Severe Thunderstorm Warning 148, NWS Blacksburg, VA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
233 PM EDT SUN JUL 21 2013

.SYNOPSIS...
A WEAK COLD FRONT WILL DRIFT SOUTHEAST TOWARD THE AREA
TODAY...BEFORE STALLING OVER OR JUST NORTH OF THE REGION TONIGHT
INTO MONDAY. THE PROXIMITY OF THIS FRONT WILL INCREASE THE THREAT
FOR SHOWERS AND THUNDERSTORMS INTO EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1015 AM EDT SUNDAY...

LATEST ROUND OF SURFACE OBSERVATIONS AND RADAR TRENDS INDICATES
THAT A WEAK COLD FRONT REMAINS STALLED NEAR THE OHIO RIVER THIS
MORNING. AN UPPER DISTURBANCE RIDING NEAR THE FRONT IS TRIGGERING
SHOWERS AND A FEW THUNDERSTORMS ACROSS CENTRAL WEST VIRGINIA...
WITH THIS ACTIVITY EXPECTED TO ENTER GREENBRIER AND SUMMERS
COUNTIES SHORTLY AFTER 10 AM. THIS AREA OF CONVECTION IS
SMALL...BUT ALSO SLOW MOVING...AND A FEW LOCATIONS IN THESE
COUNTIES MAY PICK UP A QUICK ONE HALF TO THREE QUARTERS OF AN INCH
OF RAIN.

EXPECT THE COLD FRONT WILL ATTEMPT TO SHIFT SOUTHEAST TOWARD THE
REGION TODAY AS THE DISTURBANCE CONTINUES TO THE EAST. MOISTURE
POOLING AHEAD OF THE APPROACHING FRONT WILL RESULT IN A GREATER
CONCENTRATION OF SHOWER AND THUNDERSTORM ACTIVITY ACROSS PARTS OF
SOUTHEAST WEST VIRGINIA. BELIEVE THE GREATEST THREAT WILL BE IN
THE FORM OF HEAVY RAIN...AND POSSIBLY LOCALIZED FLOODING...BUT
OTHERWISE DO NOT EXPECT MUCH IN THE WAY OF ORGANIZED SEVERE
THUNDERSTORM ACTIVITY. STILL HOLDING OFF ON A FLASH FLOOD WATCH AS
HEAVY RAIN HAS BEEN HIT AND MISS ACROSS THE NORTHWEST THE PAST
COUPLE OF DAYS...AND IS EXPECTED TO REMAIN SO TODAY.

ELSEWHERE...RAINFALL DEVELOPMENT WILL BE MORE LINKED TO DAYTIME
HEATING...WITH SPOTTY SHOWERS AND THUNDERSTORMS DEVELOPING ALONG
THE RIDGES DURING EARLY AFTERNOON...AND SPREADING ACROSS THE
PIEDMONTS BY LATE AFTERNOON OR EARLY EVENING. CLOUD COVER WAS THIN
TO START THE DAY...AND SUNSHINE HAS ALLOWED FOR RAPID WARMING OF
TEMPERATURES THIS MORNING...AND WOULD NOT BE SURPRISED TO SEE A
FEW STORMS PULSE UP QUICKLY LATER TODAY...BECOMING STRONG TO
SEVERE...SOUTH OF THE INTERSTATE 81 CORRIDOR.

COLD FRONT WILL REMAIN NORTH OF THE AREA TONIGHT...AND EXPECT MOST
OF THE SHOWER AND THUNDERSTORM ACTIVITY TO DIMINISH AFTER SUNSET
WITH THE LOSS OF DAYTIME HEATING...ALTHOUGH WILL KEEP HIGHER
CHANCES ACROSS THE MOUNTAINS AS WEAK UPPER DISTURBANCES PASS FROM
THE WEST. CONTINUED FETCH OF TROPICAL MOISTURE WILL KEEP OVERNIGHT
LOWS ON THE MILD SIDE...GENERALLY IN THE MID 60S TO LOW 70S.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 331 AM EDT SUNDAY...

A POSITIVE-TILTED UPPER LEVEL TROUGH WILL ENTER THE OHIO VALLEY ON
MONDAY. THIS SYSTEM PLUS AFTERNOON CONVECTION...WILL HELP PUSH A
WEAK COOL FRONT ACROSS THE REGION MONDAY NIGHT AND TUESDAY. THIS
FRONT MAY WASH OUT BEFORE CROSSING THE BLUE RIDGE OR GET ABSORBED
INTO A SURFACE WAVE LINGERING IN THE NC/VA COASTAL PIEDMONT ON
TUESDAY. DESPITE THE PASSING OF THIS FRONTAL BOUNDARY...THETA-E WILL
REMAIN HIGH KEEPING THE REGION IN A HUMID AIR MASS. MODEL PWATS ARE
FORECASTED TO ALSO REMAIN HIGH AND AROUND 2 STANDARD DEVIATIONS
ABOVE NORMAL (2.00 INCHES). STEERING FLOW WILL BE A LITTLE STRONGER
THAN THE LAST COUPLE OF DAYS...BUT STILL NOT FAST ENOUGH TO LIMIT
FLASH FLOOD THREAT. IF ANY ONE STORM COULD EFFECTIVELY CONVERT THIS
MOISTURE INTO RAINFALL...LOCALIZE FLASH FLOODING WILL BE POSSIBLE.
TRAINING OF CELL WILL LIKELY PRODUCE THE HIGHER FLASH FLOOD THREAT
MONDAY AND TUESDAY. ANTECEDENT CONDITIONS HAVE IMPROVED OVER THE
WEEKEND WITH SPOTTY SHOWERS AND CONSIDERING TIME OF YEAR...FLOODING
MAY JUST BE ISOLATED. WE WILL CONTINUE TO MONITOR THE SITUATION WITH
EACH FORECAST PACKAGE WITH POSSIBLE FLASH FLOOD WATCHES BEING ISSUED
FOR ALL OR PORTION OF THE FORECAST AREA.

HEIGHTS WILL LOWER AS THE UPPER LEVEL TROUGH APPROACHES THE AREA.
WITH LOWER HEIGHTS COMES SLIGHTLY COOLER TEMPERATURES ALOFT AND AN
INCREASE CHANCE FOR HAIL. MELTING HAIL AND WATER LOAD SHEDDING MAY
ALSO LEAD TO WET MICROBURST EACH AFTERNOON AND EVENING. IN THE SHORT
OF IT...SEVERE CHANCES ARE ON THE INCREASE MONDAY AND TUESDAY WITH
PULSE ENVIRONMENT GIVING WAY TO MORE CELLS CONGEALING INTO SLOW
MOVING LINE SEGMENTS. CONVECTION MAY ALSO LINGER DEEP INTO THE NIGHT
AND START EARLIER IN THE MORNING WITH WEAK SHORT WAVES TRACKING OVER
THE REGION EACH PERIOD.

TUESDAY NIGHT INTO WEDNESDAY...WINDS BECOME MORE WESTERLY AS A
STRONGER SHORT WAVE TRACKS NORTHEAST OF THE AREA. THIS WESTERLY FLOW
SHOULD REDUCE THE THREAT OF SHOWERS AND THUNDERSTORMS.
HOWEVER...HUMIDITIES WILL REMAIN HIGH AS A SECONDARY FRONT WITH
DRIER AIR STALLS ACROSS THE SOUTHERN OHIO VALLEY.

WITH BOTH AN INCREASE IN AREAL COVERAGE AND DURATION OF
SHOWERS...AFTERNOON TEMPERATURES WILL LIKELY BE CLOSER TO NORMAL
THROUGH THE FIRST PART OF THIS WEEK. MUGGY CONDITIONS WILL LIKELY
KEEP TEMPERATURES 3F-6F WARMER THAN NORMAL DURING THE OVERNIGHT
PERIOD.

&&

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

UPPER TROF OVER THE EASTERN UNITED STATES DEEPENS WITH TIME. LOOKING
AT ONLY SUBTLE DROPS IN 500 MB HEIGHTS OVER THE FORECAST AREA. 850
MB WINDS BECOME NORTHWEST TUESDAY NIGHT AND WEDNESDAY WITH 850 MB
TEMPERATURES AROUND +16...SLIGHTLY COOLER THAN THIS WEEK. ECMWF
FORECAST RELATIVE HUMIDITIES IN THE 700-300 MB LAYER SHOW DRY AIR
COMING INTO THE REGION NOON THURSDAY. WILL HAVE A LOWER
PROBABILITY OF PRECIPITATION IN THE FORECAST FOR FRIDAY AND
SATURDAY EXPECTING THE FRONT TO BE WELL SOUTH OF THE COUNTY
WARNING AREA IN THAT TIME FRAME.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
AS OF 200 PM EDT SUNDAY...

A WEAK COLD FRONT REMAINS SITUATED NEAR THE OHIO RIVER THIS
AFTERNOON...WHILE SOUTHWESTERLY WINDFLOW SOUTH OF THE BOUNDARY
CONTINUES TO PULL GULF MOISTURE INTO THE AREA. STRONG HEATING
EARLIER THIS MORNING RESULTED IN SCATTERED SHOWERS AND
THUNDERSTORMS FROM ROA WESTWARD...WHERE POCKETS OF HEAVY RAIN HAVE
REDUCED VISIBILITIES TO LESS THAN 1/2SM FOR BRIEF PERIODS OF TIME.
CONVECTION WILL ADVANCE EASTWARD DURING THE AFTERNOON...AFFECTING
LYH AND DAN THROUGH 21/22Z...BEFORE CONVECTION BEGINS TO DIMINISH
WITH THE LOSS OF DAYTIME HEATING AFTER 23Z. SPOTTY SHOWERS AND
ISOLATED THUNDERSTORMS WILL LINGER IN THE VICINITY OF BLF AND LWB
DURING THE NIGHT AS WEAK DISTURBANCES APPROACH FROM THE WEST.

PATCHY FOG WILL BE THE OTHER MAIN CONCERN FOR THE OVERNIGHT
HOURS...ESPECIALLY FOR LWB AND BCB...WHERE NOCTURNAL FOG IN
USUAL. WILL ALSO KEEP AN EYE ON RADAR AND SATELLITE IMAGERY THIS
EVENING AS PATCHY FOG WILL ALSO BE EXPECTED ACROSS AREAS WHERE
HEAVY RAIN FALLS AND CLOUDS SCATTER OVERNIGHT.

COVERAGE OF SHOWER AND THUNDERSTORM ACTIVITY WILL BE MORE
WIDESPREAD ON MONDAY AS A STRONGER UPPER LEVEL DISTURBANCE CROSSES
THE AREA FROM THE WEST. MAIN CONCERNS WITH THIS DISTURBANCE WILL
AGAIN BE HEAVY RAIN...RESULTING IN PERIODIC IFR CONDITIONS AT ALL
AIRPORTS. A FEW SEVERE STORMS WILL ALSO BE POSSIBLE...MORE SO FOR
DAN AND LYH WHERE STRONGER DAYTIME HEATING WILL ADD TO ATMOSPHERIC
INSTABILITY DURING THE AFTERNOON.

MODELS CONTINUE TO DEPICT THE STALLED FRONT HOLDING JUST NORTH OF
THE AREA THROUGH EARLY TUESDAY...BEFORE LIFTING AS A LOW PRESSURE
SYSTEM MOVES ACROSS THE WESTERN GREAT LAKES. REGARDLESS...EXPECT
DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS TO PERSIST THROUGH THE
COMING WORKWEEK AS GULF MOISTURE REMAINS ABUNDANT ACROSS THE AREA.
ANOTHER COLD FRONT WILL APPROACH THE OHIO RIVER TOWARD THE END OF
THE WORKWEEK...BUT DO NOT SEE THE FRONT ADVANCING MUCH FURTHER
SOUTH THAN THAT.

&&

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

&&

SYNOPSIS...JH/WERT
NEAR TERM...JH/NF
SHORT TERM...RCS
LONG TERM...AMS
AVIATION...JH/NF

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BLACKSBURG VA
409 AM EDT SUN JUL 21 2013

VAZ007-010-011-018>020-WVZ042>045-220815-
TAZEWELL-BLAND-GILES-CRAIG-ALLEGHANY VA-BATH-MERCER-SUMMERS-MONROE-
GREENBRIER-
409 AM EDT SUN JUL 21 2013

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

.DAY ONE...TODAY AND TONIGHT.

SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BECOME MORE WIDESPREAD
INTO THIS EVENING. THIS WILL RESULT IN MORE OF A FLASH FLOOD
THREAT TODAY WITH ISOLATED SEVERE WEATHER ALSO POSSIBLE.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

SCATTERED THUNDERSTORMS ARE EXPECTED TO CONTINUE ACROSS THE AREA
NEAR A WEAK COLD FRONT THAT WILL LINGER INTO EARLY NEXT WEEK.
THIS MAY ENHANCE THE THREAT FOR FLASH FLOODING ON MONDAY.

.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-
220815-
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-
409 AM EDT SUN JUL 21 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.

SCATTERED SLOW MOVING SHOWERS AND THUNDERSTORMS ARE EXPECTED TODAY
INTO THIS EVENING. THIS MAY RESULT IN PERIODS OF VERY HEAVY
RAINFALL WHICH MAY BE ENOUGH TO CAUSE LOCALIZED FLASH FLOODING.
ISOLATED SEVERE STORMS ARE ALSO POSSIBLE.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

SCATTERED THUNDERSTORMS ARE EXPECTED TO CONTINUE ACROSS THE AREA
NEAR A WEAK COLD FRONT THAT WILL LINGER INTO EARLY NEXT WEEK.
THIS WILL RESULT IN MORE OF A FLASH FLOODING THREAT ON MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
315 PM EDT SUN JUL 21 2013

VAZ013-014-211945-
MONTGOMERY VA-PULASKI VA-
315 PM EDT SUN JUL 21 2013

THE NATIONAL WEATHER SERVICE IN BLACKSBURG HAS ISSUED A

* SPECIAL WEATHER STATEMENT FOR...
  SOUTHWESTERN MONTGOMERY COUNTY IN SOUTHWEST VIRGINIA...
  CENTRAL PULASKI COUNTY IN SOUTHWEST VIRGINIA...

* UNTIL 345 PM EDT

* AT 311 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
  A STRONG THUNDERSTORM NEAR PULASKI...MOVING TO THE EAST AT 15 MPH.

* WIND GUSTS UP TO 50 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...
  RADFORD...
  PULASKI...
  DUBLIN...
  GRAYSONTOWN...
  AND DRAPER.

LAT...LON 3699 8081 3715 8080 3717 8053 3699 8054
TIME...MOT...LOC 1911Z 271DEG 12KT 3706 8076

KM

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
320 PM EDT SUN JUL 21 2013

VAZ033-034-044>046-058-059-212015-
HALIFAX VA-CHARLOTTE VA-BEDFORD VA-APPOMATTOX VA-FRANKLIN VA-
PITTSYLVANIA VA-CAMPBELL VA-
320 PM EDT SUN JUL 21 2013

THE NATIONAL WEATHER SERVICE IN BLACKSBURG HAS ISSUED A

* SPECIAL WEATHER STATEMENT FOR...
  NORTHWESTERN HALIFAX COUNTY IN SOUTH CENTRAL VIRGINIA...
  NORTHWESTERN CHARLOTTE COUNTY IN SOUTH CENTRAL VIRGINIA...
  SOUTHEASTERN BEDFORD COUNTY IN SOUTH CENTRAL VIRGINIA...
  SOUTHERN APPOMATTOX COUNTY IN CENTRAL VIRGINIA...
  SOUTHEASTERN FRANKLIN COUNTY IN WEST CENTRAL VIRGINIA...
  NORTHERN PITTSYLVANIA COUNTY IN SOUTH CENTRAL VIRGINIA...
  CAMPBELL COUNTY IN CENTRAL VIRGINIA...

* UNTIL 415 PM EDT

* AT 319 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
  STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM HODGES TO
  CLIMAX...MOVING TO THE EAST AT 30 MPH.

* WIND GUSTS UP TO 40 MPH ARE EXPECTED WITH THESE STORMS. EXPECT
  FREQUENT CLOUD TO GROUND LIGHTNING WITH THIS LINE OF STORMS.

* LOCATIONS IMPACTED INCLUDE...
  EVINGTON...
  HUDDLESTON...
  HURT...
  BROOKNEAL...
  AND NATHALIE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IF ON OR NEAR SMITH MOUNTAIN LAKE...GET OUT OF THE WATER AND MOVE
INSIDE A STURDY SHELTER NOW. IF YOU CAN HEAR THUNDER...YOU ARE CLOSE
ENOUGH TO BE STRUCK BY LIGHTNING.

&&

LAT...LON 3687 7895 3683 7965 3685 7964 3683 7966
      3683 7972 3724 7949 3727 7877
TIME...MOT...LOC 1919Z 266DEG 25KT 3718 7916 3686 7950