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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.


Friday, September 16, 2022

SPC Sep 16, 2022 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1234 PM CDT Fri Sep 16 2022 Valid 171200Z - 181200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE MINNESOTA/IOWA AREA... ...SUMMARY... Isolated severe thunderstorms -- and local/all-hazards severe potential -- are expected Saturday from parts of the Upper Mississippi Valley area/Upper Midwest into/across portions of the Mid Missouri Valley. ...Synopsis... An initially low-amplitude upper flow pattern over the U.S. will gradually amplify, especially over the West. This amplification will result from a broad low from British Columbia to just off the Pacific Northwest Coast early in the day, that is expected to strengthen/consolidate as it shifts southward to just off the northern California coast late. As this occurs, ridging will begin to expand across the south-central U.S., while a belt of fast southwesterly flow in between the two features persists from the Intermountain West to the Upper Great Lakes. At the surface, the primary feature of interest will be a weak low -- forecast to evolve over the eastern South Dakota/southwestern Minnesota border area during the afternoon. A weak cool front should extend south-southwestward across eastern Nebraska and into Kansas, while the warm front extends east-northeastward across northern Minnesota. The main severe potential Saturday should reside in the vicinity of the warm sector of this system. ...Minnesota to southwestern Wisconsin/Iowa, and southwestward across northeastern Kansas... Though hindered in some areas by ongoing/remnant clouds/convection early in the period, daytime heating and low-level moist advection within the southerly flow regime will result in moderate afternoon airmass destabilization from the Upper Midwest into Kansas. As a short-wave trough crosses the Dakotas early and eventually approaches Minnesota, ascent -- focused near a weak low progged to evolve near the South Dakota/Minnesota border -- will likely result in isolated storm development by late afternoon. Farther south, focus for convective initiation appears more nebulous, without a clear low-level focusing mechanism. Still, low-level warm advection across this region should result in isolated to scattered convective development -- initially during the afternoon, with a second round of storms possible as a southerly low-level jet intensifies overnight. With 35 to 40 kt west-southwesterly mid-level flow spreading across the area with time, atop low-level southerlies, a few of the stronger storms will likely acquire rotation -- posing risk for hail and/or locally damaging wind gusts. A tornado or two may also occur -- with a favored area possibly over central/northern Minnesota near the anticipated low/warm frontal position. Storms will likely continue -- especially across the Iowa vicinity -- overnight, aided by persistent low-level warm advection, though any lingering severe potential should wane gradually through late evening. ..Goss.. 09/16/2022 Read more CHECK UPDATE ZOOM GRAPHIC
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