Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0350 AM CDT Sun Jul 25 2021 Valid 281200Z - 021200Z ...DISCUSSION... ...Wednesday/Day 4 to Friday/Day 6... A large area of high pressure is forecast to remain in place across the western and central U.S. from Wednesday to Friday. Northwest mid-level flow is forecast across the upper Mississippi Valley into the Great Lakes and Northeast. The medium-range models suggest that a shortwave trough will move quickly southeastward into the Great Lakes Wednesday into Wednesday night. If this happens, an MCS could develop across the upper Mississippi Valley and western Great Lakes Wednesday evening. This scenario would be favorable for a wind-damage threat associated with the MCS. Although some solutions show this scenario, others do not suggesting uncertainty is high early in the Day 4 to 8 period. On Thursday and Friday, a cold front is forecast to advance southward across the Ohio and Tennessee Valleys. Convection will be possible near the front both afternoons. Further west, moisture advection is forecast across eastern sections of the central Plains. Isolated thunderstorms could develop at the northern end of the moisture/instability corridor Friday afternoon from northern Nebraska into South Dakota. Although an isolated severe threat will be possible in the northern Plains and across part of the Ohio and Tennessee Valleys during this timeframe, the spatial distribution of any severe threat is low this far in the forecast range. ...Saturday/Day 7 and Sunday/Day 8... On Saturday and Sunday, a corridor of very moist air is forecast to remain anchored over the Mississippi Valley. Thunderstorm development will be possible both Saturday afternoon and Sunday afternoon along the northern edge of this moist airmass in the mid Missouri and upper Mississippi Valleys. Substantial directional shear in the low to mid-levels along with steep lapse rates will make isolated severe storms possible. However, confidence is low concerning any specific scenario this far out in the forecast cycle. Read more LIVE: spc.noaa.gov
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