September 3, 2017

5pm Sunday

You’ve probably heard about the new fire that started just south of the Eagle Creek Fish Hatchery 24 hours ago.  Officials say it was started by a person, potentially from fireworks as you see from the FOX12 Oregon tweet less than one hour ago.

What kind of person takes fireworks out into the woods (our woods that the public owns) after almost 3 months of no rain and lights them off???  Well, here’s the result; thousands of burned acres and the fire is raging out of control just south of I-84 above Eagle Creek and Cascade Locks.  This is the first time in my 26 years forecasting in this area that we have a large fire burning in the WESTERN end of the Columbia River Gorge.  The last time was the Falls Fire in September 1991.  That year a fire started right around Multnomah Falls and quickly moved west toward Bridal Veil and Corbett on easterly wind.  Today the wind through the Gorge has been relatively light; first light easterly then westerly breezes arrived this afternoon.  This fire is going to be a big challenge due to the changing wind direction and two very hot days ahead.  Fire conditions will be extreme with a quick spread possible.  Late tonight through Tuesday night high pressure develops to our east pushing wind from east to west through the Gorge.  It won’t be a real strong wind, but 10-25 mph wind speed under hot conditions can cause lots of trouble.  Check out the WRF-GFS (numerical weather model) cross-section of the atmosphere over Cascade Locks the next 3 days.  Click for a better view:

Notice time goes from right to left.  The bottom is sea level (river level in this case) and where it says 850 that’s about the 5,000′ elevation.  See the easterly wind beginning around sunrise Monday and continuing for about 36 hours?  A dry easterly wind coupled with an almost record-hot atmosphere for early September could spread the fire quickly westward.  Sometimes models do “over-forecast” the offshore (easterly) wind flow so maybe we’ll get lucky this time.

Beginning Wednesday, a strong WESTERLY wind returns to the Gorge which means fire danger will go down signficantly west of Cascade Locks, but increase east of there.  In fact either Thursday or Friday a thick layer of low clouds will blanket the western Gorge with near 100% relative humidity.  So the big danger for fire spread is the next two days.

Some more bad news…satellite imagery confirms a new fire about 10 miles west of Trout Lake in the Indian Heaven Wilderness area.  Here is a pic from around 3pm:

Easterly flow the next 2 days also means very thick smoke (from both fires) will likely move into the far western Gorge and possibly into the metro area through Tuesday.  We’ll see how thick it gets…we might get lucky and see most of the thickest smoke confined within the Gorge.

Stay cool the next two days…more hot weather to go!  Today we just tied the record high for September 3rd…hitting 94 at PDX.  Tomorrow and Tuesday we’ll be in the 97-100 degree range with the return of the offshore wind flow.

Chief Meteorologist Mark Nelsen