April Powder Brings June Flowers

It's impossible to know when we will have the season's last powder day, but if today was it, that's OK.  

With perhaps 15-20 cm of new snow, Room of Doom in upper Mineral Fork was ours this morning.  One could feel the stout melt-freeze crust at times, but the skiing was still fun.  

Given our fair snowpack conditions, this storm was desperately needed.  We need more, but every little bit helps.  Some of the moisture from this most recent snow will evaporate into the atmosphere.  Some of it will be used by plants.  Some of it will recharge our soils, which are remarkably dry.  And some of it will enter Big Cottonwood Creek and provide the water we all need for taking showers, flushing toilets, and watering gardens.  Thus, it is not a stretch to say that April powder brings June flowers, at least in this part of Utah.  

The view below from the top of our climb shows the upper reaches of the vast Mill-B South drainage, also known as Lake Blanche Fork.  What you see in white is our summer water supply and one of Salt Lake City's most important water towers.  

Let's give thanks for the snow we have and hope that next season is better.  

Winter Returns (Sort of)

Yesterday we tied a record for April 4 with a maximum temperature of 79˚F at the Salt Lake City International Airport.  Impacts on snow aside, the weather was about as delightful as it could be in early April.  It's a bit of a shame we can't bottle up a day like that and open it up in mid July.  

It was very warm in the mountains as well with Alta setting a new maximum temperature record of 58˚F.  

The heat has done its damage as several SNOTEL sites have seen declines in snowpack snow water equivalent, despite their relatively protected locations, indicating that the snowpack has ripened and begun to decline to melt.  Parley's Summit SNOTEL, which is on a north aspect, dropped from 15 inches on April 1st to 12.2 inches last night.  

Source: NRCS

Even upper-elevation Brighton saw a decrease in snow water equivalent.  This site is a bit sunnier than most SNOTELs, but this is a substantial drop for early April.  

That all ends after today, at least temporarily.  A strong cold front will pass through northern Utah later today.  The latest HRRR forecast has the cold front arriving in the Salt Lake valley around 0000 UTC (6 PM MDT) this afternoon.  Expect a breezy afternoon ahead of the front as well.  

I suspect it will be an exciting period with and following frontal passage due to the strong winds and the instability that accompanies and trails the front, which could lead to some thunderstorms.  

Overall, the system is one that has an upper-level low that is tightly wound and moisture is limited primarily to northern Utah.  Precipitation will likely be greatest in the northern Wasatch.  Our downscaled GFS snowfall product shows absolutely nothing south of the Provo-area mountains, 4-8 inches in Cottonwoods, and the heaviest snowfall in the northern Wasatch and Bear-River Ranges. 

Most members of the downscaled SREF for Alta lie between 4 and 12 inches. The large range partially reflects sensitivity to the track and structure of the close low.  A few have a skunking, but there are a couple that go for bigger amounts.  

I think the most likely amounts are 4-8" for Alta-Collins, but it could be less or more depending on the gory details.  Truth be told, these are the situations where I just plan on waking up in the morning and seeing what happened. 

After this storm, it will likely be dry with a return of spring through next weekend.  There are a couple of brush-by systems that maybe could bring a few showers, but that's about it.  

Alta and Snowbird Skiers Need to Up Their Game

 In recent years, a wiggle (or snake) has appeared at Alta or Snowbird.  

Photo of the Day | 4.3.2021

The wiggle has transformed Ballroom this spring. Have you wiggled this spring?

📸: @rockomenzyk https://t.co/MRJ6yOl9lG pic.twitter.com/FXgzM89usV

— Alta Ski Area (@AltaSkiArea) April 3, 2021

Some get excited about these slope enhancements, but not me.  

During my sabbatical in Innsbruck, I encountered figl skiing, or figln (see Tirolean Figln).  Figln becomes a thing in April at Nordkette ski resort above Innsbruck in April and involves the use of short skis to go downhill, using the tails to control speed.  As I understand it, the history of figln derives from mountaineering as the light, short skis could be used to quickly descend remarkably steep slopes back in the day.  The Nordkette has ideal conditions for Figln as it is steep (especially off the upper Hafelekar Tram) and south facing.  

Here's a video demo.  Start at about 1:12 for the Hafelekar footage and slot-canyon experience at about 2:10.  

Bottom line: Alta and Snowbird skiers need to up their game. 

April Fools Snowpack Update

April 1st is near the time of peak snowpack for many Utah SNOTEL stations.  On average, lower elevations peak earlier than this, whereas upper elevations peak later, but April 1 is traditionally a good date for getting an idea of how fat the snowpack is for the spring runoff.

This year's April 1 snowpack is no joke, with the vast majority of stations below median (note the plots below are technically through March 31).

To show this, below is a plot of the percentile snow water equivalent.  This percentile represents that percentage of previous seasons in the period of record with a lower snowpack snow water equivalent (SWE) than current.  A value of 25 means that 25% of the seasons have less (SWE), whereas 75% have more.  The higher the percentile, fatter the snowpack compared to past seasons. 

Many Utah SNOTEL stations are at or below 37.5, some well below.  A handful are near or above 50.  This includes sites in the northeast Uintas, and scattered about in central and northern Utah.  

NRCS

For sites in the central Wasatch, Mill D North is at 44, Snowbird 32, Brighton 18, and Thaynes Canyon on the Park City side, 13.  This hasn't been a great snow season, but it has been especially bad on the Park City side of the central Wasatch, which is a bit of a double whammy since that area climatologically gets less snow in the first place.  

A look at the seasonal snowpack trace shows there is currently 16.3 inches of water equivalent at Thaynes Canyon (elevation 9247 feet).  Only 12% (4) of the 33 seasons in the period of record were worse than this on this date.  Median for 31 March is 21.5 inches, so we sit about 25% lower in SWE compared to a winter in the middle of the distribution.  

NRCS

The natural advantages of Little Cottonwood become apparent when you look at Snowbird (9177 feet), which is at a comparable elevation, but the SWE is nearly double that at Thanes Canyon (29.7 inches).  However, by Little Cottonwood Standards, this is still only good for the 32nd percentile.  Basically, 2/3 of the seasons had a fatter snowpack then we have presently.  

NRCS

What can I say.  It hasn't been a great snow season.  Maybe next season will be better.  There's always hope for the future. 

Dirty Corn

Yesterday's cold-frontal passage probably brought more dust to the central Wasatch than snow.  Frontal passage at the University of Utah featured the usual wind shift and temperature drop, but also a spike in PM2.5 associated with blowing dust.

Peak concentrations at the U reached almost 15 ug/m3, which equates to a moderate air quality level.  

Cameras at the University of Utah caught the post-frontal dust and gravity-current-like nose of the cold front passing through the Salt Lake Valley.

Post-frontal dust and gravity-current-like nose of cold front that just passed through Salt Lake shows up well in this video.

Watch carefully for the moonset too. pic.twitter.com/qr27dhAiu8

— Jim Steenburgh (@ProfessorPowder) March 29, 2021

And check out the terrain induced flows over western Nevada with dust from the Carson Sink providing a great tracer. 

Large dust storm pushing south through the Nevada desert towards the California border. @NWSReno #NVwx pic.twitter.com/aYdhVMydMi

— US StormWatch (@GreatWinter2017) March 29, 2021

So this event provides a new definition of "dust on crust" and puts a nail in the coffin of winter.  We might get into a good spring storm cycle eventually, but temperatures look to be rising this week and spring fever will be infecting far more people than the coronavirus.  The best options for skiing will be working the aspects for "dirty corn."  

The Transition to Spring

I hope you enjoyed the cooler and somewhat snowier weather over the past week as it appears that things will be changing moving forward.  

Over the past week, I finally got out and got some ski touring in and enjoyed skiing powder again.  Yesterday provided a weather potpourri of low visibility and occasional snow and graupel showers with the cloud over acting to preserve the powder through the day (thankfully).  

The graupel was generally light, but during one heavier period, we were treated to graupelfalls over some of the cliffs where we were touring.  

The snow over the past week on upper-elevation north-facing aspects survived quite well thanks to a progression of cold troughs.  Forecasts for the next week are not as optimistic.  The GFS and other models forecast a strong frontal passage Monday, but without a lot of moisture.  

Thus, it will be cold, but likely a dust on crust event.  The remainder of the work week looks dry, with temperatures moderating during the week.  

The NAEFS plume shows the vast majority of members generating 4 inches or less of snow for Alta with the Monday frontal passage.  There are, however, 3 that go for 10 inches or more, so I guess there's always hope. 

I'm sure we will see mountain snow at some point in April, but this coming week will probably mark a transition point in the 20/21 ski season.