Here are the snowfall totals from the February 24th storm that struck central Illinois. The amounts turned out to be less than what was forecasted (second figure) by the National Weather Service. The core area received 3 to 5 inches of snow, compared to the forecasted amounts of 6 to 10 inches. However, the storm track was forecasted accurately.
What happened? First of all, temperatures remained at or just above freezing during most of the event – right around 32 to 34 degrees in Champaign and Decatur. In addition, the soil temperatures at 2 inches were just above freezing as well (third figure). As a result, the snow was partially melting throughout the day as it fell.
The winds were strong yesterday. The maximum wind gust in our Illinois Climate Network was 54 mph at Bondville, an exposed site just west of Champaign (last figure). The Champaign site registered a maximum gust of 35 mph in a location with many trees and buildings.
Forecast totals from right before the storm, according to the National Weather Service.
Two-inch soil temperatures across Illinois at 10 am on February 24, 2016.
I was working with a U of I student on a poster about the impacts of El Niño, and we realized that this winter (December-February) does not fit the historical pattern of US temperatures and precipitation during past strong El Niño episodes (1982-83, and 1997-98).
Summary: most of the US has been warmer than average this winter, except for a few western states. Also much of the US has been wetter-than-average this winter except for the Southwest.
Details: here is how things have worked out this winter through February 22, 2016. Temperatures have been above-average for the eastern two-thirds of the US (basically east of the Rockies) as well as large areas of Wyoming, Montana, and Idaho. Noticeably absent have been the cooler-than-average temperatures often found in the Southeast in past major El Niño events.
The NWS Climate Prediction Center released their outlooks for March, Spring, Summer, and beyond. You can see the full suite of forecasts here.
The March forecast has Illinois with equal chances (EC) of above, below, and near-average temperatures (left panel). Illinois has an increased chance of below-average precipitation (right panel).
The March-May (Spring) forecast has Illinois with an increased chance of above-average temperatures and below-average precipitation.After a number of springs that were either too wet or too cool, a forecast of a warmer, drier spring may be welcome news. After all, soil moisture is in excellent shape right now and stream flows are within the normal range across most of the state.
The June-August (Summer) forecast has Illinois with an increased chance of above-average temperatures and equal chances of above, below, and near-average precipitation. The good news is that the risk of dryness in the Great Lakes region in spring does not appear to carry over into summer.
The topic of soil moisture has come up several times in recent weeks. After above-average precipitation in November and downright flooding in late December, one might expect the soils to be saturated across the state right now. But let’s take a closer look because I think soil moisture is in better shape now than it was six weeks ago.
This figure shows how heavy and widespread the precipitation was in December. It ended as the second wettest December on record with 6.66 inches of precipitation. By the end of December, many rivers and streams were in flood stage and a lot of farm fields were covered in water.
However, thanks to the generally mild temperatures, soil temperatures have spent a majority of the time above freezing this winter. This figure shows snapshots of the 4-inch soil temperature under grass for December 14 and February 14. If you flip through the soil temperature maps at our sites, you will see how rare frozen soils were. This was especially true during the the late December storm. Frozen soils will lock the moisture in place and form an impervious surface, causing precipitation to run off. Meanwhile, unfrozen soils will allow water to soak in and drain through. This is greatly enhanced in fields with tile drainage. Continue reading “Soil Moisture Status in Illinois”