Snow Wrap; More Than Expected For Some of Us

January 26, 2021

9pm Tuesday…

That was exciting! All indications were that we’d see a burst of snow/rain moving across the metro area during the mid-late afternoon. But it ended up slightly cooler than expected = more snow coverage.

I was beginning to panic around 3:30-4pm as snow was falling heavily throughout the metro area; fearing a major bust was in progress. At that point it appeared ALL of the metro area could see significant sticking snow. Luckily, (this part worked right), precipitation was lighter and temps didn’t fall as much across most of central/north/east metro. Whew! And precipitation mainly stopped by 5pm putting an end to the event.

Here are the snow totals I have so far. Notice the official Portland total means we don’t have a measurable snowfall yet this winter. There was a TRACE at the Portland NWS forecast office in Parkrose

This is always difficult because two viewers in the same area will report different totals. For example I have a 1/2″ and a 1.5″ for Happy Valley! So 1″ seems good enough. We had no accumulation at KPTV, just off Hwy 26 @ Cornell on the westside. But just a couple miles away in the hills to the northeast someone reported 2″.

IN GENERAL, the white areas saw either nothing, a brief dusting, or less than 1/2″. In those areas the forecast was right on; a snowy afternoon with a brief accumulation anywhere for a short time. That happened in Clark County and a good chunk of Portland east of the Willamette River.

These maps look amazingly similar to the WRF-GFS don’t they? This was the final morning forecast

Alright let’s recap; I’ll go negative first…

THE “BUST” OR WHAT WENT WRONG

  1. I didn’t forecast/expect Salem snow, or light totals around Silverton, Oregon City, or Clackamas county buttes (Happy Valley & Damascus). Total miss there. If only I would have paid attention to that WRF forecast a bit closer! It showed that possibility. But I’ve tended to ignore totals under 2″ due to this model “over-forecasting” light snow events in the past. Maybe that only should apply to onshore flow showers in the future. Lesson learned.
  2. Lower sticking snow in the West Hills than I forecast/expected. Temperatures a couple degrees colder than expected did the trick here. Snowy roads up there after I clearly said CLEAR ROADS METRO AREA for this afternoon
  3. Evaporative cooling was far stronger than I have seen in the past. For the geeks, I couldn’t believe Salem was 39 degrees with a dewpoint of 30 at 1pm, then one our later it was 32/30! Typically you would expect it to drop down to maybe 35-36. That was amazing.
  4. Retweeting a “NO” at the Oregonian referencing their “clickbaity” headline yesterday evening. “Oh how the turntables” was their reply as it began snowing today. So well-played! Lesson learned…you’ll get burned playing with fire kid…

WHAT WENT RIGHT TODAY

Luckily this list is longer…

  1. Models and our forecasts had the general event nailed a couple days ahead of time. A dry morning followed by evaporative cooling leading to snow in the air for just about everyone, but only signficant snow in a few spots
  2. Heaviest snow was right where models showed (and we forecast). All those 2-5″ totals against the Coast Range were impressive! There was no widespread valley snow event.
  3. Much of the central/east/north metro area only saw snow in the air and/or brief and light accumulations. Most models showed this well. I’ll be ignoring the 3km NAM in these marginal events in the future.
  4. There was little to no effect on the evening commute; except up in the West Hills. We didn’t have any sort of December 29, 2009 traffic fiasco; but only 2-4 degrees colder may have done so!
  5. Temperatures rose again after the precipitation moved on north, that was well forecast.

That’s it for tonight. This was our last “close call” for now. Notice the ECMWF ensembles show mile conditions most of the next two weeks. Sure, wet and cool at times, but not many hints of lowland snow

For tonight, most of us remain above freezing with lots of cloud cover. There might be a few icy spots high in the West Hills or in some outlying areas IF we get some clearing. But I think that’ll be patchy

Chief Meteorologist Mark Nelsen


Noon Tuesday: Snow Arriving In Coast Range and Western Willamette Valley

January 26, 2021

We’re heading into “prime time” now. All the action for the lower elevations west of I-5 will be from now through sunset or so (5-7pm). My thinking hasn’t changed. Models that were forecasting little/no snow appear to still be on track and “It’s Happening!” where they have been expecting snow. Snowing all through Coast Range now and into the lowland areas west of Salem & McMinnville too

PRECIPITATION

Precipitation spreads into the Willamette Valley and metro area next two hours and continues through the evening.

Depending on location in metro area, that precip will be rain/snow mix, or all snow. The all snow areas would be west of the West Hills (possibly at KPTV) in the western half of metro area.

THIS MEANS IT’LL GET EXCITING THIS AFTERNOON AS SNOW FLIES THROUGH THE AIR IN SPOTS, ESPECIALLY WEST METRO.

WHAT ABOUT STICKING SNOW?

Almost all sticking snow should be in far western metro, from Hillsboro and North Plains westward. But it will also stick up on Chehalem Mtn, maybe Cooper Mtn, and possibly at top of West Hills too. Expect a Trace to 3″ in these spots. Of course this includes all western valley locations from Sheridan to McMinnville, Yamhill, Forest Grove, Banks, Vernonia. I could even see a dusting in Newberg (maybe) and Amity. South Salem hills? Possibly.

Of course, if it comes down hard enough, even at 35 degrees it could stick somewhere else but it won’t last long and precipitation would need to be quite heavy.

THERE SHOULD BE NO EFFECT ON EVENING COMMUTE IN METRO AREA

After 7pm or so the precipitation dies down, plus changes to mainly rain since it’ll be warming a bit overhead.

Again, the “main action” today is 1pm-7pm. I think this HRRR model best represents what we are thinking for snow accumulation.

And the WRF-GFS; notice it gives a dusting to parts of far west metro area, West Hills, and south Salem hills. This is all reasonable.

Notice the lack of snow, even in the hills, on the east side of Willamette Valley and Clark County. That’s due to much lighter precipitation in those areas, but a few degrees warmer. And in parts of east metro the easterly wind gives a little too much “mixing” to get temps down to 33 to get that snow to stick. Yes, Banks at 300′ has a far better chance getting 1-2″ today than Sandy at 1,000′.

I’ll be on TV all through the evening, so probably no blog posts, but make sure you are following me on Facebook @marknelsenweather and Twitter @MarkNelsenKPTV. I’ll have some updates there.

Chief Meteorologist Mark Nelsen