As storm develops off the coast, New England sees limited effects
Posted by Matt Noyes November 4, 2009 at 9:09 am
Though a storm will develop off the New England coastline Wednesday night and Thursday, rapidly strengthening and becoming an impressive storm Thursday night, the storm center will keep moving – remaining progressive enough to spare New England from the bulk of its effects. Of course, that doesn’t mean the Northeast will go totally unaffected…
Wednesday satellite and radar imagery depict a well-defined, energetic disturbance moving east across the Ohio Valley. Showers have been scattered and splotchy with this energy center, owing to limited moisture in the atmosphere, but the intense energy will become a key player in the forecast as it nears the Mid-Atlantic coastline, spawning storm development over the warm waters of the Gulf Stream Wednesday night into Thursday. At first, this will mean only increasing clouds Wednesday night after a day of sunshine, with those new clouds dropping a few light rain and snow showers in Western New England Thursday morning, with most of the snowflakes limited to the higher terrain of the Southern Greens and Berkshires. Through Thursday, with the ocean storm strengthening to our southeast, there will be a weak interaction between the primary Great Lakes storm pulling into Canada, and the new storm developing off the coast. This interaction will be the result of energy and cold air moving directly over New England high in the sky, and will be evidenced by a weakness in the barometric pressure field near the surface, forming a “trough” of low pressure. In this instance, the abundance of cold air aloft, milder air near the ground, intense atmospheric energy, and a defined shift in the wind representing the trough, will combine for the development of a “Norlun trough” – known to bring bursts of rain and snow northwest of a developing ocean or coastal storm center. These bursts of rain and snow will grow heavier and more widespread as Thursday afternoon wears on, and will continue Thursday night and early Friday morning. As the ocean storm strengthens, air will rush toward its center, causing the wind to shift direction from a southeast wind early Thursday, to a north and northwest wind overnight Thursday night. This should allow enough cold air to surge southeast across New England to bring the rain/snow line southward and lower in elevation, from the mountains of New Hampshire, Maine and Vermont, all the way to Northeastern Massachusetts early Friday morning, where a few snow showers may begin the day! Regardless, the storm would be quickly marching away from New England at that point, and these more southern areas would be less likely to see any significant consequences of flying Friday flakes. By Friday afternoon, the new, chilly air coming in would be dry enough to break sunshine back out with an active wind producing wind chill values in the 30s…then another cool but dry day on Saturday. Warmer air will push toward New England Saturday night, sparking cloud development and scattered showers of rain south and snow north overnight Saturday night, but leaving morning clouds to break up by late morning Sunday, with warmer temperatures for Sunday afternoon.
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