Avalanche Advisory
Advisory: Provo Area Mountains Issued by Greg Gagne for Friday - April 6, 2018 - 6:29am
bottom line

With a deep slab avalanche problem lurking on upper elevation, northerly and easterly facing slopes, the avalanche danger in these locations is MODERATE. Avalanches that occurred last week show that this deep slab problem remains an issue in the Provo area mountains. These slides can break 2-5 feet deep and up to hundreds of feet wide. All other slopes have a LOW danger.

With heavy rain forecasted for Saturday, the Provo mountains may go through yet another significant avalanche cycle.
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current conditions

Temperatures this morning in the Provo mountains range throughout the 30's and low 40's F and winds are out of the southwest, gusting into the 20's mph at mid and upper elevations.

recent activity

No avalanche activity was reported Thursday.

There was an impressive avalanche cycle that occurred last week on Timpanogos. The snowpack in the Provo area mountains is very different and more dangerous that in the mountains just a little further north. Read the full observation HERE. Below is a list of some of these slides and a photo (J. Woodruff) of the debris pile from one of them.

  • Emerald Lake Headwall (Timp Glacier) 800' wide by 3'-5' deep. 11200' down to 10600' (600' vertical foot fall).
  • Below the summit shack on the NE face. (wind slab). 60' wide by 2' deep. 11200' down to 10400' (800' vertical foot fall.)
  • Timp Basin Ridge just north of the summer trail. 500' wide by 6'-9' deep. 11000' down to 10800' (300' vertical foot fall)
  • The largest slide and thanks to the pictures from Turley (Found HERE) we were able to determine that the entire slope to the north of the natural that he photographed including wrapping into Stairmaster bowl had avalanched. 11200' down to possibly 8500' (2700' vertical foot fall with a substantial debris pile)
Avalanche Problem 1
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 24 hours
description

The snowpack in the Provo area mountains is generally more dangerous than other areas further north. This area received less snowfall in the early months of winter, making it more shallow and weaker. Unfortunately many of those weak, faceted layers of snow remain at the upper elevation, northerly facing slopes. All it took to cause last week's avalanche cycle was strong winds. There are two layers of concern in the snowpack:

  1. One layer is faceted snow buried just underneath the February 18th dust layer. It's easy to find - dig down 2.5' in the snowpack and identify a dirty stripe of snow, just below that is a layer of weak faceted snow.
  2. The other layer is just above the ground - we call it depth hoar, which is a fancy name for larger grained faceted snow. In either case the avalanche you trigger would likely be unsurvivable.

It's best to avoid any and all steep northerly facing terrain. If going to ride some of the terrain in the Provo area mountains, it will be best to ski slopes that face a little more southerly.

With heavy rain forecasted for Saturday, the Provo mountains may go through yet another significant avalanche cycle.
weather

A weak disturbance will bring light rain and snow showers to our region today, with 1-2" of damp snow possible at the higher elevations. Mountain temperatures will range from the upper 30's and into the low 40's F. Skies will be cloudy and winds will be generally light to moderate, gusting in the teens at mid elevations, and 20's mph at upper elevations.

More interesting weather for Saturday as we are under at atmospheric river event (the dashed line in the image below). Up to 1.5" of water is possible with this system, with the period of heaviest precipitation falling later Saturday afternoon and evening. Unfortunately most of that will fall as rain, with a rain/snow line approaching 10,000'. By the time colder air arrives later Saturday night, the atmosphere begins to dry out. This will limit snowfall numbers. By Sunday morning we may measure 1-2" of snow at 9000', with slightly higher amounts above that elevation.

We can wring some hopeful news out of the longterm forecast with a possible cold system coming out of the northwest later next week.
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This information does not apply to developed ski areas or highways where avalanche control is normally done. This advisory is from the U.S.D.A. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur.