pm 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

Snow Totals Metro Area And Valley.png

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.

Snow Totals Metro Area And Valley2.png

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

WRF Snow Forecast.PNG

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...don't get cocky.

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

ecmwf-ensemble-KPDX-indiv_snow_24-1662400.png

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

snow today

Chief Meteorologist Mark Nelsen

 

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