Friday, April 28, 2023

Secrets of the Greatest Snow on Earth, 2nd Edition

I'm excited to share that the 2nd Edition of Secrets of the Greatest Snow on Earth is now available for pre-order! Preorder now at and use the code STEE23 and you'll get 40% off.  

The book has been fully updated and has two new chapters.  There's now a deeper dive into microclimates beyond Utah, especially Japan and the Austrian Alps based on extensive and "very challenging" research in both regions.  Climate change is covered in greater depth with a look at recent snow and glacier trends in the western US and Alps and projections for changes in snow at western US ski areas.  

The scheduled publication month is July.  If you're lucky, you'll have it to cool yourself off and raise the stoke for next season during the heat of summer.  

Wednesday, April 26, 2023

Alta 900!

By now this is old news, but the big 900 has fallen at Alta.  Courtesy of the Alta Ski Patrol, below is the 6" measurement on Tuesday morning that put them over the top.  

The previous seasonal snowfall record for the resort was 748 inches in 1981–82.  I wonder if they were collecting snowfall measurements then at the base or at the current Alta–Collins site and what the frequency of measurement was.  Perhaps someone from Alta Ski Patrol can comment.  Often such info is lost to the sands of time.  

I'm curious to see where Alta-Guard ends up for the year.  Records there go back to 1945–46, although they are November to April rather than October to April.  The previous record is 745.4" for November to April set in 1994–95.  They haven't sent in their April observations to the Utah Avalanche Center yet.  

A lot of people ask me about differences between the various measurement sites in upper Little Cottonwood.  There are three that I have access to.  Alta Ski Area, Alta-Guard, and the Alta Coop site.  They measure in three different locations.  They may not use the same measurement practices (i.e., times and frequency).  Finally, those locations and practices may have changed over the years.  Perhaps they used to measure every 24 hours or at the end of the storm, but have shifted to every 12 hours or some other approach.  Perhaps they moved the measurement locations.  These changes do affect the measurements and the time series.  We have discussed this previously.   

That said, there is little doubt that this year was an epic.  Congrats to Alta on the record.  700 for next season I hope.  

Monday, April 24, 2023

Another Shot at 900

Alta is now closed for the season, but the race to 900 continues.  

Snowfall since Oct 1 now sits at 894".  Tantalizingly close.  I hear rumors that Alta Ski Patrol sits at the ready to verify 900 when we get there.  These are, however, only rumors.  

It appears we have one storm to get there before the end of the month, and that's from today through tomorrow as a closed low moves through northern Utah.  Below is the GFS forecast valid 0900 UTC 25 April (3 AM Tuesday) when the 500-mb low is forecast to be right over Salt Lake City.  

With cold air aloft, this looks like a spring special.  Lots of convection with periods of mountain snow through tomorrow, possibly with thunder and lightning.  Storms will be hit or miss.  The GFS tries to get one last gasp of northwesterly flow going and the HRRR even generates a lake band Tuesday morning although it's centered over the Salt Lake Valley rather than the central Wasatch.

However, the models are all over the place on this one.  If you are praying for snow and the record to fall, you'll like the 6Z GFS, which puts out 1.22" of water and 16" of snow by 2 PM Tuesday.  Faceshots!

On the other hand, the 6Z HRRR is the Debbie Downer of this forecast suite, giving Alta nearly a Nothing burger with only 0.12" of water and 1.2" of snow.  Pathetic.  

A big reason for this difference is the HRRR keeps the precip to our north with Alta dry until 6 AM Tuesday.  Only then does it generate the lake band (mainly west of Alta over the Salt Lake Valley) and some precipitation.  In contrast, through 6 AM Tuesday, the GFS generates an incredible 1.1" of water and 15" of snow.  For meteorologists, that's a Pepto Bismol forecast if ever there was one. 

To drive that point home a bit further, the downscaled SREF also has a range from near nothin' to over 1.5" of water and 0 to 25" of snow.  The snow-to-liquid ratios its anticipating are probably too high, but even accounting for that gives a range of 0 to 18".  

I'm inclined to go with 0.5 to 1.0 inches of water and 5-10 inches of snow.  This is basically the middle of the distribution and I confess it's a low probability forecast.  That said, I don't think a total shutout is going to happen with such a deep, cold trough moving overhead.  

Odds of getting 6" and breaking 900: 80%.

Place your bets.  For those of you who thought 900 would happen last week, now is your opportunity to do double or nothing.

Friday, April 21, 2023

Closing Weekend Frosting

Closing weekend is upon us for many Utah ski resorts, including Alta.  It looks like Mother Nature will provide some frosting later today and tonight as a parting gift.  

Below is the GFS forecast valid 0000 UTC 22 April (6 PM Friday) showing strong northwesterly flow with high integrated vapor transport impinging on the Wasatch Range.  Call it an atmospheric river if you want, although vapor transport values are only marginally near what is typically used as the atmospheric river threshold (250 kg/m/s).  

Combined with a weak trough/front passage and of course great orographic forcing, we should see mountain snow showers develop during the day today and continue into the evening hours.  There may be a few snow showers into tomorrow, although right now the models are advertising minimal accumulations after tonight.  

For Alta, the HRRR is putting out 0.57" of water and 4" of high density snow.  The high-density snow reflects the strong winds that are expected.  

The GFS is a bit wetter, putting out 0.65" of water and 6" of high-density snow through 6 AM tomorrow, plus a skiff more in fits and starts during the day tomorrow. 

Probably 4-8 inches is most likely, although if this were to bust, I think it would bust high rather than low.  I have no idea how it will ski.  I haven't skied since last Sunday and don't know if the bit of snow we've had this week has smoothed things out or if we're dealing with coral reef.  High density snow and wind are sometimes helpful in situations like this.  Keep expectations low and hope for the best.  

Wednesday, April 19, 2023

Scattered Snowpack and Snowfall Snippets

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.

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.

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. 

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.  


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.  

Monday, April 17, 2023

Let's Make a Run at 900!

It may be hard to believe given the dry sunny weather over the weekend, yesterday's high at the Salt Lake City Airport of 74˚F, and today's forecast high of 72˚F, but another cold trough is on our doorstep. 

The GFS forecasts the trough to be pushing into the Intermountain West at 1200 UTC 17 April (6 AM tomorrow morning.  In advance of it, we have a cold-frontal passage with a little valley rain and mountain snow developing overnight.  

Then the deeper and colder part of the system moves in tomorrow.  Temperatures and snow levels will drop during the day and be near the valley floor by 0000 UTC 19 April (6 PM Tuesday), with 700-mb temperatures near -10˚C. 

Thus, don't be surprised to see some flakes around late tomorrow in the valley, although  accumulations look to be limited right now.   

In the mountains, let's begin with recognition of the fact that Alta Ski Area's seasonal snowfall now sits at 879".  That's 21 inches from the coveted 900" barrier. 

The models though have a great deal of spread for this event.  The 12Z HRRR is a real sour puss, giving only 0.16" of water and 2.2" of snow for Alta Collins through 6 AM Wednesday.

The 6Z GFS, on the other hand, is a wet foot, pumping out 0.86" of water and 11.4" of snow by that same time.  The Euro is also fairly wet in the central Wasatch. 

That would put us close to the coveted 900" barrier, but the GFS isn't done.  It brings a couple more weak systems through later in the week, pushing it's total water to about 1.2" and snowfall to 17.5".  

That would put us at...896.5" if it were to verify.  

That's just one model run, but tantalizingly close.  

The GFS is actually fairly wet compared to the various downscaled NAEFS members from yesterday.  Most are under 15", although there are a few above 20.  

I'll put the odds of breaking 900" this week at 35%.  Place your verbal bets below. 

Thursday, April 13, 2023

Hot and Dusty with Avalanches and Flooding

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.  

My view is it's been too hot to ski tour, so I've been perfectly happy down in the valley dreaming of cool nights and warm (not hot) days for a good corn cycle.

Unfortunately, there is a fly in the ointment for that and that is the dust that was blown into the area yesterday.  Observations from the University of Utah snowed elevated PM2.5 levels, peaking at around 25 ug/m3 during the day yesterday. 

Source: MesoWest

This dust was kicked up and transported to the area by the strong southerly and southwesterly flow.  I had hoped that with such a wet season, we might escape without such dust, but alas, that's not to be. 

Finally, there was localized flooding in several areas of northern Utah yesterday.  In Salt Lake City, water was spilling out of the Emigration Creek fed Wasatch Hollow area and onto surface streets near 1700 East and 1700 South.  Much thanks to volunteers working to sandbag the area. 

The hydrograph for Emigration Creek, taken near Hogle Zoo, shows the flow peaking above flood stage at 155 cfs.  If the data I obtained from the NWS site is correct, the peak flow at this site is 164 cfs on May 13, 1984. 


1984 is not a typo.  As much attention as 1983 gets because of the iconic photos of water flowing down State Street, 1984 was also a monster snowpack and runoff year.  At the Parley's Summit SNOTEL, for example, peak water equivalent in 1984 (blue line) exceeded that in 1983 (brown).  This year (black line) the peak was just above 1984.

Source: USDA

The good news is that we are cooling off today, and the expectations are for the flows on Emigration Creek, after dropping overnight, to continue to drop today.

Sunday, April 9, 2023

This Is Not a Goldilocks Season for Little Cottonwood

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 putting on the skinny skis.  It was incredible to see the deep snowpack at Round Valley, which must be close to all time if not all time.  There were places where you could tell the groomers were having trouble following the route and much of the sagebrush is buried.  

Mountain biking season can wait for now.  

Friday, April 7, 2023

After Chaos Comes Quiescence

I'm still having a hard time wrapping my head around the events of this past winter and most recent storm cycle.  Little Cottonwood Canyon opened temporarily for downhill traffic this morning.  Like you, I've mainly received media snippets of the cataclysm along the highway, with many natural and human-triggered avalanches burying the road.  Coalpit #4, the lowest path in the canyon with historical evidence of reaching the highway, hit the road for the first time since 1983 per UDOT interviews. 


Photos in the tweet below from Brian Schnee show aerial views of debris from several paths covering the road.

Yesterday, an avalanche above Snowbird slid across the highway and into the upper Chickadee area, sparking a return to interlodge and a search effort that thankfully confirmed nobody was involved in the slide.  I suspect the triggering of that avalanche was related to surface heating, and illustrates that although the storm is over, avalanche concerns linger.  Hats off to all of the snow safety, snow removal, public safety, service, and other "all hands on deck" workers during this long and difficult period.  

One thing is for sure, we are moving into a more quiescent period meteorologically.  A couple of weak brush-by systems will bring some clouds and maybe a spritz or two later today and tonight and some high clouds over the weekend, but by and large, it will be dry and mild.  Then, ridging builds in for early next week.

Those of you who have had enough of winter can rejoice and those of you who haven't can still take advantage of the incredible snowpack.

Here's a curious observation for you.  The Snowbird and Thaynes Canyon (PCMR) SNOTELs are still not at their highest (all time) water equivalents.  At Snowbird, the water equivalent sits at 70.6 inches.  Although a record for the date, this lags the peak water equivalents reached in May curing the 2005 and 2011 water years.  

Source: NRCS

Thaynes Canyon sits at 39.5 inches and is the only SNOTEL in the central and northern Wasatch Range not at a record for the date (it lags 2005).  It's also below the peak in 2011.  

Both sites are above 9000 feet, so they tend to see peak snowpack in late April, and this is one reason why they are not at an all-time level.  These are also point measurements and while they are generally useful for looking at year-to-year variations, they might deviate a little from the general snowpack in the surrounding area from year-to-year.  Changes in site characteristics or moves can also affect trends and comparisons from year to year.  

Blogger Bugginess

For some reason, I have not been getting notifications when people comment on my posts.  My apologies if you asked a question and I haven't responded, although I'm not sure I would have had time anyway.  I will try and look into this at some point, but it could simply be a blogger idiosyncrasy.  

Wednesday, April 5, 2023

Serious Situation But Storm Winding Down

We are deep into outlier mode with Mother Nature calling the shots in the Cottonwoods.  Storm-total snowfall reports from the NWS includes 67" at Snowbird and 63" at Alta.  Snow depth at Alta-Collins now at all-time levels, peaking at 248" last night and currently at 247".  I went to be last night hoping that the storm would end and I'd wake up to a couple of inches on the Collins stake.  Instead, it ended up being another 15.  

The situation in the Cottonwoods is quite serious.  I can't remember Big Cottonwood closing for a full day, but that's what UDOT announced this morning.  It's possible it happened when Argenta hit the road in January 1996.  The Utah Avalanche Center report for that year said it was the first time in 50 years Argenta hit the road and West Porter ran huge, dusting cabins in Porter Fork (see Utah Avalanche Forecast Center Annual Report 1995–1996, see pages 6–7).

Alta Town Marshall Mike Morey issued the update below this morning, illustrating the seriousness of the situation.  

Early this morning, upper-level winds backed from northwesterly to westerly and the coverage and intensity of snow showers has declined in the Salt Lake Valley and Cottonwoods.  The latest radar shows the strongest echoes in the northern Wasatch and in the Brigham City area.

Today looks to be changeable.  Eventually you will see some sun at times, but also some snow showers as the surface heating bubbles things up.  There could be an angry inch here or there in the Salt Lake Valley, but net accumulations will generally be light and scattered.  In the mountains, a best guess is 2-4 inches, but hope for less.  

The end is nigh.  The models are shifting the storm track to our north and bringing warmer weather our way.  Expect a reprieve through early next week.  Sun and warmth will return and many will emerge from their winter cocoons like all the whos in whoville on Christmas day singing happy tunes with big smiles on their faces.

Whether or not we will be moving from one natural hazard (dry avalanches) to others (wet avalanches and flooding) remains to be seen.  

Tuesday, April 4, 2023

Overnight Insanity

I am deeply conflicted right now.  I'm super excited to see the snow piling up.  It appeals to my meteorological and hedonistic senses.

However, I'm once again deeply concerned about the avalanche situation.  We are just so far into outlier mode.  So much snow, greased paths, over 20 inches of water since March 1st, and now another enormous storm cycle.  

Let's look at the numbers from Alta-Collins. 10 inches yesterday through 4 PM.  17 inches overnight through 5 AM.  6 inches in 2 hours from 5-7 AM.  That's 29 inches in 24 hours.  Water during that period 1.63", so that's about 5.6% water content on average.  Storm total water equivalent is now about 2.1".  

One contributor to these snow totals was a lake-effect band that formed overnight.  We haven't seen such a well developed and long-lived band of this type in a long time. 

Snowfall rates were also high mid canyon, which is consistent with the band position.  UDOT operates a snow and weather station at Elberts a bit below Snowbird.  They did not wipe the board yesterday.  24-hour snowfall there was 27 inches.  All of that snow falling into problematic mid-canyon avalanche paths. 

Forecasts suggest the periods of snow showers will continue today and tonight.  We are now deep into the post-frontal crapshoot where the timing and position of snow showers cannot be anticipated all that well.  The models agree on moisture and instability, but not necessarily on flow direction.  The 12Z HRRR for example, has NW flow at 700 mb through 0600 UTC tonight before backing the winds to westerly during the day tomorrow.  

The 6Z GFS has more of a westerly component, especially at low levels.  

From 6 AM this morning through 6 AM tomorrow, the HRRR is only producing .25" of water and 4.2 inches of snow for Alta Collins.  That would probably be a blessing.

The GFS is going for 0.79" and 14.3" of snow.  

How's that for spread.  Like I said, the post-frontal crap shoot.  

How about I do something different and go for another 8-16" from 6 AM this morning through 6 AM tomorrow and HOPE FOR LESS.

Oh yeah, as I type this, the 8 am ob just came in and Alta-Collins has reached the coveted 240 inch/20 ft snow depth mark.  


Monday, April 3, 2023

And So It Begins

We are now a few hours into a long winter-storm period.  We picked up about 3-4" of heavy snow at my place overnight, but given the mild temps, the major roads were in good shape when I drove in early this morning.  Campus looks spectacular.  

The wet snow is sticking to everything.  It makes for beautiful scenes, but might lead to downed limbs and powerlines as this stacks up.  

In the mountains, overnight totals were greatest in the northern Wasatch.  Snowbasin is reporting 13" and PowMow 11".  

Snowfall rates at Alta-Collins picked up after 4 AM.  I can't tell if the interval board was wiped at 4 AM or not from these observations.  If it was, they are up to 7" as of 7 AM.  Otherwise it's 5" with 0.45" of water.  

As of 1329 UTC (0729 MDT) radar shows the frontal band parked right over the Salt Lake Valley, Utah Valley, and the central Wasatch, as the models have been advertising for a few days.

I didn't try to save a loop, but it shows strong confluence of the large-scale flow over the area too with southwesterly flow ahead of the front and westerly flow behind it.  That's a good recipe for what meteorologists call frontogenetical forcing, meaning the tendency for the flow to strengthen the front.  This often drives vertical circulations that yield just what you see above.  A broad band of frontal precipitation. 

For today, be it in the Salt Lake Valley or the central Wasatch, expect snow.  It will be a snow-globe day for valley dwellers.  Get into the holiday spirit.  Oh wait, that season was months ago.  

As an example of what the models are doing for today, below is our HRRR-derived snowfall guidance for the six-hour period ending at 0000 UTC 4 April (6 PM MDT Monday).  Basically, this is the HRRR guidance for this afternoon.  It's putting out about 1.6" at the airport, 2.9" at Cottonwood Heights, and 6.6" at Alta.  

The GFS is roughly similar.  

In the valley, snow depths will depend some on what surface you measure on.  For the period from 7 AM through 6 PM today, I'm expecting another 4-8" on cold surfaces along the east bench and 5-10" at Alta-Collins (note that the HRRR guidance above is only for this afternoon and doesn't include this morning's snowfall). 

This is the first part of a long-duration storm.  Pace yourselves and monitor forecasts. 

Saturday, April 1, 2023

Dusty Past to be Buried

Just last Tuesday I expressed Optimism for the Corn Harvest this season with the hope that we might see more white corn this spring. 

No sooner said than on on Thursday I saw dust being reported in observations to the Utah Avalanche Center on Thursday.  I decided to have a look today while touring and lo' and behold there it was buried with the melt-freeze crust about 45 cm under the new snow from Thursday and Friday.  

We just can't catch a break. 

It's hard to say for sure where that dust came from.  I've looked over some of the PM2.5 data we have the the U and it's evolution relative to snowfall in the Wasatch and it's unclear.  It could have been during the strong southerly flow on Wednesday afternoon, but it's not a lock.  Sometimes the noise in the numbers makes conclusions difficult.  Perhaps others with eyeballs in the mountains have ideas.  

On the plus side, that dust layer is now buried.  If we don't add another layer with the strong flow today, maybe we can bury it further with the Sunday-Tuesday storm.  That storm is looking beastly right now.  The latest GFS shows snow-showers developing in the central Wasatch tonight,

continuing at times tomorrow, 

and then a strong frontal band developing over the area by Monday morning.

That and then pivots over the area as the upper-level trough moves inland over the Intermountain West during the day on Tuesday.

Then we get into a prolonged period of unstable, post-frontal snow showers for Tuesday afternoon.

Other models, like the Euro, are less excited about tomorrow's snowshowers, but like the GFS are bullish on the frontal band and post-frontal snowshowers.  

By 6 PM Tuesday our GFS-derived product for Little Cottonwood generates 3.5" of water and 50" of snow for Alta-Collins.  The often drier ECMWF HRES is around 2.25" of water.  The National Weather Service National Blend of Models, which is an ensemble comprised of a very large number of model runs, is putting out 2.68" of water and 27 inches of snow (the snow-to-liquid ratio for that product looks a little underdone).  Some snow may fall Tuesday night into Wednesday, although right now it looks like the bulk of the system will be through 6 PM Tuesday. 

I'd lean toward 2.25-3.5" of water and 30-48" of snow by 5 PM Tuesday.  

Buckle up.