Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0330 AM CDT Tue Sep 22 2020 Valid 251200Z - 301200Z ...DISCUSSION... An upper trough should advance eastward from the Pacific Northwest and northern Rockies to the northern/central Plains on Day 4/Friday. Low-level moisture is forecast to gradually increase ahead of this feature across parts of the Plains into the Upper Midwest and MS Valley. Warm mid-level temperatures may keep the warm sector capped across the Upper Midwest through much of the day Friday, although deep-layer shear is forecast to be rather strong. Still, elevated storms with a marginal severe threat may develop Friday night across a portion of this region as a low-level jet strengthens. The upper trough should continue eastward in tandem with a surface cold front this upcoming weekend. However, substantial differences in medium-range guidance emerge by Day 5/Saturday regarding the timing/amplitude of this trough, related surface features, and the degree of low-level moisture return. Depending on the upper trough's evolution, an isolated/marginal severe risk may exist across parts of the southern and eastern CONUS from Day 5/Saturday into early next week. Regardless, far too much uncertainty exists to include 15% severe probabilities at this extended time frame.
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