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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.

Monday, August 23, 2021

SPC Aug 23, 2021 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Mon Aug 23 2021 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN HIGH PLAINS TO PARTS OF MINNESOTA/IOWA... ...SUMMARY... A few strong/severe storms may occur across portions of the northern High Plains/northern Plains and eastward across the Mid Missouri Valley vicinity on Wednesday. ...Synopsis... Large-scale ridging will continue to prevail across a large portion of the U.S. Wednesday, though steady advance of a trough across the western U.S. will begin to impinge on the western fringe of the ridge's dominance. At the surface, a baroclinic zone extending from the Upper Great Lakes to the central Plains initially will weaken with time, while a second front advances across the West, in tandem with upper troughing. ...Northern High Plains east to southern Minnesota/northwestern Iowa... In the wake of early/ongoing convection gradually shifting eastward/away from the Plains, subtle height rises are expected across the north-central U.S. through the day. Resulting subsidence/capping should hinder convective development in most areas, though a couple of surface-based storms may redevelop over the Mid Missouri Valley vicinity near the weakening/remnant surface front. With moderate mid-level westerlies progged atop the region, a stronger storm or two could produce severe-caliber hail/wind. An increase in low-level warm advection after dark could sustain the convection, which would then spread eastward across Iowa, but with diminishing severe potential with time. Farther north and west, more pronounced warm advection is expected into the evening, as a southeasterly low-level jet develops across the northern and central High Plains in response to weak height falls ahead of the progressing western trough. Atop a cooling boundary layer, steep mid-level lapse rates/ample CAPE could support risk for isolated elevated/rotating storms, with a few potentially capable of producing large hail. This hail risk, spreading eastward with time, may extend across the Dakotas through the end of the period. ..Goss.. 08/23/2021 Read more LIVE: