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  • Tim McGill

Some Snow To Actually Stick

More Mild Temps First

The streak of days in a row with above average temperatures stretches to 19 today. January is now running just under 7° above average. The average high for this date is 31° and the average low is 17°. Our highs today and tomorrow will hit 40° or warmer.

Finally some peeks of hazy sun through clouds today as highs climb into the lower 40s for most of us. It will be just a bit colder in areas northwest of the city that have more snow cover.

Highs tomorrow should be about 10° above average. Temperatures finally begin to fall on Friday and the crash continues into early next week. This isn't bitterly cold Arctic air coming. We will actually fall just a couple of degrees below average.

Today will be the 15th day this winter with a high of at least 40°. Thursday could be the 16th. The forecast temperature anomaly map for Thursday afternoon (lower left image) has highs around 10° to 16° above average across Illinois and Indiana. Previous blog posts have warned about a possible upcoming shift to a much colder pattern. A "sudden stratospheric warming" could jostle the polar vortex and send some lobes of Arctic air our way. There is a hint that could be coming in the longer range temperature anomaly forecast for next weekend. The temperature anomaly forecast for early Saturday morning on January 23rd (lower right image) shows temperatures anywhere from 10° to 20° below average for northern Illinois.

Looking very long range at the GFS model shows possible sub-zero temperatures sweeping south into the Midwest in a couple of weeks. Below is the forecast for the morning hours of January 28th showing single digit lows here and sub-zero temperatures as close as southern Wisconsin. This is still a long way off and could change but it does fit with the scenario of a possible pattern shift described above.

A Few Chances For Sticking Snow

The GFS model cloud cover and precipitation meteogram shows at least two and maybe even three chances for some light snow over the next ten days. There is a chance of some light rain, freezing rain and snow late Thursday changing over to all snow for Thursday night and Friday. The next opportunity for snow comes Sunday with another possible chance early Monday. The second and third systems may start with some rain or a rain/snow mix too.

The accumulated snowfall forecast meteogram for O'Hare considers not just the GFS model but many different computer models. The range of forecasts for snowfall Thursday night into Friday is anywhere from a dusting to nearly four inches. Each line represents a model's solution for snowfall. Notice a second bump shown by many of the models later Friday. This reflects snow showers that could add some additional accumulation. Several models show a third bump Sunday with another system that could lay down some light snow.

Adding It All Up

The GFS model forecast lays down a grand total of about 1.5" to 2" for most of us from Thursday through Monday morning.

The European model is calling for a bit more snowfall overall during the same period. It spits out about 1.5" to 3" in total. I'm leaning more towards the GFS with totals by Monday around one to two inches but snow showers on Friday may bring those totals up in a few spots to nearly three inches. Most of the snow will fall Thursday night and during the day Friday.

More Misery To The South

The Accumulated Winter Season Severity Index (AWSSI) keeps a running tally on just how extreme a winter a certain location is having. It is more commonly known as the "misery index". It is interesting to note that Amarillo, Texas is having a worse winter than Chicago according to this index. Amarillo is having a "severe" winter with 7.4" of snowfall so far. The categories from least severe to most severe are mild, moderate, average, severe and extreme.

Chicago has seen just 4.7" of snow so far this winter compared to an average winter that sees just over a foot of snow by now. Our winter is considered "mild" or the least miserable of the possible index categories.

Colder Pattern Coming?

Our relatively mild month and season rolls on. January is now running 6.7° above average. That follows a December that was 5.1° above average. Today's longer range forecasts show a possible shift towards a colder pattern could be coming. The 6-10 day temperature probability forecast has Chicago outlooked for above average temperatures overall from January 18th through January 22nd. The longer range 8-14 day forecast has most of the western half of the country outlooked for below average temperatures overall during the period from January 20th through January 26th. Chicago is outlooked for near normal temperatures but the big jump in blue on this map has to be watched. This is the most blue I have seen on a longer range temperature probability forecast all winter. This could be a signal that the much anticipated flip to a more harsh winter pattern may be on the horizon.

Hinting At Shift To More Active Pattern

Our long range precipitation probability forecasts starts out drier than average and then shifts to above average precipitation. The 6-10 day forecast from January 18th through January 22nd has a strip of below average precipitation outlooked from the central plains through Chicago and on into New England. The 8-14 day forecast has a growing area of the country outlooked for above average precipitation overall from January 20th through the 26th that includes most of the Midwest. This coupled with a shift to a colder pattern may be good news for snow lovers. Stay tuned.

Looking Even Longer Range

The experimental multi-model ensemble temperature probability forecast shows equal chances of above or below average temperatures overall from January 23rd through February 5th. We can glean more information from the precipitation probability forecast. It favors us for above average precipitation overall from January 23rd through February 5th.

The experimental multi-model ensemble temperature probability forecast for February keeps the mild pattern we saw for the first two months of winter coming. Not just the Midwest but most of the country is outlooked for above average temperatures overall for next month

Here is my 7 day forecast:

Today: Partly to mostly cloudy, a bit breezy High: 42

Thursday: Mostly cloudy, light rain/freezing rain/snow mainly late Low: 30 High: 40

Friday: Mostly cloudy, occasional snow showers Low: 29 High: 35

Saturday: A.M. light snow possible, mostly cloudy Low: 26 High: 35

Sunday: Mostly cloudy, light snow showers Low: 23 High: 30

Monday: Mostly cloudy Low: 19 High: 29

Tuesday: Mostly cloudy Low: 21 High: 30



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