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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, September 18, 2021

SPC Sep 18, 2021 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1229 AM CDT Sat Sep 18 2021 Valid 181200Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER NORTHERN UTAH...SOUTHEAST IDAHO AND FAR WESTERN WYOMING... ...SUMMARY... A few storms may produce severe wind and/or hail this afternoon and evening across northern Utah, western Wyoming, and southeast Idaho. ...UT...ID...WY... Strong cooling aloft will occur over the Pacific Northwest as a strong upper jet noses into OR late in the day. Meanwhile, a lead wave will move across the Great Basin and toward WY by 00Z. Cool midlevel temperatures as well as 500 mb wind speeds around 50 kt are forecast with this leading wave. At the surface, a trough will develop over central MT, extending southwestward into northeast NV. Strong heating will occur near this surface trough, but weaker low-level lapse rates will exist across parts of UT, owing mainly to a few early day showers. Diurnal storms are expected to form over eastern NV and western UT between 18-21Z, with quick motion to the northeast. Wind profiles may actually favor a couple supercells, with 0-6 km shear over 40 kt and effective SRH over 200 m2/s2. CAM guidance suggests both cells and line segments will be possible, with a few damaging gusts as well as marginal hail. Storms may remain strong to severe as they move across far southeastern ID and western WY after 21Z. ..Jewell/Moore.. 09/18/2021 Read more LIVE: spc.noaa.gov