Tuesday, February 23, 2010

Largest Snowfall of 2009-2010 Winter Looming

The largest snowfall for the Grotonweather.com area is on our horizon. This storm has consistently been on the models since Saturday, and I've just been waiting for it to become obvious that it won't happen. Over the past day and a half, I began to believe that this storm actually was going to happen, but the models remained inconsistent with the timing and exact location. There are still plenty of uncertainties to be figured out, but its time to start nailing down the seriousness of the storm. My main concern is not how much snow actually falls, but rather the blowing of the snow as the low explodes to our southeast. It will be a significant snowfall too, probably on the order of about a foot, but winds will make it seem like its snowing even heavier with near zero visibilities at times. Lets take this storm one aspect at a time.

Overall Pattern:
Low pressure is developing off the Southern New England coast this evening and tracking north. This is not the main storm. As it moves north, it will run into a sprawling area of high pressure and begin to weaken. Meanwhile, an upper level trough will dig into the eastern third of the county. This will create prime conditions for explosive storm development off the coast yet again. This low will absorb some of the energy from the dying low and continue to rapidly intensify. As it moves north towards New England, it will encounter that same high pressure, and begin to move more westerly. Over time, the storm, which still wants to move to the northeast, will do a loop over Southern New England and Southeastern New York, before heading out to sea.

The snow will being to work into our area sometime in the morning Thursday and become heavy into the afternoon and evening. The snow will taper off in intensity Friday, but will still be around. By Saturday, everything should be pulling out, making the total time of this storm somewhere around 36 hours, with probably 12 hours of the heaviest snow.

Snowfall totals are still a bit up in the air. I am concerned that warm air wraps around the system and causes a variety of precipitation types. The further to the west this storm comes, the more a concern that is. If we did change over to rain for a while, it would be later Thursday evening most likely. The models are not in agreement with whether or not this will happen, and it will have huge impacts on the total snow fall from this storm. Assuming an all snow event, which I think it probable at this time, snow fall totals should end up around a foot, give or take a couple inches. Expect a snow map Wednesday evening.

With the low pressure coming into Southern New England and even Eastern New York, winds will become quite strong. Winds could be sustained near 25 mph for a time Thursday afternoon and evening with higher gusts. With the heavy nature of the snow, this could cause some tree damage and power outages, not to mention near zero visibilities and large snow drifts.

Temperatures during the storm should stay in the upper 20s and low 30s for Thursday (mid 30s if we change to rain, but I just am not seeing that) before dropping off a bit Friday.

Stay tuned for the latest, as I will be tweaking this forecast over the next 24-36 hours. I will try to get a forecast video done tomorrow evening.

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