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Meteorological Winter Opens With a Series of Wet Systems in Chicago; Atlantic Hurricane Season Ends—Record Warm Ocean Waters Win Over El Niño

Chicagoans basked in warmer Pacific air Thursday with high temps reaching 51 degrees at O’Hare and 55 degrees at Midway. This was the warmest day since the 54-degree high back on Nov. 19th.

It’s been a warmer-than-normal season in Chicago. Thursday marked the final day of the 3-month Meteorological/Climatological Season—and 2 of this season’s 3 months have come in well above normal.

Though 66% of November days have produced temps of 50-degree and higher this month—the fact is, only 26% of the past Nov. 30ths have generated temps 50-degrees or higher. So that places Thursday’s high among the 16% warmest closing days of November in the 153 years since 1871.

The final day of November finished close to 7° above normal—and in so doing, matched the ABOVE NORMAL TEMPS which have occurred 20 of the past 30 days.  

Low pressure is developing on the Texas/Oklahoma border and ingesting a moisture-rich flow off the Gulf of Mexico which is to allow its precip shield to grow. 

The northeast-bound system is to spread rain northward into Chicago—likely arriving in the metro area between 3 and 5 am Friday morning. It will be raining during the Friday morning commute period and through lunchtime into early afternoon Friday.  Rain is to become more occasional mid and late Friday afternoon—but patchy rain is likely to continue into Friday night before ebbing.

Colder air will allow mixed snow or periods of all snow in Chicago’s far west and northwest suburbs

In particular, sections of northern DeKalb and Kane counties—and across sections of Winnebago, Boone, McHenry, and possibly western Lake counties. There may be some accumulation on colder outdoor surfaces toward Rockford, Beloit, and possibly Belvidere before the precip exits the area late Friday night.  But with temps above freezing much of the period, it’s likely accumulations will be fairly modest. 

The pink areas in this forecast model show where there could be some wet snow:

This isn’t the last precipitation-producing system in our future in the coming week here in the Greater Chicago area. 

New chances of precipitation—occurring as rain or possible wet snow—are possible from late Saturday night into Sunday evening and again Tuesday into Tuesday evening.

While temps settle back to modestly ABOVE NORMAL LEVELS this weekend into next week, a period of warming is expected later next week into the following weekend—with 50s a good bet again toward Thursday, Friday, and Saturday next week.

December and the open of the 4-month meteorological winter season arrives tonight at midnight—and will apparently host ABOVE NORMAL OVERALL TEMPS into mid-month. Modest cooling may occur after the late next week and weekend mild spell a week from Sunday heading into the following week—a period which is looking quite wet with a rain-snow line coming closer again and likely to be the subject of monitoring next week.

Midnight Thursday, Nov. 30th, marked the close of the 2023 Atlantic hurricane season—a season which coincided with the onset of a fast-developing and now “STRONG” EL NIÑO.

The El Nino’s appearance presented tropical cyclone season forecasters with a fascinating dilemma earlier this year as these folks were faced with conflicting signals on how the 2023 Atlantic hurricane season might play out. The question facing them was this: Would tropical storm/hurricane development come in “sub-par”, as so often occurs with El Niño which contributes to hurricane-thwarting vertical wind shear of the Atlantic Basin—OR would record high ocean temps, which play such a critical role in fostering tropical storm/hurricane development–and overcoming any inhibition the El Niño might otherwise present?

We can now say, with the benefit of hindsight—RECORD WARM OCEAN TEMPS proved the “winner” over El Niño. The 2023 ATLANTIC TROPICAL SEASON proved an ACTIVE ONE—overwhelming El Nino’s often-observed tendency to thwart tropical development in the Atlantic Basin. This verified the approach of many key Atlantic hurricane season forecasters, among them the NOAA climate forecast group and the Colorado State tropical forecast team headed by Dr. Phil Klotzbach, who correctly concluded the record water ocean water were likely to prove decisive; that a MORE ACTIVE THAN TYPICAL 2023 SEASON WAS LIKELY. That’s what happened.

Tropical cyclone guru Dr. Jeff Masters and his colleague and meteorological historian and journalist Bob Henson, are out this (Thursday) morning with a fascinating article on the 2023 Atlantic hurricane season in their Yale Climate Connections blog post–and they address the conflicting early season signals which face tropical forecasters;

In a Thursday morning (11/30) post on his “Z” page ( characterizes the 2023 season in this way:

“Hurricane season ends today, and the Atlantic season was a relatively merciful one. Activity was above average, but a lack of landfalls by hurricanes in populated areas led to only 12 deaths and damages less than $4 billion, the lowest tally since 2015”

Video of lake snows downwind of the Great Lakes as the season’s coldest air swept over the warmer lake waters.

THIS IS SUCH A WONDERFUL ANIMATION filed by the folks at CIRA-RAMBB at Colorado State under the header: “Great Lakes Region Transforms into Winter Wonderland”

This GOES EAST weather satellite animation was posted Wednesday, November 29th. It employs daytime and nighttime imagery and tracks lake snows downwind of the Great Lakes as the season’s coldest air swept over the warmer lake waters. The cold spell produced a string 65-consecutive hours below freezing in Chicago which ran from 6pm Sunday (11/26) through 11am yesterday (Wednesday 11/29).

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