SPC AC 081300
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0800 AM CDT Sun Aug 08 2021
Valid 081300Z - 091200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE OZARKS TO
WISCONSIN/LAKE MICHIGAN VICINITY...
...SUMMARY...
Severe thunderstorms are possible mainly this afternoon and evening
from Wisconsin and Iowa southward to the Ozark Plateau. Isolated
severe storms are also possible across portions of Montana.
...Missouri/Ozark Plateau to Wisconsin...
Another relatively complex scenario exists across a broad region
under the influence of lingering early day convection and multiple
MCVs, with the most prominent MCV across western Iowa early this
morning. Ahead of the Iowa MCV, moderate to locally strong
destabilization is expected later this afternoon across
southern/eastern Wisconsin to the south of early day west/east
corridor of warm conveyor-related scattered showers and
thunderstorms. Weakening inhibition should lead to at least isolated
severe thunderstorm development by mid/late afternoon.
Farther south, have expanded the Slight Risk southward across more
of Missouri/Ozark Plateau, where 35-40 kt effective shear should
coincide with moderate to strong buoyancy, with the latter expected
to be maximized across southeast Kansas/southwest Missouri/northeast
Oklahoma. Multiple corridors of severe thunderstorm development
should occur, potential including supercells across the Ozark
Plateau vicinity including southern Missouri and potentially nearby
southeast Kansas/far northeast Oklahoma. Large hail and damaging
winds are a possibility, and a tornado or two could also occur.
...Western/northern Iowa and far southern Minnesota...
A somewhat separate mesoscale regime will exist across this
sub-regional area later this afternoon/early evening, with the
potential for at least isolated severe thunderstorm development.
This would be near a weak surface low/boundary layer, potentially
influenced by a weak remnant MCV/vort max immediately behind the
parent upper trough axis. Along these lines, various
convection-allowing guidance suggests that locally intense storm
development is plausible. This area will be monitored/reevaluated in
subsequent outlooks for the possibility of a somewhat higher severe
risk (Slight Risk) over a relatively confined corridor.
...Montana...
A cold front will move east-southeastward across Montana today in
conjunction with a progressive shortwave trough. Ascent focused
along the front will support development of a band of convection by
mid/late afternoon, though weak instability will limit overall
convective intensity. Even so, isolated strong/locally severe wind
gusts will be possible. Marginally severe hail might also occur with
some of the initial development across west-central Montana.
..Guyer/Mosier.. 08/08/2021
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