Berkshire County Forecast-Monday, Dec. 15

Our low overcast and small temperature range will persist for the foreseeable future, as a strong temperature inversion in the lower levels of the atmosphere (50°F at 5000 feet) prevents vertical mixing and the low sun angle and cloud cover prevent any heating of the surface. Meanwhile, a weak surface low pressure system over the Midwest will drift slowly northeastward through the eastern Great Lakes over the next few days. The occluded and cold fronts extending southeastward from the low will move through our area Tuesday evening. The associated precipitation will be predominantly in the form of rain. However, surface temperatures will be close to freezing in the higher elevations so there may be some pockets of freezing rain there. 

As a secondary surface low forms along the front junction between the occluded and cold front in the Gulf of Maine on Wednesday, the northwesterly flow around this low will produce some “wrap around” and lake enhanced showers during the afternoon on Wednesday. Temperatures will be cold enough aloft for these to be snow showers but the boundary level temperatures may be warm enough in the lower elevations for wet snow mixed with rain or even plain rain. Even in the elevated terrain snowfall accumulations should be less than an inch.

After this, the polar front (boundary between cold air to the north and warm air to the south), which is weak and zonally oriented (west to east) for this time of year, will stall well to our south, and very weak surface high pressure will build in from the north and west. As a result, temperatures will be seasonable and the weather will be dry until at least Saturday. The inversion will be gone so, hopefully, we will get some sunshine. However, with the jet stream in its weak and zonal form, systems will be weak and, thus, sunshine is unlikely to be bountiful.

It looks like a surface low will develop along the polar front on the Gulf Coast Friday night and early Saturday and then move off the North Carolina coast Saturday night. Right now, it appears that, with the jet stream having such a zonal orientation, the trough in the jet stream wave pattern responsible for generating this storm will remain fairly “flat” and non-amplified so that the storm will have a tendency to move more east than north and well off the coast to our south. However, given that this event is six days away, the track of the low is still uncertain….I plan to update this on Wednesday.

Monday Night

Overcast.

Low temperatures in the mid to upper 20s, upper 20s in South County and mid 20s over the elevated terrain.

Winds light and variable.

Tuesday

Overcast and seasonably cold. There is a chance of a little drizzle or a few sprinkles, particularly during the afternoon. Any light precipitation that falls will likely be freezing drizzle over the elevated terrain and there could even be a few pockets of freezing drizzle in the lower elevations.

High temperatures in the low to mid 30s in Pittsfield, Lee, Stockbridge, Adams, North Adams, and Williamstown; mid 30s in Great Barrington and Sheffield and; near 30 to low 30s over the elevated terrain.

Light southeasterly winds.

Tuesday Night

Rain and showers developing during the early evening and continuing off and on throughout the night. Temperatures will be close to freezing in the elevated terrain where the precipitation may fall as freezing rain during the evening hours. There may also be a few spots in the lower elevations in central and northern Berkshire where the precipitation begins as freezing rain as well. Precipitation should become all rain as temperatures rise above freezing after midnight, even over the elevated terrain. Probability of precipitation 90%. Likely rainfall totals 0.25″-0.40″. Likely ice totals over the elevated terrain around 0.10″ in spots.

Steady temperatures in the evening, near freezing over the elevated terrain and low 30s over the lower elevations of central and northern Berkshire and low to mid 30s over the lower elevations of South County. Temperatures should rise above just above freezing in the elevated terrain after midnight so that temperatures should be in the low to mid 30s everywhere by morning. 

Light easterly winds in the evening, shifting to northwesterly by morning.

Wendesday

Overcast with a few scattered rain showers likely early. Some mixed rain and snow showers are likely mid to late afternoon. These showers should be all snow over the elevated terrain and mixed rain and wet snow in the lower elevations. Probability of precipitation 60%. Likely rainfall totals 0.10″ or less and there may be a dusting of snow in spots over the elevated terrain late.

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

Light west-northwesterly winds in the morning, increasing to 5-10 mph in the afternoon.