Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Saturday, November 27th 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). This advisory will expire 24 hours from the posting date/time.
Turnagain Pass and Johnson Pass North Trail Head motorized use areas are open for snowmobile use. Adequate snow is present to prevent resource damage. These areas consist of the lands on the west side of the Seward Highway between the Turnagain Arm and Sixmile Creek and the drainage Southwest of Bench Creek adjacent to the Johnson Pass North Trailhead south to Bench Lake. Center and Divide Creek Drainages are closed to snowmachine use.
All CNFAIC Staff areas of the Chugach NF are closed to motorized use until December 1st or adequate snow to prevent resource damage.
-TEMPS: Are warming slightly on the ridges by 2-5 degrees and cooling in the valley bottoms by 2-12 degrees. Temps are forecasted by the National Weather Service to remain below freezing today.
-PRECIP: 0.0 inches of water fell within the past 24 hours and 0.0″ to 0.05″ is forecasted today; so, no additional load in the form of precip.
-WIND: Ridgetop winds have been mostly light in the last 24 hours. For the 3rd day in a row, Seattle Ridge at 2400′ has recorded the strongest winds in the region with light to strong winds averaging 1-28mph with an extreme max gust of 42mph.
Today’s avalanche danger rating will decrease to LOW with pockets of MODERATE due to the potential for small human-triggered avalanches in the form of wind slabs along ridges and medium sized natural avalanches in the form of glide cracks that are widespread throughout the region.
There is a 1/4 inch thick rain crust that extends up to the ridgetops to at least 3500′ (most likely well above 4000′). It is widespread throughout the Turnagain Arm area. This crust has all the characteristic to become a very dangerous weak layer as soon as there is more snow on top of it. The snow on top of this crust seems to be bonding fairly well at lower to mid elevations where the snow fell at warmer temps. Above 2500′, however, the snow on top of the crust IS NOT bonding well because of drier colder snow at these higher elevations.
Use extra caution on steep rollovers along ridges where there are newly formed wind slabs or pockets of snow that look fat. These isolated pockets will not bond to the ice crust very well today. Pockets like these will be the most likely areas for human-triggered avalanches today.
We are still in an active glide avalanche cycle with new ones observed yesterday on Seattle Ridge and on the southern aspect of Magnum.
The glide cracks and glide avalanches continue to be present, with new ones being observed region-wide on a daily basis. Be aware of your travel routes and try to avoid spending time below the cracks. The only way to reduce your risk from glide avalanches is to avoid traveling below the obvious cracks.
This photo shows a good example of a glide crack and a glide avalanche on the South face of Cornbiscuit taken on 11-16-10. For scale take note that the crack is 4-6 feet deep. The glide crack on the left hand side of this photo has already avalanched; while, the glide crack on the right is still a hazard that could avalanche any day. Avoid traveling underneath glide cracks just like the one on the right hand side of this photo.
The Nation Weather Service weather forecast for:
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST SAT NOV 27 2010
.TODAY…MOSTLY CLOUDY. A SLIGHT CHANCE OF SNOW IN THE AFTERNOON.
HIGHS IN THE LOWER 20S TO MID 30S…COOLEST INLAND. LIGHT WINDS
EXCEPT NORTH 10 TO 20 MPH NEAR SEWARD.
.TONIGHT…SNOW LIKELY. SNOW ACCUMULATION UP TO 2 INCHES. LOWS
15 TO 20. LIGHT WINDS EXCEPT NORTH 15 TO 20 MPH NEAR SEWARD.
.SUNDAY…SNOW LIKELY IN THE MORNING…THEN PARTLY CLOUDY WITH
SCATTERED SNOW SHOWERS IN THE AFTERNOON. SNOW ACCUMULATION UP TO
2 INCHES. HIGHS IN THE 20S…COOLEST INLAND.
TEMPERATURE / PRECIPITATION
SEWARD 31 19 29 / 20 70 70
GIRDWOOD 28 20 23 / 0 70 70
WEATHER STATION SUMMARY for Turnagain Pass:
3800′-Sunburst Wx Station
Temp: (5am): 17 (4 degrees warmer than yesterday morning)
Winds: *Anemometer is probably iced up and not working properly*In last 24 hours winds have been light averaging 0-3mph with a light max gust of 6 mph
2400′-Seattle Ridge Wx Station
Temp: (5am): 17 (same as yesterday morning).
Winds: In last 24 hours have been light to strong averaging 1-28mph with an extreme max gust of 42mph.
1800′-Center Ridge Wx Station
Temp: (5am): 18 (2 degrees colder than yesterday)
Precip: 0.0″ in last 24 hours 45″ total snowpack depth (minus 1″ due to settlement)
The next advisory will be issued tomorrow Sunday morning 11/28/2010 at 7am. If you get out in the backcountry send us your observations using the button at the top of this page or call and leave a message at 907-754-2369. Thanks and have a great day.