A cold front is entering Berkshire County from the north this afternoon with a few widely scattered light showers. It will pass through rapidly, with clearing skies this evening. However, behind the front, a surface high pressure system containing a cool Canadian air mass will drop south over the Northeast. The coolest air will remain to our north over southeastern Canada. However, we will still likely experience the coolest air of the season so far, tonight and Friday. As skies clear and winds die down overnight we will have good conditions for “radiational cooling” with temperatures dropping into the 30s in most locations by morning. There may even be some isolated frost in a few wind sheltered valleys over the elevated terrain. Despite plenty of sunshine on Friday, temperatures will not exceed the 50s in most locations.

Over the weekend, we will see a moderating trend, with temperatures in the 60s on Saturday and the 70s on Sunday. However, even though we will likely remain dry until at least Sunday evening, the milder air will come at the expense of greater amounts of cloudiness. A weak warm front, heralding the leading edge of a ridge in the jet stream wave pattern, extending south and east from a surface low pressure system moving through the northern Great Lakes, will move through our region on Saturday. As the warmer air overrides cooler air at the surface considerable cloudiness will be generated. In fact, it will likely be mostly cloudy during the morning and into the afternoon with some additional peaks of sunshine, lets call it “partly sunny”, developing late in the day. Despite the much milder air being driven in on southerly breezes around the departing high pressure system (clockwise flow), that will be over us Friday, we will still probably only peak out in the low to mid 60s on Saturday due to the extensive cloud cover.

Skies will be clearer Saturday night and Sunday once the warm front passes and with greater sunshine on Sunday temperatures could soar well into the 70s. It will likely reach the mid 70s in most places and could even touch the upper 70s, particularly in South County, if we receive enough sunshine. Once the ridge in the jet stream progresses eastward, another trough will approach, with a cold front at its leading edge passing through on Sunday evening/night. This will likely generate a band of showers during the evening or overnight Sunday night.

After the cold front passes, we may be in for an extended period of early fall weather next week as a large, sprawling surface high pressure system develops on the back side of the jet stream trough, extending westward into a broad ridge over the eastern and midwestern U.S., as the jet stream lifts north into Canada. The only fly in the ointment is a weak disturbance that may ride through the base of the trough with nothing more than a light shower Tuesday morning. Otherwise we could see mostly sunny skies from Monday through the following weekend, with cool temperatures early in the week and moderating temperatures later in the week.

Thursday Night

Clearing this evening, then mostly clear and quite cool. Isolated frost possible in a few wind sheltered valley locations over the elevated terrain.

Low temperatures generally in the mid to upper 30s, with some low to mid 30s possible over the elevated terrain.

Northwesterly winds at 5-10 mph, becoming light and shifting to north-northeasterly after midnight.

Friday

Sunny and cooler.

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

Light northeasterly winds, shifting to southeasterly during the afternoon.

Friday Night

Mostly clear during the evening. Increasing low clouds toward daybreak.

Low temperatures generally in the low 40s, some upper 30s are possible over the elevated terrain.

Light south-southeasterly winds.

Saturday

Mostly cloudy through the morning and into the afternoon. Becoming partly sunny late, particularly in South County. Somewhat breezy and slightly milder, although it will likely still feel cool with limited sunshine and a breeze.

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

Southerly winds at 8-12 mph.

Saturday Night and Sunday

Partly cloudy and unseasonably mild. A chance of a shower late on Sunday. Low temperatures averaging in the mid 50s, and high temperatures on Sunday averaging in the mid 70s.