MESO: Mesoscale Discussion 1808

ACUS11 KWNS 200014
SWOMCD
SPC MCD 200014
DEZ000-MDZ000-VAZ000-DCZ000-200145-

MESOSCALE DISCUSSION 1808
NWS STORM PREDICTION CENTER NORMAN OK
0714 PM CDT SUN AUG 19 2007

AREAS AFFECTED...PARTS OF CNTRL/ERN VA INTO THE SRN DELMARVA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 200014Z - 200145Z

TRENDS ARE BEING MONITORED FOR THE POSSIBILITY OF INCREASING SEVERE
POTENTIAL...THOUGH THE RISK FOR LOCALLY HEAVY RAIN MAY ULTIMATELY BE
THE PRIMARY THREAT WITH DEVELOPING STORMS THIS EVENING.

A GRADUAL INCREASE IN CONVECTIVE DEVELOPMENT IS UNDERWAY IN A NARROW
EAST-WEST LINE NEAR THE INTERSTATE 64 CORRIDOR. THIS APPEARS
ALIGNED WITH ZONE OF WEAK WARM ADVECTION IN THE SURFACE THROUGH 850
MB LAYER...NORTH OF WHERE THE MOIST BOUNDARY LAYER HEATED TO NEAR
90F THIS AFTERNOON. LATEST RUC GUIDANCE INDICATES THAT MIXED LAYER
CAPE IS ON THE ORDER OF 1500-2000 J/KG...WITHIN THE PRESENCE OF
MODERATE TO STRONG DEEP LAYER SHEAR BENEATH 40 KT WEST NORTHWESTERLY
500 MB FLOW. AN ISOLATED SUPERCELL APPEARS POSSIBLE THROUGH 01-02Z
NEAR RICHMOND THROUGH THE SOUTHERN DELMARVA PENINSULA AREA.
HOWEVER...SURFACE OR NEAR SURFACE-BASED CONVECTIVE DEVELOPMENT MAY
BE RELATIVELY SHORT-LIVED AS THE BOUNDARY LAYER COOLS WITH LOSS OF
DAYTIME HEATING.

AS A WEAK MID-LEVEL IMPULSE PROGRESSES SOUTHEAST OF UPPER OHIO
VALLEY/LOWER GREAT LAKES REGION THIS EVENING...MODELS GENERALLY
SUGGEST THAT A WESTERLY LOW-LEVEL JET AND ASSOCIATED LOWER/MID
TROPOSPHERIC WARM ADVECTION REGIME WILL STRENGTHEN DURING THE 03-06Z
TIME FRAME. THIS MAY OCCUR ACROSS EAST CENTRAL VIRGINIA INTO THE
DELMARVA...PERHAPS A BIT FARTHER TO THE NORTH THAN ONGOING ACTIVITY.
AND...THE POSSIBILITY EXISTS FOR A GROWING CONVECTIVE CLUSTER...IN
A WEAK TO MODERATELY UNSTABLE ENVIRONMENT WITH HIGH PRECIPITABLE
WATER NEAR 2 INCHES.

WITH FORECAST SOUNDINGS LARGELY SATURATED...DAMAGING WIND POTENTIAL
APPEARS LOW. BUT...CAPE MAY BE LARGE ENOUGH...GIVEN STRENGTH OF
SHEAR...TO SUPPORT A CONTINUING MARGINALLY SEVERE HAIL THREAT...IN
ADDITION TO THE RISK FOR LOCALLY HEAVY RAINFALL IN SLOW
MOVING/TRAINING STORMS.

.KERR.. 08/20/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PHI...AKQ...LWX...RNK...

37827885 38167907 38697907 38877696 38957653 39117544
38697453 38047439 37027555 37427781

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