SWOMCD
SPC MCD 082236
WIZ000-MNZ000-090000-
MESOSCALE DISCUSSION 1829
NWS STORM PREDICTION CENTER NORMAN OK
0536 PM CDT SAT AUG 08 2009
AREAS AFFECTED...CNTRL/SRN MN INTO NWRN WI
CONCERNING...TORNADO WATCH 677...678...
VALID 082236Z - 090000Z
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 677...678...CONTINUES.
UNCERTAINTY EXISTS AS TO WHETHER ADDITIONAL SURFACE-BASED STORM
DEVELOPMENT WILL OCCUR ACROSS REGION THIS EVENING. SOME HAIL WILL
REMAIN POSSIBLE WITH ELEVATED STORMS OVER PORTIONS OF WI.
LATEST MESOANALYSIS INDICATED SURFACE LOW S RWF WITH ASSOCIATED WARM
FRONT LIFTING NWD...EXTENDING FROM CYCLONE NEWD TO N OF MSP AND THEN
MORE EWD TO S OF RHI AS OF 22Z. AIR MASS ALONG AND S OF WARM FRONT
REMAINS WARM AND QUITE MOIST WITH MLCAPE OF 2000-3000 J/KG.
HOWEVER...MODIFICATION OF 18Z MSP SOUNDING FOR CURRENT SURFACE
CONDITIONS AND PROXIMITY AMDAR DATA INDICATE THAT A CAP STILL EXISTS
ACROSS THE WARM SECTOR. MOREOVER...WATER VAPOR IMAGERY SUGGESTS
THAT SHORT WAVE TROUGH /WHICH MOVED THROUGH PARTS OF NEB AND SD
EARLIER TODAY/ IS BEGINNING TO LOSE AMPLITUDE AS IT APPROACHES
MIDLEVEL RIDGE AXIS CENTERED OVER THE UPPER GREAT LAKES.
THUS...IT APPEARS THAT WEAKENING FORCING FOR ASCENT AND THE
MAINTENANCE OF A CAP HAVE LIKELY CONTRIBUTED TO THE DEMISE OF
LONG-LIVED SUPERCELL WHICH MOVED INTO SWRN MN EARLIER TODAY.
A BAND OF ELEVATED TSTMS HAS RECENTLY DEVELOPED FROM NE OF MSP TO
NEAR CWA...APPARENTLY DRIVEN BY MOISTENING/ASCENT ABOVE CAP. ASIDE
FROM THIS ACTIVITY...THERE IS SOME QUESTION AS TO WHETHER ADDITIONAL
SURFACE-BASED STORM DEVELOPMENT WILL OCCUR THIS EVENING. THE MOST
PROBABLE AREA APPEARS TO BE SRN MN WITHIN LOW-LEVEL THERMAL AXIS
WHERE STRONG DIABATIC HEATING MAY BE SUFFICIENT TO LOCALLY BREACH
CAP. EVEN IF STORMS DEVELOP...AREA VWPS AND PROFILER DATA INDICATE
THAT THE STRONGER LOW-LEVEL SHEAR HAS BECOME DISPLACED WELL TO THE N
INVOF WARM FRONT. THUS...THE PRIMARY SEVERE THREATS WOULD BE HAIL
AND STRONG WIND GUSTS WITH ANY STORMS THAT CAN BECOME ESTABLISHED.
..MEAD.. 08/08/2009
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...DLH...ARX...MPX...
LAT...LON 43879454 44509511 45119531 45769470 46039296 45929112
45069062 44159134 43669252 43879454
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