The Mid-Atlantic region is preparing for a major winter storm that is poised to wallop the Washington and Baltimore areas with up to 2 feet of snow this weekend. However, while this same storm was originally forecast to have a similar impact in New England, recent model runs are suggesting that the storm will take a more southern track, bringing it out to sea and sparing the Boston area from the brunt of the snowfall.
As is usually the case with Nor’easters such as this one, slight deviations in the track of the storm can result in huge variations in snowfall totals, as a too-far-offshore track causes the precipitation to miss the area, while a too-far-onshore track causes precipitation to fall as rain. This accounts for some of the uncertainty in the snow forecast several days in advance, when the atmospheric wave features that will eventually develop into a storm are located over the Pacific Ocean, where there are fewer weather observations from which data can be fed into models. On Wednesday, the features of interest with regard to this storm moved over land, where better observational coverage helped to reduce the uncertainty in numerical weather prediction model solutions, which are highly sensitive to initial conditions. As a result, the models have begun to converge on a solution that takes the storm offshore to our south on Saturday night, keeping the majority of the snowfall along or south of the Massachusetts coastline. Boston may still see some snowfall between Saturday afternoon and Sunday morning, but it is likely (roughly 85% chance as of this writing) that total accumulation will be under 5 inches.