A large severe weather outbreak took place across the south central United States on Wednesday 2 April 2025. The NWS Storm Prediction Center (SPC) anticipated a significant weather event in the region, having predicted an enhanced risk of severe weather as early as Monday 31 March and a rare high risk the night before the event. The environmental conditions ahead of storm formation largely behaved as predicted, with elevated dew points caused by significant moisture advection from the Gulf coast and an advancing cold front stretching from the Midwest to the lower Mississippi valley creating the necessary instability for deep moist convection. When combined with ample shear and jet-streak based ageostrophic lifting, the ingredients were all present for multiple long-lived tornadoes. This can be seen in the surface map, where there’s substantial northerly flow from the gulf, dew points in the Mississippi valley between the mid-60s F and 70 F, and a dominant cold front.

It was a busy day for NWS forecasters throughout much of the continental United States (CONUS). Well over 700 tornado, severe thunderstorm, and flash flood warnings were issued across much of the eastern half of CONUS. According to The Weather Channel, this day marked the 3rd highest total of NWS-issued warnings ever, trailing only the April 2011 Super Outbreak and the Memorial Day Weekend 2004 Outbreak. The SPC Storm Reports map for the day shows just how widespread this event was.

Of course, NOAA satellite infrastructure was well-situated to capture the build-up and execution of this outbreak, and provided a vast amount of valuable data to forecasters, emergency manager, mass media, and the general public. Here are a few highlights:

NUCAPS soundings may prove to be an increasingly valuable part of the global observation network due to ongoing and anticipated further reductions in the US radiosonde network. By capitalizing on both American and EUMETSAT polar orbiting hyperspectral sounders, NUCAPS can provide vertical thermodynamic profiles multiple times per day. Here is an animation of three NUCAPS soundings from near Memphis, Tennessee.

Two of these soundings are overnight while the third is in the early afternoon. The daytime heating is clearly evident, and there is also substantial moistening in the lower levels. Midlevel lapse rates remain basically unchanged between these three soundings, but the influx of near-surface sensible and latent heat results in substantial instability increases. The Microwave + infrared retrieval shows CAPE going from 0 J/kg all the way to over 2200 J/kg.

Of course, the trustworthy GOES-16 geostationary satellite also provided excellent views of the evolving atmosphere. The mesoscale sector was focused on the area and providing very finely detailed views of the storms.

This animation of 1 minute GOES-16 data from Band 2 (0.64 microns) does a wonderful job of showing the evolution of these clouds as the cold front approaches southern Illinois and the lower Mississippi River. Since this animation is near sunset and this is a visible wavelength channel, the light is fading. However, the low solar angle really helps the texture pop, highlighting numerous overshooting tops throughout the domain.

At the same time, the Band 13 imagery allows for different characteristics of the storm to be identified. A string of enhanced v structures, indicative of very strong updrafts, is readily apparent. Wavelike structures over Illinois and Ohio indicate significant turbulence in the anvils downstream of the convective cores. Large storms over central Tennessee likely initiated from cold pools advancing ahead of the cold front and tapping all of that moist, unstable air.

Numerous tornadoes were reported on this day, including several rated at EF-2 or greater. One of the most devastating tornadoes of this event hit the small down of Selmer, Tennessee in the overnight hours. The tornado, with a preliminary rating of EF-3, destroyed entire neighborhoods in this small town of 4500 people. The CIMSS ProbSevere Product was able to capture and correctly identify the approaching storm cell as a storm of concern well before it hit the town.

Selmer is located in the upper right of this animation loop, at the intersection of US Routes 64 and 45. Note how ProbSevere has encircled the cell that eventually hits Selmer 90 minutes ahead of its arrival there. A full half-hour before its arrival, ProbSevere identified its tornado probability at 87%. With fast moving storms and nocturnal storms common, tools like ProbSevere are critical for keeping people safe, all the way from Mississippi to the Québec/Ontario border.

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On a rare High Risk Convective Outlook day, a widespread outbreak of severe thunderstorms produced tornadoes, large hail and damaging winds (SPC Storm Reports) across a large swath of the central and eastern US during the afternoon and subsequent nighttime hours on 02 April 2025. As mentioned in this blog post, GOES-19 had arrived at the GOES-East position (over the Equator at 75.2ºW Longitude) and had begun broadcasting data — which presented an opportunity for a GOES-16 (the current operational GOES-East) vs. GOES-19 comparison during this severe weather outbreak. There was some overlap of one of the Mesoscale Domain Sectors from both satellites, so closer views of a few notable areas that experienced severe weather will be shown below.

Central Illinois Hail/Damaging Winds

GOES-16 vs. GOES-19 Visible images (above) and Infrared images (below) showed convection that produced hail as large as 2.00″ in diameter and wind gusts as high as 90 mph in central Illinois. In the Visible imagery, small-scale features such as thunderstorm overshooting tops were resolved equally well by both satellites; in the Infrared images, cloud-top infrared brightness temperatures of cold features such as overshooting tops were generally within very good agreement (separated by less than 0.1 K).

Missouri/Arkansas/Kentucky Tornadoes

GOES-16 and GOES-19 Infrared images (above) showed thunderstorms that produced several tornadoes across southeast Missouri and southwest Kentucky, including a fatal EF2-rated tornado in Missouri around 2332 UTC. These storms also produced hail to 2.75″ in diameter and wind gusts to 70 mph.

Indiana Damaging Winds

GOES-16 and GOES-19 Iinfrared images (above) displayed thunderstorms that produced wind gusts to 100 mph over Indiana.

Tennessee/Mississippi Tornadoes

GOES-16 and GOES-19 Infrared images (above) depicted thunderstorms that produced tornadoes across northern Mississippi and southwest Tennessee — including a fatal tornado in Tennessee around 0631 UTC. Well-defined Enhanced-V storm-top signatures were associated with some of these tornado-producing thunderstorms.

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GOES-19, scheduled to become the operational GOES-East satellite on 4 April (Friday morning) no earlier than 7 April (updated on 3 April because of a Critical Weather Day), is now on station at 75.2^oW and broadcasting data. GOES-16, to be replaced, has been shifted slightly westward; data from both satellites are remapped to a grid centered at 75^oW. The comparion above shows the airmass RGB (computed using geo2grid and its underlying Satpy libraries). The two products are similar enough to be nearly indistinguishable. Scientists at CIMSS (and elsewhere) are working to make certain that the switch to GOES-19 is seamless.

The toggle below compares LightningCast probability contours on top of a Day Cloud Phase Distinction RGB — created using the CSPP Geo LightningCast software — for GOES-16 and GOES-19; the Day Cloud Phase Distinction RGB imagery is very similar and the LightningCast contours are largely the same.

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Darker shades of red in GOES-16 (GOES-East) Day Snow-Fog RGB images on 31 March 2025 (above) highlighted areas in eastern/northeastern Minnesota, northern Wisconsin and the Upper Peninsula of Michigan that received an accrual of ice (from sleet and/or freezing rain/drizzle) as a late-season winter storm moved across the region during the previous 2 days. In the RGB images — created using Geo2Grid — snow-covered ground appeared as brighter shades of red, with bare ground exhibiting shades of green; clouds appeared as shades of white to pale yellow/green (depending on the cloud-top phase).

A sequence of GOES-16 Visible and Near-Infrared “Snow/Ice” images is shown below — areas that received significant ice accretion exhibited darker shades of black in the Snow/Ice images. The highest ice accretion amounts in northern Wisconsin were 0.50″ in Forest and Oconto County, with 0.50″ also reported in Delta County in the UP of Michigan.

On the following day, clouds had cleared enough across the eastern UP of Michigan and northern Lower Michigan to reveal a darker-red Day Snow-Fog RGB signature of the areal coverage of ice accrual in those areas (below).

In a toggle between GOES-16 Day Snow-Fog RGB and True Color RGB images (below), in northern Lower Michigan note the lack of a brighter white True Color appearance along the southern edge of the strong (darker red) Day Snow-Fog ice accrual signature — a layer of ice on the ground with no snow cover is generally translucent.

A sequence of GOES-16 Visible and Near-Infrared “Snow/Ice” images is shown below — areas that received significant ice accretion exhibited darker shades of black in the Snow/Ice images. The highest ice accretion amounts in northern Lower Michigan were 1.50″ in Oconto County, 0.76″ in Presque Isle County and 0.75″ in Oscoda County.

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