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Friday, February 23, 2007

February to end without one drop of rain or ice, March is up for grabs

No ice or rain early next week but although one battle appears won another will need to be fought between the 2nd and 4th of March. As I mentioned in previous posts, we already have one unfavorable force driving the weather pattern which is the general troughing across western North America or the negative PNA, but by early March more teleconnection indicators will turn against us and may have us on our heals by the first full week of the month. I am not at all calling the situation dire as we may yet find ways to fend off most of the trouble through even March 10th, but ominous it remains.

A mainly dry weekend
The airmass this weekend will keep temperatures below freezing, but it is a very stable one. As a result, terrain enhanced snow will be kept to a minimum Friday Night and Saturday and any clouds Sunday will of the high variety and non-snowfall producing. The high winds Friday will diminish somewhat by Saturday and completely by Sunday. Temperatures meanwhile will climb close to 20 Saturday and well into the 20's by Sunday.

Early next week
The situation for early next week has now come full circle. Downstream blocking in the jet stream is now going to suppress much of the moisture from the storm which, not more than a few days ago, was predicted by many models to produce ice and even rain for MRG. This storm is a strong one as it moves out of the Rockies today but the system will mature too quickly and begin to lose steam as it advances into the Ohio Valley. A second low is expected along the Atlantic Coast and spread precipitation into New Jersey or southern New England Sunday night or Monday but this moisture is not expected to make its way farther north. Eventually as the storms original upper level support moves into the northeast, chances for snowfall increase, particularly in the high country. If this occurs, it will not do so until late Monday or Tuesday and we will have to hope that some lingering moisture is there to be had. The chances for any new snow from this "upper level support" continue into Wednesday before high pressure dries it out.

The move into March
I have gotten a lot of emails about early March and for good reason. Typically it is a great time to ski MRG since the base usually peaks in the first two weeks of the month. Using the Mt. Mansfield snow stick as a reference, we look to be in fairly good shape going into March 2007 (above normal base) but things can turn in either direction in a big hurry depending on whatever weather decides to prevail. The events of March 2nd to 4th appear to be one very important "up for grabs" situation. If you type the Waitsfield (05673) zipcode into weather.com you will get a 10 day forecast which advertises rain/snow showers for Friday the 2nd and plain rain showers for Saturday the March 3rd which hardly does justice to the scope of the event. Weather.com 10-day forecasts are derived from The Weather Channel extended maps which are in turn derived from a computer algorithm which takes actual model data and spits out 2-4 word weather answer for the day. It's an impressive process actually that a good friend of mine from college helped to develop and continue to develop. One of the reasons for the blog was to help us skiing enthusiasts dig a little deeper for answers since 2-4 word answers rarely give us the detail we would like to see or an accurate possibility range. The storm late next week could actually turn out to be an intense one and at this time models are suggesting it tracks anywhere between the St Lawrence Valley (ugh !) and the southern New England Coast (better !). The St. Lawrence Valley track would mean ice, perhaps even rain while a track farther south could produce signficant amounts of new snow. The downstream blocking which played a key role in shunting the Monday-Tuesday event southward will shift west and take-up most of the northern Province of Quebec by this time (The NAO is therefore expected to turn slightly positive). I am hoping, even praying that the storm will simply undercut the blocking in Quebec and therefore turn into the snow producer we would all love it to become. I actually do think this occurs to some degree but can't rule out a period of icy precipitation Friday or Saturday as our worst case. Even this worst case would mean a turn to accumulating snow during the weekend.

General thoughts on the pattern in early March
After watching the ensemble data over the last few days I have decided that much of the country will see mild, spring-like above normal temperaures for the first full week in March (March 4th -11th). The exception to this will be the Rockies where a trough will amplify bringing snow to many ski areas there and northern New England which will sit on the southern fringe of colder weather which is expected to remain across Canada. I say this because there are high lattitude blocking mechanisms but barring a change, will be positioned in all of the wrong areas for below normal Eastern U.S. temperatures which goes along with the teleconnection indicators which will be generally unfavorable. The ensembles, warm as they may be for areas of the central and eastern U.S. south of 40 degrees north are not especially warm north of this line and are actually cold north of 50 north lattitude. I therefore think the outcome will be a battle between warm and cold over the northeast and this usually means weather of many varieties over the span of a week. More clarification on this will come next week.

The Quick Summary
One ice storm is avoided early next week, but another close call looms for the period March 2nd -4th as the weather pattern has clearly moved away from the completely favorable mode.

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