Avalanche Forecast for Saturday, January 19, 2019

This forecast was published 01/19/2019 at 7:21 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 01/19/2019 at midnight.


The Bottom Line

The coming winter storm will create conditions that might meet avalanche warning criteria, but today is a different story. Small pockets of wind slab formed last night add some spice to generally stable conditions. You could trigger one of these new small slabs, but they should be easy to avoid. All forecast areas have LOW avalanche danger. Widespread areas of hard snow will make long sliding falls as much of a concern in your travel this morning, and consider that visibility will generally deteriorate through the day. Using normal caution for avalanche terrain and remembering that Low doesn’t mean no avalanche danger should make today the safest conditions of the holiday weekend.

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Forecast Area

The USDA  Forest Service Mount Washington Avalanche Center has issued a backcountry avalanche watch for the Presidential Range.  Avalanche Watch criteria may also be met in other areas outside those forecast by the avalanche center. This avalanche watch does not apply to operating ski areas.

Avalanche danger will increase through Sunday and Monday,  January 20-21, 2019 creating dangerous avalanche conditions. Widespread natural avalanche activity will be possible, especially on Monday, January 21.

A potent winter storm arrives this evening  and will continue through Sunday, January 20. Expected heavy snowfall will combine with strong winds to create unstable conditions. Strong NW winds on Monday, January 21 will create conditions for very large avalanches.

Mountain Weather

Around 1” of new snow yesterday was affected by westerly wind that increased to the 60-80 mph range for much of last night. Wind is currently diminishing and will continue to do so through daylight hours. High temperature should be a few degrees colder than yesterday’s summit high of 10F, with summit temperatures in the lower single digits. Increasing cloud cover today will ultimately bring heavy snow that will begin falling in light amounts this afternoon and intensify nearer to midnight. Heavy snow should continue continue through most of tomorrow, tapering to lighter precipitation rates by evening. Snow totals currently look to be around 15” but could be more. Through the snow storm, wind is forecast to shift from SW at dawn tomorrow through E and NE by afternoon, ultimately blowing from the NW by tomorrow night. Wind speeds will increase with this shift, from 25 mph tonight to around 50 mph or stronger by tomorrow night.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

New wind slabs formed overnight should be reactive to a human trigger but small in size. While either of relatively little concern or easily avoidable, remember that small avalanches in the wrong place can be a big deal. We expect you’ll find these isolated pockets on the eastern half of the compass rose.

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

A mixed bag of upper snowpack and surface conditions precede the inbound winter storm. Most of our avalanche start zones have a relatively smooth snow surface, with a few exceptions of heavily wind textured snow and less developed paths on the west side. Snow and wind last week created this mix of layered wind slabs which vary in density and are generally quite hard and unreactive. Pockets of softer wind slab do exist in the terrain, both in the form of reactive but small new wind slabs and more stubborn, older pockets. For Sunday and Monday, consider our current mix of relatively smooth bed surfaces on thick hard slabs, some potential for an avalanche to step down to deeper layers in softer pockets, and that the December 22 crust is still present at or near the surface in some scoured locations.

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
03/26/19
05:30
0 CM 0 MM0CM245 CM-16.0 C-7.0 C-16.0 CClearNo precipitation
03/25/19
05:20
3 CM 1.7 MM 9%3CM249 CM-12.0 C-2.0 C-12.0 CBrokenNo precipitation
03/24/19
05:19
0 CM 4.0 MM32CM250 CM-10.5 C-5.0 C-13.0 CClearNo precipitationView
03/23/19
05:17
38 CM 38.6 MM 12%NC253 CM-5.5 C-2.5 C-5.5 COvercastSnowView
03/22/19
05:20
Trace Trace NC213 CM-4.0 C3.0 C-4.0 COvercastSnowView

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
03/25/1911 F-3 F .15 in 1.7 in56.5 MPH86 MPH

270 (W)

03/24/1914 F1 F .21 in 3.4 in74 MPH123 MPH

310 (NW)

03/24/1918 F4 F Trace in 0.1 in63.2 MPH98 MPH

290 (WNW)

03/23/1914 F1 F 0.21 in 3.4 in74.4 MPH123 MPH

310 (NW)

03/22/1924 F12 F 1.09 in 15.2 in38.9 MPH79 MPH

330 (NNW)

View
03/21/1926 F15 F 0.02 in 0.3 in28.8 MPH60 MPH

160 (SSE)

03/20/1917 F1 F 0.0 in 0.0 in32 MPH58 MPH

270 (W)

03/19/194 F-4 FTrace Trace 43.4 MPH63 MPH

300 (WNW)

03/18/193 F-6 F 0.03 in 0 in52.1 MPH82 MPH

280 (W)

03/17/192 F-6 F 0.07 in .5 in61.5 MPH110 MPH

270 (W)

03/16/1925 F2 F 0.24 in 2.3 in67.5 MPH97 MPH

280 (W)

03/15/1941 F25 F 0.04 inTrace 54 MPH105 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 01/19/2019 at 7:21 AM.

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