Jan 182015
 

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine will have Considerable and Moderate avalanche danger today. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway will have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Right Gully will have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Natural and human triggered avalanches are unlikely. The Lobster Claw, Lower Snowfields and Little Headwall are not posted due to a lack of snow.

Huntington Ravine will have Considerable and Moderate avalanche danger. Central, Pinnacle, Odell, and South gullies will have Considerable danger. Natural avalanches are possible and human triggered avalanches are likely. North Gully, Damnation, Yale and the Escape Hatch will have Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM: Today’s ratings are primarily based on incoming snow late today, therefore storm slabs are threat number one. The new snow is expected to fall mainly in the afternoon and overnight, so the storm slab problem will be causing the avalanche danger to rise up to their posted ratings near the end of daylight or slightly beyond, from where they are starting the day, i.e. Low or Moderate. This problem is going to impact N, NE, and E aspects the most, such as Hillman’s, Left Gully, and Chute in Tuckerman or South, Odell, Pinnacle, and Central in Huntington.

Early birds getting out before any new accumulations and slab development should be alert for existing wind slabs and persistent slabs that we have discussed in previous avalanche advisories. These problems are dispersed around the terrain with a great deal of spatial variability. Tuckerman’s Lip and Sluice yesterday held the most newly developed wind slab followed by the north side of the Huntington Fan, whereas in all other areas persistent slabs existed.

WEATHER: It’s been a slow month for snowfall in the White Mountains, which leads to eager anticipation of the incoming weather. I’ll leave you to read the forecast for yourself, but the avalanche-related highlights include 0.2-0.4″ (5-10mm) of water equivalent forecasted through 7pm today and another 0.8-1.35″ (20-34mm) from 7pm to 7am. If temperatures were colder, this would be a lot of snow. Much to our dismay, warmth will prevent us from choking on powdery face shots. Most of this precipitation is coming in overnight, but how much falls during the day and early evening will determine how far the actual hazard goes up the danger rating scale. Another key factor will be whether or not it remains snow, mixes with sleet, or becomes either freezing rain or plain rain. Through today, winds will be slowly shifting from the WSW to the S at good speeds for loading snow and creating slab.

SNOWPACK: Prior to incoming snow, much of the avalanche terrain consisted of strong, wind-scoured snow. Some locations had stiff persistent slab as well, and in other areas there were a varying amount of faceting taking place beneath the surface snow. The extent of the faceting and the strength of the snow above had led us to danger ratings in the Moderate to Low range, depending on the location. As usual, the ravines offer a wide variety of snowpack situations, especially if you were to put in the effort to get to some of the harder to reach locations.

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 8:30 a.m. January 18, 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

2015-01-18

 Posted by at 8:24 am
Jan 172015
 

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely, although unstable snow in isolated terrain features may exist.

Huntington Ravine has Low avalanche danger. All forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely, although unstable snow in isolated terrain features may exist.

AVALANCHE PROBLEM: Persistent Slabs and Wind Slabs are jockeying for position as the greatest threat depending on your location. Huntington was mostly scoured by high winds yesterday leaving pockets of wind slab on approaches through the Fan with a smattering Persistent Slabs elsewhere. Central Gully is well worth making a careful assessment for a weak layer of facets beneath harder, old slabs. Tuckerman Ravine received more snow and less scouring yesterday, with softer wind slabs a potential problem in the entrance of Right, the Sluice bowl, the Lip area where the trail traverses, across the Bowl and lower Chute. Persistent Slabs in these locations are still a threat, particularly in areas which picked up an additional load of wind slab. Left Gully is mostly scoured, particularly at the top above the choke point. Hillmans is still lacking snow, though the upper third has the most wind loaded area and, like any other Low rated area, should be assessed carefully. Lobster Claw, Lower Snowfields and the Little Headwall have very little snow.

WEATHER: Good visibility and pinkish-orange alpenglow is the reward for suffering through the well below zero F temperatures this morning which were -11F (-24C) at 7am and -24F (-31C) at 5am. Clouds will return to the summits this afternoon with temperatures rebounding to 5F (-15C) on the summit, a bit warmer below treeline. Wind speeds in the 60 mph (85 kph) range with gusts to near 80 mph (120 mph) this morning will diminish a bit this afternoon but will remain challenging for folks above treeline. Winds may then increase again later this evening.

SNOWPACK: Intense snow squalls yesterday morning dropped about an inch and a half (3.8cm) of new snow over the course of a few hours. High winds yesterday scoured most of this new snow out of Huntington Ravine and unloaded or hammered down the existing wind slabs. Over the past ten days, small amounts of accumulated snow from snow shower activity was slow to stabilize. Favorable conditions for the development of weak faceted snow beneath the Jan 4th ice crust resulted in older wind slabs becoming a persistent slab problem. Widely variable slab thicknesses and the stubborn and strong nature of these slabs combined with a lack of human-triggers in much of the terrain has allowed us to avoid avalanche activity so far this week but has done little to ease our minds about this weak layer. Avalanche conditions such as these don’t shout danger but definitely remain a threat, particularly to the unwary.  Tuckerman, being slightly lower and more leeward than Huntington, gained more wind slabs yesterday than it lost. This new loading adds to the stress and strain on existing persistent slabs as well as increasing the potential consequence if a slab is triggered. The stronger lee position of the Moderate rated areas of Tuckerman is conducive to making these slabs more touchy and prone to human triggering so be wary of people above you and assess your exposure to these slabs.

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 8:30 a.m. January 17, 2015. A new advisory will be issued tomorrow.

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

2015-01-17 print friendly