5-minute CONUS Sector GOES-19 (GOES-East) Visible images (above) showed the development of at least 2 mesolow circulations in southern Lake Superior (off the coast of Upper Michigan) on 29 January 2026. The combination of Fixed Buoy and METAR surface reports implied that there was convergence over the portion of the lake where the mesolows formed. Just west of the mesolows, the peak wind gust at the Stannard Rock buoy (STDM4) was 29 kts at 2100 UTC.

Plots of Metop-B ASCAT surface scatterometer winds valid at 1445 UTC (below) confirmed the presence of mid-lake convergence in the area where the mesolows later developed.

Interestingly, GOES-19 GLM data displayed a single lightning flash near the Stannard Rock buoy at 1356 UTC (below), several hours prior to the mesolow development.

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5-minute CONUS Sector GOES-19 (GOES-East) Water Vapor images (above) included hourly plots of surface weather type (R=rain, S=snow, ZR=freezing rain, L=drizzle, F=fog) during the 4-day period (23 January – 26 January 2026) that a major winter storm impacted much of the southern and eastern US. According to the WPC storm summary, some notable storm statistics included: 23″ of snowfall in Pennsylvania, 6.7″ of sleet accumulation in Arkansas and 1.0″ of freezing rain accretion in Louisiana, Mississippi, Alabama and South Carolina. Over 60 storm-related deaths resulted across the affected regions. (The 2025-2026 winter’s first air temperatures in the -40s F within the Lower 48 states occurred north of this winter storm — in northern Minnesota — on 24 January.)

During the day on 26-27 January, as cloud cover cleared in the wake of the departing storm, areas that received significant ice accrual (from freezing rain and/or sleet) showed up as swaths of darker black in GOES-19 Near-Infrared “Snow/Ice” imagery (below) — darker black because ice is a stronger absorber of radiation than snow at the 1.61 µm wavelength. Widespread and long-duration power outages resulted from the weight of ice build-up on power lines.

The area of ice accretion exhibited darker shades of red in GOES-19 Day Snow-Fog RGB images created using Geo2Grid (below) on 26-27 January (snow cover appeared as brighter shades of red). The Day Snow-Fog RGB uses the 1.61 µm spectral band as its green component.

According to a Storm Total Ice Accumulation analysis (below), the maximum ice accretion amount was 1.24″ just east of Oxford, Mississippi.

The darker appearance of ice accrual (from freezing rain) was first noted on this blog using VIIRS imagery over Oklahoma.

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As a strong arctic cold front moved southward across the Gulf of Mexico toward southern Mexico on 25-26 January 2026, the cold front fractured as it moved inland across Mexico’s Isthmus of Tehuantepec — the cold air was then channeled southward through Chivela Pass and emerged as a Tehuano (or “Tehuantepecer“) gap wind that eventually fanned outward across the Gulf of Tehuantepec and adjacent Pacific Ocean. 10-minute Full Disk scan GOES-19 (GOES-East) Near-Infrared images (above) showed the hazy plume of dust that was being transported offshore — along with a narrow arc cloud that marked the southern and eastern edges of this Tehuano flow.

A topography image ((below) also showed Metop-B ASCAT winds emerging from the southern coast of Mexico, after the gap winds had accelerated through Chivela Pass; wind speeds were as high as 37 kts. The Tropical Analysis and Forecast Branch had issued a polygon where Storm Force winds were likely over the Gulf of Tehuantepec.

A toggle between Metop-B ASCAT and OSCAT-3 surface scatterometer images (below) depicted the pulse of Tehuano winds off the Pacific coast of Mexico.

In a side-by-side comparison of Nighttime Microphysics RGB and daytime True Color RGB images from GOES-18 (GOES-West) and GOES-19 (GOES-East) sourced from the CSPP GeoSphere site (below), a large pulse of airborne dust was seen emerging from Mexico’s Pacific coast and spreading south-southwest across the Gulf of Tehuantepec.

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A major winter storm was brewing over most of the eastern continental United States over the weekend of 24-25 January 2026. At one point during the weekend, 185 million people were under some kind of National Weather Service-issued winter weather alert, with warnings for winter storms, ice storms, extreme cold, and others. A quick look at the map of NWS active warnings for the night of Saturday 24 Jan shows just how extensive this winter storm was:

One of the most challenging winter weather phenomena to address is freezing rain, which can cause problems ranging from widespread vehicle accidents to extensive power outages. Pinpointing where freezing rain is going to occur can be difficult, as it requires knowledge of weather conditions throughout the lower atmosphere: you have to know that the air is moist enough to support precipitation reaching the surface, that there is a deep enough layer of warm air (that is, air above freezing) to melt falling snowflakes, but surface conditions have to be below freezing to force the melted water to refreeze upon contact. While radiosondes may be ideal for this, the sparse cadence of launches makes it difficult to monitor how conditions are changing.

This is an arena where NUCAPS can be very useful. These thermodynamic profiles from polar orbiting satellites can help fill in those gaps and inform where to expect elevated moist layers. Because the NUCAPS profiles are spatially dense, it’s possible to extract surfaces from the retrieved data, like temperature at a particular level. Take a look at this plot, which shows the 850 mb temperature (shaded, in Celsius) and the surface weather conditions (station plot, in Fahrenheit). The color mapping for the NUCAPS has been changed to a NEXRAD velocity plot as that makes it easy to identify positive or negative locations. In this case, temperature below freezing are shaded as greens and blues while temperatures above freezing are shaded as reds, pinks, and oranges.

This image shows that the 850 mb temperature is above freezing for large parts of the south. However, take a look at northeast Texas / northwest Louisiana / southwest Arkansas. The Ark-la-tex (as that region is commonly called) has 850 mb temperatures above freezing but surface temperatures at or below freezing. That’s an ideal setup for freezing rain, and in fact local media in Shreveport, LA; Texarkana, TX/AR; and other places reported freezing rain throughout the region.

One thing to keep in mind with using NUCAPS profiles is the data quality. In AWIPS and in other systems, that’s given by a simple traffic light code: green means both the infrared and microwave observations produced a valid thermodynamic retrieval, yellow means that due to cloud cover only the microwave sounder was able to contribute to the retrieval, and red means that the retrieval didn’t converge and the data are of suspect quality. The data quality plot shows mostly yellow due to all the cloud coverage, but has a large swatch of red where the precipitation rates are so intense that the microwave radiometer can’t penetrate through. This means that the 850 mb temperatures from eastern Louisiana to western Tennessee shouldn’t be trusted. Regardless, there’s a large region where the NUCAPS observations are providing additional value and helping to inform about the state of the atmosphere away from the surface.

Edit: Here’s a cool update from NWS Duluth Science and Operations Officer Patrick Ayd. The blowing snow RGB can be used for identifying where ice has fallen relative to the snow. Check out the following image. Here, snow shows up as the brighter red while ice is shaded in a darker red. Note how the Ark-La-Tex has significant amounts of ice, along with a long band of ice stretching from central Kentucky southeast to western Mississippi. Thanks for sharing, Patrick!

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