Thursday Night Winter Weather Update

A significant cold weather outbreak has begun to impact the Pacific Northwest. A modified arctic front has brought a dusting to 1" of snow to areas of the lowlands, except 2-6" from Port Angeles to Southern Whidbey Island. Scattered snow showers will continue through early Friday morning, mainly from Seattle southward and along the western Strait of Juan de Fuca. 

One potential hazard is a flash freeze, where temperatures rapidly cool, causing black ice and any snow on roads to freeze. This can cause treacherous conditions, especially on side streets. Be aware when driving on Friday.

Now, let's take a look at the extreme cold temperatures, starting with lows on Friday morning, from the European model.

In the lowlands from Everett south, expect lows in the mid teens to low 20s. From Everett northward, lows will drop to the mid single digits to low teens (coldest in Whatcom County). Eastern Washington will drop to the mid single digits to mid teens, except -5° to -15° for Spokane, Pullman, and NE Washington.

Next, let's take a look at the European model forecast for high temperatures on Friday.

Highs will only reach the low to mid 20s in the lowlands, and the mid teens in Whatcom County. Eastern Washington will have highs of -5° to 10°, except up to the upper teens in the lower Columbia Basin. These will be some of the coldest high temperatures in recent years for Western Washington.

As of now, it looks like Saturday morning will be even colder than Friday morning. Below is the European model forecast.

The European model forecast shows very cold lows in the low to mid teens for the entirety of Western Washington on Saturday morning, with some areas from Everett northward dropping to the mid single digits. Eastern Washington will drop to -15° to 5°, coldest outside the Columbia Basin. 

One of the most important factors of this cold snap will be the wind chill. The wind chills across the state will be extremely cold for the next few days. Let's start by taking a look at the wind chill forecast for Friday at 10 AM.

On Friday morning, the European model shows wind chills dropping to 0-10° across Western Washington, except -5° to -15° for Whatcom and San Juan Counties. Eastern Washington is another story, with wind chills dropping to 0 to -30°, coldest for areas downwind of the Okanogan River Valley and around Spokane and Pullman. Wind chills below -5° can cause frostbite in 30 minutes or less.

Stay tuned for more wind chill information.

Winds themselves will be very cold, biting, and gusty. Below is the NAM high-resolution forecast for wind gusts on Friday morning.

On Friday morning, expect continued strong winds out of the Fraser River Valley, impacting Whatcom and San Juan Counties with gusts of 40-55 mph. The rest of Western Washington will be impacted by brisk north winds gusting 10-20 mph, which brings the extreme cold wind chills.

There is a chance of strong cross-Cascade gap winds on Saturday, impacting areas such as North Bend and Enumclaw, plus the Columbia River Gorge. Stay tuned for more information on this possibility.

Finally, let's take a look at the next storm system, which will move into Northern Oregon and SW Washington. Below is the European model forecast for precipitation Friday night.

This forecast shows the boundary of precipitation being between Grand Mound and Centralia, with snow impacting SW Washington and the Northern Willamette Valley, and potential freezing rain from the southern Portland metro toward Eugene.

Let's compare this to the GFS forecast, also for precipitation on Friday evening.

The GFS shows a similar outlook, with precipitation ending around the Lewis/Cowlitz County line. This forecast shows mostly snow for Northern Oregon and SW Washington, with some isolated areas of freezing rain south of Portland and on the Oregon coast.

This storm will likely bring an impactful 4-8" of snow from Southwest Washington into the Northern Willamette Valley, with potential for an ice storm in the Central and Southern Willamette Valley. For more information, check the NWS Portland website.

Stay tuned for another update Friday night on the continued impactful winter weather.

Arctic Air Arrives: Extreme Cold Temperatures, Chance of Snow

No FastCast tonight, but continue reading below for an important update on the incoming arctic air and frigid temperatures.

After a significant storm on Monday and Tuesday, a major weather change is ahead for the Pacific Northwest, as arctic air moves south from Canada into the region. This arctic air intrusion will begin with a modified arctic front moving southward through Western Washington on Thursday. This modified arctic front will usher in very cold temperatures, brisk and very cold northerly winds, and a chance of brief snow along the frontal boundary. 

We'll start with the European model forecast for temperatures around 1 PM Thursday.

At 1 PM, the European model shows temperatures in the mid 20s in Whatcom County, in the mid 30s from North Seattle to Mount Vernon, and in the low 40s from Seattle southward. In Eastern Washington, it is generally in the upper teens to low 30s north of I-90, while areas to the south are in the mid 30s to low 40s.

Next, the forecast for 7 PM Thursday.

By 7 PM, everywhere from Olympia northward is below freezing, with Skagit and Whatcom Counties in the mid teens to low 20s. In Eastern Washington, the arctic front is just north of the Tri-Cities, with areas north of the Tri-Cities having temperatures in the low teens to mid 20s, except in the single digits in the valleys of the North Cascades.

So, the modified arctic front will move from north to south through Washington between Thursday morning (areas near the Canadian border) and late Thursday evening (areas near the Oregon border). 

Along the frontal boundary, there is a chance of localized snow bands and snow showers. Additionally, any snow that falls will likely stick to most surfaces, as temperatures will be cooling rapidly with the arctic front.

Let's take a look at the snow forecast through early Friday morning, starting with the European model. This forecast shows the highest possibility for snow along the I-5 corridor being from Thursday afternoon to early Friday morning.

The European model shows a dusting to 1" of snow for most of Western Washington with the arctic front, with isolated areas getting over 1". In Eastern Washington, it's a similar story, with 1-2" of snow due to the arctic front. The exception is areas along the Idaho border, where 2-4" of snow is possible. Expect 6-12" of snow at the passes through Friday morning, making for difficult travel conditions at times.

Next, let's take a look at the GFS forecast for Thursday's potential snow, seen below. This forecast shows the highest possibility for snow being from Thursday afternoon to very early Friday.

The GFS forecast shows a similar pattern of a dusting to 1" for most of Western Washington, with isolated higher totals, including along the Strait of Juan de Fuca, a typical spot that is enhanced by northerly winds. This forecast indicates up to 6" possible along the Strait. The GFS gives a dusting to 3" for most of Eastern Washington around the periphery of the Columbia Basin, plus 10-16" at the passes.

Finally, here is the high-resolution NAM model, showing total snow through early Friday, and generally agreeing on timing, starting snow across the state on Thursday afternoon.

The NAM forecast is more conservative for snow, showing only a trace to 0.5" from Bellingham northward, around Everett and Lake Stevens, and from Seattle southward. Eastern Washington receives very little snow at all in this scenario, while the passes will get 4-8".

As the arctic front moves south on Thursday, it is also going to be breezy, both strong and cold northerly winds out of the Fraser and Okanogan River Valleys and breezy southerly winds to the south of the arctic front, before its arrival. Once the front arrives, winds will shift from southerly to northerly. Below is the HRRR high-resolution forecast for peak winds across Washington.

Notice strong 40-45 mph Fraser outflow winds in Whatcom County and 40-50 mph outflow winds in the Okanogan River Valley. Additionally, winds will gust 35-40 mph on the coast, 40-50 mph between Walla Walla and the Central ID Panhandle, and 30-40 mph across most of Eastern Washington. Also, note 40-60 mph gusts in the Cascades, which could bring areas of blizzard conditions on Thursday.

Last (but definitely not least), let's take a look at forecasted morning low temperatures on Friday morning from the European model.

These temperatures are very rare for Washington. On Friday morning, expect lows from Everett south to be in the mid teens to low 20s, with areas from Everett northward dropping to the mid single digits to low teens. Eastern Washington will drop to -10° to +5°, except in the low to mid single digits in the lower Columbia Basin. Even the coast is expected to reach the mid teens to low 20s. Mountain towns will drop to -10° to 0°.

What will be even more hazardous to the population is the wind chill temperature. Below is the European model forecast for wind chills (the "feels like" temperature) around 10 AM Friday.

Fraser River outflow will bring very cold wind chills of -5° to -15° for Whatcom and San Juan Counties, with extremely dangerous wind chills of -5° to -30° for Eastern Washington. Wind chills below zero can bring frostbite in under 30 minutes. On Friday morning, expect wind chills across the remainder of the lowlands and on the coast to be in the 0° to 15° range.

Please take all necessary precautions to protect yourself, your pets, and your home from these extreme cold temperatures. Make sure to drip your faucets, bring in any sensitive plants, and use heat sources to keep warm inside. Cold snaps can be just as deadly as heat waves. 

With extreme cold weather and potential snow expected over the next 4-5 days, I will be doing daily updates at least through this weekend, so stay tuned.

Monday Night Blizzard & Windstorm Update

No FastCast tonight...continue reading below for an update on the major storm impacting the Pacific Northwest.

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Main Hazards:

-Blizzard conditions (1-4 ft. of snow, wind gusts 40-60 mph) and near impossible travel in the mountains

-Strong winds in the lowlands (late Monday night/early Tuesday morning and midday Tuesday)

-High surf (20-30 foot breakers) and coastal flooding (Admiralty Inlet, Strait, ocean beaches/harbors)

-Heavy rain and a chance of thunderstorms (0.4-1" possible for lowlands through Tuesday night, heavy showers on Tuesday)

-Potential for 1-4" of snow between Chehalis, WA and Salem, OR from late Tuesday into Wednesday

-Much colder arctic air and potential lowland snow could impact the region from late this week into early next week...stay tuned for more information over the coming days.

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Helpful Websites: (good links during any weather conditions!)

-Pacific Northwest Weather Watch YouTube

-Whidbey Island Weather Page

-Washington Weather Chasers Page

-Whatcom County Weather Page

-The UW Dawgcast

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A major storm is impacting the Pacific Northwest, bringing a variety of weather hazards to the region. Let's take a look at the forecast, starting with mountain snow.

Below is the NAM high-resolution forecast for total snow through late Tuesday night.

This forecast shows an additional 10-24" of snow at the passes through Tuesday, with a dusting to 3" for the Spokane area. Notice 2-4" of snow from Chehalis to the Portland metro area, due to a weak storm coming in on the heels of our main Tuesday storm. Any snow around Portland will fall late Tuesday night into Wednesday morning.

We will compare this to the HRRR high-resolution forecast, also for total snow through late Tuesday night.

This forecast shows 15-24" of additional snow for the passes and 1-3" for parts of Eastern Washington. This forecast shows the weak Tuesday/Wednesday storm moving in a tad further north, bringing 1-4" of snow from Grand Mound south to Vancouver, with Portland getting a dusting to 1". 

We'll take a look at one last snow forecast, the UW WRF high-resolution model, through late Tuesday night.

The UW WRF forecast shows even more snow, with 16-32" possible at the passes through late Tuesday night, plus up to 1" around Spokane, and 0.5-2" from Napavine to the Portland metro.

These massive snow amounts, combined with very strong winds, will produce blizzard conditions in the Cascades, Olympics, and Blue Mountains. A blizzard is defined as blowing snow, 35+ mph winds, and visibility under 1/4 mile for 3+ hours. These conditions will be met for parts of the area's mountains through Wednesday morning. Keep these dangerous conditions in mind if you plan to attempt crossing the mountains. If you are able to delay your trip, that is the best idea.

Now, let's take a look at the wind forecast. Wind alerts are in effect for the entirety of Western Washington and most of Eastern Washington. Wind will generally come in two periods for Western Washington, the first from late Monday night to early Tuesday morning, and the second from midmorning Tuesday to Tuesday evening.

Let's start with the NAM high-resolution forecast, showing wind gusts at late Monday night.

This forecast shows winds with the cold frontal passage gusting 45-50 mph across the lowlands, and up to 55 mph on the coast.

Here is the NAM forecast for winds late Tuesday morning.

This will be the stronger burst of winds for the region, with this forecast showing the lowlands and the coast gusting 45-55 mph, with a damaging westerly surge along the Strait of Juan de Fuca bringing 55-65 mph gusts to the shores of the Strait, Whidbey and Camano Islands, and the Admiralty Inlet area. Additionally, note that winds in the mountains will be gusting 50-60 mph, causing blizzard conditions. Note the area of lesser winds from Hood Canal to Everett, where a strong Convergence Zone will bring heavy rain and a chance of thunderstorms.

Let's compare this all to the HRRR high-resolution forecast, starting with the cold frontal passage around 12 AM Tuesday.

This forecast shows winds in the lowlands gusting 40-50 mph as the front passes, except lesser in the lee of the Olympic Mountains. The coast reaches 45-55 mph during this time.

Let's fast forward a few hours to Tuesday afternoon.

The HRRR shows winds gusting 40-45 mph in the lowlands Tuesday afternoon (isolated areas of 45-55 mph gusts, including the Shelton area). This forecast shows a very strong and damaging westerly surge down the Strait, with gusts of 55-65 mph, strongest on Whidbey Island. The coast will hit 45-55 mph. This forecast verifies the expected 50-60 mph gusts in the mountains.

Finally, let's take a look at this graphic from NWS Spokane, showing peak wind gusts across Eastern Washington on Tuesday.

For most of Eastern Washington, expect winds gusting 45-55 mph, with some areas gusting up to 60 mph. Be especially aware if you're driving a high-profile vehicle in wide open areas.

Next, the European model forecast for waves off the Pacific Northwest coast on Tuesday afternoon, seen below.

This forecast shows waves reaching 25-30 feet off the Washington coast on Tuesday afternoon, with 20+ foot waves for the entire area from Vancouver Island to Northern California. Note that this is the significant wave height (aka average wave height), and the biggest waves will be higher than this forecast.

Finally, let's take a look at the NAM high-resolution forecast for total rain through late Tuesday night.

The NAM forecast shows the lowlands receiving an additional 0.5-1" of rain, most from Seattle south and from Mount Vernon north. The coast will get an additional 1-2". There is also a chance of thunderstorms and hail in heavy showers on Tuesday, so be prepared.

Whew! That's a lot of weather to cover! Be sure to pay attention to what's going on, and be prepared for power outages, tree damage, heavy rain, large waves, and of course dangerous blizzard conditions in the mountains. Stay tuned for more over the coming days!