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Friday, March 6, 2009

Rain and warm temps in the short term but winter's return is less than a week away

It is not a very exciting short term forecast and hardly worthy of another update. Friday's milder weather would be nice if we can get in on the sunshine but that may not happen until later in the day. Over the weekend, the real spring-thaw will be confined to the mid-atlantic and southeastern United States while Vermont will be in no-man's land, or stuck in the middle of a broad south to north temperature gradiant. The winter-like cold will have retreated deep into Canada and as moisture arrives from the southwest it will fall as rain. Steady precipitation is probably not going to begin until after the ski day Saturday (although we may get a shower early). This particular weather system has an elongated zone of overrunning that will extend across half of the country Saturday night. This will mean light rain into Sunday morning before the area of moisture sags south and seasonable temperatures settle into the region.

Rain Saturday, more rain/snow possible Monday and perhaps another next week
Saturday nights rain will mark the first of three occasions where precipitation will impact central and northern Vermont during this stretch of mild temps. The first two chances at precipitation are from more or less one interconnected system, which, after a dry period Sunday will threaten to bring more precipitation on Monday. Again temperatures will be a shade above freezing although in Monday's case we could see some snowfall on the upper part of the mountains. If you have been lucky enough to distract yourself from some of the dismal economic news and have tuned into what has happened weatherwise across the country you might have noticed the big snowfall totals in the Sierra Nevada mountains and other locations across the west. The unsettled weather has certainly focused itself out there for now and it means a series of west to east moving storm systems, the strongest of which approaches Vermont Wednesday. There are strong indications that this system, like its predecessor will bring a mild air northward as it tracks into Quebec and the result will be another round of rain or perhaps some ice. Fortunately this system will be a quick mover and its passage will mark the return of winter.

Winter's return

The ensemble information from our friends at the ECMWF (Europe) has really amplified on some of the ideas proposed in the last post. There are now overwhelming indications that the NAO will move decisively negative by the weekend of the 15th. When the NAO turns severely negative, an "Omega-block" often forms in the jet stream across Greenland and there is growing evidence in the forecast of such a feature. The feature may in fact become so strong that will extend to the poles and will thus turn two teleconnection indices to the pro-winter side of the spectrum. The weather as a result will swing back to the colder side of normal across New England and a few days between the 13th and 20th of March could very well be much below normal. There is yet to be any glaring signs for a big storm and in the next update perhaps we can identify a few opportunities for powder, but it would to early to venture down that road. For now however it would be fair to assume that winter will make a return and the powder days should join the party.

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