An arctic cold front moving southwestward across the Columbia Basin is bringing a plunge in temperatures. When it passed through Moses Lake on Thursday afternoon, the temperature dropped from 32°F (0°C) at 13:45 to 21°F (-6°C) at 15:30. From there temperatures continued to slowly drop to reach 18°F (-8°C) by 18:30. The cold front reached the Tri-Cities at 16:40 facilitating a rapid drop in temperature that is ongoing as of writing.
Tonight, temperatures are forecast to drop to a low around 10°F (-12°C) in the Tri-Cities with Spokane getting close to 0°F (-18°C). Bitter cold combined with strong northeasterly winds has prompted National Weather Service offices east of the Cascades to issue alerts for wind chills as low as -30°F (-35°C) through Saturday. At this temperature, frostbite on exposed skin can develop in as little as ten minutes.
Strong winds will be driven Friday and Saturday by the gradient between very cold high pressure building into the Northern Rockies and incoming low pressure forecast to make landfall on the Central Oregon Coast. The pressure gradient will be tightest across the Cascades which act as a dam, only allowing higher pressure air to escape through mountain gaps. This is where wind will be the strongest but the gradient between Spokane and The Dalles before the low makes landfall will be enough to produce gusty winds throughout the Columbia Basin.
The low pressure system is forecast to produce snow in most of Eastern Oregon. Around two to five inches (5-13 cm) of snow are forecast in places like Hermiston and Pendleton through Saturday night. The Blue Mountains are likely to see between half a foot and two feet (15-60 cm) of snow depending on the elevation with higher amounts on the western slopes.
On the north side of this storm, precipitation rates drop off quickly. Current modeling indicates the low will make landfall near Newport, Oregon, which would bring maybe up to an inch (2 cm) of snow to the Tri-Cities despite modest totals just on the other side of the Horse Heaven Hills. Because of how tight the snowfall gradient will be on the north end of the storm, small deviations in the path of the low’s center will reflect significant changes in how much snow is observed.
Based on the low making landfall near Newport, the snow/no snow line will be near a line stretching from Yakima to Milton-Freewater. Union Gap could see perhaps three inches (7 cm) of snow while Selah gets barely anything under this scenario despite being only about six miles (10 km) apart. If the low lands more toward Lincoln City or Tillamook, the Tri-Cities and Yakima will be firmly in the snow zone. If it lands down toward Coos Bay then even Hermiston may miss out on snow. Neither of those are very likely, but if the low does deviate significantly from the models the southern route appears slightly more favored.
The pressure gradient across the Columbia Basin moderates after the low makes landfall allowing winds to die down. Bitter cold temperatures are forecast to continue, however, with the Tri-Cities possibly not reaching above 20°F (-7°C) again until Tuesday. If this forecast verifies, the four day period will be the longest stretch of the Tri-Cities not getting above 20°F (-7°C) since January of 2017. Highs remain below freezing through at least Thursday.
There is a decent chance of some snow in the Tri-Cities with the next regional storm coming in Wednesday into Thursday of next week. That said, it’s not exactly a guarantee yet. The 12z ECMWF ensemble, for example, has a handful of members still saying no snow while one extreme solution comes out with seven inches (18 cm). We’ll see how models handle this pattern once we get past this weekend’s event.
Bitter cold and areas of heavy snow aren’t limited to the Columbia Basin. The intrusion of arctic air is a national event with most states getting some action out of it. The Willamette Valley in Western Oregon may recieve a crippling ice storm, a blizzard warning is in effect for much of Southern Idaho, and freezing temperatures will extend as far as San Antonio and Atlanta. Travel will be difficult this weekend throughout the Pacific Northwest, especially crossing the mountains. Portland may experience blizzard conditions – most notably in the eastern portion of that metro area.
You can have a look at up to date model guidance from several short- and medium-range models by going to my Forecast Map page.
The featured image is NAM modeled temperatures (°F) for 15:00 Saturday via Windy.
3 Comments
Thank you! As someone who lived 5 decades in warm and sunny L.A. area I keep tabs on snow. I love snow, I don’t love driving in it and many drive in it as if it’s sunny and 80°f outside, which is dangerous. Anyway, I enjoy your emails, especially when we have weather conditions like these.
Thank you for the kind words! I agree, it doesn’t take much stupid driving to create big problems during snow.