On January 28, 2022 a total of over 8 inches of snow was suddenly dropped on parts of Chicago, Illinois beginning in the late evening of January 27, 2022 and continuing throughout the night into the next morning. The snow fell at a rate of 1-2 inches per hour and was formed due to lake effect. Lake effect snow formation is caused when colder, drier air masses move across the lake. As the cold air moves across the warmer lakes, the air warms and becomes more humid and less dense. This causes the air to rise and then cool which is where it forms into clouds and precipitates. It turns to snow once over land when the moisture in the air condenses into snow creating lake effect snow (Figure 1).
Figure 1: Diagram showing the formation of lake effect snow and the factors that cause it. (Source: weathernet)
Looking at the nighttime microphysics RGB from January 28, 2022 while this lake effect snow was occurring, at 2:41 a.m. EST (0641 UTC) the cooler, water clouds can be seen by the greenish/ yellow color on the RGB map (Figure 2). The redder areas are higher, thick clouds and a clear distinction between the cooler clouds contributing to the lake effect snow and the higher clouds present that are not associated with the cooler air. The first map (Figure 2a) shows nighttime microphysics RGB without 0.5 radar reflectivity present but Figure 2b shows where the snow registered on radar (measured in dBZ). It shows the snow present in the blue/white colored areas over the greenish/yellow area. This lake effect snow event was a product of a single snow band over Chicago, Illinois which is shown accurately on this overlay (Figure 2b).
Figure 2: (a) Nighttime Microphysics RGB of 0641 UTC January 28, 2022 without radar and (b) with radar (source: CIMSS Satellite Blog)
Another RGB map used to view where the lake effect snow was present is Day Cloud Phase Distinction RGB. In this RGB, the blacker areas depict water surfaces and therefore Figure 3 depicts Lake Michigan clearly. Figure 3 shows the lake effect snow still occurring later in the day than the nighttime microphysics RGB at 11:36 a.m. EST (1536 UTC) on January 28, 2022. In this RGB, thin high-level clouds with ice particles or snow are shown in redder/ orange areas and glaciating clouds / snow is depicted by green. Looking at the Day Cloud Phase Distinction RGB map below, it highlights the narrow nature of the band as it moves inland over Chicago.
Figure 3: (a) Day Cloud Phase Distinction RGB of 1536 UTC January 28, 2022 without radar and (b) with radar (source: CIMSS Satellite Blog)
The WPC surface map below (Figure 4) depicts the surface at 10 p.m. EST (0300 UTC) January 27, 2022 (a) and 4 a.m. (0900 UTC) January 28, 2022. The two maps show the progression of a cold front extending south from Canada over the great lakes southwest to Illinois before curving north again towards Montana at 0300 UTC moving south across the great lakes and Illinois and lingering over Illinois. This cold front caused the greater temperature difference between the warmer, moist air over the lakes and the colder, drier air coming with the cold front. As stated earlier, lake-effect snow is formed by cold air moving over warm water, so the longer the cold air moves over that warm air, the greater the precipitation will be which is how the snowfall amount reached such high levels.
Figure 4: NOAA surface analysis map on January 28, 2022 (a) at 0300 UTC (b) 0900 UTC
This lake effect snow event led to high amounts of snowfall in the Chicago area with as high as 9 inches being reported in Evanston 1 E. The highest totals are listed below in Figure 5. The snowfall rates were on the order of 1 to 2 inches per hour and created dangerous travel conditions during the Friday commutes due to rapid changes in visibility and snow-covered roads. The visibility dropped to as low as ½ of a mile. This localized snow fall is unique to lake effect snow which is shown in Figure 5 as the highest totals were near the edge of Lake Michigan. Though lake effect snow is very common coming off of the great lakes, this January 28, 2022 snowfall was a high one that caused a messy day in Chicago.
Figure 5: Map of Chicago area with recorded amounts of snowfall (source: NWS)