Avalanche Forecast for Saturday, January 11, 2020

This information was published 01/11/2020 at 7:17 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 01/11/2020 at midnight.


The Bottom Line

Rain and warm air makes human triggered avalanches possible today giving us a MODERATE danger rating.  This avalanche danger will continue through the weekend and only decrease when our snowpack refreezes, possibly Sunday night. Today is a great day to avoid steep terrain, and also areas under steep terrain where debris from an avalanche sweeps through. The floor of Tuckerman Ravine and the bottom of Gully #1 in the Gulf of Slides are examples of this.  

Warm air brings concern for falling ice anywhere there are ice cliffs, particularly hanging ice at Frankenstein Cliffs in Crawford’s Notch.  

2020-1-11 Printable forecast


Mountain Weather

Overnight temperatures in the Presidential Range were above freezing, with the summit of Mt Washington rising above freezing at approximately 2am.  Warming will continue possibly reaching 40 F on the summit today. Light rain this morning will become steady rain this afternoon with .25” of rain expected before dark.  Rain will continue overnight into tomorrow delivering as much as 1.8” of rain for the weekend total. Wind today will be from the west at 80-100 mph with gusts to 140 mph.

Primary Avalanche Problem – Wet Slab

Wet Slab

Aspect/Elevation

Likelihood

Size

After multiple days of snowfall, west winds loading and building wind slabs, rain today will infiltrate and consequently weaken the snowpack. Exacerbating this problem, these slabs are resting on an icy bed surface that has been proven to be a contributor to naturally occurring avalanches earlier in the week. This avalanche problem exists not only high in steep terrain, but at the bottom of ravine gullies where sluffing snow piles up. 

An additional concern is the known and unknown water courses that run under the snowpack when we see significant melting and rain. The Lip area of the headwall has proven itself to fail catastrophically during extreme warm rain events. 

It’s worth mentioning that predicting wet snow instability involves a higher than normal amount of uncertainty. It would be wise to factor that into your decision making if you venture into the mountains today.

  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

Rain-on-snow events present challenges to avalanche forecasters.  The models we use to determine sensitivity, distribution and likelihood become less effective tools due to the fact that water infiltration is non-linear, meaning water will work itself into and through the snowpack at inconsistent rates.  We do know that water will weaken the snowpack, increasing the chance for an avalanche. We know that natural avalanches in soft or unsupported snow (if they happen at all) will tend to occur soon after the rain begins, though the increased risk remains until the snowpack has drained or refreezes.  The real difficulty lies in estimating just how much of an effect the rain has on any weaknesses within the snowpack.

Additional Information

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch.

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 01/11/2020 at 7:17 AM.

Jeff Fongemie
USDA Forest Service
White Mountain National Forest