Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0320 AM CDT Tue Sep 14 2021 Valid 171200Z - 221200Z ...DISCUSSION... An upper trough should move from central into eastern Canada on Day 4/Friday. The trailing portion of this trough may linger across parts of the Upper Midwest and Great Lakes vicinity. Greater low-level moisture should remain confined to the south of a front stretching from the central Plains to the Great Lakes. Any appreciable severe threat on Friday would likely be along/south of the front. But, both instability and deep-layer shear appear rather marginal for an organized severe risk. In addition, large-scale ascent across the warm sector appears nebulous behind the upper trough shifting eastward. Medium-range guidance is beginning to come into agreement that another large-scale upper trough should develop slowly eastward across the western CONUS this upcoming weekend into early next week. While low-level moisture is forecast to return northward across much of the central CONUS in this time frame, there are still substantial differences in the evolution of the upper trough and related surface features. Potential for organized severe storms currently appears fairly muted from Day 5/Saturday onward, but predictability also remains rather low.
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