Convective Outlook
— Day 2
No Severe Thunderstorms 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.
000 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 $$