Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0736 AM CDT Tue Oct 21 2025
Valid 211300Z - 221200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR A PORTION OF
THE SOUTHERN GREAT LAKES...
...SUMMARY...
Isolated strong to locally severe gusts are possible this afternoon
over a portion of the southern Great Lakes.
...Southern Great Lakes...
Morning water-vapor imagery indicates an upper vorticity maximum
over western IA will quickly rotate through the base of a
larger-scale trough/mid-level low centered over the Upper
Midwest/Great Lakes. This upper feature is forecast to move across
the southern Great Lakes during the afternoon as a belt of intense
mid- to high-level flow arcs from the north-central Plains through
the MS/OH Valleys and into the Mid-Atlantic states. The mid-level
cold pocket (-24 to -27 deg C at 500 mb) will overspread a boundary
layer with surface temperatures rising into the lower 60s
immediately ahead of a cold front. Latest RAP/NAM/HRRR model
guidance shows a plume of 0-3 km lapse rates in excess of 9 deg C/km
protruding northeast from IN into northwest OH as widely scattered
convection develops during the early to mid afternoon. As this
shallow convection matures, strong to locally severe gusts (50-65
mph) are possible for a few hours before this activity weakens by
the early evening as it spreads across the Lake Erie vicinity.
Elsewhere, isolated thunderstorms are possible over portions of
northwest Gulf Coast states into the southern Appalachians, and late
tonight over portions of southern New England.
..Smith/Bentley.. 10/21/2025
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