Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Tuesday December 8th at 7 am. 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).
All areas designated for snowmachines (except Placer and 20 Mile) on the Chugach National Forest are open. Please remember that Center and Divide Creek near the Johnson Pass Trailhead are always closed due to the current Forest Plan. These areas are periodically patrolled by law enforcement. We are monitoring the snow at Placer and 20 Mile and will open those areas as soon as there is enough snow, these colder temps down low are really helping these areas.
An I-phone was found on Sunburst on Sunday. Call 754-2349 for more info if it is yours.
Will recent weather effect avalanche conditions today?
Well, let’s take a closer look at the precip, winds, and temps.
Hindcast (Last 24 hours)
3800′ -Sunburst Wx Station-
Temperature Range: 41-47 VERY WARM!
Wind: averaged calm 2-13 mph out of the West with a light max gust of 19 mph
2600′-Seattle Ridge Wx Station-
Wind: averaged calm 1-4 mph out of the NE with a calm max gust of 7 mph
1800′-Center Ridge Wx Station-
Precip: 0 inches of water and 0 inches of new snow
minus 2” of total snowpack due to settlement for total depth of 60 inches
Temperature Range: 31-35
Most weather stations below 1800′ are recording colder temps than yesterday, but the temps are much warmer a mid elevations and ridgetops. Temps are currently 18 degrees at sea level (8 degrees colder than yesterday), and as high as 47 degrees at 3800′ on Sunburst (6 degrees warmer than yesterday). That’s almost a difference of 30 degrees between those elevations! Strange weather.
Skies are clear in Girdwood as of 5am, and the Middleton and Kenai Radars are clear as a bell. Winds are currently calm at all ridgetop wx stations.
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST TUE DEC 8 2009
.TODAY…MOSTLY SUNNY. HIGHS IN THE MID 20S TO LOWER 40S…
COLDEST INLAND. NEAR SEWARD…NORTH WIND 15 MPH. NEAR
WHITTIER…LIGHT WEST WIND INCREASING TO 20 MPH IN THE AFTERNOON.
VARIABLE WIND TO 10 MPH ELSEWHERE.
.TONIGHT…MOSTLY CLEAR. LOWS 10 TO 25 ABOVE. LIGHT WINDS.
.WEDNESDAY…MOSTLY SUNNY. HIGHS IN THE 20S TO 30S. LIGHT WINDS.
.WEDNESDAY NIGHT…CLEAR. LOWS IN THE MID TEENS TO LOWER 30S.
TEMPERATURE / PRECIPITATION
SEWARD 35 22 33 / 0 0 0
GIRDWOOD 24 13 24 / 0 0 0
Short Term Weather Models for higher elevations around the Kenai Mountains near Turnagain Pass
Sea-level: 0 inches of water forecasted today
3000′: temps forecasted above freezing today around 40 degrees with winds 5-10mph
6000′: temps forecasted above freezing today around 40 degrees with winds 5-10mph
Today’s weather shouldn’t contribute to the avalanche danger. The unusually warm temps at the upper elevations are a little concerning, but based on yesterday’s observations, these temps do not appear to be putting a strain on the surface snow. The NWS and the short term weather models make it look like today will be the height of the warm temps, and they are forecasted to start cooling slightly tomorrow. Since it is December, the sunlight is not as intense as it is in the spring, when we really get worried about warm temps and direct sun. We did find a strong temperature gradient in the top 6 inches of surface snow; so, this might become a factor for some near surface facets in the future. This warmer surface snow did not appear to be creeping rapidly or adding to today’s avalanche danger.
The most concerning weak layer right now are those sugary facets on the ground. In the past two days, we have done 8 compression tests at elevations ranging from 2300′-3500′ on E, NW, and SW aspects on the motorized and non-motorized sides at Turnagain Pass. These tests found hard(CTH28Q2) to no failures on those facets. Looking at the natural avalanches that occurred during last week’s storm, the largest avalanches failed in areas like Sunburst and Summit Lake where the snowpack was thinner ranging from 2-5 feet deep. We are not aware of any significant human are natural avalanches on this facet layer since last Tuesday 12/1/2009. We are still advising caution in areas that have a shallower snowpack because that is going to be the most likely area to find a surprising avalanche. Rocky areas near ridge tops are common areas of shallow snow.
Today’s avalanche danger level is rated as LOW. LOW is defined as: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human-triggered avalanches unlikely. Very small avalanches in widespread areas: or small avalanches in isolated areas. Normal caution is advised including the standard backcountry rituals of: traveling one at a time, stay spaced out, watch your partners, don’t travel above your partners, wear your beacon and know how to use it, carry your shovel, probe and rescue gear on you and know how to use these as well.
The secondary concern today are glide cracks. Tincan in particular has lots of these crevasse like features. People and dogs have fallen into these before in the past, and they can be very difficult to crawl out of. Make sure your partner knows where you are around these glide cracks.
Always remember that safe backcountry travel requires training and experience. You control your own risk by choosing where, when, and how you travel.
Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow 12/9/2009.