Winter in June? Heavy snow expected to hit Rockies before July Fourth

A rare late-June winter storm is expected to bring heavy snow, strong winds, and sharply colder temperatures to parts of the northern Rocky Mountains on June 28, with forecasters warning of hazardous travel conditions in higher elevation areas.

The National Weather Service has issued winter storm and weather alerts across portions of Idaho, Montana, and Wyoming — particularly in higher elevations along their shared borders — as a potent weather system settles over the region. The weather service has advised the public to prepare for "winter-like conditions" in the backcountry and higher elevations.

The storm is being driven by a deep upper-level trough plunging into the Rockies and Intermountain West, dragging in an unseasonably cold air mass that is dropping temperatures 15 to 20 degrees below normal in some areas, the USA TODAY Network previously reported.

Forecasters said the system could produce unusually heavy snowfall for late June. The weather service said mountain areas in southwestern Montana and central Idaho could receive significant snowfall, especially above about 6,500 feet.

Cold temperatures, gusty winds, and dense, wet snow are expected to combine to create dangerous conditions, including the risk of hypothermia and blocked roadways due to downed trees, forecasters warned.

The winter storm and weather conditions are expected to linger through June 29, with weather alerts in effect through the morning or midday, depending on location. The winter conditions may affect travel during the busy period leading up to the Fourth of July holiday.

Heavy snow totals possible in parts of northern Rockies

The weather service said the Georgetown Lake region and other backcountry and higher elevation areas in Montana could receive 4 to 8 inches of snow, with up to about 12 inches possible in the highest elevations. Forecasters noted that snow levels may "briefly lower and could produce minor slushy accumulation" at Homestake and MacDonald passes.

"Persons should consider delaying travel across the backcountry and higher elevations," the weather service advised. "If travel is absolutely necessary, consider taking a winter storm kit along with you, including such items as tire chains, booster cables, flashlight, shovel, blankets and extra clothing. Also take water, a first aid kit, and anything else that would help you survive in case you become stranded."

In northwest Beaverhead County, Montana, the weather service said heavy, wet snow was forecast for the area. Forecasters said more snow accumulations up to 3 inches were expected near pass level, with "additional amounts in excess of 6 inches above pass level."

Elsewhere, Idaho’s Fourth of July peak could see up to 6 inches of snow over the next few days, according to the weather service. In Wyoming, snowfall is expected to be limited mainly to higher elevations, with most mountain areas forecast to pick up around 4 to 6 inches in the same timeframe.

Strong winds, showers forecast for some areas

The system also brought showers and scattered thunderstorms as it moved through the region, with embedded bursts of heavier rain capable of briefly reducing visibility and producing gusty, erratic winds.

Earlier on June 28, the weather service in Great Falls, Montana, said strong winds were forecast for portions of north-central Montana. "Wind speeds are likely to peak early this evening with a few gusts in excess of 50 mph causing difficult cross-winds," according to the agency.

The weather service also warned there was a "slight risk of excessive rainfall amounts" leading to flash flooding in Glacier National Park through the night of June 28, adding that the heaviest rainfall rates were expected in the evening.

Contributing: Doyle Rice and Brandi D. Addison, USA TODAY Network