Lawinenlagebericht

Lawinenlagebericht

Payette Avalanche Center
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Lawinengefahr

Hochgebirge
4 · Gross
Waldgrenze
4 · Gross
Unterhalb
3 · Erheblich
Veraltet — dieser Lagebericht ist 3 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

1-2 feet of new snow will be accumulating throughout the day with strong SW winds. Triggering an avalanche over 2 feet thick will become very likely today, especially on slopes that have melt-freeze crusts. Avoid traveling on or underneath avalanche terrain today.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    1.5–2.5

    Mountain locations will be looking at 1-2 feet of snowfall by tonight with 4-8" of snowfall last night combined with another 8-12" throughout the day. Southwest winds picked up last night and were gusting into the 30+ MPH range already this morning at ridgetops. Wind gusts are forecasted to reach into the 50 MPH range today at upper elevations and I expect to see 60-70 MPH gusts around West Mountain and Council Mountain. This severe weather will quickly create wind slabs 2+ feet thick in upper elevation terrain above 7000'. Wind slabs will be the thickest and most sensitive on N, NE, and E-facing terrain, especially near ridgelines and below cornices. However, with weather events this intense, you can expect to encounter wind slabs on multiple aspects above 7000'. Be sure to read below for concerns on south-facing slopes. 

     ADDITIONAL DISCUSSION: Throughout the past week, we've observed some instabilities within the upper 1-2 feet of the snowpack. North-facing slopes may be hiding a layer of buried surface hoar or a weak interface of older snow. Our primary concern is south-facing slopes. Solar aspects are harboring a "sandwich" of weak, faceted snow between two different melt-freeze crusts from last week. We've had several reports over the past few days indicating this layer to be a concern. The ability for this weak layer to propagate was mixed, easy in some zones and not as easy in others. The structure of this weak snowpack is widespread throughout the forecast area and is not solely confined to solar aspects. West and east-facing slopes may have this crust-facet combination as well. Once we add an additional load of wind-deposited snow today, these weak layers will become overloaded and will likely create large avalanches.

    (3/31/2023) Photo: GH

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    Below 8000', well over a foot of new snow will be accumulating today. Instabilities are anticipated within this new snow. Triggering soft, storm slabs will become likely in wind-sheltered terrain below 8000' on all aspects. Pay attention to changing conditions throughout the day. If you observe obvious signs of instability such as collapsing or whumpfing, shooting cracks, or evidence of fresh avalanche activity, it is time to dial back your terrain selection and keep it to slopes under 30 degrees. As you travel above 7500', this problem will shift into Problem #1 mentioned above.

Avalanche Discussion

Today's avalanche forecast is sponsored by Mile High Powersports of McCall. Thanks for supporting the Payette Avalanche Center.

The West Central Mountains are currently under a Winter Weather Advisory through Saturday evening. A significant storm will be impacting our region through at least Sunday night. 1-2 feet of snow is forecasted along with strong (50 MPH) winds. Some thunder is also predicted sometime this afternoon. Today is a BIG weather event. Heavy snowfall and strong winds are a rapid change to the current snowpack. Snow does not like rapid changes. Human-triggered avalanches will become very likely today and could be large enough to bury a person or small vehicle. With obvious weather events such as this, the travel advice becomes clear: avoid avalanche terrain, especially slopes that are harboring melt-freeze crusts. Dial back your terrain selection today and avoid being underneath large avalanche paths. 

March came in like a lion and it went out like a....(what eats lions?). You get the point. Since mid-February, our region has consistently been experiencing below-average temperatures with above-average precipitation.  Since February 17th, the forecast area has had 33 out of 42 days with accumulating snowfall. During this time we've had over 10 feet of new snow (11" SWE).

If you are interested to hear more about the state of the snowpack then come join the Friends of the Payette Avalanche Center next Friday, April 7th at Toll Station Pizza for a State of the Snowpack update and a discussion of how this spring is different from years past. April 8th will be the last day of full-time forecasting for the PAC, so this event is a great chance to come to show your appreciation for our forecasters!