{"id":72688,"date":"2026-10-17T15:59:09","date_gmt":"2026-10-17T15:59:09","guid":{"rendered":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/?p=72688"},"modified":"2026-10-17T15:59:09","modified_gmt":"2026-10-17T15:59:09","slug":"lake-effect-from-wisconsins-lake-winnebago","status":"publish","type":"post","link":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/archives\/72688","title":{"rendered":"Lake Effect from Wisconsin’s Lake Winnebago"},"content":{"rendered":"\n

Lake Winnebago is the largest lake located entirely within the borders of Wisconsin. At 137,000 acres, it has approximately the same area as the famous Lake Geneva (that is, the original Lake Geneva along the borders of France and Switzerland). However, it’s a shallow lake, with an average depth of only about 15 feet. Like any body of water, however, it is much slower to change its temperature than the surrounding land, and in the early morning hours of 17 October 2026 that caused some interesting and highly localized weather conditions. <\/p>\n\n\n\n

Midwestern weather aficionados are generally familiar with the lake effect and its impact on wintertime precipitation. In short, during the winter the Great Lakes tend to be warmer than the surrounding land because they have much larger thermal inertia and it takes weeks to months for them to cool down to freezing levels. When cold air advects over the lakes, this air gets heated from underneath which destabilizes it, lots of moisture is evaporated into that air, and shallow but intense convective activity ensues. <\/p>\n\n\n\n

However, this isn’t limited to the Great Lakes, especially in the early season. Smaller bodies of water adjust their temperatures more rapidly than the vast inland seas of the Great Lakes, but in the autumn when temperature changes are rapid the lake\/lake temperature difference can be large enough to create highly localized lake effect events. That’s exactly what happened on Lake Winnebago this week.<\/p>\n\n\n\n

The University of Wisconsin-Milwaukee operates a buoy on Lake Winnebago<\/a> that monitors the water conditions, including the lake’s temperature at multiple depths. Here’s a time series of the water temperatures for the past two days. Regardless of depth, the temperatures were around 59 F. <\/p>\n\n\n\n

\"Time<\/figure>\n\n\n\n

Compare that to the evolution of the air temperature during that time. The invaluable Iowa Environmental Mesonet lets us examine the evolution of the atmospheric conditions at nearby Oshkosh, Wisconsin. Note that the axes cover slightly different time periods and the water temperature is in UTC time while the Oshkosh meteogram is in CDT. You can see that see that as of 1200 UTC (7:00 AM CDT) on the 15th, the water was about 7 F warmer than the atmosphere. However, in the overnight hours of the 16th to the 17th, a polar air mass moved in to the upper midwest, setting off some of the first freeze warnings for the season throughout the region. By 0600 UTC (1:00 AM) on the 17th, the water temperatures dropped about 4 degrees F but the air temperature plummeted nearly 20 F! This tremendous air\/lake temperature difference created the necessary conditions for a lake effect event.<\/p>\n\n\n\n

\"Meteogram<\/figure>\n\n\n\n

Here’s an animation of the GOES-19 (GOES West) Band 13 infrared window view over western Wisconsin from 2300 UTC on the 16th to 0100 UTC on the 17th (6 PM to 8 PM on the 16th in Central Daylight Time). Lake Winnebago is the lake in the middle of the image to the west of Lake Michigan. For context, sunset at Oshkosh on Winnebago’s western shore was at 2310 UTC (6:10 PM CDT), so this loop is effectively covering the period from sunset through the first hours of the night. There’s a few things to see in this loop. First, the surface water is clearly warmer than the surrounding land as is visible for Lake Michigan, Green Bay, and even the chain of smaller Madison-area lakes in the southwest region of the loop. Second, there is a good amount of lake-based convection streaming from Lake Michigan. However, we can also see the same pattern of clouds streaming southward from Lake Winnebago. This is the localized lake effect event.<\/p>\n\n\n\n

\"Animation<\/figure>\n\n\n\n

The challenge with using a single-band infrared product to monitor nighttime clouds is that the temperature difference between low clouds and the surface is often small and so it can be hard to discern where the clouds are against the relatively warm surface background. This is why there’s more contrast between the clouds and the surface over the lakes than over the land. However, other satellite products can provide more insight. The Night Microphysics<\/a> RGB exploits the way that clouds behave differently in different imager channels depending on their geometric thickness and microphysical characteristics. Below, you’ll see the the Night Microphysics animation covering the same time and domain as the infrared loop above. Since this loop begins right after sunset this is right at the start of the period of time where this product is providing useful information. The standard interpretation of the Night Microphysics product doesn’t work during the day because the 3.9 micron channel is a key part of the RGB recipe. This channel measures solar reflectance during the day like a visible channel, but observes thermal emittance at night like an infrared channel, and so its interpretation changes drastically at sunset.<\/p>\n\n\n\n

In this loop we see numerous greenish-yellow clouds originating from the warm water. This coloration is indicative of low level water clouds, consistent with what we’d expect from clouds forced by the lake effect.<\/p>\n\n\n\n

\"Loop<\/figure>\n\n\n\n

It’s worth checking out the radar to see if Lake Winnebago is creating any convection. While the lake is a little closer to the Green Bay NEXRAD than the Milwaukee\/Sullivan one, given that the clouds are streaming to the south it’s reasonable to opt to monitor that latter system for any precipitation that may be forming. Here’s an animation from the 0.5 degree reflectivity scan. Toward the end of the loop, after the sun sets, the inversion develops, and the anomalous propagation that lights up the whole radar screen kicks in, you can see a thin filament of enhanced reflectivity streaming south from Lake Winnebago at the norrth-central part of the loop.<\/p>\n\n\n\n

<\/p>\n\n\n\n

\"0.5<\/figure>\n\n\n\n

You may notice a persistent blob of enhanced reflectivity in the south-central part of the animation; this is actually the Horicon Wind Farm which lies directly in the line of sight of the radar. Ground clutter has always been a challenge for weather radars as the beams strike objects on the surface and bounce back to the radar. Clutter suppression algorithms work by identifying the Doppler velocity of the objects scattering the radar beam back. Stationary objects are assumed to be ground clutter and are removed. But wind turbines aren’t stationary; they’re constantly moving. Therefore, the suppression algorithm thinks it’s a legitimate signal. <\/p>\n\n\n\n

It was kind of challenging to see any radar return there. One alternative is to look at the Terminal Doppler Weather Radar (TDWR) from the Milwaukee airport. TDWRs are fine-scale, rapidly-updating radars located at significant airports and are deployed to provide fast and frequent observations of the environment so that airplanes can operate safely. In exchange for the higher radial resolution, TDWRs have much shorter horizontal ranges. The big advantage of the TDWR in this case is that the lowest elevation angle is 0.3 degrees instead of 0.5. Since lake effect events are so shallow this may enable us to get a better glimpse as to what’s going on than we did with the NEXRAD which could be overshooting the whole event. And here, it does look like there’s a couple of precipitaiton blobs that form downstream of Lake Winnebago when we expect them to. <\/p>\n\n\n\n

\"Loop<\/figure>\n\n\n\n

As noted above, Lake Winnebago is a shallow lake. The time series of water temperatures shown above indicates that the lake does change its temperature rather rapidly. An event like this can only happen at this time of the year as soon the lake will freeze over and cut off the moisture and latent heat necessary to sustain lake effect processes. However, we can enjoy it while it lasts.<\/p>\n","protected":false},"excerpt":{"rendered":"

Lake Winnebago is the largest lake located entirely within the borders of Wisconsin. At 137,000 acres, it has approximately the same area as the famous Lake Geneva (that is, the original Lake Geneva along the borders of France and Switzerland). However, it’s a shallow lake, with an average depth of only about 15 feet. Like […]<\/p>\n","protected":false},"author":22,"featured_media":72705,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[10,159,45,38,5],"tags":[],"class_list":["post-72688","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-general-interpretation","category-goes-19","category-redgreenblue-rgb-images","category-what-the-heck-is-this","category-winter-weather"],"acf":[],"_links":{"self":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/72688","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/users\/22"}],"replies":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/comments?post=72688"}],"version-history":[{"count":8,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/72688\/revisions"}],"predecessor-version":[{"id":72704,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/72688\/revisions\/72704"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media\/72705"}],"wp:attachment":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media?parent=72688"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/categories?post=72688"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/tags?post=72688"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}