peregrinator

Hard to tell, but I think we have some ZR mixing in with the sleet in Southeast Portland as well. And there's still 0.25-0.5" of precipitation to work with before it goes above freezing at the surface tomorrow morning.

Where exactly is this warm layer that's bringing us sleet? The SPC Mesoanalysis page says that at 3PM, Portland was still at -3C at both 925mb and 850mb. Someone also posted something earlier about the temperature at 1700' (which corresponds to 950mb) in the West Hills being 21F.

100% sleet now, although we're in a lull in the storm right now. Given how marginal the atmosphere is, I wonder if we might switch between sleet and snow for a while depending on the intensity of the precip.

About 50/50 snow/sleet here. The RAP shows the 925mb 0c line stalling somewhere in Portland for about 9 hours. Here's 8PM: http://i.imgur.com/wtYDPpK.png

Sleet mixing now.

The 18z NAM thinks we'll change to sleet here in the next couple of hours: http://68.226.77.253/text/META212/NAM212_kpdx.txt

We've been shadowed here a good bit--PDX measured 3.8" with the first batch and 1.5-3" (can't find the airport total, so I'm going off of the PNS) with the second. From this third round, I bet we've gotten at least an inch so far--I'm thinking round 3 is easily the most snow of all of them here. Depths are around 5-6" outside as moderate snow continues.

Does anyone have 12z ECMWF snowmaps, both for Portland and elsewhere? The Wunderground maps are always pretty annoying to read, but it looks like the Euro thinks it gets toasty pretty quickly here.

Whoa, visibility is down to a quarter mile here. Super heavy snow.

This time around, I don't think there's much question that precipitation amounts will be substantial here. All models have 0.50-0.80" of QPF with this upcoming batch, and the moisture feed is tapping the subtropics very well. Surface temperatures are also below freezing and there's still a good easterly gradient. What we are going to have to worry about if we want snow is the warming between 800 and 950mb. The RAP (which is very warm-biased) pushes upper-layer warmth over the area by 1PM, but it also thinks the surface temperature at PDX should be 33 right now, and insisted on turning our snow over to plain rain yesterday. The RGEM, which is also a little bit warm-biased, thinks the upper layers will be conducive to primarily sleet here as well. Thankfully, the GGEM, NAM, GFS, and ECMWF are all on the side of big snow. Of all of them, the NAM seems to be verifying the best right now at 925mb (for comparison--http://www.spc.noaa.gov/exper/mesoanalysis/s11/925mb/925mb_sf.gif?1391881161332 vs. http://mag.ncep.noaa.gov/data/nam/12/nam_namer_006_925_temp_ht.gif ). And it gives us 0.60" of QPF and doesn't turn PDX from snow to something else until 18z-00z tomorrow. And yeah, the PDX AFD was a really good read.

7" of snow would be fantastic, but I'm not so sure that we'll be all snow tomorrow--if the 06z verifies verbatim, then it would be, but there's going to be a strong southerly flow at 800-900mb tomorrow afternoon/evening and it'll be very marginal at best. A shallow warm layer producing mainly sleet is what the NAM and RGEM think will happen, so it's definitely not out of the question. The 06z version isn't out yet, but this plot for the 00z GFS shows it pretty well: http://wxweb.meteostar.com/sample/sample.shtml?text=KPDX . I agree that whatever does fall tomorrow should be frozen though--surface flow will be offshore thanks to the Gorge.

Wow, the 06z GFS hammers PDX with almost 0.75" of additional QPF falling before anywhere in the column goes above freezing. It's barely below freezing when the bulk of the precip falls, though, so I wouldn't be sold on an additional 7 inches of snow just yet. Edit: The 00z GGEM shows a similar scenario to the GFS, while the 06z NAM basically says that anything falling after 7AM will be sleet/ZR. The 06z RGEM also marginally supports a sleet profile, rather than snow.

Heavy snow here now.

The heavy band to my south has been fizzling out as it approaches Portland, especially east of the Willamette. Still a steady light snow here, though. The HRRR thought that snow would never make it past Centralia--let's see if it keeps marching northward.

Per traffic cams, it does seem to be snowing (and heavily) in Warrenton, about 10 miles away. It took about 15 minutes after echoes were over me in Portland for the snow to reach the ground.

Snow has tapered to light-moderate for the time being in SE Portland. Precip field is still working its way northward without running into too much of a brick wall; I wonder if the 25-30dbz stuff down by McMinnville will make it here intact.

21z RAP initialized very well, and shows 0.20-0.30" of post-1PM snow for the Willamette Valley (it shadows us a good bit, which makes sense), with up to 0.40" in the northern Coast Range/West Hills. Has it snowing until midnight in Portland and then shutting off. 2-5" seems like a good call right now for the Portland area. http://i.imgur.com/X1h3Brn.png

It's the snow depth, not the additional accumulation. Meanwhile, mod-heavy snow here with very nice dendrites and visibility under a half mile.

Snow picking up here. Hopefully the big band in SW Portland can make it to the east side.

I think that includes what's already on the ground--it's a map of snow depth, not accumulated snow. Thus the 48"+ readings in the Cascades. Someone posted a map of accum snow from the Euro earlier though--looked like about 4-6" in Portland.

In the long run, you're probably right. NOAA PDX also mentioned that the Gorge outflow would enhance frontogenic forcing in the northern Willamette Valley/SW WA.

Given the radar and how moist the column should be, I was thinking the snow would come in like a wall here, going from nothing to SN+ in only a few minutes. As of now, though, even with good echoes overhead, nothing's falling (EDIT: flurries just started). Hopefully the dry east winds won't be too much of a problem here. Looks like very good snow in far southwest PDX, in any case: http://www.tripcheck.com/RoadCams/cams/i5haines_pid562.jpg?1391777515

http://www.tripcheck.com/RoadCams/cams/I-5atPerkinsRd_pid797.jpg?1391774777 Heavy snow north of Salem; this band should reach PDX in an hour or so.

16z HRRR at 3hr: http://rapidrefresh.noaa.gov/HRRR/for_web/hrrr_jet/2014020716/full/1ref_sfc_f03.png Actual 11AM radar: http://radar.weather.gov/Conus/RadarImg/pacnorthwest.gif

The latest HRRR and RAP both had only about 0.25" of QPF as snow from the next round in PDX, but they also both initialized a good deal too far south. It's possible that the storm is just ahead of schedule, but it also wouldn't surprise me if this thing comes ~50 miles further north than progged. We'll see. Eyeballing 3-4" (hard to tell with drifts) from yesterday's snow here in SE Portland.