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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.

Friday, June 18, 2021

SPC Jun 18, 2021 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Fri Jun 18 2021 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE MIDWEST INTO THE GREAT LAKES AND OHIO VALLEY...AND THE SOUTHEAST... ...SUMMARY... Isolated strong to severe storms may occur Sunday across parts of the Midwest into the Great Lakes and Ohio Valley, as well as the portions of the Southeast. ...Upper Midwest into Great Lakes and Ohio Valley... A large-scale upper trough is forecast to amplify and move eastward across central Canada, much of the northern/central Plains, Upper Midwest, and Great Lakes on Sunday. A surface cold front should sweep southeastward across these regions through the period. Mainly elevated storms posing an isolated hail threat may be ongoing Sunday morning in a low-level warm advection regime across parts of the central Plains into IA. This activity should weaken through the day, and both low-level moisture and instability are forecast to increase Sunday afternoon to the south of a warm front that should be oriented generally east-west across the Midwest into the OH Valley. Current expectations are for storms to eventually develop along or just ahead of the cold front Sunday afternoon across the Midwest. There is uncertainty with how much instability will develop, but deep-layer shear should be strong enough for organized convection posing a threat for both large hail and damaging winds. This isolated severe threat may continue into evening and overnight hours across the southern Great Lakes and OH Valley regions as the cold front continues eastward. Owing to model differences on the degree of instability, placement of the warm front, and forward progression of the cold front and related convection, confidence is not high enough at this time to include higher severe probabilities across the Midwest, Great Lakes, or OH Valley. ..Southeast... Some form of a tropical cyclone should continue moving northeastward across the Southeast on Sunday. Even though this system will be inland and should gradually weaken per latest NHC forecast, strong low-level flow and shear will still be present in the eastern half of the circulation. Rich low-level moisture should also exist, and modest heating of the moist boundary-layer may support weak destabilization. The most favorable overlap of weak instability and strong shear is generally forecast across parts of GA into SC and southern NC through Sunday evening. Given the degree of low-level shear forecast, a brief tornado or two should remain the primary threat. ..Gleason.. 06/18/2021 Read more LIVE: spc.noaa.gov