Severe Thunderstorm Warning 188, NWS Blacksburg, VA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
338 PM EDT THU SEP 12 2013

.SYNOPSIS...
A COLD FRONT AN ITS ASSOCIATED SHOWERS AND STORMS WILL MOVE
THROUGH THE AREA TONIGHT. DRIER AND COOLER HIGH PRESSURE WILL
BUILD INTO THE AREA FOR THE WEEKEND. THE HIGH SHIFTS EAST TO ALONG
THE COAST EARLY NEXT WEEK AND OPENS THE DOOR FOR MOISTURE AND
MILDER CONDITIONS TO RETURN TO THE AREA BY THE MIDDLE OF THE WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 250 PM EDT THURSDAY...

A COLD FRONT EXTENDED SOUTHWEST FROM SOUTHWESTERN PA INTO CENTRAL
KENTUCKY. A TROUGH OF LOW PRESSURE HAS TAKEN UP RESIDENCY ALONG THE
LEE OF THE BLUE RIDGE IN VIRGINIA AND NORTH CAROLINA. DAYTIME
HEATING IN AN UNSTABLE ATMOSPHERE HAS ALLOWED FOR THE DEVELOPMENT OF
POPCORN SHOWERS AND A FEW STORMS OVER THE REGION...WITH THE GREATEST
CONCENTRATION NEAR THE LEE TROUGH. AS THE AFTERNOON CONTINUES INTO
THE EARLY EVENING...THE FOCUS FOR THE BEST COVERAGE WILL CONTINUE TO
BE ALONG THE LEE TROUGH. HOWEVER...WITH THE APPROACH OF THE COLD
FRONT...COVERAGE IS EXPECTED TO INCREASE ACROSS SOUTHEAST WEST
VIRGINIA. THIS ACTIVITY WILL MOVE SOUTHEASTWARD INTO THE CENTRAL
PARTS OF FORECAST AREA. HOWEVER...WITH THE LOSS OF DAYTIME
HEATING...COVERAGE IS EXPECTED TO BEGIN TO WANE AS THE FRONT
CONTINUES ITS PROGRESSION THROUGH AND THEN FINALLY SOUTH OF THE AREA
AROUND MIDNIGHT.

A REINFORCING SHOT OF ENERGY AND SECONDARY COLD FRONT BEHIND THE
FIRST COLD FRONT WILL MOVE INTO THE AREA LATE TONIGHT INTO FRIDAY.
BEHIND THIS FEATURE IS WHERE WE WILL SEE A NOTABLE CHANGE IN AIRMASS
WITH MUCH DRIER AIR ARRIVING FOR FRIDAY. A PROLONGED PERIOD OF
UPSLOPE CLOUD COVER ACROSS SOUTHEAST WEST VIRGINIA AND NEIGHBORING
SECTIONS OF SOUTHWEST VIRGINIA AND THE NORTHERN MOUNTAINS OF NORTH
CAROLINA IS EXPECTED THROUGH THE DAY FRIDAY...ALONG WITH SOME
ISOLATED SHOWERS. LOCATIONS EAST OF THE CREST OF THE BLUE RIDGE WILL
EXPERIENCE DOWNSLOPE SUBSIDENCE ON FRIDAY WITH LITTLE CLOUD COVER.
DURING THE DAY TOMORROW WE CAN EXPECT A FEATURE WE HAVE NOT HAD
FOR A WHILE...THAT BEING GUSTY WINDS. GUSTS IN THE MOUNTAINS WILL
BE AROUND 15 TO 25 MPH WITH 10 TO 15 MPH COMMON EAST OF THE BLUE
RIDGE.

TEMPERATURES TONIGHT WILL NOT BE A WHOLE LOT COOLER COMPARED TO
THOSE EXPERIENCE THIS MORNING GIVEN THE REINFORCING COLD FRONT WILL
STILL BE NORTH OF THE AREA. ON FRIDAY...THE IMPACT OF THE DRIER AIR
AND THE APPROACHING HIGH PRESSURE WILL BE REALIZED BY HIGH
TEMPERATURES SOME 10 TO 13 DEGREES LOWS THAN THOSE EXPECTED OF
TODAY.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
AS OF 335 PM EDT THURSDAY...

A GENERALLY QUIET WEATHER PERIOD EXPECTED THROUGH THIS TIME FRAME AS
AXIS OF DEEP MID-ATLANTIC/NE U.S. TROUGH SHIFTS ACROSS THE AREA AND
OFF THE EAST COAST BY THE END OF THE PERIOD. ANY REMAINING UPSLOPE
CLOUDS/-SHRA ACROSS THE SE WV MOUNTAINS SHOULD DISSIPATE FAIRLY
QUICKLY AFTER SUNSET FRIDAY EVENING. EXPECT MOSTLY CLEAR SKIES AND
BELOW NORMAL TEMPERATURES SAT AS AN AREA OF NEAR 0C 850MB TEMPS
SWINGS THROUGH THE AREA. SHOULD SEE LOWS NEAR 40 IN THE HIGHER
ELEVATIONS OF NW GREENBRIER/NORTHERN BATH. EXPECT WIND TO BE TOO
STRONG FOR ANY SIGNIFICANT RADIATIONAL COOLING EFFECT AT THIS POINT.
MAX TEMPS WILL LIKELY NOT GET OUT OF THE 50S IN THE HIGHER
ELEVATIONS ACROSS THE NORTHERN PART OF THE CWA SAT AFTERNOON...WITH
60S SW VA/NW NC MOUNTAINS...AND 70S PIEDMONT. AFTER ANOTHER VERY
CHILLY MORNING SUNDAY...MORE NOTICEABLE IN DEEPER VALLEYS WHERE
RADIATIONAL COOLING IS EXPECTED TO BE MORE EFFECTIVE...EXPECT A SLOW
REBOUND IN TEMPERATURES BY AFTERNOON. BY LATE SUN...THE MODELS SHOW
A SECONDARY SURGE OF COOL AIR APPROACHING FROM THE NW...ALBEIT NOT
AS IMPRESSIVE AS THE FIRST WITH THE 0C LINE REMAINING N OF THE PA/WV
BORDER WITH THIS SURGE. FEEL SFC MOISTURE WILL BE QUITE LIMITED FOR
ANY PRECIPITATION WITH THIS FRONT EXCEPT POSSIBLY SE WV/FAR SW VA
WHERE OROGRAPHIC LIFTING COULD COMBINE WITH SYNOPTIC SCALE FORCING TO
SUPPORT A FEW -SHRA. THE GFS IS MUCH MORE BULLISH ABOUT GENERATING
QPF ACROSS THE ABOVE MENTIONED AREAS THAN THE ECMWF...WHICH
GENERALLY KEEPS THE AREA DRY. AT ANY RATE...CLOUDS WILL CERTAINLY BE
ON THE INCREASE ACROSS SE WV/SW VA AS THIS SYSTEM SWINGS THROUGH THE
REGION SUN NIGHT.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 335 PM EDT THURSDAY...

THE LONG TERM PERIODS BECOME CONSIDERABLY MORE UNSETTLED AND ALSO
QUESTIONABLE WITH RESPECT TO THE CHANCES FOR SHRA/TSRA ON A DAILY
BASIS. THE SECONDARY FRONT THAT MOVES THROUGH THE AREA LATE SUN
NIGHT...STALLS JUST TO OUR SOUTH MON...THEN BEGINS TO RETURN NORTH
AS A WARM FRONT TUE AS THE UPPER FLOW RETURNS TO A MORE SUMMERLIKE
PATTERN...WITH A BROAD UPPER RIDGE DEVELOPING SOUTH OF 40 DEG LAT. A
SERIES OF WEAK SHORT WAVES TRAVELING THROUGH THE NORTHERN STREAM
IMPINGE ON THE NORTHERN EXTENT OF THE UPPER RIDGE AND WILL RESULT IN
AN INCREASING THREAT FOR SHRA AND TSRA AS THE WEEK PROGRESSES.
MEANWHILE...THE WEEKEND CANADIAN SFC HIGH DRIFTS TO JUST OFF THE MID-
ATLANTIC COAST...INTO A FAVORABLE WEDGE POSITION. CLOUD COVER AND
HUMIDITY LEVELS WILL PROGRESSIVELY BE ON THE INCREASE THROUGH THE
WEEK. AT THIS POINT...AT LEAST THROUGH WED...THE BEST CHC FOR TSRA
SHOULD REMAIN WEST OF I-77 WHERE THE BEST INSTABILITY SHOULD BE
LOCATED  AGAIN...THE GFS CONTINUES TO ADVERTISE MUCH MORE PCPN WITH
THIS PATTERN FROM DAY-TO-DAY THAN DOES THE ECMWF...SO HAVE KEPT POPS
IN THE SLIGHT CHC TO LOW CHC CATEGORY AT THIS POINT UNTIL WE GET A
BETTER HANDLE ON THE PATTERN AND TIMING...ALTHOUGH THE GFS WOULD
HAVE LIKELY TO CATEGORICAL POPS WED-THU. BY THU/FRI...THE ECMWF ALSO
BEGINS TO SUPPORT BETTER CHC POPS. TEMPERATURES SHOULD CREEP BACK TO
NEAR NORMAL LEVELS AND EVEN SLIGHTLY ABOVE BY MID-WEEK AS THE SUMMER
PATTERN RETURNS ONCE AGAIN AND 500MB HEIGHTS RISE BACK INTO THE
585DM RANGE WITH 850MB TEMPS BACK TO NEAR +14C.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
AS OF 135 PM EDT THURSDAY...

POPCORN SHOWERS ARE DEVELOPING ACROSS THE AREA CURRENTLY. AS THE
AFTERNOON CONTINUES...THERE SHOULD BE INCREASED COVERAGE WITH THE
CONVERGENCE OF TROUGH ON THE LEE SIDE OF THE APPALACHIANS...AND
ALSO ACROSS THE WESTERN HALF OF THE REGION IN ADVANCE OF AN
APPROACHING COLD FRONT AND WITHIN THE OROGRAPHICAL AND
DIFFERENTIAL HEATING REGIONS OF THE MOUNTAINS. MOST AREA WILL
EXPERIENCE PREVAILING VFR CONDITIONS. THE EXCEPTION WILL BE IN
THE KBLF REGION WITH A PERSISTENT MVFR CIG CONTINUES. LOCALIZED
AND BRIEF SUB-VFR CONDITIONS AND VARIABLE AND GUSTY WINDS ARE
EXPECTED UNDER ANY HEAVIER SHOWER OR STORM. COVERAGE WILL BE
MAXIMIZED EARLY THIS EVENING WITH THE ARRIVAL OF THE COLD FRONT.
THERE WILL ALSO BE A GREATER POTENTIAL FOR INCREASED COVERAGE OF
STORMS. PATCHY FOG IS AGAIN EXPECTED TONIGHT AS THE TRUE PUSH OF
DRIER AIR DOES NOT ARRIVE ACROSS THE AREA UNTIL LATE IN THE DAY
FRIDAY.

THE FRONT WILL BE SOUTH OF THE AREA BY 12Z/8AM FRIDAY WITH A
PREVAILING NORTHWEST FLOW BEHIND IT. RESIDUAL LOW LEVEL MOISTURE
WILL TAKE THE FORM OF MVFR-VFR STARTO-CU ACROSS THE SE WV
MOUNTAINS ALONG WITH ISOLATED SHOWERS. DOWNSTREAM OF THE CREST OF
THE BLUE RIDGE THE NORTHWEST FLOW SHOULD HELP ERODE ANY LINGERING
CLOUD COVER FROM THE OVERNIGHT HOURS.

HIGH PRESSURE BUILDS IN BEHIND THE COLD FRONT FOR THE WEEKEND.
SOME CONCERN THAT LOW LEVEL NORTHEAST LOW LEVEL WIND ORIENTATION MAY
BRING A COLD AIR DAMMING AND ASSOCIATED CLOUDS INTO THE REGION.
CONFIDENCE IN THIS SCENARIO IS LOW AT THIS TIME.

SURFACE HIGH SHIFTS TO OFF THE COAST BY SUNDAY/MONDAY. THIS WILL
BRING A RETURN OF SOUTHWEST FLOW TO THE AREA WITH INCREASING
MOISTURE AND MODERATING TEMPERATURES.

&&

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

&&

SYNOPSIS...DS
NEAR TERM...DS
SHORT TERM...RAB
LONG TERM...RAB
AVIATION...DS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BLACKSBURG VA
323 PM EDT THU SEP 12 2013

NCZ001>006-018>020-VAZ015>017-032>035-043>047-058-059-131930-
ASHE-ALLEGHANY NC-SURRY-STOKES-ROCKINGHAM-CASWELL-WATAUGA-WILKES-
YADKIN-GRAYSON-CARROLL-FLOYD-PATRICK-FRANKLIN-BEDFORD-AMHERST-HENRY-
PITTSYLVANIA-CAMPBELL-APPOMATTOX-BUCKINGHAM-HALIFAX-CHARLOTTE-
323 PM EDT THU SEP 12 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...THIS AFTERNOON AND TONIGHT.

ISOLATED TO SCATTERED SHOWERS AND STORMS ARE EXPECTED THROUGH THE
EVENING HOURS. WHILE MOST OF THESE WILL NOT BE SEVERE...ONE OR TWO
MAY STRENGTHEN ENOUGH TO PRODUCE SOME STRONG OR DAMAGING WINDS.
THESE STORMS ALSO MAY CONTAIN FREQUENT LIGHTNING AND LOCALLY HEAVY
RAIN.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

VAZ007-009>014-018>020-022>024-WVZ042>045-131930-
TAZEWELL-SMYTH-BLAND-GILES-WYTHE-PULASKI-MONTGOMERY-CRAIG-
ALLEGHANY VA-BATH-ROANOKE-BOTETOURT-ROCKBRIDGE-MERCER-SUMMERS-MONROE-
GREENBRIER-
323 PM EDT THU SEP 12 2013

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

ISOLATED TO SCATTERED SHOWERS AND STORMS ARE EXPECTED HEADING
INTO THE EVENING HOURS...WITH GREATER COVERAGE THIS EVENING AS A
COLD FRONT ENTERS THE REGION. WHILE MOST OF THE STORMS WILL NOT BE
SEVERE...A FEW OF THESE MAY STRENGTHEN ENOUGH TO PRODUCE SOME
STRONG OR DAMAGING WINDS. THESE STORMS ALSO MAY CONTAIN FREQUENT
LIGHTNING AND LOCALLY HEAVY RAIN.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
505 PM EDT THU SEP 12 2013

WVZ043-045-122200-
SUMMERS WV-GREENBRIER WV-
505 PM EDT THU SEP 12 2013

THE NATIONAL WEATHER SERVICE IN BLACKSBURG HAS ISSUED A

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

* UNTIL 600 PM EDT

* AT 500 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
  A LINE OF SHOWERS WITH EMBEDDED THUNDERSTORMS BETWEEN BECKLEY AND
  SUMMERSVILLE...MOVING EAST AT 30 MILES AN HOUR.

* PEA SIZE HAIL AND WIND GUSTS UP TO 30 MPH ARE EXPECTED WITH
  THIS LINE OF THUNDERSTORMS.

* LOCATIONS THAT MAY BE IMPACTED INCLUDE...
  QUINWOOD..
  RUPERT...
  LEWISBURG...
  SANDSTONE...
  HINTON...
  AND PIPESTEM.

LAT...LON 3823 8036 3811 8036 3805 8027 3806 7996
      3769 8030 3773 8066 3743 8086 3759 8109
      3771 8097 3768 8088 3782 8094 3787 8075
      3795 8081 3798 8077 3806 8080 3805 8086
      3810 8088 3810 8084 3808 8071 3827 8044
TIME...MOT...LOC 2059Z 279DEG 35KT 3801 8079

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
519 PM EDT THU SEP 12 2013

VAZ047-122215-
BUCKINGHAM VA-
519 PM EDT THU SEP 12 2013

THE NATIONAL WEATHER SERVICE IN BLACKSBURG HAS ISSUED A

* SPECIAL WEATHER STATEMENT FOR...
  NORTHEASTERN BUCKINGHAM COUNTY IN CENTRAL VIRGINIA...

* UNTIL 615 PM EDT

* AT 518 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
  A STRONG THUNDERSTORM NEAR CENTENARY...MOVING TO THE SOUTHEAST AT
  20 MPH.

* WIND GUSTS UP TO 30 MPH ARE EXPECTED WITH THIS STORM.

* LOCATIONS IMPACTED INCLUDE...
  CENTENARY...
  GOLD HILL...
  AND NEW CANTON.

LAT...LON 3764 7825 3757 7830 3758 7831 3769 7858
      3776 7855 3776 7850 3780 7849 3776 7847
      3773 7837 3772 7835 3769 7824
TIME...MOT...LOC 2116Z 292DEG 17KT 3775 7848

11

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
523 PM EDT THU SEP 12 2013

NCZ004-VAZ032-122200-
STOKES NC-PATRICK VA-
523 PM EDT THU SEP 12 2013

THE NATIONAL WEATHER SERVICE IN BLACKSBURG HAS ISSUED A

* SPECIAL WEATHER STATEMENT FOR...
  NORTHERN STOKES COUNTY IN NORTH CENTRAL NORTH CAROLINA...
  SOUTHERN PATRICK COUNTY IN SOUTHWEST VIRGINIA...

* UNTIL 600 PM EDT

* AT 520 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
  THE DEVELOPMENT OF SOME STRONG THUNDERSTORMS NEAR STUART VIRGINIA
  AND NEAR LAWSONVILLE NORTH CAROLINA.  THESE STORMS WILL CONTINUE
  TO STRENGTHEN AND BEGIN MOVING TO THE SOUTHEAST AT 20 MPH.

* PEA SIZE HAIL AND WIND GUSTS UP TO 30 MPH ARE POSSIBLE WITH THESE
  STORMS. A SEVERE THUNDERSTORM WARNING MAY BE NEEDED IF THEY
  CONTINUE TO STRENGTHEN.

* LOCATIONS IMPACTED INCLUDE...
  FRANCISCO...
  STUART...
  SANDY RIDGE...
  AYERSVILLE...
  AND PENNS STORE.

LAT...LON 3653 8045 3670 8037 3662 8005 3654 8005
      3654 8003 3636 8004
TIME...MOT...LOC 2116Z 291DEG 17KT 3659 8033

11

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