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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.

Tuesday, September 14, 2021

SPC Sep 14, 2021 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1254 AM CDT Tue Sep 14 2021 Valid 141200Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER LOWER MICHIGAN AND PARTS OF NORTHERN OHIO...INDIANA...AND EASTERN ILLINOIS... ...SUMMARY... Isolated to widely scattered severe storms are possible from the Great Lakes to the Ohio Valley and Northeast States. A few severe storms might also occur from the middle Mississippi Valley into the central Plains. A brief tornado is also possible in association with Nicholas from southeast Texas into Louisiana. ...Great Lakes to the OH Valley states... A shortwave trough will move across the upper Great Lakes today, with a surface low moving from Upper MI into Ontario. A cold front will trail south from the low, oriented roughly from southeast Lower MI into eastern IL by 00Z. Ahead of the front, mid to upper 60s F dewpoints will be common, along with good heating resulting in 2000+ J/kg MUCAPE by late afternoon. Deep-layer shear will be most favorable over northern parts of MI, with up to 60 kt into Upper MI. However, instability will be greatest farther south where shear will be less. Isolated strong storms will be possible early in the day, but the greatest threat will be with storms along the front after 21Z from central Lower MI into IL. Linear forcing along the front suggest wind may be the primary concern, but hail will also be possible. ...Northeastern States... Shortwave ridging will occur during the day, allowing a warm front to shift north across NY and southern New England. Heating will contribute to instability south of the front, from western NY into PA and NJ. A capping inversion is expected to hamper development during the day, although an isolated cell cannot be ruled out over NY with marginal hail threat. Otherwise, storm coverage will increase as the front approaches after 03Z into western and northern NY where 500-1000 SBCAPE may remain. Strong westerly flow with 40-50 kt mean midlevel speeds may support a few severe wind gusts across western NY, but degree of threat will depend on how quickly the boundary layer cools and storms become elevated. ...Central Plains... Late-afternoon storms are likely along the stalled front across MO and KS, with localized severe gusts or hail. Lack of shear should preclude much organization, but backed low-level winds near the boundary over KS beneath modest midlevel westerlies could result in a brief supercell or two with prominent hail threat. Other cells producing wind and hail will be possible forming off the Front range as a result of very steep lapse rates through a deep layer. Shear will marginal but a few storms are likely to propagate east southeast across the High Plains through early evening. ...Southeast TX into LA... What is currently Hurricane Nicholas will continue to affect the upper TX Coast and LA today. Mid 70s F dewpoints will exist near coastal areas, along with south to southeast surface winds resulting in increased SRH. However, most of the shear will likely be north of the stronger instability which is forecast to remain offshore. As such, will maintain low 2% tornado probabilities. ..Jewell/Gleason.. 09/14/2021 Read more LIVE: