Sunday, February 27, 2022

Giving Day

The University of Utah's Annual Giving Day is this Tuesday and Wednesday March 1st and 2nd.  Yes, I know that's two days and that we are a system of higher education that should be able to do math, but it is my understanding that Giving Day is 1850 minutes long rather than 1440 because the U was founded in 1850 and it is a Founder's Day Celebration.  

If you are a fan of this blog, please consider making a donation.  The first $2,700 in donations for Atmospheric Sciences Scholarships will be matched 1:1 by department faculty, including myself, and my colleague Ed Zipser will throw in another $5,000 if we hit that mark.  To donate for scholarships, go to this link, select "Give", and choose "Atmospheric Sciences Scholarships."   Donations to other college scholarship funds also appreciated!

Alternatively, you can give to our mountain meteorology fund at this link.  That's a persona favorite of mine and very relevant for this blog.  

If you make a donation before Giving Day, no worries, your donation will still be matched!  

Thanks in advance for any contributions.


Friday, February 25, 2022

Western Snowpack Limps into March

February is almost in the rearview mirror and it looks like we will enter March with snowpack across most of the western U.S. at or below median levels. 

Below is the latest as of end-of-day February 24.   The "fattest" snowpack relative to climatology is in the Northern Oregon Coastal Mountains at 131%, although this is an area that actually does not rely much on spring snowpack melt for runoff, so that number isn't all that relevant.  There are 8 additional basins between 100 and 109% of median.  The rest are below and many are below 90% of median.    

Source: NRCS

In northern Utah, the Jordan, Weber, Lower Bear, and Upper Bear sit at 76%, 73%, 78%, and 82% of median.  The Jordan covers most of the creeks that emanate from the Wasatch Range east of Salt Lake City.  Average snowpack water equivalent at SNOTEL sites in the Jordan sits today at 11.2" of water, compared to a median for the date of 14.9".  

Source: NRCS

That's a deficit of 3.7".  Median snowpack in March increases 3.1", so basically we need to more than double the median increase in water equivalent in March to get back to median by April 1st.  That's not impossible if we get into a good storm cycle, but a low probability outcome.  

It's actually a bit worse than that because when you take the median of the snowpack water equivalent each day, you get numbers that are actually below what you get if you take the median peak water equivalent of the winters due to variations in the timing of peak snowpack. Median peak snowpack in the Jordan is 20", so we have to get 8.8" of water to get there, or almost three times the median increase in March snowpack water equivalent.  

The bottom line is that we really need a monster March this year.  

Wednesday, February 23, 2022

Painful Postmortem

Apparently my excitement for everyone in Park City was irrational exuberance.  Despite easterly flow overnight, things never really lit up over there and snowfall amounts since 5 PM yesterday appear to be in the paltry 2-4" range.  Painful.

Get out and enjoy the cold weather and snow scraps we get between now and Friday.  Ridging returns for the weekend.  A system brushes by Sunday night, although it currently looks dry, then ridging again for at least the first half of the work week.  You've seen this movie before.  

From a water and snowpack perspective, we've barely bent up the flatline this week.  It will take a monster March now to get back to median.  

There's always hope...

Tuesday, February 22, 2022

A Little Something for Park City?

How about that.  It snowed.  Alta-Collins came in with about 7" through this morning, including 4" yesterday morning and afternoon and 3" overnight.  By historical standards, it ain't much, but we can't be choosy anymore.  

The next trough swings through tonight and tomorrow.  It's a deep and complicated system as it swings across Utah.  Below is the GFS surface forecast valid at 0900 UTC 23 February (2 AM MST Wednesday).  The surface low is in southwest Utah with a fairly strong warm front extending across southern Utah and a trailing cold front across Nevada.  The flow in northeast Utah is predominantly easterly.   

This general pattern extends to 700 mb (10,000 feet).

Model soundings show a very sharp transition to southerly flow above 700 mb.  Below is the sounding from Salt Lake City.  Easterlies extend right to 700 mb, above which the flow veers (turns clockwise with height) to southwesterly.
These conditions are consistent with the presence of a warm-frontal zone aloft, to the north of the surface-based warm front over southern Utah.  Additionally, temperatures through a deep layer, extending from 800 to 600 mb, are between about -10 and -20˚C, which is good for dendritic snow growth (translation: low-density snow).  

These are conditions in which the Wasatch Back sometimes does quite well.  Basically, Park City and Deer Valley will be on the windward side of the Wasatch tonight and tomorrow morning, with large-scale forcing from the warm front and good conditions low-density snow.  

Curiously, some of the models are not being very generous for precipitation totals.  Focusing on the period from 5 PM this afternoon through 11 AM tomorrow, the 6Z GFS only puts out 0.17" of water and 3.6" of snow for Alta-Collins (I don't have a product from the GFS for Park City, so we'll improvise here).  Similarly, the NAM is only putting out 0.12" and 3.5" of snow for Alta-Collins during that period.  These numbers are fairly close to the SREF mean of about 0.2" of water and 3" of snow.  The 12Z HRRR on the other hand was more excited and generating more than an inch of water for most of the central Wasatch.  

My synoptic gut tells me that the Wasatch Back is going to do better than those numbers suggest through 11 AM tomorrow morning.  I want to go for 6-12" for Deer Valley and PCMR through 11 AM tomorrow (perhaps a bit less for the Canyons Village area), but I'd be a real outlier if I did so.  The NWS has 2-4" tonight and 1-2" tomorrow for their forecast grid-point near Empire Peak.  

Thus, I'm going to remind you that this is a blog, that my gut is often wrong, and that you should monitor official forecasts, such as this one for Empire Peak.  Additionally, low expectations are the key to a happy life, plan on dust on crust and hope for the best.  

Sunday, February 20, 2022

President's Day Powder Potential

As I write this at 9 am on Sunday morning, it's been a beautiful holiday weekend so far.  Alta's Superior web cam shows sunny skies currently, but some high clouds to the west that will eventually spread over the area during the day in advance of an approaching upper level trough and cold front.  

Source: Alta

As discussed previously, the models continue to favor a solution with the cold front weakening near the Utah-Idaho border and then redeveloping over central Utah.  

Below are GFS forecasts to illustrate this point.  Each includes color fill of 3-hour accumulated precipitation in inches based on the scale at the right.

For the 3-hour period ending at 0300 UTC 21 February (8 PM MST Sunday), the front produces a continuous band of prcipitaiton from northern Nevada into southeast Idaho.  It certainly looks good.  

However, the front falls apart as it enters northern Utah.  For the 3-hour period ending at 0900 UTC 21 February (2 AM MST Monday), the frontal band has fallen apart and there's virtually no lowland precipitation.  Instead the precipitation is confined to higher elevation areas.  

Eventually, the frontal band redevelops again over central Utah on Monday, as shown by the 3-hour accumulated precipitation ending at 2100 UTC 21 February (2 PM MST Monday). 

The good news in that forecast is that the northern edge of the redeveloped frontal band is far enough north to give the central Wasatch some snowfall.  It's a sharp northern edge and not very far north of the central Wasatch, which gives me some heartburn.

The GFS-derived time series for Alta generates about 9 inches of snow from Sunday night through late in the day on Monday.  Dribs and drabs add another seven inches through Thursday.  

The downscaled SREF, which has 26 members, produces a mean of about 7 inches through 0000 UTC 22 February (5 PM MST Monday).  However, if you look carefully, you can see that the forecasts are skewed, with a bunch just below 7 inches and a few well above 7 inches. 

This is consistent with the central Wasatch being very near the north edge of the redeveloping frontal band.  More members call for that band to be a bit to the south, so that the central Wasatch gets less snow.  Those that have it to the north produce a lot of snow.  

If one were to pull numbers out of the downscaled SREF, 6/26 members (23%) generate 10" or more of snow for Alta-Collins through 5 PM MST Monday, 9/26 members (35%) 5-10" and 11/26 members (42%) less than 5 inches.  These aren't the kinds of odd that I like as a forecaster.  I like it better when there's more clustering within a snowfall range.  

If one wants to see such clustering, one need only look farther south in the heart of the redeveloping frontal band.  On the Manti Skyline, for example, the spread of the forecast is smaller and more tightly clustered around the mean.  This is why forecast confidence for central Utah is higher.

Getting back to the central Wasatch, if I had to pick numbers, they would be for 5-10" at Alta Collins, but that's not a confident forecast.  Much is going to depend on the position of the frontal band tomorrow.  If that band develops too far south, the forecast will similarly "go south."  If the band develops a bit to the north, then it could be pretty good storm.  I'm splitting the difference going for 5-10".  

Friday, February 18, 2022

Gut-Check Forecast

Wednesday's expectation exceeding storm notwithstanding, we desperately need snow.  The Jordan and Weber River Basins now sit at about 75% of median snowpack. This is no longer a matter of skiing quality, but becoming deeply concerning for water-resource availability this summer and fall.  

Our next shot at snow is Sunday night through Tuesday.  This is a gut-check forecast if ever there was one.  There has been a lot of talk about pattern changes for the past few weeks.  The storm for Sunday night through Tuesday does not reflect a major pattern change, but a slight shift upstream (westward) shift in the position of the upper-level ridge that has produced our dry spell.  This has shifted the track of troughs in the northwesterly flow east of the ridge a bit westward.  While that gives us better shot at snow, these troughs tend to be splitters, greatly increasing the forecast complexity and range of possible outcomes. 

Here's the forecast from the 0600 UTC GFS for 0000 UTC  22 February (5 PM MST Monday).  There's sa ridge over the eastern Pacific.  That ridge has been a persistent feature the past six weeks, but it is a bit farther west than it has been, enabling a couple of short-wave troughs to drop into the western United States, which at that time are over Nevada and the Pacific Northwest.  

That's all fine and dandy, but the position and track of those troughs is really critical for snow in the central Wasatch.  That run of the GFS is actually very pessimistic about snowfall and decays the frontal band associated with the upper-level trough to our north and redevelops it to the south.  For Alta, it gives a couple of inches of snow on Sunday night and then an inch and a half mid-day Tuesday with the second trough and that's it.  

On the other hand, if you looked at the run before that, initialized at 0000, you'd be pretty excited about a dump with 9 inches Sunday night and Monday and another 6.5 inches Tuesday.  

That sort of model-to-model whiplash reflects the uncertainty in the precipitation forecast for the central Wasatch.  Start the model with different initial conditions, and you get a significantly different result.  This is why one should be cautious in using one model for forecasting.  

We can look at the ensembles and see similar uncertainty.  The SREF leans toward a low-end storm.  There are 26 members in this ensemble and for Alta the average snowfall through 0000 UTC 22 February (5 PM Monday) is about 5 inches, with a range of 1 to 9 inches.  

The NAEFS is typically wetter, with an average of about 15 inches by that time.  The NAEFS extends farther out, so it also produces a bit of snow on Tuesday or later in the week by some members. 

Although we can expect a mild weekend and a shift to colder weather on Monday, there's still a wide range of possible outcomes for snowfall amounts in the central Wasatch.  Let's hope the higher forecasts come through and this isn't another case of Mother Nature snatching defeat from the jaws of victory.

Wednesday, February 16, 2022

The Winter Olympics and Snowmaking

The holding of a Winter Olympics in a region that gets very little snow has cast a media spotlight on Olympic snowmaking and climate change.  Especially attention grabbing has been the Yanqing Alpine Venue where, until a small storm a couple of days ago, featured ribbons of artificial snow covering the courses. 

The lack of natural snow at that venue really makes the extensive use of artificial snowmaking stand out.  Media reports suggest that a million cubic meters of water was used for snowmaking for Beijing.  I wanted to check that number and dis some searching.  The Beijing 2022 Pre-Games Sustainability Report estimates that the total water demand for the Winter Olympics (November to March) in the Yanqing Zone Venues was estimated to be about 890,000 cubic meters and and for the Zhangijakou Zone Venues is 1.9 million cubic meters.  These numbers include all water consumption.  For the Zhangijakou Zone, the 1.9 million cubic meters includes 730,000 cubic meters for snowmaking and 1.17 cubic meters for domestic water consumption.  Assuming the snowmaking and domestic water consumption scale similarly for Yanqing, that gives a number that is around 1.07 million.  

How does that compare with other Olympics?  Media reports from Sochi 2014 suggest that 230 million gallons of water was used for snowmaking at the Rosa Khutor Alpine Venue.  That's 870,000 cubic meters of water.  Similarly, for the Pyeongchang 2018 Jeongseon Alpine Venue 200 million gallons was used (about 750,000 cubic meters).  Those numbers are just for the Alpine Venues.  If you add in snowmaking for cross country, biathalon, ski jumping, freestyle, etc., you're probably up around or above 1 million cubic meters.  

A lot of people have argued that the Olympics should be moved to a snowier location.  For instance, what if the Games come back to Utah in 2030 or 2034?  Utah is pretty snowy right?  

My experience during the 2002 Winter Olympics was that snowmaking was used extensively to build up a sufficient snowpack early in the winter to guarantee events will be held in February.  This happened even at Snowbasin, the highest and snowiest venue.  At a venue like Soldier Hollow, which is lower and definitely not snow sure, snowmaking was used extensively and even during non Olympic years is absolutely essential for operations.  Soldier Hollow had major problems with their snowmaking system a few years ago, forcing all sorts of disruptions.  I suspect that the water consumption at Soldier Hollow for snowmaking on a per kilometer of trail basis is not dramatically different than for the Cross Country and Biathalon venues for Beijing.  If Salt Lake City hosts the 2030 or 2034 Games, expect a lot of snow to be made.  

Alternatively, let's look at snowmaking at ski resorts.  Here's an example from the Kitzbuhel area in Austria based on a paper that was published in 2008.  This is a major resort area, which in 2008 consisted of 20 cities and villages with 6.5 million overnight stays per year by tourists, 54% of which occurred from December to March.  In this region, annual public water demand was 3.5 million cubic meters, of which 1.5 million was for overnight tourist stays.  It was estimated, however, that artificial snowmaking for the resorts required an additional 2.3 million cubic meters of water.  

The reality is that the modern Olympic Games require snowmaking.  As do many World Cup events and training facilities.  There are two reasons for this.  One is climate change.  Another is course preparation demands that require substantial amounts of snow and snow farming.  There are few places where superpipes and slopestyle courses can be built from natural snow alone.  

The 2026 Winter Olympics are will be in Milano-Cortina.  The modern Winter Olympics requires a large host city (Lake Placid could never, by itself, host the current version of the Winter Olympics).  Hence Milan.  It also requires outdoor venues, which in the case of Milano-Cortina will be scattered through the Italian Alps in Livigno, Bormio Stelvio, Val di Fiemme, Cortina d'Ampezo, and Anterselva.  Snow will be made.  A lot of it.  Those resorts make a ton of snow for regular operations. 

They could also throw a lot more weather challenges at the athletes, venue managers, and local organizing committee.  As a fan and meteorologist, I'm looking forward to it already!

Monday, February 14, 2022

Avalanches and Climate Change, Part II

Avalanche debris above Innsbruck, Austria in Spring 2019. 

This is the second of two posts exploring how climate change will affect avalanches, based in part on a recent paper by Strapazzon et al. (2021) in Frontiers in Physiology.  In the previous post, we examined the influence of climate change on the weather and snow characteristics of mountainous regions, emphasizing elevational- and seasonal-dependent trends.  Let's begin with a summary of some of the most relevant for avalanche dynamics and severity:
  • Declines in snow cover duration and depth are likely and could be large at lower elevations (for high-emissions scenarios), but trends for upper elevations are smaller or in some areas less clear (especially for low-emissions scenarios)
  • Snowfall intensity may increase, especially in colder upper-elevation areas that serve as the starting zones for major avalanches.
  • Temperatures will increase, resulting in higher snowfall densities, more mid-season melt events, and more rain-on-snow events.   
Ignoring human-triggered avalanched by recreationists which is a very complex issue, the first bullet suggests a decline in avalanche activity, especially at lower elevations.  The second bullet, however, suggests an increase in avalanche activity, especially major avalanche cycles that are typically associated with extreme winter storms.  These represent two competing effects, but current thinking is that in a warming climate the overall frequency of avalanches will likely decrease in the lower elevations due to a decrease in snow cover and the areas and situations in which avalanches can occur.  At upper-elevations, frequency trends are less clear.  Note that we should still expect a lot of variability, so these are trends that will emerge from the natural year-to-year variability as we move through the 21st century.  For instance, in a given region there could have a year with a lot of low-elevation avalanches even as the overall trend in low-elevation avalanches is downward.  

The third bullet is an interesting one as it suggests that a greater fraction of future avalanches will be wet-snow rather than dry-snow avalanches.  I see this as a likely outcome of climate change and it would likely yield an increase in the ratio of wet-snow to dry-snow avalanches.  Utah's transitional snow climate with a mixture of maritime and continental characteristics could be especially vulnerable to such as shift, which would have implications for avalanche survival.  

As discussed by Strapazzon et al. (2021), dense snow in avalanche debris is more likely to interfere with respiration and the oxygenation of buried victims.  This is consistent with studies showing that the probability of survival in avalanches drops faster with time in denser, maritime snow climates.  Thus, in a warming world, there could be a more rapid decrease with time in the likelihood of survival for buried victims, with lower survival rates in avalanche burials.  

Studies also indicate that as snow depth and cover decline, terrain "roughness" is expected to increase.  In other words, there will be more rocks and other obstacles to injure or kill victims caught in avalanches.  

Year-to-year and decade-to-decade variations in weather, snow, and avalanches are very large, so what happens in Utah the rest of this year and even for the next decade or two is difficult to anticipate.  Trends in backcountry human-triggered avalanches and fatalities are also strongly affected by education and technology.  However, in the long run it seems likely that we will see a greater percentage of wet-snow avalanches.  Given that such avalanches are already prevalent in the spring, the increase as a percentage will probably be greater in the late fall, winter, and early spring.  

Saturday, February 12, 2022

Avalanches and Climate Change, Part I

I get a lot of questions about climate change that don't have a simple answer.  As the saying goes, the devil is in the details and the answers to climate change questions are not easily generalized.  

Perhaps the hardest are those pertaining to the effects of climate change on avalanches.  There are many ways that weather, snowpack, and terrain affect snowpack and there are many types of avalanches.  Climate variables that affect avalanches include temperature, cloud cover (and its effects on solar and long-wave radiation), humidity, wind, precipitation type (rain or snow), precipitation intensity, and precipitation frequency.  The influence of each of these can vary with elevation and aspect.  Beyond the effects of greenhouse gases on climate, dust and black carbon due to land-surface disturbance or fossil fuel combustion can have a strong impact on the snow.  Finally, avalanches need a natural or human trigger and, when it comes to the latter, homo sapiens are not exactly a rational or predictable species.  

This will be a two-part post on climate change and avalanches, beginning here with an overview of climate change in mountainous regions. As is well documented, we are experiencing a shift to warmer temperatures.  For example, below is the departure of the annually averaged temperature from the 20th century average for the western continental United States from the Rocky Mountains westward.  The last year with a temperature below that average in this region was 1993.  Since 1993, 9 years have been more than 2˚C warmer than that average.  Prior to 1993, only one year eclipsed that level of warmth.  We no longer live in the climate of the 20th century.  

Data Source: National Centers for Environmental Information

Other long-term trends that have been detected in many mountainous regions include an increasing frequency and severity of warm waves, a decrease in the fraction of cool-season precipitation that falls as snow, more frequent mid-season snow ablation events (i.e., snow loss due to melting or sublimation), and a decrease in the amount of wintertime precipitation retained in the snowpack at the end of the snow accumulation season.  In some cases, especially for snow-related variables, these trends are elevation dependent.  For example, decreases in the fraction of cool-season precipitation that falls as snow are largest at lower elevations and may be non-existent at upper elevations where it can be much colder and a few degrees of warming is not sufficient to result in rainfall.  

One of the best indicators of climate change in mountainous areas are glaciers, which integrate all of these effects and serve as a very effective barometer of climate change.  According to the European Space Agency, glaciers around the world have lost over nine trillion metric tons of ice since 1961, contributing 27 mm (about an inch) to sea level rise.  Below is one example of ice loss from the Vernagt glacier in Austria.  


Studies of mountainous regions indicate strong elevation-dependent and seasonal-dependent effects of climate change on snowfall and snowpack characteristics during the 21st century.  For example, the figures below include projected trends from 14 climate models in several snow variables in the European Alps from 1981–2010 to 2070–2099 assuming a high-emissions scenario.  The left hand column shows seasonal (September to May) trends as a function of elevation.  The dashed line indicates no trend with values to the left indicating percentage declines and values to the right percentage increases.  The larger filled triangles are the multi-model mean.  
Source: Frei et al. (2018)

For this high-emissions scenario, mean Sep–May snowfall (i.e., the water equivalent of snowfall) declines are largest at lower elevations (> 80% for the multi model mean) and smallest at upper elevations (< 10% for the multimodel mean).  The graphs in the top row to the right show trend by month.  The largest trends are during the fall and spring.  The smallest are during January and February.  In the < 1000 and 1000-2000 m elevation bands, there are declines every month.  Above 2000 meters, some models actually generate a slight increase in snowfall from December to March.  This may seem paradoxical, but snowfall is dependent on the amount of precipitation and the fraction of that precipitation that falls as snow.  These are cold altitudes in the current climate and warming favors an increase in precipitation, most of which will still fall as snow (see the bottom row). 

Declines in storm frequency and increases in storm intensity are expected with global warming, and at all elevations snowfall frequency declines.  The decline is largest in the lower elevations because snowfall becomes less common as more and more storms produce rain.  

Snowfall intensity as calculated for this study is pretty odd because it is the average snowfall intensity (water equivalent per day) on days with snow.  In the lowest elevations, this actually goes up because there are few snow days, but when it does snow, it snows like hell.  

Heavy snowfall might be a better measure.  This is the trend in snowfall on the top 1% of snowfall days.  Basically, the biggest events.  Those go down at all but the highest elevations.  Maximum 1 day snowfall exhibits similar trends.  It is worth noting, however, that this is for a high-emissions scenario with a great deal of warming, so many storms are producing rain.  For a lower emissions scenario, largest 1 day events in the lower-to-mid elevations might stay about the same or increase some.  It's basically a race between storms becoming more intense but temperatures increasing to result in more rain.  

So let's summarize.  It's getting warmer and warm spells are becoming more frequent and extreme.  Storms are trending to be a little less frequent and a little more intense.  Impacts on snowfall, snow fraction, and snow frequency are elevation dependent.  Trends for these variables in the Alps (and many other midlatitude mountainous areas) are expected to be large and negative in the lower elevations and smallest or possibly even positive in the upper elevations.  The size of these trends will depend on future greenhouse gas emissions.  The graphs above above assume a high emissions scenario.  Under a lower emissions scenario, declines at lower and mid elevations may be much smaller.  There could be an increase in the size of the largest snowfall events before the caustic effects of temperature increases result in more and more precipitation falling as rain. 

This sets the table for part II when we look at what all this means for snowpack and avalanches.

Friday, February 11, 2022

Spring Begins

Sadly, there was no Steenburgh winter this year, that period from when Alta-Collins reaches a 100" snow depth to 10 February when day length and solar angles start to increase rapidly, with the sun having an increasingly caustic impact on the snow.  Peak snow depth at Alta-Collins was 97 inches in early January, so we were close, but close is not close enough for the snow snobbery that we promote on this blog.  

Thus, spring begins today.  You're probably already noticing the sun rising earlier and setting later.  Maybe you'r noticing the sun more on slopes that were often topographically shaded in December (Collins Gulch I'm thinking of you).  

I continue to monitor the medium-range forecast.  It's not changing a lot on the large scale.  The ridge over the northeast Pacific continues to dominate, with out best hope being troughs that drop down into the western US from the northwest.

The next one is forecast to be affecting Utah on Tuesday.  Incredulously, in the GFS forecast below, the system is too far west for us to get a direct hit.  

The GFS is just one forecast.  There are some members of our downscaled NAEFS that are more optimistic, although a majority of members are less than the coveted 10 inch deep-powder event.  

I guess there's always hope.  

Tuesday, February 8, 2022

Olympic Snow Snobbery

It's been interesting watching social media feeds the past couple of days and all of the comments about the snow conditions at the Yanqing Alpine Venue in Beijing. 

The lack of natural snow at the venue, which is consistent with the dry wintertime climate of the region, has very much highlighted the role of artificial snowmaking in the Olympics.  

However, claims like the one below that there's something unusual about the snow surface and that it is a problem for Alpine ski racing are simply not accurate.  

The reality is that Alpine ski racers prefer a hard, icy, durable snow surface.  In a recent study, athletes and coaches were asked to rate the influence of 23 weather/snow conditions on performance, fairness, safety, and overall impact on a scale from ideal to unacceptable.  Conditions rated closest to ideal were hardpack snow, injected surface (this typically means a snow surface injected with water, which freezes and makes it harder), ice, and machine-made snow.  Fresh Powder?  It ranks amongst the most unacceptable snow conditions.  

Source: Scott et al. (2022)

Hard, icy snow is challenging and durable.  It holds up well to the onslaught of skiers who are carving ruts along a very similar track.  Soft courses deteriorate into rutty, unfair, and sometimes dangerous conditions very quickly.  

Once a course is prepared, natural snow is a detriment to skiing.  If it snows at a world cup or Olympic race, efforts are made to remove it from the course, exposing the old hard surface.  

World Cup racers are used to skiing on hard, icy snow and on artificial snow.  Snow is a very complex substance, so exactly how a snow surface feels is going to depend on many factors and how the course is prepped, the weather, etc.  Some skiers probably like the texture of artificial snow less than others, but the snow surface in Beijing has gotten solid reviews from experts and from racers.  Here are two examples.

"I am not a specialist for snow making, I'm a course designer, but what I can tell you is that the snow we find right now on the courses is absolutely perfect. You can not have it better."
- Bernhard Russi, Olympic Gold Medalist and Course Designer

"The snow surface is perfect really.
- US Alpine Skier AJ Hurt

There are a lot of things that bother me about having the Olympics in Beijing and the construction on the Yanqing Alpine Center.  I was there in 2018 when it was under construction.  It was an environmental tragedy as they were transforming an otherwise undeveloped area.  Snowmaking has environmental impacts too.  However, artificial snow is not a problem for Alpine ski racing and in many ways it is better than many natural snow surfaces.  The snow surface at Yanqing appears to be just what Olympic snow snobs are looking for.  

Friday, February 4, 2022

Cold for the Start of the Olympic Games

 Beijing China is 15 hours ahead of Salt Lake City and 8 hours ahead of the Coordinated Universal Time (UTC) used widely by forecasters.  The former means that you can watch morning and early afternoon events from the next day before going to bed and the evening events from that day on delay when you get up in the morning.  

The past two nights I've watched some of the training for the Men's Downhill.  There are multiple story lines here.  Let's begin with the venue, the Yanqing National Alpine Skiing Centre.  I visited it in 2018 as part of an educational meeting on Olympic weather monitoring and forecasting.  It was in the early stages of construction.  It certainly looked to have the vertical and steepness needed for a decent Olympic downhill, but prior to the building of the resort, the area was largely undeveloped.  

We were told that it the resort averaged 25 inches of snow a year, but it is possible that was 25 cm (about 10 inches) as some things are easily lost in translation.  I don't think anyone knew what the actual number was for that specific location except that it was considerably drier than other Olympic Alpine skiing venues and snow was rare.  No weather stations had been installed on the mountain yet (there may have been one at the base and there was a very comprehensive atmospheric monitoring station near the entrance to the valley where the National Sliding Centre was being built).  I remember we discussed the need for comprehensive monitoring of wind along the downhill course, which eventually happened.  We were not allowed to take pictures.  

Fast forward to today and the start of the Olympic Games and we now have a pretty good look at the fully constructed venue.  A good suite of photos were published a couple of days ago by Ski Racing.  Below is the finish area.  The course is covered with a sinewy path of artificial snow surrounded by barren dirt and rocks.  Below is the finish.  

Source: Ski Racing

On the other hand, it seems to be a fairly interesting and challenging course.  Artificial snow makes for a dense, hard surface that is often quite good for Alpine ski racing and the dry, cold climate and lack of natural snow at Yanqing allows for optimal course preparation.  On instagram, American skier Ryan Cochran-Siegle said that "spectacular snow and tantalizing terrain should make for some amazing race conditions" and in media reports Austrian skier Vincent Kriechmayr said that the course was "amazing" and that "the course conditions are some of the best I've ever seen."

It's been interesting watching the racers learn a new course during the first two training sessions, but I've also enjoyed watching the weather.  It has been cold and windy.  Today's start (last night Salt Lake time) for the 2nd training run was delayed for an hour.  I took a look at why.  The sea-level pressure analysis from China's National Meteorological Center for 8 am, about 3 hours prior to the scheduled 11 am start time showed a strong Siberian High with a central pressure of more than 1067 mb. Beijing and the outdoor venues on the southeast edge where there was a strong pressure gradient.  

That's a good recipe for cold, windy conditions and that's exactly what happened.  At the 11 am scheduled start time, it was -24.2˚C (-12˚F) with wind gusts of 18.8 m/s (42 mph) at the start.  

The training was delayed and started an hour later, although it was still quite cold and windy.  Beat Feuz wore a full face covering.  Others some tape.  All of the racers at the bottom were moving their jaws to free up their tightened faces.  

Another training is scheduled for 11 am tomorrow 5 February (8 PM tonight Salt Lake Time) and then the official race for the same time on 6 February.  It looks like it will be a bit warmer warmer, but if my read of the ECMWF guidance is accurate, temperatures at the start will probably still be at or just below 0˚F.  I hope the winds subside some.  Aerodynamics and safety are important and the variability of the wind may play some role in determining the outcome.  

The Nordic Center a bit farther north is also experiencing cold and wind.  Today (4 February) the morning minimum temperature was -24.2˚C (-12˚F) with a maximum of -15.3˚C (4˚F).  

It was also windy, with gusts reaching 10 meters per second (22 miles per hour), so even though the air temperature was higher, there was a pretty good wind chill. 

The first competition scheduled for 3:45 PM Beijing time tomorrow (5 February) is the Women's skiathalon, a combination of 7.5 km classic and 7.5 km freestyle techniques.  It may be a bit warmer, but it appears that the race will likely occur with air temperatures in the single digits Fahrenheit.  I'm not sure if the start time was based on broadcasting or meteorology, but it's a good thing it's in the afternoon.  I believe -20˚C is the lower limit for cross-country events.  From the 2019 FIS rule book (I couldn't find a more recent one quickly):

"If the temperature is below -20° C, measured at the coldest point of the course, a competition will be postponed or cancelled by the Jury. With difficult weather conditions (e.g., strong wind, high air humidity, heavy snowfall, or high temperature) the Jury may, in consultation with the Team Captains of the participating teams and the Chief of medical and rescue service responsible for the competition, postpone or cancel the competition."

I suspect the skiathalon will go tomorrow as it will probably be a bit above -15˚C and hope the winds will subside some.  

Welcome to winter at the edge of the Siberian High.

Thursday, February 3, 2022

The 2021/22 Ski Season, Part I and II

Each ski season is unique in its own way, but I have reached a point meteorologically and physically where it is clear that this will be a two-part ski season.  

Part I was from mid-October until mid January.  It was a herky jerky period. Snow in October and early November, followed by drought into mid December, followed by snow until early January.  There was some good skiing and some not-so good skiing, for a time primarily on upper-elevation north-facing aspects.  

The December storms opened things up for ski touring, Nordic skiing, and resort skiing.  Skiing fun in all its forms.

The spigot closed, however, in early January.  I didn't realize it at the time, but the snow season and my ski season would pivot on January 7.  Through that date, Alta had recorded 254.5" of snow.  Since then, they've had less than 10 inches.  Additionally, I woke up that morning with a sharp pain in my upper foot.  I had skate skied the prior day in some of the softest, slowest snow I'd ever encountered.  I didn't think much about it, but must have aggravated something.  I took some days off and tried to soldier along, but it is not improving.  Thus, I'm doing a hard shutdown now except for physical therapy, strength training, and maybe some light workouts on a stationary bike or in the pool.  My physical therapist suggests I might try Alpine skiing if it can be done without pain, but says to stay far away from skating and touring.  

Looking at the forecast, it looks like I won't miss much from a powder perspective.  The GFS produces no precipitation over the next 7 days and 43 out of 52 members of the NAEFS generate less than 2" of snow at Alta.  There are two members that produce 7 inches.  There's always hope that perhaps one of the roll-over troughs will produce, but it's slim.  Then there's the 8-14 day outlook from the Climate Prediction Center.

Thus, I'm calling intermission on the 2021/22 ski season.  It's hard to say when Part II of the ski season will start, but hopefully the 2nd half of February and the coming spring will be better for snow and skiing. 

Wednesday, February 2, 2022

About Last Night

A little lake-effect action last night has made a mess of the morning commute. It's been a while since we've had this much valley snowfall, so let's take a look at what happened. 

On the large-scale, there was a weak trough passage that occurred early this morning.  This trough was accompanied by deep instability and moisture, with precipitation enhanced over the Great Salt Lake.  

This transition is clearly seen in upper-air soundings from the Salt Lake City International Airport.  Yesterday afternoon it was well mixed in the lowest levels with a 700-mb (10,000 ft) temperature of -17˚C.  However, the sounding was also fairly dry and it was absolutely stable in the mid levels above 700 mb.  Thus, conditions were not favorable for the development of deep precipitation clouds, although you could find a few snow showers from shallow clouds in the mountains.  

This mornings sounding is only slightly colder at 700 mb (18˚C), but is much colder in the mid levels above 700 mb.  It is also has more moisture.  

I'm not sure if the radar loop below will successfully load in Blogger (I will try to update if this happens).  You may need to hit play twice.  If it loads, you will see some snowshowers moving from the northwest at the start of the event, the initiation of lake-effect snowshowers to expand and enhance those snow showers, and eventually a shift to northerly flow with the lake becoming the primary locus of snowshower initiation.  At the conclusion of the loop, given the northerly flow, lake-effect is confined to the eastern Tooele Valley.  

Sadly, the heaviest action was in the western Salt Lake Valley, Oquirrh Mountains, and eastern Tooele Valley.  In the central Wasatch, I suspect the most snow fell in in the Lone Peak area based on the radar.  As of 7 am this morning, an Alta-Collins reported a total of one inch with a temperature of...wait for it...-2˚F.