Pesky Mid-Slope Clouds

Mid-slope clouds are often observed on valley sidewalls in mountainous regions, especially under moist conditions.  These clouds can be produced by thermally forced flows that move upslope with daytime heating or by dynamical forcing if there is a cross-valley component to the flow that leads to upslope on one sidewall.  

Today I spent the morning skiing through a pesky mid-slope cloud at Patscherkofel, a ski area just to the south of Innsbruck.  

Patscherkofel is in many ways a cursed ski area.  It is surrounded by higher mountains, and thus is in a snow hole.  It is also at the mouth of the Wipp Valley, which descends from Brenner Pass, the lowest pass in the eastern Alps.  As a result, the Patscherkofel often experiences strong or even severe downslope winds, referred to as Foehn in the Alps.  

Foehn flow.  Source: Secrets of the Greatest Snow on Earth

That said, Patscherkofel has a number of things going for it when there isn't Foehn.  First, it is easy to access from Innsbruck.  Get on the J-bus with a pair of skis or a snowboard and you have a free ride right to the base of the Patscherkofel.  During the week, these busses run every 10 minutes.  No need to check the timetable. 

Second, the Patscherkofel has substantial vertical by American standards with a drop of 956 meters or 3136 feet, more than the Snowbird Tram.  And it's one ride to the top in a modern 10-passenger gondola.  

Third, it was the site of the 1976 Olympic Downhill, so you can retrace the route that Franz Klammer followed on his way to his famous gold medal. 

Finally, compared to many Alpine ski areas, there are actually some trees.  Mind you, it is still not the easiest place to ski in cloud, but it is better than most Alpine resorts, which is why I was there today as the options for bluebird skiing were low in Tirol (although if I was up for it I could have taken the train to Italy where it was sunny).  Plus they got some snow this week so it wasn't boilerplate from top to bottom.  

The mid-morning view from the top of the gondola tells the story. The top of the gondola was trapped in the cloud sandwich between altostratus clouds (mid-level layered clouds) and the pesky mid-slope clouds.  The photo below is taken looking toward the northwest and the mid-slope clouds were moving from right to left, wrapping around the Patscherkofel mid slope as they moved from the Inn Valley toward the lower Wipp Valley.  

The light wasn't too bad when you were above these clouds, but at times it was lights out when you descended into them. Look carefully for the skier at center right.

The Department of Atmospheric and Cryospheric Sciences here has a wind lidar, which is an instrument that uses pulses of laser light reflected off of tiny particles in the atmosphere to measure the wind speed and direction.  Using this instrument, they produce time-height sections of the flow over Innsbruck.  Below is the time-height section for a roughly 25-hour period that includes my ski this morning (between the blue lines).  I've highlighted the Patcherkofel base and the top of the gondola.  During my ski, there was flow from the ENE (I've highlightd this with a red arrow) at mid-mountain level.  This is close to an up-valley flow in the Inn Valley.  Under quiescent conditions, the flow in the Inn Valley in the morning is usually westernly (down valley), so this was a dynamically driven flow.  However, the small northerly component was probably enough to produce a little cross-valley upslope flow and cloud given the moist conditions.  

Source: University of Innsbruck

After bussing back to Innsbruck, I got a good view of the mid-slope cloud from by our apartment.  In the photo below, the top of the Patscherkofel gondola is circled and a bit below the true mountain summit.  The base is blocked by the lower ridge but I've drawn a blue arrow to indicate it's approximate location (you can see some of the trails to the right of this arrow).  The mid-slope cloud is apparent between summit and base and I've highlighted the flow with red arrows. 

I was hoping for a sunny day as this is my only possible ski day this week, but turns were had, few people were out, and interesting meteorology was observed.  

March Heat and April Snow

Forget all of that crap about March coming in like a lion and out like a lamb.  None of that stuff applies this year.  March was off-the-scale and simple sayings don't do it justice.  

This is a little premature since March 31st is not in the books yet, but let's look back on what was a remarkable and unprecedented month.  

Believe it or not, it did snow some in March.  Per the Alta Snowfall History at https://www.alta.com/weather, Alta actually got 44.5" of snow from March 1st to 6th.  That seems like a lifetime ago given the heat and dryness that followed.

With one day to go, the average temperature for March at the Salt Lake City International Airport is 53.4°F, 3.3°F higher than any previous March.  A record for the month is in the bag.  

Source: https://xmacis.rcc-acis.org/

But the mean obscures the variability and some of the extremes that occurred during the month.  This March featured five days with a maximum temperature greater than or equal to 80°F.  Prior to this year, there was only one prior March day that reached 80°F (31 March 2012).  We also reached 84°F, four full degrees higher than the previous all-time March record (also 31 March 2012) and 6°F warmer than the 20th century March record. 

Every SNOTEL station with a long-term record in the Wasatch Range currently sits at < 50% of median snowpack water equivalent and every one is at their all-time low for March 30.  EVERY ONE.  Lower-to-mid elevation SNOTELs currently do not have any snow.  Although it is not impossible that they see some snow in the future, for all intents and purposes, the seasonal snowpack at lower-to-mid elevations is gone.  For these sites, bwlow is this year's first day with no snopwack compared to the prior record in parentheses.  

Ben Lomond Trail (5970 ft): March 15 (April 2)
Farmington Lower (6850 ft): March 23 (April 4)
Parrish Creek (7760 ft): March 30 (May 2)
Parleys Summit (7590 ft): March 24 (April 4)

Timpanogos Divide currently has 0.1" of snowpack water equivalent, so it may be at zero by the end of the month too and it sits at 8180 feet.  

Parish Creek might have the most impressively anomalous snowpack of these sites.  It reached no snow yesterday (March 30).  Records for this site only go back to 2000, so not as long as some sites.  Still, they hit no snow yesterday (March 30), a bit more than a month ahead of the prior record (red line, which corresponds to the 2015 water year) and more than 6 weeks ahead of median (green line).  Illustrating the fickle nature of spring, the big peak is from the 2023 water year, which saw increasing snowpack until late April with a maximum on April 25th.  

Source: https://nwcc-apps.sc.egov.usda.gov/awdb/site-plots/POR/WTEQ/UT/Parrish%20Creek.html

Talk about a tale of two water years.  

Of course, with April Fools on tap tomorrow, a change of the weather is in store.  Showers and thunderstorms will develop later today with a trough moving through overnight bringing valley rain and upper-elevation snow, both of which could be heavy at times.  Below is the GFS forecast valid 0900 UTC 1 April (0300 MDT) showing the trough over northern Utah with widespread precipitation along and ahead of it.  

The GFS puts down 1.88" of water and 18.2" of high-density snow for Alta-Collins through 5 PM on April Fools day.  For the same period, the HRRR is at 1.33" of water and 10.6" of snow while the RRFS members are mostly around 1" of water and 10" of snow although there are a couple of low and high outliers.  A reasonable middle ground is 1–2" of water and 8–16" of high-density snow for Alta-Collins, which should be high enough to see all snow. 

For Alta-Collins, the HRRR forecast below shows most of the precipitation happening Tuesday night and early Wednesday, although it is possible that something pops up Tuesday afternoon.  Note also that the wet-bulb zero level is initially above the Alta Base and then falls to just below Elberts. Perhaps Alta will see some rain at the base late today (although in a thunderstorm the snow level could drop temporarily) and this evening before changing to wet snow.  

It's good to have precipitation in the forecast again.  

Skiing Update

With my son and his fiancé in town this week, we did a Tirolean ski trifecta hitting the Arlberg on Tuesday, Stubai Glacier on Wednesday, and Ischgl yesterday (Saturday).  All three were bluebird days and snow conditions at Stubai were quite good.

I'll focus here on Ischgl, which is located in the Paznaun Valley of western Tirol.  It's a bit of a haul on public transit (for me about 2 hours via bus, then train, then another bus), so I was glad to have a friend invite us to come along with him.  But first we had to play a game of Tetris to get four pair of 92 to 106 mm  waist-width Alpine skis and bindings into the ski slot of a Volkswagen Golf.  Somehow it worked and we were able to add three pairs of ski poles too. 

Ischgl is a big place with an abundance of high elevation northwest facing terrain.  There is a relatively flat area for "combat" skiing that seems to be popular with the tourists.  

But also some great advanced terrain, which for some reason I didn't take any photos of yesterday, so I'll drop in the one below from a few years ago which was taken looking up a chair called the Gampenbahn, which has the longest vertical rise of any six-person chair in the world (924 meters/3031 feet).  

Ischgl is also one of the hardest partying places in the Alps, infamous for a superspreader event at the beginning of COVID. One of my Tyrolean friends jokingly says that Ischgl is German for "evil place."  I probably wouldn't stay there, but I'm happy day trip to enjoy the turns and incredible scenery.  

Ischgl is also interconnected with the Swiss resort of Samnaun.  You can ski both on the same pass.  I've skied the Samnaun side before (it's got less interesting terrain than the Ischgl side), but never skied all the way down to Samnaun.  We figured we should give it a try.  The piste-route descends from off the photo to the right and then into the valley pictured below.  We enjoyed some off-piste powder turns from here though to make it interesting.  

Getting back to Ischgl involves first ascending the double-decker cable car that transports people to and from the ski area above Samnaun.  The photo below is from the top station looking back down into the Samnaun Valley. 

Perhaps if it was snowing in the Wasatch I'd feel differently, but right now I'm not missing Utah at all. 

Classic "Nord Stau" Storm

We have finally gotten a taste of winter here in Innsbruck with a storm that has lasted for a bit over 36 hours in the mountains and has provided a steady snowfall even on the Inn Valley floor.  I had a beautiful walk to the office this morning following the walking path from our flat above town and then across the Inn River.  

Explosions from avalanche mitigation work on the Nordkette ridge above town are shaking the windows of my office currently.  Skies are still overcast, so I can't see the results.  I've been here when you can watch the avalanches from town.  

The snow was produced by a cold-frontal passage Wednesday evening followed by a period of northerly post-frontal flow, or what is sometimes referred to as "Nord Stau" in which northerly flow impinges on the Alps and experiences blocking and orographic lift.  This is the eastern Alps equivalent of northwesterly flow in the Cottonwoods, although the snowfall is much more expansive in area.  Below is the ECMWF HRES analysis for 0000 UTC Thursday 26 March during the Nord Stau period of the storm showing a deep upper-level trough over Germany, Switzerland, and Austria at 500 mb (hence cold and unstable) with moist north-northwesterly flow impinging on the Alps at 700 mb.  

The European radar composite from 1630 UTC late yesterday afternoon was a classic with convective cells upstrea of the Alps over Germany and France.  These were moving south-southeastward toward the Alps where the convection became more continuous over then northern Alpine Rim of Switzerland, German, and Austria.  Note the lack of echoes over Italy, which was in the lee of the Alps.   This is all happening in the wake of a low-level cyclone (i.e., low pressure system) that was producing broader, stratiform precipitation over eastern Europe.  

The "Euroregion" comprised of the Austrian state of Tirol and Italian states of South Tyrol and Trentino collaborate extensively on snow measurements and avalanche warnings.  There is a dense array of automated snow depth sensors in this Euroregion operated by many groups.  These measure total depth and one can access the 48-hour difference in snow height from these sites athttps://avalanche.report/weather/stations.  While not strictly equivalent to new snow amounts, in this case they provide a reasonable estimate of snowfall amounts given the well-consolidated snowpack before the start of this case. 

As is typically the case in Nord Stau, snowfall from this storm was greatest in what is known as the Northern Alpine Rim, which in western Austria is north of the Inn Valley and includes the snowy region near and around the Arlberg Pass (simply called the Arlberg).  There are a number of stations with 48-hour increases in snow height over 50 cm (20 inches).    

48-hour difference in snow height for the period ending ~0730 UTC 27 March. Source: https://avalanche.report/weather/stations. 

Snowfall decreases as one moves southward into the Inner Alps of Tyrol.  For example, in the Alps around the Paznaun valley, snowfall amounts are genreally less than 45 cm and in some areas less than 20 cm.  One area of the Inner Alps with greater snowfall is in the Tux Alps just west of the Ziller Valley, which I've circled in the right of the diagram.  Not shown here are areas farther east in the Kitzbuhel, Zell am See, and Hohen Tauern that also saw more than 50 cm where storm penetration into the inner Alps is often a bit stronger than in the Innsbruck area.  

The Austrian-Italian border (and farther west the Swiss-Italian border) represents the Main Divide of the Alps, which is the hydrologic divide.  Although the highest peaks near the Main Divide are quite high, snowfall is more limited.  There are a couple of sites just north of the main divide with > 30 cm but many other sites have lesser precipitation.  This is not uncommon as Nord Stau storms tend to dump their loads on the Northern Alpine Rim with less snowfall over the Inner Alps.  

Once south of the Main Divide, snowfall decreases further into the lee and South Tyrol.  There are some light amounts in the Dolomites, but those were actually produced during the passage of the cyclone rather than in the post-frontal Nord Stau period.  In situations like this, you have your pick of powder on the northern Alpine rim or dry weather for hiking or biking in South Tyrol.  Just take the regional train from Brenner Pass on the Alpine Rim until you find the weather that you want.  

During this an many other storms, there can be a good deal of variability in the change in snow depth in any Alpine region.  In part, this reflects they large contrasts in the elevations of stations, but also the fact that there is a good deal of snow redistribution by the wind above timberline in the Alps, both prior to deposition on the ground and after.  I'm still trying to learn what sites are generally representative of the immediate surrounding area.  

The good news here is that after a break later today and tomorrow (Saturday), there's another storm coming in.  Unlike what has happened in Utah, this should enable many resorts to make it to their target closing dates.  

Heat Wave Numbers

It is snowing today (Thursday) in Innsbruck, the first valley snow since we arrived in late February.  It's just above freezing so that the snow is sticking on cold surfaces, but sidewalks and roads are snow free.  Below is the view from my office. 

I haven't thought about the weather in Utah in a few days.  I knew it was going to be hot, but now that I'm checking the numbers, I'm pretty blown away.  Multiple days at or above 80, including an 84(!) on   Saturday March 21. 

Let's put those numbers into historical context.  During the 20th century, the highest March temperature recorded at the Salt Lake City International Airport was 78°F, reached on 24 March 1956 and 26 March 1960.  During the 21st century, we have tied or topped that number 14 times.  This includes reaching 80°F for the first time on 31 March 2012 and reaching or exceeding 80°F five times in the current heat wave, including the mind-boggling 84°F.

Let's dig a little deeper.  For the 8-day period ending yesterday (Wednesday, March 25), the average maximum temperature was 78.3°F.  The previous March record for an 8-day period was 74.4°F set in 2017.  The 20th century record, 70.0°F, was set in 1960.  So, the average maximum temperature for this stretch is an astounding 8.3°F higher than anything observed in March during the 20th century.  

How about average temperature?  For the 8-day period ending yesterday (Wednesday, March 25), the average temperature was 64.2°F.  The previous March record was 61.6°F set in 2017.  The 20th century record, 57.8°F, was set in 1910.  Thus, for average temperature the current 8-day stretch is 6.4°F warmer than anything observed in March during the 20th century.  

I just pulled up the Alta website and noticed they are closing Wildcat and Collins Gulch early due to unseasonable warmth.

Source:Alta.com

We are deep in uncharted territory.  There is no historical analog for the current March heat wave.  Nothing is even close.    

You Were Warned

Mind boggling temperatures from the western United States currently.  Even watching from a distance here in Austria, they blow me away. 

As I write this, it is Friday morning in Austria and some of the numbers for Thursday in the US are not in yet.  Thus I'm going to use observations from Wednesday to illustrate the scale and intensity of this event before boring into what data I have access to from Thursday.  

Below are the rankings for high temperatures on Wednesday relative to prior March 18ths.  Wide spread records for the date across the southwest US but even all the way up into Montana (asterisks indicate a tie for the highest temperature of the date).  It appears every western state had at least one station that tied or set a record temperature for the date.  Washington was the "coolest" western state, but even there, Chelan tied their record high.   

Source: https://sercc.oasis.unc.edu/Map.php

Departures from average were impressively high.  Many sites were more than 20°F above average, and this is likely the 1991-2020 average so departure relative to the now old and obsolete 20th century average would be even bigger.  Some sites were at or above 25°F above average.  I couldn't find a +30, but maybe it's in there somewhere.    

Source: https://sercc.oasis.unc.edu/Map.php

Wednesday's highest temperature was 108°F at a location near North Shore, CA, which is not on the Pacific Ocean but instead the Salton Sea.  Yesterday (Thursday), Palm Springs hit 107, Thermal 108, and Indio 108.  I believe those 108s are all time monthly maximum temperature records for March and possibly all time for the entire US.  Adding to the misery a bit further east is 106 in Yuma and 105 in Phoenix.  

Records in the Palm Springs Area go back to 1922.  In 1938 they hit 100 in March for the first time.  In 1966 104.  In 1988 103. And now this year 106 (Wednesday) and 107 (Thursday).  In Thermal, records go back to 1951.  They hit 102 in 1966 and 1988 and now 107.  

Meanwhile in Salt Lake City, yesterdays 79 was a record for the date but not the month.  The monthly record is still 80, set on 31 March 2012.  Don't worry.  We'll likely set a new record on Friday and/or Saturday.  

Utah ski areas are suffering.  Eagle Point and Cherry Peak are closed.  Snowbasin's last day is Sunday.  That's a major Utah ski resort, ranked #1 in the US by some surveys and rankings, with a substantive snowmaking system, packing it in on March 22nd.  I looked at the webcam from the base of Wildcat yesterday and I simply could not believe it. It doesn't even seem possible.  

https://www.snowbasin.com/the-mountain/web-cams/

My heart goes out to the resort, which moved heaven and Earth for us this winter for our field campaign.  Despite a slow start to the season, we actually got some great data and will learn a lot, but never in my wildest dreams did I expect to see such a sparse natural snowpack in mid March.  

Here are a few SNOTEL observations based on data from Wednesday, the most recent data that I have available as I write this. There is no snow at Ben Lomond Trail. Median for March 18 is 17.6".  The snowpack at Ben Lomond Peak (7690 ft) appears to be ripe (i.e., it has warmed through depth to 0ºC) and has declined 3.3 inches from its peak and sits just above it's all time low for the date.  Snowbird is not at an all-time low, but it also appears to have declined some from its peak, although that site is a little flaky so I'm not going to fully endorse that as reality (maybe someone can comment).  That said, all other SNOTEL sites in the central Wasatch have seen declines in total snowpack water equivalent in the past few days.  Not necessarily a lot, but some.  

My view of these events is that they are not the new normal, but they are the new extreme, at least for now.  We should expect natural climate variability to still give our winters and snowpacks ups and downs in the coming years, including some good or even great snow years (as we just had in 2022/23).  But, we are seeing an emerging trend to warmer conditions, meaning more frequent, more intense, and longer duration heat waves, more precipitation falling as rain instead of snow, more mid-winter snowmelt events, etc.  These trends, caused by human-caused global warming, will have the biggest impact on snowfall and snowpack in the lower elevations, as we have seen this season, but will also bring change to the upper elevations.  

The reality is that you were warned.  Some of you took it seriously.  Others have called it a hoax and even today are working to dismantle the outstanding US climate-science enterprise, such as breaking up world-class research institutes like the National Center for Atmospheric Research (NCAR).  Still others are pushing fossil fuels and delaying a transition to a lower-carbon world.  

Due to the slow response of the climate system and socio-economic change, we are already committed to more warming in the next 20-30 years (maybe longer).  Will the powers that be continue to resist change and pursue a high carbon, fossil fueled future?  Good luck with that.