Valdez

Forecast Expired - 11/30/2020

Above 4,000ftConsiderable

2,000 to 4,000ftConsiderable

Below 2,000ftConsiderable

Degrees of Avalanche Danger

Low
Moderate
Considerable
High
Extreme

Avalanche Problems

Problem 1

Storm Snow:

Continued moderate snowfall have been steadily building storm slabs since 11/25.  Our thin “weak” snowpack will slowly adjust to this added weight. Natural and human triggered storm slab avalanches will be likely on 11/29.

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 2

Wind Slab:

Winds have been blowing from multiple directions since the last round of storms began 11/25.  With abundant dry snow available for transport, and changing wind direction expect wind slabs to have formed on a variety of aspects.  Avoid slopes that are actively, or have recently been loaded by wind.  Signs of recently loaded  slopes include: new snow that gets rapidly deeper over a short distance, like over a ridge or pass.  Pillowed snow surfaces, shooting cracks and freshly formed cornices.

Many Cornices are in their infancy stages of forming at this point in the season.  While traveling on or below cornices is always dangerous and never recommended. They can be especially dangerous early season when they may be made primarily of freshly drifted snow that almost surely can’t support the weight of a person or snowmachine.

The Thompson Pass RWIS wind station has been down for more than 48 hours, and the FAA camera wind station has been reporting suspect data.  With limited field observations during this last round of storms and the TP weather station not recording.  There is a lot of uncertainty with this avalanche problem and its distribution.

 

 

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Avalanche Activity

11/15: Natural avalanche observed in Loveland Basin on a South aspect, down the ridge from Tones Temple.  This slide was triggered by recent NE wind loading and failed at the ground. SS-N-R1-D2-G

11/16: Natural avalanche observed on Billy Mitchell “Cry babys shoulder”.  Released from~3500′ with a crown length of ~200 meters, North aspect. This slide was triggered by recent NE wind cross loading the slope.  SS-N-R2-D2-U

Weather

11/29- Accumulating snowfall is forecasted to continue on Thompson Pass through Sunday, before a brief break on Monday.  Warm air is forecasted to move in on Tuesday 12/1 along with another more powerful storm.  This storm will likely switch precipitation from snow to rain up to 2500′.   Updates to freezing line with this storm will happen as the event gets closer…

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
management.

                   Today        Tonight

Temp at 1000`      32 F         23 F

Temp at 3000`      27 F         25 F

Chance of precip   100%         90%

Precip amount
(above 1000 FT)    0.48 in      0.31 in

Snow amount
(above 1000 FT)    1-5 in       3-5 in

Snow level         400 ft       sea level

Wind 3000` ridges  SE 0-15 mph  E 10-20 mph

Remarks...Snow ongoing through the day, continuing into tonight.
Warming temperatures, rising snow levels, rain, snow and heavy
precipitation expected starting Monday afternoon.

 







Date: 11/28
24 hr snow (inches)
HN24W (snow water equivalent inches)
High Temp (F)
Low Temp (F)
Weekly SWE Inches (Monday-Sunday)
November snowfall
Season snowfall
HS (snowpack depth inches)




Valdez
3
.15
33
26
1.79
41
41
28




Thompson Pass
N/O
N/O
24
19
~4.4
~65
~100
~26




46 Mile
6
.6
26
22
1.6
21
21
18






Thompson Pass weather history 20/21.  Click on links below the images to see full size view




 


 


 


 


 


 


 


TP NOV as of 11/18 


 


Announcements
The avalanche hazard is Considerable at all elevations.  A series of winter storms beginning 11/25 has deposited more than 3 feet of snow on Thompson Pass.  This snow has been deposited on a thin/weak  snowpack that needs time to adjust.  Human triggered avalanches are likely and natural avalanches are possible.  Conservative terrain choices will be critical if traveling in the mountains today.  Avoid avalanche paths and terrain traps today.  Hazard will be increasing with continued heavy snowfall through Sunday.


For more information click the (+full forecast) button below.


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