Turnagain Pass

GENERAL ANNOUNCEMENTS

Good Morning backcountry travelers, this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Saturday, January 24, 2009 at 7am. This will serve as a general backcountry avalanche advisory issued 5 days a week Wednesday-Sunday for the Turnagain Arm area (Turnagain Pass is the core advisory area). Local variations always occur.

MOUNTAIN WEATHER ROUND UP

In the last 24 hours…

–The DOT weather station near the crest of the highway at Turnagain Pass at 1000 feet–

Is recording a temp of 29 degrees (same as yesterday), light NE winds and a total snowpack depth of 41 inches.

–The Center Ridge weather station at 1800 feet in Turnagain Pass–

Has a temp of 26 degrees (1 deg warmer than yesterday). Total snow depth is 63 inches with 2 inches new snow and .2 inches of water equivalent.

–Sunburst weather station along the ridge at 3800 feet in Turnagain Pass–

is off line this morning, hopefully it will show it’s face again soon?

-Surface Analysis Maps-

A 997 mob low directly to our west. I think this system hold our hopes for precip this weekend. Higher pressure in the gulf.

-Satellite-

Next band of moisture is attached to the low moving at us from the west. Generally systems that move into the advisory area from the west are not as significant for us. Anchorage generally sees snow out of this flow pattern. The big precip events for us come from the Sound.

-Radar-

Scattered snow showers. Not seeing a lot of precip. I think the weekend snow showers that are predicted are still off to the west of the Kenai radars range.

-General Weather Observations-

Moderate winds out of the SE and temps in the low 20’s on our ridge tops this morning. Slightly warmer, calmer weather at sea level. Look for scattered cloudy skies today with 1-3 inches of accumulation.

AVALANCHE THREATS

Primary avalanche concerns

-Deep slabs 2-6 feet thick on top of January facets

-thinner wind slabs

Secondary avalanche concerns

-Glide Cracks (now they are bridged over, don’t fall in)

WATCH OUT SITUATIONS

-Higher elevations above 3,000 feet

-Slopes that do not have a clean run out

AVALANCHE AND SNOWPACK DISCUSSION

Our coastal snowpack is drastically different as we climb in elevation. Heavy rains pounded the advisory area 8 days ago from sea level to 2800 ft. Rain runnels and boiler plate surface snow is present at sea level. Light snow showers yesterday and last night are helping soften the appearance. Mid elevations we see softer surface conditions as the rain crust is not as thick. Above 2800 ft the crust is not present as rains did not reach above 2800 ft in most locations.

The avalanche hazard below 2000 is low. Above 2000 feet the chance to trigger an avalanche increases as you get closer to the ridge tops where drier wind driven snow is present. I don’t suspect any natural avalanche activity today, but human triggered avalanches are possible on leeward or cross loaded alpine aspects. These areas could potentially hold thin wind slabs that could trigger large deep wind slabs.

IN MORE DETAIL

Yesterday morning we saw E and SE winds gusting to 40 mph. These quick, targeted winds were able to form some new shallow and sensitive wind slabs at Alyeska. I believe similar wind slabs were formed throughout the area. These slabs could be present on leeward and cross-loaded aspects from 2000 ft and up. These new wind slabs have a granular weak layer on a crusty bed surface under them. In general these shouldn’t be a huge threat but could cause a problem if triggered above complex terrain or terrain traps. They could also trigger larger deeper slabs above 3000 ft.

The significant weak layer in our current snowpack is the Dec. facets that were formed during the below zero deg. temps we had over the holidays. This layer of faceted snow is healing below 2800 feet due to the warm wet snow and rain we received. Above 2800 feet these cold facets are still present. In most of our tests this week we are seeing this layer strengthen with moderate Q2,Q3 sheer tests.

Crown profile of natural class 3 avalanche on west face of Magnum, 3000 ft.

There are plenty of places to stay safe in the backcountry this weekend, but we all need to work hard at keeping our human factors in check. Deep slab instabilities are present at higher elevations. You probably will not trigger them, but if you do it will be a huge avalanche. Make sure to check the snowpack you are traveling on or under. Many of you are itching to start checking some projects of the summit list. Take your time with the peaks above 3500 ft. I’ve got the same list and know Goat, Raggedtop, Big League, and Pastoral are all on it. The visibility may not allow us to get these guys this weekend but if clouds break, these high snow fields have not been tested since this last storm. Large wind slabs will be present.

Weather

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST SAT JAN 24 2009

.TODAY…CLOUDY WITH SCATTERED SNOW SHOWERS IN THE MORNING…THEN

SNOW IN THE AFTERNOON. SNOW ACCUMULATION 1 TO 4 INCHES. HIGHS

IN THE UPPER 20S TO MID 30S. NORTH TO EAST WIND TO 15 MPH EXCEPT

EAST 20 TO 35 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.

.TONIGHT…SNOW. SNOW ACCUMULATION 1 TO 3 INCHES. LOWS IN THE

MID 20S TO LOWER 30S. NORTH TO EAST WIND 10 TO 20 MPH EXCEPT

EAST 20 TO 35 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.

.SUNDAY…SNOW. SNOW ACCUMULATION 2 TO 6 INCHES. HIGHS IN THE

UPPER 20S TO LOWER 30S. NORTH TO EAST WIND TO 15 MPH EXCEPT

EAST 15 TO 30 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.

.SUNDAY NIGHT…CLOUDY WITH A CHANCE OF SNOW. LOWS IN THE 20S.

NORTH TO WEST WIND TO 15 MPH.

.MONDAY…MOSTLY CLOUDY. HIGHS IN THE MID 20S TO LOWER 30S.

NORTH TO WEST WIND 10 TO 20 MPH.

TEMPERATURE / PRECIPITATION

SEWARD 32 27 32 / 80 60 60

GIRDWOOD 32 30 32 / 80 80 60

Thanks for checking the CNFAIC avalanche advisory. Have a great day.