There is no student forecast today…..

Two more mild days and then the weather in Berkshire County will turn decidedly wintry, probably for an extended period. Interestingly, this distinct change in the weather pattern all starts with a tropical system in the western Pacific Ocean. Super typhoon Nuri has undergone what is called an “extratropical transition” whereby it looses its tropical characteristics and takes on the characteristics of a midlatitude storm as it moves north out of the tropics and begins to interact with the jet stream. This interaction with the jet stream is greatly amplifying the jet stream wave pattern and this amplification is propagating eastward over North America. It is like Nuri is yanking on a rope (the jet stream) which generates a wave along the rope that travels down the rope (you can try this at home!!??). This process is called “downstream development”. The warm tropical air and cyclonic flow around Nuri, presently in the North Pacific, is generating a very strong ridge in the jet stream wave pattern over the eastern Pacific that is extending way north into the Arctic. As a result, a very deep trough is plunging south into the U.S., bringing cold arctic air with it. It appears that once this wave pattern becomes established, it is likely to take on a “standing wave” configuration where the amplified wave is maintained over a long period as the pattern itself generates storms that continually reinforce the overall jet stream pattern and prevent the wave from propagating eastward. Bottom line….it looks like temperatures will drop below average on Thursday and stay that way for the next 7-10 days as the cold trough sets up over the eastern U.S. and stays there. 

As disturbances drop into the base of the trough and generate surface low pressure systems along the eastern side of the trough we will be under the threat that they could move up the coast close enough to us to give us snow. The first of these will be on Thursday night but the disturbance and resulting low will be weak and it looks like a dusting to 1″ would be a likely accumulation if the low passes close enough to the coast. A stronger coastal storm is possible in the Sunday/Monday time period but it is too early to determine the track or strength of that low.

For the more immediate time period, as the previously mentioned trough begins to dive into the central U.S. today it has resulted in a warm ridge developing (part of the “downstream development” I mentioned) over the Northeast. As a result, temperatures surpassed 50 today and will likely surge well into the 50s on Tuesday. There may be some low clouds tomorrow as a moist southeasterly low-level flow off the ocean develops around an ocean storm well to our east. We are likely to see some, mostly light, rain showers early Wednesday as this moist flow interacts with an approaching strong cold front (signifying the eastern edge of the trough). As the front passes through Wednesday morning, temperatures will likely drop slowly in the afternoon from morning highs in the 50s. Temperatures will drop into the 20s Wednesday night and then struggle to reach 40 on Thursday. High temperatures will then not exceed the 30s from Friday through Sunday.

Monday Night

Mostly clear. Some low cloudiness developing toward morning.

Low temperatures in the low to mid 30s.

Light south-southeasterly winds.

Tuesday

A mix of sun and clouds and unseasonably mild.

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

South-southeasterly winds at 5-10 mph.

Tuesday Night

Mostly cloudy and unseasonably mild. There is the chance of a shower, mostly light, toward morning. Probability of precipitation 40%. Likely rainfall totals 0.05″ or less.

Low temperatures near 50.

Light southeasterly winds.

Wednesday

Mostly cloudy and mild, with scattered showers likely in the morning, mostly light. Mostly cloudy and turning breezy and noticeably cooler during the afternoon. Probability of precipitation 60%. Likely rainfall totals 0.10″ or less. 

High temperatures will likely occur during the morning with highs in the mid 50s in Pittsfield, Lee and Stockbridge, Adams, North Adams and Williamstown; mid to upper 50s in Great Barrington and Sheffield and; low 50s over the elevated terrain. Temperatures will then drop into and through the 40s over the course of the afternoon.

Light southeasterly winds in the morning, shifting to northwesterly and increasing to 10-15 mph in the afternoon.