Outlook for the Rest of Winter

Summary: So far in December temperatures have been 5.6 degrees above normal, while the statewide average precipitation has been 0.28 inches, a tenth of normal.  The NWS released their outlook for the rest of this winter. Colder than normal conditions are favored in Illinois in January. Colder and wetter conditions favored in January through March. Wetter conditions favored for most of Illinois in April through June.

December (as of 12/21/2017)

So far things have been quiet for December in Illinois. The statewide average temperature is 35.5 degrees and 5.6 degrees above normal. Based on the forecasts, we can expect much colder conditions for the rest of December and we will be much closer to the statewide 1981-2010 normal of 29.9 degrees by the end of the month.

The statewide average precipitation is only 0.28 inches (left panel below). That is only about one-tenth of the normal 2.74 inches we receive in December. The driest December on record for Illinois was in 1976 with only 0.44 inches. We could come close to beating that record at the rate we are going.

Snowfall has been light in northern Illinois and mostly a no-show in central and southern Illinois (right panel).  By the way, precipitation is a measure of both the rainfall and the water content in the snow.

OUTLOOKS

January through March

Below are the NWS outlooks for January and January – March. As discussed in previous posts, La Niña conditions prevail in the Pacific and heavily influence the winter forecast.

For January (top row), climate conditions are favorable for colder than normal temperatures across Illinois and the Great Lakes. Meanwhile, there are no indications that January will be either wetter or drier than normal in Illinois. The Ohio River Valley is favored to have wetter than normal conditions in January that includes the far southeastern portion of Illinois.

For January through March, colder than normal conditions are favored in the northern two-thirds of Illinois. The odds are strongest in northeast Illinois (sorry Chicagoland). There are no indications that the southern third of Illinois will be either warmer or colder than normal. Wetter than normal conditions are favored across Illinois as well as the Great Lakes and Ohio River Valley.

The NWS doesn’t do seasonal snowfall forecasts. However, colder and wetter conditions in winter are highly correlated with more snowfall – just saying. My fearless forecast is that we will see more snow than last winter when the state-wide average was only 9.6 inches and the second lowest on record.

 

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April through June

The outlook for April through June (below) shows that warmer than normal conditions are favored in the southern half of Illinois as well as much of the southern two-thirds of the US. Climate conditions do not favor warmer or colder than normal temperatures in northern Illinois.

Most of Illinois is favored to have wetter than normal conditions and is part of the wetter pattern across the Great Lakes region.

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Chances of a White Christmas in Illinois

What are the historical chances of a White Christmas?

We define a “white Christmas” as having at least an inch of snow on the ground on December 25. The map below shows the odds across the state. It should come as no surprise that the highest odds are in northern Illinois.  In general, the odds are about 40-60 percent in the northern third of Illinois, 20-40 percent in central Illinois, and 0-20 percent in southern Illinois.

There can be large differences between nearby sites. Snowfall is notoriously difficult to measure with blowing, drifting, and melting. Two nearby sites may have different results due to exposure to the sun and the wind as well as the dedication of the observer to report on Christmas Day.

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What happened last year?

Areas north of Interstate 80 had snow on the ground Christmas morning, December 25, 2016. Chicago O’Hare reported 2 inches of snow on the ground, while Rockford reported 6 inches. The snow disappeared quickly with the mild weather in late December.

 

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Map courtesy of NOAA at https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/

 

What is the most snow on Christmas Day?

Here are the largest snow depths on Christmas Day (12/25) for selected locations around the state:

  • Chicago, 17 inches in 1951
  • Rockford, 14 inches in 1951 and 2000
  • Quad Cities, 12 inches in 1909
  • Peoria, 10 inches in 1909
  • Springfield, 10 inches in 1915
  • Champaign-Urbana, 9 inches in 1983
  • Carbondale, 9 inches in 2004

What are the odds this year?

Christmas is still 14 days away when this is being written. Single day forecasts that far out, especially for snow are too difficult to make. However, we can get a glimpse of how the models are trending for the week up to Christmas. Temperatures are expected to be near-normal; however, precipitation is expected to be below normal. Therefore, I think the odds of a white Christmas this year look very slim.

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November in Illinois – Cool and Dry with a Dash of Snow

November Summary

The preliminary numbers are in for Illinois and November was slightly cooler and drier than normal.

The statewide average temperature for November was 41.7 degrees, 0.8 degrees below normal. The warmest reading in the state was 79 degrees at Belleville on November 2. The coldest reading in the state was 11 degrees at Stockton on November 24.

The statewide average precipitation was 2.13 inches, 1.34 inches below normal. The largest precipitation amount was 5.60 inches at Paxton. Some snow was reported in northern and central Illinois. The largest snowfall amount was 1.5 inches at the Chicago Botanic Garden.

Fall (September-November)

For the traditional fall months of September through November, the statewide average temperature was 56.2 degrees, 1.8 degrees above normal and the 15th warmest fall on record.

The statewide average precipitation for fall was 7.72 inches, which is 2.22 inches below normal. Dry conditions near St. Louis have resulted in the US Drought Monitor calling for moderate drought (D1) to severe drought (D2) from Randolph to Calhoun Counties (see map at end of post).

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Precipitation for November

Here are the precipitation maps for November, accumulated amounts on the first map, departures from normal on the second map. In general, more precipitation fell in eastern and southern Illinois (2 to 4-inch totals were common), than in western and northern (totals less than 2 inches were common).  By the way, precipitation represents both the rainfall and the water content of any snowfall.

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Snowfall for November

Parts of northern and central Illinois received snow in November; however, the amounts were generally less than an inch. As mentioned earlier, the Chicago Botanic Garden near the shores of Lake Michigan received 1.5 inches for the month.

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Temperature Departures for November

Illinois experienced wide swings in temperature in November. In the end, the colder-than-normal and warmer-than-normal days nearly canceled each other out, leaving us just 0.8 degrees below normal for the month. Northern Illinois ended up 1 to 2 degrees below normal (shades of green) while the area around St. Louis was 1 to 2 degrees above normal. These warmer-than-normal temperatures coincided with the area with little precipitation in November.

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US Drought Monitor

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