THIS SNOWPACK SUMMARY EXPIRED ON April 20, 2017 @ 10:58 am
Snowpack Summary published on April 17, 2017 @ 10:58 am
Issued by Ryan Lewthwaite -

bottom line:

Another late blast of winter is here with new snow & winds. Estimates for the occurring storm snow totals will range from 24-37" by Tuesday evening. Mild temperatures & moderate winds from the Southwest will shape this precipitation event. Rain is forecasted below 8000' & post-storm warming temperatures will increase Loose Wet avalanche activity. Wind slabs will form on aspects North through Southeast & long down the deposition areas. The new snow will remain unstable for a few days & travel in avalanche terrain is not recommended.

Avalanche Character 1: Wind Slab
Wind Slab avalanches release naturally during wind events and can be triggered for up to a week after a wind event. They form in lee and cross-loaded terrain features. Avoid them by sticking to wind sheltered or wind scoured areas.

Winds will be moderate out of the Southwest 15-20 mph gusting to 70 mph in the higher elevations, with blowing snow. This blowing snow will form wind slabs & add mass to already humongous cornices around the BWRA. Expect surface wind scouring on Southwest faces & snow deposition on North through Southeast aspects. With enough wind loading slabs will be elongated further down the slope & more easily triggered by humans.

Avalanche Character 2: Loose Wet
Loose Wet avalanches occur when water is running through the snowpack, and release at or below the trigger point. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

Warm temperatures & rain are forecasted below 8000' increasing the risk of loose wet avalanches. After the storm passes sun will resume & the risk of this type of avalanche will become apparent in the higher elevations. Overnight temperatures are mild which will allow for more rapid melting overall. Look for cinnamon bun style roller-balls & point releases throughout your travels, a good instability indicator.

Avalanche Character 3: Cornice
Cornice Fall avalanches are caused by a release of overhanging, wind drifted snow. Cornices form on lee and cross-loaded ridges, sub-ridges, and sharp convexities. They are easiest to trigger during periods of rapid growth from wind drifting, rapid warming, or during rain-on-snow events. Cornices may break farther back onto flatter areas than expected.

Intricate almond-barrel looking cornices have been seen lately. Moderate to strong winds help create these delicate cornices which ultimately break & usually cause more snow entrainment as they fall. Do not approach or linger too long under these features as they can collapse without warning & contain tons of snow.

Snowpack Discussion

We have an incredibly deep snowpack which is getting deeper with spring storms. YO-yo like windy storms & high pressure periods in between have effected the snowpack in a variety of ways. Multiple melt-freeze crusts & compressed wind slabs are apparent throughout, but a right-side-up snowpack exists overall. A graupel layer had been locally deposited & was the catalyst for human-triggered avalanche propagation on a couple North facing slopes in the Leavitt Creek & Cirque.

recent observations

A layer of Graupel fell early in the last snow storm & was deposited in layers on a few Northern aspects. Three human triggered avalanches were observed Friday as a result of this situation. Please read more in the After Avalanche Investigation @ Leavitt Creek observation.


Breezy conditions and Sierra showers continue today with the next weather disturbance producing additional valley rainfall and higher elevation snowfall today through Tuesday. After a final weak system Wednesday night and Thursday, a drier trend with a significant warm up is expected heading into the weekend.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Monday Monday Night Tuesday
Weather: Cloudy. Chance of showers through the day. Cloudy. Chance of showers through the night. Cloudy. Snow and rain.
Temperatures: 45-55 deg. F. 32-38 deg. F. 36-44 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 15 to 20 mph. Gusts up to 35 mph increasing to 60 mph in the afternoon. 15 to 25 mph with gusts to 50 mph. 10 to 15 mph with gusts to 40 mph.
Expected snowfall: up to 2" in. 2 to 4" in. 3 to 6" in.
For above 10000 ft.
  Monday Monday Night Tuesday
Weather: Mostly cloudy then becoming cloudy. Chance of snow showers. Cloudy. Chance of snow showers in the evening, then snow showers after midnight. Cloudy with Snow.
Temperatures: 40-46 deg. F. 27-33 deg. F. 28-36 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 20 to 30 mph. Gusts up to 45 mph increasing to 75 mph in the afternoon. 25 to 40 mph with gusts to 70 mph decreasing to 20 to 30 mph with gusts to 60 mph after midnight. 20 to 30 mph. Gusts up to 60 mph decreasing to 50 mph in the afternoon.
Expected snowfall: up to 2" in. 3 to 6" in. 3 to 6" in.

This snowpack summary applies only to backcountry areas in the Bridgeport Winter Recreation Area. Click here for a map of the area. This snowpack summary describes general avalanche conditions and local variations always occur. This snowpack summary expires in 48 hours unless otherwise noted. The information in this snowpack summary is provided by the USDA Forest Service who is solely responsible for its content.