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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.


Monday, August 21, 2023

SPC Aug 21, 2023 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1247 AM CDT Mon Aug 21 2023 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE INTERIOR WEST...UPPER MIDWEST...AND THE LOWER TEXAS COAST... ...SUMMARY... Locally severe thunderstorms are possible across parts of the Interior West mainly during the afternoon, parts of the Upper Midwest and lower Texas coast overnight. ...AZ north through the eastern Great Basin into MT... The eastern periphery of the extratropical remnants of tropical cyclone Hilary, abutted to a central U.S. mid-level anticyclone, will yield a tightened gradient and stronger flow across this elongated south to north region. Scattered thunderstorms are forecast to develop during the afternoon owing to cloud breaks/heating and steepened low-level lapse rates. A few strong to locally severe gusts may occur with the more intense thunderstorm clusters before this activity weakens during the evening. ...Lower TX coast... Model guidance shows an area of organizing low pressure over the central Gulf of Mexico moving westward into the western half of the Gulf during the period, to the south of a mid-level high located over the lower MO Valley. Strengthening easterly low-level flow and enlarging hodographs are forecast to penetrate the beaches and the near shore areas of the lower TX coast and TX coastal bend late tonight. Forecast soundings show weak buoyancy due in part to mid-upper 70s surface dewpoints. A few transient supercells are possible beginning around 06z through early Tuesday morning. ...Upper Midwest... A belt of strong mid to high-level westerly flow will extend from the southern Prairie provinces east-southeastward into the Upper Great Lakes, to the north of a mid-level anticyclone centered over MO. A surface front will be draped west-east over the upper MS Valley. A southwesterly LLJ will strengthen tonight from the central High Plains northeastward into MN. This will favor ascent north of the surface boundary, and result in isolated to scattered thunderstorms developing primarily after 04z. Marginally severe hail may accompany the stronger cores. ..Smith/Weinman.. 08/21/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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