By Terry Eliasen, Meteorologist, WBZ-TV Exec. Weather Producer


BOSTON (CBS) – How will we remember this storm? Will it just be a footnote?

“That storm that happened before the big Patriots win in Kansas City.…”

Typically the first “big one” of the winter has a special spot in our memories, but I wonder – given the holiday weekend, no school on Monday and the Pats game – if this one won’t have that typical staying power. My opinion: I think most will remember this for the ice more than the snow. The forecast hasn’t changed much from yesterday, but the reality is that the majority of the snow that falls in this storm will be while you are sleeping. By daylight on Sunday, it will be a sleet-fest. Most of you likely will be woken up on Sunday with a “ping…ping…ping” – the sound of sleet.

Quick weather 101 lesson: Many times folks confuse sleet and freezing rain, but the two are actually very different.

(WBZ-TV graphic)

Sleet is basically small pellets of ice. It falls and can accumulate much like snow (although not nearly as readily). It isn’t all that dangerous as far as icing goes; it just makes a mess and it will compact and add weight to the snowpack already on the ground.

Freezing rain falls in the form of water, just like regular rain. However, it freezes on contact with the ground (and anything on the ground), putting a glaze of ice on everything. Freezing rain can accrete on wires and tree limbs, adding lots of weight and potentially leading to widespread power outages and damage. Think back to those nasty ice storms of the past, when power went out for days and weeks. That was almost certainly due to freezing rain.

(WBZ-TV graphic)

Freezing rain is our biggest concern with this storm. It is most likely to occur primarily in the northern and western suburbs of Boston westward into central Massachusetts and southward into at least northern Connecticut and northwestern Rhode Island. The longer the period of freezing rain, the risk of scattered power outages increases.

Back to the details. Let’s take you from the first flakes to the final sleet pellet.

TIMELINE

The snow will begin Saturday after 8 p.m. from west to east across the area. While there may be a few stray flurries from 4-8 p.m., nothing significant will fall before 8 p.m. If you have Saturday night plans, the safest bet is to get home by 10 p.m. or 11 p.m. There should be very little snow accumulation before then. After 11 p.m., all bets are off. The snow will quickly become steady and heavy, and the accumulation will mount up fast.

(WBZ-TV Graphic)

The majority of the snow accumulation will occur between 11 p.m. Saturday and 5 a.m. Sunday morning. A rather small window, but snowfall rates of 1″-2” per hour are possible for several hours within that time period.

(WBZ-TV graphic)

The areas to change over first are, of course, the areas where we expect the least amount of snowfall.

Midnight-2 a.m.: Change from snow to rain along the South Coast and Cape Cod.

(WBZ-TV Graphic)

2-4 a.m.: Change from snow to sleet and rain in Plymouth (around 2 a.m.) to just about the Mass Pike by 4 a.m.

4-9 a.m.: Rapid changeover for nearly all of Southern New England. Snow changes to widespread sleet for all areas in Massachusetts and southern New Hampshire north of the Mass Pike. A switch to freezing rain inland and rain closer to the coast is expected as well. The rain may fall heavily resulting in some roadway flooding especially where catch basins are clogged by snow and sleet.

(WBZ-TV Graphic)

The precipitation will lose intensity late Sunday morning and begin to taper off from west to east during midday.

(WBZ-TV Graphic)

As colder air wraps in behind the storm, some of the rain and sleet will change back to snow before completely shutting off.

(WBZ-TV Graphic)

After 1 p.m., the precipitation is mainly on the coast and Cape, and it should completely clear the area by 4 p.m. There will be plenty of time to clean up and get cozy for the big game.

SO HOW MUCH?

(WBZ-TV Graphic)

Coating to 2”: The Cape, Islands, and far southeastern Massachusetts … mostly rain here, snow washed away.

(WBZ-TV Graphic)

2”-4”: Marshfield to Providence and areas north to the Mass Pike, including Boston and the immediate North Shore. Areas here will flip around between sleet, freezing rain, and brief regular (non-frozen) rain.

(WBZ-TV Graphic)

4”-8”: Areas north of a line from Worcester to Ipswich, up to Manchester, NH. Changes to sleet and at times freezing rain here, and totals get compressed in the end.

(WBZ-TV Graphic)

8”-14”: The Monadnock Region to Manchester, NH and points north. This area changes to sleet Sunday morning, and while the snow won’t go away, it will get compacted with ice on top.

14”-24”: Ski country! Most of central and northern New England. In fact, some elevated areas up north could see more than 2 feet!

FLASH FREEZE POTENTIAL

The precipitation tempo will decrease during Sunday afternoon from west to east. As colder air wraps in behind the departing storm, the precipitation will change from rain back to sleet and maybe some snow showers.

As the colder air rushes southeastward, a flash freeze is probable with water on streets freezing and the slushy layer of snow and sleet turning rock solid late in the day and especially tomorrow night.

GUSTY WINDS

The strongest winds with this storm will be over southeastern Massachusetts, especially over Cape Cod and the Islands. Gusts on Sunday morning in those areas could easily top 50 mph out of the southwest.

(WBZ-TV graphic)

Winds along the rest of the shoreline (South and North Shore) will be out of the northeast early Sunday morning, turning to the north-northwest later Sunday morning. Expect peak gusts between 40-50 mph, with the possible exception of Cape Ann, where winds may top out a bit higher.

Away from the coastline, farther inland, the wind gusts will drop off quickly. In fact, the strongest winds here will occur after the storm passes and the colder air filters in on northwest winds. Gusts between 20-40 mph are likely Sunday night through Monday morning across all of Southern New England.

COASTAL FLOODING

Given that there is a full moon this weekend, the tides are going to be astronomically high. Areas of concern for minor to moderate flooding:

The South Coast, particularly south-facing beaches on Cape Cod and the Islands

The east/northeast-facing shoreline of Massachusetts, most notably the South Shore from Scituate to Sandwich and the northern-facing beaches of Cape Ann.

The one and only high-tide cycle to watch is Sunday morning, generally from 9-11 a.m.

(WBZ-TV graphic)

POWER OUTAGES

The concern for outages is low for most of the area. The combination of snow and sleet and fairly light winds (inland) don’t particularly raise any red flags. However, in the areas where freezing rain and wind are an issue (primarily in southeastern Massachusetts, Rhode Island and Connecticut), there is a real concern for the ice to weigh on tree limbs and lines. This is something we will be monitoring very closely and may become the main hazard during this entire event.

(WBZ-TV graphic)

THE GREAT NEW ENGLAND GLACIER

Following the storm, there will be a blast of brutally cold air straight out of Northern Canada. Everything will be frozen solid from mountaintop to seashore. Wind chill values on Monday morning will drop between -10 and -25 degrees. High temperatures on Monday will struggle to get out of the single digits. Morning lows will be below zero in many of the ‘burbs, both Monday and Tuesday mornings.

(WBZ-TV graphic)

As always, we urge you to stay tuned to WBZ-TV and CBSBoston.com for updates leading up to and during the storm! We’ve got you covered. Please stay safe.

Follow Terry on Twitter @TerryWBZ.

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