Note: Clicking on underlined red text provides links to various weather maps. I will be unavailable to update this forecast until Sunday afternoon.

Summary: A broad and deep trough in the polar front jet stream is now overlying a substantial portion of the central and western U.S.. This has permitted a very cold arctic air mass for this time of year to sink south over the Great Plains and upper Midwest. This type of air mass this early in the season has been unusual in recent years (global warming?). High temperatures in portions of the upper Great Plains are below zero and even in the teens below zero today. The cold air has spilled west all the way to the west coast where there were freezes in the central valley of California this morning and afternoon temperatures are having trouble reaching 50 degrees, even along the coast in San Francisco.

The cold front at the leading edge of this trough will sink slowly southward through our region over the next 24-36 hours as the trough inches south and east. Two disturbances, along with their accompanying batches of precipitation, will ride along this front as it moves through. As a result, we will have rain tonight into tomorrow morning. There will then be somewhat of a pause in the precipitation later tomorrow morning into the afternoon. The second disturbance will then move through later Friday afternoon through a good part of Friday night. By this point, colder air behind the front will be moving in and there will be a transition from rain in the mid-afternoon to freezing rain and sleet late afternoon into the evening. Roads may become slippery for the afternoon/evening commute. Sleet should change to snow over the course of the evening. It is difficult to pinpoint the changeover time. Some models suggest the vertical temperature profile will be consistent with snow as early as 6 or 7pm with others suggesting a changeover by 8 to 10 pm. The snow should then continue for several hours and then begin to taper off after midnight. Snowfall accumulations are highly dependent on the changeover time but it appears that 3 or 4 inches is a pretty good bet with as much as 6 inches over the elevated terrain if the changeover occurs early in the evening.

Skies should begin to clear on Saturday afternoon as we have a colder, somewhat blustery day as surface high pressure builds in. The coldest of the arctic airmass should remain well to our west, for the time being, as temperatures reach the low 30s on Saturday and near 30 in most areas on Sunday. The cold front will remain stalled well to our south over the weekend as high pressure builds in. However, another surface low pressure system will develop along the front and begin to push the front back towards us a warm front. The front will move through on Monday as the center of the surface low moves by to our west and dissipates as a secondary low forms along the coast and moves out to sea. Right now it looks like 2-4″ of snow after midnight on Sunday into mid morning Monday with a changeover to sleet and freezing rain mid-morning on Monday with just some leftover light rain and drizzle in the afternoon. I will update this portion of the forecast on Sunday afternoon.

As this “last” storm pulls away, the deep trough will shift east, allowing the arctic air mass to our west (which will be reinforced with more arctic air from Canada) to finally move over our region by mid-week. It is possible that high temperatures will barely reach the teens by Wednesday or Thursday. (OUCH!)

Thursday Night

Occasional rain. Rain will likely be heaviest and steadiest after midnight. Probability of precipitation near 100%. Rainfall totals near 0.25″.

Steady temperatures near 50 before midnight, falling rapidly after midnight. Low temperatures in the upper 30s by morning, mid 30s over the elevated terrain.

Southwesterly winds at 5-10 mph, shifting to northwesterly after midnight.

Friday

Rain likely early in the morning with a bit of a break from late morning through mid-afternoon and then picking up again late afternoon. The rain may change to sleet and freezing rain late. Probability of precipitation 90%. Rainfall totals near 0.25″.

Temperatures will hold steady in the upper 30s, mid 30s over the elevated terrain for most of the day and then fall toward or to freezing by nightfall.

Northwesterly winds at 8-12 mph.

Friday Night

Freezing rain and sleet changing to snow during the evening. The changeover will likely occur earlier in northern parts of the county but there should be snow everywhere by 9 or 10 pm. There could be some icing, 0.10″ or so before the changeover, particularly in South County. Snow will begin to taper off after midnight. Snowfall totals will most likely be in the 2-4″  range with as much as 6″ over the elevated terrain in central and northern Berkshire.

Low temperatures in the mid 20s, low 20s over the elevated terrain.

Northwesterly winds at 5-10 mph.

Saturday and Saturday Night

Mostly cloudy in the morning with the chance of a lingering flurry early. Partly sunny during the afternoon with a chance of a late afternoon or evening lake-effect snow shower. Nothing more than a dusting. It will be breezy and colder. Variably cloudy, breezy and cold overnight.

High temperatures in the low 30s in Pittsfield, Adams, NorthAdams and Williamstown, Lee and Stockbridge; low to mid 30s in Great Barrington and Sheffield and: upper 20s over the elevated terrain. Low temperatures overnight in the low to mid teens.

West-northwesterly winds at 10-15 mph with gusts to 25 mph, diminishing to 5-10 mph overnight.

Sunday

A veil of high, thin clouds may dim the sun in the morning. Increasing clouds in the afternoon. High temperatures will average around 30.

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

Summary: The forecast scenario is not significantly changed from my Sunday discussion. The weather will remain relatively quiet with only some light precipitation and seasonable to above normal temperatures through Thursday. Friday and beyond the forecast becomes more complex and of lower confidence as the jet stream/polar front settles slowly over the region. This will serve as a conduit for numerous jet stream disturbances to move directly over our region as the polar front waves back and forth over us. As a result, we will have numerous bouts of precipitation from Friday through Tuesday. Whether the precipitation will fall as rain, snow or mixed precipitation is highly uncertain and depends on the exact location of the front at any time and the track of the surface low pressure systems generated by the jet stream disturbances. Right now it looks like a period of rain late Thursday night into Friday morning followed by a possible period of snow, perhaps with an inch or two accumulation, Friday night. A more complex, and stronger, storm system will move through Sunday night into Tuesday with a mixture of precipitation types likely. The precipitation will likely begin as snow Sunday night into Monday with a transition to sleet and freezing rain or drizzle on Monday and possibly to just plain rain as the surface low likely tracks just to our west. The precipitation will likely change back to snow before ending sometime Monday night into Tuesday as the storm departs and it becomes drier but much colder mid-week next week as an arctic air mass settles over us.

Until all that mess occurs, it should be dry and relatively mild through Wednesday as weak surface high pressure located between a surface low pressure system departing off the coast to our east, and one moving through the Great Lakes, settles over us. The low moving through the Great Lakes will drag its warm front through the region Wednesday night into Thursday morning with a few light showers and sprinkles. This will open the door to unseasonably mild air for Thursday as we are briefly in the “warm sector” (between the warm front and cold front) of the Great Lakes cyclone. The departing storm will then drag its strong cold front slowly south over us Thursday night into Friday night. This will result in a period of rain late Thursday night into Friday morning. As the cold front drifts south a disturbance riding up the coast along it may clip us with a little snow Friday night.

Tuesday Night

Variable amounts of cloudiness and seasonably cold.

Low temperatures generally in the mid 20s, low 20s over the elevated terrain.

Light northwesterly winds.

Wednesday

A mix of sun and clouds.

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

Winds light and variable.

Wednesday Night

Increasing clouds in the evening, becoming overcast after midnight. A few scattered light showers and sprinkles are possible after midnight. Probability of precipitation 50%. Rainfall totals should be 0.05″ or less.

Low temperatures in the low 30s during the evening, rising slowly after midnight to near 40 by morning.

Calm winds in the evening, becoming southeast at 5-10 mph after midnight.

Thursday

Overcast but mild. Showers are likely although much of the day may be rain free except for sprinkles and spotty drizzle from time to time. Most of the showers will be light and are most likely early in the morning and later in the afternoon. Probability of precipitation 70%. Most likely rainfall totals 0.10″ or less.

High temperatures near 50 in Pittsfield, Adams, NorthAdams and Williamstown, Lee and Stockbridge; low 50s in Great Barrington and Sheffield and: mid to upper 40s over the elevated terrain.

Southeasterly winds at 5-10 mph in the morning, shifting to southerly and then southwesterly during the afternoon.

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

Summary: The jet stream wave pattern is quite flat (zonally oriented) and the meridional (north-south) temperature contrast is weak across the eastern U.S.. As a result, surface weather systems are also weak. Therefore, our weather should be quiet for the next few days. However, with the weak wind flow pattern, it may be difficult to shake our cloud cover.

A weak surface low pressure center will pass well to our south and east on Tuesday and not have any impact on our weather. As this is occurring, however, a significant change in the jet stream pattern will start to occur as a deep trough begins to dig well to the south over the western and central U.S.. This will generate a surface low pressure center over the upper Great Plains along the eastern edge of the trough (once again, the usual location). As this surface low moves through the Great Lakes on Wednesday, it will pull its warm front (extending southeast from the low) over us Wednesday night and into Thursday morning. This may cause a few light rain showers but the most noticeable impact will be that temperatures will be quite mild on Thursday as the front passes and we move, briefly, into the “warm sector” of the surface cyclone.

Late in the day on Thursday and overnight Thursday, the cold front extending south from the surface low will edge into the region and then stall as the deep trough in the jet stream extends over the entire country with its eastern edge stalled right over New England. This set up will make for a very tricky forecast as well as “tricky” weather for Friday through Saturday. The front will sink VERY slowly south and east over the course of those two days. Weak disturbances in the jet stream riding along the front will bring a few bouts of light precipitation. At first, rain or freezing rain is likely, and there could be some icing, as warmer air overrides the cold, heavy air moving south at low levels of the atmosphere. Later in the period, snow is more likely as the colder air becomes entrenched at all levels. Precipitation type and amounts are still highly uncertain and the computer models differ on how quickly the cold front will sink to the south late in the week.

Sunday Night

Mostly cloudy. Due to the cloud cover, it should remain relatively mild for early December.

Low temperatures in the low to mid 30s across the county.

Calm winds.

Monday

Partly sunny (more clouds than sun) and fairly mild.

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

Winds light and variable.

Monday Night

Mostly cloudy and relatively mild.

Low temperatures again in the low to mid 30s.

Calm winds.

Tuesday

Partly sunny (more clouds than sun) in the morning, becoming partly cloudy (more sun than clouds) in the afternoon. Still mild.

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

Light west-northwesterly winds.

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

Summary: First, I would like to apologize for the lack of forewarning of this morning’s snow. I was unable to update the forecast yesterday as I was with my Introduction to Meteorology class on a field trip during the afternoon and evening at the National Weather Service office in Albany (darn day job!). Most places in the county reported between 1″ and 1.5″.

The forecast is essentially unchanged from the one I made on Sunday. We may receive even heavier rain with 1.5″ to 2.5″ total tonight and Wednesday. The NWS has issued a flood watch for tomorrow. I think flooded roadways will probably be the main issue for Thanksgiving travelers tonight and tomorrow, except in far western and northern NY, where snowfall will be a problem. Wednesday evening and night frozen precipitation will likely make for some hazardous travel here as well as to the north and west. Snowfall totals should be relatively light, but the roads will likely become slippery in places.

The time frame for this storm still looks like this:

Light snow falling this afternoon will pick up in intensity late this afternoon and early this evening but will rapidly change to sleet and freezing rain around 6 or 7 pm. Additional snowfall totals should be an inch or less before the changeover. By 10 pm, the precipitation will have changed to plain rain in most locations as temperatures rise above freezing. There may still be a few pockets of freezing rain over the elevated terrain but it should be rain everywhere by midnight. I do not expect significant icing as where temperatures are not above freezing in the evening, they will be very close to freezing so there will likely be a little slush on the secondary roads but the main roads should remain wet.

The rain will pick up in intensity and will become quite heavy toward morning. Expect between 1.0″ and 1.5″ by daybreak. Temperatures will rise overnight, reaching the 40s by morning. It will also become quite breezy.

It will continue to rain heavily during the morning and then begin to taper off over the course of the afternoon. Another 0.50″ to 1.00″ of total rainfall is likely during the day Wednesday. It will be quite mild during the morning, with temperatures peaking near 50 degrees. Temperatures will begin to fall through the 40s and into the 30s during the afternoon as the surface low center passes directly over Berkshire County and the wind shifts to the northwest.

During Wednesday evening there will be a change back to frozen precipitation, first freezing rain and sleet and then, eventually snow, as the precipitation winds down with the storms departure. This period of precipitation will be relatively brief but the roads will likely become slippery in places as the wet roadways begin to freeze and the snow may come down fairly heavily. Expect and inch or so of snow in places during the evening, particularly over the elevated terrain. A few scattered, mostly light, snow flurries and showers will continue off and on through the evening once this burst of precipitation ends around 8 pm or so. However, after midnight the intensity of the snow may pick up as we get some “backlash” snow. Expect another 1-2″ by morning. This “backlash” sometimes occurs in Berkshire County if a strong storm moves directly over us and we get hit by a moist flow rotating around the storm as it departs. This moist, northwest flow is lifted by the hills and we can get some fairly heavy snow showers and squalls. This storm looks like a pretty good set up for this type of event and the high-resolution models are suggesting it will happen. Scattered snow showers should continue for Thanksgiving morning with some clearing in the afternoon. It will turn windy and much colder on Thanksgiving with high temperatures averaging out in the low 20s across the county.

Tuesday Night

Snow changing to sleet and freezing rain around 6 or 7 pm. Additional snowfall totals less than 1″. Sleet and freezing rain will change to all rain in most places by 9 or 10 pm although there may still be a few pockets of freezing rain over the elevated terrain. Precipitation should be plain rain everywhere by midnight. Rain, becoming heavy at times after midnight. It will become breezy and mild. Most likely rainfall totals 1.00″ to 1.50″. Probability of precipitation near 100%.

Temperatures near freezing during the evening will rise through the 30s and into the 40s by morning.

Southeasterly winds at 10-15 mph shifting to easterly and increasing to 15-25 mph after midnight with gusts over 30 mph.

Wednesday

Rain, heavy at times. Rain will begin to taper off during the afternoon. Probability of precipitation near 100%. Likely rainfall, an additional 0.50″ to 1.00″. The rain will likely change to sleet and freezing rain and then snow late in the afternoon into the evening. An inch or so of snow could fall in some places.

High temperatures near 50 in Pittsfield, Adams, NorthAdams and Williamstown; low 50s in Lee, Stockbridge, Great Barrington and Sheffield and: mid to upper 40s over the elevated terrain. High temperatures will occur in the morning and then fall through the 40s and into the 30s during the afternoon.

Easterly winds at 10-15 mph will shift to northwesterly, late morning to early afternoon, and increase to 15-20 mph with gusts 30-35 mph in the afternoon.

Wednesday Night

Any steady snow should end during the evening, by 8 pm or so, with scattered snow showers or flurries continuing off and on for the remainder of the evening. Heavier snow showers or squalls are likely from midnight on. Probability of precipitation 80%. Likely total snowfall accumulations 1-3″. Breezy and colder.

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

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

Thursday

Snow showers and flurries likely in the morning. Probability of precipitation 60%. Additional snow accumulation a dusting. Clearing skies during the afternoon. Windy and much colder.

Temperatures will not rise much with high temperatures in the low 20s in Pittsfield, Adams, NorthAdams and Williamstown; low to mid 20s in Lee, Stockbridge, Great Barrington and Sheffield and: upper teens to near 20 over the elevated terrain.

West-northwest winds at 15-25 mph with gusts between 30-40 mph.

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

Summary: As I expected (hoped?) the computer models have begun to converge around the same general scenario for the coastal storm Tuesday night and Wednesday. The deep trough in the jet stream wave pattern responsible for generating the strong surface low pressure system along the East Coast will be centered to our west. As a result, the track of the surface low up along the eastern edge of the trough will cause the low to hug the coast and then draw the low center inland over New England, probably directly over, or close to, Berkshire County. This will allow warm air to be drawn in from the warm Gulf Stream and result in the vast majority of the precipitation associated with this low to be in the form of rain. The only place that significant snow accumulations are likely is over western and northern NY state and, possibly, the northernmost mountains of Vermont. However, even in northern VT the snow will likely change to rain.

The time frame of this event for Berkshire County presently looks like this: There will likely be a brief period of snow and mixed frozen precipitation as the precipitation begins late Tuesday afternoon or evening. There will then be a relatively rapid transition to rain early Tuesday evening. I do not expect any significant snow or ice accumulations during this period. Any snowfall should total less than one inch and the roads should not become snow covered or icy as temperatures will likely be at or just above freezing. Rain will then fall, heavy at times, Tuesday night and through Wednesday morning. The heaviest rain will fall during the early morning hours before and after dawn. Rainfall totals will likely be over one inch and may be significantly greater than that. Rain will then taper off during Wednesday afternoon. Temperatures will rise well above freezing Tuesday night and into the 40s late Tuesday night and into Wednesday. As the low pulls away Wednesday night, very cold air will be pulled in behind the departing low and temperatures will drop precipitously. As a result, any wet roads could become icy overnight. It is also possible that the precipitation could end as a brief period of snow Wednesday evening and there may be some “backlash” snow showers later Wednesday night into Thursday morning. There could be an inch or so of snow during this period, particularly over the elevated terrain. It will turn very windy and cold for Thanksgiving Day.

If you are traveling Tuesday and Wednesday there should not be any significant travel issues except for possible flooded roadways with snowfall isolated to western and northern NY state and far northern VT. If you are traveling in Berkshire County or north and/or west of Berkshire County Wednesday night there could be some slick roads with a thin coating of snow and some ice as the rain ends as a period of snow during the evening and roads become icy. The only place I would expect snow accumulations greater than an inch or two Wednesday night would be over northern New England. If you are traveling to the south and east of Berkshire County you should only encounter wet, but possibly, flooded roadways. There could be some slick spots to our south and east late Wednesday night as any wet roadways freeze.

Sunday Night

Mostly clear, breezy and very cold. Winds will begin to diminish after midnight.

Low temperatures in the upper single digits to near 10, with some mid single digits over the elevated terrain. Wind chills in the single digits below zero.

West-northwest winds at 10-20 mph in the evening, with some gusts to 30 mph, decreasing to 5-15 mph after midnight.

Monday

Mostly sunny to partly cloudy and still cold, but considerably milder and less windy than Sunday. There may be an increase in high clouds late.

High temperatures near 30 in Pittsfield, North Adams, Adams and Williamstown; low 30s in Lee, Stockbridge, Great Barrington and Sheffield and; mid to upper 20s over the elevated terrain and hilltowns, depending on elevation.

West-northwesterly winds at 5-15 mph in the morning, shifting to southwesterly at 5-10 mph during the afternoon.

Monday Night

Increasing clouds during the evening, becoming mostly cloudy after midnight. There is the chance of a snow shower toward morning. Probability of precipitation 40%. Any accumulations should be nothing more than a dusting. Not nearly as cold as previous nights.

Low temperatures generally in the low 20s.

Southwest winds at 5-15 mph.

Tuesday

Mostly cloudy. There is a good chance that light snow or mixed precipitation will develop late. Probability of precipitation 50%. Snowfall accumulations 1″ or less.

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

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

Tuesday Night

Any light snow or mixed precipitation will change rapidly to rain during the early evening. Rain, becoming heavy at times after midnight. Probability of precipitation near 100%. Most likely rainfall totals 1.00″ to 1.50″. It will become milder, with temperatures will rise through the 30s and into the 40s by morning.

Wednesday

Rain, heavy at times during the morning, particularly early, tapering off late morning and during the afternoon. Probability of precipitation near 100%. Likely rainfall, an additional 0.25-0.50″. The rain may end as a period of snow late in the afternoon or evening and an inch or so of snow could fall in some places. It will be in the 40s during the morning but temperatures will begin to fall rapidly during the afternoon.

Summary: The question that everyone is asking is “Are we going to get a big snowstorm for Thanksgiving?”. The answer is….it is way too early to tell but, probably not. The long-range computer models have been consistently generating a coastal low (Noreaster) for next Tuesday night and Wednesday since this Tuesday’s model runs. Therefore, I would say with fairly high confidence that there will be a storm somewhere along the East Coast next Tuesday and Wednesday. However, the models have been very inconsistent within, as well as between, models as to the track the surface low will take. As most people who have lived in the Northeast for any length of time know, it is the track of the low that determines the amount of precipitation and, in particular, the precipitation type any area will get from one of these “wintertime” coastal storms. My gut feeling right now from looking at the different scenarios the models have been generating, is that if the surface low is far enough off the coast for it to be cold enough for Berkshire County to get snow, we will be to the northwest of the heaviest precipitation, and may not get any precipitation at all. If the storm hugs the coast, which my gut (and experience?) suggests is more likely, the atmosphere will most likely be too warm for snow here but with significant snow possible to our north and west (Albany, Catskills, Adirondacks, Vermont). However, it is Friday, so we are talking about a 4-5 day forecast which is still very fluid. I will update this forecast over the weekend. I suspect (hope?) that by Sunday or Monday the models will begin to converge and I will have a better handle on the type and amount of precipitation, as well as the exact timing of the event.

For this weekend, Saturday looks like the better of the two days. A weak surface low pressure system pushed its warm front through here this morning with a bout of mostly light rain. This afternoon we are in the storm’s “warm sector” between the warm front and the cold front trailing to the south and west of the low. Therefore, temperatures are more mild right now than we will likely see for quite some time. As is typical of autumn, the jet stream has been wavering back and forth over us for many weeks. However, as is also typical when we get into late November, the jet stream has begun to strengthen as the pool of cold air over the Arctic builds and begun shifting to the south of us as this pool of cold air expands. This transition will be highly noticeable by Sunday, which will be a day more typical of January than November. We have already had a few cold spells over the last few weeks. However, this will be different on two counts. First of all, this air mass is truly of Arctic origin and it will be brutally cold on Sunday for this time of year. Secondly, it looks like this time the jet stream may stay to our south for a prolonged period so that, even though the coldest air will only stick around for a few days (Sunday and Monday), with temperatures likely moderating back into the 30s for a time next week, I don’t see a return of above normal temperatures for awhile.

For the more immediate future, the previously mentioned weak surface low passing by to our north will drag its cold front through this evening, generating a few rain showers. The precipitation could end as a few flakes of snow, particularly over the elevated terrain. The frontal passage will usher in cooler and breezy weather for Saturday but there should also be a good amount of sunshine. A second “arctic” cold front will pass through late Saturday afternoon and evening. This will likely generate a few snow showers, but no accumulating snow. This frontal passage will usher in much colder air for Saturday night and Sunday. We will also likely be in the tail end of a lake-effect snow band for a time Saturday night and scattered snow showers and flurries may leave a coating of snow in a few places. It will be quite breezy on Sunday as well, so it will feel much colder than the (already cold) air temperatures in the upper teens to low 20s. Fortunately, wind speeds now look to be a little lower than they looked a few days ago.

Friday Night

Mostly cloudy with scattered light rain showers likely before midnight. There may be some snowflakes mixed in toward the end. Clearing skies after midnight. Probability of precipitation 60%. Rainfall totals generally 0.05″ or less. Becoming breezy and colder from late evening on.

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

Light southwesterly winds early, shifting to west-northwesterly before midnight and increasing to 10-20 mph, with gusts to 25-30 mph.

Saturday

Partly cloudy and seasonably cold. Still a bit breezy. It will turn mostly cloudy with the chance of a snow shower very late in the afternoon. Probability of precipitation 30% very late.

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

West-northwest winds at 10-15 mph.

Saturday Night

Variably cloudy with scattered snow showers and flurries. Probability of precipitation 50%. There may be a coating in a few locations, particularly over the elevated terrain. It will become increasingly breezy and much colder.

Low temperatures in the low to mid teens with wind chill temperatures near 0.

West-northwesterly winds at 10-15 mph, increasing to 15-20 mph after midnight with gusts 30-35 mph.

Sunday

Partly sunny, windy and unseasonably cold.

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

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

Sunday Night

Partly cloudy, breezy and very cold, with low temperatures upper single digits to low teens.

Monday

Partly cloudy, breezy and cold, although not as windy or cold as Sunday. High temperatures averaging in the mid to upper 20s.

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

Summary: Surface high pressure will be centered directly over New England tonight which will result in ideal radiational cooling conditions; clear, calm and dry. As a result, we will likely have the coldest night of the season thus far, with temperatures falling to between 10 and 15 degrees in most locations. High pressure will then drift to our east on Thursday and Friday. An approaching very weak low pressure system and its associated warm front will move through on Friday. As a result, there will be an increase in cloudiness on Thursday and there is the chance of some very light precipitation, predominantly on Friday morning. This should be mostly light rain and sprinkles although there could be a little mixed precipitation at the start.

A very strong cold front will plow through Friday night and it will get progressively colder and windier through the weekend. Saturday will probably not be a bad day, with a fair amount of sun, fairly light winds and temperatures in the 30s as the deep trough in the jet stream (and its core of arctic air) behind the front make their way gradually to the east. However, it will turn absolutely brutal by Sunday with daytime temperatures holding in the 20s (at best) with very strong northwesterly winds dropping wind chills into the single digits.

The long-range computer models have been generating a coastal storm for next Wednesday over the past few days. Even though the current runs suggest this storm will go out to sea to our south, it is still way too early to draw any conclusions about this. However, it may be best to stay tuned if you are planning on traveling for Thanksgiving (oh no, I’m starting to sound like the “Weather” Channel).

Wednesday Night

Mostly clear, calm and cold.

Low temperatures will reach 10-15 degrees in most locations.

Calm winds.

Thursday

Mostly sunny through mid morning, then increasing cloudiness. It will average out partly sunny during the afternoon.

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

Winds light and variable early, becoming south-southwesterly at 5-10 mph.

Thursday Night

Mostly cloudy. There is a chance of a light rain shower or sprinkle toward daybreak. This could begin as a little light mixed precipitation, particularly over the higher terrain. Probability of precipitation 40%. Rainfall totals less than 0.05″.

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

Light south-southwesterly winds.

Friday

Mostly cloudy to overcast. Scattered light rain showers are likely, predominantly during the morning. Probability of precipitation 60%. Rainfall totals 0.10″ or less.

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

Southwest winds at 5-10 mph.

Note: Clicking on underlined red text provides links to various weather maps. In bold, italicized font are all of the ingredients necessary for tornadoes to form.

Summary: A rapidly intensifying surface low pressure system over the Great Lakes drove its trailing strong cold front into an unusually warm, moist air mass for this time of year over the Midwest yesterday. This created the “lift” that created upward motion in the atmosphere. Instability in the warm air mass in advance of the cold front was intensified by a pocket of very cold air aloft in an amplifying trough in the jet stream wave pattern, diving to the south. This instability accelerated the upward motion to generate strong thunderstorms in advance of the cold front. The strong meridional temperature contrast also generated a strong jet streak aloft which combined with a strong wind field being generated by the deepening low pressure system to create strong vertical wind shear (change in speed and direction of the wind with height). This wind shear created the rotation necessary to turn many of the thunderstorms into long-lived, rotating thunderstorms called “supercell” thunderstorms that produce the majority of strong and violent tornadoes. As a result, there was a tornado outbreak over Illinois, Indiana and Kentucky yesterday afternoon. The National Weather Service has not had time to “rate” the tornadoes yet but some of the damage in the photos and video is at least EF-4 (wind speeds 166-200 mph) in a few of the tornadoes. As strange as it may seem, tornado outbreaks are not unusual in November. In fact, a devastating tornado outbreak occurred during the “Super Tuesday” primary elections in the Southeast U.S. as recently as 2008. However, this outbreak was farther north than usual for November. Most November outbreaks occur in the Southeast or along the Gulf Coast. However, there have been 60 November tornadoes in Illinois and 50 in Indiana and Kentucky since 1950. I am curious to see the rating for yesterdays tornadoes since there has never been an EF-5 tornado and only 20 EF-4 tornadoes anywhere in November since 1950.

As the surface low departs northeastward into Canada and its trailing cold front moves well off the coast, surface high pressure will once again build into our region and give us fair weather through at least Thursday and probably into Friday. Late in the week, the jet stream wave pattern will again amplify with a cold trough driving south over the Great Plains and Midwest. This will generate a surface low along the eastern edge of the trough (the usual location) on Saturday. It looks like this low will develop to our northwest. As a result, we may get some mixed precipitation as it drags its warm front by on Saturday but we should get mostly rain as we move into the “warm sector” to the southeast of the low. I’ll have a better handle on precipitation type as the week progresses. In any case, after the low moves by it should open the door to what looks like the coldest air of the season as the cold trough moves over us for Sunday and Monday.

Monday Night

Variable cloudiness, becoming mostly cloudy after midnight. There is the slight chance of a snow shower or flurry, predominantly over the elevated terrain to the north. Becoming windy and much colder.

Low temperatures near 30 in the valleys, mid to upper 20s over the elevated terrain. Wind chills in the single digits to teens at times.

West-northwest winds at 10-15 mph in the evening, increasing to 15-25 mph after midnight (highest winds over the elevated terrain) with 30-40 mph gusts.

Tuesday

Some lingering cloudiness through mid-morning, then becoming mostly sunny for the remainder of the day. It will be blustery and colder.

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

Northwesterly winds at 15-25 mph with gusts to 30-40 mph. Winds diminishing later in the afternoon.

Tuesday Night

Mostly clear and cold.

Low temperatures generally in the upper teens with mid teens over the elevated terrain.

Northwest winds at 5-15 mph in the evening, becoming light and variable by morning.

Wednesday

Mostly sunny, calm and not quite as cold.

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

Winds light and variable.

I have posted an updated forecast on the BCC weather station website: http://www.rainwise.net/weather/bcc

One note…there is a severe weather out break ongoing in the midwest. The SPC has issued a “high” probability of severe storms for Illinois and Indiana, which is quite unusual, with a 30% probability of tornadoes within 25 miles of any given point. As of 1 pm today there are already numerous supercell thunderstorms on radar over Illinois and at least one large tornado has already touched down in Illinois. If you would like to follow this developing situation go to the Storm Prediction Center’s (SPC) website: www.spc.noaa.gov . In addition, I am sure the Weather Channel will be giving this quite a bit of coverage (their ratings have been flagging with the slow hurricane season this year).

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

Summary: The large surface high pressure system which has dominated our weather this week continues to drift to the east, its center moving well off the coast. However, it will hold sway over our weather for one more day, giving us a mostly sunny and mild Saturday.

Two very weak mid-level disturbances in the westerly wind flow will drift by to our south and east over the weekend. The first will bring some cloudiness into Berkshire County late tonight but most of the precipitation should stay well to our south. There is, however, the slight chance of a sprinkle or light shower toward daybreak, mainly in South County. Skies should then clear for the day on Saturday. A second disturbance will generate a very weak surface low pressure system just off the coast on Sunday. This disturbance will pass closer to Berkshire County. Therefore, Sunday should have mostly cloudy to overcast skies as the southeasterly flow around the weak low brinks a lot of low-level moisture and clouds, with accompanying drizzle and sprinkles, into the county. It also appears that the western edge of the precipitation shield will be very close to us so there is a good chance we will see scattered showers as well, particularly in eastern parts of the county.

A strong surface low pressure system will move north through the Great Lakes and eastern Canada on Sunday night and Monday and drag its trailing cold front through our region with a bout of steadier rain and showers near daybreak on Monday. Temperatures will rise overnight on Sunday to near 60 degrees but once the front clears, temperatures will begin to plummet through the 40s during the day on Monday. However, the jet stream wave pattern will be a little “flatter” (less amplified) and farther to the north than early this week, so the coldest arctic air will stay well to our north. Therefore, it will not be as frigid as early this week, with temperatures more seasonable, with highs in the upper 30s to mid 40s Tuesday through Thursday. Once again (our repetitive autumn pattern continues), sprawling surface high pressure will move in behind the cold front and we should have dry, and fairly sunny, conditions through the entire work week.

Friday Night

Partly cloudy this evening, becoming mostly cloudy after midnight. There is the slight chance of a sprinkle or light shower near daybreak, predominantly in South County. Probability of precipitation 10-20%.

Low temperatures generally in the low 30s, with some mid 30s in South County, near 30 over the elevated terrain.

Light southwesterly winds.

Saturday

Mostly sunny and unseasonably mild.

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; low 50s over the elevated terrain and hilltowns, depending on elevation.

Light southwesterly winds in the morning, increasing to 5-10 mph in the afternoon.

Saturday Night

Mostly clear in the evening, becoming mostly cloudy to overcast after midnight.

It will remain unseasonably mild, with low temperatures generally in the low 40s.

Light southeasterly winds.

Sunday

Mostly cloudy to overcast with scattered drizzle and sprinkles. There is a good chance of a shower, particularly in eastern portions of the county. Becoming breezy. It will remain quite mild, despite the cloud cover. Probability of precipitation 50%. Most likely rainfall totals 0.10″ or less.

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; low 50s over the elevated terrain and hilltowns.

Southeasterly winds at 10-15 mph.