Good morning backcountry travelers this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Saturday, February 20th at 7 am. This will serve as 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).
Announcements Alaska State troopers have will be leading recovery efforts in the Grandview Area today weather dependent. Avalanche control work using explosives and helicopters will be occurring. Please stay out of the Grandview Area for public safety reasons.
The jet stream continues to bump into the panhandle and Olympic ridge and turn north right at us. This strong south to north flow is responsible for our warm wet weather. This jet stream pattern is expected to break up next week. The radars are currently showing limited precip. The satellites show scattered cloud cover. Very warm temperatures remain over the area. The snow line remains very high at 2800ft. Winds have let up slightly but are still significant. Yesterday’s winds were ripping off every peak and ridge. Large avalanches were naturally triggered by this wind event. Today’s warm temperatures, wind, and the chance of rain and snow could trigger natural avalanches.
Today’s avalanche danger will remain HIGH This means we have dangerous avalanche conditions and travel in avalanche terrain is not recommended. Natural avalanches likely and human triggered avalanches very likely. Avalanche terrain includes slopes steeper than 25 degrees and areas below these slopes. Flat terrain attached and directly adjacent to steep terrain is included.
Yesterday, we saw more natural and human triggered avalanches from Girdwood to Summit Lake. Here are a few of the many natural avalanches Lisa recorded yesterday:
-Every path on Sunnyside ran from Johnson to Repeat Offender
-The majority of the West face of Magnum, and a medium sized avalanche on the SW face Magnum possibly
pulled out to the ground
-South face of Tincan between Proper and Common…(see photo in photo gallery)
-Eddies- two avalanches on south face, two avalanches on west face
-Pyramid – North and Northwest faces, multiple paths puled out.
We have passed the apex of the storm and avalanche cycle but we can’t let our guard down. Days like today are when most people get caught and killed in avalanches. If skies clear you will be tempted to push into steeper terrain. The mountains don’t care that your an expert rider or that the skies are clear and skiing and riding is good. They are looking for something or someone to tip the scale and trigger an avalanche. This trigger could be new snow, rain, wind driven snow, or a human on skies, board, or sled. Long time forecasters in the area are reporting large avalanches occurring on slope angles lower than you normal. This is an indicator of the sensitive nature of the snowpack.
Our coastal snowpack harbors good stability most of the time. This is not one of those times. If you trigger an avalanche today it will be very large and you run the risk of not going home tonight.
Let me remind us that this is the exact setup we had two years ago when we had a fatal avalanche in Seattle Creek, followed by a very large storm, followed by anCNFAIC Staff large human triggered avalanche on Sunburst that buried a skier for 15-20 minutes. The Sunburst avalanche happened with the same type of weak layers present and the same 5-10 feet of new storm snow.
There are two main weak layers in our snowpack:
1.A thin breakable melt-freeze crust with surface hoar on top of it. We have seen this weak layer up to 3000′ on multiple aspects on both sides of highway at Turnagain Pass. This weak layer is generally buried 4-6 feet deep. Surface hoar has been observed on top of this layer in several pits, as recently as Sunday 2/15/2010. This combination of surface hoar on top of a crust is historically responsible for the majority of avalanche surprises and fatalities.
2.The Jan 7 rain crust is generally buried 6-8 feet deep. This particular weak layer has been reactive to explosive triggers and naturally triggered during our current avalanche cycle. This persistent weak layer has been showing significant signs of instability since its formation last month. This weak layer is widespread on all aspects up to 3000 feet.
WEATHER FORECAST (National Weather Service)
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST SAT FEB 20 2010
.TODAY…RAIN IN THE MORNING…THEN A CHANCE OF RAIN IN THE
AFTERNOON. HIGHS IN THE LOWER TO MID 40S. EAST WIND 10 TO 15 MPH
EXCEPT EAST 20 TO 35 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.
.TONIGHT…RAIN AND SNOW LIKELY IN THE EVENING…THEN
A CHANCE OF SNOW AND RAIN AFTER MIDNIGHT. NO SNOW ACCUMULATION.
LOWS IN THE 30S. EAST WIND 10 TO 15 MPH EXCEPT EAST 10 TO 25 MPH
THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.
.SUNDAY…SNOW AND RAIN LIKELY. NO SNOW ACCUMULATION. HIGHS
AROUND 40. VARIABLE WIND 10 MPH EXCEPT EAST 10 TO 20 MPH THROUGH
PORTAGE VALLEY AND TURNAGAIN ARM.
.SUNDAY NIGHT…MOSTLY CLOUDY WITH A CHANCE OF SNOW AND RAIN.
LOWS IN THE UPPER 20S TO MID 30S. VARIABLE WIND TO 10 MPH.
.MONDAY…MOSTLY CLOUDY WITH ISOLATED RAIN AND SNOW SHOWERS. HIGHS
AROUND 40. LIGHT WINDS EXCEPT NORTHWEST 15 MPH
TEMPERATURE / PRECIPITATION
SEWARD 41 34 39 / 80 60 80
GIRDWOOD 41 34 39 / 60 40 50
WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS
3800′-Sunburst Wx Station
Current Temp: 26 degrees F
Winds: very strong averages and extreme gust all day yesterday. Currently we are seeing averages in the 30’s and gusts in the 50’s. All winds have been out of the east.
2600′-Seattle Ridge Wx Station
Broken. We will fix as soon as possible.
1800′-Center Ridge Wx Station
Current Temp: 35 (same as yesterday)
Precip: .6 inches of water and no new snow. Total snowpack depth dropped from 109 to 102 with rain and settlement.
Thanks for checking today’s avalanche advisory. Lisa will post again tomorrow morning, February 21st by 0700.