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Snowpack Summary March 2, 2023
Posted by Allen Giernet @ 8:30 am (this summary expires in 24 hours)
This summary applies to backcountry areas only.
The Bottom Line –
3-3-23 - Weekend outlook - Avalanche danger will be settling but will still remain as the snowpack adjusts to the recent load. High daytime temperatures will move Loose Wet avalanches up the problem list. There are some reports of a buried weak layer yet to be confirmed on how widespread this problem is. Be cautious and conservative when heading out, avalanche danger still remains and when uncertain move to low angle simple terrain.
With limited to no access into most mountain areas we have little first hand information. The San Bernardino Mountains reported another 28” of snow in the last 24 hours. Avalanche Danger will remain High for that range. We can expect some settling in the San Gabriel mountains as the storm moved south clearing that area yesterday morning. Danger in that range will be Considerable and may be High in areas. Remember this is an unusual amount of snow for our mountains creating a complex layering of the snowpack. Without getting out to observe we can only base the forecast on weather information. Wind Slab Avalanches to be Likely, still touchy and possibly large in areas. Storm slabs will still be likely and large and could be settling except in the San Bernardino Mountains as they received more snow yesterday. Higher elevation terrain will have received more snow increasing potential danger. Adding to the problems today in the San Gabriel Mountains will be Loose Wet Avalanches at lower elevations on Southerly and sun exposed aspects as temperatures are forecast to move well above freezing. As access opens into the mountains the best strategy will be to remain conservative on terrain choices by staying off of, out from under or connected to slopes over 30°. Use simple terrain until conditions have time to accommodate the significant amount of load added to the snowpack
Please share your observations with us at the avalanche center Submit Reports page.
Posted by Allen Giernet @ 8:30 am (this summary expires in 24 hours)
This summary applies to backcountry areas only.
The Bottom Line –
3-3-23 - Weekend outlook - Avalanche danger will be settling but will still remain as the snowpack adjusts to the recent load. High daytime temperatures will move Loose Wet avalanches up the problem list. There are some reports of a buried weak layer yet to be confirmed on how widespread this problem is. Be cautious and conservative when heading out, avalanche danger still remains and when uncertain move to low angle simple terrain.
With limited to no access into most mountain areas we have little first hand information. The San Bernardino Mountains reported another 28” of snow in the last 24 hours. Avalanche Danger will remain High for that range. We can expect some settling in the San Gabriel mountains as the storm moved south clearing that area yesterday morning. Danger in that range will be Considerable and may be High in areas. Remember this is an unusual amount of snow for our mountains creating a complex layering of the snowpack. Without getting out to observe we can only base the forecast on weather information. Wind Slab Avalanches to be Likely, still touchy and possibly large in areas. Storm slabs will still be likely and large and could be settling except in the San Bernardino Mountains as they received more snow yesterday. Higher elevation terrain will have received more snow increasing potential danger. Adding to the problems today in the San Gabriel Mountains will be Loose Wet Avalanches at lower elevations on Southerly and sun exposed aspects as temperatures are forecast to move well above freezing. As access opens into the mountains the best strategy will be to remain conservative on terrain choices by staying off of, out from under or connected to slopes over 30°. Use simple terrain until conditions have time to accommodate the significant amount of load added to the snowpack
Please share your observations with us at the avalanche center Submit Reports page.
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.
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old
snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
General Summary
#1 Wind slab avalanche – Will be likely and large at the upper elevations on NE and E aspects and possible on all aspects below ridgelines and on sides of gullies. Look for signs of wind drifted snow. Actual blowing snow, sculpted snow, scoured ridges and cornices, pillowed snow and firmer hollow sounding snow. These are all signs of wind loaded snow. If you encounter these signs avoid pillowed areas of snow or stick to lower angle terrain below 30°.
#2 Storm slab avalanche – Storm slabs will be likely and have large natural avalanches and have been observed already. Due to copious amounts of snow expect to find these conditions on all aspects and increasing in danger and size as you gain elevation. Travel into near or beneath avalanche terrain is not advised at this time.
#3 Loose Wet Avalanches – will become possible as he day warms and sun puts energy into the snowpack. This will happen on Southerly aspects SE,S,SW,W through the day at the lower elevations. Look for signs of roller balls and pinwheels especially near rock bands and outcroppings. These will indicate wet snow instability.
Weekend outlook - Avalanche danger will be settling but will still remain as the snowpack adjusts to the recent load. High daytime temperatures will move Loose Wet avalanches up the problem list. There are some reports of a buried weak layer yet to be confirmed on how widespread this problem is. Be cautious and conservative when heading out, avalanche danger still remains and when uncertain remain in low angle simple terrain.
Exercise caution if venturing out into the mountains and use avalanche protocols, travel with a partner and bring your beacon, shovel and probe.
Please share any information when you are out in the mountains. Even a photo is helpful. Submit observations to Submit Reports page.
#1 Wind slab avalanche – Will be likely and large at the upper elevations on NE and E aspects and possible on all aspects below ridgelines and on sides of gullies. Look for signs of wind drifted snow. Actual blowing snow, sculpted snow, scoured ridges and cornices, pillowed snow and firmer hollow sounding snow. These are all signs of wind loaded snow. If you encounter these signs avoid pillowed areas of snow or stick to lower angle terrain below 30°.
#2 Storm slab avalanche – Storm slabs will be likely and have large natural avalanches and have been observed already. Due to copious amounts of snow expect to find these conditions on all aspects and increasing in danger and size as you gain elevation. Travel into near or beneath avalanche terrain is not advised at this time.
#3 Loose Wet Avalanches – will become possible as he day warms and sun puts energy into the snowpack. This will happen on Southerly aspects SE,S,SW,W through the day at the lower elevations. Look for signs of roller balls and pinwheels especially near rock bands and outcroppings. These will indicate wet snow instability.
Weekend outlook - Avalanche danger will be settling but will still remain as the snowpack adjusts to the recent load. High daytime temperatures will move Loose Wet avalanches up the problem list. There are some reports of a buried weak layer yet to be confirmed on how widespread this problem is. Be cautious and conservative when heading out, avalanche danger still remains and when uncertain remain in low angle simple terrain.
Exercise caution if venturing out into the mountains and use avalanche protocols, travel with a partner and bring your beacon, shovel and probe.
Please share any information when you are out in the mountains. Even a photo is helpful. Submit observations to Submit Reports page.
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Disclaimer:
This Bulletin is designed to generally describe conditions where local variations always occur. Travelers are advised to exercise caution and make slope specific evaluations. As always, please treat this bulletin with appropriately guarded skepticism and make your own assessments. Help to provide more information to the community by reporting your observations
This Bulletin is designed to generally describe conditions where local variations always occur. Travelers are advised to exercise caution and make slope specific evaluations. As always, please treat this bulletin with appropriately guarded skepticism and make your own assessments. Help to provide more information to the community by reporting your observations
Latest Observtions
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Observation type
Snowpack Location - Wrightwood Date (yyyymmdd) -20230301 Comment The epic snow event of 2023 has delivered as promised, and more. Below are some contemporaneous notes from observations at/near approximately 6,400ft in the Swarthout Valley. - Very cold, dry snow fell on 2/23 night along with gusty winds. Pockets of slabby windboard were observed on leeward slopes. - Friday 2/24 morning through Saturday 2/25 afternoon was the main event, with consistent snowfall rates of 6-9cm/hr. Best guess is snowfall ratios were 12-15:1. Totals were approx. 1.5 meters. Likely 2-3m in the high country. - Sunday 2/26 was clear and mild, with slightly above-freezing temps up to ~7000ft. Solar aspects were turning to hot pow and mank. Some - Snow and gusty winds resumed evening of 2/28, increasing in intensity overnight. By Wednesday 3/1 there was 20-30cm of new snow, with local pockets of 40-50cm in wind-loaded areas. - Several D1.5 natural avalanches were spotted on ~40deg slopes around 7300ft on 2/26. - I observed several large “whumphs” while shoveling snow from my car onto the adjacent slope, presumably from the added load. - Tl;dr – a LOT of snow has fallen in the past week, on top of variable surfaces ranging from bare earth to refrozen corn to old facets. We are now faced with a much deeper and more complex snowpack than is typical for the SoCal mountains. Roads are virtually impassable in mountain towns, so please respect residents by obeying CalTrans and CHP closures. |
Observation type
Snowpack Location - Wrightwood Date (yyyymmdd) - 20230225 Comment - Ventured out with a conservative route plan as this mega storm was winding down to see how much fell and what the snowpack is like. My partners and I toured to a ~25deg stand of oak and pine that would almost certainly never be skiable in normal years. Snow in our low-ish elevation tour seems right side up with high quality cold, dry powder rounding out the storm. Pit at ~6500ft on a 25deg North slope. 110cm deep 0-5 knife hard ice (remnants from earlier this winter) 5-55 4F 55-110 fist CT14 at 40cm, Q3 shear Snow hasn't bonded well to the icy/corn base but wasn't reactive in column test We did observe a D1 dry loose slide on a small ~40deg slope on our return home. However, there were not other observed signs of instability during our tour. |
Observation type -
Snowpack Location - Wrightwood Date (yyyymmdd) - 20230220 Comment - Leisurely afternoon trek up the ridge for some surface condition scouting and beacon practice before the mega storm rolls into town. Snow coverage below 7000' is spotty, but above that on stepper N-NW aspects there is still a decent base covering most bushes and rocks. Aspects with solar input have corned up nicely. Steeper, shaded aspects in the trees have a melt/freeze crust with 4-5cm of near surface facets sitting atop the previous crust (see image). Below that is pretty much all pencil to knife hard consolidated snow. Recent warm days seem to be rounding the facets; it will be worth watching what happens as things cool down in the coming days. Biggest concern for me is the very firm crust on which the potentially huge amount of snow will fall onto. |
Observation type
Snowpack Location - San Bernardino Mtns. Alta Diablo Date (yyyymmdd) - 20230215 Comment - Comment On February 15, 2023 I skinned up the north side of Alto Diablo on my skis. I observed shooting cracks and whumps on two slopes. On one of the slopes the crack propagated about 10 feet above me and 20 to 30 feet across the slope. If this had been on a steeper slope I believe it would have released a significant slab approximately 8 - 10" deep. This appears to be an old layer that is collapsing underneath the surface crust. This was only observed at lower elevations. Use caution moving through avalanche terrain at lower north facing elevations, especially on slopes exceeding 35 degrees. Additionally there were many areas of wind loaded snow at all elevations and a lot of snow could be seen blowing off the ridges above 10,000 feet. Even though the recent storm only brought about 1 - 2" of new snow to the area, the potential for windslabs around ridge lines is currently high. Avoid slopes above 30 degrees where wind loaded snow could accumulate especially near ridge lines. |
General Caution
You should always use safe terrain management and carry avalanche rescue equipment in the backcountry. Most avalanches are triggered by someone in the party or the victim. Practice with your rescue gear often and be prepared should the worst happen. Though we do not have an avalanche forecast center in this area as of yet, the information posted and shared here as well as the resources available on this site will help to make informed decisions for your backcountry travels. Use avalanche forecasts in your travels wherever available and be aware that avalanche ratings are general information. Elevation, location, geographic variability’s, slope aspect and angle all have effects on the particular area you travel in. This is only one piece of the information you should use in your decision making process. There is no substitute for avalanche education, for more resources and information as well as education please refer to our resources page.
You should always use safe terrain management and carry avalanche rescue equipment in the backcountry. Most avalanches are triggered by someone in the party or the victim. Practice with your rescue gear often and be prepared should the worst happen. Though we do not have an avalanche forecast center in this area as of yet, the information posted and shared here as well as the resources available on this site will help to make informed decisions for your backcountry travels. Use avalanche forecasts in your travels wherever available and be aware that avalanche ratings are general information. Elevation, location, geographic variability’s, slope aspect and angle all have effects on the particular area you travel in. This is only one piece of the information you should use in your decision making process. There is no substitute for avalanche education, for more resources and information as well as education please refer to our resources page.
