For the first time since last February, an icy chunk of the polar vortex is set to spin into the Berkshires and southern Vermont later this week, sending temperatures and wind chills into below zero territory.
The winter season whirlpool of frigid Arctic air spinning around the North Pole, northern Canada and Siberia has been blocked from the Northeast U.S. so far this winter because a strong jet stream fueled by a potent El Nino weather phenomenon has been funneling relatively mild air into the region, making January the warmest on record in the county.
But by Friday, according to meteorologist Ingrid Amberger of the National Weather Service in Albany, N.Y., a chunk of the polar vortex will break off from the Arctic Circle and shift southward through Ontario, Quebec, and New England.
The bitter, potentially brutal cold over the weekend will be an unwelcome reminder of what last February felt like, when temperatures at Pittsfield Municipal Airport plunged below zero on 12 nights, with a minus 14 low for the month on Feb. 21. It was the county's coldest February, according to records dating back to 1938.
This weekend, the coldest air mass of the season will send nighttime temperatures as low as 7 below zero in the Berkshires, with daytime highs on Saturday and Sunday struggling to reach 10 degrees. Brisk, gusty northwesterly winds will yield "potentially dangerous to life-threatening wind chills, particularly Saturday night into Sunday," Amberger stated. Wind chill advisories and warnings are likely to be issued.
Sunday, Valentine's Day, is expected to be a repeat of Saturday's deep freeze, with only slight improvement predicted for Monday, the Washington's Birthday legal holiday.
But low temperature records at the Pittsfield airport for those dates should survive: 20 below in 1943 for Feb. 14, 25 below for Feb. 15 the same year.
It has not been below zero in Pittsfield since last March 7, when a minus 4 reading ended a prolonged cold spell. This winter, the airport low so far has been minus 1 on Jan. 4 and Jan. 5.
"The combination of wind, cold air and other conditions will likely make the Arctic outbreaks through this weekend the most dangerous of the winter for the homeless and those not properly dressed when venturing outdoors," AccuWeather meteorologist Edward Vallee warned.
Although no major snowstorms are forecast for the next seven days, snow showers with light accumulations are possible through Thursday, and again Friday night, the National Weather Service predicted.
Monday's snowfall on the outer fringe of an intense coastal storm that socked southeastern Massachusetts, the Cape and the Islands came in on the high end of forecasts for Berkshire County. With some additional light snowfall before dawn on Tuesday included, totals ranged from a high of 7 inches in Savoy to just over 2 inches in North Adams and Bennington, Vt.
The preliminary estimate at the Pittsfield airport was 3.6 inches, with a bit more in South County. But, with 10 inches on the ground so far this winter, the area is still far below the average snowfall of 45 inches from October to mid-February. The full-season average is 78 inches.
Snowfall totals ...
Savoy: 7 inches
Lee: 5 inches
Pittsfield Airport: 3.6 inches
Lenox Dale: 4.4 inches
Lanesborough: 4 inches
Clarksburg: 3.5 inches
Adams 3.3 inches
North Adams (airport): 2.4 inches
Bennington Vt: 2.1 inches
Sources: National Weather Service compilation; AccuWeather.com