Posted at 2:30 pm, Friday 12/30

Summary and Analysis:

Yesterday’s storm has moved into the Canadian Maritime and the surface low has become quite deep, with central pressure around 965 mb. This is creating a strong pressure gradient which is generating strong west-northwesterly winds across our region. As these cold winds blow across the mild, unfrozen Great Lakes numerous bands of lake-effect snow have developed across New York state and into Berkshire County. A few of these bands contain fairly heavy snow and, in fact, one of these moved across central Berkshire near noon today and dropped a quick inch of snow. These will continue to wave back and forth, north to south and then back to the north again tonight as the snow within them diminishes. An Alberta Clipper type low will move across the Great Lakes and to our north Saturday and Saturday night. The low may be close enough to give Berkshire County a quick dusting of snow Saturday evening, with the greatest likelihood in northern portions. Our weather should be quiet Sunday into Monday as surface high pressure develops over the Northeast.

As evening approaches on Monday there could be some travel issues and this will need to be watched closely over the next few days. Warm air aloft well in advance of an approaching warm front will begin to override cold air near the surface, possibly generating a little light precipitation Monday evening into Tuesday morning. Any precipitation should be quite light but will fall in the form of sleet or freezing rain/drizzle. As the warm front, associated with a surface low moving northward into the Great Lakes. As the warm front moves through on Tuesday afternoon and evening the precipitation will increase in intensity but surface temperatures will likely have moved above freezing by that point so, hopefully, we will see just plain rain.

As the surface low over the Great Lakes moves northeastward it will drag its trailing cold front through our area overnight Tuesday. As a result, it will be colder but dry on Wednesday and Thursday. However, it is beginning to look like the cold front, at the leading edge of a broad trough in the jet stream wave pattern, will stall to our south. One or two surface lows may develop along the front in the Southeast and move northeastward off the Mid-Atlantic coast, the first on Friday and the second over the weekend. If this does occur we could see another snow event (or two). However, this situation is still a week away…..

Berkshire County Forecast:

Friday Night

Partly to mostly cloudy breezy and colder. Scattered snow flurries and snow showers are still possible. Probability of precipitation 50%. Little or no additional snow accumulation. Low temperatures near 20, mid to upper teens over the elevated terrain and low 20s in the lower elevations of South County. Westerly winds at 10 – 15 mph this evening, diminishing after midnight, becoming southwesterly at 5 – 10 mph by morning.

Saturday

Cloudy and seasonably cold, becoming breezy in the afternoon. There is the chance of a snow shower toward evening, particularly in North County. Probability of precipitation 30%. High temperature near 30 in the lower elevations of central and northern Berkshire (including Pittsfield, Adams, North Adams and Williamstown), low 30s in the lower elevations of South County (including Great Barrington and Sheffield) and upper 20s over the elevated terrain. Light southwesterly winds becoming southerly and increasing to 10 – 15 mph in the afternoon.

Saturday Night

A quick burst of light snow or snow showers is likely during the evening, with increasing likelihood as one moves further north in the county. Probability of precipitation 70% in North County, 60% in central Berkshire, and 50% in South County. Any accumulations should be light, on the order of a dusting to 2″. Otherwise, mostly cloudy with near steady temperatures overnight. Low temperatures in the upper 20s, mid 20s over the elevated terrain and near 30 in South County. South-southwesterly winds at 10 – 15 mph in the evening, becoming westerly at 5 – 10 mph toward morning.

Sunday

Mostly cloudy in the morning, clearing skies during the afternoon. High temperature in the low 30s in the lower elevations of central and northern Berkshire, mid 30s in South County, and upper 20s over the elevated terrain.

Summary:

A weak surface low pressure system located off the New Jersey coast will intensify rapidly as it moves north/northeastward this afternoon and tonight across Cape Cod and into the Gulf of Maine. As of early afternoon, it is snowing moderately across the county with approximately 2″ of accumulated snow (Richmond). It appears that the storm will move more rapidly and track slightly to the east of the forecast from yesterday. In addition, the low pressure center should be slightly less intense. Therefore, although we will still receive significant accumulations, totals should be a bit less than forecast yesterday, the snow should taper off a few hours earlier this evening, winds won’t be quite as strong tonight and Friday, and there will likely be less in the way of “wrap around” snow showers.

Analysis (General):

As the surface low pressure system moves rapidly into the Canadian Maritime tonight and Friday, the trough in the jet stream wave pattern which generated the surface storm will move over us Friday and Friday night, giving Berkshire County a brief period of colder and windy weather, although temperatures will still be near normal for the date. Strong west-northwesterly winds circulating around the departing surface low will flow across the still unfrozen Great Lakes and generate some significant lake-effect snow later tonight and during the day on Friday across western and central NY state. Some of this snow will reach Berkshire County in diminished form, scattered off and on snow showers and flurries.

The jet stream wave pattern then begins to flatten out (zonally [west to east] oriented) on Saturday and remains that way into early next week. A weak Alberta Clipper type low will move to our north Saturday night but may be close enough to give the county a little light snow or snow showers overnight Saturday. However, accumulations should be only on the order of 1 – 2″ at most. A deep trough in the jet stream wave pattern will develop over the western US on Monday with concurrent “ridging” over the eastern US. As a result, it will become unseasonably mild here Monday night into Wednesday. In addition, a surface low will develop along the easter edge of the trough and move northeastward into the Great Lakes on Tuesday. The low will drag is attached warm front across Berkshire County and generate a pretty large dose of rain here during the day on Tuesday. This will, unfortunately for winter sports lovers, destroy any powder we accumulate today.  The trough will then propagate eastward and then “broaden out”, resulting in much colder temperatures through next weekend. A storm in the southeast may make a run at us next Friday……

Berkshire County Analysis:

Snow will be moderate to occasionally heavy through the afternoon, tapering off and ending from west to east between 5 and 7 pm. It will become windy overnight with scattered snow showers developing after midnight. It will be windy and chilly Friday, with temperatures holding steady. Off and on lake-effect snow showers will be around for most of the day Friday. It will remain cloudy and turn colder Friday night, with a few lingering snow showers or flurries and diminishing winds. It will remain cloudy on Saturday as the Clipper low approaches from the west. Light snow or snow showers will likely develop Saturday evening.

Revised total snow accumulation forecast (by end of the day Friday):

South County: Generally 3 – 6″, with the lowest amounts in the lower elevations near the Connecticut border and highest amounts in the hill towns to the east. There could be as much as 8″ in a few spots in the hill towns to the east (i.e., Otis, Becket). Expect 4 or 5″ in Great Barrington.

Central Berkshire: Generally 4 – 8″, with the lowest amounts in the lower elevations to the west and highest amounts in the eastern hill towns. There could be as much as 10″ in a few spots over the elevated terrain to the east. Expect 5 – 7″ in Pittsfield.

North County: Generally 5 – 9″, with lowest amounts in the lower elevations and highest amounts in the hill towns to the east. Expect 5 – 7″ in Adams, North Adams and Williamstown. A few spots over the elevated terrain to the east could see up to 10″.

Berkshire County Forecast:

Thursday Night

Snow tapering off during the evening and ending by 6 or 7 pm. It will remain cloudy and become breezy/windy overnight with scattered snow showers developing after midnight. Low temperature in the mid 20s, upper 20s in the lower elevations of South County and low 20s over the elevated terrain. West-northwesterly winds at 10 – 20 mph.

Friday

Mostly cloudy and breezy/windy and seasonably cold, with scattered snow showers and flurries. Snow accumulations a dusting to as much as 1″. There could be as much as 1 – 2″ if a persistent band sets up, particularly over the elevated terrain. Temperatures holding fairly steady in the upper 20s in the lower elevations of central and northern Berkshire (i.e., Pittsfield, North Adams), low 30s in the lower elevations of South County (i.e., Great Barrington) and mid 20s over the elevated terrain. Westerly winds at 15 -20 mph with gusts up to 30 mph.

Friday Night

Mostly cloudy and turning colder, breezy in the evening with diminishing winds after midnight. Scattered flurries and snow showers are still possible with little or no additional accumulation. Low temperatures in the mid to upper teens. Westerly winds at 10 – 20 mph in the evening, diminishing after midnight to 5 – 10 mph by morning.

Saturday

Mostly cloudy and seasonably cold. There is the chance of a snow shower toward nightfall. High temperatures near 30, low 30s in South County, upper 20s over the elevated terrain. Winds shifting to southerly and increasing to 10 – 15 mph during the afternoon.

As I had feared (this has happened to Berkshire County before, you would think I would learn, haha), the storm appears to be moving faster and developing slightly further to the east than it appeared yesterday. Therefore, snowfall totals will likely be a bit less than originally forecast. Still expect a plowable snowfall, with a range of 4 – 10″, with the lowest amounts in that range in southern and western portions and the highest amounts in the hilltowns to the east. I will give a more detailed snowfall forecast later this morning as more data becomes available.

Summary:

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…..

Analysis (General):

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:

Wednesday Night

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.

Thursday

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.

Thursday Night

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.

Friday

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.

Due to the impending storm, I have decided to restart posting to this blog today. There will be a post by around 3:00 today. As in the past, I will generally post every other day when the weather is relatively inactive, daily if there is active weather and updates over the course of the day as warranted if a storm is approaching or occurring.

If anyone is still paying attention to this page after such a long layoff, I will resume the blog after the New Year. Stay tuned…….