Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0342 AM CDT Wed Sep 23 2020 Valid 261200Z - 011200Z ...DISCUSSION... Medium-range guidance is in reasonably good agreement that large-scale upper troughing will develop and subsequently amplify over the eastern CONUS this upcoming weekend into early next week. Meanwhile, a highly amplified upper ridge will likely develop over the western states in the same time frame. A surface cold front associated with the upper trough is forecast to move across parts of the Midwest, OH Valley, and Northeast from Day 4/Saturday through Day 6/Monday. Although mid-level flow should be quite strong as the frontal passage occurs, low-level moisture and related instability are forecast to remain rather limited. This casts uncertainty on whether any meaningful severe risk will develop across these regions. A reinforcing cold front attendant to another, stronger surface low may move across much of the central/eastern CONUS in the Day 6/Monday to Day 8/Wednesday time frame. Deep-layer shear should be strong as this second front progresses east-southeastward. However, instability may once again be fairly weak. Too much uncertainty exists regarding the both degree of instability and robust storm development with either cold front passage to include any 15% severe areas at this time.
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