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Sunday, January 13, 2013

From very mild to very cold in the span of a week

It's always darkest before the dawn and Sunday's 40-plus temperatures marks the peak of what should be our bleakest period this month. Honestly though, this stretch of mild weather could have done even more damage. 2-weeks ago I was honestly concerned that the pattern would produce multiple days of 50-degree temperatures and some heavy rain to go along with it. Much of the rain with the approaching cold front will actually occur in the Midwest and across the Canadian provinces of Ontario and Quebec. A minimal period of rain in the pre-dawn hours Monday morning will probably amount to less than a quarter of an inch and falling temperatures should finally end the snow melt. The SCWB, in some previous posts, had teased about wintry precipitation resulting the one or two waves of low pressure that are expected to form along the suppressed stationary boundary in the coming week. This boundary however will be further south however and forecast for the coming days is substantially drier and colder.

The remaining base will obviously have hardened considerably as temperatures fall. The sooner we can get some new snow, the sooner we can forget about the past few days. As was indicated via twitter, we are headed from one extreme to the other as the pattern will go from one that supported mild weather to one that will support very cold weather. The arctic air will come in the form of a teaser blast late this week before the motherload arrives next week. It seems like it has been forever but at least for a short time, the prevailing negative NAO will align itself with a positive PNA or west coast ridge. This will ultimately lead to a widespread cold outbreak for the eastern United States and conditions will be especially cold across New England beginning Friday and persisting at least a week. Within this stretch we will mostly have to depend on clippers or quick moving upper air disturbances rotating through the polar jet. The first such system comes Thursday with the initial teaser blast of cold. We may only get an inch or two out this and perhaps even less if we are unlucky but this should be the first of many chances. Two clippers, one over the weekend and one marking the bigger arctic outbreak early next week both should bring some new snow to the mountain. One of these two clippers could also blow up into something more significant upon interacting with the Atlantic coast.

Big snows come to Vermont once you add the southern branch of the jet stream into the mix. The southern branch gets involved when it undercuts the ridging in the Pacific. We don't expect this to happen over the next 10 days or so but beyond 10 days (beyond January 24th), it does appear more promising. We will continue to have at least weak support from the AO/NAO combination through the rest of the month but we do lose the support of the PNA. This will cause the arctic air to relax its grip on the region but allow for more storminess in the pattern.

3 comments:

Kristen S. said...

I was distressed to read on the MRG Facebook page that this weather caused them to shut down. Hopefully this influx of cold air will stick around and some snow will fall and they'll get back up-and-running!

More Cowbells said...

tomorrow's mini-feature will hopefully get us back on the road to recovery...

city said...

thanks for share..