Cold Air Stuck in Gorge: Ice & Snow Continue Tonight

December 9, 2016

4pm Friday…

Well, in the past 24 hours here in Portland the temperature has warmed…wait for it…3 degrees.  But it’s worse.  I see it’s only risen 1-2 degrees at Troutdale, which is the location where the freezing cold air coming out of the Gorge enters the metro area.  But I know better and shouldn’t have fallen for the “quick warming” again!

plot_temps_metro

After countless events like this, I should have realized (again) that unless models forecast a significant southerly wind push up the valley (like they have been showing for days for Saturday), or a decent westerly wind in the Gorge, temps won’t warm up quickly at all.  As a result we are still in the same low-level air mass we were in yesterday at 4pm, and it has modified (warmed) by just a few degrees.  You can see how thin the cold air is overhead.  Check out the Troutdale profiler (in place for a Gorge wind study through this winter only):

ttd_profiler

The left side is the most recent data, and time is in UTC.  23 is 3pm our time.  See the warmer layer above?  It’s less than 1,500′ above us.  So basically just above the top of the West Hills and Mt. Scott it’s in the 40s right now!

This situation will continue through tonight as well with no obvious warming until a gusty southerly wind picks up midday Saturday.

TONIGHT:  East of I-205 through the western end of the Gorge (and on the hilltops) temperatures remain at or below freezing and ice accumulation will continue.  That’s especially true on objects vs. roads.  I don’t think any metro roads are WORSE than they were this morning, but the increasing load of ice is going to be taking more of a toll as we go through the evening and overnight hours.  So the NWS is continuing the Freezing Rain Advisory for these areas and the Ice Storm Warning continues in the western Gorge.

markwarningswinter-wx2

I saw one inch of ice in Corbett at 1-2pm when I headed into work:

icesign2

That’s a 6×6 or 8×8 sign post and of course because of the wind the ice is only on the upwind side.  By the time temperatures warm above freezing Saturday morning/midday, there could easily be 1.5″ to 2″ of ice accumulation, one of the biggest ice events we’ve seen out there since the disastrous December 1996 back to back ice storms.

Farther east, in the central/eastern Gorge (Bonneville to The Dalles) snow is continuing to fall so the Winter Storm Warning continues there through the night.  A total of 18″ is possible in spots:

markwarningswinter-wx

Although we’ll see quite a warm southerly wind in the valley tomorrow (and into parts of the western Gorge), that’s unlikely to translate into a big push of warming west wind farther east.  There won’t be a dramatic warming in the central/eastern Gorge tomorrow and temperatures will only rise a few degrees above freezing.  The kids can enjoy the snow for another day.

Sunday the slow thaw will continue with a better chance of a good westerly push of wind.  Regardless, temps should rise to around 40 degrees.

Chief Meteorologist Mark Nelsen