Good morning backcountry travelers this is Kevin Wright with the Chugach National Forest Avalanche Information Center on Saturday, April 2nd 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).
Today’s avalanche danger rating is MODERATE with pockets of CONSIDERABLE developing. Recent new snow on top of persistent weak layers is the primary concern. New snow today and high wind will increase the hazard rating.
Sometimes it’s difficult to use snowpit data to show dangerous conditions. Right now our test results are screaming bad news. The recent storm from the last week buried well developed surface hoar on all aspects and upper elevations. The recipe is classic unstable, tricky, and dangerous. (photo of buried surface hoar)
Primary concern is recent snow on top of buried surface hoar. The complicated layering structure is low strength, collapsing, and propagates easily. Immediately after the storm on Tuesday there were many natural avalanches through the region. Those avalanches were breaking high up to ridges (see photo),
triggering sympathetic avalanches nearby, and propagating widely. We also got a report of several snowmachine triggered avalanches off Seattle ridge yesterday.
With several days of rest to allow the snow to settle after the storm the snow is less sensitive, but difficult to manage. It is still possible to find pockets of snow sitting on the tenuous edge between stress and strength, ripe for a trigger to let loose an avalanche. Everything is adding up to suggest that avalanches can happen this weekend if given that trigger, which could be a person, new snow, or freshly wind deposited snow.
Check out a video here from an extended column test 2 days ago. Yesterday we found similar or worse results on a sunny south aspect with ECTP11 Q1. The column fully propagated, falling into the pit on the first moderate force hit. See the photo gallery for more recent test pits.
Staying safe in the backcountry this weekend will require good judgment and restraint. Conservative, low angle terrain is the most appropriate choice given the conditions we’ve seen.
Encyclopedia of avalanche terms.
Yesterday we found partly cloudy skies, moderate wind, and mild temperatures. Any sunny aspect had a significant surface crust from the warm sunny days recently. No snow fell overnight, and temperatures dropped to the low 20s at higher elevations. Today look for strong wind with snowfall beginning this morning and increasing this afternoon. Rain line at 400ft.
Wendy 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 SAT APR 2 2011
…STRONG WIND THIS AFTERNOON THROUGH SUNDAY EVENING THROUGH PORTAGE
VALLEY AND TURNAGAIN ARM…
.TODAY…A CHANCE OF SNOW AND RAIN IN THE MORNING…THEN RAIN IN THE
AFTERNOON. HIGHS IN THE MID 30S TO MID 40S. NORTH TO EAST WIND 15 TO
25 MPH. THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…EAST WIND 15 TO 25
MPH INCREASING TO 30 TO 45 MPH IN THE AFTERNOON.
.TONIGHT…RAIN AND SNOW. SNOW ACCUMULATION UP TO 4 INCHES OVER
HIGHER ELEVATIONS. LOWS IN THE UPPER 20S TO MID 30S. NORTH TO EAST
WIND 20 TO 30 MPH. THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…EAST
WIND 35 TO 50 MPH.
.SUNDAY…SNOW AND RAIN IN THE MORNING BECOMING RAIN IN THE
AFTERNOON. NO SNOW ACCUMULATION. HIGHS IN THE 40S. NORTH TO EAST WIND
15 TO 30 MPH. THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…EAST WIND 35
TO 50 MPH.
.SUNDAY NIGHT…RAIN IN THE EVENING BECOMING SCATTERED RAIN AND SNOW
SHOWERS AFTER MIDNIGHT. LOWS IN THE LOWER 20S TO MID 30S. NORTH TO
EAST WIND 10 TO 20 MPH. THROUGH PORTAGE VALLEY AND TURNAGAIN
ARM…EAST WIND 25 TO 45 MPH DECREASING TO 10 TO 25 MPH AFTER
.MONDAY…CLOUDY WITH SCATTERED RAIN SHOWERS. HIGHS IN THE UPPER 30S
TO UPPER 40S. VARIABLE WIND TO 10 MPH.
TEMPERATURE / PRECIPITATION
SEWARD 42 34 46 / 80 80 80
GIRDWOOD 41 27 44 / 60 80 60
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
Currently 19 degrees at 6am. East wind gusting to 26mph.
-2600′ Seattle Ridge Wx Station-
22 degrees at 6am. SE wind to 23mph.
-1800′ Center Ridge Wx Station-
26 degrees at 6am. No new snow recorded.