Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Saturday, December 4th at 7am. 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). This advisory will expire 24 hours after the posting date/time.
Carl Skustad, the Director of the Chugach National Forest Avalanche Information Center has accepted a promotion and will be moving with his family to Minnesota. Carl created this avalanche center and his leadership will be missed. The Skustads have been an important part of the Girdwood community for over 10 years. Thanks Carl for all your good work here on the Chugach!
-TEMPS: Are slightly warmer today by 1-4 degrees at all elevations compared to yesterday.
-PRECIP: 0.9 inches of water fell within the past 24 hours at Turnagain Pass with ~10″ of new snow.
-WIND: Ridgetop winds have calmed down at all weather stations this morning, but extreme average wind speeds made it up to 52mph at Sunburst with extreme max gusts up to 82mph in the last 24 hours.
We are within 24 hours of a significant wind and precip weather event. Most avalanches occur during storms and within 24 hours following a storm. The weather in the past 24 hours will most likely have created dangerous avalanche conditions on specific terrain today.
Today’s avalanche danger rating is CONSIDERABLE due to significant precip and wind in the last 24 hours.
The structure of the snowpack will be poor in many areas today especially on steep terrain near ridges where wind slabs formed yesterday. There will be warmer denser snow sitting on top of colder drier snow on top of a slippery bed surface. These are the 3 main ingredients for an avalanche.
MEDIUM to LARGE human-triggered avalanches are the primary concern today. It is uncertain how reactive these slabs will be to human-triggers, but DO NOT test your luck today. Snow science is not an exact science, but there are a few facts that are common in the majority of avalanche accidents:
1.Most avalanches occur during storms and within 24 hours following a storm. (WE ARE IN THAT TIME FRAME TODAY)
2.Most avalanches occur on slopes with a 38 degree slope angle (THIS IS THE EXACT TYPE OF TERRAIN TO AVOID TODAY)
3.Most avalanche deaths occur when the avalanche danger is rated CONSIDERABLE (IT IS RATED CONSIDERABLE TODAY)
Stay away from big slopes steeper than 30 degrees today. Managing your terrain is the best way to stay alive in avalanche terrain on days like today when the structure of the snowpack is poor and the uncertainty level is high.
The glide cracks and glide avalanches continue to be present, with new ones being observed region-wide on a daily basis. Be aware of your travel routes and try to avoid spending time below the cracks. The only way to reduce your risk from glide avalanches is to avoid traveling below the obvious cracks.
This photo (taken 11/16/2010) shows a good example of a glide avalanche and a glide crack on the southern aspect of Cornbiscuit. For scale take note that the crack is 4-6 feet deep. The glide crack on the left hand side of this photo has already avalanched; while, the glide crack on the right is still a hazard that could avalanche any day. Avoid traveling underneath glide cracks just like the one on the right hand side of this photo.
The Nation Weather Service weather forecast for:
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST SAT DEC 4 2010
.TODAY…MOSTLY CLOUDY WITH A CHANCE OF SNOW SHOWERS. PATCHY FOG.
HIGHS IN THE UPPER 20S TO MID 30S. VARIABLE WIND 10 MPH.
.TONIGHT…MOSTLY CLOUDY WITH A CHANCE OF SNOW SHOWERS. LOWS IN
THE MID TEENS TO LOWER 20S INLAND AND MID TO UPPER 20S ALONG THE
COAST. VARIABLE WIND 10 MPH.
.SUNDAY…MOSTLY CLOUDY. A SLIGHT CHANCE OF SNOW SHOWERS IN THE
MORNING. HIGHS IN THE LOWER 20S TO LOWER 30S…COLDEST INLAND.
VARIABLE WIND TO 10 MPH. NEAR SEWARD…NORTH WIND 15 TO 25 MPH.
.SUNDAY NIGHT…SNOW LIKELY. LOWS IN THE 20S. VARIABLE WIND TO
TEMPERATURE / PRECIPITATION
SEWARD 33 27 33 / 40 40 20
GIRDWOOD 30 22 27 / 40 40 20
WEATHER STATION SUMMARY for Turnagain Pass:
3800′-Sunburst Wx Station
Temp: (5am): 19 (4 degrees warmer than yesterday morning)
Winds: In last 24 hours have been light to extreme averaging 2-52mph with extreme gusts up to 82mph
2400′-Seattle Ridge Wx Station
Temp: (5am): 21 (4 degrees warmer than yesterday morning).
Winds: In last 24 hours have been calm to extreme averaging 0-46mph with an extreme max gust of 68mph.
1800′-Center Ridge Wx Station
Temp: (6am): 24 (same as yesterday)
Precip: 0.9″ in last 24 hours with ~10″ new snow for a total snowpack depth of 54″
The next advisory will be issued tomorrow Sunday morning 12/5/2010 at 7am. If you get out in the backcountry send us your observations using the button at the top of this page or call and leave a message at 907-754-2369. Thanks and have a great day.