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  • Tim McGill

Nasty Now But Treat For Halloween

Updated: Oct 29, 2021

Wet & Windy End To Week



Wednesday was the 5th day of the past 6th to be below average. We'll be cool for a couple more days and then warm up slightly this weekend before the coldest air of the season so far settles in early next week. It's possible by Monday night we could have wind chills in the 20s and even a few flakes could fly south of I-80 early Tuesday.


Clouds with a wind off the lake and rain today means another day with highs in the 50s. Average highs for today's date are around 58°. The GFS Model has our highs reaching the middle 50s.



Temperatures won't budge a bit through tonight into Friday. Tonight's temperatures will stay fairly steady in the lower to middle 50s. The GFS Model has our highs reaching the middle 50s Friday.



We are still expecting a weather treat on Halloween. It will be mostly sunny and milder with a high in the upper 50s to near 60°. Temperatures will cool into the upper 40s to lower 50s for prime trick or treat time during the evening hours Sunday.


Sunday might be the mildest day we see for at least the next two weeks. The coldest air of the season so far comes crashing in early next week. The GFS temperature anomaly forecast for Wednesday has our temperatures between 4° to 6° below average. Average highs for that date are around 54° so our highs Wednesday afternoon could fail to make it out of the 40s.



The GFS Model continues to hint at the first flakes of the season flying south of the city late Monday night into early Tuesday. It keeps the snow mainly south of I-80. There could be some minor accumulation in central Illinois. I'll continue to watch to see if this nudges any further north.


A cool rain starts to fall today and continues through Friday evening before tapering off early Saturday. A few lake effect spotty sprinkles or showers could linger into Saturday morning near the lakefront but the weekend looks dry overall.


Temperatures stay steady once we climb into the middle 50s today. They hold there through early Friday night.


Our winds will be a bit breezy but become blustery tomorrow when they will gust at times over 30 mph.








Coolness Could Linger


The National Blend Of Models has our highs near normal with middle to upper 50s through the weekend. It then has highs fall into the 40s for next Monday through the following weekend. This will be the coldest air here in about six months.



Our cooler than average pattern could continue well into November. Both of the longer range temperature outlooks keep us cooler than average overall for next week and just beyond. The 6-10 day outlook has us favored for below average temperatures overall from November 2nd through November 6th. The longer range 8-14 day forecast favors us for below average temperatures from November 4th through November 10th. Average highs for this period are in the lower to middle 50s.





The even longer term 35 day temperature anomaly forecast has us near normal overall for the period from the end of October through all of November. There is a growing area of blue that is expected to see cooler than average temperatures encircling us. We are outlooked to be around average overall for the period from October 26th through November 30th. 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.









Wet End To The Week


O'Hare has seen nearly 5 inches of rain so far this month. We now have a surplus of 1.75" of rain above average. The deficit since the start of fall on September 1st has dropped to just .21" below average. Another round of rain today and tomorrow will diminish that deficit further. More on that below.


I expect our recent rain will have a major impact on the drought conditions in northern Illinois that will be reflected in the updated drought status that will be released this week. I will discuss that in tomorrow's post.


The most recent US Drought Monitor analysis was released last Thursday. It was the second report in a row to bring mostly good news for Illinois. It does not reflect Sunday and Monday's rainfall though. Here is a recap:


The area in at least a moderate drought (level 1 our of 4) dropped dropped slightly compared to the previous analysis. The area in an at least severe drought (level 2 out of 4) did not change. The only big of discouraging news is the area consider "abnormally dry" jumped by almost 25%. That is the area most likely to slip into at least a moderate drought if conditions don't improve.



It's hard to see much change when looking at the side by side comparison of this week's Illinois drought map next to last week's. The only thing that stands out is the growing area of yellow or "abnormally dry" conditions.




Here is a summary of the impacts the ongoing drought is having on northern Illinois from the National Weather Service:


Volunteer observers across far northern Illinois indicate much lower then typical stream flows on area creeks and rivers, particularly along Beaver Creek and the Kishwaukee River.

Reports also indicate that lawns have gone dormant and there has been some stress to the trees. Few impacts to agriculture have been received recently, though the dry conditions and stressed crops have resulted in an early start to the harvest season across northern Illinois. Data available from the Illinois State Water Survey, USGS, and NCEP indicate that soil moisture, groundwater, and surface water levels remain below normal.


The Midwest receive more good news. Every drought category saw a reduction in area. The biggest drop was for portion of the region in an extreme drought. It was reduced by more than half compared to the last analysis.


The soaking we received last Sunday into Monday has left most of the area with a healthy surplus of rain compared to average. Most of the Chicago area has received between 150% to 300% of average rainfall for October so far with a few spots even seeing up to 300% to 400% of average.



The GFS model's meteogram for O'Hare shows today and tomorrow's round of rain. It also suggest some light rain early Tuesday with another shot at light rain late next Friday.




The GFS model's total precipitation forecast through Saturday morning still squeezes out about a half inch to nearly an inch of rain. The amounts are heavier in and just south of the city because of expected lake effect rain at times that could linger into Saturday morning.



The longer range precipitation forecasts don't favor us for either above average or below average rainfall. We are outlooked for near normal precipitation well into next month. The latest 6-10 day forecast has the Chicago area favored for about average rainfall from November 2nd through November 6th. The longer range 8-14 day forecast has us outlooked for about average precipitation too for the period from November 4th through November 10th.







Here is my 7 day forecast:


Today: Cloudy, rain by midday, breezy High: 56


Friday: Cloudy, rain likely, windy (gusts to 30 mph) Low: 53 High: 57


Saturday: A.M. spotty showers, partly to mostly cloudy Low: 51 High: 58


Sunday: Mostly sunny Low: 45 High: 60


Monday: Partly to mostly sunny Low: 38 High: 49


Tuesday: Partly to mostly sunny Low: 36 High: 48


Wednesday: Partly to mostly sunny Low: 33 High: 48

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