Turnagain Pass

Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, November 29 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

Turnagain Pass snowmachine area is open to motorized use. All CNFAIC Staff areas including Johnson Pass, Placer, Twenty-Mile, and all areas on the Seward Ranger District will remain closed until there is more snow. The Turnagain Pass open riding area is on the west side of the highway from Bertha Creek Campground north to the Forest boundary near the Turnagain Arm.

ATTENTION SNOWMACHINERS!!!

Avalanche danger may exist at any time in backcountry areas like Turnagain Pass on the Chugach National Forest, whether these areas are open or closed. The US Forest Service does not close areas due to avalanche danger. When areas designated for use by snowmachines on the Chugach National Forest are closed, a primary reason is for the protection of natural resources in accordance with the current Forest Plan. Similarly, on open sign does not mean that it is safe. There are many inherent dangers associated with traveling in the backcountry including avalanches. Safe backcountry travel requires training and experience. You Control Your Own Risk by choosing where, when and how to travel. The Chugach National Forest Avalanche Information Center provides pertinent information to assist you in making your own decisions for traveling in these backcountry areas. Opening of these motorized areas in the early season can be subject to immediate closure based on sufficient snow to prevent the tracks of a snowmachine from tearing up vegetation. If the weather changes and the snowpack gets too thin to prevent resource damage, then areas may be closed again. It is your responsibility to check the official open/closed status of these areas with the Chugach National Forest. CNFAIC Staff resources for information regarding these motorized areas can be found through the Glacier Ranger District, and/or the Chugach National Forest Avalanche Information Center.

An educational opportunity is coming up to learn more about mountain weather on Dec 5th: “Weather for the Backcountry Traveler” Lecture Series. Given by AK Avalanche School and the NWS 9am-5pm; visit www.alaskaavalanche.com for more info.

WEATHER ROUNDUP

Yesterday Turnagain Pass picked up an additional 6 inches of new snow, and mountain temperatures remained in the low to mid 20’s. Ridgetop winds averaged 10-20 mph out of the east with gusts in the 30’s for most of the morning yesterday but died down by mid-day. The winds down at Summit Lake, however, were blowing 25+mph out of the north for most of the day. As of 4am this morning, mountain temperatures ranged from 17-22 degrees F with light winds in Turnagain Pass and the Girdwood Valley. It is currently snowing lightly in Girdwood. An additional 3 inches of snow is forecasted for today with mountain temperatures cooling down to the low to mid teens. Winds are expected to remain light, averaging 5-15 mph out of the west. Closer to the sound, stronger winds out of the northwest are expected this morning.

-The NRCS Center Ridge weather station at 1800 feet in Turnagain Pass-

recorded 6 inches of new snow and 0.8 inches of water. The current temp is 22F (5 degrees colder than yesterday) with a total snowpack depth of 58 inches.

-The Sunburst weather station at 3800 feet in Turnagain Pass-

recorded moderate easterly winds averaging 10-20mph with gusts in the 30’s up until noon yesterday. The winds calmed down mid-day and are currently light and variable. The current temp is 19F (same as yesterday).

The weather forecast for:

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST SUN NOV 29 2009

…HIGH WIND WATCH IN EFFECT FROM MONDAY AFTERNOON THROUGH LATE

MONDAY NIGHT FOR PORTAGE VALLEY AND ALONG TURNAGAIN ARM…

.TODAY…CLOUDY WITH SNOW SHOWERS WITH ACCUMULATIONS UP TO 3 INCHES.

AREAS OF BLOWING SNOW NEAR SEWARD AND WHITTIER THIS MORNING. HIGHS IN

THE LOWER 20S TO MID 30S. SEWARD AND WHITTIER…NORTH TO WEST WINDS

15 TO 25 MPH. GUSTS 30 TO 45 MPH THIS MORNING. WEST WINDS 5 TO 15 MPH

ELSEWHERE.

.TONIGHT…SNOW LIKELY IN THE EVENING…THEN SCATTERED SNOW

SHOWERS AFTER MIDNIGHT. SNOW ACCUMULATION UP TO 3 INCHES. LOWS 10 TO

20 ABOVE. VARIABLE WIND TO 10 MPH. NEAR WHITTIER…WEST WIND 15 MPH

SHIFTING TO THE EAST AFTER MIDNIGHT.

.MONDAY…A CHANCE OF SNOW IN THE MORNING…THEN SNOW AND RAIN LIKELY

IN THE AFTERNOON. VISIBILITY BRIEFLY FALLING BELOW ONE HALF MILE IN

BLOWING SNOW THROUGH PORTAGE VALLEY…ALONG TURNAGAIN ARM…AND

TURNAGAIN PASS IN THE AFTERNOON. SNOW ACCUMULATION 1 TO 4 INCHES.

HIGHS IN THE LOWER TO MID 30S. THROUGH PORTAGE VALLEY AND

TURNAGAIN ARM…EAST WINDS INCREASING 35 TO 55 MPH IN THE AFTERNOON

WITH POSSIBLE GUSTS TO 80 MPH. ELSEWHERE…SOUTH TO EAST WINDS 25 TO

45 MPH DIMINISHING TO 15 TO 30 MPH AFTER MIDNIGHT.

TEMPERATURE / PRECIPITATION

SEWARD 30 15 36 / 30 40 90

GIRDWOOD 26 11 31 / 30 60 60

AVALANCHE DISCUSSION

For today, a CONSIDERABLE avalanche hazard still exists on all slopes steeper than 35 degrees. The weak faceted snow at the bottom of our snowpack continues to show signs of instability. This weak layer is now buried 4-5 feet deep in most locations. Dangerous avalanche conditions still exist. Careful snowpack evaluation, cautious routefinding and conservative decision-making will be essential. Human-triggered avalanches are certainly likely today if you push the envelope.

Several parties reported widespread whumphing yesterday from Turnagain Pass south to Summit Lake. Most folks agreed that this collapsing occurred on the weak layer of facets at the bottom of our snowpack. One of our observers reported seeing a natural avalanche occur yesterday afternoon on an east aspect in the bowl directly below the Fresno Ridge weather station at Summit Lake. AnCNFAIC Staff one of our observers reported seeing the aftermath of several large natural avalanches on Penguin Ridge and Raggedtop in the Girdwood Valley. AnCNFAIC Staff ski party on Fresno Ridge reported poor stability with collapses propagating 50+ feet in the higher elevation wind-affected terrain. They decided to ski down their low angle skin track.

Of all these bottom-dwelling facets, my biggest concern is the facets on top of a melt-freeze crust that formed up to 2400 feet elevation in early November. On Friday one of our observers reported seeing shooting cracks on Tincan breaking all the way down to this layer near the ground. Carl and I got clean fast Q1 shears on top of this crust yesterday at 2000 feet on Tincan (CTH24Q1@150cm). Although it took a bit of pounding on our shovels to get the layer to fail, once it fractured it popped off the column. This tells me there is energy in the snowpack to propagate a fracture, and if it goes, it’s going to go big. To see what I’m talking about, check out the two YouTube videos I took of Carl yesterday by clicking on the button at the top of this page.

If you have observations for us please send them using the observations button at the top of the advisory page of our website. This concludes today’s advisory. The next advisory will be Monday, November 30th. Have a great day.