Turnagain Pass

Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Tuesday January 5th 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

Will recent weather effect avalanche conditions today?

Well, let’s take a closer look at the precip, winds, and temps.

Hindcast (Last 24 hours)

3800′ -Sunburst Wx Station-

Temperatures have been increasing from 23 to 26 degrees F with light to moderate winds averaging 5-23 mph from the E with a strong max gust of 42 mph

2400′-Seattle Ridge Wx Station-

Winds have been light to moderate averaging 9-26 mph from SE with a max gust of 39 mph

1800′-Center Ridge Wx Station-

Precip: 0.0 inches of water

Total depth of 57 inches

Temperatures have increased from 30-33 degrees F

Nowcast

A few stars are visible over Girdwood as of 5am. The Middleton radar shows some moderate scattered precip moving north directly over Turnagain Pass, but the Kenai radar only shows light scattered precip. Compared to yesterday, temps are warmer by 1-7 degrees at all wx stations. Temps range 33 degrees F at sea-level to 26 degrees F at 3800′. Winds have backed off a bit since yesterday at most ridgetip wx stations.

Forecast

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST TUE JAN 5 2010

…STRONG WIND WEDNESDAY MORNING THROUGH WEDNESDAY EVENING

THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…

.TODAY…CLOUDY. PATCHY MORNING FOG. HIGHS IN THE MID 30S

TO LOWER 40S. NORTH TO EAST WIND TO 15 MPH.

.TONIGHT…CLOUDY. LOWS IN THE UPPER 20S TO MID 30S. NORTH

TO EAST WIND TO 15 MPH. GUSTS TO 30 MPH NEAR SEWARD AND

THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.

.WEDNESDAY…A CHANCE OF RAIN AND SNOW IN THE MORNING…THEN

RAIN IN THE AFTERNOON. HIGHS IN THE MID 30S TO LOWER 40S.

NORTH TO EAST WIND 10 TO 25 MPH EXCEPT EAST 35 TO 50 MPH

THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.

TEMPERATURE / PRECIPITATION

SEWARD 37 32 37 / 0 0 70

GIRDWOOD 37 32 37 / 0 0 70

Short Term Weather Models (NAM, WRF, QPF) for the Kenai Mountains near Turnagain Pass

Sea-level: 0.0-0.1 inches of water forecasted today

3000′: temps forecasted between 23 and 32 degrees F with winds 5-10mph

6000′: temps forecasted between 23 and 32 degrees F with winds 10-35mph

AVALANCHE DISCUSSION

Today’s weather should not contribute to the avalanche danger today at Turnagain Pass. Yesterday’s wind was from the normal prevailing direction, and it did not have much snow to transport. We did observe some plumes of snow yesterday, but nothing remarkable. We did not observe any significant wind slab stability problems.

There are two main points of interest in the current snowpack defined by elevation.

1.Below 2200′, there is a layer buried surface hoar generally buried about 10-12 inches deep. Plus there is an ice layer at these lower elevations. These could become very dangerous weak layers in the future. Luckily they are confined to lower angle slopes at lower elevations. We will have to be careful at lower elevations in places like Placer Valley if that area ever opens this year. Plus anCNFAIC Staff layer of surface hoar formed with the largest crystals in the bathtub ring where the fog layer was hanging out on the valley walls like the water in a bathtub.

2.Near ridgetops, we continue seeing an instability 6-12 inches deep under the surface. It only shows itself in isolated column stability tests, but it has not been reactive to skis, snowboards, or snowmachines. As of Monday 1/4/09, this layer was reported on Lipps failing with easy to moderate shears in a compression test.

These 2 points of interest are not a problem for today’s stability.

Due to a lack of significant weak layers and a mild weather forecast, the avalanche danger for Turnagain Pass will decrease today to LOW. LOW is defined as: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human-triggered avalanches unlikely. Small avalanches in isolated areas or extreme terrain.

AnCNFAIC Staff concern today will be the glide cracks. A couple of large glide cracks have opened north of the snowmachine uptrack to Seattle ridge. Odds are there are numerous more of these crevasse like features which may be difficult to see. People and dogs have fallen into these cracks before, and they can be very difficult to get out of. Sometimes these glide cracks will avalanche, but this does not appear to be a concern today. It’s always a good idea to treat glide cracks like cornices and avoid traveling underneath their path. Like cornices, glide cracks are very difficult to predict.

Always remember that safe backcountry travel requires training and experience. You control your own risk by choosing where, when, and how you travel.

Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Wednesday January 6th.