Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 231131
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
731 AM EDT WED JUL 23 2014

.SYNOPSIS...
UPPER TROUGH OVER THE GULF COAST STATES SHIFTS WEST THROUGH
TODAY LEAVING A RESIDUAL WEAK BOUNDARY AND LOW LEVEL MOISTURE
OVER THE AREA. A COLD FRONT WILL BE ARRIVING THURSDAY FROM THE
NORTHWEST...THEN EXITING BY THURSDAY NIGHT. HIGH PRESSURE BUILDS
IN ON FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 350 AM EDT WEDNESDAY...

HIGH MOISTURE CONTENT REMAIN IN THE LOW LVLS OF THE ATMOSPHERE EARLY
THIS MORNING. DESPITE BEING IN A SUBSTANTIALLY DRY PATTERN IN THE
PAST MONTH OR SO...THE VEGETATION COMBINED WITH HIGH MOISTURE IS
STILL ENOUGH FOR FOG...WHICH IS STARTING TO COVER THE ERN
CWA...DAN/FVX AREA. FURTHER WEST...FOG IS PATCHY AS THERE ARE A FEW
MORE CLOUDS IN THE MID LVLS.

THE OVERALL FORECAST TODAY THROUGH TONIGHT IS NOT CHANGING MUCH FROM
THE PREVIOUS ONE WE HAD. MODELS STILL IN AGREEMENT IN STARTING
CONVECTION OVER THE SRN BLUE RIDGE BY LATE MORNING...THEN SPREADING
IT NWD THROUGH THE AFTERNOON WITH STORM MOTION CARRYING IT SE INTO
THE FOOTHILLS AND PIEDMONT. MODELS ALSO SHOWING CONVECTION FIRING IN
KY AND WRN WV THIS AFTERNOON AND MOVING IT INTO SE WV...WELL AHEAD
OF THE FRONT. THIS AREA IS EXPECTED TO BE A BETTER REGIME FOR
STRONGER STORMS...THOUGH OVERALL DYNAMICS FAVOR BEST THREAT STAYING
WEST OF THE CWA. GIVEN SOME LACK OF COVERAGE IN THE PAST DAY...THE
COVERAGE THIS AFTERNOON WILL BE MAINLY ISOLATED/SCATTERED...THOUGH
THINK THE SRN BLUE RIDGE WILL HAVE A BETTER THAN 50 PERCENT COVERAGE.

WITH NOT MUCH CHANGE IN THE LOW LVL THICKNESS BUT SOME CHANGE IN SFC
WINDS...THINK HIGHS TODAY WILL BE A FEW DEGREES WARMER THAN TUESDAY
ESPECIALLY OUT EAST WHERE MORE SUNSHINE WILL OCCUR. WENT WITH MID TO
UPPER 80S WEST TO LOWER 90S EAST. KEPT THE NC MOUNTAINS IN THE UPPER
70S/LOWER 80S BECAUSE OF CONVECTION FIRING EARLIER.

TONIGHT...STILL WILL SEE SOME CONVECTION AROUND BUT DISSIPATING OUT
EAST AFTER MIDNIGHT. FRONTAL BOUNDARY WILL MAKE ITS WAY TOWARD THE
WV/KY LINE BY THU MORNING...AND MODELS AGREE THAT PRECIP WILL BE IN
THE SE WV/FAR SW VA CORRIDOR BY LATE TONIGHT SO HAVE KEPT LIKELY
POPS HERE FADING TO SLIGHT CHANCE EAST OF THE BLUE RIDGE. MORE CLOUD
COVER AND HIGH DEWPOINTS WILL KEEP LOWS ELEVATED IN THE MID 60S TO
LOWER 70S.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
AS OF 345 AM EDT WEDNESDAY...

WILL START THURSDAY OFF WITH THE COLD FRONT MAKING ITS WAY ACROSS
WEST VIRGINIA TOWARD OUR AREA. WITH THE FRONT IN SUCH CLOSE
PROXIMITY...WILL ALREADY HAVE SPOTTY SHOWERS AND A FEW THUNDERSTORMS
PASSING MAINLY ACROSS THE MOUNTAINS BY SUNRISE...WITH COVERAGE
INCREASING THROUGH LATE MORNING AS THE FRONT ENTERS OUR AREA AND
DAYTIME HEATING INCREASES. WHILE MUCH OF OUR AREA WILL EXPERIENCE
RAINFALL DURING THE MORNING AND AFTERNOON...BELIEVE INSTABILITY WILL
BE MORE MUTED COMPARED TO WEDNESDAY DUE IN PART TO THE INCREASED
CLOUD COVER. AS SUCH...MOST OF THE THUNDERSTORM ACTIVITY THAT
DEVELOPS ACROSS THE MOUNTAINS WILL BE WEAK...ALTHOUGH CANNOT RULE
OUT A FEW STRONG STORMS ACROSS THE SOUTHSIDE DURING THE AFTERNOON/
EVENING WHERE HEATING AND INSTABILITY WILL BE STRONGEST. AFTERNOON
HIGHS WILL RANGE FROM THE MID 70S ACROSS THE MOUNTAINS TO THE MID
80S ACROSS THE SOUTHSIDE.

THE COLD FRONT IS EXPECTED TO SHIFT SOUTH OF OUR AREA THURSDAY NIGHT
BEFORE STALLING ACROSS THE CAROLINAS FRIDAY MORNING. REGARDLESS...
HIGH PRESSURE BUILDING IN BEHIND THE FRONT IS NOT VERY STRONG...AND
WITH MID TO UPPER 60 DEGREE DEWPOINTS LINGERING ACROSS THE
SOUTHSIDE...MAY STILL SEE A FEW SHOWERS AND ISOLATED THUNDERSTORMS
DEVELOP WITH AFTERNOON HEATING. OTHERWISE...INCREASED SUNSHINE WILL
HELP AFTERNOON HIGHS REACH NEAR NORMAL FOR LATE JULY...WITH
TEMPERATURES RANGING FROM THE UPPER 70S WEST TO THE UPPER 80S EAST.

WIND FLOW ALOFT WILL SHIFT NORTHWESTERLY FRIDAY AS AN UPPER LEVEL
TROUGH PASSES EAST ACROSS THE GREAT LAKES...WHILE A LARGE DOME OF
HIGH PRESSURE REMAINS SITUATED OVER THE SOUTHWEST U.S. THIS WILL
OPEN THE DOOR FOR UPPER LEVEL DISTURBANCES TO ENTER THE AREA FROM
THE MIDWEST FOR THE WEEKEND. THE NAM/ECMWF/CANADIAN MODELS ALL ARE
PICKING UP ON ONE DISTURBANCE APPROACHING BY SUNRISE SATURDAY...MOST
LIKELY TRIGGERING A BAND OF STORMS THAT WILL BE SIGNIFICANTLY
WEAKENED AS IT ENTERS OUR SOUTHEAST WEST VIRGINIA/MOUNTAIN EMPIRE
COUNTIES. STILL NOT ENTIRELY CONFIDENT IN THIS SCENARIO PLAYING OUT
AT THIS POINT...SO WILL STICK WITH A SLIGHT CHANCE OF SHOWERS AND
STORMS FOR SATURDAY MORNING.

MORE DISTURBANCES ARE SLATED TO ARRIVE ON SATURDAY AND SATURDAY
NIGHT...ALTHOUGH TIMING OF THESE DISTURBANCES THIS FAR IN ADVANCE IS
ALWAYS DIFFICULT.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
AS OF 400 PM EDT TUESDAY...

INTO EARLY NEXT WEEK...THE AREA REMAINS VULNERABLE TO NW FLOW
DISTURBANCES TRACKING AROUND THE LARGE WESTERN/CENTRAL CONUS UPPER
RIDGE. A PARTICULARLY STRONG DISTURBANCE...NOTED BY ALL THE
MODELS...PROMISES TO AMPLIFY THE EASTERN LONG WAVE TROUGH...A
FEATURE THAT 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.

THE BEST CHANCE FOR SHOWERS/STORMS LOOKS TO BE SUNDAY AS THE
SURFACE FRONT ASSOCIATED WITH THE STRONG DISTURBANCE CROSSES THE
FORECAST AREA FROM THE NORTHWEST. POTENTIAL EXISTS FOR STORMS TO
BE ORGANIZED WITH UPSTREAM MCS IMPACTING THE FORECAST AREA.

GENERALLY FOLLOWED HPC GUIDANCE THROUGH THE PERIOD. TRENDED POPS
UP FOR SUNDAYS FROPA...THEN DOWN FOR A DAY OR TWO AFTER SUNDAYS
FRONTAL PASSAGE. TENDENCY FOR FRONTAL PASSAGES IS TO BRING SOME
DOWNTIME AS WITH RESPECT TO POPS BEFORE MOISTURE AND INSTABILITY
CAN RETURN.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 725 AM EDT WEDNESDAY...

FOG BECAME DENSE AT LWB/BCB WITH MVFR AT DAN/LYH. FOG WILL
DISSIPATE BY 13Z...WITH VFR EXPECTED MUCH OF THE DAY. HIGH-RES
MODELS ARE FAVORING CONVECTION OVER THE BLUE RIDGE AND ALLEGHANY
HIGHLANDS BY 18Z...SO HAVE VCTS AT ROA/BCB/BLF/LWB...PER HRRR. THE
CONVECTION WILL WANE LATE AFTERNOON/EARLY EVENING BEFORE FRONTAL
PRECIP ARRIVES AFTER MIDNIGHT IN THE BLF/LWB CORRIDOR. AMENDMENTS
MAY BE NEEDED FOR TSRA TODAY IF TERMINALS ARE THREATENED.
OTHERWISE...COVERAGE DOES NOT DICTATE HAVING PREDOMINANT TSRA IN
THE TAFS.



EXTENDED AVIATION DISCUSSION...

NEXT NORTHERN STREAM UPPER TROUGH AND ITS ASSOCIATED COLD FRONT
WILL APPROACH 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.

&&

.EQUIPMENT...
AS OF 405 AM EDT WEDNESDAY...

KFCX RADAR IS DOWN. TECHNICIANS WILL AGAIN BE WORKING ON THE
RADAR TODAY..

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.

&&

$$
SYNOPSIS...JH/WP
NEAR TERM...WP
SHORT TERM...NF
LONG TERM...PM
AVIATION...PH/WP
EQUIPMENT...PH/WP


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