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Logan area Avalanche Advisory


7:30, Sunday April 13, 2008

Hello and good morning, this is Toby Weed of the Utah Avalanche Center with your Logan Area backcountry avalanche and mountain weather advisory.  It’s Saturday April 19th, at 7:30 in the morning.  Today’s advisory is brought to you in part by the Friends of the Utah Avalanche Center in Logan with help from Avalanchetools.com.  

We’ve issued a Special Avalanche Advisory due to the rapid warm-up and increasing natural wet avalanche activity in the mountains.  We urge backcountry travelers to avoid and stay out from under steep slopes with saturated snow and large ridge-top cornices, especially in the heat of the day…..

Current Conditions:

Overnight temperatures stayed above or near freezing at most mountain stations and the refreeze of yesterday’s saturated snow is marginal.  Surface crusts that formed overnight will quickly loose strength after exposure to the powerful high angle spring sun and warmth today.  We found nice settled powder conditions on upper elevation north facing slopes and reasonably solid and supportable snow on mid-elevation south facing slopes yesterday, but I don’t expect it will stay that way as today’s heat will surely accelerate the melt-down.  It is currently 34 degrees at The Tony Grove Snotel, and with 95 inches of total snow, the station sits at 109% of average water content for the date.  

Avalanche Conditions: 

We’ve received numerous reports of natural and triggered wet avalanches involving fresh snow from the past week.  The problem is more pronounced in the Central Wasatch Mountains because more snow fell there last week, but we’ve observed fairly widespread natural wet activity locally as well.  On Friday, in the Mount Naomi Wilderness we triggered a few soft slabs on steep slopes where fresh snow was cross-loaded into and around west and north facing gullies at upper elevations, (new photos).   Wind slabs around a foot deep could still be active on very steep north facing slopes at upper elevations today, but with the hottest day yet of the season here now, wet avalanches are the obvious concern…Along with many new loose wet point-release type avalanches that I observed yesterday, I also noticed at least one fresh wet or persistent slab release on an upper elevation northeast facing slope on the ramparts of Mount Gog.

Solar warming from the intense, high angled spring sun and the warmest mountain air temperatures of the year will cause last week’s new snow to quickly become saturated and prone to wet avalanching.  Upper elevation snow that’s stayed dry up until now is starting to melt, and we’ve seen an increase in natural wet avalanche activity as a result.   This weekend you should avoid and stay out from under steep slopes with saturated snow, especially in the heat of midday.  The most obvious red flag here is recent avalanches on similar slopes, but if you trigger sluffs or developing roller balls, or if you start sinking into moist snow, its time to be back home doing yard work.

Large cornices could be sensitive to your weight today and may break further back than you expect, and they’ll start to sag and deform with the heating.  Some are likely to spontaneously collapse with the heat, a few catastrophically.   It is always a good idea in the spring to stay off of and out from under these monsters.


Bottom Line: 

  There’s a MODERATE danger in the backcountry, and you could trigger wet or persistent slab avalanches on steep slopes in exposed upper elevation terrain.  Very warm mountain temperatures will cause the danger of wet avalanches to rise to CONSIDERABLE on steep slopes with saturated snow at mid and upper elevations.  Triggered wet avalanches are probable and naturals are possible on slopes with recent new snow.   Avoid and stay out from under steep slopes with saturated snow and large ridge-top cornices, especially in the heat of the day…..

Mountain Weather: A high pressure ridge will be over the region today and we can expect even warmer temperatures in the mountains.  Highs at 8800 feet will approach 50 degrees today. Monday looks like the warmest day in the series, but with a breeze and high clouds moving in ahead of a potentially convective cold front scheduled for Tuesday.

General Announcements: 

                  Even though you can ride anywhere these days, you should be sure to keep motor vehicles in terrain that’s open. Riding on public lands designated as “closed to motor vehicles” or as a National Forest Wilderness only jeopardizes the future of our sport, and fines for motor vehicle trespass have been recently increased.  (MV wilderness trespass photos)

Check out the images page for photos of some of this season’s 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.