Heights will increase dramatically in northern latitudes with a large positive anomaly positioning itself near Alaska/Western Canada, in conjunction with increasingly negative NAO values by the end of this week. The inland runner on Thursday will be a catalyst in terms of changing the upper air regime -- a rapidly intensifying low propagating NE up the appalachains should send temps well through the 50s Wednesday night with even the possibility of some elevated thunder in association with the frontal passage. It's a fairly dynamic storm overall, which should bomb sub 985mb over northern New England Thursday afternoon, before shooting into the north atlantic. This is when the important part comes in -- this powerful cyclone will aid in mechanically forcing a height rise over Greenland and thus sending the NAO negative at least for the time being. The negative AO is able to come about via a weakening polar vortex in arctic -- which by the way, is very likely due to the easterly QBO this winter. Anyway, this regime shift brought on partially by the big, wound-up late week storm will shift the mean trough axis eastward, allowing continental polar air to finally reach the east coast. A couple of models are already detecting a shortwave rolling around the base of this trough and near the benchmark position for this weekend (Dec 5th/6th). Could this short wave produce the first accumulating snowfall in many Northeast coastal areas? That remains to be seen, but the pattern this weekend will be more conducive for snow due to some semblance of blocking upstream. Now, as we head out further into the future, we run into some problems. The ECMWF and GFS to an extent are indicating that the mean trough will retrograde westward into the Plains/midwest after this weekend, allowing the next series of arctic outbreaks to spill into that region initially. This is not surprising and it could very well play out as depicted by the ECMWF for a number of reasons.


Phase 6 right now - expected to return to the "circle of death" for a little while before possibly heading back into phases 5 or 6. But there is no signal for the MJO moving into phases 7, 8 or 1 on any of the modelling, which is a bit disconcerting as those are the more typical phases for sustained troughiness in the Eastern US.


Even heading into phase 7 for the 500m composities, the signal in December is for some SE-ridge resistance. And that does appear to be what the ECMWF is portraying down the road in Days 8-10. Just to clarify, the upcoming pattern will definitely NOT be one that blowtorches the east coast, but at the same time, I'm not confident we'll be very cold either considering unfavorable tropical forcing. The PNA is now progged to decrease to around neutral/slightly negative over the next week which also indicates the retrograding of the mean trough axis into the Rockies/Central US.

In summation -- the next 5 days will be mild, with an intense, warm inland runner Thursday which will aid in forcing the NAO negative. Our first potential snow threat is this weekend w/ a numer of models keying in on a short wave near the east coast. As we move into next week, Dec 7th-12th, the bulk of the bitter cold air should be contained in the Upper Mid-west, although the Northeast will also see some cold air intrusion. However, I'm worried another inland runner or two may impact the region after this weekend's potential snow threat. Overall -- a seasonal temperature pattern through December 15th, with a chance for snow this weekend. Moderate nino climatology says we wait until Jan/Feb for the real fun stuff, but I do think December will offer some snow opportunities as well, just not nearly as cold as it'll be further west.