2:57AM
Once upon a time, indications of a significant storm appeared on computer generated forecast maps as they chugged through programs created in an attempt to simulate the behavior of the atmosphere over a period of time, given a set of initial conditions at the surface and multiple levels above the ground. Though these prognostications are never perfect, they are often accurate enough to provide adequate notice of impending significant occurrences. Such is the case with the upcoming storm threat, which now looms so much closer than when it appeared as a distant star in the night sky of meteorology. The storm threat has become an asteroid hurtling toward our tiny little place in the universe. Will it crash into us with major impact, will it sideswipe the region with a scary close pass, or will it pass harmlessly as just an awesome sight just too far away to do anything?
This is what we do know: High pressure will build across the region today after having delivered yet another late season blast of Arctic air – a bright and cold start to the week. Two disturbances, a weak one drifting eastward from the Great Lakes region, and a slightly stronger one off the US Southeast Coast, will merge and intensify into a monster ocean storm off the US Mid Atlantic and Northeast Coast Tuesday through early Wednesday, tracking northeast to north. Eventually this storm will plow into the eastern Maritime Provinces of Canada, but before it does that, it will have some impact on southeastern New England.
The uncertainty arises out of the fact that a subtle shift in storm track one way or another will have significant influence on the details of the envelope of snowfall, the intensity of it in a given location, and of course, the snowfall amounts. A first call on snow amounts will appear below, based on where I expect the most likely path to be, which is a little east of where the tracks of heaviest snow-producers are. Strong northerly winds around the western side of the intensifying low may result in some damage with the most vulnerable place being Cape Cod in the early to middle hours of Wednesday morning. It is very important to remember that a slight shift of storm track will significant impact the snow amounts (eastward shift, amounts go down / westward shift, amounts go up). Coastal flooding especially near high tide time Wednesday morning is most likely along north-facing shores especially Cape Cod Bay and Nantucket.
The reasoning for going with a track a little further east is due to a lack of blocking in the steering currents that would help slow the storm down and push it a little closer to the coast. But the explosive development and size of the storm will still allow for a significant impact especially near the coast and especially far southeastern MA and Cape Cod.
Once this progressive system is by the region, rapid improvement in the weather will be seen by Thursday as high pressure builds in. By Friday, this high will already be moving offshore with a milder southerly wind developing. An approaching cold front from the west may send showers into the region as early as Friday afternoon. There are some questions regarding the speed and timing of this front and the potential for an extra wave of low pressure that may develop and move along it, keeping unsettled weather going into Saturday, which will likely turn out cooler than some current extended forecasts indicate. By Sunday, a chilly high pressure area will be in place, though it does not look as cold as it will be to start this week out.
Updated forecast for southeastern New England…
TODAY: Sunny. Early temperatures around 10 recovering to highs around 30. Wind NW 10-20 mph.
TONIGHT: Mostly clear. Lows around 15. Wind light N.
TUESDAY: Increasing cloudiness. Chance of light snow especially south and west of Boston by late in the day. Highs around 30. Wind light E.
TUESDAY NIGHT: Cloudy. Snow likely. Lows around 20. Wind E 5-15 MPH.
WEDNESDAY: Cloudy. Snow likely, possibly heavy for a time near the coasts of NH and MA and especially Cape Cod and Nantucket, and light to moderate elsewhere, tapering off west to east midday and afternoon. Early snowfall estimate: 1-3 inches east central MA, RI, and interior southern NH, 3-6 inches coastal NH, and most of east coastal MA, through southeastern MA, and 6-12 inches Cape Cod and Islands. Will change with any shifts in storm track! Highs around 30. Wind N 15-25 MPH gusting 30-40 MPH inland, 25-35 MPH gusting 45-55 MPH coastal areas especially Cape Cod.
THURSDAY: Mostly sunny. Low 20. High 45.
FRIDAY: Partly sunny. PM rain showers. Low 40. High 60.
SATURDAY: Mostly cloudy. Chance of rain. Low 40. High 50.
SUNDAY: Partly cloudy. Low 30. High 45.