Deep persistent weaknesses are still reactive in snowpack tests. Very large avalanches are still possible.
Confidence
Fair - Intensity of incoming weather systems is uncertain on Friday
Weather Forecast
Unsettled weather is expected to bring a mix of sun and cloud with isolated flurries on Thursday, before a more organized system brings 5-15 cm of snow on Friday and another 5 cm on Saturday. Daytime high freezing levels are expected to hover around 1300 m for the forecast period and winds are expected to pick up to moderate southwesterlies on Friday.
Avalanche Summary
Over the past few days, explosives testing produced storm and wind slab avalanches and cornice releases to size 2.5. Since the Size 2.5 persistent slab avalanche on Cowboy Ridge in the Fitzsimmons Range on the weekend, we have not received any new reports of persistent avalanche avalanche activity, suggesting that these high consequence avalanches are becoming more stubborn.
Snowpack Summary
Another 5-20 cm of low density storm snow adds to the 40 cm of recent moist snow capped by a thin crust, that overlies a rain crust buried last Saturday. Reports suggest this crust exists up to at least 2200m. Strong southwest winds have shifted these new accumulations into touchy wind slabs in exposed terrain. A facet/crust persistent weakness buried mid-March is down approximately 70-130 cm and is still producing hard but sudden results in snowpack tests. This remains the chief concern amongst avalanche professionals in the region due to it's potential for very large avalanches.
Problems
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.
Storm 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.