Hot Sunday and Monday, Then Some Relief

11 pm Saturday

After the coldest spring on record for portions of the Pacific Northwest, true summertime warmth has finally arrived! Seattle reached 77 Friday and 86 today, and Portland hit 84 Friday and 93 today – both under bright sunny skies. And even hotter weather is expected Sunday and Monday, with triple digit temperatures possible in the Willamette Valley Sunday and low 90s possible in the Seattle metro by Monday. A major marine push will occur Monday night, bringing cool and cloudy conditions Tuesday and Wednesday before temperatures moderate towards the end of the week.

This is a rather pedestrian, “run of the mill” Pacific Northwest heat wave. It just seems so abnormal because we’ve been so cold for so long. For reference, today was Seattle’s first 80+ degree day of the year, and before Friday, Portland only reached 80 degrees two other times in 2022 (meaning 4 total 80+ degree days by 6/25). For comparison, Portland had already seen 25 80+ degree days by June 25th of last year!

A Note on the 2021 “Heat Dome”

This event is occurring on the anniversary of the Great Pacific Northwest “Heat Dome” that peaked from 6/26-28, 2021. However, that’s where the similarities end. The Heat Dome was an exceptional event, with a deadly combination of extreme upper-level and surface features that combined to create unprecedented heat for the Pacific Northwest. At upper levels, it was associated with a record-strong and nearly stagnant ridge of high pressure, and the intense sinking motion generated by this high pressure helped warmed temperatures to extreme levels. Because this ridge was so strong and stationary, it acted as a “cap” to keep the superheated air confined underneath the strongest sinking motion, where the continued sinking motion would warm it further. It was basically an atmospheric pressure cooker – the continuous sinking motion provided the energy to heat the atmosphere, and the high pressure overhead acted as a lid to prevent the heat from escaping.

The upper-level pattern alone, combined with the timing near the solstice, would have brought all-time record temps. However, the extremely dry soils near the surface (the 2021 spring was the driest on record and quite warm) helped raise lowland temperatures another 3-5 degrees, as most of the heat energy went into increasing temperatures at the surface and very little went towards evapotranspiration (evaporating liquid water from soils, vegetation, etc) or melting snowpack.

Out of all the major weather events the Pacific Northwest has seen, from the Columbus Day Storm of 1962 to the Labor Day Fires of 2020, nothing even approaches the 2021 Heat Dome in terms of the intensity and rarity of the respective pattern. If the Heat Dome had been centered over California instead of the Pacific NW and Canada, there’s no doubt in my mind that we would have seen rolling blackouts across the Western Energy grid due to load shedding and inadequate power supply, as California saw rolling blackouts with a far weaker heat wave in August 2020. For a summary of the Heat Dome, read my analysis here.

Current Conditions

The 500mb height/satellite imagery below shows a broad, amplifying ridge along the West Coast flanked by upper-level troughs to its east and west. The trough on the west will help usher in a strong “marine push” Monday night, but until then, we’ll be under the influence of this ridge. Away from the Pacific Northwest, you can also see some monsoonal moisture streaming into the Desert Southwest, as well as Tropical Storm Celia off the coast of Mexico.

At the surface, we can see a tongue of hot air extending north from the Great Basin into the Willamette Valley and portions of Puget Sound. This hot air is associated with lower surface pressure (since air becomes less dense the hotter it gets), so since it is centered west of the Cascades, both Western Washington and Western Oregon have seen moderate offshore flow today. Tillamook, along the Oregon Coast, reached 95 degrees today due to strong downslope flow along the Coast Range.

As of 415 pm, Tillamook is the hotspot in NW Oregon at 95 degrees, with many locations in the region in the lower 90s. And Astoria hit 86 to break their previous record of 84 for the date. https://t.co/QlTpWzaHNE #orwx #wawx #heatwave #pdxtst pic.twitter.com/VfNfTGYhaH

— NWS Portland (@NWSPortland) June 25, 2022

Sunday – Monday: Peak Of The Heat Wave

Sunday will be the hottest day for Portland, with highs approaching 100 degrees and light winds. Seattle should make it up to the mid-upper 80s due to the cooling influence of the Sound at the surface and cooler temperatures at upper levels.

On Monday, weak onshore flow will trickle into Portland throughout the day and bring temperatures back into the low-mid 90s, but Seattle should see its hottest day of the entire event, with highs rising into the low 90s. In the chart below (5pm Monday), note how Portland is clearly seeing moderating onshore flow, while Northern Washington and BC are much hotter than Sunday due to the heat continuing to progress northward. Seattle is a bit of a compromise – weak onshore flow Monday will moderate temperatures by a couple degrees, but forecasts still call for Monday to be approximately 3-5 degrees hotter than Sunday.

Monday night: The Marine Push

Monday night into Tuesday morning, the entire Pacific Northwest will get a strong “marine push” as this ridge/hot air moves east of the Cascades and cool, Pacific air rushes inland to take its place. Marine pushes are one of my favorite Pacific Northwest weather features – I love listening to the leaves rustle overnight as cool, moist oceanic air marches inland and shoves the heat east of the Cascades. With the Olympics and Coast Range dominating the western horizon, it can be easy to forget that the Pacific Ocean is just 50-100 miles to our west. A strong marine push is one of the most tangible reminders of its existence.

We stay cool Wednesday and should experience more typical summertime warmth towards the end of the week. Although I don’t see any additional heat waves over the next ten days, its safe to say that summer is finally here and it’s highly unlikely that we’ll see a continuation of the wet, cool weather that dominated early/mid June.

Heat Wave And Snowmelt

This heat wave will hasten the decline of the well-above-average snowpack currently over the Pacific Northwest. As the below image shows, all of the higher elevation/northern sites that still have snowpack are well-above-average.

Since it is June, we’ve already seen a ton of snowmelt this month regardless of how temperatures have trended compared to average. I’ve experienced this first-hand at my energy trading job, where one of my main tasks is scheduling and trading the power produced from several Columbia River hydroelectric dams. So far this month, there has been far more water flowing through the Columbia than can pass through the turbines on these dams, so the dams have had to open their spillways and the Pacific Northwest has been flooded with excess electricity.

Much of the trading strategy in the Western US this time of the year involves sending this cheap, plentiful hydropower in the Pacific Northwest south to California, but there’s been far more power available here than can be sent along transmission lines to California. So the power has either been sold to other low-demand places at low (or even negative!) prices, or it has had to be limited at the source (ex: curtailing wind generation or opting to spill water instead of running it through turbines, in addition to the water that is being spilled simply because flows exceed turbine capacity). To specifically fix the issue with oversupply without limiting carbon-free generation, we need to find ways to either increase demand within a certain region or transfer the energy to higher demand regions. This can be done in a variety of different ways – from “demand response” programs (ex: automatically turning on people’s hot water heater heaters during low demand hours to increase system load) and battery storage, to having more efficient market structures that make use of existing transmission and automatically resolve energy imbalances, to upgrading the bulk electric system itself and building/enhancing transmission lines to move power from low to high-demand areas.

The snowmelt and warm temperatures will create great conditions for experienced river rafters. My cousins live in Peshastin and love to go river rafting/kayaking on the Wenatchee River – they say conditions are best when flow is above 8,000 CFS, and I’ve heard that some experts will ride it up to 25,000 CFS. I kayaked it at 4,000 CFS and thought it was pretty intense, so I’ll definitely have to improve by abilities before I can raft or kayak the ~16,000 CFS peak expected on the 28th/29th.

Enjoy the heat Sunday/Monday and the big marine push Monday night, and look forward to warmer, sunnier days ahead!

Charlie