Happy 1st of December to everyone and its an exciting time in the world of weather blogging because it's an exciting weather pattern. Those that may have followed some social media banter may have noticed that I've voiced some disagreement, mainly regarding the interpretations of what might occur in this jet stream structure. It might sound like a "downplay", but its not. We are headed toward a terrific weather pattern for east coast snow but there's been a considerable amount of hype for extreme early winter cold and I've been repeatedly suggesting that this is a misinterpretation. I would reiterate that today. This is a pattern conducive for east coast storms not so much extreme cold. The big picture weather pattern tends to be dominated by the elephant in the room and that elephant will be the formation of a large Greenland jet stream blocking structure, capable of sending the NAO toward a -2 index which in a historical context is quite intense. I do expect some garden variety chill to maintain a grip on much of New England for the two week period beginning next Wednesday 12/7 and persisting at least through the winter solstice but temperatures should stay within a standard deviation of normal (generally ranging from 8 below normal to 2 above). At the very least it should consist of an extended period of sub-freezing temperatures which will allow both natural and artificial snow to accumulate a healthy base.
There are still a few ugly details to get through, but after yesterday's wind driven abomination, the time left before we begin our extended stretch of winter weather is getting smaller and smaller. I noticed at dusting of snow at MRG Thursday but whatever falls will get obliterated by one final torch this Saturday. We should see a nice day Friday with sunshine and temperatures in the 30's before clouds, milder temperatures and some rain arrive for Saturday with readings besting 40 up on the mountain and 50 in the valley's. It should be the last we see of that for a while.
Colder air won't completely take over for early next week, but will be involved enough to at least make things interesting for our next weather system on Tuesday December 6th. It doesn't look cold enough throughout the lower troposphere for snow but it does look like it could be cold enough at the surface for sleet and a bit of ice. I don't expect temperatures to venture too far above freezing during the day Tuesday if at all (on the mountain) and drier, colder early season arctic air will then build across the region Wednesday. Tuesday's weather system will be the first to get trapped underneath the building Greenland block. Recall last year when we could never trap systems in the Canadian maritimes and we lost out on opportunities for additional snowfall as a result. This pattern will produce the opposite and will feature storms spinning in the Gulf of St Lawrence/Newfoundland region for days and days. Tuesday's system will do that and although Wednesday might be dry, we could see moisture return later in the week in some form presenting the Green Mountains it's first opportunity for snowfall with the new regime.
Alright, now I get a chance to talk more about this weather pattern, a blocked weather pattern supported disproportionately by the -NAO or a downstream block over Greenland. In my opinion there has been an irresponsible level of cold weather hype for this pattern though there is little historical correlation between a weather pattern supported almost entirely by a -NAO and bitterly cold arctic air. Ensemble data really doesn't suggest it either but it has not stopped folks from predicting extreme temperatures. I should expect we see some garden variety below normal temperatures, likely peaking around the 9th and 10th of the month in New England, but I don't think the cold weather will be especially distinctive this month or during this pattern. Storminess ? Now that's a different story. I would never belittle a -NAO, I just think it's misunderstood sometimes. The most defining event of the 21st century so far, Superstorm Sandy struck the northeast and in October of 2012, a month that featured an aggregated -NAO measured at -2 (similar to what is expected in the coming weeks. So, I think the hype is misguided and should be focused on storm potential and not cold and I would not at all want to understate the former in this type of setup.
How will such a storm happen and when ? That's why weather forecasters get paid the big bucks, to be as vague as possible ! But actually, we can come up with some idea. Though we don't have a ton of support from the other teleconnection indices, we do have a little, particularly in the Pacific where jet stream energy is expected to continue undercutting a ridge trying to establish itself in the north Pacific. Such a feature would allow storms to enter the southern Rockies and then gather moisture from the Gulf of Mexico while the -NAO helps to keep the storm track south. We can add this to what was discussed earlier, the potential for storms and moisture getting wrapped up in the maritimes of Canada and perhaps even getting sucked westward underneath the blocking to the north. It's not out of the realm to see snowfall from moisture entering our picture from regions several hundred miles northeast of us in Canada. It's an atypical situation, but very typical in a pattern like this. The downside and unusual in December would be for the storm track to remain southeast of us as it has done in months like February of 2010 (until the end). So, stay tuned this could get interesting.
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