Here Comes The Wind!

December 5, 2017

7pm Tuesday

I mentioned in Sunday’s post that we’re in this weather pattern for the long haul.  Now, two days later, all models are keeping us dry or almost dry through the beginning of many school’s Christmas Vacation.  That’s Saturday the 16th for many kids.  Some schools are waiting one more week though…it’s a bit staggered this year.   Regardless, I’m quite confident the weather pattern will be VERY slow the next 10+ days.  Check out the ECMWF model’s ensemble precipitation forecast.

ecmwf_24hrqpf

It looks extremely complicated but it’s really not.   Each horizontal line on the upper half of the image is just one of 51 ensemble members; a slightly different version of the same model run.  We’re looking at 24 hour rain/snow totals.  Time goes from today on the left side to two weeks from now on the right side.  The bottom section is just the average of all of those ensembles.  Two key points here  1) The first decent rain chance isn’t until Friday/Saturday the 15th/16th.  2) Very few members show a rainy pattern and 3) A few produce no rain at all through the 19th/20th.

High pressure is developing east of the Cascades and will strengthen as cool air deepens in the lower elevations over there…

Mark EastWind ColdAir Builds Basin

That cool/dense air can only move through the Cascades in the Gorge if it’s less than 3,000′ thick.  That layer of cool air gets squeezed down much thinner as it moves into Western Oregon.  The wind accelerates as it moves from Cascade Locks to the Troutdale/Camas areas.  This pattern will continue as long as the upper-level ridge sits along the West Coast…through the next 10 days.  So you folks in the western Gorge and eastern metro area have a long period of screaming easterlies ahead…sorry!  This will be what we call a “gap wind” event where the areas downwind from the Gorge get the wind, the yellow areas on the map:

Warnings Gorge and Metro East Wind

Other parts of the metro area stick with mainly light wind.  The strongest wind will at the western “exit region” of the Gorge.

Warnings Gorge and Metro East Wind2

Peak gusts there should generally be in the 60-80 mph range the next few days.  Of course if you’re right on an exposed point (Crown Point), the wind can be even stronger.  This is the setup where you can easily record 100+ mph gusts on the steps at Vista House.  Enjoy, but bring a ski mask and a thick jacket!

Temperatures will be gradually cooling at the lower elevations the next few days (no more 50 degree highs!) while the mountains warm up as the upper-level ridge builds overhead.

On a brighter note, today’s sunset is the earliest of the year…it’ll be 4:27pm for the next 10 days.  By New Year’s Eve we’ll gain 10 minutes of daylight in the evening.  Summer isn’t far away right?

Chief Meteorologist Mark Nelsen