Avalanche Forecast for Friday, January 4, 2019

This forecast was published 01/04/2019 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

Ten inches of new snow fell in the past 36 hours. West wind, possible sunshine, and rapidly warming temperatures this afternoon will combine to continue the threat of natural avalanches. Wind slabs forming this morning are likely to be touchy to a human trigger and may fail naturally with no help from a person. All upper elevation avalanche paths, particularly larger slopes and gullies in the eastern half of the compass rose, are rated CONSIDERABLE today. Lower elevation slopes and gullies not affected by wind or with less new snow are rated MODERATE. Intense sunshine on a slope could wet and weaken the snow in these wind slabs. Today is a good day to stay in terrain below 30 degrees and out of larger, wind loaded avalanche paths.

2019-01-04 Printable PDF

Danger Rating by Zone

Mountain Weather

Wednesday night brought 7-8” of new, very low density snow (6%) to the higher elevations of the Presidential range. Light snow continued off and on yesterday, with steadier snowfall again last night, bringing another 2” of slightly denser (8%) snow to Hermit Lake. Wind speeds remained low by local standards through yesterday afternoon, blowing in the 50 mph range on the summit while shifting from the WSW to WNW. Wind speed this morning has ramped up to a steadier 50-60 mph, with 70 mph recorded at 6am. Temperatures remained cold at 7F overnight though the warming trend is starting as of 6am. Wind may gust a bit higher this morning before diminishing this afternoon as skies clear and temperatures warm to the upper 20s F on the summit. Periods of sun at lower elevations and facing the sun may push the mercury above freezing.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slab avalanche danger remains today as winds increase to a speed well suited to moving snow into reactive slabs. These slabs may be touchy in steep terrain due to the soft, low density snow beneath the wind drifted snow.  These wind slabs could be triggered from below and may fail wall to wall in a gully. Signs of wind loading may be hard to identify this morning as summit fog lingers.

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.

Secondary Avalanche Problem – Wet Slab

Wet Slab

Aspect/Elevation

Likelihood

Size

Intense sunshine on a steep slope could wet and weaken the snow in existing wind slabs. Narrow gullies can intensify this effect. Air temperature will warm this afternoon and set the stage for solar gain to affect the snow if skies clear.

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

Yesterday, thick summit fog obscured visibility and reduced contrast so observations were limited. Dry loose avalanche activity in Left Gully piled up debris around a meter deep and appeared to have run yesterday morning. Though it didn’t appear to trigger a slab, it was a little more than harmless. A trip to Gulf of Slides revealed no obvious signs of avalanches though the somewhat thinner fog but did reveal that avalanche paths remain fully developed though choked with trees in the runouts.

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
05/20/19
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 01/04/2019 at 7:15 AM.

Frank Carus
USDA Forest Service
White Mountain National Forest