Think Snow, Tweet Snow !!!

Tuesday, January 13, 2015

Snowier forecasts and squashed warm-ups - These are a few of my favorite things !

Lots to discuss today as the expected weather map going forward is taking on a fundamentally different look, particularly in the period beginning MLK day and persisting through a good chunk of next week. This is simply one of those days where guys like me look at the Chess Board and come to the realization that its time to wipe the slate clean and start anew. In one of our recent discussions, we talked about, to put it kindly, the erratic performance of some of the medium range ensembles this winter. Specifically as it relates to the weather beyond a week out. The rapidly evolving weather scenario for next week is underscoring this point. I mean even the larger scale ideas that were advertised with vigor only a few days ago have been thrown completely out the window today. There are reasons for this and opinions will vary as to those reasons. Generally speaking, many of the super-warm ideas that have been indicated on some of the long range weather maps have failed due to feedbacks related to that big expansion of snow and ice that we saw leading up the winter. There is simply a lot of cold air that has pooled at the high latitudes and it is fighting hard to move south in spite of whatever weather pattern is present. The Pacific Decadal Oscillation has soared to near record positive levels making it very difficult to position any type of upper ridge across eastern North America for any significant length of time, even when the ensembles suggest as much. And lastly, the presence and absence of the southern branch of the jet has wreaked havoc on the longer range ensembles. The positions of even subtle "ridges" and "trough's" in the southern branch can have a profound impact on the evolution of the pattern. It's really just chaos theory. If you integrate through time and get something significantly wrong 5 days out, even something seemingly subtle, the dominos start to fall and errors magnify exponentially 10 days out.


But none of us should be complaining in this case since the changes should, by in large, benefit our beloved Mad River Glen skiing community. Maybe even those that planned to venture up on the upcoming long holiday weekend and plan to ski on what looked to be a quiet and possibly even mild MLK Day.


So lets get to it. The short run looks dry and on the chilly side. Sub-zero temperatures during each of both Wednesday and Thursday morning will get boosted into the teens Wednesday and 20's Thursday by healthy dose of sunshine. A weak clipper Thursday night, passing well to the region's north will spread some limited moisture and very light snow to the mountain and an inch or two of accumulation by early Friday. Blustery conditions prevail for the duration of Friday and those winds will introduce another night of sub-zero temperatures.


Saturday appears on the chilly side but free of snow. There were hints that some overrunning moisture associated with a push of warmer temperatures might impact the mountain and this will occur but much farther north. Clouds will then increase Saturday night in advance of another, much stronger, clipper system. This particular piece of energy might be capable of grabbing some southern stream moisture as it heads toward the eastern seaboard. If this does indeed occur, the system is expected refocus itself along the coast and intensify Sunday. From there, the system will either head out over the ocean or remain close enough to the coast to spread rain along the coast and snow in some of the elevated interior areas such as MRG. Either scenario means some snow for the mountain Sunday night into Monday since we will either get it from the decaying clipper (a light accumulation) or more from the rapidly intensifying coastal system. All this is a very welcome change from a scenario which was shaping up to have this clipper pass well to our north and potentially spreading mild above-freezing temperatures into the region late Sunday into Monday. In a day or two, I'll have a better idea as to amounts of snow when we know for sure whether or not this storm will come to fruition.


The later part of MLK days into Tuesday Jan 20 looks substantially colder with temperatures only the teens by day and sub-zero by night. This was in a period where the ensembles advertised a potential thaw maybe 3-4 days ago. The other big change involves the southern branch of the stream which continues to look dormant. It is the only real piece of semi-lousy news I could come up with today. We simply can not seem to re-ignite this branch of the jet since it went quiet in late December. Perhaps a slight weakening of the current El Nino has allowed southern stream energy to be less prevalent but I hope to see more activity in the future. The combination however of a much weaker ridge across eastern Canada next week and the apparent continued absence of the southern branch of the jet stream gives the middle to end of the weak a much different look. There are indications of a weather system in the mid-week period (Jan 21-22) but a much weaker one and the good news, a much snowier one since warm-up has been squashed in successive recent runs of model data.


Looking beyond the 22nd, the teleconnection support gets a little better, mainly since the positive NAO will be reduced while PNA ridging in western North America is maintained. We are expected to see a small tightening in the jet stream however which could throw a couple of strong storms into the Pacific Northwest around the time of January 24th-25th. I would expect at least some arctic air to be battling it out with these storms in the last week of January. This feels more like a guess right now given how poorly some of these longer range simulations have performed in the last month or so.

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