By James M. Arnold, Weather Specialist
Region – Now we sit and wait. The storm continues to develop and track pretty much on schedule as outlined over the past few days. Not only will it be very intense, but will cover a very large geographical area, large enough so that minor changes in track will go unnoticed for the most part. It also will be very slow moving leading to a prolonged period of severe impacts, as outlined below.
Snow: A wide swath of southern New England, and central Massachusetts is right in the middle of it, will be looking at 1.5 to isolated areas of 3 feet or possibly a bit more when the storm is over. Latest data indicates that we will see between 2.5 and 3 inches of liquid equivalent precipitation during this storm. The standard rule of thumb is 1 inch of water will yield about 10 inches of snow. This ratio is dependent on temperature and the “fluff factor” of the snow – that is how dry it is. In temperatures like we currently have, even with a modified marine layer at higher levels, I would expect the ratio to be at least 15 to 1, which would mean 45 inches of snow from 3 inches of water. I doubt we will see 3 inches of water equivalent, but 2 to 2.5 inches is within reason, hence my forecast of up to 3 feet of snow in isolated areas.
Timing: Although there may be some flurries or very light snow (not associated with the main storm) beginning in the early afternoon, I do not expect the main snow shield to impact the greater Shrewsbury area until later this afternoon, likely around 5:00 P.M., give or take a little bit. Snow will become moderate to heavy around 7:00 to 8:00 P.M. and continue throughout the night and into Tuesday afternoon before tapering to light snow. The light snow or flurries will continue until the early morning hours of Wednesday before finally ending.
Wind: The wind will begin to pick up later this afternoon from the northeast, and will increase during the night to speeds of 20 to 25 mph with gusts at times approaching 50 mph. Strong winds will continue until later Tuesday afternoon when they will begin to diminish and shift to the north and northwest during Tuesday night. The strongest wind should be from midnight tonight through about noon Tuesday. The major impact will be to visibility and drifting. Visibility will fall to zero at times with heavily falling snow being blown around and drifting could become severe in exposed areas.
Temperature: Very cold arctic air is in place and will remain so for the duration of the storm. Temperatures will be limited to a narrow range, with highs topping off around 20 today through Wednesday and nighttime lows in the mid to high single digits. With the strong wind expected, wind chill values will sink to well below zero at times.
Summary: This storm will be talked about in the same sentences as the Blizzard of ’78 when it is all over. Strong winds will create blinding, white out conditions from time to time. Travel will become dangerous if not impossible. Temperatures and wind chill values will be low enough to threaten frostbite/hypothermia for persons outside without proper protection. Drifting could make exposed roadways impassable. Snow depths will be extreme, potentially reaching 3 feet in isolated locations. The general population should stay indoors and not venture out until the storm is over, to avoid getting in trouble and potentially putting first responders at risk as well.
Other Concerns: Along the coast winds will gust to hurricane force at times tonight and tomorrow, particularly over the outer Cape and Nantucket. There will be somewhat less snow in those locations but it will be wetter and stickier than here. That combination will most likely result in substantial tree and power line damage along the coast, and widespread and extended power outages are likely.
Coastal Flooding: There will be at least two tide cycles where pockets of moderate to major coastal flooding will occur, and beach erosion will be major to severe along east facing beaches through tomorrow into tomorrow night.
Marine Interests: Due to the long fetch and long duration of this storm, waves on the outer waters could be as high as 40 feet. Mariners at sea should proceed to safe harbor to take shelter from this storm and if still in port, do not venture out until wind and sea conditions moderate with the passage of this storm.
Beyond This: There are several more storms and rumors of storms in the pipeline. Also, there is a cold blast coming early next week that could be as extreme against temperatures as this approaching storm will be to snow. More on that later.
James M. Arnold is a Weather Specialist working with Shrewsbury Emergency Management Agency; town of Princeton; Worcester Emergency Communications and Emergency Management Agency; Southborough Emergency Management Agency; town of Grafton and Wachusett Mountain Ski Area