Salt Lake Avalanche Advisory
Tuesday, December 16, 2008
Created at 6:39 am
Updated at 7:23 am
Forecaster: Drew Hardesty

BOTTOM LINE

The danger is MODERATE with pockets of CONSIDERABLE danger on most mid and upper elevation 
west through north through east facing slopes. The danger may be more pronounced in the wind 
loaded areas of the immediate periphery of the Cottonwood Canyons, to include the Mill Creek 
and Park City ridgeline. Human triggered avalanches are probable, and may still be triggered 
at a distance. These are unusual circumstances and avalanche conditions, with even the most 
savvy backcountry skiers and professionals on edge. It's worth giving that steep line another 
look, then moving on to something more manageable.

CURRENT CONDITIONS
	
wind jacked, adj. 1. Of, or relating to, being hammered by the wind, often used to describe wind 
damaged snow surface conditions. 2. The current state of our riding conditions in nearly all but 
the most protected areas. The southeasterly and southerly winds tore through the landscape 
yesterday, blowing 20-35mph, gusting to near 50, accentuating the wind chill with temperatures 
already low in the single digits. Most of the snowfall tracked through the southern Wasatch 
overnight, with the Provo mountains picking up 21” (YES, 21 inches, of new. Areas north of 
Timpanogos divide uniformly received 2-3” of snow. Nonetheless, it would be complimentary to 
describe the riding conditions as wind jacked, threadbare, and dangerous. And not necessarily 
in that order.

RECENT ACTIVITY

By our count, we've had 12 avalanches triggered in the backcountry over the past three days, 
with about half of those unintentionally triggered. Yesterday, Grant and I went to investigate 
the accident from the day before that occurred near Squaretop in the Canyons backcountry. The 
skier triggered the soft slab about a foot deep and 75' wide, taking the Thanksgiving rain crust 
with him. He was lucky to have been pinned against a tree, avoiding a potential burial, and 
escaped with a broken pelvis and fractured lower vertebrae. Grant put together an excellent report 
which should be posted off our accidents and photos page in the next couple of hours.

Enroute the investigation, we saw that a 1' deep and 40' wide soft slab had released naturally 
on Squaretop from the strong southerly winds. Prudently, we stayed on the safe descent ridge, 
collapsing the snow the whole way. From other's reports, collapsing of the various weaknesses 
associated with the buried rain crust, is now nearly the rule and not the exception. And along 
one of the upper starting zones in Hidden Canyon, in the Brighton backcountry, a skier triggered 
a 1' deep and 30' wide soft slab breaking on faceted snow a few inches above the crust. This was 
on a steep northwest facing slope at around 10,100'.

THREAT #1

I would like it more if we just had a blockbuster storm with plenty of snow and blow and just be 
done with it. This would produce a widespread natural and human triggered avalanche cycle and then 
maybe, maybe we could start again. Instead, we're seeing snow and wind in just drips and drabs, 
making it locally unstable here, but where you might be able to get away with it there. It's too 
much. The snowpack is thin, weak, fraught with multiple failure planes and issues. Most of the 
hullaballoo surrounds the weak faceted snow above and below the rain crust, but a fair amount of 
the activity over the past couple of days has initiated a few inches above in some thin faceted 
snow, only to collapse the crust and step into the older weak, faceted snow.

THREAT #2
	
Adding to the fray now are the soft and hard slabs from yesterday's stronger, punishing southerly 
winds. These may be just off the ridgelines or further down on the slope. Remember, cracking and 
collapsing are immediate signs of instability. I'd recommend sticking to the lower angle slopes 
(meadow skipping) for a while.

MOUNTAIN WEATHER
	
We'll see snow and snow showers for much of the day, but it shouldn't produce more than a few 
inches. The southwesterly winds are expected to relax some as they veer to the west, averaging 
speeds in the 15-20mph range. Temps will remain cool at 11 degrees at 10,000' and the mid to upper 
teens at 8000'. Looks like we'll have a quick break in the action tomorrow ahead of what may be a 
good producer for the southern Wasatch Wednesday night into Thursday. Cold arctic air crashes into 
Utah for the weekend, dropping temps to -8F in the mountains.