Flash Flood Warning 24, NWS Blacksburg, VA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
752 PM EDT SUN JUL 29 2007

.SYNOPSIS...
WEAK SURFACE HIGH PRESSURE WILL BUILD SLOWLY SOUTHEAST OUT OF THE
UPPER GREAT LAKES...REACHING THE MID ATLANTIC REGION BY MID WEEK.
DRIER AIR SPREADING INTO THE AREA FROM THE NORTH WILL MINIMIZE THE
THREAT OF RAIN FROM MID WEEK INTO NEXT WEEKEND.

&&

.NEAR TERM /THROUGH MONDAY/...
WEAK SHORTWAVE ENERGY PUSHING THRU THE OHIO VALLEY BEGINNING TO
PRODUCE SCATTERED CONVECTION MAINLY NORTH OF THE COUNTY WARNING AREA
THIS AFTERNOON WHERE UPPER LEVEL TEMPS ARE A LITTLE COOLER AND WHERE
MORE SOLAR INSOLATION HAS OCCURRED. BASED ON MORNING SOUNDINGS...SOME
MID LEVEL CAPPING APPEARS TO BE INHIBITING CONVECTION OVER OUR CWA
DESPITE SOME LIGHT UPSLOPE LOW LEVEL FLOW. WHERE STORMS DO FORM
LATER TODAY...THEY WILL BE MOVING SLOWLY...SO THE POTENTIAL FOR
TORRENTIAL RAINFALL EXISTS.

CONVECTION WILL WANE THIS EVENING WITH LOSS OF HEATING. HOWEVER...
SHORTWAVE ENERGY MOVING OVERHEAD WILL KEEP THE THREAT OF ISOLATED
SHOWERS MOST AREAS. MEANWHILE OVERNIGHT...EXPECT PERSISTENT LOW
LEVEL SOUTHEAST FLOW TO RESULT IN MORE STRATUS CLOUDS WHICH WILL
LIKELY BECOME QUITE THICK IN MANY AREAS...LASTING INTO THE FIRST
HALF OF THE DAY OR LONGER ON MONDAY. THIS IN TURN WILL KEEP TEMPS
DOWN A BIT...RESULTING IN LESS INSTABILITY AND LESS CONVECTION.
HAVE LOWERED POPS A BIT FOR TMRW AFTN.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
LAST IN A SERIES OF SHORT WAVE TROUGHS DROPPING SOUTHEAST ON
BACKSIDE OF EASTERN UPPER LONG WAVE TROUGH WILL MOVE SOUTHEAST OF
THE BLACKSBURG FORECAST AREA EARLY MONDAY NIGHT. PASSAGE OF WAVE
WILL SUPPORT THE SOUTHEASTWARD PUSH OF SLIGHTLY DRIER AIR IN
ADVANCE OF AN APPROACHING WEAK SURFACE RIDGE. ANY LINGERING
CONVECTION FROM MONDAY AFTERNOON SHOULD EITHER DISSIPATE OR MOVE
OFF TO THE EAST AND SOUTH WELL BEFORE MIDNIGHT...WITH GRADUAL
DRYING TREND EXPECTED THEREAFTER.

INCREASING SUBSIDENCE AND ADVECTION OF DRIER AIR ALOFT SHOULD
MINIMIZE THREAT OF DIURNALLY DRIVEN SHOWERS/THUNDERSTORMS TUESDAY
THROUGH WEDNESDAY NIGHT OVER THE BLACKSBURG AREA OF CONCERN.
HOWEVER...SOME CONCERN EXISTS AROUND INFLUENCE OF ANOTHER SHORT
WAVE TROUGH SWINGING SOUTHEAST THROUGH THE DELMARVA REGION TUESDAY
AFTERNOON...AND WHETHER PROXIMITY TO LIMITED MID LEVEL COOLING
AND WEAK FORCING ASSOCIATED WITH THIS FEATURE WILL INFLUENCE AREAS
FURTHER TO THE SOUTHWEST.

CURRENT THINKING IS THAT SUBSIDENCE CAPPING INVERSION PER GFS
FORECAST SOUNDINGS TUESDAY INTO WEDNESDAY WILL BE MORE THAN
SUFFICIENT TO MINIMIZE THREAT OF PRECIPITATION FROM THIS
FEATURE. THE NAM SOLUTION OF GENERATING SCATTERED PRECIPITATION
EAST OF THE BLUE RIDGE TUESDAY AFTERNOON IN A LARGELY UNCAPPED
ENVIRONMENT HAS THEREFORE BEEN DISCARDED.

DESPITE SLIGHTLY DRIER AIR ADVECTING INTO THE AREA WITH THE APPROACH
OF THE SURFACE RIDGE...TEMPERATURES ARE NOT EXPECTED TO BE ANY
LOWER THAN THE PAST SEVERAL DAYS. DRIER AIR WILL ALLOW FOR MORE
DAYTIME HEATING...RESULTING IN TEMPERATURES EQUAL TO OR EVEN
HIGHER THAN THOSE EXPERIENCED DURING THE PAST SEVERAL DAYS WHERE
DAYTIME HIGHS WERE LARGELY GOVERNED BY EXTENT OF CLOUD COVER AND
COOLING CONVECTIVE OUTFLOW BOUNDARIES. NUMERICAL NUMERICAL GUIDANCE
FOR ALL AREAS WAS FAIRLY CONSISTENT THROUGH THE MID WEEK PERIOD
AND WAS GENERALLY ACCEPTED.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
LITTLE CHANGE IN THE OVERALL WEATHER PATTERN EXPECTED LATER IN THE
WEEK INTO NEXT WEEKEND. MEAN UPPER TROUGH WILL GRADUALLY FILL AS
HEIGHTS INCREASE...TRANSITIONING TO MORE OF A WEAK ZONAL FLOW WITH
STAGNANT SURFACE REFLECTIONS. INCREASING HEIGHTS AND STAGNANT LOWER
TROPOSPHERIC FLOW WILL RESULT IN SLOWLY INCREASING TEMPERATURES
AND DEW POINTS...BUT WITH LITTLE TRIGGER TO SUPPORT THE
DEVELOPMENT OF ANY ORGANIZED CONVECTION.

HOWEVER...WOULD NOT BE SURPRISED TO SEE AN ISOLATED DIURNALLY DRIVEN
THUNDERSTORM DURING THE PERIOD OVER THE HIGHER TERRAIN PROVIDED
THAT DIFFERENTIAL HEATING CAN BE SUSTAINED LONG ENOUGH TO OVERCOME
A WEAKENING MID LEVEL CAPPING INVERSION. CONSIDERING VERY LOW
PROBABILITY AND LIMITED POTENTIAL AREAL COVERAGE...WILL CONTINUE
TO EXCLUDE THREAT OF PRECIPITATION IN THE LONG TERM PERIOD.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
THERE WILL BE THREE MAIN AREAS OF INTEREST AVIATION-WISE THROUGH
EARLY MONDAY EVENING.

FIRST...NUMEROUS SHOWERS AND THUNDERSTORMS HAVE TAKEN UP RESIDENCY
ALONG THE I-64 CORRIDOR FROM SE WV INTO PARTS OF CENTRAL VA.
OUTFLOW BOUNDARIES HEADING SOUTH FROM THIS ACTIVITY MAY HELP
TO GENERATE AN ISOLATED SHRA/TSRA IN THE KLWB AND KLYH AREAS
THROUGH ABOUT 03 OR 04Z

SECOND...LOW LEVEL FLOW ACROSS THE AREA IS PREDOMINATELY EAST OR
JUST SOUTH OF EAST. WITH ABUNDANT MOISTURE IN THE LOW LEVELS
DEVELOPMENT OF MVFR CEILINGS ARE EXPECTED IN MANY PARTS OF THE
AREA AFTER 06Z. ALSO THE DEVELOPMENT OF PATCHY MVFR FOG IN LOW
LYING AREAS AND RIVER VALLEYS IS EXPECTED...WITH A FEW SPOTS
TOUCHING IFR LEVEL BRIEFLY TOWARDS DAWN. IMPROVEMENT TO VFR AFTER
SUNRISE WILL NOT BE OVERLY RAPID...ESPECIALLY CONCERNING CEILING
HEIGHT. BY 14 TO 16Z VFR CONDITIONS ARE EXPECTED MONDAY.

THIRD...DEVELOPMENT OF AFTERNOON SHRA/TSRA LOOKS MORE PROMISING
MONDAY ALONG AND EAST OF A KLYH-KDAN LINE AS THE UPPER TROUGH
WHICH HAS BEEN OVER THE REGION BEGINS TO SHIFT EAST OFF THE COAST.

DRIER AIR BEGINS TO FILTER IN MONDAY NIGHT INTO TUESDAY WITH VFR
CONDS LIKELY THROUGH THURSDAY.

&&

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

&&

SYNOPSIS...WERT
NEAR TERM...JS
SHORT TERM...WERT
LONG TERM...WERT
AVIATION...DS/JS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BLACKSBURG VA
633 AM EDT SUN JUL 29 2007

NCZ001>006-018>020-VAZ007-009>020-022>024-032>035-043>047-058-059-
WVZ042>045-301045-
ASHE-ALLEGHANY NC-SURRY-STOKES-ROCKINGHAM-CASWELL-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-PITTSYLVANIA-
CAMPBELL-APPOMATTOX-BUCKINGHAM-HALIFAX-CHARLOTTE-MERCER-SUMMERS-
MONROE-GREENBRIER-
633 AM EDT SUN JUL 29 2007

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

.DAY ONE...TODAY AND TONIGHT

THERE IS AN ISOLATED THREAT OF SEVERE THUNDERSTORMS THIS AFTERNOON
AND EVENING. ANY OF THE STRONG TO SEVERE THUNDERSTORMS WILL PRODUCE
WIND GUSTS OR HAIL...AND VERY HEAVY RAINFALL.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
805 PM EDT SUN JUL 29 2007

WVZ045-300100-
GREENBRIER WV-
805 PM EDT SUN JUL 29 2007

AT 802 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 2 MILES NORTHEAST OF RUPERT...MOVING NORTHWEST AT
15 MPH. THE STRONG THUNDERSTORM WILL BE NEAR...DUO AT 810 PM
EDT...QUINWOOD...RAINELLE AT 820 PM EDT...BINGHAM AT 840 PM EDT.

EXPECT SMALL HAIL AND FREQUENT DANGEROUS LIGHTNING IN THE PATH OF
THIS STORM. BRIEF WIND GUSTS TO 40 MPH ARE ALSO POSSIBLE.

LISTEN TO NOAA WEATHER RADIO OR YOUR FAVORITE MEDIA OUTLET FOR
UPDATES OR POSSIBLE WARNINGS.

JH

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
838 PM EDT SUN JUL 29 2007

VAZ047-300145-
BUCKINGHAM VA-
838 PM EDT SUN JUL 29 2007

AT 836 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 12 MILES NORTHEAST OF BENT CREEK...OR ABOUT 3
MILES EAST OF WINGINA...MOVING SOUTHEAST AT 35 MPH. THE STRONG
THUNDERSTORM WILL BE NEAR...BUCKINGHAM AT 845 PM
EDT...ANDERSONVILLE...TOGA AT 850 PM EDT.

EXPECT SMALL HAIL AND FREQUENT DANGEROUS LIGHTNING IN THE PATH OF
THIS STORM. RAINFALL AMOUNTS OF UP TO AN INCH IN A 30 MINUTE PERIOD
MAY ALSO OCCUR.

LISTEN TO NOAA WEATHER RADIO OR YOUR FAVORITE MEDIA OUTLET FOR
UPDATES OR WARNINGS.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
905 PM EDT SUN JUL 29 2007

VAZ034-045-300200-
BEDFORD VA-CAMPBELL VA-
905 PM EDT SUN JUL 29 2007

AT 901 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 4 MILES SOUTHEAST OF FOREST...OR ABOUT OVER
TIMBERLAKE. THIS THUNDERSTORM WAS NEARLY STATIONARY. THE STRONG
THUNDERSTORM WILL REMAIN ALONG THE BEDFORD AND CAMPBELL COUNTY
BORDER DURING THE NEXT HOUR.

EXPECT RAINFALL AMOUNTS OF ONE TO THREE INCHES IN THE AREA BETWEEN
GOODE...FOREST...AND TIMBERLAKE. THIS MAY CAUSE LOCALIZED FLOODING
OF DITCHES AND POOR DRAINAGE AREAS. IN ADDITION FREQUENT LIGHTNING
ALONG WITH WIND GUSTS TO 40 MPH CAN BE EXPECTED IN THE VICINITY OF
THIS VERY STRONG THUNDERSTORM.

LISTEN TO NOAA WEATHER RADIO OR YOUR FAVORITE MEDIA OUTLET FOR LATER
UPDATES OR POSSIBLE WARNINGS.