Forecast for the Ogden Area Mountains

Evelyn Lees
Issued by Evelyn Lees for
Sunday, February 3, 2013

The avalanche danger is an overall MODERATE, with area of CONSIDERABLE danger on steep, north through easterly facing slopes, for triggering a deep, hard slab avalanche. Large human triggered avalanches are possible in isolated areas. Particularly avoid any steep slope with recent wind drifting. It’s a low probability of triggering a slide, but high consequences, including death, if you do. The danger of wet loose slides will rise to MODERATE with day time heating on all steep sunny slopes and the low to mid elevation shady slopes..

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Moderate
Considerable
High
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Weather and Snow

Scattered to overcast thin clouds helped keep temperatures warmer overnight – most readings are in the mid to upper 20s this morning. The westerly winds are very light, boarding on calm, from Ogden to Provo. Good dense dry snow does exist on shady slopes amidst the rime, wind and sun damage.

Recent Avalanches

Ogden area mountains: Bruce visited and is continuing to update the Monte Cristo accident report. In addition, he noted a large, natural hard slab avalanche, also southeast facing, from Trappers Loop, timing unknown.

SLC/Park City area mountains: A huge 4’ deep hard slab avalanche was triggered by the third person off of peak 9924 into Mill B, north facing, that ran 2000’ vertical. The person was stopped by a tree after a short distance, probably preventing a lethal ride. Also, in a previously skied chute in upper Days Fork, a hard slab broke out about 2’ deep and 50’ wide above a skier, who managed to escape. There is evidence of a natural cycle in parts of Alexander Basin from the storm.

Provo area mountains: in Woolly Hole, a fairly large soft slab triggered remotely from about 400’ away, northeast facing slope. On east facing Box Elder, a small deep slide triggered remotely from a cornice drop, on Ants Knoll, a 200' x 2' deep snowmobile triggered slide. A natural cycle occurred on upper east facing Cascade Thurs night or Friday.

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Avalanche Problem #1
New Snow
Type
Location
Likelihood
Size
Description

The Red Flags of avalanches, collapsing and poor stability tests remain. Many of yesterday’s avalanches were remotely triggered from a distance; one was on a previously skied slope, another was triggered by the 3rd person. These are hallmark characteristics of the nasty, tricky faceted weak layer we are dealing with. It is really complicated out there – many slopes are stable, but if it goes, it can go deep and big.

The steep, shady slopes, especially with wind drifted snow, are where there are weak buried facets, and are the places for triggering a slide. Slopes and drainages with a shallower snow pack before the last storm more suspect. Many times there is a hard wind slab involved, possibly buried beneath the powder. Collapsing is an indication of an unstable snowpack, and you need to stay off of and out from under steep slopes.

Other slopes that have been collapsing are more the more heavily loaded places where the graupel has rolled down and pooled – below cliff bands and where steep slopes flatten out. This layering can be on slopes of any aspect – the west facing aprons in Cardiff Fork were collapsing yesterday.

Avalanche Problem #2
Wet Snow
Type
Location
Likelihood
Size
Description

Another warm day, with decreasing clouds and very light winds, will heat the snow on the steep sunny slopes. As the snow become damp, it will become increasingly easy to trigger wet loose sluffs in steep terrain, particularly near cliff bands. Snow on the low and mid elevation shady slopes may heat, too, depending on the cloud cover.

Additional Information

High pressure will remain centered just to the west of the area through mid-week. This morning’s high thin clouds will disappear, transitioning to most clear skies by mid-day. 10,000’ temperatures will remain in the mid to upper 20s, 8000’ temperatures will warm into the mid-30s today. The southwesterly winds will remain very light, with only the highest peaks occasionally gusting into the 20s.

Slightly stronger westerly flow around Wednesday, with more clouds and a slight cool down. Next chance for snow looks to be about Friday.