I've seen a few good "cold holes" over the last 15 or so years across North America. Most recently they've been occurring out west over deep snow cover in the darkest months of the year such as December or January and out of the way of the jet stream. They happen in New England as well under many of these same circumstances with the critical contributing factors being very little wind, deep snow and low sun angle. Though the shallow layer of cold is decaying and might look especially impressive on a weather map, there simply aren't enough daylight hours to burn through the inversion. It's not cold enough to snow because of the air just above Mt Washington, but it's cold enough at the surface for sub-zero temps and in the case of the most recent week, a rather excellent week for skiers following the snow on Christmas Eve.
The inversion fell apart early Saturday over the Champlain Valley and is slowly doing so over the rest of Vermont and unfortunately temperatures are supporting rainfall for Sunday into early Monday and quite decisively. Models indicate a period of light rain perhaps as early as very late in the ski day Sunday and then the question becomes how heavy the rain might get Sunday night into early Monday. Most of the data I've seen suggests less than a half an inch with the heaviest rain staying to our south and east. A higher resolution run of a shorter term model did show over an inch Sunday night though it remains the outlier not the consensus. Temperatures are again, not expected to get excessive while the rain is falling, hovering around the 40 degree mark through early Monday. Westerly winds late Monday and into Tuesday (New Year's Eve) will likely bring the mildest period we will see in the period between late last week and mid January.
Now on to the better stuff. Cold air will remain in short supply as the next and very legitimate storm system approaches in the last hours of 2024 yet I think we can squeeze a decent elevation sensitive event out of the whole deal. We need the storm to track favorably and the storm to strengthen in such a way that it can manufacture an environment conducive for snowfall. We've seen a bunch of these events in recent years and they are quite common later in the winter season. Surface temperatures in valley areas are indicated to be a bit too warm initially to support snowfall and I am not so sure they support snow over the mountains until precipitation becomes heavier early New Year's Day. As the day progresses however, atmospheric cross sections look better and more supportive of snow. I want to be careful not to get too giddy about it since models aren't projecting hefty amounts of snowfall, I have to show some respect for the data. That said, this is certainly a setup that could produce 1-2 feet above 2,000 feet while valley areas are relegated to a few gloppy inches. By later New Year's Day into the evening and then into Jan 2, temps might get cold enough for snow conditions to dry out some on the highest areas of the mountain.
The New Year's elevation event marks the end of mild threat with the ridge in eastern Canada forecast to weaken and the fundamentals increasingly supporting colder weather. We won't see excessive temperatures through the first full weekend of the month/year and this should aside from keeping the comfort level in check on what should be some windy days, also keep the snow threat alive from weaker disturbances and Lake Champlain enhancement. Models/ensembles have been signaling a potential significant event between Jan 6-8.
The first half and I hope more of January just looks terrific. Anchored by my favorite tag team of negative EPO and AO indices where the jet in the Pacific appears tranquil and then more blocked in the arctic regions. The risk in January is that storm track shifts too far south but with the Great Lakes and Lake Champlain remaining mostly ice-free, I wouldn't have my money on a dry cold.
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