UDOT PLANNED AVALANCHE CLOSURES!!
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Observation: Brighton Perimeter

Observation Date
4/30/2018
Observer Name
B
Region
Salt Lake » Big Cottonwood Canyon » Brighton Perimeter
Location Name or Route
Brighton Perimeter
Weather
Sky
Obscured
Precipitation
Light Snowfall
Wind Direction
Southwest
Wind Speed
Moderate
Weather Comments
Variable winds with channeling effecting direction in multiple locations. The predomenent wind directions in the late morning hours appeared to be WSW; yet there were definitely times when the direction was WNW. Speeds were consistent from 1000 on in the moderate range with strong gusts. Wind blown and or transport was moderat even intense at brief periods. Temperatuers rose 6 degrees from 0900 until 1200 and hit 36 at 8700. In the upper elevations the cloud cover and wind felt much cooler and likely were in the upper to mid 20's. Snowfall remained constant and maintained average rates of S1.
Snow Characteristics
New Snow Depth
7"
New Snow Density
Medium
Snow Surface Conditions
Powder
Wind Crust
Melt-Freeze Crust
Damp
Snow Characteristics Comments

Low angle riding remained the best bet for soft turning conditions. Slopes with angles 25 degrees and greater were scratchy. Above 9500 feet the refreeze was substantial with m/f crust developing before the new snow came and they were up to 15 cm deep. At lower elevations the residual heat radiating from the snowpack made the old snow surface damp under the new snow at 8900 feet and down; and as a result the new snow was becoming damp by noon. By 1400, the cloud cover began to break apart and the snow ended. Storm totals ranged from 4 to 7 inches dependent on location. It appeared that LCC got a significant boost in precip compared to upper BCC. As a result at 8000 feet in Silverfork where we are right on the line to get the LCC booster effect HST was 6 inches and at least one inch of water. Settlement during the morning hours kept the depth of new snow from adding up, and this appeared to be a result of the warmth radiating up from the snowpack.

Fortunately the new snow at least laid a blanket down to help smooth things out temporarily and as well cover the dirty snow surface that has plagued us for a while now.

Red Flags
Red Flags
Wind Loading
Cracking
Red Flags Comments
Small shallow wind slabs were observed on loaded terrain features facing predomenently NE. Cracking in these small observed wind drifts was widespread. And despite not traveling to any upper elevation potentially loaded ridgelines, it was very likely that significant wind loading was occuring on similar aspects. No naturals observed. It appeared that the combination of the prestorm rough and textured snow surface and the residual warmth radiating from the snowpack allowed for good bonding at the new snow/old snow interface.
Avalanche Problem #1
Problem
Wind Drifted Snow
Trend
Decreasing Danger
Problem #1 Comments

See above.

Avalanche Problem #2
Problem
Wet Snow
Problem #2 Comments

With the sun coming out in the afternoon, and the intense April sun, wet loose avalanches were probably likely; yet the tour ended by 1400, so no activity actually observed.

Depending on how much wet loose activity occurs in the afternoon on the afternoon of the 30th, this problem may still be an issue on May 1. The thickness of the cloud cover on Monday afternoon will play a big part in how long this problem remains an issue.

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