We’re a lot nearer to the potential occasions this week: shut sufficient in time to have the higher-resolution fashions accessible.
As I’ll clarify, the upcoming scenario has the potential for lowland snow however just isn’t optimum. Heavy snow within the mountains is a positive factor.
The SnowTrick
Let me remind you, it is tough to get lowland snow west of Cascade crest. Moist air coming off the Pacific is just too heat for lowland snow, and it’s troublesome for chilly air within the continental area to succeed in us due to the blocking results of the Rockies and Cascades.
So to get snow we’d like one thing unique to happen. The preferred trick is to get a low middle off the southern Washington coast and chilly excessive strain over the BC inside. The distinction in strain causes chilly air to be drawn southwestward by means of the Fraser River Valley or throughout low terrain into NW Washington, which then spreads southward. The low on the Washington coast and an accompanying upper-level trough of low-pressure ends in rising air that produces precipitation that falls into the chilly air close to the floor.
That may result in snow.
The opposite approach to safe lowland snow is to have chilly air in place (from the above), whereas a entrance pushes inland. Precipitation begins as snow after which turns to rain.
We could get a little bit of each this week.
The Present Scenario
Final night time a comparatively robust chilly entrance moved by means of and temperatures aloft (and close to the floor) have fallen considerably.
The chilly entrance additionally produced a surge of robust northwesterly winds within the Strait of Juan de Fuca and downstream round Everet, producing wind gusts as robust as 50-60 mph final night time (see a plot of gusts beneath). A couple of thousand clients misplaced energy.
Tonight, a weak low will transfer over western Washington, and chilly, excessive strain will construct into British Columbia (see forecast floor map for 4 AM Monday). Blue colours are chilly sufficient for snow by the way in which. Monday morning will carry a tough freeze to western Washington will lows within the 20s.
Chilly, unstable air can be transferring into the Cascades throughout the subsequent day, with some snow accumulation within the mountains (see whole snowfall by means of 4 PM Tuesday beneath)
The Wednesday Scenario
The massive motion will probably happen on Wednesday. A powerful upper-level trough will method, producing preicpitation over the world….the place chilly air can be in place (upper-level map proven for 4 AM Wednesday)
A robust floor low will method northern Vancouver Island, with an related entrance making landfall on the Washington coast Wednesday morning (floor map at 1 AM Wednesday is proven). This entrance will ultimately drag in hotter air, however the precipitation might effectively begin as snow at low ranges on Wednesday morning. Massive quantities of snow will fall within the mountains. I
Let me stress that this isn’t an optimum scenario for western WA snow. For a giant snow occasion, you actually need that low to be parked alongside the southern WA coast, drawing in chilly air from BC.
The most recent UW high-resolution forecast for snowfall by means of 3PM Wednesday is proven beneath. Many ft within the mountains, however be aware the band of snow from Seattle to Everett (a number of inches). Jap Washington will get some snow as effectively. Snow depth can be lower than snowfall, after all.
The lower-resolution European Heart mannequin has an analogous resolution (see whole snowfall for a similar interval..now till 4 PM Wednesday). A lot of mountain snow, snow over NE Washington, and a band of lowland snow from Seattle to Everett.
Our confidence within the Puget Sound snow forecast will improve as we get nearer in time and high-resolution ensembles change into accessible.
