Upper level ridging continues to dominate conditions throughout the Pacific Northwest. This has produced highs above 70°F (21°C) in many lowland locations over the weekend. Quillayute, near Forks on the Olympic Peninsula, even recorded a high of 80°F (27°C) on Saturday.
The Tri-Cities joined the club on Sunday with a high of 73°F (23°C). March 17 falls a few days before the average first 70°F high, which is March 22. Highs above 70°F have been observed in the Tri-Cities every month of the year.
| Threshold | 2024 | Average |
|---|---|---|
| 70 | Mar 17 | Mar 22 |
| 80 | ————— | Apr 23 |
| 90 | ————— | May 19 |
| 100 | ————— | Jun 27 |
Northeasterly flow kept the Columbia Basin fairly cool over the weekend but was also responsible for the warm temperatures west of the Cascades. The ridge shifts a bit east Monday and Tuesday to change the flow pattern and generate warmer weather in the Tri-Cities.
Look for highs in the mid-70s (24°C) on Monday and upper-70s (25°C) on Tuesday under mostly sunny skies. Hermiston has a chance of tapping 80°F (27°C) on Tuesday. The ridge begins to break down midweek for a return to cool and moist conditions.
The first regional system is forecast to come Wednesday but won’t be strong enough to do much in the basin except possibly some wind into Thursday. Clouds increase Thursday and a chance of rain returns to the Tri-Cities on Friday and lasts into the weekend.
With no strong signal for a large regional storm it looks like inland lowland areas will only see periods of light rain heading into next week. Some isolated thunderstorms are also possible but it’s too far out to nail down specifics on anything yet.
Snow levels under the new weather regime will be lower. Pacific Northwest snowpack was 89% of median for the end of day March 15. 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. Both the ECMWF Weekly and the GEFS Extended models favor generally cool conditions in place for the next couple of weeks. That chance decreases further out into the future.
