Avalanche Advisory
Advisory: Provo Area Mountains Issued by Evelyn Lees for Monday - February 20, 2017 - 7:09am
bottom line

The avalanche danger is rapidly rising to CONSIDERABLE as the wind blows the snow into sensitive drifts. These wind drifts will be easily triggered by a person, and most widespread on upper elevation northwest through north through easterly facing slopes. Cornices are growing and can break back further than expected.

Out of the wind-affected terrain, the avalanche danger is MODERATE for triggering smaller new snow slides or, at the mid and low elevations, wet loose sluffs.




current conditions

After 2 days of unimpressive light snow, the last wave burst onto the scene, with heavier snow and rain.

Storm totals since Friday are 15 to 17” of snow in the Ogden area mountains, 9 to 14” along the Park City ridge line, 14 to 23” in the upper Cottonwoods, and up to 6” at the mid elevations in the Provo area mountains and 3/4 of an inch of water. The rain/snowline was often near 7 - 8000’, and there was significant rain at the lower elevations.

This morning, under partly cloudy skies, temperatures are in the low to upper 30s in the low to mid elevations of the Provo area mountains. The southwesterly winds are quickly ramping up, already 35 mph, gusting to 45 in the Provo area mountains. The highest peaks to the north are gusting in the 50s.

recent activity

No new backcountry reports from the Provo area mountains. There were 10 skier triggered slides reported from the SL and PC backcountry yesterday, all of storm snow. 6 of these slides failed on the old faceted snow surface, with 4 failing within the new snow. Most were on north and northeast facing slopes, above 9400', averaging 8 - 13" deep. One was on a southeast facing slope and debris from a couple slides was observed on the south face of Superior.

A 200' wide slide in Days Draw, at 9400, NE facing slope, failing on near surface facets. Photos: Spencer D


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

Just as we get a re-set on winter, here come the winds to ruin it. Already strong enough this morning to drift snow along the highest ridgelines, they are forecast to increase all day long. Keep a sharp eye on the wind speeds where you are today. The new wind drifts will be rounded, scalloped, dense and cracky. They will be most widespread along the upper elevation ridge lines, on slopes facing the north ½ of the compass. As the winds continue, the drifts will become more widespread, deeper, and also down onto mid elevations slopes.

Cornices are still an issue. A person can trigger both big old cornices and fresh new cornices today. Cornices continue to break back further than you would expect, and could trigger a new snow slide on the slope below

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

Out of the wind-affected terrain, the new storm snow should be rapidly stabilizing on most slopes. The exception is on northwest, north and northeasterly facing slopes, where the layer of faceted snow beneath the storm remains weak. Slides averaging foot deep and 100’ or wider can be triggered, definitely large enough to take a person for a ride. On other aspects, the old hard frozen crusts are acting as good bed surfaces, and a triggered slide can be longer running than expected.

Avalanche Problem 3
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 10 hours
description

We just can’t lose the Wet Loose avalanche problem this winter - you'd think we were in the northwest or something. Overnight, temperatures made only a brief foray below freezing at low to mid elevations and are already climbing this morning. Rapid warming today of the rain soaked snow will produce wet sloppy snow at the mid and lower elevations, and wet loose sluffs will be easily triggered on steep slopes. Avoid terrain traps such as gullies and creek and road banks and avoid steep rollovers on your exits. The sun should be minimal today, but if the clouds are thin where you are, the upper elevation sunny slopes will also become damp and sloppy.

weather

A mild southwest flow will be over the Wasatch today through Tuesday with occasional snow showers.

SNOW: 1 to 2” possible today, and again tonight, with the rain/snow line around 7,500’.

TEMPERATURES: warming today to near 40 at 8000’ and into the upper 20s at 10,000’. Tonight, a poor overnight refreeze under cloudy skies, and even warmer tomorrow.

WIND: southwesterly winds will increase throughout the day, reaching 20 to 25 mph averages, with gusts to 40. Across the highest peaks, averages will reach 35 mph, with gusts to 50 by midday.

It will be even windier and warmer on Tuesday, but a welcome cold front will arrive Tuesday night, bringing periods of cold, dry snow through Thursday

general announcements

Remember your information can save lives. If you see anything we should know about, please help us out by submitting snow and avalanche conditions. You can also call us at 801-524-5304, email by clicking HERE, or include #utavy in your tweet or Instagram.

To get help in an emergency (to request a rescue) in the Wasatch, call 911. Be prepared to give your GPS coordinates or the run name. Dispatchers have a copy of the Wasatch Backcountry Ski map.

Backcountry Emergencies. It outlines your step-by-step method in the event of a winter backcountry incident.

If you trigger an avalanche in the backcountry, but no one is hurt and you do not need assistance, please notify the nearest ski area dispatch to avoid a needless response by rescue teams. Thanks.

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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 exist.