It’s been a tough winter for snow-lovers living in the Puget Sound region. It’s not because we haven’t seen any snow – we saw a widespread snowstorm December 8-9 that dropped an inch of snow at Sea-Tac, and a persistent but highly localized convergence zone over South Seattle delivered another 3 inches to Sea-Tac in the early morning hours of January 1 to ring in 2017. No, it’s just that Portland has been an getting an unfairly large share of winter weather. They saw an inch on December 8th (with gusty winds and freezing rain to boot), 2 inches on the 14th, and half an inch on January 7th (again, with extremely gusty winds and heavy freezing rain). And they getting more tonight as a system crosses just to their south, giving them moisture and cool, northeasterly winds.
Let’s start by looking at one of my favorite maps, the water-vapor satellite map over the Northern Pacific. This map shows the concentration of water vapor in the upper levels of the atmosphere, with green/blue corresponding to moist air and black/orange corresponding to dry air. The reason I love this map so much is that it allows us to get a clearer picture the general structure and characteristics of the atmosphere over a given area, including the precise location of low pressure systems. Also, it’s a lot prettier than a plain ol’ black and white infrared satellite picture.
Right now, you can see a large low pressure system currently impacting the West Coast. This system has tapped into an impressive atmospheric river originating near Hawaii that has given high winds, flooding rains, and astounding snow totals to some ski resorts in the Sierra Nevada. Heavenly Mountain Resort is reporting 42 inches of “overnight” (4pm to 7am) snowfall, with 114 inches in the past week. Sounds pretty “Heavenly” to me. Slightly further south, the summit of Mammoth Mountain has picked up 101 inches in the last three days, with 14 feet over the past week. These are incredible totals and definitely worthy of a blog post, which I will write in the next couple days.
Precipitation is currently falling over Northern Oregon and Southern Washington right now, with temperatures in the mid-upper 30s. According to social media, rain has JUST turned to snow in the Portland area.
Tue 10 Jan 2017
These temperatures will cool below freezing tonight thanks to strong east winds funneling cold air from the Columbia Basin through the Columbia River Gorge. These winds will be nowhere near as strong as those we saw on Saturday and Sunday with the ice storm, but they will still be strong enough to blow snow around and lower visibility. The high-resolution WRF-GFS shows widespread 25-35 mph sustained easterly winds in the Portland metro area by 9 pm.
Because temperatures are still slightly above freezing in many locations, don’t expect a solid layer of snow on the roads tonight – a slushy mess is more likely. Temperatures will cool below freezing nearly everywhere and the showers will transition into a steadier, heavier snow later tonight, allowing this slush to slowly freeze into ice and causing more snow accumulation on the roads for the Wednesday morning commute. Snow tapers off midday Wednesday as the storm moves inland, but temperatures will struggle to make it to freezing tomorrow, and with highs in the low-mid 30s for Thursday through Saturday, expect this snow to stay around until next week when we resume a warmer and wetter pattern with highs in the upper 40s.
The National Weather Service is calling for 1-4 inches of snow in the Portland metro area, with higher amounts over the West Hills and less in the Eastern Metro due to dry Gorge flow eating away at moisture and reducing snow totals in that area.
Enjoy the snow if you are in Portland! If you are in Seattle, you can take comfort in knowing we still have a lot of winter to go through.
- Charlie