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Forecast for the Moab Area Mountains

Eric Trenbeath
Issued by Eric Trenbeath on
Sunday morning, December 18, 2022
The avalanche danger has trended down to MODERATE but deep and dangerous, human triggered avalanches failing on a buried persistent weak layer remain possible. The danger is greatest on steep northerly aspects near treeline and above where accumulated and drifted snow has built slabs 2'-4' thick over this weak layer. Avoidance of slopes steeper than 30 degrees remains the best policy.
NW winds at upper elevations have blown and drifted this week's low density snow, and a MODERATE danger for triggering an unstable slab of wind drifted snow exists on all aspects above treeline.
Mid and low elevation south facing terrain offers generally LOW danger and good snow can still be found on many slopes with these aspects.
Low
Moderate
Considerable
High
Extreme
Learn how to read the forecast here
Special Announcements
See my recent blog post for a personal account of being caught in an avalanche with a persistent weak layer problem during a period of moderate danger.
Road Conditions: A few inches of snow has fallen on the road since Grand County plowed on Tuesday but it has been well packed in by traffic. It is slick, and AWD and good tires are required.
Grooming: Matt groomed all trails yesterday and conditions are excellent. Thanks to all the volunteers who showed up for yesterday's training!
Weather and Snow
24 Hour Snow 0" 72 Hour Snow 5" Season Total Snow 79" Base Depth at Gold Basin 48"
Winds on Pre Laurel Peak SW 5-10 Temp 13F
Weather
SW winds are light and temps are about 10 degrees warmer than yesterday at this time. It's going to be another beautiful day in the mountains with mostly sunny skies, light southerly winds, and high temps climbing up into the 20's. We may see some high clouds associated with a low pressure system passing by to the south. Monday will also be nice. Tue and Wed bring clouds and breezy conditions associated with an ill defined system tracking north. I don't see anything significant on the horizon through the remainder of the month.
General Conditions
Conditions remain excellent if not a little thin. NW winds backed off quick yesterday and did little to no damage. Even many southerly aspects still have dry snow. For more complete details, see my observation here. Reed Kennard and Ed Grote were also out and about, read their observation here. The avalanche danger is slowly dialing down, but a well defined persistent weak layer of faceted snow exists and the consequences remain the same. Deep, dangerous, and potentially un-survivable human triggered avalanches remain possible, particulary on steep, northerly aspects near treeline and above.
Snowpack and Weather Data
Gold Basin Storm Stake (10,000')
Gold Basin SNOTEL site (10,000')
SNOTEL site near Geyser Pass Winter Trailhead (9600')
Wind Station on Pre-Laurel Peak (11,400')
NWS forecast for the La Sal Mountains.
Click here for a list of recent observations. If you're getting out in the backcountry please let us know what you are seeing by submitting observations here.
Recent Avalanches
No new avalanches have been observed. The most recent avalanches ran on or around Dec 13. Here is a complete list of avalanches in the La Sals.
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Avalanche Problem #1
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
A persistent weak layer of faceted snow that developed during the cold dry period in mid November exists on aspects that face W-N-SE. Incremental loading from recent and wind drifrted snow has kept the pressure on this weak layer but the danger is slowly decreasing. The greatest danger exists on slopes facing NW-N-E, where wind drifted snow has built thick slabs on top. These hard slabs are 1-4' thick and can produce very large, deep, and potentially deadly avalanches. Slopes steeper than 30 degrees should be avoided in these areas.
I dug a snowpit and peformed an extended column test on a NE aspect at 11,200' yesterday and acheived propagation on 18 taps. In the photo below you can see how a well defined slab failed on the persistent weak layer of facets in the middle of the snowpack.
This chart illustrates the layering in the above photo. We are looking for harder layers over weak layers. In the chart, the further a layer is drawn to the left, the harder it is. From the chart, you can see the weak layer where failure occurred between 40-45 cms.
Avalanche Problem #2
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
NW winds at upper elevations Friday night into Saturday morning blew and drifted the recent snow, creating potentially unstable slabs on all aspects above treeline. Areas of wind drifted snow are recognizable by their smooth, rounded appearance, and cracking is a sign of instability. On northerly aspects, recent drifts will only add more stress to the buried persistent weak layer, and steep northerly facing terrain should be avoided due to the possibility of a much deeper and more dangerous avalanche.
Additional Information
The Neff's Canyon Accident up in SLC got Dave and I talking. It occurred on a lower elevation, northerly aspect with burned out trees. This is similar terrain to what exists in the burned out section of the North Woods. Slope angles hover in the low 30's but do reach 35 degrees in places. This is avalanche terrain, and it harbors weak, faceted snow. It should not be considered safe.
General Announcements
This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur. This forecast will be updated by 7:30 tomorrow morning.
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