TL;DR

The NOAA Storm Prediction Center (SPC) has issued an Enhanced Risk for severe thunderstorms across portions of the Upper Midwest and Great Lakes today, with the highest threat focused on Wisconsin and Iowa. Supercells capable of large hail, damaging winds, and a few strong tornadoes are expected to develop late this afternoon and continue through tonight.

Where is the highest risk today?

The Enhanced Risk area covers portions of Iowa and Wisconsin—the highest severe weather threat level issued by SPC today. Within this zone, cities including Madison, Milwaukee, Green Bay, Cedar Rapids, and Dubuque face the most significant severe weather potential.

A broader Slight Risk surrounds the Enhanced area, extending across much of the Upper Midwest and into the Great Lakes. A separate Slight Risk covers parts of North Carolina and far southern Virginia, where isolated damaging wind gusts are possible this afternoon and evening.

According to the SPC Day 1 Convective Outlook, "Severe thunderstorms are expected across portions of the Upper Midwest and Great Lakes vicinity, especially late this afternoon and tonight. Swaths of damaging winds, large hail, and a few tornadoes will all be possible."

What's driving today's severe weather setup?

This morning's radar and satellite imagery shows a decaying mesoscale convective system (MCS) over far northern Iowa into west-central Wisconsin, with warm-advection storms moving east-southeast atop the MCS cold pool. This convective activity is occurring downstream of a seasonably potent mid-level shortwave trough and associated jet streak.

A surface low over western Ontario is forecast to track east across north-central Ontario today, pushing an attendant cold front southeast across the Upper Midwest. Meanwhile, a front over the mid- to upper Mississippi Valley will advance northeast as a warm front, creating an increasingly narrow warm sector with northward extent in the northern Wisconsin vicinity.

Behind this morning's showers and thunderstorms, a warm and seasonably moist airmass will advect northeast into Wisconsin. Surface dewpoints in the upper 60s to lower/middle 70s F will contribute to a very unstable boundary layer by mid-to-late afternoon. A plume of elevated mixed-layer air will overspread the region from the west, adding to the volatile atmospheric conditions.

When will the storms hit?

Initial storms are expected to develop later this afternoon across Iowa and quickly organize into supercells given strong deep-layer shear and ample buoyancy ahead of the cold front. The SPC notes that "it is plausible the initial storms that develop later this afternoon will quickly organize into supercells."

Peak severe weather is forecast for late afternoon through tonight, roughly between 5 PM and 2 AM local time. Forecast soundings show elongated hodographs with 35-50 knot winds at 700 millibars, which will enlarge hodographs and perhaps support a couple of strong tornadoes.

As the evening progresses, individual supercells will likely evolve into a few clusters, with a continued damaging wind and tornado risk persisting southeastward before eventually waning overnight.

What are the specific hazards?

Tornadoes: A corridor of tornado risk will extend from Iowa across Wisconsin. The combination of strong low-level wind shear and significant buoyancy creates an environment favorable for supercells capable of producing tornadoes. The SPC specifically mentions the potential for "a couple of strong tornadoes," suggesting EF2 or greater intensity is possible with the most intense storms.

Large hail: Hail is a significant threat with today's supercells. The deep moisture and strong updrafts will support hailstones of golf ball size (1.75 inches) or larger, with isolated stones reaching baseball size (2.75 inches) possible in the most intense cells.

Damaging winds: As storms evolve into clusters this evening, widespread damaging wind gusts become increasingly likely. Swaths of wind damage could affect communities across the Enhanced Risk area, with gusts potentially exceeding 70 mph in the strongest storms.

Carolinas and southern Virginia outlook

A separate severe weather threat exists across North Carolina and far southern Virginia this afternoon and evening. Strong heating south of a west-east oriented stalled front will contribute to moderate buoyancy by early to mid afternoon.

Rich low-level moisture with surface dewpoints in the 70s F and moist tropospheric profiles will yield high precipitable water values. This setup favors water-loaded downdrafts with the more intense thunderstorm cores. Scattered thunderstorms with an isolated to scattered wind-damage threat will probably focus during the 18-00 UTC period (2 PM to 8 PM EDT).

Cities including Raleigh, Durham, Charlotte, and Greensboro should monitor conditions this afternoon. While the threat level is lower than in the Upper Midwest, isolated damaging wind gusts remain possible.

Recent severe weather activity

Over the past 24 hours, 64 wind reports and 10 hail reports were documented across the United States, with no tornado reports. The severe weather was spread across Alabama, Michigan, New Mexico, North Carolina, North Dakota, South Carolina, South Dakota, Texas, Virginia, and Wyoming.

Notable reports included 2-inch diameter hail 7 miles south of Lake Isabel, North Dakota, and numerous trees down across Alabama, North Carolina, and Virginia yesterday afternoon and evening.

What should you do to stay safe?

If you live in the Enhanced Risk area across Iowa, Wisconsin, or Upper Michigan, take these steps now:

  • Know your shelter location. Identify the lowest floor of a sturdy building, away from windows. Interior rooms, bathrooms, or closets offer the best protection from tornadoes.
  • Charge your devices. Ensure your phone and backup batteries are fully charged before storms arrive this afternoon.
  • Monitor conditions. Keep multiple ways to receive warnings, including NOAA Weather Radio, local news, and smartphone alerts. Wireless Emergency Alerts for tornado warnings bypass silent mode on most phones by default, though third-party weather apps are silenced by Do Not Disturb.
  • Have a plan for tonight. The tornado threat will continue after dark. Nighttime tornadoes are particularly dangerous because they're difficult to see and people may be asleep when warnings are issued. VORTEX Pro places phone calls when a tornado warning is issued for your location—calls can ring through Do Not Disturb once you enable Emergency Bypass for the number, providing an extra layer of protection when traditional app notifications won't wake you.
  • Don't wait for a siren. Outdoor warning sirens are designed to alert people outside, not indoors. Rely on indoor warning methods.
  • Act immediately on warnings. When a tornado warning is issued for your location, move to your shelter immediately. Don't wait to see the tornado—many are rain-wrapped and invisible until it's too late.

Looking ahead

Tomorrow's SPC Day 2 outlook maintains an Enhanced Risk, this time focused on Kentucky, Indiana, Ohio, Pennsylvania, Virginia, and West Virginia as the storm system progresses eastward. The severe weather threat will continue into Tuesday across the Ohio Valley and Mid-Atlantic before gradually diminishing.

By Wednesday (Day 3), a Slight Risk covers Virginia and North Carolina as the system moves offshore and weakens.

Stay weather-aware today and tonight, especially if you're in the Enhanced Risk area. Conditions are favorable for significant severe weather, and the tornado threat should not be taken lightly.

VORTEX is a free web app at vortexintel.app that monitors severe weather nationwide. Pro ($4.99/month) places phone calls to your phone when a tornado or flash flood warning is issued for a location you care about — calls can ring through Do Not Disturb once you enable Emergency Bypass for the number, unlike most third-party app notifications.