It's Never Been So Warm So Early in the Year

Yesterday was a remarkable day at the Salt Lake City Airport with a minimum temperature of 56°F and a maximum temperature of 66°F.  Each of these is the warmest temperature observed so early in the calendar year, meaning they are both records for the period from 1 January through Feb 3.

The minimum temperature of 56°F blew everything prior out of the water, eclipsing the prior record by a remarkable 7 degrees.  Curiously, many of the prior highest minimum were set in January in the early 1900s.  At that time, the NWS observing site was in downtown Salt Lake City.  

Source: https://xmacis.rcc-acis.org/

But that 56°F is even more remarkable than that.  It is the highest minimum temperature observed on any day between 3 November and 17 March, tying 9 November 1927.  The 66 is not as much of a black swan, but still a very impressive maximum for early February.  And of course the warmth continues today.  

Extending back into the weekend, this has been a disastrous period for the low-elevation snowpack between the rain, clouds, and temperature.  It is remarkable how long snow can persist in shady areas this time of year if its cold and cloud or even clear with maximum temperatures in the low 40s.  However, low-and mid clouds with such warmth strongly modify the snow energy balance by providing long-wave radiation input to the snowpack.  Such radiation is typically an equal-opportunity offender, meaning it affects the snow on all aspects.  Like that, poof, the snow behind my house was gone.  

Similarly, this period has been a catastrophe at Mountain Dell.  Such a shame for the Nordic skiers. 

Source: https://utahnordic.org/mtndell/

Wind and warmth look to continue into tomorrow.  There is a front coming in during the day tomorrow, but temperatures will remain above seasonal norms even after the frontal passage.  This is no way to run winter.

When Forecasts Diverge

The last few days, the ensembles have been producing a pretty wide range of possible forecast outcomes for the central Wasatch for the storm that begins tonight and extends, potentially, into Monday.  This was discussed in the prior post (Shift in the Weather), and continues to be a forecast issue today.  

Last night's Utah Snow Ensemble exhibits some spread in the forecasts through 0000 UTC 2 February (5 PM MST Saturday; red line below), but the means of the ECMWF ENS and GEFS ensembles are relatively similar and around 0.72" of water and 6.5" of high-density snow for Alta Collins.  The latest GFS and HRRR are also around about 7" of snow, so going for something in the 5-10" range through 5 PM MST Saturday makes sense. 

After that, the two ensemble systems diverge, with the ECMWF going for less water and snow than the GEFS, although there is some overlap of the members from each ensemble.  The reason for this, and the uncertainty in the forecasts through Monday morning is uncertainty in the amplitude of the upper-level wave pattern and position of the atmospheric river and concomitant frontal system.  The wave pattern in the wetter members, especially those in the GEFS ensemble, is less amplified, resulting in more zonal (west-to-east) flow and a longer period with the central Wasatch under the influence of the atmospheric river.  In contrast, the wave pattern in the drier members, especially those in the ECMWF ensemble, is more amplified, resulting in a bit more southwesterly flow and a shorter peirod with the central Wasatch under the influence of the atmospheric river.  

The ECMWF was actually drier a couple of days ago and it has shifted a bit more toward theGEFS and gotten a bit wetter.  The EMCWF mean a couple of days ago was under and inch for the entire period, whereas now it is closer to 1.5 inches.  Whether or not that trend will continue remains to be seen.  

If you are into stats, we can look at some numbers from the Utah Snow Ensemble for Alta-Collins.  We provide these at https://weather.utah.edu/text/ensgefsdslccforecast.html. In tables available at that link and reproduced for last nights run below, time increases to the right (local time is labeled).  For each time, we provide the minimum, 10th percentile (P10), 25th percentile (P25), 50th percentile or medan (P50), 75th percentile (P75), 90th percentile (P90), and maximum accumulated water equivalent and accumulated snowfall (as well as other variables although I'm not presenting them here.  These take a little while to wrap your head around, but one way to think about a percentile is that in the ensemble that percentage of the members is producing less than or equal to that amount.  So, P25, or the 25th percentile means that 25% of the members are at or below that amount, whereas 75% are above it. For P75, 75% are at or below that amount, whereas 25% are above it.  

For the latest forecast through Monday morning, P25 is 1.17" of water and 9.7" of snow.  So, 25% of the members are at or below those amounts, whereas 75% are above it.  The middle 50% of the ensemble (between P25 and P75) is between 1.17" and 2.35" of water.  

Its not uncommon for forecasters to lean toward that range between P25 and P75.  This middle 50% of the members is sometimes referred to as the interquartile range or IQR.  In this case, if one were to round a bit, that would yield a storm total through Monday morning of 1.2-2.4" of water and 10-20" of high density snow.  There would be a 25% chance of being below this and a 25% chance of being above this.  If you are in the snow-safety business, you're probably most worried about the latter happening as adding even more weight to the snowpack has serious implications for avalanche hazard.  In this case, the wettest and snowiest member of this ensemble puts out a whopping 5.45" of water and 48.2" of snow.  That is, however, a significant outlier and not a likely outcome (but it is worth recognizing).  For that to verify, we would probably need to be in the atmospheric river for most of the period.  

The above is a look at how one might use statistics for forecasting.  One thing I haven't done is to adjust for model bias.  That can be important in some situations (for example, the models tend to be too dry at Alta-Collins during northwesterly post-frontal flow, although that's not happening during this storm period).  Another challenge for real forecasters (unlike those of us who work in the ivory tower like myself) is how to summarize all of that into actionable information for the public, clients, or other stakeholders.  That takes real talent.  

Shift in the Weather

The models have been hinting at a pattern shift for the start of February, with the west-coast ridge weakening and a new high-over-low blocking pattern developing farther upstream over the Pacific.  

The GFS forecast valid 0000 UTC 2 February (5 PM MST Saturday) shows the high-over low block well upstream of the Pacific Coast with the confluence of two very different airstreams downstream of it over western North America.  The first is a colder airstream originating over the high latitudes that turns counterclockwise (cyclonically in meteorological speak) and into the Pacific Northwest (see northernmost yellow arrow below).  The second is a warmer, moister airstream originating over the subtropics that extends northeastward and eastward over the Great Basin (see southernmost yellow arros).  This second airstream is also associated with an Atmospheric River that extends across northern California and into northern Utah (see red arrow).

The confluence of these two airstreams results in strong to westerly flow over the Great Basin.  This is a pattern that can be good for precipitation generation in the Wasatch if the location of the atmospheric river and the confluence are right.  If it sets up right, we could get a good deal of wet, high density snow at upper elevations (with rain at lower and possible mid elevations at times).  On the other hand, a slight shift to the north and we'll be warm with some scraps.  

As a result, there is enormous spread in the forecasts from the Utah Snow Ensemble, with members of the GEFS generally producing more water and snow than members of the ECMWF for Alta-Collins.  The red box below highlights the forecast period from 0000 UTC 1 Feb (5 PM MST Friday) to 00000 UTC 4 Feb (5 PM MST Monday). Several members of the GEFS are going for more than 2 inches of water (20 inches of snow), including one that is over 4 inches (40 inches of snow).  The GEFS mean is near 2" water/18" of snow.  The Euro members are, however, much drier, with a mean of about 0.6" of water and 5" of snow. 

A look at the forecasts for the 0.5ºC wetbulb level shows a big shift from the cold weather we've had of late.  By 0000 UTC 3 Feb (5 PM MST Sunday) the median wet-bulb 0.5ºC level is over 8000 ft, which would put the snow level at maybe 7000-7500 feet.  There are a few members that are lower, but the violins show a tight clustering between 7500 and 9500 feet (I suspect the highest forecasts are from the ECMWF and they aren't as wet).  Regardless, this is a big warm up and the net result are snow-to-liquid ratios that are fairly low.  In fact, medians are below 7.5 to 1 and in the Cascade Concrete Range.  

So, high confidence of a shift in the weather, but the details of just how warm and how much snow remain uncertain, especially given the lack of agreement between the ECMWF ENS and the GEFS.    

Is the U Heading in the Wrong Direction?

This year marks my 30th as a tenure-track faculty member at the University of Utah, a position that I have enjoyed immensely.  I've been able to pursue my scientific and educational passions with zeal and I've been able to work with a lot of great students, faculty, and staff.  I think it was the perfect place for me to land.  Plus the skiing was great!

However, things have changed in recent years, perhaps reflecting an acceleration of long-term trends in higher education.  The U has become increasingly top heavy, with more administrators being paid increasingly high salaries.  There's less interest and respect for the knowledge and perspectives of the regular faculty and more top-down management.  There's increasing digital bureaucracy, often obtuse in design, interfering with our ability to work "efficiently" (I put that in quotes because that word is being thrown around a lot these days as if it were the holy grail of higher education).  More and more, my position is being treated as a commodity, broken down into discrete chunks to ensure that my workload is properly "managed" by formulas designed by beancounters who can quantify everything but value.  

These trends are sucking the soul out of higher education. They will degrade educational quality and research innovation and they will limit our ability to recruit and retain high-quality faculty.  

Today the Salt Lake Tribune reported that the U spent $6 million to hire a consultant (McKinsey & Company) to help "streamline processes and reduce wasteful redundancies across campus."  The first $3.2 million involved "looking at the University's internal data, studying its systems, and developing an understanding of what's working and what's not".  You know, the stuff that our administrators are supposed to be doing, potentially in consultation with our faculty, staff, and students.  When I started at the U, I knew administrators who had deep knowledge of the internal workings at the University, who had won teaching awards, and who understood the challenges of pursuing teaching and research excellence as a faculty member.  Today we talk about workload policies, key performance indicators, and how we can make more "data-driven" decisions.  

Certainly the U needs to evolve, but the pendulum has swung too far, resulting in tyranny of the metrics and depreciation of the deep knowledge and experience of our faculty.  I expect to see it increasingly challenging to recruit and retain the best faculty, a situation that may be exacerbated when programs are cut later this year, as being proposed by the legislature.  During the 2008 recession, when we faced deep budget cuts, I remember the administration saying that they would never cut programs because it would be so damaging to the reputation of the U and make it difficult to recruit the best faculty.  

One of my colleagues left the U last summer after almost 20 years and I am aware of others who are pursuing external opportunities.  The latter is not unusual with high-performing faculty, but there are people who I believe would prefer to stay and who are now considering other options.  The U is an economic driver for the state through research innovation, but the $691 million in external funding we received last year was down from $768 million the prior year, a decline of about 10%.  I have served as the principal investigator for 22 externally funded grants during my career and co-investigator on several others, but am not pursuing as many opportunities now due to inadequate post-award support.  Talk about penny wise and pound foolish.   

I share these views because I love the University of Utah and its students, faculty, and staff.  I don't know how widely my perspectives are shared by others and perhaps I am an outlier.  My views are personal and the U is a big, diverse place and everyone has different experiences.  I feel the need though to share them because I am concerned about the future of our institution, which I believe provides incredible value for its students and the State of Utah.  

Any opinions or views expressed in this article and on this web site are those of the author and do not necessarily reflect those of the University of Utah.  They were prepared on a Sunday, during non-work hours, on my personal computer.

Snow in Southtown

If you've ever seen the Rankin-Bass holiday classic "A Year Without A Santa Claus" you know that there is a long negotiation between Mrs. Claus, Snow Miser, Heat Miser, and Mother Nature to bring snow for just one day to Southtown.  If you have seen it, then maybe like me you were thinking of it yesterday when it was snowing along the Gulf Coast.  And if you haven't seen it, you should check it out as it is a must for the meteorologically inclined.

In any event, the snow totals from the Gulf Coast are impressive, with many CoCoRAHS observers from Louisiana to the Florida Panhandle coming in at more than 8.3 inches (red shade below).

Source: CoCoRAHS

The highest amounts reported by state were 13.3" in Grand Cotaeu (LA), 10.5" in Waveland (MS), 9" in Summerdale (AL), and 9.4" in Pennsacola (FL).  

I'm not versed in southeast meteorology, but it appears that this was truly a historic event.  For example, the Pensacola News Journal was reporting that official snowfall at the NWS site there had broken Florida's all-time snowfall record with 5" of snow (I'm not sure if this was the final total or not). 

Many weather records are based on daily (or 24-hour) totals and storms can sometimes cross over days.  Thus, I decided to pull up the largest 2-day total snowfalls for the Pensacola Area and indeed 3" is the prior record.  The one disadvantage of this approach is that a single one day storm can be listed twice (e.g., the 2.3 and 2.1 inch totals), but a quick subjective analysis suggests 9 unique events that produced an inch or more of snow in the Pensacola Area since 1880.   

Source: xmACIS2

Given the cold airmass combined with snow cover, minimum temperatures overnight set or were near all-time records.  Lafayette, LA dropped to 4F, an all-time record with observations back to 1893.  Mobile, AL hit 6F, their third lowest on record.  Incredibly, Mobile's all time record is -1 set on 13 Feb 1899.  

This event is a catastrophe for the unhoused and those in buildings that are poorly equipped for these extremes or lose power. The 2021 cold-air outbreak in Texas resulted in 246 deaths, a disaster was compounded by widespread power outages.  I am seeing reports of up some power outages this morning, which taken on huge significance in that region.  I am hoping that they remain localized and short lived.  

A Rare January Great Salt Lake Dust Event

The sun had not yet crested the Wasatch this morning when I awoke and when I looked out the window I saw this odd band of white extending at low levels through the western Salt Lake Valley.  

My first thought was what the hell is that.  It's too shallow to be a lake band and it doesn't look like fog.  I took a look at the weather observations and the relative humidity in that area was less than 60%.  What could it be. 

I then looked at PurpleAir thinking it might be dust, but even then the PM2.5 numbers didn't seem very impressive.  

I kept digging, soliciting the input of some meteorological friends.  Eventually, with some help of specialized observing sites, satellite imagery, and weather cams, it became clear that it was blowing dust originating from the exposed Great Salt Lake bed east of Antelope Island.  

A quick look at the evidence.  The most damning was a video of web cam images from the MesoWest web cam at Syracuse near the eastern end of the Antelope Island Causeway.  The view toward the southwest and Antelope Island clearly showed lofting dust in the northerly flow. 

Dust is sometimes hard to see in visible satellite imagery, but an increasing sun angle clearly showed dust pouring off the Farmington Bay area southward into the Salt Lake Valley with a well-defined plume over the central valley.  If you look carefully, you can see evidence of the plume over Utah Lake too.  

My colleagues in the Department of Atmospheric Sciences operate a study site on the Farmington Bay playa abut 7 km south of the causeway entrance.  It might be a bit upstream and east of the biggest dust emissions sources, but it has clearly shown some significant spikes in PM2.5 concentrations.  

I took a look at the PurpleAir data, however, and it didn't show much.  This was a bit of a headscratcher for me. The image below was grabbed at 12:06 PM and for the most part, it looks like good air quality. That was what I observed most of the morning.

However, the University of Utah and DAQ sensors told a different story.  The data below is from a bit before noon and those sensors showed areas with moderate air quality due to elevated PM2.5. At just before noon, the highest values were around 24 ug/m3 near and just north of Murray.  

I'm a fan of Purple Air, but there are sometimes absolute errors in their estimates and this seems to be such a case.  

Overall, this is a remarkable event.  I cannot recall such a strong, well defined, and long-lived dust emission event from the exposed lake bed of the Great Salt Lake in the month of January.  It took me a while after seeing the plume to convince myself it was happening, but it's hard to deny at this point.  It raises a lot of questions about dust emissions processes on the playa during winter.  I don't have a sufficient background in soil physics to speculate about what might be happening.  

Snowbird Magic

In the previous post (Real Winter), I commented that the storm for Friday Night and Saturday was "a crap shoot situation given the limited moisture" and that "much will depend on instability, lake influences, and, for Little Cottonwood Canyon which might have the best chance of something, maybe some Alta magic."

In hindsight, I really didn't have any idea how complicated and productive the storm was going to be and that it was really "Snowbird Magic" that we were going to get.  

What Actually Happened

Automated data from Alta-Collins showed that at upper-elevations in Collins Gulch (9962 ft), about 11 inches fell with only 0.5" of water, yielding a 22:1 snow to liquid ratio or 4.5% water content. In other words, very low density snow, even if the use of gauge water equivalent measurements, which often don't catch all the snowfall, might result in a low estimate of water content.  However, remarkable contrasts of snowfall occurred in Little Cottonwood and Alta was not the big winner.  

As noted in the Utah Avalanche Center report "some areas of Upper Little Cottonwood received 20.5 inches of snow (0.97 inches of water)." That 20.5 inches appears to be from Snowbird, which reported a 48-hour total of 20 inches on their mountain report this morning. I wasn't skiing yesterday, but from what I've heard, snowfall appeared to increase with decreasing elevation at the Little Cottonwood resorts, with perhaps the base of Snowbird serving as the snow capital of Utah for a day.  

How Could This Happen?

I can only put forth some hypotheses that might be worthy of greater investigation.  These are based in part of my analysis of the event and other storms that have done some oddball things like produce more snow on the east bench than in upper Little Cottonwood Canyon. These are sometimes called "upside down storms" because snowfall decreases with elevation (see Classic "Upside Down" Storm), not to be confused with upside down snowfall in which higher density snow sits on top of low density snow. 

First, let's establish the time period that the snow fell.  To do this I'm going to use data from Alta-Collins since I don't have access to observations from the Snowbird Base.  Measurable water-equivalent precipitation was recorded at Alta-Collins in all but two hours from 0600 UTC 18 January (11 PM MST Friday) to 0100 UTC 19 January (6 PM Saturday). The break was from 1800 to 2000 UTC (11 AM to 1 PM Saturday).  Water-equivalent rates were unimpressive throughout this event and less than or equal to 0.07" for the entire period and automated measurements suggested that at no time did snowfall rates exceed 1" an hour.  This doesn't mean that there couldn't have been some short bursts (less than an hour) that were heavy, but they never produced more than an inch increase in interval-board snow at this location.

Snowbird, however, had nearly double the snowfall.  Peak hourly water equivalent and snowfall rates there were certainly higher. 

Large-Scale Environment

The large-scale environment in which that snow fell featured the passage of an upper-level trough in large-scale north-northwesterly flow.  This was a cold system and somewhat moisture starved compared to troughs that approach us from the west or northwest (even at Snowbird where snowfall was heaviest, the low-density nature of the snowfall in this event was certainly an inch or less).  Below is the GFS analysis for 1200 UTC 18 Jan (5 AM MST Saturday) showing the trough just upstream of northern Utah.  

The sounding from the Salt Lake City Airport at 1200 UTC 18 January (5 AM MST Saturday) is below.  This is upstream and not necessarily representative of what was going on in Little Cottonwood at that or other times, but there are some things that capture my attention. First, the atmosphere below 700-mb (roughly 10,000 ft) was consistent with the shallow convective clouds that I observed during the event.  It was well mixed at low levels with the dewpoint depression (the difference between the temperature and dewpoint decreasing with height to an apparent shallow cloud layer between 750 and 700 mb (for whatever reason, the NWS soundings rarely show the same dewpoint and temperature even in cloudy air). I've identified this layer with a purple box.  

That layer also had temperatures between -12 and -18C, or what is called the dendritic growth zone or DGZ.  Those are the temperatures that given suitable relative humidities, favor the development of dendritic snow crystals (the six armed beauties that we have all come to know and love).  Given the low-density snow in this event, I'd expect a lot of snow growth in this layer.  

Above the apparent snow layer, the dewpoint and temperature diverge again with height.  In addition, that layer is weakly stable, which would make it difficult for convective clouds to penetrate to higher altitudes.  

So, this one sounding suggests this was a shallow system and that the layer for dendritic growth was confined to below 700 mb or 10,000 feet.  

Radar Analysis

Finally, we have the radar.  There are a lot of problems using radar to estimate precipitation in a situation like this.  First the beam is partially blocked by the topography, and the influence of that blockage varies depending on location.  Second, this is a very shallow storm, so the storm clouds may only partially fill the beam.  Finally, this was lower density snow, which is notoriously problematic for radar precipitation estimates.  With those caveats in mind, below is the estimated water equivalent precipitation for the 24-hour period ending at 0300 UTC 19 January (8 PM Saturday).  The highest amounts are on the Cottonwood ridge (green squares indicate 0.5 to 0.75" of water) from about Mt. Superior westward. Amounts decrease as one moves eastward and northeastward from Mt. Superior into upper Big Cottonwood Canyon. 

That estimate is roughly consistent with what I observed on radar during the storm which was that echoes tended to be stronger and more frequent not in the highest reaches of Little Cottonwood, but west of Alta. Because of terrain blockage, however, the radar cannot tell us much about the local snowfall variations within the canyon itself, especially near the canyon floor and the base of Snowbird.   

An Initial Hypothesis

My best guess of what was happening in this event is as follows.  It was a shallow storm in flow that was generally from the northwest (on Hidden Peak and Mt. Baldy the flow was WNW or NW for the entire storm period).  The latter is consistent with enhancement in Little Cottonwood, but the shallow nature of the cloud layer and the weakly stable and dry nature of the airmass above crest level may have limited storm penetration into the interior of the central Wasatch and certainly into the lee.  This, or maybe just dumb luck, led to greater precipitation frequency and intensity west of Alta. 

In addition, this was a cold storm.  Temperatures on Hidden Peak and Mt. Baldy were at or below -18C for most of the storm period.  As a result, the dendritic growth zone was below crest level, potentially resulting in greater crystal growth within the canyon volume (i.e., below the ridge tops), leading to greater accumulations not at the highest elevations, but instead at mid elevations.  

There could be other factors at play.  Feel free to share your observations of snowfall or your ideas for mechanisms in the comments.  

Summary

What a storm!  Snowbird Magic 1, Alta Magic 0.

Real Winter

The GFS 500-mb forecast for 1800 UTC 19 January (1100 MST Sunday) is one that should put a smile on the face of anyone who misses "real winter."  An incredibly deep and broad trough, centered near Hudson Bay, covers most of North America.  

As a result, the 5-day average forecast surface temperature anomalies, or the departure from average, centered on that period is negative (or below average) across much of the United States and Canada, with a bull's-eye near the border of North Dakota and Saskatchewan.  

Source: tropicaltidbits.com

It's nice to know that Mother Nature can bring it still from time to time.  

It will be getting cold in Utah, but really we are going to miss out on the coldest of the air thanks to protection from the Continental Divide.  Forecasts from the National Weather Service National Blend of Models for KSLC show maximum temperatures dropping from 39-43F today to the low 30s tomorrow and then possibly into the 27-32F range on Monday.  Minimums eventually get down to the low to mid teens on Monday night.  

Winter, but not brutally so.  For perspective, the average high/low for this time of year is 39/24 (based on 1991-2020 observations).  

There are a couple of short-wave troughs that drop down the back side of the long-wave trough during this period, but they are pretty moisture starved.  Probably the best shot for mountain snow is from late today through tomorrow morning.  The GFS forecast valid 1500 UTC 18 January (0800 MST Saturday) shows the trough right over northern Utah with some precipitation over the mountains.  

This is a crap shoot situation given the limited moisture.  Much will depend on instability, lake influences, and, for Little Cottonwood Canyon which might have the best chance of something, maybe some Alta magic.  There isn't much model agreement for snowfall through noon tomorrow.  The 12Z HRRR is pretty much a nothing burger (.06" water with 1" of snow).  The GFS is a bit more enthused (0.35" water with 6" of snow).  Most of the Utah Snow Ensemble members are between .22 and .47" of water and 3.5-8" of snow.  

You may be able to tell from those numbers that what we get is likely to be of the low-density variety where it isn't trashed by the wind.  Temperatures tomorrow morning are going to be frigid, with our forecast for Mt. Baldy (11,000 ft) of -4F and Alta-Collins (9600 ft) of 2F.  

Keep your boots and toes warm.

Mainly Quiet on the Western Front

The current snowdepth at Alta Collins sits at 83" after peaking at 92" on Saturday.

Some people have asked me about the prospects of a Steenburgh Winter this year, that period from when Alta-Collins first reaches 100 inches to February 10th when the mid day sun angle and day length start to really increase and have an increasingly caustic influence on snow, first on south aspects and eventually as we go deeper into spring on all aspects.  Steenburgh winter is the creme-de-la-creme of backcountry ski conditions with a deep snowpack to enable good coverage across a lot of terrain and low-angle sun for powder preservation.

The potential for the start of Steenburgh winter looks quite low for the next ten days.  Ridging is in firm control currently along the Pacific coast this morning.

That ridge meanders a bit, but remains in place really for the next 10 days or so.  About all we can hope for is a trough to slide down its front side and drop into our area.  Unfortunately, such systems are often fairly moisture starved.  Below is an example from the GFS forecast valid 5 PM MST Sunday. 

The Utah snow ensemble thus has just a couple of weak systems coming through such as the one above, with some variations in intensity and timing between the ensemble members.  There's always the hope that one of those systems gives us a decent dump of low-density dendrites, but 75% of the members are producing less than 6" of snow over the next 10 days.  

Thus, I'll call it mainly quiet on the western front, with the hopes that we at least get a little bit of a refresh with the passage of one of these moisture starved systems.  Sometimes a bit of moisture and instability does the job in Little Cottonwood, so maybe we'll get lucky, but the start of Steenburgh winter looks unlikely during this period.  

A Banner Season in Japan

There's so much bad news on the weather front in the US due to the wildfire catastrophe in SoCal, that I thought I would talk about something more uplifting: The remarkable snow season that they are having in Japan.  

I like to say that if Utah has the Greatest Snow on Earth, but Japan has the Greatest Snow Climate on Earth.  Really, there is nothing like Japan's "Gosetsu Chitai" or heavy snow region near the Sea of Japan.  It is the snowiest, densely populated region on Earth with Sapporo the snowiest city in the world with a population of more than 1 million and Sukayu Onsen in the Hakkoda Mountains in northern Honshu the snowiest inhabited place on Earth.  The numbers below are based on 1981-2010 climate normals.

There are three things that make Japan's Gosetsu Chitai so special for snow.  First, it lies downstream of Eurasia, the world's biggest continent, which results in frequent and prolonged cold-air outbreaks over the Sea of Japan during the East Asian Winter Monsoon.  Second, the Sea of Japan is an enormous body of water, 12 times bigger than Lake Superior, the largest of the North American Great Lakes.  The Tsushima Current that flows through the Korea Strait also ensures a steady supply of warm water along the Japanese coast during the winter.  Third, the sea-effect precipitation systems that form over the Sea of Japan (basically the equivalent of lake-effect snow) run into the formidable topography of Honshu and Hokkaido Islands.  

Utahn's are rightfully proud of the snowfall in Little Cottonwood Canyon, but it is worth comparing the numbers from the Town of Alta to Sukayu Onsen.  Not only is the seasonal snowfall more plentiful at Sukayu Onsen, but after a slow start in October and November, it also comes much faster, especially during the peak of the East Asian Winter Monsoon from December to February.  Basically, climatology is a 3-month pig wallow with an average of more than 140" in each of those months, peaking at 180" in January, more than double the Town of Alta.  

This year the snow in has come fast and furious, with skiasia.com reporting remarkable snow depths last month.  Current snow depths in central Honshu include 169 cm/67" at Shirakawa (478 m/1568 ft elevation), 150 cm/59" at Tsunan (452 m/1483 ft), 163 cm/64" at Oisawa (440 m/1444 ft), and 188 cm/74" at Hijiori (330 m/1083 ft).  All of these sites are south of 38.6ºN and at relatively low elevation.

Source: JMA

Given that the Japanese Meteorological Agency (JMA) does not have any high elevation observing sites in central Honshu, I took a look at the snow report for Hakuba Cortina Ski Resort in the northern Hakuba Valley near the Sea of Japan (location on map below).  It is reporting at current snow depth of 340 cm/134 inches.  Event that is probably an observation from below 1400 m/4593 ft as the resort is on the lower slopes of the Hida Mountains.  

Source: Google Maps

A look at the map above for central Honshu illustrates the remarkable transition in snow climate across Japan.  At low elevations near the coast, snow depths are < 35 cm/14".  These areas are actually quite wet during the East Asian Winter Monsoon, but they experience more precipitation in the form of rain.  Going inland and up in elevation and you get into much deeper snowpacks, even at the lower (< 1600 ft) observing sites operated by JMA.  Go across the mountains to the east side of Honshu and there is no snowpack at lower elevations.  

In northern Honshu and southwest Hokkaido, Sukayu Onsen (890 m/2920 ft) is at 380 cm/150", which is down from their peak at over 400 cm.  Kutchan (176 m/577 ft), which is near the base of the Niseko United Resorts, is at 147 cm/58".  

Source: JMA

Media reports suggested that Kutchan was at record snow depths at times in December.  I suspect that's not the case currently, but cannot confirm this.  Regardless, it is an impressive start to the Japanese snow season.  

About Yesterday's Snow Bomb

Impressive snow totals and snowfall rates occurred yesterday in Little Cottonwood Canyon.  The big winner was Alta.  As readers of this blog are well aware, the Alta Ski Patrol maintains a great snow-study plot in the upper elevations of Collins Gulch.  The hourly measurements from this site are a treasure trove to meteorologists like me who are starved for observations from higher-altitude locations.  The "snow interval" data below is collected by an ultrasonic snow-depth sensor that is mounted on a pole above a white snowboard that is wiped every 12-hours.  It recorded 20" of snow over and 11 hour period prior to being wiped just after 1600 MST.  

Really, the 20" mark was attained in only 9 hours, from 0400 to 1300 MST, yielding a mean snowfall rate of more than 2 inches and hour for that period, with a peak snowfall rate of 5 inches from 0600 to 0700 MST.  Due to roundoff of the measurement, there is a little uncertainty in that estimate, but it's safe to say it was snowing very hard at that time.  A bit more snow fell 1300 MST, but its rate of accumulation was roughly balanced by new-snow settlement, so the final tally remained 20 inches.  

Observations from Mt. Baldy show that the first 6 inches fell as the flow switched from WSW to WNW and the temperature dropped about 4F from 0400 to 0600 MST.  That indicates a frontal passage, but even during this period, there wasn't a strongly organized frontal band, although there were scattered showers and clear evidence of orographic modulation of the precipitation, meaning related to flow interaction with the topography.  Radar imagery at 0425 MST (1125 UTC) when snow was picking up at Alta showed strong modulation of radar echoes by the Oquirrhs and the Wasatch with echoes strongest over and/or windward of those features and strong precipitation shadowing in their lees, including over the western Salt Lake Valley.  So, this was very much an orographic storm right from the beginning. 

During the period of heaviest snowfall from 0600 to 0700 MST, the flow on Mt. Baldy was WNW and radar coverage became more extensive.  Still, echoes were strongest over and windward of the Oquirrhs and Wasatch Range, including the northern and central Wasatch and weakest over the western Salt Lae Valley.  

Finally, by 0848 MST (1548 UTC), the influence of the Oquirrhs and central Wasatch remain apparent, but there is also an elongated band of higher reflectivity extending from the Great Salt Lake to the central Wasatch.  

We have done computer model simulations of similar storm periods in the past in which we were unable to reproduce such a precipitation pattern unless we included both the lake and the topography.  Below is an example from one northwesterly flow storm in which we ran with the best representation of the lake and terrain possible (CTL), removed the lake and the topography (FLAT-NL), removed only the topography (FLAT), included the lake and the Wasatch (WAS), included the lake and the downstream terrain but no upstream terrain (DT), and removed the lake (NL).  There's a lot to digest there, but if there's no topography, the event only produces some light downstream snowshowers.  If there is no lake, only light precipitation occurs over the higher terrain including the Oquirrhs and central Wasatch.  However, when you run with them both (CTL), you get a solid storm.  Thus, both lake- and terrain-driven processes contribute. 

Source: Alcott and Steenburgh (2013)

I suspect this may have been the case for this later stage of the storm yesterday, although that's just a hypothesis at this point.  Overall though, I see yesterdays storm as one that was strongly driven by flow interaction with topography, with perhaps some lake influences thrown in later in the event.  

A few more thoughts

Yesterday's storm was impressive for snowfall rate as measured by depth, but less of an outlier from a water-equivalent perspective.  The 20" of snow that fell had a water content around 5%.  During the period when 5" fell, only 0.15" of water equivalent was observed.  That would be around 3% (although that estimate may be a little low due to gauge undercatch of snowfall).  Peak 1-h water equivalent rates were around 0.17".  That's not bad, but it's also not exceptional.  If you are wondering, the highest 1-h water equivalent was 0.17".  That's not bad, but it's also not exceptional.  The record hourly water equivalent snowfall rate at Alta-Collins is 0.54", which occurred from 0300 to 0400 MST 5 Jan 2008 in southwesterly flow accompanying a "warm and juicy" atmospheric river event just ahead of an approaching trough.  

I share these observations to highlight to different ways that one might measure and evaluate extreme snow rates.  One is based on snowfall amount.  The other is based on water equivalent amount.  Yesterday's snowfall extreme occurred due to the high snow-to-liquid ratios (i.e., low water content).  From a water perspective, it all that impressive.  Storms that produce high water equivalent rates are often warmer, with lower snow-to-liquid ratios, yielding lower snowfall amount rates.  For these storms, my eyebrows pick up when we start approaching 0.3" per hour.  

Thus, much depends on the metric that you use, although none of these scientific semantics take away from what I hear was an outstanding day of skiing. 

Yes, 2024 Was Warm

Final numbers will become available in a few days, but it is likely that 2024 will be the warmest year on record globally.  I'm not sure if the difference from 2023 will be statistically significant, but that doesn't really change the story of long-term warming.  

With an average temperature of 57.4F, it was also the warmest year on record in the Salt Lake City area based on observations collected by the National Weather Service, and by a pretty wide margin.

Source: https://xmacis.rcc-acis.org/

If fact, it beat the previous record holder, 2012, by 0.8F.  Given the inevitable grousing about the representativeness of the airport site, I'll also add that this was also the warmest year on record at the Bountiful Bench site, which has continuous records back to 1975.

That site observed an average temperature of 55.0F, topping the previous record holder, 2012, by 0.6F.  

Precipitation for the year at the airport was 14.78" which was just a skiff below normal (15.52").  Snowfall for the year was 26.2" which was about half of average (51.9").  I have not had a chance to carefully break that down to see if that was due to dry cool months or a greater fraction of cool-month precipitation falling as rain, but a quick look at the graphs suggests the latter dominated.  

As an anecdote, we have now made it roughly through my 2024/25 "snow blowing season", that period during which I normally blow out my south-facing driveway after storms since the sun is too low to melt it out in a short period of time.  I haven't run the snow blower once.  It's sitting in the garage collecting dust.  Nothing that has fallen on our driveway or sidewalk has survived for more than a few hours.