Avalanche: Timpanogos

Observer Name
Observation Date
Saturday, March 31, 2018
Avalanche Date
Saturday, March 31, 2018
Location Name or Route
Observed from a distance. 3 large slides. 1st on north facing saddle east of Mt Timp. (glacier/snowfield). Other two were in the lower basin off th west headwall.

Forecaster Comment: Below here we are copying and pasting in the words of UDOT forecaster John Woodruff. " Here is a quick write up of what we are seeing in the Provo area mtns. Last weeks rapid warm up in temps had kicked the free flowing water into high gear for the start of the spring run off even at the upper elevations on everything but the upper N1/2 of the compass. Low elevation snow that still remains has gone isothermal, and the mid elevation snow is gradually moving that direction. Upper elevation snow is still a mix of damp round DH, crusts, fine grain damp rounds, large wet rounds, and slush.

Problem #1 - This is the trickiest and easiest to overlook, but the persistent slab problem from the week layer that sits anywhere from 4cm to 20cm below the the Feb 18th dirt layer is still reactive. Pit tests on Cascade and Timp have both confirmed this with Compression tests yielding results ranging from CT23SP, CT25SP, to CT23SC in the past 2-8 days. This week layer is slowly turning into a deep slab problem as it joins the large wet rounding DH sitting on the bottom 20cm-35cm of the snow pack. All of this water percolating down is going to make these full depth releases a greater possibility.

Problem #2 - Wet Slab activity will be increasing as this water pools above MF and rain crusts still intact with in the snow pack. Attached is a picture of a pit at 9900', ESE, 41deg slope on the east side of Timp. HS-90cm with wet saturated snow down to 76cm and water percolating through damp fine grained rounds and ponding just above the crust at 50cm in the snow. (The dirt layer sits at 33cm for reference). Until the water develops some reliable runnels and escapes through the rain/MF crusts these will form nice bed surfaces for these wet avalanches to start, and then step down to the ground once their weight overwhelms the weak damp basil layers.

Problem #3 - Wind slabs (most likely to encounter). We have noted isolated wind slabs at mid elevations to large widespread uniform wind slabs at upper elevations that formed on the 27th-28th of Feb. They are gaining strength, however you can still pry them out.

We noted 4 separate avalanches on the upper elevations of Timp yesterday (April 1). All were on NE faces around 11000'. All 4 avalanches likely occurred on Wed the 28th from strong SW winds transporting snow onto the NE faces. We observed isolated wind slab formations in Primrose Cirque on the 28th that were easily triggered by a skier.

The first was on the Emerald Lake Headwall (Timp Glacier) a HS-NC-R2D3-O. 800' wide by 3'-5' deep. 11200' down to 10600' (600' vertical foot fall).

Second was below the summit shack on the NE face. HS-NC-R1D2 (wind slab). 60' wide by 2' deep. 11200' down to 10400' (800' vertical foot fall. Mostly due to steepness of area)

Third was off the Timp Basin Ridge just north of the summer trail. HS-NC-R2D3-O. 500' wide by 6'-9' deep. 11000' down to 10800' (300' vertical foot fall)

Fourth was the largest. Thanks to the pictures from Turly we were able to determine that the entire slope to the north of the natural ax that he photographed including wrapping into Stairmaster bowl had avalanched. 11200' down to possibly 8500' (2700' vertical foot fall with a substantial debris pile)

The snow pack in the Hidden Lake Basin is around 145cm-270cm deep with the Feb 18th dirt layer at 70cm. Most of the snow depth in the Southern Wasatch has come after Feb 18th which means that we have a still reactive buried weak layer sitting on top of large moist just barely starting to round DH with a lot of very dense damp snow capping all of that. My personal take away point for all of this is that while this deep dense snow is capping the weak layers if you do manage to trigger something on the NE-NW upper elevations of the Southern Wasatch it will be big, deep, and not good. I suspect that these rapid warmups will increase the likely hood of pulling one of these slides out by tipping the stress on the snow pack close to the breaking point. There is still A LOT of the upper north side of the Timp Massif that has not avalanched yet."