No FastCast tonight...continue reading below for an update on the major storm impacting the Pacific Northwest.
------------------------------------------------------------------------
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.
-------------------------------------------------------------------------
Helpful Websites: (good links during any weather conditions!)
-Pacific Northwest Weather Watch YouTube
-Washington Weather Chasers Page
------------------------------------------------------------------------
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!
No comments:
Post a Comment