Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Monday, December 28 at 7 am. This will serve as a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (advisory does not apply to highways, railroads, or operating ski areas).
Placer River Drainage and Twentymile are closed to snowmachining due to heavy rain and warm temps at sea level.
Yesterday a trace to one inch of new snow fell at the higher elevations of Turnagain Pass while the rain/snow line hovered around 2000 feet. The rain at the lower elevations tapered off by afternoon, and skies partially cleared. Ridgetop winds averaged 20-30mph out of the east and southeast while mountain temperatures ranged from the mid 20’s to mid 30’s.
As of 4 am this morning, ridgetop winds in Turnagain Pass are currently averaging 10-15mph out of the east with gusts in the 20’s. Skies are partly cloudy in Girdwood right now with temperatures ranging from 40F at sea level to 26F at 3800 feet. The freezeline looks to be around 2000 feet this morning. After 7 days of rain and strong winds, high pressure is building in behind the last remaining shortwave bringing cooler and drier weather to the area. Expect light easterly winds today averaging 10-15mph with stronger winds closer to Turnagain Arm. We may see a few scattered showers this morning, but skies should clear off by this afternoon. Mountain temperatures will remain in the mid 20’s to lower 30’s.
-The Center Ridge Wx Station at 1800 feet/Turnagain Pass-
recorded no new snow and 0.2 inches of water in the last 24 hours. The current temp is 33F (1 degree colder than yesterday) with a total snowpack depth of 63 inches.
-The Sunburst Wx Station at 3800 feet/Turnagain Pass-
recorded moderate to strong east winds yesterday averaging 20-30mph with gusts in the 30’s and 40’s. The current temp is 26F (1 degree colder than yesterday) with winds averaging 10-15 mph out of the east.
-The Summit Lake Wx Station at 1200 feet-
recorded 0 inches of new snow in the last 24 hours. The current temp is 31F (1 degree colder than yesterday) with a total snowpack depth of 31 inches.
-The Fresno Ridge Wx Station at 3400 feet/Summit Lake-
recorded moderate southeasterly winds yesterday averaging 15-20mph with gusts in the 30’s. The current temp is 26F (1 degree colder than yesterday) with winds continuing to average15-20mph out of the southeast.
The weather forecast for:
WESTERN PRINCE WILLIAM SOUND-
.TODAY…CLOUDY. SCATTERED RAIN SHOWERS AND SNOW SHOWERS IN THE
MORNING…THEN ISOLATED RAIN SHOWERS IN THE AFTERNOON. HIGHS IN THE
MID 30S TO LOWER 40S. NORTH TO EAST WIND TO 15 MPH EXCEPT EAST WIND
20 TO 30 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.
.TONIGHT…MOSTLY CLOUDY. PATCHY FOG AFTER MIDNIGHT. LOWS IN THE
MID 20S TO MID 30S. VARIABLE WIND 10 MPH.
.TUESDAY…PARTLY CLOUDY. PATCHY MORNING FOG. HIGHS IN THE
UPPER 20S TO UPPER 30S. VARIABLE WIND 10 MPH.
TEMPERATURE / PRECIPITATION
SEWARD 43 29 38 / 40 0 0
GIRDWOOD 36 28 34 / 20 0 0
The avalanche danger remains MODERATE today on slopes steeper than 35 degrees. Human-triggered avalanches are possible on the new storm snow/windslab above 2000 feet and on the buried surface hoar below 2000 feet. Natural avalanches are unlikely today.
The surface hoar that formed the second week of December is now buried 1-2 feet deep below 2000 feet elevation in Turnagain Pass. It was reactive as recently as 4 days ago when numerous natural and human-triggered avalanches occurred on this layer. Most were small in size, up to 50 feet wide, and confined to steep rollovers below treeline. I would still approach these lower elevation steep slopes with caution, especially on the northern end of Turnagain Pass where the surface hoar is buried deeper and thus more protected from the warm temps and rain. Above 2000 feet in Turnagain Pass, surface instabilities from the new storm snow and windslab still exist in the top foot or so, but these should stabilize quickly as temps cool off. I would approach steep unsupported rollovers with caution and gradually ease back into steeper terrain.
As skies clear and the temps cool off the next few days, the wet glop at the lower elevations will freeze up solid making for some classic coastal Alaska skiing and riding conditions. At least the stability will improve. Thankfully there is great snow above 2000 feet if you can negotiate the breakable crust below.
Some notes from Summit Lake….Jon toured up Tenderfoot Ridge (the old ski hill) yesterday and observed winds out of the NE actively loading lee slopes near the ridgetops. He also saw numerous recent natural avalanches that occurred sometime this past week on windloaded south to west aspects above 2500 feet. Although his group observed no collapsing or cracking, the surface windslab fractured easily during their stability tests above 2500 feet elevation. They also found some small surface hoar (1.5mm) buried 10 inches deep at 2500 feet on a southwest aspect, but it did not fracture in their stability tests. The snow on the ridge was windhammered, but off the ridgetops above 2000 feet it was wind-buffed and carvable.
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.