Top 2023 Weather Story

There's no doubt that the top 2023 weather story in Utah was the record setting snowfall and snowpack.  

Technically, this is a story that began with the first mountain snowstorms in October 2022.  Below was the scene on the "Collins Glacier" at Alta on October 29th, 2022, when the snow depth at the Collins observing site was already a solid 23 inches.

Early season powder skiing was then had into early November.  By November 11, when the photo below was taken, we had already crested a 60 inch snow depth at Collins, my mark for the start of "good early season conditions." 

It's hard to believe now, but the spigot actually shut off after that and we went a couple of weeks without any major storms.  You may have forgotten about this brief lull in the action, but the dark purple line in the graphic below shows how the snowpack water equivalent at Snowbird flatlined from November 11 to November 28. 

After that, it started snowing, with only some short breaks until early April.  Collins reached the coveted 100" mark, officially beginning Steenburgh winter, on December 15.  It settled back below that for a time, but powered by for the final time just before the New Year's ball drop during the epic late December/early January storm cycle which added more than 10" of water and 60" of total snow depth to the snowpack.  

After that storm cycle, the snowpack was eating 3.2 meter probes for lunch.   

A little fun for Monday morning for those wondering how deep the snowpack is in Little Cottonwood Canyon, UT. This probe is 3.2 meters (125") long and doesn't reach the ground. Credit: E. Steenburgh. pic.twitter.com/Ul6xIz8L4h

— Jim Steenburgh (@ProfessorPowder) January 23, 2023

But Mother Nature wasn't finished.  Take a look at that dark purple line in the Snowbird graph above and how it starts to climb at a steep rate around February 15 and doesn't letup until early April.  The snow kept coming.  And coming.  And coming.  A sampling of the titles from my posts in March:

• Mother Nature Can't Be Stopped
• You Ain't Seen Nothin' Yet
• It May Never Stop
• Deep Trouble
• I'm Exhausted But Thankful
• We Need This to Stop

The snow depth at Collins peaked on April 4th at a record 248 inches.  This measurement was only possible because Alta Ski Patrol was able to find a way to extend the measurement pole for their automatic snow depth sensor, which was about to be buried. The period with no data in early April was probably when they were extending it.  

It was during this period in March and early April that it became apparent that we were well past a Goldilocks season in Little Cottonwood Canyon.  On April 5th, the Alta Town Marshall issued the ominous update below.

Indeed, if we learned anything last year, it's that there can be too much of a good thing in Little Cottonwood.  I now comment that perhaps 750 inches is the upper limit of a Goldilocks season.  Although avalanche risk in the canyon is a function of many factors besides total snowfall, and major cycles can occur in lower snow years, last season pushed us too deep into the extreme, resulting in prolonged canyon closures and extended periods of stress and risk for essential workers in the canyon.  

On April 25th, Alta eclipsed the 900" mark for the season at the Collins observing site.  Below is a photo of the measurement that put them over the top.  

Courtesy Alta Ski Patrol

When all was said and done,  Alta recorded 903" for the season at Alta Collins.  

Statewide, the average snowpack water equivalent reached 30", which was also a record.  

The winter of 2022/23 left many lasting scars in Little Cottonwood that will take a long time to heal.  The tree damage from the Coalpit #4, Lisa Falls, Maybird, and Tanners slide paths is extensive and will be reminders of just how dangerous Little Cottonwood Canyon can be for years to come.  The video below from Tony Korologos shows some of the damage. 

I conclude, by thanking all of the essential workers in Little Cottonwood for keeping us safe.  Your efforts are greatly appreciated.  

About That Alpine Snow

The northern and western Alps are generally off to a good start to the ski season, but there are some caveats.  Given our current snow drought, I thought we would have a look, focusing on the eastern Alps of western Austria and northeast Italy.  

Below is an analysis of total snow depth from the avalanche.report.  This is based on computer modeling and includes observations in colored circles.  Due to frequent northerly and northwesterly flow storms, snow depths are greatest (and impressive) at upper elevations along the northern Alpine Rim, especially near the Arlberg Pass (resort areas of Zurs, Lech, and St. Anton) and in the Karwendal Alps immediately north of Innsbruck.  Snow depth is lower, but still very healthy for this time of year, in the inner Tyrol (resort areas of Ischgl, Obergurgl, Sölden).   On the other hand, the Dolomites of Northeast Italy are really hurting.  The highest snow depth I could find there was 53 cm (about 21 inches).  This is because northerly and northwesterly flow puts them in the precipitation shadow of the Alps and often results in a warm downslope wind known as the Foehn (Föhn in German).   

Source: https://avalanche.report/weather/map/snow-height

On the other hand, there have also been some exceptional warm spells in the northern Alps and a quick look at the map above reveals that there is no snow at valley level in the Inn Valley and relatively little snow at lower elevations near the Arlberg.  For instance, there is only 67 cm reported in Warth (1490 m/4888 ft) and 40 cm (16 inches) in St. Anton (1285 m/4215 ft).  So, there is an incredible gradient of snowfall with elevation in that area from low amounts in the valleys to exceptional amounts at mid- and upper-elevations.  In St. Anton, for example, one goes from 40 cm/16 inches in town to 216 cm/85 inches at the Galzig Schneeestation (2025 m/6643 ft) and 352 cm/139 inches) at the Ulmerhütte (which is also right on the divide).  

A couple photos show the situation quite well.  The first is from just south of Obertsdorf, which is in the Bavarian Alps of Germany just north of the Arlberg, near an elevation of 800 m/2624 feet.  There is no snow at valley level.

Source: https://www.foto-webcam.eu/webcam/scheibenhaus/2023/12/26/0940

Similarly, the view looking south across the Inn Valley above Innsbruck shows no snow on the valley floor and in fact no natural snow cover even on north facing aspects up to about 1300 m/4265 ft. If you take a close look, you can see the artificial snow covering the lowest ski runs of the Patscherkofel just to the left of center. 

And it is still exceptionally warm.  In fact, at the time the photo above was taken, it was 4.5˚C/40F at the camera location, which is at 1921 m/6300 ft.  

The combination of heavy snowfall interspersed with warmth resulted in snow creep issues, such as this fissure that opened up on a ski run above St. Anton about a week ago.

Source: https://www.tt.com/artikel/30871819/pisten-brachen-weg-nasser-schnee-macht-tirols-skigebieten-zu-schaffen

The steep, grassy slopes of the Alps are also prone to glide avalanches, and they have been a big concern in the recent avalanche reports.  Glide avalanches typically occur on smooth surfaces, with the entire snowpack releasing down to the ground.  Melt water often lubricates the ground to enable this to occur, with glide cracks opening up over time as the snowpack begins to creek down the slope before catastrophically releasing. A friend sent me the photo below a few days ago of some impressive glide avalanches. I think these are from near Samnaun, just south of the Austrian border in Switzerland.

So, lots of snow at upper elevations in some portions of the Alps.  The analysis above shows quite nicely how variable snowpack and snow conditions can be with region and elevation in this part of the world. I suspect there are many people traveling over the Brenner pass from Italy to Austria in search of snow this holiday season.

Low Cloud Magic

'Twas a cold but beautiful Christmas Eve in upper Little Cottonwood Canyon.  Alta was solidly above the clouds through our departure at 2 PM.  The photo below taken at about 11:30 AM from Gunsight shows the low clouds lingering over the Salt Lake Valley and in portions of the lower canyon.  

By about 2:15 as we were headed down canyon, patch low clouds had reached the Snowbird base area and producing just enough ice crystals to produce a halo.  Very pretty.  

Photo: Libby Snethen

The clouds were likely forming just beneath an elevated inversion that had its base near 700 mb (10,000 feet), as suggested by the HRRR analysis for 1800 UTC (11 AM MST).  

We normally think of inversions as being near the valley floor, but they are typically elevated when we are downstream of an upper-level ridge.  They descend with time as the ridge moves overhead.  That will happen over the next couple of days.  In fact, if you look at the HRRR forecast for 1800 UTC (11 AM) tomorrow, we don't have true inversion conditions, but there is a strong stable layer with a base near 850 mb.  Essentially, Mother Nature is warming the air aloft while cutting off an increasingly shallow cold pool near the valley floor.  

Pollution though will probably be slow to build as traffic tends to be lighter on Christmas, although I suspect you will see a bit of haze tomorrow, in contrast to todays pristine airmass. 

Show Your Christmas Spirit

It's been some time since we had a significant storm.  The Alta Snowfall History pretty much shows a flatline since December 8th, other than a slight blip for the 1.5 angry inches we got yesterday.  

Source: Alta Ski Area

That snow was mainly at high elevations.  Lower elevations saw rain.  I miss winter storms.

The models suggest scant chances for precipitation until the 23rd, so basically nearly 2 weeks without a major storm.  For Alta, most of the downscaled NAEFS ensemble members are producing less than 0.75" of water and 7.5" of snow, but perhaps 25% of the members are more excited.  

Overall, the odds of us getting a minimal Goldilocks storm with 10" or more are fairly low.  I try to be religiously neutral for this blog, but desperate times call for desperate measures.  It could be that all that is needed is a bit more Christmas spirit.  If it worked for Santa in Elf, it can work for Wasatch skiers.  

Inversion Intricacies

Last night, the cold pool beneath the inversion got shallower and the upper Avenues emerged from the smog.  I took the photo below from near 13th Avenue on my way into work.  It shows the clear skies at upper bench level, but also the thin lens of smog enveloping downtown and the lower valley.  

Upper air soundings collected at the airport yesterday morning and this morning show very subtle but important changes.  Yesterday morning, the inversion base was elevated and near 860 mb (about 400 to 500 feet above the valley floor.  Beneath the inversion was the valley cold pool that contained the fog and low-level stratus clouds.  The flow was weak in and above this layer and didn't reach 20 knots until about 775 mb (about 3300 feet above the valley floor).  

Source: SPC

This morning, however, the inversion is based right on the valley floor and temperatures below about 800 mb (about 2500 feet above the valley floor) have warmed, whereas they have cooled aloft.  20 knot winds are now evident at around 800 mb.  

Source: SPC

So, we have scoured out some of the cold air at the lowest levels (resulting in the low-level warming), leaving the fog and pollution to being confined to near the valley floor.  

A look at the PM2.5 concentrations from PurpleAir shows we are still in the unhealthy for sensitive group levels across much of the valley floor, but along the east bench, there is a rim where concentrations are either good or moderate.  

Source: PurpleAir

This is an example of what meteorologists call top-down cold pool erosion.  The flow aloft is increasing and beginning to scour out the coldest air.  It's a tough job though.  It takes a lot of energy to scour out the remarkably cold and dense air that is currently at the lowest elevations.  It would be easier to scour that air out if we had a bonafide trough with cold air moving in at upper levels, but that's not on the docket for the next few days.

The models, due to lack of resolution, an inability to properly include the presence of such shallow features, and the challenges of incorporating the complicated nature of near-surface physical processes, are not particularly good at dealing with these top-down mixout events.  I'm not exactly sure how things will play out today, but my best guess is that a shallow layer of cold air and pollution will remain resident over the Great Salt Lake and the central and northern Salt Lake Valley.  It might retreat for a short time, only to return, including to the University of Utah and some bench areas, as the flow becomes upvalley and upslope with surface heating during the day.  

I'm also not sure about how things will play out over the next few days, but at the moment, I don't think we will fully crack the inversion and get a total mixout everywhere.  I think we will see a persistent cold air pool at low levels near the lake and in many low elevation areas in the Salt Lake Valley and along the Wasatch Front.  The southern Salt Lake Valley and upper bench areas may luck out at times with clearer air.  

Hopefully I'm wrong and we crack this thing.  

Inversion Hell

Salt Lake City descended into Inversion Hell with the development of low clouds and increasing PM2.5 levels.

Today's MODIS imagery, taken around 1:30 PM local time, showed the coverage quite well with widespread low clouds (in some inastances fog) over much of the central Great Salt Lake, Skull Valley, Tooele Valley, northern Salt Lake Valley, and Davis County.  

During the satellite overpass above, the avenues foothills were cloud free, but that changed at around 4:30 when the clouds pushed into the upper Avenues.

The fog and low clouds would only be depressing if they weren't also accompanied by poor air quality.  Observations from Hawthorne Elementary along 700 East in Salt Lake City show a major increase in PM2.5 concentrations today to 45-49 ug/m3, solidly at Unhealthy for Sensitive Groups levels.  

The high temperature today at the Salt Lake City International Airport was only 32˚F.  For comparison, the maximum temperature on Mt. Baldy (11,000 ft) above Alta reached 33˚F.  

Given the meteorology of the day, I was interested in having a look at things from Ben Lomond Peak above north Ogden.  Being able to enjoy that summit in the wintertime on a clear day with light winds is extremely rare.  It is one of the most wind-raked places in the Wasatch.  Today, however, although the snow was wind jacked, the view was spectacular.  One could really see the majesty of the Wasatch Range from Willard Peak (to the north), then southward where the western face of the Wasatch rises abruptly from Ogden.  One could see pollution around North Ogden and Ogden, but then the northern edge of the low clouds, also evident in the MODIS image above, near border of Weber and Davis County.  

Here's a broader perspective.  

I'll be taking the day off tomorrow to recover and avoid breathing the outside air.