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Unusually cold autumn weather to blast eastern U.S. next week

Temperatures could fall some 20 degrees below average

NOAA's Climate Prediction Center's outlook for next week. (Pivotal Weather)

A blast of frigid air is set to descend on the eastern United States next week, in some places offering an early taste of winter, with snow even possible for some. Freezing lows and killer frosts could extend all the way south to near Atlanta and Birmingham, Ala., with temperatures in the upper 30s reaching the Gulf of Mexico.

How harsh will winter be? Six organizations issue forecasts.

The cold blast looks to set in beginning Monday and could last about a week before relenting. Even thereafter, there are signs that chilly weather could stick around for the remainder of the month.

There’s also a chance that snowflakes may fly in parts of the Great Lakes, Midwest or New England. Accumulations, if they occur, won’t be much, but it’s a harbinger of the coming winter season.

Across the West, meanwhile, the seesaw weather pattern, bottomed out in the East, will feature a northward bulge in the jet stream that will allow anomalous heat to swell. Hot, dry weather is expected in the Pacific Northwest, with highs 20 degrees above seasonal norms.

Sharp cold front to surge southeast

A cold front was pushing across the Ohio Valley on Thursday morning, set to swing through the East Coast during the evening and overnight. It was bringing a slug of showers and a few thunderstorms, a day after having produced at least a half-dozen quick-hitting tornadoes in southeast Wisconsin.

That cold front is paving the way for a more potent blast of cold air to follow on its heels early next week. This second, more robust front will take shape in south central Canada near the international border late Sunday or early Monday. By Monday night, temperatures will be 15 degrees below average in Chicago and across the majority of the Midwest and Great Lakes. The chill will surge south and east, reaching the Gulf and Atlantic coastlines by later Tuesday.

The air that will be heading southward has origins as far north as Siberia. NOAA’s Hysplit model, which attempts to simulate the trajectories of air parcels, suggests that next week’s air mass is working over the Yukon in Canada after having traveled over Alaska and the Bering Strait on its way east out of extreme northern Russia and the Arctic.

Temperatures to plummet

On Sunday, the first hints of impending frosty weather will lap at northern Minnesota and Wisconsin, where temperatures will peak in the 40s. Most of the Dakotas and western Minnesota will then plummet into the 20s overnight as the frigid air mass expands south and east into Monday morning.

By the start of the workweek, Minneapolis will be teetering around 40 degrees — compared with an average high around 57 degrees — and Chicago will struggle to reach 47. By then, the cold front’s leading edge will just be beginning to shove across the Appalachians.

There is a chance that, on the leading edge of the cold air, a few lake-effect snow showers could form thanks to the comparatively mild waters of the Great Lakes. That could paint a localized dusting to an inch or more on the eastern shores of lakes Michigan and Erie. There’s a low-end chance that a few additional snow showers make it to Ohio or western Pennsylvania by Tuesday morning, with “upslope” snows also possible on the western side of the Alleghenies in West Virginia.

Some models indicate that additional lake-effect snows are possible later in the week, but confidence is very low.

The entire Upper Midwest will dip into the 20s on Monday night, and the remainder of the Midwest and Great Lakes will fall through the 30s. Kansas City will even dip below freezing, and both Indianapolis and Columbus should hover around that 32-degree mark.

On Tuesday, Nashville, D.C., Raleigh and Philadelphia will be on the fringe of the more significant cold air mass, with highs in the mid- to upper 50s projected. Deeper within the core of the cold, another day in the 40s is anticipated.

By Wednesday, low temperatures will plunge into the 20s and 30s from the Midwest to the Northeast and Mid-Atlantic, where frosts and freezes will end the growing season in many locations.

Some models are highlighting the potential for the upper 30s to around 40 to even make it into the Florida Panhandle and along the Interstate 10 stretch during this time frame.

It appears as though the cold episode should persist until the end of the workweek, potentially easing some before a reinforcing batch of cold air wafts southeast.

Toasty weather in the West

Isaac Newton’s third law states, “for every action, there’s an opposite and equal reaction.” In a sense, that will be the case in the atmosphere next week. The cooldown in the East is matched by a late-season heat dome in the West.

Though the jet stream is dipping south in the eastern United States, it’s riding up and over high pressure banked in the western half of the Lower 48. That will afford highs 10 to 20 degrees above average through at least the middle of next week, most prominently in the interior Pacific Northwest.

Seattle is already getting a head start on the anomalous mildness, with projected highs around 77 degrees for Thursday. An average high this time of year is 62 degrees. It could flirt with 80 degrees Sunday, which would be the latest it’s been that warm on record.

Portland has already set an October record for most 80-degree days and is predicted to add more with the coming warmth.