April storm brings elevated avalanche activity

Snow pack in Hoback Canyon watched closely

By Stephanie Harsha

The Wyoming Department of Transportation avalanche crews were very busy this season.

A deep low-elevation snow pack persisted well into the spring thanks to cold temperatures through the winter.

With spring temperatures rising in April, crews monitored canyons in northwest Wyoming with apprehension.

On Monday morning, April 10, Avalanche Supervisor Don Lawless and Avalanche Technician Ted Stegman were driving through the canyons, discussing the impact of temperatures on the snow pack, knowing the daytime temperatures could mean a failure of the snow pack in lower elevation avalanche paths. They then made the call to schedule some avalanche mitigation work in the Hoback Canyon on US Highway 191 south of Jackson.

“We discussed the timing to perform mitigation work on the Cow and Calf of the Woods slide paths and settled on Tuesday at 2 p.m., when we thought we would have minimum strength and hopefully could clean the most snow out,” Lawless said.

However, the warm weather forced their hand earlier with some immediate activity in the Hoback Canyon.

Monday evening, April 10

The evening prior to the scheduled avalanche mission, an avalanche occurred near Granite Creek on US 191 at milepost 152.4. A second slide accompanied it shortly after in the same area, trapping

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13 vehicles between them and hitting two vehicles that were stopped behind the initial slide.

WYDOT’s Transportation Management Center immediately notified Lawless and Stegman, along with maintenance forces, including Richard Wilson on the rotary plow, Brett O’Dell on the front loader, and Foreman Troy Jerup to start clearing the debris.

Crews immediately began clearing a passable lane through the north slide, and traffic was cleared out from between the two slides. Crews then began to free the two vehicles that had been hit by the second slide.

Miraculously, no one was injured, and the two vehicles that were struck by the hurdling snow and debris were able to drive their vehicles out of the canyon.

The official highway closure time lasted from roughly 7-11:20 p.m.

Tuesday, April 11, 2023

Temperatures dipped during the nighttime hours, but continued to warm in the morning hours. The avalanche crew spent the morning preparing the rotary plow and front loader for the planned mitigation work at two well-known slide paths, the Cow of the Wood and the Calf of the Wood.

Lawless and Stegman shuttled the rotary snow plow down to the Stinking Springs pullout and returned to the office to get the loader. Lawless was just getting on the road with the loader when he received a phone call from Wyoming Highway Patrol Lt. Matt Brackin at a little after 1 p.m.

There had been an avalanche at the Cow of the Woods slide area blocking the highway.

Due to the proactive planning of the Jackson maintenance and avalanche teams, equipment and personnel was already staged in anticipation of the scheduled mitigation meeting.

The response was quick. Crews immediately closed the road and made the call to continue with the planned mitigation mission to clear any additional debris out of the slide paths.

Stegman connected to and detonated the O’Bellx in the Cow of the Woods slide path with no additional results. He then connected to the Calf of the Woods O’Bellx and successfully fired it with similar limited results.

Later that evening, at about 7 p.m., Lawless received another call from the TMC informing him of a reported avalanche on Wyoming Highway 22/Teton Pass at milepost 13 that partially covered the westbound lane.

As crews worked to clear the snow debris on Teton Pass, Lawless received news of more avalanche activity. The Snake River Canyon on US Highway 89 was now coming down, as well at milepost 131.7, also known as the Goldmine slide path.

Lawless headed back to the office and grabbed the rotary snowplow from the shop and headed down the Snake River canyon. The Goldmine avalanche was fairly large, and covered most of the roadway with snow 3 feet deep. The Snake River would remain closed from roughly 8-10 p.m.

Wednesday, April 12, 2023

Temperatures continued to remain warm during the day, but also freezing overnight, except in the high elevations. These weather patterns concerned WYDOT’s avalanche team as they braced for more avalanche activity in the three canyons surrounding Jackson.

At roughly noon on Wednesday, Lt. Brackin again phoned Lawless with information that there had been another slide at milepost 156 in the Hoback Canyon that had blocked both lanes of travel. The avalanche team was currently working on the other side of WYO 22/Teton Pass and immediately headed south on US 191. Jackson maintenance crews also headed in that direction.

Despite mitigation efforts the day before, the Cow of the Woods slide path had come down again, burying both lanes of travel 10-12 feet deep. Crews worked quickly and were able to clear a single lane through the debris, clearing traffic from the area.

Crews immediately fired the O’Bellx again in both the Cow of the Wood and the Calf of the Woods slide paths.

“The Cow had a little more that dribbled out and hit the roadway, while a bit of snow came out of the Calf slide path and triggered a slab on the apron that buried the road about 3 feet deep,” Lawless said.

The debris was cleared and the roadway was officially opened up at about 3:38 p.m. after being closed for about three hours.

The evening would bring more calls from the TMC. At a little after 6 p.m., Maintenance and avalanche crews were again called to the Hoback Canyon at milepost 155. The slide, smaller than the initial activity earlier that day, was cleared in about two hours.

Over a three-day period, the Hoback Canyon saw two avalanche mitigation missions and had produced four slides that breached the roadway. In addition, crews saw several smaller slides on Teton Pass as well as on US 89 in the Snake River Canyon.

“It’s been a busy winter, with lots of moisture and avalanche activity in the northern part of our district,” District 3 maintenance engineer Tory Thomas said. “Our avalanche team and maintenance forces did a great job protecting the public and our canyon roadways. We are very proud of the work they do and how well they do it.”

Although the bulk of winter is over, WYDOT maintenance is still watching the Hoback Canyon closely.

“We may not be out of the woods yet,” Thomas concluded.