A much slower night at work, so a time to reflect on last night…
Around 9pm I noticed the increasing coverage of showers on the radar heading into the Coast Range and IR satellite image showing a nice vorticity maximum (an area of curl in the atmosphere) moving towards the northern Oregon Coast. At the same time the southerly pressure gradient up the Valley was beginning to weaken quickly.
Seeing that, I changed the forecast graphics to say “up to an inch” anywhere in the lowlands. From that time through about midnight we saw almost all of Northwest Oregon and SW Washington fill in with rain that changed to moderate to heavy snow at times. That plus calm wind allowed the sticking snow level (and temps around 32-33) to drop right down to sea level. When I left the station at 11:45pm it was snowing very heavily here in Beaverton and it mainly snowed (with rain mixed in at times) all the way home to Corbett. Roads were snow-covered over there from about 500′ on up in elevation.
So I didn’t sleep well thinking the forecast is totally busting. Wake up around 6:30am at first light, look out the window and see a tall pile of snow on the railings…about 6″ at home. Ugghh! It’s cold enough that 4-6″ might have fallen in Portland, at least that’s what I was thinking, but I went back to bed. Getting up around my usual 9am time, coffee and computer, then I realized that only some of the viewers got over that 1″ mark…apparently the precipitation intensity backed off enough along with temps staying above freezing, to keep big accumulations off the Valley floor in most areas.
The low elevation spots that went above 1″ were the Salem-Mt. Angel areas, Clark County, and east of I-205 above maybe 300′ (Gresham, Happy Valley, etc…). The majority of the Metro area (all the westside, inner and outer N, E, SE Portland, and southern suburbs) had less than 1″ and the official total was only 0.3″ So in the end I only busted for a few, but I hate these close calls and don’t like to miss forecasts.
Last night’s little event shows what precipitation intensity and lack of mixing can accomplish with a chilly air mass.
Okay, now of course (for obvious reasons), I’ve had a few comments on Facebook, and even here on this blog, about my “cancelling winter” two weeks ago.
In fact I wrote this on February 15th’s posting:
“Could we still get snow here in the cities such as Longview, Vancouver, Portland, or Salem? Sure! But it would be a brief wet snow that is on the lawns in the mornings and gone in the afternoon…similar to what we saw for a few days late last February. But as of now that is unlikely in the next 7-10 days at least.” (SHOULD HAVE LEFT OUT THAT SENTENCE)
“So go ahead and turn on your outdoor water, uncover the faucets, and for the love of all things weather, please take off your studded tires if you have no plans to leave the lowest elevations in the next 3 weeks. I just turned on my outdoor faucets today.”
Since that time, we haven’t had flooding, an arctic blast, or a widespread snow event. And you haven’t needed studs in the lowest elevations either as I mentioned when I showed this graphic:
It would help if I was more clear about what a LOWLAND SNOWSTORM is. I should have explicitly written “an all day or several day snowy event that ties up traffic with icy roads”. But you can’t fit that in one line.
Okay, so where do we go now that we’re into March? A warmer air mass with maybe a 60 degree day coming up on Sunday; we haven’t done that yet in Portland this year. Then another cold trough Tuesday next week. This one is faster moving, doesn’t dig as deeply over us, and has 850mb temps bottoming out around -6 to -8 when compared to what we just saw.
12z ECMWF and to a lesser extent the 00z GFS show some warming again later next week, but this first week of March still ends up cooler than average.
Here are the two ensemble charts:
I’ll be off tomorrow, heading up to the Pacific Northwest Weather Conference in Seattle. So probably no postings until Sunday when I work again.
Chief Meteorologist Mark Nelsen