Avalanche Forecast for Monday, April 22, 2019

This information was published 04/22/2019 at 6:59 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 04/22/2019 at midnight.


The Bottom Line

Wet avalanches and springtime hazards will present equal danger to those traveling in avalanche terrain today. Wet loose avalanches, commonly known as sluffs to skiers and riders, will be possible to initiate in steep terrain, but can easily be managed by moving to the side and letting debris pass. The outside threat of a wet slab, while unlikely, makes lingering under avalanche paths a poor choice. All forecast areas have LOW avalanche danger. Holes where  the snowpack in undermined by flowing water, both obvious ones and others that may open today, horizontal glide cracks near cliffs, and falling ice and rock will further complicate travel. Many of these spring hazards can be avoided by travel management, particularly if you can see where the hazards will present themselves.

Printable 2019-04-22


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Mountain Weather

After a wet weekend, today looks like we’ll get a break, though the April showers weather pattern will likely continue this week. High temperatures yesterday were 45F on the Summit and 50F at Hermit Lake. Rain in the morning produced 0.21”. Today, light wind from the SE may increase to 20mph from the NE this evening. Fog interspersed with sunshine to start the day will give way to increasing clouds. Rain should hold off until the evening hours, with up to ¼” arriving tonight. Mostly cloudy skies with possible rain Tuesday will give way to a chance of below freezing temperatures overnight tomorrow.

Primary Avalanche Problem – Wet Loose

Wet Loose

Aspect/Elevation

Likelihood

Size

Wet loose avalanches will be small and slow moving. These are likely to be caused by skier induced sluff and can be managed by waiting off to the side and letting this sluff move downhill first. Such sluffs are often small enough that they won’t bury you, but could easily carry a person towards other hazards like an opening glide crack or over an ice bulge if they catch you unaware.

  Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

Secondary Avalanche Problem – Wet Slab

Wet Slab

Aspect/Elevation

Likelihood

Size

The wet slabs that remain a relevant avalanche problem are largely driven by our concerns of significant water running under the snowpack. A thorough soaking of the snowpack this past weekend penetrated deep into the snow and likely stabilized most deep layers of concern. Today’s weather will continue to drive warmth into the snow, but we are likely close to a fully isothermal snowpack, making deeply buried weak layers less likely to drive a wet slab.

  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.

Forecast Discussion

For those who have not had eyes on the snowpack since last week, expect to see major changes the next time you visit. Falling apart or shrinking rapidly are accurate ways to describe what’s currently going on in avalanche terrain. Springtime hazards are appearing and the following should be discussed equally with avalanche hazards today:

  • Opening creeks and streams
  • Holes near trees, rocks, and cliffs
  • Undermined snow that could easily collapse
  • Glide cracks on wide open snow slopes
  • Falling ice

We believe the time of rapid change has passed and the snowpack is becoming more stable. That being said, the weather pattern we are currently experiencing (above freezing temperatures since Thursday evening) could be described as a little weird. Weird weather has the potential to create weird avalanches. A freeze will help, but a solid freeze looks far off at the moment. All this indicates the snowpack is trending toward stable, but the time to let your guard down has not yet arrived.

Additional Information

The Sherburne and Gulf of Slides ski trails are deteriorating quickly. Expect water crossing to be the big challenge, along with bare patches, exposed rocks, and ice.

Details on daily snowfall totals, precipitation type, total depth of snow and other information can be found on our page devoted to snow study plot data. Click here to check it out.

Recent snowpack and avalanche observations can be found here and on Instagram. Your observations help improve our forecast product. Please take a moment and submit a photo or two and a brief description of snow and avalanche information that you gather in the field.

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
05/25/2054 F46 F 0.0 in 0.0 in18.7 MPH44 MPH

260 (W)

05/24/2054 F40 F 8.3 in 21 in8.3 MPH21 MPH

280 (W)

05/23/2055 F43 F 0.0 in 0.0 in15 MPH45 MPH

300 (WNW)

05/22/2055 F40 F 0.0 in 0.0 in37.4 MPH67 MPH

290 (WNW)

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)

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 04/22/2019 at 6:59 AM.

Helon Hoffer
USDA Forest Service
White Mountain National Forest