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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, April 26th, 2015 - 7:00AM
Expires
Mon, April 27th, 2015 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger has risen to MODERATE overnight for wet loose avalanches and cornice falls on all aspects and elevations. Southerly slopes that did not re-freeze and Northerly slopes that have wet surface snow will be the most likely places to trigger an avalanche. These wet slides could entrain significant amounts of snow if the slope is steep and sustained. Cornices may also begin to release with the warm conditions.

A  LOW avalanche danger will be found on Southerly slopes that re-froze overnight and Northerly slopes harboring dry snow.

There will be no advisory issued tomorrow.

AVALANCHE OUTLOOK for Monday, April 27th:
With similar weather forecast for tomorrow (cloudy skies and warm temperatures), we are expecting similar avalanche conditions. A MODERATE danger for wet loose slides will be the primary concern.

Special Announcements
  • Avalanche Center operations are wrapping up this week. We will issue an advisory on Tuesday, April 28th, and post our end of the season/springtime tips report on Thursday, April 30th. A BIG thank you to all of you for tuning in this winter despite the challenging snow year!!
Sun, April 26th, 2015
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
0 - No Rating
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Dangerous avalanche conditions. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Avalanche Problem 1
  • Wet Loose
    Wet Loose
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
More info at Avalanche.org

After several days of mostly clear skies and a springtime melt-freeze regime, we have very warm temperatures and cloud cover that has moved in overnight. Ridgetop temperatures are reading between 30 and 32F this morning and cloud cover has likely limited the amount of surface re-freeze. What this means is an increase in wet avalanche potential as daytime warming does not have to soften surface crusts before destabilizing the snowpack. This also is how our springtime “shed cycle” begins; the shed cycle is when we see large natural wet avalanches as the snowpack melts away and sluffs off the mountainsides. Will this week’s warming initiate a true shed cycle? It’s too soon to say, but we need to keep the idea in mind as there is still plenty of snow at the higher elevations that has yet to transition into a summer snowpack. Watching for recent wet avalanche activity throughout the next several weeks should be on our minds.

WET LOOSE AVALANCHES:
If you are headed out today, paying attention to the amount of overnight re-freeze on Southerly aspects will be key. If the snow is unsupportable and saturated – stay off of steep slopes as large wet loose avalanches are possible. On Northerly aspects, watch for the soft settled powder to become damp, or even wet. If this occurs, damp and wet sluffs will be possible on steep Northerly slopes.

CORNICES:
Cornices could start calving with the warm temperatures this week. As always, steering clear of these from both above and below is wise. Cornice crevasses are also showing up along ridgelines; this is where the cornice pulls away from the underlying terrain or snow.

Photo below is of a cornice crevasse from the CFR ridge on Tincan this weekend.

Weather
Sun, April 26th, 2015

Yesterday was yet another inviting and mostly sunny day in the backcountry. Ridgetop winds were light from the East and temperatures warm, near 30F on the ridgelines and mid 40’s F at 1,000′.  

Today, we have cloud cover and very WARM air being ushered in as large low pressure system spins in the Gulf. We are too far North of the system for precipitation but we should see overcast skies and season high temperatures in the 34-38F range on the ridgelines. Ridgetop winds are expected to be light to moderate, 10-20mph, from the North and East.

For Monday, intermittent cloud cover, warm temperatures and light precipitation is expected. Accumulations look to be only 1-3″ at the upper elevations with a rain/snow line ~1,500′. Ridgetop winds are expected to be from the North as West as the low-pressure in the Gulf moves off to the Southeast and a wrap-around flow pattern sets up.

PRECIPITATION 24-hour data (6am – 6am)

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′)  41 0    0 70  
Summit Lake (1400′)  40   0    0   13  
Alyeska Mid (1700′) 42   0   0   43  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 28   E    11    34  
Seattle Ridge (2400′) 32   n/a    11  29
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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.