ACUS02 KWNS 200549
SWODY2
SPC AC 200547

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1247 AM CDT Mon Apr 20 2026

Valid 211200Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms will be possible across the western CONUS, the
south-central CONUS, and the southern Great Lakes on Tuesday.
Potential for severe weather appears low.

... Synopsis ...

Midlevel ridging will be in place from the eastern Great Basin into
the Plains at the start of the forecast period, while persistent
northwesterly flow aloft continues across the Upper Midwest and Ohio
Valley. Farther west, an upper trough will gradually advanced inland
across California into the Great Basin by the end of the period.

At the surface, a broad area of high pressure centered over the
Southeast and adjacent Atlantic will maintain southerly flow across
the central US. This will promote a gradual moisture recovery across
the central Plains into the southern Great Lakes. A weak frontal
boundary pushing south through portions of the central Plains and
Great Lakes will denote the northern edge of the moisture return.

... Lower Great Lakes ...

Thunderstorm development along the frontal zone may be delayed until
later in the day or evening as moisture slowly returns northward.
While relatively cold temperatures aloft should support steep lapse
rates, the quality and depth of the boundary-layer moisture is
expected to be the biggest unknown. The NAM is the most aggressive
with the depth and quality of the moisture return, and if moisture
quality is close to what is shown in the NAM, enough instability
should materialize to take advantage of the stronger vertical shear
to support a few organized cells capable of gusty winds or small
hail. However, most model guidance is less aggressive with the
quality of the moisture return so no probabilities have been added
at this time.

... South-central US ...

Convection will likely be ongoing at the start of the forecast
period. Modest vertical shear and elevated instability may support a
couple strong thunderstorms capable of hail and gusty winds.
However, overall thunderstorm intensity should wane through much of
the period as upper ridging overspreads the region.

... Western US ...

As the upper trough moves inland, ascent will increase across the
Pacific Northwest, northern California, and portions of the Great
Basin. Within the Central Valley and nearby terrain, pockets of
diurnal heating, combined with cool midlevel temperatures may
support isolated thunderstorm development during the afternoon.
Despite this modest instability, weak vertical shear should limit
any organized severe potential.

..Marsh.. 04/20/2026

$$
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