Big Picture Weather Pattern:

A tall ridge of high pressure will build over the Interior Northwest U.S. and Canada, resulting in continued hot temperatures across this region.

The center of high pressure will be near the Nevada/Oregon/Idaho border, and winds blowing clockwise around the high pressure center will favor north-to-south thunderstorm motions across the Southern Rockies where monsoonal moisture is present.

Moisture will also sneak into the Sierra Nevada Range this weekend with an uptick in thunderstorm activity expected, while some dry thunderstorm activity is possible over the Southern Cascades.

5-Day Temperature Outlook:

Temperatures will be well above average across the Interior Northwest, Great Basin, and Central California during this period, while areas east of the Continental Divide in Wyoming, Colorado, and New Mexico will see below-average temperatures. 

Fire and Smoke Outlook:

Active wildfires are burning across the Northwest and smoke from these fires will continue to impact portions of the West through the weekend and beyond.

Friday:

In the map below, active wildfires producing significant smoke (as of Thursday PM) are denoted with red flames. The black arrows denote the forecast wind direction in the upper atmosphere, with areas downwind of these fires more likely to experience smoke.

Let's take a closer look at our high-resolution smoke forecast maps for Friday PM. These forecasts go out to 2 days from the current time.

The High-Res Smoke (Surface) Map projects smoke transport and concentration near ground level, including valleys, towns, and lower-elevation terrain below or near the base of mountain ranges.

 

The High-Res Smoke (Sky) Map projects smoke in the upper levels of the atmosphere, which can impact visibility and may also air quality on mountain summits and higher-elevation terrain.

Saturday:

The high pressure ridge over the Western U.S. will become more amplified on Saturday, resulting in winds aloft blowing from the south near the West Coast and winds blowing from the north/northwest over the Rockies.

This wind pattern may transport smoke from California fires toward the coastal regions of Oregon and Washington. Across the Rockies, northwest winds could transport smoke as far south as Northern Utah and Colorado. Also, smoke from Northern Canada may also reach the Western U.S. by Saturday (especially east of the Divide).

Sunday-Monday:

The pattern will become even more amplified with stronger southerly winds near the West Coast, which will keep areas from California to Washington and BC in play for smoky conditions. Also, winds will become more due northerly (blowing from the north) across the Eastern Rockies, which could transport smoke even further south into Colorado.

Keep in mind that smoke outlooks are always subject to change on a daily basis depending on changes in fire behavior, new fire starts, and subtle changes in winds and stability in the atmosphere. 

Fire danger will remain high across the Interior Northwest and California through the weekend where temperatures will be hottest relative to average, with moderate danger elsewhere across the West. 

Rain and Thunderstorm Forecast for Fri (Jul 19) to Sun (Jul 21):

A "moderate" monsoon pattern will be in place across the West this weekend, meaning that moisture and water vapor content in the atmosphere will be near seasonal levels for mid to late July.  

Thunderstorm activity will favor Colorado and New Mexico with heavy rain expected under stronger storms. Scattered coverage across Arizona, Utah, and Wyoming. Higher terrain in California and Nevada will also see some thunderstorms, while the Interior Northwest and Far Northern Rockies could see isolated dry thunderstorms.

Colorado:

Thunderstorms can be expected statewide this weekend, with the eastern and southern ranges favored for the most widespread storms and heaviest rainfall. 

Check out the forecast for the Crestone Needle in Colorado's Sangre de Christo Range on Saturday. There is a high likelihood of lightning and heavy downpours on Saturday afternoon, so if you have climbing plans, be sure to get an early start. The same is also true for each of the next 5 days.

New Mexico:

The eastern ranges of New Mexico, including Taos, Wheeler Peak, Ruidoso, and the Sacramento Mountains will see the heaviest rainfall this weekend with localized flash flooding possible under stronger storms. Western New Mexico will see plenty of thunderstorm activity as well with locally heavy rain possible.

Arizona:

Thunderstorm activity will favor the Flagstaff region, Grand Canyon North Rim, Mogollon Rim, and the mountain ranges east of Tucson. Storms will be capable of producing locally heavy rain with isolated flash flooding possible in slot canyons and dry washes. 

Utah:

Scattered thunderstorms can be expected statewide, favoring the higher terrain of Southern Utah as well as the Uinta Range in Northern Utah. Flash flooding will be possible in slot canyons, dry washes, and small streams in Southern Utah. Eastern Nevada will also see an uptick in thunderstorm activity this weekend.

Northern Rockies:

Thunderstorms will favor the Wind River, Absaroka, Beartooth, and Bighorn Ranges in Wyoming, with only some isolated activity for the Tetons and Yellowstone and for most of Idaho and Montana. 

Sierra:

Thunderstorms will favor the Southern and Central Sierra from Mt. Whitney to just south of Lake Tahoe. There will be a mix of wet and dry thunderstorms, with the potential for isolated dry thunderstorms across Northern California (near and north of Tahoe).

Forecast for Mon (Jul 22) to Tue (Jul 23):

There will be little change to the weather pattern during this period with thunderstorm activity continuing to favor Colorado and New Mexico, with isolated to scattered thunderstorms favoring higher terrain elsewhere across the West. 

Forecast for Wed (Jul 24) to Thu (Jul 25):

A slow-moving trough of low pressure is expected to reach the PNW Coast during this period, and southwest winds ahead of the trough may help to pull in more monsoonal moisture to areas west of the Divide and northward into the Northern Rockies, especially by Thursday.

Areas near the Divide in Colorado and New Mexico will hang onto routine afternoon thunderstorm chances as well.

Outlook for Fri (Jul 26) to Tue (Jul 30):

A trough of low pressure moving into the West will bring heat relief to areas west of the Divide with temperatures trending to more seasonal values, while the Pacific Northwest can expect below-average temperatures.

Areas east of the Divide, on the other hand, will see a warm-up with above-average temperatures expected.

South/southwest winds ahead of the trough should transport some monsoonal moisture northward with areas West of the Divide favored for thunderstorms from Arizona northward into Utah and Idaho/Wyoming early in this period. A drying trend is possible by late in the period, however. 

Thanks so much for reading and have a great weekend! Next update on Monday (July 22).

Alan Smith