Triggered by sledders on Saturday (4/4/20). Photo: @scottmooney
19-20
GNFAC Avalanche Forecast for Mon Apr 6, 2020
<p>There is a full bag of avalanche concerns to watch for which is common this time of year. Over the weekend avalanches involved wet snow, wind-drifted snow, buried persistent weak layers and cornices (<a href="https://www.mtavalanche.com/node/22663"><strong>details</strong></a>, <a href="https://www.mtavalanche.com/node/22657"><strong>photo</strong></a>, <strong><a href="https://www.mtavalanche.com/images/20/cornice-triggered-slides-bridger"…;, <strong><a href="https://www.mtavalanche.com/node/22674">details</a></strong>). Today’s weather forecast has relatively high uncertainty, so conditions may change unexpectedly (also common during spring). If there is more snow than expected, fresh drifts could grow large. If there is more rain at higher elevations, wet loose and wet slab avalanches will be possible. Any brief sunshine will make wet avalanches possible, and above freezing temperatures will weaken large cornices (<a href="https://www.mtavalanche.com/images/20/massive-cornices-beehive"><strong…;).</p>
<p>Just a few inches of new snow will create minimal hazard, but more than a drizzle of rain will increase wet avalanche hazard. If it rains hard, or if you see roller balls, pinwheels or natural wet slides avoid steep slopes. Where you find dry snow (higher elevation, northerly aspects), avoid fresh drifts and slopes where you find or suspect buried weak layers (<a href="https://www.mtavalanche.com/images/20/buried-surface-hoar-crystal"><str…;, <a href="https://www.mtavalanche.com/images/20/ectp-surface-hoar-s-madison"><str…;, <a href="https://www.mtavalanche.com/images/20/ectp-surface-hoar-mt-ellis"><stro…;). Also stay far back from the edge along ridgelines and avoid slopes below large cornices.</p>
<p>Through the middle of the week sunny skies and above freezing temperatures will make wet avalanches the main concern. Freezing overnight temperature will minimize large wet slab activity, but expect stability to decrease through each day for possible wet loose and shallow wet slabs. Start early when the snow is frozen or dry and be off and out from underneath steep terrain before the snow becomes wet. If you sink past your boot top into wet snow then it’s passed the right time to turn around, but not too late. See this <strong><a href="https://www.mtavalanche.com/blog/transitions-spring-snow-avalanche-prob… info below for general spring snowpack and travel advice.</p>
<p>Please continue to send us your observations. You can fill out an <a href="https://mtavalanche.us17.list-manage.com/track/click?u=6653a830e4819c9e…; target="_blank">observation form</a>, email us (<a href="mailto:mtavalanche@gmail.com" target="_blank">mtavalanche@gmail.com</a>), leave a VM at 406-587-6984, or Instagram (#gnfacobs). We greatly appreciate your support.</p>
Natural wet loose in Absarokas
From obs 4/5/20: "...saw a ton of tracks and a lot of natural dry loose activity. D1-D1.5 slides on steep E to NE terrain between 8000 and 9500'. Everything pictured released between 1200 and 1400 when the sun was out. Looked like rollerballs were heating up on the cliffs and triggering dry loose slides below."
Cornice triggered wind slab at Bridger
Cornice triggered avalanches in Mundy's Bowl at Bridger Bowl. Unsure if natural or skier triggered from the ridgeline. Observed the morning of 4/5/20. Appear to be dry slab/loose. Photo: T. Gittins
Forecast link: GNFAC Avalanche Forecast for Mon Apr 6, 2020
GNFAC Avalanche Forecast for Sun Apr 5, 2020
<p>Yesterday a skier triggered a thin wind slab on Beehive Peak which caught and carried a four-legged group member (<strong><a href="https://www.mtavalanche.com/node/22663">photos and details</a></strong>). All were unharmed. Although seemingly small, a shallow slab can carry you over cliffs or into trees. Today you can trigger fresh wind slabs that formed the last couple days with moderate southwest wind. Be cautious of wind loaded slopes, and avoid terrain where any size slide has large consequences.</p>
<p>Larger avalanches can break 2-3 feet deep on buried weak layers. Yesterday in the northern Gallatin Range a snowmobiler triggered a 2 foot deep slide that likely failed on buried surface hoar, facets or a crust. All of which have produced avalanches, collapsing and unstable test results for the last week (<strong><a href="https://www.mtavalanche.com/avalanche-activity">avalanche log</a></strong>). Dig a few feet to look for weak layers and avoid slopes where you suspect they exist. Weak layers 2-3 feet deep have consistently been found and breaking in stability tests from the Bridger Range (<strong><a href="https://www.mtavalanche.com/images/20/buried-surface-hoar-crystal">phot…;) to West Yellowstone (<strong><a href="https://www.mtavalanche.com/images/20/ectp-surface-hoar-s-madison">phot…;, <strong><a href="https://www.mtavalanche.com/images/20/ectp-surface-hoar-mt-ellis">photo…;).</p>
<p>Also avoid slopes where you can trigger wet avalanches if the snow becomes wet, and stay away from large cornices (<strong><a href="https://www.mtavalanche.com/images/20/massive-cornices-beehive">photo</…;). As Doug explains in his recent <a href="https://www.youtube.com/watch?v=1j2Y8NWOuHs&list=PLXu5151nmAvSbcbVf…;, even though things may look good there are various hazards and stability can change quickly. Today avalanches are possible and avalanche danger is MODERATE.</p>
<p>Since Wednesday there were two tragic avalanche fatalities in Wyoming and Idaho (<strong><a href="https://avalanche.state.co.us/caic/acc/acc_report.php?acc_id=752&ac…;, <strong><a href="https://avalanche.state.co.us/caic/acc/acc_report.php?acc_id=755&ac…;), and in the last two weeks two avalanche accidents in Colorado required heli-evac for serious injuries (<strong><a href="https://avalanche.state.co.us/caic/acc/acc_report.php?accfm=inv&acc…;, <strong><a href="https://avalanche.state.co.us/caic/acc/acc_report.php?accfm=rep&acc…;). <strong>All of these accidents occurred during moderate avalanche danger.</strong> A lot of people are out skiing and riding, and distancing themselves into new and untracked terrain. Please make conservative choices. Choose terrain where a slide will not carry you through rocks, over cliffs or into trees, no matter how certain you are of stability. Avoid avalanche terrain entirely to greatly reduce your risk of being injured or killed. Please consider the greater risk to rescuers, EMS resources and yourself at this time.</p>
<p>We will post general weather and avalanche bulletins every Monday and Friday through April. Please continue to send us your observations. You can fill out an <a href="https://mtavalanche.us17.list-manage.com/track/click?u=6653a830e4819c9e…; target="_blank">observation form</a>, email us (<a href="mailto:mtavalanche@gmail.com" target="_blank">mtavalanche@gmail.com</a>), leave a VM at 406-587-6984, or Instagram (#gnfacobs). We greatly appreciate your support.</p>
Closures and Stay-at-home Order
A Stay at Home order is in effect for the State of Montana due to COVID-19. This order specifically discourages “outdoor recreation activities that pose enhanced risks of injury or could otherwise stress the ability of local first responders to address the COVID-19 emergency (e.g., backcountry skiing in a manner inconsistent with avalanche recommendations or in closed terrain)”.
From obs. (4/4/20): "Rode Tepee today... Got ECTP 24 & 25 on a thin layer of SH... We also saw a few cornice drops that pulled out small slabs, new snow only..." Photo: E. Knoff
Forecast link: GNFAC Avalanche Forecast for Mon Apr 6, 2020
From email (4/4/2020): "...HS 215cm - ECTP19@165cm on preserved 4-7mm surface hoar... Also found a whole variety of crusts in the slab above the propagation from the frequent recent warm ups it seems... Kept it low angle with the surface hoar lingering..." Photo: Z. Miller
Forecast link: GNFAC Avalanche Forecast for Sun Apr 5, 2020