MESO: Mesoscale Discussion 2280

ACUS11 KWNS 231732
SWOMCD
SPC MCD 231731
IAZ000-MOZ000-NEZ000-KSZ000-231930-

MESOSCALE DISCUSSION 2280
NWS STORM PREDICTION CENTER NORMAN OK
1231 PM CDT TUE SEP 23 2008

AREAS AFFECTED...N-CNTRL IA SWWD INTO NERN KS

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 231731Z - 231930Z

PRE-FRONTAL BAND OF TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY THIS AFTERNOON. SEVERE HAIL AND LOCALLY DAMAGING WIND
GUSTS WILL BE THE PRIMARY HAZARDS AND A WW MAY BE NECESSARY BEFORE
20Z.

REGIONAL RADAR IMAGERY SHOWS TSTMS SLOWLY INTENSIFYING IN A NE-SW
ORIENTED BAND FROM SIOUX AND PLYMOUTH COUNTIES IN NWRN IA TO OSBORNE
AND RUSSELL COUNTIES IN N-CNTRL KS AS OF 17Z. THIS ACTIVITY IS
OCCURRING ALONG A COLD FRONT PUSHING EWD INTO THE MID MO
VALLEY...AND ALONG THE SRN FRINGE OF STRONGER HEIGHT FALLS/DYNAMIC
FORCING FOR ASCENT ATTENDANT TO SHORT WAVE TROUGH TRANSLATING EWD
THROUGH THE DAKOTAS AND NEB. SCATTERED CLOUDINESS WITHIN
PRE-FRONTAL AIR MASS IS ALLOWING FOR RELATIVELY STRONG DIABATIC
HEATING TO OCCUR WITH TEMPERATURES WARMING THROUGH THE 70S.
CONTINUED HEATING COUPLED WITH BOUNDARY LAYER DEWPOINTS IN THE LOWER
60S AND MIDLEVEL LAPSE RATES OF AROUND 7 C/KM /PER 12Z SOUNDINGS/
ARE EXPECTED TO RESULT IN A MODERATELY UNSTABLE AIR MASS LATER THIS
AFTERNOON WITH MLCAPES APPROACHING 1000-1500 J/KG.

SURFACE WINDS HAVE TENDED TO VEER THIS MORNING WITH THE DEEPENING OF
THE BOUNDARY LAYER WITH VERTICAL WIND PROFILES BECOMING LARGELY
UNIDIRECTIONAL. VWP/PROFILER DATA AND FORECAST SOUNDINGS SUGGEST
THAT THE STRONGER DEEP-LAYER SPEED SHEAR AND ASSOCIATED
ORGANIZED/SEVERE STORM THREAT WILL EXIST FROM E-CNTRL NEB/W-CNTRL IA
NWD. FARTHER S...THE THREAT FOR ISOLATED HAIL AND LOCALLY DAMAGING
WIND GUSTS WILL EXIST WITH THE MOST INTENSE STORMS...BUT THE
WEAKENING SHEAR WITH SWD EXTENT SHOULD TEND TO LIMIT A MORE ROBUST
STORM DEVELOPMENT.

..MEAD.. 09/23/2008

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

ATTN...WFO...DMX...EAX...FSD...OAX...TOP...GID...

39249779 40549707 42579592 43369521 43459442 43369358
42849355 39049663 38969747

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