Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1238 AM CDT Tue Aug 27 2024
Valid 271200Z - 281200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE GREAT
LAKES AND PORTIONS OF THE MIDWEST...
...SUMMARY...
Severe thunderstorms are possible across the Great Lakes region and
portions of the Midwest. A lower risk for a few strong/severe storms
will extend southwest across the lower Missouri Valley into northern
Kansas.
...Great Lakes/Midwest...
Seasonally strong short-wave trough is advancing into the northern
High Plains early this morning. This feature is forecast to shift
into the eastern Dakotas by 18z as a 500mb speed max translates
across southern MN. Gradual deamplification is expected during the
latter half of the period as the short wave ejects across the upper
Great Lakes. At the surface, primary synoptic boundary is forecast
to extend across the eastern U.P. of MI-central WI-central
IA-southern NE at the start of the period. Westerly flow will deepen
across the Great Lakes region by midday, and this will encourage the
surface front to shift downstream as west-southwesterly LLJ
strengthens across southern WI/Lower MI.
Long-lived, mature MCS is currently propagating across
northern/central WI, in line with latest HREF guidance. This complex
of storms will track across northern Lake MI into Lower MI later
this morning as it turns southeast. Convective outflow will likely
influence subsequent thunderstorm development ahead of the short
wave/surface front. Latest thinking is modest boundary-layer heating
will extend across northern IL into extreme southern WI, east into
the northern OH Valley region. This will be the northern extent of a
very unstable airmass which should support afternoon thunderstorm
development/intensification. It's not entirely clear where the
early-day outflow will establish itself, and uncertainty
necessitates some caution trying to focus higher severe
probabilities. Even so, there may be a need to expand SLGT risk a
bit south if the boundary advances further than currently expected.
Severe gusts and hail are the primary risks with convection today.
Farther southwest across the lower MO Valley into northern Kansas,
very strong surface heating will negate CINH and convective
temperatures will be easily breached as readings rise through the
mid 90s. Isolated-scattered thunderstorms may focus along the
synoptic front, though this activity will evolve within a vertical
wind profile that is fairly weak and supports mostly pulse to
multicell updrafts. In the absence of any short-wave trough, surface
heating will prove instrumental in thunderstorm development, and the
lack of a strong LLJ may also be a limiting factor in upscale
growth.
..Darrow/Squitieri.. 08/27/2024
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