MESO: Mesoscale Discussion 1374

ACUS11 KWNS 292137
SWOMCD
SPC MCD 292136
NEZ000-SDZ000-292300-

MESOSCALE DISCUSSION 1374
NWS STORM PREDICTION CENTER NORMAN OK
0436 PM CDT MON JUN 29 2009

AREAS AFFECTED...WRN SD AND WRN NEB

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 292136Z - 292300Z

AN ISOLATED THREAT OF LARGE HAIL AND DAMAGING WINDS WILL EXIST
DURING THE AFTERNOON AND EVENING OVER WRN SD AND WRN NEB. AT THIS
TIME...A WW DOES NOT APPEAR NECESSARY.

SUBJECTIVE SURFACE ANALYSIS INDICATES THE PRESENCE OF WEAK LOW
PRESSURE OVER WRN/CENTRAL SD...WHICH IS ACTING TO FOCUS LOW LEVEL
CONVERGENCE AND A NW TO SE ORIENTED THERMAL GRADIENT. TEMPERATURES
ACROSS THE REGION HAVE WARMED INTO THE 90S...AND ARE ACCOMPANIED BY
UPPER 40S TO LOW 50S DEWPOINTS. THESE SURFACE CONDITIONS...COMBINED
WITH STEEP MID LEVEL LAPSE RATES /AOA 7.5-8.0 C PER KM/...AS
INDICATED BY RUC FORECAST SOUNDINGS AND 18Z LBF RAOB...ARE
CONTRIBUTING TOWARD A MODERATELY UNSTABLE ENVIRONMENT /MLCAPE VALUES
APPROACHING 2000 J PER KG OVER WRN SD/.

STRONG BOUNDARY LAYER DESTABILIZATION COMBINED WITH AN APPROACHING
UPPER LEVEL IMPULSE EMBEDDED WITHIN A S/W RIDGE OVER THE REGION IS
FAVORING SCATTERED THUNDERSTORM DEVELOPMENT OVER WRN PORTIONS OF SD.
LOW LEVEL SSELY WINDS VEERING TO 30 KT/S OF WNWLY FLOW IN THE
MID/UPPER LEVELS WILL CONTRIBUTE TOWARD SUFFICIENT EFFECTIVE BULK
SHEAR FOR ORGANIZED MULTICELLS AND PERHAPS BRIEF SUPERCELL
STRUCTURES. LOW LEVEL FLOW IS FAIRLY WEAK...WHICH MAY HAMPER THE
DEVELOPMENT OF PERSISTENT UPDRAFT ROTATION. HOWEVER...THE FAVORABLE
CAPE/LAPSE RATES COMBINED WITH MODEST VERTICAL WIND SHEAR WILL
PROMOTE LARGE HAIL AND DAMAGING WINDS WITH THE STRONGER UPDRAFT
CORES. THESE STORMS MAY EVENTUALLY DRIFT SE INTO PORTIONS OF WRN NEB
DURING THE EVENING...WITH SOME POTENTIAL FOR UPSCALE GROWTH INTO A
LOOSELY ORGANIZED MCS.

..GARNER.. 06/29/2009

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

ATTN...WFO...ABR...LBF...UNR...CYS...

LAT...LON 45350363 45830268 45560121 42789987 41760050 41860367
45350363

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