For the second time in as many weekends, snow is in the forecast for parts of the Western Washington lowlands, although once again it appears the best chances will remain well north of Seattle.
Arctic air is, once again, likely to build into the interior of British Columbia and, once again, push through the Fraser River Valley and into Whatcom and San Juan Counties, starting late Friday.
Last time, the tricky part of the forecast was how far the cold air would spread (Answer: The Whatcom/Skagit County line) as there was plenty of moisture around -- don't forget Seattle had over 30 consecutive hours of rain. This time, it's the challenge of how far the cold air spreads and whether there's enough moisture for snow, especially Saturday, and for how much.
We're in the clear Thursday and Friday -- just a few light showers late Thursday. It's late Friday when the winds begin to blow again out of the Fraser River Valley, cooling of that far north Interior again.
Models disagree on whether a weak trough will develop in southern B.C. and will bring any moisture on Saturday and Saturday night. If so, the Whatcom County/San Juan Islands areas could see some light snow again -- perhaps 1-3 inches, and a sliding scale downward as you go south, to maybe a dusting to slushy inch as far south as Everett by Saturday night. Not looking like a big deal but we'll keep our eye on it, and again, really not looking like anything for Seattle Metro area to be concerned with.
Another main model even stays dry Saturday with no snow concerns. I'd lean toward at least a little snow up north for now. Temperatures will be in the mid-upper 30s around Bellingham but should be safely into the low 40s elsewhere.
The model that does have more moisture would add another 1-2 inches of snow for Whatcom County areas Saturday night. Again, there is not much agreement on this yet, so consider this an initial stab at the forecast. It will be windy and cold up there again with temps in the 30s and gusts 35-45 mph.
If there is moisture around, could see a mix or slushy accumulations on highest Seattle hilltops and the Eastside foothills with snow levels around 500-700 feet.
After a fairly calm start to Sunday, we will have another warm front move in sometime during the day -- either early afternoon or late evening. This could bring a decent period of snow to Whatcom/San Juan County again as with last time the precipitation falls into their cold dome of air until the warmer air erodes it away.
Models are not thinking it'll be cold enough to snow much anywhere else as of now. Again maybe the foothills and San Juan Islands, and the higher hills south of Highway 101 along the northern Olympic Peninsula.
Looks like we're all warmed up and out of any fringey snow by midday Monday with rain changing to showers. Long range models do suggest a few more rainy systems during the week now.