Cold blast engulfs Eastern U.S. as summer warmth swells in West

WEATHER NEWS: Cold blast engulfs Eastern U.S. as summer warmth swells in West


The nation is divided, atmospherically speaking, with clashing air masses battling it out over the Lower 48. Temperatures over the eastern United States are plummeting to values more typically seen in December, with readings 15 to 20 degrees below average. The opposite is true in California and the Pacific Northwest, where summerlike warmth has swelled north and set records.

Over 100 million Americans in the Midwest, Mid-South and Mid-Atlantic are under frost and freeze alerts signifying an early-season cold-air outbreak that will spell an end to the growing season. Freeze warnings, which include the entirety of Arkansas and Tennessee, have been expanded all the way to the gulf coasts of Mississippi and Alabama to account for lows in the 30s on Tuesday night.

Dozens of record lows were set from Minnesota to Texas on Tuesday morning, with temperatures dipping into the teens and 20s. Des Moines, Omaha and Kansas City were among locations that set record lows.

Over the Great Lakes, meanwhile, lake-effect snows have been delivering an early dose of winter’s worst. A full-fledged snowstorm — sourced from the waters of Lake Superior — is burying parts of the Upper Peninsula of Michigan, with additional snows emanating from Lakes Erie and Ontario.

Nearly 30,000 power outages have been reported in the Upper Peninsula as double-digit snowfall totals and strong winds have snapped tree limbs and power lines.

Snowflakes were also spotted in Chicago on Monday, while Madison, Wis., posted its earliest measurable snow in 32 years with a light dusting.

On the West Coast, in contrast, the start of the workweek featured highs in the 80s and 90s. A spattering of wildfires erupted amid the brief warm-up, with air-quality issues becoming a problem as smoke wafts over Oregon and Washington.

Historic October heat shatters records in the Pacific Northwest

Things are about to change in big ways, however — the atmosphere will pull a 180-degree switcheroo. A damp, chilly autumn pattern will set its sights on the northwestern United States by the end of this week, while the core of unseasonable warmth builds eastward. It’s a classic example of the atmosphere’s caprice, with roller-coaster changes in store.

Instigating the dynamic contrast is a highly amplified, or wavy, jet stream. It’s surging north over the western United States, allowing ridging, or the establishment of high pressure. That deflects inclement weather up into Canada.

In the East, there’s a different story. A bowling-ball upper-level low — or pocket of high-altitude cold air, low pressure and spin nestled within a dip in the jet stream — is parked over the Great Lakes. It’s slowly inching into Ontario. Frigid air is spilling south within that jet stream dip, with freezing temperatures all the way down to the Gulf Coast.

On the backside of the low, northerly winds passing over the warm waters of the Great Lakes are inducing lake-effect snowfall along with giant waves predicted to reach up to 25 feet on Lake Superior on Tuesday.

Tuesday morning brought record-cold temperatures from the Upper Midwest to the mid-South. Des Moines dipped to 21 degrees Tuesday morning, setting a record for the day and representing the chilliest weather this early in the season since 1987. Kansas City, Mo., also broke a record morning low at 25 degrees, and Omaha snagged a record low at 16 degrees, the coldest on record this early in the season. Kansas City’s morning temperature would have been an average low for Dec. 12.

Wind chills in Minnesota dipped below zero Tuesday morning.

The core of the cold is on the move eastward.

In the East, high temperatures in the 40s and 50s will be common on Tuesday and Wednesday. Chicago’s projected high is around 43 degrees Tuesday and 48 on Wednesday, compared with an average mid-October high of about 62 degrees. Highs in Detroit are predicted to hover in the mid-40s through Wednesday, with rain showers; the average there is also in the lower to mid-60s.

Columbus, Ohio, normally would be around 65 degrees; both Tuesday and Wednesday, it will be close to 45 degrees. And in Nashville; Washington, D.C.; Philadelphia; and New York City, it’s the same thing — highs in the 50s through Wednesday.

Lows on Wednesday and Thursday morning will be in the 20s and 30s across most of the eastern half of the nation.

To the west, temperatures have been spiking. Calgary, Alberta, jumped to 77.4 degrees on Monday, beating out the previous record of 75.9 degrees. According to Kyle Britain, a meteorologist at the Weather Network, that’s a degree or two warmer than the average high temperature on July 16.

Seattle experienced a similarly extreme anomaly. On Sunday, the city hit 88 degrees, the second-warmest October day on record in nearly 130 years of observation, and the warmest day this late in the season on record. Monday was 21 degrees cooler, peaking at 67 degrees, but it was still warmer than normal — it proved the fifth-warmest Oct. 17 in the past 78 years.

The hot, dry weather allowed a number of wildfires to erupt, pouring smoke into the skies over the Pacific Northwest. Now Seattle, Tacoma and Olympia in Washington and Portland, Ore., are under air-quality alerts.

“Everyone, especially sensitive groups, should limit time spent outdoors, avoid strenuous activities outdoors, and choose light indoor activities,” the National Weather Service warned. The smoky conditions are forecast to ease by Friday.

What to know about the Nakia Creek Fire forcing thousands to evacuate

Like a seesaw, warmth and cold will swap places in the contiguous United States. The jet stream will completely reverse its positioning, swinging a strong cold front through the Northwest on Friday as warm high pressure builds in the East.

“Mountainous regions will experience the first snowflakes of the season,” wrote the National Weather Service in Portland. “Snow levels will drop between 3000-4000 feet Saturday night into Sunday morning.”

Over the eastern half of the country, highs in the 70s will return, including in some places that recently saw snow. It appears that mildness will linger thorough much of next week.

Source link