Avalanche Forecast for Wednesday, January 23, 2019

This forecast was published 01/23/2019 at 7:10 AM.
A new forecast will be issued tomorrow.

The Mount Washington Avalanche Center will no longer issue daily avalanche forecasts for the 2018/19 season. Read more

The Mount Washington Avalanche Center will no longer issue daily avalanche forecasts for the 2018/19 season. Instead, we will post an updated General Bulletin as needed, in case of significant snow or weather events that might vary from the typical daily changes that come with spring weather. We will also keep you informed about the official closure of the portion of the Tuckerman Ravine Trail from Lunch Rocks through the Lip and Headwall as well as the switch from the Lion Head Winter Route to the summer trail. Observations from the field will continue to be a valuable resource, so please keep submitting photos, videos and observations here and we will do the same. Check the Forecast page for update on Sherburne Trail closures, which are imminent as spring snowmelt continues.

The switch to a General Bulletin does NOT mean that the mountains are now a safe place to ski. The hazards which emerge in the spring are significant and require careful assessment and strategic management. If you have never skied Tuckerman, peruse our Incidents and Accidents page for spring related incidents involving avalanches, long sliding falls, icefall, crevasse and moat falls, and other incidents related to diurnal changes in the snowpack. These will help you understand and plan for these hazards.


The Bottom Line

Hard, wind slabs built during the extreme wind that followed the MLK weekend winter storm remain a concern today. Settlement and bonding that usually occurs after a snowfall were put on hold as temperatures hovered well below zero. Use normal precautions if you go looking for smooth snow for skiing today. Crampons and an ice axe may be useful on the more wind exposed steep areas near ridgetops. The combination of hard wind slabs, some smaller but softer and possibly more reactive wind slabs, and warming temperatures keep our range-wide rating elevated at MODERATE today. It remains possible for a person to trigger an avalanche on specific terrain features today. Evaluate snow and terrain carefully. Rain on snow conditions tomorrow will likely keep avalanche danger elevated with challenging travel conditions.

2019-1-23 Printable

Danger Rating by Zone

Mountain Weather

A frigid air mass moved in after the recent winter storm deposited 13” of increasingly dense snow on the range. That cold air was ushered in on extreme NW wind that raged over 100 mph for close to 12 hours in the early hours of Tuesday morning. After reaching a low of -31F just prior to the wind event, the mercury is continuing its upward journey from Arctic to temperate through the day and into tomorrow. This warm up will bring sleet and freezing rain late this afternoon, with rain later tonight. Some snow showers will fall today but shouldn’t amount to much more than an inch. Temperatures on the summit will climb from the current 10F to 29F by dark to close to 40F tomorrow. Rain tomorrow seems likely to fall all the way to the summit.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Winds over 100 mph pounded snow into our primarily east facing terrain. Extreme winds often scour ridgetops while depositing snow and building stubborn slabs lower down the slope, especially beneath steep features and along gully walls. Softer slabs may have formed as wind was slowing so look for more reactive slabs further around the terrain rose. Lower elevation areas weren’t as wind affected but most of the snow was capped by a temperature crust which is likely unreactive.

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

Numerous crown lines were observed during the brief period of clear conditions yesterday afternoon with most avalanche activity likely having occurred Sunday night. Refilled and eroded crown lines indicate that easterly aspects avalanched more than once. Significant scouring occurred in the higher elevation, but small fetch, Huntington Ravine with similar effects likely in other high elevation areas. The upside down nature of the storm made for touchy conditions on Sunday but this wetter layer has refrozen since then and is likely lacking the energy to propagate a crack anywhere. As stated earlier, the biggest concern is the low probability, high consequence hazard of finding and triggering a thin, weak spot in a large wind slab. The human-triggered avalanche in the Lower Snowfields avalanche in 2013 followed similar weather and wind conditions. The MLK weekend storm and more specifically the wind that followed, filled in and developed many of the more ephemeral east and south east facing avalanche paths like the ‘69 slide path on the Summer Lion Head trail.

Additional Concerns

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch. Several large trees were down yesterday on the Tucks and Sherburne ski trails with wind damage likely elsewhere around the range.

Avalanche Safety Information Study

Please contribute to the effort to improve backcountry avalanche forecasts! Researchers in Canada devised a study to better understand how we communicate the avalanche risk, and we need your help. Please fill out this survey. It will take a few minutes, but it will help us as we work on new ways to give you the most important avalanche information.

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
05/22/19
05:25
Trace 6.2 MMTrace60 CM0.5 C2.0 C-1.0 CClearNo precipitationView
05/21/19
05:25
0 CM 4.2 MM0CM60 CM2.0 C15.0 C2.0 COvercastNo precipitation
05/20/19
05:30
0 CM 20.4 MM0CM68 CM11.0 C12.0 C3.5 CObscuredNo precipitation
05/19/19
05:25
0 CM 0.0 MM0CM72 CM4.0 C6.0 C2.0 COvercastNo precipitation
05/18/19
05:20
0 CM 7.6 MM0CM80 CM1.0 C6.0 C1.0 COvercastNo precipitation

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
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)

05/18/1934 F26 F 0.06 in 0.5 in39 MPH74 MPH

300 (WNW)

05/17/1940 F28 F .22 in .05 in37 MPH81 MPH

300 (WNW)

05/16/1932 F25 F .03 in 04 in22.8 MPH40 MPH

310 (NW)

05/15/1926 F20 F .05 in .4 in32.1 MPH67 MPH

330 (NNW)

05/14/1928 F17 F .2 in 2 in19.1 MPH57 MPH

100 (E)

05/13/1928 F19 F .07 in 0.9 in34.6 MPH67 MPH

100 (E)

05/12/1931 F17 F 0 in 0 in20.5 MPH47 MPH

330 (NNW)

05/11/1932 F18 F .1 in 0 in53.6 MPH84 MPH

300 (WNW)

05/10/1944 F27 F .85 in 0 in50.1 MPH88 MPH

220 (SW)

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 01/23/2019 at 7:10 AM.

Frank Carus
USDA Forest Service
White Mountain National Forest