Bollettino valanghe

Provo

Pubblicato il Dec 18, 2020valido fino al Dec 19, 2020Utah Avalanche Center

Pericolo valanghe

Alta quota
Limite del bosco
Sotto il limite del bosco

Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

An Avalanche Warning has been issued and the avalanche danger is HIGH on all aspects at the mid and upper elevations. Travel in avalanche terrain is not recommended. Stay off of and out from underneath slopes 30° degrees and steeper at the mid and upper elevations. If you trigger an avalanche, it is likely to break down 18-24" and up to several hundred feet wide.

The avalanche danger is Moderate at the low elevations.

Problemi valanghivi

Persistent Slabs
N
NE
E
SE
S
SW
W
NW
Alta quota
Limite del bosco
Sotto il limite del bosco
Probabilità
Very Likely
Dimensione
3
Weak faceted snow from storms in early and mid November are present on most aspects at the mid and upper elevations. This past week we slowly put about a foot of snow on top of this weak snowpack, with nearly an inch of water. The snowpack began to show signs of its fragility this week with widespread cracking and collapsing and several human-triggered avalanches. Over the past 12-18 hours, we quickly added around another foot of snow (or more), an inch of water, and threw in some strong winds at the mid and upper elevations. On Thursday, the fragile snowpack was predictably very reactive with six human-triggered avalanches reported in the Salt Lake mountains. Most of these avalanches were triggered remotely, and some were quite large, up to 2' deep and a few hundred feet wide.

You are very likely to trigger an avalanche in terrain steeper than 30° that has the persistent weak layer of faceted snow buried underneath the storm snow. These avalanches can be triggered remotely and from below.
Storm Slabs
N
NE
E
SE
S
SW
W
NW
Alta quota
Limite del bosco
Sotto il limite del bosco
Probabilità
Possible
Dimensione
2
Several observations from Thursday indicated sensitive storm snow during periods of higher precipitation intensity (PI), especially later in the day. You may find sensitive storm slabs in areas that received the most snow (a foot or more) or in areas that also had some wind-drifting. Triggering an avalanche that initially fails in storm or wind-driven snow will likely break down more deeply into the weak faceted snow down 2'.

Avalanche Warning

THE AVALANCHE DANGER FOR THE MOUNTAINS OF NORTHERN AND CENTRAL UTAH, INCLUDING THE WASATCH RANGE...THE WESTERN UINTAS AND THE MANTI-SKYLINE PLATEAU IS HIGH. RECENT HEAVY SNOWFALL AND DRIFTING FROM STRONG WINDS HAS CREATED WIDESPREAD AREAS OF UNSTABLE SNOW. HUMAN TRIGGERED AND NATURAL AVALANCHES ARE LIKELY. TRAVEL IN AVALANCHE TERRAIN IS NOT RECOMMENDED. STAY OFF OF AND OUT FROM UNDERNEATH SLOPES STEEPER THAN 30 DEGREES.

Recent Activity

We received no reports from Thursday in the Provo mountains. Just to the north in the Salt Lake mountains, it was very active where were six human-triggered avalanches reported from Thursday. What is noticeable of these slides is many were triggered remotely (from a distance) failing in weak faceted snow that is now buried 18-30" deeply, an indication of the fragility of our weak snowpack structure:

- Two in Days Fork (Days Draw and Chicken S*!t Ridge)

- No Name Bowl Park City Ridgeline (10" deep, 30' wide, 450' vertical)

- Emma Ridgeline

- Catherine's Pass (18" deep, 250' wide, ran 200-300' vertical)

- Dog Lake Chutes in the Brighton backcountry (2' deep, 175' wide, 300' vertical)

The Dog Lake Chutes slide really got the attention of the Salt Lake forecasters due to its size and remote trigger:

In the video below, Mark Staples discusses the avalanche he and UAC colleague forecaster Nikki Champion triggered in Days Fork on a 30° slope.

Snow and Weather

Currently, temperatures range through the teens F and winds are from the west/northwest. At mid elevations winds are averaging around 10 mph, with gusts in the teens and low 20's mph. However, winds remain fairly strong at the upper elevations, averaging in the 20's mph with gusts in the 30s mph at 11,000'.

Storm totals in the Provo mountains since Thursday morning are 8", although higher amounts are likely at upper elevations. Water totals are 0.5" to nearly an inch in areas that received the most snow.

For today, expect mostly-cloudy skies with occasional snow flurries, although additional totals should be at most 1-2". Temperatures will reach the upper teens F. Winds will be northerly, averaging in the teens with gusts in the 20's mph at mid elevations, and averages in the 20's with gusts in the 30's mph at 11,000'.

Although Salt Lake-centric, our first Week in Review - where we summarize snow and avalanche conditions for the past week - has been published.

Additional Info

Writing an avalanche forecast is a team process. On Thursday evening, Salt Lake forecasters Trent Meisenheimer, Mark Staples, and Greg Gagne discussed current conditions and thoughts for putting out Friday's forecast. We like to share these with the public so you have a bit better of an idea of how we communicate and the shared thinking that goes into each forecast.

General Announcements

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This information does not apply to developed ski areas or highways where avalanche control is normally done. This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.

Observations and Avalanches

Backcountry Emergency Procedures