South Dakota Mesoscale Discussion

Areas affected…Portions of southern MN…northern/central IA…far
southwestern WI…and northeastern NE

Concerning…Severe Thunderstorm Watch 593…595…

Valid 180500Z – 180630Z

The severe weather threat for Severe Thunderstorm Watch 593, 595

SUMMARY…A strong to damaging wind threat continues across Severe
Thunderstorm Watch 593 and 595. Downstream watch issuance is
possible in the next 1-2 hours depending on observational trends.

DISCUSSION…A small bow echo is occurring across southwestern MN
into northwestern IA per recent radar imagery. Measured severe wind
gusts with this bow have generally remained sub-severe (50-56 mph)
over the past couple of hours. Still, isolated strong to damaging
wind gusts will remain possible with these storms as they continue
eastward across northern IA and south-central MN over the next
couple of hours. Instability decreases with eastward extent into
northeastern IA and far southwestern WI per 04Z mesoanalysis. This
lends some uncertainty to the intensity of this convection through
the overnight hours. But, a 35-45 kt southwesterly low-level jet and
similar values of effective bulk shear may support continued storm
maintenance/intensity. Depending on observational trends, a
downstream watch may be needed within the next 1-2 hours. In
addition, some backbuilding of convection along a surface cold front
may occur from northeastern NE into central IA. This activity would
also pose an isolated wind/hail threat. Severe Thunderstorm Watch
593/595 may need to be extended in area and/or time to account for
this potential.

..Gleason.. 08/18/2019

…Please see for graphic product…


LAT…LON 42559823 43089701 43189580 43369523 43859498 44329532
44619497 44039186 43679081 42529081 41849228 41679520
41709749 42559823

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