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Logan area Avalanche advisory

Thursday March 15, 2007:

Hello, this is Toby Weed of the Forest Service Utah Avalanche Center with your Logan Area backcountry avalanche and mountain weather advisory.  Itís Thursday March 15th, and itís 9:30 in the evening.  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 sopping snow refroze nicely in the Central Bear River Range last night, and we found nice solid corn snow conditions today on upper elevation sunny slopes.  East facing slopes stayed nice until around noon and southwest facing slopes were still good when we left at around 2:00.  I expect temperatures to drop below freezing again tonight for a few hours, and you might find decent, though short-lived, spring-like snow conditions in a lot of areas on Friday morning.  You might want to take advantage because the weekend looks to be a real cooker, with at best, superficial nighttime surface refreezes and very hot long days in the mountains.  Under clear skies, temperatures on the highest peaks will reach the mid-fifties by mid-afternoon, and after tonight many areas will not see below freezing temperatures well into next week.

Avalanche Conditions:

Wet loose and slab avalanches were quite common across the region this week.  Most steep sunny slopes in the region show signs of recent wet avalanche activity, and some of this has been fairly significant.  As far as I can tell, weíve so far escaped the huge warmth related avalanche cycle which has been producing very impressive natural and human triggered slides in the Central Wasatch for the past several days.  A ski patroller checking avalanche conditions on a steep slope within the Solitude Ski Resort triggered a deep and dangerous slab avalanche this afternoon.  Thankfully, he escaped a nasty ride alive though seriously injured.  Iíve noticed fresh-looking natural slab avalanches caused by the rapid heat-up in the Mount Naomi and Wellsville Wildernesses, Steep Hollow, and in the Upper South Fork of Boss Canyon near the Idaho State-line.

With continued exceptionally hot weather forecast through the weekend, wet avalanches will become a serious problem in the backcountry.  With a reasonable refreeze likely tonight, your best bet for the weekend will be an early Friday start.  Itís always a good idea in these conditions to get the pre-dawn start and be heading home by early afternoon.  If we donít get a freeze for a few consecutive nights, as is forecast for the weekend, the superficially frozen surface snow gets mushy and dangerous earlier and earlier in the days.  The warmth this weekend will continue to deform cornices, and some could fail, potentially triggering avalanches on slopes below.  Wet avalanches are possible on steep slopes at all elevations with saturated surface snow.  Persistent dryer slab avalanches are also possible on some steep upper elevation slopes, and the problem is worsened by the continuing heat-wave.  Heat induced creep and glide may be the cause the recent huge natural avalanches in the Wasatch, while slab softening (also due to the heat) may be partly to blame for the numerous recent human triggered avalanches.  Dangerous persistent slab avalanches are most likely in areas with shallow overall snowpack, facing west through southeast, and above around 8000í in elevation. In some areas, a wet avalanche overrunning a steep slope with persistent buried weak layers could cause a deeper, potentially deadly hard slab release.

Bottom Line:

There will be a MODERATE danger in the backcountry on Friday morning, with triggered avalanches possible on some steep slopes.  The danger will rise with heating during the day and will reach CONSIDERABLE on numerous steep slopes by mid-afternoon.  Wet loose and slab avalanches will be probable on many saturated slopes at all elevations in the backcountry.  Some avalanches might step down into buried weak layers and be large, destructive and deadly. Avoid and stay out from under slopes steeper than about 35 degrees, especially those with saturated surface snow. 

Mountain Weather:

A strong high pressure system will set up over the region for the weekend, and unseasonably hot temperatures will continue.  A progressively more productive looking storm will bring increasing clouds and warm prefrontal wind to the region on Tuesday.  Snowfall is likely Tuesday night and Wednesday, and with any luck weíll see some relief from the heat wave.

General Information:

Check out photos of last week's 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 also recommend the recently-released Media Page, which shows the forecast danger for our coverage areas across the state.

Please e-mail me at [email protected] or leave me a message at 755-3638 if you see or trigger avalanches in the backcountry.  The information you provide may save lives...

This advisory will expire on Friday evening.  I will update it again on Saturday morning.

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.