Turnagain Pass

Good morning backcountry travelers this is Kevin Wright with the Chugach National Forest Avalanche Information Center on Saturday, December 11th 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).

ANNOUNCMENTS

Today and tomorrow, December 11-12, there will be an Interagency Avalanche Rescue Training taking place at Turnagain Pass. Alaska Mountain Rescue Group, Alaska Search and Rescue Dogs, Alaska State Troopers, Nordic Ski Patrol, and US Forest Service will be some of the agencies participating in this two day event. There will be scenarios on both the motorized and non-motorized sides of Turnagain Pass. The parking lot on the eastern side of the Seward Highway will still be open to the public, but will also be the location for the staging area for this training exercise. There will be some helicopter use in the area for the purpose of this training event. If you have any comments or concerns, please contact Matt Murphy by phone at 907-754-2349 or email at mattmurphy@fs.fed.us. Thank you for your cooperation with this important safety training.

AVALANCHE DISCUSSION

The avalanche hazard rating is holding steady at MODERATE. We did get 2-3 inches of snow yesterday and moderate wind. I don’t believe this will change our danger rating into the considerable range, but it should be a small increment higher than yesterday. The wind was strong enough to blow that new snow onto the lee side, and you could find accumulation pillows in specific areas. This new snow fell on top of a significant surface hoar layer. We now have multiple layers of surface hoar sandwiched between different storm slabs. The good thing for stability is that recent snowfalls have been relatively minor amounts of snow. This means gradual stable buildup for now, but be prepared for dangerous instabilities to happen when we do get a major storm.

For today, natural avalanches are unlikely and human triggered avalanches possible in specific terrain. Pay attention to the snow depth as you travel to identify wind loading near the ridge tops. Use extra caution in areas where wind loading has occurred and in convex unsupported terrain.

Recent observations show why we need to stay cautious:

-Collapsing (whoomphing) of the snowpack in the Girdwood valley and full propagation in snow pit tests.

-Multiple buried surface hoar layers to the ridgetops nearly everywhere in Turnagain pass. Isolated columns in test pits are failing, but difficult to initiate and mostly not clean shears.

-A snow pit yesterday in Summit found faceting above and below the Thanksgiving Rain Crust, and it was possible to fail the slab on top of the crust. This is a shallower and colder snowpack than Turnagain, but may provide an accelerated model of the Turnagain stability over time.

Surface hoar crystals on Seattle ridge. A future weak layer when it gets buried.

WEATHER ROUNDUP

Before yesterday clear skies, colder temps, and light wind was ideal surface hoar growing conditions. Surface hoar has been found nearly everywhere in Turnagain pass.

Yesterday we received 2-3 inches in the Turnagain pass area with moderate wind.

Lisa 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. Thanks and have a great day.

The NWS weather forecast for:

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST SAT DEC 11 2010

.TODAY…NUMEROUS SNOW SHOWERS. SNOW ACCUMULATION UP TO 2 INCHES.

HIGHS IN THE MID 20S TO MID 30S…COOLEST INLAND. VARIABLE WIND TO 10

MPH. NEAR SEWARD…NORTH WIND 15 TO 25 MPH. NEAR WHITTIER…WEST WIND

10 TO 20 MPH

.TONIGHT…CLOUDY. ISOLATED SNOW SHOWERS IN THE EVENING. LOWS

15 TO 25. VARIABLE WIND 10 MPH EXCEPT NORTH 15 TO 25 MPH NEAR

SEWARD. NEAR WHITTIER…WEST WIND 10 TO 20 MPH INCREASING TO 20 TO 35

MPH AFTER MIDNIGHT.

.SUNDAY…DECREASING CLOUDS. HIGHS IN THE LOWER 20S TO MID

30S…COOLEST INLAND. LIGHT WINDS EXCEPT NORTH AND WEST WIND 20 TO 35

MPH NEAR SEWARD AND WHITTIER. GUSTS TO 45 MPH NEAR WHITTIER.

.SUNDAY NIGHT…MOSTLY CLEAR. LOWS 5 TO 25 ABOVE…COOLEST

INLAND. NORTHWEST WIND 10 TO 15 MPH EXCEPT NORTH 25 TO 35 MPH

NEAR SEWARD. NEAR WHITTIER…WEST WIND 30 TO 45 MPH.

.MONDAY…PARTLY CLOUDY. HIGHS IN THE LOWER TEENS TO LOWER 30S…

COOLEST INLAND. VARIABLE WIND 10 MPH EXCEPT NORTH 15 TO 25 MPH NEAR

SEWARD.

.MONDAY NIGHT…PARTLY CLOUDY. LOWS 5 TO 15.

.TUESDAY THROUGH WEDNESDAY NIGHT…PARTLY CLOUDY. HIGHS 15 TO 25.

LOWS ZERO TO 10 ABOVE.

.THURSDAY AND THURSDAY NIGHT…PARTLY CLOUDY. HIGHS 5 TO 15. LOWS

5 BELOW TO 5 ABOVE.

.FRIDAY…PARTLY CLOUDY. HIGHS 15 TO 25.

TEMPERATURE / PRECIPITATION

SEWARD 35 23 32 / 60 20 0

GIRDWOOD 30 18 25 / 60 0 0

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

Temperatures rose slightly to 20 this morning. Wind was moderate with a max gust of 24, mostly from the east.

-2600′ Seattle Ridge Wx Station-

Temperatures dropped yesterday then rose this morning. Currently 23 degrees. Wind is picking up, steady in the teens and gusting up to 20 from the SE.

-1800′ Center Ridge Wx Station-

Only recorded .1 inch of water, but I suspect a little more than that.