Summary: Surface high pressure will continue to dominate our weather for the next several days. As a result skies will be clear to partly cloudy through Friday with virtually no threat for rain. As the high pressure system moves slowly to our east, the clockwise flow around it will bring warmer air, with a bit more humidity and cloudiness, into the region on southwest winds toward the later part of the week. In fact, temperatures should rise into the 70s Thursday through Saturday, which is several degrees above normal for this time of year (normal high is ~ 67°).

The next wave in the jet stream will bring another cold front through over the weekend, giving us a period of rain and/or showers beginning Saturday evening or overnight Saturday. Unfortunately, it is starting to look as if the front will move very slowly and the rain will likely continue into Sunday as well. Following frontal passage, surface high pressure will again build in, giving us fair weather for most of next week (poor timing, I hope we aren’t getting into one of these repetitive cycles where it rains on the weekend and then is nice all week). Actually, the pattern which we appear to be moving into is a fairly typical (dry) autumn pattern where surface high pressure systems are, only periodically, interrupted by relatively short bursts of rain or showers triggered by cold front passages. The reason this pattern tends to occur in autumn is because the jet stream is still relatively weak, since meridional (north-south) temperature gradients have yet to strengthen (as they will as winter approaches and the sun continues its southward migration). Therefore, waves in the jet stream tend to be flat/shallow and are thus only able to develop weak surface low pressure systems (along the eastern side of the wave trough). This weak surface low pressure tends to track to our north and only drag its trailing cold front over us. This is because the jet stream has begun its southward progression but is still, generally, to our north. Since the air that the cold fronts are lifting is cooler, drier and more stable than in the summer, the cold front passages tend to be drier and lack thunderstorms. Once the jet stream troughs lift back to our north (once the weak wave passes) surface high pressure will build back in until the next weak jet stream wave approaches with the next cold front.

On a more immediate note, it will be clear, calm and dry again tonight so there is, once again, the risk of frost in Berkshire County tonight. I think the frost may be less widespread than last night since dewpoints have risen slightly (into the low 40s). However, the air will be very calm for the entire night (didn’t calm until after midnight last night) so I think we will get enough radiational cooling so that many places will again have frost.

Tuesday Night

Clear, calm and cold.

There is, once again, the risk of frost. Low temperatures in the mid to upper 30s with a few low 30s in some of the colder valley locations.

Calm winds.

Wednesday

Sunny and milder.

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

Light west-southwesterly winds.

Wednesday Night

Clear, calm and seasonably cool.

It will be slightly milder than previous nights with low temperatures near 40 countywide.

Calm winds.

Thursday

Mostly sunny and mild.

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

Light west-southwesterly winds in the morning, becoming southwest at 5-10 mph in the afternoon.