Avalanche Advisory
Advisory: Ogden Area Mountains Issued by Paige Pagnucco for Thursday - January 11, 2018 - 6:08am
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The avalanche danger is CONSIDERABLE on steep mid and upper elevation slopes. The added weight of the recent storm rain/snow has put the snowpack on edge and human triggered avalanches are likely on steep slopes that harbor a poor snowpack structure. Cracking and collapsing are likely and are bullseye clues for instability. Avoid steep slopes with freshly wind drifted snow as even a small wind slab could break down in to deeper weak layers and create a larger avalanche.

Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route finding and conservative decision making are essential. The key to safe travel today is to stick to slopes less than 30 degrees which are not connected to or below steeper terrain.




current conditions

Temperatures are much colder this morning hovering around 20 F at 8000'. Winds are out of the west northwest at 10-15 mph with ridgetop gusts higher. Ben Lomond (7688') got a whopping 3.5" of snow water equivalent out of the last storm while the rest of the zone averaged around 1-1.5" equating to about 6-10" of heavy wet snow. Hopefully the colder overnight temperatures will "dry" the surface snow out a bit and make for better traveling conditions.

recent activity

Activity quieted down a bit yesterday but resorts were still producing sizeable avalanches with explosives. No natural activity was observed. Three days ago, there were large remote avalanches triggered in the Ogden area mountains. Poor snowpack structure is still the main concern with persistent weaknesses still present across the zone. See recent Ogden observations here.

Here's a great video illustrating the shallow poor snowpack structure:

https://youtu.be/vkGJMHIulRk

Yesterday, riders in the Salt Lake mountains were able to remotely trigger multiple large destructive avalanches while walking along rigelines likely due to more water weight and a generally weaker snowpack. See SLC observations here.

Avalanche Problem 1
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 12 hours
description

Though 6-10" of snow may not seem like much, it is enough to trigger any one of the persistent weak layers that exist in the Ogden area snowpack. I expect that collapsing and cracking will occur today as you travel across the fresh slab of snow - a sure sign the snowpack is unstable and you should avoid being on or traveling under slopes steeper than 30 degrees. An avalanche starting in the new snow may step down in to deeper weak layers and become much larger as it entrains snow down the slope. Given the still unseasonably shallow snowpack, you'll find better riding conditions on lower angle, sheltered terrain.

Avalanche Problem 2
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 12 hours
description

Winds have drifted snow at the high and mid elevations, potentially overloading weak layers in the snowpack. Avoid steep slopes and terrain features like gullies or outcroppings that hold freshly wind-drifted snow as even a small wind slab could step down and become a larger, more destructive avalanche. Southwest winds are expected to slowy increase throughout the day so pay attention to and avoid building wind drifts.

weather

Today the Ogden area mountains will turn cloudy with the chance for an inch or two of snow. Temps will stay in the mid 20's F and winds will move around to the the west southwest blowing 10-20 mph but steadily increasing throughout the day. Temperatures will climb a bit tonight and westerly winds will start cranking as a quick hitting system moves through the area bringing with it another chance for a few inches. High pressure returns for the weekend.

general announcements

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This information does not apply to developed ski areas or highways where avalanche control is normally done. This advisory is from the U.S.D.A. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur.