Observation Date
2/20/2017
Observer Name
Zimmerman Wall
Region
Provo » American Fork » Mary Ellen Gulch
Location Name or Route
Mary Ellen Gulch
Weather
Sky
Overcast
Wind Direction
Southwest
Wind Speed
Strong
Weather Comments
Dynamic weather day with wind and visibility changing throughout. Strong Westerly to start, but switching to moderate by noon. Ceiling moved from 11,000 to 10,000 and then began to lift again after 1300. Temps were comfortable and snow received minimal solar input. Greenhousing was not an issue. By 1530, winds above 9,500 feet were ramping up, and the highest ridgelines bordered on violent. Incredible wind transport taking place as winds went nuclear and switched to the south.
Snow Characteristics
New Snow Depth
16"
New Snow Density
High
Snow Surface Conditions
Powder
Snow Characteristics Comments
The settled storm depth at 9500 feet North facing in upper AF canyon is 40cm. Overall HS is 350cm. New snow is bonded quite well to the old sun crust on solars and was surfy and supportable. Wind buffed snow skied well and drifts were stiff and not as sensitive as days prior.
Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Wind Loading
Red Flags Comments
Certainly the storm came in warm and windy. H20 totals the previous day were respectable and the slew of skier triggered slides Sunday 2/19 was impressive. While of consequence in certain terrain, they were fairly manageable with ski cuts. Today, the snow was more spongy and felt like it had settled quite a bit. No avalanches were seen from the last 12 hours in our terrain today, natural or otherwise. The slab is gaining cohesion and with the wind transport happening at high elevations, would expect the hazard to spike for Tuesday.
Avalanche Problem #1
Problem
Wind Drifted Snow
Trend
Increasing Danger
Problem #1 Comments
NW through E facing were getting actively loaded all day, but really prevalent in the hours after 1500. The sensitivity of these slabs were increasing as the day wound down.
Avalanche Problem #2
Problem
Cornice
Trend
Same
Problem #2 Comments
Massive cornices continue to grow. It reminds me of the Sierra Crest and some of these boxcars are amazing. Car sized cornices are now starting to grow to top of the older cornices that have sagged below the ridgelines.
Comments
Photos:
1.Early clouds and wind in upper MEG
2. Massive Cornice on Silver Creek Peak/Outhouse Ridgeline
3. Pagan Basin Cornice has a cornice on its cornice
4. Photo of Sunday's skier triggered avalanche in Sinner's Pass.
Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
Considerable
