Toby Weed
Forecaster
Plenty of nice snow snow fell and it was a busy winter season in the Logan Zone. Luckily there were no avalanche tragedies and no injuries were reported. Even so, there were numerous dangerous human-triggered and natural avalanches, several close calls were reported, and a handful of people were caught and carried, with at least three partially buried. People apparently made good choices for the most part, wisely avoiding travel on slopes where dangerous avalanche conditions were mentioned in our forecast, and there were many days with fantastic, deep powder and generally stable snow. More than normal snow at low elevations in early January allowed for rare access to many areas and significantly increased the acreage of regular avalanche terrain in the zone. A persistent weak layer of faceted snow developed in the shallow early season snowpack, and several serious near misses occurred in early January 2019. Elevated avalanche danger at lower elevations threatened people in areas where avalanches are generally uncommon, and large avalanches occurred in the foothills of Cache Valley within sight and easy walking distance of residential areas. Scattered natural avalanches occurred across the zone at all elevations during regular storms and periods of rain at lower elevations through the rest of January and February. In early March we received reports of a few good-sized unintentionally triggered storm slab avalanches failing on a thin layer of near surface facets associated with a sun-crust. A thick layer of well developed surface hoar was buried and preserved intact by a few inches of light snow mid-month, most widespread north of the Idaho State Line. The buried frosty feathers became the culprit weak layer in a few subsequent close calls. Numerous wet loose and a few wet slab avalanches occurred with warming temperatures across the zone in April, and there was a natural glide avalanche reported on Wilderness Peak in northern Franklin Basin around the beginning of May.
Water Year 2019 Precipitation and SWE close to average at the 8400' Tony Grove Snotel. More than normal snow at lower elevations allowed for excellent backcountry access but significantly increased the acreage of avalanche terrain in the Logan Zone.
On 1/4/19 in Providence Canyon, a party of three riders triggered a large hard wind slab avalanche failing on a faceted persistent weak layer. The 6’ deep and 250’ wide avalanche on a drifted south facing slope broke just a few feet below the party as they worked to free a stuck sled. It was an isolated event, with a generally Low danger observed and no other avalanche activity reported that day in the Logan Zone or in the backcountry across the mountains of Northern Utah. This near miss revealed the existence of poor snowpack structure, and was a precursor of several close calls that would occur in early January.
There were several large avalanches that occurred below about 5500’ in elevation. On 1/8/19 a party of two skiers triggered and escaped a 400’ wide and 2’ deep wind slab avalanche, failing on faceted snow just above the green canyon residential area. On the same day, a hiker walking a dog witnessed a group of deer trigger a couple similar wind slab avalanches above the bench in River Heights.
On 1/12/19, a snow bike rider triggered this large persistent hard slab avalanche in Fairgrounds Bowl on the east side of Logan Peak in Providence Canyon.
Riders and skiers triggered avalanches in March failing on persistent weak layers consisting of near surface faceted snow, radiation recrystallization, and surface hoar. A snowmobile rider triggered this avalanche on 3/8/19 under Mount Magog in White Pine Canyon.
Surface hoar, buried in mid-March, was a common failing persistent weak layer in a series of close calls in the Bear River Range north of the Idaho State Line.
- On 3/23/19, backcountry skiers were surprised near Danish Pass when they remote triggered a 2' deep and 150' wide soft slab avalanche on a 32 degree slope.
- On 3/30/19, two snowmobile riders were caught and carried, but managed to ride out of separate avalanches in Bloomington Canyon above Bear Lake.
- Also on 3/30/19, two riders, a snowboarder and a snow biker were caught, carried through trees, and partially buried by a 2' deep and 500' wide avalanche in White's Canyon out of Franklin Basin.
