Latest Round of Snowfall in Illinois

Just a quick note showing how the recent winter storm played out. The snow was widespread across the upper Midwest, including northern Illinois. Amounts of 5 to 10 inches were common in northeast Illinois. Two sites in McHenry County had over 10 inches of snow: Harvard (IL-MCH-66) with 11.7 inches and Bull Valley (IL-MCH-13) with 10.8 inches. Central and southern Illinois were warmer and received mostly rain instead of snow. Rainfall amount in southern Illinois were in the neighborhood of 0.5 to 0.75 inches.

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Will It Ever Snow Again in Illinois?

With the streak of warm weather this fall, thoughts of snow are far away – but not for much longer. The first significant winter storm for the Midwest is on the horizon on Thursday and Friday. It will likely hit Nebraska, the Dakotas, and Minnesota, but miss Illinois (blue shading on the map below).

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So when can we expect to see that first measurable snowfall (0.1 inches or more) in Illinois?

Here is a map that we constructed a few years ago using data from 1971-2000. No surprise – the earliest dates are in the Chicago area and cluster around November 20. For the rest of the northern half of the state, the average date is towards the end of November. In central Illinois, I have always considered Thanksgiving to be the start of the snowfall season. The average dates get dramatically later as you go southward, getting closer to Christmas by the time you get to Carbondale and southward.

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Southern Illinois snowstorm

Southern Illinois experienced freezing rain, sleet, and snow on December 6-7, 2013.  Here are some maps showing snowfall totals – both from the NWS. For some locations, this winter storm produced a season’s worth of snowfall in the course of a few days. The largest snowfall total I have seen so far is 13.0 inches at Waltonville, IL (Jefferson County). Other heavy snowfall totals include 12.6 inches at Chester, and 11.5 inches at Lawrenceville and St. Francisville.

www.srh.noaa.gov ridge2 snow
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Storm Totals
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Paducah NWS Office

The Gales of November: Storms on the Great Lakes

The Great Lakes has had its share of infamous storms in November. The worst weather-related disaster on the Great Lakes occurred on November 7-10, 1913, and was covered in another blog post. The two other storms in the November Big Three are the Armistice Day Storm of November 11, 1940 (covered here and here) and the Edmund Fitzgerald Storm of November 10, 1975 (covered here and here).

Why is November so notorious for these storms? There are a number of factors involved. One is that November is the beginning of the transition between fall and winter in the Great Lakes region. As a result, there is a strong gradient between warm, moist air to the south and cold, dry air to the north. Storms, called extratropical cyclones, form and travel along these boundaries. In fact, researchers have documented that storms out of western Canada (aka Alberta Clippers) and out of Colorado track over the Great Lakes in the October/November time frame.

Predominant storm tracks for the Great Lakes region in fall.
Predominant storm tracks for the Great Lakes region in fall. The exact position of these tracks varies from study to study, but the overall pattern remains.

In addition to the storm tracks, the waters in the Great Lakes are still relatively warm so they inject heat and moisture into any passing system, causing them to intensify as well as  produce lots of lake-effect snow.

Finally, November is typically the tail end of the Great Lakes shipping season. So boats are making that one last trip and may be pressing their luck on the weather. November is an active time for hunters. In the Armistice Day Storm of November 11, 1940, numerous duck hunters were caught in the open and at least 13 died in Illinois.

The title of this article is a nod to Gordon Lightfoot’s “Wreck of the Edmund Fitzgerald”. That song and the story of the Edmund Fitzgerald inspired my life-long interest in Great Lakes storms.

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Edmund Fitzgerald (1971) from Wikimedia Commons.

Impact of the February 1-2 Storm on Highways

The impact of the February 1-2, 2011, storm on highways in Illinois was significant. Using snowfall data and Illinois DOT highway data, our GIS specialist Zoe Zaloudek was able to calculate the number of miles of interstate, US highways, and state roads covered by selected amounts of snow.

Below is the resulting map showing both the roads and significant snowfall. A table at the bottom of the map shows the number of miles affected by 6, 8 and 12 inches or more of snow. The impacts were felt all the way from Quincy to Chicago. We chose a starting point of 6 inches as the threshold for significant disruption of traffic and higher removal cost, based on earlier studies in Illinois.

For example, about 1,132 miles of interstate roads in Illinois received 12 inches or more of snow. Including 1,762 miles of US highways and 4,099 miles of state roads, it adds up to an incredible 6,993 miles of roads with a foot or more of snow to plow.

These estimates do not include the thousands of miles of county roads as well as city streets and alleys in the Chicago metropolitan area and elsewhere. However, we did not have a complete database of those road systems. Also roads covered by less than 6 inches of snow were treated as well for additional costs.

February blizzard affect roadways
The number of miles of Illinois roadways affected by selected amounts of snowfall during the February 1-2, 2011, winter storm.

Snowfall Totals from around Illinois

The winter storm of February 1-2, 2011, will be remembered by many in northern and central Illinois. The National Weather Service (NWS) did an excellent job of producing forecasts and warnings on this storm. In the aftermath, we have began collecting the snowfall measurements from a variety of networks. Rather than list all the data here, I have provided some links to data sources.

Snowfall totals and some maps provided by NWS offices are available here:

Here is a preliminary look at snowfall totals across the Midwest. Snowfall amounts in excess of 12 inches extend from Oklahoma, into Missouri, the northern half of Illinois, and on into northern Indiana and southern Michigan.

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Preliminary snowfall totals map for the February 1-2, 2011 storm (NWS image).

And zooming in on northern Illinois.

Snowfall totals for the February 1-2, 2011, event in northern IL (NWS image).