Berkshire County Forecast-Thursday, February 21

Summary: The computer models have begun to diverge on their solutions to this weekend’s storm. Just on the basis of precipitation totals being generated by the models, we could get anywhere from a few inches of snow (European-ECMWF) to 6-12″ (American-GFS) to 2 feet (American-NAM). However, you are counting on me to use my experience and knowledge of the atmosphere to try to sort this out (since mathematical models can’t “think”…theoretically). So here goes…..

I think that my suspicion yesterday (see CAVEAT) that the set-up in the atmosphere for a big snowstorm did not look right will probably be correct. To begin with, I do not think the NAM model solution looks realistic so, for now, I am going to disregard it and concentrate on the two models which look more realistic and tend to be more reliable with winter coastal storms (ECMWF and GFS). The disturbance in the jet stream which will be responsible for generating the surface low pressure system along the coast looks to be weaker than it did yesterday. Upward motion and the surface low should be relatively weak which should limit precipitation rates somewhat. It will also take a while for the storm to get going so that by the time it “intensifies” much of the precipitation will be to our south and east. In addition, in part because of the weakness of the coastal low, above freezing air will likely sneak in aloft (about 5000 feet up) for a time Saturday evening and turn the snow to sleet. This will almost certainly happen in South County, possibly in central Berkshire as well. This will limit snowfall totals further. Also, temperatures at the surface will be close to freezing so the snow should be fairly “wet”, limiting accumulation as well.

The timeline looks like this: Steady precipitation should not begin until Saturday evening. There may be some widely scattered snow showers during the day on Saturday, but nothing more than that. Steady snow should begin sometime Saturday evening and continue into Sunday morning. The snow will vary in intensity, mostly light to moderate. Snow will likely change to sleet in South County during the evening, and stay sleet til well past midnight. It may change to sleet for a time in central Berkshire as well. It will likely stay all snow in North County. By the time the “storm” ends on Sunday I think the most likely snowfall totals will be as follows: South County 1-4″, central Berkshire 3-6″, North County 4-7″. Expect the higher totals in these ranges to be over the elevated terrain and where/if there is less sleet. These estimations are somewhat of a guess at this point since the “storm” is somewhat complex and fluid and still 2-3 days off. I will continue to update this forecast…..

Before this mess arrives we should have a fairly tranquil end to the work week as surface high pressure builds in, briefly, on Friday. However, clouds will begin to build in during the afternoon and overnight.

Thursday Night

Partly cloudy this evening, becoming mostly clear after midnight. Winds will diminish (finally) and it will be quite cold.

Low temperatures in the low teens in most locations, upper single digits over the elevated terrain.

Northwest winds at 10-15 mph in the evening will diminish overnight, becoming light northerly toward morning.

Friday

Mostly sunny, with only some high, thin clouds in the morning. Increasing clouds during the afternoon. Much milder than previous days.

High temperatures in the mid 30s in Pittsfield, mid to upper 30s in Adams, North Adams and Williamstown, upper 30s in Great Barrington and Sheffield, and low 30s over the elevated terrain and hilltowns.

Winds light and variable.

Friday Night

Mostly cloudy to overcast, with only the slight chance of a snow shower or flurry.

Temperatures will not drop much with the cloud cover. Low temperatures in the mid to upper 20s in most locations.

Light southeast wind in the evening, increasing to 8-12 mph by morning.

Saturday

Overcast with the chance of a snow shower through mid afternoon. Light snow or, possibly sleet in South County, is likely to develop sometime late afternoon or, more likely, in the early evening. Little if any accumulation expected by dark.

High temperatures in the mid to upper 30s in most locations with some low 30s over the elevated terrain.

East-southeast wind at 10-15 mph.