SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1248 AM CDT Wed Oct 21 2020 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MIDWEST AND CENTRAL PLAINS... ...SUMMARY... Thunderstorms associated with marginally severe hail and strong wind gusts will be possible in the Upper Midwest Thursday evening. The hail threat could extend into parts of the central Plains. ...Upper Midwest/Central Plains... An upper-level trough will move into the Rockies on Thursday as southwest mid-level flow becomes established from the central Plains to the Great Lakes. At the surface, a strong cold front will advance southeastward across the central Plains, mid Missouri Valley and upper Mississippi Valley. Strong low-level convergence will likely result in thunderstorm development just behind the front Thursday evening. Although the strongest instability will be ahead of the front, weak instability and moderate deep-layer shear is forecast behind the front. Thunderstorms that develop in this environment could have a hail threat. Isolated thunderstorms may also initiate ahead of the front in the stronger instability. In the pre-frontal airmass, MLCAPE is forecast to be near 1000 J/kg with 0-6 km shear of 30 to 40 kt. Although conditional, rotating storms would be possible in this environment. For this reason, hail, strong gusty winds and a marginal tornado threat would be possible. Further southwest into the central Plains, thunderstorm development is forecast just behind the front during the mid to late evening. Although instability will be weak behind the front, 0-6 km shear is forecast to be in the 40 to 50 kt range. This would be enough for a marginal hail threat with the stronger thunderstorms. ..Broyles.. 10/21/2020
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