Snowpack and Avalanche Information for Monday, May 18, 2020

This information was published 05/18/2020 at 8:18 AM.
A new bulletin will be issued when conditions warrant.


The Bottom Line

Four consecutive days above freezing at all elevations, and a stable weather pattern this week reduces concerns for new snow avalanche problem types, but increases concerns for springtime snowpack hazards. Warm days and cold nights, at least through mid-week, create conditions for a dynamic snowpack that changes by the hour. Be aware of temperature: refrozen snow in the morning will be firm, with long sliding falls possible, and as temperatures rise melting snow at the surface will weaken as it becomes wet or slushy with loose-wet sluff avalanches a rising concern. Generally small in size, sluff avalanches have the ability to entrain skis and carry a person over a cliff or into glide cracks that are now beginning to open up. 

As days above freezing stack up, springtime hazards emerge while the snowpack shrinks. Review the objective hazards listed in the Forecast Discussion below and keep these in mind as you plan your day. With some thought on timing and route selection up and down, all of these hazards are avoidable. 

 

Danger Rating

On Sunday May 17, 5 people were caught as they attempted to ski in Tuckerman Ravine and each were issued a Federal Citation and fined. Please remember that Tuckerman Ravine, Huntington Ravine, Gulf of Slides and the East Snowfields remain closed until May 31 and possibly later.  

MWAC has moved to a Snowpack and Avalanche Information bulletin (known in prior years as a General Bulletin) until the end of the season. Snowpack and Avalanche Information is issued when unstable snow may exist within our forecast areas but after 5-scale avalanche forecasts have stopped. Please remember that avalanches can and do occur after 5-scale avalanche forecasts have ceased! 

Tuckerman Ravine, Huntington Ravine and the Gulf of Slides will remain closed to all use until May 31 and possibly later as winter conditions and deep snow remain. 

On March 30th, the USFS MWAC took a tactical pause in forecasting operations. Since that time, forecasting and closure monitoring have continued, though forecasts were sent directly to local mountain rescue organizations only.  As the public continues to recreate and winter conditions persist in the mountains, it is apparent that current snowpack and avalanche information could be helpful in reducing risks. 

Please realize that volunteer rescue resources are currently limited due to concerns about community spread of the coronavirus. 

Mountain Weather

Above freezing temperatures during the day, refreezing at night and light winds are forecast for the next few days. Except for a slight chance of rain early on Monday, no precipitation is expected through at least Wednesday.  

Despite the date on the calendar, new snowfall and winter conditions are possible during any month of the year at higher elevations in the Presidential Range. Spring and early summer bring rapid changes to our upper snowpack, with conditions often changing by the hour. Plan accordingly for these changes by reading the weather forecast before you head out (MWObs Higher Summits and NWS Hourly forecast). 

One tool to help reduce the chance for unwelcome surprises is the hourly weather information produced by MWObs summit staff. The NWS displays the hourly data going back 7 days here.  

Forecast Discussion

Melting snow will be the main factor for snowpack problems over the next several days. The 20” of new snow last week has had 4 days of above freezing temperatures, an inch of rain and has stabilized as we continue towards an isothermal snowpack of generally clear weather, warm days and cool nights. This daily melt-freeze cycle creates the large grained round crystals we know as “corn snow” which will be stable at night and in the early morning when free water is refrozen, but as the day warms melting water percolates through the snowpack dissolving bonds between the crystals, decreasing the strength of the snowpack. Boot penetration is a good indicator of how much loose snow is available for a wet loose sluff avalanche. 

As the snowpack melts and recedes, mountain hazards become a significant problem to be aware of. Keep the following spring mountain hazards in mind as you make terrain decisions:

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
04/13/20
06:15
0 CM 0.1 MM0CM206 CM-3.5 C7.5 C-7.0 COvercastRain
04/12/20
06:20
Trace 1.8 MMTrace216 CM-7.0 C-4.0 C-7.0 CFewNo precipitation
04/11/20
06:20
14 CM 23.1 MM 14%62CM222 CM-8.0 C-6.0 C-8.0 COvercastNo precipitation
04/10/20
06:30
53 CM 49.5 MM 12%NC200 CM-6.0 C-2.0 C-6.5 COvercastSnowView
04/09/20
06:25
0 CM 0.0 MM0CM158 CM-1.0 C8.0 C-4.5 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
05/21/2053 F38 F 0.0 in 0.0 in29.4 MPH59 MPH

280 (W)

05/20/2050 F34 F 0.0 in 0.0 in29.4 MPH59 MPH

280 (W)

05/19/2041 F27 F 0.0 in 0.0 in15.3 MPH36 MPH

100 (E)

05/19/2050 F34 F 0.0 in 0.0 in11.4 MPH25 MPH

30 (NNE)

05/18/2045 F30 F 0.0 in 0.0 in14.7 MPH36 MPH

70 (ENE)

05/17/2040 F30 F 0.0 in 0.0 in17 MPH35 MPH

270 (W)

05/16/2037 F28 F .16 in 0.0 in38.8 MPH101 MPH

310 (NW)

05/15/2042 F32 F .95 inTrace 31.5 MPH95 MPH

250 (WSW)

05/14/2035 F19 FTrace 0.1 in42.8 MPH85 MPH

300 (WNW)

05/13/2022 F9 F 0.0 in 0.0 in66.3 MPH98 MPH

300 (WNW)

05/12/2018 F12 F .51 in 3.5 in58.5 MPH100 MPH

310 (NW)

05/11/2034 F18 F .65 in 5.1 in35.1 MPH73 MPH

280 (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 05/18/2020 at 8:18 AM.

Jeff Fongemie
USDA Forest Service
White Mountain National Forest