A cooler fall pattern has helped to significantly reduce fire and smoke activity across the West since late last week, confining smoke impacts to localized areas closed to active wildfires. Many of us can finally breathe fresh air again!

Fall colors are also off to an early start for some areas, which combined with cooler temperatures and cleaner air has led to ideal conditions recently.

The smoke forecast map for Monday afternoon shows this pattern well – fires are burning at a lower intensity compared to the hot and unstable summer days, and smoke transport downstream of the fires has been significantly reduced. 

During the fall months, fire season tends to be worse in California where dry and windy conditions are common (this is the season for "Santa Ana" offshore wind events), so let's hope this fall ends up not being as bad compared to recent years. 

Forecast Smoke (surface)

Forecast Smoke (sky)

Current Air Quality

As of Monday, a weak disturbance over the Rockies is departing from the East, but we will see some minor weather impacts from this disturbance early in the week.

A maximum in the jet stream known as a "jet streak" is located over Northeast Utah, Southern Wyoming, and Northern Colorado, and this feature will help to trigger some widely scattered showers and thunderstorms through Monday afternoon.

Check out the forecast radar for Monday afternoon to get a general idea of how this pattern will evolve. The Uinta Range in Utah and the Flat Tops, Gore Range, Park Range, and Front Range in Colorado have the best chance of seeing storms.

Current Radar

Lightning Density

Forecast Radar

After a relatively quiet middle of the week period, a large trough of low pressure will take hold across the Pacific Northwest late in the week with cooler temperatures and significant precipitation expected starting on Friday. 

Generally speaking, temperatures will be cooler than average across the Northwest during the next 5 days and warmer than average for the rest of the West. Winds will be strong across the Northern and Central Rockies most days this week, so keep this in mind if you have climbing/peak-bagging plans.

Forecast for Monday, September 13th

Northeast Utah, Northern Colorado, Southern Wyoming, and the eastern ranges of Wyoming and Montana will see the best chance of showers and thunderstorms on Monday afternoon.

Forecast for Tuesday, September 14th

Lingering moisture and instability will result in another round of afternoon showers and thunderstorms across Colorado, Northern New Mexico, and Eastern Wyoming, favoring areas along and east of the Continental Divide. 

In addition, a weak storm system will impact the Pacific Northwest with showers developing across the Olympics and Cascades in Washington, extending as far south as the Mt. Hood area in Oregon. Northern Idaho and NW Montana will also see some showers arrive on Tuesday night.

Forecast for Wednesday, September 15th

Lingering showers will taper off over the Cascades early in the day. Only a little bit of moisture will make it further inland with only light/spotty showers expected across Northern Idaho and Western Montana. A drying trend will also ensue for Colorado with perhaps a stray afternoon storm for Southwest Colorado and New Mexico.

Forecast for Thursday, September 16th

A dry pattern is expected for most areas including the Northwest during the daytime hours. However, an approaching storm system will result in rain developing over the Olympic Peninsula on Thursday night.

Forecast for Friday, September 17th

A strong storm system will arrive in the Northwest with heavy rain expected across Western Washington and Northwest Oregon, while the Northern Idaho Panhandle and perhaps Glacier NP in Montana getting in on the action Friday night. Colder air arriving will result in snow levels dropping to 6,000 ft. or so on Friday afternoon/Friday night. 

There is still some uncertainty with the timing and placement of this system on Friday/Saturday, and it's possible that rain could extend southward into Northern California as well.

Outlook for Sat, Sept 18th - Wed, Sept 22nd

The previously mentioned storm system will impact the Northwest over the weekend with lingering impacts into early next week for interior regions. Portions of Idaho and Montana could see significant precipitation, and the Central Rockies (Utah, Colorado) may see lighter precipitation from this system as well. As colder air arrives, snow should be expected across higher elevations throughout the Northwest and the Rockies. 

Northern California will likely see some rain at some point over the weekend, but uncertainty remains with how far south the moisture with this system will reach.

Thanks so much for reading! Next update on Wednesday (9/15).

ALAN SMITH

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