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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.

Wednesday, July 21, 2021

SPC Jul 21, 2021 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1223 PM CDT Wed Jul 21 2021 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHWEST INTO CENTRAL/EASTERN MT...NORTHEAST WY...WESTERN DAKOTAS... ...SUMMARY... Thunderstorms capable of strong to potentially severe wind gusts are possible Thursday afternoon and evening across much of Montana into parts of northeast Wyoming and the western Dakotas. ...Montana and vicinity... A seasonably deep mid/upper-level trough is forecast to move eastward from the Pacific Northwest into parts of Montana and the Canadian Prairies by Thursday evening. In conjunction with this trough, a surface cyclone is expected to move from MT into ND by evening, as a cold front accelerates southeastward across much of MT by Thursday night. Scattered thunderstorms are expected to develop by Thursday afternoon across the higher terrain of the northern Rockies, and perhaps further east across the northern High Plains, where strong heating will erode the cap. Increasing southwesterly mid/upper-level flow may support a few organized cells and/or clusters. Some hail cannot be ruled out, especially with storms that develop in closer proximity to the approaching trough. However, the primary severe threat is currently expected to be severe/damaging wind gusts, especially if outflow-dominant clusters move into parts of central/eastern MT, where very strong heating and mixing is expected during the afternoon. A Slight Risk may eventually be needed for some portion of MT, if trends favor the potential for one or more persistent clusters with strong outflow winds. ..Dean.. 07/21/2021 Read more LIVE: