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Observation: Moab

Observation Date
3/19/2020
Observer Name
T. Matthews
Region
Moab
Location Name or Route
Laurel Highway to North Woods.
Weather
Sky
Overcast
Wind Direction
Southwest
Wind Speed
Moderate
Weather Comments
Overcast skies the few hours I was out in the field today with S-1 to S1 snowfall rates. Light winds with an occasional gust in to the moderate range below treeline. As soon as I reached treeline the wind speeds felt like they were more in the moderate rate out of the SW. Blowing and drifting snow was evident. Snowfall was very small graupel, or small rimed Stellars. Trees were starting to grow rime on their south facing branches. Temps felt warm in sheltered terrain and colder as I neared treeline where the winds were blowing harder.
Snow Characteristics
New Snow Depth
14"
New Snow Density
Medium
Snow Surface Conditions
Powder
Snow Characteristics Comments
I measured about 14" of new snow in a sheltered location at approximately 11K. The snow falling out of the sky was small graupel or rimed stellars. It skied nicely.
Red Flags
Red Flags
Heavy Snowfall
Wind Loading
Cracking
Collapsing
Poor Snowpack Structure
Red Flags Comments
>12" of new snow has fallen in many location in the La Sals within the past 24 hours. That combined with it's medium density and greater SWE values has added a critical new load of snow to a wide variety of snow surfaces. With wind speeds in the moderate range above treeline there is plenty of new snow available for transport. I was able to find new wind drifts in the 24"-30" range that felt hollow and I'm certainly could avalanche in steep terrain. I had some localized cracking within the new storm snow at the Gold Basin test slop located just above the shortcut where I know the snowpack structure is horrible. I experienced my only collapse of the day at this spot. The sun only popped out for a few seconds at a time near the end of my tour today, but if it's out tomorrow the solar aspects will see rapid warming and wet loose avalanches in steep rocky terrain.
Avalanche Problem #1
Problem
New Snow
Trend
Decreasing Danger
Problem #1 Comments
With poor visibilty today I never got to see any steep avalanche terrain. Had I been able to it's likely I would have seen some new storm slab avalanches. On my small test slope I was able to get cracking within the new snow.
Avalanche Problem #2
Problem
Wind Drifted Snow
Trend
Decreasing Danger
Problem #2 Comments
Lots of new snow to blow around and it was. As I reached terrain above treeline the light winds ramped up to moderate and snow was blowing around and forming lots of new drifts. I measure some at up to 30" on flat terrain. Had visibilty be good I'm pretty certain I could have spotted some new wind slab avalanches. Winds speeds as of now have backed off with only some gusting in to the moderate range. If they stay this way the wind slabs will become more stubborn and harder to trigger, but if the winds ramp back up again there is now a lot of new snow to transport.
Comments
Problem #3 Persistent Weak Layer. >12" of new medium density snow has fallen in the past 24 hours. This is a critical loading event, and the snowpack doesn't like rapid change. Add to the the wind drifting that has taken place and the new load just increased again. The terrain on the north half of the compass is where you will find this weak sugary snow in the snowpack. It's been quite a while since the snowpack in the La Sals has been tested with a critical load like this. With poor visibilty today it was hard to see in to big avalanche terrain, but with storm slabs and wind slabs being likely today it's quite possible that triggering one of these avalanches could steep down deeper in to the snowpack and pull out a persistent slab avalanche. Most suspect are areas on the north half of the compass 10k and up in elevation on steep rocky slopes with a thin snowpack.
Photo 1: Riming on the south facing tree branches.
Photo 2: 14" of new snow at 11K.
Video: Cracking within the new storm snow.
Video
Today's Observed Danger Rating
Considerable
Tomorrows Estimated Danger Rating
Moderate
Coordinates