I have updated the weekend forecast on the BCC Weather Station page: https://www.rainwise.net/weather/bcc

Note: Clicking on underlined red text provides links to various weather maps.

Summary: A highly amplified, negatively-tilted jet stream trough over the western U.S. is generating a deep surface low pressure system along its eastern margin in the Midwest today. This system has a well developed classic midlatitude cyclone structure, with a warm front extending out well to the east of the surface low and a strong cold front extending well to the south of the low. As the cold front plows into the unstable air in the warm sector (between the two fronts) it will generate a squall line (at the cold front) and a few pre-frontal bands of thunderstorms. The air in the warm sector is unstable and there is enough vertical wind shear so that some supercell thunderstorms will likely form late this afternoon over the lower Mississippi Valley and then the Tennessee and Ohio Valleys overnight as the cold front plows eastward. The Storm Prediction Center has forecast a moderate probability of severe thunderstorms in parts of the Ohio and Tennessee Valleys, mainly for strong winds and hail, although there is a 5% probability of tornadoes within 25 miles of any point within this region. It is only late February, but we are already heading into tornado season (March-June, with a peak in May). There is no concern for severe thunderstorms here since, by the time the cold front reaches us late in the day on Friday, it will be moving into much more stable air.

The center of the low is located over the upper Mississippi River near the Iowa, Missouri Illinois borders. As a result, heavy snow is falling to the northwest of this low, in Iowa and Minnesota. As the low moves northeastward, through the western Great Lakes tonight, northern and western Wisconsin will also receive heavy snow. As the low moves through the Great Lakes and into Canada, it will pull its warm front over us tonight and, eventually, drag its cold front through here late in the day tomorrow.

We will see the typical progression of precipitation types associated with a warm frontal passage this time of year overnight. Precipitation will likely be moderate to heavy at times from around 7 pm until well after midnight tonight with liquid total precipitation equivalent of 0.25″-0.50″ from southern into central Berkshire and 0.50″-0.75″ from central into northern parts of the county. The precipitation will likely start as snow but then changeover fairly quickly to sleet (ice pellets), by 9 pm or so. The changeover will be a little sooner to the south and a little later to the north. It may snow hard at the outset, particularly in North County, with only a dusting in South County, a dusting to 1″ in central Berkshire with 1-2″ possible in North County. The higher elevations in North County may see as much as 2-3″. The sleet will then change fairly rapidly to rain and freezing rain, by 9 or 10 pm in South County and 11 pm or midnight in North County. There should only be a coating of sleet on top of whatever snow falls.

Beyond this changeover the forecast gets tricky. As the precipitation changes to liquid form, temperatures will be at or just above freezing in the lower elevations but near 30 over the elevated terrain. Temperatures will rise very gradually after midnight so, even if the rain freezes initially in the lower elevations, there should not be much ice accumulation there as temperatures that are not over 32 at the outset will rise above this level shortly after rain starts falling. Over the elevated terrain, freezing rain may persist all night, with temperatures not rising above freezing until the steady rain ends about 4 am. Therefore, in the elevated terrain of central to northern Berkshire as much as 0.25″ of ice could accumulate on some surfaces. Hopefully, this will not be enough to create any power outages. In any case, travel may be treacherous everywhere this evening for a time, with the risk greater and for a longer period in North County. After midnight conditions should improve in the lower elevations but may remain slipper over the elevated terrain for a time.

Steady rain and freezing rain should end by 4 am with only spotty drizzle or freezing drizzle persisting through the morning hours. Any freezing drizzle over the elevated terrain should change to plain drizzle by daybreak or shortly thereafter as temperatures rise above freezing. We will be in the warm sector for a good part of the day but cold air is likely to be trapped near the ground so temperatures will likely have trouble rising out of the 30s in most locations. The approaching cold front will generate a band of steady rain that will move through from mid afternoon until evening. The rain may mix with a little wet snow for a brief period before it ends early Friday evening.

Once this mess clears Friday evening, it looks like we are in for a fairly nice weekend as surface high pressure builds in to give us mostly sunny skies and mild temperatures on Saturday, although it will be breezy. A weak, secondary cold front will rotate through Saturday night with nothing more than the chance of a few mixed snow and rain showers. Sunday should be a little cooler, but high temperatures will still be in the 30s, with partly cloudy skies.

Don’t get too used to the milder temperatures because it looks like a deep trough in the jet stream will settle over us next week and allow a cold arctic air mass for this late in the winter to drift south over us from Canada by late in the week and into the weekend.

Thursday Night

Snow developing by 7 or 8 pm, changing rapidly to sleet and then rain in South County. In central and northern Berkshire the snow and sleet will likely persist a little longer, with snow changing to sleet by 9 or 10 pm and then rain or freezing rain by 11 pm. In the lower elevations, temperatures will be near or just above freezing at the onset of the rain but then will rise gradually so if there is any freezing rain it should change to plain rain by midnight or just after. Freezing rain could persist in some spots in the elevated terrain. Likely snowfall totals a dusting in South County, a dusting to 1″ in central Berkshire and 1-2″ in North County. Ice accumulation should be minor in the lower elevations but could reach 0.10″- 0.25″ in a few locations in the elevated terrain. Any rain/freezing rain should taper to drizzle or freezing drizzle by 4 am or so. Probability of precipitation near 100%. Liquid equivalent totals 0.25-0.50″ South County to central Berkshire and 0.50-0.75″ in North County.

Low temperatures this evening in the low 30s, near 30 over the elevated terrain. Temperatures rising a few degrees after midnight, reaching the low to mid 30s by morning.

Light east-southeasterly winds this evening, increasing to 5-10 mph by morning.

Friday

Overcast with spotty light rain and drizzle until mid-afternoon. A steadier period of rain and showers developing mid-afternoon and continuing until early evening. Probability of precipitation 90%. Likely rainfall totals 0.20-0.35″.

High temperatures in the upper 30s in Pittsfield; near 40 in Lee, Stockbridge, Adams, North Adams and Williamstown; low 40s in Great Barrington and Sheffield and; mid 30s over the elevated terrain.

East-southeasterly winds at 5-10 mph, shifting to westerly late.

Friday Night

Some lingering clouds early, then becoming mostly clear.

Low temperatures in the mid 20s.

West-southwesterly winds at 5-10 mph.

Saturday

Mostly sunny, breezy and mild. Clouds may increase late in North County with just the slight chance of a rain shower there toward evening.

High temperatures in the mid 40s in Pittsfield, Lee, Stockbridge, Adams, North Adams and Williamstown; mid to upper 40s in Great Barrington and Sheffield and; low 40s over the elevated terrain.

Southwesterly winds at 10-15 mph.

Saturday Night and Sunday

Variable clouds with the chance of a rain or snow shower, mainly before midnight. Turning colder after midnight with low temperatures in the low 20s. Sunday will likely be partly cloudy and cooler, with high temperatures in the 30s.

Note: Clicking on underlined red text provides links to various weather maps.

Summary: Another disturbance, similar to today’s, will ripple along the zonally oriented jet stream and over Berkshire County tomorrow. However, an importance difference with today’s situation is that the lower levels of the atmosphere (the lowest 5000 feet or so) will be much milder tomorrow, hovering near the freezing mark. As a result, there will likely be mixed rain and snow across the county, with rain more likely in the lower elevations, particularly in South County with wet snow over the elevated terrain.

The precipitation should begin around noon and come down fairly hard for 2 or 3 hours. We should receive about 0.25″ of liquid equivalent. Any snow in the lower elevations should be limited to a slushy inch or so but the higher terrain could receive 1-3″ during a brief period of heavy snow between around noon and 3 pm. Towards evening any precipitation will turn to snow everywhere as we see some lingering light snow and snow showers well into the evening.

Travel should not be as treacherous as today in the valley locations as temperatures will be in the 30s in most locations so roads should be predominantly wet, even if it snows. However, during the period of heavy snow over the elevated terrain during early to mid afternoon, roads could become snow covered and slippery as snowfall rates may reach 1-2″/hour and temperatures will be hovering around the freezing mark.

Sunshine should make a return on Thursday and it will become much milder, reaching 40 in many locations as surface high pressure builds in briefly. A surface low pressure system will move through the western Great Lakes on Thursday night and Friday. It will push its warm front through here with some rain showers Thursday night. This will put us, briefly, in the warm sector of the cyclone on Friday. As a result, temperatures should rise into the 40s on Friday before the low’s trailing cold front moves through late in the day on Friday with another band of rain showers.

Tuesday Night

A few lingering snow flurries early this evening, then becoming partly to mostly cloudy for the remainder of the night.

Low temperatures in the mid teens.

Light west-northwesterly winds this evening, becoming light southerly after midnight.

Wednesday

Mostly cloudy and milder in the morning. A period of moderate to heavy mixed rain and wet snow is likely between about noon and 3 pm. Rain is more likely in the lower elevations, particularly in South County. Snow is more likely over the elevated terrain. Precipitaion should change to all snow late in the afternoon with intermittent light snow or snow showers continuing into the evening. Probability of precipitation 90%. Total liquid equivalent 0.25-0.30″. Any snowfall accumulations in the lower elevations should be limited to a slushy inch or less. The elevated terrain could receive 1-3″ of snow.

High temperatures in the mid 30s in Pittsfield; mid to upper 30s in Lee, Stockbridge, Adams, North Adams and Williamstown; upper 30s in Great Barrington and Sheffield and; near 30 to the low 30s over the elevated terrain.

Southeasterly winds at 5-10 mph, shifting to westerly late.

Wednesday Night

A few lingering snow showers and flurries early, then becoming partly cloudy and breezy.

Low temperatures near 20.

West-northwest winds increasing to 1o-20 mph during the evening, diminishing toward morning.

Thursday

Mostly sunny in the morning, increasing clouds during the afternoon. Mild.

High temperatures near 40 in Pittsfield; near 40 to low 40s in Lee, Stockbridge, Adams, North Adams and Williamstown; low 40s in Great Barrington and Sheffield and; mid to upper 30s over the elevated terrain.

West-northwesterly winds at 5-10 mph in the morning, becoming light southerly during the afternoon.

It appears that the heaviest band of snow will slide just to our east this afternoon. As a result, snowfall totals should be a little less than originally expected, on the order of 2-4″. In addition, the burst of snow with tomorrow’s disturbance looks to be heavier, with 1-3″ falling from late morning to mid-afternoon.

Note: Clicking on underlined red text provides links to various weather maps.

Summary: The jet stream disturbance moving our way for tomorrow is much more vigorous than it appeared it would be when I made Friday’s forecast. The disturbance is moving rapidly eastward, being propelled by a zonally oriented jet stream. This rapid motion is not permitting much development of a surface low pressure system but is generating very strong vertical motion in the atmosphere. As a result, there is a relatively narrow band of heavy snow falling in the Midwest this afternoon. This band will move rapidly eastward, arriving here by late morning on Tuesday. Even though the resulting period of snow will be relatively short, it will fall heavily at times during the afternoon. As a result, snowfall totals look to be in the 3-6″ range, with the lower end of that range most likely in the lower elevations, particularly in South County, and the higher end of that range more likely over the elevated terrain to the east. Snow will likely begin falling lightly and intermittently in the early to mid morning but then should begin falling moderately to heavy by late morning to around noon. Snow will then continue moderately to heavy, occasionally 1″/hour, through the afternoon as the disturbance moves directly over Berkshire County. Snow should diminish in intensity by 4 or 5 pm and then end by 5 or 6 pm.

Another weak disturbance will roll through Wednesday afternoon and give us another bout of light snow or snow showers. Accumulations should be light, however, on the order of a dusting to 1″ and travel will likely not be an issue with temperatures then in the 30s. We should then get a bit of a reprieve from our endless winter on Thursday and Friday as a warm front moves through Thursday and temperatures “soar” into the 40s on Thursday and Friday. A cold front will move through late on Friday with a band of rain or rain showers. It looks dry at this point over the weekend with seasonable temperatures in the 30s.

Monday Night

Increasing and thickening cloudiness this evening. Becoming overcast after midnight.

Low temperatures in the upper single digits to around 10.

Winds light and variable this evening, becoming east-southeasterly at 5-10 mph after midnight.

Tuesday

Intermittent light snow or snow flurries through mid morning. Snow, moderate to heavy, developing late morning to around noon and continuing through most of the afternoon. Snow should decrease in intensity by 4 or 5 pm and end by 5 or 6 pm. Probability of precipitation near 100%. Likely snowfall totals 3-6″ with the lesser amounts in that range most likely in the lower elevations, particularly in South County, and the greater amounts over the elevated terrain to the east.

High temperatures in the low to mid 20s in Pittsfield, Lee, Stockbridge, Adams, North Adams and Williamstown; mid 20s in Great Barrington and Sheffield and; near 20 to low 20s over the elevated terrain.

East-southeasterly winds at 5-10 mph, shifting to northwesterly late in the afternoon.

Tuesday Night

A few lingering flurries early, then becoming partly cloudy.

Low temperatures in the mid teens.

West-northwest winds at 5-10 mph, becoming light southerly by morning.

Wednesday

Mostly cloudy, breezy and milder. A period of snow showers is likely during the afternoon. Probability of precipitation 70%. Snowfall totals a dusting  to no more than 1″.

High temperatures in the mid to upper 30s in Pittsfield, Lee, Stockbridge, Adams, North Adams and Williamstown; upper 30s in Great Barrington and Sheffield and; low to mid 30s over the elevated terrain.

Southerly winds at 10-15 early, veering to southwesterly late morning and then westerly during the afternoon.

Note: Clicking on underlined red text provides links to various weather maps.

Summary: Snowfall totals reported to the National Weather Service are as follows: Stockbridge – 8.5″, Clarksburg – 9.5″, Pittsfield – 10″, Adams – 14.7″, Williamstown – 15″, Lanesborough – 16″ and Becket – 21″. Savoy reported 12.5″ but that was yesterday at 11 pm last night so I suspect they recieved closer to 18″. As expected, the heaviest band of snow overnight set up just to our west, over western Columbia and eastern Greene and Albany counties, as well as northern Ulster and Duchess counties. Snowfall totals in these regions were in the 18-27″ range. Fortunately (or I guess unfortunately if you are a snow lover) this band of heavy precipitation rotated through here fairly quickly, moving southeast to northwest, between around 11 pm and 1 am before setting up to our west. Most of that precipitation fell here as heavy sleet until the atmospheric column cooled enough to change the sleet to snow around 12:15 or so. It then snowed heavily for an hour or so before the band moved west. The snow did fall heavily at times after that, but not the persistent 1-3″/hour that they received in the strong “frontogenesis” band to our west.

As that surface low rockets away through the Canadian Maritime today another jet stream disturbance is rotating through the base of the same persistent jet stream trough. This upper-level disturbance is generating a weak surface low over Kentucky that is spreading a band of moderate snow into the Ohio Valley. As this low hits the Mid-Atlantic Coast tomorrow, it will intensify rapidly as it moves up the coast to the east of Cape Cod by tomorrow evening. By this point, it will be to far to the east to have too much of an impact on us, although eastern MA is likely to get another dumping of snow. We will see a fairly prolonged period of mostly light snow but should only get on the order of 2-4″ as the low slips by to our south from late morning through the evening tomorrow.

As this low departs, surface high pressure will build into the region in its wake for the remainder of the 3 day weekend. As a result, both Sunday and Monday should have some sunshine, with the greatest amounts on Monday. The sun is feeling pretty warm this time of year, which should help, but air temperatures will be quite cold as the northwest flow behind the departing surface low drags the cold axis of the upper-level trough directly over us. Therefore, temperatures will struggle to get out of the teens both days. In addition, the pressure gradient between the strong departing surface low and the incoming surface high pressure system will generate strong winds for Sunday so wind chills will be pretty low. The wind should die down on Monday so that will probably be the nicer of the 2 days.

The trough will begin to lift out to our northeast on Monday and the jet stream will temporarily become quite flat (zonally oriented) on Tuesday and Wednesday. As a result, a disturbance in the jet stream will have trouble producing much in the way of upward motion as it generates a weak surface low. That low will move directly over us on Tuesday with more snow but it should only be a minor event, possibly a few inches.

Once that low passes by, the jet stream will undergo a bit of a pattern shift that has been quite uncharacteristic for the past month. A trough will dig into the western U.S. and a ridge will build over the eastern U.S.. As a result, a warm front should move through here on Thursday and bring much milder weather for the end of the week and into next weekend. In fact, we could reach 50 degrees! Enjoy it while you can though since the long-range models are suggesting the jet stream may revert to its usual pattern (cold trough over the east) for the following week.

Friday Night

Partly cloudy and breezy this evening. Becoming mostly cloudy with light winds after midnight.

Low temperatures in the mid to upper teens.

Westerly winds at 10-15 mph this evening, becoming light after midnight and calm by morning.

Saturday

Overcast with snow developing mid to late morning and continuing through the afternoon. The snow should be mostly light, although there may be a few moderate bursts. Probability of precipitation 90%. Likely snowfall accumulations 1-3″ 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.

Light easterly winds in the morning, shifting to northeasterly and then northerly at 5-10 mph during the afternoon.

Saturday Night

Snow through the evening, diminishing and ending by midnight. Probability of precipitation 80%. An additional inch of snow is likely with total accumulations of 2-4″ likely. The greater accumulations are more likely in the elevated terrain with the lesser amounts more likely in the lower elevations. Clearing skies, windy and becoming much colder after midnight.

Low temperatures near 10, single digits over the elevated terrain. Wind chill temperatures as low as -10.

Northwest winds at 10-20 mph with gusts to 30-35 mph.

Sunday

Partly cloudy, windy and much colder.

High temperatures in the mid to upper teens in Pittsfield; upper teens in Lee, Stockbridge, Adams, North Adams and Williamstown; near 20 in Great Barrington and Sheffield and; low to mid teens over the elevated terrain. Wind chill temperatures in the single digits below zero at times.

West-northwest winds at 10-20 mph with gusts to 30 mph.

Sunday Night and Monday

Clear skies and very cold overnight. Mostly sunny on Monday, still cold but with lighter winds than Sunday.

Low temperatures in the single digits below zero Sunday night. High temperatures ranging from mid teens over the elevated terrain to low 20s in the lower elevations of South County.

Northwest winds at 10-15 mph Sunday evening lightening to 5-10 through Monday morning, becoming light during the afternoon.

Note: Clicking on underlined red text provides links to various weather maps.

Summary: Still don’t see much change in the forecast. Things are pretty much progressing as expected. The dry slot which has rotated into the center of the storm is now moving over Berkshire County (4:30 pm) and the last band of heavy snow is moving south to north through the county. Precipitation should pretty much shut down within the next hour. There will be intermittent spotty mixed precipitation, mostly sleet (ice pellets) through the evening hours. Between 10 pm and midnight the band of precipitation wrapping around the back of the low will begin to move into the county. Right now, this feature is represented by an area of heavy snow and rain over Virginia, Maryland and Delaware. It still looks like the heaviest of this precipitation should stay just to our west. Precipitation will become steady and increase in intensity between 10 pm and midnight. The precipitation should start as sleet and we may see 1/2″ to 1″ of ice pellets accumulate before the sleet changes to snow between midnight and 1 am. Snow will continue, varying in intensity, for the remainder of the night and begin to taper off around daybreak. Most likely additional snow accumulations for this period will be 3-6″. In contrast to today’s snow, the heaviest amounts overnight are most likely in the northwestern parts of the county. Light snow may persist for a good part of the morning as the wrap around moisture is lifted by the elevated terrain. In fact, intermittent snow showers and/or flurries may persist into the afternoon. An additional dusting to 1″ of snow may fall during the day. Most likely storm total snow accumulations will be 10-16″.

Believe it or not, we will only get a brief break from the snow. After this storm departs, another jet stream disturbance will quickly follow, rotating through the base of the same trough. As a result, a much weaker surface low pressure system will scoot off the coast to our south on Saturday. A period of light snow is likely from mid-morning to mid-afternoon. Likely accumulations will be 1-3″.

Thursday Night

Overcast and breezy. Intermittent and spotty light mixed precipitation, mostly sleet until sometime between 10 pm and midnight. Sleet will then become steady and increase in intensity before changing to snow by midnight to 1 am. Snow, varying in intensity, for the remainder of the night. Snow will begin to taper off by daybreak. Probability of precipitation near 100%. Likely sleet accumulation of 1/2″ to 1″. Likely additional snowfall 3-6″, with the greatest amounts in northern and western portions of the county.

Temperatures will remain steady for most of the night and then drop a few degrees late. Low temperatures generally in the low 20s, near 20 over the elevated terrain.

Northeasterly winds at 10-20 mph, with gusts 30-35 mph, shifting to northwesterly after midnight.

Friday

Mostly cloudy and windy with light snow likely continuing off and on through most of the morning, scattered snow showers or flurries possible into the afternoon. Partial clearing late. Probability of precipitation 60%. Additional snowfall a dusting to 1″. Most likely storm total snow accumulation 10-16″.

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.

West-northwesterly winds at 15-25 mph with gusts up to 35-40 mph.

Friday Night

Partly cloudy with diminishing winds in the evening, becoming overcast after midnight.

Low temperatures in the mid teens, low teens over the elevated terrain.

Westerly winds at 5-10 mph during the evening, becoming calm after midnight.

Saturday

Overcast with light snow likely, developing early to mid morning and continuing through mid-afternoon. Probability of precipitation 70%. Likely snowfall accumulations 1-3″.

High temperatures mid 20s in Pittsfield, Lee, Stockbridge, Adams, North Adams and Williamstown; mid to upper 20s in Great Barrington and Sheffield and; near 20 to low 20s over the elevated terrain.

Light northeasterly winds in the morning, shifting to northwesterly at 5-10 mph in the afternoon.

The storm is progressing as forecast. Snow will be heaviest between 11 am and 4 pm today (as forecast) with snowfall rates 1-3″ per hour at times. Expect 6-12″ of accumulation by evening, with heaviest totals in southern and eastern portions. By 5 pm, the snow will lighten up and change to light sleet and/or light freezing rain and drizzle. It now looks like the entire county will see this changeover. This light icy precipitation will continue off and on until 10 or 11 pm tonight. The sleet/freezing rain will then become steady and increase in intensity. We will likely get a total of 1″ or so of icy sleet from 5 pm to midnight. Around midnight the precipitation should change to all snow. Snow will then continue, varying in intensity, for the remainder of the night, ending in the early morning. It still looks like the heaviest portion of the “frontogenesis” band will be located just to our west during this “backlash” period after midnight. In those locations snowfall rates will be 1-3″ per hour. Even though the band will be focused to our west most of the time, portions of it may rotate through parts of the county (mostly north and west portions) during early and late parts of the period. Otherwise, snowfall will be light to moderate in Berkshire County during this period. I think we may get a little more than my forecast 2-4″ during the after midnight period, perhaps 3-6″. In contrast to our daytime snowfall, the highest totals during this period will likely be in the northwestern parts of the county. By the time all of the snow and ice is totaled up expect widespread 10-16″ totals.

I will post another update by 5 pm……

Note: Clicking on underlined red text provides links to various weather maps.

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.

Note: Clicking on underlined red text provides links to various weather maps.

Summary: Even though the U.S. computer models have been all over the place with Thursday’s storm (or lack there of), they are finally beginning to converge on the solution that the European Model (ECMWF) has been very consistent with for several days now. Therefore, although there are still important difference’s between the models, I am tempted to find the ECMWF solution more reliable at this point. First, let me lay out what all of the models are agreeing upon…..

A weak surface low pressure system, presently developing over the Gulf of Mexico, will drift slowly northeastward to a location along the southeast U.S. coast Wednesday evening. The low will then drift more northerly to a position right over Cape Hatteras, NC by Thursday morning. At this point, the low will still be fairly weak with a central pressure near 1000 mb. However, it will be carrying loads of moisture from the Gulf of Mexico and Gulf Stream so it will have already wreaked havoc on the Southeastern states with large amounts of wintertime precipitation that they are unaccustomed to (hopefully lessons will have been learned from the snow “storm” in Georgia a few weeks ago). In particular, the southern Appalachians will likely receive over a foot of heavy wet snow during this time.

During the period from now until Thursday morning the trough in the jet stream configuration responsible for generating this surface low will become more amplified and during the day on Thursday it will become “negatively tilted”. This configuration will create a large amount of “divergence” of the jet stream winds above the surface low that will enhance the upward motion and deepen the surface low. As a result, the storm will undergo rapid development as it moves northeastward along the Mid-Atlantic and New England coast, attaining a very low central pressure around 970 mb by the time it reaches the Gulf of Maine Friday morning.  Therefore, precipitation will become heavy, winds will strengthen, particularly along the coast, and there will likely be some coastal flooding Thursday and Thursday night in the Mid-Atlantic states and New England.

The million dollar question is…where will the heaviest precipitation fall and it what form? This is where there are important differences between models. There will be a band of heavy snowfall which will have a very sharp northwestern margin with a changeover to sleet and freezing rain to the southeast of the band. The U.S. models track the surface low off the coast, moving southeast of Cape Cod. These models also move the low relatively quickly so that precipitation will begin here near daybreak but end during the evening on Thursday.  This track would keep most of New England cold enough at all levels of the atmosphere so that snow would fall everywhere except Cape Cod. In this scenario, the band of heaviest snow, over one foot and possibly well over, would fall to the southeast of Berkshire County. In addition, the northwestern edge of the heavier snow would lie right across Berkshire County for much of the storm. If this scenario was realized, the northwest corner of the county (e.g. Williamstown) would receive about 4-6″ of snow and the elevated terrain to the southeast (e.g. Otis, Becket, Sandisfield) would receive near 12″ with amounts elsewhere in the county increasing in amount from northwest to southeast between these two locations.

The ECMWF model scenario differs somewhat. It has consistently tracked the surface low more slowly and had it hugging the coast closely, moving directly over southeast MA. In this scenario, the heaviest band would lie over southeastern parts of Berkshire County during the day Thursday with enough warm air off the ocean overriding the cold air at the surface to possibly change the precipitation to sleet there briefly sometime during the afternoon or evening before changing back to snow. This track could also enable the “dry slot” (dry air wrapping into the low) to move over Berkshire for a time. A band of “backlash” snow would then rotate through the county Thursday night, affecting northern portions of the county to a greater extent, with snow not ending until well after midnight on Thursday night.

So, enough blather, what do you think is going to happen? You’re a meteorologist, make a forecast already!

I think the most likely scenario at this point is that snow will develop across Berkshire County from south to near daybreak Thursday morning. The snow will likely be light at first but become moderate to heavy at times, particularly  in central and southern portions from mid morning through the afternoon. The snow may change to sleet briefly in the south late in the afternoon. I would expect the snow to lighten or end for a time during the evening with mostly light snow, with some heavier bands, redeveloping later in the evening. This backlash should have its greatest impacts over the elevated terrain, particularly in North County. Snow should end sometime after midnight, probably during the early morning hours. Predicting snow fall totals is almost a guess at this point but I think we are in for a substantial snowfall, with 8-12″ likely for most of the county. However, I would not be surprised to see over a foot, maybe well over a foot in the elevated terrain, if the cards all align right (wrong). I will update this forecast late tomorrow afternoon. Hopefully, the forecast will have a higher degree of certainty at that time. However, my gut tells me that we won’t have a definite answer until the snow ends with this one. One thing I do know with a fairly high degree of certainty is that there will be places in the Appalachians and along the east coast that receive more than a foot of snow from this storm.

Tuesday Night

Mostly clear and very cold.

Low temperatures in the single digits below zero. Most locations will be in the mid single digits below zero but some valleys, particularly over the elevated terrain, could fall to -10° F.

Northwest winds at 5-10 mph this evening, becoming light after midnight.

Wednesday

Sunny skies, except for a thin veil of high clouds at times during the afternoon. Still cold, but not quite as cold as the past few days. In particular, it will feel milder since winds will be light and the sun is fairly strong in mid-February.

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.

Winds light and variable.

Wednesday Night

Increasing clouds with snow likely developing from south to north near daybreak. Probability of precipitation 60%. 1″ or less accumulation by 8 am.

Low temperatures in the low to mid teens during the evening, rising to near 20 by daybreak.

Southeast winds at 5-10 mph, shifting to northeast after midnight and increasing to 10-15 mph by morning.

Thursday and Thursday Night

Snow and becoming windy. Snow will likely be moderate to heavy at times from mid-morning into the evening. There may be a brief changeover to sleet in southern portions late afternoon or early evening. Likely snowfall totals by evening 6-10″. Snow will lighten or end for a time during the evening. Light snow with a few moderate bursts will likely re-develop later in the evening ending after midnight. Most likely total snowfall accumulations 8-12″ although greater amounts are possible.

Daytime high temperatures low to mid 20s in most locations, upper 20s over South County and near 20 over the elevated terrain. Temperatures only falling a few degrees overnight, ranging from upper teens to low 20s by morning.

Northeast winds at 10-15 mph during the morning, shifting to northerly and increasing to 15-25 mph during the afternoon, shifting to northwesterly at 15-25 mph during the evening and decreasing to 10-15 mph after midnight.