Turnagain Pass Avalanche Forecast

Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, January 17th at 7am. 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

There are still spots available for next weekend’s snowmachine avalanche workshop in Turnagain Pass. Sign up at the Alaska Avalanche School (alaskaavalanche.com) or call (907)345-0878. They will cover rescue procedures and snow assessments with some class room and lots of field work.

WEATHER ROUNDUP

AnCNFAIC Staff 6-8 inches of new snow fell in the last 24 hours in Turnagain Pass. This is in addition to the 7 inches that fell Friday night, bringing our snowfall total for the week to around 20-24 inches. Yesterday ridgetop winds were all over the board, averaging 5-20mph out of the east on Sunburst and 0-5mph out of the southeast on Seattle Ridge. Mountain temperatures were in the mid to high 20’s. The winds picked up last night in Turnagain Pass and are currently averaging 20-30mph out of the east and southeast with gusts in the 30’s and 40’s. Temperatures warmed up by a few degrees last night turning snow to rain at sea level. Skies are mostly cloudy right now while temps currently range from 22F at 3800 feet to 36F in Portage. A complex low pressure system in the gulf is responsible for this long-awaited new snow. Expect continued snow showers today at the higher elevations with an additional 1-4 inches forecasted. Mountain temps will remain in the mid to high 20’s while winds will average 10-25mph out of the southeast and east.

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

recorded 6 inches of new snow and 0.6 inches water in the last 24 hours. The current temp is 28F (1 degrees warmer than yesterday) with a total snowpack depth of 71 inches.

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

recorded light to moderate easterly winds yesterday averaging 5-20mph. The current temp is 22F (2 degrees warmer than yesterday) with winds averaging 25-30mph out of the east.

-The Summit Lake Wx Station at 1200 feet-

recorded 2 inches of new snow and 0.1 inches water in the last 24 hours. The current temp is 23F (4 degrees colder than yesterday) with a total snowpack depth of 29 inches.

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

recorded moderate southerly winds yesterday averaging 15-25mph with gusts in the 20’s and 30’s. The current temp is 23F (1 degrees warmer than yesterday) with winds averaging 10-15mph out of the southeast.

The weather forecast for:

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST SUN JAN 17 2010

.TODAY…PERIODS OF SNOW. POSSIBLY MIXED WITH RAIN AT TIMES. SNOW

ACCUMULATION 1 TO 4 INCHES. HIGHS IN THE 30S. EAST WIND 10 TO 20 MPH

EXCEPT NORTH WIND 10 TO 25 MPH NEAR SEWARD.

.TONIGHT…SNOW LIKELY. ADDITIONAL SNOW ACCUMULATION UP TO 3 INCHES.

LOWS IN THE 20S. VARIABLE WINDS 10 MPH. NEAR SEWARD…

NORTHEAST WIND 15 MPH SHIFTING TO THE SOUTHEAST AFTER

MIDNIGHT.

.MARTIN LUTHER KING JR DAY…SNOW AND RAIN LIKELY. ADDITIONAL SNOW

ACCUMULATION UP TO 3 INCHES. HIGHS IN THE 30S. VARIABLE WINDS 10 MPH

EXCEPT NORTHEAST 10 TO 20 MPH SOUTH OF MOOSE PASS.

TEMPERATURE / PRECIPITATION

SEWARD 36 29 37 / 80 70 70

GIRDWOOD 36 26 34 / 80 60 60

AVALANCHE DISCUSSION

It should come as no surprise that the avalanche hazard has increased since yesterday. Today, the avalanche danger is rated CONSIDERABLE on all slopes steeper than 35 degrees. We now have 20-24 inches of new snow on top of a slick crust and strong winds transporting this snow to leeward aspects. Dangerous avalanche conditions exist, especially on windloaded slopes. Human-triggered avalanches are likely today on slopes steeper than 35 degrees with natural avalanches possible on any actively loading slopes.

We received numerous reports of avalanche activity yesterday from Turnagain Pass to the Girdwood Valley. One of our observers reported big soft slabs releasing on steep rollovers on Tincan while anCNFAIC Staff observer reporting whumphing in the flatter areas below treeline. Ski cuts in the upper elevations of the Girdwood Valley produced 4-6 inch thick soft slabs running on the crust, propagating down the walls of a steep chute. On Thursday of this past week, one of our observers reported a skier triggered avalanche in a west facing, windloaded chute at 3800 feet on Pastoral. This slide ripped out wall to wall and ran 900 feet on a crust layer. The crown face ranged from 6 inches to 1.5 feet deep.

The buried rain crust extends to 3000 feet with buried wind crusts and old hardslab above 3000 feet. In CNFAIC Staff words, we have up to 2 feet of new snow sitting on slick bed surfaces at all elevations. The snow that fell this past week came in “upside down”, meaning it started off light and dry on Monday and is now warm and heavy…not the ideal setup for snow accumulating on top of a slick crust. The light, dry snow did not bond very well with the crust, and now we have an increasingly thick and heavy slab forming on top….a sure recipe for avalanches. Layers of facets and surface hoar exist on top of and below the crust at the lower and mid elevations, which means we’ll be dealing with instabilities on this layer for an unfortunate while.

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.