SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1221 AM CDT Wed Apr 09 2025 Valid 091200Z - 101200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are possible across portions of the Midwest, the Upper Midwest, and the northern High Plains, though severe storms are not expected. ...Synopsis... A shortwave trough in the northern Plains early this morning will move southeastward into the mid-Mississippi Valley and undergo modest amplification. A weak surface low will move swiftly southeastward along with the trough. A warm front will be positioned within parts of the Upper Midwest with a cold front southwestward from the low into the central/southern Plains. With the recent intrusion of cooler air into much of the Gulf, moisture availability will be quite limited -- which is also quite evident in this evenings observed soundings in the Southeast. Even so, some thunderstorm activity will be possible as warm-air advection into the warm front promotes lift. To the northwest of the surface low, steep low/mid-level lapse rates may allow for isolated to widely scattered storms in parts of the northern/central Plains. ...Mid-Mississippi/Lower Ohio Valleys... Showers and thunderstorms are possible early this morning driven by the amplifying shortwave trough and low-level warm advection. Mid/upper-level clouds are already moving into the region late on Tuesday and forecast soundings suggest some cloud cover will persist into the afternoon as well. With a generally dry boundary layer and weak destabilization, most activity in Illinois into the Ohio Valley region will likely be elevated. severe potential appears quite limited, but small hail could occur with the strongest storms. Closer to the surface low/cold front in northeastern Missouri and far west-central Illinois, it is possible that greater destabilization could occur. Models show some signal for a narrow zone of greater moisture return ahead of the front and these areas will be on the eastern periphery of a steep mid-level lapse rate plume. Current surface observations still suggest the moisture return depicted in models may be too aggressive. If upper 40s F dewpoints can reach farther north than expected, there would be some potential for a surface based storm. The upper-bound severe potential would likely be marginally severe hail. Uncertainty is too high and coverage is too low for unconditional severe probabilities. ...Lower Missouri Valley Vicinity... Despite dewpoints around the mid 30s F, very cold temperatures aloft (-20 to -24 C at 500 mb) will support isolated to widely scattered convection during the afternoon. Buoyancy is expected to be quite weak, but large boundary layer dewpoint depressions could promote some stronger wind gusts. ..Wendt/Squitieri.. 04/09/2025