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  • Tim McGill

Leaves Fly Today But Snowflakes Fly By Friday

First Fall Snow Is Overdue


It's almost two weeks past due on average but our first snow of the fall will come tonight and during the day on Friday. This will not be a big snowstorm but rather just scattered snow showers that could stick to some grassy surfaces. There is a better chance for some light accumulation Saturday night into Sunday. Key word there is "light".


Some snow stats from Tuesday's post:


The average first date of a few flakes of snow here is October 31st although it has come as late as December 5th. The average first date of measurable snow (.1" or more) is November 18th but it has come as late as December 20th. The average first date of 1" of snow or more is December 7th but it has come as late as January 25th.


We need to first get cold enough to support some snow. After starting off with a mild morning our temperatures today the HRRR model has temperatures falling into the upper 40s by late in the day. Average highs for today are around 51°.



Temperatures tumble further for Friday. The GFS Model has our temperatures tomorrow afternoon near 40°. That will be around 10° or more colder than average.



That is cold enough but gusty winds will make it feel even colder Friday. Our wind chills will be in the upper 20s to lower 30s most of the day.



The GFS Model says the cold will keep on coming through the weekend. Highs on Saturday will struggle to get into the lower 40s.



This wintry pattern continues through the weekend. The GFS model temperature anomaly forecast for Sunday afternoon shows temperatures here between 3° to 6° below average. That means highs Sunday in the lower 40s.





Strong winds, falling temperatures and snow are all a part of the weather story the next two days.


Winds will gust to near and even over 30 mph this afternoon and during the day Friday. Those gusty winds will combine with falling temperatures to drop our wind chills into the 20s by midday tomorrow.


Snow showers develop tonight and the best chance for those overall is Friday afternoon and evening.









Colder Pattern Sticks Around


Thanks to our mild morning today was the 6th straight day with above average temperatures. The National Blend Of Models has our highs falling into the 40s Friday and staying near 40° through Monday. We bounce back a bit towards the end of next week. We may have something to look forward to a week from this Saturday and Sunday. This weekend will be wintry but the following weekend could see highs near 60°.



The longer range temperature outlooks has us near normal overall for most of next week and on through that following weekend. The 6-10 day outlook still has us favored for about average temperatures overall from November 16th through November 20th. The longer range 8-14 day forecast favors us for about average temperatures overall from November 18th through November 24th. Average highs for this period are in the middle 40s to upper 40s with average lows in the lower 30s.






The even longer term 30 day temperature anomaly forecast has not changed much from previous forecasts. Most of the area is outlooked to be near normal overall but a small area south of the city is outlooked to be a bit above average. Some of our south suburbs are forecast to be about 1° to 3° below average. This forecast covers the period from November 8th through December 8th. The Global Ensemble Forecast System (GEFS) is a weather forecast model made up of 21 separate forecasts, or ensemble members The model tries to give an idea of the amount of uncertainty in a forecast by running an ensemble of multiple forecasts which are each tweaked a bit with their initial conditions.








Snow On The Way


I don't think this is bothering too many of us but we are running a snowfall deficit. We should normally have about a four tenths of an inch of snow by now. More on the snow in the forecast below but first an update on the drought.


The most recent US Drought Monitor analysis was released last Thursday. Here is a recap:


After three reports in a row with good news for Illinois the latest report is a bit more ambivalent. There is no areal increase in any of the drought categories but there is no decrease either. Things have not changed at all compared to the previous report. 9.29% of the state is in a moderate drought (level 1 out of 4) and 1.22% is in a severe drought (level 2 out of 4). The drought continues to be focused in northern Illinois entirely.


The report was more of a mixed bag for the Midwest region. While the areas in a severe to extreme drought decreased slightly, the area in a moderate drought increased slightly.


The GFS model's total snowfall forecast through Monday morning lays down around one to three inches of snow. This is probably overdone. The ground is still warm so more likely we might get a coating of some slushy snow on some grassy surfaces with Friday's snow showers. More light accumulation could come Saturday night into Sunday.



The European model is again suggesting less snowfall. It spits out around a third of an inch to about an inch with the heavier part of that range north and west of the city. This is the total snowfall forecast through Monday morning.




The GFS model's meteogram for O'Hare shows today's rain and then snow showers for Friday. Some light snow is also suggested for Sunday.




The longer range precipitation forecasts trend us from below normal to near normal. The latest 6-10 day forecast has most of the Chicago area favored for below average precipitation (which can take the form of rain or snow now) from November 16th through November 20th. The longer range 8-14 day forecast also has us outlooked for about average precipitation for the period from November 18th through November 24th.






Here is my 7 day forecast:


Today: Morning rain then partial clearing, windy with falling temperatures High: 57 (temps fall into the 40s)


Friday: Mostly cloudy, windy, rain & snow showers Low: 38 High: 42


Saturday: Mostly cloudy, breezy, a few flurries possible Low: 32 High: 40


Sunday: Mostly cloudy, light rain and snow possible Low: 30 High: 40


Monday: Partly to mostly sunny Low: 29 High: 40


Tuesday: Partly to mostly sunny Low: 32 High: 48


Wednesday: Mostly cloudy, chance of rain Low: 38 High: 54

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