Greater Boston saw a two-week stretch of milder weather, where only two days had the average temperatures dip below the seasonal normal. But that’s all about to change with an extended blast of dangerously frigid air set to envelope New England thanks to a weakened polar vortex.
A massive Arctic cold front will push into New England from the northwest beginning early Friday morning, plunging temperatures into the teens with biting wind chills only in the single digits to below zero through the weekend.
Friday’s temperatures will peak in the morning, reaching the low 30s across Greater Boston, before free-falling into the single digits by the time the clock strikes midnight. Add in the wind chill from the breezy weather with this heavy, dense front, and it’ll feel like it’s in the negatives, especially at night. Take a look at how our forecast temperatures remain stuck in this deep freeze through Monday morning.
Here’s an early alert: If you have plans out on the town Friday and Saturday nights, make sure you bundle up. Frostbite will be a concern if you’re outside with exposed skin for more than 30 minutes. When wind is factored in, it can get dangerously cold.
We are already in the depths of winter, where we usually see the coldest temperatures; however, Boston and the rest of New England could experience temperatures as much as 30 degrees below normal during this cold spell.
Here’s a timeline of when the intense cold settles in:
Friday: Free-falling into the single digits and below
We will actually hit the high temperatures in the morning on Friday before the Arctic air settles at the surface. Temperatures will reach 30 degrees across Greater Boston by late morning before getting dramatically colder through the afternoon.
Folks up north won’t be as fortunate, as the cold air arrives shortly after the sun rises, holding high temperatures on Friday to the low 20s.
With the strong cold front arriving in the afternoon, winds will turn blustery and wind chills will plunge across all of New England. This type of breeze will remain steady, so you could expect it to truly feel like it’s in the negatives.
This may come as a shock to many who are not prepared. As I mentioned, make sure that you are bundled up and not spending too much time outside if you have plans Friday night.
The National Weather Service has issued an Extreme Cold Watch for Western Massachusetts, Vermont, and parts of New Hampshire and Maine, with dangerous wind chills set to plummet as low as 40 below Friday night into Saturday.
Saturday: Don’t let the sun fool you
The only benefit to Saturday is that you may see some sun at times during the day, but the strong high-pressure system settling above will continue to bring sinking polar air to the surface.
High temperatures will barely reach the teens across Massachusetts, with most of Northern New England only rising into the single digits. I expect numerous daily records to be shattered for low “highs” across Northern and Western New England. Not so much for Boston, where the city’s record minimum high temperature for Jan. 24 is 8 degrees, set in 1907.
The blustery conditions don’t subside on Saturday, which will once again bring wind chill values into the negatives across the entire region once the sun goes down.
Sunday: Still in the teens
Turning the page to Sunday, there’s hardly any improvement. Sure, the strongest of the cold air will begin to slip away, but only marginally. To be honest, we won’t really feel the difference because it will remain in the teens across Southern New England and single digits up north.
In addition to the epic cold gripping New England on Sunday, we’re tracking a blockbuster of a storm that will bring the Southeast and Mid-Atlantic to a standstill. At the same time, the heaviest snow in over three years is expected across Southern New England. The storm should arrive here sometime Sunday afternoon to evening, but the question will come down to intensity, which will determine whether we see modest or major snowfall totals.
We’ll have a better idea of snow totals by Friday, because simply put, this storm hasn’t even materialized yet. However, early indications suggest at least a couple of inches across Massachusetts, Connecticut, and Rhode Island.
Looking ahead: Cold could linger into Monday
You could expect this cold wave to continue into Monday. And after a very brief hiatus, another shot of cold, there is expected to push into the region throughout the second half of next week.
This means that the warmer air that we experienced over the last two weeks was nothing more than a fluke, as winter is still going to keep its grip on the region well through the turn of the month.
The polar vortex influence
It does appear that this cold wave, set to grip New England, is stemming from a weakening polar vortex. The map below shows the stratosphere, where the polar vortex lives, sinking closer to the tropopause, where we experience our weather. The deep purple and pinks, even shading to a white at times, reveal the polar air originating from the polar vortex.
The surface high-pressure system already holds frozen air temperatures, but with a piece of the polar vortex sinking low enough, the surface high-pressure system acts as if you’re pulling down a garage door, dragging some of that epic cold to the ground to make already cold air just that much more bone-chilling.
The polar vortex is a tight band of wind that holds exceptionally frigid air high in the atmosphere above the Earth’s poles, primarily in the stratosphere, about 10 to 30 miles above the Earth’s surface. It’s the layer of the atmosphere above the troposphere, where weather occurs.
If the polar vortex is tight and fast, it very often keeps the Arctic air below it locked in place. When the polar vortex becomes disrupted or weakens, it interacts with the polar jet stream below, allowing that stream to move farther south. In turn, cold Arctic air may move into the Lower 48.
Beware of frostbite and hypothermia
Here’s a great chart revealing just how long it takes to catch frostbite, given air temperatures and wind speeds. Exposed skin may take less than 30 minutes for the risk for frostbite across Greater Boston this weekend, but less than 10 minutes or less for folks across Northern New England.
Also, be mindful of your pets! Dog paws can absolutely get frostbite in as little as 30 minutes when wind chills sink below zero.
Frostbite occurs when your body tissue freezes, which often begins with extremities and less insulated parts of the body, such as fingers, toes, ears, and nose. The most severe stage of frostbite can cause permanent skin damage.
Hypothermia occurs when your core body temperature, normally around 98.6 degrees, falls below 95, or just 2 to 4 degrees below what an individual’s typical body temperature is. Hypothermia can be life-threatening if left untreated.
Just be careful out there and cover up over the weekend, and you’ll be all right.
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Ken Mahan can be reached at ken.mahan@globe.com. Follow him on Instagram @kenmahantheweatherman.