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Logan area Avalanche advisory

 

A special avalanche advisory has been issued for the mountains of northern Utah for the weekend.  A weak snowpack and record breaking temperatures have created a Considerable to High avalanche danger, with both human triggered and natural avalanches probable.  These dangerous avalanches have the potential to be very large and long running.  Steep slopes and the areas below steep slopes should be avoided.  People without excellent backcountry and route finding skills should stay out of the backcountry this weekend.

Saturday March 17, 2007:

Hello and happy Saint Patrickís Day, this is Toby Weed of the Forest Service Utah Avalanche Center with your Logan Area backcountry avalanche and mountain weather advisory.  Itís Saturday March 17th, and itís 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:

Other than recommending a color choice for your shorts, Iím afraid Iíll have to leave any mention of green out of todays advisory.  My calendar tells me itís still winter, but temperatures will be mid-summer-like in the mountains today.  In fact with the solar-oven-effect in full play, it will actually be much hotter in some places than it generally gets in July.  Record-setting heat is wrecking havoc on our sorry snowpack, and lower elevation roads and trails are completely melted out.  Across the region last night overnight temperatures stayed well above freezing at all elevations.  Any surface refreeze will by superficial and supportable snow conditions wonít last long this morning.  Under clear skies, temperatures on the highest peaks will reach the mid-fifties by mid-afternoon, and you could probably cook the corn-beef and cabbage in the intense reflected heat of a sunny bowl.

Avalanche Conditions:

Wet loose and slab avalanches were quite common across the region earlier this week.  A couple nights with below freezing temperatures settled down the natural activity in the last couple days, but things will probably get moving again in todayís heat.  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. This week Iíve observed fresh 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. Yesterday, I noticed a fairly large wet slab release off the rocks above Sherwood Hills in Wellsville Canyon, which had to have happened since Monday.

With continued exceptionally hot weather forecast through the weekend, wet avalanches will be a serious problem in the backcountry. Today the superficially frozen surface snow will get mushy and dangerous much earlier than yesterday, and tomorrow it will ďgo offĒ even earlier.  The warmth this weekend will continue to deform cornices, and some are likely to fail, potentially triggering avalanches on steep slushy slopes below.  Once the snow gets saturated by heat-induced melt, wet avalanches will become likely on steep slopes at all elevations.  Persistent slab avalanches are very possible on steep upper elevation slopes, and the problem is most certainly worsened by the continuing heat-wave.  Heat induced creep and glide could easily cause large natural slab avalanches, like the recent huge natural avalanches in the Wasatch. Slab softening (also due to the heat) will make previously thick hard slabs more susceptible to human triggering.  Slopes that easily may have supported your weight yesterday may be sensitive to the weight of a snowshoe hare today.

Bottom Line:

Thereís a CONSIDERABLE danger today, and wet avalanches are probable on steep slopes with saturated snow at all elevations in the backcountry.  The danger will rise with heating during the day and may increase to HIGH in some areas. Some avalanches might step down into buried weak layers and be large, destructive and deadly. Some avalanches could be fairly long-running, and are likely to descend well below the existing snow-line into dry lower elevation terrain. Avoid and stay out from under obvious and historic avalanche paths and all saturated slopes steeper than about 35 degrees.

Mountain Weather:

A strong high pressure system will be over the region through the weekend, and unseasonably hot temperatures will continue.  An approaching Pacific storm will bring increasing clouds and warm prefrontal wind to the region on Monday.  We could see a little lightning and gusty conditions on Tuesday, and a bit of Snowfall is likely Tuesday night into Wednesday.

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...

  I will update this advisory again on Sunday 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.