Forecast for Monday Afternoon/Evening:

An active start to the week is underway with a trough of low pressure located over Utah. Counterclockwise (cyclonic) winds are transporting significant moisture around the low pressure center, favoring widespread thunderstorms and locally heavy rain across the Colorado Front Range, portions of the Northern Rockies, and westward into the Wasatch, Great Basin, and Sierra Nevada Range. 

As of early Monday afternoon, strong to severe thunderstorms have been ongoing across the Colorado Front Range. A significant hailstorm has impacted Boulder, with a couple of inches of hail covering the ground across the city, while street flooding is also occurring. 

Locally heavy rain and flash flooding will be a possibility under stronger storms across a large portion of the West on Monday. But as is usual at this time of year, rainfall will also be hit or miss in nature with some areas seeing little to no rain. 

A few thunderstorms are also possible across the Cascades and Western Canada, but these will be more of the "dry thunderstorm" variety with minimal rainfall. 

While much of the West is in a wet pattern right now, an uptick in wildfire activity has occurred across Western Alberta in recent days, resulting in smoky conditions across the Canadian Rockies. Some of this smoke has also worked its way into Northern Montana, and may occasionally sneak into portions of the Northern U.S. this week. 

Smoke (Surface) Map – Forecast smoke map near ground level out to 48 hours

Air Quality Forecast Map – Lower resolution forecast smoke/air quality map globally out to 5 days

Forecast for Tuesday:

A similar pattern will remain in place on Tuesday with thunderstorms favoring the Sierra, Great Basin, Wasatch, Northern Rockies, and Colorado. Stronger storms will be capable of producing heavy rain.

Meanwhile, a trough of low pressure will be moving into Western Canada from the northwest, resulting in much-needed rainfall across Interior BC and Alberta.

Forecast for Wednesday:

The trough will move across the Northern Rockies with significant rainfall expected across Southeast BC and Western Alberta. Great news as this area really needs the rain, and hopefully, it will help to at least temporarily reduce fire behavior as well.

North/northwest winds may transport some smoke into parts of the Northern U.S. on Wednesday, but confidence is low. 

Further south, a secondary trough of low pressure will contribute to another active day of thunderstorms across the Sierra, Central Nevada, Utah, and Colorado. The Wasatch in Utah looks like one of the more favored regions with locally heavy rain possible.

Forecast for Thursday to Friday:

The focus of thunderstorm activity and heavy rain potential will be concentrated across Central/Southern Wyoming and Colorado during this period, while the Sierra, Wasatch, and Southern Utah will also be active. 

Storms will be more isolated further north across Idaho/Montana while another trough of low pressure will be deepening across the Gulf of Alaska with rain developing across Western and Northern BC on Friday. 

Outlook for Saturday (June 17) to Thursday (June 22):

A deepening trough over the Gulf of Alaska will work its way into the Western U.S. during the weekend of the 17th-18th and into the week of the 19th, and this will act as the main weather driver during this period. The result will be an uptick in showers and thunderstorms across the Northwest and Northern/Central Rockies, and possibly into Northern California and the Sierra as well.

Temperatures are also expected to be cooler than average west of the Continental Divide throughout the Western U.S., while a warm-up is expected east of the Divide.

Thanks so much for reading! Next update on Wednesday (June 14).

Alan Smith

An El Niño is officially underway. Learn more → El Niño Onset & The Western U.S. Summer Outlook