Forecast for the Salt Lake Area Mountains

Mark Staples
Issued by Mark Staples for
Wednesday, November 30, 2022
The snowpack gave clear warning signs yesterday in the form of human-triggered avalanches and collapsing and shooting cracks. The biggest and most dangerous avalanches will be at upper elevations on slopes with wind drifted snow where the avalanche danger will be CONSIDERABLE today. Most of these wind loaded slopes have a cohesive slab of wind drifted snow resting on a persistent weak layer.
Mid and low elevations have a MODERATE danger with heightened avalanche conditions on any slope loaded by winds which should be increasing from the southwest today. Even on non-wind loaded slopes, you can trigger a soft slab avalanche breaking on a persistent weak layer.
These are serious conditions that will become much more dangerous with strong winds and more snowfall over the next few days. The danger ratings alone don't tell the full story.
Low
Moderate
Considerable
High
Extreme
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Weather and Snow
The storm ended yesterday around 9 a.m. with total snowfall amounts 10-18 inches of snow (0.64-1.06 inches of water).
This morning, temperatures are hovering mostly in the upper teens F. Winds have increased a bit since yesterday and are blowing 12-24 mph with gusts up to 33 mph from the west and southwest.
Today will be noticeably warmer than yesterday with temperatures rising into the mid 20s F. Lower elevations will have temperatures near freezing. Winds from the southwest will increase this afternoon averaging 20-30 mph with gust at upper elevations reaching 55 mph.
Snow conditions and coverage are fantastic, especially for Nov 30th. Total snow depths are 3-5 feet above 9000 ft.

Tomorrow will have even stronger winds from the southwest ahead of another storm with snowfall beginning late tomorrow afternoon. It will be a fast moving storm with a lot of water that could bring similar snow and water amounts as yesterday's storm.

From Ogden to the central Wasatch to the Provo mountains, we have received several excellent observations. You can find them HERE. Please keep these reports coming.
Recent Avalanches
There were a handful of observations and avalanches from yesterday as the snowpack gave clear warning signs. Avalanches were generally 12-16 inches deep. None of the reported slides were breaking over very wide areas...YET. That may change over the next few days with strong southwest winds and more snowfall coming.
Photo (S. Thackeray) of a slide yesterday in Mineral Fork at 7,800 ft on a northeast facing slope.
Photo (M. White) of an avalanche triggered in Cardiff Fork on a NW facing slope at 8700 ft (17 inches deep and 160 feet wide). More photos and a description here.
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Avalanche Problem #1
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
Winds will be increasing from the southwest today and transporting snow to the leeward (or downwind) side of ridges, gullies, and other terrain features. Cohesive slabs of this wind drifted snow will create the largest and most dangerous avalanches today that should be easy to trigger. On most slopes these wind slabs will be resting on a weak layer of faceted snow that formed during two weeks of dry weather in the middle of November.
These wind slabs will cover wide areas, and the most likely places to find them will be upper elevations where southwest winds will be the strongest. However, look for them at mid and low elevations as well. Avoid these slopes.
Avalanche Problem #2
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
Dry and cold weather during the middle two weeks of November created a persistent weak layer (PWL) of facets on nearly all slopes. This weak layer was capped by an inch or two of snow over the weekend, and it was then loaded by yesterday's storm which created a soft slab of snow on top of it.
On slopes that received sunshine during a brief warmup around Thanksgiving, there is a fragile ice crust on top of this persistent weak layer of facets. This ice crust doesn't really change the situation except on steep slopes facing due south where the ice crust is much thicker and stronger.
As mentioned above, the biggest and most dangerous avalanches will be on wind loaded slopes because the slab of snow on top of this weak layer is more cohesive and thicker. I still expect avalanches will be triggered on this layer on slopes not loaded by winds, but these slides will be smaller and not break over such wide areas. Warmer temperatures today should help consolidate the new snow, helping it become a more cohesive slab.
General Announcements

This information does not apply to developed ski areas or highways where avalanche control is normally done. 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.