| Posted: 8:17 a.m., Friday, December 28, 2007 |
Huntington Ravine has CONSIDERABLE avalanche danger. Natural avalanches are possible and human triggered avalanches are probable. Unstable slabs are probable in steep terrain. Be increasingly cautious in steeper terrain.
A quick moving weather maker dumped a blanked of new snow on the mountain totaling 5.1" (13 cm) of 10.7% snow at Hermit Lake and 4.5" (11.5 cm) of 11% snow at the Harvard Cabin. The summit recorded 3.7" (9.4 cm) of 13% snow over the past 24 hours. Precipitation began yesterday afternoon around 1:00 pm and initially fell as sleet, rimed snow grains and large needles. Chris observed needles as long as 7 mm. Winds were initially out of the S and SSW and moved to the west around 10:00 last night. Wind speeds steadily increased through the night from the 20 mph range to the current speed of 76 mph (120 kph). The new snow and steadily increasing winds are ideal for creating unstable slab conditions in both Ravines. Looking at wind direction through this event, you can expect that northerly aspects to have been loaded early in the storm. Since the winds have shifted to the west, there has become equal concern about instabilities on east facing aspects which is one reason why areas in Tuckerman Ravine are rated at High. The other factor is these areas provide the largest continuous bed surfaces for the new snow. Expect areas in Huntington to be at the upper end of the Considerable rating due to the possibility of natural avalanche activity. Visibility is limited this morning, but we can tell that Hillman's Highway has already avalanched and ran farther down into it's runout than it has this season. Today's winds are forecasted to diminish through the day which will also decrease the amount of wind transporting that can occur. While this may reduce the amount of snow loading, expect touchy slabs to exist all day.
Another system is on our heels bringing more snow to the mountains tomorrow. The weather models still don't agree on what is going to happen but a blend of all likely scenarios has led to a forecast of 2 to 7" (5 to 18 cm) of snow around northern New Hampshire. Check the weekend update this afternoon for more information on this event. It does look like it will create more stability issues on the mountain so keep your plans flexible this weekend.
The John Sherburne Ski Trail is open with continuous snow from top to bottom. Expect hard icy conditions. THE LION HEAD WINTER ROUTE IS OPEN. This is a steep and challenging route for mountaineers. Crampons, an ice axe and the ability to properly use this equipment are recommended for safe travel on this route.
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Avalanche Advisory Archives.
United States Avalanche Danger Descriptions.
Échelle Canadienne de risque d’avalanche.
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