4 13 26} PM Update Heavy Rainfall, Severe Storms, and Flooding Risk This Week

Attached is the briefing from this afternoon's 1:30 PM webinar regarding the multiple rounds of rainfall and thunderstorms this week, including the potential for severe thunderstorms and flooding. Bottom Line Up Front · Scattered to numerous severe thunderstorms are likely late this afternoon into late tonight. o Initiation occurring between 4-6 PM. Main time frame for severe: 6 PM to 1 AM. o Large hail up to 2 inches in diameter, damaging winds, a few tornadoes, and heavy rain/localized flash flooding. · Strong to severe thunderstorms possible Tuesday afternoon and evening. o Mainly south of a line from Marshfield to Sturgeon Bay. o Greatest risk for severe between 4-10 PM. o Large hail up to 2 inches in diameter, damaging winds, and heavy rain/localized flash flooding. · Periods of heavy rain will lead to additional river rises and possible localized flooding this week. o Several rivers have already reached flood stage or are forecast to within the next 24-36 hours. o Runoff and snowmelt from far northern WI and Upper MI will likely cause moderate to possible major flooding on the Menominee River by midweek. o Indications suggest thunderstorms may train over the same area—mainly central into northeast and east-central WI—potentially resulting in very high rainfall totals and rates that will lead to flooding. o Heavy rain is again possible Wednesday afternoon and night, and then again Friday night into Saturday. What has changed? · Minor changes to the Severe Weather Outlooks for today and Tuesday. · A River Flood Warning has been issued for the Wisconsin River at Merrill until Thursday afternoon.

NWS Green Bay Briefing 4-13-2026 PM.pdf