Turnagain Pass

Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Monday, January 4th at 7am. 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).

ANNOUNCEMENTS

All areas designated for snowmachines on the Chugach National Forest are open to snowmachining except Placer and 20 Mile. Please remember that Center and Divide Creeks near the Johnson Pass North Trailhead are always closed due to the current Forest Plan.

WEATHER ROUNDUP

A trace to one inch of new snow fell in the last 24 hours in Turnagain Pass. Yesterday ridgetop winds averaged 15-30mph out of the east and southeast while mountain temperatures warmed up to the low to mid 20’s. As of 4 am this morning, ridgetop winds in Turnagain Pass are averaging 25mph out of the east and southeast with gusts in the 30’s and 40’s. Temperatures currently range from 22F at 3800 feet to 37F at sea level. The passage of a warm front will generate strong winds along Turnagain Arm and the higher elevations today. We will see even warmer mountain temperatures in the mid/high 20’s to low 30’s as strong southerly flow dominates. Any remaining snow showers should taper off by midday while ridgetop winds will remain strong, averaging 20-30mph out of the east and southeast.

-The Center Ridge Wx Station at 1800 feet/Turnagain Pass-

recorded 1 inch of new snow in the last 24 hours. The current temp is 31F (8 degrees warmer than yesterday) with a total snowpack depth of 58 inches.

-The Sunburst Wx Station at 3800 feet/Turnagain Pass-

recorded moderate to strong easterly winds yesterday averaging 15-30mph with gusts in the 30’s and 40’s. The current temp is 22F (6 degrees warmer than yesterday) with winds averaging 25mph out of the east.

-The Summit Lake Wx Station at 1200 feet-

recorded 1 inch of new snow in the last 24 hours. The current temp is 29F (8 degrees warmer than yesterday) with a total snowpack depth of 29 inches.

-The Fresno Ridge Wx Station at 3400 feet/Summit Lake-

recorded light southeasterly winds yesterday averaging 10-15mph. The current temp is 23F (6 degrees warmer than yesterday) with winds averaging 15mph out of the southeast.

The weather forecast for:

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST MON JAN 4 2010

.TODAY…CLOUDY WITH RAIN AND SNOW…MAINLY ALONG THE COAST.

SNOW ACCUMULATION UP TO 2 INCHES AT HIGHER ELEVATIONS. HIGHS

IN THE 30S. EAST WIND 10 TO 20 MPH EXCEPT 25 TO 40 MPH THROUGH

PORTAGE VALLEY AND TURNAGAIN ARM.

.TONIGHT…MOSTLY CLOUDY IN THE EVENING WITH SCATTERED RAIN

AND SNOW SHOWERS…THEN BECOMING PARTLY CLOUDY. LOWS IN THE

LOWER 20S TO LOWER 30S…COLDEST INLAND. NORTH TO EAST WIND

TO 15 MPH WITH GUSTS TO 25 MPH THROUGH PORTAGE VALLEY AND

TURNAGAIN ARM.

.TUESDAY…PARTLY CLOUDY IN THE MORNING THEN BECOMING MOSTLY

CLOUDY. HIGHS IN THE UPPER 20S TO MID 30S. NORTH TO EAST WIND

10 TO 20 MPH.

TEMPERATURE / PRECIPITATION

SEWARD 36 32 36 / 90 20 0

GIRDWOOD 35 28 33 / 70 30 0

AVALANCHE DISCUSSION

Due to strong easterly winds, small human-triggered avalanches are possible today at the higher elevations in Turnagain Pass on recently formed windslabs and any CNFAIC Staff actively loading slopes. Although only 1-2 inches of new snow fell in the last few days, there is still quite a bit of old powder to move around above 2000 feet. For the most part I would expect any newly formed windslabs near ridgetops to be shallow, but watch for thicker windslabs midslope on crossloaded terrain features. For today, the avalanche danger is rated MODERATE on all actively loading slopes steeper than 35 degrees. Non wind-affected slopes will continue to have a LOW avalanche hazard.

This past week we enjoyed the rare trifecta of good stability, good visibility, and great snow up high. It has been almost 2 weeks since our last reported human-triggered avalanche. I would expect to see some sensitive windslab today above 2000 feet elevation, but not much more in terms of instability. Below 2000 feet, recently formed surface hoar is sitting on ½ -1 inch thick breakable rain crusts. I’m hoping the wind and warm temps will destroy these feathery crystals before they are buried intact and upright. The old buried surface hoar from the second week of December is buried 1-1.5 feet down and has not been especially reactive in our stability tests.

Some Summit Lake observations….Jon toured up Tenderfoot Ridge (the old ski hill) yesterday and found that the recently formed surface hoar went up to 2500 feet elevation and was sitting on a thin crust. The winds were light down there yesterday with 1-2 inches of new snow from the last few days.

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.