Turnagain Pass Avalanche Forecast

Good morning backcountry travelers this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Wednesday, December 23 at 7 am. This will serve as a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (advisory does not apply to highways, railroads, or operating ski areas).

ANNOUNCEMENTS

Placer River Drainage is currently open to snowmachining. With all this rain we will be watching the snowpack. Placer may need to close if the snowpack gets to skinny. Twentymile remains closed.

WEATHER ROUNDUP

In the last 24 hours, 4 inches of new snow fell in Turnagain Pass and 0 inches fell in Summit Lake. The winds have chilled out slightly but continue to gust into the mid 40’s on ridgetops. Two days ago we saw winds gusting in the 60’s out of the east. Total 48 hour snow fall in Turnagain Pass is approximately 9 inches, Summit Lake 3, and Girdwood 5-6 inches. These amounts are above the snowline. The snowline is approximately 0 to 500 ft. For the most part rain fell at sealevel the last few days, it looks like a trace of precip turned to snow in the Girdwood Valley last night.

AnCNFAIC Staff low pressure system in moving into the area today. A 987mb low will move onshore this morning. The radar and satellite are packed with colorful precip. The NWS is forecasting up to 5 inches of snow for higher elevations. Most likely Turnagain Pass. This is a short lived precipitation event and should be spent by late afternoon.

-The Center Ridge Wx Station at 1800 feet/Turnagain Pass-

recorded 4 inches of new snow and 0.4 inches of water in the last 24 hours. The current temp is 29F (1 degrees colder than yesterday) with a total snowpack depth of 60 inches.

-The Sunburst Wx Station at 3800 feet/Turnagain Pass-

is showing 13 mph winds out of the ENE, with gust 23-38 mph. The current temperature is 23 deg F

-The Summit Lake Wx Station at 1200 feet-

recorded 0 inches of new snow and 0.1 inches of water in the last 24 hours. The current temp is 29F (1 degree colder than yesterday) with a total snowpack depth of 30 inches.

-The Fresno Ridge Wx Station at 3400 feet/Summit Lake-

recorded is showing 23 mph winds with gust of 21 -41 mph out of the SE.

The weather forecast for:

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

.500 AM AKST WED DEC 23 2009

.TODAY…SNOW IN THE MORNING BECOMING SNOW AND RAIN IN THE

AFTERNOON. SNOW ACCUMULATION UP TO 2 INCHES ALONG THE COAST TO 5

INCHES THROUGH TURNAGAIN PASS. HIGHS IN THE 30S. NORTH AND EAST WIND

10 TO 20 MPH.

.TONIGHT…CLOUDY WITH SCATTERED SNOW SHOWERS. LOWS IN THE MID 20S

TO LOWER 30S. SOUTH TO EAST WIND 10 TO 15 MPH.

.THURSDAY…CLOUDY. SNOW AND RAIN LIKELY IN THE AFTERNOON. SNOW

ACCUMULATION UP TO 1 INCH. HIGHS IN THE 30S. NORTHEAST WIND 10 TO 20

MPH.

.THURSDAY NIGHT…SNOW LIKELY. LOWS IN THE LOWER 20S TO MID 30S.

EAST WIND 10 TO 20 MPH.

.CHRISTMAS DAY…SNOW AND RAIN LIKELY. HIGHS IN THE 30S. EAST

WIND 10 TO 25 MPH.

TEMPERATURE / PRECIPITATION

SEWARD 39 29 37 / 100 40 80

GIRDWOOD 39 34 37 / 100 80 40

AVALANCHE DISCUSSION

With additional precipitation forecasted today the avalanche hazard will remain CONSIDERABLE on steep wind loaded slopes. Dangerous avalanche conditions exist on terrain 35 degrees or greater. Careful snowpack evaluation, cautious routefinding and conservative decision-making is essential. Natural avalanche possible during the snow event and human triggered avalanches likely. All CNFAIC Staff terrain has a MODERATE avalanche hazard.

Observations form yesterday prove that the buried surface hoar and faceted snow 1-2 feet deep is still reactive. A skier on Eddies was able to trigger a small to medium sized avalanche yesterday approximately 12 inches deep. CNFAIC Staff professional observations indicate this instability is real and ranges from Seward to Girdwood. The surface slab of snow is 12-24 inches thick and resting on surface hoar and faceted snow formed the second week of Dec. This new, slab snow has gained energy from recent winds gusting to 70 mph. If you remember the buried surface hoar reached approximately 2000 ft. I have reason to believe it is actually higher in some locations. This is one of those times that the avalanche hazard is greater at low and mid elevations than above 3000 ft.

We have not seen the natural avalanche cycle peak on this weak layer yet. AnCNFAIC Staff inch of water or foot of snow may tip the balance. Remember the stress vs strength concept? Enough stress or load will trigger this weak layer. This may be the case this afternoon.

I will issue the next advisory tomorrow morning at 7am. If you get out in the backcountry give us a call at 754-2369 or send us your observations using the button at the top of this page