Avalanche Advisory for 2015-02-13 07:03:44

Get those flip-flops and shade hats back out because sun is in the box for the next 7 days! That said, Mt Shasta received a doozy of a storm last weekend that dumped 3-4 feet of new snow above 7,000 feet. We issued an avalanche watch and saw the avy danger hit high for a brief period on late Friday and Saturday. Evidence of avalanche debris was observed in Avalanche Gulch and slide activity was certain in other areas, though by the end of the storm evidence was scarce. The first wave of the storm that arrived on late Thursday and Friday was the most powerful, followed by scattered showers mid-weekend, and finished off with a strong last punch of water and even thunder and lightening! It was quite exciting and some areas locally saw some flooding, culvert blockage and compromised roads. Wind was a big theme the entire weekend...southerly winds cranked and blew not only a lot of snow around, but uprooted and broke limbs off many green, live trees.

The skies began to clear on Monday evening and by Tuesday morning the sun was shining and Mt Shasta withdrew its cloudy veil. Since Tuesday, we've seen a crescendo in temperature, reported from the 7,600 foot Old Ski Bowl weather station. Sun and warming temps have begun to transition all that new snow into a melt/freeze cycle and development of our famed corn snow! Transitional is the operative word... aspect, elevation and temperatures are driving good skiing. Low to mid elevation southeast to south slopes are seeing the best daytime softening. Upper elevations SW through NE are still are hosting some wintery, wind packed powder in areas. And of course, due to wind that always seems to blow at some point on Mt Shasta, scoured, icy areas exists on exposed ridgelines.

Observations over the week noted a consolidating/stabilizing snow pack. Numerous extended column tests from Mt Shasta, Gray Butte and Ash Creek Butte resulted in ECTX test scores. This means that no fracture occured during the test. A few ECT tests did produce ECTN20-30, indicating a more stable snowpack. If there was a layer of concern to be labeled, it was the wet, saturated layer below the near-surface crust layers that were widespread throughout the forecast area at low and mid elevations up to about 9,000 feet. 

Yesterday, we saw a spike in westerly winds which moved some snow around above 8,500 feet. A wind slab avalanche on the East aspect of Green Butte was triggered by a snowmobiler. The slide was about 150 feet wide with an 8 inch crown and slid 500-800 feet vertically on a non-persistent weak layer. (See photo below / Photo: Malee)

Overall, we have different avalanche problems at different elevations on Mt Shasta. For lower to mid elevations, today we could see wet/loose related avalanche probelms though unlikely due to high clouds. LOW danger with pockets of MODERATE danger on sunny, southeast/south slopes steeper than 35 degrees may see roller balls, pinwheels and point releases. While these slides today probably won't pose a threat, always beware of potential for these slides to knock one off their feet and into undesireable terrain. As one gains elevation, slopes southwest through northeast on the compass or otherwise shady, colder slopes  will see LOW danger with pockets of MODERATE avalanche danger for dryer, wind slab avalanches. These slides would look the same as we saw with that snowmobile triggered slide on the cool, east aspect of Green Butte. Remember that even though it's not snowing, avalanche are still possible!

Snowmobile triggered slide below Green Butte / Photo: S Malee
Shastina area looking toward summit of Mt Shasta / Photo: S Larsen
Avalanche Gulch, 2.11.15 / Photo: H Meyers
Shastina, 2.11.15 / Photo: H Meyers
Pit profile showing widespread near surface crust layers / N Meyers

Report your observations to the MSAC! A photo, a few words... send them in! (nimeyers@fs.fed.us or 530-926-9614)

Castle Lake area has a shallow snowpack. Be careful of shallow buried objects. Skiing has been reported as poor to non-existent.

Sand Flat Winter Trails: OPEN, trail conditions are firm and getting thin with some tree debris on snow surface. 

Pilgrim Creek Snowmobile Park: OPEN, however due to lack of low elevation snow, one must drive up the road several miles before enough snow is encountered. One CANNOT DRIVE over Military Pass.

-------------------------------------------------------------------------------------------------------------------------------

Terrain:  Remember most of the terrain that we like to play on is greater than 30 degrees.  Avalanches are possible on anything steeper than 30 degrees.  Avoid cornices, rock bands, terrain traps and runout zones of avalanche paths.

Weather:  Most of our areas avalanche danger will occur 24-48 hours after a storm. We still can see persistent weak layers from time to time and we always will be sure to let you know about that!  Heed the basic signs: Wind (significant snow transport and depositions), Temperature (rain/snow/rain/snow, which in turn weakens the snowpack), and Precipitation (Snow or rain add weight and stress to the current snowpack).

Snowpack:  If snow accumulates, give the snowpack a chance to adjust to the new snow load before you play on or near steep slopes (greater than 30 degrees).  Most direct action avalanches occur within 24-48 hours of recent snowfall.  Watch for obvious signs of snowpack instability such as recent natural avalanche activity, collapsing of the snowpack (often associated with a “whumphing” sound), and shooting cracks. If you see these signs of instability, limit your recreation to lower angle slopes.

Human Factor: Don’t forget to carry and know how to use avalanche rescue gear. You should NOT be skiing or climbing potential avalanche slopes without having beacons, shovels, and probes.  Only one person in a group should be exposed to potential avalanche danger at a time.  Remember, climbing, skiing, and riding down the edge of slopes is safer than being in the center.  Just because another person is on a slope doesn’t mean that it is safe.  Be an individual!  Make your own decisions.  Heed the signs of instability: rapid warming, “whumphing” noises, shooting cracks, snowing an inch an hour or more, rain, roller balls, wind loading, recent avalanche activity.

The Five Red Flags of Avalanche Danger any time of year include:  1) Recent/current avalanche activity  2) Whumpfing sounds or shooting cracks  3) Recent/current heavy snowfall  4) Strong winds transporting snow  5) Rapid warming or rain on snow.