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Weather conditions on bar directly above are near Lakefront. Tabs under Moon Phases refer to O'Hare (official).

Archives for SPC Convective outlook are updated daily with a live map a the beginning of the article. Touch or click map to get possible update, and follow link at end of article for referral to NOAA/NWS Storm Prediction Center. Archives for Chicago's hourly weather data were updated 24-48 hours after end of each day prior to Dec. 2020.

Monday, October 11, 2021

SPC Oct 11, 2021 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Mon Oct 11 2021 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE MID MISSISSIPPI VALLEY AND GREAT LAKES... ...SUMMARY... Severe thunderstorms are possible from the mid Mississippi Valley into portions of the Great Lakes, with the greatest threat expected from late morning into the afternoon and early evening. Locally damaging wind, isolated hail, and a couple of tornadoes will be possible. ...Mid MS Valley into portions of the Great Lakes region... A mid/upper-level trough and associated cyclone will move quickly northeastward from portions of western MO this morning into the upper Great Lakes region by late tonight. While some weakening of this system is expected with time, seasonably rich low-level moisture will support multiple rounds of convection across IL/southeast WI/northwest IN/western lower MI. Cloudiness/precipitation and generally modest midlevel lapse rates are expected to limit destabilization across the warm sector, though MLCAPE may increase into the 500-1000 J/kg range where pockets of heating can occur. Strong deep-layer southerly flow will support effective shear in excess of 40 kt, supporting the potential for organized convection. Generally unidirectional wind profiles will likely favor a mixed mode of clusters/small line segments and a few semi-discrete cells, with strong low-level flow favoring a damaging-wind threat with the stronger storms. If sufficient destabilization can occur in the wake of early day convection, locally backed low-level flow along/east of the surface low track may support some tornado threat with redeveloping storms across portions of IL and southern WI by mid/late afternoon. Isolated hail will also be possible with any sustained semi-discrete cells. ..Dean/Marsh.. 10/11/2021 Read more LIVE: spc.noaa.gov