Expires at Midnight Sunday 12/15/2013
This is the initial 5-scale avalanche danger rating forecast for the season. You will now see daily advisories. Tuckerman and Huntington Ravines have CONSIDERABLE avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route finding and conservative decision making is essential.
AVALANCHE PROBLEM– We have been watching the development of bed surfaces in our avalanche terrain carefully over the past several weeks. They have been in a slow constant growth mode and have seen snow 13 out of the past 15 days. In our forecaster’s discussion this morning we felt this storm is clearly sending us over to having more concern for natural avalanche activity. The avalanche problems today are a combination of Storm Slabs and Wind Slabs. It is plausible we may see a number of small natural avalanches today due to the low density touchy soft slabs that will develop all day and into tomorrow. The largest of these would occur in places that have the most sizeable bed surfaces, namely Left Gully and the Chute in Tuckerman and Central Gully in Huntington.
WEATHER— A WINTER STORM WARNING is in effect until noon today. Snow began last night and picked up in intensity early this morning with periods likely at the S-3 rate. As of 630 there is about 10+ inches (25cm) on the mountain with more coming. As snow dissipates in the valleys upslope showers will continue for the higher terrain giving us an additional 1-3” (2.5-7.5cm) tonight and a bit more into the early Monday morning. Clearly we will be at 12”+ (30cm) by the time precipitation wraps up. Winds will be from the SE up to 75mph (120kph) moving to the W later today and diminishing to perhaps as low as 30 mph (48kph)
SNOWPACK— The snowpack preceding this event has be quite variable depending on location put a consistent theme has been many layers due to our nickel and diming snowfalls. Some of these have started to move to early facets due to our cold conditions lately. Today’s cold, low density, storm and wind slabs will load early on N and NW facing aspects predominately due to SE winds. Expect some crossloading and anticipate our larger dominate bed surfaces facing E to receive more loading late in the day as winds shift to the W. Strong overnight winds causing additional loading and temperatures dropping to about -15F will keep new slabs unstable.
This event should kick our day to day avalanche concerns up a notch as it will undoubtedly add substantially to snowfield sizes. With this said as conditions clear up in the next 24-48 hours we expect to also see areas that were quite meager a few days ago to still be that way. So although today we have a blanket Considerable forecast you will likely see us not forecast for some areas by middle of the week. Stay tuned.
- Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
- Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
- For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.Posted 0815 Sunday 12-15-2013 A new advisory will be issued tomorrow.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856