What you need to know

The Storm Prediction Center has issued a Slight Risk for portions of North Dakota and northern Minnesota today, where severe thunderstorms capable of large to very large hail, damaging winds, and isolated tornadoes are expected late afternoon through evening. Additional areas of thunderstorm activity—with localized severe potential—will develop across the coastal Carolinas, southern High Plains, and scattered portions of the Intermountain West.

Where is the highest risk today?

The Slight Risk area covers eastern North Dakota into northwest and northern Minnesota. This is where the most organized severe weather is expected, driven by a favorable combination of strong instability and increasing wind shear.

Cities and communities in or near the Slight Risk zone include:

  • North Dakota: Grand Forks, Devils Lake, Jamestown
  • Minnesota: Bemidji, International Falls, Thief River Falls

Outside the Slight Risk, Marginal Risk areas extend across:

  • The coastal Carolinas and southeast Georgia
  • Eastern New Mexico into the Texas Panhandle
  • Portions of the Great Basin and northern Rockies

What's driving today's severe weather?

An amplifying upper-level pattern is allowing multiple shortwave troughs to move east-southeastward from the northern Rockies toward the northern Plains. A surface trough trailing from a deep low pressure system over northern Manitoba and Ontario will serve as the primary focus for storm development.

According to the Storm Prediction Center's Day 1 outlook, "A plume of relatively steep mid-level lapse rates will overspread a warm and moist boundary layer along/east of the surface trough, with MLCAPE increasing above 2000 J/kg across parts of North Dakota into northern Minnesota by late afternoon."

The combination of strong instability and strengthening west-northwesterly flow aloft will create a conditionally favorable environment for supercells.

When will storms develop in the Dakotas and Minnesota?

Widely scattered thunderstorms are expected to develop along the surface trough by late afternoon across eastern North Dakota into northwest Minnesota. Storm initiation is most likely between 3 PM and 6 PM local time (CDT).

The SPC notes that "elongated hodographs and favorable instability will favor supercell development, though some clustering will be possible with time during the evening."

Peak severe threat window

The highest severe weather threat will occur during the late afternoon and evening hours, roughly 5 PM to 10 PM CDT. Individual supercells will pose the greatest risk for large to very large hail initially, with tornado potential increasing as low-level wind shear and storm-relative helicity gradually strengthen into the evening.

Some storms may persist into late evening as they move into a larger portion of northern and central Minnesota, though a general weakening trend is expected overnight as atmospheric instability decreases.

What hazards are expected?

Large to very large hail

Hail will be the primary threat with any supercells that develop. The SPC specifically highlights "large to very large hail" as the initial hazard, meaning stones of golf ball size (1.75 inches) or larger are possible.

Over the past 24 hours, scattered severe weather across the Intermountain West and central Plains produced 5 hail reports and 15 wind reports. The largest hail was 1.75 inches near Towner, Colorado, early this morning.

Isolated tornadoes

Tornado potential exists with any persistent supercells, particularly during the evening hours as low-level shear increases. The environment will support isolated tornadoes, though the tornado threat is not the primary concern with today's setup.

Damaging winds

If storms begin to cluster into a more linear system during the evening, "localized corridors of greater severe-wind potential" could develop, according to the SPC. Organized clusters of storms can produce swaths of damaging straight-line winds.

What about other regions?

Coastal Carolinas and southeast Georgia

Scattered thunderstorms will develop by early to mid afternoon across the coastal Carolinas and southeast Georgia. While deep-layer wind shear will be weak, the SPC notes that "locally damaging downbursts and outflow winds will be possible within the warm and very moist environment."

Precipitable water values above 2 inches will support heavy rainfall with any storms that develop.

Southern High Plains

A nearly stationary front draped from eastern New Mexico into the Texas Panhandle will serve as a focus for thunderstorm development by late afternoon and early evening. Deep-layer winds will be weak, but strong boundary-layer heating may support localized damaging wind gusts.

Great Basin and northern Rockies

Widely scattered high-based storms are expected this afternoon from parts of the Great Basin into the northern Rockies. The SPC assessment is that "any such severe-caliber wind potential should remain very isolated and somewhat marginal in nature."

What should you do?

If you're in the Slight Risk area across North Dakota or northern Minnesota:

  • Monitor radar and warnings closely beginning mid-afternoon. Conditions will be favorable for rapid storm development.
  • Have multiple ways to receive warnings. Outdoor sirens may not be audible indoors, and third-party weather apps are silenced by Do Not Disturb, though Wireless Emergency Alerts for tornado warnings still break through on most phones.
  • Identify your safe place now. If a tornado warning is issued, move immediately to the lowest floor of a sturdy building, away from windows. Interior rooms or hallways are best.
  • Secure outdoor items. Large hail can damage vehicles, windows, and anything left outside.
  • Avoid travel during the peak threat window if possible, especially in open or rural areas where shelter options are limited.

For residents in Marginal Risk areas, stay weather-aware and be prepared to take action if a warning is issued for your location.

Looking ahead

SPC Day 2 (Saturday) shows a Marginal Risk across portions of the central Plains, Midwest, Southeast, and Northeast. Day 3 (Sunday) upgrades to a Slight Risk for parts of the southern Plains, northern Plains, Midwest, Great Lakes, and Mississippi Valley, indicating that active weather will continue into the weekend.

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.