What is an Avalanche Watch? What is an Avalanche Warning?
NOAA’s National Weather Service partners with the US Forest Service Avalanche Centers to issue avalanche watches and avalanche warnings. These terms can be slightly confusing, but these watches and warnings exist in order help spread the word about the lurking avalanche hazard. The goal is to save lives of anyone who may head in to the backcountry.
Watch Know Before You Go Avalanche Safety Video
The NWS is the primary source of weather data that avalanche forecasters need to do their job. It is their source for precipitation, new snow totals, temperature, wind, snow water equivalent, cloud cover and solar radiation data. Combine this weather data with snowpack observations and terrain, and avalanche forecasters are able to produce their daily avalanche forecasts and avalanche danger ratings.
When snow conditions are particularly hazardous, these forecasts help to formulate Avalanche Watches, Avalanche Warnings, and Special Avalanche Bulletins that are designed to alert the public of the danger. But what do avalanche watches and avalanche warnings really mean?
The National Avalanche Center’s Avalanche Warning Criteria Document set guidelines in 2012 on when to issue avalanche warnings and avalanche watches. According to Weather.gov:
Avalanche Watch (AVA) – “A message issued by authorized officials when conditions are forecast to become favorable for natural or human triggered avalanches that could affect roadways, structures, or backcountry activities.”
An avalanche watch is the first warning to alert the public that dangerous avalanche conditions are expected to develop in the next 24-48 hours. It’s generally issued with the forecast confidence is relatively low like when a large snow storm or powerful wind event is forecast.
Avalanche Warning (AVW) – “A warning of current or imminent avalanche activity when avalanche danger is considered high or extreme. Authorized officials may recommend or order protective actions according to state law or local ordinance when natural or human triggered avalanches are likely to affect roadways, structures, or backcountry activities. ”
Avalanche warnings are issued immediately before an event or in advance if things line up like expected in the avalanche watch time frame. Warnings are issued with high confidence. They are issued with a start and stop time and can be issued for 24 hour periods. Avalanche warnings can be updated, reissued, or expire after their 24 hour window. They can continue for as long as necessary
Avalanche warnings are always issued when the avalanche danger rating is Extreme – the highest danger rating. They are also issued when widespread portions of the forecast zone is rated High. Usually this applies to all elevation bands (below treeline, near treeline, above treelike).
Here’s a sample Avalanche Warning copied from the NWS:
Avalanche Warning
MTZ015-055-231215- URGENT – IMMEDIATE BROADCAST REQUESTED AVALANCHE WARNING GALLATIN NATIONAL FOREST AVALANCHE CENTER RELAYED BY NATIONAL WEATHER SERVICE GREAT FALLS MT 511 AM MST TUE DEC 22 2015
THE FOLLOWING MESSAGE IS TRANSMITTED AT THE REQUEST OF THE GALLATIN NATIONAL FOREST AVALANCHE CENTER. ISSUED ON DECEMBER 22 2015 AT 04:58 AM
THE GALLATIN NATIONAL FOREST AVALANCHE CENTER IS CONTINUING A BACKCOUNTRY AVALANCHE WARNING FOR THE MOUNTAINS AROUND COOKE CITY, THE LIONHEAD AREA NEAR WEST YELLOWSTONE AND THE SOUTHERN GALLATIN AND MADISON RANGES. THE AVALANCHE DANGER IS RATED HIGH ON ALL SLOPES. ANOTHER FOOT OF SNOW WITH STRONG WINDS FELL IN THESE MOUNTAINS LAST NIGHT. NATURAL AND HUMAN TRIGGERED SLIDES ARE LIKELY TODAY. AVALANCHE TERRAIN AND AVALANCHE RUNOUT ZONES SHOULD BE AVOIDED.
YOU ARE URGED TO CONTACT THE GALLATIN NATIONAL FOREST AVALANCHE CENTER FOR MORE DETAILED INFORMATION. WEBSITE: WWW.MTAVALANCHE.COM AVALANCHE HOTLINE: 406-587-6981 THIS WARNING WILL EITHER EXPIRE OR BE UPDATED BY 6:00 A.M. ON DECEMBER 23, 2015. $$
Special Avalanche Bulletins (SAB) are issued when the guidelines/requirements for watches and warnings are not met. They are typical when unusual or dangerous avalanche conditions exist – possibly out of season or under unique circumstances. They may also be issued when a large increase of public backcountry use is expected and dangerous conditions still exist.
All three of these avalanche alerts are important. The big difference is that Avalanche warnings are happening right now, while Avalanche watches are most likely going to occur soon. Not only do these alerts signal to seasoned backcountry travelers to steer clear of avalanche terrain, but they also help to alert the general public, who might not be too backcountry savvy, of the avalanche danger.
If you see an avalanche warning, avalanche watch, or a special avalanche bulletin, use your judgement and experience to guide your backcountry decision making. Be safe and be aware of the danger that exists in the snow pack.
Every avalanche center will note any current alerts in the daily avalanche forecast, but they alets will also send out Warnings and Watches to the media and even on Google so they are seen by the masses. Done correctly these avalanche alerts will and can save lives.
If I missed something, let me know in the comments below.
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Read more about Avalanche Watches, Avalanche Warnings, and Special Avalanche Bulletins from these sources:
- UtahAvalancheCenter.org
- NOAA.gov
- AlaskaSnow.org
