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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.

Wednesday, August 4, 2021

SPC Aug 4, 2021 1630 UTC Day 1 Convective Outlook

SPC 1630Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Wed Aug 04 2021 Valid 041630Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF MT... ...SUMMARY... Isolated severe thunderstorms are possible across parts of Montana from mid-afternoon through this evening. ...MT... A shortwave impulse near the WA/ID/BC border area will dampen as it gradually slides east then southeast into MT. Isolated to possibly scattered thunderstorms are expected downstream of this feature later this afternoon and persisting into this evening. This convection should be rather high-based as deeply mixed thermodynamic profiles ensue at peak heating, with only weak buoyancy as MLCAPE holds below 1000 J/kg. The somewhat more favorable overlap of buoyancy with effective shear should occur across northwest MT just ahead of the mid-level impulse. Here, a threat exists for marginally severe hail in addition to isolated severe wind gusts. Farther east in central MT, the wind hazard should dominate with small hail also possible. ...Coastal southern New England... Guidance differs with the potential inland penetration of a surface-based warm sector tonight, ahead of a broad upper trough over the eastern U.S. and embedded shortwave impulses along the Eastern Seaboard. The 14Z RAP is more aggressive than the 12Z NAM with this scenario, advecting low 70s surface dew points into coastal southern New England overnight. Extensive stratiform and embedded convective elements off the Mid-Atlantic and Northeast coast at present suggests that this degree of destabilization appears unlikely. Thus, have refrained from an upgrade to cat 1/MRGL risk at this juncture. ..Grams/Squitieri.. 08/04/2021 Read more LIVE: spc.noaa.gov