WeatherWatcher: Dreaming of a White Christmas?

Wednesday, December 23, 2015

Have you been dreaming of a White Christmas? Maybe a lot of us have, and maybe that's why the chance of snow Christmas Eve into Christmas morning has become more likely.

I wanted to talk about all this talk of lowland snow. I've been watching the forecasts now for over a week and they've all been flirting with rain/snow mixed showers for Christmas Eve and Christmas morning. Well, now a lot of things seem to be all in agreement about it.

So, let's define what a White Christmas is. National Weather Service and Accuweather both define a white Christmas as 1 inch or more of accumulated snow on the ground at any time December 25th.

Now let's talk about the weather pattern. The jet stream (strong river of winds at 30,000 feet in the air) right now is diving in a southeast direction from the gulf of Alaska down past Washington state, cutting east into Oregon/California. It is in a strong northwest flow, bringing cold air down from the arctic over the Pacific waters and into our area. This set up typically brings the marginal wet snow showers/systems. Sometimes it can create a convergence zone which can produce a significant but narrow band of heavy snow along an east west oriented line anywhere between Marysville and Tacoma.

Decorated house under 8 inches of snow, Shoreline, WA December 2008.
Photo by Carl Dinse

The Forecast:
What's in the forecast with agreement is a slight chance of some mixed wet snow after Midnight tonight. Christmas Eve appears to be a mix of showers and snow showers. Accumulations are expected to be short lived and maybe up to an inch. Overnight into Christmas morning is when the temperatures drop into the low 30's or upper 20's with moisture still present. This could produce an accumulation that might stick around through at least the mid-morning hours for Christmas Day.

I want to stress that this is a very marginal forecast. It might get cold and we might have some snow showers after the cold arrives.  Could be a convergence zone but nothing can really pin point that small of a weather system with any confidence. So bottom line, the possibility is stronger this year than most years here, and all the right things are coming together to make it very possible. One thing for sure is, it will get cold Christmas morning. High temperatures are going to range to the upper 30's to about the 40°F mark. Lows in the low 30's to mid-20's depending on location. Saturday-Sunday appears to be warming back up a little to seasonal temperatures with a new Pacific rain storm moving in Saturday afternoon.

If you were wondering, the last two White Christmas's we've had were December 2008 and December 1990.

For current weather conditions and updates, you can visit my website at ShorelineWeather.com



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