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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Due to a lack of radar coverage over American Samoa, WSO Pago Pago requested a 1-minute Mesoscale Domain Sector over the islands to monitor convective development and the potential for flash flooding. GOES-18 (GOES-West) Clean Infrared Window (10.3 µm) images (above) showed rain showers and thunderstorms that developed in the general vicinity of the American Samoa island of Tutuila (where Pago Pago International Airport NSTU is located) on 24 January 2026. GLM Flash Points indicated that intermittent lightning occurred near Tutuila — and thunderstorms were occasionally reported at NSTU. The development of deep convection was enhanced by the presence of a surface trough of low pressure across the area (1500 UTC | 1800 UTC | 0000 UTC).

The coldest cloud-top infrared brightness temperatures were in the -85 to -89ºC range (darker shades of purple embedded within brighter white regions) — which represented a slight overshoot of the Most Unstable (MU) air parcel’s Equilibrium Level (EL), which was around 15 km (or 50 kft) according to a plot of rawinsonde data from NSTU at 0000 UTC on 25 January (below).

The GOES-18 Infrared image at 1850 UTC (below) included a sample of the corresponding NSTU METAR — which indicated that a thunderstorm with heavy rain showers was reducing the visibility to 3 miles at that time. Note that the coldest cloud-top infrared brightness temperatures of that particular thunderstorm (violet pixels) were displaced to the southwest of NSTU, due to a GOES-West parallax offset associated with a cloud-top altitude around 50 kft or 15.2 km.

The GOES-18 Infrared image at 2058 UTC (below) included a sample of the corresponding NSTU METAR — which indicated that a thunderstorm had earlier occurred from 1800-1856 UTC, and heavy rain showers had occurred from 1811-1951 UTC.

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Pago Pago recorded 2.76″ of rainfall during their calendar day of 24 January (above) — with most of that occurring during the ~2 hour period from 1811-1951 UTC (below). WSO Pago Pago issued Flash Flood Warnings at 1812 UTC and 2100 UTC on 24 January.

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5-minute CONUS Sector GOES-19 (GOES-East) Red Visible and Near-Infrared “Snow/Ice” images (above) displayed a cluster of aircraft dissipation trails or “distrails” (in contrast to aircraft condensation trails or contrails) that drifted eastward across Ohio on 24 January 2026.

These distrail features were caused by aircraft that were either ascending through or descending through a cloud layer composed of supercooled water droplets — cooling from wake turbulence (reference) and/or particles from the jet engine exhaust acting as ice condensation nuclei caused the small supercooled water droplets to transform into larger ice crystals (many of which then often fall from the cloud layer). The darker gray appearance of the distrails in 1.61 µm imagery confirmed that those features were composed of ice crystals (since ice is a strong absorber of radiation at that wavelength).

The corresponding GOES-19 Day Cloud Phase Distinction RGB images created using Geo2Grid (below) provided another view of the distrails — the brighter shades of green were indicative of glaciating cloud features. Interestingly, numerous long/narrow contrails were also apparent over the supercooled cloud layer (shades of white) to the south and east of the distrails.

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A prescribed burn in far western Arizona’s Havasu National Wildlife Refuge became uncontrolled as northerly winds unexpectedly increased (gusting to 36 mph at RAWS site QHAA3 just north of the fire, and gusting to 28 mph at Needles Airport just west of the fire around 2300 UTC) — and grew to become the Havasu Fire on 19 January 2026. The fire’s thermal signature was evident in a 2-day animation of 5-minute PACUS Sector GOES-18 (GOES-West) Microphysics RGB images and Next Generation Fire System (NGFS) Fire Detection polygons from 19-21 January (above).

Although the initial fire detection signal was seen in the GOES-18 Microphysics RGB image at 1521 UTC, the initial NGFS Fire Detection polygons appeared at 1606 UTC (below).

A probe of the NGFS Fire Detection polygons at 0451 UTC on 20 January (below) revealed a 3.9 µm infrared brightness temperature of 137ºC — which is the saturation temperature of GOES-18 ABI Band 7 detectors.

On 20 January, GOES-18 GeoColor RGB images (below) showed the south-southeast transport of smoke from the Havasu Fire — hazy conditions were reported in Lake Havasu City during the day. The smoke affected school activities: students were kept inside for recess that day, and the evening Lake Havasu High School Boys Soccer game was postponed for another date.

The southward transport of Havasu Fire smoke could be seen in True Color RGB images from both GOES-18 (GOES-West) and GOES-19 (GOES-East), sourced from the CSPP GeoSphere site (below).

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