Thursday, December 31, 2020

The 2020 "Hot Drought" in Salt Lake City

With one day still to be added to the record books, it's safe to say that 2020 was an exceptional year meteorologically in Salt Lake City.  

Let's look at the numbers through December 30th, although they won't change by more than a hair after today (December 31 is added).  

2020 featured both exceptional warmth and dryness.  The plot below is a scattergram of mean annual temperature and precipitation. 2020 will rate as the 6th warmest (behind 2012, 2015, 2018, 2016, and 2017) and the 2nd driest (behind 1979) on record.

This is the hallmark of a "hot drought," with higher temperatures, which lead to increased evapotranspiration and water demand for irrigation, making a moderate drought severe or a severe drought even worse. 

For July to December, 2020 was the driest on record and the 4th warmest. 

This is essentially uncharted territory for the combination of low prcipitaiton and warmth in Salt Lake City.  Prior to the 21st century, no July-December had an average temperature above 60˚F (we've now had 5 years above that threshold including 2020).  

Not surprisingly, the US Drought Monitor released earlier this morning shows about 2/3 of Utah, including the Salt Lake Valley in exceptional drought. 


As we move forward through the 21st century and temperatures continue to increase, we will see more hot drought years with higher temperatures exacerbating average or below average precipitation.  Near-average precipitation will increasingly feature moderate drought and below average years even more severe drought that would have occurred during the 21st century due to the effects of higher temperatures.  

So we have that to look forward to...

Tuesday, December 29, 2020

God Bless the Groomers

It's a pretty lean snow season so far across the west.  A look at NRCS SNOTEL snow-water equivalent data for the contiguous western United States showing most major drainage basins running at or below median. 

Source: NRCS

In northern Utah, there isn't a single SNOTEL at or above median.  The closest is Hickerson Park in the northeast Uinta Mountains (where median is pretty pathetic to begin with), which sits at 96%.

Source: NRCS

In the central Wasatch, Snowbird, Mill D, Brighton, and Thaynes Canyon are at 81%, 68%, 51%, and 56% of median.  Records at the snowbird SNOTEL go back to 1990.  We're currently running at about the 30th percentile for snow water equivalent since then, meaning that 30% of the seasons were below current levels and 70% were above.  30th percentile doesn't sound that bad, but the difference between 30th percentile and the absolute lowest year on record is only a couple of inches of SWE and not that much.   

Source: NRCS

On the Park City side, Thaynes Canyon is even uglier.  Records go back to 1989 and this season almost has the lowest SWE on record (4.5" vs. 4").  

Source: NRCS

Given instrument accuracy and the like, a half inch difference is essentially a dead heat for worst snowpack on record.

Keep in mind that the SNOTEL records don't include 1976/77, which is probably the worst snow year on record.  Nevertheless, the snowpack situation is pretty poor.  

Dare I say it?


The resorts though have snowmaking.  The real Christmas miracle is happening at Mountain Dell.  I've gotten in four or five days up there now and, as I drive up the canyon, I can hardly believe they are open.  Trails are limited with a 0 to 5 cm base, but the Mitten-Main loop "goes" and the thin spots can be avoided.  

God bless the groomers who have made it work with scant natural resources.

Monday, December 28, 2020

Will This Be the Driest July–December on Record?

Salt Lake City is close to a dubious record: The driest July–December on record.  

Since July 1, the airport has received only 1.86 inches of precipitation. 

Source: NOAA Regional Climate Centers

If no more precipitation fell through the end of the calendar year, this would easily break the old record for lowest July–December precipitation of 2.20 inches set in 1958.  

However, the question is will we make it to the end of the year with no more than 0.34" of precipitation at the airport?

It's going to be close.  We have two precipitation systems affecting us before the end of the year.  Today we have a system moving across southern Utah.  It brings some light precipitation, most likely in the form of snow, to the Salt Lake Valley today.  

Accumulations are, however, limited and likely to be less than an inch of snow and a few hundredths of an inch of water equivalent. 

Then there's another storm on New Year's Eve.  The GFS forecast below shows a front moving across northern Utah at 1800 UTC (11 AM) on New Year's Eve, bringing widespread precipitation.  

Right now, the numbers being put out by the models don't seem high enough to get us the 0.34" of precipitation, but we'll have to see how the forecast evolves the next couple of days.

We really need some snow, so this is one time I'm hoping Mother Nature snatches "defeat from the jaws of victory" and we don't break the record.

A lot of people have been asking me about the "plume" products on  They, and most other downscaled snowfall products are currently down or intermittently available.  Our Center for High Performance Computing has been having some infrastructure problems following their most recent downtime.  Given the holidays and all, I don't know when it is likely that we will have things fixed or a work around.  

Saturday, December 26, 2020

Some Thoughts on the Belleayre (New York) Avalanche

Yesterday afternoon, I learned via social media feeds and news reports of a possible early Christmas morning avalanche at Belleayre Mountain Ski Center in the Catskill Mountains of New York (see Avalanche damages lodge at Belleayre Mountain Ski Center from CBS6 News in Albany).  

Photos provided to CBS6 by Belleayre Mountain Ski Center show the damaged Overlook Lodge filled and surrounded by debris.

Source: Belleayre Mountain Ski Center via CBS6 News

Source: Belleayre Mountain Ski Center via CBS6 News

The ski center also reported that they were closed and that "supersaturated snow from the Yahoo trail let loose and slid into the Overlook lodge."

Source: Belleayre Mountain Ski Center

Belleayre is located in the Catskills of southern New York.  Those from the New York City area would describe it as "upstate," but it was definitely "downstate" for someone like me who grew up northwest of Albany.  

The ski center has a vertical drop of 1,404 feet and a top elevation of 3,429 feet.  The Overlook Lodge is a mid-mountain lodge (although you can drive to it) located at 2,542 feet and in the center left of the ski map below.    

Source: Belleayre Mountain Ski Center

Imagery from Caltopo shows the lodge near the base of Triple Chair #7 (click on image below to enlarge).  The colored slope angle shading (legend at upper right) suggests slope angles <27º immediately above the lodge with about 100 vertical feet with slopes of ≥ 27º and pockets ≥30º near the summit.  


Under ordinary circumstances, one might say "c'est impossible!" for an avalanche to occur on this slope, but the circumstances leading up to the avalanche were hardly ordinary.  In fact, they were quite extraordinary.  In fact, it's hard to believe Santa was able to deliver toys to good girls and boys early Christmas morning! 

Let's begin, however, several days prior to Chirstmas.  The area received substantial snowfall on December 16 and 17.  Reports to the National Weather Service show that the heaviest band of snowfall followed I-88 from Binghamton to Albany, but reports near the ski center suggest anywhere from 12-24 inches in the area.  

A citizen weather observing site that provides data to MesoWest from Halcott Center near Belleayre and at a comparable elevation to the lodge (2254 feet) shows temperatures from 19-23 December between about 20 and 40˚F.  Data from the Claryville New York State Mesonet site (farther below) suggest a natural snow depth of about 8 inches on December 23rd.  However, on December 24, temperatures climbed steadily, peaking at around 57 or 58˚F early Christmas morning.  During this period, about 5 inches of rain fell in 12 hours.  

Source: MesoWest

Data from the New York State Mesonet site in Claryville tell a similar story with temperatures climbing on Christmas Eve and peaking at 57˚F at 5 AM on Christmas morning. At that time, the relative humidity was 94% and over 3 inches of rain fell in the prior 12 hours.  The snow depth at this site actually dropped to zero prior to the heaviest rain.  


So the weather was one of rapid melting and water loading of the snowpack at all elevations.  

With some effort, I found a photo online looking up the hill from the ski lodge on the New York Ski Blog Forum.  One can see a grassy area up the hill and then the track entering the lodge.

Based on this photo and the description on the Belleayre Mountain Ski Center web site, one possibility is that the grassy area represents the starting zone for the avalanche.  Most avalanches occur on slopes with angles of 30˚ or more.  It looks unlikely that the grassy area is >30˚, but some wet snow and slush-flow avalanches can start on lower angle slopes.  

Slush-flow avalanches in particular are major threats in some high-latitude areas of, for example, Norway, Iceland, Swalbard, and Alaska.  They involve mixtures of snow and water and I wonder given the heavy rainfall if what happened at Belleayre might be an example of one.  A recent review article from the Annals of Glaciology with some examples is available here.  

These are, however, educated guesses.  Boots on the ground to look farther upslope and investigate the snowpack and soil are essential.  It's easy to dismiss the potential for avalanches at eastern ski resorts, but they have happened.  Check out, for example, this paper presented at the 2004 International Snow Science Workshop entitled Man-Made Snow Avalanches in the Eastern United States.  Situational awareness may be valuable for future rain on snow events in the region.  

Comments from those with a deeper knowledge of avalanche mechanics and processes appreciated!

Tuesday, December 22, 2020

Last Second Shopping

If you are looking for a late Christmas gift for a snow lover, pick up my book Secrets of the Greatest Snow on Earth.  

You can get it from this Amazon link, but if you live in the Salt Lake or Park City area, consider calling my friends at King's English, Weller Book Works, or Dolly's Bookstore and see if they have any copies in stock.  

Friday, December 18, 2020

Storm Post Mortem

Yesterday's and last-night's storm delivered in spades in the Wasatch Range.  The Utah Avalanche Center reports 8-17" since yesterday morning with the highest amounts in upper Little Cottonwood.  Given the faceted, weak snowpack that existed prior to the storm, a backcountry avalanche warning has been issued for the mountains of northern and central Utah. 

Data from Alta-Collins suggests a storm total of about 17" if one adds up the 7 inches through 1600 yesterday, when the board was wiped, and then the 10 inches overnight.  The heaviest snowfall was from about 1600-1800 when 6 inches fell with about .24" of water content.  

Several of my University of Utah colleagues in Mechanical Engineering and Atmospheric Sciences, including Trent Meisenheimer (also affiliated with the Utah Avalanche Center), Tim Garrett, Eric Pardyjak, and Peter Veals are running a suite of instruments in the Alta area this winter.  Some of the data they are collecting is simply spectacular.  Below, Tim provides a tweet of data from the Differential Emissivity Imaging Distrometer or DEID.  Without getting into details, this instrument provides frequent measurements of the density (% water) of falling snow.  The plot he shares below presents the data in a way that resembles a profile through the depth of new snow, in this case the accumulation through 1833 MST.  It shows very nicely that the initially (bottom of the graph) the snow was about 7-8.5% water content, but the water content decreased with time and for most of the storm through 1833 MST, it was in the 5-7% range.  

I don't have data for overnight, so I can't comment on that period.  

We really needed this storm and hopefully it will help a lot.  The Alta-Collins snow depth sits presently at 43".  I use 40 as the threshold for the start of real "early season" skiing, although we may settle to below that in the next day or two.  

One forecast shortcoming was that it warmed just enough yesterday that precipitation fell as rain at the lowest elevations, limiting accumulations.  Commuters probably appreciated that, but I didn't :-).   I'm also not sure if Mountain Dell got enough snow for Nordic skiing to get off the ground there.  The weather station there shows only 0.12" of water from the storm.  If accurate, that's maybe an inch or two of snow. 

Thursday, December 17, 2020

Wasatch to Get Some Too

Some HUGE storms have struck other regions of the Northern Hemisphere in recent days.  Previous posts describe 2+ meter dumps in the southern Limestone Alps of Europe (Another Alpine Dumpage Update) and Japan (Gosetsu Chitai Dumpage).  Adding insult to injury, huge snowfalls overnight in northern Pennsylvania and southern New York, including 44" at Newark Valley with snowfall rates of 4-5" per hour.

Lord have mercy!  

I can't promise snow totals of that magnitude for the storm that is developing today, but let's have a quick update on where things stand. 

We are currently in the prefrontal stage of the storm with the latest radar imagery showing the heaviest precipitation in the northern Wasatch as of 1625 UTC (0925 MST).  

As of 0900 MST, Alta-Collins has picked up .06" of water equivalent, but not enough snow on the board yet to tick off an inch.  The water numbers from the automated weather stations at Snowbasin show .02" or less by 0900 MST but the latest snow stake photo shows about an inch of snow.  Basically, things are just getting going.

In the Salt Lake Valley, we're presently in a "virga storm" situation with dry air at low levels.  The photo below, taken at 0820 MST shows snow virga falling aloft, but much of the snow sublimating before reaching the valley floor.  I did get hit by a few flakes while I was out on my walk.  

For the Salt Lake Valley and central Wasatch, we will remain pre-frontal today with southerly flow and periods of precipitation increasing in frequency and intensity as the day goes on.  Snow may mix with rain at times at the lowest elevations.  This morning, I saw a mixture of snow and "slush" as I was walking at 5000 feet elevation, but it changed over to snow when intensity increased.  The NWS is expecting impacts for the evening commute in Salt Lake County, so be alert.  The CDC recommends that you wear a mask when social distancing is not possible and the Utah Highway Patrol recommends that you slow down when the roads are wet, slushy, snowy, or icy.  

The HRRR is bringing the front through the northern Salt Lake Valley between 0200 and 0300 UTC (1900-2000 MST).  Should be an all elevations storm at this stage.  I like seeing the Salt Lake Valley and the central Wasatch covered in HRRR precipitation!  

We are having some networking problems and our usual products are not all available this morning.  Below is the NWS forecast summary is below.  2-4" for Salt Lake City, 3-5" for Ogden, 4-6" for Park City, and higher amounts in the mountains.  

Source: NWS

The Utah Avalanche Center is still advertising 8-14" for the central Wasatch, and that seems reasonable based on what I have.  Maybe we can do a bit better if things come together.  I'm inclined to think that less than 8" is unlikely for Alta from this one.  Tomorrow is a likely deep powder day, although the meager natural snowpack means low-tide conditions and as noted in the Utah Avalanche Center report, the backcountry avalanche hazard will likely be high.  The green light will not be on.  Let's be careful out there. 

Wednesday, December 16, 2020

Gosetsu Chitai Dumpage

As we await our next storm on Thursday, we once again look elsewhere for big dumpage.  

Today it is Japan's Gosetsu Chitai, or heavy snow region.  Some huge totals are coming in from the Echigo Mountains of central Honshu.

Below are observations tabulated by the Japanese Meteorological Agency and run through Google Translator.  The big winner is at Fujiwara in Gunma Prefecture with 128 cm (50 inches) in 24 hours, 196 cm (77 inches) in 48 hours, and 203 cm (80 cm) in 72 hours.  

Coming in second for the 48 and 72 hour totals is Tsunan with 149 and 173 cm (59 and 68 inches), respectively.  Tsunan is a long-term observing site at 452 meters above sea level (1483 feet) and 37˚N with a mean annual snowfall of 1349 cm (531 inches).  To put this into perspective, this would be like the Diablo Foothills in the Bay Area getting as much snow as Alta.  

I've identified each of these with thumbnails in the image below.  Sea-effect storms in this region come in two flavors.  Some produce the heaviest snow very near the Sea of Japan.  Others can penetrate inland and dump more precipitation on the mountains.  With such heavy precipitation at Fujiwara, well inland, this is definitely a case of the latter.  

For more on the snows of Japan, see my recent article with Sento Nakai of the Nagaoka Snow and Ice Research Center, which appeared earlier this year in the Bulletin of the American Meteorological Society (available here).  

Tuesday, December 15, 2020

Thursday Storm Must Come Through

The snow accumulation season has gotten off to a slow start.  In my view, the Thursday storm must come through to get the Nordic season off life support and help more with the upper-elevation snowpack.  The time has come.  Let winter begin.  

The forecasts are optimistic.  The GFS has a productive, slow moving frontal system moving across northern Utah on Thursday.  The forecast below is for 5 PM Thursday afternoon.  Temperatures are low enough that even if the storm starts out as rain at the airport, it should be cold enough to snow at Mountain Dell and the lower trailheads in the Cottonwoods and Mill Creek.

Water and snowfall totals for Alta from todays 6Z initialized GFS for 8 AM Thursday through 4 PM Friday are .91 and 12.8 inches, respectively.  The NAM is a bit less enthusiastic with 0.54 and 7.6 inches, respectively.  

The downscaled SREF is unusually excited, with all but 2 members producing 12" or more (including the light snow prior to Thursday's main event), with a maximum of about 28 inches. The mean is about 17 inches.  Deducting the mean from the weaker pre-Thursday events and you have a mean storm total of about 15 inches.  

One of the things I like about the storm is the frontal passage Thursday afternoon and evening looks to be quite productive.  That will be good for all elevations, and we need snow everywhere right now.  

The downscaling we do sometimes overdoes the snowfall at upper elevations in those periods, so perhaps the higher SREF members are overly optimistic.  I suspect to get to 2 feet or so at Alta we will need the post-frontal northwesterlies to come through big time.    

Personally, I like the 8-14" forecast advertised this morning in the Utah Avalanche Center advisory.  That seems like a good number for the upper Cottonwoods.  This will be a significant event for the valleys as well and should help with Nordic skiing at Mountain Dell.  

Thursday, December 10, 2020

Recent Precipitation Extremes

Here are a couple of ongoing examples of precipitation extremes for your entertainment this Thursday.  

We've discussed the heavy snowfall in the Alps in previous posts.  I've found a new winner for extreme snowfall during the event, the Connyalm at 2105 meters in the Gailtaler Alps of East Tirol in Austria, just to the north of the Porzehütte site we've discussed previously.

The time series below shows a remarkable increase in the height of the snowpack (HS) from about 20 cm at about 1800 CDT on 4 December to nearly 300 cm at 1200 on 9 December.  


If you prefer US units, that's an increase in snow depth of about 110 inches in 114 hours (4 3/4 days).  Remarkable stuff.  

The camera at that location was down when I tried to pull it up.  Here are a couple of photos from the region to remind you of the beauty of snow.


Shifting gears to Utah, it's quite remarkable how dry it has been since July 1.  From then to yesterday (December 9), total precipitation at the Salt Lake City International Airport was only 1.52 inches, easily the lowest on record.  

Source: NOAA Regional Climate Centers

In fact, there's only one other year under 2 inches for that period since records begain in 1874, 1958 (1.80 inches).  In addition, 1.52 inches is actually less than what Las Vegas averages for July to November (1.92 inches).

The US drought Monitor now shows a huge chunk of the state in exceptional drought, including Salt Lake City and the central Wasatch.  

Forecasts are more optimistic for the coming week than they have been in a while, with a series of troughs coming through.  Let's hope they produce.  

Tuesday, December 8, 2020

What It's Like to Ski 2 Meters of Fresh Snow

With the recent snowfall of 2 meters (80") or more in the Carnic Alps and surrounding region, one might wonder what it's like to ski in so much snow.  

Not as good as you might think. 

The reality is that powder skiing, like many things in life, requires some level of moderation, or what many call the Goldilocks storm.  In other words, not too big, not too small, but just right.

Where the threshold is for too big is somewhat ambiguous as it depends on the condition of the underlying snowpack or surface (alpine meadows in the Alps often serve as the bed for glide avalanches) and the characteristics of the snow during the storm.  As storm totals go over about a half a meter (20") you can have great skiing when conditions are right, but as the storm rages on and accumulations deepen, it becomes increasingly difficult to maintain momentum except on the steepest hills, where avalanche hazard is likely to be high.  

When you get a meter (40") of snow, especially if it falls in a day, it's pretty unlikely you can safely ski anything steep enough to slide except perhaps under the best of conditions in the lowest density snow (and I wouldn't tempt fate in such a situation).  Two meters in two days and you've got a good snowpack for the rest of the season, but otherwise you're probably hunkered down or interlodged.

I've skied twice in conditions where two meters of snow fell in two days.

Crystal Mountain, WA

The first was in the early 1990s at Crystal Mountain in Washington.  They received two meters (80") of snow in two days and 65" in 24 hours, the latter a record for the State of Washington and indicative of unusually dry snow for the Cascades.  

I have vivid memories of skiing after that storm, although psychologists will tell you that memories change.  I remember driving at high speed through Seattle to pick up a buddy and then up to Crystal.  I can't remember if we got the first chair for the public, but if we didn't, we were close.  We waited forever at the base.  Not only had we gotten up there early, but it's pretty much impossible to open a ski area when you get 2 meters of snow in two days.  In fact, they only opened one chair, the lower lift that takes you to the base of Rainier Express.  

After riding that chair, we were the "tip of the spear" breaking trench out northward to the only terrain that *might* be steep enough to ski.  It was like a breakaway during a road race rotating through trail breaking responsibilities with competitors with the chasing peloton gaining minute by minute.  

At the time, I was probably skiing on a pair of slalom racing skis, possibly the Salomon 2S.  Long and skinny, as were all skis at the time.  The snow was so deep and I sunk in so far that turning was not an option.  I just pointed them straight down, tried to maintain speed, and bounced up every now and then to make sure I wasn't going to run into anything and to cough out snow.  I survived to the bottom, looked back up the hill, and, other than a few others who made it down like me, saw most had fallen and augured in.  Many spent the morning looking for lost skis.  

We took a few more runs on the same hill, which became more manageable with time as it was cut up, and then went home.


Myoko Kogen, Japan

In January 2017 I was on a difficult business trip to the Nagaoka Snow and Ice Research Center.  Following the science meetings, I spent a few days in the high-mountain and especially snowy Myoko Kogen region near Joetsu.  I ski toured on the first day, afterwhich the heavens opened up and we got about a meter of snow in two days in Akakura Onsen where I was staying and a reported two meters on the upper mountain.  It might have been closer to a meter and a half, but who's counting?  

On the first day of the storm, I had a great day at Seki Onsen, a small ski area with a couple of lifts, including a single chair that, I kid you not, they were loading every other chair.  I think Powder Mountain called Seki the "soul of skiing."  It was a great experience.  

On the second day, I skied at Akakura Onsen, a ski resort that is the epitome of "deep not steep."  Average annual snowfall of 500+ inches but, as it turns out, pretty damn low angle.  I think our options were limited, however, since travel was getting pretty difficult at this time.  

I began the day with some Kiwis who were staying at my lodge.  I took a photo of one of them getting an "official" measurement of the new snow depth next to the top chair as we waited for it to open.  

During this time, patrollers were out begging everyone not to ski off piste or enter the backcountry.  Terrain traps were likely to be death traps.  The possibility suffocation in a tree well or from inversion was very real.  

We weren't first in line and thankfully, the two pistes off the top had been skied the prior day and were already somewhat cutup when we got there.  That made the skiing possible in the low-angle terrain, although it was a struggle for many.  

The Kiwis then decided to do some sidecountry skiing.  I had brought my touring pack and gear, but was not going to succumb to powder fever and we split for the day.  It's painful to ski low-angle cutup, but going home is mandatory.  

After skiing, I had an iconic walk through the winter wonderland of Akakura Onsen.  I regularly use several of these photos in talks.

Later that day, the Kiwis arrived back at the lodge.  All were safe, but they had to perform a rescue of a snowboarder who had fallen into a creek bed and nearly suffocated.  

The storm continued that evening, quickly filling up the walkway into the Myoko Mountain Lodge where I was staying.  

The next day I was flying out of Tokyo.  That morning, through the Herculean efforts of the lodge owner, we were able to get out and he was able to transport me inland to the first train station that was actually open.  Remarkably, it wasn't that far away.  Maybe 10 km.  Sea-effect storms, even big ones, sometimes decay rapidly with inland extent. 

Monday, December 7, 2020

Another Alpine Dumpage Update

Some incredible snow totals continue to come in from the south side of the eastern Alps.  The biggest increase in the Height of Snowpack (HS) that I could find was at the Porzehütte, an Austrian Alpine Club hut in the Carnic Alps just north of the border of Italy.  I grabbed the screen shot below fortuitously when they peaked at around 2.34 meters, which represents more than a 2 meter increase in less than 24 hours.  


I don't know how to access tabular data to get precise numbers for total water equivalent, but a guesstimate from the graph yields about 400 mm, so we're talking some serious concrete with 20% water content if those numbers are accurate.  

The Carnic Alps, as well as the Julian Alps and Dolomites to the south, are one of the wettest parts of the Alps and prone to heavy precipitation.  An analysis of average annual precipitation in the Alpine region shows the highest values along the northern and southern "rims" of the Alps.  In the central and eastern Alps, precipitation actually decreases as you move into the Inner Alps, despite the terrain getting higher.  

Average annual precipitation (mm) in the Alpine Region. Source: Isotta et al. (2013).

There are also two precipitation "hot spots" on the southern rim.  The first is in the Ticino, Lombardia, and Piemonte regions of Switzerland and Italy.  The second is in the Dolomites, Julian Alps, and Carnic Alps of Austria, Italy, and Slovenia.  These precipitation hot spots are produced by flow interactions with the Alps and the surrounding mountain ranges, which focuses vapor transport and precipitation dynamics in these areas.  

In addition, these are areas that receive the greatest fraction of their precipitation on days with moderate to high precipitation intensity, so their precipitation climatology is biased to big events.  

Fraction of precipitation from moderate to high precipitation intensity days. Source: Isotta et al. (2013).

In contrast, moderate to high precipitation intensity days produce a lower fraction of the precipitation along the northern rim.  Thus, the southern rim and hot spots get their precipitation when Mother Nature hits home runs (big events), whereas the northern rim scores with lots of base hits (lots of smaller events).  Note that this doesn't mean that the northern rim doesn't see extremes, because it does, but it tends to see more frequent smaller events than the southern rim.

A few photos of this event from @weathertoski are provided below.  The area is still seeing snow and will see periods of snow, possibly heavy again on Tuesday, until Wednesday.  Impressive!

Sunday, December 6, 2020

Alpine Storm Update

As we sit mired under a ridge in Utah, we look once again to the Alps for interesting mountain weather. 

The storm discussed in prior posts has had quite an impact on the southern Limestone Alps of Austria and northeast Italy.  The Tyrolean newspaper Tiroler Tageszeitung reports level 5 (highest possible) in the East Tyrol, with power outages and mudslides in other areas. 


The Tirol Avalanche Report shows level 5 avalanche hazard in the East Tirol and portions of the Dolomites.  Heavy snow also fell along the Carnic Alps further east and south of Villach, Austria, not covered by the Tirol Avalanche Report.


In fact, one of the more impressive meteograms I could find was from the Porzehütte, an Austrian Alpine Club hut on the Carnic main ridge south of Obertilliach (red dot below) where the height of the snowpack (HS) climbed from about 20 cm to 199 cm in less than 2 days.  That's a snowfall rate of about a meter (40") per day.  The water equivalent of that snowfall is around 250 mm (10"), so this is some high-density base builder.  


A look at avalanche reports for mountain areas around Cortina and elsewhere not covered by the avalanche reports above shows level 4 (high) danger.  Snow levels in that area were fairly high.  Observations from Seiser Alm Zallinger at 2055 meters above Val Gardena show temperatures for much of the event hovering near 0˚C.  Snowpack height observations are spotty, but show an increase of about 100 cm.  


At lower elevations, rain and wet snow has fallen.  An example is the village of Castelrotto at about 1000 m.


It would be great if we could get a good base builder storm like that.  How about a multi-day storm with 40-70 inches of high density snow and a snow level of around 6500 feet so we can continue COVID hikes in the foothills?  

One can dream.