Severe Thunderstorm Warning 126, NWS Blacksburg, VA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
311 PM EDT WED JUL 17 2013

.SYNOPSIS...
STRONG UPPER LEVEL HIGH PRESSURE JUST WEST OF THE APPALACHIANS
WILL CONTINUE TO DRIFT WEST AND WEAKEN THROUGH THE END OF THE WEEK.
WEAK UPPER LEVEL DISTURBANCES WILL ROTATE SOUTH INTO THE AREA
THROUGH THURSDAY RESULTING IN WIDELY SCATTERED SHOWERS AND STORMS
AT TIMES. A COLD FRONT WILL SINK INTO THE OHIO VALLEY NEAR THE END
OF THE WEEK BEFORE SLIDING SOUTH ACROSS THE REGION LATER THIS
WEEKEND INTO EARLY NEXT WEEK.
&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 240 PM EDT WEDNESDAY...

WIDELY SCATTERED CONVECTION CONTINUES TO DEVELOP ACROSS THE NORTH
THIS AFTERNOON WHERE HIGHER INSTABILITY RESIDES WITH MORE
MULTICELL CLUSTERS ALONG THE SRN BLUE RIDGE PER LIGHT EASTERLY
FLOW INTO AN AXIS OF VERY HIGH SURFACE THETA-E. HOWEVER FORCING
ALOFT REMAINS RATHER WEAK WITH PULSE NATURE DEEPER STORMS DRIVEN
BY STEEP LAPSES AND AIDED BY OUTFLOW FROM EARLIER SHRA TO THE
NORTH. LATEST NAM SEEMS TO HAVE A BETTER HANDLE ON THE ONGOING
SCENARIO ATTM WITH MORE CONVECTION EARLY ON BEFORE ACTUALLY
DECREASING THIS EVENING AS THE CORE OF THE UPPER VORT SHIFTS OFF
TO THE SW. THUS RUNNING WITH THE HIGHER SCATTERED POPS OVER THE
WEST/SW INTO EARLY THIS EVENING...THEN QUICKLY CUTTING BY MIDNIGHT
AS ACTION SHOULD BE ISOLATED BY THEN IF NOT SOONER. OTRW EXPECTING
MORE CLEARING AFTER MIDNIGHT WITH FOG FILLING IN ACROSS THE
VALLEYS AND WHERE HEAVY RAIN OCCURRED FROM EARLIER IN THE DAY.
LOWS AGAIN ON THE WARM/MUGGY SIDE BUT MAINLY 65-70 WEST AND LOW
70S EAST.

UPPER SUPPORT EVEN MORE LACKING ON THU WITH PART OF THE 5H RIDGE
OVERHEAD AND THE RESIDUAL TROF AXIS FARTHER TO THE SW. FLOW AT ALL
LEVELS VERY WEAK WHILE FOCUS FOR CONVECTION LOOKS TIED TO OLD
OUTFLOW AND PERHAPS OROGRAPHIC DIFF HEATING. HOWEVER THE LOW LEVEL
FLOW STARTS TO TURN A LITTLE MORE SE ACROSS THE FAR WEST LATER IN
THE AFTERNOON WHICH SHOULD ACT TO INCREASE COVERAGE THERE A BIT
MORE. IN ADDITION...ANY SUBTLE FEATURE THAT MODELS FAIL TO PICK UP
COULD BE ENOUGH TO SPARK ISOLATED COVERAGE SO BASICALLY RUNNING
WITH A SHOTGUN TYPE PATTERN FOR SCTD POPS THU WITH HIGHER CHANCES
WESTERN THIRD AND LEAST EAST WHERE A LITTLE DRIER ALOFT. HIGH
TEMPS SHOULD BE SIMILAR TO WED GIVEN ONLY A SLIGHT DECREASE IN
THICKNESS SO LOW/MID 90S LIKELY AGAIN EAST WITH 80S WEST.
&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 300 PM EDT WEDNESDAY...

500 MB HEIGHTS FALL SLIGHTLY AS UPPER TROF BECOMES ESTABLISHED OVER
THE NORTHEAST UNITED STATES. WILL HAVE ANY ONGOING STORMS FROM
THURSDAY CONTINUE WELL INTO THURSDAY EVENING.

NO ORGANIZED TRIGGERS FOR SHOWERS AND THUNDERSTORMS ON FRIDAY. WILL
HAVE CHANCE PROBABILITIES IN AFTER NOON. BY SATURDAY...FORECAST AREA
GETS INTO RIGHT REAR QUADRANT OF UPPER JET AND THIS LIFT WILL HELP
BROADEN THE AREAL COVERAGE OF PRECIPITATION SATURDAY.

FORECAST AREA IS STILL AHEAD OF THE COLD FRONT THROUGH SATURDAY.
LITTLE CHANGE IN AIR MASS. GUIDANCE LOOKED REASONABLE FOR HIGHS AND
LOWS THROUGH THE PERIOD.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 1140 AM EDT WEDNESDAY...

BY THIS TIME UPPER RIDGE IS GONE AND TROFFING HAS DEVELOPED OVER THE
NORTHEAST UNITED STATES. LONG WAVE TROF REMAINS OVER THE EAST
THROUGH TUESDAY. GFS CONTINUES TO SHOW A MORE AMPLIFIED UPPER RIDGE
IN THE WEST AND MOVES THE SURFACE FRONT FURTHER SOUTH IN THE
EAST...WHILE THE ECMWF IS LESS AMPLIFIED WITH THE UPPER PATTERN AND
NOT AS FAR SOUTH WITH THE SURFACE FRONT. TAKING A BLEND OF THESE TWO
SOLUTIONS AS RECOMMENDED BY WPC...THE SURFACE FRONT STALLS ACROSS
THE CAROLINAS AND TENNESSEE VALLEY SUNDAY THROUGH TUESDAY. DUE TO
THE CHANCE OF SHOWERS AND THUNDERSTORMS BEING IN THE FORECAST FOR A
NUMBER OF DAYS...WILL HIGHLIGHT THREAT OF HEAVY RAIN IN THE
HAZARDOUS WEATHER OUTLOOK.

WHILE 850 MB TEMPERATURES DO NOT CHANGE MUCH...THE CLOUDS AND CHANCE
OF PRECIPITATION WILL LEAD TO NEAR NORMAL TO SLIGHTLY BELOW
TEMPERATURES.
&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
AS OF 1240 PM EDT WEDNESDAY...

CONVECTION STARTING TO FORM IN SPOTS ALONG THE BLUE RIDGE ATTM
WITH OVERALL MOVEMENT OFF TO THE SW TOWARD THE INTERIOR TAF
LOCATIONS FROM KLYH TO KROA. EXPECT A CONTINUED INCREASE IN
COVERAGE THROUGH MID/LATE AFTERNOON WITH LOCATIONS ACROSS THE NW
AND SW SEEING MORE WIDESPREAD MULTICLUSTERED CELLS. HOWEVER LOW
CONFIDENCE GIVEN SCATTERED NATURE TO WHETHER OR NOT ANY OF THE
TSRA WILL DIRECTLY IMPACT ANY OF THE TAF SITES SO STAYING WITH
MAINLY VCTS WITH PERHAPS KDAN HAVING THE LEAST CHANCE OF SEEING A
STORM. ANY STORMS WILL BRING SOME LIMITED VSBYS...GUSTY WINDS AND
LOWER CIGS WITH A PERIOD OF MVFR OR IFR POSSIBLE.

CONVECTION ENDS FOR MOST AFTER SUNSET...WITH LINGERING POTENTIAL
OVER KBLF AND POINTS SOUTH TIL SHORTLY AFTER MIDNIGHT...BUT
COVERAGE WILL BE ISOLATED/WIDELY SCATTERED BY THEN GIVEN LOSS OF
HEATING.

CYCLE OF FOG FORMATION CONTINUES OVERNIGHT INTO THU MORNING AT
THE USUAL LOCATIONS AND IN AREAS THAT RECEIVE RAIN THIS
AFTERNOON/EVENING.

SUPPORT A BIT LESS FOR TSRA ON THURSDAY ALTHOUGH COULD SEE AN
ISOLATED STORM POP UP ACROSS THE MOUNTAINS ABOUT ANYWHERE DURING
THE AFTERNOON. APPEARS BEST LOCATIONS TO SEE CONVECTION WILL BE
MAINLY KBLF/KLWB BUT BEYOND THE END OF THE VALID TAF PERIOD LATER
THU SO LEAVING OUT MENTION FOR NOW.

FOR FRIDAY AND BEYOND...PROGRESSIVELY MORE COVERAGE OF STORMS
BY THE WEEKEND AS THE UPPER RIDGE FLATTENS AND A TROUGH STARTS TO
BUILD SOUTH INTO THE GREAT LAKES. A BOUNDARY WILL BE SINKING SOUTH
INTO THE OHIO VALLEY THIS WEEKEND. SOME MVFR/IFR VSBYS/CIGS CAN
BE EXPECTED IN SHRA/TSRA ACROSS THE MOUNTAINS SATURDAY...AND AT
TIMES ACROSS MUCH OF THE REGION SUNDAY. FRONT SHOULD STALL OUT
NEAR THE REGION EARLY NEXT WEEK WITH A CONTINUED SCATTERING OF
MAINLY DIURNALLY DRIVEN SHRA/TSRA INTO AT LEAST MONDAY.

&&

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

&&

SYNOPSIS...JH/WP
NEAR TERM...JH
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...JH/KK/WP

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE BLACKSBURG VA
331 PM EDT WED JUL 17 2013

NCZ001>005-018>020-VAZ007-009>020-022>024-032>035-043-WVZ042>045-
181945-
ASHE-ALLEGHANY NC-SURRY-STOKES-ROCKINGHAM-WATAUGA-WILKES-YADKIN-
TAZEWELL-SMYTH-BLAND-GILES-WYTHE-PULASKI-MONTGOMERY-GRAYSON-CARROLL-
FLOYD-CRAIG-ALLEGHANY VA-BATH-ROANOKE-BOTETOURT-ROCKBRIDGE-PATRICK-
FRANKLIN-BEDFORD-AMHERST-HENRY-MERCER-SUMMERS-MONROE-GREENBRIER-
331 PM EDT WED JUL 17 2013

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

A FEW THUNDERSTORMS INTO THIS EVENING MAY BE STRONG TO POSSIBLY
SEVERE. THE MAIN SEVERE THREATS WILL BE DAMAGING WIND
GUSTS...HAIL UP TO THE SIZE OF QUARTERS...AND LOCALIZED FLOODING.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH WEDNESDAY.

THUNDERSTORMS WILL BECOME MORE NUMEROUS OVER THE WEEKEND WITH THE
CONTINUED THREAT FOR ISOLATED SEVERE STORMS ALONG WITH FLOODING
FROM VERY HEAVY RAINFALL INTO EARLY NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

NCZ006-VAZ044>047-058-059-181945-
CASWELL-PITTSYLVANIA-CAMPBELL-APPOMATTOX-BUCKINGHAM-HALIFAX-
CHARLOTTE-
331 PM EDT WED JUL 17 2013

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

AN ISOLATED SEVERE THUNDERSTORM WILL CONTINUE INTO THIS EVENING
WITH THE MAIN THREAT BEING DAMAGING WIND GUSTS AND HAIL UP TO THE
SIZE OF QUARTERS.

ALSO...HEAT INDICES OF AROUND 100 DEGREES WILL PERSIST UNTIL LATE
THIS AFTERNOON.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

HIGH TEMPERATURES IN THE LOWER TO MID 90S COMBINED WITH HIGH
HUMIDITY WILL AGAIN RESULT IN HEAT INDICES OF AROUND 100 DEGREES
THURSDAY AFTERNOON.

THUNDERSTORMS WILL BECOME MORE NUMEROUS OVER THE WEEKEND WITH THE
THREAT FOR SEVERE STORMS AND HEAVY RAIN INTO EARLY NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
516 PM EDT WED JUL 17 2013

WVZ043-045-172215-
SUMMERS WV-GREENBRIER WV-
516 PM EDT WED JUL 17 2013

THE NATIONAL WEATHER SERVICE IN BLACKSBURG HAS ISSUED A

* SPECIAL WEATHER STATEMENT FOR...
  SUMMERS COUNTY IN SOUTHEAST WEST VIRGINIA...
  SOUTHWESTERN GREENBRIER COUNTY IN SOUTHEAST WEST VIRGINIA...

* UNTIL 615 PM EDT

* AT 512 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
  A STRONG THUNDERSTORM NEAR MEADOW BLUFF...MOVING TO THE SOUTHWEST
  AT 25 MPH.

* PEA SIZE HAIL AND WIND GUSTS UP TO 35 MPH ARE EXPECTED WITH THIS
  STORM. VERY HEAVY RAIN IS FALLING...AND WILL CAUSE WATER TO POND
  ON ROADWAYS AND QUICKLY FILL ROADSIDE DITCHES AND SMALL STREAMS.

* LOCATIONS IMPACTED INCLUDE...
  HINTON...
  ALDERSON...
  SANDSTONE...
  HIX...
  AND JUMPING BRANCH.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

PROLONGED HEAVY RAINFALL MAY CAUSE WATER TO FLOW OVER THE ROADWAY. DO
NOT DRIVE YOUR VEHICLE WHERE THE ROAD HAS BECOME FLOODED.

&&

LAT...LON 3783 8043 3772 8064 3773 8066 3770 8067
      3755 8096 3766 8103 3771 8097 3770 8092
      3768 8090 3768 8088 3774 8092 3778 8090
      3782 8094 3787 8081 3787 8076 3791 8078
      3799 8054
TIME...MOT...LOC 2112Z 61DEG 20KT 3788 8057

KK