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Forecast for the Salt Lake Area Mountains

Evelyn Lees
Issued by Evelyn Lees on
Friday morning, December 7, 2012

The Avalanche Danger is MODERATE today at the upper elevations. Avoid any steep slope with fresh drifts of windblown snow, which will be most widespread on northeast through southeasterly facing slopes. In very isolated places, slides could break into a deeper weak layer.

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Weather and Snow

Skies are clear in the mountains this morning, but overnight we managed to squeeze a trace to an inch of snow out of the moist, northwesterly flow. Temperatures are in the teens and 20s and the west to northwesterly winds gusty and increasing. While most stations have speeds of less than 15 mph, with gusts in the 20’s, the high peaks are averaging 25 to 35 mph averages, with gusts to 50.

I got out for a few turns yesterday afternoon, and had no complaints with the dense powder at the upper elevations – supportable for snowshoers, snowmobilers and turning. Today, search for wind sheltered slopes, and for everyone, rocks remain issue, coupled with icy slopes at the lower elevations.

Recent Avalanches

No avalanches were reported from the backcountry yesterday, though the Cottonwood resorts managed to pry out 2 slides with explosives or cornice drops (upper elevation, northerly facing slopes). Explosive control work in the Ogden area mountains had no results. In the Provo area mountains, a large natural sluff on east facing Robert’s Horn was noted, that probably occurred two days ago.

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Avalanche Problem #1
Persistent Weak Layer
Type
Location
Likelihood
Size
Description

Along the high ridge lines, the strong northwesterly winds will find some dense snow to drift, and these new wind slabs may be poorly bonded to the old snow on some slopes. Drifts may be right along the ridge lines, or cross loaded off the ridges on mid slope break overs, gully walls or around sub ridges.

Avalanche Problem #2
New Snow
Type
Location
Likelihood
Size
Description

It’s quite the complex snowpack that is developing – a strong rain crust at the low to mid elevations, transitioning to very variable thinner crusts and crust/facet sandwiches at the upper mid to upper elevations, and finally a cold winter snow pack at the highest elevations. Currently, on most slopes there isn’t enough of a load on the various weak layers to be a problem. The Saturday storm looks to be less than ½” of water, so currently, the most likely cause of any overloading of these weak layers would be from the winds.

Check out all of yesterday’s great observations in All the Good Stuff.

Additional Information

The moist northwesterly flow will persist today and tonight, with partly cloudy skies and increasingly strong winds at the high elevations. Exposed ridges will see speeds ramping up into the 30-40 mph range today through tonight, with gusts in the 50s. Off the ridge lines, average wind speeds should remain below 15 mph, with gusts to 30 mph. Cooler temperatures today, with 8,000’ highs in the low to mid 20s, and 10,000’ temperatures remaining in the teens.

A sharp arctic trough will move into the area beginning Saturday morning, bringing 4 to 9” of low density powder and continued strong winds. Temperatures will bottom out on Sunday, in the single digits. Several more small storms are in the forecast for next week

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