Hatcher Pass Avalanche Center
Hatcher Pass

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, April 4th, 2021 - 7:00AM
Expires
Mon, April 5th, 2021 - 7:00AM
Forecaster
Allie Barker
Avalanche Warning
Issued: April 4, 2021 9:00 am
Travel in avalanche terrain is not recommended. Avoid being on or beneath all steep slopes.
Avalanche risk The Bottom Line
Update 6:00 pm Sunday, April 4th, 2021
Avalanche Danger is HIGH at Hatcher Pass.
HUMAN TRIGGERED AVALANCHES ARE VERY LIKELY
NATURALS ARE LIKELY
VERY DANGEROUS CONDITIONS
TRAVEL IN AVALANCHE TERRAIN NOT RECOMMENDED
HP has received 11″ of snow and almost 2″ inches of water along with SSW winds gusting 20-41 for 21 hours.
Every RED FLAG exists right now.
We have confirmed that a D3+ VERY LARGE AVALANCHE has crossed both the upper and lower road btw Skeetawk and Gold Mint. This has not occurred since the 1980’s.
Other large natural avalanches from today are being verified.
The road will be CLOSED at Gateway. Please DO NOT go up to Hatcher Pass for your own safety and the safety of others. Most avalanches occur within 24 to 48 hours of a storm. It’s time to give the mountains a big break.

Update at 9am: An AVALANCHE WARNING is in effect. The avalanche danger has been elevated to HIGH. HUMAN TRIGGERED avalanches are VERY LIKELY. NATURALS are LIKELY. VERY DANGEROUS CONDITIONS. Travel in Avalanche Terrain is not recommended today. The Hatcher Pass road is closed  at Gold Mint. Please respect the closure for your safety.

HP has received 6″ of snow overnight into this morning with almost 1″ of water, combined with SSW winds gusting 20-34 mph for 12 hrs. 5″ to 12″ of snow are expected today with SW winds changing to WNW this evening with gusts upwards of 30mph.

Several human triggered avalanches were reported on Thursday and Friday, large enough to bury, injure, or kill a person.

Sun, April 4th, 2021
Upper Elevation
Above 3,500'
4 - High
Avalanche risk
Mid Elevation
2,500'-3,500'
4 - High
Avalanche risk
Low Elevation
Below 2,500'
4 - High
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Recent Avalanches

For more information on recent avalanches , see Saturdays forecast HERE.

Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.
Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

Persistent slabs, up to 2′ feet deep, will be very likely to human trigger today on NW to NE aspects and up to 12″ inches deep on E to S to W aspects at all elevations today. Naturals will be likely.

3-4″ of snow overnight combined with moderate to strong SSW wind gusts have built and will continue to build wind slabs on NW through NE aspects today. 5-12″ of additional snow are forecasted for today combined with strong wind gusts expected to shift from South to W/NW tonight.  There is some uncertainty with this storm, but it is likely to increase the avalanche danger.  Todays biggest concern will be wind slabs stepping down into the persistent slab on NW to E aspects where the facet/drizzle crust is buried.

Persistent slabs are sitting on a widespread weak sugary faceted layer on top of a widespread sun crust/drizzle crust combo in many locations at Hatcher Pass.  The key take away is that the current hazard is already elevated with slab avalanche problems and will be exacerbated with any additional new load today.  Whumping, cracking, collapsing, and recent avalanches are RED FLAGS for this avalanche problem.

This is an unusual set up for Hatcher Pass for April. Unfortunately this problem is not going away and will likely get worse before it gets better.

 

Avalanche Problem 2
  • Wind Slabs
    Wind Slabs
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.
Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

Wind slabs, 4″ to 6″ thick,  will be very likely to human trigger today on NW, N, and NE aspects at mid and upper elevation. Naturals will be likely. Wind slabs will be building and increasing in size throughout the day with additional snow and wind in the forecast. Wind slabs will have the potential to step down into the PERSISTENT SLAB and fail 18″ to 24″ deep, increasing the size and consequence of the avalanche.

Avalanche Problem 3
  • Dry Loose
    Dry Loose
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.
Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

Small to Large Dry loose sluffs will be likely to human trigger today at all elevations, on steep slopes above 40º. Naturals will be possible. The size of sluffs will increase today with another 5″ to 12″ of snow forecasted throughout the day. Getting sluffed into a terrain trap will increase the size and consequence of any avalanche.

Weather
Sun, April 4th, 2021
HP received approximately 3-4" of snow overnight with .6" of water. Temperatures increased from 20ºF to 27ºF
overnight at 3550'and hovered in the 20'sF at 4500'. Winds SSW gusted 20-34 mph for 8 hours overnight.
Southcentral Alaska Mountain Forecast
NATIONAL WEATHER SERVICE Anchorage AK
408 AM AKDT Sun Apr 4 2021


                   Today        Tonight
Temp at 1000`      27-33 F      3 F

Temp at 3000`      26 F         7-23 F

Chance of precip   100%         80%

Precip amount
(above 1000 FT)    0.64 in      0.11 in

Snow amount
(above 1000 FT)    4-10 in      1-2 in

Snow level         500 ft       sea level

Wind 3000` ridges  SW 15-35 mph NW 10-25 mph

Remarks...Snow will continue through this afternoon with the
heaviest snow falling through mid to late morning.




NWS Rec Forecast here.


NWS point forecast here.


State Parks Snow Report and Motorized Access information here.



			

		

		
	

		
	

		

			

				
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