Turnagain Pass

Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Wednesday December 16th 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 have been dropping from 20-15 degrees with calm winds averaging 1-10 mph from variable directions with a light max gust of 17 mph

2400′-Seattle Ridge Wx Station-

Winds have been calm averaging 0-5 mph from variable directions with a calm max gust of 5 mph

1800′-Center Ridge Wx Station-

Precip: 0.1 inch of water and 2 inches of new snow

Total depth of 56 inches

Temperatures have been dropping from 22-12 degrees F

Yesterday’s snow stake totals

Eddies Lot: 3″ new

Motorized Lot: 4″ new

Sunburst Lot: 5″ new

Johnson Pass North Lot: 4″ new

*These parking lot totals show a bit more snow than was recorded by the Center Ridge wx station yesterday morning which reported 2″.

Nowcast

Light snow is falling in Girdwood as of 5am. The Middleton radar shows moderate precip moving north mostly over PWS and Cordova and the Kenai radar shows light precip moving north toward Anchorage. Temps are 3-10 degrees colder at most wx station with temps ranging from 18 degrees at sea-level to 15 degrees at 3800′. Winds are calm to light at all ridgetip wx stations this morning.

Forecast

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST WED DEC 16 2009

.TODAY…SNOW. SNOW ACCUMULATION UP TO 3 INCHES EXCEPT 6 TO 12

INCHES FROM WHITTIER TO GIRDWOOD. HIGHS 15 TO 25. VARIABLE WIND

TO 10 MPH. NEAR SEWARD…NORTH WIND TO 15 MPH SHIFTING TO SOUTH

15 TO 25 MPH IN THE AFTERNOON.

.TONIGHT…SNOW IN THE EVENING FROM WHITTIER TO GIRDWOOD WITH

UP TO 4 INCHES ADDITIONAL ACCUMULATION. CNFAIC StaffWISE…SCATTERED

SNOW SHOWERS. LOWS 5 BELOW TO 15 ABOVE…COLDEST INLAND. SOUTH

TO EAST WIND TO 15 MPH.

.THURSDAY…MOSTLY CLOUDY WITH SCATTERED SNOW SHOWERS. HIGHS

5 TO 15 ABOVE. VARIABLE WIND TO 10 MPH. NEAR WHITTIER AND

SEWARD…LIGHT WINDS BECOMING NORTH TO WEST 15 TO 30 MPH IN

THE AFTERNOON.

TEMPERATURE / PRECIPITATION

SEWARD 23 11 12 / 70 40 40

GIRDWOOD 17 10 12 / 100 80 60

Short Term Weather Models (NAM) (MM5) for the Kenai Mountains near Turnagain Pass

Sea-level: 0.0 – 0.25 inches of water forecasted today

3000′: temps forecasted below freezing today around 14-23 degrees F with calm winds 5-10mph

6000′: temps forecasted below freezing today around 5-14 degrees F with light winds 10-15mph

AVALANCHE DISCUSSION

The weather should not contribute significantly to the avalanche danger today at Turnagain Pass. The NWS and weather models directly over Turnagain Pass are not forecasting much wind for the Turnagain Pass area. Plus the models really jive with the NWS forecast because they show most of the precip between Whittier and Girdwood and not in the Kenai Mountains.

Due to insignificant results in recent snow stability test pits, zero significant natural or human-triggered avalanches reported or observed recently, and a lack of wind forecasted 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 Thursday December 17.