Forecast Expired - 03/22/2020

Above 4,000ftModerate

2,000 to 4,000ftLow

Below 2,000ftLow

Degrees of Avalanche Danger

Avalanche Problems

Problem 1

Wind Slab:


  • Almost Certain
  • Very Likely
  • Likely
  • Possible
  • Unlikely


  • Historic
  • Very Large
  • Large
  • Small


  • Increasing
  • Steady
  • Decreasing

Problem 2

Deep Slab:


  • Almost Certain
  • Very Likely
  • Likely
  • Possible
  • Unlikely


  • Historic
  • Very Large
  • Large
  • Small


  • Increasing
  • Steady
  • Decreasing

Avalanche Activity

3/14: Numerous D1 wet loose avalanches observed 3/14 on south aspects in steep terrain. 

  • Glide crack release on the north side of slater creek “east peak zone”, south aspect ~3500′.

3/11: 2 Human triggered avalanches observed on the Thompson Pass corridor.

  • Snowmachine triggered avalanche directly above the Thompson Pass airstrip.  Released from a thin section of windslab which then stepped down and released the entire snowpack on an unsupported slope. Crown was about 10 feet deep.  HS-AMu-D2-G

    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.

  • Natural D3 occurred directly across from the Tsaina lodge on a south aspect of Hippie Ridge.  Originated at 4000′, ~1500′ wide, stepped down twice and ran to the ground .

  • Natural D2 on south aspect of Hippie Ridge 1 mile north of previously mentioned avalanche. 4500′ created 2 sympathetic avalanches on either side at 4000′

  • Natural D3 on the south face of South Tiekel. Originated from 3 smaller slides at ~5700′ and stepped down multiple times and eventually ran to the ground.  Initial step-down propagated an avalanche 2-3000′ wide. Ran full path.  There were reports that sympathetic avalanches were associated with this avalanche over a mile away.  Photo from over 2 miles away. 

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.

  • At the headwaters of Quartz Creek, MP 54, a large group of snowmachiners potentially remotely triggered a D2 avalanche.  See observations page.

2/21: Multiple natural and human triggered avalanches were observed 2/21.

  • A natural avalanche hit the road near 39 mile.  This natural originated from mid-slope elevations and put a small amount of debris onto the road.  DOT mitigation efforts produced a D 3.5 avalanche that originated from the upper mountain ~6000′ and stepped down multiple times.  Crown depths were reported as significant.  Debris 6-15 feet deep buried 1000′ of the Richardson Highway. 


Debris along the highway after DOT cleanup work.

Debris that over ran the highway and was deposited into the Tsaina Gorge.

  • A natural released at the toe of Worthington Glacier on a slope just south of the toe on a north east aspectCrown was over 400′ wide and crown depth averaged 3-5 feet and stepped down to over 10′ deep at one point. There was a small sympathetic associated as well.
  • A small deep pocket (50′ across ~4′ deep) was observed on the east side of the highway below Gully 1 that was remotely triggered by snowmachines high marking above.
  • Two small avalanches released off a south slope above the airstrip with unknown trigger.  Many snowmachine tracks were present in the area around the slides.

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.



3/21: A quick moving low pressure system will briefly affect our area today creating cloudy conditions and minor snow accumulations. As this low pressure system exits to the southeast outflow winds will become strong.

The Thompson Pass Mountain Forecast covers the mountains (above
1000 ft) surrounding Keystone Canyon through Thompson Pass to
Worthington Glacier.

This forecast is for use in snow safety activities and emergency

                   Today        Tonight

Temp at 1000`      40 F         24 F

Temp at 3000`      26 F         21-27 F

Chance of precip   90%          70%

Precip amount
(above 1000 FT)    0.16 in      0.04 in

Snow amount
(above 1000 FT)    0-2 in       0 in

Snow level         900 ft       sea level

Wind 3000` ridges  S 8-16 mph   SE 8-16 mph

  24h snowfall (inches) HN24W (inches)* Hi Temp (F) Low Temp (F) March snowfall Season Snowfall Snow height 
Valdez 0 0 43 29 33 194 92
46 mile 0 0 40 25 4 99 30

Thompson Pass “DOT”

0 0 30 22 30 501 84

 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 Jan 2020

TP WX chart February 2020

TP WX chart through 3/5


Additional Information

Very cold and dry conditions in January created a weak faceted snowpack.  The effect of this weather was more pronounced on the north side of Thompson Pass, where temperatures were colder and the snowpack was thinner.

The Valdez/Thompson Pass area has received fairly regular snow storms since late January with strong outflow winds following every storm.  These wind events have redistributed the snow and created a snowpack with a high degree of spatial variability.

On 3/1, our area received 2 feet of low density snow that was quickly followed by our strongest wind event of the season, with wind gusts reaching 106 mph.  On 3/5, during the peak of wind intensity, numerous natural avalanches released north of Milepost 31.  Many of these slides stepped down to the ground. This shows us that deep persistent weak layers, formed during the January cold snap, still exist in our intermountain and continental zones.  Wind slabs created 3/4-3/6 have gained strength and consist of a variety of very hard surfaces.  These surfaces will likely act as a bed surface for subsequent storms.

New windslabs created 3/5 will make affecting deeper layers in the snowpack more difficult.  Although these layers deep within the snowpack may be more difficult to affect, they are not gone.  Once temperatures warm up in the spring, watch for these deep layers to “wake up” and produce very large, dangerous avalanches.

3/7-3/12: Our area has received 6-12 inches of new snow.  Winds have ramped up once again 3/10 and have created another layer of wind slab on lee aspects.  

3/13-3/17: Clear and calm conditions with warm temperatures during the day and cool temperatures at night have been working to stabilize our snowpack.

We received a few inches of snow 3/17 followed by moderate to strong northeast winds. Temperatures got into the 40’s in valley locations followed by cold nights.  This cycle of melt/freeze has sent our low elevation snowpack into diurnal cycle of stability.  In the morning the snowpack is locked up and the hazard is low.  As the day progresses and the sun warms the surface of the snow making it moist to wet.  This allows deeper penetration of the snowpack by a skier or snowmachine, which can produce loose wet avalanches, as well as affect deeper layers in the snowpack and potentially cause wet slab avalanches.

Forecast Confidence is High.

Resolution 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

Thanks to Spencer Byson for shredding in this photo!



The avalanche hazard is moderate at upper elevations, and low at mid and low elevations.   Small, shallow pockets of wind slab could be present on southeast through northwest aspects.  Avoid wind loaded terrain with consequences and terrain traps.