Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0359 AM CDT Thu Oct 08 2020 Valid 111200Z - 161200Z ...DISCUSSION... Medium-range guidance indicates that the westerlies will undergo considerable further amplification during this period. It appears most certain that mid-level ridging will build along a sharpening axis just west of the U.S. Pacific coast into British Columbia. Downstream, ensemble output depicts broad mean troughing east of the Rockies through the Atlantic Seaboard by late next week, but solutions are rather dispersive concerning embedded short wave developments. Greatest certainty exists concerning mid/upper trough amplification along a negatively tilted axis east of the Rockies through the upper Mississippi Valley late this weekend into early next week. This is forecast to be accompanied by significant surface cyclogenesis across Saskatchewan into the vicinity of Hudson Bay, with a trailing cold front surging across and east of the U.S. Great Plains. The most appreciable severe weather potential with this system still appears to exist on Sunday, across eastern portions of the northern Great Plains into the upper Mississippi Valley. The extent of northward moisture return in the wake of Delta remains uncertain, and could remain fairly marginal for vigorous convective development. However, a plume of initially steep lapse rates associated with elevated mixed-layer air may still contribute to a pre-frontal corridor of sufficient conditional and convective instability to support severe thunderstorm development. Aided by 40-50+ kt mean lower/mid tropospheric flow, severe wind gusts may be the primary hazard across the eastern Dakotas into Minnesota and parts of the middle Missouri Valley. With the suppression of the elevated mixed layer, severe weather potential east-northeastward into the upper Great Lakes region on Monday still looks more marginal due to less favorable thermodynamic profiles. Through the remainder of the period, pattern predictability remains problematic, but severe weather potential still appears generally low at this time.
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