Fire and Smoke Update:

Much of the Western U.S. and Western Canada have seen improving smoke conditions this week as cooler and wetter conditions have helped to reduce fire behavior.

However, the Smith River Complex Fire in NW California and the Tyree Ridge Complex Fire in SW Oregon have been contributing to smoky conditions and poor air quality across western portions of Oregon and California.

These fires are expected to see cooler temperatures, higher relative humidity, and some rain over the next few days, though heavier rainfall is expected further east. We will see how the fires react to the pattern change, but there is some hope that fire behavior will decrease and that smoke conditions could improve over time.

On Friday, the heaviest smoke is expected in coastal areas of NW California and SW Oregon.

On Saturday, improving smoke conditions are expected in California with southerly winds focusing heavier smoke into coastal regions of Oregon.

More smoke maps:

• Smoke (Surface) Map → Regular | U.S. Lower 48 States & Canada
• Smoke (Surface) Map → High Resolution | U.S. Lower 48 States

Weather Pattern – Big Picture:

A deep trough of low pressure will set up along the West Coast on Friday and Saturday before tracking across the Interior West on Sunday and Monday.

Pacific moisture associated with this trough will impact the West Coast states – especially California and Oregon – while southwest winds ahead of the trough will transport monsoonal moisture into the Southwest, Great Basin, and Northern Rockies.

A cooler airmass will also take hold across the West through the weekend, resulting in damp and chilly conditions for many areas. Also, the highest peaks of the Sierra, Cascades, and Northern Rockies will be dusted with snow.

Forecast for Friday:

Widespread showers can be expected across Southern Oregon and Northern California with areas of heavy rain expected, including the Tahoe area. Thunderstorms are also possible in Southern Oregon and Far Northern California, while the threat of lightning will be much lower around Tahoe.

Monsoonal moisture will also be increasing across the Southwest with widespread showers and thunderstorms expected across Arizona, Southwest Utah, Nevada, and Southeast California. Heavy rain can be expected in these areas along with the potential for flash flooding in slot canyons and dry washes.

Strong to severe thunderstorms are also possible across Arizona, Utah, and Eastern Nevada with strong wind gusts, frequent lightning, and moderate to large hail possible.

Thunderstorm activity will be more isolated in nature further north and east across Colorado, Wyoming, and Idaho. 

Forecast for Saturday:

The trough will weaken somewhat on Saturday and temporarily shift westward, but widespread showers and thunderstorms can still be expected across a large portion of the West, favoring the Sierra, Southern Cascades, Southwest, Great Basin, and Idaho.

Locally heavy rain will be possible throughout these regions, with the highest threat of flash flooding expected in Arizona, Southern Nevada, and Southwest Utah.

Colorado will be on the eastern fringe of this pattern with only isolated thunderstorms expected favoring the higher peaks.

Forecast for Sunday:

The trough will start to move inland on Sunday with widespread showers and thunderstorms favoring the Sierra, Great Basin, Northern Utah, Idaho, Western Wyoming, and Montana. Locally heavy rain will be possible across this region, especially in Eastern Idaho and Western Wyoming.

Scattered thunderstorms can be expected in Colorado but this area will still see drier conditions compared to areas to the west and north. Also, Arizona will see more isolated storms compared to prior days.

Another trough will reach the PNW Coast, resulting in showers across BC, Washington, and Oregon while Interior BC and Alberta will see showers and thunderstorms.

Forecast for Monday:

Widespread showers and heavy rain can be expected across Wyoming, Southern Montana, Eastern/Central Idaho, and Northern Utah with more scattered activity across Northern Idaho and NW Montana. Areas west of the Divide should see a reduction in lightning with the best chance of lightning existing east of the Divide.

Isolated thunderstorms will be possible across Northern Colorado with drier conditions across Southern Colorado. A drying trend is also expected across the Southwest and California while isolated light showers will be possible across the Cascades.

Forecast for Tuesday:

Conditions will finally start to dry out across most of the West, though some lingering showers will remain possible across the Northern Rockies – especially east of the Divide.

Another system will reach the west coast of Canada with showers developing across BC. Northern Washington may get clipped with this system, but it will be a close call.

Outlook for Wednesday (Sep 6) to Sunday (Sep 10):

Most of the West is expected to dry out during this period with pleasant early fall conditions. The only exception will be the Pacific Northwest where showers can be expected from time to time.

Temperatures are expected to be near average across the West Coast states, while the Rockies and the Intermountain West will be warmer than average.

Thanks so much for reading! Next update on Wednesday (September 6).

Alan Smith