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.