Turnagain Pass

Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Tuesday January 12th 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).

ANOUNCEMENTS

Thanks to the group that removed the snowmachine jump on the motorized side of the highway so quickly.

WEATHER ROUNDUP

Hindcast (Last 24 hours)

3800′ -Sunburst Wx Station-

Temperatures ranged between 9 to 23 degrees F with light average winds between 3-13 out of the ENE with a light max gust of 16 mph. Current temp 14.

2400′-Seattle Ridge Wx Station-

Winds have been light averaging 1-6 mph out of the N with a light max gust of 10mph

1800′-Center Ridge Wx Station-

Precip: 0.1 inches of water and 1” of new snow

Total depth of 56 inches

Temperatures ranged between 3-10 degrees F

Current temp 10

Nowcast

Temps are have increased at all wx stations this morning by 3-7 degrees. There is a slight inversion this morning with warmer temps on the ridgelines compared to the valley floors. Winds are starting to increase to the north and south of Turnagain Pass but are still only averaging light to moderate. Precip totals are consistent at all wx stations with about .1 inch of water and 1” of new snow. The Middleton radar shows moderate but scattered precip over PWS moving west toward Turnagain Pass, and there is light precip on the Kenai radar moving west over Turnagain Pass. It’s currently snowing lightly in Girdwood with about 1 inch accumulation

Forecast

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST TUE JAN 12 2010

…STRONG WIND THIS MORNING NEAR SEWARD…

.TODAY…SNOW. SNOW ACCUMULATION 2 TO 5 INCHES. PERIODS OF BLOWING

SNOW NEAR SEWARD AND WHITTIER. HIGHS IN THE MID TEENS TO LOWER

30S…COLDEST INLAND. NORTH TO WEST WINDS 5 TO 15 MPH. GUSTS TO 25

MPH NEAR WHITTIER THIS MORNING. NEAR SEWARD…NORTH WINDS 15 TO 25

MPH WITH GUSTS TO 50 MPH THROUGH EARLY THIS AFTERNOON.

.TONIGHT…SNOW LIKELY. SNOW ACCUMULATIONS 2 TO 4 INCHES. LOWS 15 TO

25. VARIABLE WIND 10 MPH EXCEPT NORTH 10 TO 20 MPH NEAR SEWARD.

TEMPERATURE / PRECIPITATION

SEWARD 28 25 32 / 80 60 40

GIRDWOOD 22 21 29 / 80 40 40

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

Sea-level: GFS shows 0.5 inches of water forecasted today, but the WRF shows the majority of precip tapering off by 9am with the majority of the precip southwest of Seward.

3000′: temps forecasted between 23 and 32 degrees F with winds 10-15mph

6000′: temps forecasted between 14 and 23 degrees F with winds 25-30mph

AVALANCHE DISCUSSION

Today’s weather could contribute to the avalanche danger today at Turnagain Pass if the weather picks up; however, not enough weather has happened yet (as of this morning) to increase the danger. The NWS is calling for strong wind mostly south of Turnagain Pass. The models only show about ½ an inch of water; so, the forecasts don’t look like this storm is going to pack too big of a punch.

Today’s avalanche danger will remain at LOW with the potential for some small wind slabs later this afternoon. LOW is defined as: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human triggered avalanches unlikely (except glide cracks are possible). Small avalanches in isolated areas of extreme terrain.

In simple terms, we have a variety of weak layers below 2800′ and one weak layer at higher elevations between 2800′ up to the ridgelines.

The big picture right now is the rain crust that formed up to 2800′ has a lot of potential to become a very dangerous weak layer in the future. This will be to first bad weak layer at a higher elevation that we have seen all season (except for the facets on the ground in the early season). Turnagain Pass has plenty of terrain steep enough to avalanche at 2800′ including the bowls along Seattle Ridge. It’s difficult to say exactly how this rain crust will react to new snow on top; so, we all need to take it easy once the next big storm comes in.

The wild card right now are the glide cracks. One of these crevasse like features avalanched last week for no obvious or apparent reason (see photo gallery). Nostradamus couldn’t have predicted that one; so, it adds to the theory that glide cracks are like cornices in that they are very difficult to predict. Sometimes they avalanche when it’s cold, sometimes when it’s warm, sometimes when it rains. We have not seen or had any reports of any more glide crack failures in the past week, but it would still be wise to avoid traveling on, near, or underneath the path of any glide cracks.

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 13th.