Jan 292015
 

This advisory expires at midnight.

Tuckerman Ravine has Moderate and Low avalanche danger.  The Lobster Claw, Right Gully, Sluice, Lip, Center Bowl, and the Chute have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  Left gully, Hillman’s Highway, the Lower Snowfields, and the Little Headwall have Low avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features.

Huntington Ravine has Moderate and Low avalanche danger.  North, Damnation, and Yale gullies have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  Central, Pinnacle, Odell, South, and Escape Hatch have Low avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features.

AVALANCHE PROBLEM: Wind Slabs that developed from about a foot of snow from the recent storm are the #1 problem today.  Wind slabs formed initially on very high winds with an easterly component.  This created very hard slabs initially as the Ravines were on the windward side of early storm winds.  The second half of the Tuesday/Wednesday storm came in on a diminishing NE and N wind.  This loaded softer wind slabs on S facing aspects.  Expect wind slabs to be softer and easier to trigger on these S facing slopes and anticipate slabs facing directly E and N to be harder, more difficult to trigger, but resulting in larger avalanches if they fail.

WEATHER: Wind loading shut down yesterday afternoon as winds fell to 50 mph resulting in excellent visibility.  Today very low winds and sun will dominate the day until late when a shifting wind moves from the NW to the S and increase.   Late in the day gusts may move into the 60’s mph. (96kph).  This may cause some light new loading on N facing slopes.  New snow moving in tonight and all day tomorrow is expected to bring 4-8” of new snow causing an increase in avalanche danger for Friday and perhaps Saturday.

SNOWPACK: There are some slopes, facing towards the E, which lost snow due to wind gusts over 100mph (160kph) during the early parts of the storm. As winds subsided a bit and moved to the NE, NNE and then N, some of these slopes were cross-loaded and wind packed. Meanwhile, S facing slopes became heavily loaded with soft wind slab.  As some examples, you can expect soft slabs in the upper start zones of Huntington’s Damnation and Yale gullies as well as Tuckerman’s Lobster Claw, Right Gully and the Sluice.  These are considered as having Moderate danger and should be easier to trigger than the harder slabs facing E and N.  A number of these harder slopes such as the Center Bowl and the Chute also harbor Moderate danger, but will be more stubborn and difficult to trigger. However if they fail expect these harder slabs to propagate farther resulting in larger avalanches.  So areas posted as Moderate have some different issues within the same definition.  Both issues may result in dire consequences, but softer slabs will be a bit more straight forward to manage for avalanche skilled users than firmer wind hardened slopes.  I would be wary traveling out into the middle of a large hard slab so soon after this storm.  In areas posted at Low danger keep your eyes open for isolated snow instabilities such as the mid slope sections of Hillman’s and Left gully.

Late in the day a shifting, increasing, wind from the S may pick up some snow in alpine areas that have been protected by terrain features during the recent N wind.  Look for plumes late this afternoon as clues that some light loading on N facing slopes may be occurring.  Saying this, the probability this will cause new problems is remote, but worthy to note.  Expect snow tonight and all day tomorrow, adding up to 4-8” (10-20cm), to increase the avalanche danger into the beginning of the weekend.

We are now using the Winter Lion Head Route which is marked by orange signs half way up to Hermit Lake at the bottom and at treeline up top.  Expect a post holing slog until it is packed out, snowshoes could be helpful.   The Sherburne Ski Trail has improved dramatically.

Please Remember:

  • 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 8:45 a.m. January 29, 2015. 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

2015-1-29

 Posted by at 8:53 am
Jan 282015
 

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger. Lobster Claw, Right Gully, the Sluice, Lip, Center Bowl, and Chute have High avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. Left Gully, Hillman’s Highway, and Lower Snowfields have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The Little Headwall has Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible.

Huntington Ravine has HIGH and CONSIDERABLE avalanche danger. North, Damnation, Yale, Central, and Pinnacle have High avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. Odell, South, and Escape Hatch have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely.

Although the Winter Storm Warning has expired, avalanche conditions will remain very dangerous. Travel in avalanche terrain is not recommended.

AVALANCHE PROBLEM: Wind slab is the primary avalanche threat today. These will continue to develop as winds redistribute recently fallen snow into the forecast areas. S-facing slopes will be the areas of greatest concern, such as North and Damnation in Huntington and Lobster Claw, Right Gully, and Sluice in Tuckerman. Anticipate large avalanches reaching farther into the lower portions of the ravines, as well as avalanche runouts crisscrossing in flat ground well before you enter anything steep. You don’t need to be on a steep slope to be at risk today!

WEATHER: It looks like we’re in a good pattern right now, with two more storms possible in the short term.  Yesterday’s winter storm was a good one, even if we didn’t get the 2+ feet that coastal towns received. The snow plot at Hermit Lake had 9.5″ (24.5cm) of 5% density snow. Given the wind speeds and drifting that complicate snow collection and measurement at various locations, this is the amount that I’ll hang my hat on. Other measurements such as the summit and at Pinkham show ~10% density snow, but I can tell you that what fell yesterday was not that dense. At Hermit Lake the snow was relatively unaffected by wind at the measurement site. Strong NE winds blew during the event yesterday, gusting to 111mph (179kph) on the summit (hence the challenge with measuring snow!). Today they will be shifting the the N and remaining strong, which will continue to load snow into avalanche paths around the mountain.

SNOWPACK: Once again your attention should be focused on what’s going on at the surface rather than looking for deeply buried weak layers. Obviously, we weren’t about to go poking around the ravines at the height of the storm yesterday, so at this time we don’t have much direct information about what actually happened. This is the kind of day where we rely on a long history and experience forecasting for this mountain. Today we expect continued loading of S and E facing aspects. Although it is very likely that these slopes have already had some avalanche activity, it remains likely that there will be more avalanches today. As one runs on top of the other, they often go farther down the slope than previous slides, extending the reach of avalanche terrain. It’s a good day to be cautious about where or when you decide to turn around.

We will begin to switch over to the Lion Head Winter Route. All signs should be swapped out and the summer trail closed by later this morning. If you are on either of these trails today, pay attention as they both will bring you very close to, or even into, avalanche paths. This will be especially true in the flat section from the Lion Head to the base of the summit cone. The John Sherburne Ski Trail improved tremendously with this storm, but remember that there may be some wind-exposed sections of thick ice crust.

Please Remember:

  • 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 8:10 a.m. January 28, 2015. A new advisory will be issued tomorrow.

Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2015-01-28

 Posted by at 8:06 am