Coldest air mass of season likely this weekend; Snow in the interior northeast?

Weather Pattern Change Could Bring Snow?

A shift in the weather pattern across North America may bring the coolest air mass so far this fall to parts of the Midwest and East.

It looks like the cooler pattern will develop from the upper-Mississippi Valley to the Great Lakes, Ohio Valley and parts of the Northeast by this weekend. In fact, some locations may see their frost and/or freeze of the season. A coating of snow is also not out of the question for the higher elevations of the interior Northeast depending on the timing of the cool air and how much moisture is available.

(MORE: When the First Snow of the Season Typically Falls)

Let's take a dive into what these changes may look like for this upcoming week:

Chilly Changes Could Bring Frost or Freeze

After an initial warm start to the week on Monday, with above-average temperatures, a series of cold fronts through the week will allow cooler air from Canada to filter south.

The first wave will bring cooler air for midweek, but it's the end of the week and this weekend that may present the coldest air of the season so far. Many cities could see their first official readings in the 30s so far this fall. This would result in the first frost and/or freeze of the season for parts of the Upper Mississippi Valley, Great Lakes, Ohio Valley and interior Northeast.

Here is a breakdown of what we can expect (click the city name for the latest 10-day forecast):

Minneapolis/St. Paul: First official 30s and possibly the first official freeze (32 degrees) of the season expected this weekend. Highs in the 50s forecast late this week into the weekend. Friday may not get out of the 40s.
Chicago: First 30s of the season possible this weekend. Highs only in the 50s Friday-Sunday.
Cincinnati: First 30s of the season possible Sunday morning, which could result in the first frost. Highs will only be in the 50s this weekend.
Buffalo: Above average highs in the 70s on Monday will transition to around 60 on Tuesday with only 50s for the remainder of the week. Highs may not get out of the 40s on Saturday. Lows in the 30s are possible for the first time this season next weekend.
Cleveland: After starting the week with 70s on Monday, Tuesday through Friday may only reach the 50s or lower 60s. Highs in the upper 40s or low 50s expected next weekend. First lows in the 30s of the season possible this weekend.
Hartford: The week starts warm with low to mid 70s on Monday and Tuesday, but will give way to highs struggling to reach 60 by Friday. Highs may struggle to reach the 50s this coming weekend.
New York City: Highs in the 70s Monday and Tuesday will give way to 60s for the rest of the workweek. 50s are possible next weekend.
Pittsburgh: Also starting the week in the 70s, highs later cool into the 60s for the middle of the week and slide below average with 50s Friday-Sunday. First lows in the 30s of the season possible next weekend.

Interior Northeast Snow?

While these temperatures may not be cold enough for snow in most areas, some computer models suggest that parts of the interior Northeast could see some wintry precipitation between Friday and next weekend.

Things can change, but there is growing evidence that, in some locations, the first accumulating snow of the season may be on the horizon. The area we are watching for this potential snowfall includes a swath from the Catskills and Adirondacks of upstate New York to the higher elevations of northern Vermont, northern New Hampshire and northern Maine.

(FORECAST: Burlington, Vermont | Saranac Lake)

Parts of northern Maine have already seen their first bout of wintry precipitation this season in the past few days. Caribou, Maine, reported a brief period of sleet on Friday, which qualifies as a trace of snow in meteorological records. The National Weather Service said the 138-day period without a trace of snow in Caribou that began May 24 and ended Oct. 8 was the shortest such period on record for that location. A second bout of light snow was reported in Caribou on Sunday morning before changing to rain.

Mount Washington, New Hampshire, also saw its first coating of snow this season Friday into early Saturday.

(MORE: Mount Washington Sees First Snow)

The upcoming cold shots will be quite a contrast from the near-record to record warmth the region saw in September. Burlington, Vermont, and Sault Ste. Marie, Michigan, were among the cities that observed their warmest September on record last month.

(MORE: Record Warmth Hit Some Cities in September)

Meteorology Behind the Pattern Change

The jet stream, or flow of air tens of thousands of feet up in the atmosphere, has been in a state of change so far this October.

This is nothing unusual, as the pattern annually shifts from a more benign summer-like pattern, to an increasingly active, high-amplitude pattern through the fall and winter months. This also means a farther south movement of the jet stream.

Think of a see-saw and the jet stream pattern is kind of like that. It is rarely completely flat (west-east) across North America. A ridge on one side, generally featuring warm weather, is usually offset by a trough, or cooler air, on the opposite side.

(MORE: October Temperature Outlook from The Weather Channel)

As we move through mid-October, the jet stream will be driven north through western Canada, thanks to a building ridge across the western United States. This means that warm weather continues across the western states and extends down into the south-central states as well.

(MORE: Fall Is Missing in Parts of the West)

Conversely, the jet stream tilts south with eastward progression. The polar jet stream will penetrate south across eastern Canada, eventually bringing bouts of chilly air into the Upper Great Lakes and Northeast in the coming week.

With time, the cooler air will ultimately become cold enough to support some snow in the region, given a supply of adequate moisture.

Meteorologist Chris Dolce contributed to this article.

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