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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.

Friday, August 27, 2021

SPC Aug 27, 2021 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1211 PM CDT Fri Aug 27 2021 Valid 281200Z - 291200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM FAR EASTERN SOUTH DAKOTA ACROSS MINNESOTA AND INTO NORTHWEST WISCONSIN... ...SUMMARY... Scattered to isolated severe storms will be possible Saturday from the western Upper Great Lakes/Upper Mississippi Valley region, southwestward to the central High Plains. ...Synopsis... An upper trough will move eastward across the northern Plains on Saturday, reaching the upper MS Valley early Sunday. This wave will have a positive tilt, with midlevel southwesterlies of 50-60 kt. Ahead of this trough, an upper ridge will shift into the Northeast, with an upper high over the Carolinas. A surface trough will deepen during the day, roughly from southwest MN into eastern CO ahead of a cold front. Southerly winds ahead of this trough will maintain a moist and unstable air mass, which when combined with the strong flow aloft will result in severe storm potential from Nebraska into Upper Michigan. Elsewhere, Ida is forecast to become a hurricane over the central Gulf of Mexico, with the stronger shear and instability expected to remain offshore. ...Northern Plains into the Great Lakes... Southwest flow aloft will gradually increase as the upper trough shifts east, with deep-layer shear of 40-50 kt common by late afternoon, with vectors oriented nearly parallel to the surface front. The exception will be near the warm front from central MN into northern WI which may prove most favorable for supercells or rotation embedded within a line. Here, effective SRH is expected to average 200-300 m2/s2. Scattered showers or storms may occur early in the day from eastern SD into MN where low-level theta-e advection will be maximized. Marginal hail cannot be ruled out. Otherwise, increasing convergence along the front and an uncapped air mass by 21Z should result in rapid storm formation across eastern SD, northeast NE and western MN. A linear storm mode appears likely, with damaging wind potential spreading east. The very strong instability may support significant wind gusts. Aforementioned favorable SRH downstream of these storms may support supercell structures within the line as well. ..Jewell.. 08/27/2021 Read more LIVE: spc.noaa.gov