Wet, Windy, and Snowy Pattern Returns Thursday Afternoon

Morning clouds didn’t burn off as fast as expected today, so most folks were shrouded in our typical wintertime blanket of low clouds and fog. But after a stunning Sunday and Monday, I’m completely fine with a gray day! I had a three-day weekend and got to spend a ton of time outside, and I was honestly a little unprepared for how refreshing the sunshine was. You can now see buds on most of the deciduous trees in the city, and some are even beginning to flower!

We’ll have a pleasant day tomorrow with decreasing clouds as a ridge of high pressure moves over the area. However, a deep upper-level trough will follow this ridge on Thursday, ending our much-needed taste of spring and giving us lowland rain, mountain snow, and breezy conditions just about everywhere.

500mb temperature, heights, and winds at 10pm PST Wednesday 2/12/2020. A ridge will build over the Pacific Northwest on Wednesday but the deep trough to the west of this ridge will move over the Pacific NW Thursday evening.
Credit: WeatherTogether Models
A cold front approaching the Pacific NW at 10am Thursday. Expect a few hours of steady rain with this system, followed by frequent post-frontal showers Thursday night/Friday morning. 
Credit: UW Atmospheric Sciences

Even though this front isn’t carrying a ton of moisture, the mountains will see favorable orographic enhancement due to the westerly flow both with and behind this front. Models show 8-16 inches of snow with this system, with snow levels dropping to 2,000 feet Thursday afternoon over Washington and early Friday morning over NW Oregon. Snow advisories will certainly be issued for the Cascades and travel through the passes will be difficult Thursday afternoon through Friday, and I wouldn’t be surprised if low-end Winter Storm Warnings are eventually issued for the Washington Cascades.

24-hour snow between 4pm Thursday and 4pm Friday. 
Credit: UW Atmospheric Sciences

Morning showers will give way to afternoon sunbreaks on Valentine’s Day, but our strongest storm for the foreseeable future arrives on Saturday. Models show a strong front bringing an extended period of wind/rain/mountain snow to the Pacific Northwest. This morning’s 12Z WRF-GFS run from the UW shows around an inch of rain over Portland from 4am Saturday to 4am Sunday, but the details here are subject to change. I’ll be snowshoeing Tamanawas Falls on Saturday… assuming we can make it up to the trailhead!

24-hour precipitation ending 4am Sunday 2/16
Credit: University of Washington

After a brief break next Monday and Tuesday, cool, unsettled, NW flow should return for the latter half of next week. This is a fantastic pattern for mountain snowfall; I’ve only been up once this year but I plan on changing that over the next several weeks!

GFS Ensembles showing the 850mb temp and 6-hour precip expected for the next 16 days. Current forecasts favor a brief respite from the wet weather on Monday/Tuesday (2/17-18) before returning to a cool and wet pattern for the second half of next week.
Credit: WeatherTogether Models

Our high-elevation snowpack saw significant gains from last week’s atmospheric river, and most of the West now has above-normal snowfall. We’ll see significant low-elevation snowpack gains with the drier but cooler storms expected over the next 10 days. If you like winter sports or simply looking at snow-encrusted mountains from afar, low-elevation snowpack is what you want!

Credit: National Resources Conservation Service (NRCS)

I’ll have a blog later this week summarizing the epic atmospheric river that brought record flooding to normally-dry SE Washington and NE Oregon. Thanks for reading, and enjoy the sunshine tomorrow afternoon!

Charlie

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