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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.

Thursday, August 19, 2021

SPC Aug 20, 2021 0100 UTC Day 1 Convective Outlook

SPC 0100Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0800 PM CDT Thu Aug 19 2021 Valid 200100Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN PLAINS... ...SUMMARY... Scattered severe thunderstorms with large hail and wind damage are expected across the central and northern Plains this evening and tonight. An isolated tornado threat will be possible for a couple more hours in parts of the central Plains. ...Central and Northern Plains... The latest water vapor imagery shows an upper-level trough over the intermountain west with a plume of mid-level moisture extending eastward into the central Rockies. A cluster of strong to severe thunderstorms is ongoing at the eastern edge of this plume in the central High Plains. A moist airmass is located across much of the Great Plains. Surface dewpoints in the central and northern High Plain are mostly in the 60s F. This is contributing to a corridor of moderate instability located from western Kansas into western Nebraska, where the RAP is estimating MLCAPE in the 1500 to 2500 J/kg range. On the northwestern end of the instability corridor, the cluster of strong to severe thunderstorms will be maintained through much of the evening, with more isolated storms located across the central Plains. Regional WSR-88D VWPs across the central High Plains have supercell wind profiles. The most favorable WSR-88D VWP is at Goodland where 0-6 km shear is 45 to 50 kt, the hodograph is looped and substantial directional shear is present in the lowest 3 km above ground level. In addition, the edge of an elevated mixed layer is evident over far northeast Colorado and far northwestern Kansas. The combination of instability, deep-layer shear and steep mid-level lapse rates will be favorable for isolated large hail with the supercells embedded in the cluster. An isolated tornado threat will also be possible with the stronger supercells for a couple more hours this evening. Supercells along with multicells that remain organized will also be capable of producing damaging wind gusts. The severe threat should gradually develop east-northeastward across central Nebraska sand south-central South Dakota this evening. Isolated severe storms will also be possible across northwest Kansas. An isolated severe threat may persist into the overnight period as an MCS moves east-northeastward across the central and northern Plains. ..Broyles.. 08/20/2021 Read more LIVE: