Utah Avalanche Bulletin

This bulletin is from the UAC, which is part of the US Forest Service.

Utah Avalanche Center (UAC) Advisory

The information in this advisory is from the US Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur.

- Contributors can log in for advertising-free pages.

Friday, May 11th 2012

Current Conditions:

In our absence, you have a plethora of great information on current conditions:

Snow Page is one-stop shopping for most everything you will need to know about mountain weather.

SNOTEL Map

Satellite Imagery

Radar Imagery

Recent Activity:

Visit the Current Conditions section of our web page to view posts by others of avalanche activity and general observations.

Each spring, avalanche conditions generally become more predictable and our avalanche advisories end up repeating themselves like a broken record. So here is the usual spiel:

As my 95-year-old Czech mother-in-law reminds me, "Spring is always a fight between winter and summer." We have alternating, cold, dry powder storms followed by warm, sunny weather that quickly turns the snowpack soggy.

First for storm snow: we have to worry about the usual round of avalanche activity that occurs during storms, namely instabilities within the new snow and wind slabs. Luckily, in spring, the new snow usually falls on a very stable pre-existing snowpack, so all the monkey business is near the surface. Be sure to use your usual round of tricks like jumping on small test slopes to see how they respond and dig down with your hand to see how well the snow is bonded. Also, you should never commit yourself to a slope without first putting a good slope cut across the slope to test it. If the slope fractures, hopefully, your momentum will take you off the moving slab. And as always, avoid steep slopes with recent wind deposits.

Between storms, the new snow turns soggy in a hurry with warm temperatures and strong spring sun. Always avoid steep, sun-exposed slopes when they begin to turn wet for the first time. They will often produce roller balls or pinwheels as a precursor to producing larger, wet or damp sluffs.

Second, watch for several unusually warm days in a row because percolating melt water can lubricate and weaken deeply buried weak layers, which produce large, dangerous, wet slabs. We often see these occur during very warm weather after 2 or 3 nights of no freezes or limited freezes, especially on a layered, winter-like snowpack, which has not experienced percolating melt water before. When playing on corn snow be sure to get out early and head home early--before the snow surface gets punchy. This year, especially, we have buried layers of faceted snow still left over on the upper elevation northerly facing slopes and they are always the last to produce large, wet slab avalanches. These will be difficult to trigger but they are very large and destructive.

Third, you need to avoid snow resting on steep, rock slabs, which often produce glide avalanches in which the entire snowpack moves slowly like a glacier until it releases catastrophically. These releases can occur any time of day and counter intuitively seem to release more in the early morning hours, just when you expect it the least. In the Salt Lake mountains, glide avalanches occur like clockwork in places like Stairs Gulch, Broad's Fork and Mill B South, which are always good places to avoid in spring.

Mountain Weather:

Luckily, we also have an embarrassment of riches when it comes to weather forecasting. Here are some links we use regularly:

Graphical forecast for Alta you want by using the map, which generates a forecast for where you

To get fancy - and - if you know how to read weather maps...

Penn State

U of U time-height sections for SLC left to display the graph. Time is on the bottom axis and height in the atmosphere on the vertical axis--well--you just have to stare at it

- Contributors can log in for advertising-free pages.

The USFS posts some additional information through the season:

• Snow Profiles
• Photos
• List of Avalanches

SUBSCRIBE! to receive these by email: Text

Hazard Scale - [Full Size] [Pocket Reference] Archives for this bulletin

www.avalanche-center.org