Avalanche Forecast for Monday, December 31, 2018

This forecast was published 12/31/2018 at 7:16 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

All forecast areas have LOW avalanche danger today. Areas of wind slab can be found, but these have proven unreactive and can be avoided in most terrain by traveling on the exposed melt-freeze crust. The potential for long, sliding falls should be as much or more of a concern today. Bear in mind that crampons and ice axes are tools for fall prevention and will be of little use after a slip due to the firm nature of the current snowpack.

Tonight’s inbound storm may produce significant snowfall on increasing wind before this forecast expires at midnight. Avalanche danger will exceed our current low rating once this takes place. Watch for the red flags of heavy snowfall and wind blown snow to guide cautious route-finding if you are out late today.

2018-12-31 Printable PDF

Danger Rating by Zone

Mountain Weather

On Sunday, temperatures remained in the single digits with broken and overcast cloud cover for most of the day. Shifty wind in the morning with speeds less than 20 mph became NW around 40mph in the evening. A trace of snow fell in the morning followed by 0.4” overnight. Today, summits will be in and out of the clouds with temperatures increasing to the teens F by dusk. Wind will remain in the 30-50 mph range from the W and SW for daylight hours with up to an inch of snow falling during the day. Once nighttime arrives, the storm will begin with up to 5” falling by midnight on shifting and increasing wind. Snow continues into tomorrow morning with high wind speeds, bringing a storm total of up to 12” of snow by the end of Tuesday. Warm temperatures may mix in sleet at high elevations with rain likely down low.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slabs formed during a period of extreme NW wind on Saturday in the lee of terrain features. Areas in the lee of our largest fetch contain the largest and thickest wind slab, but in most of our terrain they are isolated and can be avoided. These firm wind slabs have been unreactive to human triggers and appear well bonded to the melt-freeze crust.

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

Currently, our snowpack has very good stability. A robust melt-freeze crust that formed December 22 and 23 exists on all aspects and elevations with recently formed, firm wind slab in isolated locations. The melt-freeze crust offers excellent climbing as well as providing the opportunity for long sliding falls. This surface snow will also provide a smooth bed surface for avalanches to occur as snow arrives tonight into tomorrow.

Additional Concerns

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch. If you’re interested in giving your brain a workout, check out the list of upcoming events on our website. You can find the calendar on our home page or the full list here. These are all free and hosted in part by the White Mountain Avalanche Education Foundation and Friends of Tuckerman Ravine.

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 12/31/2018 at 7:16 AM.

Helon Hoffer
USDA Forest Service
White Mountain National Forest