Turnagain Pass

Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, December 12th 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 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 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.

BOTTOM LINE

Today the avalanche hazard will remain MODERATE overall. Natural avalanches are unlikely, but small human triggered avalanches are possible in steep upper elevation windloaded terrain where multiple layers of buried surface hoar exist in the upper 12 inches of the snowpack. The primary concern today is triggering a slide on one of these layers, especially if buried under newly formed windslab. If the north winds pick up later this afternoon, wind driven snow will further stress the buried surface hoar layers and increase the avalanche danger on leeward aspects.

AVALANCHE DISCUSSION

It has been about a week since our last reported human triggered avalanche. The buried surface hoar layers have lost a lot of their reactivity due to the small incremental snowfall amounts and mostly light winds this past week, but that could easily change with strong winds moving snow around. Surface hoar tends to survive down off of windswept ridgelines in more protected areas, so be prepared for buried pockets midslope and always have an escape route.

As far as the Thanksgiving Rain Crust (TRC), we continue to receive varying observations. It’s buried anywhere from 4 inches to 1.5 feet deep. Some folks are reporting collapsing of the snowpack under the crust where facets are starting to develop while CNFAIC Staff folks are reporting no failures above or below the crust in their snowpit stability tests. Jon got full fracture propagation under the TRC in an Extended Column Test a few days ago in the upper Girdwood Valley in addition to collapsing and whumphing. I got numerous failures under the crust yesterday in my snowpit tests, but the shears were rough and I really had to wail on the shovel. At this point, I think it’s going to take a much bigger snow load before we see any action on this layer.

I thought we could put the glide crack saga to bed, but no…they are appearing again. I saw some nice ones yesterday mostly on southerly aspects between 2000 and 3000 feet elevation on Tincan, Pete’s North, and Lips. Several new cracks were also found on the south side of Superbowl Peak.

WEATHER ROUNDUP

A trace to possibly 3 inches of new snow fell last night in Turnagain Pass. Winds were light out of the east yesterday while mountain temperatures hovered in the low 20’s. An inversion has set up above the fog this morning with sea level temps dropping to the single digits and mountain temps remaining in the low 20’s. Moose Pass is already down to -5F. Northerly flow will bring clearing skies and colder temperatures to most of southcentral starting today. Expect the north winds to pick up this afternoon at least around Seward and Whittier.

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. Thanks and have a great day.

The NWS weather forecast for:

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST SUN DEC 12 2010

…STRONG WIND SUNDAY NIGHT THROUGH MONDAY NEAR WHITTIER…

.TODAY…MOSTLY SUNNY. AREAS OF FOG IN THE MORNING. HIGHS IN THE MID

TEENS TO LOWER 30S…COOLEST INLAND. LIGHT WINDS INLAND. NEAR

SEWARD…NORTH WIND 20 TO 35 MPH. NEAR WHITTIER…LIGHT WINDS

BECOMING WEST 20 TO 35 MPH IN THE AFTERNOON.

.TONIGHT…MOSTLY CLEAR. PATCHY FOG. LOWS ZERO TO 10 ABOVE EXCEPT

IN THE LOWER 20S NEAR SEWARD AND WHITTIER. LIGHT WINDS INLAND NEAR

SEWARD…NORTH WIND 20 TO 35 MPH. NEAR WHITTIER…WEST WIND 30 TO 45

MPH WITH GUSTS TO 55 MPH.

.MONDAY…PARTLY CLOUDY. PATCHY MORNING FOG INLAND. HIGHS IN THE

LOWER TEENS TO LOWER 30S…COOLEST INLAND. LIGHT WINDS EXCEPT NORTH

WIND 15 TO 30 MPH NEAR SEWARD. NEAR WHITTIER…WEST WIND 30 TO 45

MPH.

TEMPERATURE / PRECIPITATION

SEWARD 28 21 27 / 0 0 0

GIRDWOOD 17 8 15 / 0 0 0

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

recorded light easterly winds yesterday averaging 5-10mph and temps ranging from 20F to 21F. The current temp is 21F with light winds out of the north.

-2600′ Seattle Ridge Wx Station-

stopped working at noon yesterday but recorded temps ranging from 22F to 24F yesterday. The current temp is 20F.

-1800′ Center Ridge Wx Station-

recorded 3 inches(?) of new snow and 0.1 inch of water in the last 24 hours. Temps yesterday fluctuated from 22F to 15F to 20F. The current temp is 20F with a total snowpack depth of 53 inches.