Avalanche Forecast for Monday, January 28, 2019

This forecast was published 01/28/2019 at 6:53 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 01/28/2019 at midnight.


The Bottom Line

Ideal wind speed and direction for loading easterly terrain has created wind slabs overnight that will continue to grow today. You are likely to trigger these slabs which are becoming large in size. Look for pillowy wind drifts and continued wind loading today to identify this avalanche problem. Some terrain, particularly at upper elevations on the west side of the range, may be scoured to the hard January 25th rain crust, which presents a long sliding fall hazard in addition to today’s avalanche problem. We have CONSIDERABLE avalanche danger today, with the Northern Gullies of Huntington Ravine and the Right Side of Tuckerman Ravine being the exceptions at MODERATE avalanche danger. Avalanches will be unlikely at lower elevations where today’s avalanche problem is generally absent.

2019-1-28_printable_pdf

Forecast Area

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Mountain Weather

Six inches of snow accumulation was recorded at the summit of Mount Washington yesterday, with 5” at our snow plots. This snow initially fell on S and SW summit winds in the 40-50 mph range. Wind shifted W and increased to 50-70 mph as snowfall tapered after dark yesterday. Wind should remain westerly around 60 mph before tapering off this evening. Summit temperatures will increase slowly though the day from the current -8F to the single digits above 0, and continue to rise through tonight to peak in the teens tomorrow. Cloud cover will decrease through the day today but increase again by tomorrow afternoon as another winter storm arrives. We may receive double digit snow totals by Wednesday.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slabs, which will continue to grow in size today, will be reactive to a human trigger. West winds loading lee terrain and cross loading other terrain will make this avalanche problem relatively widespread on the eastern half of the compass rose. New slabs will be largest in areas with large upwind fetch zones for wind to pull snow from, like the Headwall area of Tuckerman Ravine and east facing terrain in the Gulf of Slides. Be sure to account for this variability in size that is common with wind slabs as you make snowpack observations today.

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

Five to six inches of new snow in the past 24 hours, which resulted from upsloping snow showers at higher elevations, has been affected by W wind in the 50-70 mph range since last night. These conditions produce wind slabs which can be much thicker than storm snow totals, often by a factor of 5 or more. Wind transport continues currently and slabs will continue to grow at least some through the day, though it is likely that instability peaked overnight. Instability in these new wind slabs, which continue to be stressed by new wind loaded snow, are the primary concern today with a few pockets of wind slab on similar terrain existing prior to the current storm above the melt/freeze crust formed last Friday. Stability concerns are limited to snow above this crust. This crust may be a player in potential avalanches today, but generally good bonding to the crust makes the weak layer of concern a density change or interface within snow deposited in the past 3 days.

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
05/31/19
05:20
0 CMTrace 0CM0 CM8.0 C11.0 C0.5 CBrokenNo precipitation
05/30/19
05:25
0 CM 0.0 MM0CM0 CM7.5 C7.5 C1.0 CScatteredNo precipitation
05/29/19
05:25
0 CM 22.3 MM0CM0 CM1.5 C4.0 C0.0 COvercastNo precipitation
05/28/19
05:25
0 CM 0.0 MM0CM0 CM0.5 C11.0 C0.5 CClearNo precipitation
05/27/19
05:15
0 CM 0.0 MM0CM10 CM8.0 C15.5 C8.0 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
05/30/1946 F36 F 0 in 0 in27.9 MPH55 MPH

290 (WNW)

05/29/1947 F33 F 0 in 0 in20 MPH48 MPH

290 (WNW)

05/28/1934 F28 F .71 in 3.7 in20 MPH48 MPH

290 (WNW)

05/27/1940 F27 FTrace 0 in38.9 MPH68 MPH

300 (WNW)

05/26/1948 F39 F .77 in 0 in48.7 MPH75 MPH

290 (WNW)

05/25/1947 F31 F .42 in 0 in17.7 MPH63 MPH

240 (WSW)

05/24/1942 F32 F .66 in 0 in44.8 MPH105 MPH

05/23/1944 F30 F .16 in 0 in26.8 MPH71 MPH

270 (W)

05/22/1934 F21 F 0 in 0 in36.2 MPH115 MPH

330 (NNW)

05/21/1934 F23 F .57 in 1.9 in73 MPH135 MPH

330 (NNW)

05/20/1951 F33 F 0.57 in 0.0 in48 MPH82 MPH

250 (WSW)

05/19/1951 F34 F .6 in 0 in34.2 MPH66 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 01/28/2019 at 6:53 AM.

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