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Forecast for the Moab Area Mountains

Eric Trenbeath
Issued by Eric Trenbeath on
Sunday morning, January 22, 2023
An isolated or MODERATE danger exists for human triggered avalanches involving slabs of wind drifted snow on all aspects primarily above treeline. Drifts may also be found at lower elevations in wind exposed terrain so keep your eyes out for smooth, rounded deposits of wind drifted snow.
On northerly aspects, a low probability/high consequence scenario remains for dangerous, human triggered avalanches failing on a buried persistent weak layer. Thinner snowpack areas, and areas of very steep, rocky, radical terrain are where you are most likely to find this problem.
Low
Moderate
Considerable
High
Extreme
Learn how to read the forecast here
Special Announcements
Road Conditions: The road is plowed but it is extremely narrow with high banks, and much of it is one lane only. You may have to back up a significant distance if you encounter a vehicle from the opposite direction. Widening is scheduled for Monday.
Grooming: All trails are groomed and conditions are excellent.
Great day for an avalanche class! Thanks to all who participated in making our Backcountry 101 a huge success!
Weather and Snow
24 Hour Snow 0" 72 Hour Snow 0" Season Total Snow 169" Base Depth at Gold Basin 77"
Winds on Pre Laurel Peak WNW 10-15 Temp 8
Weather
Look for increasing clouds today as a closed low-pressure system slides into the Great Basin. Winds will shift to southwesterly as the axis of the system moves into Utah mid-day and then turn southerly as the low digs into Arizona on Sunday night and Monday morning. We'll see a 50/50 chance for snow tonight with a couple inches possible. Monday should see cloudy skies in the morning turning to partly sunny later in the day. A mostly dry, northwest flow will be in place for the coming week with a weak embedded short wave bringing clouds on Tuesday night into Wednesday.
General Conditions
Wind and sun the past couple of days have affected the snow surface in some, but not all, exposed locations, and good settled powder conditions remain abundant. Strong SE - E winds on Friday formed fresh slabs of wind drifted snow on all aspects above treeline as well as in some exposed terrain below. NW winds yesterday continued to blow and drift snow in the high country. By today, most wind slabs will have gained a lot of strength but some may still be sensitive to the weight of a skier or rider. Be cautious in approaching steep slopes that have a smooth, rounded appearance or that are "fat" with recent deposits of wind drifted snow. Choose an escape route, try to get a feel for how the snow is behaving before committing to steeper lines.
The November persistent weak layer (PWL) has just been given a significant load test and in our travels on Thursday we found an area where it failed producing a large, long running, un-survivable avalanche. The odds of triggering this kind of avalanche with the weight of a skier or rider are growing increasingly unlikely, however it still may be possible in outlying areas that have a combination of radical terrain and a thinner, weaker snowpack.
For more snowpack information see a complete list of observations here.
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.
Recent Avalanches
In our travels on Thursday we encountered a large avalanche (detailed in the video above) that failed on the November persistent weak layer sometime during this week's storm cycle.
This avalanche occurred on a steep northerly aspect near treeline in an area that has a thinner, weaker underlying snowpack. The starting zone is susceptible to heavy windloading and the terrain is fairly extreme with a steep convexity at the fracture line.
For a complete list of avalanches see the La Sal Avalanche database here.
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Avalanche Problem #1
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
With plenty of snow available for transport, moderate to strong ESE winds on Friday created fresh slabs of wind drifted snow on the leeward sides of ridge crests and terrain features in wind exposed terrain. Northerly winds yesterday continued to blow and drift snow. Most of the drifting has occurred above treeline, but in our travels yesterday, I also observed some drifting in exposed terrain at lower elevations. Most of these drifts will have gained strength today but some may still be sensitive to the weight of a skier or rider. Recognizable by their smooth, rounded appearance, wind drifts may also sound hollow underneath. Approach steep slopes that have this appearance with caution. Choose an escape route, and try to get a feel for how the snow is behaving before committing to steeper lines.
Older drifts that formed mid-last week will be covered up now, and though they have mostly stabilized, steep slopes that have a smooth, rounded, "fat" appearance should be approached with caution, especially slopes that have steep convexities. In very isolated, thinner snowpack areas, an avalanche triggered in the wind drifted snow could to step down to the November PWL causing a deeper and much more dangerous avalanche.
Avalanche Problem #2
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
If you've been following along, you know that The November persistent weak layer (PWL) has been gaining strength and is deeply buried in most areas. Prior to this storm event, the last round of avalanches failing on this weak layer was during the New Years storm cycle. Before putting this problem to bed so to speak, we wanted to see what this latest load of heavy snowfall would do, and lo and behold, it produced a very large avalanche. Avalanche activity was not widespread, and stability tests indicate that the odds of a skier or rider triggering this kind of avalanche are unlikely, however it still may be possible in outlying areas that have a combination of radical terrain and a thinner, weaker snowpack, particularly on slopes facing the north side of the compass.
Photo illustrates what is now a thin weak layer of faceted snow about a meter below the surface. The weak layer used to be much thicker, and then snow beneath was much weaker and looser. Time, and compressive weight from above has helped to strengthen this layer, but it was still capable of producing an avalanche under the stress of a rapid, heavy load.
In most areas, the weak layer is deeply buried, and hence very difficult, if not impossible to affect by the weight of a skier or rider. The trick then, is to avoid areas where the snowpack is thinner such as in wind exposed terrain, along slope margins and near rocky outcrops, and in areas of very steep, rocky, radical terrain.
Additional Information
What's happening to the persistent weak layer? Salt Lake forecasters Nikki Champion and Dave Kelly discuss what has happened to it in the Wasatc Mountains. Down here in the La Sals we are trending toward this scenario.
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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