Wasatch Weather Weenies

Let's have some fun with a post based on what I'll call "sidewalk science."   The Hall of Fame Baseball catcher Yogi Berra once said "you can observe a lot just by watching."  This applies for sure to both meteorology and snow science. This afternoon, right near my house, I encountered an avalanche in the front yard of a house on 16th Avenue in the upper Avenues. Oh, I didn't actually see the avalanche happen, but I did see the aftermath, which I've summarized in the below.  It contains many of the hallmark characteristics of an avalanche.  The first is the starting zone, which in this case I measured to be 35°.  Most avalanches start on slopes between 30 and 45 degrees, so the slope here was right in that range. There is also the crown or crown line, which is the upper fracture line of the slab that broke away to create the avalanche, as well as the flank or fracture line along the side of the avalanche.  There is one on the other side, although ...

If you are looking for a good gift idea this holiday season, one that will expand the snow knowledge of your friends and family (or maybe yourself), look no farther than Karl Birkeland's recently published "book" The Starting Zone, available from avalanche.pressbooks.pub  ($49.95). I put book in quotes because The Starting Zone is an e-book available from the Friends of the Colorado Avalanche Information Center.  The Starting Zone is a living document, with tons of figures and videos and more references than you can shake a stick at (these are footnotes, so they don't clutter up the reading).  Everything is hyperlinked, allowing you to watch videos or access supporting materials with the click of the mouse or a tap of the finger (I read it on my tablet).   I am not an avalanche professional or researcher, so my perspective is of a scientist in a complimentary field (meteorology) who has been backcountry skiing for more than 30 years but has little formal avala...

 Ron Perla, an pioneering avalanche researcher and Little Cottonwood legend, was recently named a distinguished alumnus of the University of Utah Department of Atmospheric Sciences. As described in this College of Science online article , Ron was an Alta Ski Patroller and US Forest Service Snow Ranger in the 1950s and early 1970s who researched slab properties, avalanche rescue methods, etc.  He commuted back and forth from Alta to the U to complete his classes in meteorology and conduct his research.  Ron was also a mountaineer who established first routes on Mt. Robson (Canadian Rockies), Grand Teton, and our own Lone Peak in the Wasatch.   Ron Perla, US Forest Service, 1968 Alta skiers may be familiar with a run called "Perla's" on Mt. Baldy, which is named for Ron.  Ron tells the story of how he survived an avalanche on Mt. Baldy in 1967: “In 1967, I was working as a USFS Snow Ranger near the top of Mt. Baldy,” Perla says. “The cornice broke off prematu...

It's snowing, not in Utah, but in the Alps.  And probably enough to ski in some areas. Today's snow depth analysis for western Austria shows significant snow depths for September at mid and upper elevations.   Source: https://avalanche.report/weather/map/snow-height There are a few questionable observations, mainly due to the need to recalibrate (i.e., some stations strated with no snow but a measured snow depth of say 10 cm) but here's one that looks legit:  76 cm (30 inches) at Seegrube (1921 m) above Innsbruck.   Source: https://avalanche.report Here's a corresponding web cam view confirming that it looks legit. Source: https://www.foto-webcam.eu/ The GFS forecast for 0600 UTC 14 September shows a great setup for heavy precipitation in the northern Alps of Austria and the Alpine Foreland (i.e., the upstream plains) of Austria and Germany with a deep closed low centered over the Balkan States and strong integrated vapor transport wrapping c...

This has been a ski season characterized by dramatic boom and bust cycles that are very clear in the snowpack water equivalent trace for Snowbird below.  Evident are two major storm periods from December 1 to 10 and from Jan 3 to 22 that added 6.4 inches and 8.6 inches of water, respectively.  Together, these two periods account for 15 inches of the total water equivalent in the Snowbird snowpack, or about 75% of the 20.1" total.   Source: NRCS During the January storm period, it is likely that we eclipsed the 100 inch mark on the Alta-Collins total snow depth stake, but due to some erratic reports, it was difficult to know with confidence if that was the case.  The time series of total snow depth at that site over the past two weeks is below and it shows 100" first being eclipsed late in the evening on January 13.  Shortly after that though, the measurements drop abruptly back down to 94 inches and then bounce around from the high 90s to 118 inches until t...

I'm up early and looking at the overnight numbers.  It was quite windy last night, so there is more uncertainty in the automated observations than usual, but from 5 PM yesterday to 5 AM this morning, the Collins gauge measured 1.91" (48 mm) of water and probably about 20 inches of snow (the 33 below is spurious).  The drop in total snow depth is odd, and that is one reason why I mention the uncertainty.   Assuming it came in around 48 mm in 12 hours, that's somewhat unusual.  Below is a histogram of twice-daily 12-h snowfall and water equivalent (called liquid precipitation equivalent in the chart) over a 22 year period at Alta.  48 mm or more happened 10 times in that period, so about once every 2 years.   Source: Wasserstein and Steenburgh (2024) Since those are twice daily measurements, we would probably expect a few more events than that for any 12-hour period, but still, it appears we were in unusual territory.  Combined with wind and a ...

Snow continues to stack up in the Wasatch and the red flag continues to fly for the backcountry avalanche danger. Utah Avalanche Center Forecast Summary Issued 13 January 2024 From 5 AM MST Wednesday to 5 AM MST Saturday, the Alta-Collins automated snow-depth sensor has ticked off 30" of snow, putting us half way to the over-under that I set at that time for the remainder of the storm cycle through Monday (see Shall We Set the Over Under for This Storm Cycle ?).  It also lifts us up to about 43" since Jan 9 and 68.5" since Jan 4.  These numbers are based on a mixture of data from the Alta Snowfall history and the automated snow stake so they may differ slightly from other estimates, especially given yesterday's wind.  I notice that the Alta web page is listing the storm total as 44", so they must be using Jan 9 as the start date.  As I write this at 7:20 AM, we are in a bit of a lull, but I say that with a caveat. There are still some snow showers around, includ...

The storm is over.  Automated observations from Alta-Collins indicate a storm total of 15" and a settled snow depth this morning of 12".  The High Rustler cam shows it's white.  If I squint, I think I see some tracks on Nina's.   By and large though, this puts us solidly in ski purgatory.  Enough snow to whet the appetite, but not really enough to ski.  I'm sure some people will get out, but the current snowpack situation is below my tolerance level and I'm not inclined to risk injury.  Additionally, the forecast looks ridgy.  The NAEFS downscaled ensemble forecast is pretty much a flatline for the next 6-7 days, although there is one plucky member that generates six inches.   There is always hope.   I suspect, however, that most of the snow on sunny aspects will melt out over the next several days.  It will survive on upper-elevation shadier aspects, but likely facet and weaken.  Expect heterogeneous avalanche c...

In the wake of this season's historical avalanche cycle, I was curious about the resilience of the proposed Little Cottonwood gondola to such an assault. I haven't located gory details, but a basic summary is found on page 2-48 of the Little Cottonwood Canyon Environmental Impact Statement, Vol. 1 .  I had assumed that they would locate towers outside of avalanche paths, but that apparently was not possible.  Instead, the report says that gondola alignment and towers avoided avalanche paths to the extent feasible .  Otherwise, the towers would be designed to be stronger and taller, the latter for cabins to avoid the powder blast. Source:  https://littlecottonwoodeis.udot.utah.gov/wp-content/uploads/2022/08/LCC_FEIS_Volume1.pdf This season illustrates that this is a critical aspect of the gondola plans.  I obtained the image below from the Little Cottonwood Canyon Alternative Interactive Maps web site.  It shows the location of the angle station and, with a...

These are eventful times, and there is much to talk about today. First let's talk about the temperatures.  The monster swing over the past 10 days or so is well illustrated by the graphic below which is produced by the National Weather Service Forecast Office in Salt Lake City.  It shows the range of average temperatures (1991-2020) in green, record highs (top of red), and record lows (bottom of blues).  The range of observed temperatures each day are the dark blue bars.  On April 4th, the high temperature was only 33˚F.  By April 11th, it was 83˚F, a record high for the date.  Source: NWS Yesterday was a touch cooler, although we still hit 78˚F, marking three days in a row above 70˚F and five days in a row above 60˚F. As readers of this blog are well aware, this led to elevated avalanche hazard as we transitioned from dry to wet avalanches, a prolonged closure of Little Cottonwood Canyon, and regular afternoon closures of Big Cottonwood Canyon.  ...

Watching the goings on in Little Cottonwood Canyon makes me realize that when it comes to snow, there is such a thing as too much of a good thing in a season as well as in a storm. For Little Cottonwood, we have simply had too much snow this year and especially in the past few weeks.  Too many road closures, resort closures, etc. More importantly, too much risk for everyone working to keep the road open, the resorts open, services running, etc.   We would have been better off if we had gotten say 700 inches of snow at Alta instead of 877 inches, especially if the spigot was slowed over the past few weeks? Perhaps this year helps to delineate the upper boundary of the Goldilocks season in Little Cottonwood above which there is simply too much snow? Let the debate begin. Meanwhile, I've hung up the touring skis temporarily.  Yesterday I went skate skiing for the first time this season.  I've really missed it, although there are good reasons why I haven't been putt...