Key Headlines:
- The Storm Prediction Center (SPC) has flagged a widespread area of Moderate risk (level 4 out 5) through Thursday morning across the Upper Midwest, including much of the state of Wisconsin. Moderate risk issuance is relatively rare, occurring approximately ten times a year.
- From a timing standpoint, storms are expected to develop across northern Minnesota and northwest Wisconsin during the late afternoon or early evening and move southeast as the evening progresses. Severe, damaging winds, possibly exceeding hurricane force (>74 mph), are possible.
- Weather model trends analyzing conditions before initiation of thunderstorm activity on Wednesday are increasingly suggesting that storms will maintain strong wind potential across Lake Michigan into Indiana, Michigan and potentially northwestern Ohio through Thursday morning.
Expected Impacts:
- Straight-line winds are the primary threat expected with today’s storms, followed by hail and tornado. Forecast confidence remains high on the general magnitude and overall timing of the event, with the possibility of a large swath of damaging winds potentially exceeding 70-80+ mph.
- Widespread power outages can be expected along with extensive tree damage. Variable structural damage due to wind gusts is also probable. Wind-driven hail and any tornadoes will also drive potential modes of structural damage.
- As storms move southeast across the state of Wisconsin this evening, a bowing effect is anticipated, enhancing the probability of significant wind damage possibly across Lake Michigan into northern Indiana, southwest Michigan and northwest Ohio. The possibility of the line of thunderstorms growing into breadth and length to be classified as a derecho is very possible.
- A similar event to what may come to fruition later today occurred on June 11, 2001, resulting in thousands of downed trees and widespread property damage. Winds in excess of 75 mph were recorded across portions of Minnesota and Wisconsin.
Severe Thunderstorm Outlook for July 28 with the red area indicating moderate risk for severe weather. Source: NOAA/SPC
High resolution FV3 weather model projection of severe thunderstorm development and propagation through Thursday morning July 29, 2021. Source: TropicalTidbits.com
Storm Prediction Center forecast for high wind potential, including a significant severe designation with winds in excess of 75 mph possible in hatched regions. Source: SPC