Extraordinary file highs, adopted by maybe the quickest cool-down in Northwestern (US) historical past – so?

Reposted from the Cliff Mass Weather Blog

If you live west of the Oregon and Washington Cascade Ridge, tomorrow will be a day you will never forget.

The latest model runs, all in very high resolution, show even more profound extremes than previously forecast. And the end of the event will be extraordinary, with temperatures dropping as much as 50 ° C within a few hours.

Our coming weather

Records already broken

Many records fell yesterday, including a new all-time high in Portland (108F) and daily or monthly records at dozen of stations. But its nothing compared to what is about to happen now.

Situation at the moment (Sunday noon)

A fascinating diagram (below, click on the image to enlarge) shows you the 24-hour temperature change – how we behave in terms of temperature compared to exactly one day ago.

Along the SW WA coast, some places are 15-30F warmer as the wind blows to the east (from the east), displacing the cool sea air. But check out the Portland area… many places are 10-15F warmer due to increased offshore currents, with the air being warmed by compression as it sinks over the western slopes of the Cascades.

The new 108F record in Portland will be CLEARED today. 115F is quite possible.

But north of Seattle the temperatures were a bit cooler.

Ironically, it’s linked to the warmth along the coast and around Portland! To explain this, here is the predicted map of sea level pressure at 5:00 p.m. today. You can see the low winds and lines of constant pressure (isobars). You’ll also notice a low pressure area – the thermal trough – that is centered in the Willamette Valley. It is the result of warm air created by the easterly current that carries down the western slopes of the Cascade. With low pressure in the south and high pressure in the north, the thermal trough created northerly winds over Puget Sound, cooling the air as it moved north over cooler waters.

But that low pressure will move north overnight and Puget Sound will “enjoy” the hot conditions that are now burning in Portland.
Here is the latest temperature forecast for 5:00 p.m. today. You can see the very warm conditions around Portland (dark brown is 109-112) and you will see very warm conditions along the lower western slopes of the central Washington Cascades and the nearby lowlands. Near the water around Seattle, near the water, it’s going to be the upper 90s ONLY.

Tomorrow: the day of unimaginable extremes
But tomorrow everything will go terribly wrong. The thermal trough moves north and west and pushes the strong easterly, sloping current to the north over the central cascades (see map for Monday 11:00 a.m.). The sinking air is compressed / heated as it sinks.

The onset of declining compression warming will cause temperatures to warm beyond the experience of any living resident in the area (see forecast temperatures for Monday at 5:00 p.m.). Temperatures will rise above 112 ° F on the east side of Puget Sound and above 100 ° F for anyone more than a few miles from the water. Portland gets similarly warm. And so are the lower elevations of the Columbia Basin. Heat apocalypse. What else can you say?

You all know that just looking at a forecast is not enough. We have to examine many (ensembles) to evaluate our confidence in the forecast. Well, here are the high resolution ensemble temperature forecasts at SeaTac Airport. The time is indicated on the x-axis (00Z29 is Monday 5:00 p.m.). Almost every model run brings SeaTac to around 112F.

And there is more … .. after the temperature peak at around 5 p.m. it crashes steeply, like a crazy meteorological roller coaster. Some of you will sweat around dinner in temperatures as high as 110 ° C, but look for a light sweater around 6 a.m.
The reasons for this profound change? The thermal trough begins to move east over the cascades, with a sea thrust on land bringing in cool air from the Pacific (see forecast map on Tuesday at 2 a.m., green and blue colors indicate cool temperatures).

On Tuesday it will still be warm (80s for many) but the wild heat will be broken. Good luck tomorrow. They’ll talk about it for a long time.
This is the “perfect storm” that creates extreme temperatures for our region. If you want to see how I feel, watch the video (60 seconds in) [I cued it up for the WUWT audience~cr]


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