Our area is forecasted to receive 6-10 inches of snowfall along with northeast winds that may reach 30 mph in channeled terrain. This is enough snow and wind to create instabilities at the surface in specific locations. Convex terrain, cross loaded gullies and places where northeast wind has moved new snow into deeper storm slabs in terrain steeper than 30° will be the most suspect. Watch for signs of instabilities such as shooting cracks and areas where wind has deeply loaded new snow. The avalanche hazard will be higher if we receive more than the 6-10 inches that are forecasted.
In many locations developed facets exist in our mid snowpack. This weak snow has been bridged over by knife hard wind slabs in most areas above 3000′, making it more difficult to affect. The snowpack has adjusted to recent storms, and at this point affecting this layer is unlikely. New snow that is forecasted for 1/19 will probably not be enough to overload this persistent weak layer. Difficult to affect does not mean impossible, and if initiated an avalanche of this size would likely carry heavy consequences. The most likely place to trigger a persistent slab avalanche would be in areas north of Thompson pass that remained protected during the new years wind event. Protected areas will be lacking the knife hard wind board that is bridging facets in most areas, making them more difficult to affect. Pole probing is a good way to gauge what is overlying faceted snow.
It looks as though this situation will change this weekend with heavy precipitation and warm air driving the snow line up to 2000′. If the weather plays out as currently forecasted it is likely that our persistent weak layer will become overloaded and we will see a natural avalanche cycle.
Photo of developed facets found on Catchers Mitt on 1/6, 2mm grid. The depth of these facets varies greatly depending upon wind redistribution. These were found just below the surface in a wind scoured area. On lee sides of terrain features facets may be found beneath 2-3+ feet of knife hard wind slabs.
1/13- Multiple large natural avalanches were noted following the snowfall on 1/13. Most were near high elevation ridge lines, although mid elevation storm slabs were noted on north aspect of Catchers Mitt and south aspect of Mile high. Other avalanche not shown in photos include Goodwills north aspect and Oddeyssey north aspect.
1/1-1/4- The new years day wind event created an avalanche cycle that was difficult to document due to crowns being rapidly reloaded by 80 mph winds. Below are photos of a couple very large slides that were still visible in the Hippie ridge area. Naturals were also noted on Three Pigs, 40.5 Mile, Crudbusters, Python Buttress.
12/29- Multiple natural wet loose D1-D2’s were observed in the Port of Valdez with no step downs noted.
12/23- Berlin Wall north face ~5000′ HS-N-R3-D2-O. It is possible this occurred on 12/21, although it was not observed until 12/24.
12/21- Numerous natural avalanches observed all along the north side of Thompson Pass, as a result of strong NE wind event along with a couple inches of new snow and rising temperatures. Observed naturals on all aspects except windward slopes with crowns originating from 1000 feet to 5500 feet in elevation. Most of these were hard slab avalanches. Crown depths were difficult to discern due to reloading, although some crowns looked to be up to 2 meters in depth.
12/19- D 2.5 natural avalanches were observed on the north facing buttress west of Gully 1 and Schoolbus.
12/14- Several natural avalanches were observed although poor visibility prevented a full view of the action. The most notable natural was observed in Nicks Happy Valley on a NW aspect ~4000′. Crown depth was not visible. Debris ran down the valley and piled up at the typical snowmachine pickup.
12/8- Large remote trigger/ sympathetic avalanche event occurred 12/8 with avalanches extending from Gully 1 to Nicks. Avalanches were soft slabs that ranged in size from D1-D3. Over 10 separate avalanches were counted with crown depths averaging 2-3′. One avalanche had a crown length of half a mile while another was triggered over a mile away from the point of collapse. See observation section for full report and more photos.
12/7- Only a few natural avalanches were noted during the last storm. It is likely there were more during the storm, but crowns may have been filled in by subsequent wind and snow.
D2’s on Town mountain was observed ~3000′
A couple of D2’s were noted in N. Oddessey gully and Big Oddessey.
D2 on 40.5 mile peak ~5500′.
12/2-12/3- Several natural D2 avalanches were noted on south aspects of Three pigs, Hippie Ridge and Averys. These windslab avalanches originated between 4000-5500 feet elevation.
NWS Watches and Warnings
Northeast Prince William Sound-
Including the cities of Valdez and Thompson Pass
407 AM AKST Wed Jan 19 2022
...WINTER WEATHER ADVISORY IN EFFECT FROM 9 AM THIS MORNING TO
11 PM AKST THIS EVENING THROUGH THOMPSON PASS...
* WHAT...Snow and blowing snow expected. Northeast winds 15 to 30
mph. Total snow accumulations of 6 to 10 inches.
* WHERE...Thompson Pass.
* WHEN...From 9 AM this morning to 11 PM AKST this evening.
* IMPACTS...Plan on slippery road conditions. Areas of blowing
snow will reduce visibility to one half mile at times.
Point forecast for Thompson Pass
Detailed forecast for Thompson Pass (mid elevation 2000-4000′)
DATE WEDNESDAY 01/19 THURSDAY 01/20
TIME (LT) 06 12 18 00 06 12 18 00 06
CLOUD COVER OV OV OV OV BK OV OV OV OV
CLOUD COVER (%) 100 100 100 85 55 75 100 100 100
TEMPERATURE 21 20 19 17 14 22 27 28 29
MAX/MIN TEMP 22 13 26 26
WIND DIR NE NE NE NE E SE SE SE E
WIND (MPH) 11 16 13 10 6 8 12 17 10
WIND GUST (MPH) 36
PRECIP PROB (%) 100 100 100 70 20 30 80 80 100
PRECIP TYPE S S S S S S S S S
12 HOUR QPF 0.39 0.23 0.03 0.19
12 HOUR SNOW 5.8 3.5 0.0 2.2
SNOW LEVEL (KFT)0.0 0.2 0.1 0.3 0.3 0.1 0.4 0.6 1.1
Snow and Temperature Measurements
All snowfall measurements are expressed in inches and temperature in Fahrenheit. 24 hour sample period is from 6am-6am.
* 24 hour snow water equivalent/ SWE.
** Season total snowfall measurements for 46 mile began December 1st.
Season history graphs for Thompson Pass
Click on links below to see a clear and expanded view of above Season history graphs
TP WX Nov 21
TP wx Dec 21
TP wx as of 1/6
Winter weather began early this season, with valley locations receiving their first snowfall on the last day of Summer (September 21st). Following this storm, above average temperatures and wet weather occurred from late September through early November. During this time period Thompson Pass received 96 inches of snowfall by November 7th and Valdez recorded 7.73″ of rain.
After the 7th of November our region experienced a sharp weather pattern change. Temperatures dropped below seasonal norms and snowfall became infrequent. Between the time frame of November 7th- November 28th Thompson Pass only reported 19″ of snow with 1.1″ of Snow water equivalent (SWE). Temperatures remained below 0° F for most of the period. This cold/dry weather caused significant faceting of the snowpack, with poor structure the result.
Moderate snowfall returned to our area the last day of November and deposited 6-12 inches of new snow. The amount varied depending upon the locations’ proximity to the coast. As the storm exited on the 2nd of December it was quickly replaced by moderate to strong northeast winds.
On 12/5-12/6 Valdez received 2 feet of new snow with Thompson Pass reporting 16″. Blaring red flags like collapsing, shooting cracks and propagation in stability tests were immediately present. On 12/8 a significant remote/ sympathetic avalanche event occurred from Gully 1 through Nick’s Happy Valley.
Strong outflow winds began on 12/11 with periods of light snowfall. This has caused slab thicknesses to become variable in areas exposed to NE winds.
A fair amount of natural avalanche activity occurred during the 12/11 wind event mostly on southerly aspects. The week following this wind event fairly benign weather occurred which allowed the snowpack to adjust and for stability to improve although snowpack structure has remained poor.
On 12/21 our area received a couple inches of snow along with temperatures rising and strong outflow winds. This combination of weather kicked off a fairly significant natural avalanche cycle. Many of the slabs appeared to be deeper wind slabs that were created from the 12/11 wind event. These failed on faceted snow created in November. The event is yet another indicator of our poor snowpack structure and its inability to receive any major change in weather without the avalanche hazard rising in conjunction.
On 12/26-28 warm air moved in at elevation and caused light rain to fall up to ~4000′. A very thin rain crust was formed in many locations that was unable to support a persons weight.
A prolonged period of strong north winds began on new years day with wind speeds reaching 80 mph. As winds tapered to 30-40 mph on the 5th temperatures plummeted with lows exceeding -30 F in the Tsaina valley.
Snowfall returned to our area on 1/13 with a foot of snow reported on Thompson Pass. An additional ~6 inches of snow were received on 1/15 with settled storm totals of 2.5 feet above 5000′.
Moderate outflow winds kicked up on 1/16, but were short-lived and not wide spread. This was followed by two days of calm and mild weather.
The avalanche hazard is moderate at all elevations. Human triggered avalanches are possible today up to 1 foot deep. The most likely place to encounter instability will be in convex terrain and ares where the wind has created deeper storm slabs in terrain steeper than 30°. The avalanche danger will be higher if we receive more than the 6-10 inches that are forecasted.
Click the + Full Forecast button below for a list of current avalanche problems, travel advice, weather resources and more.
Help to improve your local avalanche center and contribute an observation to the website. You can also contact me directly at [email protected] (907) 255-7690.
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