Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Monday, February1st 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 saw light ridgetop winds out of the southeast, mostly cloudy skies, and mountain temps ranging from the upper 20’s to mid 30’s. As of 4am this morning, ridgetop winds are light with cloudy skies and light freezing rain falling at sea level. Temps currently range from 27F at 3800 feet to 30F at sea level with a band of warmer temps in the low 30’s at the mid elevations. Winds will gradually shift to the north today but will remain light while the remnants of a weak low in the gulf will keep skies mostly cloudy. Our spring-like temperatures will gradually fade away this week, but for today, expect only slightly cooler mountain temps in the mid 20’s to lower 30’s.
Today the avalanche hazard remains at 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 mid-way down leeward slopes. Skier and rider-triggered sluffs are also possible on slopes steeper than 40 degrees.
During our tours up Sunburst and Eddy’s this past weekend, we found the buried surface hoar that formed January 20-26 buried 4-8 inches deep up to 3500 feet elevation. It failed easily in all of our stability tests but only produced shallow sluffs when ski cut. It is certainly possible the skier-triggered avalanches on Cornbiscuit and Superbowl Peak on Friday failed on this surface hoar layer where it was buried under a thicker slab of windblown snow. It is also possible these slides simply failed on the recently wind-loaded, and thus sensitive, new snow/old snow interface.
We saw no obvious signs of instability this past weekend CNFAIC Staff than skier and rider-triggered sluffs on steep slopes. Numerous groups reported finding stable conditions and felt comfortable skiing and riding steep slopes in the 40 degree range. On direct southern aspects, we saw point-release sluffs and rollerballs from the warm temps and intense solar radiation on Friday and Saturday. Sunday’s cloud cover kept this to a minimum. 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.
We found the old rain crust that formed January 7 buried 1.5 feet deep on Sunburst and 2-3 feet deep on Eddy’s. (The crust goes up to 3000 feet elevation on all aspects.) This layer was last reactive 2 weeks ago but continues to produce highly variable results in our snowpits, ranging from no failure at all to easy shears underneath the crust in the 1800 to 2000 ft. range. At 2000 and 2800 feet yesterday on Eddy’s, we got several hair-raising Q1 shears on top of the crust where we found a thin layer of surface hoar hiding out. Although it took quite a bit of force to get it to fail, the slab popped off the column fast and clean (CTH24,25 and ECTP30+ all Q1’s). Check out a video of Matt doing an Extended Column Test on this layer by clicking on the button at the top of this page. I think at this point it’s going to take quite a shock-load to get this layer to fail…like a “full-on pineapple express dumping feet of snow with hurricane-force winds” type of load.
Safe backcountry travel requires training and experience. You control your own risk by choosing where, when, and how you travel.
Matt 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 MON FEB 1 2010
.TODAY…CLOUDY WITH SCATTERED RAIN AND SNOW SHOWERS. ISOLATED AREAS
OF LIGHT FREEZING RAIN INLAND THIS MORNING. PATCHY MORNING FOG. HIGHS
IN THE LOWER TO MID 30S. VARIABLE WIND TO 10 MPH. NEAR SEWARD…
NORTH WIND 10 MPH.
.TONIGHT…MOSTLY CLOUDY. ISOLATED RAIN AND SNOW SHOWERS IN THE
EVENING. PATCHY FOG AFTER MIDNIGHT. LOWS IN THE MID TEENS TO LOWER
30S. LIGHT WINDS EXCEPT NORTH 15 MPH NEAR SEWARD.
.TUESDAY…PARTLY CLOUDY. PATCHY MORNING FOG. HIGHS IN THE
UPPER 20S TO MID 30S. LIGHT WINDS EXCEPT NORTH 15 MPH NEAR
TEMPERATURE / PRECIPITATION
SEWARD 35 25 34 / 20 20 0
GIRDWOOD 35 24 33 / 0 0 0
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
recorded light southeasterly winds yesterday averaging 5-8mph. The current temp is 27F (5 degrees colder than yesterday) with winds averaging 2mph out of the east.
-2600′ Seattle Ridge Wx Station-
recorded light southeasterly winds yesterday averaging 5-15mph. Winds are currently averaging 7mph out of the southeast.
-1800′ Center Ridge Wx Station-
recorded no new snow in the last 24 hours. The current temp is 32F (1 degree colder than yesterday) with a total snowpack depth of 63 inches.