Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, January 31st 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).
No new snow fell in the last 24 hours in Turnagain Pass. Our last snowfall was this past Wednesday and Thursday when 4-6 inches fell along with strong easterly winds. Yesterday was a beautiful day to be in the mountains…blue sky, sunshine, light winds, and temps ranging from the upper 20’s to upper 30’s. As of 4am this morning, ridgetop winds are light out of the southeast with partly cloudy skies above the dense fog in the arm. We have a more pronounced inversion this morning with temps currently ranging from 32F at 3800 feet to 21F at sea level. A weak low in the gulf will bring mostly cloudy skies today, mountain temps in the upper 20’s to low 30’s, and light easterly ridgetop winds.
Today the avalanche hazard is LOW with pockets of MODERATE danger on slopes steeper than 35 degrees. Last week’s 4-6 inches of new snow and strong easterly winds created sensitive soft slab that was reactive to skiers as recently as Friday. In some areas this new snow buried a layer of surface hoar that formed up to 3500 feet elevation. The surface storm snow instabilities seem to have lost their reactivity, but it is still possible to find and trigger a pocket of buried surface hoar especially on leeward aspects. Skier and rider-triggered sluffs are also possible on slopes steeper than 40 degrees.
Jon and I toured up Sunburst yesterday and took advantage of the stellar weather conditions by digging seven snowpits with over 25 stability tests at 2000, 2500, 3000, and 3500 feet elevation. We sporadically found the buried surface hoar that formed January 20-26 buried 4-8 inches deep up to 3500 feet. It failed easily in all of our stability tests. It is certainly possible the skier-triggered avalanches on Cornbiscuit and Superbowl Peak on Friday failed on this buried surface hoar layer. It is also possible they just failed on the recently wind-loaded, and thus sensitive, new snow/old snow interface. (Check out our photo gallery for a shot of the Superbowl Peak slide.)
We found the old buried rain crust that formed January 7 down about 1.5 feet on Sunburst. This layer was last reactive 2 weeks ago but continues to produce highly variable results in our snowpits. (CT8,9,11,13,15,29,30++,CTN) The most “unstable” results are below 2000 feet where we get consistent failures underneath the crust on a thick layer of facets and isolated reports of whumphing.
We saw no obvious signs of instability yesterday CNFAIC Staff than skier and rider-triggered sluffs on steep slopes. On direct southern aspects, we continued to see point-release sluffs and rollerballs from the warm temps and intense solar radiation. Up valley from Tincan Proper in the Library, one of these wet sluffs entrained quite a bit of snow and created a large debris pile on the valley floor. The most recent rain crust that formed 3 days ago is very thin and only goes up to 1600 feet thankfully.
Always remember that safe backcountry travel requires training and experience. You control your own risk by choosing where, when, and how you travel.
I will issue the next advisory tomorrow morning at 7am. If you get out in the backcountry give us a call at 754-2369 or send us your observations using the button at the top of this page.
The NWS weather forecast for:
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST SUN JAN 31 2010
…DENSE FOG ADVISORY IN EFFECT UNTIL NOON AKST SUNDAY…
.TODAY…MOSTLY CLOUDY. AREAS OF DENSE FOG THIS MORNING…MAINLY
ALONG TURNAGAIN ARM. LOCAL VISIBILITIES TO ONE QUARTER MILE OR LESS
AT TIMES THIS MORNING. ISOLATED RAIN AND SNOW SHOWERS IN THE
AFTERNOON. HIGHS IN THE 30S. VARIABLE WIND 10 MPH EXCEPT NORTH 10 TO
20 MPH NEAR SEWARD.
.TONIGHT…MOSTLY CLOUDY WITH SCATTERED RAIN AND SNOW SHOWERS. PATCHY
FOG. LOWS IN THE LOWER 20S TO MID 30S. VARIABLE WIND 10 MPH EXCEPT
NORTH 10 TO 20 MPH NEAR SEWARD.
.MONDAY…PATCHY MORNING FOG. MOSTLY CLOUDY WITH SCATTERED SNOW AND
RAIN SHOWERS. HIGHS IN THE UPPER 20S TO MID 30S. VARIABLE WINDS 5 TO
10 MPH EXCEPT NORTH 10 TO 20 MPH NEAR SEWARD.
TEMPERATURE / PRECIPITATION
SEWARD 35 27 35 / 20 40 40
GIRDWOOD 36 28 34 / 0 0 0
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
recorded light and variable winds yesterday averaging 1-5mph. The current temp is 32F (same as yesterday) with winds averaging 5mph out of the southeast.
-2600′ Seattle Ridge Wx Station-
recorded light easterly winds yesterday averaging 1-10mph. Winds are currently averaging 5mph out of the southeast.
-1800′ Center Ridge Wx Station-
recorded no new snow in the last 24 hours. The current temp is 32F (2 degrees warmer than yesterday) with a total snowpack depth of 64 inches.