MESO: Mesoscale Discussion 2009

ACUS11 KWNS 231952
SWOMCD
SPC MCD 231951
SDZ000-NEZ000-COZ000-232145-

MESOSCALE DISCUSSION 2009
NWS STORM PREDICTION CENTER NORMAN OK
0251 PM CDT SUN SEP 23 2007

AREAS AFFECTED...NERN CO THROUGH WRN NEB THROUGH WRN AND CNTRL SD

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 231951Z - 232145Z

THUNDERSTORMS ARE EXPECTED TO DEVELOP BY 21Z FROM NERN CO THROUGH
WRN NEB AND WRN SD AND INTENSIFY AS THEY MOVE EWD. ISOLATED LARGE
HAIL AND DAMAGING WIND GUSTS WILL BE THE MAIN THREATS.

A COLD FRONT EXTENDS FROM WRN SD SWWD THROUGH WRN NEB INTO NERN
CO...PRECEDED BY A PRE-FRONTAL TROUGH. LIFT AND A PLUME OF DEEP
MOISTURE STREAMING NWD THROUGH THE ROCKIES IS CONTRIBUTING TO
WIDESPREAD CLOUDS WEST OF THE FRONT. MOSTLY CLEAR SKIES HAVE
RESULTED IN GRADUAL DESTABILIZATION IN THE PRE-FRONTAL WARM SECTOR
THIS AFTERNOON. INSTABILITY HAS BEEN MODERATED SOMEWHAT BY MODEST
LOW LEVEL MOISTURE WITH DEWPOINTS GENERALLY IN 50S TO AROUND 60
CONTRIBUTING TO AN AXIS OF MLCAPE AROUND 1000 J/KG FROM W CNTRL NEB
THROUGH CNTRL SD. CUMULUS IS INCREASING WHERE BOUNDARY LAYER MIXING
IS WEAKENING THE CAP IN VICINITY OF THE FRONT FROM NERN CO INTO WRN
NEB AND SWRN SD. EXPECT STORMS TO DEVELOP WITHIN AXIS OF CONVERGENCE
ALONG THE FRONT NEXT HOUR OR TWO. DEWPOINTS HAVE MIXED DOWN TO NEAR
50 IN THIS REGION...WHILE TEMPERATURES HAVE WARMED TO AROUND 90.
THIS SUGGESTS INITIAL STORMS WILL BE HIGH BASED...BUT STORMS WILL
LIKELY INTENSIFY AS THEY MOVE EAST INTO THETA-E AXIS. BELT OF 50+ KT
MID-UPPER FLOW ALONG ERN PERIPHERY OF UPPER TROUGH IS GRADUALLY
SHIFTING EWD WITH UNIDIRECTIONAL 40 KT DEEP SHEAR IN VICINITY OF THE
FRONT. SOME STORMS WILL LIKELY EXHIBIT SUPERCELL STRUCTURES BUT
ACTIVITY MAY EVENTUALLY EVOLVE INTO LINE SEGMENTS AS IT DEVELOPS
EWD.

.DIAL.. 09/23/2007

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

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

41770119 40740216 40450325 40750354 42400278 44840218
44620024 43040057

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