By James M. Arnold, Weather Specialist
SNOW/RAIN: The model guidance is still all over the place, but if there is a trend, it is to bring the storm further north than earlier runs did. Right now, the European (ECMWF) and American (GFS) models in my opinion are underdone as far as their snow forecasts. The thought appears to be that with the absence of any arctic air to our north and northeast this storm will produce mostly rain and a lot of it. On the other hand, the North American Model (NAM) looks to be overdone at this time, as it shows around 33″ of snow for parts of the central Massachusetts area. As high as this is, their potential snow total is in line with the total amount of precipitation expected from this storm.
The coastal plain, Cape Cod and the Islands will see mostly rain from this storm although there could be a change to snow near the coast as the precipitation winds down. There is potential for widespread 2 to 4 inch totals and there could be isolated pockets of up to 5 inches. The potential exists for considerable inland/urban flooding to occur, including some of the smaller main stem rivers that are susceptible to rapid rises from a long duration heavy rain. Inland areas are where it gets interesting and most difficult to pin down. Precipitation will begin as rain in most or all areas but I think it will transition over to a wet, sticky snow as colder air mixes down from above due to dynamic cooling from the heavy rain falling. This will likely occur first in our northwestern sections and gradually work to the east and south, likely staying as mostly a mix of rain and snow south of the Mass Pike and east of the Route 495 corridor. Snow totals are awfully hard to estimate this far out, but we could get several inches of wet sticky snow when it is all said and done.
WIND: This storm will produce a lot of wind, and coastal areas will take the brunt of this. The National Weather Service will likely issue a “Storm warning” for the waters to the east of the Cape, and there is even a low probability of a “Hurricane Force Wind Warning” for gusts that could reach 75 mph to perhaps as much as 85 mph during the height of the storm, although this is not a certainty at this time. Coastal implications are pretty serious, as this is a time of high astronomical tides. In addition, this will be a long lasting event covering several tide cycles, which will be compounded by a storm surge that could be in excess of 2 feet. The strong winds mentioned above will persist and build very high and battering waves, contributing to some moderate to major coastal flooding and undoubtedly causing some areas of massive erosion damage along east facing beaches. Conditions at sea will become hazardous (ECMWF shows maximum wave height of 70.8 feet!) and the marine community is encouraged to monitor this situation closely and consider heading for safe harbor on Thursday.
Inland areas will not experience such extreme wind, but will still see strong winds throughout this storm. Should poles, wires and trees get plastered by wet and heavy snow, there could be some damage and a chance for isolated power outages. The more snow and the higher the wind the greater this threat is. Central Massachusetts should see winds of 20 to 30 mph with some gusts of 40 to 45 mph. The greatest threat for this is in the high ground areas to our north and west.
TIMING: Rain should begin later Thursday evening and precipitation will likely continue into Saturday morning at varying rates. As far as when the mix with and/or the change to snow occurs it is too early to pin that down. This event is still 2 days out and minor differences in track at this time of year can yield profound differences in outcomes. If the storm tracks a bit to the west of the Benchmark and we could get a lot of snow or coming inland over Southern New England would guarantee all rain.
This storm could be a serious event, so stay tuned for your latest forecast on the radio, TV, your NOAA weather radio and the internet.
James M. Arnold is a former Weather Specialist who worked 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