Avalanche Advisory for Saturday, April 8, 2017 at 7am

Issued: Sat, Apr 08, 2017 at 7AM

Expires: Sun, Apr 09, 2017

Saturday, April 15th will be the last HPAC advisory of the season. We will continue to monitor the observation platform and highly encourage you to post your observations!

Above 3,500ft Moderate

2,500 to 3,500ft Moderate

Below 2,500ft Moderate

Degrees of Avalanche Danger ?

1. Low
2. Moderate
3. Considerable
4. High
5. Extreme

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

Bottom Line: The avalanche hazard is MODERATE today for Wet-Loose , rising to CONSIDERABLE in the afternoon at all elevations on E through W aspects , on slopes above 35º. Human triggered avalanches are possible, increasing to likely in the afternoon with naturals possible. Cautious route finding and conservative decision making will be integral to avoiding these avalanches today.

The avalanche hazard is MODERATE for Persistent Slabs at mid and upper elevation, on all aspects, on slopes above 35º. Human triggered avalanches are possible.  Expect small avalanches in specific areas or large avalanches in isolated areas. It will be possible for wet-loose avalanches to trigger persistent slabs and vice versa, potentially compounding the hazard. Identify features of concern and evaluate snow and terrain carefully.

 


 

Problem 1: Wet-Loose

It is springtime in Alaska which means- put the bunny boots away, and pull out the Xtra Tuffs. In these times, forecaster Drew Hardesty would say….”There is some uncertainty with the weather factors, so if you’re seeing the classic precursors to wet activity (rollerballs, pinwheels, unsupportable snow), head to cooler aspects or lower angle slopes.” Good advice!

There has been a surge of wet-loose avalanche activity this week, mostly on 4/5 and 4/6 where temps reached 43ºF at 3450′. Expect wet-loose activity on E through W aspects, the majority occurring SE through SW, at all elevations, on slopes above 35º.  The return of the sun combined with April’s quick shift out of frigid winter is likely to take you by surprise with a rapidly changing snowpack. Numerous wet-loose avalanches have been observed this week, many running to the ground with sizable debris. If you are touring and the snow under your feet feels like mashed potatoes, tuck tail and run. Go have a beer in the parking lot instead.

Pay attention to the distance these avalanches are running and make sure you are not in the runout. Don’t get complacent with the beautiful, warm weather, and sunshine- cause these avalanches – although typically slow- entrain a considerable amount of debris and are capable of burying, injuring, or killing a person. Terrain traps can quickly compound the risk of getting sluffed.  Good terrain management and decision making can make all the difference in avoiding these predictable and avoidable avalanches.

Human triggered
Wet-Loose
Lower Eldo E aspect 3500′ 4/6

Natural Wet-loose
Marmot W face 3700′ 4/6


In the photo below- notice the proximity of the avalanche debris to the skin track.

Marmot Wet-loose SE-SW
3500-4000′ 4/5


 

Problem 2: Persistent Slab

Although the persistent slab is being, well… persistently stubborn, in some locations… , see pit... we are seeing outliers and expect them to be more frequent as temperatures increase. A handful of natural persistent slabs were observed this week around 3500′ on SW and NW aspects, on slopes above 35º. The mid-pack persistent slab appears to be warming up- rounding- and gaining strength over its weaker brethren below.

Expect slabs to be 4-10″ deep and to fail in the old facets (the culprit) under the rapidly warming surface slabs. It will be possible to human trigger theses slabs on all aspects at mid and upper elevation on slopes above 35º. Expect to be able to trigger these slabs in specific areas including: gully side walls, starting zones, and where slabs exist. Look and listen for whumping, collapsing, or cracking as indicators of instability- or better yet- a recent avalanche on a similar aspect and elevation!

Idaho Peak
SW aspect 3400′
Sluff triggers Persistent Slab 4/6

Recent Avalanche Activity

Natural and human trigigered avalanches were observed and reported this week. Numerous wet-loose avalanches occurred on E thorough W aspects- mostly SE through SW- on slopes above 35º, on 4/5 and 4/6 as a result of rapid warming. A handful of persistent slab avalanches also were observed on SW and NW aspects around 3500′. These slabs also triggered wet-loose or were triggered by wet-loose.

Skyscraper S aspects
Wet-loose avys 4/6 coming pretty close to the “trail”


Martin Mine
Natural Wet-Loose
SE aspect 4000′ 4/6


Idaho Peak
Wet-loose and Persistent Slab 4/5-4/6
SW aspect 3400′


Arkose Ridge
Natural Wet-Loose ripped to the ground
S aspect, 4/6, 3300′


Marmot “Lodge Slide”
NW aspect 3500′
Persistent slab 4/5?

 

Recent Weather

This week’s weather at 3550′:

Temps averaged  30ºF, with a low of  18ºF and a high of  43ºF.

No new snow since 3/28-3/29.

Overnight at 3550′:

Temperature averaged 25° F.

No new snow overnight.

This week’s weather at 4500′:

Temps averaged  25ºF, with a low of 16ºF and a high of 37ºF.

Wind averaged  7 mph SE, with gusts averaging 13 mph . Winds gusted 20-29 mph SE on 4/1-4/2 and 25-28 mph E on 4/3.

Overnight at 4500′:

Temps averaged 23º F overnight.

Winds averaged 2 mph S, gusting 4 mph S.

Additional Info & Media

 

 

A slight cooling trend should keep the avy danger the same this weekend. Any significant increase in temperature, combined with the blazing sun, will weaken bonds in the snowpack, increasing the likelihood of avalanches, and increasing the avalanche hazard.


AK State Parks snow report for Hatcher Pass here.


NWS point forecast for Hatcher Pass here.

Posted in HPAC Forecasts.
Allie Barker

Forecaster: Allie Barker