Avalanche Forecast for Wednesday, February 6, 2019

This forecast was published 02/06/2019 at 7:07 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

Warm temperatures and sunshine will again bring the potential for wet slab avalanches today. If you find yourself sinking into the snow to your boot-tops or more, you have found the avalanche problem. Yesterday’s warm up did not reach beyond 20-30 cm so plenty of dry snow beneath is waiting to get wet and contribute to the possibility of a human-triggered avalanche today. Evaluate snow and terrain carefully for signs of this heating and find another aspect or lower angle slope to ski on. MODERATE avalanche danger exists at all elevations today due to the potential of stubborn but large slabs in isolated areas. Wet slabs and wet loose avalanches will be more reactive in steep terrain where heating is most intense. Be alert for cloud cover and cooling temperatures that could refreeze the snowpack this afternoon and create the potential for a long sliding fall.

2019-2-6 Printable

Danger Rating by Zone

Mountain Weather

The temperature on the summit reached 34F for the second day in a row yesterday with mixed sun and clouds and temperatures at 3800’ reaching 42F. Temperatures cooled to 12F on the summit late last night before climbing to 25F again at 3am, with warmer temps at ravine elevations. Another warm day is on tap after last night’s brief cool down. Expect temperatures near 30F on the summit with temps likely to be well into the 40’s in the ravines. Relatively light wind on the summit, 20-35 mph, will allow maximum heating mid-day prior to clouds rolling in later in the afternoon. Freezing conditions may return before dark.

Primary Avalanche Problem – Wet Slab

Wet Slab

Aspect/Elevation

Likelihood

Size

Wet slab avalanches are likely to be stubborn today. Softer snow or thinner slabs will make it easier for a crack to propagate. An icy bed surface beneath the most recent snowfall and wind loaded slopes make today’s avalanche problem worse, particularly in areas of previously wind drifted snow. Wet slabs could be large enough to bury a person.

What is a Wet Slab Avalanche?

  Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

Snowpack and Avalanche Discussion

Warm air temperatures, a bit of rain and some sunshine started the upper snowpack on the road to becoming isothermal yesterday. The process only made part of the way down into the snowpack where wet snow was above dry snow to variable depths at observed locations. You may have noticed fractures and slides from metal roofs, snow falling off of evergreen tree branches. If you were in avalanche terrain, you would have seen wet snow that could easily form a snowball in one hand, but only in the top few inches unless you dug in a an area where a drainage channel was established. As long as dry snow remains sandwiched between the warming, wetting and weakening upper snowpack and the thick and durable ice crust formed on January 25th, avalanche danger will remain elevated.

Additional Concerns

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch.

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
05/22/19
05:25
Trace 6.2 MMTrace60 CM0.5 C2.0 C-1.0 CClearNo precipitationView
05/21/19
05:25
0 CM 4.2 MM0CM60 CM2.0 C15.0 C2.0 COvercastNo precipitation
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

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
05/21/1934 F23 F .57 in 1.9 in73 MPH135 MPH

330 (NNW)

05/20/1951 F33 F 0.57 in 0.0 in48 MPH82 MPH

250 (WSW)

05/19/1951 F34 F .6 in 0 in34.2 MPH66 MPH

250 (WSW)

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)

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 02/06/2019 at 7:07 AM.

Frank Carus
USDA Forest Service
White Mountain National Forest