The past 5 days have been quite a ride with the snowstorm, then raging east wind, and very cold temps. In fact today was the coldest day in Portland in 3 years; we only made it to 28 degrees under full sunshine.
THAT is a cold low-level airmass and it isn’t going anywhere until sometime Tuesday when southerly wind arrives. Check out the warming in the Cascades today:
So we now have a trapped cold airmass below about 1,500′ and cold air still pouring through the Gorge. In fact the flow from the east has increased again this evening. Wind gusts over 70 mph have returned at Corbett…like the relative that left and is back at the front door. Easterly gradient through the Gorge is back above 8 millibars.
Models don’t handle the lowest part of the atmosphere well in this case. The WRF-GFS thinks it’ll be about 45 tomorrow, our RPM says about 45 as well, so…30 seems like a good number to me. At least we know humans are still needed in certain weather patterns.
A very wet and warm weather southwesterly flow of air arrives overhead Tuesday and continues through Wednesday. This means lots of rain, but not historic, Noah-like totals. We’re NOT in for some sort of 1996 flood. In fact we’ll likely just have localized flooding/ponding of water due to the snowmelt Tuesday night and Wednesday. By Thursday we’re back to light showers. Here’s the WRF-GFS, showing 3″+ in the mountains and 1.50-3.00″ in the valleys. The snow on the ground is probably worth about 1″ as well once it’s melted
I see two big issues in the next 48 hours:
1. Roads & Commuting
- Those roads with solid packed ice, ruts, & snow will be exactly the same Monday morning and almost the same Tuesday AM. The current rough conditions continue through the Tuesday AM commute.
- I don’t see how schools can have widespread openings Tuesday with all the snow/ice on the ground in a good chunk of the metro area.
- Finally by Tuesday evening after some rain and temps above freezing the solid ice should soften up, but then you have deep slush all over…what a mess!
- Wednesday morning’s commute will likely be the first in a week that is pretty close to normal.
2. Freezing Rain Tuesday
Rain arrives soon after sunrise Tuesday west of the Cascades. With temperatures below freezing, this is a perfect setup for a freezing rain event in at least part of the metro area and an ice storm in the Columbia River Gorge. There is no sudden warming southerly wind in the metro area during the daytime Tuesday. Lighter easterly flow continues through the Gorge through even early Wednesday. The very cold airmass will only slowly modify Tuesday and Wednesday in the Gorge. Since temps are starting very low in this cold airmass, I think there is a very good chance temps in the Gorge remain at/below freezing through at least morning/midday Wednesday!
- Assuming temps are below freezing in the metro area Tuesday morning, prepare for freezing rain (liquid rain freezing on contact) for at least a few hours in the morning for at least a part of the metro area. We’ll have a better idea of the coverage by tomorrow afternoon/evening.
- By afternoon temps should be above freezing in most of the metro area and most of us should be in the clear.
- Roads may become “freshly iced” for many of us Tuesday
- The Columbia River Gorge has a major ice storm coming Tuesday and at least early Wednesday. Very heavy rain is on the way this time…possible 2-3″ liquid in the central Gorge through midday Wednesday. IF temperatures remain below freezing this will be a crippling event east of Multnomah Falls.
By the way, this ongoing snow/ice fiasco on metro (mainly Oregon) highways and arterials (5 days after the storm) is well covered by Cliff Mass in his blog post today: http://cliffmass.blogspot.com/2017/01/portland-fails-to-clear-snow-and-ice.html. I call him the “Godfather of NW Weather” and of course he has his own opinions. I won’t rehash all his points, but it’s definitely worth a read. It’s too bad there isn’t some better alternative (than salting), but a metro area of almost 2 million people shouldn’t need to shut down for day after day after day when we have an event like this every 4-8 years. It last happened in 2008, and 2004 before that. I really like his idea of sharing snow removal equipment too since the two metro areas usually don’t have snow/ice storms at the same time! Seems like it probably wouldn’t work logistically, but interesting.
Chief Meteorologist Mark Nelsen