5/1: Small to moderate wet loose avalanches were observed on solar aspects up to 5000′.
4/18: Numerous moderate to very large wet loose and wet slab avalanches were seen and reported on south aspects from sea level up to 6000′.
4/17: Full depth wet slab avalanches were observed on south faces of Town Mountain, Hogsback and Hippie Ridge.
4/16: Widespread wet loose avalanches observed in the Port of Valdez up to 5000′ on east through west aspects.
A soft slab avalanche was observed on Hogsback that initiated from a rockband at ~4500′, west aspect, ~500′ wide. Looked to be about 2-3′ deep, but was observed through binoculars so that is just a guess. Avalanche may have been snowmachine triggered as there were tracks directly adjacent to the avalanche, but that is unconfirmed.
4/14: Observed numerous small to moderate wet loose slides off solar aspects up to 4000′.
4/6: Small to moderate dry loose “sluffs” were observed on east through northwest aspects above 3000′ in terrain steeper than 40°. Did not observe any soft slab avalanches triggered by dry loose slides.
3/26: Small natural wet slab avalanche that originated from a point release was observed at MP 40 on a south aspect. 100′ wide, originating from ~2000′, ran to ground.
3/22: Small snowboard triggered wind slab avalanche reported in skate park. ~3000′, southeast aspect, 1 foot deep, ~40′ wide. SS-ARu-R1-D1.5-I. Other small natural releases were reported in the area as well.
3/14: Numerous D1 wet loose avalanches observed 3/14 on south aspects in steep terrain.
3/11: 2 Human triggered avalanches observed on the Thompson Pass corridor.
Skier triggered avalanche in Nicks Happy Valley. Skier was traversing the wind loaded northwest aspect of the gully and released a slab ~1 foot deep and 100′ wide, ran ~150 vertical feet to the bottom of the gully. SS-ASu-D1.5-I.
3/5: -Natural D 2.5 occurred on the NW aspect shoulder of the Python Buttress “Ptarmigan Drop” milepost 31. Avalanche crown was reported to be 10-15 feet deep by DOT and ran to the ground. Crown was quickly filled back in by intense snow transport.
3/4: A natural D3 avalanche ran above the 37 mile tsaina bridge. South aspect ~5500′, stepped down multiple times, ran to the ground in places. The main debris fell short of the highway, mature uprooted trees 6-12 inches in diameter were thrown onto the road by powder blast.
-The gully downstream of Bridal Veil Falls produced a large avalanche, D2.5, that buried the river with over 10′ of debris, the powder blast pushed sticks into the parking lot on the other side of the road.
3/3: DOT mitigation work produced another large avalanche that affected the Richardson Highway at ~ mile 39. Initial reports stated that the avalanche buried the highway under 15 feet of debris for ~500 feet.
2/28: Natural wind slab avalanche 4000′. N-HS-R2-D2, West aspect slope that descends from Crudbuster basin into IguanaBacks. Stepped down immediately below initial crown, to the ground in places.
2/26: Large natural observed at 48 mile off Point 5064 (Stuart). N-HS-R3-D3, N-W aspects. Observed from the highway. Looked fresh, probably within the last 24 hours. Appears to have released from a N aspect bowl ~40-45° at~4500′, then stepped down and wrapped around the corner onto NW-W aspects. Crown on step down is estimated to be over 3 meters deep in places. Couldn’t see extent of track length. Crown was over 1/2 mile wide. 3 small, sympathetic pockets were observed over 1/2 mile away in moderate terrain with crowns ~1-2 meters. Picture taken from over 3 miles away.
2/24: Natural avalanche observed on the north face of Goodwills’ ~5500′, D-2.5, 200-300′ wide. Ran to the bottom of the slope ~600′, crown ~5′ deep.
2/23: – Natural avalanches D2-2.5 on the east face of Mt. Tiekel were observed.
2/21: Multiple natural and human triggered avalanches were observed 2/21.
Debris along the highway after DOT cleanup work.
Debris that over ran the highway and was deposited into the Tsaina Gorge.
Natural near the toe of the Worthington Glacier.
2/20: Two side by side avalanches were observed on the NW shoulder of the Python buttress ~3500′. Crown 2-300′ across and ~3’+ deep. These slides ran into the flat ~800 vertical feet. Slides were triggered by DOT mitigation work 2/19.
2/20: 2 paths on Three Pigs at MP 42 slid naturally to the middle to lower portion of their aprons, D2.5. Low clouds prevented ability to see what elevation they originated from.
2/20: A natural avalanche was reported on the north shoulder of Mt Tiekel at ~4500′. Details were limited but the entire slope avalanched and crown was reported to be 2 meters deep. R5-D2.5~.
2/19: A natural avalanche at 32 mile buried the Richardson Highway under 10 feet of snow for ~100′. This caused the highway to close for the majority of the day. This slide released from the lower bench of RFS on a north aspect.
2/14: Dry loose D1-2 natural avalanches were observed running over the Wowie Zowie ice climb in Mineral Creek.
2/13: Natural and human triggered D1 avalanches were observed in Keystone Canyon.
2/12: A D3 avalanche at MP 38 hit the Richardson Highway and closed the road. Released on a south aspect in the upper elevation start zones, ~5500′, and stepped down around 4-4500′. Further DOT mitigation efforts on Three Pigs and 40.5 Mile produced no results.
5/3: Clouds will move in through the day with moderate northeast wind becoming light. Expect highs on Thompson Pass to be in the mid 40’s.
Thompson Pass “DOT”
HN24W= total water received last 24 hours in inches
Thompson Pass weather history 19/20 season beginning 12/21. Click on links below to see full size image.
TP DEC 19
TP Jan 2020
TP WX chart February 2020
TP wx chart March 2020
TP wx chart April 2020
Pay attention to what the sun is doing to the slope you are traveling on, and what is above you. Cooler temperatures and light to moderate winds limited natural wet loose avalanche activity at the end of April. New snow along with warmer forecasted temperatures 5/1-5/3 will make natural and human triggered wet loose activity more likely this weekend.
Faceted snow still exists at the base of our snowpack in Intermountain and Continental locations. This faceted snow was created by the dry, brutal cold temperatures in January. It is possible that we will see these layers re-activate in Continental locations when heat penetrates down to these deep layers.
Our area has encountered the first part of our Spring shed 4/15-4/20, caused by temperatures remaining above freezing at elevation without overnight refreezes. A lot of snow has fallen off the mountains which has relieved a lot of stress from our transitioning snowpack. On 4/21 temperatures began to fall below freezing along with cloudy skies at Thompson Pass and above, which has allowed for natural avalanche activity to slow down.
Our area is forecasted to receive mostly sunny skies from 4/25-4/29. This will allow the next phase of our spring shed cycle to begin. Temperatures are forecasted to dip below freezing at night which should make natural activity less significant than the last shed cycle 4/15-4/20, but will not eliminate it.
Forecast Confidence is Moderate.
If you see something in the mountains that could contribute to this forecast, leave a public observation. The more observations we receive, the better we can tune our forecast. If you would rather not post an observation publicly, feel free to send me an email at [email protected]
Send in your best mountain recreation photos to [email protected] so we can post a photo of the week!
Photo of the Week
The avalanche hazard is moderate at all elevations. Human triggered wet loose avalanches are possible on slopes steeper than 35° where more than 4 inches of slushy snow is present. Avalanches could be small to moderate in size depending upon the the vertical fall of the slope that they originate from. Although unlikely there is also a chance to trigger a large wet slab avalanche that could be large enough to injure, bury or kill a person. There are often good indicators in the spring that wet avalanche activity is becoming likely. These include: pinwheels or rollerballs at the bottom of slopes, a snowpack that can no longer support a persons weight on their feet and steep rocky terrain producing wet loose or slab avalanches. Thompson Pass did not receive a strong refreeze the morning of 5/3. Expect wet loose conditions to develop quickly in the day, especially if incoming clouds hold off longer than forecasted. Avoid slopes where the snowpack has become isothermal, and traveling on or below cornices.
This will be the last weekend for public avalanche forecasts for the 2019/20 season. Thanks to everyone who contributed and used the forecast this season!
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