Turnagain Pass Avalanche Forecast

Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, March 28th at 7am. 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

Today is the last day of Telepalooza 2010. Check out details at www.telepalooza.com. The uphill/downhill race starts at 9am at the daylodge plus on-going free demos, lessons, beacon park games, and a raffle at the Sitzmark. The raffle tonight has HUGE prizes with all proceeds going to the Friends of the Chugach National Forest Avalanche Center.

WEATHER ROUNDUP

15 inches of heavy wet snow fell in the last 24 hours in Turnagain Pass while 17 inches fell in Grandview, 16-24 inches in the upper elevations of the Girdwood Valley, and 3 inches in the Summit Lake area. Mountain temperatures warmed up to the low 20’s to low 30’s yesterday while ridgetop winds averaged 20-30mph out of the east with gusts to 44mph. The monster-sized snowflakes turned to rain at sea level late yesterday afternoon and then back to snow early this morning. Only a few inches of snow accumulated at sea level. The winds tapered off last night and are currently averaging 5-10mph out of the east. Temperatures cooled down by a few degrees last night and currently range from 21F@3800′ to 25F@1800′ to 32F@sealevel. A strong frontal wave moving northwest out of the gulf will bring more snow and rain today. We could see anCNFAIC Staff 2-5 inches of snow at the higher elevations and rain below 1000 feet. Easterly ridgetop winds will average 5-15mph while mountain temperatures will warm up to the mid 20’s to mid 30’s this afternoon.

AVALANCHE DISCUSSION

The avalanche danger has increased to CONSIDERABLE today on all slopes steeper than 35 degrees. This means that human-triggered avalanches are LIKELY on steep slopes while natural avalanches are possible. The addition of 1-2 feet of heavy wet snow, and winds strong enough to move the snow onto leeward aspects, means that dangerous avalanche conditions exist. Please remember that the majority of human-triggered avalanches occur during or within 24 hours of a storm. If by chance we see the strong springtime sun today, even for a short period of time, expect almost instant wet sluffs possibly triggering slab avalanches on steep southerly slopes.

Deb and I toured up Tincan yesterday and easily triggered new snow slabs on small convex test slopes. At 2500 feet we got long shooting cracks breaking a foot deep down to a sun crust on actively loading rollovers. Small natural avalanches were also reported late yesterday afternoon in the Girdwood Valley and Summit Lake area. The 1-2 feet of new snow fell on a layer of surface hoar that formed on all aspects up to 4000 feet this past Thursday and Friday. The new snow also buried a slick sun crust on southerly aspects and cold powdery snow on north aspects. Remotely triggered slides are a concern today where the surface hoar was buried intact standing upright, so watch the slopes above you. This feathery crystal is famous for producing long-running fractures, and it’s even more dangerous when it forms on a slick crust.

Of equal concern are the multiple buried weak layers in the top 2 to 4 feet of the snowpack that formed during the last few weeks. New snow avalanches triggered today could step down to these deeper layers. These weak layers include numerous sun crusts on SE-S-SW aspects, a 1-inch thick melt-freeze crust below 2000 feet on all aspects, large developed facets on shallow north aspects above 3000 feet, and 3 separate scattered layers of buried surface hoar on multiple aspects. These layers were responsible for five skier-triggered avalanches this past Thursday and Friday:

– North aspect of Granddaddy Chute (Bertha Creek drainage), 2.5 feet deep, 150-200 feet wide.

-South face of A1 in the Upper Girdwood Valley between 4000 and 5000 feet. No information reported on this slide.

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. Thanks and have a great day.

The NWS weather forecast for:

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKDT SUN MAR 28 2010

.TODAY…SNOW AND RAIN. A SLIGHT CHANCE OF FREEZING RAIN IN THE

MORNING. SNOW ACCUMULATION UP TO 2 INCHES. HIGHS IN THE UPPER 30S TO

MID 40S. VARIABLE WIND 15 MPH. THROUGH PORTAGE VALLEY AND TURNAGAIN

ARM…LIGHT WINDS BECOMING EAST 15 TO 30 MPH IN THE AFTERNOON.

.TONIGHT…RAIN AND SNOW. SNOW ACCUMULATION UP TO 2 INCHES. LOWS IN

THE UPPER 20S TO MID 30S. NORTHEAST WIND 10 TO 15 MPH.

MONDAY…NUMEROUS RAIN AND SNOW SHOWERS. SNOW ACCUMULATION UP TO 1

INCH. HIGHS IN THE UPPER 30S TO MID 40S. VARIABLE WIND 15 MPH.

.MONDAY NIGHT…SNOW AND RAIN LIKELY. LOWS IN THE MID 20S TO

LOWER 30S. LIGHT WINDS.

.TUESDAY…SNOW AND RAIN LIKELY. HIGHS IN THE MID 30S TO LOWER

40S. LIGHT WINDS EXCEPT WEST 10 TO 15 MPH NEAR WHITTIER.

TEMPERATURE / PRECIPITATION

SEWARD 44 31 42 / 100 80 80

GIRDWOOD 41 28 42 / 80 70 50

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

recorded moderate to strong winds yesterday averaging 20-30mph with gusts to 44mph. The current temp is 21F (2 degrees warmer than this time yesterday) with winds averaging 10mph out of the east.

-2600′ Seattle Ridge Wx Station-

recorded moderate winds yesterday averaging 15-25mph with gusts to 40mph. The current temp is 25F (3 degrees warmer than this time yesterday) with winds averaging 5mph out of the east.

-1800′ Center Ridge Wx Station-

recorded 15 inches of new snow and 1.2 inches of water in the last 24 hours. The current temp is 26F (1 degree warmer than this time yesterday) with a total snowpack depth of 142 inches.