Turnagain Pass

Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Tuesday February 23rd at 7 am. 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).

WEATHER ROUNDUP

-The winds have decreased since yesterday, and are currently light at all ridgetop weather stations this morning. Moderate to strong average wind speeds were recorded yesterday averaging as high as 23-27mph with some extreme gusts up to 41 mph.

-The current radars are mostly clear except for some very light precip way out over the Gulf of Alaska.

-In the last 24 hours (4am-4am), the snotel sites recorded 0 inches of water at Turnagain Pass, 0 inches at Grandview, and 0 at Summit Creek. The total snowpack has settled and/or melted 1-2” since yesterday

-Temps are 3-6 degrees colder at most wx stations this morning compared to yesterday. Temps range from 30 degrees F at sea-level and 24 degrees F at 3800′. *Note temps have remained above freezing at 1800 in Turnagain Pass for the past 5 days with high temps reaching as high as 40 degrees.

AVALANCHE DISCUSSION

Today’s avalanche danger will decrease to MODERATE due to time since the last major avalanche cycle and due to a lack of significant weather in today’s weather forecast.

Some recent avalanche observations include: the formation of glide cracks, small wind slabs, and a sensitive cornice on Seattle Ridge. The winds have been the biggest factor for avalanches recently, and although they have backed off this morning, be careful along ridges for small isolated avalanches. Additionally, be especially careful near cornices. We received a report of a close call on the cornice above Zero Bowl (No Name Bowl) at the top of the snowmachine up-track on Seattle Ridge. A snowmachiner accidently triggered a chunk of cornice that fractured underneath the ski of his snowmachine.

Although temps at mid elevations have been above freezing for 5-7 consecutive days, the snowpack has not been showing any obvious signs of instability. It has still been getting cold enough for a thin crust to form on top of the wet snow at these elevations. The weather stations have not been showing any drastic changes in the total snowpack depth. The snowpack has only settled/decreased by 1-2 inches in the past 48 hours.

The snowpack is starting to pull away from the ground in many locations creating glide cracks. Glide cracks are very difficult to predict. Sometimes they avalanche when it is cold, sometimes when it is warm, sometimes when it rains, sometimes when it snows. The point is that we are having an active glide crack cycle right now. There have been no reports of any glide-crack avalanches yet, but they are noticeably moving and growing throughout the day. It’s always best to avoid traveling underneath or anywhere near glide cracks especially during times that they are actively moving. These crevasse-like cracks in the snow are total wild cards.

WEATHER FORECAST (National Weather Service)

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST TUE FEB 23 2010

.TODAY…MOSTLY CLOUDY. A CHANCE OF RAIN IN THE AFTERNOON. HIGHS IN

THE MID 30S TO LOWER 40S. VARIABLE WIND 10 MPH.

.TONIGHT…CLOUDY WITH A CHANCE OF SNOW. LOWS IN THE MID 20S TO

LOWER 30S. VARIABLE WIND 10 MPH.

.WEDNESDAY…CLOUDY. A CHANCE OF SNOW IN THE MORNING…THEN A

CHANCE OF RAIN AND SNOW IN THE AFTERNOON. HIGHS IN THE 30S. LIGHT

WINDS.

.WEDNESDAY NIGHT…CLOUDY WITH A CHANCE OF SNOW. LOWS IN THE MID

20S TO LOWER 30S. LIGHT WINDS.

Temperature / Precipitation

SEWARD 40 28 38 / 30 60 40

GIRDWOOD 39 28 38 / 0 20 30

Short Term Weather Model Forecasts (NAM, WRF, GFS) for the Kenai Mountains near Turnagain Pass

Sea-level: temps are forecasted between 28-39 and between 0.0”-0.1” of water forecasted

3000′: temps are forecasted in the range of 23-32 degrees F with winds 10-15mph

6000′: temps are forecasted in the range of 23-32 degrees F with winds 10-15mph

WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS

3800′-Sunburst Wx Station

Current Temp: 24 (6 degrees colder than yesterday)

Winds: averaging light at 5mph with light gusts up to 9mph

2600′-Seattle Ridge Wx Station

Winds: averaging light at 6mph with light gusts to 10mph

1800′-Center Ridge Wx Station

Current Temp: 32 degrees (4 degrees colder than yesterday)

Precip: 0 new water, 0 new snow, 2” of total snowpack settlement/melting

Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Wednesday February 24th.