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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.

Friday, August 20, 2021

SPC Aug 21, 2021 0100 UTC Day 1 Convective Outlook

SPC 0100Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0752 PM CDT Fri Aug 20 2021 Valid 210100Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL PLAINS...MID MISSOURI VALLEY AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Thunderstorms associated with damaging wind gusts, isolated large hail and possibly a tornado threat will continue this evening into tonight across parts of the central Plains, mid Missouri Valley and upper Mississippi Valley. ...Central Plains/Mid Missouri Valley/Upper Mississippi Valley... Water vapor imagery currently shows a negatively-tilted upper-level trough over the northern Plains, with the southern extension of the trough in the central Plains. At the surface, a cold front is currently moving eastward across the eastern Dakotas. The front extends southward into far northwest Iowa and then southwestward into central Kansas. A moist airmass is located ahead of the front with surface dewpoints mostly in the 70s F. Instability is strong due to the moist airmass with the RAP estimating MLCAPE in the 4000 to 5000 J/kg range from eastern Kansas into western Iowa. This area will have the greatest potential for severe storms this evening. In addition, regional WSR-88D VWPs at Omaha and Topeka have 0-6 km shear in the 35 to 40 kt range. This will support supercell development, especially in areas where cells can remain discrete. Supercells should be capable of producing wind damage, isolated large hail and possibly a tornado or two. Linear mode is expected to become the dominant mode later this evening as an MCS organizes across the region. Wind-damage will be possible along the leading edge of the strong line segments. Further to the north across northern Iowa and Minnesota, the RAP is estimating MLCAPE in the 1250 to 2500 J/kg range. Scattered thunderstorms are ongoing along the eastern edge of the instability corridor. The WSR-88D VWP in southern Minnesota has 0-6 km shear near 35 kt, but shear is likely stronger across central and northern Minnesota due to the presence of a mid-level speed max. The stronger deep-layer shear should be favorable for rotating storms with large hail potential. An isolated wind-damage threat will also be possible, especially with the more intense line segments. The severe threat in the upper Mississippi Valley is expected to become minimal by late evening as instability drops off across the region. ..Broyles.. 08/21/2021 Read more LIVE: spc.noaa.gov