Avalanche Forecast for Sunday, December 30, 2018

This forecast was published 12/30/2018 at 7:15 AM.
A new forecast will be issued tomorrow.

The Mount Washington Avalanche Center will no longer issue daily avalanche forecasts for the 2018/19 season. Read more

The Mount Washington Avalanche Center will no longer issue daily avalanche forecasts for the 2018/19 season. Instead, we will post an updated General Bulletin as needed, in case of significant snow or weather events that might vary from the typical daily changes that come with spring weather. We will also keep you informed about the official closure of the portion of the Tuckerman Ravine Trail from Lunch Rocks through the Lip and Headwall as well as the switch from the Lion Head Winter Route to the summer trail. Observations from the field will continue to be a valuable resource, so please keep submitting photos, videos and observations here and we will do the same. Check the Forecast page for update on Sherburne Trail closures, which are imminent as spring snowmelt continues.

The switch to a General Bulletin does NOT mean that the mountains are now a safe place to ski. The hazards which emerge in the spring are significant and require careful assessment and strategic management. If you have never skied Tuckerman, peruse our Incidents and Accidents page for spring related incidents involving avalanches, long sliding falls, icefall, crevasse and moat falls, and other incidents related to diurnal changes in the snowpack. These will help you understand and plan for these hazards.


The Bottom Line

Yesterday’s snow and wind deposited wind slabs in isolated areas and behind or below specific terrain features. Wind slab should be easy to identify and avoid in contrast  to the refrozen scoured surfaces that exist in many locations. Terrain which contains these wind slabs has MODERATE avalanche danger. Wind scoured areas of icy, hard snow create conditions prime for long, sliding falls. Evaluate snow and terrain carefully to identify and avoid these hazards. Equipment to perform avalanche rescue as well as crampons and an ice axe should be included in today’s kit.

2018-12-30 Printable PDF

Danger Rating by Zone

Mountain Weather

Friday morning brought two inches of snow to our highest elevations that was followed by a half inch of rain in the afternoon. Lower elevations saw the changeover to rain sooner, with higher rainfalls totals and less snow. After an overnight lull, precipitation resumed Saturday morning as temperatures dropped. The summits received all snow (2.1”) with a trace at Gray Knob and at Hermit Lake. At 6am this morning, skies are overcast, north wind is blowing 20 mph and the air temperature is 6F. Today, temperatures will climb to 10F with wind shifting to the north and increasing to 30-45 mph, and some mid and high level clouds passing the region. Monday will start similar to today, though New Year’s Eve celebrations will involve significant snowfall on the summits with rain likely at lower elevations.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

High wind speeds transported the two inches of snow that fell on the summit yesterday into areas of wind slab in lee locations of a NW wind. This wind slab is likely stubborn to human triggers, though specific locations may harbor wind slab close to a foot thick. You may be able to avoid today’s avalanche problem by staying on scoured surfaces, but some pinch points of gullies or narrow slopes may hold wall to wall wind slab.

What is a Windslab Avalanche?

  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.

Snowpack and Avalanche Discussion

Two inches of snow fell at higher elevations as our snowpack was refreezing on Saturday. This snow arrived on NW wind around 80mph. Wind of this magnitude likely transported most available snow onto slopes in the lee of NW or into the trees. Traveling surfaces today will be  areas of wind slab mixed with wind scoured crusts. Remember that hard wind slabs that are present today may not release or fail in response to the first skier or rider. Traveling one at a time across suspect slopes will be key to safe travel today.

Additional Concerns

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch. If you’re in the greater Boston area in a week (January 8) be sure to head to Arc’teryx Boston for evening avalanche awareness presentation with Ryan Matz.

Avalanche Safety Information Study

Please contribute to the effort to improve backcountry avalanche forecasts! Researchers in Canada devised a study to better understand how we communicate the avalanche risk, and we need your help. Please fill out this survey. It will take a few minutes, but it will help us as we work on new ways to give you the most important avalanche information.

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
05/20/19
05:30
0 CM 20.4 MM0CM68 CM11.0 C12.0 C3.5 CObscuredNo precipitation
05/19/19
05:25
0 CM 0.0 MM0CM72 CM4.0 C6.0 C2.0 COvercastNo precipitation
05/18/19
05:20
0 CM 7.6 MM0CM80 CM1.0 C6.0 C1.0 COvercastNo precipitation
05/17/19
05:25
0 CM 0.8 MM0CM84 CM4.0 C10.0 C0.0 CClearNo precipitation
05/16/19
05:20
0 CM 0.0 MM0CM84 CM1.0 C1.5 C0.0 CFewNo precipitation

Avalanche Log and Summit Weather

Daily Observations


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
05/18/1934 F26 F 0.06 in 0.5 in39 MPH74 MPH

300 (WNW)

05/17/1940 F28 F .22 in .05 in37 MPH81 MPH

300 (WNW)

05/16/1932 F25 F .03 in 04 in22.8 MPH40 MPH

310 (NW)

05/15/1926 F20 F .05 in .4 in32.1 MPH67 MPH

330 (NNW)

05/14/1928 F17 F .2 in 2 in19.1 MPH57 MPH

100 (E)

05/13/1928 F19 F .07 in 0.9 in34.6 MPH67 MPH

100 (E)

05/12/1931 F17 F 0 in 0 in20.5 MPH47 MPH

330 (NNW)

05/11/1932 F18 F .1 in 0 in53.6 MPH84 MPH

300 (WNW)

05/10/1944 F27 F .85 in 0 in50.1 MPH88 MPH

220 (SW)

05/09/1942 F20 F .04 in 0 in18.6 MPH44 MPH

190 (S)

05/08/1927 F18 F 0 in 0 in38.3 MPH65 MPH

330 (NNW)

05/07/1939 F26 F .54 in 0 in40 MPH66 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 12/30/2018 at 7:15 AM.

Helon Hoffer
USDA Forest Service
White Mountain National Forest