SPC MD 2045



MD 2045 CONCERNING SEVERE THUNDERSTORM WATCH 669… FOR SOUTHEAST MINNESOTA THROUGH NORTHWEST WISCONSIN

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Mesoscale Discussion 2045
NWS Storm Prediction Center Norman OK
0833 PM CDT Mon Sep 30 2019

Areas affected...southeast Minnesota through northwest Wisconsin

Concerning...Severe Thunderstorm Watch 669...

Valid 010133Z - 010230Z

The severe weather threat for Severe Thunderstorm Watch 669
continues.

SUMMARY...Storms will continue to pose a modest threat for locally
strong wind gusts and hail through 03Z from southeast Minnesota
through northwest Wisconsin. Storms will approach the eastern bound
of WW 669 between 02-03Z, but given convective trends and the
somewhat marginal nature of the remaining threat, a downstream WW is
not anticipated.

DISCUSSION...A broken band of storms persists from northwest WI into
southeast MN moving east at near 30 kt. Some marginal supercell
structures continue to be observed, but overall intensity of the
storms have remained below severe levels so far. Despite presence of
moderate instability with 2000-2500 J/kg MLCAPE, the 00Z RAOB from
Minneapolis confirms presence of a warm layer between 700 and 500 mb
resulting in a top-heavy CAPE that is limiting low-level updraft
accelerations. This RAOB also sampled the dry air in the 700-500 mb
layer which is also likely mitigating mid-level updraft strength
through the effect of dry air entrainment. Storms remain embedded
within a favorable kinematic environment with sizeable low-level
hodographs and 50 kt effective bulk shear, which will continue to
support occasional supercell structures. But given a stabilizing
boundary layer along with the previously mentioned limitations in
the thermodynamic environment, the remaining threat will probably
begin to wane by 03-04Z.

..Dial.. 10/01/2019

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...DLH...ARX...MPX...

LAT...LON   43719402 44659323 45729262 46039232 46109179 45859119
            44979127 44019233 43529354 43719402 

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