Summary: I am going to provide links to various images, in this and future forecast posts, to help illustrate my discussion in the summary portion of the post. These links can be accessed by clicking on any text that is normal font and red in color. For example, in the paragraph below, if one clicks on “A broad trough in the jet stream” the reader will be linked to a combination “analysis” surface map and “1000-500 mb thickness” map from the GFS numerical model. The surface portion is represented by isobars (lines of equal atmospheric pressure) with “H”s and “L”s designating areas of high and low pressure respectively. The dashed red and blue lines represent lines of equal atmospheric “thickness”. The higher this number (red lines) the warmer the atmosphere and the lower the number (blue lines) the colder the atmosphere. The jet stream will be located where these lines are closest together. For the polar front jet stream (the main jet stream) this is usually near the junction of the blue and red lines (540 thickness).

A broad trough in the jet stream wave pattern has descended over the eastern two-thirds of the nation, bringing below normal temperatures as far south as Florida, where freeze warnings have been issued for tonight for northern and parts of central portions of the state. As the jet stream stagnates in this configuration over the next few days, our temperatures will remain below normal. In addition, the counterclockwise circulation around a deep surface low pressure system along the eastern edge of the trough, off the coast, will bring moisture off the ocean and over New England. There will also be a “pressure gradient” between the surface low and surface high pressure to our west. As a result, in addition to the unseasonably cool temperatures (normal high temperatures should be in the upper 40s to near 50) we will also have somewhat breezy conditions (pressure gradient) and a few cloudy periods with even a chance of a few scattered light snow showers (or sprinkles during the day in the lower elevations) for the next few days. (This typical “prolonged” Berkshire County winter is starting to get kind of old……)

However, as the weekend approaches, the trough will begin to flatten out and propagate slowly to the east. As a result, surface high pressure (on the western side of the trough, as usual….downward motion in the atmosphere, dry and sunny) will build into the region so the weather should improve considerably on Friday, with a relatively sunny and milder weekend!! (Hang in there…)

Tuesday Night

Mostly clear and seasonably cold. Clouds may increase near daybreak with the slight chance of a snow flurry. Probability of precipitation 20%.

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

West-northwesterly winds at 3-8 mph.

Wednesday

Skies will average out partly cloudy. However, there will likely be more sun in southern portions of the county than northern. It will likely become mostly cloudy in central and northern Berkshire later in the afternoon with the slight chance of a flurry or sprinkle, particularly over the elevated terrain. It will be breezy and relatively cold for this time of year.

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

West-northwesterly winds at 5-15 mph in the morning, increasing to 10-20 mph in the afternoon, with the higher end or this range (as usual) over the elevated terrain.

Wednesday Night

Mostly cloudy, a bit breezy and seasonably cold. There is a good chance of a period of snow flurries or snow showers, particularly after midnight, as a weak upper-level disturbance moves through. Probability of precipitation 30%, increasing to 50% toward morning. There may be a dusting to as much as 1/2″ in places, particularly over the elevated terrain.

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

West-northwest winds at 8-15 mph.

Thursday

Mostly cloudy and remaining cooler than normal. There is a good chance of a snow shower early in the morning (50% POP), with probability decreasing as the day progresses. Some partial clearing is likely later in the afternoon.

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

North-northwesterly winds at 8-15 mph.

This will be my last forecast for awhile. I will be on vacation for spring break and will not post again until Monday, March 25 or Tuesday, March 26. 

Summary: The jet stream wave pattern over the U.S. has become quite amplified, with a strong ridge over the west and a very deep trough over the east. As a result, temperatures are unseasonably warm in the southwest (80s and 90s in southern CA and AZ) and unseasonably cold in the east (high temps in the 40s as far south as GA). Temperatures over Berkshire County at 5000 ft. altitude are near zero (Fahrenheit) so that even with some sunshine today and a high sun-angle, we are struggling to make it into the 20s across the county and it is only in the mid to upper teens across the higher elevations. The cold, arctic air moving across the lakes today is generating some lake-effect snow and one of these lake-effect squalls made it into Berkshire county early this morning, giving central and south-central portions of the county a quick coating-1″ of snow.

This deep trough will lift a bit northward, but broaden, over the next few days, so that, even though it won’t be as cold as today, Berkshire County will still see below normal temperatures for the next several days. As the trough broadens, a few weak upper-level disturbances moving along the jet stream  will keep us fairly cloudy through Saturday and there is even a pretty good chance of snow showers late Friday.

As the trough shifts a little further east, skies may finally clear as surface high pressure (as usual, located under the western side of the trough) finally builds in for Sunday and Monday. A relatively weak storm will move through the Great Lakes and drag first its warm front and then its cold front through here during the day on Tuesday. There may be some mixed precipitation at the outset but right now this event looks to be mostly rain. The Weather Channel has been making a big deal about this “storm” over the last several days (since this past weekend) and I have received many questions about “the big storm we are going to get next week”. The Weather Channel must really be desperate now that we are in a lull after some relatively significant winter storms over the past several weeks. However, they should know better than to get people worked up over “something” that is over one week away. Even with the great advances in mathematical modeling that have been made in recent years, a forecast for more than one week out has very limited “skill”.

Thursday Night

Partly to mostly cloudy this evening with more clouds over the elevated terrain. There is still the slight chance of a lake-effect snow shower or flurry before midnight. Probability of precipitation 20%. No accumulation expected. Becoming partly cloudy after midnight. It will remain breezy and unseasonably cold.

Low temperatures in the low to mid teens in most locations, near 10 over the elevated terrain. Wind chill temperatures will be near zero.

Northwesterly winds at 10-15 mph, diminishing somewhat toward morning.

Friday

Mostly cloudy and continued cold, although not nearly as cold as Thursday. There is a good chance of a snow shower or two mid to late afternoon. Probability of precipitation 50%. There may be a dusting in a few places.

High temperatures in the low to mid 30s in Pittsfield, Adams, North Adams and Williamstown, mid 30s in Great Barrington and Sheffield, and upper 20s over the elevated terrain and hilltowns.

West-southwesterly winds at 5-10 mph in the morning, becoming southwesterly and increasing to 10-15 mph during the afternoon.

Friday Night

A chance of a lingering snow shower early, then partly to mostly cloudy, becoming overcast toward morning.

Low temperatures in the low 20s in most locations, upper teens over the elevated terrain.

West-northwest winds at 5-10 mph.

Saturday

Mostly cloudy and continued cold. Some light snow associated with an upper-level disturbance should remain well to our south.

High temperatures in the low to mid 30s in Pittsfield, Adams, North Adams and Williamstown, mid 30s in Great Barrington and Sheffield, and upper 20s over the elevated terrain and hilltowns.

Light west-northwest winds.

Summary: After several days of above average temperatures, Berkshire County will see a return to more seasonable temperatures for Wednesday and then very cold weather for Thursday.

A strong cold front at the leading edge of a deep trough in the jet stream wave pattern is bringing us moderate to heavy rain this afternoon. There will be some clearing overnight, after the front passes this evening, and most of the day on Wednesday will be fairly sunny with much cooler, but seasonable, temperatures. A secondary cold front will then pass through during the late afternoon to early evening with scattered snow showers, and even a few snow squalls. This frontal passage will usher in an even colder arctic airmass. As a result, Thursday will be a windy and unseasonably cold day, with low wind chills and air temperatures remaining in the 20s.

Tuesday Night

Rain should end by 7 or 8 pm. There may be a few lingering light showers for a few hours after that. There will be partial clearing after midnight, although the low clouds will hang tough and there may even be some patchy fog.

Temperatures will drop precipitously into the 30s countywide as the surface cold front passes around 6 pm, then drop more slowly through the 30s overnight. Likely overnight low temperatures in the upper 20s in most locations, mid 20s over the elevated terrain.

West-northwesterly winds at 10-15 mph this evening, decreasing to 5-10 mph after midnight.

Wednesday

Mostly sunny (5-25% cloud cover) to partly cloudy (25-50% cloud cover) for most of the day. Clouds will increase late and there is a good chance of a snow shower or squall towards evening as the arctic front passes through. Probability of precipitation 50%. There is likely to be a quick coating of snow in places, with up to 1/2″ in any heavier squalls, most likely over the elevated terrain.

It will be much cooler than recent days, with high temperatures in the low 40s in Pittsfield, Adams, North Adams and Williamstown, mid 40s in Great Barrington and Sheffield, and upper 30s over the elevated terrain and hilltowns.

West-northwesterly winds at 8-15 mph, with the higher end or this range (as always) over the elevated terrain.

Wednesday Night

Good chance of a snow shower during the early evening as the front passes, then becoming partly cloudy, breezy and colder, with only a slight chance of a snow shower or flurry for the remainder of the overnight. Probability of precipitation 50% early, then 20% after the front passes.

It will be colder, with low temperatures near 20 in most locations, mid to upper teens over the elevated terrain. Wind chill temperatures dropping into the single digits after midnight.

West-northwest winds at 10-15 mph.

Thursday

Partly sunny early, then mostly cloudy, breezy and unseasonably cold. There is a slight chance of a snow flurry. Probability of precipitation 20%. No accumulation expected.

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

West-northwesterly winds at 10-20 mph with gusts over 30 mph.

Summary: Snowfall totals from across Berkshire County, as reported to the National Weather Service office in Albany: Alford – 5.0″; Lanesborough – 5.5″; Williamstown – 6.3″; Lenox Dale – 7.9″; Pittsfield – 8.0″; Sheffield – 8.0″; North Otis – 10.0″; Savoy – 11.0″; and an unofficial report from Peru of over 12.0″.

We are receiving a welcome, albeit brief, visit from spring this weekend into early next week, but winter will make an abrupt return for the middle and latter parts of the week. As a mild ridge (northward lifting) in the jet stream wave pattern propagates slowly eastward, surface high pressure (associated with descent and, thus, drying in the atmosphere) along its eastern edge will crest over the Northeast Saturday night and Sunday. This is giving us a beautiful, sunny day with unseasonably mild temperatures today. It will remain fairly clear, with a good amount of sunshine and mild temperatures through Sunday. As the ridge crests over the Northeast on Monday, the surface high pressure along its leading edge will move off the coast and a bit more cloudiness, but even milder air will move in on a warm, moist southerly return flow around the surface high (clockwise circulation around high pressure). It looks like high temperatures should reach into the 50s on both Sunday and Monday.

As the jet stream wave pattern continues its slow propagation eastward, a cold trough (southward dip) in the jet stream will approach the region, with a strong cold front at the leading edge of the trough pushing through on Tuesday with rain, as the advancing heavy, cold air lifts the lighter warm, moist air. This front will usher winter back into the region with strong northwesterly winds and much colder temperatures for Wednesday through Friday. There may be some scattered lake-effect snow showers and flurries for a day or two after the cold front passes but I do not see any threats for any additional accumulating snow for Berkshire County.

Saturday Night

Mostly clear, calm and cold.

As surface high pressure crests over us, we will have ideal radiational cooling conditions with clear skies, calm winds and a snow cover (or what’s left of it) and, despite the mild day, temperatures will drop quite a bit overnight. Likely overnight low temperatures near 20 in most locations with mid to upper teens in the hollows and depressions, particularly over the elevated terrain.

Winds calm.

Sunday

It will average out mostly sunny (5-25% cloud cover) but there will be more clouds than Saturday (not difficult to accomplish since there was not a single cloud in the sky today). Most of the clouds will be of the thin, high to mid-level variety and will, generally, only dim the sun from time to time.

It will be unseasonably mild, once again, with high temperatures in the low 50s in Pittsfield, low to mid 50s in Adams, North Adams and Williamstown, mid 50s in Great Barrington and Sheffield, and near 50 over the elevated terrain and hilltowns.

Light southeasterly winds in the morning, becoming south-southeasterly winds at 5-10 mph during the afternoon.

Sunday Night

Partly cloudy.

It will be seasonably cold, but not quite as cold as Saturday night with a little more cloud cover and some light south-southeasterly winds. Low temperatures in the low to mid 20s in most locations.

Light south-southeasterly winds.

Monday

Variable amounts of clouds, although I think there will still be more sun than clouds.

Unseasonably mild with high temperatures in the mid 50s in Pittsfield, mid to upper 50s in Adams, North Adams and Williamstown, upper 50s in Great Barrington and Sheffield, and low 50s over the elevated terrain and hilltowns.

Southerly winds at 10-15 mph.

Monday Night and Tuesday

Increasing clouds and mild Monday night with temperatures remaining in the 40s. There will likely be rain for a good part of the day Tuesday, mostly late morning through the afternoon. It will remain mild, with temperatures rising to near 50, until the cold front passes sometime in the late afternoon or early evening.

Summary: There are no major changes to the forecast for tonights snowfall. I think the snow should be a little heavier than it looked yesterday so I have increased the likely snowfall accumulations a bit.

Snow should begin to pick up in intensity toward evening. There is unlikely to be any accumulation over the lower elevations before dark this afternoon, with temperatures generally in the mid 30s and the high-sun angle this time of year. There could be an inch or so of accumulation over the elevated terrain, where temperatures range from near 30 to the low 30s. However, even there the high sun-angle will limit accumulations. After sunset, the snow should begin to accumulate, first on grassy surfaces but as snowfall intensity increases to moderate to heavy at times, with a drop in temperatures into the 20s overnight, road surfaces will likely become snow covered as well. I expect snowfall totals to be in the 4-8″ range across the county during the overnight hours, with the lower end of that range more likely in the lower elevations (all of the large towns) and the higher end of that range over the elevated terrain, particularly in the eastern portions of the county.

Snow should continue through the morning on Friday and end by early afternoon. Temperatures will remain fairly cold but as the sun gets higher in the sky, the snow is likely to melt as fast as it accumulates. An additional 1-2″ could fall in the lower elevations early in the morning with 2-4″ additional accumulation over the elevated terrain before this happens. There will likely be some snow covered roads early in the morning, although the treated main thoroughfares should be wet to slushy. By mid to late morning the roads should just be wet. I expect total snowfall accumulations from this afternoon through Friday morning to be highly variable throughout the county, mainly on the basis of elevation. This is very common in March when the sun-angle is high and surface temperatures are close to freezing. Likely storm total snowfall: 5-8″ for the lower elevations, including all of the main towns. Likely accumulations over the elevated terrain will be in the 8-12″ range. However, I would not be surprised to see some reports over 12″ come in from Savoy and Peru, possibly Otis as well.

The two upper-level disturbances responsible for the snow will continue to spin around each other (“Fujiwara” effect) which will serve to propel the entire upper-level trough/cut-off low eastward as the weekend approaches. This will allow the jet stream wave pattern to resume its eastward progression (has been stalled by the blocking pattern caused by the cut-off high/ridge to the north over eastern Canada and cut-off low/trough to the south over us). This wil permit a mild ridge to propagate eastward with a surface high pressure system at its leading edge cresting over the Northeast over the weekend. As a result, Saturday will likely be a bright, sunny day, with temperatures well into the 40s. Sunday will have a few more clouds but there will still be plenty of sunshine, and slightly milder as well, with temperatures approaching 50.

Thursday Night

Snow, moderate to heavy at times. Probability of precipitation 100%. Likely snowfall totals 4-8″ overnight, with the lower amounts in the lower elevations and the higher amounts more likely over the elevated terrain.

Low temperatures in the upper 20s in the lower elevations, mid 20s over the elevated terrain.

North-northwest winds at 10-15 mph.

Friday

Snow, moderate to heavy at times in the morning, tapering off during the early afternoon. Partial clearing mid to late afternoon. Probability of precipitation 100%. Additional snowfall accumulations 1-2″ in the lower elevations, 2-4″ over the elevated terrain. Likely storm total snowfall accumulations 5-8″ over the lower elevations and 8-12″ over the elevated terrain.

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

Northerly winds at 10-15 mph.

Friday Night

Becoming mostly clear.

Low temperatures in the low 20s in most locations with some upper teens over the elevated terrain.

North-northwest wind 10-15 mph in the evening, diminishing to 5-10 mph after midnight.

Saturday

Sunny and much milder.

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

North-northwest winds at 5-10 mph.

My forecast from yesterday still looks pretty solid (pat myself on the back). The only adjustment I would make from yesterday is to increase the probability of precipitation from Thursday afternoon til Friday morning from 70% to 90% and to increase likely snow accumulations for that period from 3-6″ to 4-8″. The greatest accumulations within this range should be in the elevated terrain in central and southern Berkshire (e.g. Peru, Otis, Becket) and the least in lower elevations in northwestern locations (e.g. Williamstown, North Adams). For more details on this interesting storm, see yesterday’s post. I will give a more in-depth forecast tomorrow afternoon.

Summary: The forecast for the mid-week coastal storm is coming more into focus and I now have a higher level of confidence in the forecast as the storm approaches. However, the scenario remains complex and somewhat “fluid” so additional updates will likely be necessary over the next few days.

Fortunately, I think we will avoid the very large heavy, wet snow accumulations that portions of the Mid-Atlantic will see over the next few days. There will likely be portions of the Appalachians, in northern Virginia, eastern West Virginia, and western Maryland that see between one and two feet of heavy wet snow as the surface low redevelops off the Mid-Atlantic coast and intensifies during the day on Wednesday. Even Washington, D.C. and Baltimore could see 10 inches of heavy wet snow after an initial period of rain. As the storm intensifies, winds will also increase to over 20 mph, which, combined with the heavy, wet snow is likely to cause widespread power outages in these regions.

Even though this scenario is unlikely for Berkshire County, I do think we will see some accumulating wet snow. It looks like the surface low will initially move due east off the Mid-Atlantic Coast during the day and overnight Wednesday, prevented from moving north by the blocking ridge over eastern Canada. The wave containing the “sharp” trough in the jet stream, which was responsible for generating the surface low, will be forced to “break” (wave-breaking) as it runs into the strong upper-level ridge backed up over eastern Canada. As a result, the entire system will be forced to slam on the breaks as the surface low becomes “stacked up” under the upper-level low/trough/cold pool. This is what is called a “cut-off” low. The impact that this will have in the real world (not crazy “atmospheric science” world) is that the system will stall off the coast and cause a protracted weather event for Berkshire County that will begin Wednesday and not end until Friday.

The timeline looks something like this: As the surface low intensifies on Wednesday as it moves slowly east, the strong northeasterly flow around the low (counterclockwise flow-“Nor’easter”) will likely bring low level moisture off the ocean which will be lifted by our local terrain. Therefore, it looks like there is a good chance for snow showers during the day Wednesday, particularly over the elevated eastern terrain, even though the main area of precipitation will still be well to our south. Temperatures will be in the 30s and with a high sun-angle this time of year there should be little, if any accumulation for most of the county. The one exception would be over the elevated terrain to the east where up to 1″ could fall.

As the surface low drifts by to our south Wednesday night into Thursday morning we should fall under the northern edge of its precipitation shield. Light snow will be likely in southern and eastern parts of the county where 1-3″ could fall in the elevated terrain in the southeast (e.g. Otis and Becket). The likelihood of accumulating snow decreases as one moves north and west within the county. Pittsfield may receive and inch or so, and there is only a chance of snow in the northwest part of the county.

As the day progresses on Thursday, through Thursday night and into Friday morning, something unusual will likely happen (actually, this whole event is somewhat unusual). Another upper-level disturbance along the jet stream will drop southeast into the cut-off low. As it does this, it will create what is called a “Fujiwara” effect where this new disturbance “dumbells” with the original disturbance (now cut-off). This will do two things; 1) it will pull the surface low a bit back to the northwest, closer to the coast and 2) the new disturbance will enhance the snowfall along the northwest margin of the precipitation shield. As a result of all this strangeness we are most likely to see accumulating snowfall during this period, especially since the snow will mostly be falling overnight when there is no incoming radiation from the sun (can pass through clouds during the day, especially this time of year) and temperatures will be colder, probably in the 20s. The most likely snowfall accumulation during this period looks like 3-6″, with the highest amounts in the elevated terrain to the east.

Once the cut-off incorporates this new disturbance it will help swing the whole mess to the east and allow a milder ridge, with associated surface high pressure to build in from the west for the weekend. As a result, we are likely to see abundant sunshine for Saturday and probably most of Sunday with much milder temperatures in the 40s. This should help melt whatever snowfall we get in the next several days.

Tuesday Night

Increasing cloudiness. There is the chance of a snow shower after midnight, predominantly over the elevated terrain to the east. Probability of precipitation 30%. Nothing more than a dusting.

Temperatures will fall to the upper 20s in most locations, near 30 in the lower elevations of South County and mid 20s over the elevated terrain before midnight and then hold steady for the remainder of the night.

Light northeast winds this evening, increasing to 10-15 mph by morning.

Wednesday

Mostly cloudy with a chance of snow showers, snow showers likely over the elevated terrain to the east, particularly during the middle part of the day. Probability of precipitation 50%, 70% over the elevated terrain to the east. Accumulations, nothing more than a dusting in most locations, up to 1″ over the elevated terrain to the east.

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

Northeast winds at 10-15 mph, increasing to 15-20 mph during the afternoon. There will be some gusts over 30 mph later in the afternoon, particularly over the elevated terrain.

Wednesday Night

Overcast with a steady light snow likely developing over southern portions of the county, particularly the elevated southeastern terrain, after midnight. Probability of precipitation in these locations 70%. Accumulation of 1-3″ likely, with the highest amounts over the elevated southeastern terrain. There is a good chance of light snow (POP 50%) in central locations (Pittsfield) with an inch or so of accumulation possible. There is only a chance of light snow (40%) in the north, particularly the northwest where nothing more than a dusting is expected.

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

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

Thursday

Overcast and cold. Any light snow will likely taper off during the morning but then return during the afternoon. Probability of precipitation 70% during the afternoon. Up to 1-2″ of snow possible by evening, particularly over the elevated terrain.

High temperatures in the low 30s in Pittsfield, Adams, North Adams, and Williamstown, low to mid 30s in Great Barrington and Sheffield, upper 20s to near 30 over the elevated terrain.

Thursday Night and Friday

Light snow likely overnight and into Friday morning. Snow could be moderate at times. Snow should taper off during the morning and end by noon. Probability of precipitation 70% into Friday morning. Most likely snow accumulation from Thursday afternoon through Friday morning 3-6″ with the greatest amounts in the elevated terrain.

Summary: The pesky upper-level cold pool (low pressure) which has been rotating above us for the past several days, reminding us either of why we love winter, or why we want winter to end, will finally weaken and drift eastward on Tuesday. One last disturbance, rotating around the cold pool, will give us one last bout of snow flurries/showers tonight. Our weather will then improve a bit tomorrow as the northwest winds finally die down, temperatures rise slightly (almost normal) and we may, may actually see a little of the sun during the afternoon.  The big forecast question then will become: How will the mid-week coastal storm affect Berkshire County?…..

Divergence of the upper-level flow associated with a strong disturbance in the jet stream, diving south out of the upper Great Plains today, is generating ascent in the atmosphere above a developing surface low pressure system in the central Great Plains. This “dynamic” weather system will progress slowly eastward over the next two days, with the surface low centered over West Virginia by Tuesday evening. Overnight Tuesday this “primary” surface low will weaken as it begins to lag behind its upper-level support and a new, “secondary” surface low will develop off the Mid-Atlantic Coast as the upper-level energy moves out over the warm waters of the Gulf Stream. During the day on Wednesday, the surface low will begin to deepen (intensify) as the trough in the jet stream containing the previously mentioned upper-level disturbance becomes negatively tilted, enhancing the divergence in the jet stream flow. The increasing ascent in the atmosphere (which generates the clouds and precipitation) will be enhanced further by increasing environmental instability (warm at surface [Gulf Stream], cold aloft [the “upper-level disturbance” is a cold pool aloft]). Bottom line: There will be a broad swath of fairly heavy snow accumulations, 6-12″ or so along the path of the surface low from the upper Great Plains trough the Midwest and into the Mid-Atlantic states. As the low intensifies off the coast on Wednesday, precipitation will be enhanced and heavy, wet snow could really begin to pile up over the mountains of West Virginia, eastern Kentucky and western Virginia, with snowfall totals well over one foot. Heavy wet snow will also likely pile up in the Baltimore and Washington, D.C. areas but this will likely be likely be limited, in D.C. in particular, since they will be right on the snow/rain line and it will probably rain for a while before changing to snow. However, given how wet the snow will be, and because winds will be picking up as the surface low strengthens, I suspect power outages could become quite widespread across these regions.

All of the computer models pretty much agree on the preceding scenario. However, beyond this point there is disagreement as to the track along the coast and its impact on New England. As I suspected, all of the models have had a bit of a northward drift in their storm track over the past few days. All of the models have the storm weakening as it drifts slowly eastward off the Mid-Atlantic Coast, as it moves directly under the upper-level cold pool (so that it becomes “cut-off” from its upper-level support) and is prevented from moving up the coast by a blocking upper-level ridge (warm pool) over eastern Canada. “Cut-off” high pressure like this is more unusual than the more common cut-off lows, but they do occur more commonly than people realize.

However, the models differ on the exact track of the low and its impact on New England. The European model (ECMWF) has been quite consistent from run to run, with a slight northward drift in the track with each run. This model presently has us getting brushed by the northern edge of the precipitation shield late Wednesday night and into Thursday morning as the surface low drifts due east, well off the Mid-Atlantic Coast, giving us little, if any, snow accumulation. The greatest likelihood of accumulation would be in South County. This model actually gives us the greatest likelihood of accumulation from some wrap around moisture on Friday as a disturbance circulates back over us from the cut-off low over the ocean. This would still only amount to an inch or so at most. The U.S. higher resolution NAM model has had a much less stable outcome from run to run but the latest run has come into line with the ECMWF model. However, this model tends to be the not particularly reliable with East Coast snowstorms. The U.S. GFS model (fairly reliable with these scenarios, but not as consistently good as the ECMWF) has been all over the place. One run the storm misses us, the next run we get crushed. In this morning’s run the surface low drifts much further northeast than the other models, right off Cape Cod, and we get a foot of heavy, wet snow.

Although the ECMWF has been better this winter than the GFS, the northward trend in the track of the storm over the past several days’ model runs is more consistent with my gut feeling about this storm from my past experience and I think there is a significant possibility that we could get a heavy, wet March snowstorm Wednesday night into Thursday.

Bottom line: We may only get brushed by the storm and receive a few bothersome inches of wet snow Wednesday night into Thursday morning. However, my tendency right now is to lean toward the possibility that we could receive a more significant heavy, wet snowstorm. I will post an update tomorrow afternoon….

Unfortunately, the northwest flow around the resulting cut-off low will drag chilly air down over New England and prevent the warm-up late this week and this weekend that I had hoped for last week. It does appear, however, that we may get sunny weather this weekend with temperatures possibly reaching the 40s as surface high pressure builds in.

Monday Night

Mostly cloudy to overcast with a period of snow showers likely this evening. Probability of precipitation 60%. There will likely be a dusting in a few locations, and up to 1/2″ in a few spots over the elevated terrain. There is just a chance of a snow shower after midnight. Probability of precipitation 30%.

Low temperatures generally near 20 to low 20s, upper teens over the elevated terrain.

Northwest winds at 10-15 mph, diminishing a bit toward morning.

Tuesday

 Mostly cloudy with a few sunny breaks. It may actually become partly sunny for a time during the afternoon, particularly in South County.

It will be slightly milder than recent days, with high temperatures in the mid to upper 30s in Pittsfield, Adams, North Adams and Williamstown, upper 30s in Great Barrington and Sheffield, and low 30s over the elevated terrain and hilltowns.

Northwest winds at 5-10 mph, becoming northerly in the afternoon.

Tuesday Night

Becoming overcast with a chance of snow showers, particularly after midnight. Probability of precipitation 30%. Nothing more than a dusting.

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

Light north-northeasterly winds in the evening, shifting to east-northeasterly and increasing to 8-12 mph by morning.

Wenesday

Mostly cloudy in the morning, becoming overcast in the afternoon. There is the good chance of light snow or snow showers, predominantly over the elevated terrain to the east. There is the chance that a steadier snow could develop toward evening. Probability of precipitation 60% over the elevated terrain to the east, 50% elsewhere. A coating to 1″ could fall in the elevated terrain, a coating to 1/2″ elsewhere.

High temperatures in the mid 30s in Pittsfield, Adams, North Adams, and Williamstown, mid to upper 30s in Great Barrington and Sheffield, upper 20s to low 30s over the elevated terrain (depending on elevation).

Summary: It looks like we may have seen the last of the sun until at least Monday. Welcome to March! The cold pool aloft (upper-level low) continues to spin over us as it has become separated (cut-off) from the jet stream to our south. This will keep us cloudy and relatively cold with scattered flurries and snow showers over the entire weekend. In addition, a disturbance within that cold pool will generate some divergence aloft that will result in considerable ascent above Berkshire County on Saturday afternoon and Saturday evening. As a result, probabilities are fairly high that we will see a period of snow/snow showers that may result in some minor accumulations. The greatest chance for accumulation is over the elevated terrain in central and, particularly, northern Berkshire where 1″-2″ is likely. In the lower elevations in central and northern Berkshire and the elevated terrain in South County, a coating to 1″ is likely with probably nothing more than a coating in the lower elevations of South County.

There will likely be some minor improvements to our weather on Monday and Tuesday and into Wednesday as the trough in the jet stream over the eastern half of the country flattens out a bit and tries to lift to the north. This will pull the cold pool aloft a little farther to our north and east. It will still be fairly cloudy and cool but we may see a little bit of sun and snow showers will be less likely.

Also on Monday and Tuesday, a strong disturbance in the jet stream will move across the Northern Rockies and then dive south into the base of the trough (same stubborn trough I have been talking about) over the eastern U.S.. This will serve to amplify the trough greatly, eventually causing it to become negatively tilted (east to west tilt) as it reaches the East Coast on Wednesday. This will generate a large amount of divergence in the upper-level (jet stream) winds causing marked ascent in the atmosphere and development and intensification of surface low pressure along the Carolina/Mid-Atlantic coast. It appears that this surface low will eventually weaken as it becomes separated from the jet stream and drifts slowly to the east off the coast. This is the scenario at least, with some significant differences between models, that the two main long-range mathematical models (GFS and ECMWF) depict. According to the GFS model, the low will become a bit deeper and will drift northward along the coast before it begins to weaken and drift east. This would result in a fairly significant wet snowstorm Wednesday night and Thursday for Berkshire County. According to the ECMWF model, the storm will stay south of us and we will receive no precipitation at all. The ECMWF model has been better in the long-range so the smart money would say that the storm will miss us. However, there are certain aspects to the GFS scenario that I find more realistic. Also, throughout this entire winter, the projected tracks of these storms 5-7 days out have drifted north as the day of the storm approaches. I am already seeing this in the last few days. So…..I would tend to think we are going to get some wet snow here sometime Wednesday (probably late) into Thursday. I will be away this weekend but I think the picture should be much clearer when I post a forecast on Monday. In any case, the warm-up I discussed yesterday for late next week may be a bit harder to produce with this storm moving near to us. However, the long-term trend into the following week looks much milder for us as the jet stream pattern becomes more zonally (west to east) oriented and drifts a bit to the north.

Friday Night

Mostly cloudy to overcast with a chance of a snow shower or flurry. Probability of precipitation 30%. Nothing more than a dusting in a few locations, mostly over the elevated terrain.

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

Northwest winds at 5-10 mph.

Saturday

Overcast with a chance of a snow shower or flurry in the morning. A period of mostly light snow or snow showers will likely develop mid to late afternoon and continue into the evening. Probability of precipitation 70%.

It will remain on the cool side with high temperatures in the mid 30s in Pittsfield, mid to upper 30s in Adams, North Adams and Williamstown, upper 30s in Great Barrington and Sheffield, and low 30s over the elevated terrain and hilltowns.

Northwest winds at 10-15 mph.

Saturday Night

Overcast. Light snow or snow showers are likely during the evening. There is just a chance of a flurry or snow shower after midnight. Probability of precipitation during the evening 70%, dropping to 30% after midnight. Total snow accumulation from any afternoon and evening snow is: nothing more than a coating in the lower elevations of South County, a coating to 1″ in the elevated terrain in South County and the lower elevations of central and northern Berkshire, and 1″-2″ over the elevated terrain in central and northern Berkshire.

A little colder than Friday night with ow temperatures in the mid to upper 20s in most locations, low to mid 20s over the elevated terrain.

Northwest wind at 5-10 mph.

Sunday

Overcast and continued fairly cold. Still a chance of a snow shower or flurry, predominantly in central and northern areas during the afternoon. Probability of precipitation 30%. Nothing more than a coating in a few spots.

High temperatures in the low to mid 30s in Pittsfield, mid 30s in Adams, North Adams, and Williamstown, mid to upper 30s in Great Barrington and Sheffield, upper 20s to low 30s over the elevated terrain (depending on elevation).

Winds will continue a bit breezy, out of the northwest at 10-15 mph.