Saturday, February 11, 2017 at 7:00am

Issued: Sat, Feb 11, 2017 at 7AM

Expires: Sun, Feb 12, 2017

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Above 3,500ft Moderate

2,500 to 3,500ft Moderate

Below 2,500ft Low

Degrees of Avalanche Danger ?

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

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

Bottom Line:

For today, human triggered avalanche likelihood has diminished, however it is still possible to trigger a significant avalanche in specific locations. Natural avalanches are unlikely.

Hatcher Pass looks like an avalanche battle zone, with old avalanche paths exposing the ground and tundra, large, hard slab blocks littering the landscape, numerous avalanche debris piles, and wind scoured ridgelines all covered in a light dusting of new snow.

A myriad of conditions exist with highly variable snow depths, including sun crust, wind crust, and harder to find, beautiful recrystallized powder.

Last week’s warm temps (high of 45°F at 3550′ on 2/4-2/5) and blazing sun, on steeper slopes with angle of incidence to the sun, formed supportable sun crusts. These conditions make for challenging, slippery uphill progress on skis and boards.


AVALANCHE PROBLEM: PERSISTENT SLAB

Human triggered avalanches have trailed off this week as the snowpack has had time to adjust and increase in stability. While this means it is becoming more difficult to trigger avalanches, it is still possible in specific locations, on all aspects, at mid to upper elevation, mostly on slopes 35º and steeper. Avoid large slopes funneling into terrain traps. Persistent slabs will be difficult to predict or assess, be up to 1-3′ deep in specific leeward locations, stubborn to trigger, fail at the ground, and may take a number of people to find a trigger point. Hard slabs means punishing blows, so while the likelihood is fairly low, the consequences of an avalanche can be high.

Moderate to strong winds (24-35 mph) from last weekend and early this week scoured windward ridgelines and features down to the brush, tundra and rock, and loaded leeward slopes, generally W to N. The newest wind load is fairly small and not significantly contributing to the avalanche problem. There may be isolated places where it could be possible to trigger a thin, 4″ thick, wind slab that could sweep you off your feet, or carry you into terrain traps.

The same old tune at the base of the snowpack is rotten, weak, snow which has not healed. Basal, weak facets, and depth hoar are willing to fail if you apply enough force or find a shallow trigger point, however, natural avalanches are unlikely. Without a rapid new load, these weak layers are just taking a smoke break until their supervisor, the weather, puts them back to work. Any rapid change, such as strong winds, heavy precipitation, or sudden warming (possible monday/tuesday), will wake up this dormant, resilient layer, for avalanche activity again.

View of snowpack showing cohesive slab over weak facets

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Depth Hoar at base of snowpack

 

 

 

 

 

 

 

 

 

 

 

Video of the basal facet problem using a Propagation Saw Test:

 

Recent Avalanche Activity

No avalanche activity has been reported since Saturday, Feb 4th.

 

Recent Weather

This week’s weather at 3550′:

3-4 inches of new snow and 0.3 inches of water accumulated this week.

Overnight at 3550′:

A trace of new snow.

This week’s weather at 4500′:

Temperatures averaged 17ºF. Temps started the week at 34ºF on 2/5, dropping all week, reaching 0°F and remaining in single digits on 2/10.

Winds averaged 4 mph, with gusts averaging 8 mph SSW. Winds picked up with gusts in the mid 20’s mph ENE on 2/6.

Overnight at 4500′:

Low of 0°F

2°F at 6:00am this morning

Winds averaged 5 mph SSE, gusting up to 20 mph.


National Weather Service HP Recreational Forecast at 6:27am

Click here for the link and updated information.

THE HATCHER PASS MOUNTAIN FORECAST COVERS THE MOUNTAINS IN THE
HATCHER PASS RECREATION AREA.

THIS FORECAST IS FOR USE IN SNOW SAFETY ACTIVITIES AND EMERGENCY
MANAGEMENT.

                   TODAY        TONIGHT

TEMP AT 1000`      6 F          -4 F

TEMP AT 3000`      9 F          2- 8 F

CHANCE OF PRECIP   0%           0%

PRECIP AMOUNT
(ABOVE 1000 FT)    0.00 IN      0.00 IN

SNOW AMOUNT
(ABOVE 1000 FT)    0 IN         0 IN

SNOW LEVEL         SEA LEVEL    SEA LEVEL

WIND 3000` RIDGES  LGT/VAR      LGT/VAR

AK State Parks Snow Report here.

Additional Info & Media

The avalanche hazard will remain the same through the weekend.

New snow is forecasted for Sunday night into early next week, along with strong winds Sunday afternoon, and a warming trend into Tuesday. Any rapid change in the weather will have the chance of tipping the balance, awakening the weak basal facets, and increasing the avalanche hazard.

Posted in HPAC Forecasts.
Jed Workman

Forecaster: Jed Workman