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Power plant plumes within a supercooled cloud layer over Wisconsin

By Scott Bachmeier •

5-minute GOES-19 Nighttime Microphysics RGB + daytime True Color RGB images, from 0901-1801 U11TC on 02 December [click to play MP4 animation]

5-minute CONUS Sector GOES-19 (GOES-East) Nighttime Microphysics RGB + daytime True Color RGB images from the CSPP GeoSphere site (above) showed numerous power plant plumes (shades of red) embedded within a supercooled water droplet c  loud layer (shades of yellow) that covered much of Wisconsin on 02 December 2025.

The GOES-19 Cloud Top Phase derived product (below) confirmed that the cloud layer across the region was predominantly Supercooled (light green). The power plant plumes were classified as Uncertain (black).

5-minute GOES-19 Cloud Top Phase derived product, from 0806-1801 UTC on 02 December [click to play MP4 animation]

An animation of GOES-19 Night Fog brightness temperature difference (BTD) + daytime Near-Infrared “Snow/Ice” (1.61 µm) images (below) also included plots of METAR surface reports — some of which showed light snow (denoted by the * symbol) in the the vicinity of the larger power plant plumes. These power plant plumes had the effect of eroding the supercooled water droplet cloud layer — via glaciation, initiated by the power plant emission of particles that acted as efficient ice nuclei, which then caused snow to fall from that portion of the cloud.

5-minute GOES-19 Night Fog BTD (10.3-3.9 µm) + daytime Near-Infrared “Snow/Ice” (1.61 µm) images, with/without plots of METAR surface reports, from 0901-1801 UTC on 02 December [click to play MP4 animation]

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GOES-19 Near-Infrared “Snow/Ice” image at 1451 UTC on 02 December, with/without a cursor sample of the 1453 UTC Madison WI (KMSN) METAR surface report [click to enlarge]

One notable power plant plume in southern Wisconsin originated in west-central Dane County — and as this plume passed near/over the Madison airport (KMSN), the observer remarked that snow began at 1400 UTC and ended at 1451 UTC (above). The visibility at the 1453 UTC report time had improved to 8 statute miles — while the visibility at the Middleton airport, located just SW of KMSN, was only 4 statute miles at that time (Middleton is an AWOS site, which does not report precipitation type).

3 hours later, KMSN was reporting light snow with a visibility of 3 statute miles as the same power plant plume was passing near/over the airport (below) — while the visibility at Middleton was 2-1/2 statute miles (where it was also likely snowing). During the 1400-1900 UTC (0800-1300 CST) time period, intermittent reductions in visibility due to light snow were apparent in UW-AOS rooftop cameras facing north and northwest.

GOES-19 Near-Infrared “Snow/Ice” image at 1751 UTC on 02 December, with/without a cursor sample of the 1753 UTC Madison WI (KMSN) METAR surface report [click to enlarge]

A closer view of the power plant plumes originating in Dane County is shown in a comparison of Suomi-NPP VIIRS True Color RGB and False Color RGB images valid at 1820 UTC, visualized using RealEarth (below). By that time, the leading edge of the Dane County plume had traveled northeastward over Columbia County; plumes from the Columbia Energy Center near Portage were also apparent.

Suomi-NPP VIIRS True Color RGB and False Color RGB images valid at 1820 UTC on 02 December — with plots of surface observations and either county outlines or labels [click to enlarge]

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In northern Wisconsin, during the overnight hours a large power plant plume in Marathon County — likely the Weston Power Plant, located south of Wausau — was producing enough light snow to reduce the visibility to 1 mile at Wausau (KAUW), as seen in the GOES-19 0901 UTC Night Fog BTD image (below).

GOES-19 Night Fog BTD image at 0901 UTC on 02 December, with a red box highlighting the Wausau WI (KAUW) METAR surface observation [click to enlarge]

Since the Moon was in the Waxing Gibbous phase (at 93% of Full), it provided ample nighttime illumination to reveal that the power plant plume originating near Wausau was causing enough light snow to fall from the supercooled cloud layer that a hole (or at least a significant cloud thinning) had developed — as seen in VIIRS Day/Night Band imagery from NOAA-21 and Suomi-NPP (below).

GOES-19 Night Fog BTD and NOAA-21 VIIRS Day/Night Band (0.7 µm) images at 0806 UTC on 02 December [click to enlarge]

GOES-19 Night Fog BTD and Suomi-NPP VIIRS Day/Night Band (0.7 µm) images at 0836 UTC on 02 December [click to enlarge]

During the subsequent daytime hours, the Marathon County power plant plume was drifting far enough northeastward to produce light snow that reduced the visibility to 3 statute miles at Antigo (KAIG) (below).

GOES-19 Near-Infrared “Snow/Ice” image at 1536 UTC on 02 December, with/without a cursor sample of the 1535 UTC Antigo WI (KAIG) METAR surface report [click to enlarge]

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5-minute GOES-19 “Red” Visible images (0.64 µm, left) and Near-Infrared “Snow/Ice” images (1.61 µm, right), from 1316-1601 UTC on 02 December [click to play MP4 animation]

As an aside, another interesting feature seen in the imagery was a packet of cloud-top waves associated with a bore that was moving inland (westward) across east-central Wisconsin during the morning hours (above). This bore had no influence on surface wind direction, indicating that the feature was not surface-based.

A plot of rawinsonde data from nearby Green Bay, Wisconsin at 1800 UTC (below) showed a pronounced temperature inversion from 948-900 hPa (1038-2058 ft) — within which the bore was likely being ducted as it propagated westward.

Plot of rawinsonde data from Green Bay, Wisconsin at 1800 UTC on 02 December [click to enlarge]

Categories: GOES-19, NOAA-21, RealEarth, Red-Green-Blue (RGB) images, Suomi NPP, VIIRS, Winter weather