This time of the year the annual battle between winter and spring gets fully underway. Although we have not had much cold and snow this year, this battle will still take place as it always does. Late tomorrow, cold air from the north and mild air to the south will fight for control over New England. Areas of snow and rain will travel along this dividing line starting late Wednesday and continuing through Thursday.
A storm thousands of miles away will cross the country during the next several days. This storm is going to produce blizzard conditions across the upper Midwest, (see image left) severe weather in the Deep South (see map left) and a mix of rain and snow locally.
The northern part of the storm will be where the heavy snow falls. The southern part of the storm will be where the weather is severe. In the middle, the fight between warm and cold air will produce a swath of precipitation. It's in this middle area, that southern New England will be, and of course this will make for a very difficult forecast.
It appears there will be two shots of precipitation that move across the area Wednesday afternoon through Thursday afternoon. The first shot of snow and rain looks stronger than the second. Meteorologically, these two precipitation events are being caused by different mechanisms, but for most folks, itís just going to be unsettled for about 24 hours.
The first round of precipitation will begin tomorrow in the form of rain and wet snow. Right now, I don't expect any significant accumulation of snow on the roads from Boston south and east through the first part of the evening commute Wednesday. Just to the north and west of the city, some slushy accumulation is possible. Further north, several inches of snow should accumulate and the plows may need to be called out. The best chance for snow will be across the New Hampshire border and further north. The line of accumulating snow, can and will, shift between now and the time the snow and rain begins tomorrow.
As the night goes on Wednesday, snow will further accumulate on the grass, the sidewalks and eventually the roads. The challenge with the forecast is going to be does the accumulating snow get into Boston and points south during Wednesday night? I may be that Newton gets 2, 4, even 5 inches of snow and Fan Pier in Boston has slush. It will be that kind of a storm.
The exact thermal profile of the atmosphere from the clouds down to the ground is going to be critical as to whether or not we end up with just a touch of slush or many inches of snow from Route 128 to the coast.
Some of the other factors, this time of the year, that determine snow accumulation will be, how hard the snow comes down and how much residual heat is left in the roads from the daylight hours. A one degree difference in temperature can make all the difference in the world in these late winter, early spring storms. With the sun higher, it is also increasingly difficult to get snow to accumulate during the day on the roads when temperatures hover around freezing. (this is the case even with clouds)
On Thursday, our second precipitation event will occur. Temperatures look cold enough for snow north of Route 2 and warm enough for rain down towards Cape Cod. In the middle, once again some wet snow will fall, but how much, if any accumulates remains to be analyzed later today and tonight. I am thinking that most of the accumulating snow will fall overnight Wednesday until about 8 A.M. Thurs.
How much snow is possible?
If you were to get all snow, and all the snow accumulated you could see up to 4-8 inches of snow. The most likely areas for those amounts would be to the north of Route 2 and into southern New Hampshire. In Boston, several inches of wet snow is not out of the question. As we have all seen this winter, any forecast of accumulating snow has not materialized in Boston very much. So, with this storm, I am urging patience on snowfall amounts until I analyze a couple of more sets of computer models during the day today and even into early Wednesday morning. We may even have to wait until the snow and rain begin to get a good handle on that exact thermal structure as it runs from Boston to Worcester and 20 miles north and south of that line.
The funny thing about this storm is that if this were not a leap year we would have our third February, since the late 1800s with no measurable snow. The other two years were back in 1925 and again in 1937, neither a leap year. Of course, the way this winter has been going, I wouldnít be surprised if the record is set.
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