A Great Storm in Utah

A Great Storm in Utah is something we are all waiting for but is also an essay that John Muir wrote while visiting the Salt Lake Valley in 1877.  The essay was sent to me by a former student, Matt Jeglum, who knows how much I enjoy this sort of weather and nostalgia, and contained within Muir's book Wilderness Essays.

In the essay, Muir describes a storm on May 19, 1877.  The date is very close to the peak time of year for strong cold fronts in northern Utah and he was impressed.

"Utah has just been blessed with one of the grandest storms I have ever beheld this side of the Sierra.  The mountains are laden with frsh snow; wild streams are swelling and booming adown the cañons, and out in the valley of the Jordan a thousand rain-pools are gleaming in the sun." 

But before describing the storm, he provides some great observations of Utah snow and weather.  First, he suggests a late start to the snow season with snow piling up in the spring.

"In all the upper cañons of the mountains the snow is now from five to ten feet dep or more, and most of it has fallen since March." 

He also describes frequent afternoon thunderstorms, as we often see in the spring:

"Almost every day during the last three weeks small local storms have been falling on the Wahsatch and Oquirrh Mountains, while the Jordan Valley remained dry and sun-filled."

Then there's the storm, which sounds like it packed a wallop.  Read this passage out loud, pausing at each comma, for great effect.

"But on the afternoon of Thursday, the 17th ultimo, wind, rain, and snow filled the whole basin, driving wildly over valley and plain from range to range, bestowing their benefactions in most cordial and harmonious storm measures.  The oldest Saints say they have never witnessed a more violet storm of this kind since the first settlement of Zion, and while the gale from the northwest, with which the storm began, was rocking their adobe walls, uprooting trees and darkening the streets with billows of dust and sand, some of them seemeed inclined to guess that the terrible phenomenon was one of the signs of the times of which their preachers are so constantly reminding them, the beginning of the outpouring of the treasured wrath of the Lord upon the Gentiles for the killing of Joseph Smith."

Muir's essay describes blowing dust and sand (I suspect primarily the former).  In the passage below, I suspect he is describing pre-frontal virga (precipitation evaporating before it reaches the valley floor) and dust in the pre-frontal southerly flow.

"Clouds, with peculiarly restless and self-conscious gestures, were marshaling themselves along themountain-tops and sending out long, overlapping wings across the valley; and even where no cloud was visible, an obscuring film absorbed the sunlight." 

Muir loses me meteorologically for a bit in the passage below, but perhaps he is describing pre-frontal snow falling over the Wasatch and Oquirrhs while the Salt Lake Valley is still dry and perhaps hasn't mixed out yet to produce strong winds on the valley floor. 

"Some of the denser clouds came down, crowning and wreathing the highest peaks and dropping long gray fringes whose smooth linear structure showed that snow was beginning to fall.  Of these partial storms there were soon ten or twelve, arranged in two rows, while the main Jordan Valley between them lay as yet in profound calm." 

But then, the great front arrives, and it arrives at what is typically the optimal time for a strong spring cold-frontal passage with what I suspect is a dark shelf cloud and strong, dust-laden post-frontal winds.

"At 4:30 P.M. a dark brownish cloud appeared close down on the plain towards the lake, extending from the northern extremity of the Oquirrh Range in a northeasterly direction as far as the eye could reach. Its peculiar color and structure excited our attention without enabling us to decide certainly as to its character, but we were not left long in doubt, for in a few minutes it came sweeping over the valley in a wild uproar, a torrent of wind thick with sand and dust, advancing with a most majestic front, rolling and overcombing like a gigantic sea-wave."  

The essay continues to describe important meteorological details.  In particular, the rain followed the dark cloud and dust by an hour.  This indicates that the front preceded the frontal precipitation band and could have been an outflow boundary initiated by precipitaiton-cooled downdrafts beneath the frontal precipitation band.  Today we can see these details in many spring cold fronts thanks to surface weather observing systems and the National Weather Service radar. 

"The gale portion of the storm lasted over an hour, then down came the blessed rain and the snow all through the night and the next day, the snow and rain alternating and blending in the valley."

The description above also suggests that the precipitation persisted through the night.  Most frontal precipitation bands pass over Utah in a few hours, so perhaps there was a contribution from lake effect or orographic precipitation overnight.  The snow and rain alternating suggests the valley floor was probably in or near the melting layer with snow levels dropping during heavy precipitation periods and rising during lighter precipitation periods.  

Muir, however, did not find the snow in the city attractive or share a view that could be used by the Chamber of Commerce to attract tourists:

"It is long since I have seen snow coming into a city.  The crystal flakes falling in the foul streets was a pitiful sight." 

I include below a couple of photos of the essay describing the great storm.  Enjoy the reading. 

All Hail Lindsey Vonn!

Source: AP Photo/Luciano Bisi

It's easy to become cynical about sports these days, but there are some athletes who deliver performances that are truly uplifting and inspiring.  

Lindey Vonn winning the World Cup in St. Moritz on Friday is one of the most remarkable and astonishing performances I can think of in skiing if not all of sports.  

Before Friday, the oldest woman to ever win a World Cup race was Federica Brignone at the age of 34.  Brignone herself is a force of nature and one of my favorite skiers as she sends it with such passion (she is currently recovering from a major knee injury and I am hoping will return for the Olympics).  Vonn is 41. 41!  

Most of you know her story.  She won in every discipline on the world cup and fell just short of what was then Ingemar Stenmark's record of 86 world cup winds with 82 when she retired.  She is unquestionably the greatest speed skier of all time.  

She retired in 2019.  A knee replacement and a hell of a lot of hard work later, she is on top of the world, with Stenmark in her sights again (although she won't catch Mikaela Shiffrin), not to mention a shot at Olympic gold in Cortina.  

Simply incredible.  

Whither the Start of Ski Season

Sigh...what a start to December.

First let's have a look at the northwest storm.  Some bit water totals so far.  For the 3-day period ending at 6 AM PST/1200 UTC today (11 December), more than 10" of liquid precipitation equivalent at many sites in the Washington Cascades including 14.2" at Paradise SNOTEL (agreeing well with the expectations from the previous post) and 18.6" at the Lynn Lake SNOTEL between Paradise and Snoqualmie Pass.

Source: https://www.weather.gov/wrh/hazards

Crystal Mountain is reporting this morning that WA-410 is closed between Enumclaw and Greenwater, essentially cutting them off given that WA-410 is also closed over Cayuse and Chinook Passes to the south.  Most of their web cams are down but sadly, even at 6800' at the top of the Green Valley Express where a cam is working, it looks like a net loss from this storm.

Source: https://www.crystalmountainresort.com/the-mountain/mountain-report-and-webcams/webcams

Could be worse.  Below is the Summit West cam from Snoqualmie Pass.

Source: https://www.summitatsnoqualmie.com/webcams

Meanwhile in northern Utah, December continues to be the new October with yesterday's high of 61 at the Salt Lake city International Airport the average high on October 25.  

I keep thinking how fortunate we are that this low-amplitude ridge developed in a way that we stayed relatively mild at low levels.  If there had been a strong cold pool in place over the valley earlier this week, we would probably be much cooler.  If we can't have snow, then we may has well have a mild conditions in the valley.  We were also fortunate to have that storm last Friday Night and a few days of good snowmaking conditions before the warmth returned.  

A look at the ensembles shows a few members flattening out the ridge just enough to bring some precipitation into northern Utah the middle to end of next week.  An example is the ECMWF HRES. Forecast below for 1800 UTC Thursday 18 December.  

Indeed, for Alta-Collins the Utah Snow Ensemble has a few enthusiastic members, although most of the forecasts are still in the low-end snowfall range and most are warm through the 10-day forecast period.  

Median total water equivalent and snowfall are 0.91" and 8.0" through 5 PM Saturday 20 December, so we will set that as the over/under.  

Now is the time to burn skis.  I'd suggest human sacrifice, but some of you might just take that quip seriously. 

The Northwest Deluge

I've mentioned in prior posts that the storm track will be just to our north over the next several days.  Indeed, the Pacific Northwest is in for a deluge as they are raked by a series of storm systems.  Below is the Utah Snow Ensemble forecast for the 10-day period ending 0000 UTC 18 December.  Ensemble mean (upper right) liquid precipitation equivalents above 9" for most of the Cascades from Mt. Hood to Canada.  

It's worth a look at the plume for Paradise Ranger Station on Mt. Rainier, one of the wetter locations in the Cascades.  The ENS mean is > 20" over the 10 day period with the GEFS mean > 15".  There is tight clustering over the first 5 days of the forecast with most ensemble members between about 12.5 and 17.5".  We see a lot of spread in the ensemble forecasts sometimes, but this is pretty tight clustering for a major events.  

The ensemble grid point for Paradise is at 4942 ft, which is a bit lower than the actual ranger station (~5400 feet), but over the first five days from all of that water most ensemble members are only producing up to 20" of snow.  Rain rather than snow for much of the period.  What a waste of water. 

It's already a sad picture at Crystal Mountain today.

Source: https://www.crystalmountainresort.com/the-mountain/mountain-report-and-webcams/webcams

Worth watching forecasts if you are in the Northwest.  

The Europeans and Americans Simply Cannot Get Along

The overnight Utah Snow Ensemble forecast for Alta-Collins may be the crazies I've ever seen.  Most of the European Ensemble (ENS) members are producing little to no precipitation over the next 10 days including during during the period from 10-11 December (more on those dates in a minute).  The wettest ENS member puts out about 0.8" of water and 11" of snow.  

Some members of the American Ensemble (GEFS) have very different ideas.  There are 31 GEFS members and 10 of them put out more than 1.5" of water just through 00Z 12 December.  Several more put out between 1 and 1.5" of water.  There are some that track with the ENS (hard to see but they are there), but many GEFS members are much wetter.

What gives?

I don't plot or attempt to look at forecast plots like our four panel synoptic diagnostic for all 82 members of the Utah Snow Ensemble.  Nobody has time for that.  So I'm going to start here with the ECMWF HRES forecast that serves as the ENS control and is valid 0000 UTC 11 December.  This forecast captures many of the salient details of the pattern that is going to prevail over western North America the next few days.  A broad, low-amplitude upper-level ridge is centered near the Pcific coast (upper left) with an atmospheric river rolling over this ridge and across the northern US Rockies (lower right).  Heavy orographic precipitation occurs where the atmospheric river crosses major western mountain barriers.

So in the HRES the central Wasatch is just to the south of the action.  There are a few dribs and drabs that make it in, but accumulations are scant.  Most ENS members have a similar forecast.

Some of the GEFS members, however, shift the storm track far enough south to get us in on the action.

Diagnosing the why this occurs in this case is beyond my abilities.  I'll just say that I lean heavily toward the view that the central Wasatch may see some dribs and drabs over the next week but it's unlikely we'll see the game changing major accumulations that we need. 

Mother Nature Delivers the Concrete

Twenty-four hour totals at the Alta-Collins automated observing site added up to 1.79" of water and 15" of snow, yielding a mean water content of 12%.  Snowbasin-Boardwalk came in with 1.26"/8"/16%.  As evidence of the wet, windy, and rimey nature of the storm, I couldn't verify our 70 mph forecast for Mt. Baldy because the sensor rimed and is no longer spinning.  The Utah Avalanche Center report this morning says that "at 11,000 feet the wind is absolutely ripping, with sustained speeds at 50–60 mph with gusts pushing into the upper 70s."  That's good enough for me.  

The Alta-Collins snowstake photo this morning is one of the most comical I've ever seen.  Dense snow apparently carved by wind?  Perhaps with the flow wrapping around the Alta sign?  Who knows.  Come up with your own explanation.  

Snowfall at lower elevations is certainly lower and probably a soggy mess between 6000 and 7000 feet (or higher), but that's just a guess.  

The Cottonwoods might get a bit before things taper down later this morning.  The extended forecast shows that you should continue to root for America.  The European Ensemble (ENS) is giving Alta practically nothing after today.  The American (GEFS) is more generous around the middle of the work week.   

USA. USA. USA.