WeatherWatcher: Dreaming of a Winter Wonderland

Saturday, December 3, 2016

As many of you probably already heard, snow is in our forecast. I've been waiting for models to be a little more consistent on what is going to happen before writing a forecast. As always with our snow events, they are extremely uncertain with computer models and difficult to predict with any scientific methods currently used.

Here's what is happening, a surge of cold air is pushing south out of Canada Sunday night into Monday morning behind a storm front. Then, a surface low is predicted by computer models to develop off the southwest Washington coast pushing moisture in from the water over the cold air. This is a classic snow producer for our region, this is expected later Monday into Tuesday morning.

After Tuesday morning skies are expected to clear, temperatures cold, lows in the mid-low 20's and highs in the 30's. Another strong, warm system is moving in Wednesday. This system is expected to start as snow, and turn over to rain sometime Thursday. This storm will probably be our most significant portion of this series of snow events.

Longer range: Rain is expected Friday through Saturday night, another possible shot of cold air bringing us renewed snow chances next Sunday into the week of 12th - 16th. This is way too far out still to have any decent skill in a forecast, but as far as long range trends go, it's looking like we will have a cold December with several opportunities for snow.

What timeline we can expect in Shoreline and Lake Forest Park: 

Rain Saturday into Sunday afternoon, changing over to showers. Highs in the 40's and lows in the 30's. Sunday evening change over: A convergence band might develop behind the cold front, and center over Shoreline to bring us heavier showers, with snow mixing in or changing over to snow Sunday evening into Monday morning. Roads and the ground is still warm so accumulations are not really expected.

Monday afternoon - Tuesday morning: The low pressure I mentioned earlier develops off the southwest Washington coast, pulling a second surge of cold air down into our region, and pushing bands of moisture up into the Puget Sound. This combination is a fairly classic set up for Seattle area snows. Temperatures are expected to drop into the 20's with snow or snow showers. There is still a lot of inconsistency with the computer models on accumulations. I suspect we will see between 1-4 inches of snow from Monday afternoon into Tuesday morning.

Wednesday night - Thursday: A warmer Pacific storm moves in for renewed precipitation beginning as snow. This makes it even more uncertain as to how much snow we will get, if any. All depends on when that conversion from cold to warm happens. In the past this set up has produced as much as 12 inches of snow before changing to rain. Other times it's started as only rain, with no snow at all.

In summary: This will probably be the most significant snow event we've had since January 2012. Most favorable snow conditions could generate a total accumulation over the next few days of 1-6 inches, depending on if a convergence sets up or not overnight Monday morning. Wednesday-Thursday is still too uncertain but it has the potential to become a major event, so be ready in case the worse occurs mid-week.

At this time, no watches or warnings have been issued as we are still far too early in the forecast. I'll continue to watch this developing weather event and post updates.

With that, I leave you with my favorite photo from January 17, 2012, with the view from the Shoreline Weather Station in the Echo Lake neighborhood of Shoreline.

Photographed by Carl Dinse on January 17, 2012.

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