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Weather conditions directly above are near Lakefront. Top tabs refer to O'Hare (official).

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, September 8, 2022

SPC Sep 8, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Thu Sep 08 2022 Valid 082000Z - 091200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MIDWEST...WYOMING/BLACK HILLS...FLORIDA PENINSULA...AND THE MIDDLE TEXAS COAST... ...SUMMARY... Isolated severe hail and locally damaging winds may occur this evening into the overnight across parts of the Upper Midwest. Isolated severe wind gusts remain possible across parts of Florida, the middle Texas Coast, and Wyoming to the Black Hills vicinity through the rest of the afternoon and into the early evening. ...20Z Update... Aside from trimming low wind probabilities behind ongoing convection across the FL Peninsula, no appreciable changes have been made to the ongoing forecast. See Mesoscale Discussion 1769 for more details on the near-term threat for strong to locally severe thunderstorm wind gusts across parts of WY and vicinity. ..Gleason.. 09/08/2022 .PREV DISCUSSION... /ISSUED 1130 AM CDT Thu Sep 08 2022/ ...Upper Midwest... No changes warranted for this region. Low/mid-level warm advection is expected from a stout upstream EML regime, emanating from where record high temperatures have been set in prior days over a large portion of the interior West. This, in combination with a return-flow process that lacks robust connection to the western Gulf and therefore limits rich boundary-layer moisture, should keep an impinging cold front capped from thunderstorm development through late afternoon. By evening, mid-level height falls should overspread the front in advance of a broad upper trough reaching the Prairie Provinces to northern Great Plains. Strengthening low-level convergence and low-level arm/moist advection may provide sufficient ascent to weaken the EML and yield isolated thunderstorms initially from west-central to northeast Minnesota. Some guidance suggest this process will be more pronounced overnight and thus displaced southward. Regardless, convection is most likely to be rooted on and to the cool side of the southeast-progressing cold front. Deep-layer winds will largely be stronger deeper into the stable air mass away from the immediate front, but still adequate to support rotating updrafts amid moderate elevated buoyancy. Isolated large hail is the primary threat, but locally damaging winds from strong gusts are possible. ...Wyoming/Black Hills vicinity... The trailing portion of a cold front will move south from eastern Montana into northern Wyoming this afternoon. As this occurs, isolated to scattered thunderstorms should develop over the higher terrain of far southern Montana and northwest/north-central Wyoming and then spread east-southeast. Moisture will be poor with surface dewpoints generally in the 30s F, but steep low/mid-level lapse rates should support meager MLCAPE to around 300 J/kg. High-based, skeletal convection may produce isolated severe gusts, augmented by momentum transport from strengthening mid-level winds, and small hail. This threat should diminish rapidly near sunset. ...Central/south Florida Peninsula... To the east of a low centered over the northern Gulf of Mexico, scattered, semi-organized, slow-moving thunderstorms will move across the Florida Peninsula through late afternoon and evening. While low/mid-level winds are not overly strong, ample veering and as much as 20-25 kt effective shear may support a couple of weak/transient supercells, and more prevalently, semi-organized linear segments otherwise. A localized severe storm or two could occur mainly through the afternoon. ...Middle Texas coast/South-Central Texas... In a somewhat similar regime to yesterday across east Texas, modestly enhanced northerly winds aloft in conjunction with moderate buoyancy could yield a few stronger storms this afternoon, with localized wind damage the most probable hazard. Read more CHECK UPDATE ZOOM GRAPHIC