White Christmas Unlikely For Metro Area

December 23, 2017

9am Saturday

Some of us woke up to a little snow this morning!  Precipitation is dwindling to just about nothing now but as the first cold air poured through the Gorge that area has seen 1-5″ snowfall (as forecast) and even a dusting fell in Portland’s West Hills and far east metro area (Troutdale & Gresham).

Today will be a dry day with increasing sunbreaks & cool temps.  The cold easterly wind will pick up in the Gorge and central/east metro.  Gusts 30-40 mph are likely in the windy parts of the metro area and 60-70 mph in the Gorge by this evening/overnight.

Of course the big question is Sunday and Christmas

THE BIG PICTURE

  1. The chance for a metro area ice or snow storm has gone downhill since yesterday, models are pushing that area of low pressure farther north.  This isn’t a “sure deal”, but models are heading in a warmer direction.  Sorry kids!
  2. Yesterday I gave the metro area a 50/50 chance of widespread snow (A White Christmas). I give it a 20% chance now.  It’s going to be too warm overhead to support snow for most of us in the metro area after the early morning hours.
  3. After some icy spots Sunday AM, most likely driving conditions will be okay Christmas Eve & Day across MOST of the metro area.  Best chance for icy roads midday & beyond would be top of West Hills and east of I-205/into the Gorge.

NOW TO CHRISTMAS MORNING WEST OF THE CASCADES

  • Oregon Coast will be a bit too warm for either freezing rain or snow through this event.  Good driving conditions out there, although the Coast Range could have brief freezing rain or snow around sunrise Sunday and it’ll be a mix of rain/snow through Sunday afternoon over those summits.
  • Dry through late tonight; gusty east wind blows through the Gorge and into metro area…high around 40 today.
  • Around sunrise Sunday. or a bit before, the western valleys will get a brief mix of freezing rain/snow/rain.  Some areas will be a bit too warm and just liquid rain.  We’re talking spotty stuff.  Temperatures hover right around freezing so there should be some spots of ice on roads.  I expect nothing to 1/2″ snow in spots…that’s itThat’s all you get folks! This includes down into the central Willamette Valley and up to Kelso/Longview too.
  • By mid/late morning tomorrow (and for the rest of the day), temperatures will be above freezing in just about all parts of the metro area and roads above freezing as well.  Again, I don’t expect significant travel problems for most of us tomorrow in the lowlands.
  • Tomorrow afternoon steadier precipitation picks up.  By that time temperatures a couple thousand feet overhead will be too warm to support snow.   But to get freezing rain to freeze on roads at that time of day our temperatures would have to be at least down to 30.  That’s not going to happen except right near/in the Gorge and possibly the top of the West Hills.  Thus my reasoning for expecting little/no traffic impacts after early tomorrow.
  • After sunset Christmas Eve and into Christmas Morning temperatures should hover at least a few degrees above freezing in most of the metro area, with freezing rain (ice accretion) continuing only near & in the western Gorge.  I’m thinking mainly right around Troutdale/Gresham/Camas areas
  • Most likely 90% (or more) of the metro area wakes up to 35-40 degree rain showers Christmas morning.

IN THE GORGE & HOOD RIVER VALLEY

  • A snowstorm is coming tomorrow from Multnomah Falls east
  • Expect some light snow right around sunrise, probably less than 1″.
  • Then midday tomorrow through Christmas morning expect 2-6″ new snow.  That should make for a nice 5-10″ snow on the ground for a White Christmas morning…enjoy!
  • Western Gorge will see more freezing rain than snow tomorrow afternoon/evening.  Watch out around Cape Horn, Bridal Veil, & Corbett later tomorrow.

 

Of course all the above points are based on the system moving inland just to the north as shown in this AM’s WRF-GFS model.  You see the surface low up in SW Washington at 7pm tomorrow:

And you see the result in the model snowfall forecast…almost nothing west of the Cascades.  Forecast soundings don’t support snow after early in the morning…the layer of cold air coming through the Gorge is and will continue to be very shallow.

All models seem to be coming into line with this setup (warmer than yesterday’s Euro model).  This is one time the Euro is getting beat by the others…a sad day!

IF FOR SOME REASON MODELS ARE OFF BY 50-100 MILES AND THE LOW MOVES IN SOUTH OF US, WE GET SNOWSTORM TOMORROW AFTERNOON.  But even the Euro doesn’t show that now.

So continue on with your normal pre-Christmas & Christmas plans but keep a close eye on the forecast, this blog, & temperature around your home.

Chief Meteorologist Mark Nelsen