We are now close enough in time to be quite certain that the Pacific Northwest mountains will receive a major snow dump.
We also know that the first half of January will NOT be characterized by El Nino warmth, as had December.
And it is now clear that there is a possibility for snowflakes reaching sea level in some parts of western Washington.
So let’s get to the details.….
The latest high-resolution UW forecast for total snow accumulation over the next 4 days (96-h, through 4 AM Monday) predicts 1-2 feet in the central and northern Washington Cascades and the mountains of southwest British Columbia. Very consistent with previous forecasts.
The freezing level is relatively high this morning (about 5000-4500 ft) and will decline to around 2000 ft this weekend.
The snow will arrive in two events, both associated with incoming Pacific fronts. One today and the other Saturday.
A nice start for local skiers….but not enough!
It will be the second act on Tuesday and Wednesday that will really put a smile on the faces of snow lovers.
A strong upper trough/low will move into our region which will be the key feature (see the 500-hPa, roughly 18,000 ft map at 1 PM Tuesday below).
This upper level is associated with a surface low (see level pressure forecast for Tuesday morning below, as well as low-level temperatures), with the track of the low bringing it across the north-central WA coast. Also, note the cool air (blue and purple) in the interior.
The location of the surface low is critical. If it moved 100 miles to the south, western Washington could be snow-bound. And this low has been moving around in recent model runs. Thus, there is uncertainty.
The result of the approaching low/trough on Tuesday will be substantial additional snowfall in the mountains.
To see this, first look at the accumulated snow over Washington through 4 AM Monday (the closer version of what I provided above).
Compare that to the accumulated snowfall through 4 PM Thursday. A LOT more. More than 3 feet of new snow in the mountains in total starting today.
Not much lowland snow except for one location… in Whatcom County northeast of Bellingham.
This area will be cold enough for snow– from outflow through the Fraser River Valley.
To show you this, here is the wind speed forecast for 4 AM Wednesday. You can see the strong, cold northeasterly flow hitting those poor folks in Whatcom County and on Orcas Island!
A close-up shows the Fraser River winds clearly.
There may be some occasional snowflakes mixed in to rain over the rest of the lowlands, but nothing of note IF THE ABOVE FORECAST IS CORRECT.
This far out there is still considerable uncertainty, so stay tuned.
The European Center model is generally in agreement with the above, but does place a band of substantial convergence-zone snow over the north Sound on Thursday/early Friday.
24-h snowfall ending 4 AM Friday.
