Good morning backcountry travelers. This is Jon Gellings with the Chugach National Forest Avalanche Information Center on Wednesday, March 30th 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).
The avalanche danger will remain at CONSIDERABLE today, but will begin to decrease throughout the day. Only 3” of new snow has fallen at Center Ridge in the past 24 hrs, but the station is recording .8” SWE, which means rain has been saturating the surface snow at and above this elevation. Natural avalanches could still come down, and it is likely that someone would be able to kick off a slab in steeper terrain.
With the cloud layer being obscure and at a low elevation yesterday, we were unable to observe any new avalanches, which does not mean they aren’t out there. The wind loading process has simmered down, and precipitation is slowing down as well. I am able to see Penguin Ridge right now, so hopefully we can get a look around today to see what the extent of new avalanches is.
We currently have a few layers of persistent weak layers buried underneath this new snow. Surface hoar and small facets are buried above a very hard layer of wind affected snow from last month, and are the newest layers of concern. There was a report of whumpf sounds at tree line on Tincan yesterday, which means one of these layers was reactive to the weight of a skier. With around 3-4 feet of new snow on these layers at upper elevations, be sure to scrutinize the snowpack for instabilities before making any type of commitment to steep terrain. An avalanche of this depth could easily ruin someone’s day.
So, backing up and looking at the big picture, we have a hard layer (bed surface), underneath surface hoar and facets (weak layers), all of which is below a layer of moist and/or wind deposited snow (slab). These textbook signs for potential avalanches exist in the vicinity of Turnagain Pass.
Many areas in South Central Alaska with a shallow snowpack contain persistent instabilities deeper down, which could potentially break under the weight of a recreationist. Staying away from likely trigger points or thin areas is the easiest way to avoid this hazard.
Encyclopedia of avalanche terms.
Winds have slowed down, which should limit the amount of snow being loaded onto leeward terrain. Temperatures got well above freezing at Center Ridge, and are forecast to do so again today. We could still see some more precipitation from this storm, but the majority has already fallen. Anything new today should be confined to a few inches of snow at upper elevations.
Kevin 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:
WESTERN PRINCE WILLIAM SOUND-
500 AM AKDT WED MAR 30 2011
.TODAY…RAIN…MIXED AT TIMES WITH SNOW. NO SNOW ACCUMULATION.
HIGHS AROUND 40. VARIABLE WIND TO 10 MPH. NORTH TO EAST WINDS 10 TO
.TONIGHT…RAIN AND SNOW SHOWERS LIKELY. SNOW ACCUMULATION AROUND 1
INCH. LOWS IN THE LOWER 20S TO MID 30S. NORTH TO WEST WINDS 5 TO
.THURSDAY…SNOW AND RAIN SHOWERS LIKELY IN THE MORNING…THEN A
CHANCE OF RAIN AND SNOW SHOWERS IN THE AFTERNOON. SNOW ACCUMULATION
UP TO 1 INCH. HIGHS IN THE UPPER 30S TO MID 40S. VARIABLE WIND TO 10
MPH. NEAR SEWARD…NORTH WIND 10 MPH.
TEMPERATURE / PRECIPITATION
SEWARD 43 31 43 / 80 60 60
GIRDWOOD 42 23 40 / 80 50 60
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
25 degrees. ENE wind 10mph gusting to 17mph.
-2600′ Seattle Ridge Wx Station-
28 degrees. SE wind 7mph gusting to 9mph.
-1800′ Center Ridge Wx Station-
30 degrees. 3 inches new snow. Storm total snowfall is 12-13 inches.