A two part weather system over the next twenty-four hours will bridge leap day and March. Snow and rain will start the new month more like a lion than a lamb. Part one, a burst of precipitation for this afternoon and overnight, mostly in the form of snow. We are right on the rain-snow line with this event so accumulations will differ greatly depending on your exact location. This is not going to be a storm where everyone ends up with the same amounts. There will be a big difference in snow totals over very short distances. For example, the North End of Boston may see 1-2 inches of snow increasing to 3" as you start moving west towards West Roxbury and Newton. We will have to watch temperatures hour by hour even 1/2 of a degree is going to make a big difference in what accumulates. It's that tough of a forecast.
A storm that produced blizzard conditions across the upper Midwest is sending a shield of precipitation eastward today. Snow is now falling across much of the region, if It began as rain in your area, it will change to snow. The extreme south coast will stay more rain than snow. It looks like even though temperatures are going to go above freezing, once the precipitation begins, colder air will come down from above us and change any rain quickly to snow in most areas.
Even along the shore, the air will be cold enough at the start of the event for snow to fall. How much snow accumulates is going to be a tough call. Roads are warm from the past few days of sunshine. Some of that heat will melt the snow as it falls. So, the first inch of snow may accumulate on the grass but you never get that first inch on the roads.
I expect the snow to be heaviest up through midnight. After that, it will remain cloudy with very light snow or drizzle. Some melting may even happen overnight towards morning. Lets talk amounts. Right now, I expect the heaviest amounts north and west of Route 128. However, there appears to be our best chance of accumulating snow even into Boston, since January. See map below. The lines can move 10 or 20 miles in either direction and that would impact areas close to Boston the most. If it snows just three hours longer in Boston then even there 7 inches is not out of the question. I will be updating all day long here as well as on my Twitter account. Follow me on Twitter at @growingwisdom
Thursday, new bands of snow are going to set along the Mass Pike and north. We will be on the southern fringe of this second area of precipitation. The best chance for any additional snow accumulation will be along the New Hampshire border moving about 20-30 miles south. It will snow much of the day even into Boston, but what accumulates on the grass versus the roads will be vastly different. The reason the snow fall total map shows so much snow along Route 2 is that Thursday's system will add additional snow. I will update the map to only include what will fall tomorrow after tonight's snow ends.
A foot of snow
In those places that stay all snow the entire length of both bursts of precipitation, through Thursday, 12 inches of snow is more likely. Notice on the accumulation map that amounts increase dramatically moving north. Temperatures are going to have to be monitored hour by hour and adjustments to the forecast amounts are inevitable.
This time of the year, once we get beyond 8 or 9 A.M., it becomes very difficult for snow to accumulate on the roads. Although it is cloudy, the sun is high enough in the sky that some solar radiation gets trough and heats the asphalt. It's the same reason you can get burned on a cloudy day in the summer. The sun is really that powerful.
By tomorrow night, the storm is over and skies will begin to clear.
Friday looks dry with sunshine and temperatures around 40°F. As we head towards the weekend it does get quite mild with a period rain for Saturday. Looks like any white on the ground will be gone come next week.
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