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.