What you need to know

The NOAA Storm Prediction Center (SPC) has issued a Slight Risk for severe thunderstorms across parts of the Ohio and Tennessee Valleys for Saturday, August 1. Damaging wind gusts are the primary threat this afternoon into evening, with an isolated tornado risk possible near the surface low across Indiana and northern Kentucky. Storms will develop between 3pm and 10pm local time, with the strongest activity expected across Indiana, Kentucky, Tennessee, and Alabama.

Where is the highest risk today?

The Slight Risk area covers portions of seven states, stretching from southern Illinois and Indiana southward through Kentucky, Tennessee, northern Alabama, and northern Mississippi, and eastward into western Ohio. The SPC Day 1 outlook identifies the Ohio and Tennessee Valleys as the primary focus for severe weather.

Major metros in the risk area include:

According to the SPC, "Thunderstorms with severe wind gusts and an isolated tornado threat are expected across parts of the Ohio and Tennessee Valleys this afternoon into evening."

What's driving today's severe weather?

A positive-tilt mid-level trough is drifting east-southeastward from the middle Mississippi Valley toward the lower Ohio Valley through tonight. A surface low will develop eastward across Illinois and Indiana, creating a narrow warm sector ahead of an advancing cold front.

The moist air mass should moderately destabilize across the Tennessee Valley this afternoon, with MLCAPE (mid-level convective available potential energy) values supporting organized thunderstorm development. Destabilization will be more modest and uncertain farther north into Indiana and western Ohio, where residual early-day cloud cover may limit heating.

Deep-layer wind shear will range from 20-35 knots across the region. The strongest effective shear—upward of 35 knots—is expected across Kentucky into Indiana and Ohio, though the SPC notes "a low-to-mid-tropospheric flow weakness will tend to persist." Across the Tennessee Valley, deep-layer winds will be stronger overall, but a near-surface westerly flow component will reduce effective shear to 20-25 knots.

When will the storms hit?

Scattered clusters of storms are expected to develop initially across Indiana and Kentucky this afternoon, beginning around 3pm local time. Activity will expand southward into Tennessee and Alabama a bit later, likely between 5pm and 7pm.

The SPC outlook indicates storms will intensify through the afternoon and continue into the evening hours, with the severe threat gradually diminishing after 10pm as the system moves eastward and loses daytime heating.

What are the main threats?

Damaging winds are the most probable hazard regionally as storms intensify this afternoon. The combination of moderate instability and sufficient wind shear will support organized clusters capable of producing wind gusts exceeding 58 mph.

Isolated tornadoes are possible, particularly near the surface low and triple point vicinity across Indiana and northern/east-central Kentucky. The SPC notes this tornado risk is contingent on "adequate destabilization" in an environment where cloud cover and earlier convection may limit instability. Any tornadoes that do form would most likely occur between mid-afternoon and early evening.

Large hail is not emphasized in today's outlook, though some storms may produce marginally severe hail given the available instability.

Other areas to watch

Beyond the Slight Risk area, isolated severe wind gusts will be possible in two other regions today:

Southern High Plains: Moderate diurnal heating and surface dewpoints in the 50s to lower 60s°F will support scattered thunderstorm development across the Texas and Oklahoma Panhandles. MLCAPE between 1000-2000 J/kg and deep-layer shear around 30 knots, combined with steep low-level lapse rates, will likely produce isolated severe wind gusts as storms spread south-southeastward later today, reaching parts of west Texas this evening.

Southwest and central New Mexico, southeast Arizona: Another round of thunderstorms is expected beginning around mid-afternoon, influenced by orographic lift and a moist environment. Enhanced northerly winds aloft will aid storm organization, and some storms may produce isolated severe-caliber wind gusts through early evening.

Yesterday's severe weather

Friday saw active severe weather across the High Plains and portions of the Midwest. The SPC received 41 wind reports, primarily from Wyoming, Texas, New Mexico, and Missouri, and 7 hail reports from South Dakota. No tornadoes were reported.

Notable wind reports included a 77 mph gust 2 WNW of Hereford, Texas, at 0124 UTC, where an uprooted tree was photographed in a front yard. Golf ball-size hail (1.75 inches) was confirmed in Argyle, South Dakota, with photos showing large holes punched in outdoor plastic storage containers.

Looking ahead

SPC Day 2 (Sunday, August 2) shows a Marginal Risk across portions of the Southeast, Ohio Valley, and Great Lakes as the system continues eastward. Day 3 (Monday, August 3) introduces a Slight Risk across the Central and Northern Plains, where another round of severe weather is possible early next week.

What should you do?

If you're in the Slight Risk area today:

  • Monitor local NWS forecasts and radar through the afternoon and evening
  • Have multiple ways to receive warnings—NOAA Weather Radio, a weather app, and local news
  • If a severe thunderstorm warning is issued for your location, move to an interior room away from windows
  • If a tornado warning is issued, move immediately to your safe place: a basement, interior room on the lowest floor, or a small interior closet

Nighttime tornadoes are particularly dangerous because people are less likely to receive warnings while asleep. Third-party weather apps are silenced by Do Not Disturb, though Wireless Emergency Alerts for tornado warnings still break through on most phones. VORTEX Pro places phone calls when a tornado warning is issued for a saved location—calls can ring through Do Not Disturb once you enable Emergency Bypass for the number, ensuring you're alerted even while sleeping.

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.