MD 2087 CONCERNING SEVERE THUNDERSTORM WATCH 669… FOR UPPER-MISSISSIPPI VALLEY VICINITY
Mesoscale Discussion 2087
NWS Storm Prediction Center Norman OK
0609 PM CDT Tue Sep 05 2023
Areas affected…Upper-Mississippi Valley Vicinity
Concerning…Severe Thunderstorm Watch 669…
Valid 052309Z – 060045Z
The severe weather threat for Severe Thunderstorm Watch 669
continues.
SUMMARY…Strong to severe storms remain possible along an outflow
boundary in east-central MN and northwest WI as well as within a
confluence band along the MS River. Large hail (1-1.75 in.) and
damaging winds (50-60 mph) will be the primary threats.
DISCUSSION…The strongest activity in WW 669 is currently west of
Duluth. The supercell storm in Aitkin County, MN is just north of an
outflow boundary. With the stronger forcing from an upstream trough
in this area, it seems possible that this activity could continue
even if its inflow is more likely to be convectively processed with
time.
Farther south, roughly from the Twin Cities southward to the MN
border, a pre-frontal confluence band has shows signs of increasing
cumulus development on visible satellite. Shear is weaker with
southward extent, though shear vectors are slightly more orthogonal
to the confluence band and may support marginally more discrete
storms initially. Convective coverage is more questionable given
weaker forcing.
The greatest threat for severe weather will exist with storms that
can anchor along the outflow boundary along with any discrete storms
that can develop within the confluence band. Large hail (1-1.75 in.)
and damaging winds (50-60 mph) will be the primary threats.
..Wendt.. 09/05/2023
…Please see www.spc.noaa.gov for graphic product…
ATTN…WFO…DLH…ARX…MPX…
LAT…LON 44599176 43879191 43599225 43549289 43679328 43979346
44589338 45599364 46069444 46269454 46599432 47009314
47159202 47169155 47139140 46779136 45899145 44599176
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