Avalanche Advisory
Advisory: Provo Area Mountains Issued by Mark Staples for Tuesday - February 20, 2018 - 7:36am
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Today the avalanche danger is CONSIDERABLE on upper elevation slopes for wind slabs and persistent slab avalanches. The danger is MODERATE at mid elevations and LOW at low elevations. Watch for any fresh wind loading which will make avalanches more likely, and go to southerly facing slopes to avoid the persistent slab avalanche problem.
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current conditions

Winter continues and it's great to see. Overnight another 1/2 inch of snow fell. Storm totals are 9-13 inches of snow (0.7-0.9 inches of snow water equivalent). Yesterday this snow was reported to be slightly upside down, meaning that it was slightly denser on top and lighter underneath. The storm snow has settled a bit since yesterday and should be fairly consistent today with a few inches of fluff on top.

Temperatures are generally in the single digits F but below zero at upper elevations. Winds at ridgetops are averging 10 mph and gusting 15-20 mph. They blew from the NW yesterday and are westerly this morning. There has been some wind transport and wind drifting of the new snow which is easy because the snow is so light; however, this wind transport has mostly been confined to ridgetops and hasn't been too significant.
recent activity

No avalanches have been reported in the Provo area mountains. However, there were two slides observed in the SLC area mountains which could be indicative of what you may find at upper elevations in the Provo area.

One occurred in Alexander Basin (above Mill Creek Canyon) north of Gobblers Knob. This slide happened on a NE aspect at 9400 feet and it broke near an ice crust just below snow that fell last Thursday. It was skier triggered but no one was caught and it broke 200 feet wide. Read more about it here and see the photo below (Gustafson photo)

Another occurred on a westerly aspect in Davis Gulch on Gobblers Knob. It broke 3 feet deep and 80 feet wide. A skier triggered sluff triggered a soft storm slab which then triggered this avalanche. (Grainger, Young, Olafsen photo).
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

Winds are the main weather factor to watch out for today because the new snow can easily be transported. Even though winds are not too strong, they are transporting some snow at ridgetops and upper elevations with westerly winds at 11,000 feet averaging 25 mph this morning from the W. The slightest wind loading will make avalanches in the new snow more likely. The photo below shows a prime location for wind slabs just under cornices (Grainger, Young, Olafsen photo)

Don't let your guard down on non-wind loaded slopes. The potential for storm slabs and dry loose avalanches is much less compared to yesterday, but they remain a possibility.
Avalanche Problem 2
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 24 hours
description

Buried layers of weak facets mostly exist at the upper elevations on northerly aspects and have been stressed by the weight of snow from yesterday's storm. The best way to avoid this problem is ride southerly facing slopes or mid and low elevation slopes. Many low elevation slopes only have snow from the last two storms and don't have this problem at all.

Watch out for any wind loading. Wind slabs are an avalanche problem by themselves, but they also add weight and stress to the snowpack which will make deeper persistent slab avalanches more likely.
weather

A band of lake effect snowfall moved over the area this morning. The lake effect snowfall will end but there should be some snowflakes in the air today. Skies will be mostly cloudy this morning and slowly breaking up this afternoon when some sunshine may appear. Overall conditions will remain cold, with mountain temperatures struggling to reach 10 degrees F. Winds at ridgetops will remain westerly and blow 5-15 mph with gusts of 25 mph. Winds at the highest peaks feet will blow 10-20 mph.
general announcements

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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.