE
INFLUENTIAL FACTORS IN THE OVERALL INSTABILITY.

SOME GOOD CONVERGENCE IN LEE TROUGH DEVELOPS LATER MONDAY AFTERNOON
WHICH SUGGEST THAT THERE MAY BE BETTER SEVERE POTENTIAL ALONG AND
EAST OF THE BLUE RIDGE. IN GENERAL...DECREASED MORNING POPS AND QPF
ESPECIALLY OUT EAST. KEPT THE HIGHEST POPS IN THE WEST BUT NUDGED
THE EAST UP MONDAY AFTERNOON. PLAYED HIGH TEMPERATURES CLOSE TO
ADJMAVBC WITH READINGS FROM THE LOWER 80S IN THE WEST TO THE MID 90S
IN THE EAST.

SCATTERED SHOWERS AND A FEW THUNDERSTORMS CONTINUE MONDAY NIGHT WITH
PLENTY OF MOISTURE AND FRONTAL BOUNDARY MOVING INTO WEST. LOW
TEMPERATURES MONDAY NIGHT WILL RANGE FROM THE LOWER 60S IN THE
MOUNTAINS TO THE LOWER 70S IN THE PIEDMONT.

COLD FRONT WILL MOVE EAST ACROSS THE REGION TUESDAY WITH SHOWERS AND
THUNDERSTORMS. MODELS SUGGESTING A MUCH STRONGER LEE TROUGH
DEVELOPING AND IDEA THAT THE SFC FRONT WILL JUMP INTO THE PIEDMONT
TUESDAY AFTERNOON. ANY SEVERE POTENTIAL SHOULD BE ACROSS EAST...AND
DEPENDING ON WHERE THE BOUNDARY IS BY MID AFTERNOON...IT COULD
ACTUALLY BE JUST SOUTHEAST OF THE FORECAST AREA. SWODY3 PLACED THE
SLIGHT RISK OF SEVERE THUNDERSTORM WITH 15 PERCENT ACROSS THE
CAROLINA AND SOUTHEASTERN VIRGINIA. WENT WITH THE COOLER ADJMET
HIGHS FOR TUESDAY FROM THE MID 70S TO THE MID 80S

DUE TO EXTENSIVE CLOUD COVER AND SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS.

SOME COOLER AND SLIGHTLY DRIER AIR TO BEGIN PUSHING IN FROM WEST
OVERNIGHT TUESDAY NIGHT...BUT TRENDS ARE TO SLOW THIS MOISTURE
BOUNDARY DOWN A BIT...AND STILL THINK THERE COULD BE LINGERING
SHOWERS IN THE EAST MUCH OF THE NIGHT WITH SLOWLY MOVING BOUNDARY.
LOW TEMPERATURES TUESDAY NIGHT WILL DROP TO THE MID 50S IN THE WEST
TO THE MID 60S IN THE EAST.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 1230 PM EDT SATURDAY...

BY 12Z WEDNESDAY MORNING THE COLD FRONT WILL BE ALONG THE EAST
COAST. 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 DEWPOINTS 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 /08Z SUNDAY THROUGH THURSDAY/...
AS OF 125 AM EDT SUNDAY...

HIGH PRESSURE WAS OFFSHORE WITH BROAD SOUTHWEST FLOW BRINGING DEEP
MOISTURE BACK INTO THE REGION. MVFR FOG HAD DEVELOP AT KBCB WHERE
IT RAINED BRIEFLY SATURDAY EVENING. VISIBILITY MAY OCCASIONALLY
DROP TO LIFR THROUGH 12Z/8AM AT KBCB. EXPECTING VFR CONDITIONS
FOR THE REST OF THE NIGHT AT KROA/KDAN AND KBLF. SOME MVFR FOG MAY
DEVELOP AT KLYH AND KLWB...BUT THIS WILL BE DEPENDENT ON THE
AMOUNT OF CLOUD COVER. AT 06Z/2AM SATELLITE PICTURES SHOWED A BAND
OF MID LEVEL CLOUDS FROM NEW YORK TO NORTHWEST NORTH CAROLINA
MOVING EAST. HIGH CONFIDENCE THAT MORE CLOUDS FROM OUT OF THE OHIO
VALLEY AND FROM THUNDERSTORMS OVER ILLINOIS WILL REACH THE
FORECAST AREA THIS MORNING.HOWEVER...CEILINGS WILL REMAIN VFR.

SUNDAY WILL BE COMPARABLE TO SATURDAY WITH MAINLY VFR CONDITIONS.
CLOUD BUILD-UPS EXPECTED BY EARLY AFTERNOON...WITH SCATTERED
MID/LATE AFTERNOON SHOWERS...PRIMARY DEVELOPMENT VCNTY OF THE
MOUNTAINS. KBCB AND KROA ARE THE MOST LIKELY LOCATIONS TO BE
IMPACTED WITH A THUNDERSTORM.

EXTENDED AVIATION DISCUSSION...

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 A DEEP UPPER
LEVEL LOW/TROUGH AND ITS ASSOCIATED DYNAMICS 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...AMS
SHORT TERM...KK
LONG TERM...CF
AVIATION...AMS/PM


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