The National Weather Service office in Pocatello issued a Red Flag Warning for southeastern Idaho on Thursday afternoon, citing dangerous fire weather conditions expected to persist through evening hours.
The warning took effect at 2:01 p.m. MDT and remains in place until 8:00 p.m. MDT. It applies specifically to Fire Weather Zone 427, which encompasses the Goose Creek area, the Raft River Valley within the Southern Sawtooth National Forest, and Bureau of Land Management lands south of the Snake River near Twin Falls.
Forecasters identified a combination of gusty winds and critically low humidity as the primary drivers for the alert. Southwest winds are expected to sustain speeds between 10 and 20 mph, with gusts reaching up to 35 mph. Relative humidity levels have dropped to approximately 12 percent in affected areas.
These figures exceed the critical fire weather thresholds established by the National Weather Service and local fire management agencies for southeastern Idaho. The criteria for a Red Flag Warning in this region include relative humidity at or below 15 percent, sustained wind gusts of at least 25 mph in mountainous terrain, and gusts of at least 30 mph across the Snake Plain.
The warning also accounts for potential thunderstorm activity. A coverage criterion of 25 percent is used to assess lightning risk, which can serve as a natural ignition source during dry conditions. No specific rainfall amounts are required to trigger this aspect of the alert.
Fire officials typically issue these warnings when atmospheric conditions create an environment where fires can start easily and spread rapidly. The combination of dry air and strong winds reduces the time available for emergency responders to contain potential blazes.
Residents in the warned zones are advised to exercise extreme caution with any outdoor activities that could produce sparks or flames. This includes grilling, welding, and equipment operation near dry vegetation. The warning expires at 8:00 p.m., after which conditions are expected to improve as humidity rises and winds decrease.