Flash Flood in West Virginia, August 8, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
102 PM EDT THU AUG 8 2013

.SYNOPSIS...
WEAK UPPER LEVEL DISTURBANCES WILL CONTINUE TO MOVE EAST ACROSS
THE REGION INTO FRIDAY AHEAD OF A SLOW MOVING COLD FRONT
APPROACHING FROM THE NORTHWEST. THIS FRONT MOVES INTO THE
MOUNTAINS BY SATURDAY...AND SHIFTS SLOWLY TO THE SOUTH OF THE
REGION AFTER THE WEEKEND.
&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 925 AM EDT THURSDAY...

INIT VORT LOBE CROSSING THE BLUE RIDGE ATTM SHOULD PUSH EAST
INTO THE PIEDMONT BY THIS AFTERNOON AHEAD OF THE NEXT WAVE
ARRIVING FROM THE WEST. THIS WESTERN FEATURE LOOKS TO BE THE MAIN
CONVECTIVE FOCUS PROVIDED ENOUGH HEATING GIVEN SUCH HIGH PWATS AND
BACKING LIGHT SW FLOW. STEERING ALOFT OFF MORNING RAOBS ALSO
RATHER WEAK BUT APPEARS AN OVERALL 10-15 KNOT MOVEMENT IN ORDER
PER LATEST SOUNDING ANALYSIS. LATEST MODELS DIFFER IN HANDLING OF
HOW WIDESPREAD SHRA/TSRA BECOMES WITH SOME LEAVING CURRENT AXIS
OVER TN JUST TO THE WEST...WHILE OTHERS DEVELOP A BIGGER SWATH OF
DEEPER CONVECTION PER MORE INSTABILITY...AND PUSH THAT AREA EAST
TO THE BLUE RIDGE IN A MORE ORGANIZED LINE FEATURE LATER ON.
OVERALL TREND HAS BEEN FOR GUIDANCE TO BE TOO WET/FAST BUT COULD
SEE MORE CLUSTERING OF HEAVY RAIN PROUDUCING STORMS WEST GIVEN
AXIS OF HIGHER 85H THETA-E ALONG THE WESTERN SLOPES. THUS WILL
BUMP UP LIKELY POPS A BIT TO CATEGORICAL FAR WEST AND EXTEND
LIKELYS EAST TO THE BLUE RIDGE BY LATE AFTERNOON. SINCE STILL
SOME UNCERTAINTY WILL AGAIN HOLD OFF ON ANY WATCH ISSUANCE FOR NOW
AND SEE HOW THINGS EVOLVE LATER ON ESPCLY FAR NW WHERE FFG IS
LOWEST. BUMPED UP HIGHS A LITTE IN THE EAST GIVEN WARM
THICKNESS...ALTHOUGH OVERALL TREND OF MID 70S TO LOW 80S LOOKS ON
TRACK WITH MORE CLOUDS AROUND AGAIN THIS AFTERNOON ESPCLY
CENTRAL/WEST.

THE ONE MAIN VORT MOVES EAST OF THE CWA BY EVENING SO EXPECT
SOME WEAKENING/DIMINISHING TREND IN THE POPS OUT EAST. THE FLOW
ALOFT AND MODEL VORTICITY FIELDS OF THE ECMWF CONTINUE TO SHOW
EMBEDDED WAVES MOVING FROM KENTUCKY INTO VIRGINIA/WEST VIRGINIA
TONIGHT...AND POSSIBLY INTO NC. LIKE THE ECMWF IDEA OF MAINTAIN
HIGHER POPS ACROSS SE WV INTO FAR SW VA...WITH LESS IN THE
SOUTHEAST.

FOR TONIGHT...SAME AIRMASS SO LOWS SHOULD BE IN THE MID TO UPPER
60S WEST TO LOWER 70S EAST.
&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
AS OF 400 AM EDT THURSDAY...

LOOKING AT AN INCREASED THREAT OF LOCALLY HEAVY RAIN AND POSSIBLY
FLASH FLOODING ON FRIDAY AS A STRONG SHORTWAVE TROUGH PASSES EAST
ACROSS THE GREAT LAKES DURING THE AFTERNOON AND EVENING. THE
COMBINATION OF DEEP ATMOSPHERIC MOISTURE BUILDING ALONG THE CENTRAL
APPALACHIAN CHAIN AHEAD OF THE TROUGH...MODEST INSTABILITY AND
RELATIVELY LIGHT WINDS ALOFT WILL RESULT IN SCATTERED SLOW MOVING
STORMS WITH HIGH RAINFALL RATES. THE NEED FOR A FLASH FLOOD WATCH
APPEARS LIKELY FOR SOME AREAS WEST OF THE BLUE RIDGE FOR FRIDAY...
BUT WHICH COUNTIES TO INCLUDE IN A WATCH REMAINS UNCLEAR. WOULD LIKE
TO SEE HOW RAINFALL DEVELOPS THURSDAY AFTERNOON AND EVENING BEFORE
FINALIZING ANY DETAILS OF A POTENTIAL WATCH. IN ANY EVENT...RAINFALL
WILL DIMINISH IN INTENSITY DURING LATE EVENING AS INSTABILITY
DECREASES AND WINDS SHIFT MORE WESTERLY...RESULTING IN MORE OF A
DOWNSLOPE WINDFLOW.

THE SHORTWAVE TROUGH WILL PASS RAPIDLY ACROSS EASTERN CANADA
SATURDAY MORNING...GIVING A SOUTHWARD PUSH TO A STATIONARY FRONT
NEAR THE OHIO RIVER VALLEY. THE FRONT WILL ADVANCE TO AROUND THE
INTERSTATE 81 CORRIDOR BY SATURDAY EVENING...AND INTO THE CAROLINAS
BY SUNDAY EVENING. SIGNIFICANTLY DRIER AIR WILL LAG BEHIND THE COLD
FRONT HOWEVER...AND WILL EXPECT REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS FOR SATURDAY AND SUNDAY AFTERNOON/EVENING...MORE
SPOTTY IN NATURE...WITH COVERAGE CONCENTRATED MORE ACROSS THE
MOUNTAINS...ESPECIALLY IN OUR NORTHWEST FLOW UPSLOPE AREAS. BY LATE
SUNDAY NIGHT...DRIER AIR WILL WORK ITS WAY INTO THE MOUNTAINS...
LOWERING DEWPOINTS INTO THE UPPER 50S AND LOW 60S.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 400 PM EDT WEDNESDAY...

WITH THE UPPER RIDGE CONSOLIDATING AND MOVING TO THE FOUR CORNERS
REGION...TROUGHING WILL DEEPEN AND STRENGTHEN ACROSS THE EAST AND
MIDDLE ATLANTIC. WITH THE COOLER TEMPS AND LESS MOISTURE...SHOWERS
AND STORMS WILL BECOME LESS LIKELY AND SUPPRESSED SOUTH AS THE WEEK
WEARS ON. HOWEVER...CAN'T TOTALLY RULE OUT A FEW POP UP SHOWERS
REGIONWIDE WITH SUCH CHILLY TEMPS ALOFT FOR THIS TIME OF YEAR.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AS OF 1230 PM EDT THURSDAY...

EXPANSIVE CLOUD COVER REMAINS IN PLACE ACROSS THE REGION THIS
AFTERNOON MAKING FOR VFR TO MVFR CIGS AT TIMES. SHOWERS POPPING UP
WILL ALSO AFFECT A FEW SITES INTO EARLY THIS EVENING WITH BEST
CHANCES AT KBLF/KLWB WHERE MORE WIDESPREAD SHRA LOOKS TO ARRIVE
BY MID AFTERNOON. COULD ALSO BE EMBEDDED TO ISOLATED TSRA ESPCLY
EASTERN LOCATIONS WHERE HAVE SEEN A BIT MORE HEATING. HAVE KEPT
PREDOMINANT SHOWERS AT MANY OF THE WESTERN SITES WITH CONFIDENCE
HIGH THAT KBLF/KLWB WILL GET MVFR VSBYS WITH MODERATE SHOWERS AND
ISOLATED THUNDER THROUGH THE AFTERNOON. EVEN KDAN COULD SEE AN
ISOLATED SHRA/TSRA SO ADDED MENTION THERE. BRIEF PERIOD OF IFR
POSSIBLE AS WELL WITHIN THE HEAVIER SHRA ACROSS THE WEST WHERE
MORE WIDESPREAD LOWER CIGS ARE LIKELY.

THE SHOWERS WILL BE LINGERING INTO THIS EVENING AS ANOTHER WAVE
MOVES INTO THE MOUNTAINS LATER TONIGHT. WILL BE ENOUGH CLOUD COVER
FOR MVFR TO POTENTIAL IFR CIGS AT ALL SITES TONIGHT WITH POTENTIAL
FOG IF LOWER CLOUDS CLEAR OUT SOME OR WHERE EARLIER HEAVIER RAINFALL
OCCURRED. HAVE INCLUDED A VCSH MENTION IN SPOTS ACROSS THE WEST
WHEN APPEARS AT LEAST SCATTERED NATURE SHRA MAY PERSIST ALTHOUGH
LOW CONFIDENCE AT THIS POINT.

FRONT REMAINS JUST TO THE NORTHWEST ON FRIDAY WITH PERHAPS A PRE-
FRONTAL BAND OF LIFT HELPING TO ENHANCE AFTERNOON/EVENING
CONVECTION. LOOKS TO BE MORE HEATING THAN SEEN THU SO EXPECTING
TSRA MAY ORGANIZE MORE ESPCLY WEST/NW...THEN SPILLING SE ACROSS
MANY OF THE SITES DURING THE AFTERNOON. COULD BE SOME EARLY
MOUNTAIN SHRA AS WELL BEFORE HEATING KICKS IN WITH A GRADUAL
IMPROVEMENT TO VFR BY MID/LATE MORNING AS FOG/STRATUS SLOWLY
DISSIPATES.

FRIDAY NIGHT-MONDAY A FRONTAL BOUNDARY WILL BE IN THE VICINITY TO
SEE MORE COVERAGE OF SHOWERS/STORMS AREA WIDE. THIS WILL KEEP
TERMINALS DEALING WITH DELAYS DUE TO STORMS...BUT OVER HALF THE
TIME...IT SHOULD BE VFR. DRIER AIR PUSHES INTO NORTH ON MONDAY
WITH SCATTERED CONVECTION STILL POSSIBLE ESPECIALLY IN THE SOUTH.
ANOTHER COLD FRONT DROPPING IN FROM THE NW MAY CAUSE ADDED
SHRA/TSRA TUESDAY WITH SUB-VFR CONDITIONS POSSIBLE AT TIMES.

&&

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

&&

SYNOPSIS...JH/WP
NEAR TERM...JH/WP
SHORT TERM...NF
LONG TERM...KM
AVIATION...DS/JH/WP

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE BLACKSBURG VA
413 AM EDT THU AUG 8 2013

VAZ007-010-011-018>020-WVZ042>045-090815-
TAZEWELL-BLAND-GILES-CRAIG-ALLEGHANY VA-BATH-MERCER-SUMMERS-MONROE-
GREENBRIER-
413 AM EDT THU AUG 8 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWEST VIRGINIA...WEST
CENTRAL VIRGINIA AND SOUTHEAST WEST VIRGINIA.

.DAY ONE...TODAY AND TONIGHT.

HEAVY RAIN WILL BE A THREAT THIS AFTERNOON THROUGH THIS EVENING AND
COULD BRING SOME LOCALIZED FLASH FLOODING. AN ISOLATED SEVERE
THUNDERSTORM WITH DAMAGING WINDS WILL BE POSSIBLE AS WELL.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

SHOWERS AND THUNDERSTORMS WILL BECOME MORE WIDESPREAD FRIDAY INTO
SATURDAY. ALTHOUGH A FEW STORMS COULD BECOME SEVERE...HEAVY RAIN
AND FLASH FLOODING ARE THE BIGGEST THREAT...AND A FLASH FLOOD
WATCH MAY BECOME NECESSARY AT SOME POINT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

NCZ001>006-018>020-VAZ009-012>017-022>024-032>035-043>047-058-059-
090815-
ASHE-ALLEGHANY NC-SURRY-STOKES-ROCKINGHAM-CASWELL-WATAUGA-WILKES-
YADKIN-SMYTH-WYTHE-PULASKI-MONTGOMERY-GRAYSON-CARROLL-FLOYD-ROANOKE-
BOTETOURT-ROCKBRIDGE-PATRICK-FRANKLIN-BEDFORD-AMHERST-HENRY-
PITTSYLVANIA-CAMPBELL-APPOMATTOX-BUCKINGHAM-HALIFAX-CHARLOTTE-
413 AM EDT THU AUG 8 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL NORTH
CAROLINA...NORTHWEST NORTH CAROLINA...CENTRAL VIRGINIA...SOUTH
CENTRAL VIRGINIA...SOUTHWEST VIRGINIA AND WEST CENTRAL VIRGINIA.

.DAY ONE...TODAY AND TONIGHT.

LOCALLY HEAVY RAIN WITH THUNDERSTORMS IS EXPECTED TODAY WHICH
COULD BRING SOME ISOLATED FLASH FLOODING. A STRONG TO SEVERE
THUNDERSTORM WITH DAMAGING WINDS IS POSSIBLE AS WELL.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

SHOWERS AND THUNDERSTORMS WILL BECOME MORE WIDESPREAD FRIDAY INTO
SATURDAY. ALTHOUGH A FEW STORMS COULD BECOME SEVERE...HEAVY RAIN
AND FLASH FLOODING ARE THE BIGGEST THREAT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.