Freezing Rain, Snow, and Rain: Messy Storm Ahead

Note: Now-Cast blog post will be posted by 3 PM Tuesday, and will be updated hourly through Tuesday night. Stay tuned.

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A messy storm is ahead from Tuesday evening through Wednesday, with a variety of different impacts across the region. Let's take a look at the forecast.

First, let's take a look at forecast lows on Tuesday morning, starting with the European model.

Expect lows in the lowlands to drop to the upper teens to low 20s, with cold air from the Columbia River Gorge bringing lows in the low to mid teens for the Willamette Valley and areas of WA from Kelso southward. Eastern Washington will remain very cold, with lows of -5° to 15°.

Now, let's take a look at the forecasts for the incoming storm. Expect precipitation to begin moving into Western Washington from the south late Tuesday afternoon, spreading into the lowlands by 6-9 PM, continuing through Wednesday. Here's how this will work:

Skagit County & southward: Temperatures rise above freezing on Tuesday, cooling below freezing Tuesday evening as precipitation rates bring temperatures down. Precipitation likely begins as freezing rain, roughly from 6-9 PM Tuesday through 3-7 AM Wednesday, changing to rain by Wednesday morning. Some areas closer to sea level may only see rain.

Whatcom County: Precipitation likely falls as snow from 9-11 PM Tuesday through Wednesday evening, with a brief period of rain or freezing rain Wednesday afternoon.

Now, in the forecasts below, we will look at freezing rain, snow, and rain in greater detail, starting with freezing rain.

Below is the European model forecast for total freezing rain through Wednesday.

This forecast shows the lowlands receiving 0.1-0.3" of freezing rain, with areas from Seattle north near the water getting under 0.1", and the Kitsap Peninsula getting up to 0.35". It only takes a light glaze (0.1") of ice to cause significant impacts, mainly to vehicle and air travel. Generally, this will be a quicker and less impactful ice storm than the previous ice storm in December 2022.

Let's compare this to the NAM high-resolution forecast, also for freezing rain through Wednesday.

The NAM forecast shows 0.2-0.4" of freezing rain from Chehalis to Olympia, with 0.1-0.25" from Tacoma northward. This forecast also highlights heavier areas of freezing rain (that are more uncertain) around Bellingham (0.5-0.7", on the line between rain and snow), and in the Cascade foothills from Enumclaw to Gold Bar (0.1-1"). 

It will be best to stay off the roads from Tuesday evening through Wednesday morning, as it only takes a light glaze of freezing rain to cause impacts and bring dangerous road conditions.

Now for the snow forecast. First, the European model, seen below (showing total snow through Wednesday).

This forecast shows a trace to 1" of snow along the Strait of Juan de Fuca and from Everett to Mount Vernon. Areas from the Whatcom/Skagit County line northward will receive 4-7" of snow in this forecast. The passes will receive 18-24" through Wednesday in this forecast, with Eastern Washington receiving 1-4", except 6-10" north of Pullman and east of Ritzville, including the Spokane metro area.

Next, let's take a look at the NAM high-resolution snow forecast, also through Wednesday.

This forecast shows a trace to 2" of snow for northern Island County, areas from Sequim to Lake Crescent on the Strait, and 2-6" for San Juan and Whatcom Counties, except 7-10" for the northern half of Whatcom County. Additionally, this forecast shows 18-30" for the passes through Wednesday, and 2-6" for Eastern Washington, except 0.5-2" for the Tri-Cities and Walla Walla, and 8-12" for Pullman, Spokane, and areas in between.

Finally, below is the European model forecast for rain through Wednesday, since precipitation in the lowlands will fall as rain after freezing rain ends.

This will be all snow for the Cascades and all areas east, along with most of Whatcom County. In the lowlands, expect 0.4-0.6", with a rain shadow from Sequim to Whidbey Island. The Willamette Valley will pick up 0.8-1.1" of rain with these systems, with the coast picking up 0.4-1".

I will post a "now-cast" update blog on Tuesday evening, and will try to update that blog semi-regularly through Tuesday night. Stay tuned & stay safe!