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Logan area Avalanche Advisory

Saturday January 12, 2008

Hello and good morning, this is Toby Weed of the Utah Avalanche Center with your Logan Area backcountry avalanche and mountain weather advisory.  It’s Saturday January 12th, and it’s about 7:30 in the morning.  This advisory is brought to you in part by the Friends of the Utah Avalanche Center in Logan with help from Simmons Flexi-ski of Providence.

Current Conditions:

Upper elevations in the Central Bear River Range picked up another nice shot of snow yesterday, and there’s more powder in the backcountry than you know what to do with. The Tony Grove Snotel reports 1.1 inches of water equivelent accumulation in the last 24 hrs, and there’s now 80 inches of total snow on the ground. The CSI weather station atop Logan Peak recorded light to moderate northwesterly winds for the last 24 hrs, with hourly averages generrally less than 10 mph. It’s 5 degrees this morning at 9400’ and 25 degrees down here in Logan. Once again we found tedious trail breaking conditions yesterday, and today you might well have issues with getting your sled stuck in deep powder if you get too far off the beaten path.

Avalanche Conditions:

Recent local activity in the backcountry has been confined to new or freshly drifted snow, and I suspect that most of the culprit upper level instabilities have healed. I’m still finding sugary or faceted snow near the ground in many areas, with the worst or weakest in areas with generally shallow snow cover. I’ve noticed and observers report a widespread warm rain-crust from last Saturday everywhere below around 7000’ in elevation. Above that elevation, the solid, plaster-like layer is spottier in nature, easy to find in some areas and non-existent in others. A rime-crust formed on Thursday in the Wasatch Range and may have in the southern part of the forecast area, but I’ve seen no sign of this in the Central Bear River Range.

With only fairly light northwesterly winds recorded in the last 24 hrs on Logan Peak, I wouldn’t expect to see large deposits of wind drifted snow. But, from past experience I can say that northwest winds effect upper elevations in the Central Bear River Range more, and with all this light powder around you are likely to find drifts and a few sensitive wind slabs in exposed upper elevation terrain. Soft cornices may break further back than you expect. Loose dry snow avalanches or sluffs of significant size are also a good bet on steep slopes.

Unfortunately, I still must mention the possibility of dangerous and destructive deep slab avalanches. You can find sugary or faceted snow near the ground in many areas. It appears in many areas that this is pressed into the terrain, (bushes and rocks) by the weight of the overlaying snow, and the slab is well anchored. At upper elevations and areas with a lot of snow, the slab on top of the weak snow is so thick that your weight probably isn’t enough to trigger an avalanche. The suspect facets are effectively bridged by the slab. But there are probably some slopes in the region where the deep slab is not well anchored to the underlying smooth terrain and where it is thin enough for the instability to be activated by the weight of your sled and yourself. Possible trigger spots include rocky or generally shallow areas, like cliffy lower elevation areas or upper elevation slopes scoured by previous winds. Overrunning wind slab avalanches or cornice falls might trigger a deeper release, leading to a much larger avalanche.

Bottom Line:

There’s a MODERATE danger and you could trigger wind slab or loose snow avalanches at any elevation on slopes steeper than about 35 degrees in the backcountry. Although less probable, deadly triggered deep slab avalanches are possible on slopes with existing weak snow near the ground, mainly in exposed upper elevation terrain. Use good snow assessment and safe travel techniques to minimize your risks.

Mountain Weather:

A high pressure system is beginning to build over the region today and will strengthen over the weekend. A rapidly weakening storm will push some cloudiness and perhaps a little snowfall through the area tonight, but sunny conditions in the mountains and haze in the valleys are on tap for Sunday and Monday. Another weak storm may shoulder its way through the high on around Tuesday, but most indications point toward the development of a somewhat sustained dry weather pattern…

General Information:

Check out photos of avalanches in the Logan Area on our images page.

Go to the Avalanche Encyclopedia if you have any questions about terms I use in the advisory

I'm very interested to know what you're seeing out there.  Please e-mail observations to me at [email protected] or leave me a message at 755-3638, especially if you see or trigger an avalanche in the backcountry. We keep all observations confidential.

This advisory will expire in 24 hours from the posting time.

The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content.  This advisory describes general avalanche conditions and local variations always occur.