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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 23, 2021

SPC Aug 24, 2021 0100 UTC Day 1 Convective Outlook

SPC 0100Z Day 1 Outlook Day 1 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0813 PM CDT Mon Aug 23 2021 Valid 240100Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF SOUTH DAKOTA... CORRECTED FOR NDFD WIND GRAPHIC ...SUMMARY... Isolated strong severe thunderstorms will move across parts of the northern Plains and upper Mississippi Valley this evening into tonight. Isolated large hail will be the primary threat although a few strong wind gusts could occur. ...Northern Plains/Upper Mississippi Valley... The latest water vapor imagery shows west to southwest mid-level flow across the north-central U.S. At the surface, a 1001 mb low is located in southeast Montana with backed east to southeasterly flow located across much of the northern Plains. A surface trough extending southeastward across western South Dakota. Isolated strong to severe thunderstorms are ongoing to the east of the surface trough in central South Dakota. This activity is forecast to gradually expand in coverage, moving eastward across eastern South Dakota and may impact parts of southwest and central Minnesota later tonight. The RAP is currently showing moderate to strong instability across parts of the central and southeastern South Dakota, with MLCAPE estimated to be in the 2000 to 3500 J/kg range. However, some capping is present across the area. In spite of the cap, a 50 to 60 kt low-level jet will likely provide the lift necessary for continued thunderstorm development this evening. In addition to the instability, the RAP is showing effective shear in the 45 to 55 kt range and 700-500 mb lapse rates near 8.0 C/km suggesting that a supercell threat will continue this evening. Hailstones of greater than 2 inches will be possible across parts of the central South Dakota over the next couple of hours. An isolated large hail threat could develop further to the east across parts of eastern South Dakota. Further to the north across North Dakota, weak instability is present. However, the low-level jet will result in strong moisture advection. This will help instability to increase late this evening into the overnight period. Thunderstorm development should take place near the axis of the low-level jet, and spread east-northeastward across central and eastern North Dakota after midnight. RAP forecast soundings across central North Dakota after midnight increase MUCAPE into the 2500 to 3500 J/kg range. The soundings also show steep lapse rates and 40 to 50 kt of effective shear. Although a sharp low-level temperature inversion will be present, the shear and instability should be enough to support an elevated supercell development. Hail would be the primary threat. ..Broyles.. 08/24/2021 Read more LIVE: spc.noaa.gov