Ad
The National Forest Service Logo
icon-add Observation
Forecasts
Logan Ogden Salt Lake Provo Uintas Skyline Moab Abajos Weather Archives How to read the forecast
Observations & Avalanches
Submit Observation Observations Explorer All Observations Avalanches Fatalities Weather Place Names Map Archives
Education
Avalanche Class List UAC Class List Online Classes Resources and Tutorials Avalanche Awareness Develop Skills
Events
Store
About
Contact Who we are Core Values Staff Board of Directors Past Forecasters Sponsors Annual Reports Sign In
Blog
icon-add Observation
Donate / Join

Observation Date
4/8/2015
Region
Salt Lake » Big Cottonwood Canyon » Brighton Perimeter
Location Name or Route
Brighton: Back Bowls and Figure 8, Twin Lakes Pass, East Bowl Silverfork and Flannigans
Weather
Sky
Obscured
Precipitation
Moderate Snowfall
Wind Direction
Southwest
Wind Speed
Moderate
Weather Comments
Day began with Heavy PI around 9:00. By noon there was 3 inches at 8000 feet in Silverfork. Totals appeared similar with 4 inches by 12:30 at 9800 feet in Brighton. A lull in the precip occurred for the next hour with a brief period of Greenhousing. Fortunately the cloud cover came back in quickly and the Greenhousing damage was limited to flat and or low angle terrain that was facing mostly south. The precip picked up again after 1:00 and immediately it was snowing again at 1 inch per hour. These rates were maintained until 3:30 and then the snow became more showery for the remainder of the day. Winds were initially out of the SW and were in the Moderate Range. Along with the 1:00 squall, the winds veered more out of the WNW and they increased. Transport and or Wind Blown Snow was occurring in the Moderate Range throughout the day regardless of it's direction. Temperatures appeared to remain in the upper 20's throughout the day. Visibility was limited due to the cloud cover.
Snow Characteristics
New Snow Depth
8"
New Snow Density
Medium
Snow Surface Conditions
Powder
Wind Crust
Damp
Snow Characteristics Comments

Storm totals by the end of the day were 8 inches in upper Silverfork. The storm totals were vastly affected by altitude with the lower elevations experiencing intense settlement and much higher densities.

At upper elevation, the snow was mostly right side up with Light density snow falling in the last half of the afternoon. There was density inversion after the first inch or snow fell during the day due to increasing late morning and mid day temps.

Greenhousing adversely dampened the snow surface as previously described.

Upper elevation exposed terrain was affected by the winds with scoured areas apparent.

Low angle riding was the best with most other slope angles yielding "Bottomfeeding" and scrapy riding conditions.Upper elevation teep North facing slopes appeared to ride well with the thin M/F crust breaking down and allowing for a softer riding base surface.

Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Wind Loading
Rapid Warming
Red Flags Comments
Limited sun and cool temperatures appeared to keep wet activity at a minimum in the Upper Cottonwoods. Thursday may bring a different story with the temperatures forecasted to be at least 10 degrees warmer, with partial clearing by the afternoon. Of Note: Wind Loading was able to build Four Finger Soft Slabs of up to at least 14 inches in depth. These isolated pockets were illustrating some sensitivity with stability tests indicating Moderate Shears running directly above the old M/F pre-strom snow surface. Pre-Frontal dirty intense winds were able to help build these slabs. There was evidence of widespread Natural Dry Loose Snow Avalanche activity that appeared to occur during the first PI event in the late morning hours.
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Decreasing Danger
Problem #1 Comments

Pockets of Wind Slab were observed on mostly NE aspects at the upper elevations. The late afternoon WNW winds may have helped develop more pockets on E and SE aspects.

Winds are forecasted to die down and this may help decrease this hazard by Thursday along with these slabs settling out over the next 12 to 24 hours.

Avalanche Problem #2
Problem
Wet Snow
Trend
Increasing Danger
Problem #2 Comments

With the increasing temperatures forecasted for Thursday, there may be a period of Wet Loose Snow Avalanche activity with daytime heating and sun exposure.

With the high angle of the April Sun, this activity may not be limited to just the lower half of the compass.

As a result, Natural Wet Avalanches may be possible on Thursday, and a Considerable Rating may be appropriate for this Avalanhe Problem.

Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
Considerable