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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.

Thursday, August 5, 2021

SPC Aug 5, 2021 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1153 PM CDT Wed Aug 04 2021 Valid 061200Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE NORTHERN HIGH PLAINS AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Isolated severe storms are possible over parts of the northern High Plains and upper MS Valley Friday. ...Synopsis... A shortwave trough will move from ID across WY and MT during the day, and into the northern Plains by Saturday morning. Midlevel winds to 50 kt will result in favorable deep-layer shear, and lapse rates will steepen aloft with -10 C at 500 mb. Meanwhile, a surface low is forecast to develop over western SD and NE, with easterly surface winds across ND and MT. A cold front will accompany the shortwave trough as it moves across MT and WY, and will provide a focus for daytime storms as it interacts with the 50s F dewpoints. Elsewhere, a weak upper trough along the length of the MS River will drift east, providing cool temperatures aloft atop weak surface flow. A moist air mass and weak low-level theta-e advection over the Southeast will support storms throughout the period, but severe weather appears unlikely there. Strong instability will also develop over parts of the mid and upper MS Valley, and isolated strong storms will be possible there. ...Northern High Plains... Strong heating combined with cooling aloft will result in very steep lapse rates across WY, SD and NE. Southeasterly surface winds near and north of the SD low will maintain 50s F dewpoints westward into southern MT, resulting in MUCAPE to 1000 J/kg. Straight-line hodographs of modest size will support cells or small bows capable of marginally severe wind or hail. Storms are expected to form over southern MT and northern WY between 18-21Z, with expanding coverage as storms progress into western SD. ...IA...southern WI...northern IL... A moist and unstable air mass will develop during the afternoon with MUCAPE of 2000-3000 J/kg common. The cool midlevel temperatures will favor strong updrafts, however, ascent will be weak. Aside from sporadic afternoon development, additional storms may develop in the weakly capped air mass during the evening, aided by southwesterly 850 mb winds. ..Jewell.. 08/05/2021 Read more LIVE: spc.noaa.gov