Severe Thunderstorm Warning 242, NWS Blacksburg, VA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
354 PM EDT MON AUG 10 2009

.SYNOPSIS...
A FRONTAL BOUNDARY WILL APPROACH THE REGION BY LATE TUESDAY AND
STALL OVER THE AREA WEDNESDAY AND THROUGH THE REMAINDER OF THE
WEEK.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
WHILE CONVECTION CROSSING THE NORTHERN PORTION OF THE FCST AREA
THIS AFTERNOON SHOULD WEAKEN BY EVENING AS IT CROSSES THE BLUE RDG
UNDER WRLY FLOW...KEPT A LINGERING LOW CHC POP ACROSS THE
FOOTHILLS OF NW NC DUE TO LEE TROUGH AND SOME OF THE MODELS...NAM
ESPECIALLY....CONTINUING ACTIVITY THROUGH THE EVENING HOURS.
OTHERWISE SCATTTERED CONVECTION CLOSER TO THE FRONT IN THE OHIO
VALLEY COULD ALSO LINGER MUCH OF THE OVERNIGHT...SO A LOW CHC POP
FAR WEST AS WELL. WITH DEBRIS CLOUDS COVER...ESPECIALLY IN THE
WEST...TEMPS SHOULD ONCE AGAIN BE MILD AS THEY WERE LAST
NIGHT...SO WENT A LITTLE HIGHER THAN GUIDANCE IN MINS.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
FRONTAL BOUNDARY APPROACHES BY LATE TUES...AND WILL BE RIGHT OVER
THE FCST AREA BY WED AS WEAK UPPER TROUGH DIGS JUST WEST OF
APPALACHIANS. TRICKY FCST IN TERMS OF THE DETAILS AND TIMING
CONVECTION...WITH POSSIBILITY OF WEAKENING OVERNIGHT ACTIVITY IMPACTING
THE WEST EARLY IN THE DAY...BUT AT THE SAME TIME ANY SHWRS OR
CERTAINLY CLOUD COVER COULD PUT A DAMPER ON NEW CONVECTION LATER
IN THE DAY. IF LITTLE MATERIALIZES OVERNIGHT TONIGHT...WILL SEE
BETTER CHANCE ALL LOCATIONS IN THE WEST BY MIDDAY. WRLY FLOW
SHOULD KEEP ACTIVITY AT A MINIMUM MOST OF THE DAY TUESDAY...BUT
SFC-BASED CAPE IN THE 1000-1500 J/KG RANGE COULD STILL BE ENOUGH
TO GET RELATIVELY WEAK AND LIKELY ISOLD CONVECTION GOING BY LATE
AFT. A LITTLE MORE SUN EXPECTED IN THE EAST...SO SHOULD BE ANOTHER
HOT ONE WITH TEMPS IN MID 90S AND HEAT INDEX VALUES UPPER 90S TO
NEAR 100...DOWN JUST A CUPL DEG FROM TODAY.

BY TUES NIGHT FRONTAL BOUNDARY SHOULD BE MOVING INTO WRN PORTION
OF AREA AND GOOD CHC OF ONGOING CONVECTION MOVING IN FROM WEST
OVERNIGHT. IF ORGANIZING ENOUGH...COLD POOLS COULD PUSH BOUNDARY
TO THE SOUTHEAST DURING THE DAY WED...OTHERWISE WE MAY SEE
ACTIVITY IN THE WEST DURING THE MORNING...JUMPING ACROSS INTO THE
LEE TROUGH IN THE EAST BY AFTERNOON WITH A RELATIVE MINIMUM IN
ACTIVITY IN THE MIDDLE...EXPECIALLY FROM ROANOKE UP THE I-81
CORRIDOR. WENT MAINLY WITH HIGH CHC POPS...EMPHASIS ON WEST EARLY
AND EAST LATER...BUT WITH BAND OF LOW LIKELY POPS IN THE FAR
SOUTHEAST WHICH WILL BE THE MOST LIKELY LOCATION FOR COMBINATION
OF CONVERGENCE AND MAX HEATING.

THURSDAY...BIG QSTNS AS TO HOW FAR OF A SOUTHEAST PUSH THE
BOUNDARY GETS...WITH MOST GUIDANCE SUGGESTING IT GETS INTO CNTRL
CAROLINAS...STILL CLOSE ENOUGH TO GIVE THREAT AGAIN ACROSS THE
SOUTHERN PORTION OF CWA. 12Z NAM NOW HAS STRONGER WAVE LIFTING
NORTH DURING THE DAY...SPREADING PRECIP NORTH AND WESTWARD
AGAIN...BUT PROBABLY OVER SHALLOW FAIRLY STABLE AIRMASS...BUT
BELIEVE THERE WILL BE SOME ELEVATED CONVECTION WITH THIS. SO WENT
WITH CHC POPS EVERYWHERE...BUT HIGHER ACROSS THE SOUTH. COOLER
HIGHS DUE TO PLENTY OF CLOUD COVER AND MAY NEED TO GO EVEN COOLER
IF LOOKS LIKE WELL HAVE STEADIER RAIN OVER THE EASTERLY FLOW AT
LOW LEVELS.

TENDED TO GO WITH MILDER MET GUIDANCE FOR MINS AND COOLER GUIDACE
FOR MAXS DURING THE PERIOD...EXCEPT FOR TUES GOING WITH WARMER MAV
FOR HIGHS.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
REGARDLESS OF WHETHER THE FRONTAL BOUNDARY MANAGES TO MAKE IT
SOUTHEAST OF THE AREA BY EARLY THURSDAY OR NOT...THERE APPEARS TO BE
MODEL AGREEMENT THAT THE BOUNDARY WILL EITHER WASH OUT OR SLIDE BACK
TOWARD THE NORTH BY THURSDAY EVENING.  WITH WEAK UPPER TROUGH
REMAINING JUST TO THE WEST OF THE CWA WHICH IS CONSENSUS THINKING
FROM 00Z AND 06 OPERATIONAL AND ENSEMBLE GUIDANCE...AND NOW
SUPPORTED BY THE 12Z GFS...THIS SHOULD KEEP A MOIST SOUTHERLY FLOW
THROUGH THE WEEKEND WITH 850MB SOUTHERLY FLOW RETURNING BY FRIDAY.
SFC FLOW MORE SOUTHEASTERLY THROUGH EARLY PART OF WKND...SO POSSIBLE
ENHANCEMENT OF CONVECTION AND PRECIP ALONG THE BLUE RDG...THEN
SHIFTING MORE SW BY LATE IN THE WKND AS UPPER TROUGH FADES AND RIDGE
BUILDS A LITTLE.  PLENTY OF CONVECTIVELY INDUCED WAVES HEADING IN
FROM WEST DURING OVERNIGHT HOURS DURING THIS PERIOD SO COULD HAVE A
NUMBER OF NIGHTS WITH CONVECTION CONTINUING...SO GENERALLY KEPT CHC
POPS INTO THE NIGHT PERIODS. BY MONDAY...WARMER TEMPS ALOFT AND
PERHAPS MORE WESTERLY FLOW...ALBEIT WEAK...COULD HELP SUPPRESS
CONVECTIVE CHANCES...HOWEVER ENOUGH UNCERTAINTY THIS FAR OUT...AND
CONSIDERING CLIMATOLOGY OF THE SEASON...CERTAINLY NOT GOING TO DROP
POPS ALL THE WAY...BUT LOWERING TO SLIGHT CHC TO SUGGEST POSSIBILITY
OF A DRIER DAY. CONSIDERING THAT THIS WILL BE AN EXTENDED RATHER WET
PERIOD...WITH MANY AREAS GETTING A CHANCE TO PICK UP SOME HEAVY
RAINFALL BY THE END OF THE WEEKEND...A DRY DAY MAY BE A WELCOME
RELIEF...BUT NOT ENTIRELY SURE ITS GOING TO HAPPEN.  ALSO SEEING
SOME SIGNS OF TROPICAL WAVES MAKING IT INTO THE GULF BY EARLY NEXT
WEEK..SO WILL HAVE TO KEEP OUR EYE ON THIS POTENTIAL ADDITIONAL MSTR
SOURCE.  WENT WITH HPC GUIDANCE FOR TEMPERATURES DURING THE PERIOD
BUT WITH A SLIGHT UPWARD BOOST ON MONDAY.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
HEATING TODAY ALONG WITH DEWPOINTS IN THE LOWER 70S HAS ALLOWED
FOR A MODERATELY UNSTABLE AIRMASS...THOUGH TEMPS ALOFT ARE WARM
ENOUGH THAT MID LEVEL LAPSE RATES ARE STILL FAIRLY WEAK.
RADAR/SATELLITE SHOWS SCAT TSTMS DEVELOPING OVER THE WESTERN
SLOPES OF THE MTNS. WESTERLY FLOW SHOULD TEND TO KEEP TSTMS FROM
MOVING TOO FAR EAST OF THE MTNS. HAVE INCLUDED VCNTY TSTMS IN THE
BLF AND LWB TAFS...WITH TEMPO GROUPS WHEN THEY HAVE THE BEST CHC TO
SEE SHOWERS AND MVFR CONDS. FOR ROA...WITH TSTMS PASSING THRU
RIGHT NOW...I HAVE A 1 HOUR TEMPO GROUP...WITH 2 HOURS OF VCNTY
TSTMS. TSTM ACTIVITY SHOULD BE MAINLY DIURNAL TODAY...SO CHCS ARE
TOO LOW TO MENTION IN TAFS AFTER MID EVENING. THINK THAT DEBRIS
MID AND HIGH CLOUDS WILL KEEP MUCH FOG FROM DEVELOPING
OVERNIGHT...BUT HAVE INCLUDED SOME MVFR FOG AND CIGS AT
BLF/LWB...AND MVFR FOG AT DAN. THERE WILL BE A GOOD CHC FOR TSTMS
AGAIN ON TUESDAY...BUT SHOULD BE MAINLY AFTER 18Z.

THE APPROACH OF A COOL FRONT AND ASSOCIATED SHOWERS/THUNDERSTORMS
IN THE TUESDAY AFTERNOON - THURSDAY TIME FRAME WILL RESULT IN A
MORE WIDESPREAD THREAT OF MVFR/POSSIBLE IFR RESTRICTIONS WITH
SHOWERS AND THUNDERSTORMS. MORE TYPICAL AIRMASS TYPE AFT/EVE
THUNDERSTORMS ARE EXPECTED FRIDAY AND SATURDAY...WITH THE BEST
COVERAGE IN THE MTNS.

&&

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

&&

SYNOPSIS...SK
NEAR TERM...JJ
SHORT TERM...SK
LONG TERM...SK
AVIATION...AMS/JJ

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BLACKSBURG VA
1134 AM EDT MON AUG 10 2009

NCZ004>006-VAZ043>047-058-059-111545-
STOKES-ROCKINGHAM-CASWELL-HENRY-PITTSYLVANIA-CAMPBELL-APPOMATTOX-
BUCKINGHAM-HALIFAX-CHARLOTTE-
1134 AM EDT MON AUG 10 2009

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

HEAT INDEX VALUES WILL BE 100 TO 104 DEGREES THIS AFTERNOON.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

NO HAZARDOUS WEATHER IS EXPECTED.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

NCZ003-019-020-VAZ022>024-032>035-111545-
SURRY-WILKES-YADKIN-ROANOKE-BOTETOURT-ROCKBRIDGE-PATRICK-FRANKLIN-
BEDFORD-AMHERST-
1134 AM EDT MON AUG 10 2009

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.

NO HAZARDOUS WEATHER IS EXPECTED.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

THE PROBABILITY OF HAZARDOUS WEATHER IS LOW. HOWEVER...THERE WILL
BE SCATTERED THUNDERSTORMS TUESDAY AFTERNOON AND EVENING. A FEW
OF THE STORMS MAY BECOME STRONG ENOUGH TO PRODUCE DAMAGING WIND
GUSTS...AND ANY OF THE STORMS MAY HAVE HEAVY DOWNPOURS THAT COULD
PRODUCE LOCALIZED FLOODING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

NCZ001-002-018-VAZ007-009>020-WVZ042>045-111545-
ASHE-ALLEGHANY NC-WATAUGA-TAZEWELL-SMYTH-BLAND-GILES-WYTHE-PULASKI-
MONTGOMERY-GRAYSON-CARROLL-FLOYD-CRAIG-ALLEGHANY VA-BATH-MERCER-
SUMMERS-MONROE-GREENBRIER-
1134 AM EDT MON AUG 10 2009

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THE PROBABILITY OF HAZARDOUS WEATHER IS LOW. HOWEVER...THERE WILL
BE SCATTERED THUNDERSTORMS THIS AFTERNOON AND EVENING. A FEW OF
THE STORMS MAY BECOME STRONG ENOUGH TO PRODUCE DAMAGING WIND
GUSTS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

THE PROBABILITY OF HAZARDOUS WEATHER IS LOW. HOWEVER...THERE WILL
BE SCATTERED THUNDERSTORMS AGAIN TUESDAY AFTERNOON AND EVENING. A
FEW OF THE STORMS MAY BECOME STRONG ENOUGH TO PRODUCE DAMAGING
WIND GUSTS...AND ANY OF THE STORMS MAY HAVE HEAVY DOWNPOURS THAT
COULD PRODUCE LOCALIZED FLOODING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
344 PM EDT MON AUG 10 2009

NCZ020-102045-
YADKIN NC-
344 PM EDT MON AUG 10 2009

...A STRONG THUNDERSTORM WILL AFFECT YADKIN COUNTY...

AT 343 PM EDT...A STRONG THUNDERSTORM WAS LOCATED 8 MILES WEST OF
YADKINVILLE...MOVING EAST AT 15 MPH.

WIND GUSTS TO 40 MPH ARE POSSIBLE WITH THIS STORM. VERY HEAVY RAIN
WILL FALL FROM THIS STORM...AND WILL CAUSE WATER TO POND ON ROADS AND
QUICKLY FILL ROADSIDE DITCHES AND SMALL STREAMS. EXPECT FREQUENT
CLOUD TO GROUND LIGHTNING FROM THIS STORM. DO NOT STAY IN THE OPEN OR
SEEK SHELTER UNDER TREES WHEN LIGHTNING THREATENS...MOVE INDOORS WHEN
A THUNDERSTORM APPROACHES.

THIS STORM WILL BE NEAR LONE HICKORY AROUND 405 PM...YADKINVILLE
AROUND 420 PM...COURTNEY AROUND 430 PM...SHACKTOWN AROUND 435 PM AND
HUNTSVILLE AROUND 445 PM.

THE PUBLIC IS ENCOURAGED TO RELAY REPORTS OF STRONG WINDS...HAIL OR
FLOODING TO THE NATIONAL WEATHER SERVICE IN BLACKSBURG BY CALLING
1...8 6 6...2 1 5...4 3 2 4...WHEN YOU CAN DO SO SAFELY.

LAT...LON 3604 8065 3604 8079 3605 8088 3621 8087
      3620 8044 3612 8044 3609 8050 3604 8050
      3604 8064

EXPERIMENTAL

JJ

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