1-minute Mesoscale Domain Sector GOES-19 (GOES-East) True Color RGB images from the CSPP GeoSphere site (below) showed ice that had formed in far southern Lake Michigan (within the nearshore waters of Wisconsin, Michigan and Indiana) on 20 January 2026.

1-minute GOES-19 Visible images with plots of surface winds and air temperatures (below) depicted the cold air temperatures — from single digits below 0ºF to single digits above 0ºF — that were present near the Lake Michigan coast shortly after sunrise.

A toggle between the 1500 UTC GOES-19 Visible image with and without an overlay of the 1500 UTC GOES-19 Sea Surface Temperature (SST) derived product (below) indicated that SST values were as warm as 3.54ºC in the open waters just east of the sea ice.

A 30-meter resolution Landsat-8 Natural Color RGB image visualized using RealEarth (below) provided a more detailed view of the lake ice in the vicinity of Chicago.

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Unseasonably cold temperatures were found in the early morning hours of 20 January 2026. This map of observed temperatures from 0800 UTC (2:00 AM CST) shows that a tongue of cold air has plunged southward with subzero temperatures found even in the southern portions of Minnesota and Wisconsin while single-digit temperatures were common throughout the Midwest.

Of particular interest, however, are the isolated temperatures between -11 and -18 in southwestern Wisconsin. Are these temperatures observational outliers with no physical basis, or are they really representative of the conditions on the ground? Let’s use satellites to see if we can learn more about what’s going on.

We’ll start with a regional view of Band 13 from GOES-19. This is the standard 10.3 micron infrared band used to identify the positions of clouds at all hours of the day. However, interpreting this band during abnormally cold conditions can be a challenge, because the color scale used to identify higher-altitude clouds paints the cloud-free surface in the same colors because the temperatures are so low. This animation shows this quite well: there is clearly a lake effect band on the western shore of Michigan’s lower peninsula, and yet it has the same cyan and blue colorization as the immobile parts of Minnesota and Wisconsin.

The infrared-observed surface temperatures of the upper midwest are clearly heterogeneous. But what is contributing to all of that variability? To analyze this, let’s adjust the color scale of the infrared image. This is a still frame from the 0800 UTC image above, merely adjusted to cnhance the dynamic range over the observed surface temperatures. Light is warmer than dark.

Compare the patterns in the infrared image above to this terrain map from the Wisconsin Department of Natural Resources. Note how the colder (darker) regions on the infrared map in southwestern Wisconsin correspond to the valleys in the terrain map, with that pair of -11 F temperatures confined to the Wisconsin River valley. The -18 F temperature is found in the valley of the La Crosse River. Both of these rivers flow through the Driftless Area, the rugged heart of the upper midwest that avoided being flattened by glaciers in the most recent ice age.

We commonly associate increasing altitude with decreasing temperatures. So why are the valleys colder than the tops of the ridges? This is a result of cold air pooling and katabatic flow. The night was clear and calm; see how the surface winds in the earlier figure were between 0 and 5 knots everywhere. In the absence of synoptic scale forcing, smaller scale forcing can take effect. In this case, the air at the top of the terrain experiences strong radiative cooling. After all, there were no clouds above to absorb and emit outgoing infrared radiation. Cold air is also dense air, and so these radiative-cooled air masses flowed downhill into the valleys, where they pooled. This downward flow of radiatively-cooled air is known as a katabatic wind. On the scale of the relatively shallow terrain of the Driftless the flow would be difficult to measure directly, but in mountainous regions they can be quite significant.

Based on all of this, it is likely that the anomalously low temperatures in southwest Wisconsin aren’t false readings, but actually representative of their local microclimate.

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Strong northerly winds created blowing snow and blizzard conditions across parts of eastern North Dakota and western Minnesota — particularly within the Red River Valley — on 17 January 2026. 5-minute CONUS Sector GOES-19 (GOES-East) Near-Infrared “Snow/Ice” images (above) showed the development of Horizontal Convective Rolls (HCRs) where winds were channeled down the Red River Valley (topography) — with gusts in excess of 30 knots, reducing the surface visibility to less than 1 mile due to blowing snow at several METAR sites.

GOES-19 Blowing Snow RGB images created using Geo2Grid (below) provided a more distinct view of the HCRs.

===== 18 January Update =====

Even stronger winds in the wake of a cold frontal passage (with gusts in excess of 40 knots) produced a second day of blowing snow and blizzard conditions across eastern North Dakota and western Minnesota on 18 January — and HCRs were once again very prevalent in GOES-19 Blowing Snow RGB images (above), across a larger area than the previous day. The surface visibility was reduced to near zero at some METAR sites.

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Much of the state of Alaska is finds itself impacted by a strong atmospheric river on Friday, 16 January 2026. Moisture has been plunging due north from the tropics to the southern coast of Alaska. The river has brought with it precipitation and temperatures well above normal. One of the best ways to monitor the location and strength of an atmospheric river is with the CIMSS MIMIC-TPW product, which merges polar-orbiting and geostationary products to provide microwave-like observations of total precipitable water at a much greater frequency than is possible with the polar orbiter microwave instruments. A quick glance at the MIMIC-TPW product makes it easy to identify the area of anomalous moisture.

Zooming out enables us to see the plume in a global context. Here, it appears as a direct plume linking Alaska directly to the high moisture region of the tropical Pacific. Note that this also appears to be not the only atmospheric river that is impacting Alaska, with another plume in the north central Pacific. According to the GFS model, these two rivers are forecasted to merge over the weekend.

The impacts of this river on sensible weather are significant. Temperatures in southern Alaska are elevated compared to normal. The normal high temperature for Anchorage on January 16 is 22 F, but temperatures reached 39 F by midday. Reports from Anchorage note rain falling on snow-packed roads, creating slippery conditions despite the greater-than-freezing temperatures. Numerous avalanche warnings have also been issued in southern Alaska due to large areas of heavy rain and snow created by the atmospheric river.

The GOES-18 water vapor channels (in this case, channel 8, 6.2 microns) can also provide some insight into the strength of this event. Here, it is easy to see how the moist air is streaming north to the southern Alaska shore where it then starts dispersing into the interior of Alaska as well as the Yukon and Northwest Territories of Canada. This loop also shows the challenges associated with using geostationary imagery in polar regions: the significant displacement from the sub-satellite point over the equator means oblique viewing angles and very coarse pixel resolution; just compare the size of the pixels at the top of this loop to those at the bottom.

At these higher latitudes, polar orbiting satellites offer a promising alternative. The primary disadvantage of polar orbiters, the relatively coarse temporal resolution relative to geostationary satellites, is lessened near the poles as orbits are constantly overlapping. However, neither the United States’s VIIRS nor EUMETSAT’s AVHRR have water vapor sensitive channels, so while views of the clouds from visible or infrared imagery are possible, additional information about the water vapor distribution at the fine horizontal resolution of a polar orbiting satellite is not possible.

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