Area Forecast Discussion
Issued by NWS Blacksburg, VA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KRNK 222318
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
718 PM EDT TUE JUL 22 2014

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 205 PM EDT TUESDAY...

WEAK SURFACE RIDGE ACROSS THE REGION THIS AFTERNOON COMBINING WITH
LIMITED INSTABILITY AND LACK OF FORCING TO KEEP OVERALL CONVECTIVE
COVERAGE AT A MINIMUM ATTM. BEST LOW LEVEL THETA-E ALSO SHOWING UP
JUST SOUTH OF THE REGION WHICH COULD STILL INTERACT WITH RESIDUAL
OUTFLOW TO PRODUCE A BIT BETTER COVERAGE OF MAINLY SHRA ACROSS THE
SOUTH/SE INTO THIS EVENING. ELSW APPEARS ANY LATE DAY COVERAGE
WILL BE QUITE ISOLATED AND PERHAPS ONLY OVER THE FAR NW ON THE
EDGE OF THE CURRENT CLOUD SHIELD WHERE MORE HEATING HAS OCCURRED.
THUS MAINTAINING THE HIGHEST POPS FAR SOUTH WITH MID TO LOW
CHANCES ELSW INTO EARLY EVENING.

UPPER LOW WELL TO THE SW WILL CONTINUE TO SHIFT WEST OVERNIGHT
LEAVING THE REGION IN A MOIST ENVIRONMENT BUT WITH LACK OF MUCH
SUPPORT FOR ADDED SHRA. IN ADDITION THE LOW LEVEL WEDGE WILL BE
BREAKING DOWN AS THE SURFACE HIGH SHIFTS ACROSS AND TO THE SOUTH
ALLOWING THE FLOW TO TURN LIGHT WESTERLY AFTER MIDNIGHT. THIS
SHOULD LIMIT MUCH -DZ POTENTIAL WITH ONLY SOME WEAK LEFTOVER
CONVERGENCE WESTERN SLOPES LATE TONIGHT. APPEARS MAY BE ABLE TO GO
DRY AFTER THIS EVENING BUT WITH DEEPER MOISTURE STILL OVER THE SW
LEFT IN A TOKEN POP THERE OVERNIGHT. LOWS AGAIN WARM/MUGGY WITH
MOST IN THE 65-72 RANGE GIVEN HIGH DEWPOINTS AND PATCHY FOG
AROUND.

NEXT STRONG 5H TROF AND ASSOCIATED COLD FRONT WILL BE APPROACHING
ON WED AS HIGH PRESSURE SHIFTS FARTHER SOUTH ALLOWING DEEPENING
WESTERLY FLOW AND A SUBSEQUENT LEE TROF WELL EAST OF THE BLUE
RIDGE. MODELS SPARK MOST AFTERNOON CONVECTION ALONG THE SOUTHERN
BLUE RIDGE GIVEN THE WEAK BOUNDARY LAYER SW FLOW AND BETTER
DIFFERENTIAL HEATING BUT STILL IFFY GIVEN WESTERLY FLOW ALOFT AND
ONLY FAINT LIFT. ELSW APPEARS RATHER ISOLATED DESPITE LINGERING
MOISTURE GIVEN DRY AIR ALOFT AND DOWNSLOPING WEST WINDS ACROSS
THE EAST SO KEEPING SHOTGUN CHANCE POPS. HOWEVER THE UPSTREAM PRE-
FRONTAL BAND OF TSRA WILL LIKELY BE NEARING THE NW SLOPES LATE.
THUS KEPT IN LOW LIKELYS EXTREME WEST...BUT MOSTLY TOWARD SUNSET
AT THIS POINT. SOME ISOLATED SEVERE POSSIBLE IF PULSE STORMS
ORGANIZE MORE EARLY...AND UPSTREAM ACTIVITY MOVES INTO THE WEST IN
MORE OF A LINE FEATURE...ALTHOUGH THIS MAY BE AFTER INSTABILITY IS
STARTING TO FADE. OTRW SHOULD SEE CLOUDS BREAK QUICKER UNDER THE
WESTERLY FLOW ALLOWING INSOLATION AND 85H TEMPS AROUND +20C TO AID
WEAK COMPRESSION IN PUSHING HIGHS INTO THE 80S WEST AND 90-95
EAST.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 345 PM EDT TUESDAY...

WEDNESDAY NIGHT...PREFRONTAL MCS LIKELY TO IMPACT AT LEAST THE
WESTERN HALF OF THE CWA...ACTIVITY FADING WITH LOSS OF DAYTIME
HEATING. REMNANT OUTFLOW MAY REACH PIEDMONT BY DAYBREAK THURSDAY
AND DEBRIS CLOUDINESS WILL LIKELY REMAIN TO START THE DAY
THURSDAY. MODELS ARE IN AGREEMENT THE ACTUAL COLD FRONT WILL
ENTER OUR SOUTHEAST WEST VIRGINIA COUNTIES LATE MORNING/EARLY
AFTERNOON ON THURSDAY...AND CONTINUE EAST THROUGH THE DAY. ATTM
THINK ABUNDANT CLOUDINESS EARLY THURSDAY MAY INHIBIT SOLAR
INSOLATION...LIMITING INSTABILITY OVER ALL BUT THE FAR
SOUTHEASTERN CWA...THE GREATEST CHC FOR SHOWERS/STORMS OCCURRING
FROM OUR PIEDMONT EASTWARD INTO THE TIDEWATER OF VA/NC.

FOR NOW WILL MAINTAIN HIGH POPS BOTH WEDNESDAY NIGHT AND
THURSDAY...THEN END THE PRECIP THREAT QUICKLY FROM WEST TO EAST
WITH THE PASSAGE OF THE FRONT...LEAVING MAINLY DRY CONDITIONS
FOR THE AREA BY FRIDAY.

WEAK HIGH PRESSURE WILL BUILD INTO THE AREA BEHIND THE
FRONT...AND SHOULD PROVIDE A DAY...MAYBE TWO...OF PRECIP FREE
CONDITIONS.

TEMPERATURES THURSDAY WILL BE TEMPERED BY CLOUDS ASSOCIATED WITH
THE FRONT...THEN TREND DOWN A FEW DEGREES FOR FRIDAY. THE AIRMASS
CHANGE IS NOT OVERLY DRY NOR COOL...SO WHEN THE SUN POPS OUT
FRIDAY...READINGS MAY FEEL JUST AS WARM AS THURSDAY...ALTHOUGH THE
DEWPOINTS WILL NOT BE AS ROBUST.

&&

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

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. 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 /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 715 PM EDT TUESDAY...

ONLY ISOLATED STORMS WERE NOTED ON RADAR...MAINLY NEAR KDAN AND
ACROSS THE HIGHER TERRAIN OF SOUTHEAST WV. THIS SMALL AREA OF
CONVECTION WILL DISSIPATE SHORTLY AFTER SUNSET...AND INCLUDED ONLY
AN HOUR OR TWO OF VCSH AT KDAN/KLWB/KBLF THIS EVENING.

AS WEAK HIGH PRESSURE CONTINUES TO BUILD SOUTHWEST...LIGHT SFC
WINDS WILL VEER TO THE SOUTH AND SOUTHWEST. THIS SHOULD RESULT IS
LESS CLOUD COVER COMPARED TO WHAT HAS BEEN EXPERIENCED FOR THE
PAST FEW MORNINGS. HOWEVER...LIGHT WINDS AND A MOIST LOW LEVEL
AIRMASS WILL LEAD TO THE DEVELOPMENT OF FOG AFTER 05Z.
THOSE CLIMATOLOGICAL FAVORED AREAS...KLWB AND KBCB...WILL HAVE
THE BEST CHANCE OF SEEING IFR VISIBILITIES LATE TONIGHT/EARLY
TOMORROW DUE TO FOG. MVFR VISIBILITIES ARE POSSIBLE AT KLYH AND
KDAN.

ANY FOG WILL QUICKLY BURN OFF EARLY WEDNESDAY...THANKS TO A
SOUTHWEST LOW LEVEL FLOW IN ADVANCE OF AN APPROACHING COLD FRONT.
HOWEVER...THIS WILL USHER IN DEEPER MOISTURE AND EXPECT BETTER
COVERAGE WITH AFTERNOON SHOWERS AND STORMS...ESPECIALLY ACROSS THE
SOUTHERN BLUE RIDGE. AS A RESULT...INTRODUCED VCTS FOR THE
MOUNTAIN TAF SITES WEDNESDAY AFTERNOON.

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.

&&

.EQUIPMENT...
AS OF 715 PM EDT TUESDAY...

KFCX RADAR REMAINS DOWN. TECHNICIANS ARE STILL AT THE SITE
WORKING ON THE PROBLEM...AND HOPE TO HAVE THE RADAR BACK ONLINE
THIS EVENING.

&&

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

&&

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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.