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Weather conditions directly above are near Lakefront. Top tabs refer to O'Hare (official).

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.

Thursday, August 25, 2022

SPC Aug 25, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Thu Aug 25 2022 Valid 252000Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER WESTERN MONTANA AND ACROSS PORTIONS OF THE NORTH-CENTRAL HIGH PLAINS... ...SUMMARY... Isolated severe hail and thunderstorm gusts will be possible across portions of western Montana and the north-central High Plains today. ...Discussion... No appreciable change was made to the previous convective outlook. Minor adjustments were made to the 10-percent thunderstorm probability area based on visible-satellite imagery and lightning data. ..Smith.. 08/25/2022 .PREV DISCUSSION... /ISSUED 1120 AM CDT Thu Aug 25 2022/ ...Western MT... Slow-moving closed upper low over near the international border in the vicinity of northern ID will begin to move slowly east late today. Diurnal heating of initially 50s surface dew points will result in a deep mixed layer, and steep midlevel lapse rates will contribute to 1000-1500 J/kg MLCAPE this afternoon. Although winds throughout the cloud-bearing layer will be generally modest (30 kts or less), veering low/midlevel flow will contribute to 30-35 kts of effective shear. Widely scattered to scattered thunderstorm development is expected this afternoon across western MT, with multicell/supercell modes possible. Deep mixed layer will result in a risk for isolated severe wind gusts, and large hail will be possible with a few stronger updrafts/supercell structures. ...North-Central High Plains... Midlevel perturbation currently over western WY will continue east, with a region of ascent favorably timed to develop over the Big Horn/Black Hills region during the mid/late afternoon. Despite ongoing cloud cover, heating of mid/upper 50s surface dew points beneath reasonably steep midlevel lapse rates should result in pockets of MLCAPE of 1000-1500 J/kg. Modest midlevel west/northwest flow will contribute to around 30 kts of effective shear which will favor a mixed multicell/transient supercell mode. Isolated stronger storms will be capable of strong/damaging gusts and hail through early evening. Read more CHECK UPDATE ZOOM GRAPHIC