The National Weather Service office in Great Falls issued a Special Weather Statement early Saturday morning after patchy dense fog developed around Helena, Lincoln, Craig, and Augusta, with visibility dropping below a half mile in some locations. A formal Dense Fog Advisory followed at 4:34 a.m., extending through 11 a.m. MDT.
At its worst, the advisory warned of visibility below a quarter mile at times — conditions where highway driving becomes genuinely hazardous, particularly on routes like U.S. 287 north toward Craig and Lincoln, and Interstate 15. The NWS advised drivers to slow down, use headlights, and leave extra following distance. Fog in the Helena Valley can be deceptive in the early morning hours, lifting quickly in some spots while persisting in low-lying areas along the Missouri River drainage.
The advisory covered portions of central, north central, and southwest Montana, a broad swath that includes the Helena commuter corridor. Conditions were expected to improve as temperatures rose through the late morning. Residents who were on the road during the advisory window were urged to stay alert for rapidly changing visibility, particularly at highway speeds.