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Summary: We are in for a prolonged, and possibly, a large impact snow event. Snowfall totals could exceed 12″ in some locations. Also, in contrast to previous recent snowfalls, the snow will have a heavier consistency (higher water content), and winds will be stronger, so there will be greater potential for damage to trees and even possible power outages.
The models are still struggling with the details of what will be a complex and, eventually, very deep surface low pressure system hugging the Atlantic Coast. The difficulty in forecasting snowfall totals accurately with this storm lies in the smaller scale (mesoscale) structure within the overall storm. The models struggle with these small scale features and their location and intensity is difficult to predict. In particular, the precipitation is likely to vary in intensity in “bands” so that if you are located within a heavy band for any length of time snow may be falling at 1-3″ and hour so that you will receive a much higher accumulation than areas not within one of these bands. This will have the largest impact Thursday night when a band of heavy snow forms to the west of the surface low pressure center as it intensifies rapidly as it moves over eastern Long Island and Cape Cod. In my experience, this type of band, which forms in an area of strong “frontogenesis” (a region of low level convergence where warmer, moist air from the ocean is being force up agains cold dense air to the west) tends to form to our west, over Albany and the Catskills. This is where the European Model (ECMWF) is placing it. The U.S. models place it directly over Berkshire County. Therefore, my tendency is to find the ECMWF solution more likely.
Another uncertainty is that a dry and milder wedge of air will likely wrap into the low and lighten the precipitation considerably between about 5 pm and 10 pm. This “wedge” of air will also likely bring above freezing air in aloft, between 5 and 10 thousand feet and change precipitation to light sleet for a time during the period in South County and, possibly, central Berkshire. I was pretty set on a total snow accumulation of 6-12″ with the reason for the large range being due to the banded precipitation and the dry slot. However, the latest data coming in this afternoon suggests that the storm is carrying more moisture and that the snow tomorrow morning and afternoon will be heavier than it looked earlier. Therefore, I think 8-16″, with highest amounts in the elevated terrain to the east (particularly in North County [e.g. Savory, Florida] where a changeover to sleet is less likely), by the time the storm ends Friday morning is a better estimate.
Here is my take on the timeline for the upcoming storm….
Snow should develop across the county from south to north between 5 and 7 am. Snow should continue fairly continuously moderate to heavy at times through the morning and afternoon. Likely snowfall accumulations are 3-6″ by lunch time (12 or 1) and 6-12″ by 5 pm. Between 5 and 10 pm the precipitation will lighten considerably and even shut down completely as the dry “wedge” of air wraps into the storm and over us. Precipitation is likely to change to light sleet and/or freezing drizzle during that period in South County and central Berkshire. Precipitation should then pick up again about 10 pm and continue, mostly light but possibly with an embedded period of moderate to heavy snow, from 10 pm until it ends near daybreak or early morning on Friday. The precipitation during this latter period may begin as sleet and/or freezing rain for an hour or two before changing back to snow by midnight. An additional 2-4″ of snow is likely overnight. By Friday morning, I expect likely snowfall accumulation totals to be 8-16″ with the highest totals most likely in the elevated terrain to the east, particularly northeast (e.g. Savoy, Florida). I will try to give updates on this rapidly evolving event as frequently as possibly as things progress…..
Wednesday Night
Increasing clouds with snow developing from south to north between 5 and 7 am.
Low temperatures in the low teens during the evening, then rising slowly to near 20 by morning.
Light southeasterly winds this evening, shifting to northeasterly after midnight.
Thursday
Snow, moderate to heavy at times, through the morning and afternoon, until about 5 pm. Snow should be heaviest from late morning through early to mid afternoon. Breezy. Snow will lighten in intensity and possibly change to light sleet and/or freezing drizzle after 5 pm. Probability of precipitation near 100%. Likely snowfall accumulations 3-6″ by noon or 1 pm and 6-12″ by evening.
High temperatures in the mid to upper 20s in Pittsfield, Lee, Stockbridge, Adams, North Adams and Williamstown; upper 20s in Great Barrington and Sheffield and; low to mid 20s over the elevated terrain.
East-northeasterly winds at 5-10 mph early, increasing to 10-20 mph by afternoon. Winds shifting to north-northeasterly late.
Thursday Night
Intermittent light snow until about 10 pm. Precipitation may be in the form of light sleet and/or freezing drizzle in central and southern Berkshire. Breezy. Precipitation will become more continuous and increase in intensity after 10 pm. Precipitation will change to snow everywhere by midnight. Snow continuing, mostly light, with a possible period of moderate to heavy snow after midnight, ending by daybreak or during the early morning. Probability of precipitation near 100%. Additional likely nighttime snowfall accumulations 2-4″.
Temperatures near steady, falling a few degrees after midnight, with low temperatures in the low to mid 20s by morning, near 20 over the elevated terrain.
North-northeasterly winds at 10-20 mph, shifting to northwesterly after midnight.
Friday
Snow tapering off and ending during the early morning. Likely storm total accumulations 8-16″, with the highest totals in the elevated terrain to the east, particularly where no changeover to sleet occurs (e.g. Savoy, Florida). Mostly cloudy in the morning, becoming partly sunny in the afternoon. Breezy.
High temperatures near 30 in Pittsfield, Lee, Stockbridge, Adams, North Adams and Williamstown; low 30s in Great Barrington and Sheffield and; mid to upper 20s over the elevated terrain.
Westerly winds at 10-20 mph.