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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.

Tuesday, June 29, 2021

SPC Jun 29, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0301 PM CDT Tue Jun 29 2021 Valid 292000Z - 301200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FOR PARTS OF THE GREAT LAKES AND SOUTHERN GREAT BASIN... ...SUMMARY... Isolated severe thunderstorms are possible across parts of the Great Lakes States, mainly this afternoon through early evening. Isolated severe wind gusts are also possible in parts of the Desert Southwest from late afternoon through dusk. ...Discussion... The only changes made to the previous outlook were the removal of 5-percent wind probabilities for parts of north-central WI and southeast Lower MI where convective overturning has led to cooler temperatures and a likely lower potential for severe in those areas. ..Smith.. 06/29/2021 .PREV DISCUSSION... /ISSUED 1131 AM CDT Tue Jun 29 2021/ ...Upper Midwest/Great Lakes through this evening... A midlevel trough will move eastward over the upper MS Valley toward the upper Great Lakes through this evening, while a convectively modified surface boundary extends from central IL into Lower MI. The stronger surface heating and larger buoyancy is expected along and south of this weak surface front/outflow, and this boundary will focus thunderstorm development through the afternoon. Isolated wind damage will be possible with the stronger storms from northeast IL into Lower MI where the southern fringe of the stronger (30-40 kt) midlevel flow overlaps the north edge of the larger buoyancy along the surface boundaries. Farther northwest, a persistent band of thick cloud cover will limit surface heating across southeast WI. Pockets of stronger surface heating from southeast MN into western/northern WI may result in sufficient destabilization for storms with isolated wind damage, though poor lapse rates will tend to limit any hail threat. ...Southern Great Basin this afternoon/evening... A gradual increase in midlevel moisture and inverted-v profiles will support a threat for isolated severe outflow gusts with southward moving convection this afternoon/evening across southern NV and vicinity. New storm development should be focused from the east slope of the southern Sierra Nevada eastward, and possibly along remnant outflows from ongoing morning convection. ...Western TN and vicinity this afternoon... Convective bands on the north-through-west periphery of the remnant tropical cyclone Danny circulation will continue to spread westward through the afternoon. Surface heating/destabilization to the west of this convection, and a small area with somewhat enhanced easterly flow, could support isolated strong outflow winds this afternoon, prior to boundary-layer stabilization this evening. However, the threat for severe gusts/damage appears a bit too low to warrant an outlook area. Read more LIVE: