Snow To Sea Level Up North, But A Chilly & Wet Weekend For Us

November 2, 2017

7pm Thursday

November is here but the weather pattern the next 5 days looks more like December.  That means cold rain showers in the valleys and lots of mountain snow, plus some snow (above freeway level) is likely in the Columbia River Gorge too before the weekend is out.

Today we actually have an “arctic front” sitting across the northern part of Washington State draped east and west from an area of low pressure over the Strait of Juan de Fuca.  I’ve colored it in red on this sea level pressure map.  You can see the cold air north of that line.

It’s a boundary line between chilly/moist Pacific air to the south and dry/cold modified arctic air to the north.  North of the line sticking snow is falling down to sea level (or very close).  A gusty northeast wind is blowing across NW Washington and snow fell today (on November 2nd!) at the border crossings you’ve likely used to get to Vancouver BC.  The arctic air has pushed south due to a northerly flow in the upper atmosphere from NW Canada all the way down to Washington

Overnight the low pressure will weaken and drift south.  But the cold burst of northeast wind won’t make it any closer to us then around Seattle west of the Cascades.  That leaves us with scattered showers and a snow level down to around 2,000′ or so the next two nights in our area.  Friday will feature a mix of showers, sunbreaks, and cooler temperatures.

A 2nd disturbance drags more of that arctic air over the Pacific Ocean and spins up a low pressure center Saturday evening.  That low moves inland across SW Washington Saturday night and Sunday.

This means another burst of snow in the Cascades and valley showers later Saturday through Sunday.  Luckily the low is passing by to the north which will minimize any cold air getting pulled westward through the Gorge.  One of the inferior models (GFS) was showing just this setup in the past few days, but it has now come around to the “warmer” models.  That said, in such a chilly airmass it’s always possible we’ll see snow at the eastern end of the Gorge.  If you live in the upper Hood River Valley or anywhere else near/above 1,000′ at the east end of the Gorge there’s a pretty good chance you’ll wake up several inches of snow Sunday morning.  If the low comes any farther south than forecast, snow could fall very close to river level too…if it does.  Here in the metro area our wind should be southerly, pushing snow levels up to around 3,000′.

To summarize:  The next few days will be cool and showery in the lowlands, with highs only in the 40s Saturday and Sunday.  Lots of snow will fall in the mountains, but snow won’t stick at any point below 2,000′. 

How much snow in the Cascades?  The ECMWF seems reasonable bringing a total of around 2 feet above 5,000′

Once the Sunday system exits, we’ll be left in a cool and mainly dry beginning of the week (Monday & Tuesday).  Models diverge quite a bit for the 2nd half of next week.

The more reliable ECMWF shows mild atmospheric river event the 2nd half of the week and into the following weekend.  This would of course bring more rain than snow to ski areas.

But other models keep us in a cooler pattern with several more surges of cool air coming in from the northwest the next two weeks.  Regardless, you can enjoy this early taste of a winter chill!

Chief Meteorologist Mark Nelsen