Turnagain Pass

Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, January 3rd 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

All areas designated for snowmachines on the Chugach National Forest are open to snowmachining except Placer and 20 Mile. Please remember that Center and Divide Creeks near the Johnson Pass North Trailhead are always closed due to the current Forest Plan.

WEATHER ROUNDUP

A trace to one inch of new snow fell in the last 24 hours. Yesterday ridgetop winds in Turnagain Pass averaged 10-15mph out of the southeast while mountain temperatures remained in the teens.

As of 4 am this morning, ridgetop winds in Turnagain Pass are averaging 5-15mph out of the east with gusts in the upper teens. Temps have warmed up a bit and range from 16F at 3800 feet to 24F at sea level. The most dramatic temperature swing goes to Summit Lake where temps went from -7F to 20F in 24 hours. Warm southerly flow gradually returns to our area as a significant blocking ridge over the west coast of North America will divert low pressure systems our direction. We will see warmer mountain temperatures today in the upper teens to low 20’s while ridgetop winds will increase later this evening, averaging 20-30mph out of the south and east. Expect cloudy skies and a couple inches of new snow near the coast.

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

recorded 1 inch of new snow and 0.1 inches of water in the last 24 hours. The current temp is 23F (10 degrees warmer than yesterday) with a total snowpack depth of 59 inches.

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

recorded light southeasterly winds yesterday averaging 10-15mph with gusts in the 20’s. The current temp is 16F (4 degrees warmer than yesterday) with winds averaging 5mph out of the east.

-The Summit Lake Wx Station at 1200 feet-

recorded 1 inch of new snow and 0.1 inches of water in the last 24 hours. The current temp is 20F (27 degrees warmer than yesterday) with a total snowpack depth of 30 inches.

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

recorded light southerly winds yesterday averaging 5-15mph with gusts in the 20’s. The current temp is 17F (5 degrees warmer than yesterday) with winds averaging 10-15mph out of the south.

The weather forecast for:

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST SUN JAN 3 2010

.TODAY…CLOUDY WITH AREAS OF SNOW…MAINLY ALONG THE COAST.

SNOW ACCUMULATION UP TO 3 INCHES. HIGHS IN THE LOWER 20S TO

LOWER 30S…WARMEST ALONG THE COAST. VARIABLE WIND TO 15 MPH.

.TONIGHT…SNOW…MAINLY ALONG THE COAST. SNOW ACCUMULATION UP

TO 3 INCHES. NEAR STEADY TEMPERATURES IN THE LOWER 20S TO LOWER

30S…COLDEST INLAND. EAST WIND TO 15 MPH. THROUGH PORTAGE

VALLEY AND TURNAGAIN ARM…EAST WIND INCREASING TO 15 TO 30 MPH

AFTER MIDNIGHT.

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

SNOW AND RAIN IN THE AFTERNOON. SNOW ACCUMULATION UP TO 2 INCHES.

HIGHS IN THE MID 20S TO MID 30S…WARMEST ALONG THE COAST. EAST

WIND TO 15 MPH EXCEPT EAST 20 TO 30 MPH THROUGH PORTAGE VALLEY

AND TURNAGAIN ARM.

TEMPERATURE / PRECIPITATION

SEWARD 29 27 34 / 70 70 60

GIRDWOOD 26 25 32 / 70 60 70

AVALANCHE DISCUSSION

Today, a LOW avalanche danger exists on all slopes with pockets of MODERATE hazard developing later this evening on actively loading slopes steeper than 35 degrees. We are looking at generally stable avalanche conditions for most of the day, but that will change whenever the southeast winds pick up and start loading lee aspects. Pockets of shallow sensitive windslab will develop, but watch for localized winds and wind channeling off the ridgelines loading different aspects.

No news is good news in our book as it has been over 10 days since the last reported human-triggered avalanche. Folks have been skiing and riding big lines everywhere without incident. The snow above 2000 feet has been incredible to say the least. Below 2000 feet conditions are drastically different and downright challenging. The top foot or so is a veritable matrix of ½ -1 inch thick rain crusts, faceted powder, and windslab topped off by recently formed surface hoar. So undoubtedly there are a number of future instabilities within this top foot of snow that will become sensitive to human triggers once buried with enough of a load.

Jon and I toured up Cornbiscuit yesterday and found that the recently formed surface hoar goes up to about 2000 feet elevation. The old buried surface hoar from the second week of December was buried 1.5 feet down and not especially reactive in our stability tests (CTM20Q2 and CTH23Q2). At 3300 feet elevation we found a few density changes in the top 6-10 inches that failed easily in our stability tests, but subsequent ski cuts and slope testing by the masses produced nothing on these layers.

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.