Avalanche Advisory
Advisory: Moab Area Mountains Issued by Eric Trenbeath for Thursday - March 5, 2015 - 6:51am
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Today there is a concern for 3 types of avalanches including wind slabs, deep and dangerous persistent slabs, and loose wet avalanches. Areas of CONSIDERABLE danger exist for dangerous wind slabs and persistent slabs, primarily right around tree line and above on slopes steeper than 35 degree that have a NW-N-E aspect. There is MODERATE danger for shallow winds slabs along upper elevation ridge crests on slopes with a SE-SW aspect.The danger for wet slide activity will rise on sun exposed slopes as the day progresses.




current conditions

La Sal Mountains

If this were the Wasatch, yesterday would have been one of those days in the mountains when people were out triggering avalanches everywhere (and in fact they were). Clearing skies after 5 days of storm, and fresh, sparkling powder snow everywhere made conditions nearly irresistible. All told, we picked up close to 30" of snow in the past week with 18" falling between Sunday night and early yesterday morning when the last wave brought in a final 4". Today will be a gorgeous day in the mountains with winter like temperatures and a brilliant sun, which will quickly effect exposed slopes. NW winds have been on the increase and are averaging 20 mph along the ridge tops, and temps are in the single digits.

La Sal Mountains Current Weather

Wind speeds and temperature at 11,700' on Pre-Laurel Peak.

New snow totals and temperature at Geyser Pass Trailhead.

New snow totals and temperature in Gold Basin.

Abajo / Blue Mountains

The Abajos picked up about half as much snow from this storm series and totals are around 15" since last Friday. Snow cover in the range is still very thin. "Spatial variability" is the key term. This means you can find snow up to four feet deep on on a sheltered, northerly aspect while a more exposed, adjacent slope will still be showing rocks and grass.

Abajo / Blue Mountains Current Weather

Winds and temperature on Abajo Peak.

Snow total at Buckboard Flat.
recent activity

Brian Murdock and I had a good look around in Gold Basin yesterday and saw the remains of a significant avalanche cycle. The strong SW winds and heavy snows on Monday produced numerous natural avalanches, mostly all on N-NE aspects right around tree line and above. Several of these involved old, deeper snow, (persistent slabs) and one slide in Horse Creek was up to 5' deep. The cycle continued through Tuesday when additional snow sluffed off or released as soft slab / new snow avalanches between 18" and 3' deep.


Note the distribution of deep, persistent slabs right around tree line.


This deep, persistent slab at the head of Horse Creek was 5' deep, approximately 200' wide and ran for over 1000'.
Avalanche Problem 1
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 24 hours
description

Several weak layers exist in the snow pack, and this last round of snow demonstrated just how re-active they can be. The danger for triggering a large and dangerous, persistent slab avalanche is now very real. This danger is most prevalent right around, and just above tree line on steep rocky slopes that face the north half of the compass. Check out this video on persistent slabs from Trent Meisenheimer at the UAC up in SLC.
Avalanche Problem 2
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 24 hours
description

Today you will have to contend with both newly deposited wind slabs, and older, hard wind slabs formed earlier in the week. The new, shallow wind slabs, formed by the recent NW wind, will be found along upper elevation ridge crests on slopes that face primarily SE. These will be mostly easy to detect and manage with a slope cut. Less manageable, and harder to detect, will be buried wind slabs up to 3' deep formed earlier in the week. Though gaining in strength, they are overlying weak snow, and if triggered, they also have the potential to step down creating a larger and even more dangerous avalanche. This danger is most prevalent on slopes steeper than 35 degrees that have a NW-N-E aspect. Suspect any area with smooth, rounded pillows of wind drifted snow and be alert to signs of instability such as cracking in the snow surface and collapsing of the snowpack.


Avalanche Problem 3
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 10 hours
description

Though it will remain cool, a strong sun, getting higher in the sky will quickly heat up the abundance of loose, dry snow out there creating the potential for loose, wet avalanches. Pay attention as sun exposed slopes begin to turn moist and eventually even sloppy as the day progresses. When you observe this beginning to happen it is time to stay of and out from under steep, sun exposed slopes.

weather

High pressure has again returned to the region. Today look for sunny skies but with winter like temperatures in the mid 20's at 10,000'. winds will be northwesterly averaging 15-25 mph along the ridge crests. More of the same for the next several days.
general announcements

Road Conditions: The road was not plowed yesterday and you may encounter, and have to wait for the snow plow this morning. 

Observations: If you are out and about, I would love to know what you are seeing. Please post your observations here.

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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 exist.