The main, polar front jet stream is located well to our north, over Canada. However, even though this usually means fair and warm weather (like this past weekend), the lack of a steering current has enabled some weak, mid and upper-level disturbances, located well south of the main jet stream, to wander into the Northeast. Thus the cloudy and, with the paucity of sunshine, somewhat cooler weather the past few days. Unfortunately, although these “meandering” disturbances have been relatively harmless in regard to our weather until now, that is about to change. One, very weak disturbance is generating an area of rain over southeastern New England. This disturbance will drift slowly out to sea. A second, stronger disturbance is presently located over the eastern Great Lakes. This disturbance is generating a weak surface low pressure system associated with clusters of slow moving showers and thunderstorms over Pennsylvania and New York state. As this disturbance drifts eastward overnight, it will begin to feed on abundant moisture off the southern New England coast. As a result, it looks like a more “coherent” area of rain and showers will develop over southern New England after midnight. As the low pressure system spins counter-clockwise the associated rain shield will likely “back up” a bit with rain and showers moving southeast to northwest back over Berkshire County toward morning. It looks like showers will likely continue off and on during the day, and even into the evening. Most of the rain should be relatively light and occur during the morning hours, with showers much more scattered during the afternoon as the disturbance drifts very slowly eastward off the coast. A caveat here…..as is usually the case with weak and poorly organized systems, this is not a high confidence forecast in terms of rainfall coverage and amounts across the county.

Since it will take quite some time for the disturbance to pull away we will probably not see clearing skies until sometime on Thursday afternoon. Weak surface high pressure will then build in to give us a mostly sunny and mild day on Friday. In the meantime, quite cold Arctic air will begin to plunge south out of Canada, being drawn south into a fairly deep trough in the jet stream wave pattern developing over the central U.S. on Friday. A strong cold front at the leading edge of this trough will plow through Berkshire County during the day on Saturday. As a result, it is looking like a period of fairly substantial rainfall will likely occur sometime on Saturday. It should then turn much cooler on Sunday, with high temperatures remaining in the 50s.

Tuesday Night

Partly to mostly cloudy this evening. Becoming mostly cloudy after midnight with rain or showers likely developing toward morning. Probability of precipitation 60%. Likely rainfall totals 0.05″ to 0.15″.

Low temperatures in the low to mid 50s.

Light east-northeasterly winds.

Wednesday

Mostly cloudy with scattered, on and off, rain showers likely. Showers are mostly likely during the morning hours but could occur at any time during the day. Probability of precipitation 60%. Any rainfall totals likely 0.10″ or less.

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

Northeasterly winds at 5-10 mph.

Wednesday Night

Mostly cloudy. There is a chance of a few lingering showers before midnight. Probability of precipitation 40%. Rainfall totals likely 0.05″ or less.

Low temperatures near 50.

Light north-northeasterly winds.

Thursday

Mostly cloudy in the morning. Some clearing during the afternoon.

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

Light north-northeasterly winds.