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Sunday, December 31, 2006

New pattern January 10th but with plenty of hurdles

I was hoping that a New Years eve update would be filled with much better news, not so much for the first full week of January but beyond that in particular. I unfortunately do not have very good news but instead filled with more consternation. First we have to contend with another non all-snow event and by the looks of the most recent model updates, we may be hard-pressed to see any snow until January 2nd. I have been watching the period after January 10th very closely since the Arctic Oscillation has shown signs of a shift. What has been confirmed in the last two days is that there will be mechanisms developing in this newly emerging pattern that will bring arctic air back into North America and get several regions of the country very cold. Still we are presented with problems even after our return more seasonable temperatures begins next weekend.

New Years Day Storm
I have looked at all the temperature profiles concerning our upcoming new years storm and am not encouraged. It is unlikely, based on the latest data that we will see any signifcant accumulation of snow Sunday Night before the changover to freezing rain occurs; instead, after perhaps a little snow, there will be a period of freezing rain that may in fact go to plain rain before ending sometime New Years Day. We won't see much of a snow melt with any rain that falls as it is not expected to get much above freezing. We should see some snow as the upper air environment becomes more favorable Tuesday.

Mild weather late next week
It then becomes mild as we head into the end of next week. It would still be a little early to be too definite but record warmth is a big possibility at least on one day late next week. Records (the warm version) in northern and central Vermont in January are defined by 40's across the mountains and 50's in many of the valleys. The unfortunate part of mild weather in the northeast, at least for us skiers, is that a return to colder weather is usually preceded by rain. This too is not a definite for next week but appears very possible either on Friday or sometime during the weekend. The return to more seasonable weather which will follow this onslaught of warmth will mark the beginning of a somewhat new regime, but what excactly will it be and how much will it benefit New England remains to be seen.

The January 10th change
Changes in the Pacific are what look to finally bring arctic air deep into North America. One of the many features that has been a fixture in this most recent pattern is a deep trough situated across western Alaska. This feature will be removed by next weekend and looks to be replaced by a ridge which will extend from the mid-lattitude Pacific up to the poles. This in effect will act as the mechanism for the southward transport of Artic air and if this feature emerges as advertised much of Western Canada and the eastern Rockies stand to get a huge onslought of cold as we head toward the middle of January. Indications are that some of this cold gets transported east but the ridge-trough position is not shown to be favorable for the eastern states to maintain a healthy stream of colder temperatures. Such a pattern would instead favor outbreaks of below normal temperatures interlaced with brief outbreaks of milder temperatures. It is a pattern one would normally see more of in a La Nina as opposed to a El Nino year and I am somewhat skeptical that as we get closer to this January 10th target date, some of the changes and consequences of these changes are handled differently by the models.

Quick Summary
Still signs of a change on January 1oth but many undesirable events await us next week.

Friday, December 29, 2006

Real change may come by January 10th

The positive AO pattern which has prevailed since early December continues to reign supreme, but in the last few days we have made the most out of a rather lousy situation. First we managed to get some snow, a concept which has lately seemed quite foreign. Although the snow was wet and was interlaced with periods of drizzle, we did manage to sneak some cold into the area in the wake of this storm system. I would define this as relative cold since it has moved temperatures to within a few degrees of normal after over 2 consecutive weeks of much above normal temperatures. In the larger view, we have not changed the pattern and in my view it will continue to haunt through most of next week. There are hints of changes however in the overall pattern that could very well manifest itself as early as the first full weekend in January. By January 10th, the ever-so-stubborn AO index may finally get turned on its head and begin to work in our favor. We still have a ways to go and a storm to talk about this weekend, but if we can flip the AO for the middle and end of January while keeping the southern branch alive, we could be looking at a dramatic and much needed turn-around in the skiing at MRG and the rest of the northeast.

Normal temps this weekend then snow then ice for New Years Day

The normal temperaturatures across normal which again will feel quite cold in a relative sense is a result of a large confluence area in the Jet Stream which is emerging in the Canadian maritimes. Whatever cold air is available in the eastern part of Canada is therefore driven southward as a result of this feature and our very battered northern New England skiing industry will get a much needed stretch of below freezing temperatures as a result. Impulses running through this fast moving Jet Stream will also provide some help. This occurs Saturday as wave will likely be the catylist for a few light and fluffy inches of snow.

The real precipitation producer though comes Sunday. The track of this system is a concern only because the storm arrives as the once cold air becomes stale and modifies; otherwise we might be in light healthy thumping of snow. Instead, precipitation will begin as snow and likely to change sleet and freezing rain. Although the cold air is stale it will be difficult to flush out the below freezing temperatures in many areas so I would not be surprised to see some icing in this case, particularly early on New Years Day. A prolonged break in the action then occurs for the duration of the day Monday during which conditions will remain cloudy along with some drizzle. The upper air system then comes to the rescue, cooling the atmosphere and providing perhaps a few inches of snow for Tuesday. Its not an ideal situation by any means but my gut feeling here is that most of the heavy precipitation occurs before the atmosphere is capable of supporting plain rain Monday although the ice is more than a possibility.

Mild weather and maybe rain targeting New England late next week

Whatever snow does fall early Tuesday will not officially get us out of the woods. The pattern is still being driven by the very adverse positive AO and indications are that there will be another push of much above normal temperatures later next week. We were able to escape a potential warm-up which was originally slated for late this week and we will have to pull another rabbit out of the hat if we intend to escape another round of potentially very mild weather and ultimately some rain late next week. To be honest, it will take quite a tap dancing performance to get us out trouble late next week. We may avoid 1 or 2 of the mild days the models are currently advertising but at least one day of above freezing temperatures along with some rain is a good bet. Models indicate that this occurs next Friday although I would expect some shifting in the predicted outcome.

Pattern change speculation

By late next week, there will be so much warm air piling up at Jet Stream level across Eastern North America that it will attain some fairly significant “ northern hemispheric” significance. It is also expected to get shoved eastward and what we are hoping for is that this area of warmth at jet stream level can get gradually pushed toward the northern latitude Atlantic Ocean thereby working as a block in the jet stream and changing our destiny for the better. Such an occurrence will shift the North Atlantic Oscillation to negative. By January 10th, the American Ensembles switch the sign of the Arctic Oscillation to negative which would end a devastating 6-week stretch where the index has been positive. This solution has not gotten the full support from the European Ensemble package as of yet but even the European shows some degree of change with the AO by 2nd week of January. There are no immediate signs of arctic cold air for the weekend of the 6th and 7th of January or “significant” snowfall. There are indications of a cool-down however and further indications that this might be the first step in a process which could lead to more serious cold by the weekend of the 13th or 14th of the month. Like I mentioned in the opening paragraph, if we can successfully make these changes while keeping the southern branch awake it will represent a very appetizing scenario for us. Lets hope !

The Quick Summary

A little snow and an icy mixture of weather around New Years day and then some more warm weather late next week, but a more significant pattern change may finally beginning to emerge.