Avalanche Forecast for Wednesday, February 6, 2019

This forecast was published 02/06/2019 at 7:07 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 02/06/2019 at midnight.


The Bottom Line

Warm temperatures and sunshine will again bring the potential for wet slab avalanches today. If you find yourself sinking into the snow to your boot-tops or more, you have found the avalanche problem. Yesterday’s warm up did not reach beyond 20-30 cm so plenty of dry snow beneath is waiting to get wet and contribute to the possibility of a human-triggered avalanche today. Evaluate snow and terrain carefully for signs of this heating and find another aspect or lower angle slope to ski on. MODERATE avalanche danger exists at all elevations today due to the potential of stubborn but large slabs in isolated areas. Wet slabs and wet loose avalanches will be more reactive in steep terrain where heating is most intense. Be alert for cloud cover and cooling temperatures that could refreeze the snowpack this afternoon and create the potential for a long sliding fall.

2019-2-6 Printable

Forecast Area

Mountain Weather

The temperature on the summit reached 34F for the second day in a row yesterday with mixed sun and clouds and temperatures at 3800’ reaching 42F. Temperatures cooled to 12F on the summit late last night before climbing to 25F again at 3am, with warmer temps at ravine elevations. Another warm day is on tap after last night’s brief cool down. Expect temperatures near 30F on the summit with temps likely to be well into the 40’s in the ravines. Relatively light wind on the summit, 20-35 mph, will allow maximum heating mid-day prior to clouds rolling in later in the afternoon. Freezing conditions may return before dark.

Primary Avalanche Problem – Wet Slab

Wet Slab

Aspect/Elevation

Likelihood

Size

Wet slab avalanches are likely to be stubborn today. Softer snow or thinner slabs will make it easier for a crack to propagate. An icy bed surface beneath the most recent snowfall and wind loaded slopes make today’s avalanche problem worse, particularly in areas of previously wind drifted snow. Wet slabs could be large enough to bury a person.

What is a Wet Slab Avalanche?

  Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

Snowpack and Avalanche Discussion

Warm air temperatures, a bit of rain and some sunshine started the upper snowpack on the road to becoming isothermal yesterday. The process only made part of the way down into the snowpack where wet snow was above dry snow to variable depths at observed locations. You may have noticed fractures and slides from metal roofs, snow falling off of evergreen tree branches. If you were in avalanche terrain, you would have seen wet snow that could easily form a snowball in one hand, but only in the top few inches unless you dug in a an area where a drainage channel was established. As long as dry snow remains sandwiched between the warming, wetting and weakening upper snowpack and the thick and durable ice crust formed on January 25th, avalanche danger will remain elevated.

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 02/06/2019 at 7:07 AM.

Frank Carus
USDA Forest Service
White Mountain National Forest