Weather

Accumulating snow on the way for Tuesday morning

In spite of many of us getting to spend a lot of time outside in the warmth over Christmas, it’s time for a reality check: Snow is on the way.

There are basically two things you need for snow, moisture and cold. Tuesday morning we will have each of those in place. My forecast is predicated on the cold hanging around long enough to keep the precipitation in the form of snow. The map below is for Tuesday morning.

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This is the type of system where if the cold air hangs in long enough then snowfall amounts could be an inch or two higher, and if the warm air takes over earlier, they could be an inch or two lower. When you are dealing with a storm bringing a small amount of snow quickly, an hour or two of additional snow makes a big difference.

When does the snow arrive?
This is a quick thump of snow starting before the morning commute Tuesday and ending in the middle of the day as some light rain or drizzle. The map below shows where the snow and mixed line will be around 4 a.m. Tuesday. This is subject to change before the event, but you should plan on a messy Tuesday morning drive. Since schools are closed already, we don’t have to worry about that aspect of the forecast.

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Will the snow be fluffy or wet?
Temperatures will be increasing during the event, and the air above us is not very cold. Therefore, I expect the snow to be on the heavier and wetter side. Remember, most storms last winter were exceptional in the light weight of the snow, I expect more storms this winter to be accompanied by wetter, heavier snow.

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How much snow?
This is always the million dollar question. There are three maps below to help you know how much snow is coming. The first is my map and my prediction. I followed that by a map produced by NOAA. Their map has specific numbers due to the way it’s rendered, not ranges.

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Finally, there is a map of probability. This map shows the odds of seeing two inches of snow or more. Notice the odds decrease rapidly as you get south of the Mass. Pike.

will you reach two inches of snow.png

Could accumulation change?
There are still several model runs Sunday and Monday. As each new bit of information arrives, I will modify the forecast. If the cold air linger longer, then amounts will increase, with the opposite also being true. I will update the forecast here and on Twitter @growingwisdom. Please follow me there.


How will the recent warm weather affect the storm?
Soil temperatures are still in the 40s, and while they will cool down Monday, the ground won’t be frozen. Roads are also relatively warm. This means some of the snow will melt from the bottom up during the afternoon Tuesday and the rest of the week. I think you can expect to see much of the snow disappear before the New Year arrives.

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Colder pattern
In the years since records have been kept around southern New England, we have never had a December this warm. January is the coldest month of the year, and even a milder than average month is still cold. I expect January to average either slightly above or slightly below average, but not be exceptionally cold or warm.

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