The National Weather Service in Pocatello has issued a Red Flag Warning for scattered thunderstorms combined with gusty winds and low relative humidity, which is in effect from noon to 10 PM MDT Thursday. * AFFECTED AREA. Fire Weather Zone 413 Caribou Range/Caribou NF and Fire Weather Zone 427 Goose Creek and Raft River Valley/Southern Sawtooth NF/Twin Falls BLM south of the Snake River. * THUNDERSTORMS. 30 to 50 percent coverage. * OUTFLOW WINDS. A dry low level environment will promote stronger storms capable of producing wind gusts up to 60 mph. * WINDS. West 10 to 15 mph with gusts up to 25 mph. * RELATIVE HUMIDITY. As low as 14 percent. * IMPACTS. Critical fire weather conditions are expected Thursday afternoon and evening. Lightning may generate new fire starts. Any new fire starts or existing fires may spread rapidly.