Wasatch-Cache National Forest  In partnership with:  Utah State Parks and Recreation, Friends of the Utah Avalanche Center-Logan, and Utah State University College of Natural Resources.

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Logan area Avalanche advisory

Thursday February 15, 2007:

  Hello and good morning, this is Toby Weed of the Forest Service Utah Avalanche Center with your Logan Area backcountry avalanche and mountain weather advisory.  It’s Thursday  February 15th, and it’s 7:00 in the morning.  This advisory is brought to you in part by the Friends of the Utah Avalanche Center in Logan with help from Black Diamond.

Bottom Line:

With heavy snowfall overnight, warming temperatures, and strong westerly winds, there'll be a CONSIDERABLE avalanche danger in the backcountry on Friday.  Avalanches are most likely above about 8000' in elevation and on slopes facing northwest through southeast, but you are likely to trigger dangerous wind slab avalanches on all  slopes steeper than about 35 degrees with emergent deposits of drifted snow.  If the overnight weather forecast verifies, especially if strong winds continue into Friday, the danger at upper elevations on steep slopes with significant new deposits of wind-blown snow could easily rise to HIGH during the day.  That means that both natural and triggered avalanches could become likely, and you should avoid travel in avalanche-prone terrain.

Mountain Weather:

The National Weather Service has issued a Snow Advisory for the mountains of Northern Utah and a Winter Storm Warning for those in far Southeast Idaho until 11:00 AM on Friday.  A foot of accumulation or more, containing 1 to 1.5 inches of water is possible in areas of the Bear River Range favored by a westerly flow (like Tony Grove and Franklin Basin).  In addition to heavy snowfall, west winds will intensify overnight and continue to be very strong on Friday. Hourly average wind speeds on exposed ridges are forecast to be in the  40 mph range.  To top it all off, and to potentially make avalanche conditions even more acute, mountain temperatures increased significantly during the day today and will again be fairly mild on Friday.   A short-lived high pressure system will build over the region for the weekend bringing a break in precipitation and potentially very warm daytime temperatures.  The next wave of moist Pacific weather, (and more snow?) will arrive around Sunday night.

Current Conditions:

It will definitely be a powder day on Friday, but dangerous avalanche conditions in the backcountry will keep me far away from the steep and deep.  It could be a good day to ride the lifts at the Beav. or head up for a ride in the Sinks.  At least you should stay in safer, lower angled terrain and off of and out from under the big hills.  The Tony Grove Snotel picked up 6/10s of an inch of water in the last 48 hours and up to 1.5 additional inches are forecast by mid-morning on Friday.  West winds are likely to intensify overnight and be strong on Friday, and with all the nice soft powder around, blowing and drifting snow will certainly be an issue in the backcountry.

Avalanche Conditions:

 While most of the rest of Northern Utah experienced a fairly significant avalanche cycle resulting from last weekend's windy storm, the Bear River Range received substantially less snow and was hauntingly quiet.  We're plagued by extremely weak snow just like everyone else, but a slab heavy enough to break into the weaknesses under bridging crusts hasn't yet formed.  Tonight's storm might just be enough to turn the tables, and I'm planning on playing a very safe game in the backcountry this weekend.

Wind slabs will cause the most obvious avalanche danger.  Extensive drifting will occur overnight along exposed ridges, and significant slabs will form in lee-slope starting zones.  Vertical cross-loading will  build drifts along exposed sub-ridges and around terrain features like gully walls, tree bands and rock out-croppings.  Whenever we get a combination of heavy snowfall and strong or sustained winds, large loads of wind-blown snow can be rapidly deposited over vast areas and often well off of exposed ridge-lines.  In some normally sheltered areas, the sheer weight of the new snow overloading existing very weak sugary layers could be enough to cause soft slab or storm snow avalanches.  Existing old hard slabs might become active with the substantial new load and could release on any of a number of buried persistent weaknesses.  I'm always wary when temperatures warm up during a storm, as they are now.  This just makes the new snow stick better to itself and adds significantly to the formation of heavy, cohesive slabs.  In addition to other obvious clues to instability like natural avalanches, whoompfing noises, and shooting cracks, I'll be on the lookout for inverted new snow, with heavier wetter snow accumulated on top of lighter fluff.  The same kind of upside-down snowfall that makes for difficult traveling often can also point toward serious avalanche conditions.

 General Information:

Check out the recently-released Media Page, which shows the current and forecast danger for our coverage areas across the state.

The Utah Avalanche Center compiled a good collection of photos from this week's avalanche cycle in the Wasatch Range.  Click here to visit this season's photos.  Check out photos of avalanches in the Logan Area on our images page.

Please send me an e-mail at [email protected] or leave me a message at 755-3638 if you see evidence of recent avalanche activity or avalanches in the backcountry.  The information you provide may save lives...

 This advisory will expire on Friday night. I will update it again 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.