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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.

Saturday, July 23, 2022

SPC Jul 23, 2022 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0754 AM CDT Sat Jul 23 2022 Valid 231300Z - 241200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MIDWEST AND SOUTHERN GREAT LAKES REGIONS... ...SUMMARY... Damaging thunderstorm gusts (some over 75 mph), a few tornadoes and large to very large hail will be possible today across parts of the Upper Midwest and southern Great Lakes regions. ...Synopsis... A zonally elongated, mid/upper-level cyclone will persist over the southern Hudson Bay region. With that orientation, the flow belt to its southwest through southeast -- across the north-central/ northeastern CONUS, will be zonal to gently cyclonic through the period, with the cyclonic influence mainly related to a series of shortwave troughs now apparent in moisture-channel imagery over the northern Plains and Canadian Prairie Provinces. The leading/southern such trough -- now over parts of western ND and eastern MT -- will influence convective potential most directly. This perturbation will move east-southeastward to the MN Arrowhead and southeastern MN/western WI by 00Z. Then with some convective vorticity enhancement, the perturbation should cross Lake Michigan and Lower MI overnight. At the surface, 11Z analysis showed a low in central SD near PIR, with warm front across eastern SD, northern IA, and southern WI, becoming diffuse north of a complex of severe thunderstorms in IN. A cold front was drawn from the low southwestward across southwestern SD to east-central/central WY. The low should move to southern MN by 00Z, perhaps diffused by convective processes, with cold front southwestward across northeastern NE, northwestern KS and southeastern CO. The warm front also may be somewhat muddled by convection, but in general, should extend from the low across central to northern parts of WI, Lake Michigan and Lower MI to parts of OH and western PA. By 12Z, the low should reach the eastern Lake Superior/eastern Upper MI vicinity, with cold front over southern WI, southern IA, and west-central KS, to another low near the CO/KS/OK border junction. ...Upper Midwest and southern Great Lakes... Complexes of thunderstorms are expected to cross the corridor today from the northeastern Plains across the southern Great Lakes to the mid/upper Ohio Valley, offering severe gusts throughout, as well as a threat for significant gusts, a few tornadoes and large to very large hail in and near the "enhanced" area. Two main convective regimes already are apparent to anchor the broader outlook. The first -- initially over northern parts of IL/IN -- is expected to continue merging/growing into a quasi-linear MCS and move southeastward into a moist and destabilizing air mass (from both warm advection and diurnal heating). See SPC severe-thunderstorm watches 487 and 488, and related mesoscale discussions, for near-term coverage of this activity. Present indications are this complex will move out of the most favorably moist/buoyant corridor near or just past the Ohio River. Severe probabilities have been expanded considerably southeastward from the previous outlook to account for this activity. The second, but potentially most damaging, may evolve upscale from strong-severe convection now over northern SD. For near-term coverage of the morning through midday severe threat, see SPC severe-thunderstorm watch 489 and related mesoscale discussions. This activity should move east-southeastward along a pronounced low-level instability gradient and near a moist axis, each associated with the warm front, with large available low/middle level lapse rates apparent on modified 12Z MPX/OAX soundings. This activity also ultimately will encounter a diurnally destabilizing and very moist air mass across MN, with theta-e advection aiding in supportive airmass recovery at least into WI and adjoining parts of Lake Michigan. 3000-5000 J/kg MLCAPE, 40-55 kt effective-shear magnitudes, and effective SRH of 200-400 J/kg will present a favorable parameter space for all severe types across southern MN into parts of WI, with localized storm mode driving relative distribution of hail and wind, and at least a few tornadoes expected. Extent of recovery into Lower MI is uncertain at this time, but at least marginally favorable buoyancy should sustain a wind threat across the lake and into that region this evening. ..Edwards/Gleason.. 07/23/2022 Read more CHECK UPDATE ZOOM GRAPHIC