SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0754 AM CDT Sat Jul 23 2022
Valid 231300Z - 241200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE UPPER MIDWEST AND SOUTHERN GREAT LAKES REGIONS...
...SUMMARY...
Damaging thunderstorm gusts (some over 75 mph), a few tornadoes and
large to very large hail will be possible today across parts of the
Upper Midwest and southern Great Lakes regions.
...Synopsis...
A zonally elongated, mid/upper-level cyclone will persist over the
southern Hudson Bay region. With that orientation, the flow belt to
its southwest through southeast -- across the north-central/
northeastern CONUS, will be zonal to gently cyclonic through the
period, with the cyclonic influence mainly related to a series of
shortwave troughs now apparent in moisture-channel imagery over the
northern Plains and Canadian Prairie Provinces. The
leading/southern such trough -- now over parts of western ND and
eastern MT -- will influence convective potential most directly.
This perturbation will move east-southeastward to the MN Arrowhead
and southeastern MN/western WI by 00Z. Then with some convective
vorticity enhancement, the perturbation should cross Lake Michigan
and Lower MI overnight.
At the surface, 11Z analysis showed a low in central SD near PIR,
with warm front across eastern SD, northern IA, and southern WI,
becoming diffuse north of a complex of severe thunderstorms in IN.
A cold front was drawn from the low southwestward across
southwestern SD to east-central/central WY. The low should move to
southern MN by 00Z, perhaps diffused by convective processes, with
cold front southwestward across northeastern NE, northwestern KS and
southeastern CO. The warm front also may be somewhat muddled by
convection, but in general, should extend from the low across
central to northern parts of WI, Lake Michigan and Lower MI to parts
of OH and western PA. By 12Z, the low should reach the eastern Lake
Superior/eastern Upper MI vicinity, with cold front over southern
WI, southern IA, and west-central KS, to another low near the
CO/KS/OK border junction.
...Upper Midwest and southern Great Lakes...
Complexes of thunderstorms are expected to cross the corridor today
from the northeastern Plains across the southern Great Lakes to the
mid/upper Ohio Valley, offering severe gusts throughout, as well as
a threat for significant gusts, a few tornadoes and large to very
large hail in and near the "enhanced" area.
Two main convective regimes already are apparent to anchor the
broader outlook. The first -- initially over northern parts of
IL/IN -- is expected to continue merging/growing into a quasi-linear
MCS and move southeastward into a moist and destabilizing air mass
(from both warm advection and diurnal heating). See SPC
severe-thunderstorm watches 487 and 488, and related mesoscale
discussions, for near-term coverage of this activity. Present
indications are this complex will move out of the most favorably
moist/buoyant corridor near or just past the Ohio River. Severe
probabilities have been expanded considerably southeastward from the
previous outlook to account for this activity.
The second, but potentially most damaging, may evolve upscale from
strong-severe convection now over northern SD. For near-term
coverage of the morning through midday severe threat, see SPC
severe-thunderstorm watch 489 and related mesoscale discussions.
This activity should move east-southeastward along a pronounced
low-level instability gradient and near a moist axis, each
associated with the warm front, with large available low/middle
level lapse rates apparent on modified 12Z MPX/OAX soundings. This
activity also ultimately will encounter a diurnally destabilizing
and very moist air mass across MN, with theta-e advection aiding in
supportive airmass recovery at least into WI and adjoining parts of
Lake Michigan. 3000-5000 J/kg MLCAPE, 40-55 kt effective-shear
magnitudes, and effective SRH of 200-400 J/kg will present a
favorable parameter space for all severe types across southern MN
into parts of WI, with localized storm mode driving relative
distribution of hail and wind, and at least a few tornadoes
expected. Extent of recovery into Lower MI is uncertain at this
time, but at least marginally favorable buoyancy should sustain a
wind threat across the lake and into that region this evening.
..Edwards/Gleason.. 07/23/2022
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/SVNpdr
