Avalanche Forecast for Tuesday, January 15, 2019

This forecast was published 01/15/2019 at 6:57 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 01/15/2019 at midnight.


The Bottom Line

Varied snow surface conditions are generally quite firm or scoured to old crusts, and you’re unlikely to trigger an avalanche in these layers. Keep your eyes open for softer pockets of snow which may hold lingering stability concerns. The variable conditions make both crampons and avalanche rescue gear appropriate for today. Visibility may challenge your ability to judge the snow surfaces you plan to travel on. All forecast areas have LOW avalanche danger. Do continue to look for unstable snow on isolated terrain features.

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Forecast Area

Mountain Weather

A high temperatures of 21F, clear skies, and light winds yesterday has given way to increasing NW wind and partial cloud cover. Partially to mostly cloudy skies should persist through today with a slight chance of snow flurries producing no measurable precipitation. Temperatures will be a few degrees colder than yesterday, but still remain in the teens F for daylight hours. The current NW wind of 47 mph on the summit will decrease slightly through today and shift W tonight before ramping up towards 70 mph tomorrow. A fast moving storm tomorrow may bring a few inches of snow.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Hard wind slabs which are quite large in some terrain should be unreactive to a human trigger. Still, on the off chance that you find a weak point in one of those slabs, it’s worth treating them with respect. Smaller pockets of softer slabs can also be found in the alpine, particularly on S and SE aspects where some of the largest hard slabs also exist. These softer pockets of wind slab are likely stubborn to a human trigger. You probably won’t trigger an avalanche today, but it’s not the kind of Low avalanche danger that provides truly green light conditions.

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.

Snowpack and Avalanche Discussion

Field time and observations through much of the central presidential range has illustrated an interesting pattern of wind loading and scouring from last week’s storm. Terrain lacking a significant upwind fetch area for loading on a NW wind, like Huntington Ravine and the Great Gulf, experienced as much or more scouring than loading last week. Areas of December 22 crust are exposed and wind slabs are generally small. Oppositely, terrain with a significant fetch zone for a NW wind, like Tuckerman Ravine, Gulf of Slides, and Oakes Gulf experienced a great deal of wind loading and corresponding large avalanche activity. In most locations, wind slab formed late last week is hard and unreactive to a human trigger. The current conditions show that when wind is the primary driver of snowpack development, similar aspects and elevations in relatively close proximity do not always mirror each other. Another key characteristic of our snowpack is the December 22 rain crust. We think a number of avalanches last week ran on this robust and fairly smooth crust as a bed surface, and it may continue to act as a bed surface for future avalanches. You will also likely find this crust as the dominant snow surface in middle and upper elevation Westerly terrain where the avalanche problem is absent.

Additional Concerns

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

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
02/18/19
05:22
Trace Trace NC201 CM-14.5 C-9.0 C-16.5 COvercastSnow
02/17/19
05:24
Trace Trace Trace204 CM-16.5 C-9.5 C-16.5 CClearNo precipitation
02/16/19
05:22
13 CM 10.7 MM 12%13CM205 CM-10.0 C-2.0 C-10.0 COvercastNo precipitation
02/15/19
05:22
Trace 0.1 MM30CM195 CM-7.0 C-5.0 C-15.0 COvercastNo precipitation
02/14/19
05:24
11 CM 6.5 MM 10%NC196 CM-14.0 C-6.0 C-15.0 COvercastSnow

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
02/17/1914 F-3 F 0.00 in 0 in37 MPH74 MPH

310 (NW)

View
02/16/198 F-5 F .05 in .8 in52.4 MPH84 MPH

310 (NW)

02/15/1925 F7 F .37 in 2.7 in45.3 MPH84 MPH

240 (WSW)

02/14/1919 F-4 F .13 in 1.1 in56.2 MPH90 MPH

280 (W)

02/13/1916 F0 F .87 in 5.1 in46.3 MPH92 MPH

280 (W)

View
02/12/1912 F2 F .54 in 3.3 in37.5 MPH76 MPH

130 (SE)

02/11/196 F-9 F 0 in 0 in59.0 MPH86 MPH

330 (NNW)

02/10/19-4 F-13 F 0 in 0 in65.3 MPH101 MPH

290 (WNW)

02/09/19-7 F-14 F .01 in .2 in87.5 MPH148 MPH

280 (W)

02/08/1937 F-8 F .20 in .2 in71 MPH124 MPH

230 (SW)

02/07/1934 F22 F .04 in .2 in32.2 MPH56 MPH

250 (WSW)

02/06/1932 F17 F .23 in .4 in30.9 MPH68 MPH

330 (NNW)

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 01/15/2019 at 6:57 AM.

Ryan Matz, Snow Ranger
USDA Forest Service
White Mountain National Forest