Frank Carus

Mar 302015
 

This advisory expires tonight at 12:00 midnight.

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

Huntington Ravine has Moderate and Low avalanche danger. Central, Pinnacle, Odell, South and Escape Hatch have Moderate avalanche danger. Evaluate snow, weather and terrain carefully. North, Damnation and Yale have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: Wind Slabs developing today, in some areas on an already poor snow structure, are the primary problem. With the exception of the Lip, which was raked down to the bed surface yesterday, Considerable rated areas contain the largest expanses of older wind slab going into today’s weather event. This wind slab was reactive to human triggers yesterday and is most likely still reactive. South facing gullies in both Ravines, though still containing pockets of the older wind slab, benefitted from a period of settlement yesterday due to warming and, in Tuckerman, was also cut up by ski traffic.

WEATHER: Wintry weather continues as a cold front pushes through today bringing some moisture and wind to the region. The main weather factor affecting stability will be the wind. Currently, west winds in the 50 mph range are pushing some snow into east aspects. The wind is expected to pick to the 50-70 mph range later today. These wind speeds are the highest since roughly 6” of snow fell late last week which means that there is enough snow laying around higher terrain to provide the building blocks for new hard wind slabs. Light snow and snow showers through the afternoon hours may contribute 1-3” more snow to the slab building process.

SNOWPACK: Avalanche danger is starting out one rating lower in each forecast area that isn’t already rated Low. The above ratings are based on wind transported snow, plus 1-3” of new snow falling today, which will cause danger to rise.

A crown profile in the 50cm x 20m natural avalanche in the Lower Snowfields revealed that the failure layer of the slab was within soft (4F) snow and rimed snow particles. The overlying harder slab (1F) was softer than we often see due to the light winds that built it being only around 40 mph. This crown thickness and structure is very similar to that in the much larger Lip avalanche and is the same as you might find in other slopes and gullies, only in varying thicknesses and distribution.  In summary, signs of recent avalanche activity in the previous 24-48 hours are one red flag to consider today. Another is active wind loading, as evidenced by snow moving along the ground at the ridgetop and above treeline, A third is a small amount of new snow and a weather forecast that includes wind speeds capable of moving that snow and building wind slabs. It’s pretty hard to miss these signs today, so if you choose to enter avalanche terrain, do so very carefully and limit time spent in avalanche runouts or, better yet, avoid them entirely.

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 8:16 a.m. Monday, March 30, 2015. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2713

2015-03-30

Mar 282015
 

This advisory expires tonight at 12:00 midnight.

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

All forecast areas of Huntington Ravine have Moderate avalanche danger. Natural are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM: Wind Slab and Storm Slab are the primary concerns today with Dry Loose avalanches also on the list. 3.5” (8cm) of new snow in the past 2 days has created a variety of soft slabs in our terrain. Due to the low wind speeds, the new snow is piling up beneath steeper terrain and forming slabs just cohesive enough to create potentially dangerous slabs. Small avalanches could turn larger by entraining the surprising amount of low density snow laying around.

WEATHER: The Low pressure trough continues to feed clouds and moisture into the area. 1-3” (2.5 – 7.5cm) of new snow is expected today on very lights winds shifting to the North. Expect flat light at best and possibly denser fog to create some challenges for navigating and keeping eyes on the skier. It is likely that the overcast skies above the summit fog will limit incoming solar heating on southern aspects today, unlike yesterday.  The height and intensity of the spring sun is a factor this time of year and could conceivably have a positive effect on stability on these aspects again today. Quite a bit of warming occurred yesterday, in spite of the dense fog.

SNOWPACK: Currently, very low density snow is sluffing off steep terrain and contributed to these slabs. In Tuckerman, Chute holds the greatest amount of soft slab, with boot-top and deeper snow in and above the choke. The narrows of Left, as well as near and above the fork of Hillman’s, were also a concern yesterday. Cracking and increasingly deep snow lead experienced parties to turn around in both locations. 1” (2.5cm) of new snow on even lighter winds last night plus 1-3” more today will contribute to this problem. It is impressive how this paltry amount of snow piles up beneath steep terrain like cliff bands, ice bulges and sidewalls of gullies. Huntington is a mixed bag of Moderate. Greenhouse warming yesterday contributed to stability on south facing aspects so expect more stability concerns from Central to Escape Hatch with more stability from Yale to North.

Field time in Tuckerman confirmed that we still have a dynamic snowpack. Despite cold air temperatures, greenhousing conditions over the past several days have begun to drive heat into the upper 30-40 cm of snow, though the temperatures beneath are far from isothermal. Stability tests yesterday confirmed the new snow was well bonded to the hard surfaces but was slabbing up due to either surface heat gain, light wind effect or sluffing. The older bed surface was just barely negotiable without crampons (2-3cm boot penetration) yesterday but has refrozen more solidly this morning. Expect a slippery, dust on crust surface especially on southerly aspects unless heating occurs. Deeper in the snowpack pooled graupel and a thick, decomposing melt/freeze crust failed cleanly but are well bridged and not much of a concern for the time being.

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 8:23 a.m. Saturday, March 28, 2015. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2713

2015-03-28