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Logan area Avalanche Advisory

7:30, Saturday March 8, 2008

Hello and good morning, this is Toby Weed of the Utah Avalanche Center with your Logan Area backcountry avalanche and mountain weather advisory.  Itís Saturday March 8th, at 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 Avalanchetools.com.

Current Conditions: Northwest winds posted average hourly wind speeds in the mid twenties for several hours overnight, with gusts around 40 mph at the CSI Logan Peak weather station.With plenty of soft, transportable snow about, youíd be forced to assume that a fair amount of drifting must have occurred in exposed upper elevation terrain. A weak Pacific storm crossing the region as I write will produce some snowfall this morning and keep snow showers going through the day. It is snowing lightly in Logan at this time, and the Tony Grove Snotel reports around 3 inches of new snow this morning containing 2/10ths of an inch of water. As one would expect this time of year, the new snow is falling on a wide variety of surface snow conditions in the backcountry, ranging from bomber crusts that might support a tank to almost fluffy, re-crystallized and powdery snow on shady and sheltered slopes at middle and upper elevations. Iím reading 16 degrees on Logan Peak and 19 up a Beaver Mountain.

Avalanche Conditions:††

I have reports of a handful of small triggered wind slab avalanches yesterday at upper elevations in the Central Bear River Range.The sensitive wind slabs on steep east facing slopes were less than a foot deep and ranged from about 10 to nearly 30 feet wide. Without knowing its hard to say what the weak layer was, but Iíve observed lots of frost or surface hoar crystals and small sugary near surface facets in the past couple days, and the slabs or drifts may well have built up on such a surface, (snow photos). Yesterday in the northeast part of the forecast zone, I found somewhat sensitive cornices and my party triggered a couple small audible collapses or whumpfing noises in drifted terrain. Iím still a bit concerned about a graupel layer from the February 25th storm capping a stout sun-crust and now buried by close to two feet of snow on some upper elevation slopes.

There are a number of steep upper elevation slopes and/or slopes exposed to significant wind drifting in the region where you might trigger shallow wind slab avalanches.And, there are probably a few where you might trigger larger and more dangerous hard slabs running on one of a few possible persistent weak layers. The danger is most likely to be found at upper elevations and on slopes facing the eastern third of the compass. Watch for and avoid obvious drifts or wind slabs on slopes steeper than about 35 degrees. Remember that hard wind slabs can be quite tricky, sometimes waiting until you get well out on them before releasing.Clues may include chalky looking or hollow sounding stiff snow, audible collapses, or shooting cracks. A few inches of new snow may now be obscuring obvious signs.

 

Bottom Line:Thereís a MODERATE danger and triggered wind slab avalanches are possible on steep drifted slopes in the backcountry. Youíre most likely to trigger freshly formed or older wind slabs at upper elevations near ridge lines or in fetch areas and on easterly facing slopes exposed to loading from northwest winds. Thereís a LOW danger on most other sheltered slopes. Use good snow assessment and safe travel techniques to minimize your risks in the backcountry today.

Mountain Weather: A weak Pacific storm will bring a little snow to the area this morning, with snow showers lingering through the day.Tomorrow will be partly cloudy, and another weak storm is likely early next weekÖ.

General Announcements:

The Friends of the Utah Avalanche Center in Logan is presenting an Avalanche Fundamentals, Level 1 Class (Certification), starting March 14, with field sessions on the 15th, and 22nd.Please register in advance with the Friends via e-mail or for more information contact [email protected].

Check out the images page for photos of some of this seasonís avalanches.

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.