I have a number of thoughts running through my head about our snowpack and snowfall that I'd like to share. These do not really add up to a coherent story, so we'll call this scattered snowfall and snowpack snippets.
Snowbird and Thaynes Canyon Not at All-Time Records
Lots of records broken for snowpack water equivalent this season, but curiously the Snowbird and Thaynes Canyon (PCMR) SNOTEL stations are still not at all-time record snowpack water equivalents. Snowbird hit 73.8" and currently sits at a record for the date, but its all-time record maximum is 75.1", set on May 23 and May 31, 2011.
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| Source: USDA |
Thaynes Canyon hit 40.1, but that isn't even a record for the date, and the maximum is 45.2" set on May 14, 2005.
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| Source: USDA |
This is an interesting curiosity and it suggests to me that the snowpack in the highest elevations of the central Wasatch, while near the upper end of what has been observed previously, might not be that much of an outlier compared to other big seasons. Emphasis on other big seasons as it is still an impressive snowpack at those measurement sites.
Snow Depth at Alta-Collins
Expanding on that point is the snow depth at Alta-Collins. Alta Ski Patrol had to extend their measurement system a few weeks ago to enable measurements to continue to be made above 240 inches. Ultimately, the snow depth maxed at 248", a new record.
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| Source: MesoWest |
It has since settled back to a "paltry" (lol) 189" at 9 am this morning. We were at 183" at the same time in 2011. A big difference between those two seasons, as might be inferred from the Snowbird SNOTEL plot above, is there was a bit of a lull in 2011 from late February through mid March, whereas this season Mother Nature just kept pouring on the coals. This enabled the total snow depth to reach a record high this season, but now that the snowpack has settled, the two seasons are fairly close.
Snowfall Amount vs. Snowfall Water Equivalent at Alta
Here's another curious comparison between this season and 2010/11. So far this season, Alta has reported 884.5" of snow with a water content of 68.19". The 884.5" number is insanely high (the prior record was 745" if I remember right) and one reason for that is the relatively low mean water content of 7.7%. The average water content of snow at Alta is 8.4%. If the 884.5" of snow had an average water content, the total water content for the season would be 74.3" and the snowpack would be even fatter.
Curiously, the snow in 2010/11 had an anomalously high water content. Through April 18 in 2010/11, Alta measured 661.5" of snow with 62.2" of water. That's a water content of 9.4%. Thus, to this point in 10/11, we had 34% less snowfall, but only 10% less water equivalent of snowfall.
Conclusion
As noted at the beginning of this post, these snippets don't really add up to a coherent story, except perhaps that snowfall and snowpack observations are measures of different things. They are typically based on measurements at a specific location, but snowfall and snowpack exhibit a good deal of spatial variability. Snowfall and snowpack observations aren't truth, and they shouldn't be treated as such, but they are useful if you consider the uncertainties.
Hi Jim. Follow you from the PNW and we definitely use SWE as an important tool for streamflows and summer irrigation etc..but I always hear local skiers talk about that figure and SMH. Like you said not a way to define a ski season. But it’s worse in the NW where it rains a lot. It powder dumps 2 feet, and rains on it 9 times. You got 6” SWE.
ReplyDeleteThis year for example, considerably less precipitation than normal, but SWEs are above average. We received average snowfall on a lot less precipitation. So we squeaked out a decent ski season given our position.
All of these snow measures have their weaknesses.
DeleteFor looking at trends and the like, I'm a big fan of the fraction of water year precipitation retained in the snowpack at the end of the snow accumulation season. That accounts not only for precipitation, but also ablation. Useful not only in the PNW, but also in the low to mid elevations around here (and eventually upper elevations in the coming decades).
The high snow pack has also made some weird measurements at Ben Lomond Peak, measuring eqt was buried. I suspect adjustments have been made. One way or another, it's still a bunch of water +/- 5%( or something like that?)
ReplyDeleteI haven't been up to the SNOTEL site yet this year, but have seen pictures. The pillow measurement might still be good, but unless the snowpack has settled (which may have happened) or someone dug it out, the gauge measurements could have problems.
DeleteThe Thaynes one is weird, given how much above their yearly record PCMR is. And my perception is that is has been exceptionally snowy in Park City. Lots of storms hitting from the north. Maybe much less water content than normal?
ReplyDeleteIt seems like Alta Collins underreports liquid relative to the Snotel sites in the area (especially Atwater). Any insight into how SWE recording might differ at Collins vs Snotel?
ReplyDeleteCollins has a precip gauge. They are known for undercatch (meaning not capturing all the snowfall). SNOTEL has a gauge, but the snowpack measurements are based on a pillow that is under the snow. No undercatch issues.
DeleteImportant to remember 10/11 had a 2" rain event to the peaks in Jan. That has to be a factor in the higher water content.
ReplyDelete