A midlatitude cyclone (storm/low pressure system) will develop along the Mid-Atlantic coast tomorrow (Thursday) morning and then deepen rapidly during the afternoon and particularly Thursday night as it moves north/northeastward across eastern New England and into the Canadian Maritime region. Snowfall rates to the northwest of the surface low will likely reach 1-2″ hour and, as a result, snow accumulations will total 1 – 2 feet across inland New Hampshire and Maine. Berkshire County will be at the western edge of the heavy snow shield of this rapidly moving storm and will likely receive a plowable, heavy wet snowfall. As of early this afternoon the most likely snowfall totals for us appear to be in the 6-12″ range with least amounts in the southern and western parts of the county and the greatest amounts in the northern and eastern parts of the county. However, due to multiple variables, this is not a particularly high confidence forecast as this time. More on this ahead…..
A trough in the jet stream wave pattern located over the western US this afternoon will propagate rapidly eastward and amplify overnight and will be centered over the Midwest by Thursday morning. A strong mid/upper-level disturbance (spin/vorticity) will rotate through the base of this trough, helping to amplify and tilt the trough, resulting in strong forcing for upward movement (upper-level divergence) in the atmosphere along the leading edge of this trough. This upward motion will be enhanced as the disturbance moves over the warmer ocean waters (atmosphere destabilizes). As a result, a surface low pressure system will develop along the Mid-Atlantic coast Thursday morning and then deepen “explosively” as it moves over eastern Long Island to Cape Cod by Thursday evening and then across Maine Thursday night. In fact, models are predicting a drop in surface atmospheric pressure (mean sea-level pressure [MSLP]) from 1004 millibars (mb) Thursday morning to 976 mb around midnight when the surface low is located along the Maine coast.
Berkshire County Analysis:
Snow should develop in Berkshire County during the mid morning tomorrow. The snow should be light to moderate at first with only an inch or two accumulating by noon. Snow will likely intensify during the afternoon and could be quite heavy for a time during the mid to late afternoon, with snowfall rates possibly reaching 1″ per hour, as the surface low along the coast begins to deepen rapidly. Snow should taper off during the evening and be mostly over by midnight, although off and on snow showers are likely to continue into the day Friday as moisture wrapping around the deepening low is lifted by our elevated terrain. Although the precipitation should be predominantly snow, there is a chance that rain could mix in for a time in the southernmost parts of the county as mild maritime air is driven inland by the southeast winds circulating around the surface low. Likely snowfall totals for most of the county should be in the 6-12″ range by the time the snow winds down Friday, with most of that falling during Thursday afternoon and evening. It will become windy as well overnight Thursday and during the day Friday as the storm intensifies. I will delineate more detailed snowfall forecasts for the county below but first a few caveats….
First and foremost, this storm will be moving away from us as it intensifies so if the track of the storm is slightly east of presently forecast the heavy snow may miss us or be brief. In fact, this happened once last winter (or was it the winter before….I am getting old, haha). The models were forecasting over 1 foot of snow for Berkshire County with similar scenario with a rapidly developing coastal storm. Fortunately (or unfortunately) the storm did not intensify as far to the west as forecast and we ended up with only a couple of inches. Also, rain could mix in for a time in southern parts of the county when precipitation is the heaviest and this could keep snowfall totals down there. However, even though the high-resolution models are suggesting this could happen, I think that this is unlikely.
Important to note: The snow will be fairly wet, with temperatures near freezing. Although the wind will be relatively light during the afternoon, winds will pick up overnight as the pressure gradient strengthens around the intensifying surface low. If the snow is wet, and accumulates on tree branches during the afternoon, there could be tree damage and power outages. However, a few degrees can make a big difference. If the temperature is 31 or 32 there could be problems but if it is 29 or 30 we will be in much better shape.
Detailed Snowfall forecast:
South County: Generally 4 – 8″ with the lowest amounts within that range near the Connecticut border. Great Barrington most likely will receive in the 6 – 8″ range. The hill towns to the east, such as Otis and Becket will likely get a bit more, likely 8 – 10″.
Central Berkshire: Generally 6 – 10″, 6 – 8″ in western portions, including Pittsfield, with 8 – 10″ in eastern portions but the hill towns to the east, including Windsor and Peru will likely receive 10 – 12″, with up to 14″ in a few of the higher elevations.
North County: Highest accumulations should be here with generally 8 – 12″, including Adams, North Adams and Williamstown. The hill towns to the east, including Florida and Savory will likely see 10 – 14″, with up to 16″ in a few isolated spots.
Berkshire County Forecast:
Partly cloudy and seasonably cold with low temperatures in the low to mid 20s county wide. Upper teens are possible over the elevated terrain. Light westerly winds during the evening, shifting to southeasterly and increasing to 5 – 10 mph by morning.
Snow developing during the morning, becoming heavy at times during the afternoon. Heaviest snow should fall from mid afternoon until early evening. Most of the snowfall totals listed above will have occurred by 8 or 9 pm. High temperatures in the upper 20s over the elevated terrain, near 30 to low 30s in the lower elevations. Southeast winds at 5 – 10 mph during the morning, increasing to 10 – 15 mph during the afternoon.
Snow tapering off from southwest to northeast during the evening. Snow will generally end by midnight, although off and on snow showers will develop after midnight. It will become windy with winds 15 – 20 mph in the lower elevations and 20 – 25 mph in the elevated terrain. Wind gusts 25 – 35 mph. Low temperatures in the mid to upper 20s.
Mostly cloudy and windy with off and on snow flurries and snow showers. A dusting to an inch accumulation is likely in spots, particularly over the elevated terrain to the west. Temperatures holding steady in the upper 20s in the lower elevations of central and northern Berkshire, low 30s in South County, mid 20s over the elevated terrain.