Avalanche Advisory
Advisory: Abajo Area Mountains Issued by Eric Trenbeath for Saturday - December 19, 2015 - 6:36am
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Today there is a CONSIDERABLE avalanche danger on slopes steeper than 35 degrees in upper elevation, wind exposed terrain, particularly on slopes with a NW-N-E aspect and riders should avoid these areas today. Choose terrain at lower elevations or with a different aspect for safer riding options today.




current conditions

It's still pretty thin but the storm from earlier this week is a vast improvement. All told, the mountains picked up 12-18" of new snow that has now settled to half that. Base depth varies from about 23" at Buckboard flat to about 30" at North Creek Pass. There are still plenty of obstacles lying just beneath the surface, especially on sun exposed slopes that were nearly bare ground prior to this storm. Excellent powder conditions remain in sheltered areas, but a strong sun and warm temperatures have crusted over sun exposed aspects.

24 hour winds on Abajo Peak have been light an southwesterly, but they are on the increase and wil be in the 25-30 mph range with possible gusts to 50 mph. It is currently 31 degrees at Butler Flat.

Winds, temperature and humidity on Abajo Peak.

Snow totals at Buckboard Flat.

Conditions are improving but it is still thin.

This tree is down over the road just below North Creek Pass.


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

In my travels yesterday I observed lots of collapsing of the snowpack, a sure sign of instability that means the new snow load isn't sitting very well on top of the underlying, weak, sugary, faceted snow that was on the ground before the storm. What this means is that the weight of a rider will likely trigger a persistent slab avalanche on upper elevation slopes that face the north half of the compass that are steeper than 35 degrees. As winds begin to move snow around, fresh wind drifts will add additional stress to these slopes making them even more dangerous. On slopes that are well anchored, meaning that you can still see lots of grass and or bushes sticking out, this danger is not as likely. Stick to slopes such as this, or ones that face the south half of the compass today, stay down at lower elevations.

Very weak, sugary snow called facets is creating a very unstable base for new snow.

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

With winds on the rise, be alert to increased wind slab development in exposed, upper elevation terrain. This danger will be most prevalent on slopes that face NW-NE-E. Look for recent deposits of wind drifted snow on the lee sides of ridge crests and terrain features, and be alert to signs of instability of such as cracking or collapsing. A triggered wind slab also has the danger of stepping down into buried weak layers causing a larger and more dangerous persistent slab avalanche.

weather

Today will be the last mostly sunny day for awhile as a series of Pacific storm systems are lining up for a potentially snowy and wintry week. The first trough in the series will weaken as it moves through our area bringing a chance of snow. We'll get a little break on Monday before a stronger impulse moves through Tues-Wed followed by another Christmas Day.

Today

Mostly sunny, with a high near 39. Windy, with a south southwest wind 15 to 20 mph increasing to 25 to 30 mph in the afternoon. Winds could gust as high as 50 mph.

Tonight

Mostly cloudy, with a low around 16. Windy, with a south southwest wind 25 to 30 mph, with gusts as high as 45 mph.

Sunday

A 30 percent chance of snow, mainly before 11am. Partly sunny, with a high near 21. Breezy, with a west wind 20 to 25 mph decreasing to 10 to 15 mph in the afternoon. Winds could gust as high as 45 mph.

Sunday Night

Mostly cloudy, with a low around 12. Northwest wind 5 to 15 mph becoming west southwest in the evening.

Monday

Partly sunny, with a high near 21. West northwest wind 5 to 15 mph.

general announcements

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.