Avalanche Forecast for Monday, January 6, 2020

This information was published 01/06/2020 at 7:43 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 01/06/2020 at midnight.


The Bottom Line

Human triggered avalanches are possible where the wind has drifted recent snowfall. Any new snow later this afternoon will be blown by the wind to form new slabs of drifted snow. Cliffs, trees, and terrain traps can increase the consequence of being caught in a slide. Picture where an avalanche would carry you before skiing or climbing steeper slopes. The avalanche danger is MODERATE today.

2020-1-6-printable


Mountain Weather

The 2.6” of snow Saturday and the 2.2” of snow Sunday was transported, drifted, packed and scoured (depending on where you look) by WNW wind in the 60-70 mph range on Sunday.  Today, we start the day with a rare zen-like calm and clarity with a summit temperature of 7F and SSW at 6mph. Clear skies won’t last long, clouds and the chance for snow showers return early this afternoon. Wind will shift west and increase through the day to 45-60 mph. Up to 1” of new snow is possible by the end of the day. Tonight 1 to 2 more inches of snow are possible on continued W wind of 50-70mph. Tomorrow is forecast to be clearing with decreasing wind.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

New wind slabs formed from yesterday’s strong wind will generally be stiff with good bridging strength especially where most exposed to the strongest winds.  However, even a stiff wind slab can be triggered to slide if you find a weak point in the form of a convex terrain feature, or a thin spot over buried rocks or bushes. Be alert to the consequences of triggering an avalanche and evaluate the terrain as you move about the mountains today.  Watch for additional snow this afternoon and tonight drifting into new and possibly more sensitive wind slabs. 

  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.

Forecast Discussion

It has been 4 days since the last known avalanche activity (link 1, link 2) and we expect the snow from the New Year’s Eve storm to be largely settled and likely unreactive. As predicting the stabilization of wind slabs includes a fair bit of uncertainty, and the fact that it’s been just 4 days, it would be wise to respect these older but larger wind slabs. With yesterday’s strong wind, new slabs will be mixed in with scoured terrain and feel stiff and supportive, while still susceptible to a human trigger.

Additional Information

The Lion Head Winter Route is open and remains the safer choice for accessing the summit of Mount Washington from the east. An ice axe and crampons are needed near treeline and above with micro-spikes useful in wind scoured areas.

Conditions on the Sherburne ski trail have improved with the recent snowfall though a few rocks and ice patches have emerged.

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.

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
04/13/20
06:15
0 CM 0.1 MM0CM206 CM-3.5 C7.5 C-7.0 COvercastRain
04/12/20
06:20
Trace 1.8 MMTrace216 CM-7.0 C-4.0 C-7.0 CFewNo precipitation
04/11/20
06:20
14 CM 23.1 MM 14%62CM222 CM-8.0 C-6.0 C-8.0 COvercastNo precipitation
04/10/20
06:30
53 CM 49.5 MM 12%NC200 CM-6.0 C-2.0 C-6.5 COvercastSnowView
04/09/20
06:25
0 CM 0.0 MM0CM158 CM-1.0 C8.0 C-4.5 CClearNo precipitation

Avalanche Log and Summit Weather

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
05/25/2054 F46 F 0.0 in 0.0 in18.7 MPH44 MPH

260 (W)

05/24/2054 F40 F 8.3 in 21 in8.3 MPH21 MPH

280 (W)

05/23/2055 F43 F 0.0 in 0.0 in15 MPH45 MPH

300 (WNW)

05/22/2055 F40 F 0.0 in 0.0 in37.4 MPH67 MPH

290 (WNW)

05/21/2053 F38 F 0.0 in 0.0 in29.4 MPH59 MPH

280 (W)

05/20/2050 F34 F 0.0 in 0.0 in29.4 MPH59 MPH

280 (W)

05/19/2041 F27 F 0.0 in 0.0 in15.3 MPH36 MPH

100 (E)

05/19/2050 F34 F 0.0 in 0.0 in11.4 MPH25 MPH

30 (NNE)

05/18/2045 F30 F 0.0 in 0.0 in14.7 MPH36 MPH

70 (ENE)

05/17/2040 F30 F 0.0 in 0.0 in17 MPH35 MPH

270 (W)

05/16/2037 F28 F .16 in 0.0 in38.8 MPH101 MPH

310 (NW)

05/15/2042 F32 F .95 inTrace 31.5 MPH95 MPH

250 (WSW)

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 01/06/2020 at 7:43 AM.

Jeff Fongemie, Snow Ranger
USDA Forest Service
White Mountain National Forest