Hatcher Pass Avalanche Center

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Sat, November 23rd, 2019 - 7:00AM
Sun, November 24th, 2019 - 7:00AM
HPAC Staff
Conditions Summary

5-7″ of new snow with 0.4″ of SWE was reported at the IM Snotel overnight. Temperatures remained just below freezing.  Gold Cord weather station at 4050′ reported 5.5″ of new snow overnight with temperatures in the lower 20’s F. The Marmot snow stake, at approximately 3000′, appears to have accumulated 6″ of new snow overnight. Strong winds this week tapered off significantly yesterday. At 4500′, winds remained light overnight, SE to SW, with a few gusts hitting 20-21 mph.

NOAA is calling for an additional 2″ of new snow today with a snow line at 500′. Winds are forecasted South 5-10mph with a high of 26°F at 3000′ today. Temps should cool significantly tonight with the freezing level dropping to sea level. More here on the Recreational Forecast for HP.

Storm snow avalanches and loose dry avalanches will be possible to human trigger and natural avalanches will be unlikely, on all aspects, at mid to upper elevations today. Both storm snow and loose dry avalanches are expected to be small in size. Loose dry will be more likely on SE to SW aspects where new snow accumulated over exposed, patchy, firm crusts. New storm snow instabilities should be short lived. In the long term, we expect the new snow to bond well to existing snow surfaces.

Glide avalanches, which are unpredictable in nature and may release at any time, will remain possible, large in size, and are a high consequence hazard. Numerous glide crack avalanches have occurred this season. Please review past observations to familiarize yourself with the location and widespread nature of this hazard. Avoid areas with signs of old glide cracks, glide avalanches, and new glide cracks. Old glide cracks and glide crack avalanche bed surfaces may be covered with new snow and will be more difficult to pick out. Other glide cracks will present as a “brown frown“. No new glide crack avalanches have been observed this week.

It is important to note that some unknowns exist surrounding wind slab avalanches sliding on previous glide avalanche bed surfaces on opposing aspects at upper elevation this week. Read more under avalanches at the base of the page.

The lower elevations will continue to lack an avalanche hazard through the weekend. At low elevation we expect limited snow accumulation.

Earlier this week:

Strong winds persisted this week, mainly out of the SE to SW, which transported abundant low density snow, depositing wind slabs on West to North aspects, at mid to upper elevations. Wind slabs bonded quickly to old snow surfaces, including an old rain crust layer down 12″-18″ at 4500′. Stability remained good through the week.

Temperatures at 3050′ pushed above freezing on the 19th, and then stayed at or just below freezing for the rest of the week.

Approximately 11″ of new snow was recorded at the Gold Cord Weather Station (4050′) between 11/16 and 11/18 in a couple storm cycles. 3″ of new snow was recorded at Gold Cord on 11/20-21.

Windward aspects, East to West, at mid to upper elevations, are scoured down in a patchy distribution to a rain crust layer in many locations. The exposed, firm but textured crust has made travel in the backcountry quite challenging.

Cloudy skies with short windows of sunshine have made for a challenging week, but a few short windows allowed folks to harvest powder in golden rays. The crust layer is still felt when riding, however, on the leeward aspects it is beginning to get buried deep enough where it can not be felt.

Other than some possible wind slab activity on pre-existing glide avalanche paths, over the past two days we have not observed recent natural wind slab activity (due to recent strong winds), and could not produce ski cut results or find propagation on test slopes or starting zones.  We experienced no collapsing in the snow, only localized cracking, and one isolated shooting crack on a very steep sidewall at mid elevation on a northerly aspect. In light of numerous slopes tested, we felt that this one isolated shooting crack was not representative of the big picture. Our observations revealed good bonding of recent wind slabs present on slopes at mid to upper elevation, on North facing aspects, on steep slopes, 30-50°.  We observed wind slabs to be 4-12″ thick.  

Riding conditions have remained acceptable to good on leeward aspects. Coverage is excellent, with rocks and facet gardens near extinct. If you have been disappointed in the current surface quality, look on the bright side of life. We have excellent coverage for early season, a solid, thick base, which will resist any hurricane the Matauska, Sustina or Knik blows our way. This likely means great coverage for the entire season, and all we require is a “freshen up” for the riding to be superb, which we just received overnight, and are scheduled for a little more today.

Special Announcements

Avalanche forecasts with danger ratings are scheduled to begin Thanksgiving weekend.

Recent Avalanches

Eldorado Headwall, E, 4400′. Picture from Nov 22

There remains some question as to whether or not natural avalanches occurred this week, over the last 3 days. The pattern was easy to spot over the last two days, but clues will likely be covered up today from new snow overnight. The pattern is relegated to only old glide avalanche paths which failed previously at the ground at upper elevation on opposing aspects. A few previous glide avalanche paths, but not all, were missing 11/17- 11/22 new snow coverage and showing ground.

Two explanations are currently being debated.

One: Strong winds from this week created wind slabs that failed naturally on exposed ground surfaces from previous full depth glide avalanches. In this case a few new wind slab avalanches could have occurred this week.

Two: Strong winds scoured new snow, exposed the old bed surfaces, and deposited the snow elsewhere. In this case no new avalanches occurred.

If you get out into the backcountry this weekend, our community and avalanche center needs your observations! Thanks to everyone who has submitted observations this season, we appreciate your incredible support. Submit your obs here!

Sat, November 23rd, 2019

NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.

Recent Observations for Hatcher Pass