Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0358 AM CDT Wed Oct 21 2020 Valid 241200Z - 291200Z ...DISCUSSION... ...Saturday/Day 4 to Sunday/Day 5... The medium-range models are in decent agreement on Saturday, establishing southwest flow from the Great Plains into the Great Lakes. At the surface, a cold and dry airmass will be in place across much of the central and northeastern U.S. Thunderstorms could develop in parts of the Gulf Coast States Saturday afternoon but weak instability is expected to limit any severe threat. On Sunday, the models reinforce the cold airmass in the central U.S. as a front moves quickly southward into the southern Plains and mid Mississippi Valley. Thunderstorms will be possible along the front, mainly from the mid Mississippi Valley into the southern Great Lakes. Instability will most likely be weak ahead of the front, keeping any severe threat marginal Sunday afternoon. ...Monday/Day 6 to Wednesday/Day 8... Southwest mid-level flow is maintained by the model solutions on Monday and Tuesday as a cold front moves from the Ohio and Tennessee Valleys into the Southeast. Thunderstorms could develop along the front Monday and Tuesday afternoon. However, instability is forecast to be very weak suggesting a severe threat would be limited. On Wednesday, the models solutions diverge. Some models move an upper-level low into the southern Plains during the day. Other solutions move the upper-level low through the Desert Southwest. This solutions move the system into the central Rockies Wednesday night. Under that scenario, thunderstorms associated with a marginal severe risk could develop in the Red River Valley Wednesday night as low-level moisture return occurs. However, uncertainty is very high due to the large spread of model solutions.
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