Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1230 PM CDT Tue Oct 27 2026

Valid 281200Z - 291200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
UPPER MISSISSIPPI VALLEY...

...SUMMARY...
Isolated severe thunderstorms are possible over the Upper
Mississippi Valley on Wednesday.

...Synopsis...
Broad mid-level troughing will encompass the upper air pattern over
much of the CONUS on Wednesday, with a pronounced embedded impulse
poised to traverse the northern Plains and impinge on the Upper MS
Valley by late afternoon into early evening. The approach of this
mid-level impulse will support rapid surface troughing over the
Upper MS Valley, with some low-level moisture return expected. While
buoyancy will be relatively weak, strong tropospheric flow
accompanying the passing mid-level and surface troughs, along with
adequate deep-layer ascent, will promote thunderstorm development
over the Upper MS Valley by evening. There is some potential (albeit
conditional) that a couple of these thunderstorms may become severe.

...Upper MS Valley...
As the surface trough intensifies through the day, a narrow ribbon
of 60+ F surface dewpoints will advect northward ahead of the
trough, beneath 7+ C/km mid-level lapse rates, contributing to
500-1000 J/kg MLCAPE. Furthermore, the strengthening of the surface
trough will also encourage the development of a 40+ kt
south-southwesterly low-level jet just before sunset, when buoyancy
should be relatively maximized. Considerable veering and
strengthening flow fields with height will support enlarged and
curved low-level hodographs, especially closer to a warm front along
the MN/WI border. 

The vertical shear profile and expected MLCAPE magnitudes would
certainly support supercells capable of producing all severe
hazards. However, potential cloud cover may inhibit robust
boundary-layer heating, and some MLCINH may linger just above the
boundary layer as well. Therefore, any surface-based severe
potential that can materialize will be highly dependent on stronger
surface heating and subsequent CIN erosion. Still, at least some
elevated buoyancy may be realized in the absence of stronger surface
heating, so thunderstorms forced along the lee trough/cold front may
still be accompanied by a hail threat.

..Squitieri.. 10/27/2026