MESO: Mesoscale Discussion 1877

ACUS11 KWNS 122103
SWOMCD
SPC MCD 122103
IAZ000-NEZ000-SDZ000-122230-

MESOSCALE DISCUSSION 1877
NWS STORM PREDICTION CENTER NORMAN OK
0403 PM CDT WED AUG 12 2009

AREAS AFFECTED...CENTRAL-WRN IA...SERN SD...FAR NERN NEB

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 122103Z - 122230Z

A CONDITIONAL THREAT OF ISOLATED LARGE HAIL/DAMAGING WINDS EXISTS
OVER PORTIONS OF CENTRAL-WRN IA...SERN SD AND FAR NERN NEB. A WW IS
NOT EXPECTED DUE TO THE ISOLATED NATURE OF THE THREAT.

SURFACE MESOANALYSIS INDICATES A SURFACE LOW POSITIONED OVER
SWRN/S-CENTRAL SD...WITH A WARM FRONT EXTENDING EWD INTO SERN SD AND
THEN SEWD THROUGH WRN-CENTRAL IA. S-SWLY SURFACE WINDS AND
TEMPERATURES IN THE 80S AND 90S WERE OBSERVED ACROSS THE WARM
SECTOR...AIDING IN BOUNDARY LAYER DESTABILIZATION/STEEPENING LOW
LEVEL LAPSE RATES. MEANWHILE...SURFACE DEWPOINTS ALONG THE WARM
FRONT HAVE INCREASED INTO THE 70S. THE COMBINATION OF STRONG HEATING
AND INCREASING BOUNDARY LAYER MOISTURE ARE AIDING IN THE DEVELOPMENT
OF MLCAPE VALUES AOA 3000 J/KG /PER HOURLY OBJECTIVE ANALYSIS/ WHILE
MINIMIZING CINH ALONG AND E OF THE MO RIVER.

A BAND OF HIGH LEVEL CIRRUS IS MOVING E ACROSS THE REGION...WITH
LITTLE IN THE WAY OF SURFACE BASED CUMULUS GROWTH OBSERVED IN VIS
IMAGERY. HOWEVER...A WEAK MID LEVEL TROUGH WILL APPROACH THE AREA
FROM THE W...WHILE LOW LEVEL WAA INCREASES WITH NOCTURNALLY
STRENGTHENING LLJ THIS EVENING. THESE FEATURES COULD PROVIDE
SUFFICIENT ASCENT AND ADDITIONAL DESTABILIZATION FOR ISOLATED STORM
DEVELOPMENT BY LATE AFTERNOON OR EARLY EVENING. GIVEN THE HIGH CAPE
ENVIRONMENT...INITIAL STORM DEVELOPMENT COULD BE POTENTIALLY
EXPLOSIVE...AND MAY POSSIBLY PRODUCE LARGE HAIL/DAMAGING WIND GUSTS.
HOWEVER...VERTICAL WIND SHEAR IS FAIRLY WEAK...PER AREA PROFILER
DATA...WHICH WILL LIMIT STORM PERSISTENCE AND LIKELY NEGATE THE NEED
FOR A WW.

..GARNER.. 08/12/2009

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

ATTN...WFO...DVN...DMX...FSD...OAX...

LAT...LON 43389568 43229359 42129234 41349238 40759304 40709399
41129505 41409560 42059666 42899671 43389568

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