Friday brought Portland’s first afternoon with temperatures above 70°F (21°C) for 2024 with a high of 71°F (22°C) at Portland International Airport. Numerous other stations throughout lowland areas of Western Oregon and parts of Western Washington also achieved 70°, though the Puget Sound Region missed out.
This comes as a ridge of high pressure builds over the Pacific Northwest to generate sunny skies. Temperatures around Portland gained an additional boost from northeast flow aloft generated by an upper level low near Las Vegas.
Northeast flow is generating some downslope wind off the Cascades. As this descends into west side lowlands, it warms from compression to add a few degrees to already seasonally warm conditions.
Ridging with northeast flow due to the Desert Southwest low is forecast to continue through the weekend. Look for highs around 75°F (24°C) Saturday, Sunday, and Monday in the Portland area under this weather pattern. Surface pollutants are likely to slowly increase over the weekend.
Threshold| 2024 |
Average |
|
|---|---|---|
| 60 | Feb 1 | Feb 18 |
| 70 | Mar 15 | Apr 2 |
| 80 | ————— | May 8 |
| 90 | ————— | Jun 14 |
Portland hit 70°F (21°C) a bit earlier than average this year but this comes in about two weeks later than the record. In 1988, Portland recorded a high of 71°F (22°C) on February 28.
Somewhat moderated warm weather continues Tuesday. The ridge axis begins to shift eastward, which will shut off the northeasterly flow coming across the Cascades. The Portland metro will remain under sunny skies but lose the downslope temperature amplification.
The ridge begins to break down midweek opening up the possibility of repeated wet systems reaching the Pacific Northwest. There isn’t a signal for a strong storm or atmospheric river, but generally cool and wet is closer to average for March.
Snow levels under the new weather regime will be lower. Pacific Northwest snowpack was 89% of median for the end of day March 14. Mountain snowpack has probably peaked for the season but this sort of weather pattern will help slow the melt.
The exception to this is British Columbia where snow water equivalent may see minor gains or sit flat for a while. The interior of southern British Columbia lies within the Columbia River watershed and water supply in that region impacts water supply in large portions of the Pacific Northwest.
Long range models also don’t show a strong signal for anything specific into the beginning of April. The GEFS Extended model oscillates between warm and cool periods while the latest ECMWF weekly run favors seasonally cool conditions for the few weeks beyond the end of this warm spell.
