Significant Storm Bringing Strong Winds, Heavy Mountain Snow, and Heavy Rain

No FastCast tonight...continue reading the full blog below for a full briefing on the significant storm that will impact the region on Wednesday. This storm will bring strong winds, heavy mountain snow, and heavy rain to Western Washington.

Let's start with the forecast for wind gusts. Below is the NAM high-resolution forecast, showing peak winds through early Thursday morning.

This forecast shows winds peaking from around 10 AM to 9 PM, with gusts across the lowlands reaching 40-50 mph, strongest near the water. Areas around Whidbey and Camano Islands could gust over 50 mph. The coast will gust 45-50 mph, except up to 55 mph from Westport southward. This also shows gusts of 40-50 mph in the mountains, something to be prepared for, especially at higher elevations.

Let's compare this to the HRRR high-resolution forecast, also showing peak winds through early Thursday morning.

This forecast shows a similar solution for the lowlands, with gusts of 40-50 mph expected. However, this forecast has stronger winds in Island County, Western Snohomish County, and the northern Hood Canal area, with those areas gusting 50-55 mph. Similar gusts are expected on the coast.

Winds are already ramping up as I write late Tuesday night, and expect winds to peak from midmorning to late night on Wednesday. There is potential for a brief lull Wednesday evening, before the passage of the cold front around 8-10 PM.

Next, let's take a look at the forecast for mountain snow, starting with the European model, showing snow through Thursday morning.

This forecast shows 1-3 feet of snow at the passes through Thursday morning. This will bring (and is already causing) difficult driving conditions across the passes. One important note is that actual totals will likely be lower than these amounts shown since warmer air will raise the snow level to around 4,500 feet from Wednesday morning through late evening, before the snow level crashes as the cold front moves through.

Let's compare this to the HRRR high-resolution snow forecast, also through early Thursday morning.

This forecast also shows 1-3 feet of snow at the passes through early Thursday, with upwards of 5 feet expected at higher elevations such as Paradise. Remember that actual pass totals may be less than these forecasts due to the rain changeover on Wednesday.

Finally, let's take a look at the rain forecast for the lowlands. This will be quite a rainy system, with ponding, localized street flooding, and on-and-off heavy rain expected.

First, the European model forecast for total rain through early Thursday.

This forecast shows the lowlands receiving 1.5-2" of rain, with 1.5-2.5" on the coast, and a rain shadow from Everett to Bellingham, bringing lesser totals of 0.8-1.25" for that area.

Let's compare this to the NWS NBM high-resolution forecast for total rain through Thursday morning.

With a higher resolution, this forecast can pick up on features such as the rain shadow much better. As you can see, a much more defined rain shadow is seen in this forecast, with areas from Everett to the San Juans only getting 0.2-0.7" of rain. Outside that area, this forecast shows 1-1.5" of rain, except 1.5-1.75" from Olympia south and west, and for most of the Kitsap Peninsula. The coast will pick up 1.5-2" with this storm.

This is a multi-faceted storm, and wind, snow, and rain impacts are possible across the region. After this storm, the activity doesn't end, with more active weather likely over the coming days. Stay tuned and stay safe!