Thursday, June 21, 2007

MESO: Mesoscale Discussion 1238

ACUS11 KWNS 211913
SWOMCD
SPC MCD 211913
WIZ000-ILZ000-IAZ000-MNZ000-NEZ000-SDZ000-212015-

MESOSCALE DISCUSSION 1238
NWS STORM PREDICTION CENTER NORMAN OK
0213 PM CDT THU JUN 21 2007

AREAS AFFECTED...SERN SD/SWRN MN/NWRN IA

CONCERNING...SEVERE THUNDERSTORM WATCH 433...434...

VALID 211913Z - 212015Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
433...434...CONTINUES.

IR SATELLITE IMAGERY INDICATED PERSISTENT COLD CLOUD TOPS WITH MCS
MOVING ESEWD WITH STRONGEST STORMS LOCATED ALONG THE SERN SD/NWRN IA
BORDER REGION. SURFACE ANALYSIS INDICATED A WARM FRONT EXTENDING
FROM SWRN WI NWWD INTO SERN MN AND THEN WWD TO A WAKE LOW OVER
CENTRAL SD. ANOTHER BOUNDARY THEN EXTENDED SWWD FROM THE WAKE LOW
TO THE MAIN SYNOPTIC LOW OVER WRN NEB. MEANWHILE... OUTFLOW
BOUNDARY FROM SERN SD/NWRN IA MCS EXTENDED SWWD THROUGH NERN TO
CENTRAL NEB.

INHIBITION HAS WEAKENED DOWNSTREAM ACROSS FAR SRN MN AND ALL OF IA
WHERE STRONG SURFACE HEATING /TEMPERATURES IN THE MID 80S TO AROUND
90/ WITHIN A VERY MOIST AIR MASS ARE SUPPORTING MLCAPE OF 2500-3000
J/KG. GIVEN THE DEGREE OF INSTABILITY AND SUFFICIENT DEEP LAYER
SHEAR FOR STORM ORGANIZATION...FORWARD PROPAGATING MCS IS EXPECTED
TO CONTINUE TO MOVE TO THE ESE WITH A CONTINUE THREAT FOR DAMAGING
WINDS AND LARGE HAIL. DISCRETE STORMS WILL ALSO HAVE THE POTENTIAL
TO PRODUCE A TORNADO. ADDITIONAL STRONG TO SEVERE TSTM DEVELOPMENT
IS ALSO POSSIBLE IN ADVANCE OF MCS ACROSS WW 434...WHERE THE AIR
MASS IS UNCAPPED AND VISIBLE IMAGERY ALREADY INDICATED DEVELOPING CU
FIELD.

FARTHER W...WEAKER SHEAR INTO NERN NEB APPEARS TO BE LIMITING TSTM
ORGANIZATION ALONG THE SEWD MOVING OUTFLOW BOUNDARY. MEANWHILE...
VISIBLE/REGIONAL RADAR IMAGERY INDICATED DEEPENING ACCAS CLOUDS OVER
CENTRAL SD /ALONG AND WEST OF WW 433/ IN THE VICINITY OF THE WAKE
LOW IN REGION OF INCREASING LOW LEVEL CONVERGENCE. GIVEN MODERATE
INSTABILITY AND STRONG DEEP LAYER SHEAR OVER SRN SD/NRN
NEB...POTENTIAL WILL EXIST FOR ADDITIONAL TSTM DEVELOPMENT AND
ATTENDANT SEVERE THREAT AS ACTIVITY MOVES EWD INTO WW 433.

.PETERS.. 06/21/2007

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

ATTN...WFO...MKX...DVN...ARX...MPX...DMX...FSD...OAX...ABR...GID...LBF...UNR...

44619658 44619585 45019412 44659193 44149048 43279013
41939036 41739068 41799401 41859575 41589713 41639819
42099952 42550018 43440036 44389968 44689915

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