General Bulletin for Saturday, December 28, 2019

This information was published 12/28/2019 at 6:58 AM.


This is an archived avalanche forecast.

The Bottom Line

Summit temperatures fell 15F Friday night following a mixed bag of mostly wet precipitation at ravine elevations. The resulting icy crust on the snowpack will create hazardous travel conditions starting with long sliding fall conditions and ending with new snow falling on a slick bed surface Sunday night and Monday. High winds and seasonably cold temperatures in the teens F will complicate your travel plans Saturday. Sunday will bring diminishing winds and clearing skies until the next round of precipitation arrives.  If you plan to venture to treeline where crampons and an ice axe are needed, expect a gamut of conditions from shin-scraping crusts in lee areas to bullet-proof old surface in steep, previously wind-hammered terrain. Rope up early and recognize that self-arrest is ineffective in steep AND icy terrain with dire consequences for a fall above the many boulders and cliffs that remain uncovered by snow.

The Tuckerman Ravine and Huntington Ravine trails are challenging climbs with significant avalanche hazard during winter. The summer Lion Head Trail remains the safer choice for accessing the summit of Mount Washington from the east. The Winter Lion Head Route still needs more snow. An ice axe and crampons are needed near treeline and above with micro-spikes useful on trails below. The Sherburne ski trail has taken another beating. Consider sharpening your rock skis before taking a lap.

General Bulletins are issued when unstable snow may exist within our forecast areas but before conditions warrant  or available resources allow 5-scale avalanche forecasts. Thank-you to everyone who has submitted observations! We will start 5-scale forecasts on Wednesday, January 15 or earlier, if possible. Please remember that avalanches can and do occur before 5-scale avalanche forecasts are issued.

2019-12-28 General Bulletin printable

Mountain Weather

Northwest winds in the 70 mph range on Saturday will diminish Sunday as High pressure builds in then is replaced by a low, bringing a warm front and the next round of precipitation. Some flurries and summit fog may hamper visibility Saturday before finally clearing out. Expect much calmer west winds, warmer temperatures and thickening clouds overhead on Sunday. The low pressure systems set to affect our weather early next week come with a lot of uncertainty as to the amount and type of precipitation. An optimist would consider the incoming weather Sunday night and Monday to be the next opportunity to build up the base, with a mix of snow and sleet on tap. Mid-week brings more upslope snowfall. Expect the avalanche hazard to increase overnight Sunday and Monday morning as temperatures rise and snow becomes wetter or turns to sleet. Be sure to check the Higher Summits forecast when making plans.  

You can keep tabs on daily details of snow on the ground and 24 weather at our snowplots at the bottom of the forecast page of this website along with the weather resources, including a daily F6 report, produced by the Mount Washington Observatory on the summit.

Forecast Discussion

A trace of snow, freezing rain and rain fell at Hermit Lake on Friday totaling just 4.4 mm of liquid. Summit temperatures rose above freezing for 8 hours with a much longer period above freezing at Ravine elevations due to the mid-level warm elevation band created by cold air damming in the valleys. While warm rain falling on snow can often penetrate the surface and leave behind a porous and somewhat “grippy” surface with some reasonable bonding ability, freezing rain falling on a frozen snowpack creates a much slicker surface that resists bonding with new snow. If the latter situation is widespread in the terrain, we will be set up for a relatively widespread avalanche cycle if we receive a significant amount of snow this week. I say relatively only because our developed snowpack is mostly limited to easterly terrain downwind of a good fetch. In other words, outside of Tuckerman and Huntington Ravine, we really aren’t there yet, with Gulf of Slides being mostly trees while south and west facing terrain having very limited snow coverage, for skiing at least. Most all of the Whites are snow and ice covered enough above around 2000’ that you’ll find some kind of traction devices useful on most every trail. 

In Huntington, you’ll likely find some water running on ice climbs until falling temperatures lock things up. Though we didn’t have a lot of rain, I would anticipate some ice dams, and damage to ice and bonding due to the period of above freezing temperatures.

Additional Information

There will be an avalanche awareness talk at 5:30-7:30pm, Thursday, January 2nd at Bissell Brothers in Portland. Come on down for a chat and a brew!

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.

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 12/28/2019 at 6:58 AM.

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