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Boston Weather: 54.0°F | Overcast

Weather: Weather on a Hair Line Trigger

By Greg Lawson
Staff Meteorologist

An overhead front is being held stationary by two out of phase high pressure systems, one to the northwest of the front up in Ontario and Quebec, the other to its southeast out over the Atlantic east of the Delmarva area. The front is the leading edge of a large trough of very cold air which originated in western Canada. As the edge is held stationary it will be able to support small waves propagating northward on it, much like a taunt guitar string. One such wave is now rapidly approaching the northeast, and a broad low over Texas will soon likely feed the front another wave. Predicting whether these short waves will bring us snow is a delicate matter of predicting the pull-and-tug effects of the two highs on the front a matter of a few hundred kilometers could make all the difference.

The National Weather Service is officially forecasting an 80% chance of precipitation for today, with accumulations of snow around one or two inches. I believe that there will definitely be snow in the afternoon, but no more than an inch, and perhaps some light rain in the morning. As the high out over the ocean drifts eastward and as the Canadian high is pushed eastward, the stationary front will begin to slowly drift southeastward, ensuring we will be on the cold side of the trough. Temperatures will drop steadily during the day tomorrow leaving us with a blustery night and a frigid Thursday. The second short wave will arrive Thursday evening sometime and threatens yet more snow. It may only be rain, however, thanks to the Canadian high passing to our north and bringing in relatively warmer air from off the ocean with its easterly winds. The easterly wind will help to warm things up a bit on Friday and hopefully bring us a less active weekend.

Wednesday: Temperatures dropping. Light rain in the morning giving way to snow in the afternoon. Accumulations of an inch at most. Northerly winds with speeds increasing through the day. High early on of 37F (3C).

Wednesday Night: Blustery. Snow will stop, but persistent winds to continue. Bone-chilling low of 14F (-10C).

Thursday: Frigid. Winds shifting to northeasterly. Chance of snow throughout day, but most likely in late evening. High of only 21F (-6C), which is also the nighttime low as a warming trend begins.

Friday: A bit warmer. Snow or rain will slow and stop. Easterly winds. Highs in the low 40s (5-7C).