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  • Tim McGill

Mild Week But Some Snow In Forecast

Above Average Streak Continues


Today will be the 17th straight day with above average temperatures. This winter has only seen five days that were below average. The average high for this date is 31° and the average low is 17°. We could see highs of 40° or warmer at least two days this week before temperatures tumble a bit by the weekend.


We will see a lot of clouds but possibly some peeks of sun today as highs climb into the lower 30s.


The temperature trend is onward and upward with highs of 40° or warmer by Wednesday. Temperatures finally fall for Friday with the coldest couple of days in this forecast arriving this weekend. No bitterly cold Arctic air though in sight though.



Thursday's highs will flirt with 40°. Most of the country will be milder than average that day. The temperature anomaly forecasts has most of the Midwest around 15° to 20° above average. Only parts of the Pacific Northwest, Rockies and Florida will be below average.






Light Snow Late This Week


The GFS model cloud cover and precipitation meteogram shows a couple of chances for some light snow over the next ten days. There is a chance of some light rain and snow late Thursday but the best chance of snow is on Friday.



No official snowfall recorded at O'Hare this weekend although there were some flurries at times in the area. The disparity has deepened between the snowfall we have seen this winter compared to what we normally see in a typical winter. There has been 4.7" of snow since December 1st but we normally have 11.7" by now.


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 on Friday is anywhere from a dusting to just under an inch.





Sticking Snow Friday


The GFS model forecast lays down about a half inch to an inch of snow in total between now and Sunday. Most of that would come Friday.


The European model is calling for a bit more during that same period. It suggests a little over an inch to nearly two inches could fall.





Plane Effect Snow


If you live in Chicago you are familiar with lake effect snow but have you ever heard of "plane effect snow"? We saw some Sunday evening. The Chicago office of the National Weather Service tweeted about it last night.


Aircraft moved through a layer of super-cooled water droplets to produce some light snow showers or flurries. They actually showed up on radar screens.


Super-cooled means an environment where water droplets are still liquid but their temperature is below freezing. Tiny particles in the exhaust of the plane provide a surface for the super cooled droplets to freeze onto. This "heterogeneous nucleation" process can also be aided or triggered by turbulence. Airplanes descending into both O'Hare and Midway airport provided both enough turbulence and "condensation nuclei" or particles for super-cooled water to freeze onto. That process produced snowflakes that ended up falling to the surface.






Near Normal Temps


It says something when a forecast calling for near normal temperatures catches your attention. That is the case though this winter where December ended up more than 5° above average and January is now running about 7° above. Most of the longer range temperature probability forecasts have favored us for above average temperatures so far this season. Today's longer range forecasts are both suggesting near normal temperatures for a change. The 6-10 day temperature probability forecast has Chicago outlooked for about average temperatures overall from January 16th through January 20th. The longer range 8-14 day forecast has us outlooked for also for about average temperatures overall during the period from January 18th through January 24th.





Near Normal Precip Pattern Too


The longer range precipitation probabilities forecasts has us outlooked for about average precipitation. The 6-10 day forecast from January 16th through January 20th has us outlooked for near normal precipitation as well as the 8-14 day forecast which covers the period from January 18th through the 24th.






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: Cloudy, a few peeks of sun, a bity breezy High: 31


Tuesday: Partly to mostly cloudy Low: 27 High: 37

Wednesday: Partly to mostly cloudy Low: 28 High: 40


Thursday: Mostly cloudy, light rain/snow late Low: 33 High: 41


Friday: Mostly cloudy, light snow (up to 1" accumulation) Low: 29 High: 36


Saturday: Mostly cloudy Low: 24 High: 30


Sunday: Partly to mostly sunny Low: 20 High: 30


#ilwx

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