Avalanche Forecast for Thursday, December 27, 2018

This forecast was published 12/27/2018 at 7:03 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

Lingering pockets of wind slab exist scattered across the hard, refrozen surface snow in our steep terrain. The hard surface will require crampons, an ice axe and good climbing technique to avoid a slip which could quickly turn into a long, sliding fall. Ice climbs were damaged by the recent rain so be on the lookout for pressure building behind ice with the potential for rupturing.

2018-12-27 Printable Forecast PDF

Danger Rating by Zone

Mountain Weather

2cm of new snow fell at Hermit Lake with half an inch recorded on the summit of Mt. Washington during snow shower activity in the past 24 hours. Around 4.5” of snow has fallen on the summit in the past five days. Current temperature on the summit is -2F with wind from the NW at 56mph. Temperatures will warm to the teens on the summits through the day as wind subsides and shifts west at 30-45 mph, and even lower in the afternoon. The next round of precipitation arrives tonight and continues through tomorrow with 4-6” of snow falling overnight on increasing south west winds before a transition to sleet, freezing rain and finally rain by afternoon all the way to the higher summits.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slabs built over the past few days are likely to be stubborn but assess them before committing to steep slopes with newer snow. Even a small avalanche can have significant consequences in steep terrain, particularly with our currently icy surface conditions.

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

There has been no reported avalanche activity since the 3” of rain fell December 21-22 and “reset” our snowpack. New snow and mixed precipitation coming tonight and tomorrow will be arriving with building winds and increasingly dense snow before changing over to sleet and rain. The window of enough snow to slide on without avalanches due to building wind slab or wet slab danger seems tiny if it exists at all.

Additional Concerns

The Sherburne and Gulf of Slides ski trails have snow and ice coverage to Pinkham Notch. Heavy rain on December 21-22 did some damage and melted snow in some waterbars.

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 12/27/2018 at 7:03 AM.

Frank Carus
USDA Forest Service
White Mountain National Forest