A Blisteringly Hot Stretch for March

Although we didn't hit the 80˚F US unit psych point for maximum temperatures, the last three days have been blisteringly hot.  

Salt Lake City area weather records begin in 1875 based on observations collected in downtown Salt Lake City prior to the 1920s and the Salt Lake City Airport thereafter.  In terms of the mean maximum temperature and average temperature, the last 3 days were the warmest on record during 1-27 March.  

Source: http://xmacis.rcc-acis.org/

Source: http://xmacis.rcc-acis.org/

For minimum temperature the mean was the 2nd warmest on record, behind 1907.  1910 also had a warm 3-day period, although the observations in those years were collected in downtown Salt Lake City, not at the airport.  

Source: http://xmacis.rcc-acis.org/

Additionally, thin high clouds meant net longwave cooling was limited.  I didn't bother skiing this weekend, but the Utah Avalanche Center notes this morning that most mountain locations have remained above freezing now for nearly 4 days.  There are many reports of large wet avalanches, including naturals reported by snow safety teams overnight.  Simply incredible.  Below is one example.

Source: Utah Avalanche Center

Not surprisingly, there has been significant snowpack loss in many areas.  Below is the mean water equivalent of snowpack at SNOTEL sites in the Jordan basin.  It has dropped from a peak of 14.2 inches on March 24 to 12.4 inches today.  

Source: NRCS

Even the Snowbird SNOTEL has declined about 0.8".  I'm not sure if this is the result of sublimation, or an indication that the snowpack there has ripened and is already losing mass to melt, but it's never a good sign when upper-elevation SNOTEL sites are losing snow in late March.  

Source: NRCS

Nevertheless, the storm track returns this week.  The pattern looks more typical of late March and early April than the late May/early June like weather we have had the past few days. 

Is Eighty Doable?

There's lots of chatter right now about the warmth this weekend and the potential of a maximum temperature at the airport of 80ºF on Saturday or Sunday.  That would be the earliest 80˚F on record.  The current first 80˚F was observed on March 31, 2012 [Note from Jim: This was corrected from 2021, which was an error].  After April 5, all days through the summer have record maxima at or above 80˚F.  

To do this, we'll take a look at forecasts produced by the National Weather Service National Blend of Models, or NBM.  The NBM is a system that takes forecasts from many modeling systems, puts them together in a big ensemble, and then applies statistical techniques to yield forecasts, including those of maximum and minimum temperature at locations like the Salt Lake City international airport.

The NBM forecast for the Salt Lake City airport is below.  The maximum (red) and minimum (blue) temperature forecasts for the next 10-11 days are presented in the left hand panel using box-and-whisker plots to summarize the forecasts derived from all the input model forecasts.  

Source: https://hwp-viz.gsd.esrl.noaa.gov/wave1d/?col=2&hgt=1&obs=true&fontsize=1&location=KSLC

For each day, the red box denotes the middle 50% of forecasts produced by the models. This is known as the interquartile range. For Saturday, the interquartile range of maximum temperature forecasts covers 77 to 81˚F.  A horizontal line in the box denotes the median forecast, which is right in the middle of all of the forecasts. For Saturday, the median is 79˚F.  The "whiskers", which are the thin vertical lines, denote lower and upper "extremes."  Only 10% of the forecasts are at or below the lower end of the bottom whisker and only 10% of the forecasts are at or above the upper end of the top whisker.  In this case the lower "extreme" is 76˚F and the upper extreme is 82˚F.  

Roughly half of the model-derived forecasts call for a maximum temperature at or above about 80˚F.  The other half are at or below 80˚F.  It could be that the actual median is a bit above or below 80˚F.  I can't determine this without access to more than this graph, but for the purposes of this blog post, we'll call that good enough.  

Sunday is also potentially an 80ish degree day.  The interquartile range on Sunday is 78 to 84˚F, with the median also sitting very near 80˚F.  

Source: https://hwp-viz.gsd.esrl.noaa.gov/wave1d/?col=2&hgt=1&obs=true&fontsize=1&location=KSLC

Assuming these NBM forecasts are reliable and unbiased, 80˚F would be the "over/under" for maximum on Saturday and Sunday.  

Ultimately, time will tell.  Both days look nice, although the southerly winds will be picking up on Sunday and that will raise the prospects for blowing dust.  

Another Last Day of Winter

Steenburgh winter never happened this year.  Meteorological winter ended on March 1st.  Astronomical winter ended on March 20th.  

However, today might have been the last day of winter at ski resorts in upper Little Cottonwood.  At least that's what we called it at Snowbird this morning where the life expectancy of chalky groomers is now no longer than a day.  For groomer, Regulator Johnson was really outstanding this morning.  

Temperatures today are climbing and they will continue to do so, with the usual nighttime interruption, through the weekend.  We will se snow again in the future, but the transformation this week is going to be dramatic.  Check out the National Weather Service Forecast for the Salt Lake City International Airport.  81˚F on Saturday!  81˚F!  

Source: NWS.  Downloaded 1:10PM 23 March 2022

That's insane.  The earliest 80 on record was recorded on March 31, and that was in 2012.  

We'll see what we hit on Saturday, but things will be changing and changing fast.  Don't forget to sunblock. 

Astronomical Spring Begins

Astronomical spring began yesterday, so it is worth taking a moment to examine the snowpack situation across the west.

As you may recall, we entered March with the western snowpack generally at or below median in most drainage basins.  

Source: NRCS

For the most part, things haven't changed much over the past 3 weeks.  Some basins have climbed a bit closer to median (e.g., southern and eastern Utah, Colorado), whereas others have lost a bit (e.g., Washington, Sierra Nevada).  

Source: NRCS

Northern Utah basins now sit at 80-85% of median, compared to 71–80% on 1 March.  That's good, but still concerning.  For the Jordan, which includes the central Wasatch, we now sit at 13.8" of average water equivalent at SNOTEL stations compared to a median of 16.9". 

Source: NRCS

However, the situation is arguably worse than that for two reasons.  First, the green line above is the median daily water equivalent.  Because of differences in the timing of peak snowpack from year to year, it underestimates the median maximum water equivalent, which is the green x on the graph above and sits at 20".  The median date of that maiximum is April 8, so we have a lot of ground to make up with 2 weeks to go.  

This week will not help.  The dice are stacked for little to no precipitation through the 27th.  

It will also be warm.  Our GFS-derived forecasts show temperatures on Mt. Baldy about Alta (11,000') climbing through the week and peaking at 37˚F Saturday afternoon.  

So basically, this will be a warm, dry week with substantial losses of snowpack at low elevations and on sunny aspects.  

I'm hoping the trails dry out for valley mountain biking.  

Saharan Dust

A major multi-day Saharan dust event has ravaged the snowpack in the Alps and the air quality across parts of Europe this week.

Below is a composite MODIS image from Tuesday (15 March) showing a cyclone off the coast of Morocco with extensive dust streaming northward from the Sahara across Spain and France.  

If you think snirt (snow+dirt) is bad around here, check out the video below from Spain's Sierra Nevada.  

Sierra Nevada pic.twitter.com/ukUhZkYud6

— Esteban Villarejo (@Villarejo) March 15, 2022

Dust coverage was extensive.  Here's a web cam from this afternoon at Mölltaler Glacier in the eastern Alps of Austria. 

Saharan dust events are not uncommon in parts of Europe, but this one looks especially severe.  In addition to making for a less-than-ideal ski surface, such dust does accelerate the spring melt by increasing the amount of solar radiation absorbed by the snowpack.  On the other hand, the dust also provide nutrients for ecosystems.  

Often such events are called sand storms, but sand particles are larger than dust particles and typically do not travel such long distances.  Thus, I prefer to call them dust storms.  Regardless of the name, they are not good for skiing.  

Barrieto Avalanche

I don't have much to say today.  Some periods of mountain snow beginning this evening through tomorrow.  GFS says 3" or so for Alta through Wednesday and most members of the downscaled SREF are under 2.5", although 6 of the 26 members go for 3-6.5".  

Nothing to get excited about.  

Footage of yesterday's skier-triggered avalanche on a run known as Barrieto in Mineral Fork is below (per reports, the skier was performing a ski cut and was able to avoid harm).  I'm not sure who to credit for the video or the photo below, but click here for the report on the Utah Avalanche Center site  I think it is the largest skier-triggered avalanche I've seen a video of from the Wasatch Backcountry.

Below you can see the full path with the crown near the Mineral Fork – Lake Blanche Fork ridgeline to the toe in the bottom of Mineral Fork.  

Debris covers a good portion of the Jeep/ATV road that switchbacks up through the base of the slide path and where there are often skin tracks heading up to Room of Doom.  A long time ago, a young man who was renting an apartment from our neighbor was killed by a natural avalanche in this general area while he was snowshoeing.  It was a tragic loss and I'm sure he had no idea what he was getting into on that stormy day.  I didn't really know him at all, but I think of him whenever I am skiing or driving by Mineral Fork.  

Climatology suggests that this time of year we are usually dealing with new-snow instabilities, wind slabs, issues related to warmth and solar heating, etc.  However, thanks to our long drought, we have a persistent weak layer that is not to be trifled with. 

Closing Day

Today is the last day of Nordic operations at Mountain Dell.  Although a foot injury has shut down my skating (and touring) adventures since the end of January, I felt well enough to do a short 5 K skate today.  It was great to get out on the skinny sticks again!  Additionally, given the ephemeral nature of the snowpack at Mountain Dell, coverage was quite good for the last day of the season thanks to recent storms.

I thank The Utah Nordic Alliance (TUNA) and the groomers for maintaining this great community resource again this year.  We are so fortunate to have cross-country skiing a short drive from Salt Lake City.  Efforts to farm snow this year really paid off and enabled nearly continuous operations since mid December despite another poor snow season.  The closure today reflects contractural obligations with Salt Lake City and the golf course rather than lack of snow.   It's a shame they can't try for one more weekend.  

Addendum @ 8:50 AM Monday March 14:

Although on Thursday the MD groomers report said they were contractually obligated to close on Sunday, March 13, it appears a stay of execution has been granted and there's a grooming report from this morning saying they're open today (Monday) with a fresh groom.  Hooray!  Would be great if they can go for another week.  

Professor Piste

For groomers and skiing fast, days don't come much better than this morning.  We have some friends in town from back east and I'm fairly certain it was the best day of skiing they've ever had.  Other than a bit of a north wind, the snow and weather conditions were as good as you can get without powder.  

Over the past few weeks, I've been Professor Piste instead of Professor Powder due to a foot and ankle injury.  Touring and Nordic skiing have been verboten, and even walking has been difficult.  I've been able to do two a little Alpine skiing on groomers though, and that has helped me keep my sanity.  It has been a stingy injury, but it improved quite a bit over the past week.  Keeping my fingers crossed that the trend is my friend.  If you see someone struggling through a 5 K skate sometime in the next week or two, that would be me.

If you were up in Little Cottonwood, you may have noticed a great Asperitas cloud display.  I took the photo below toward Snowbird and the American Fork Twin at around 1 PM.  

I call them "dementor" clouds as they remind me a bit of the dementors in Harry Potter.  They are typically rough and wavy.  They can be thick and dark, but these were thin and wispy.  Spectacular!

Mother Nature Finally Delivers!

Mother Nature has finally delivered a proper deep-powder day to the central Wasatch.  As of 9 am this morning, total snowfall at the Alta Collins since yesterday morning was 19 inches.  As storms go, that's about as Goldilocks as it gets.  In other words, not too big, not too small, but just right. 

Additionally, this was a great storm pretty much for everyone.  Some additional reports from earlier this morning include 13 inches at Spruces (6 AM), 9.5 inches at Canyons Village/Park City (8800 ft, 9.5"), and 13 inches at Summit Park (7 AM).  For the central Wasatch, Deer Valley reported the lowest total this morning (8"), so everyone is close to my minimum threshold for a deep-powder day (10").  It's possible that the additional snow pushed everyone to that level.  

For the Nordic skiers, I suspect the snowpack at Mountain Dell might be as fat as it has been all year.  

Expect periods of snow in the Cottonwoods today due to unstable northwesterly flow.  The GFS time-height section below suggests the passage of a weak trough this evening, which will bring in drier air later tonight.  

That will mark the end of this storm cycle, unless the lake can get going and that's always a crapshoot.  

Our GFS-derived forecast below shows that it will be quite cold tonight and tomorrow, with 11,000 ft temperatures near or below 0˚F.  

Enjoy the cold powder. 

More Snow on the Way

We have a decent setup for snow on the way, one that will extend the Nordic season at Mountain Dell and maybe even provide a proper deep powder day at Alta.

The GFS large-scale forecast of 500-mb geopotential height (black contours), precipitable water (color contours)m and 6-hour accumulated precipitation (color fill) for 0000 UTC 9 March (5 PM MST this afternoon) is below.  It's actually not a hell of a lot different than we've seen quite a bit over the past two months.  There is a ridge off the Pacific coast with a trough dropping down out of Canada.  

However, there are a few favorable wrinkles this time.  First, there is a plume of moisture associated with a decaying atmospheric river remnant that has snuck under the ridge and is extending into the Pacific Northwest ahead of the approaching trough.  Thus, the system is not as moisture starved as many of the recent troughs.  Second, the pattern is shifted a bit farther upstream, so instead of sliding into Colorado, this trough will extend far enough west to give us some action (and cold air).  

The GFS time-height section for Salt Lake City shows this is a 3-part storm.  It begins with the prefrontal stage, which is already bringing a little light snow to the high elevations this morning and will continue to this evening.  I expect accumulations during this period to be light, perhaps adding up to 1-3 inches by 5 PM this afternoon at Alta Collins.  

This evening and tonight, we have a low-level frontal passage, with the front complex in structure.  During this period, snowfall rates will increase.  For example, from 5 PM tonight through 5 AM tomorrow morning, the GFS generates about 0.5 inches of water and 8 inches of snow at Alta Collins.  

After that, we move into an unstable post-frontal period on Wednesday with the flow predominantly west-northwesterly in the current forecast.  The GFS generates an additional .34" of water and 6 inches of snow at Alta Collins from 5 AM to 5 PM tomorrow.  It also keeps things going overnight on Thursday.  

The total tally for the GFS is 1.29" of water and 22.5" of snow for Alta Collins from this morning through Thursday morning.  

Note that this will be a cold storm, with snow levels at the valley floor throughout.  Monitor official forecasts for the Wasatch Front and your commutes.  For the Nordic skiers, it will add to the snowpack at Mountain Dell and Round Valley and help extend the ski season at those locations.  Expect less than Alta of course, but every inch at this stage helps.  You can thank me later.  

Getting back to Alta, the ECMWF is a bit drier than the GFS, as usual, with 0.72 inches of water.  The downscaled SREF is has a pretty tight cluster around 0.7 to 1.2 inches of water and 14-22 inches of snow, although there are a few above and below those numbers.  This is a tighter distribution that we saw from the previous storm. 

Right now, tomorrow (Wednesday) morning looks to be on the cusp of a deep powder day with 6-12 inches at Alta-Collins by 9 AM.  Total snowfall for Alta-Collins of 10-18 inches by Thursday morning.  

Avenues Snow Bomb

There aren't many days when the Avenues get the bragging rights for snowfall, but today is one of them.  

During the day yesterday, a frontal boundary developed over northern Utah, with the band especially strong along the I-80 corridor from the area near Stansbury Island to the Salt Lake City International Airport and the lower avenues.  Below is the radar imagery for 02:42 UTC (7:42 PM MST) illustrating the situation.  

Source: NCAR/RAL

A sounding collected at the airport at just before 0000 UTC (5 PM) showed shallow northerly flow associated with the front below about 725 mb, with southeasterly flow aloft.  

Source: SPC

Additionally, the sounding was very moist at low levels and near what meteorologists call moist neutral, meaning that the stability was weak to non-existent or even weakly unstable for moist flows (i.e., with a relative humidity of 100%).  Thunder was even reported in some parts of the Salt Lake Valley that afternoon.  

At about 6:30 we were getting takeout on 400 South where it was starting to rain hard with a little bit of melting snow at times.  We drove through the melting layer when we returned to our home at about 5000 ft elevation.  From that point on it was game on for the next 3.5 hours with heavy snowfall.  I took the photo below at 7:47 PM when perhaps two inches had accumulated.  

By 9:30 several inches had fallen.  A plow had finally gone up Virginia to 11th Avenue and I opted to drive my son and his girlfriend home near the U of U campus.  The drive was sporting, although the snow was deep enough that on the unplowed roads in the upper avenues braking wasn't a problem.  Just take your foot off the gas and let the car auger in.  

I got home at about 10 and made an unofficial measurement of about 10 inches on our front lawn.

We have an automated snow-depth sensor at the mouth of Red Butte Canyon on the University of Utah campus.  Snow depth increased 4.3" from 9–10 PM MST and 7.7" from 8-10 PM.  

Source: MesoWest

Those are impressive snowfall rates!

Meanwhile, in the central Wasatch, the Utah Avalanche Center reported 6.5" along the Park City Ridgeline, 8" in Big Cottonwood, and 6" in Little Cottonwood overnight.  What can I say?  Mother Nature isn't giving much love to our mountains this year.  

Snowfall totals through 10 AM this morning reported to the National Weather Service maxed at 14" in Salt Lake City (5088 ft) and the upper avenues (5000 ft).  I'm not sure where that Salt Lake City site is.  It could be in the avenues or the east bench above Foothill, but I'm going to say that Avenues were the big winners in this one.  Take that Alta!  Given that my ankle is still not allowing me to ski powder, the storm was greatly appreciated.

Patience Is a Virtue

Most skiers and snowboarders are salivating right now at the prospects of a deep-powder day.  Snow is in the forecast and excitement is running high.  

However, this is a classic patience is a virtue pattern.  Today's early action is scattered, with accumulations hit and miss and primarily consisting of high-density snow at upper elevations.  Most of the precipitation is being produced by surface heating.  You may even have heard some thunder.  

The precipitation tonight is also scattered.  If you're lucky, your favorite ski area might get hit by something that is intense and moves slowly, but it might also get little.  

A look the GFS shows a more organized frontal system developing Saturday night, pivoting over northern Utah, and then rotating through the area on Sunday.  Below is the GFS forecast for 1500 UTC 6 March (8 AM Sunday) with a moist front producing a band of organized precipitation extending from southwest to northeast across Salt Lake City and the Wasatch Range.  

A look at the GFS-derived forecast for Little Cottonwood shows only 0.5" of water equivalent and about 7" of higher-density snow through 5 PM Saturday.  

That's better than nothing, but things really pick up late Saturday and Saturday night.  and then continue through Sunday.  From 5 PM Saturday through 5 PM Sunday, the GFS generates another 0.8" of water and 14" of lower density snow for Alta.  

Most members of the SREF are similarly most excited for late Saturday and Saturday night (i.e., around or after 06/00Z, which is 5 PM MST Saturday).  There's a great deal of spread, with 3 members producing less than 10" of snow total for the period and 5 more than 30, but most are in the 12 to 22 inch range for Alta, which would be great.  

The bottom line is that there won't be much snow today.  Although not out of the realm of possibility that things light up a bit tonight or early tomorrow, chances are it won't be until tomorrow afternoon or evening that things really start to get going.  If it comes in early, late Saturday laps might be fun tomorrow at Alta.  If not, deep powder will need to wait until Sunday.  In times like these, I tend to monitor the Alta-Collins interval stake religiously and adjust plans based on if and when Mother Nature brings the goods.  

Snow Will Return, but How Much?

Don't be fooled by our current stretch of splendid spring weather.  Periods of snow are coming back to the mountains starting late Friday and continuing through the weekend, although it's a bit of a crap shoot how much the resorts will get.

Basically, we will see a series of three troughs moving across the region.  The GFS forecast below shows the first trough over southern Utah and northern Arizona at 0000 UTC 5 March (5 PM MST Friday), with some scraps of snow showers extending northward through northern Utah and a trailing trough over northern California. 

That trailing trough similarly tracks to our south and at 0000 UTC 6 March (6 PM MST Saturday) it also has some snow showers extending northward through northern Utah.  

As that trough exits, a third trough drops across Utah from the north-northwest, bringing additional snow showers.  

As things stand now, there's no clear consensus amongst the various models concerning the timing and intensity of the storm pieces that may move through northern Utah.  The latest GFS below shows things getting started late Friday, with periods of snow in fits and starts totaling about 1.4 inches of water and 23" of snow through very early Monday morning.  

As is often the case, the euro is drier, generating 0.79" of water equivalent.  

The downscaled NAEFS ensemble has a mean closer to 2" of water and over 30" of snow, with a pretty good amount of spread.  This product has been an overproducer all winter though.  

The NAEFS suggests there's a wide range of possibilities.  Much will depend on the tracks of the troughs and other storm details that are difficult to reliably predict at these time scales.  It is worth noting, however, that since early January, the biggest 3-day accumulation at Alta is only 13 inches.  Thus, even the low end forecasts are looking pretty good by recent standards.