Avalanche Forecast for Wednesday, January 8, 2020

This information was published 01/08/2020 at 7:15 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 01/08/2020 at midnight.


The Bottom Line

  • Hollow snow over weaker snow may be triggered by a skier or climber this morning
  • Large natural avalanches will be  likely this afternoon
  • Do not linger in or skin up avalanche paths including the floor of Tuckerman Ravine

Avalanche danger will increase to CONSIDERABLE quickly early this afternoon from it’s already tricky Moderate rating. Cautious route finding and careful snowpack evaluation will be essential today.

2020-1-8 Printable forecast


Avalanche danger will increase further today due to more new snow and wind loading. East facing terrain will develop wind slab avalanches which could occur without a human trigger. Don’t be fooled by the small amount of snow in the forecast. The shift in wind direction and speed will access soft drifts tucked away in the alpine and contribute more snow to wind slabs that will create avalanches easily large enough to bury a person in the Gulf of Slides and Tuckerman Ravine. Other areas with less available snow could still produce dangerous avalanches. 

Mountain Weather

Low pressure systems passing near the area followed by upslope showers will produce 3-5” of new snow. Wind speeds will be relatively light this morning but will increase steadily through the day with effective loading speeds in the 50-60 mph range beginning in the early afternoon. Temperatures which have become seasonably cold in the past couple of days will grow even colder with mid-single digits during daylight hours dropping to -8F tonight.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

New snow and light to moderate wind this morning will create sensitive wind slabs on top of our lingering wind slab problem. Remember that small amounts of new snow over the past several days have continued to stress existing wind slabs and today’s new snow will only create more stress and strain on already weak bonds. The base of steep areas and lee terrain are both habitats for today’s wind slab problem.

  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

The disparity that exists in the QPF between NWS and the MWObs is largely irrelevant to the rating today. Wind loading which occurred yesterday built wind slabs which have not yet stabilized. Temperatures and time are not on our side, even this morning with human triggered avalanches certainly possible due to the recency of these slabs development. The icy layer deep in the snowpack has resisted bonding and may even be developing some early facets, though overcast conditions overnight have not made for ideal facet farming. More snow tonight, cold temperatures and further high winds will keep our stability concerns alive tomorrow and while the threat of natural avalanches may pass tonight, the fresh and thick wind slabs will keep the threat real tomorrow. Expect a solid Moderate rating and a continued need to be really wary of what appear to be stubborn hard slabs. We have limited observations from the west side but sheltered locations appear to hold enough snow to recreate on. Scouring has likely taken it’s usual toll in more exposed location and it is doubtful that typical streambeds are entirely closed in, though they may be close. Gulf of Slides has certainly filled in with the problematic ice bulge trigger points close to but not yet entirely covered.

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
01/19/20
05:15
8 CM 7.3 MM 10%NC112 CM-6.5 C-6.5 C-15.0 COvercastSnow
01/18/20
05:15
0 CMTrace 0CM103 CM-18.5 C-12.0 C-22.0 COvercastNo precipitationView
01/17/20
05:11
22 CM 16.6 MM 9%26CM107 CM-20.0 C-4.0 C-22.0 CFewNo precipitation
01/16/20
05:15
3 CM 2.9 MM 11%NC85 CM-7.0 C-4.0 C-7.0 COvercastSnow
01/15/20
05:16
2 CM MM 16%NC82 CM-4.0 C-3.5 C-7.0 COvercastSnowView

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
01/17/204 F-18 F .03 in .4 in75 MPH110 MPH

320 (NW)

01/16/2018 F-11 F .048 in 6.1 in43.3 MPH117 MPH

330 (NNW)

01/15/2020 F11 F 0.25 in 1.8 in9.3 MPH74 MPH

290 (WNW)

01/14/2020 F10 F 0.03 in 0.7 in32 MPH69 MPH

280 (W)

01/13/2022 F14 F .04 in .8 in49.5 MPH81 MPH

240 (WSW)

01/12/2045 F8 F .84 in .4 in58.4 MPH104 MPH

260 (W)

01/11/2042 F29 F .32 in 0 in68.8 MPH119 MPH

230 (SW)

01/10/2030 F12 F .22 in 1.3 in63.4 MPH102 MPH

260 (W)

01/09/2015 F-14 F .04 in .4 in50.1 MPH114 MPH

310 (NW)

View
View
01/08/2013 F-8 F .52 in 5.2 in43.5 MPH95 MPH

290 (WNW)

01/07/2016 F1 F .17 in 1.6 in41.8 MPH90 MPH

280 (W)

01/06/2010 F3 F .2 in 2.2 in32.8 MPH71 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 01/08/2020 at 7:15 AM.

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