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Logan area Avalanche Advisory

7:30, Sunday February 24, 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 Sunday February 24th, at 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 Import Auto.

Current Conditions:  A strong winter storm is upon us and the National Weather Service has sustained a Winter Storm Warning for the mountains around Logan through tomorrow evening.  A wicked south wind picked up overnight, and this morning the Campbell Scientific weather station on Logan Peak reports winds from the south-southwest averaging in the mid forties with a gust as high as 66 mph, and its 22 degrees at 9400’.  It got pretty warm under the greenhouse effect yesterday and the skiff of new snow at mid and low elevations was essentially absorbed into the existing pack.  At higher elevations, a few inches of new snow caps a wide variety of surface conditions including sun and wind crusts in exposed terrain and shallow, frosty, and reconstituted “loud powder” in sheltered shady areas.  The Tony Grove Snotel reports one tenth of an inch of water in the last 6 hrs and 4/10ths in the last 48.  I’m reading 83 inches total snow and bit over 100% of average water content for the date.

  Avalanche Conditions:  

It was an other active day in the Central Wasatch backcountry yesterday with smallish but long-running triggered new snow avalanches running far and fast on solid or crusty bed surfaces (Wasatch action)  No recent avalanche activity has been reported or observed in the Logan Area since last weekend, but the last windy storm on Valentine’s Day caused some fairly large and widespread natural wind slab avalanches. 

Although I suspect that yesterday’s heat destroyed the frost crystals and sugary snow on many slopes especially at lower elevations, this weekend’s light snow fell with little or no wind, and in some areas it now may be nicely preserving weak layers that formed on or near the snow surface during the recent high pressure. (snow photos)

Today, with high winds and heavy snowfall, freshly formed and forming wind slabs in exposed terrain will present a significant danger.  Strong southerly winds will shift around from the west and then northwest and new snow will be drifted onto steep slopes and into lee slope starting zones.  Cross-loading could deposit significant slabs along sub-ridges and in and around terrain features like gullies or cliff bands.  Wind slab avalanches could run fast and far today on existing hard bed surfaces.

Sluffing and soft slab avalanches will also become probable during periods of heavy snowfall once significant snow builds up on steep slopes.  Natural avalanches are a possibility as the storm intensifies, and even relatively small new snow avalanches are likely to pick up steam and run far and fast, especially on big slopes.  So, you’ll want to avoid travel below steep slopes and stay clear of gullies which might collect and funnel long-running avalanches.


   Bottom Line:  This morning you’ll find a MODERATE danger in the backcountry and wind slab avalanches are possible, mainly in exposed upper elevation terrain.  With heavy snowfall and strong winds during the day, the danger will likely become much more widespread and the overall danger will probably rise to CONSIDERABLE. This means that you are likely to trigger wind slab or storm snow avalanches on steep slopes with significant deposits of wind-blown or new snow, and a few spontaneous natural avalanches may occur in places.

   Mountain Weather:   The National Weather Service continued a Winter Storm Warning for the regional mountains for now through Monday evening. Along with periods of heavy snow, strong southwest winds will continue into the afternoon and switch around from the west and then northwest before diminishing. Expect snowfall to continue at higher elevations through Sunday night and Monday.  A high pressure will build in for much of next week, with another storm likely for next weekend.

General Announcements: 

Upcoming avalanche class: February 29th-March 1st, Avalanche Basics, USU Outdoor Recreation Center, Friday February 29th, 6:30p, Field Session Saturday March 1st, 9:00a.  ($35, Please register in advance with the ORC.)  For more information contact [email protected].

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.