Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0356 AM CDT Mon Jun 21 2021 Valid 241200Z - 291200Z ...DISCUSSION... An upper trough should gradually amplify over the north-central states late this week into the upcoming weekend. Multiple low-amplitude mid-level perturbations should move eastward across the northern/central Plains to the Midwest in the same time frame, encouraging convective development each day. An EML emanating from the Rockies and High Plains should extend eastward into parts of the Upper Midwest on Day 4/Thursday. This EML coupled with increasing low-level moisture and diurnal heating should support moderate to perhaps locally strong instability ahead of a front which should be located from parts of the northern/central Plains to the Upper Midwest by Thursday afternoon. At least some severe risk is evident across these regions along/ahead of the front as deep-layer shear appears adequate. But, there is still considerable uncertainty regarding the placement of convective development. Predictability remains too low at this time to include a 15% severe area across any portions of the central Plains or Upper Midwest for Thursday, but severe probabilities will likely be needed in a later outlook. An isolated severe threat may continue on Day 5/Friday across parts of the mid MS Valley and Midwest as the upper trough becomes established over the north-central CONUS. However, there may be considerable convection ongoing Friday morning, which limits confidence on where the greatest instability will exist ahead of a front. A lingering threat for organized severe storms may persist this upcoming weekend across parts the southern Plains to the OH Valley, but predictability remains low.
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