The following warning was issued by the Yellowstone County Emergency and General Services Director.
The stage has been set for a very active three day period of fire behavior in the Northern Rockies area. An approaching cold frontal system will likely bring critical fire conditions to the area and may enable current and new fires to grow significantly. Area response organizations are encouraged to prepare now for how they will respond to a fire or to help other response organizations.
Friday, Saturday, and Sunday may have significant fire behavior activity with warm temperatures, low humidities, and moderate to strong gusty winds — creating critical fire conditions!
All organizations should monitor weather reports for warnings, watches or predicted changes in weather
Rates of Spread
Rates of Spread in light fuels on Friday could approach 3-4 miles/hour. Saturday’s rates of spread could be slightly higher prior to the frontal passage, but after the front if no precipitation occurs, the rate would slow to roughly 3 miles/hour.
Timbered fuel models can often burn as crown fires. Under the forecast conditions, if crown fire develops in timbered stands, rates of spread could be up to 1.5 miles/hour.
Spotting will be common in the next two days, especially in the timbered fuel models. Observed spotting distances have already exceeded ½ mile. With a running crown fire in mountainous terrain, spotting distances in the 2-3 mile range are a definite possibility.
Terrain will have an influence on all fires. Obviously steeper south and west aspects will have faster rates of spread. Deeply incised drainage systems that aren’t oriented to the wind flow will actually provide some shelter from the winds. Areas with more rolling terrain and any drainages or ridge systems that are oriented with the wind direction will see the largest fire growth. The largest fire growth that has historically occurred in the Northern Rockies has happened in these types of areas. Overall spread approaching 10-15 miles or more for a burn period is definitely a possibility given the fuel conditions that are present.
The next two days are obviously critical days. All fires will have the potential for escape, whether it is during initial attack on a new fire or from an existing fire that is under extended attack. Having escape routes and safety zones identified will be extremely important. New fire starts should be approached from a safe direction, not from above or out front. Any suppression actions will need to make sure that a good safe anchor point is established.
Source: Yellowstone County Emergency and General Services Director