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Observation: Big Cottonwood Canyon

Observation Date
5/17/2017
Observer Name
B
Region
Salt Lake » Big Cottonwood Canyon
Location Name or Route
Millicent Bowl, Brighton Back Bowls, Wolverine Cirque, Figure 8
Weather
Sky
Overcast
Precipitation
Light Snowfall
Wind Direction
Northwest
Wind Speed
Light
Weather Comments
Sporadic short wave impulses throughout the day with periods of S2. WNW winds were mostly in the Light Range, with periods of Moderate asssociated with the impulses as they moved through. Wind Blown and or Transport was occurring throughout the day and in the high end of the Light category. Cloud cover was predominently Overcast, yet a few periods of Broken allowed for the intense May sun to come through for brief moments.
Snow Characteristics
New Snow Depth
7"
New Snow Density
Low
Snow Surface Conditions
Powder
Wind Crust
Melt-Freeze Crust
Damp
Snow Characteristics Comments

The occasional periods of sunshine breaking through the clouds promoted Greenhousing in some locations, and at the very least adversely affected the snow on all aspects except due north slopes with angles of 30 degrees and greater. Fortunately the sun did not dampen any of the cold dry light density snow until 1000, and the upper elevations stayed good until around 1200 hours on all aspects except NE and E. Steep W aspects remained good until the mid afternoon, but this same upper elevation exposed terrain was scoured down to the old Melt-Freeze Crusts from the winds in many locations.

Riding was good on low and moderate angled slopes, and they rode the best with the new snow providing a soft/cake-like spongy turning surface. The graupel that fell in the beginning of the event helped cushion and improve the riding. On slopes with angles greater than 30 degrees you could feel the old snow surface at the bottom of your turns.

Red Flags
Red Flags
Wind Loading
Poor Snowpack Structure
Red Flags Comments
Four Finger Wind Slabs of up to 14 inches deep were observed from cross loading in the exposed areas. These slabs were mostly stubborn and unreactive. Yet, due to the interface issues associated with the previously cited graupel, very steep wind loaded terrain features may have bene able to produce more sensitive wind slabs. Poor Snowpack Structure observed above 9000 feet where there was a 4 to 5 inch Knife Hard Melt Freeze Crust at the surface with large damp round grains below, and at least 2 feet down.
Avalanche Problem #1
Problem
Wind Drifted Snow
Trend
Decreasing Danger
Problem #1 Comments

See above, and with the winds becoming more calm during the day this problem may not increase overnight. Yet, in any areas experiencing significant winds during the next 24 hours (especially in the highest elevation very steep NW, N, NE and SE facing terrain) there may be the potential for isolated pockets of sensitive wind slabs.

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

Very little Wet Loose observed today due to the limited solar activity at the upper elevations. Thursdays forecast for warmer temperatures combined with any periods of direct sunshine should help activate this problem.

Very large and overhanging Cornices still remain an issue of concern on N, NE and E facing upper elevation ridgelines. The next time we experience any sustained lengthy periods of intense warming may help initiate a cycle of concern. Along with this, this same kind of intense warming may also bring about an avalanche cycle on upper elevation northerly facing terrain.

Finally, an issue of concern today was the rock hard leftover debris/clinckers from a previous warm up period.

Danger observed on Wednesday appeared to be mostly Low with only manageable sluffing an issue. Thursday may see a Moderate Danger due to increasing temperatures and more sunshine on the new snow.

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