Observation: Park City Ridgeline

Observation Date
01/19/2018
Observer Name
B

Region:

Location Name or Route
Park City mid elevations
Weather
Sky
Overcast
Precipitation
Light Snowfall
Wind Direction
Southwest
Wind Speed
Light
Weather Comments
Day began with unseasonably warm temperatures and calm winds out of the SW at protected mid elevations. By late afternoon the winds picked up to the light range and the temperatures began to lower slowly. Wind blown and or transport was noted as light at 1600. S minus 1 snowfall rates began at 1600 and at 1730 rates and intensity ramped up as the forecast was indicating. Between 1730 and 2200 rates were S2.
Snow Characteristics
New Snow Density
Low
Snow Surface Conditions
Faceted Loose
Wind Crust
Melt-Freeze Crust
Damp
Snow Characteristics Comments

During the time in the field no measurable snow was observed, yet at 7000 feet at 0530 on Saturday the 20th, 5 inches of light density snow is on the stake. Variable conditions out there, and of interest was how the protected shady aspects away from heat gathering sources maintained cold settled surface snow conditions at 9000. When near thicker trees the ambiant temperatures were able to dampen the snow surface. Minimal wind effect was noted in some more protected locations on northerly slopes, yet it was not widespread and or possibly significant enough to destroy the surface hoar that was on many aspects before the southerly winds picked up on Thursday evening. Riding was actually still good on low angle protected slopes. 

Red Flags
Red Flags
Poor Snowpack Structure
Red Flags Comments
Poor snowpack structure still in place, yet the wild card is how well the SH was preserved. Observations indicated SH still in place in isolated areas out of the winds on NW, N and E aspects at mid elevations. With the new snow coming in in the evening hours and being light density there is definitely a possibility that SH was capped and preserved.
Avalanche Problem #1
Type
Persistent Slab
Trend
Same
Problem #1 Comments

Of note, the pit results from 8900 feet, NNW showed slight rounding at the two buried weak layer interfaces of concern. The HS for the pit was 90 cm; there was a thin m/f crust at 49 cm with small (.5) rounding facets below the crust. The basal facets were 20 cm thick and they were also showing signs of rounding. Despite these observations, the low altitude of this pit may be not indicating the potential for both mid pack and basal layer potential instabilities at higher elevations on similar aspects ranging from NW through N through E. 

Avalanche Problem #2
Type
Wind Slab
Trend
Same
Problem #2 Comments

As noted, the winds were only in the low end of the light range in areas traveled, yet remote weather stations were indicating much more significant winds in many locations. And, as a result the possibility of localized sensitive wind slabs was very likely at more exposed locations. These were increasing as the day progressed, and with the winds expected to die down on Saturday they may now be buried with the new snow. 

The danger rating in the limited areas traveled was Low, yet Moderate appeared to be the overall rating for the day due to the lingering Persistent Weak Layer situation, as well as the possibility of Wind Slab development throughout the day. 

For Saturday, Storm Snow Slab avalanches my also be possible as well once the totals begin to hit the possible forecast pops due to the weak lingering interfaces. 

Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
Considerable
Snow Profile Coordinates