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Sunday, January 10, 2021

Light mid-week snow foreshadows excicting late January weather pattern

The weekend has been on the blustery side, but the sub-freezing temperatures were accompanied by decent amounts of sunshine. It's been approximately 6 above average for the first 10 days of January but temperatures haven't ventured above freezing above 2000 feet. This of course means good snowmaking for all of Vermont ski country in spite of the continued lackluster amounts of natural snow. 

We can expect more clouds for the upcoming week with snow flurries for Tuesday and some light snow Tuesday night. The southern branch storm currently producing snow in central Texas was a feature we once had hoped could evolve into a big east coast snow producer. Unfortunately, it will meet a rather embarrassing North American fate, moving off the North Carolina coast Monday night, whimpering as it does and confining light rain to a small area of the southeast. 

Our snowfall forecast has not been zeroed out for the week however, we will just have to be a little patient. A slow but steady push of mild temperatures will certainly help, providing an overrunning surface that will help produce some light snow Tuesday night as mentioned in the above paragraph. I would expect this snow to be pretty minimal but a couple of inches are possible from Smuggs northward to Jay Peak by Wednesday morning. A slightly stronger impulse Wednesday night will then bring another chance for light snow and a better chance for a small accumulation in and around the MRV.  Whatever falls, will be followed by one of the milder days of 2021 Thursday with temperatures potentially eclipsing the freezing mark, especially across valley areas. 

There's plenty of details to unpack regarding the overall weather pattern going forward, which, in short, will produce a lot more excitement. We've had the Sudden Stratospheric Warming (SSW) event and the polar vortex disruption which will be marked by the emergence of a block in the jet stream over the Arctic, strengthening the persistently negative AO. There's been some questions however about how arctic the pattern will get over North America and there are many indications that the strongest area of cold will be trapped on the Eurasian continent. It's already been very cold over portions of Asia with Europe expected to get a healthy dose over the next few weeks. Mid-latitude North America will also get cold but likely not bitterly cold which I think is a preferable outcome since most of us are snow hounds first and cold hounds much later if at all. I will discuss my one concern below but I think the garden variety outbreak of cold for the back half of January will be accompanied by several chances for accumulating snow and the first will come well ahead of any arctic air late this week. 

By Friday, temperatures will be well above average and likely hovering at or even above the freezing mark in the morning. Meanwhile the jet stream will undergoing a very intense amplification. Were we to have a decent focusing southern branch feature to go along with this dynamic looking jet stream, we could be guaranteed of some east coast fireworks. I don't see anything like that now but a feisty clipper system could nonetheless have a rather wild interaction with the eastern seaboard and at the very least will bring a bit of wet snow to northern Vermont during the day Friday. Lingering instability during the Saturday and Sunday of MLK weekend will allow for additional snow showers along with temperatures in the 20's. 

We can expect arctic cold to be back on the playing field the last two full weeks of January beginning around MLK day. There are signals of possible storminess around Tuesday, January 19th and then again around the weekend of January 23rd and 24th. My one concern isn't with the availability of cold but rather the continued and persistent strength of the Pacific Jet. It was a concern going into the season because of the sea surface temperature anomaly configuration in the eastern Pacific and has invariably been problematic through the early part of this winter. As the pattern continues to evolve, and the +EPO pattern restrengthens, will much of the cold and unsettled weather focus on the western U.S. ? Ensembles have been suggesting that both the west and eastern U.S. will share in the snow-wealth in this pattern which, as of now is at least encouraging.

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