Drizzle Tuesday Night/Wednesday, Sunny and Warm Thursday/Friday

When one thinks of springtime weather in the Pacific Northwest, fires are one of the last things that typically come to mind. However, a fire flared up on Easter Sunday at the Swanson Bark and Wood Products company in Longview, Washington and quickly hopped from pile to pile of wood products under dry, brisk northerly winds. Apparently, the Cowlitz County Fire Department gets some 100 calls per year for fires near the facility, and smaller fires are common due to the heat generated from decomposing organic matter.

I am actually up in Washington right now and didn’t experience any smoke from this fire, but with gusty northerly winds, other folks in Portland did. My friend David Hagen told me of the sub-par air quality in Eastern Portland. I’ll give a shout-out to Dave here – he is an exceptional multi-instrumentalist and composer and is one of the most innately gifted musicians I’ve ever had the pleasure of working with, and he’s a good guy too!

Another fire – the Alpenhof Fire – broke out near Leavenworth, WA on Sunday afternoon. As of Monday evening, the fire was approximately 5 acres and continuing to move up a steep slope under cool but dry/gusty winds.

Current Conditions:

The sunny, breezy conditions we’ve seen over the past couple days are courtesy of northerly flow aloft resulting from the juxtaposition of a strong ridge in the Eastern Pacific and a deep trough over the Central US. The image below shows the current infrared satellite along with the overlaid 500mb ‘heights’ in meters, which are literally the elevation of the 500mb pressure level of the atmosphere. Higher heights correspond to ridges and warm/dry weather, and lower heights correspond to troughs with cool and often wet weather.

At the surface, winds have now switched lightly onshore, with the strongest winds in the Strait of Juan de Fuca. Despite the switch to onshore flow, relative humidities remain very throughout the Pacific Northwest.

This Week’s Forecast

Tuesday will be another beautiful mid-April day, with highs rising into the upper 60s under mostly sunny skies. However, onshore flow will increase Tuesday night as a weak system passes to the northeast into Interior BC, bringing a morning ‘marine layer’ of low stratus for Western Washington/Oregon and some light precipitation, primarily to the coast/Cascades.

A ridge will build behind Wednesday’s system, and Portland should see highs in the low 70s on Thursday as a thermal trough extends along the California/Oregon Coast. Onshore flow will increase for the Coast on Friday, but the Willamette Valley should see its warmest day of the year, with the Portland metro area likely hitting the mid 70s.

A weak upper-level trough will move inland this weekend, bringing increasing onshore flow and clouds and another round of light precipitation for the coast/Cascades. Next week and beyond, models give us seasonable temperatures and precipitation with a few weak systems clipping the area at times.

The tl;dr:

• This week, we’ll see a weak system Tuesday night/Wednesday morning that will bring light precipitation to the Cascades and coast, and potentially some drizzle to the Western Washington and Oregon Lowlands
• We warm into the low 70s on Thursday as a thermal trough extends north into the Willamette Valley and gives us warm/dry offshore flow, and Friday may be our warmest day of the year for the Portland metro area with highs hitting the mid 70s.
• Temps moderate again for the weekend as an upper-level trough comes through, with the threat of more light rain for the coast/Cascades and drizzle in the lowlands
• We may see a more seasonable pattern towards the latter half of next week and beyond, with weak systems coming through the area every couple days or so and near average temperatures.

Thanks for reading, and have a great week!
Charlie