The following forecast is provided by Caitlin Wehry, in conjunction with the  instructor, Joe Kravitz, as part of lab work for the Introduction to Meteorology course:

Summary:  Surface high pressure will continue to dominate our weather for one more day, Saturday, and then we are in for a prolonged bout of inclement weather as a series of complex storm systems impact our area from Sunday through Wednesday.

At present, the jet stream remains weak and zonally oriented (east to west). The jet stream lies right over the Northeast U.S. and mild subtropical and cold polar air masses (surface high pressure systems) are battling for control of our weather. The subtropical air won out today and we had above normal temperatures, into the 40s countywide. A weak cold front will move through with nothing more than some cloudiness tonight as the jet stream shifts a bit to the south. Colder surface high pressure (continental polar air mass) behind the front will then nose into the region for Saturday and into Sunday. This will give us a fair and seasonably cold day on Saturday, but it will be 5-10 degrees colder than today. This cold low-level air then sets the stage for an array of precipitation types as the surface low pressure system presently giving the southern Rockies some snow is pushed rapidly eastward by the zonal jet stream, reaching the eastern Great Lakes by Sunday. However, the low will weaken considerably as it moves east and precipitation amounts will be fairly light.

The counterclockwise flow around this low pressure system will bring milder air northward, as a warm front, to the east of the low. As milder air rides up and over the colder air at the surface, clouds and precipitation will develop over our region on Sunday. Initially, the air will be below freezing at all levels of the atmosphere and snow will fall. Surface temperatures will be near freezing in most parts of Berkshire County so the snow will be relatively wet and will not accumulate much. Since it will be a little colder over the elevated terrain and hilltowns there will likely be more accumulation in those locations. Late in the afternoon, as temperatures go above freezing aloft, precipitation will transition rapidly to sleet and freezing rain and, eventually, rain. It is not yet clear whether surface temperatures will go above freezing sometime Sunday night or not until Monday during the day. Right now, it appears that temperatures will be at, or just above freezing during the night Sunday. If it stays just below freezing we could have a little icing, mostly on tree branches, overnight Sunday. However, at this point, since temperatures will be close to freezing, and precipitation amounts will be relatively light, any icing, if it occurs, should not be heavy enough to cause any real problems in most parts of the county (certainly no power outages and the roads should stay relatively clear). The greatest danger for icing is over the elevated terrain, particularly to the north. This situation should become clearer over the next day or so.

A weak coastal low pressure system will develop along this warm front to our south and east on Sunday night which will enhance the precipitation somewhat before it moves east and takes the precipitation with it during Sunday night. At that point we will be to the south of the jet stream (on the warmer side of the jet) for the following few days. Therefore, it now looks like the stronger low pressure system that the long range computer models have been generating will form and track to our north and west. This will leave us more “wet” than “white” as this storm moves through. In fact, it may get quite mild here on Tuesday. In addition, the jet stream will likely not be as amplified as it looked a few days ago. Therefore, the storm should not be as strong and will move through sooner and faster, giving us rain Monday afternoon through Tuesday night before it departs on Wednesday, leaving us with somewhat colder air but only a few snow showers/flurries. So, right now, it is not looking too good for a white Christmas but there is still hope as it looks like we likely will get much colder here by next weekend. At least, hopefully, we will get finals in on time next week.

Friday Night

Mostly clear this evening. There will be a mostly cloudy period as the cold front moves through late this evening into the early morning hours. Skies should clear by daybreak.

Low temperatures in the mid 20s in most locations. There may be some low 20s in the elevated terrain and in North County.

West-northwesterly winds at 5-10 mph this evening, shifting to north-northwesterly after midnight. Winds becoming light by daybreak.

Saturday

Mostly sunny for most of the day. The sun will be dimmed at times as high clouds increase later in the afternoon.

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 in the elevated terrain and hilltowns.

Light northerly winds.

Saturday Night

Becoming overcast. There is the slight chance of a snow shower near daybreak. Probability of precipitation 20%.

Low temperatures in the mid 20s will occur early and then temperatures should rise into the upper 20s as the cloud cover moves in. It should fall to the low 20s over the elevated terrain and then rise to the mid 20s overnight.

Light northerly winds early will shift to light easterly late in the evening.

Sunday

Overcast with occasional light snow or snow showers developing during the morning and continuing into the afternoon. Precipitation should change rapidly to light sleet and then light freezing rain late in the afternoon. It may change to rain in South County by the end of the day. Probability of precipitation 80%. Snowfall accumulations will be an inch or less in the lower elevations. There could be as much as two inches over the elevated terrain and possibly three inches in a few isolated spots over the elevated terrain to the south and east.

High temperatures will be near freezing in most locations with low 30s in Pittsfield, Adams, North Adams, and Williamstown, low to mid 30s in Great Barrington and Sheffield, and near 30 over the elevated terrain and hilltowns.

Light easterly winds in the morning will shift to southeasterly and increase to 5-10 mph during the afternoon.