| Posted: 8:46 a.m., Friday, January 19, 2007 |
Another storm that wasn't. It currently appears that the brunt of the precipitation will fall to our East and North. Although the NWS still has a range of 4-9" (10-22.5cm) for the next 48 hours a close scrutiny of the mountains points to less. Through conversations with the Observatory we should be at the bottom end of the range for each 12 hour forecast period. We expect an inch (2.5cm) for our mountains today with another 1-2" (2.5-5cm) for the overnight into Saturday morning. Snow should begin a bit later today as we are currently in a dry slot between moisture to our south moving northeasterly and a system moving east from upper New York State. I believe snow accumulations today will keep the avalanche danger at Low, however be prepared to move into Moderate if we pick up 2" (5cm) during daylight hours. This is primarily due to the anticipated winds for the day. Winds have already moved from the SW to the W as of 7am and are expected to continue to the NW and increase from 30mph to 70+ (48-112+kph) late this afternoon. Snowfall will therefore be loaded on mostly E to SE aspects with an increasingly dense slab over softer slab from the beginning of the event. This will all depend on the wind speeds and direction when the precipitation initiates and how much we actually receive. We have been watching a facet layer beneath the crust and believed it could be a stability issue for this weather event. I don't feel this is the case any longer. In addition to diminished snowfall expectations field observations in Tuckerman witnessed an incredible amount of spatial variability. There were different things going on with every quick pit, I can't come up with a consistent theme to focus on except variability. Even the crust differs from location to location with a fair amount covered by hard slab from Tuesday and Wednesday morning. With warming temperatures the gradient driving facet growth has slowed down keeping near surface faceting to 1mm-1.5mm in size. As new snow comes in it will cover the Ravine's great surface diversity which will make it challenging to know what it may be attempting to bond with below when seeing the old surface is no longer an option. Did snow fall on a slick crust, a textured wind effected slab, or a smooth hard slab? All of these scenarios will occur with enough snow. So be ready to exercise caution this weekend and consistently re-assess snow stability.
The other main concern besides snow stability for tomorrow will be very high and very gusty winds with a dropping temperatures. We are expecting gusting over 110mph (177+kph) with a high temperature of only -15F (-26C). As tomorrow is a Saturday this is very concerning as more people will consider attempting to go to the summit. Do not consider this a personal challenge to overcome. If the forecast plays out these are truly desperate conditions. High winds are underestimated by many because they have been in 70mph (112kph) winds so what could another 40mph (65kph) matter? Trust me, A LOT! Anyone being out at all should have the best arctic mountain clothing possible. Feet, hands, and face are the locations have we have seen the most frostbitten. So good boots, mittens and the often-neglected face gear is extremely important.
Check out our "Weekend Update" this evening for more info on this developing weather event.
The Lion Head Summer Trail is still open. The Summer Trail crosses an avalanche prone slope that has not developed as of yet. The Winter Route is not built for travel without adequate snow cover, so although we are in winter, please help keep the Winter Route in good shape by using the Summer Trail.
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Avalanche Advisory Archives.
United States Avalanche Danger Descriptions.
Échelle Canadienne de risque d’avalanche.
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