Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Monday, February 15th 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).
Pouring rain below 1000 feet, heavy wet snow at the higher elevations, and gale force easterly winds sum up the last 24 hours. 17 inches of new snow (and 2” water) fell yesterday and last night in Turnagain Pass, bringing our snowfall total for the last 10 days to around 5.5 feet of snow and 6 inches of water. Ridgetop winds averaged 20-50mph out of the east yesterday with gusts to 68 mph while the snowline hovered around 1000-1500 feet. Rain is pounding on my windows this morning with temps ranging from 26F at 3800 feet to 38F at sea level. Winds are currently averaging 30mph out of the east. Expect the deluge to continue today as the gulf low moves inland…rain below 1000 feet, up to 8 inches of additional snow at the higher elevations, and gale force winds averaging up to 50mph. Thanks El Nino!
The avalanche danger has increased to HIGH today. Natural and human-triggered avalanches will be very likely on steep slopes. Some of these avalanches may step down into deeper weak layers making very large and dangerous avalanches. We are in the middle of a big storm that continues to add more stress to an already stressed out snowpack. If you decide to play in the flats today, stay out from under avalanche runout zones. Travel in avalanche terrain is not recommended today!
It’s a no brainer today folks! High winds, rain, and 17 inches of heavy wet storm snow falling on a snowpack with numerous buried weak layers equals extremely dangerous avalanche conditions. Matt and I saw several new natural avalanche debris piles yesterday below the clouds on the southern end of the motorized side before this storm really got cranking. An Alaska Avalanche School class reported several collapses of the snowpack below 1700 ft. on Lips yesterday and stopped short of their initial objective because of deteriorating conditions. And most of you know that 2 snowmachiners were killed in an avalanche 2 days ago near Grandview.
We have some significant weak layers in the snowpack right now, most notably several layers of buried surface hoar that formed in January and early February. Numerous natural and human-triggered avalanches failed on buried surface hoar layers this past week on leeward westerly aspects, including one that partially buried a skier last Saturday on Tincan. The entire southwest face of Pete’s North ripped out on a layer of small buried surface hoar 3 days ago. And the three medium sized natural avalanches that happened on Friday on Tincan’s northwest aspect failed on buried surface hoar layers as well (see photo gallery). We’re finding these feathery crystals buried anywhere from 1.5 to 3.5 feet deep up to 3000 feet elevation on both sides of the highway. In some areas the buried surface hoar sits on top of a crust, an especially dangerous combination. The Grandview avalanche on Saturday most likely failed on this surface hoar/crust combo.
The deeply buried January 7 rain crust finally reared its ugly head in the upper Girdwood Valley 3 days ago when a small hand charge triggered a large avalanche on this layer. The fracture propagated over 1000 feet wide and broke 4-5 feet deep. We also received reports that several large natural avalanches broke 6-7 feet deep in the Placer Valley this past Friday, running on this buried rain crust. New snow avalanches could easily step down to this deep weak layer today, creating a huge and most likely unsurvivable avalanche.
Matt will issue the next advisory tomorrow morning at 7am. Thanks and have a great day.
The NWS weather forecast for:
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST MON FEB 15 2010
…STRONG WIND THIS MORNING THROUGH PORTAGE VALLEY AND TURNAGAIN
.TODAY…RAIN…MIXED WITH SNOW AT TIMES AT HIGHER ELEVATIONS.
PRECIPITATION MAY BE HEAVY AT TIMES IN THE MORNING. NO SNOW
ACCUMULATION. HIGHS IN THE MID 30S TO NEAR 40. EAST WIND 10 TO 25 MPH
EXCEPT EAST 35 TO 55 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM
DIMINISHING TO 20 TO 35 MPH IN THE AFTERNOON.
.TONIGHT…RAIN AND SNOW. NO SNOW ACCUMULATION. LOWS IN THE UPPER
LOWER TO MID 30S. EAST WIND 10 TO 20 MPH EXCEPT EAST 15 TO 30 MPH
THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.
.TUESDAY…RAIN AND SNOW LIKELY. NO SNOW ACCUMULATION. HIGHS IN
THE MID 30S TO LOWER 40S. EAST WIND 10 TO 15 MPH EXCEPT EAST
15 TO 25 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.
TEMPERATURE / PRECIPITATION
SEWARD 42 33 40 / 100 80 70
GIRDWOOD 37 32 38 / 100 80 60
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
recorded strong to gale force easterly winds yesterday averaging 20-50mph with gusts to 68mph. The current temp is 26F (1 degree warmer than yesterday) with winds averaging 30mph out of the east.
-2600′ Seattle Ridge Wx Station-
is not working.
-1800′ Center Ridge Wx Station-
recorded 17 inches of new snow and 1.9 inches of water in the last 24 hours. The current temp is 32F (same as yesterday) with a total snowpack depth of 107 inches.