Wasatch Cache National Forest

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Avalanche advisory

THURsday, April 4, 2002 07:30 AM

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Good morning, this is Tom Kimbrough with the Forest Service Utah Avalanche Center with your backcountry avalanche and mountain weather advisory. Today is Thursday, April 4, 2002, and it’s 7:30 a.m.

Current Conditions:

Overnight mountain temperatures are in the upper twenties and low thirties, about the same or just a couple of degrees warmer than on Wednesday. Skies are clear. Winds are 5 to 15 mph over the ridges, with the highest peaks getting speeds in the twenties, with gusts to 40. With temperatures around freezing, combined with the clear skies, the snow pack will have a decent re-freeze this morning that will last for several hours.

The supportable corn crusts are thickest below about 10,000’. But start early, as the crusts become breakable on east facing slopes by about 10 am; south is lasting until nearly noon and you can get a few runs on west facing into the afternoon. Temperatures are a couple of degrees warmer today and the daytime highs will also be a little warmer so these times may be a little optimistic. To help you with those alpine starts, we are doing an early morning corn report on the (801) 364-1581 line by 6:00 am for the rest of the season.

Avalanche Conditions:

Temperatures this week have been low enough at night to produce solid surface crusts but the cooling isn’t penetrating far into the pack. After a few hours of sun and as the air temperature warms, the surface crusts weaken and the snow loses its strength, becoming dangerously wet and loose. On Tuesday, a backcountry traveler near Brighton was on a steep east facing slope too late in the day and triggered a loose wet snow slide at about 12:45. While only about 100’ wide, the debris piled up over 7 feet deep in places. Potentially even more dangerous are full depth wet slab avalanches that may release naturally. These can be massive, catastrophic events. This year’s snow pack, containing some very weak layers that formed in January, is unusually susceptible to this type of slide. Some of these avalanches have already pulled out around the range and more are sure to follow. While the timing this type of slide is less predictable than we would like, watching overnight lows and early starts and finishes give you a fair amount of protection.

As the snow becomes wet and sloppy, change slope aspect or head for home and also get out from under steep slopes because natural avalanches may become possible. There is also a chance of triggering a large slide in dry snow on that January weak layer, especially on a very steep slope in shallow snow pack areas.

Tonight is forecasted to be very warm with at least partly cloudy skies. Assuming that this comes to pass, Friday may not be a good day to be on or around steep terrain in the backcountry.

Bottom Line:

The avalanche danger is generally LOW early this morning but will rise to MODERATE on sunny slopes by midmorning. The danger will increase and become more widespread later in the day. There is also a danger of very large full depth avalanches, possibly releasing naturally, especially in very steep rocky terrain. While this danger increases with rising temperatures, it is not limited to the warmer parts of day.

(Ogden Area and Western Uinta Mountains)

Same as Salt Lake Mountains.

(Provo Area Mountains)

Same as Salt Lake Mountains.

Mountain Weather:

The Wasatch has been under a rather strong northwest flow for the past week but that is about to change. A trough is developing off the west coast that will shift our winds to the southwest and bring much warmer temperatures into Utah tonight. Clouds will increase this afternoon and winds will become moderate from the west, shifting southwest late today. Highs today will be around 50 at 8,000 feet and near 40 at 10,000. A weak cold front should arrive Friday night, possibly bringing a few inches of new snow to the mountains.

General Information:

Wasatch Powderbird Guides may not be flying today. For more information call 521-6040 ext. 5280.

To report backcountry snow and avalanche conditions, especially if you observe or trigger an avalanche, you can leave a message at (801) 524-5304 or 1-800-662-4140. We have a new avalanche and backcountry observation page that we’d like to encourage folks to try out. It can be found on our home website at avalanche.org. You can also fax an observation to 801-524-6301.

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.

I will update this advisory by 7:30 Friday morning.

Thanks for calling!

________________________________________________________________________

For more detailed weather information go to our Mountain Weather Advisory

National Weather Service - Salt Lake City - Snow.

For an explanation of avalanche danger ratings:

http://www.avalanche.org/usdanger.htm