Summary: It appears that I have returned home to the beginning of an early January thaw. The polar front jet stream has become extremely zonally oriented (flat, E to W), and is located farther north than normal for this time of year, riding along the U.S./Canadian border. This will bring an unusually warm period for this time of year for the entire U.S. as most of the country is within the milder air to the south of the jet stream. This “flat”  jet stream pattern will also prevent any storms (surface low pressure) from developing early this week.

There is a cut-off low pressure system presently over Texas, well to the south of the jet stream (a.k.a. “cut-off” from the jet stream). Later this week the polar front jet stream will begin to dip well to the south over the western U.S. and “pick-up” this low, propelling it to the northeast, through the central U.S. and over the Great Lakes. This will result in RAIN, not frozen precipitation (weird in January) for this entire region late this week. The warm front extending eastward from this surface low will move over us on Friday, giving us some rain as well. This warm front passage will open the door to unseasonably warm weather this weekend as the subtropical high (Bermuda High) builds over the Eastern U.S. and the jet stream pushes north into Canada. This high pressure system may even hold into next week.

For Berkshire County, surface high pressure is building into the region and we should not receive any precipitation, and should have generally fair and mild weather until Thursday night or Friday as the previously mentioned warm front passes through. Temperatures may reach 40 degrees somewhere in the county every day this week, with temperatures approaching 50, and possibly into the 50s, this weekend after the warm front passes by.

Monday Night

Mostly clear.

Clear skies and a snow cover will allow for significant radiational cooling. However, a light SSW breeze developing after midnight should limit the drop in temperatures somewhat. Overnight low temperatures should be in the mid teens in most locations with low teens likely in the colder valleys.

Light southerly winds will become south-southwesterly at 5-10 mph after midnight.

Tuesday

Mostly sunny, although a few high clouds may dim the sun from time to time, and unseasonably mild.

Temperatures aloft are quite mild. In fact, if it were spring the high temperatures would reach well into the fifties. However, a radiation inversion in the morning, with a low sun angle this time of year, will result in high temperatures “only” the upper 30s in Pittsfield, near 40 in Adams, North Adams and Williamstown, near 40 to low 40s in Great Barrington and Sheffield, and mid 30s over the elevated terrain and hilltowns.

Southwest winds at 5-10 mph, becoming light during the afternoon.

Tuesday Night

Partly cloudy and a little milder than Monday night.

Low temperatures in the mid 20s in most locations with mid to upper 20s in some parts of South County.

Calm winds.

Wednesday

Variable cloudiness, with more sun than clouds, and unseasonably mild. It may turn a bit cooler with more cloudiness late in the day as a very weak cold front moves through as the jet stream, briefly, meanders to the south a little.

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 upper 30s over the elevated terrain and hilltowns.

Light southwest winds in the morning, increasing to 10-15 mph in the afternoon, shifting to west late.