From Drought to Flood Worries in Illinois

Illinois has had a quite the shift in the weather pattern in the last few days with widespread rains across the state, including areas that have been dry for some time. Here are the rainfall totals for the past 7 days as of this morning (February 20th), both observed and departures from normal. In the top map, areas in yellow received between 2 and 3 inches. Many areas of the rest of the state received between 1 and 2 inches. As the bottom map shows, that’s above normal for this time of year, especially in the areas that received 2 to 3 inches of rain.

February 20, 2018 7-Day Observed PrecipitationFebruary 20, 2018 7-Day Departure Precipitation

Precipitation Forecast: And it continues to rain as I write this. Many areas in northern and central Illinois are currently in a flood watch or warning, according to the National Weather Service. And more rainfall is on the way. Here are the potential rainfall totals over the next five days. Southern Illinois could see between 5 and 7 inches while central Illinois could see 2 to 5 inches. Northern Illinois could see between 0.75 and 2 inches, depending on where you are. Continue reading


Outlook for Spring and Summer from NWS

The new outlooks for March, Spring, and Summer from the National Weather Service’s Climate Prediction Center are out.  You can click on any map to see the larger version.

Overview: The NWS says that La Nina conditions continued through January and into early February across the equatorial Pacific Ocean, as indicated by oceanic and atmospheric observations. The CPC/IRI consensus ENSO forecast indicates that La Nina conditions are expected to decay rapidly and transition to ENSO-neutral conditions during Spring. ENSO-neutral conditions are favored to persist through at least the summer.


Parts of Illinois shaded in blue have an increased chance of colder than normal conditions. This is part of a larger area of expected colder conditions that extend from the Midwest westward and is a classic La Nina signal for this region. Current climate conditions do not favor colder or warmer than normal conditions in the rest of Illinois. Current climate conditions do not favor wetter or drier than normal conditions in Illinois in March.


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Cold, Snowy, Cloudy Weather – Welcome to February

I will have to admit, February is not on my list of favorite months. It’s a good thing it’s only 28 days long. Here is the rundown for the first half of February.


The big story is the snowfall across northern Illinois. Many areas north of Interstate 80 have received between 15 and 20 inches of snow. In fact, Chicago experienced an impressive 9 days in a row with snowfall. A few stations have reported over 20 inches of snow. The largest total that I’ve seen is 24.0 inches at Chicago Heights (IL-CK-296), followed closely by Aurora (COOP) with 23.5 inches, and Somonauk (IL-DK-24) with 22.7 inches. Meanwhile, the snowfall totals dropped precipitously (pun intended) moving southward. Areas south of Springfield have received less than an inch and many locations in southern and southwestern Illinois have reported no snowfall in February.



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January in Illinois, Cold and Dry

January in Illinois was colder and drier than normal without much snow.


The statewide average precipitation (rain and water content of snow) was only 1.31 inches, 0.76 inches below normal. The largest precipitation total for the month was 4.07 inches at Rosiclare (Hardin County).

From the viewpoint of climate, January is one of our driest months of the year with an average of only two inches of precipitation. However, we don’t notice it because most of our precipitation falls as snow. It just seems like a lot until you melt it.

Most of the state received 1 to 1.5 inches of precipitation (figure below, left panel) with drier patches in northern and western Illinois, and much of southern Illinois. Overall, most of the state was within an inch of normal (right panel). Click to enlarge.


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NWS Outlook for First Half of 2018

The NWS released their new outlooks for the first half of 2018. First of all, the NWS notes that La Niña conditions continue across the Pacific Ocean and will likely persist through the rest of winter. It will likely fade this spring, leading to so-called “ENSO-neutral” conditions, which will continue through summer. “ENSO-neutral” just means that we are between La Niña and El Niño conditions, in other words, neutral.


The shorter-range forecasts out to 14 days indicate a shift in the weather pattern bringing warmer and wetter than normal conditions across Illinois. By this Sunday we could be in the 40s and 50s in Illinois (left panel, below) while the prospects of rainfall are high with potential totals of 1/2 to 1 inch over the next 7 days (right panel).

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First Half of January – Colder, Snowier than Last Year

Summary: we are halfway through January and so far the statewide average temperature is 16.5 degrees, 7.3 degrees below normal. Last year, by mid-January the average temperatures is 25.2 degrees and 1.4 degrees above normal.

The statewide average precipitation is only 0.6 inches, two-thirds of normal for the first half of January. Last year, by mid-January the average precipitation was 0.82 inches, just 0.07 inches below normal. Note that precipitation is a measure of both the rainfall and the water content of snowfall.

Snowfall has been widespread with 2 to 5 inches common in all but western Illinois. For most areas, that is near to slightly below normal. So far our snow has come from fast-moving low-pressure systems out of Canada (so-called Alberta clippers) that are noted for bringing light, fluffy snow without much water content. Last year, some areas in northern Illinois had received zero snowfall in the first half of January and many areas reported less than an inch. Continue reading

Snowfall Changes Over Time in Illinois

The snowiest winter on record was 1978-79 with a statewide total of 44.5 inches. The winter of 2011-12 had the least amount of snow with a statewide total of 9.2 inches.

While a few stations recorded snowfall in the 1800s, our statewide snowfall records in Illinois began in 1902. There is no long-term trend in the snowfall totals; however, some decades were snowier than others, such as the 1910s, 1960s, and 1970s. In fact, the 1970s were the snowiest decade on record with an average snowfall of 27.2 inches.

Since the 1970s, snowfall amounts dropped steeply with less year to year variability for much of the 1980s and into the early 2000s. However, snowfall amounts in the last six winters have been more variable with the winter of 2013-14 being about as snowy as the late 1970s while the winters of 2011-12 and 2016-17 had the lowest and third lowest snowfall totals, respectively, for the state.


Snowfall is accumulated from July 1 of the first year to June 30 of the second year. The second year is used in the plot and table (for example, 2006 refers to the 2005-2006 season). Illinois State Water Survey, 2018.


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