Wasatch Weather Weenies

The gap between the snowpack haves and have nots in the Wasatch Range right now is staggering.  There's essentially little to no snow below 7500 feet and on south aspects.  On the other hand, there is a very stout 30+ inches on north aspects at and above 9500 feet in upper Little Cottonwood Canyon.   Collins Gulch is the one percenter of the Wasatch by snow depth.  Alta-Collins has 31" on the snow stake.  On the other hand, look across the canyon and there's little to no snow left on the south facing slopes.   Today Alta had Collins, Sugarloaf, Sunnyside, and Supreme spinning.  Cover on the main runs is pretty good.  Off piste coverage is pretty good in some areas too (although not so good in others).  Contrast this with other Utah ski resorts that are either closed or spinning a couple of short lifts.   I see this season as a harbinger of things to come, with the gap between the snow haves and have nots growing during the...

No.  Last night's 0600 UTC GFS below.  Nothing.  Granted its one model and only for 7 days into the future, but if you extrapolate this out it won't ever snow again.   Did I mention it's also warm?  

  If all goes well, I will be working this spring on a new edition of my book Secrets of the Greatest Snow on Earth .  Thus, I'm taking requests.  Let me know of any topics you'd like to see covered better or in greater depth.  

Yesterday morning we discussed how a meteorological inversion had developed, but that the air quality was still good to moderate.  There just wasn't time yet for emissions to accumulate within the valley cold pool. However, by late afternoon, it was clear that the air quality was declining, with smog evident over the Salt Lake Valley as the sun set over the Oquirrhs.   This morning, one can still see a veil of smog over the valley.  It seems to be particularly bad over the western valley.   The way that sunlight is scattered by pollution is such that one needs to be cautious assuming that what looks more polluted is more polluted, but that's not the case this morning.  Purple air observations confirm what one infers from the photo above with a clear increase in PM2.5 concentrations across the Salt Lake Valley.  On the east bench, PM2.5 concentrations are at good to moderate levels, whereas in the West Valley, they are higher and in some cases in t...

Don't be fooled by the lack of snow and sunny skies.  Inversion season is here and this morning a fairly strong one exists over the Salt Lake Valley. The term inversion has different meanings for meteorologists and the public.  Meteorologists consider an inversion to be a situation in which instead of temperature decreasing with height, it increases.  We have such an inversion in place this morning.  As shown in the sounding below, the temperature at the surface this morning at the Salt Lake City airport was -0.30˚C, but as you went up, it climbed to 4.2˚C at 767 mb (about 8000 feet).  That is a meteorological inversion.   Source: NOAA/NWS/SPC To the public, an inversion is a situation with poor air quality, typically occurring the winter.  These events often feature high PM2.5 concentrations and in some cases fog.   However, meteorological inversions and what the public calls an inversion are equivalent.  It is possible to have a ...

 Closing day of touring season at Alta was a beautiful one with a low-angle sun lighting the scene. Conditions offered up a mixture of cream on crud, gunpowder, and groomers as the resort prepares to open for lift-served skiing on Wednesday.  Natural cover in upper Collins Gulch is quite good for mid-to-late November.   It was a pretty interesting day meteorologically if you're into the snow energy balance.  Check out the observations from the top of Mt. Baldy.  Temperatures climbed during the day, reaching almost 31˚F by 2 PM, but dewpoints were quite low.   As a result, the area in the shade of Mt. Baldy was a pretty good icebox.  With clear skies and very very low humidities, conditions were ideal for radiative cooling due to the lack of incoming short-wave and long-wave radiation, as well as sublimational cooling.   Alta should have good lift-served conditions for opening day on Wednesday.  If you are hoping to see more nat...

The weekend approaches with guns blazing early this Thursday morning.  Below is a shot from Deer Valley illustrating the lack of natural snow cover at lower elevations and the ongoing artificial snowmaking efforts. Temperatures, however, climbed overnight at upper elevations and today will not be as favorable as yesterday for snowmaking once the cold pools that remain at lower elevations burn off. Observations within 1 hour of 14:51 UTC (0751 MST) show temperatures near or above 32˚F in mid elevations, but still well below freezing at some lower elevation sites.  For example, it was 15˚F along SR-224 near the base of Park City Mountain Resort, but 31˚F at the top of Jupiter.  In Big Cottonwood Canyon it was 16˚F at the Cardiff Fork parking lot, but 33˚F on Reynolds Peak.  It will help that the airmass is currently extremely dry.  The dewpoint on Mt. Baldy is about -30˚F, and this results in the wet-bulb temperature being much lower than the actual temperature....

The original title for this post was "when will winter return," but it's only November 15th, so it hasn't really started yet.  Better to say "when will winter begin."  This has been one of the more bizarre starts to a ski season that I can remember. Alta is reporting 81" of snow so far this season, based largely or entirely on observations taken at the Alta-Collins site at 9662 feet.  The Alta Coop site in town has reported 58.7".  Long-term records for that site indicate an average of 30.6 inches of snow in October and 62.8 inches of snow in November, so we'll round it to an average of about 45" through November 15.  Clearly we are running above average, which sounds good.   Indeed, there is a very solid 31" of snow at Alta-Collins and we are running above average for snowpack water equivalent at the Snowbird SNOTEL site at 9177 ft.  If you are above 9000 feet on north aspects, there's a pretty healthy snowpack in the central Was...

I've been posting some new GFS-derived forecast guidance products for upper Little Cottonwood Canyon in posts over the past few weeks and just added a link for them to weather.utah.edu.  You can find them in the top navigation bar by clicking on LCC GUIDANCE (NEW).  The old guidance is still available there too, but eventually I'll get rid of it.   The old guidance includes tabular data from the 12-km NAM and the 3-km NAM, but these modeling systems are aging, so I'm not spending any more time on them.  I'm going to start deemphasizing them for the most part.  weather.utah.edu is also horribly old and ancient, but I simply don't have the time to rewrite everything, so we'll keep limping along.   The new LCC Guidance page is pretty basic and includes forecast meteograms of several variables at the top and a window with scrollable tabular output.  Yeah, it's not mobile friendly, but you get what you pay for here at the Wasatch Weather Weenies :...

 The models have advertised a possible riming event today and tonight in the upper elevations of the central Wasatch and it seems to be setting up as advertised. As illustrated by the photo below, taken about 8:15 AM looking south from my office on the University of Utah campus, shallow altostratus clouds are now impinging on the highest peaks of the central Wasatch. The GFS forecast sounding valid 2100 UTC (1400 MST) this afternoon suggests that by this afternoon, the altostratus layer will extend from about 750 mb (8000 ft) to 650 mb (11,775 ft), enveloping much of the upper elevations of the central Wasatch.   Cloud base temperature will be 0˚C and cloud top temperature about -7˚C, so this cloud will largely be "subfreezing."   However, water droplets in clouds do not necessarily freeze if the temperature is below 0˚C.  To freeze, water needs an ice nucleating particle to serve as the nucleus for ice crystal formation.  These particles are typically...

  So, you think you know snow?  Well, Ed LaChapelle certainly new more than you.  Probably the preeminent American avalanche researcher, Ed wasn't fooled by the marketing hype about dry snow.  There's more to skiing than the average water content of freshly fallen snow.   Case in point: Today.  Alta-Collins measured 11" of 13% water content snow.  Average at Alta is 8.4%.  Average at the Central Sierra Snow Lab near Truckee is about 12.5%.  So basically, Sierra Cement.  However, it skied great.  Lots of graupel.  Wonderful body.  Below is a septuagenarian friend of mine getting the goods on lower West Buffler.   Of course I have had better skiing than today, but not in 20" of 4%.  More typically when the snow is stacked right with lower density on top of higher density.  That gives you flotation and bounce and makes for the hero snow we all love.  Body is more important than bone dry. Tha...

If you are into grey, today is your day. Morning dawned with a very November scene.  Valley smog trapped beneath and inversion with cirrostratus clouds aloft.  Radar shows a harbinger of things to come with echoes moving into the western part of the state at 1440 UTC (0742 MST). Its pretty dry at low levels, so I suspect that's virga or light rainfall on the desert floor, but precipitation is coming with rain developing in the Salt Lake Valley today, and snow at upper elevations. A look at the latest (0600 UTC) GFS-derived forecast for Little Cottonwood shows not much has changed from yesterday, although it has gotten a bit wetter and snowier compared to yesterday's run discussed in the prior post.  Winds on Mt. Blady begin to shift beginning around 11 AM today, veering from southerly to westerly through evening.  Temperatures are mild this morning and sitting at 39˚F at the base of Alta, but the wet-bulb temperature is around 30˚F and the GFS wet-bulb zero level for...

We need snow.  Yes, I know I'm being greedy, but despite significant snowfall in October, conditions are deteriorating, as discussed in the previous post.   Fortunately, it looks like we will get something tomorrow as a cold front and upper-level trough move through the area.  It's not a monster storm, but it is reasonably well put together and accompanied by Pacific moisture.   Our GFS-derived forecast for Little Cottonwood below pretty much tells the tale.  The GFS brings the cold front in at around 11 AM tomorrow morning.  It's accompanied by an abrupt wind shift from southerly to westerly, but a more gradual decrease in crest-level temperature and wet-bulb zero levels.  Precipitation occurs mainly with and following the front over approximately a 12-hour period.  GFS water equivalent from just before 11 AM Tuesday to just after 11 PM is about an inch.  Snow to-liquid ratios will be low to start (perhaps 7:1) , but increase in ti...

After being out of town last weekend, I was able to get out for a quick ski dawn ski tour this morning.   I'm really not sure what to make of the past couple of weeks and current state of the snowpack. Alta is reporting 69" of snow so far this season, which is likely an upper mountain measurement taken at the Collins observing site.  The Alta COOP site in town and about 1000 feet lower has recorded 48.5 inches. On the south aspects, most of this snow is gone.  Photo below taken this morning from the lower slopes of the "Collins glacier."  Apologies for the thumb, but it's precarious to take a photo there if you don't have crampons on.  The glacier is down to firn.  There have also been significant loses on slopes with western exposures.   I like to tell my students that all generalizations are wrong .  Saying the ski season is off to a good start is such a generalization.  Much depends on altitude aspect. For early November, we're o...

For those who didn't catch my talk Secrets of the Greatest Snow on Earth for the "U to You" lecture series, check out the recording of the live stream below.   It's hard to give a talk online!  There's no audience feedback so you don't hear laughter (or lack thereof) or see quizzical looks on their faces to tell you to better adapt the material.  One comment on the YouTube site that says "pure blasphemy!" so I must have done something right.   The lecture is based on my book of the same title.  If you are in the Salt Lake City area, King's English has copies available at last check ( https://www.kingsenglish.com/book/9780874219500 ) or you could call Weller Book Works to see if they have a copy.   In Park City, Dolly's Bookstore sometimes has copies.  If not, there's Amazon ( https://www.amazon.com/Secrets-Greatest-Snow-Earth-Mountains/dp/0874219507 ).  

Sorry for the delinquency in posting, but we've been down in the Sonoran Desert visiting our daughter at Arizona State.  Highs in Tempe were near 90˚F each day, but manageable due to the lower angle sun and the short day length.  There's lots of outdoor dining there as well, which is a bonus given the ongoing pandemic.   We spent a day in the Superstition Mountains east of Tempe.  This was my first trip to the area since I was 16.  It's beautiful country.   Although I've been to Tempe many times, we made my first visit to the Desert Botanical Garden, which was simply spectacular even if most of the plants were out of bloom.  It's definitely worth a couple of hours of time to meander the walkways and check out the desert plants. We are in the process of designing a new building for the University of Utah that would house the Departments of Physics and Atmospheric Sciences.  I'm big on secure bike storage, which is sorely lacking on campus...