20+ inches of snow could fall in Boston area this weekend. Maps show the latest storm forecast.
The Boston area is bracing for its biggest snow storm and coldest stretch of weather in several years, the latest forecast shows.
It starts with a bitter blast of air straight from the Arctic and we cap it off with a major winter storm.
The National Weather Service has issued winter storm watches and warnings that span more than 2,000 miles across the country from the desert Southwest through New England. More than a foot of snow will blanket major cities from the Texas Panhandle through the Ohio Valley and into the Mid Atlantic and Northeast.
Just south of those areas, a debilitating and destructive ice storm that will undoubtedly shut down airports and entire cities for days leaving millions without power.
Extreme cold watch
Let's begin with the cold. Temperatures will begin to plunge Friday evening behind an Arctic cold front.
By Saturday morning, air temperatures will fall to between -10 and 10 degrees in southern New England. Wind chills will be downright dangerous, ranging from -25 to -15 degrees through Saturday morning.
Under these conditions, frostbite can occur on exposed skin in less than 30 minutes.
The winds will tend to relax later on Saturday but air temperatures will remain frigid through the entire weekend.
Snow timeline in Massachusetts
Up next, the snow. Winter storm watches have already been issued across all of southern New England from Sunday morning through Monday evening.
Light snow will break out across our area mid to late Sunday morning. It will slowly ramp up in intensity in the afternoon, becoming steady and somewhat heavy by nightfall.
The peak of the storm will occur from roughly 5 p.m. Sunday through 5 a.m. Monday.
After dawn on Monday and through about 5 p.m., the snow will continue but it will become lighter and more spotty and scattered.
By that measure, expect the roads to deteriorate Sunday late afternoon and become snow-covered shortly after dark.
The most hazardous travel will be between about 7 p.m. and 7 a.m. with a very slow, gradual improvement during the day Monday.
How much snow will Boston get?
We are forecasting a widespread 10-20" of snow for all of southern New England. As we get closer to the storm, we will likely refine this area and try to pick out some possible "jackpot zones."
The snow for most of you will be very light and fluffy, easy to move around. In some cases you may even be able to clean off you cars with a leaf blower.
The advantage to this type of snow is that is does not stick to the trees and powerlines as readily and because of that, power outages should remain low.
The majority of the snow accumulation will occur Sunday night through very early Monday.
This timeline is meant to give you an approximation of what will be on the ground (and on the roads) as the storm progresses. Needless to say, the later you are traveling, the worse the conditions.
Weekend storm uncertainties
A few things we are watching that will factor into our final snow forecast:
South Coast/Cape Cod/Islands: There may be a brief period of mixing with ice or rain in this area. Obviously, that would bring the snow totals down a bit should that occur.
Coastal and most of southeastern Massachusetts: With many of our bigger winter storms, we typically see a localized phenomenon called a coastal front set up right around I-95. This front is essentially formed by the milder Atlantic Ocean air being pushed inland (therefore warming areas east of the front up by several degrees).
There could be as much as a 10–20-degree temperature difference between towns on either side of this front. Should this occur, the snow could be somewhat heavier (wetter) in far eastern areas for a time.
495 and areas northwest, including elevated parts of Worcester County: Meanwhile, on the western side of that coastal front, temperatures are frigid and the fluff factor really kicks in. Under ideal conditions, we could get much higher snow totals in these areas as lighter/fluffier snow stacks up very quickly. Therefore, we will watch to see if some towns here end up overproducing in the snow department.
Fluff factor could impact snow totals
Just to give you an idea of the lower and higher ends for this event:
Lower end totals, 6-12": This could occur if one of two things happen. First if there is some mixing with rain or ice to the south. Second, Arctic air is very dry. Sometimes with such a cold, dry airmass in place, it can take longer than expected to saturate the air and get the snow accumulation going.
Upper end totals, 18-24"+: This could occur where temperatures remain in the teens for the entire storm, and the fluff factor really takes off. We may also see higher end totals if the leftover snow falling on Monday is a bit heavier or more banded in nature.
There is always the chance in big storms like this one for a heavy snow band or two to setup over a small area and dump 1" per hour snowfall for several hours. These highly localized bands are near impossible to predict but often can occur near or on the west side of a coastal front or due to some ocean-enhancement right at the coastline.
Blizzard conditions?
Finally, some good news.
We have very little concern about the wind with this storm. We will see northeasterly gusts between 20-40 mph right at the immediate coastline late Sunday night through early Monday. This is much lower than our typical strong and destructive nor'easters. Can we call this a nor'easter? Technically yes, but the winds will only be a minor issue.
A reminder that in order to achieve "blizzard conditions" you need to have three consecutive hours with sustained winds or frequent gusts at or over 35 mph and visibility less than a quarter of a mile. That is not likely in the storm given the wind forecast. We may flirt with these types of conditions right at the coast at times but sustaining them seems unlikely.
Stay tuned to WBZ-TV, WBZ.com and CBS News Boston for frequent updates before and during the storm. The WBZ NEXT Weather team has you covered.
