The Avy Rose shows the forecasted danger by elevation and aspect.
It adds more detail about where you are likely to find the dangers mentioned in the forecast. The inner circle shows upper elevations (mountain top), the second circle is middle elevations, and the outer circle represents lower elevations.
Think of the Rose as a birds-eye view of a mountain, looking down from above. The rose allows our forecasters to visually show you which parts of the mountain they are most concerned about.
The 12/11 storm snow was found to be upside down on 12/12 with signs of instability like shooting cracks and collapsing. Clear weather will have helped storm slabs to settle, although temperatures dropped slowly and not to a great degree.
More snow is forecasted for our area today (up to 6 inches). This will not allow the surface snow ample time to bond and stabilize. The avalanche hazard has cooled off some from yesterday, although it remains elevated at Considerable. Human triggered avalanches are likely the distribution of this problem is widespread. Cautious route finding and conservative terrain choices are recommended. Pay attention to signs of instability like shooting cracks, collapsing and natural avalanche activity that is telling us to stick to lower slope angles.
Storm slab avalanches will have the potential to step down to deeper layers in our snowpack to create hard slab avalanches.
We currently have a thin (weak) snowpack in place. Prior to this storm the pack was comprised of thick windslabs on lee aspects that overly various old rain crusts. Windward aspects were scoured to old rain crusts, ground and old wind affected snow at upper elevations. Old rain crusts have promoted faceting above and below them creating significant faceting in the mid and lower snowpack.
Weak layers in our snowpack are being put under pressure during this week. It is possible that these layers may reach the tipping point sometime late Wednesday early Thursday as the next significant storm effects our area with high snowfall amounts and warmer temperatures.
Storm slab avalanches may have enough force to step down to these deeper layers creating destructive hard slab avalanches.
11/14- Debris from a D3 natural avalanche at snow slide gulch ended 100 vertical feet above the Lowe river.
Large avalanches (D2-2.5)also occurred in multiple other locations including Berlin Wall, Catchers Mitt, South Three Pigs and Billy Mitchell. The activity extends beyond this list, and mostly occurred during the peak of warming and precipitation on 11/13.
Multiple natural D1-1.5 avalanches were observed on multiple aspects at low elevation. No step downs noted.
12/1- 2 D2.5 natural avalanches were noted on Three Pigs (Beaver slide, Pig Leg). Pig leg ran into the top 1/3 of the fan and Beaver Slide stopped near the end of its track. These both likely occurred during the outflow wind event 11/26-11/29.
D2 natural wind slab was observed on 40.5 mile peak on a west aspect ~3000′. Crown depth range estimated 1-2 feet and 200′ long
12/9- Several D2 natural wind slab avalanches were observed on S-W aspects at mid elevation in the intermountain region. Crowns appeared to be 1-3 feet deep. Catchers Mitt and Gully 1 were among the spots affected.
12/12- Observation of natural activity was prevented by clouds and continuing snowfall on Thompson Pass and Valdez.
Check out our updated weather tab! A collection of local weather stations are available for viewing with graphs and tabular data included.
NWS Watches and warnings
...A WINTER STORM WITH MIXED PRECIPITATION IS POSSIBLE WEDNESDAY
After a relatively small snowfall today, another round of
precipitation is expected to move across the eastern Kenai
Peninsula and Prince William Sound areas Wednesday through
Thursday. Precipitation is expected to begin as snow for most
locations, but as warm, southerly flow brings additional moisture
into the area, snow could transition to rain near coastal areas.
Cold air will filter behind the frontal passage and could add to
the potential for slippery surfaces. Be aware that the forecast
may change considerably as this storm develops.
NWS Point forecast for Thompson Pass
Date Tuesday 12/13/22 Wednesday 12/14/22
Time (LT) 06 12 18 00 06 12 18 00 06
Cloud Cover OV OV OV OV OV OV OV OV OV
Cloud Cover (%) 85 100 90 85 95 95 100 100 100
Temperature 14 20 25 24 25 23 25 25 31
Max/Min Temp 25 23 27 23
Wind Dir SE SE S SW S SE SE S S
Wind (mph) 6 10 12 8 4 4 9 23 25
Wind Gust (mph)
Precip Prob (%) 30 80 70 60 50 70 100 100 90
Precip Type S S S S S S S S S
12 Hour QPF 0.28 0.10 0.41 1.25
12 Hour Snow 3.8 0.7 4.1 14.2
Snow Level (kft) 0.0 0.0 0.1 0.0 0.1 0.4 0.9 1.1 1.4
Click on link below for Thompson Pass weather history graph:
*HN24W- 24 hour Snow water equivalent in inches
*SWE– Snow water equivalent
**46 mile seasonal snowfall total begins December 1st.
Our snow season began with above average precipitation and temperatures. Beginning in September, snow lines generally hung around 4500′ until 10/12. At that point our area received the first snow down to sea level with 12-16 inches on the north side of Thompson Pass.
On 10/15 wet conditions continued with the freezing line rising to 5000′ or higher. As skies finally cleared on 10/22 we were left with a thin rain saturated snowpack capped by a stout rain crust up to 4500′. Above 4500′ much deeper snowpacks existed due to significant early season snowfall at upper elevations.
Dry and cold conditions along with moderate outflow winds finished out the month of October.
On 11/1 precipitation returned with 18 inches of snow and ~1″ of SWE on Thompson Pass. This new snow was initially reactive with several natural D2 avalanches reported on Thompson Pass. These slides were running on a firm bed surface consisting of old rain crusts and old wind slabs from October.
On 11/4 a strong north wind event kicked up with 65 mph+ winds on Thompson Pass. Our snowpack received significant damage as already thin snow below 4500′ was stripped down to old wind slabs, rain crusts and the ground.
Precipitation returned on 11/8 and became heavy on 11/11. Storm totals of around 50 inches were recorded at Thompson Pass DOT between 11/8-11/13. Snow lines rose to ~3000′ near the tail end of the storm with heavy rain occurring in low lying areas.
Skies cleared on 11/14 through 11/18 with a strong temperature inversion setting up. Valley temperatures north of Thompson Pass fell to 0° F with above freezing temperatures existing above 4000 feet. Valdez temps remained mild. This weather allowed for widespread surface hoar up to 1 cm to develop in low lying areas.
Precipitation returned on 11/19, with incremental snowfall on Thompson Pass and areas north. The Valdez area received rain during this period. 12 inches have been recorded at TP DOT between 11/9-11/23.
11/26-11/29- Strong outflow (N) wind event. Many areas below 3000′ were stripped to the 11/13 rain crust, destroying the 11/19 BSH layer. Widespread very hard snow surfaces were the result.
Precipitation returned to our area on 12/5, with higher accumulation amounts near the coast. As storms cleared out on 12/7, they were directly followed by another round of strong north winds. These winds once again incurred severe damage to our snow stripping surfaces back to the 11/13 rain crust on windward aspects and further building pencil hard slabs on lees.
12/11- Significant snowfall event that dropped 12-24 inches+ in a 12 hour period.
The avalanche hazard is Considerable at all elevations. Human triggered avalanches are likely 1-3 feet deep . Natural avalanches are possible. Clear skies overnight have allowed the new snow to settle somewhat, but continued snowfall today will keep the hazard elevated.
Posted by Gareth Brown 12/13 8:00am.
For a description of current avalanche problems, weather information, season history and more click the (+ full forecast) button. Avalanche forecasts will be issued Wednesday-Sunday.
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