Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 291141
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
741 AM EDT WED JUL 29 2015

.SYNOPSIS...
UPPER RIDGE WILL STAY CENTERED OVER THE SOUTHERN U.S. TODAY INTO
TONIGHT. A FRONT WILL SLIDE ACROSS OUR REGION THURSDAY...STALLING
ALONG THE SOUTHEAST COAST FRIDAY INTO SATURDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 345 AM EDT WEDNESDAY...

RIDGE ALOFT REMAINS ANCHORED FROM THE DESERT SOUTHWEST INTO THE
LOWER MS VALLEY AND ELONGATED TOWARD THE SOUTHERN APPALACHIANS. FOR
OUR AREA WILL SEE A COUPLE OF WEAK VORTS MOVE ESE ALONG THE NE SIDE
OF THIS RIDGE THIS AFTERNOON INTO THE EVENING. AM BANKING ON ASCENT
FROM DIFFERENTIAL HEATING...LEFTOVER BOUNDARIES AND WEAK UPPER LEVEL
DISTURBANCES FOR THUNDERSTORMS TO FIRE UP THIS AFTERNOON IN THE
MOUNTAINS FIRST...THEN DRIFTING TO THE ESE TO THE PIEDMONT. THE WIND
FLOW STAYS WEAK AT 5-15 KTS...SO A FEW STORMS WILL HAVE THE
POTENTIAL FOR HEAVY RAINERS LIKE TUESDAY. WILL MAINTAIN WORDING IN
THE HWO FOR LOCALIZED FLOODING THREAT.

EXPECT THE HUMIDITY TO STAY ELEVATED TODAY KEEPING IT FEELING LIKE
THE TYPICAL DOG DAYS OF SUMMER. HIGH TEMPS WILL RUN FROM THE LOWER
TO MID 80S WEST TO UPPER 80S/AROUND 90 EAST.

ANOTHER WEAK WAVE MAY ACROSS US BY 12Z THURSDAY THOUGH THINK ATTM
WILL SEE LIMITED SHOWERS OVERNIGHT. WILL SEE LINGERING CONVECTION IN
THE EVENING BEFORE THINGS FADE AROUND MIDNIGHT. LOWS WILL RANGE FROM
THE UPPER 60S TO LOWER 70S FOR MOST OF THE REGION.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
AS OF 415 AM EDT WEDNESDAY...

SOME SUBTLE SYNOPTIC CHANGES WILL LEAD TO AN END OF THE DAILY
THUNDERSTORM REGIME THIS PERIOD AND ALSO BRING A PERIOD OF
RESPITE FROM THE HIGHER DEWPOINTS/RELATIVE HUMIDITY LEVELS. THE
CHANGES WILL BE THE RESULT OF A DEEP UPPER LOW TRACKING EASTWARD
ACROSS CENTRAL INTO EASTERN CANADA...FORCING THE STRONG
SUBTROPICAL RIDGE...WHICH HAS BEEN ANCHORED ACROSS THE SOUTHERN
PLAINS FOR THE PAST SEVERAL DAYS...TO RETROGRADE INTO THE DESERT
SOUTHWEST.

THE COLD FRONT THAT WILL BRING THE CHANGE IN AIR MASS TO THE
REGION WILL BE ON OUR WESTERN DOORSTEP AT 12Z THU. AS WITH THE
PAST SEVERAL EVENTS...THERE WILL LIKELY BE AN AREA OF SHOWERS AND
ISOLATED THUNDERSTORMS ALONG AND NEAR THE FRONT AT DAYBREAK THU.
THIS ACTIVITY WILL BE IN A DIMINISHING/DECAYING STATE...BUT WILL
LIKELY REDEVELOP FAIRLY QUICKLY...DEPENDING ON DOWNSTREAM CLOUD
DEBRIS AND SUBSEQUENT MORNING HEATING...AS THE ASSOCIATED OUTFLOW
BOUNDARY MOVES TOWARD THE BLUE RIDGE. INSTABILITY IS MEAGER FOR
LATE JULY AND DYNAMICS ARE WEAK...BUT STRONG HEATING AND PWATS
NEARING 2.00 INCHES EAST OF THE BLUE RIDGE SHOULD YIELD SOME
FAIRLY ROBUST STORMS...ALSO WITH LOCALLY HEAVY RAINFALL. SPC HAS
CONTINUED TO OUTLOOK AREAS MAINLY EAST OF THE BLUE RIDGE FOR A
MARGINAL RISK OF SEVERE ON THU.

CONVECTION SHOULD BE DIMINISHING AND MOVING EAST OF THE AREA
FAIRLY QUICKLY THU NIGHT. SOME ACTIVITY WILL LIKELY LINGER ACROSS
THE CHARLOTTE TO HALIFAX COUNTY AREA OF THE PIEDMONT TOWARD
MIDNIGHT...BUT AFTER THAT IT SHOULD ALL SHIFT EAST OF THE CWA.

FOR THE REST OF THE PERIOD...THE FRONT IS STILL PROGGED BY MOST OF
THE SYNOPTIC-SCALE MODELS TO BE PUSHED WELL SOUTH OF THE CWA AS
THE UPPER FLOW AMPLIFIES...WITH A STRONG UPPER RIDGE WESTERN U.S.
AND A DEEPENING TROUGH EASTERN U.S. THUS...THE FRONT SHOULD MOVE
TO NEAR CENTRAL GA/CENTRAL SC AND TOWARD THE CENTRAL NC COAST
BEFORE STALLING. THERE ARE STILL INDICATIONS THAT THE TAIL END OF
THE TROUGH WILL BECOME CUTOFF ACROSS SOUTH GA/FL PANHANDLE...WITH
AN ELONGATED TROUGH AXIS STUCK ALONG THE SOUTHEAST TO THE NC
COASTLINE INTO EARLY NEXT WEEK. WAVES OF CONVECTION WILL LIKELY
RIDE ALONG AND NEAR THIS BOUNDARY...BUT ALL OF THIS IS EXPECTED TO
REMAIN WELL SOUTH OF OUR AREA.

COOLING BEHIND THE FRONT WILL BE NOMINAL AT BEST...LIKELY ON A FEW
DEGREES. 850MB TEMPS ARE NOT EXPECTED TO DROP MUCH BELOW +20C
THROUGH THE PERIOD. MORE IMPORTANTLY...MOST OF THE MODELS ARE IN
AGREEMENT THAT DEWPOINTS WILL FALL INTO THE 50S ACROSS THE
MOUNTAINS AND 60S ACROSS THE PIEDMONT...BUT WILL HOVER NEAR 70 IN
THE DANVILLE AREA. THIS WILL BE SOMEWHAT REFRESHING...BUT THE LATE
JULY/EARLY AUGUST SUN WILL STILL FEEL QUITE WARM IN THE DAYTIME.
EXPECT MIN TEMPS CLOSER TO NORMAL...WITH MAX TEMPS STILL LIKELY
AVERAGING ABOVE NORMAL THROUGH MUCH OF THE PERIOD.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
AS OF 430 AM EDT WEDNESDAY...

AS NOTED ABOVE...MODELS HAVE FINALLY COME INTO GOOD AGREEMENT IN
KEEPING ANY CUTOFF UPPER LOW/WEAKNESS/PSEUDO-TROPICAL DEVELOPMENT ALONG
THE SOUTHEAST U.S. COAST WELL SOUTH OF OUR REGION...EVENTUALLY
BEING PUSHED OUT TO SEA OFF THE SC/NC COAST. SOME MODELS...ESPECIALLY
THE ECMWF...TRY TO PUSH MOISTURE INTO THE FAR SOUTHEAST PART OF
THE CWA OVER THE WEEKEND...BUT MOST MODELS SUGGEST THAT ANY
PRECIPITATION WILL REMAIN FURTHER SOUTHEAST. HAVE HEDGED ON THE
FAR SOUTHEAST CORNER WITH SOME LOW POPS...BUT HAVE GENERALLY KEPT
IT RAIN FREE ELSEWHERE.

NORTHWEST FLOW ALOFT WILL DOMINATE THE REGION AS THE UPPER TROUGH
REMAINS IN PLACE ACROSS THE EASTERN CANADIAN PROVINCES.
EVENTUALLY...A SERIES OF NORTHWEST FLOW DISTURBANCES APPEAR
DESTINED TO END THE DRIER CONDITIONS EXPECTED FRI-SUN. THE FIRST
OF THESE DISTURBANCES IS SLATED TO SKIRT THE NORTHERN PART OF THE
CWA SUN NIGHT/MON. THERE IS ENOUGH INSTABILITY AND MOISTURE AT
THAT POINT TO SUPPORT ISOLD SHRA/TSRA ACROSS THE MOUNTAINS AND
I-64 CORRIDOR...SO ADDED SOME LOW POPS. THE NEXT SUCH DISTURBANCE
SHOULD ARRIVE TOWARD THE MID PART OF NEXT WEEK. OVERALL...THE
PATTERN IS GENERALLY DRY...WITH NO WIDESPREAD SYNOPTIC OR
MEANINGFUL RAINFALL EVENTS INDICATED FOR THE PERIOD.

TEMPERATURES WILL BE MOSTLY NEAR NORMAL THROUGH THE PERIOD...LOWS
60S WEST TO AROUND 70 EAST...WITH HIGHS 70S MOUNTAINS AND 80S
ELSEWHERE...CREEPING CLOSER TO 90 PIEDMONT AS 850MB TEMPS HOVER
MOSTLY IN THE +15C TO +20C RANGE THROUGH MOST OF THE PERIOD.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 740 AM EDT WEDNESDAY...

FOG IS THE IMMEDIATE CONCERN AS A STAGNANT AIR MASS AND LATE
EVENING RAINFALL TUESDAY HAS LEFT FAIRLY WIDESPREAD IFR-LIFR FG
ACROSS THE REGION. EXPECT CONDITIONS TO IMPROVE AFT 14Z...WITH
CIGS BECOMING MVFR OR BETTER BY LATE MORNING. OTHERWISE...MAIN
STORY AGAIN TODAY WILL BE THE WEAK LINGERING FRONTAL BOUNDARY AND
SCATTERED AFTERNOON/EVENING SHOWERS AND THUNDERSTORMS. LOCALIZED
MVFR CIGS AND MVFR-IFR VSBYS IN SHRA/TSRA AFTERNOON THROUGH EARLY
EVENING. AGAIN...NOT ENOUGH CONFIDENCE TO PUT ANY MORE THAN VCTS
IN THE TAFS AT THIS TIME. OVERALL...IT APPEARS AREAS EAST OF THE
ALLEGHANY FRONT WILL BE THE MOST FAVORABLE FOR CONVECTION TODAY.
ANY STORMS FADE WITH LOSS OF HEATING WED EVENING WITH FOG FORMING
AGAIN BY THURSDAY MORNING. A NEW FRONTAL BOUNDARY WILL BE
APPROACHING LATE TONIGHT/EARLY THURSDAY...BUT SHOULD REMAIN FAR
ENOUGH WEST BEFORE 12Z TO PRECLUDE ANY MORE THAN A MENTION OF
APPROACHING MID CLOUDS. EXPECT SHRA/TSRA TO REMAIN ACROSS RLXS
AREA THROUGH THAT TIME.

EXTENDED AVIATION FORECAST...

MORE WIDESPREAD SHOWERS AND THUNDERSTORMS ARE EXPECTED ON THURSDAY
AS A COLD FRONT CROSSES THROUGH REGION FROM THE NORTHWEST. THIS
FRONT SHOULD PUSH SOUTH OF THE AREA AND ALLOW FOR DRIER AND MOSTLY
VFR CONDITIONS FRIDAY THROUGH SUNDAY.

&&

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

&&

$$
SYNOPSIS...WP
NEAR TERM...WP
SHORT TERM...RAB
LONG TERM...KK/RAB
AVIATION...RAB/WP



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