Avalanche Forecast for Friday, April 19, 2019

This forecast was published 04/19/2019 at 7:02 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 04/19/2019 at midnight.


The Bottom Line

Wet avalanche types will come into play today. In addition to managing your sluff, consider that the most recent wind slabs will continue to heat up and lose strength. As our snowpack continues to warm and become saturated, the concern for deeper weak layers being impacted or water flowing onto buried ice crusts will increase. In addition to avalanche hazard, remember that falling ice and rocks, undermined snow above drainages, emerging crevasses, and moats around rocks will become a problem starting today. Consider what hazards exist overhead and beneath your feet, and don’t linger in runouts. All forecast areas have LOW avalanche danger though more rain than forecast today, or greenhouse solar gain, could create more hazard. The exception is the Headwall area of Tuckerman Ravine which has MODERATE avalanche danger due to the increasing volume of flowing water there.

2019-4-19 Printable

Forecast Area

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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.

Mountain Weather

The summit temperature rose above freezing at 6pm last night. A quarter inch of rain fell overnight with another tenth of an inch possible today. High temperature on the summit will rise further and ultimately reach the high 40’s F. The warm and rainy trend will continue through the weekend with heavy rain on the way Saturday and Sunday bringing up to two inches of rain to our snowpack and no freeze overnight.

Primary Avalanche Problem – Wet Slab

Wet Slab

Aspect/Elevation

Likelihood

Size

Newer, whiter snow that loaded in earlier in the week will be first to react to the warm-up. Be increasingly cautious when softening allows foot penetration into wet snow to reach your boot tops. Wet loose activity often precedes wet slabs. Water flowing in known drainages also increases the risk.

  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

Rain on snow caused this wet slab avalanche release last year in the Lip/Headwall area of Tuckerman Ravine. The potential for this type of avalanche will increase today through the weekend. The crown height on the right side is close to 20′ thick. Our snowpack is currently much deeper than that pictured.

Wet slab avalanches require weather that allows extended periods of temperatures above freezing, intense solar radiation, and rain on snow, especially dry snow. The combined effect of more than one of these is greater than the sum of the parts. While our snowpack is not dry in the upper meter of so, it is likely that preserved weak layers still exist deeper in the snowpack. Wet avalanches are notoriously hard to predict. That fact, combined with a snowpack that is thicker than in recent memory, brings a lot of uncertainty to any predictions of when or where avalanche activity will occur and how large the resulting avalanche will be. Fortunately heavy rain tends to keep most people home but footprints in the snow following other warm-ups suggest that some folks can’t resist the urge to be out in the weather. If that person is you, this weekend may be a good time to at least avoid major avalanche paths.

A view of the runout that reached into the drainage and almost to the rescue cache. Note where the trail enters the floor of the Ravine. Rocks and wet debris would make this avalanche unsurvivable.

Additional Concerns

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch, though this is changing by the day. Expect ice patches, opening stream crossings and the occasional bare patch.

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
11/11/19
07:30
0 CMTrace 0CM18 CM-5.0 C-2.0 C-5.0 COvercastNo precipitation
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

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 04/19/2019 at 7:02 AM.

Frank Carus
USDA Forest Service
White Mountain National Forest