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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, July 26, 2021

SPC Jul 26, 2021 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1235 AM CDT Mon Jul 26 2021 Valid 261200Z - 271200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF MINNESOTA INTO NORTHERN WISCONSIN AND THE UPPER PENINSULA OF MICHIGAN... ...SUMMARY... Severe thunderstorms capable of large hail and damaging wind will be possible Monday afternoon and evening across parts of Minnesota, Wisconsin, and the Upper Peninsula of Michigan. ...MN/WI/Upper Peninsula of MI... Broad upper ridging will hold across the northern Rockies through the day1 period with troughing across ON/QC into the lower Great Lakes. Resultant northwesterly flow aloft will persist across the southern prairie Provinces into the upper Great Lakes region. This flow regime will dislodge a surface low off the northern High Plains into south central ND by late afternoon as a synoptic front settles across northern ND/MN/UP MI. Latest model guidance suggests strong boundary-layer heating will be noted across the northern Plains such that convective temperatures will be breached by 21z as surface temperatures approach 100F just ahead of the surface low. Early in the period, scattered convection may be ongoing across parts of the upper MS Valley due to weak low-level warm advection. Although a strong updraft can not be ruled out with this activity, stronger storms are anticipated later in the afternoon/evening. While large-scale heights are not expected to change appreciably during the day, a weak disturbance may approach northern MN by late afternoon then dig toward northern lake MI by 27/06z. Strong heating should encourage a few thunderstorms to develop ahead of the surface low but this mid-level feature is expected to aid scattered robust updrafts along the synoptic front which will organize then propagate southeast during the evening. Forecast wind profiles/shear suggest supercells are possible, especially early in the convective cycle; however, upscale growth/clustering should result in a larger complex of storms spreading into northern WI after sunset. Hail and wind are the primary threats, although a tornado can not be ruled out with supercells near the front. ...Middle Atlantic... West-northwesterly flow, on the order of 20kt, will extend across the Middle Atlantic this afternoon within the base of a broader trough. Seasonally high PW values (2 inches) will extend across NC/southern VA along the southern fringe of the stronger northwesterly flow which will support some thunderstorm clustering. Isolated damaging winds may accompany this activity. ...Northern New England... Strong boundary-layer heating will be noted across southern ON into northern New England late this morning. Forecast soundings suggest convective temperatures may be breached by 18z and a few thunderstorms should develop within modestly sheared westerly flow. While instability is not forecast to be that significant, gusty winds could be noted with a few storms. ..Darrow/Bentley.. 07/26/2021 Read more LIVE: