Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Monday, February 22nd 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 48 hours in Turnagain Pass. Under cloudy skies yesterday, winds averaged 5-25mph out of the east while mountain temps ranged from the upper 20’s at 3800 feet to low 40’s at 1800 feet. Temperatures have cooled off slightly this morning but are still well above average, ranging from 30F@sea level to 35F@1800′ to 30F@3800′. It’s worth mentioning that temperatures have been above freezing at the mid elevations for at least the last four days, and in some areas the last seven days. Skies are clear this morning, and ridgetop winds are light averaging 10-15mph out of the east. Looks like we have a pretty nice day in store today before the next low moves into the region tomorrow. Expect partly cloudy skies, continued warm temps in the upper 20’s to upper 30’s, and moderate easterly winds averaging 15-25mph.
Today the avalanche danger remains CONSIDERABLE. Human-triggered avalanches are likely on slopes steeper than 35 degrees while natural avalanches will be possible on south facing sun-affected slopes. The biggest storm of the season ended only 3 days ago, bringing 7.5 feet of snow and 9 inches of water to Turnagain Pass. Although we are well past the apex of the natural avalanche cycle (Feb. 18), the avalanche hazard remains elevated due to four straight days of unusually warm temperatures. Our main concerns today are sensitive windslab at the higher elevations and wet slab avalanches at the mid and lower elevations, especially on south facing slopes.
Below freezing temperatures above 3000 feet have helped to stabilize the new snow, but Friday’s high winds left us with some sizeable windslabs and a somewhat windhammered snowpack up high. Shooting cracks and hollow hardslab were reported near ridgetops yesterday. Of greater concern is the possibility of wet slab avalanches on south facing slopes and at the mid elevations where the snowpack remains saturated. Rollerballs, pinwheels, and point-release sluffs are all indications that the surface snow is unstable and that it is time to get off the slope.
The big unknown right now is the condition of our deep slab instabilities, most notably several layers of buried surface hoar and the Jan. 7 rain crust. Numerous large natural and explosive-triggered avalanches ran on the deeply buried Jan. 7 rain crust during this latest storm. And the buried surface hoar was responsible for many natural and human-triggered slides before the storm really got cranking. I’m guessing that a majority of the natural avalanches that happened during the storm ran on or stepped down to these layers. Avalanches triggered today could possibly step down to these deep weak layers, creating a much larger avalanche.
We received a report of new glide cracks forming in the upper Girdwood Valley (2200 feet on Raggedtop) that opened up noticeably since Saturday. Cornices were also noted to be sagging, probably from the April-like temperatures the last 4 days. As always, give both glide cracks and cornices a wide berth.
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. Thanks and have a great day.
The NWS weather forecast for:
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST MON FEB 22 2010
.TODAY…MOSTLY CLOUDY WITH AREAS OF FOG IN THE MORNING. PARTLY
CLOUDY IN THE AFTERNOON. HIGHS IN THE MID 30S TO LOWER 40S. EAST WIND
10 TO 20 MPH.
.TONIGHT…MOSTLY CLOUDY. SCATTERED SNOW SHOWERS AFTER MIDNIGHT. LOWS
IN THE MID 20S TO MID 30S. EAST WIND 10 TO 20 MPH.
.TUESDAY…CLOUDY. A CHANCE OF SNOW IN THE MORNING…THEN A CHANCE OF
SNOW AND RAIN IN THE AFTERNOON. HIGHS IN THE MID 30S TO LOWER 40S.
EAST WIND 10 TO 15 MPH.
.TUESDAY NIGHT…SNOW LIKELY. LOWS IN THE MID 20S TO MID 30S.
LIGHT WINDS EXCEPT NORTH 10 MPH NEAR SEWARD.
.WEDNESDAY…RAIN AND SNOW LIKELY. HIGHS IN THE MID 30S TO LOWER 40S.
LIGHT WINDS EXCEPT NORTH 10 MPH NEAR SEWARD.
TEMPERATURE / PRECIPITATION
SEWARD 39 32 39 / 10 30 40
GIRDWOOD 38 28 37 / 0 30 30
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
recorded light easterly winds yesterday averaging 5-15mph. The current temp is 30F (1 degree colder than yesterday) with winds averaging 13mph out of the east.
-2600′ Seattle Ridge Wx Station-
recorded moderate southeasterly winds yesterday averaging 15-25mph with gusts to 36mph. Winds are currently averaging 15mph out of the southeast this morning.
-1800′ Center Ridge Wx Station-
recorded no new snow in the last 24 hours. The current temp is 35F (2 degrees colder than yesterday) with a total snowpack depth of 93 inches (3 inches of settlement since yesterday, 21 inches settlement since 2/18). The temperature has been above freezing for the last four days.