Avalanches in Big & Little Cottonwood Canyon, Early April 2023
Alternately, The Epic Utah Winter of 2022-23
Published by Internet Salmagundi, April 9, 2023, Updated May 5, 2023
By Matthew Wallace
This all captures just a small piece of what happened in the Wasatch the last week of March and first two weeks of April, 2023…
During the last week of March and first week of April, Big & Little Cottonwood Canyons saw an epic snow cycle the likes of which have never been seen before. Little Cottonwood Canyon (“LCC”) closed due to avalanche danger on Sunday April 2, 2023. Copious amounts of snow fell on the Wasatch and the canyon generally did not open again until Saturday April 8. (There were two brief periods when the canyon was open to the public to downhill travel only, so that people who needed/wanted could leave. Otherwise, the general public was prohibited from going up or down the canyon during the period April 1-8.
On April 8th, UDOT indicated that LCC would open temporarily “for downhill & uphill travel 5-9AM: downhill travel permitted 7-9AM: uphill travel permitted.” That same evening UDOT indicated “SR210 will open temporarily tonight & tomorrow (4/9) AM 7-10PM Tonight (4/8): downhill travel permitted, #SR210 will be closed after this period Tomorrow (4/9): 6-9AM: ALL travel permitted, #SR210 will be closed after this period.”
The most recent UDOT update as of the time of this writing is that “#SR210 will open temporarily tonight & tomorrow (4/10) AM 8-10PM Tonight (4/9): downhill travel permitted. #SR210 closed after this period 5-9AM Tomorrow (4/10): downhill permitted, #SR210 closed after this period with no ETO for any travel.” That is to say that LCC will now be closed indefinitely for the next few days. This has never happened before, unprecedented to say the least.
Big Cottonwood Canyon (“BCC”) likewise closed for extended periods of time during the same timeframe. BCC generally does not close as often as LCC. BCC has closed several time during the last week of March and first week of April. The word going forward from 4/10 is BCC will be closed from the mouth to Cardiff from 11am to 4pm daily until Thursday 4/13. That is remarkable and to my knowledge has never happened to this extent before.
In the context of the above, this post features a variety of articles and social media posts covering the epic week. In addition, the Winter of 2022-23 has likewise been epic with records having been set throughout the Wasatch Mountains and the state of Utah.
— Regions Map – Northern Utah Snow Totals April 3-5, 2023 – Updates – Snowbird – Alta
— Avalanches: Little Cottonwood Canyon (“LCC”) Road (SR210) – Big Cottonwood Canyon (“BCC”) Road (SR190) – Other Areas in Northern Utah
— Glide Cracks & Avalanches – Cornices & Cornice Falls – Roofalanche – Runnels
— Avalanche Encyclopedia
Utah Avalanche Center Regions Map:
Most of the avalanches highlighted here include observation reports from the Utah Avalanche Center (“UAC”). Most included here are from the Salt Lake region. This map orients to the regions covered by the UAC:
Northern Utah Snow Totals April 3-5, 2023:
Let me add to the chorus of thanks and appreciation going out to all those working with UDOT, UDOTavy, Alta & Snowbird Snow Safety and everyone else whose toiled mightily the past few weeks keeping LCC safe. The work is often thankless and goes unseen by many of those who count on their work, i.e. those who go up LCC to ski and otherwise recreate. Bravo! Thank You!
Update Friday, May 5, 2023:
The saga continues… Seven Sisters disgorged a wee bit more goop at 1:04 PM and closed SR210 for a few hours today. “Natural mudslide occurred today that crossed the road…” It re-opened by 4:34 PM.
Little Cottonwood Canyon Snowpack Update
We’re still sitting on a good bit of snow in the upper Wasatch. Alta has 167 inches (13.9 feet) and Snowbird is at 130 inches (10.8 feet) at mid-mountain locations. Spring run-off has been getting a lot of attention in the local news, and while some of the creeks surrounding the Salt Lake Valley (City Creek, Emigration Creek, and Mill Creek) have been running pretty high, Big and Little Cottonwood Canyons have really not even started their major run-offs. (They are both full with exceptionally deep snowpacks.) That will come once the upper elevations are exposed to higher temperatures, which could be any day now, once we get through our current cool spell. It’ll be an interesting ride once they start flowing heavy…
Update Wednesday, May 3, 2023:
More cleanup at Seven Sisters (which is now referred to as Seven Turns) from the mud & debris flows.
– 5/03 at 3:01 PM: “SR210 OPEN to all travel. Potential for large, naturally occurring mud/landslides exists. Road open: extra safety measures during day until (5/8): 12pm-6pm: spotter/signal to stop traffic if hazard present. 6pm-12pm: no spotter, travel at own risk. [I think UDOT means to say 6pm-12am no spotter… then closed midnight to 6am, but not sure.]
– 5/03 at 8:57 AM: “REMINDER: SR210 CLOSED NO ETO – closed to all travel. Crews have cleaned up mudslide debris, @UDOTavy, & @UtahDOT continue to assess/clear drainage & hazards in the area. Water currently flowing on road in spots. : Seven Turns. [See second set of photos and video in the same thread.] Additional video.
Update Tuesday, May 2, 2023:
SR210 in Little Cottonwood Canyon is still closed.
Beginning on April 27 at 10:50 AM UDOT indicated “Travelers need to be prepared for potential prolonged road closures [both SR190 & SR210] at any time over next few weeks. Could start as soon as tomorrow (4/28).”
Then on April 28 at 4:27 PM it was “SR210 will be closed tomorrow (4/29) at 11:00am due to avalanche hazard ETO: ~7pm, estimate only & dependent on conditions. Uphill: closed at mouth Downhill: closed at Snowbird Entry 1/Gate C, travel above Gate C is allowed.”
On April 29 at 4:47 PM UDOT said “SR210 will be CLOSED tomorrow (4/30) at 9am due to avalanche hazard NO ETO for any public travel periods after tomorrow 9am: Uphill closed at mouth 9am: Downhill closed at Snowbird Entry 1/Gate C, travel above Gate C is allowed.” UDOT added to it with “SR210 ROAD CLOSURE: (4/30) 9am due to avalanche hazard NO ETO: Plan your travel to @SnowbirdAlerts, @AltaAlerts, @AltaCentral & other areas wisely, last known public travel period. Limited travel periods for residents, employees, etc. will be assessed by @UDOTavy daily.” In addition notice to backcountry users “SR210 BACKCOUNTRY USERS: Entire road between Gate C and the mouth, including the White Pine parking lot exit, will be closed at 9am (4/30) with no ETO. Visitors who do not want to be in canyon indefinitely need to exit the canyon/parking lot by 9am, gate will be closed.”
Then on April 30 at 7:25 AM UDOT said “REMINDER: SR210 will be closed today at 9am due to avalanche hazard NO ETO for any public travel periods after today 9am: Uphill closed at mouth 9am: Downhill closed at Snowbird Entry 1/Gate C, travel above Gate C is allowed.
After that there were a couple of short openings for (public) downhill traffic only. April 30 at 5:19 PM “SR210 will open temporarily tonight & tomorrow (5/1). TONIGHT 8-10pm. All downhill travel allowed. NO public uphill travel. Limited uphill travel allowed for residents, employees, etc. vetted by resorts/@AltaCentral.”
Stating the obvious, which may not be so obvious to the uninitiated, on May 1 at 9:20 AM UDOT said “IMPORTANT Deep snowpack & warming temperatures create unpredictable spring wet avalanche hazard conditions. @UDOTavy closely monitoring and assessing to determine if/when road closures are needed.”
Then on May 1 at 4:46 PM “SR210 temporarily open TOMORROW (5/2): 5:30-8am. All downhill travel allowed. NO public uphill travel. Limited uphill travel allowed for residents, employees, etc. vetted by @AltaCentral, @AltaAlerts, @SnowbirdAlerts. 8am (5/2): #SR210 closed. No ETO.”
One might reasonably ask “Why all the fuss?”
Here are a few of the reasons for concern:
On May 2 at 3:37 PM UDOT said “REMINDER: SR210 CLOSED. NO ETO. Mudslide crossed the road earlier today, ~4’ deep, 100’ wide with large woody debris. Slow moving debris flow, @UtahDOT & @UDOTavy are slowly and cautiously assessing impacts.” Mudslide at Seven Turns or what we also call Seven Sisters in LCC. More images and video of this event here.
In the meantime, SR190 up Big Cottonwood Canyon has been closing daily from about 11:00 AM to 5:00 PM due to “avalanche hazard.” The closures have been “Uphill: closed at mouth Downhill: closed at Cardiff (MP 10.7), travel above Cardiff is allowed.” As of May 2 at 3:30 PM “SR190 OPEN to all travel. NO avalanche closures currently planned. Safe travels & enjoy your afternoon if you’re headed to @BrightonResort, @SolitudeMTN, @BrightonUT and other areas in the canyon!”
Update Saturday, April 29, 2023:
The roads up Big & Little Cottonwood Canyons will be closing this week due to the increasing temperatures forecast for the next 5 days. Combined with the current snow depths (Alta reports 182 inches at mid-mountain, Snowbird reports 140 inches at mid-mountain) and temperatures getting into the 60s at ski area bases, the hazard for wet avalanches is once again considerable. Thus, both SR190 & SR210 will be closing this week. LCC will be closing for longer durations, and may stay closed overnight for a few days. Have to play it by ear and see how warm it gets and how the snowpack reacts.
– #SR210 [Little Cottonwood Canyon] will be CLOSED tomorrow (4/30) at 9am due to avalanche hazard. ETO: ~7pm, estimate only & dependent on conditions.
– #SR190 [Big Cottonwood Canyon] REMINDER Road will close tomorrow (4/30) from 12pm – 5pm due to avalanche hazard.
Weather forecast for Salt Lake City/Wasatch Front. These records setting temperatures will hasten the snow melt. (Average high temps for now are mid-60s, not high 70s and low to mid-80s.) This is why the situation is so serious.
Here’s a story about what it was like up Little Cottonwood Canyon in early April when SR210 was closed for extended periods over a two week time span.
Avalanches and an egg run: What was it like to be trapped in Little Cottonwood Canyon?
UDOT workers felt urgency to open SR 210 so stranded skiers could get home.
Update Wednesday, April 26, 2023:
900 inches! Take a quick lap of the Collins Study Plot with Jonathan Morgan of the Alta Avalanche Office.
[Yes, this must have been recorded prior to hitting 903″, but 903 holds, Alta has not taken that number down. Hell, what’s 3 inches anyway?]
• Snowiest season on record: 900” and counting
• Deepest settled snow depth: 248” [20.6 feet!]
• Single Snowiest month (March 2023): 229”
Update Tuesday, April 25, 2023:
Alta hits 903 inches or 75.25 feet for the season! (With 197 inches or 16.4 feet still on the ground mid-mountain.) This is the most snow ever received in a single season in the Wasatch Mountains, bar none.
Update Saturday, April 22, 2023:
In the interim from April 13 to today avalanche activity subsided and avalanche danger is presently considered generally low and moderate in the Salt Lake region. Little Cottonwood Canyon was closed once again April 17 from roughly 11am to 2pm. Otherwise, SR210 appears to have remained open. There have been a few rock and debris slides on SR190 such as wet slide debris at Laurel Pines. Otherwise, the story has shifted from hazards in the mountains to flooding and land slide hazards in the valleys.
Current Snow Depths and Seasonal Snowfall for Alta & Snowbird. (It’s been a record year to say the least! Only 7 more inches needed at Alta to break 900 inches, which has never happened before, ever.)
Update Thursday, April 13, 2023:
As of 6:31 pm today Little Cottonwood Canyon road (SR210) is “OPEN to ALL travel.” UDOT cautions: “Travelers need to be prepared for road closures any time for remainder of season.”
A significant cold front moved through the region today and temperatures are down 20 to 40° from yesterday. As of 10:30 pm temps are 7° at Hidden Peak, 9° at Mt. Baldy, 13° at Alta’s Atwater Study Plot. Those are all down considerably from recent high temps: Hidden Peak 43° 04/11 @ 5:15 to 7:15 pm; Mt. Baldy 44° 04/11 @ 6:00 to 7:00 pm; Atwater Study Plot 56° 04/10 12:00 pm & 5:00 pm, 04/11 5:00 pm, and 46° 04/12 2:00 pm. The well below freezing temps will slow the snow melt.
It appears that White Pine Chutes slid yet again today leaving sizable debris on the road which has been cleared and the road is open.
Update Wednesday, April 12, 2023:
LCC is still closed, again, no surprise there. White Pine and White Pine Chutes both went pretty big, among no doubt others.
Update Tuesday, April 11, 2023:
As of 9:00 pm today Little Cottonwood Canyon is still closed, no surprise there. This wet slide in White Pine Chutes is an example of why. It is tagged as “White Pine Chutes ~7pm (4/10).” UDOT indicates that “wet avalanche activity continued into the evening yesterday.” Watch the video, there’s a road under there somewhere…
After record cold last week, when we had a record low maximum high temp of 33° on April 4th, we set a record high today of 83° at the SLC Int’ Airport. This kind of heat is not kind to snow and adds to why LCC is shut down…
Update Monday, April 10, 2023:
As of 9:00 am today Little Cottonwood Canyon is closed and will not open until approximately, maybe Friday April 14. (That’s not a typo, you read that right.) According to UDOT, there will be no public access up or down the canyon. There is no estimated time of opening. Only time will tell. That’s an unprecedented and remarkable statement. This has never happened before. As Jim Steenburgh (“Prof. Powder”) says “For Little Cottonwood, we have simply had too much snow this year and especially in the past few weeks.” Very hazardous large wet avalanches are running in LCC. While it is difficult to predict exactly when and where they will occur, it is with high confidence that it can be predicted they will occur over the next few days. That is why LCC is closed indefinitely with no ETO.
LCC Snowpack on April 10, 2023:
At April 10th it is highly unlikely that we will see any additional appreciable snow falling. So this shows the total snow received by Alta and Snowbird by there own reporting.
Significant snowfall occurred the last week of March with Snowbird reporting over 6 feet of new snow. Starting March 30 UDOT Cottonwood Canyons began issuing short term road closure notices for both Big and Little Cottonwood Canyons due to avalanche mitigation work. The first notice for LCC was on March 30th.
#RoadClosureAlert #SR210 will be closed at 9:00pm (3/30) tonight for @UDOTavy avalanche mitigation. 9pm: Uphill traffic closed at mouth 9pm: Downhill traffic closed at Snowbird Entry 1/Gate C No ETO [Estimated Time of Opening] based on forecast – we will update when time known.
Numerous subsequent updates indicated that significant snowfall was forecast and that Snowbird was closing the Mineral Basin area early.
@Snowbird Resort Status Update: Snowbird will be closing early today due to the incoming storm. Mineral Basin lifts and terrain will close at 2:00 pm. The rest of the resort will be closing at 3:30 pm.
Snowbird did not open for skiing on March 31st and was in interlodge for the day until 3pm when interlodge was lifted and the road (SR 210) opened. (Interlodge means people are prohibited by law from being outside due to avalanche hazards.)
Snowbird Snow Gauge:
Deepest Mid-Mountain Base Depth at Snowbird for 2022-23 Season:
Alta generally receives more snow that neighboring Snowbird. Alta is at the top of LCC and naturally squeezes more snow out of passing storms. Alta was equally inundated with snow during the last week of March storms.
Deepest Mid-Mountain Base Depth at Alta for 2022-23 Season:
(Note that I missed getting a screenshot of the base depth measurement of 248 inches which in fact was the deepest it got this season at Alta.)
A sampling of recent avalanches in the Wasatch Mountains:
Little Cottonwood Canyon (“LCC”) Road (SR210):
Little Cottonwood Canyon Road has been inundated by avalanches. To begin, here is a map of all avalanche paths in LCC that are known to be able to hit and cross the road. (There are of course many other slide paths within both Alta and Snowbird and in the wlidlands away from the road.)
Coal Pit #4
Best as anyone can remember Coal Pit has not hit the road since 1983.
“This was a natural avalanche that occurred on April 4, 2023. The debris is massive and set new trim lines. The debris crossed Little Cottonwood Creek. This is one of the more impressive avalanches of an impressive cycle.” —UDOT/UAC Staff
Salt Lake Twins & Lisa Falls:
Lisa Falls and Salt Lake Twins went big. The amount of brush and branches in the second video is remarkable.
UDOT’s Jake Brown discusses the Lisa Falls and Salt Lake Twins slides and mentions the Coalpit #4 slide that hadn’t slid to the road since 1983.
White Pine Chutes:
Misc in LCC:
Scenic drive up LCC: Monday April 8th Matthew Bennett drove up LCC and captured the scene from just below Lisa Falls to Alta. “If you look carefully you will notice 15 of the 18 different avalanches that crossed the road over a 7-mile journey. Some of the avalanches appear so wide you cannot tell if it is one or multiple slides.”
Utah’s record snow is so deep it buried measuring equipment:
Front loader buried:
Big Cottonwood Canyon (“BCC”) Road (SR190):
Circle Awl / Laurel Pines:
Somewhere in BCC:
Other Areas in Northern Utah:
Mt. Olympus (Olympus Cove):
Avalanche mitigation near Deer Creek Reservoir from Utah Highway Patrol dashcam:
Old Logway Canyon:
Mitton Peak, North Ridge:
Glide Cracks & Avalanches:
Glide [or Glide Cracks] is the process of the entire snowpack sliding as a unit on the ground.
A Glide Avalanche is a release of the entire snow cover as a result of gliding over the ground.
—Avalanche.org, American Avalanche Association & National Avalanche Center
“Glide avalanches are a threat this time of year, and glide cracks are starting to open up more with each passing day. Continued warm temperatures and water greasing rocky bed surfaces have opened up glide cracks throughout the range. These full-depth catastrophic avalanches could release triggering a wet slab avalanche as they take off down slope. Because of how much snow we have had this season I would keep an eye out for glide avalanches in zones that don’t normally see glide cracks. Avoidance is the key to this problem and I would avoid traveling in areas known for glide avalanches like Stairs Gulch, Broads Fork, Mill B, Mineral Fork, Mineral Slabs, (Provo), Chili Peak Slabs (Ogden) and many others. ” —Utah Avalanche Center, April 11, 2023
According to the UAC some of the reported glide areas include Stairs Gulch, Broads Fork, Mill B South, Mineral Fork, Porter Fork, Ben Lomond, Chilly Peak Slabs, Black Canyon and others.
Cornices & Cornice Falls:
A Cornice Fall is the release of an overhanging mass of snow formed by wind deposits.
—Avalanche.org, American Avalanche Association & National Avalanche Center
Little Cottonwood Canyon:
Big Cottonwood Canyon:
Roof Avalanche or Roofalanche:
A Roof Avalanche is an avalanche that falls from the roof of a man-made structure.
—Avalanche.org, American Avalanche Association & National Avalanche Center
Big Cottonwood Canyon – Brighton:
Millcreek Canyon – Porter Fork:
Little Cottonwood Canyon – Alta:
It slide a second time…
A runnel is a narrow channel on or in a snowpack that water follows as it passes through the snow pack. They are more commonly seen during Spring time.
Avalanche.org offers their Avalanche Encyclopedia of snow and avalanche terms that can shed light on the terms used on this page. Avalanche.org is hosted by the American Avalanche Association & the National Avalanche Center.
That’s it for now. Will there ever be another season like this one? Only time will tell…