Pattern Change & Active Weather to Start the Year

 FastCast—Wednesday, Jan. 3 to Friday, Jan. 5:

An active start to 2024 is expected for the Pacific Northwest, with a pattern change bringing an increase in rain and mountain snow. On Wednesday, expect showers across the lowlands, up to 0.2”, with an exact repeat on Thursday. Friday looks to start off dry, with a potentially more impactful system moving in later in the day, with details still uncertain. For the lowlands, expect highs in the mid to upper 40s, with lows in the upper 30s to low 40s. In the mountains, the passes will receive up 8-12” of snow through Friday, with a potential for multiple feet of snow in the mountains over the coming weeks…so stay tuned for more information!

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Active weather will impact the Pacific Northwest to begin 2024, so let’s dive in and take a look at the forecast.

Below is the European model forecast for rain through Friday.

Through Friday (including some rain that fell on Tuesday afternoon), the lowlands will receive 0.4-0.8” of rain. The coast will get 0.8-1.5” of rain in this time, with Eastern WA getting 0.3-0.6” for the western half and 0-0.2” for the eastern half. 

Let’s compare this to the American (GFS) forecast for rain through Friday, seen below.

The GFS forecast shows a rain shadow from Seattle to Bellingham, with 0.1-0.4” of rain for that area. The rest of the coast and lowlands will get 0.4-0.7” through Friday. Eastern Washington will get less rain in this forecast, only getting 0.1-0.3”.

Now, let’s take a look at the snow forecasts for the mountains. We’re in desperate need of an increase in snowpack. First, the European model forecast for snow through Friday.

This forecast shows 10-14” of snow at the passes through Friday, including some snow that already fell on Tuesday. The Spokane area will get up to 1”, with the eastern slopes (including Wenatchee and Ellensburg) getting up to 4”. 

Let’s compare this to the GFS forecast, also showing snow through Friday.

This forecast shows 6-10” for the passes, up to 3” for the eastern slopes, and 1-2” for the Spokane area, plus a dusting for parts of the Palouse. 

Now, let’s take a look at some extended outlooks from the NWS Climate Prediction Center (CPC) for January 8-12 (next week).

First, the temperature outlook, seen below.

This outlook shows a 40-50% probability of below average temperatures for Washington through January 12th.

Now, let’s take a look at the precipitation outlook for this same time (January 8-12).

This outlook shows a 33-50% probability of above average precipitation for Washington.

As you would expect with below average temperatures and above average precipitation, the mountains across the Pacific Northwest will likely receive large amounts of snow over the next few weeks. Below is the European EPS forecast for snow at Stampede Pass (near Snoqualmie Pass) through mid-January.

This graphic shows all 50 ensemble “members” (slightly different forecasts), with snow accumulating from left to right (days and times on bottom). The big bar at the bottom is the average of all the ensemble members. Through mid January, the average is around 44” of snow, with most ensemble members showing 30-60”! Keep in mind, this station is only at 3,700 feet, so higher areas could have much more snow.

Stay tuned over the coming days as an active start to 2024 continues!