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Summary: The forecast for tomorrow’s snowstorm is, once again, not significantly changed. The computer models have been very consistent from run to run as well as between models for the last few days so this is a fairly high confidence forecast. One “concern” that I have for the forecast is that the models are suggesting there will be very high snowfall rates tomorrow morning, on the order of 1-2″ per hour and that most of the accumulating snow will fall in a relatively short period, between about 4 or 5 am and noon. Two things; 1) If that scenario occurs travel will be extremely difficult tomorrow morning. 2) However, sometimes with a strong storm a “gravity wave” (not usually picked up by the computer models) develops, which may result in snow completely stopping for a few hours where the “downward” portion of the wave moves through. If this were to occur, since most of the snow is expected to fall during a short period, if the very high snowfall rates are not maintained anywhere in the county during that period, snowfall accumulation forecasts would be way too high. However, I think this scenario is not particularly likely since this type of wave “usually” forms with a low pressure system developing explosively just off the coast, which is not the expected scenario with this storm.
To summarize, the most likely timing of events looks like this: Snow will likely begin between 3 and 5 am. However, do not expect a gradual increase in snowfall intensity. Once the snow begins it should become fairly heavy relatively quickly. It should be snowing heavily during the morning commute with 2-4″ accumulation by 7 or 8 am. Snow should continue heavy at times throughout the morning with snowfall rates occasionally 1-2″ per hour. The majority of the snow accumulation with this storm will have occurred by noon, with 6-10″ of snow and 12″ over the elevated terrain to the east. Around midday, the center of the primary surface low pressure system will be just to our northwest. Drier and milder air wrapping counterclockwise around this low at 5-10 thousand foot elevation will briefly move over the county. As a result, the precipitation will lighten fairly abruptly and may even stop for a short time. As the milder air moves over the cold air at the surface the snow may mix with or change to sleet for a short time in South County. This is not likely to impact snowfall totals much since precipitation will be light at that time. At the same time, jet stream energy will be in the process of being transferred to a developing surface low south of Long Island. This will enable moisture to wrap back into the county so that snowfall will resume, at much lighter intensity, during the remainder of the afternoon and into the evening. An additional 1-3″ of snowfall is likely during this period (noon til 8 or 9 pm) before the snow ends during the evening. Total snowfall will likely be 8-12″ in most locations with more than a foot (12-15″) in a few locations in the elevated terrain to the east (e.g. Windsor, Peru, Savoy).
Tuesday Night
Increasing cloudiness this evening. Overcast after midnight with snow likely developing between 3 and 5 am, then snow, heavy at times until morning. Probability of precipitation 90%. Likely snowfall accumulation 2-4″ by 7 or 8 am.
Low temperatures in the mid to upper teens.
Calm winds, becoming east-northeasterly at 5-10 mph after midnight, increasing to 10-15 mph toward daybreak.
Wednesday
Snow, heavy at times during the morning, with snowfall rates occasionally 1-2″ per hour. Likely snowfall accumulations 6-10″ by noon, with 12″ in some spots in the higher terrain to the east. Precipitation will lighten or stop briefly around midday and may mix with or change to sleet for a time in South County. Light snow will resume during the early afternoon and continue into the evening. An additional accumulation of 1-3″ is likely during this time. Snow should end by 8 or 9 pm. Total accumulations 8-12″, with 12-15″ in some spots in the elevated terrain to the east (e.g. Windsor, Peru, Savoy).
High temperatures in the low 20s in Pittsfield; low to mid 20s in Lee, Stockbridge, Adams, North Adams and Williamstown; mid 20s in Great Barrington and Sheffield and; upper teens to near 20 over the elevated terrain.
East-northeasterly winds at 10-20 mph, shifting to northerly and decreasing to 5-10 mph during the afternoon.
Wednesday Night
Light snow ending during the evening, then remaining overcast, with partial clearing toward morning, and turning colder.
Low temperatures in the mid to upper single digits, low single digits over the elevated terrain.
Northerly winds at 5-10 mph, shifting to northwesterly after midnight.
Thursday
Partly cloudy and cold.
High temperatures near 20 in Pittsfield; near 20 to low 20s in Adams, North Adams, Williamstown, Lee and Stockbridge; low 20s in Great Barrington and Sheffield and; mid to upper teens over the elevated terrain.
West-northwesterly winds at 5-10 mph.