Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0355 AM CDT Sun Jun 20 2021 Valid 231200Z - 281200Z ...DISCUSSION... Medium-range guidance is starting to come into better agreement regarding the synoptic-scale pattern across the CONUS from the middle to latter portion of the upcoming week. Upper ridging centered over the Rockies on Day 4/Wednesday should become suppressed through Day 6/Friday as multiple shortwave troughs evolve across south-central Canada, the northern Plains, and Midwest. Low-level moisture is still forecast to return northward ahead of these mid-level perturbations, and an EML emanating from the High Plains may advect as far east as the mid/upper MS Valley and Midwest by Day 5/Thursday. A cap may inhibit robust storm development across the Midwest on Day 4/Wednesday. Still, the severe risk should increase as both instability and shear are forecast to strengthen by Day 5/Thursday. Portions of southern MN into IA and vicinity may have the best potential for severe storms on Day 5/Thursday, but predictability regarding the timing and placement of these shortwave troughs remains too uncertain to introduce a 15% severe area. Some severe threat may continue on Day 6/Friday across parts of the Midwest and mid MS Valley ahead of a cold front, as an upper trough/low possibly amplifies and develops from the north-central CONUS towards the Great Lakes. Read more LIVE: spc.noaa.gov
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