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

Summary: It looks like we may get our first significant precipitation since October 7 tomorrow night into Friday morning as a surface low pressure system presently developing over the Great Plains deepens rapidly, moves through the Great Lakes, and drags its trailing strong cold front through Berkshire County. As the storm moves northeast on Thursday, it will first drag its attendant warm front through our region during the afternoon. Most of the forcing with this front will be to our north and west but we will still likely get some scattered rain showers during the afternoon as the front passes. This frontal passage will open the door to subtropical air in the “warm sector” of the cyclone. Temperatures will rise into the upper 50s during the afternoon and then continue to rise slowly overnight, reaching the low 60s by morning. Even more notable may be the “mugginess” of the air as dewpoints soar to close to 60. After the warm front passes we will have scattered showers during the evening until the cold front approaches with a band of heavier rain and showers after midnight and into Friday morning. Temperatures will continue to soar on Friday, well into the 60s, before the cold front passes around mid-day or early afternoon. After the front passes, skies should begin to clear and temperatures will drop as the afternoon progresses.

The surface cyclone (low pressure system) will deepen rapidly as it moves over the Great Lakes as a double jet streak pattern develops above it at the tropopause. This will result in marked divergence aloft, with a rapid drop in pressure at the surface, as air is “sucked out” of the atmospheric column by the jet stream. The practical relevance of this for us is that, as central pressures fall to 970 mb, the pressure gradient between the low and a departing high pressure system off the coast will generate very strong southerly winds across the county. Winds will likely reach 15-25 mph on average (strongest over the high terrain) with gusts to 40 mph possible Thursday night.

It still looks like a gradual cooling trend over the weekend as the cold front passes. It should still be in the 50s on Saturday but the coldest air will arrive on Sunday on blustery northwest winds. Temperatures will struggle into the low 40s for highs on Sunday. It should be mostly dry over the weekend aside from a few scattered light lake-effect and instability showers Saturday afternoon.

Wednesday Night

Mostly clear this evening. Clouds will increase after midnight and it will likely be mostly cloudy by daybreak.

Low temperatures in the mid to upper 30s.

Light and variable winds becoming light southerly after midnight.

Thursday

Mostly cloudy in the morning. Becoming overcast during the afternoon with scattered rain showers likely developing. Becoming breezy and mild. Probability of precipitation 60%. Any showers will be generally light, with rainfall totals generally 0.10″ or less.

High temperatures in the upper 50s in Pittsfield, North Adams, Adams and Williamstown; near 60 to low 60s in Lee, Stockbridge, Great Barrington and Sheffield and; mid 50s over the elevated terrain and hilltowns.

Southerly wind increasing to 10-15 mph during the afternoon with some higher gusts, particularly over the elevated terrain.

Thursday Night

Scattered showers likely during the evening. Rain will become steadier and heavier after midnight. It will become quite windy and unseasonably mild. Probability of precipitation near 100%. Rainfall totals near 0.50″ to as much as 0.75″ in spots.

Temperatures will actually rise a few degrees overnight, reaching near 60 over the elevated terrain and the low 60s in most lower elevation locations.

South-southwest winds at 10-15 mph in the evening, increasing to 20-25 mph after midnight. Gusts to 40 mph are possible.

Friday

Rain and showers will taper off over the course of the morning and end by midday. Skies will clear during the afternoon. It will be windy and unseasonably warm in the morning into early afternoon with temperatures dropping during the afternoon after the cold front passes. Probability of precipitation 80%. Most likely rainfall totals between 0.10″ and 0.25″.

High temperatures will be reached around midday to early afternoon and should be in the mid 60s in Pittsfield, North Adams, Adams and Williamstown; mid to upper 60s in Lee and Stockbridge; upper 60s in Great Barrington and Sheffield and; low to mid 60s over the elevated terrain and hilltowns.

It will be windy but winds will tend to diminish somewhat as the day progresses. South-southwesterly winds at 15-25 mph in the morning will shift to southwesterly at 10-20 mph in the afternoon and then westerly at 10-15 mph late. Gusts to 35 mph are possible, particularly during the morning.

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

Summary: A cold front is moving through Berkshire County this afternoon. As skies clear and winds become light, temperatures will plummet overnight. Most places will see temperatures fall into the lower 20s and any place that has yet to experience a killing freeze should tonight. (Addendum: the latest data suggests we may have more cloud cover than expected, with temperatures only falling into the mid 20s).

Tomorrow should be a fairly nice fall day as surface high pressure builds over the region behind the cold front. As today’s cold front moves back to the north as a warm front, skies will cloud up for Tuesday night and Wednesday. We are even likely to see some light mixed precipitation on Wednesday morning. Right now it appears that this will be mostly in the form of rain but it could start as a period of light snow, particularly in the higher elevations. It should be much milder on Thursday after the warm front passes.

Meanwhile, an early season snowstorm in the northern Rockies today will gradually drift into the Great Plains and then northeastward, passing north of the Great Lakes on Thursday and Friday. As this surface low pressure system passes to our north, it will drag its warm front through on Thursday afternoon. This warm front will bring even warmer air into our region Thursday night and Friday as the southern branch of the jet stream passes to our north and subtropical air floods in. There is the chance for some rain showers with the warm frontal passage but rain, possibly heavy, is much more likely as the low drags its strong cold front through during the day on Friday. This will lead to a much cooler weekend, probably windy on Sunday, as the jet stream again dips to our south.

Monday Night

Mostly clear with light winds. Becoming quite cold across the county by morning. Cloud cover will increase somewhat toward morning, particularly over South County, which may keep temperatures up a bit.

Low temperatures in the mid 20s in most locations, temperatures could reach the low 20s in a few wind protected spots over the higher terrain. Low temperatures may only fall to the upper 20s over portions of South County due to some cloud cover.

Light north-northeasterly winds.

Tuesday

Partly cloudy in South County during the morning, otherwise mostly sunny and seasonably cool. There will likely be an increase in clouds late in the day.

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

Northwesterly winds at 5-10 mph.

Tuesday Night

Mostly cloudy. There is the chance of a rain shower, possibly a snow shower over the elevated terrain, toward daybreak. Probability of precipitation 30%.

Low temperatures generally in the upper 20s with temperatures rising into the low 30s by daybreak.

Winds light and variable, becoming light south-southwesterly toward morning.

Wednesday

Mostly cloudy with a good chance for showers in the morning. Any precipitation should be predominantly rain, although there could be a period of wet snow over the elevated terrain. Probability of precipitation 50%. Precipitation should be light, with 0.10″ or less liquid and no more than a light dusting of snow. Skies should begin to clear during the afternoon.

It will be a bit milder than Tuesday with high temperatures near 50 in Pittsfield, North Adams, Adams and Williamstown; low 50s in Lee, Stockbridge, Great Barrington and Sheffield and; mid 40s over the elevated terrain and hilltowns.

West-northwesterly winds at 5-10 mph.

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

Summary: The cold winds should finally begin to die down tonight as the deep trough in the jet stream begins to flatten out and surface high pressure builds more into the region. However, we may still avoid a hard freeze since winds will not go completely calm since the center of the high will be located well to our south over the Middle Atlantic states. Interestingly, because of this, the Ohio Valley, including places such as Tennessee, of all places, where the average high temperature for this date is still 70 degrees, will likely get their first hard freeze before us.

It appears that the previously mentioned Alberta Clipper will track a little farther north than expected and will likely only impact us with some cloudiness over the weekend. Temperatures will remain slightly below normal, averaging in the upper portion of the 40s during the day both Saturday and Sunday.

A deep trough in the jet stream will dive south over the northern Rocky Mountains early next week, giving them a pretty good early season snowstorm on Monday and Tuesday. This trough, and its associated surface low pressure system, will likely get cut-off for a time over the Great Plains. As a result, surface high pressure will build over us from Monday into Wednesday, keeping us dry with seasonable temperatures. The low will likely eventually get picked up by the jet stream and brought our way. The timing is a little uncertain, as it usually is once these storms get “cut-off”, but it looks like it will be late in the week before we see any effects from this storm.

Friday Night

Partly cloudy and cold. A freeze is possible in some locations, particularly in wind protected areas over the elevated terrain.

Low temperatures in the upper 20s in most locations, mid to upper 20s over the elevated terrain.

Light west-northwesterly winds this evening, shifting to southwesterly after midnight.

Saturday

Skies should be fairly clear early but then will become partly sunny to mostly cloudy for the remainder of the day. It will become quite breezy as the day progresses.

High temperatures in the mid to upper 40s in Pittsfield, North Adams, Adams and Williamstown; upper 40s to near 50 in Lee, Stockbridge, Great Barrington and Sheffield and; low to mid 40s over the elevated terrain and hilltowns, depending on elevation.

South-southwesterly winds increasing to 10-15 mph in the valleys, 15-20 mph over the elevated terrain. Gusts to 25-30 mph.

Saturday Night

Mostly cloudy in the evening, decreasing clouds after midnight. It will still be somewhat breezy in the evening.

Low temperatures generally in the low 30s.

South-southwesterly winds at 10-15 mph in the evening, shifting to westerly after midnight and diminishing somewhat toward morning.

Sunday

Mostly sunny to partly cloudy skies in the morning. The afternoon will be cloudier, averaging out partly sunny. It will be a bit breezy and cool.

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

West-northwesterly winds at 10-15 mph.

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

Summary: As the developing coastal low moves out to sea, the cold trough in the jet stream wave pattern will settle over the region for the next several days. As the low departs and intensifies, surface high pressure will begin to build in from the west. Wow, that sounds great, high pressure=nice, sunny weather, right?! Not always. In this case, the pressure gradient between the low and high will generate brisk winds. Also, the winds will be west-northwesterly which will be carrying moisture/cloudiness generated over the Great Lakes as cold air moves over the still warm lake water. As a result, it will be fairly cloudy and cold with a brisk west-northwesterly breeze for the next several days. However, it won’t be completely overcast and we will see some sun at times.

The cold air moving over the warm lakes will generate some lake-effect snow streamers. One of these streamers may breifly reach us and pass over Berkshire County Thursday evening but we should only have a chance of a snow shower or flurry at that time.

An Alberta clipper (our first of the season) will ride just to our north Saturday night. However, enough warm air will have moved in ahead of the low that we should only see rain showers (not snow).

Wednesday Night

Mostly cloudy with the chance of a light snow shower or flurry this evening. Partial clearing after midnight, becoming partly cloudy by morning. Probability of precipitation 30% this evening.

Low temperatures in the low 30s in most locations, near 30 over the elevated terrain.

West-northwesterly wind at 5-10 mph, 10-15 mph over the higher terrain.

Thursday

More sun than clouds during the morning and early afternoon. Becoming mostly cloudy during the mid and late afternoon. Breezy and cool.

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

Westerly winds at 10-15 mph in the valleys, 15-20 mph over the elevated terrain. Gusts to 25-30 mph.

Thursday Night

Mostly cloudy. There is the chance of a snow shower or flurry during the evening. Probability of precipitation 30%.

Low temperatures near 30 in most locations, upper 20s over the elevated terrain.

Westerly winds at 10-15 mph in the evening, diminishing to 5-10 mph after midnight.

Friday

A mix of sun and clouds, breezy and unseasonably cool.

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

West-northwesterly winds at 10-15 mph with some higher gusts.

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

Summary: It appears that the developing coastal low tomorrow will be to far off the coast to impact Berkshire County. As a result, I have changed Wednesday’s forecast to reflect this, with the removal of precipitation from the forecast as well as slightly higher temperatures due to the lack of precipitation and less in the way of overcast skies. Otherwise, the forecast is unchanged, with colder air moving in for mid to late week.

Tuesday Night

Partly cloudy and much colder. Clouds increasing toward daybreak.

Low temperatures near 30 in most locations, low 30s in South County and upper 20s over the elevated terrain.

Light west-northwesterly winds becoming calm toward morning.

Wednesday

Mostly cloudy and cool. There is just a slight chance of a sprinkle or a flurry late in the afternoon.

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

Light northwesterly winds.

Wednesday Night

Decreasing clouds during in the evening, partly cloudy after midnight.

Continued cold, with low temperatures near 30 in most locations, upper 20s over the elevated terrain. A freeze is possible in some locations but may be prevented by increasing winds after midnight.

Light northwesterly winds in the evening, becoming westerly at 5-10 mph after midnight, 10-15 mph over the elevated terrain.

Thursday

Partly cloudy in the morning. Becoming mostly cloudy in the afternoon. There is a slight chance of a sprinkle or flurry, particularly over the elevated terrain to the north. Breezy and unseasonably cool.

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

Westerly winds at 10-20 mph with some higher gusts.

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

Summary: A strong cold front, signaling the leading edge of a cold trough in the jet stream wave pattern, will pass through during the day tomorrow. The air in advance of the front is quite dry so that there will only be some scattered light rain showers as the front passes through the region. However, once the front passes, the jet stream will dip to our south, and cold air that has been building over central Canada for the past week will move in. As a result, even though the air will be modified by streaming over warmer land and Great Lakes water, temperatures will be significantly below normal, for the first time this autumn, through the end of the week.

A somewhat interesting scenario may develop on Wednesday after the front passes to our south. A disturbance in the jet stream, rotating through the base of the trough will generate a surface low pressure system along the front off the coast to our south. The global U.S. (GFS) and European (ECMWF) models have the low developing far enough off the coast so that the significant precipitation stays to the south and east of Berkshire County. However, the higher resolution U.S. (NAM) model develops the low close enough to the coast to give us significant precipitation. The way that the atmosphere is set up for this event, if we get precipitation, believe it or not, it would be an elevation type snowfall event, with mixed rain and wet snow in the valley locations with all wet snow in the elevated terrain. However, in my experience, these types of storms usually develop too far off the coast to impact us. Therefore, at this point, I find the GFS and ECMWF scenarios more realistic and I suspect we will get nothing more than light amounts of wet snow at most on Wednesday (sorry snow lovers). I will update this tomorrow afternoon.

One thing that is fairly certain is that we will have much colder weather than we have become used to with high temperatures in the 40s at best and lows in the 20s Wednesday through Friday. There may be a bit of moderation over the weekend as the jet stream wave pattern becomes less amplified and the coldest air shifts to our north and east.

Monday Night

Mostly clear this evening, then increasing clouds after midnight.

Low temperatures generally in the low 40s, near 40 over the elevated terrain.

South-southwesterly winds at 5-10 mph.

Tuesday

Mostly cloudy with the chance of a few scattered, light showers through mid-afternoon. The best chance for a shower is during the early afternoon. Skies will clear during the mid to late afternoon hours. Probability of precipitation 40%. Any rainfall should be 0.05″ or less.

High temperatures in the low to mid 50s in Pittsfield, North Adams, Adams and Williamstown; mid 50s in Lee, Stockbridge, Great Barrington and Sheffield and; upper 40s to near 50 over the elevated terrain and hilltowns, depending on elevation.

Southwesterly winds at 10-15 mph, shifting to northwesterly mid-afternoon.

Tuesday Night

Partly cloudy and much colder. Clouds increasing toward daybreak.

Low temperatures in the low 30s in most locations, low to mid 30s in South County and near 30 over the elevated terrain.

Light northerly winds shifting to northeasterly toward morning.

Wednesday

Overcast and unseasonably chilly. There is a good chance of a little light mixed rain and wet snow over the valley locations, possibly just rain in the lower elevations of South County, with all wet snow in the elevated terrain and hilltowns. Probability of precipitation 50% in central Berkshire, 40% in North County and 60% in South County. Any snow that falls will likely be no more than a coating in the valley locations and less than an inch over the elevated terrain. Liquid equivalent precipitation 0.10″ or less.

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

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

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

Summary: We should have a relatively tranquil weekend as we continue our gradual transition from recent mild weather to a much cooler regime. The transition should really take hold following the passage of a final strong cold front on Tuesday at the leading edge of the trough in the jet stream containing the coldest air from Canada. This “arctic” air will be modified markedly as it passes over the still warm land and water of the Great Lakes region. However, it still looks as if low temperatures will fall into the 20s with high temperatures in the 40s late next week. In fact, we may even see (dare I say it) some snowflakes in the air Thursday or Friday. The long range models are suggesting that this cold regime, with a deep trough over the eastern U.S. and pronounced ridge over the western U.S. will continue at least through next weekend.

This weekend we will have mixed sun and clouds both days with fairly seasonable temperatures, although a little cooler Sunday than Saturday. There is the chance for a few scattered light showers Saturday night with the passage of another weak cold front. Otherwise we should remain dry.

Friday Night

Mostly clear and much cooler than previous nights.

Low temperatures generally in the upper 30s, mid 30s over the elevated terrain.

Westerly winds at 5-10 mph in the evening becoming light southwesterly after midnight.

Saturday

Except for some passing thin high clouds, it will be mostly sunny in the morning into early afternoon. Clouds will be on the increase during the mid to late afternoon.

High temperatures in the low 60s in Pittsfield, North Adams, Adams and Williamstown; low to mid 60s in Lee, Stockbridge, Great Barrington and Sheffield and; upper 50s to near 60 over the elevated terrain and hilltowns, depending on elevation.

Light southerly winds in the morning, increasing to 10-15 mph in the afternoon.

Saturday Night

Mostly cloudy with the chance of a shower in the evening. Showers should be light and widely scattered for the most part. Probability of precipitation 40%. Likely rainfall totals 0.05″ or less. Any showers should end by 2 or 3 am, followed by clearing skies.

Low temperatures near 40.

South-southeasterly winds at 5-10 mph in the evening, shifting to westerly after midnight.

Sunday

Mostly sunny in the morning. There will be more cloudiness during the afternoon, with skies becoming partly sunny. Breezy and cooler.

High temperatures in the mid 50s in Pittsfield, North Adams, Adams and Williamstown; mid to upper 50s in Lee, Stockbridge, Great Barrington and Sheffield and; upper 40s to low 50s over the elevated terrain and hilltowns, depending on elevation.

Westerly winds 10-15 mph with gusts to 25 mph.

Summary: Yesterday’s forecast still holds, for the most part, with one significant change. It appears that the strongest upper-level forcing (divergence in the jet stream wind field), and thus the greatest upward motion in the atmosphere (vertical velocity) will be focused to our north tonight. As a result, the heaviest rain will also fall to our north. Instead of 0.50″ of rain it now looks more like 0.10 to 0.25″. It is still looking like a fairly nice fall weekend with good amounts of sunshine both days, although a bit cooler on Sunday.

Thursday Night

Clouding up quickly this evening. Periods of rain developing between 10pm and midnight and ending by 3 or 4 am. Probability of precipitation 90%. Most likely rainfall totals between 0.10″ and 0.25″.

Low temperatures in the low 50s, a few degrees cooler over the elevated terrain.

South-southeasterly winds at 5-10 mph early this evening, increasing to 10-15 mph by late evening and then shifting to northwesterly after midnight.

Friday

Partly cloudy, breezy and cooler.

Temperatures will not rise a great deal over the course of the day with high temperatures near 60 in Pittsfield, North Adams, Adams and Williamstown; low 60s in Lee, Stockbridge, Great Barrington and Sheffield and; mid to upper 50s over the elevated terrain and hilltowns, depending on elevation.

West-northwesterly winds at 10-15 mph, 15-20 mph over the elevated terrain with gusts to between 25-30 mph. Winds will diminish late in the afternoon.

Friday Night

Mostly clear and much cooler than previous nights.

Low temperatures generally in the upper 30s, mid 30s over the elevated terrain.

Westerly winds at 5-10 mph in the evening becoming light southwesterly after midnight.

Saturday

Partly cloudy. Clouds may increase late.

High temperatures in the low 60s in Pittsfield, North Adams, Adams and Williamstown; low to mid 60s in Lee, Stockbridge, Great Barrington and Sheffield and; upper 50s to near 60 over the elevated terrain and hilltowns, depending on elevation.

South-southwesterly winds at 5-15 mph.

Saturday Night

Mostly cloudy with the chance of a shower. Probability of precipitation 40%. Low temperatures in the upper 30s.

Sunday

Partly cloudy and cooler. High temperatures in the low to mid 50s, upper 40s to near 50 over the elevated terrain.

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

Summary: The change in the jet stream wave pattern discussed yesterday appears to be taking hold and it looks like, after one more mild day temperatures will become more seasonable on Friday and Saturday, then slightly below normal from Sunday through Tuesday and then quite cool mid to late week next week. The drop in temperatures will occur in steps as a series of cold fronts move through the region, each one generated by disturbances rotating through the base of the trough. As each subsequent disturbance rotates through, it will drive the cold trough further to the south and east, moving us closer to the core of the cold Canadian air.

The threat for showers tonight has decreased since yesterdays forecast with only the chance of a few scattered light showers or sprinkles overnight as the southern branch of the jet stream begins to settle south and east, pushing a weakening cool front over us. The cool front will weaken and stall over us on Thursday, providing fairly cloudy but dry conditions. A fairly vigorous disturbance in the jet stream will generate surface low pressure which will move along the cool front and directly over the region Thursday night. A several hour period of rain, moderate at times, will accompany the passage of this low pressure system, beginning mid to late evening and continuing into the early morning hours. Skies should clear for Friday, with a fresh northwest breeze making it feel a bit more like mid October, although temperatures will remain slightly above normal.

Over the weekend, the jet stream wave pattern will further its amplification. As the cold trough dives south, the northern and southern branches of the jet stream will begin to merge to our north and west.  Saturday will be a transitional day, with partly cloudy skies and seasonable temperatures as weak surface high pressure develops in advance of the trough. A disturbance in the jet stream along the southeastern edge of the trough will develop as the two branches merge. This will generate surface low pressure in southern Quebec. As the low moves north and east it will drag its trailing cold front over us Saturday night. There is only a chance of scattered showers with this cold front passage but significantly cooler air will filter in behind the front and temperatures on Sunday may have trouble making it past the low 50s.

Wednesday Night

Mostly cloudy. There is a good chance of a few scattered light showers or sprinkles. Probability of precipitation 50%. Rainfall totals will likely be .05″ or less.

It will be fairly mild, with low temperatures in the low 50s.

Light southerly winds shifting to southwesterly after midnight.

Thursday

Partly sunny and mild.

High temperatures in the mid to upper 60s in Pittsfield, North Adams, Adams and Williamstown; upper 60s in Lee and Stockbridge; near 70 in Great Barrington and Sheffield and; low to mid 60s over the elevated terrain and hilltowns.

Westerly winds at 5-10 mph.

Thursday Night

Rain, moderate at times, developing in the mid to late evening and ending in the early morning hours. Probability of precipitation 90%. Most likely rainfall totals around 0.50″.

Low temperatures generally near 50, mid to upper 40s over the elevated terrain.

South winds at 5-10 mph in the evening, increasing to 10-15 mph and shifting to west-northwesterly in the early morning hours.

Friday

Partly cloudy, breezy and a bit cooler.

High temperatures in the low 60s in Pittsfield, North Adams, Adams and Williamstown; low to mid 60s in Lee, Stockbridge, Great Barrington and Sheffield and; mid to upper 50s over the elevated terrain and hilltowns, depending on elevation.

West-northwesterly winds at 10-15 mph in the lower elevations, 15-20 mph over the elevated terrain, with gusts 25-30 mph at times, particularly over the elevated terrain.

Saturday and Sunday

Partly cloudy skies both days. There is a chance of a shower with the passage of a cold front overnight Saturday. It will be considerably cooler on Sunday than Saturday with high temperatures averaging in the low 60s on Saturday and low 50s on Sunday.

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

Summary: We have been basking in unusually mild and dry autumn weather for the past several days as the jet stream remains weak and located to our north. Presently the jet stream is “split” with a northern branch located over central Canada and a southern branch over the Great Plains and Midwest. We are under the influence of an unseasonably mild air mass, which is actually part of the semi-permanent subtropical high pressure belt (Bermuda High) to the south of both these branches. However, the mid to long range computer models are suggesting the jet stream wave pattern is about to undergo a fairly pronounced change, which could ultimately result in a change to more seasonable temperatures Friday through Sunday, transitioning to below normal temperatures for early next week. In fact, if the models are to be believed this far in advance, we may have below normal temperatures mid to late next week with high temperatures only in the 40s.

The scenario looks like this…..relatively cold air is beginning to build over north-central Canada. As the jet stream wave pattern amplifies and the two branches merge over the next several days a ridge will build over western North America and a deep trough will begin to dig south over central and eastern Canada and eventually the Midwest and Northeast U.S. This will permit the cold Canadian air to plunge southward.

As this jet stream pattern transitions, we will be impacted by a few periods of rain and showers over the next few days as the two branches pass southeastward and merge over our region. More specifically, the southern branch of the jet stream will push a cool front through the region Wednesday night into Thursday morning, accompanied by a a few showers . It will then stall over the region, allowing a disturbance in the jet stream to generate a weak low pressure system that will likely move through with more substantial rain on Thursday night. Weak high pressure should then build in over the weekend as the two jet stream branches finally merge and the jet stream “stretches out” and settles over the eastern U.S., resulting in a dry weekend with seasonably cool temperatures.

Tuesday Night

Mostly cloudy this evening, then clearing skies overnight. Becoming mostly cloudy again toward morning.

Low temperatures in the mid 40s.

Calm winds.

Wednesday

It will be variably cloudy but there will be considerably more clouds than sun in most locations.

It will be unseasonably mild, with high temperatures in the mid to upper 60s in Pittsfield, North Adams, Adams and Williamstown; upper 60s to near 70 in Lee, Stockbridge, Great Barrington and Sheffield and; low to mid 60s over the elevated terrain and hilltowns.

Southeasterly winds at 5-10 mph in the morning, shifting to southerly and increasing to 8-12 mph in the afternoon.

Wednesday Night

Mostly cloudy and mild. Scattered showers are likely after midnight. Probability of precipitation 60%. Rainfall totals 0.10″ or less.

Low temperatures in the mid 50s, low 50s over the elevated terrain.

Southerly winds at 5-10 mph, shifting to westerly near daybreak.

Thursday

Chance of a few lingering light showers early. Remaining mostly cloudy through mid to late morning, then becoming partly cloudy.

Remaining mild, with high temperatures in the mid 60s in Pittsfield, North Adams, Adams and Williamstown; mid to upper 60s in Lee, Stockbridge, Great Barrington and Sheffield and; near 60 to low 60s over the elevated terrain and hilltowns.

West-northwesterly winds at 5-10 mph.

Thursday Night

Increasing cloudiness in the evening. A period of rain, moderate at times, likely developing after midnight. Probability of precipitation 70%. Rainfall totals between 0.25″ and 0.50″. Low temperatures in the mid 40s.

Friday

Mostly cloudy early, then decreasing clouds. Partly cloudy during the afternoon. Slightly cooler, although still pleasant, with high temperatures averaging near 60 to the low 60s.