The “Gorge Cloud”

January 2, 2011

Have you seen this cloud the last few days while looking from the east side of the Portland Metro area up into the west end of the Gorge?  In some east wind events it’s clearly visible from the Glen Jackson Bridge as you travel from Washington to Oregon.  I’ve been noticing  it since I was a kid around 1980, and I’m guessing it has appeared for countless generations of people, animals, and a few thousand years back…extinct animals that called the Gorge home.  I call it the Gorge Cloud; at least in my head it’s called that.  Heading home early this afternoon, I said something like “I’ve got to finally get a picture of that cloud”, my wife shrieked “no!” as I veered off I-84 just east of Troutdale.  But this is the best pic I could get with the free “KPTV-Issued” phone.  Click for a better view, but it’s still blurry.  Actually it’s barely visible in the picture now that I look at it closely.  Tyler or any of the other better photographers, please take a better picture of it at some point for our grandchildren.  Sometimes it’ll sit there for many days, and once I timelapsed it from the Skyline Cam.  It moves from left to right. 

What is it?  It’s a good indicator of the top of the cold airmass pouring through the Columbia River Gorge.  You can see the top of Larch Mountain at 4,000′ in the picture, and during these real cold outflow events it tends to be in the same location.  So I suppose the top of the cold air IN THAT LOCATION must be around 3,000′.   The cold airmass quickly thins in the next few miles as it spreads out into the east side of the Metro Area.  In the case of today it wasn’t a real stark looking cloud; sometimes if it isn’t moist enough for condensation, it’s just a line of haze.  I saw something new today too…it’s hard to see in the second picture that I took from Larch Mountain road at the
“summit” right around 1,100′ beyond the Viewpoint Inn.  This whole area has snow-covered trees (away from the east wind), but higher up on Larch Mountain the snow appears to have melted off the trees.  I could see the area around the haze was still all white from the snow on the trees.   Like a tongue of colder air coming through the saddle up there.  Good weather geek stuff!

It’s been a cold weekend; high temps in the 30s in the metro area as the cold air keeps coming in from the east.  No records here in Portland because we’ve had several cold spells this time of year in the past.  I have really enjoyed the bright sunshine, cold temps and clear/cold nights.  Quite an invigorating change from drippy 45 degree weather.  But my heat pump is working overtime and the wood pile is getting smaller…

Upper level ridge builds overhead the next three days with warmer temps aloft creating a nice inversion.  Generally in this setup the easterly wind would increase through the Gorge, but at the same time pressure is lowering to the north as surface low pressure systems move into British Columbia.  This tends to kill the Columbia Basin cold high quite a bit easier than systems coming at us from the west or southwest.  Due to that, it’s going to be a quick warmup Wednesday and Thursday as surface flow turns southerly.  Of course such a cold airmass and moisture approaching often leads to freezing rain or snow.  In this case snow is very unlikely…too warm above.  Depending on when precipitation arrives, let’s say early Wednesday morning though, temps will be quite warm up around 1,500-3,000′ as warm southwest wind will have kicked in up there.  So freezing rain is likely this time around in some spots.  What I DON’T see is a big ice storm anywhere in the metro area and probably not even in the Gorge either.  More likely (depending on when the precipitation arrives) is a few scattered spots of freezing rain very briefly.  It’s also possible that we get cloud cover Tuesday afternoon, temps stay well above freezing as the east wind dies Tuesday night, and it just rains Wednesday.  Remember that if we lose the cold easterly flow it’s REALLY tough to get freezing rain.  Something to keep an eye on.

More interesting to me is the variability of the long-range models.  Some sort of change comes late this week and early next week.  Either real cold air from the north and dry weather, or cold air from the north meets warmer systems and an active jet coming in from the west.  Either way it appears the weather action MIGHT be about to pick up again as we head towards mid-January.   Hmmm…each weekend I’ve worked this winter I think something interesting has happened; I’m scheduled to work this weekend too.

Chief Meteorologist Mark Nelsen