The mild winter weather is not expected to last in Illinois, but you probably already knew that.
How mild has December been? As of December 18, the statewide average temperature for December stands at 34.3 degrees, 2.1 degrees above average. Precipitation (both rain and the water content of snow) stands at 1.13 inches. Areas north of I-70 are much drier with amounts closer to half an inch, while south of I-70 amounts of 1-4 inches are common. At this point there has been very little snow in December, although that is about to change soon.
The latest NWS outlooks for January and the rest of winter are shown below (click to enlarge).
The temperature forecast for both January and the January-March period show almost all of Illinois with a higher chance of below-average temperatures. Only far northern Illinois escapes this forecast. On the other hand, precipitation has a higher chance of being below average across Illinois and the Great Lakes region. In most cases, these long-range forecasts only nudge the temperature by a few degrees. So, there is still little sign that this winter will be as severe as last.
The NWS does not issue a winter snowfall forecast. And, a combination of colder temperatures and less precipitation does not always translate into less snow. Many times colder weather produces lighter fluffy snow that accumulates but has less water content. We saw a lot of that last winter. However, even if this forecast of colder and drier conditions captures the overall pattern of this winter, we could still see some significant winter storms. Be prepared.
I just heard Bing Crosby on the radio and it reminded me that it’s time to do the annual post on …
What are the historical chances of a White Christmas (defined as at least an inch of snow on the ground on Christmas Day)? The first map below the 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 the potential for two nearby sites having different results due to exposure to the sun and the wind.
After a cold November, December has been much milder this year. The latest NWS 8-14 day forecast includes December 25 and continues to show Illinois with a good chance of warmer-than-average temperatures. And today there is not much snow in Illinois (map below). Stay tuned to your local forecast as we get closer. Continue reading
The National Climatic Data Center released their November report, confirming that Illinois experienced it’s 4th coldest November on record as reported here.
Is the extremely cold November part of the trend? Apparently not. A look at November temperatures in Illinois since 1895 show that November temperatures have warmed by slightly more than 2 degrees since 1895. There are only a few cases of back-to-back cold November’s including 1910-11, 1950-51, and 1995-96.
You can see the interactive graph and the data behind it here.
Here is how Illinois stacked up to the rest of the country in terms of ranking November temperatures – several states in the central and eastern regions made the top ten list.
There is still a 65 percent chance of El Niño arriving this winter, according to the December 4 ENSO forecast released by the NOAA Climate Prediction Center. My understanding is that the Pacific Ocean is warm enough to suggest that a weak El Niño event is almost here, but that the associated changes in weather patterns have not kicked in.
Even without El Niño’s arrival, the NWS 6-10 and 8-14 day forecasts, as well as the forecast for all of December, all show a higher chance of above-average temperatures for this month. However, that does not mean we won’t have a few excursions into real winter weather. In fact, there is a little snow shower outside my window as I write this.
This warmer December forecast comes after we experienced the 4th coldest November on record in Illinois. Historically, there is not a strong connection between November and December temperatures.
Click on the maps below to enlarge.
November finished both colder and drier than average for Illinois. The statewide average temperature for November 2014 in Illinois was 34.3 degrees, 8.2 degrees below average and the fourth coldest November on record. November 1976 was the coldest at 33.4 degrees.
The cold November was not confined to Illinois. November was colder than average for most states from the Rockies eastward (greens and blues in the map below). Just like the winter of 2013-14, the Midwest saw the largest departures from average. Meanwhile, warmer than average conditions prevailed in California and the Southwest. I discussed the cold central US from January through October in 2014 and how it does not match the rest of the world here. It will be interesting to see the global results for November.
January – November Temperature
The average temperature for January through November 2014 was 50.9 degrees, 3.5 degrees below average. It was the second coldest January-November on record and tied with 1917. The coldest January-November on record was a 50.8 degrees, which occurred in both 1904 and 1979.
Here are the temperature departures by month for 2014 for Illinois. The NWS outlook for December shows an increased chance of warmer-than-average temperatures for the month.
The statewide average precipitation for November 2014 was 1.94 inches, 1.53 inches below average. The statewide average for January through November was 39.41 inches, which is 2.14 inches above average. Neither total was near a record.
Here are the monthly precipitation departures for 2014. After wetter-than-average conditions in August, September, and October, the drier November was not a concern for soil moisture or stream flows.
November snowfall was interesting in that many areas in southern Illinois saw more snow than some areas in central and northern Illinois. Amounts of 2 to 5 inches were seen south of Interstate 70, while amounts were generally less than 2 inches north of Interstate 70.
Disclaimer: These numbers and graphs are based on preliminary data and subject to change as more data arrive.