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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, June 25, 2021

SPC Jun 25, 2021 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0223 AM CDT Fri Jun 25 2021 Valid 271200Z - 281200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF CENTRAL/EAST-CENTRAL ILLINOIS...NORTHERN INDIANA...FAR NORTHWEST OHIO...AND LOWER MICHIGAN... ...SUMMARY... Isolated severe thunderstorms are possible across portions of central/east-central Illinois, northern Indiana, far northwest Ohio, and Lower Michigan Sunday afternoon. ...Synopsis... A strong Rex block, with the high centered over southern British Columbia and the low centered well off the northern CA coast (near 130W), will likely be in place over the western CONUS early Sunday. Farther east, the western periphery of an expansive upper ridge (centered well off the Mid-Atlantic coast over the western Atlantic Ocean) will cover much of the eastern CONUS. Upper troughing will exist between these two features, likely extending from the Upper Midwest through the Southwest on Sunday morning. At the surface, a low is forecast to begin the period over southern WI, with an attendant cold front extending back southwestward into the southern High Plains. This low is expected to progress northeastward throughout the day while the associated front becomes increasingly diffuse. However, even as the front weakens, low-level convergence within the moist and unstable air mass will likely be enough to promote thunderstorm development. Much of this thunderstorm development will occur in a weakly sheared environment with the cold front/composite outflow displaced south and east of the stronger mid-level flow. The only exception will be in the vicinity of the surface low as it moves from southern WI across Lower MI. Here, a few more organized updrafts are possible, with an attendant threat for damaging wind gusts, isolated hail, and perhaps a tornado or two. Higher severe probabilities may be needed in later outlooks once frontal position and the effects of antecedent precipitation are more certain. ..Mosier.. 06/25/2021 Read more LIVE: