BOSTON (CBS) – Just days after our biggest snowstorm in years, there is no rest for the weather weary. As Bill Belichick would say, “we’re on to Friday.” This storm will be very different than last Saturday’s blizzard. In fact I’m not even sure we can call it a storm. It is more like a frontal passage or a weather boundary. (Try describing that to news producers looking for a headline!). There will be no wind issues. There will be no coastal flooding, no splashover, no waves battering the houses in Scituate. In fact, there really won’t even be that much snow in southern New England!
So what’s the big deal?
Well, despite the mild weather Wednesday and Thursday, we will still have a decent snowpack when the precipitation arrives Thursday, somewhere between 6 and 12 inches in most areas. This “system” will be loaded with moisture. Total liquid amount (rain, ice and snow) will be close to 2”, that’s a lot of “stuff” falling from the sky. And then to top it off, it’s going to be cold all weekend. The entire region plunges into the teens Friday night and we won’t get out of the 20s Saturday. So, any standing water will freeze up and we are left with an ice-encrusted mess.
Let’s back up a bit and take this piece by piece.
TIMELINE:
Rain arrives during the day Thursday, becoming steadier and heavier by the afternoon and evening. The snow and ice are confined to central and northern New England.
Thursday night the cold air starts to push southward. By midnight we see a change to sleet in parts of southern New Hampshire. By dawn Friday, the sleet has worked all the way down through northern Mass., perhaps nearing Boston and the Mass Pike.
During the day Friday, it’s a sleet-fest for most of southern New England. Rain will hold on over the South Coast, Cape and Islands until the very end of the storm Friday evening. There will be some pure snow on the northern fringes of the precipitation shield. The sleet should change to snow as far south as about Boston before everything begins to taper off late Friday afternoon/evening.
SLEET vs FREEZING RAIN:
Some brief thoughts on the impacts of sleet vs freezing rain. We believe that for the vast majority of southern New England sleet will be the main precipitation type (once the rain changes over) and not freezing rain.
Freezing rain occurs when you have mild air (above 32 degrees) above the ground but a shallow layer of below freezing air right at the surface. So as the rain falls, it hits the cold ground (streets, sidewalks, patio, driveway, trees) and instantly freezes. This is the most treacherous and dangerous precipitation type and, in larger amounts, can cause massive damage to trees and power lines. All of our infamous ice storms, when you may have lost power for days, are due to freezing rain.
(WBZ-TV graphic)
Sleet occurs when you get a larger layer of cold air. The rain falls from above into a thick layer of atmosphere that is below freezing. Therefore, it has time to ice up into tiny pellets. These hit the ground and tend to bounce off of everything and have that pinging sound. Sleet, in large amounts, can accumulate but much less readily than snow. Most importantly, it does not accrete on trees and wires so the power outage risk is minimal.
ACCUMULATIONS:
Given that we are forecasting a rain-to-sleet situation for most of southern New England, the accumulations will be low.
There could be as much as 1-to-3 inches of sleet and snow in northern Massachusetts (north of Pike, mainly in northern Worcester and northern Middlesex counties).
Over the Mass. and New Hampshire border 3-to-6” of snow and sleet are possible up through Manchester, Concord and Lake Winnipesaukee.
(WBZ-TV graphic)
Great news for skiers. The snow jackpot will be in the mountains, particularly the northern Greens and the Whites. We expect 6-12” in those areas with perhaps as much as 18” in some of the higher, northernmost peaks.
THE FREEZE:
Temperatures will be dropping all day on Friday. By late afternoon all of southern New England is below 32 degrees and everything that has fallen, any standing water, will ice up. Any untreated surfaces and roadways will become very slippery. We stay below freezing all weekend long. Thankfully, we will see a good deal of sunshine Saturday and Sunday, so despite the cold temperatures, some melting is still likely to occur.
(WBZ-TV Graphic)
Timing is critical and we will keep you updated as new data comes in. Stay with WBZ-TV, CBSBoston.com and CBS News Boston.