UDOT PLANNED AVALANCHE CLOSURES!!
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Observation: Catherines

Observation Date
5/1/2019
Observer Name
B
Region
Salt Lake » Big Cottonwood Canyon » Catherines
Location Name or Route
Catherines Basin
Weather
Sky
Broken
Precipitation
Light Snowfall
Wind Direction
Northwest
Wind Speed
Light
Weather Comments
High end light WNW winds observed at mid elevations and on the upper ridges in exposed areas. Light transport and or wind blown. Temperatures overnight and throughout the morning hours unseasonably cold. Overcast skies until 1000 hours when the cloud deck began to break up. Periods of S1 snowfall throughout the morning with accumulations of 2 to 4 cm.
Snow Characteristics
New Snow Depth
8"
New Snow Density
Medium
Snow Surface Conditions
Powder
Wind Crust
Melt-Freeze Crust
Damp
Snow Characteristics Comments
20 cm overnight in most locations with the lower 10 cm consisting of mostly graupel, and the upper 10 cm light density stellars. The riding was excellent on slopes 30 degrees or less, with turns on the steeper terrain digging down into the pre-storm m/f crusts. Regardless, superb riding and especially for May 1. The sporadic sunshine was able to warm the SE and S aspects by 1100, and this was noticed when exiting back to Brighton. Shady aspects, even low angle ones, were still good at that hour. Yet, reports from others that were out later in the day appeared to indicate that only upper elevation north aspects survived the solar and warmth. Wind scouring on upper elevation west through north facing terrain was observed, and these slopes were stripped down to the slick pre-storm m/f crusts.
Red Flags
Red Flags
Wind Loading
Rapid Warming
Red Flags Comments
Stubborn/unreactive 4 finger wind slabs were observed on the upper elevation NW aspects, and they were up to 60 cm in depth. Besides these very isolated areas, the new snow appeared to lack any kind of slab properties. The upper 10 cm of the new snow was sensitive in the morning hours allowing for manageable Loose Dry/Sluffing while turning on slopes 35 degrees and steeper. No Wet Loose was observed, yet with the sun coming out more significantly in the afternoon hours it is very likely that this problem became active on S and SW aspects. Of note, the cold temperatures for the past 72 hours has appeared to help lock of the lower layers that were very wet over the past weekend. The structure below 9500 feet still consisted of damp grains below a 15 cm knife hard m/f crust, yet these grains had grown in size and had significantly larger pore spacing than previously observed. Above 9500 feet the m/f crust was a much harder knife and verging on ice, and it was at least 20 cm deep.
Avalanche Problem #1
Problem
New Snow
Trend
Decreasing Danger
Problem #1 Comments
See comments on Dry Loose and Wind Slab, and both of these should become even less reactive over the next 24 hours.
Avalanche Problem #2
Problem
Cornice
Trend
Increasing Danger
Problem #2 Comments
See photo of cornice that was observed in Catherines Basin, and interestingly the upper part of this cornice rests on the common summer trail leading to Sunset Peak. Early season hikers may need to pay strict attention to these significant hazards in unlikely areas for quite some time. As we proceed back into periods of sustained warming, these giants may continue to remain suspect.
Comments
Todays hazard appeared to Low in all areas traveled, yet it may have elevated to Moderate with daytime heating. Continued rapid warming and intense solar may promote it to a brief periods of Considerable on Thursday if Wet Loose becomes an issue in the new snow resting on slick bed surfaces. Yet this will be very isolated.
Today's Observed Danger Rating
Low
Tomorrows Estimated Danger Rating
Moderate