An Unusually Strong Cold Cold Front Is Moving Through The Northwest

Over the eastern U.S., the passage of a strong cold front, with a rapid decline of surface temperature, is a frequent winter treat.

In contrast, here in the Northwest, low-level cold fronts are generally weak because the cold air, starting over Alaska and vicinity, passes over relatively warm water.  To illustrate, the current water temperatures (in °C) today are shown below.

The water is well above freezing the whole way (note 4°C is 39°F).

Today, an unusually strong Pacific cold front will be moving through, and you will notice its impact, including substantial snow in the mountains and even a few flakes reaching sea level in "favored" locations this week.

The visible satellite image this morning shows the story (below).  Arctic air is moving southeastward from Alaska, and as it warms from below, it becomes unstable, producing huge fields of cumulus convection (the black circle shows an example).  

The location of the cold front is shown by the red arrow, and the position of the clouds/light showers from a Puget Sound Convergence Zone is indicated by the black arrow.

As the cold front moves through today and cold air sweeps in, the temperature of the air aloft will decline rapidly.

Near sea-level, as at Olympia Airport (below), temperatures will plummet from the mid-50s today to highs in the low to mid-40s tomorrow and Tuesday, with lows reaching freezing.

But go a bit higher, where the low-level warming influence of the ocean is less noticeable, and the cooling will be much greater.  For example, at the Fire Training Academy, just east of North Bend, WA, temperatures will barely get about freezing during the day and decline into the mid-20s on Tuesday.

The forecast temperatures over Washington for Tuesday morning (shown below) will be very cold for onshore flow, with higher terrain dropping into the teens and nearly the entire state below freezing (blue and purple colors).  Only near the water will temperatures get to freezing and above.

You want snow in the mountains?  

You're in luck.  By Wednesday morning, the Olympics and the north Cascades will get a few feet, but this is just the appetizer.  

The main course is later in the week.  Here are the snow totals from the European Center model through Saturday morning (below).  As much as TEN FEET in some locations.  Many locations have a yard or more of snow.

Anyway, the influx of cool/moist air this week is very welcome and will go a long way to help the water situation this summer.