Turnagain Pass

Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Tuesday December 15th 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).

ANNOUNCEMENTS

All areas designated for snowmachines (except Placer and 20 Mile) on the Chugach National Forest are open. Please remember that Center and Divide Creek near the Johnson Pass Trailhead are always closed due to the current Forest Plan. These areas are periodically patrolled by law enforcement. We are monitoring the snow at Placer and 20 Mile and will open those areas as soon as there is enough snow, these colder temps down low are really helping these 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 were 19-20 degrees with calm winds averaging 3-8 mph from the E with a max calm gust of 12 mph

2600′-Seattle Ridge Wx Station-

Winds have been calm averaging 4-14 mph out of the ESE with a max light gust of 21 mph

1800′-Center Ridge Wx Station-

Precip: 0.1 inch of water and 1 inch of new snow

Total depth of 55 inches

Temperature Range: 19-27

Nowcast

Light snow is falling in Girdwood as of 5am with about 4 inches of new accumulation in the parking lot. The Middleton radar shows scattered to moderate precip mostly over Cordova and the Kenai radar shows light precip moving north. Temps and precip were pretty consistent at most of the weather stations that I checked this morning. One difference is Summit Lake is showing 3 inches of new snow compared to 1 inch at Turnagain Pass. Temps currently range from 23 degrees at sea level to 20 degrees at 3800′ and all ridgetop winds are still calm.

Forecast

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST TUE DEC 15 2009

.TODAY…PERIODS OF SNOW. SNOW ACCUMULATION 1 TO 3 INCHES.

HIGHS IN THE LOWER 20S TO LOWER 30S…WARMEST ALONG THE COAST.

LIGHT WINDS EXCEPT NORTH TO 15 MPH NEAR SEWARD.

.TONIGHT…SNOW. SNOW ACCUMULATION 4 TO 8 INCHES. LOWS IN THE

TEENS TO LOWER 20S INLAND AND MID TO UPPER 20S ALONG THE COAST.

LIGHT WINDS EXCEPT NORTH TO 15 MPH NEAR SEWARD.

.WEDNESDAY…SNOW LIKELY. SNOW ACCUMULATION UP TO 2 INCHES

EXCEPT 4 TO 8 INCHES IN THE PORTAGE VALLEY TO GIRDWOOD AREA.

HIGHS 15 TO 25. LIGHT WINDS EXCEPT NORTH TO 15 MPH NEAR SEWARD.

TEMPERATURE / PRECIPITATION

SEWARD 28 23 23 / 80 70 60

GIRDWOOD 25 21 21 / 100 90 80

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

Sea-level: 0.1 inches of water forecasted today

3000′: temps forecasted below freezing today around 20 degrees with winds 5-10mph

6000′: temps forecasted below freezing today around 15 degrees with winds 10-20mph

AVALANCHE DISCUSSION

Recent weather will not contribute to the avalanche danger today, and the NWS is not forecasting much precip or wind for the Turnagain Pass area.

Due to insignificant results in recent snow stability test pits, zero significant natural or human-triggered avalanches reported or observed recently, and a mild weather forecast from the NWS, today’s avalanche danger level will remain at LOW. LOW is defined as: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human-triggered avalanches unlikely. Very small avalanches in widespread areas; or small avalanches in isolated areas.

Normal Caution is advised.

The next avalanche concern that we are watching out for is on the current surface snow. There are widespread firm or slippery surfaces created by the wind, sun, and warm temps from last week. Surface hoar formed from sea level to as high as 2800′, however, the most defined surface hoar and faceted surface snow is below 1600′; so, due to the slippery surfaces and formation of surface hoar and faceted sugary surface snow, the worst weak layer in the near future will be below 2800′. These mid to lower elevations could become our next big problem when we get the next big weather event. Just as a reminder, most of the bowls along Seattle Ridge are below 2800′. CNFAIC Staff areas with steep terrain below 2800′ include but are not limited to the lower part of Eddies, Pete’s North, and the terrain behind the “Welcome to the Kenai” sign near Pyramid along Seattle Ridge.

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 December 16.