California Smoke Overhead But MUCH Cooler Temperatures and Rain are Ahead

Today is the last warm day for the region for a while--before the weather abruptly shifts to cooler, moister onshore flow.    And the California smoke over two-thirds of WA State this morning will soon be blown to the east.

The regional satellite image this morning is very dramatic, with a thick plume of California wildfire smoke moving across western Oregon into central and eastern Washington.  Only the northwest part of the domain is clear.

The California origin of the smoke is made clear by the NOAA HRRR model simulation, with the forecast for 2 PM shown below.

Fortunately for the residents of western Oregon and Washington, the smoke is aloft, with little of it reaching the surface.   

An east-west vertical cross-section from the NOAA model simulation shows this fortunate situation (below).  No smoke at the surface over western WA, but serious smoke aloft.  So if you are in the western lowlands from Eugene OR to Vancouver BC,  you can breathe easily.  And the smoke aloft will provide some cooling so today will be a few degrees cooler than yesterday.

But tomorrow EVERYTHING changes!  You better have your sweater or jacket handy.

A strong upper-level trough of low pressure will approach and move through on Friday and Saturday, something illustrated by the upper-level (500 hPa pressure, about 18,000 ft) map for 11 AM Friday.

The increased onshore flow through depth produced by this disturbance will push the smoke out of much of the Northwest, something illustrated by the vertical cross-section of smoke forecast for 5 AM tomorrow.  

And temperatures will fall.  Here are the temperature predictions from the University of Washington high-resolution ensemble (many forecasts) for Seattle.  Today will rise to the lower 80s, around 75F tomorrow, and around 70 on Saturday.  Where the forecasts are the same, there is less uncertainty.  

Rain?   You bet.  Here are the predicted totals through 5 AM Sunday  Good wetting in the mountains and southern BC.

Of particular importance will the cooling in eastern Washington, where high temperatures will drop into the 80s by Saturday.   And relative humidity, a key factor for wildfires, will rise substantially (see the prediction for Ephrata below for the next several days).  Low relative humidity today (only peaking around 40%), but rising to around 70% for the next four days.  Expect major progress in getting control of current wildfires in the state.

Finally, let me provide you with a visual treat.  Greg Johnson's cam at his wonderful Skunk Bay Weather site on north Kitsap captured the plume of smoke moving in this morning.  Absolutely spectacular.  View it below.  Enjoy.