A sprawling winter storm impacted the east half of the country Monday night through Tuesday, January 9, 2024. The strong low pressure center tracked from the Texas Panhandle Monday morning (9 AM) to Southern Illinois Tuesday morning (9 AM), and to far eastern Quebec Wednesday morning. The low crossed northern Indiana Tuesday afternoon (3 PM). This track was favorable for heavy precipitation across eastern Iowa, southern Wisconsin and northern Illinois.
Mean Sea Level Pressure Surface Analysis at 21Z (3 PM CST) Jan 9, 2024
Here is a map of the estimated snowfall totals across southern Wisconsin. Most of the snow fell between 9 AM and 9 PM Tuesday, but 1 to 3 inches of light snow fell early Tuesday morning on the leading edge of the system. Highest snowfall totals were west of Madison and lowest were along the lakeshore. There was also a local minimum from Fond du Lac to Watertown. The NWS Milwaukee/Sullivan office measured 5.6" total. Notice on the map below that there was a localized maximum in Washington and Waukesha Counties. This was due to some lake enhancement (the northeast winds gathered a little extra moisture off the lake) and a little extra lift from the hills of the Kettle Moraine.
Summary of Snowfall Totals:
Location Amount Time/Date Lat/Lon ...Wisconsin... ...Columbia County... Portage 5.7 WSW 7.5 in 0600 AM 01/10 43.51N/89.57W Lodi 4.8 in 0926 PM 01/09 43.32N/89.53W ...Dane County... 1 SW Shorewood Hills 9.8 in 0800 AM 01/10 43.06N/89.46W De Forest 9.5 in 0827 PM 01/09 43.25N/89.35W 1 WSW Oregon 9.0 in 1040 PM 01/09 42.92N/89.40W 1 W Oregon 9.0 in 1040 PM 01/09 42.92N/89.40W 2 SSE Oregon 9.0 in 0500 AM 01/10 42.90N/89.37W Cross Plains 8.2 in 0700 PM 01/09 43.11N/89.64W Windsor 8.2 in 1000 PM 01/09 43.22N/89.34W 3 NNE Verona 8.0 in 0910 PM 01/09 43.03N/89.51W 2 NW Sun Prairie 8.0 in 1000 AM 01/10 43.20N/89.25W 1 NW Sun Prairie 8.0 in 1000 AM 01/10 43.20N/89.25W 2 SSE Middleton 7.8 in 1124 PM 01/09 43.08N/89.49W 1 SSW Oregon 7.5 in 0720 PM 01/09 42.92N/89.39W 3 SW Shorewood Hills 7.5 in 0730 PM 01/09 43.05N/89.49W Verona 7.4 in 0830 PM 01/09 42.99N/89.53W Windsor 7.0 in 0600 PM 01/09 43.22N/89.33W Windsor 7.0 in 0600 PM 01/09 43.22N/89.34W 2 ESE Maple Bluff 7.0 in 1000 PM 01/09 43.10N/89.34W Windsor 0.3 ENE 6.8 in 0700 AM 01/10 43.22N/89.34W 3 NNE Verona 6.5 in 0324 PM 01/09 43.03N/89.50W 2 N Brooklyn 6.3 in 0736 AM 01/10 42.88N/89.38W Sun Prairie 6.0 in 0647 PM 01/09 43.18N/89.23W 2 NNE Maple Bluff 5.7 in 1100 PM 01/09 43.14N/89.35W 1 SE Verona 5.1 in 0340 PM 01/09 42.98N/89.52W 2 NNE Maple Bluff 4.8 in 0600 PM 01/09 43.14N/89.35W 3 SW Shorewood Hills 4.5 in 0300 PM 01/09 43.05N/89.49W Cottage Grove 2.2 E 4.5 in 0700 AM 01/10 43.08N/89.16W Madison 3.2 E 4.2 in 0700 AM 01/10 43.08N/89.32W Cambridge 3.9 in 0900 AM 01/10 43.00N/89.02W 1 E Maple Bluff 3.0 in 0210 PM 01/09 43.11N/89.35W Verona 4.2 NNW 3.0 in 0700 AM 01/10 43.05N/89.55W ...Dodge County... 2 W Beaver Dam 6.0 in 0551 AM 01/10 43.47N/88.88W 2 WNW Beaver Dam 6.0 in 0551 AM 01/10 43.47N/88.88W Mayville 0.5 NE 5.5 in 0600 PM 01/09 43.50N/88.54W Theresa 0.1 ESE 4.5 in 0700 AM 01/10 43.52N/88.45W 2 WNW Beaver Dam 4.2 in 0511 PM 01/09 43.47N/88.88W 1 NE Horicon 4.0 in 0539 PM 01/09 43.45N/88.63W 1 NNE Horicon 4.0 in 0539 PM 01/09 43.45N/88.63W Iron Ridge 3.9 in 0800 PM 01/09 43.40N/88.53W 3 SSW Clyman 3.8 in 0420 PM 01/09 43.27N/88.75W Mayville 3.5 in 0539 PM 01/09 43.50N/88.55W ...Fond du Lac County... 1.8 E South Byron 3.5 in 1200 AM 01/10 43.63N/88.45W St. Peter 3.0 in 0700 AM 01/10 43.83N/88.35W Fond Du Lac 1.7 E 2.0 in 0700 AM 01/10 43.77N/88.41W ...Green County... Blanchardville 5.4 ESE 7.8 in 0642 AM 01/10 42.79N/89.76W New Glarus 7.1 in 0430 PM 01/09 42.81N/89.64W ...Green Lake County... Berlin 6.0 in 0557 AM 01/10 43.97N/88.95W ...Iowa County... 5 ENE Mineral Point 10.7 in 0834 PM 01/09 42.89N/90.10W 6 N Waldwick 10.7 in 0932 PM 01/09 42.90N/90.05W Dodgeville 10.0 in 0915 PM 01/09 42.96N/90.13W 7 SE Avoca 8.5 in 0800 PM 01/09 43.12N/90.21W 5 N Waldwick 5.5 in 0130 PM 01/09 42.90N/90.06W ...Jefferson County... 4 SSE Sullivan 5.6 in 1200 AM 01/10 42.97N/88.55W Fort Atkinson 5.5 in 0722 AM 01/10 42.93N/88.84W Jefferson 5.0 in 0900 PM 01/09 43.00N/88.81W 4 SSE Sullivan 4.9 in 0600 PM 01/09 42.97N/88.55W Fort Atkinson 1.2 WNW 3.5 in 0700 AM 01/10 42.93N/88.86W Jefferson 0.9 E 3.0 in 0653 AM 01/10 43.00N/88.79W 5 SW Fort Atkinson 3.0 in 0900 AM 01/10 42.87N/88.90W ...Lafayette County... Benton 10.0 in 0800 PM 01/09 42.57N/90.38W Belmont 8.5 in 0900 AM 01/10 42.74N/90.33W ...Milwaukee County... 1 SSW Greendale 3.1 in 0820 PM 01/09 42.92N/88.00W Greenfield 2.5 in 0539 PM 01/09 42.97N/88.00W 2 SSE Wauwatosa 2.1 in 0420 PM 01/09 43.04N/88.02W 1 SSW Greendale 2.0 in 0200 PM 01/09 42.92N/88.01W Wauwatosa 1.9 E 2.0 in 0600 AM 01/10 43.06N/88.00W Brown Deer 0.8 NW 2.0 in 0700 AM 01/10 43.18N/87.98W ...Ozaukee County... 2 W Fredonia 6.8 in 1100 PM 01/09 43.47N/87.99W Grafton 3.5 in 0645 PM 01/09 43.32N/87.96W Saukville 0.9 SSW 3.2 in 0700 AM 01/10 43.37N/87.95W Mequon 3.0 in 1100 PM 01/09 43.23N/87.98W Saukville 3.0 in 0630 AM 01/10 43.37N/87.94W 1 SW Mequon 2.0 in 0421 PM 01/09 43.22N/88.00W ...Racine County... 3 E Waterford 2.5 in 0926 PM 01/09 42.76N/88.16W ...Rock County... Evansville 6.0 in 0800 PM 01/09 42.78N/89.30W 2 NE Janesville 4.5 in 1100 PM 01/09 42.71N/88.99W 1 WNW Beloit 4.5 in 0900 AM 01/10 42.53N/89.03W 2 SW Janesville 4.5 in 0900 AM 01/10 42.66N/89.04W Janesville 3.1 W 4.2 in 0700 AM 01/10 42.68N/89.08W 0.5 NE South Beloit 3.3 in 0530 AM 01/10 42.50N/89.03W Beloit 3.3 E 2.5 in 0700 AM 01/10 42.52N/88.96W ...Sauk County... Plain 11.5 in 0943 PM 01/09 43.28N/90.04W 3 W Lake Delton 10.5 in 0752 AM 01/10 43.59N/89.84W Baraboo 10.0 in 1100 PM 01/09 43.47N/89.74W 1 ESE Rock Springs 9.0 in 0602 PM 01/09 43.48N/89.90W 1 E Rock Springs 9.0 in 0602 PM 01/09 43.48N/89.90W 4 SW Lake Delton 9.0 in 1100 PM 01/09 43.55N/89.84W 2 NE Baraboo 9.0 in 1100 PM 01/09 43.49N/89.72W Baraboo 8.5 in 1217 AM 01/10 43.47N/89.74W 3 W Lake Delton 8.0 in 0752 AM 01/10 43.59N/89.85W Spring Green 6.5 in 0900 PM 01/09 43.18N/90.06W Lake Delton 6.3 in 0625 PM 01/09 43.59N/89.78W Prairie Du Sac 6.0 in 0700 PM 01/09 43.29N/89.73W ...Sheboygan County... 1 NNW Plymouth 7.0 in 0730 PM 01/09 43.76N/87.98W 1 SW Plymouth 7.0 in 0800 AM 01/10 43.73N/87.99W 1 SW Plymouth 7.0 in 0800 AM 01/10 43.73N/87.99W Adell 6.5 in 0800 PM 01/09 43.62N/87.95W Plymouth 5.4 NE 2.0 in 0500 AM 01/10 43.81N/87.91W ...Walworth County... 1 WSW Williams Bay 5.5 in 1000 AM 01/10 42.57N/88.56W 1 W Elkhorn 4.8 in 0506 PM 01/09 42.67N/88.56W 1 WNW Elkhorn 4.8 in 0506 PM 01/09 42.67N/88.56W East Troy 2.5 in 1158 PM 01/09 42.79N/88.40W ...Washington County... 1 SE Germantown 7.5 in 1030 PM 01/09 43.22N/88.10W 3 SSE Hubertus 6.0 in 0542 PM 01/09 43.20N/88.20W Germantown 0.6 S 6.0 in 0700 AM 01/10 43.23N/88.12W 1 SE Germantown 5.8 in 0710 PM 01/09 43.23N/88.11W 4 NW Richfield 5.7 in 0815 PM 01/09 43.27N/88.30W 1.9 SE Hubertus 5.2 in 0600 AM 01/10 43.21N/88.21W 1 WNW Richfield 5.0 in 0600 PM 01/09 43.24N/88.25W Richfield 5.0 in 0600 PM 01/09 43.24N/88.25W 1.4 S Germantown 4.6 in 0700 AM 01/10 43.22N/88.12W 1 W Jackson 4.5 in 0600 PM 01/09 43.32N/88.18W Jackson 4.5 in 0600 AM 01/10 43.32N/88.16W Allenton 1.4 WSW 3.8 in 0600 AM 01/10 43.42N/88.37W ...Waukesha County... 1 ENE Merton 7.1 in 0755 AM 01/10 43.14N/88.29W 2 NW Sussex 6.1 in 0340 PM 01/09 43.16N/88.24W Pewaukee 4.5 in 0539 PM 01/09 43.08N/88.26W 1 WSW Butler 4.4 in 0603 AM 01/10 43.10N/88.09W 2 N Oconomowoc 4.3 in 0721 AM 01/10 43.13N/88.49W Hartland 5.0 NNE 4.1 in 0700 AM 01/10 43.16N/88.30W 2 NNW Brookfield 2.5 in 0120 PM 01/09 43.09N/88.13W Mukwonago 5.3 W 2.4 in 0700 AM 01/10 42.85N/88.44W Oconomowoc 2.3 WSW 2.2 in 0500 PM 01/09 43.09N/88.54W 1 W Muskego 2.0 in 0610 PM 01/09 42.89N/88.14W Muskego 1.1 WSW 2.0 in 0613 PM 01/09 42.88N/88.14W Observations are collected from a variety of sources with varying equipment and exposures. We thank all volunteer weather observers for their dedication. Not all data listed are considered official.
Some people in southern Wisconsin would say "yes", while others would say "no". As you can see in the snowfall total map, the storm totals varied a lot across southern Wisconsin. Why did this happen? As with most winter storms, there are usually bands of heavier snow that develop within the general area of falling snow. One of the forcing mechanisms for these embedded bands of higher snowfall is frontogenesis. Areas west of Madison were under a band of upper level (600mb) frontogenesis while areas east of Madison did not have any dominant, stationary band. As a result, the forecast liquid precipitation for this event was higher than what actually occurred.
The other major factor that played into the lower snowfall totals for some (mainly east of Madison) was that the mild air caused the snow to be exceptionally wet or to be all rain instead of snow or a rain/snow mix. This was especially true along the lakeshore where steady east winds ushered the warmer lake air inland. The snow ratio, or the ratio of snow and liquid, ended up being very low in eastern Wisconsin. When snow ratios are less than 6:1, the snow/rain that reaches the ground is very slushy. For areas west of Madison, the snow ratios were higher, from 10:1 to 12:1.
One other thing that cut down on the snowfall totals for southeast Wisconsin was the snowfall rate. The rates were not as high (transient or absent frontogenesis and other upper level forcing), so the lighter precip fell as rain or melted once it reached the ground. The snowfall rates are a key part of accumulating snow and if the temperatures are hovering around freezing and the snowfall rates are not high (less than 1" per hour), the snowfall amounts will be lower.
This graphic shows the last forecast we issued before the main event began early Tuesday morning. There had already been 1 to 3 inches overnight, so that was included in this forecast snowfall total.
Believe it or not, we played the forecast snowfall totals conservatively. The models were excited to give us a high amount of liquid precip over southern WI so we cut back on that. Given the mild environment, we also cut back on the snow ratios. In the end, the forecast worked out for western areas and came up short in our eastern areas.
There are many similarities and a few differences between the two systems. In short, there are similar "failure points" with the potential for rain or a rain/snow mix near Lake Michigan, lower snow ratios than forecast (even though we have a slightly cooler environment), and there will be time periods with lower snowfall rates. These factors can lead to lower snowfall amounts.
Keep up with the forecast and pay close attention to the time of day when there will be impacts.
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