Avalanche Advisory
Advisory: Ogden Area Mountains Issued by Greg Gagne for Friday - January 19, 2018 - 6:49am
bottom line

The avalanche danger is MODERATE on all mid and upper elevation slopes facing the north half of the compass west through east for triggering a persistent slab avalanche. Fresh wind drifts are also possible at the mid and upper elevations.

Although many low elevation and southerly facing slopes have largely melted out, where snow remains the hazard is LOW.

With a storm forecasted beginning later today, the avalanche hazard is expected to rise. Be sure to check Saturday's advisory before heading out.
current conditions

Warm and windy. Temperatures in the Ogden mountains range throughout the 30's F. Winds are the highlight - blowing out of the south/southwest, averaging in the teens and 20's mph. At the mid elevations, gusts are in the 20's and 30's mph, and gusting in the 50's mph at the upper elevations, with Mount Ogden leading the way (as usual) with gusts in the 60's mph.
recent activity

No avalanches were reported from Thursday, and the last reported backcountry avalanche was this past Tuesday (which occurred in the Salt Lake area mountains). However, during this last avalanche cycle, 8 people were caught in avalanches, with several close calls. Click HERE for a list of all reported avalanches in Utah.

Doug Wewer submitted excellent photos of avalanche activity in Cutler Basin that occurred during last week's avalanche cycle. Click on the link to view all of the photos.
Avalanche Problem 1
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 12 hours
description

Weak, faceted snow plagues our snowpack on aspects facing west through east at the mid and upper elevations. The storm snow from Wednesday January 10 overloaded these weaknesses, leading to an avalanche cycle with avalanches reported through Tuesday January 16. Although the snowpack has shown signs of adjusting to last week's load, we have a storm on our doorstep, including strong pre-frontal winds.

Persistent weaknesses follow the pattern of increasing avalanche hazard with any new load such as storm and/or wind-driven snow. Over time, the snowpack slowly adjusts, making avalanches harder (but still very much possible!) to trigger. With a new load, the hazard increases once again.

With a storm forecasted beginning later today, I've highlighted with a red arrow where I am estimating the current avalanche hazard is with respect to our persistent weaknesses [image courtesy of Jay Gagne]:
Avalanche Problem 2
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 12 hours
description

Although most solar aspects will be crusted and therefore should not provide much snow available for transport, there is plenty of soft snow on the shady aspects. Today's moderate to strong winds out of the south/southwest may find some of that snow and create fresh drifts at the mid and upper elevations. Although these drifts will likely be on leeward aspects, terrain may channel the wind creating drifts on a variety of aspects. Although I am not expecting these drifts to be large, they may be sensitive as they sitting on top of weaker snow.

The good news about these winds (and warm temperatures) is they should help destroy faceted snow and surface hoar on our current snow surface that observers have been finding in the Ogden mountains.
weather

A desperately-needed storm is on its way! Mountain temperatures will rise into the 30's and low 40's F this morning, and drop this afternoon ahead of a cold front that should arrive in the Ogden mountains by late afternoon. Increasing clouds with snow showers possible this afternoon. It will be blustery, with winds out of the south/southwest, averaging in the 20's and 30's mph, with gusts from 45-65 mph.

OK, what we all really care about: Snowfall will pick up overnight, with 4-8" possible in the Ogden mountains by Saturday morning. Winds will rapidly diminish overnight, so the snow should fall straight out of the sky. A period of northwest flow later on Saturday should lead to additional snow with decreasing densities (aka right-side up storm). By the time it clears out later on Sunday, the Ogden area mountains are likely to pick up 6-10", with the higher amounts in areas favored by a northwest flow.
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.