Dec 26, 2017, Tatoosh and Paradise NWAC Site Visit

Tatoosh Freezing-Fog Crust Atop Powder and Paradise NWAC Telemetry Site Visit, 26Dec2017

Well, this post started off as just a reply to this TAY thread (12-21-17 Paradise telemetry) about the sudden 30" drop in snowdepth value at the NWAC telemetry site that day. The next day, NWAC added a note to the Paradise telemetry which stated "Total snowdepth artificially lowered 30 inches 2 pm 12-21", which really made it seem as if NWAC thought that someone had dug away 30" of snow, and then on December 23 NWAC updated the note to read "Total snowdepth out 2 pm Dec 21", while completely blanking the total snowdepth column in the data (see Reply #1 below for the complete set of Paradise telemetry data from December 21-28 showing the ongoing snowdepth anomaly and notes). That other thread explores the possibility that this sudden drop in snowdepth may be part of a deliberate conspiracy by the Park Service and perhaps extending higher up in the government! But as I was about to post my reply there, I realized that it had grown into almost a trip report too, so I decided to add a few nice ski touring photos and post it as a separate TR instead.

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Panorama of the Paradise NWAC telemetry site. (click for double-size version)

I had also noticed this telemetry anomaly shortly after it occurred, and given how often I'm up at Paradise skiing, I figured that I'd be able to take a personal look at the NWAC telemetry site sometime soon to see what might have happened. But the weekend of December 23-24 was spent enjoying nice light foot-deep powder in the Tatoosh Range on both Saturday and Sunday, with great visibility both days too, and so there was no time left to make it up to Paradise from Narada Falls to check the NWAC site before gate closure time.

I headed back to the Tatoosh on Tuesday after Christmas with 4 good friends, hoping to find the same combination of fresh powder and clear skies again. Sadly, although there was 7-8" of new powder as expected from telemetry (and it was still totally untracked with apparently no one heading into the Tatoosh on Christmas day), there was also a thin icy crust atop the light powder! Right from the parking lot and all along the road skin and all the way up the north facing bowls, only a few millimeters thick in most areas, ranging up to several millimeters in the worst spots. It looked and felt like a sun crust, but given the lack of sunlight this time of year reaching anything but steep south faces, that was totally impossible. And given the cold temperatures with snow levels down near sea level throughout the previous 2 days, the only possible culprit to produce such a crust had to have been freezing fog, which consists of supercooled water droplets which remain liquid despite air temperatures below freezing, but freeze instantly on contact with any surface. It's the same process that produces rime.

This very unwelcome Christmas present is apparently widespread now throughout a large length of the Cascades from at least Stevens Pass to south of Mount Rainier. Not at all predicted in any forecasts I had seen, but reports from Crystal, Snoqualmie, and Stevens Pass on Christmas mentioned the freezing fog. And perhaps it should have been evident that something strange had happened given the telemetry data during Christmas day (see Reply #1 below) showing 0.3" of additional precip at Paradise, which produced barely 1" of additional snowfall despite temps in the low-to-mid 20s F.


Skinning up the steep slope above the Narada Falls lot, tough going in spots with thin icy crust atop powder snow atop thick old icy crust, with numerous protruding rocks and deep holes too.


Skinning along the road above the Narada Falls lot, glad to be done with the crux of the day.


Skinning up past The Castle with cool clouds drifting by.

Just as we had arrived at the parking lot, my friend Gordy was heading out, and said he would break trail for us. And he certainly did, re-breaking the entire length of the snow-filled weekend skin track for us, all the way from the parking lot to the Tatoosh ridgeline!


Distant zoomed shot of Gordy breaking trail up the bowl left of The Castle.


Out of the cold north-facing bowls and back into the sunlight for the first time in over an hour.


My 4 ski partners (seated) and Gordy, atop the Tatoosh ridgeline at 6250 ft.


Looking south at Mounts Adams, Hood, and Saint Helens on the horizon.


Dropping into the crust-topped powder.


The 22-degree solar halo above some of the best turns of the day.

Anyway, after skinning up to the Tatoosh ridgeline and skiing a long run down to the road, in somewhat mediocre conditions given the thin crust atop medium-density powder, my partners weren't too eager to ski a 2nd lap as we had originally planned. So we decided to bail out and skinned back the 1.7 miles of road from Sunbeam Creek to Narada by 2pm, with plenty of time left in the day for a couple of short hikes in the snow.


All smiles at the end of the run, but all done too!


Enjoying the long skin back to Narada.


First was a quick jaunt along the summer trail to Narada Falls, still safely doable with snowdepths about 1 ft below the top of the safety railing at the falls viewpoint (this short hike can be lethally dangerous once the snowpack is deep, given the steep slopes atop cliffs atop water). Awesome view of the mostly frozen falls with a curtain of huge icicles extending over the long overhang at the base of the andesite lava flow cliffs:



Next it was time to drive the 3 miles up to Paradise and visit the NWAC site. We parked in the former visitor center lot near the ski dorm and had barely walked to the far end of the lot, when suddenly an LE ranger pulled up in his SUV and started asking out his window what we were doing! (Clearly there is a massive conspiracy to keep people away from seeing the nefarious activities going on at the NWAC site!) I explained to him where we were headed and why (not that I should have even had to!), and asked him if he knew anything about what had happened to the telemetry site. He had no idea, hadn't even heard of the snowdepth anomaly, and had just gotten on duty that day after being off someplace else. Anyway I assured him that I knew what I was doing and that we would cause no harm to the site, and he warned us not to go inside the roped enclosure at the site before driving off. The NWAC site is located within sight of the very busy Nisqually Vista trail, which probably gets hundreds of snowshoers going past it every weekend (although very few skiers ever ski along that trail), so his concerns and warnings would have been better spent directed at the snowshoe tourists than at us.

Here's that overview panorama of the NWAC telemetry site again:

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(click for double-size version)

At right is the instrument tower, which extends about 30 ft high above the bare ground. The platform at the top includes the heated tipping-bucket hourly precip gauge and a louvered white box which contains the temperature sensor. The snowdepth sensor is mounted at the end of the long arm extending left from the tower, about 300" above bare ground, and consists of a temperature-corrected ultrasonic sensor which measures the distance to the top of the snowpack. Also at right partially buried by recent snowfall are the two 24-hour snowdepth boards, one with a similar ultrasonic sensor mounted 48" above the board, and a second manual board with a yardstick mounted to it. Sadly, neither board has been cleaned off since December 20th, perhaps there is some staffing issue or other issue responsible for that omission, although daily manual weather data is still being submitted to the National Weather Service. There is also an unknown object near the tower and 24-hour snow boards, which looks like a snow-covered bush, but given the 8 ft snowdepth it must be something else -- no idea what it might be, and I did not want to mess with anything inside the rope line.

At the left side of the roped enclosure are the manual snowdepth stake (which is the official value for Paradise in the daily weather records, not the NWAC telemetry number) and a manual precip bucket. The manual stake consists of multiple segments each roughly 7-8 ft long, which are screwed onto the previous lower segments as the snowdepth increases throughout the winter and spring. Maximum snowdepth ever recorded on the Paradise manual snowstake was 367" on March 10, 1956!! Daily snowfall and snowdepth records at Paradise extend back to 1916, although the measurement location has shifted several times in the past, and there are a substantial number of data gaps over the years, both large and small.

The NWAC telemetry site has been operational since at least 1991, and the maximum snowdepth recorded on the snowdepth sensor (as far as I can determine) appears to have been 283" on March 4, 1999. That record-setting year saw Paradise top 1000" of snowfall for the first time since the 1970s, with 1033" for the 1998-99 snow season (short of its maximum of 1122" in 1971-72), while Mount Baker Ski Area set an all-time world record for measured snowfall in a single season at 1140". Paradise still holds the all-time record for measured snowfall in any one-year period with 1224" (that's 102 ft!) from February 19, 1971, to February 18, 1972, as well as the record for average annual snowfall at any measurement site with an average of about 680". Yes, this is the single snowiest snowfall-measurement site in the entire world!!

And here's a closer look at the snowdepth sensor tower:



The snow surface under the sensor looks smooth, and matches the height and angle of the surrounding snowpack. Even though about 16"+ of new snow has fallen since the snowdepth anomaly on December 21, there is no evidence of any 30" deep hole having been dug beneath the sensor, nor of any artificial lowering of the snowdepth at the entire site.


Manual snowdepth stake and manual precip bucket, with zoomed inset showing the 90" depth.

The current snowdepth on the manual snowdepth stake was 90" as of 3pm on December 26, which matches the official value submitted to the National Weather Service that day (to view the daily manual data, go to http://w2.weather.gov/climate/xmacis.php?wfo=sew and pick 1. Rainier Paradise, WA; 2. Daily data for a month; 3. 2017-12; 4. Click Go to view the data). Here is the daily data thus far for December 2017:



So it seems clear that there was no vandalism or tampering with the snowpack beneath the snowdepth sensor. It's probably just a flaky snowdepth sensor which has failed and needs to be replaced, which is quite evident when you look at the telemetry data below for the first 7 days after the initial anomaly at 2pm on December 21. Very incorrect and wildly fluctuating snowdepth values, with a temporary return to (perhaps) near-normal operation for about 30 hours starting late on December 25 before lapsing into wild inaccuracy again on December 27. It's definitely an unusual failure mode for that snowdepth sensor to start showing a new (apparently realistic) value about 30" less than previous, instead of just totally random values or zeros that would have been obviously spurious. Luckily these