It has been mild recently across the Pacific Northwest. In fact, Seattle tied their record high temperature of 60 degrees yesterday (11/12/13), also set in 1953. That is all about to change as we head into the weekend.
A mid-level trough will cut across the area Thursday, initiating a slight cooling trend in temperatures. Precipitation with this initial trough will be very light and portions of the Washington Cascades will see anywhere from 1 to 3 inches of snow above 3,500 feet.
The trough of interest will start diving into the Pacific Northwest Friday and will likely bring some of the coldest air yet this season to the region. Precipitation will start Friday morning/afternoon across western Washington and will continue progressing south and east through much of the rest of Washington and into Oregon by Friday night.
Snow levels will initially start out around 3,000 feet in Washington, but will fall to around 2,000 feet by late Friday night or Saturday. Farther south, across the Oregon Cascades, snow levels will start out around 4,000 feet or so and will fall to near 2,700 feet by Saturday night.
Snow will be heaviest across the Washington Cascades late Friday through Friday night and will begin to taper off Saturday afternoon. Snowfall totals of 3 to 6 inches are expected above 2,500 feet and 6 to 12 inches appears likely above 3,000 feet. Of course, mountain peaks and favored upslope regions could see more than a foot of snow.
The Oregon Cascades will see their heaviest snow late Friday night through Saturday before it tapers off Saturday night. Totals of 1 to 3 inches are expected above 3,000 feet with amounts of 3 to 6 inches likely above 4,000 feet. As you get above 5,000 feet in elevation, totals may exceed 6 inches, especially in favored upslope regions.
In addition to snow falling in the Cascades, snow will fall across the Blue Mountains of Oregon and portions of the Northern Rockies and eventually across the Wasatch Range and Central Rockies. I am not going to talk about totals here just yet, though it does appear pretty safe to say these areas will see accumulating snow.
As far as temperatures go, Seattle will likely see lows in the middle 30s or perhaps even lower 30s Saturday and Sunday night. Portland will see temperatures dip into the upper, perhaps even middle, 30s Sunday night.
A majority of the precip will fall before the coldest air arrives, so there is an extremely small chance of there being any lowland snow. Sorry, snow lovers in Portland and Seattle.
The cold blast won’t last long as the ridge across the eastern Pacific shifts east a bit early next week significantly warming things up.