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Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, December 22nd, 2009 - 7:00AM
Expires
Wed, December 23rd, 2009 - 7:00AM
Forecaster
CNFAIC Staff
The Bottom Line

Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Tuesday, December 22 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 open to snowmachining. Twentymile remains closed.

WEATHER ROUNDUP

In the last 24 hours, 5 inches of new snow fell in Turnagain Pass and 3 inches fell in Summit Lake with possibly up to 10 inches at the higher elevations. The winds were nuking yesterday from sea level to the ridgetops, and it proceeded to rain down low on the first day of “winter”. Turnagain Pass saw gale to storm-force east winds yesterday averaging 35-45mph with gusts in the 60’s and 70’s. The winds at Summit Lake averaged 25-40mph with gusts in the 50’s and 60’s. Mountain temperatures ranged from the mid 20’s to low 30’s while the rain/snow line in Turnagain Pass hovered around 600-700 feet.

As of 4 am this morning, ridgetop winds are currently averaging 20-40mph out of the east to southeast with gusts in the 40’s and 50’s in Turnagain Pass and Summit Lake. It is lightly raining in Girdwood right now with temperatures ranging from 38F at sea level to 22F at 3800 feet. The storm force front over the western gulf will gradually weaken today with the rain and snow tapering off by this evening. Hot on its tail, however, is anCNFAIC Staff strong low, so get ready for round two tomorrow. Expect east winds decreasing to 15-30mph today along with a couple more inches of snow at the higher elevations. Mountain temperatures will remain on the warm side, ranging from the low 20’s to low 30’s.

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

recorded 5 inches of new snow and 0.4 inches of water in the last 24 hours. The current temp is 30F (2 degrees colder than yesterday) with a total snowpack depth of 58 inches.

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

recorded gale to storm-force east winds the last 24 hours averaging 35-45mph with gusts in the 60’s and 70’s. The current temp is 22F (same as yesterday) with winds averaging 40 mph out of the east.

-The Summit Lake Wx Station at 1200 feet-

recorded 3 inches of new snow and 0.1 inches of water in the last 24 hours. The current temp is 30F (1 degree colder than yesterday) with a total snowpack depth of 32 inches.

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

recorded strong to gale-force southeasterly winds the last 24 hours averaging 25-40mph with gusts in the 50’s and 60’s. The current temp is 23F (2 degrees colder than yesterday) with winds averaging 30mph out of the southeast.

The weather forecast for:

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST TUE DEC 22 2009

…STRONG WIND TODAY THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…

…STRONG WIND WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT…

.TODAY…RAIN AND SNOW TAPERING OFF TO SHOWERS THIS AFTERNOON. SNOW

ACCUMULATIONS SNOW SHOWERS AND RAIN. SNOW ACCUMULATION 1 TO 4 INCHES.

HIGHS IN THE MID 30S TO LOWER 40S. NORTH TO EAST WINDS 15 TO 30 MPH

DECREASING TO 10 TO 20 MPH IN THE AFTERNOON. THROUGH PORTAGE

VALLEY AND TURNAGAIN ARM…EAST WIND 35 TO 50 MPH DECREASING TO

TO 30 MPH IN THE AFTERNOON.

.TONIGHT…RAIN AND SNOW LIKELY. SNOW ACCUMULATION 1 TO 4 INCHES.

LOWS IN THE UPPER 20S TO MID 30S. NORTH TO EAST WINDS 15 TO 25 MPH

WITH GUSTS TO 40 MPH.

.WEDNESDAY…SNOW AND RAIN. SNOW ACCUMULATION 1 TO 4 INCHES.

HIGHS IN THE MID 30S TO LOWER 40S. NORTH TO EAST WINDS 15 TO 30 MPH

WITH GUSTS TO 50 MPH. HIGHER GUSTS TO 65 MPH THROUGH PORTAGE VALLEY

AND ALONG TURNAGAIN ARM.

TEMPERATURE / PRECIPITATION

SEWARD 38 31 39 / 100 80 80

GIRDWOOD 36 29 37 / 100 50 60

AVALANCHE DISCUSSION

Gale to storm-force winds plus 5-10 inches of new snow in the last 24 hours means that human-triggered avalanches are likely on steep windloaded slopes. Although the snow and wind will taper off today, the snowpack is still adjusting to this heavy load from new and windblown snow. For today, the avalanche danger is rated CONSIDERABLE on all wind-loaded slopes steeper than 35 degrees. All CNFAIC Staff slopes have a MODERATE danger. Careful snowpack evaluation, cautious routefinding, and conservative decision-making are essential today.

Yesterday and last night’s wind and new snow added considerable energy to the snowpack and increased the avalanche hazard. The good news is the warm temperatures are pasting together these new windslabs. Keep in mind, however, these warm dense slabs are sitting on weak faceted snow that formed the second week of December during the inversion, most notably at the low to mid elevations up to 2500 feet.

Jon and I toured up to the top of the alders on Sunburst yesterday looking to see how the buried surface hoar was reacting to the extra load from windblown snow. We stayed off the upper slopes because a) we couldn’t see anything above treeline and b) the wind was blowing so hard it sounded like freight trains roaring down the mountainside. The biggest, most well-preserved surface hoar is below 2000 feet on protected slopes below treeline. From 1000 to 2000 feet elevation, the surface hoar was buried under 6 inches of warm slabby snow and was not reactive on any of our tests slopes. This is still not enough of a load to cause problems on this layer. Newly-formed surface windslab, about 1-4 inches thick at these lower elevations, easily cracked around our splitboards as we skinned up. This was just a small scale version of what was going on up higher.

Carl 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

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Tue, December 22nd, 2009
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
Considerable (3)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Considerable (3)
Below Treeline
Below 1,000'
Avalanche risk
Considerable (3)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
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Updated Fri, May 01st, 2020

Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: mailroom_r10_chugach@fs.fed.us

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This is 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.