December 1st marks the start of meteorological winter and as such it’s a good time to take another look at the month ahead.

Coincidentally, as if right on cue, there is the first winter weather advisory of the season posted for western Maine for the possibility of freezing rain.

One of the elements of winter I think we will see much more of this year, as compared to last, is mixed precipitation, freezing rain and the rain-snow line. I am basing this on fewer arctic outbreaks and more frequent intrusions of warm air during stormy periods.

The next 12 weeks are the coldest and typically snowiest of the year. Although March can bring plenty of cold and snow, December to February is considered the core of winter. March is more of a fickle month usually starting wintry and ending more spring-like. This is why meteorologists mark winter beginning today.

There are a few aspects of December which are predictable. On average, our temperatures typically fall another 8 degrees. Afternoon highs run in the 40s at the start of the month and 30s by the end. Daylight shrinks to its shortest levels at the beginning of the third week, before gaining a few minutes by New Year’s Eve.

You’ll likely be surprised to note, because of the shape of the Earth, the location of you on the Earth and the orbit of the Earth, that the earliest sunset and the latest sunrise are actually not on the winter solstice. Rather our earliest sunset is Dec. 9, while the latest sunrise is Jan. 4. (Technically, our latest sunrise was actually Oct. 31, but that was due daylight saving time.)

Snowfall in December is highly variable. While average snowfall is about 14 inches in Portland, each year sees very different results. The chart below shows how much snow has fallen seasonally since the early 1990s. Notice December has an enormous range in terms of accumulation. This year, due to a strong El Nino, arctic air being locked up in Canada and other non-favorable winter patterns, I expect December to see less snow than average especially the first several weeks of this month.

December 2015 and beyond
Most of the models agree this is going to be a milder than average month overall and the stormiest weather will be south of New England. This means when we get to New Year’s Eve in four weeks, we should look back at a month without much in the way of prolonged arctic air and few snow events. The odds heavily favor significantly less snow than average as well.

I am posted three maps below for you to review. The first shows predicted temperatures for December. Notice the northeast is forecast to have above average readings.

The next map is for precipitation. What’s interesting is the wetter than average prediction across the southeast and the average to drier than average forecast here.

This is a similar pattern to the fall. I’ll spend more time in upcoming blog writing about the snowfall forecast. My quick statement is average to below average snowfall this season, but not above.

Finally, I’ll leave you with the latest prediction for the overall three month period December through February. Once again, we see the overall numbers, when averaged on March 1st, should be warmer than average. This of course doesn’t mean there won’t be several cold periods within the next three months, but the odds continue to favor a very different winter than what we all experienced a year ago.