Active winter weather pattern developing; a big hemispheric pattern change suggests a colder pattern looms.

We have an active winter weather pattern starting to come together. It could include some snow—enough to stick modestly commencing in the early hours of Saturday morning and continuing lightly into the day. It’s the product of precip and cloudiness beneath the far northern flank of a storm system which is to move from New Mexico eastward through the Gulf States then turn northeastward and potentially turn into a big snow producer from the interior Mid-Atlantic north into New England.

That’s an area which, like Chicago, has seen a lackluster winter snow season—so it’s a system sure to generate notice and some headlines there.  Boston may be among the areas hit with significant snow.

THAT SYSTEM will spread clouds into the Chicago area Friday and Friday night and light snows on its far north side could accumulate—perhaps laying down a half inch to an inch and a half Saturday.  A moistening air mass means the snow could mix with some drizzle as the day warms on Saturday.  Clouds in the wake of that system are to linger Sunday with some flurries or a bit of drizzle at times.  

Things rev up with a more powerful storm system that approaches Monday and appears likely to be producing wet snow Monday night into Tuesday and Tuesday night in an increasingly windy environment.  The storm is to generate cold air and is likely to produce snow of some substance.  But dew points creep toward or just above freezing Tuesday in at least parts of the area on current model guidance. This suggests VERY WET snow and also the chance parts of the metro area could see a mix of precip. 

THE STORM SYSTEM is still days away and forecast features with it will be refined as fresher data comes in. 

The hemispheric change suggests a colder pattern is ahead beginning the back half of next week into mid-January

Nature appears about ready to introduce a “chink in El Niño’s armor”. The abnormally mild temps which have led to the lack of snow and radically reduced Great Lakes ice coverage among other weather features, have been influenced by a strong El Niño in the equatorial Pacific superimposed on a planet that is undergoing warming as a part of climate change.

But, when it comes to cold season weather, other developments can dampen El Niño’s warming influence—and modeling suggests we may see such a change coming together.

Warming aloft at high latitudes—over regions including Greenland and a swath of northern Canada in the coming weeks—is leading to the development of a “GREENLAND BLOCKING PATTERN”.

Forecast models are indicating a GREENLAND BLOCK appears in the northern hemisphere’s future if the current computer model forecast over the coming 2 weeks is verified.

Greenland Blocks often serve as “COLD SIGNALS” for the Midwest. The development of vast warm pools aloft over Greenland and sections of northern Canada there often produces shifts in jet stream steering winds which send colder air sweeping south into the Midwest and often the eastern two-thirds of the Lower 48.

Jet streams over North America grow “wavy”—reaching high into the Arctic then diving southward into the Lower 48 with cold air in tow. That’s what models—including the Weather Service’s “GEFS” model show happening in the coming weeks. This could produce Winter 2022-23’s first break in the prolonged milder than normal temps.

The question becomes—once in place, will the colder pattern last?—or is it to merely be an “interruption” to the mild, snow-less pattern that has dominated this cold season to date driven in large part by El Niño? That will be interesting to monitor.

Great Lakes’ total ice cover as of the January 3, 2024 analysis is only 0.3%.

Unseasonably mild weather and the lack of prolonged cold spells and sustained low temps have impeded the formation and maintenance of significant ice coverage. The analysis below shows the water temperatures in blue and green, and the ice concentration in black and gray:

Here’s an interesting analysis, not only on the lack of Great Lakes ice but also on the lackluster natural snowpack at several U.S. ski resorts. The piece is written by highly regarded environment reporter Axios’ Andrew Freedman:

A “cold signal” for the Midwest

FORECAST OF THE ARCTIC OSCILLATION (AO) off the European Centre’s ensemble model. This is a “COLD SIGNAL” for Chicago and the Midwest and has implications on the weather pattern over the eastern two-thirds of the Lower 48.


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