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Logan area Avalanche Advisory

Monday December 31, 2007

Hello and Happy New Year, this is Toby Weed of the Utah Avalanche Center with your Logan Area backcountry avalanche and mountain weather advisory.  Itís Monday December 31st, and itís 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 Backcountry Access.

†††††††††††† Current Conditions:

The Central Bear River Mountains picked up gobs of snow over the weekend, with the Tony Grove Snotel reporting 2.7 inches snow water equivalent in the last 72 hrs. Youíll find deep snow and seriously drifted conditions in the backcountry today, and you should continue to avoid steep wind drifted slopes and avalanche paths or run-out zones. Yesterday we found the new, wind effected snow inverted or heavier on top, which makes for difficult trail breaking conditions.At mid and lower elevations the snow is bottomless, and youíll have problems getting your sled stuck if you venture off the beaten tracks. Itís currently -1 degrees with a light north wind at the CSI weather station on Logan Peak. Iím reading 7 degrees and at least 6 new inches of accumulation with 1.1 inches of equivalent water in the last 24 hrs at the Tony Grove Snotel site, and thereís 62 inches of total snow on the ground.

††††††††††† Avalanche Conditions:

Yesterday was an active day in the Central Wasatch, with wind slab avalanches keeping snow safety personnel busy all day.Natural and human triggered avalanches were common during periods of heavy precipitation rates and strong winds.Although I didnít see any avalanches and none were reported in the Logan Area yesterday, that doesnít mean they didnít occur.The storm kept suspect slopes obscured all day and thankfully, common sense and the deep inverted snow kept most of you out of danger in avalanche terrain.We are likely to see evidence of natural avalanching from the weekend storm with better visibility today.††† I suspect instabilities will settle out fairly quickly and the majority of natural avalanches have already done their thing.The danger lies on slopes that didnít avalanche during the storm and are now hanging in a delicate balanceÖ.

Strong winds made it down into lower elevations yesterday and we experienced lots of wind drifting at all elevations. Cornices hanging over northeast and east facing slopes grew significantly during the last couple days as winds deposited loads stiffened snow on the slopes below.†† In some areas, wind slabs likely formed on weak sugary surface snow called near surface facets, and these are likely to still be sensitive to your weight today.Watch for the effects of cross-loading around terrain features like sub-ridges, rock outcroppings, and gullies. I noticed new snow drifts at least 3 feet deep at 8000í yesterday, and I suspect significantly deeper wind slabs in exposed upper elevation terrain.Last nightís fresh powder may obscure normally obvious recent drifts or slabs, so donít only trust your eyes.††† Pay attention to obvious signs of instability like recent avalanches on similar slopes, collapsing or woomphing noises, cracking, or hollow sounding snow, and be willing to reassess your route.

Iím still concerned by the possibility of deeper slab avalanches in some areas, which will be quite destructive and potentially deadly.Suspect weak layers are made up of snow that was on or below the snow surface in early December.The old underlying snow is faceted or sugary and weak, and instabilities caused by overloading slab layers are notoriously slow to heal.In most cases, your weight alone probably wonít be enough to trigger one of these deep dwelling monsters, but you might awaken one from a thin spot on the slab. Watch out for steep rocky areas and slopes with generally shallow snowcover. The weight of a few snowmobiles at one time on a slope or an overrunning smaller wind slab avalanche might also do the trick.

†††††††††††††† Bottom Line:

Today thereís a CONSIDERABLE avalanche danger on many steep slopes at mid and upper elevations in the backcountry.You are likely to trigger dangerous avalanches if you venture onto slopes with significant deposits of new or wind drifted snow steeper than about 35 degrees.Some natural avalanches are also possible in areas exposed to drifting from northerly winds.Avalanche training and experience are essential for safe backcountry travel.

Mountain Weather:

Looks like a cold night to celebrate the New Year, with forecast temperatures well below zero.A ridge of high pressure will build into the region today and strengthen on Tuesday, bringing significant warming to the mountains and hazy inversion conditions to Cache Valley.A series of Pacific Storms on tap for later in the week will drive the haze out of the valleys and bring a threat for more snowfall to the mountains.

General Information:

I will give a free avalanche awareness talk for teens and their families at the Stokes Nature Center in Logan Canyon at 9:00 on Saturday January 5th.

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.