Snowpack and Avalanche Information for Thursday, April 30, 2020

This information was published 04/30/2020 at 7:11 AM.
A new bulletin will be issued when conditions warrant.


The Bottom Line

Rain and freezing rain are on tap for the next two days (Friday and Saturday). Temperatures may not reach below freezing until Saturday night and then only for a short period. After that, temperatures continue to warm. Look for stronger warming to create deeper instability until the snowpack becomes isothermal. These deeper concerns should be limited but beware of deeper wet loose, point releases in most other avalanche terrain. See photos below.

Travel has been difficult with untracked and unpacked snow at mid and upper elevations. Floatation in the form of snowshoes or skis is highly recommended, even on normally well-travelled trails. More remote ski descents, which are seeing a fair amount of traffic, could create challenging rescue problems.

Danger Rating

Mountain Weather

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. One tool to help reduce the chance for unwelcome surprises due to snowfall, icing conditions or just raw, hypothermia weather is the weather record produced by MWObs summit staff. The NWS displays the hourly data here.  You can retrieve up to 7 days of data b toggling the switch at the top of the page. 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).

Forecast Discussion

As spring conditions arrive, our deeper snowpack becomes more stable and avalanche concerns are mostly reduced to direct action avalanches during snow and wind-loading events. Generally, warming and rain bring stability, but only when the warming occurs slowly enough for the snowpack to adjust. Additionally, late season storms can certainly deliver more than enough snow to generate dangerous avalanches. The month of May brings 12.2” of snow to the summit on average. In 1997, 95.8” of snow fell on the summit in May.  As a reminder, the following red flags indicate that avalanche danger may be elevated:

Crown line in Gully 3 in Gulf of Slides, likely from wind loading a week ago, but possibly a wet slab due to recent warming.

Wet debris below Yale. This D1.5 occurred yesterday, April 29, 2020.

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 04/30/2020 at 7:11 AM.

Frank Carus
USDA Forest Service
White Mountain National Forest