Storm Update: Heavy Snow, Strong Winds, and Heavy Rain Ahead

No FastCast today. Continue reading below for an update on this dynamic storm impacting Western Washington.

There is a plethora of different weather conditions impacting Western Washington on Tuesday evening. The radar image below shows the stark contrast between rain and snow.

As of 8 PM, heavy snow is falling from Everett to Shoreline, with accumulations on all roads, including I-5. Heavy snow is also falling on the Eastside and in the foothills, with chains now required on SR-18 over Tiger Mountain and accumulations in Issaquah and North Bend. 

South of the Seattle/Bellevue area, rain is falling. There is snow on parts of the Kitsap Peninsula and north of Bellingham, especially near the Canadian border, where significant snow is impacting the Vancouver BC metro area.

Earlier in the day, 0.5-1" of snow fell in parts of the South/Central Sound, more than previously forecast.

Let's take a look at the upcoming forecast. Below is the HRRR forecast for snow through 4 AM Wednesday.

This forecast shows 2-6 inches of snow from Shoreline to Stanwood, which seems to be verifying. The mountains will be hammered with 1-3 feet of snow in 12 hours, with very difficult to nearly impossible travel at the passes. Additionally, expect 2-8 inches on the Kitsap Peninsula.

The UW snow forecast through 4 AM Wednesday is below.

Note that this forecast includes snow in the South Sound that has already fallen Tuesday morning. 

The UW forecast also shows 2-6 inches from Shoreline to Stanwood, 1-2 feet in the mountains, and 2-8 inches on the Kitsap Peninsula, with the potential for up to 12 inches near Hood Canal.

Snow will accumulate 2-6 inches in the Cascade foothills, roughly from Black Diamond northward.

Now for the interesting part...snow will change to rain overnight, but the timing differs slightly between the high-resolution models. Generally, expect snow to change to rain area-wide by 2 AM Wednesday.

Now for the other significant weather hazard overnight...strong winds. Gusts over 50 mph have been reported in the San Juan Islands and Admiralty Inlet Area as of 8 PM Tuesday, and strong winds will continue across the region overnight. 

Below is the HRRR forecast for gusts at 11 PM Tuesday.

The HRRR shows winds peaking from 10 PM-2 AM, with peak gusts of 40-50 mph across the region, with isolated higher gusts possible, especially north of Everett.

Next, let's take a look at the NAM forecast, showing peak gusts at 2 AM Wednesday.

The NAM shows winds peaking from 11 PM-3 AM, roughly the same as the HRRR. The NAM shows peak gusts of 40-50 mph for the entire region, with higher gusts north of Everett and in parts of the Willamette Valley and Eastern WA/OR.

Rain is also expected with this system, heavy at times overnight. The HRRR rain forecast is below, showing rain through 12 PM Wednesday.

For areas where it is snowing, this won't all fall as rain, but will instead be the total amount of water going through a rain gauge. For areas from Seattle southward into the Willamette Valley, expect a total of 0.8-1.25 inches of rain, with 1.5-2.5 inches on the coast.

To recap, heavy snow will continue falling through around 12-2 AM for areas on the Kitsap Peninsula, north of Shoreline, in the foothills, and north of Bellingham into BC. It will be windy across the region overnight, with peak winds from 10 PM-3 AM across the region.

More snow chances are possible in post-frontal showers on Wednesday, potential Convergence Zone bands, and in future systems on Thursday and Friday, so stay tuned.