Avalanche Forecast for Sunday, January 5, 2020

This information was published 01/05/2020 at 7:00 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 01/05/2020 at midnight.


The Bottom Line

The avalanche danger will be CONSIDERABLE today in terrain currently loading with wind driven snow. Natural avalanches are possible and human-triggered avalanches likely in steep, wind loaded terrain.

  • Strong winds are building slabs which could be triggered by skier or climber. 
  • Wind slabs may be on the small side but could be large enough to carry a person and bury them in a terrain trap.
  • These slabs are reloading an already icy bed surface across some areas such as Chute to Sluice in Tuckerman Ravine.
  • The potential exists for an avalanche to trigger naturally due to continued wind loading or by a person from well below the starting zone.

2020-1-5 Printable Forecast


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The Lion Head Winter Route is open and remains the safer choice for accessing the summit of Mount Washington from the east. An ice axe and crampons are needed near treeline and above with micro-spikes useful in wind scoured areas.

Mountain Weather

The summit recorded about 3” of snow Saturday which fell on light winds through the day.  Wind velocity increased rapidly around 4am this morning and will continue to blow from the northwest through the day in the 55-75 mph range with higher gusts. This is an ideal wind speed and direction for loading our prime avalanche terrain. Temperatures will remain in the teens on the summits today with the potential for another 2” of snow to fall.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

New wind slabs began to form early this morning and may be at peak instability and a dangerous size mid-day. Carefully evaluate the terrain and snow pack and give a wide berth to avalanche paths. Best to keep the angle low and avoid any overhead hazard if skiing. Continuous sluffing from steep pitches of ice and cliff bands will grow these wind slabs as well.

  Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Forecast Discussion

It has been three days since any reported avalanche activity that followed the snow and wind loading event around the New Year. There have been many observations of clean shears in the moderate range at various depths in that snow though. New snow falling yesterday and today could lead to more avalanches despite the small amount of new snow fall. History has shown that a northwest wind can quickly turn small amounts of snow falling onto the plateau-like feature above the east facing ravines and gulfs into thick and dangerous slabs. The new snow which fell yesterday may have bonded to the various textures of existing snow surfaces but that is not relevant when considering a wind slab growing on top. That new snow is more likely to be the soft, weak layer that is unable to support the wind slab growing above.

Additional Information

Conditions on the Sherburne ski trail have improved with the recent snowfall though a few rocks and ice patches have emerged after heavy holiday traffic. A few partly open water bars remain. 

Details on daily snowfall totals, precipitation type, total depth of snow and other information can be found on our page devoted to snow study plot data. Click here to check it out.

Recent snowpack and avalanche observations can be found here and on Instagram. Your observations help improve our forecast product. Please take a moment and submit a photo or two and a brief description of snow and avalanche information that you gather in the field.

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
01/19/20
05:15
8 CM 7.3 MM 10%NC112 CM-6.5 C-6.5 C-15.0 COvercastSnow
01/18/20
05:15
0 CMTrace 0CM103 CM-18.5 C-12.0 C-22.0 COvercastNo precipitationView
01/17/20
05:11
22 CM 16.6 MM 9%26CM107 CM-20.0 C-4.0 C-22.0 CFewNo precipitation
01/16/20
05:15
3 CM 2.9 MM 11%NC85 CM-7.0 C-4.0 C-7.0 COvercastSnow
01/15/20
05:16
2 CM MM 16%NC82 CM-4.0 C-3.5 C-7.0 COvercastSnowView

Avalanche Log and Summit Weather

Thank you Mount Washington Observatory for providing daily weather data from the summit of Mount Washington.

DateMax TempMin TempTotal (SWE)24H Snow & IceWind AvgWind Fastest MileFastest Mile DirAvalanche Activity
01/17/204 F-18 F .03 in .4 in75 MPH110 MPH

320 (NW)

01/16/2018 F-11 F .048 in 6.1 in43.3 MPH117 MPH

330 (NNW)

01/15/2020 F11 F 0.25 in 1.8 in9.3 MPH74 MPH

290 (WNW)

01/14/2020 F10 F 0.03 in 0.7 in32 MPH69 MPH

280 (W)

01/13/2022 F14 F .04 in .8 in49.5 MPH81 MPH

240 (WSW)

01/12/2045 F8 F .84 in .4 in58.4 MPH104 MPH

260 (W)

01/11/2042 F29 F .32 in 0 in68.8 MPH119 MPH

230 (SW)

01/10/2030 F12 F .22 in 1.3 in63.4 MPH102 MPH

260 (W)

01/09/2015 F-14 F .04 in .4 in50.1 MPH114 MPH

310 (NW)

View
View
01/08/2013 F-8 F .52 in 5.2 in43.5 MPH95 MPH

290 (WNW)

01/07/2016 F1 F .17 in 1.6 in41.8 MPH90 MPH

280 (W)

01/06/2010 F3 F .2 in 2.2 in32.8 MPH71 MPH

270 (W)

Please Remember:

Safe travel in avalanche terrain requires training and experience. This forecast 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.

Avalanche danger may change when actual weather differs from the higher summits forecast.

For more information contact the US Forest Service Snow Rangers, AMC visitor services staff at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or seasonally at the Harvard Cabin (generally December 1 through March 31). The Mount Washington Ski Patrol is also available on spring weekends.

Posted 01/05/2020 at 7:00 AM.

Frank Carus, Lead Snow Ranger
USDA Forest Service
White Mountain National Forest