SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1127 PM CST Tue Nov 24 2020 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE LOWER OHIO VALLEY TO THE LOWER MISSISSIPPI VALLEY... ...SUMMARY... Isolated strong to severe thunderstorms are possible today from the lower Mississippi Valley to the lower Ohio Valley. Locally damaging winds should be the main threat, although a tornado or two could also occur. ...Lower Ohio to Lower Mississippi Valley... Strong mid-level vort/upper low centered along the KS/OK border will progress into eastern MO by 18z before ejecting into OH by the end of the period. Latest model guidance suggests the associated surface low will advance to near STL by mid day and an arcing corridor of enhanced boundary-layer heating is expected ahead of the front. It appears surface temperatures should warm into the lower 60s as far north as southern IL/IN which would yield upwards of 800-900 J/kg of SBCAPE where dew points should be in the mid-upper 50s. Forecast soundings suggest isolated thunderstorms will likely develop ahead of the upper low by 17-18z within a strongly sheared environment that would favor organized updrafts. This activity would spread/develop east during the afternoon, possibly developing in an arcing fashion across western KY into middle TN. Locally damaging winds are the primary risk, but some tornado threat does appear possible. At this time will maintain MRGL Risk due to low confidence in storm coverage; however, this region will be monitored for higher severe probabilities if confidence in organized severe increases. Farther south, band of frontal convection is currently noted across east TX. This activity should progress into the lower MS Valley by sunrise. With the primary forcing expected to spread across the OH/TN Valley region, convection along the trailing front may not be that organized and will be less sheared than convection farther north. Even so, locally damaging winds may be noted with the strongest storms. ..Darrow/Squitieri.. 11/25/2020
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