This advisory expires at Midnight Friday 2-03-2012
Tuckerman Ravine has MODERATE and LOW avalanche danger. The Right Gully, Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Left Gully and Hillman’s Highway have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features, which do exist. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when warranted.
Huntington Ravine has MODERATE and LOW avalanche danger. Damnation, Yale, Central, Pinnacle, Odell, and the Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. North Gully and South Gully have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.
Beautiful clear skies dominate Mount Washington this morning with a stunning alpenglow to top it off. As micro-scale forecasters, alpenglow is one of the holy grails for confirming some of our assessments when we can get it. This special pink light brings out tremendous contrast to surface conditions highlighting old from new surfaces, wind effect, old sluff tracks, fracture lines, ski tracks, etc. It obviously can’t tell much about stability of new snow, but it adds more information and data for our final evaluation. It helped enormously this morning for dropping some areas to Low from Thursday’s Moderate and gave clarity to why other locations need to stay at Moderate. New snow that came in following the rain event on Wednesday hasn’t added up to much, but has been enough to create some instabilities. The summit has reported 3.5” over the past 2-3 days, half of which occurred during periods of icing and mixed conditions when the summit hit a maximum of 30F ( -1C). The second half was dry cold snow, causing most of the present cold slabs. This snow has been transported on W and NW winds peaking at 86mph (138kph) 36 hours ago with velocities up and down ever since. Speeds dropped briefly into the single numbers yesterday and now are back into the 40’s mph range which is causing some light loading in a few locations. Light afternoon snow showers may continue this loading trend but it shouldn’t make much of difference for today. We’ll discuss anything that becomes of it in Saturday’s advisory.
In areas that are posted at Moderate in Tuckerman, you will find some old surface and stability in some locales, but enough concern exists about the amount and size of new snow within the forecast area they warrant the Moderate rating. Right Gully and the Sluice are on the lower end of the Moderate definition. From the Lip over to the Chute new snow can be found mostly in a band at the Headwall ice elevation and immediately below this feature. This is acting as our primary new snow concern today. As you move into Left Gully isolated pockets of instability can be found on the climber’s right side from down low up to the narrows. The upper climber’s right “Y” exit chute of Hillman’s Highway also harbors some instability. In both these “Low” areas, this new snow can be avoided by staying to the hard left on your ascent.
In Huntington, North and South gullies have Low avalanche danger due to either the lack of snow or strong wind effect. The rest of the Huntington forecast areas have Moderate avalanche danger with little wind effect and some locations picking up a good amount of new loading in strong lee areas such as under steep ice like the Pinnacle approach. Because of the thin nature of the Yale and Damnation exits 2-3 days ago these noticeably stand out as doing quite well from a seemingly scant amount of new snow.
We will be getting into the field today to see how areas of cold slab are adhering to the old surface and how facets are doing beneath the rain crust. We’ll pass along any pertinent info we determine today in the “Weekend Update” early this evening. Look for it on www.mountwashingtonavalanche center.org. Post-holing through crust will be a real issue in numerous off trail locations making travel rather arduous. Ice climbers should also be prepared for ice dams, or water under pressure, beneath the ice from Wednesday’s rain and freeze up afterwards. An ice tool or crampon placement can release this with explosive results. Bulges and rollovers are more likely to harbor these hazards than depressions.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856