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Monday, January 20, 2020

We got a 1 in 3 chance for some decent weekend snows but I woudn't be taking anything to the bank with this upcoming pattern

About 2 feet of snow over the past several days propelled us to another successful MLK weekend as bluebird weather carries us to the finish line. There are times when Vermont can experience long stretches of time with predominantly cloudy conditions. In the case of this week, storminess off the southeast coastline and later over Texas will help promote a sustained stretch sunshine and excellent visibility. Tuesday will be on the chilly side but that aforementioned sunshine and minimal wind will allow 15 degrees to feel relatively comfortable. Another dose of sunshine on Wednesday will push temperatures well into the 20's followed by a Thursday/Friday where we might touch the freezing mark. Don't expect any new snow through the rest of the week but we won't lose much of what has fallen in recent days, especially across the high country.

In spite of the upcoming stretch of sunny dry weather, the pattern across the lower part of North America will be pretty active. The activity will not have much support from the polar jet however which will retreat deep into Canada for the rest of January. New snowfall remains possible between January 25th and the end of the month but with every possible storm we will only have a limited amount of cold weather to work with and will be heavily dependent on an optimal storm path and favorable storm maturation process. The upcoming weekend will present us with the first such scenario as a storm advances from the lower Mississippi Valley to the northeast coast. The absence of the polar jet will allow the storm to move slowly and it is expected to mature well in advance of a potential impact. I am thus and have been a bit skeptical of this system, but forecast models have been moving in the right direction over the past day or two and are suggesting at least something late Saturday into Sunday (Jan 26). I would quantify the various possibilities (roughly speaking) into thirds. 33 percent chance we miss out on the event entirely, 33 percent chance of a minimal 1-4 inch impact and a 33 percent chance for something more significant. Embedded within that "significance" outcome is some serious upside because the storm will be moving slow enough to drop some big accumulations.

Temperatures are expected to moderate back into the "above normal" zone by the end of the week and pretty much stay there for the remainder of the month. The impact of any potential storm during the upcoming weekend will be accompanied by readings in the 20's or low 30's and this should continue in the wake of such a storm. Though we could get a few above freezing afternoons between the 25th and 31st, there are no glaring indications of a major thaw. There are however indications of another storm sometime around the middle of the week. Again, we will need a few of those same things (mentioned above) to go right to score additional snowfall. We are enjoying the benefits of the coldest climatological part of the winter which provides us with a little room to maneuver through a less than optimal pattern. It's not a lot of room though and mixed precipitation or a bit of the "R" word is not out of the question next week.

In the end,  the pattern never did fully flip to a fully optimal scenario and is not expected to through early February. It could remain "good enough" to keep the good times rolling but the AO is expected to remain positive indicating a relatively unblocked arctic. The AO has been positive for much of December and January with the exception of about 1 week. The same can be said for the EPO which is an index measuring, indirectly the strength of eastern Pacific jet stream. It did, as expected, turn negative over the past week but not as much as was initially expected and is now expected to resume what has been a largely positive posture for much of this winter season. The NAO has been a similar story. For the time being I am taking solace in the fact that though the pattern appears a little short of optimal, it is expected to remain out of that disastrous zone. The door will be open (with the storm this weekend for instance) for a few really solid days. Happy MLK day.


2 comments:

  1. Flip of the ole three-sided coinn, eh? :) for once the NWS is more optimistic than you! Im remaining optimistic yet realistic. thanks Josh.

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  2. It looks better today and my update will reflect that !!

    ReplyDelete