|
Good morning, this is Sue Burak with the Inyo National Forest with an avalanche advisory for the weekend of January 3 and 4, 2009.
MOUNTAIN
WEATHER
Strong southwest and north winds were the main feature of this weak storm. A Peak wind gust of 97 mph occurred Friday afternoon at the top of Mammoth Mountain. Today’s winds will be less dramatic. A northwest flow aloft will cause temperatures to plummet and north winds will continue through the weekend. Look for northerly winds this weekend in the 10-15 mph range at the 8,000 to 10,000 ft elevations. Above 10,000 ft, winds will be in the 15-20 mph range with gusts up to 45 mph.
Daytime highs also tumble with northerly flow aloft. Highs at the 8-10,000 ft elevation will be in the upper teens to low 20’s and lows will be in the mid teens. At higher elevations, highs will be from 12-18F with lows in the single digits.
By Monday, high pressure begins to build into the area with a resulting dramatic warmup. I would not be surprised to see highs qt the 8,000 to 9,000 ft elevations see highs close to 50 F by Thursday.
SNOWPACK
AND AVALANCHE DISCUSSION
The northern trajectory of this storm is supported by snowfall totals. Leavitt Lake picked up 8 inches of new snow with Slide Canyon picking up 6 inches. Mammoth Mountain and the Mammoth Pass area picked up about 3 inches. Rock Creek and Bishop Creek picked up 2 inches.
The primary avalanche concern is wind drifted snow. Winds were strong enough from both the southwest and north to detach snow particles from the old snow surface,. Once winds shifted to the north, there was plenty of material to move around and deposit on south and southeast aspects. Since most of the terrain we ski is on northern aspects, I assume most folks will continue to ski those wind stripped slopes. Expect places like the Red Cone Bowl and other high north facing bowls and shallow gullies to have lost a lot of snow and where there once powder, then lots of tracks, there might be sastrugi.
Wind drifted new snow could form very shallow slabs but the combination of pre storm winds and the north winds later Friday could result in thicker wind slabs. .Expect variability in the location of these features.
Skiing in open trees where the snowpack is shallow might be a popular place for people to congregate this weekend. Be advised that in the Mammoth area the depth hoar, weak snow layer still exists. Virginia Lakes also had a well developed depth hoar layer. An observer visited the main gully, also known as Mc Coy’s on Friday and found a layer of faceted snow 16 inches thick that was not reactive in compression tests. Rock Creek reports mature depth hoar 4-6 inches thick and occasional whumpfing in higher terrain
BOTTOM
LINE
The avalanche danger rating is estimated to be Moderate; Dangerous conditions exist within areas that are generally safe. Evaluate the snow and terrain carefully. Use good travel habits to minimize risk.
Please note that the avalanche danger rating in this advisory expires in 24 hours. This advisory is our best interpretation of snow pack conditions and NWS forecasts issued today. Backcountry travelers should be aware that elevation and geographic distinctions are approximate and that a transition zone exists between upper and lower elevations.
Avalanches do not happen by accident and most human involvement is a matter of choice not chance. Most avalanche accidents are caused by slab avalanches that are triggered by the victim of member of the victim's party. Even small slides can be dangerous. Always practice route finding skills and carry avalanche rescue gear. Remember that avalanche danger ratings are only general guidelines. Distinctions between geographic areas, elevations, slope aspects and slope angles should be made.
This
month's advisory brought to you by:
Look at our Advertising
page or contact Nate
Greenberg to find out more about how
you can sponsor a month's worth of avalanche
advisories through ESAC. Get some great
targetted marketing, and help support
the Center for the 2006/2007 season.
|
