A potent wind event is moving through the northern Rockies and High Plains, with advisories and watches stretching from the Snake River Plain of Idaho north through eastern Montana to the Helena Valley — where a High Wind Watch warns of gusts potentially reaching 60 mph in two separate waves on Wednesday.
Dangerous Conditions on Montana’s Largest Lake
The first alert affecting recreationalists is a Lake Wind Advisory from the National Weather Service in Glasgow, Montana covering Fort Peck Lake from 2 PM Tuesday through 6 PM Wednesday.
West winds of 15 to 25 mph with gusts up to 40 mph will build rough waves across Montana’s largest reservoir, creating hazardous conditions for small watercraft across its 134-mile length.
According to Visit Montana via KMMSAM, “More than 50 different kinds of fish swim in Fort Peck Reservoir, Montana’s largest body of water.” That fishing reputation draws boaters from across the region, but Tuesday and Wednesday are days to stay on shore.
The reservoir was created from 1933 to 1937 during the Depression by damming the Missouri River with a 3.8-mile embankment — one of the largest earthen dams in the world — and its 1,500 miles of shoreline host 27 designated recreation sites.
Wind Advisory Across the Idaho Falls Corridor
To the southwest, the National Weather Service in Pocatello has a Wind Advisory in effect from 10 AM to 9 PM MDT Tuesday for the Arco/Mud Lake Desert and Upper Snake River Plain — including Idaho Falls, Rexburg, St. Anthony and Craters of the Moon National Monument.
Southwest winds of 25 to 35 mph with gusts up to 45 mph are expected, strong enough to make driving difficult for high-profile vehicles and blow unsecured objects across campgrounds and parking areas.
Visitors to Craters of the Moon should be especially aware — the exposed lava fields offer no windbreak, and unsecured gear can be sent flying in 45 mph gusts.
High Wind Watch for Helena and Central Montana
The most severe alert in the batch is a High Wind Watch for a broad swath of central Montana, in effect from Wednesday morning through late Wednesday night. The watch covers the Helena Valley, upper Blackfoot and MacDonald Pass, Gates of the Mountains, the Little Belt and Highwood Mountains, Judith Basin and the Big Belt, Bridger and Castle Mountain ranges.
West winds of 30 to 40 mph with gusts up to 60 mph are possible — in two separate rounds. The first arrives Wednesday morning and lasts through early afternoon. A brief lull follows in the mid-afternoon before the wind picks up again Wednesday evening and continues into early Thursday morning.
Helena, Lewistown, White Sulphur Springs and Lincoln are all within the watch zone. High-profile vehicles including RVs, trailers and large trucks should use extreme caution crossing MacDonald Pass and the other mountain passes on Wednesday. Power outages, downed trees and property damage are possible during peak gusts.
Monitor the latest updates at weather.gov/ggw, weather.gov/pih and weather.gov/tfx.
