Weather Whiplash

In Wednesday's post, we mentioned the likelihood of unseasonably warm temperatures in the mountains this weekend (temperatures in valley and bench locations will also be mild, but how warm will depend on how stingy the valley cold pool is). 

We are on track for that as the NAM continues to bring in +4˚C air at 700 mb (10,000 ft) for Saturday afternoon. 

As I mentioned, I think this will cause a touch of spring fever.

However, not far behind that warmth is a cold trough that will drop temperatures greatly by Monday.  The NAM forecast for Monday afternoon local time shows a deep trough over Utah with 700-mb temperatures around -14˚C over Salt Lake.   

Looking at the numbers right from the model grid over Salt Lake shows 700-mb temperatures of 3.5˚C at 5 PM MST Saturday, 5.5˚C at 5 AM Sunday, -3.7˚C at 5 PM Sunday, -9.9˚C at 5 AM Monday, and -14.1˚C at 5 PM Monday.

If that's not cold enough for you, the GFS is even colder and eventually drops the 700-mb temperature to -20.1˚C by 8 AM Tuesday.

I have a rule that I call the 20/20 rule.  700-mb temperatures at Salt Lake City above 20˚C or below -20˚C are unusual and get my attention.  Below -20˚C is not exceptional (the all-time record is -30˚C and the record for February is -25.9˚C), but it is cold.  Usually it ensures sub-zero temperatures at upper elevations. 

The models are also generating precipitation with and following frontal passage.  The SREF ensemble gets things started near or following 0000 UTC 3 February, so late Sunday or Sunday night and by 0000 UTC 4 February (5 PM MST Monday), all but two members generate at least 8 inches of snow and many are over 10 inches. 

Thus, early next week is looking good, but Tuesday is going to be COLD. 

Saturday Spring Fever Potential

February arrives on Saturday and with it will be one of the warmest days we've seen in the mountains so far this winter.

The GFS forecast for 2100 UTC (2 PM MST) Saturday shows high pressure in control, but a trough in the Pacific Northwest. Ahead of that slowly approaching system, 700 mb (10,000 ft) temperatures are forecast to be nearly +4˚C in the central Wasatch. 

Balmy.  Such a temperature would not be a record for January or February and we once reached 5.8˚C on February 1st, but it is quite warm. 

I suspect this will incite a weak case of spring fever as people enjoy the warmth and hopefully sun.  On the plus side, this is still Steenburgh winter, so the snow on upper-elevation north aspects should stay dry and continue to support good skiing. 

Sneaker Storms and Winter Perspectives

I haven't been blogging much about the forecast of late and maybe that's a good thing.  I keep looking at the models and thinking the next storm is sort of ho hum, and then it overproduces, resulting in a so-called sneaker storm.

Last night provided yet another example.  SREF forecasts initialized at 0900 UTC 25 January (2 AM MST Saturday) produced anywhere from 3-12 inches with last night storm with a mean of about 8. 

Thusfar, we're up to a 12 inch total, at the top of the ensemble range, and it's still snowing. 

I could dig further, but who wants to jinx this run?  Let it keep coming.

Shifting gears, it's now January 27th, which puts us nearly 2/3 of the way through meteorological winter (December-February) and the snow accumulation season.  In the Salt Lake Valley, it's been a relatively mild meteorological winter with a mean temperature at the Salt Lake City Airport through Jan 26 of 34.6˚F, the 16th warmest on record (i.e., since 1875). 

The coldest temperature observed so far this winter at the airport is a relatively balmy 20˚F, which was the minimum on three days in December and two in January.  That's pretty pathetic.  We've never gone so deep into meteorological winter without a colder temperature.

Source: NOAA Regional Climate Centers

Note, however, that we did get below 20 on two days in October, but that's not winter.  It's fall.  Remember, on October 30 we had the coldest day on record in October with a low of 14˚F.  We haven't been within 6˚F of that this winter!  

Finally, a quick comment on the state of the snowpack.  It's been a good snow season, but the snowpack is not as fat as you might think.  The Snowbird SNOTEL sites at 148% of median, but as of yesterday elsewhere in the Salt Lake and Bountiful area mountains Brighton is 113%, Thaynes Canyon 111%, Mill-D North 114%, Parleys Summit 112%, Lookout Peak 125%, Louis Meadow 110%, Hardscrabble 105%, Parrish Creek 111%, Farmington 105%, and Farmington Lower 112%.  To the south, Timp Divide and Cascade Mountain are below median (94% and 89%, respectively).  

Last night's snow will help a bit, but if I was a water manager, I'd keep doing my snow dances.  

Reading the Clouds

Yesterday (Saturday) provided some great cloud displays that help illustrate important atmospheric circulations.

We'll start with the most "benign" —thermally forced cumulus clouds that formed on the mountains immediately north of Little Cottonwood Canyon yesterday morning.  These are a common site in Little Cottonwood and are the result of upslope flows that form over the canyon sidewalls.  It is likely that such flows form earliest in the morning on the south facing sidewall this time of year.

In contrast, nocturnal downslope flows can linger later in the morning on the north facing sidewall.  The upslope flow helps to form cumulus clouds when the temperature and moisture profile is right.

I also noticed some evidence of vertical wind shear and associated turbulence in the clouds near the Pfeifferhorn that morning, but nothing as dramatic or beautiful as what Luke Stone saw over Mount Timpanogos.

Kelvin Helmholtz Waves above Mt. Timpanogos in American Fork Canyon today. @TimNBCBoston @WeatherNation @judah47 pic.twitter.com/KDmnsW0ICt

— Luke Stone (@LukeLStone) January 26, 2020

 As he notes, such clouds provide an example of Kelvin-Helmholtz waves, which occur where strong wind shear overwhelms the atmospheric stability, leading to overturning of the atmosphere.  If a cloud is present, the resulting pattern can look like water waves breaking near the beach.

Unfortunately, upper-air soundings are not collected mid-day, but if we look at the evening (5 PM) sounding from the Salt Lake City airport, we see that there was a layer (horizontal green line) at about 630 mb that is near saturation and in which the winds are increasing with height.  Mt. Timponogos is just a bit lower than this at about 660 mb.

Sounding source: SPC

Alternatively, the clouds could have been produced by shear right at the base of the inversion that was near crest level at about 690 mb.  Given the difference in time and distance, either of these are plausible. 

Finally, Allan Gardner posted the video below on Twitter.  This is an example of a hydraulic jump in which flow is moving rapidly downslope, becomes "supercritical", and then rises rapidly in the hydraulic jump.  

One of those happy accidents yesterday. We opted to hike on Antelope Island to get out of the inversion and snow and enjoyed a mesmerizing hour of Mother Nature playing with fog and clouds. pic.twitter.com/jmsZAL7E8Q

— Alan Gardner (@alangardner) January 26, 2020

 The process is very similar to what can happen during flow over a rock in a stream.

Source: Aokomoriuta via Wikipedia Commons

As one might gather from the photo and video above, the region near and downstream of the jump can be quite turbulent. 

It's great when clouds provide guidance about the flow in the atmosphere, but Kelvin-Helmholtz instabilities and turbulence associated with downslope flows and hydraulic jumps can occur in the clear air.  They represent important hazards for aviation or recreationists such as parasailers.  In particular, both hazards and produce severe turbulence, often in areas that are otherwise free of clouds.  Just one of the reasons why I always wear my seatbelt on an airplane.

Perspectives on Linkages Between Arctic Warming and Severe Winter Weather

A hot climate topic in recent years has been the possible linkage between a warming arctic and midlatitude weather extremes, including severe winter weather.  An example of the types of headlines you've probably seen before is provided below from The Guardian. 

Source: The Guardian

This is a subject that has caused me a good deal of indigestion and that I've largely avoided in this blog.  This is because most of the evidence for this linkage has been based on observational studies, whereas model based studies have obtained differing results.  

A new review article is now out in Nature Climate Change discussing the differing perspectives obtained form observational and modeling studies.  The paper is led by Judah Cohen and involbes a large number of authors including HongPing Gu and Simon Wang of Utah State University and the Utah Climate Center.  

Source: Nature Climate Change

Sadly, the paper is paywalled, but the National Science Foundation Public Affairs Office has issued a plain-language summary that describes the issues at play.  It is available at https://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=299896&org=NSF&from=news, although I've included a screenshot below if you want to take a quick look (click to blow up).

Source: NSF

To summarize the issues at play, the Arctic has been warming twice as fast as the global average, a trend that has long been anticipated and is known as Arctic Amplification.  The causes of this amplification are multifaceted and complex.  Feedbacks related to a loss of Arctic ice are most commonly cited by popular media, but as summarized below, there are others.  

Source: Cohen et al. (2020)

In turn, it has been hypothesized that Arctic Amplification may be affecting midlatitude weather.  For example, the decline of Arctic sea ice in the fall can intensity Arctic storm systems, which could potentially lead to weakening of the polar vortex.  A weaker jet stream might also be expected due to the weakened temperature gradient between the arctic and the lower latitudes.  These are simple generalizations and ultimately linkages between the Arctic and the midlatitude depend on several factors and are sensitive to regional changes in sea-ice loss and other subtleties.  

What one would hope is that observational and modeling evidence would like up and agree, but at present, they do not.  Observational studies reveal relationships and suggest linkages.  The period that can be investigated observationally is, however, relatively brief given the amount of variability in the atmosphere.  Modeling studies allow us to simulate much longer periods of time and conduct experiments in which we can hold one thing constant but change another, but are limited by model imperfections.  

At present, observational studies have identified some relationships between Arctic Amplification and midlatitude severe winter weather.  Recent modeling studies suggest, however, that the atmospheric response to recent Arctic sea ice trends is negligible.  As noted by Coehen et al. (2020), "A number of large ensemble modeling studies have come to the same conclusion — that is, there is little modeling evidence of an atmospheric response to the pan-Arctic sea ice trend."  

This is how science works.  Hypotheses are put forth and tested, often using multiple approaches.  Discrepancies are then investigated, methods refined, and hypotheses revised and retested.

I don't know how this process will conclude.  It is possible that we will learn that recent trends reflected variability and it was coincidental that there appeared to be a linkage between arctic warming and midlatitude severe winter weather.  It is possible that deficiencies in the modeling system or experimental designs will be identified.  Finally, it is possible that we're just not looking at the problem properly and that new theory and better theory will be developed.  Eventually we will figure this all out.  

Japan's "Nonsoon" Season

Western Japan has one of the most remarkable and reliable snow climates on Earth, but as the saying goes, climate is what you expect and weather is what you get.

During the East Asian Winter Monsoon, which over Japan features quasi-persistent northwesterly to northerly flow between the Siberian High and Aleutian Low, frequent cold-air outbreaks drive sea-effect storms near the Sea of Japan coasts of Honshu and Hokkaido Islands.  Mean annual snowfall exceeds 500 inches in some mountain areas, much of it falling from December to February.  

This year, however, the winter monsoon has been more of a winter "nonsoon."  Snow depth observations as of today, 22 January, show many sites with under 50 cm of snow and only four over 100 cm (about 40 inches).  

Snow depth observations in cm.  Source: http://www.data.jma.go.jp/obd/stats/data/mdrr/snc_rct/index_snc.html.

This is unusual as nearly all sites are well below average, especially on Honshu where many sites are below 40% of average.  One can find a few sites in northeast Honshu that are above 100%, but these are not in the heavy snow region near the Sea of Japan and thus snowpack in those areas is still scant.  For instance, Sannohe in Aomori Prefecture is at 142% of average, but that's with only 27 cm on the ground.  

Percent of average snow depth.  Snow depth observations in cm.  Source: http://www.data.jma.go.jp/obd/stats/data/mdrr/snc_rct/index_snc.html. 

Near Niseko Resorts on Hokkaido, Kutchan currently has a 78 cm snow depth, which is only 61% of its 128 cm average on this date.  Kutchan is near the base of Niseko and snow depths are probably greater on the mountain, but with records going back to 1944, it does illustrate the unusual low-tide conditions.  

Perhaps not surprisingly, the deepest measured snowpack, indicated by the reddish-orange square in the top image above, is Sukayu Onsen in Aomori Prefecture on the north end of Honshu.  Sukayu Onsen has a mean annual snowfall of 694 inches, so a bad year there is still better than a good year most anywhere else.  There, in the Hakkōdo Mountains, the snow depth is 191 cm, but average is 248 cm.  

One reason for the "nonsoon" so far this winter is that the Siberian High and Aleutian Low are weaker than average.  Below is an analysis of the sea level pressure "anomaly" (or departure from average) for the one month period ending January 15.  Negative anomalies over much of northern Eurasia are consistent with a weak Siberian High and positive anomalies over much of the north Pacific are consistent with a weak Aleutian Low.  

One might ask why those pressure systems are weaker than average.  Ha ha.  I don't know the answer to this and I don't have the time to investigate.  You get what you pay for with the Wasatch Weather Weenies blog.  If you want me to investigate further, buy me a ticket to Hokkaido.

Thursday's Frontiers of Science Evening Lecture

This Thursday Evening's Frontiers of Science Lecture is one you don't want to miss.  Dr. Craig Clements, Professor and Director of the Fire Weather Research Laboratory at San José State University will be speaking on Advances in Observing the Wildfire Environment: Understanding the Role of Fire-Atmosphere Interactions. 

The talk is scheduled for 6 PM in 220 ASB (Aline W. Skaggs Biology Building).  Free parking is available in the Chemistry Lots.  Complete information is available at https://science.utah.edu/news/frontiers-of-science/.

Craig is a University of Utah alum and the "Indiana Jones" of wildfires.  You've probably heard of tornado storm chasing.  Well, Craig is an extreme wildfire chaser, using scanning Doppler lidars and other instruments to better understand how fire-atmosphere interactions yield extreme fire behavior. 

Craig is a great and engaging speaker.  This is definitely a lecture you don't want to miss. 

Greed Is Good

One of the "worst" days I've had this year.  Photo: Erik Steenburgh.

It's been a pretty good ski season thus far and, thinking like Gordon Gecko, I think our motto going forward should be "Greed Is Good."  

NRCS SNOTEL data as of 18 January shows that most northern Utah observing sites are at or above median.  In the Wasatch Range, only Timpanogos Divide (93% of median) and Cascade Mountain (82%) are below median.  

Source:NRCS

The Snowbird SNOTEL has both the highest water equivalent (23.8") and percentage above median  (143%) in the Wasatch Range.  A look at this water year's trace (blue line below) compared to water years since 2011 shows we are running well above all water years except 2019 and 2011 (year denotes the last year of the water year — i.e., 2019 = 2018/19).  Further, we were ahead of 2019 during much of December and are only a little behind, so the difference is negligible.  

Source: CBRFC

The bottom line is that this year is pretty good by recent standards.  We've discussed how the 2010s were pretty "meh" for snowfall compared to the 1980s and 1990s in previous posts (see Your Parents Had More Powder Than You).  A look at the the traces above shows that the 2010s were characterized by either really big snow years or really bad snow years.  There's no middle ground and no seasons that end up near median maximum SWE, which is 43 inches. 

How the rest of the year ends up is anyone's guess, but we can look forward to the week ahead and see what is likely.  We have a system passing to the south tonight and tomorrow and then another system passing to the north Tuesday night and Wednesday.  While not a direct hit, the Wasatch should see some periods of snow tonight through Wednesday morning.  Through 11 AM Wednesday (22/18Z in the plumes below), the SREF generates a mean of about 8 inches of snow at Alta-Collins, with most members between about 3 and 12 inches.  

After that, it's a bit of a dirty ridge scenario for Thursday, but accumulations, if it snows, will probably be light.  Thus, a reset this week depends on coming in on the high end of projections through Wednesday morning.  The most likely scenario is 4-8 inches in upper Little Cottonwood this week.  Let's hope we do better than that and get a real reset.  Greed is good.

Oh the Places You'll Go!

There are places in the Wasatch that make me think of Mount Crumpit from Dr. Seuss' How the Grinch Stole Christmas.  Whoville in this case is, however, not a small town.

My favorite passage from Dave Hanscom and Alexis Kelner's essential guidebook Wasatch Tours: The Northern Wasatch describes the route up Mount Crumpit as follows.

"No ski area developers have cleared the willows and oak, so considerable ingenuity and determination are required to get through the brush.  True cross country touring is, after all, a character developing and strengthening form of recreation." 

Yup, it's not easy.  However, the Grinch favors the route below, which was skied by some of his assistants prior to our arrival.

And one need look no farther than Dr. Seuss for inspiration for your next mountain adventure.

"You're off to Great Places!
Today is your day!
Your mountain is waiting,
So...get on your way!"
-Dr. Seuss, Oh, the Places You'll Go! 

Going Out with a Bang

Our latest storm cycle certainly ended with a bang this morning.  Observations from Alta-Collins show a total of 16 inches as of 3 PM, but 10 inches fell in the 4 hours and 6 inches in 2 hours ending at 8 AM. 

Storm winds were also strong.  With a peak ridge-top wind gust at 11,000 ft of 80 mph around 9 AM.  The heavy snowfall and perhaps wind transport led to some natural avalanche activity in the Y and Y-Not Couloirs on the south side of Little Cottonwood Canyon.  

Video avalanche in Y and Y-Not Couloirs in Little Cottonwood Canyon which has seen intense snowfall. #utavy @UDOTavy @UDOTcottonwoods pic.twitter.com/rRE3uX3fRy

— UtahAvalancheCenter (@UACwasatch) January 17, 2020

Strong winds were also observed at mid-elevations, even in some tree-protected areas.  Having returned from Boston after a long work trip, I headed out this morning and found it necessary to stay layered up even on the long climb. 

The MLK weekend looks dry, although there could be some periods of mid and high clouds at times.  Snow safety teams have earned this break. 

Catching Up and Looking Back

I've been unable to prepare a blog post in a few days, so it's time to catch up on several subjects.

AMS 100

I've been away from Utah for several days attending the Annual Meeting of the American Meteorological Society (AMS).  It is a noteworthy meeting as it is the 100th anniversary of the AMS.  When the AMS began, routine upper-air observations did not exist and the concepts of upper-level waves and the jet stream weren't developed.  Digital computers hadn't even been invented.  Radar wasn't invented.  Wireless radio communication was in its infancy.  Today, we observe the atmosphere from space, surface observations are ubiquitous and shared instantaneously, we get near instantaneous information about storms using radars, and some of the world's biggest computers are dedicated to weather prediction.  It is clear that meteorology has made incredible progress over the last century and that we should be excited about the next 100 years.

Alta 100 and Steenburgh Winter

During my absence, the snow has continued to fall in Utah. Alta reached a 100" snow depth at 1900 MST January 11. 

Technically, that might be a 96" snow depth as last summer the automated sensor was reading 4" when there was no snow on the ground.  I'm not sure if Alta has recalibrated it yet, but we'll assume the current reading is close enough for government work and will call it an even 100. 

That observation also means we'll have a full month of Steenburgh Winter this season.  Steenburgh Winter is the crème de la crème of backcountry skiing conditions with a deep snowpack (i.e., > 100" or 250 cm) and a low angle sun (i.e., the period prior to February 10 when the sun angle and day length are starting to increase rapidly).  All of this is of course a bit vain and contrived, but this is a blog about snow snobbery and the backcountry cognoscenti know that a deep snowpack and frequent snowfalls in December, January, and February enable more days of good skiing on more aspects than they do in March and April when the sun has an increasingly caustic effect on the snow. 

Steenburgh Effect

I didn't name this, but if you believe in it, I've been gone for some time and it's been snowing.  I return late tonight and after a last gasp of heavy snow very late Thursday night and Friday, there will be a break for a few days.  Coincidence? I think not.

Austria

One year ago today, Andrea and I arrived in Innsbruck to begin a semester as a Fulbright Visiting Professor at the University of Innsbruck.  We arrived to a Tyrolean winter wonderland as a major storm cycle had just ended in the northern Alps.

It was a great trip and it is likely that I'll do some reminiscing during posts in future months.

Steenburgh Winter Is Almost Here

The snow continues to pile up and the automated snow depth sensor at Alta Collins reached 96 inches at 6 AM this morning.

This puts us on the cusp of Steenburgh winter, my vain name for the crème de la crème of backcountry ski conditions when the snowpack is deep and the sun angle low.  Officially, Steenburgh winter extends from the day when the Alta-Collins snow depth reaches 100 inches to February 10 when the sun begins to have an increasingly caustic influence on the snow as spring approaches. 

We haven't had many Steenburgh winters in recent years.  A quick look shows that seasons with Steenburgh winter conditions since I began this blog in 2010 are: 2010/11, 2016/17 (barely - we hit 1000 inches on Feb 10),  and 2018/19. 

It could get close, but I don't think we will reach the start of Steenburgh winter today.  We need another four inches and things seem to be winding down as I write this.  Our next storm, which looks to be a good one, develops tomorrow.   It's possible that Saturday will be the first day of Steenburgh winter.  If not, it will come no later than early next week. 

One thing is for sure, the forecast through next Wednesday looks like a powderhound's dream with cold storms coming in one after the other.   This is probably the result of the similarly vainly named Steenburgh effect as I will be leaving town tomorrow for the annual meeting of the American Meteorological Society in Boston.   Enjoy, but be safe out there. 

Avalanches at US Ski Resorts

Sad news from Idaho where 2 skiers were killed in an avalanche at Silver Mountain.  Media reports indicate that the avalanche occurred in in-bounds terrain that had been open for less than an hour (see this article from The Spokesman-Review). 

This is an unfortunate reminder that mitigation efforts reduce avalanche hazard at ski resorts, they do not completely eliminate it.  As discussed in my book Secrets of the Greatest Snow on Earth, on average slightly less than one avalanche fatality occurs per year in in-bounds terrain that has been opened by ski patrol at US ski areas.  Although this is much lower than the number of deaths in backcountry areas, it is not zero.  Avalanche mitigation and hazard assessment is inexact.  It is a human endeavor in an environment in which there is not complete knowledge. 

That being said, there is little doubt that snow-safety teams do great work.  Just check out the photo below of Alta after it was raked by avalanches in 1885.  Imagine living or skiing at Alta without their heroic efforts. 

Alta, UT on July 3, 1885.  Courtesy Utah State Historical Society.  

Active Stretch Ahead

The pattern over the next 7-10 days looks pretty good for Wasatch snow lovers as several weak systems move through the region.

Ten-day total accumulated precipitation from the ECMWF model (top image below) indicates roughly 1-2 inches of water equivalent in the central and northern Wasatch, while the GFS generates greater amounts.  Such results are fairly consistent with model biases as the GFS tends to be wetter than the ECMWF.

Source: Pivotal Weather

Source: Pivotal Weather

Our downscaled NAEFS product for Alta over the next seven days (i.e., through 0000 UTC 14 January) shows that after dry weather prevails today, a progression of weak systems through the area.  There are no huge one-day dumps if the GEFS members, but instead a series of systems that slowly but surely add up to a mean of just over 2 inches of water equivalent and 35 inches of snow.  Some Canadian members are more inclined to produce heavier snowfalls.  That's not out of the realm of possibility, but it's not a likely outcome.  

All of the members of the NAEFS produce over an inch of water and 20 inches of snow, so confidence is high that we will at least be at or above what we would expect climatologically during the forecast period. 

Enjoy the continuing favorable pattern. 

Flashback Japan

Three years ago I was in Japan on a trip that involved some skiing and collaborative work with scientists at the Nagaoka Snow and Ice Research Center (SIRC).  Joining me for the trip was University of Utah graduate student Peter Veals. 

Exactly three years ago today we were ski touring in the Hida Mountains, also known as the northern Japanese Alps.  Hokkaido gets a great deal of press, but the Hida Mountains on Honshu offer up some of Japan's highest terrain.  Whoever said Japan is deep not steep has never been to the Hida Mountains. 

The tricky part in the Hida Mountains is having a day with stable snow and good visibility, and we were fortunate to have one.  It is possible to purchase a single ride ticket at Happo Ono or Tsugaike ski areas to begin your tour in the alpine.  Given the relief of the Hakuba Valley, I suspect this is greatly preferred by most ski tourers when the alpine is accessible, although you won't be alone as many opt to do this.  This was also necessary while we were there as the winter monsoon was off to a late start, so low-elevation snow was meager. 

Conditions were really outstanding and we enjoyed a couple of pleasant powder laps.  Here's a shot of Peter, or as I called him that day, the luckiest graduate student on the face of the Earth. 

There are things you can do in Japan that you can't do in Utah.  Here I am enjoying cold pot stickers with bamboo in the background as we exited the tour. 

I often get questions about the snows of Japan and if you are interested, see out blog post A Primer on Sea-Effect Snows of Japan, or our forthcoming article for the Bulletin of the American Meteorological Society Perspectives on Sea- and Lake-Effect Precipitation from Japan’s “Gosetsu Chitai”.   The latter is coauthored by Sento Nakai of SIRC, who graciously hosted us during our trip and is pictured below with Peter and I and one of SIRC's snow-measurement systems. 

For readers who may be attending the Annual Meeting of the American Meteorological Society next week in Boston, I'll be speaking on sea-effect storms of Japan at 11:30 on Tuesday in room 258A. 

Today's Cloud Atlas

It was a pretty good day for cloud viewing today.  First, there was a brief display of altocumulus undulatus at Alta. 

Such cloud billows were likely produced by a phenomenon known as Kelvin-Helmhotz (KH) instability, which occurs when strong vertical wind shear leads to atmospheric overturning. 

Source: https://www.eoas.ubc.ca/courses/atsc113/flying/met_concepts/01-met_concepts/01b-special-clouds/billow.html

Then there was a beautiful sunset, with lenticular clouds hanging over the central Wasatch.  

These stationary clouds were generated as the atmospheric flow was forced over the Wasatch Range.  Below is a web-cam video looking south from the University of Utah illustrating the stationary nature of the clouds (apologies if Blogger has coarsened the resolution, but my time is tight). 

Finally, there's nothing too exciting about the altocumulus clouds below, but it was a pretty sunset over the Oquirrhs with a weak sun pillar, a vertical beam of light that in this case is above the sun and is caused by light reflecting off of ice crystals. 

Paradoxes of Snow Measures

With the holiday's winding down, I think it is safe to say that we have been blessed with some outstanding skiing for December and the first couple of days of January.  Really, the entire month is a blur to me.  This morning, walking up the stairs to my office felt like climbing an 8000-meter peak (not that I know what that feels like), but I'm hoping to rally in time for a short skate ski later today.

Snowpack water equivalent (i.e., the amount of water in the snowpack) is above median at most SNOTEL sites.  The few sites that are below median are barely below median.  In the central Wasatch, Snowbird, Brighton, Mill D North, and Thaynes Canyon are at 138%, 119%, 122%, and 110% of median.  In the northern Wasatch, Ben Lomond Trail and Ben Lomond Peak are at 127% and 117% of median. 

Source: NRCS

Snowbird and Ben Lomond Peak have the largest snowpack water equivalents with 16 and 15.1 inches, respectively.  I did some ski touring in the Ben Lomond area a few days ago and was pleased to find a robust snowpack at all elevations.  Ben Lomond Trail, at 5972 ft, as 10 inches of snowpack water equivalent, virtually identical to the 10.1 inches at Mill D North, which sits at 8963 feet in the central Wasatch.  Some pretty robust snowpack numbers can also be found in the Oquirrhs (Rocky Basin Settlement - 12.1 inches) and Stansburys (Mining Fork 10.8 inches).  All of this indicates a great start to the ski and snow accumulation season.

Although these snowpack numbers are very healthy, you might be surprised to learn that snowfall is below average at Alta Guard.  As reported by the Utah Avalanche Center in their Jan 2 forecast, Alta Guard recorded 149" of snow in November and December, compared to an average of 162".  How can we explain this paradox?

Simply put, while the depth of new snow has been below average, the water content of that snow has been above average.  As a result, we got a lot of bang for the buck in terms of cover and I would argue ski quality. 

Many people love blower pow, but I'm not one of them.  My impression of the skiing the past few weeks is that we've had a lot of right-side up snowfalls with somewhat higher density mean water content.  In my view, that makes for great skiing.  Yesterday was the first day that I was out ski touring and the snow felt a little upside down because we had higher density snow fall on top of some lower density snow from previous days (resort skiers probably didn't notice this as much as that lower density snow was tracked thoroughly before the New Years storm).  Even then, the skiing was still good.

Please note that all of this has happened while I was in town.  Is the Steenburgh Effect is a myth borne from small sample size and confirmation bias?  Only time will tell.