Big Picture Weather Pattern:

A strong ridge of high pressure will remain the dominant pattern over the Western U.S. this weekend and the heat wave will persist. However, the center of high pressure will continue to shift eastward, which will open up the door for monsoon moisture to move into the Western U.S. from the south. 

The moisture uptick will be gradual and some areas will see dry thunderstorms initially this weekend, with a better chance of wet thunderstorms (locally heavy rain) by early next week as moisture levels increase. 

5-Day Precipitation Forecast:

Thunderstorm activity will gradually ramp up across the West over the next 5 days. Thunderstorm activity will be scattered in nature for most areas with the Colorado Rockies favored for the heaviest rainfall totals. Areas that see thunderstorms with only light rainfall will be at a greater risk for wildfires. 

5-Day Temperature Departure from Average:

Temperatures will remain above average throughout the West this weekend and into early next week. Temperatures will not be quite as brutal compared to this past week when numerous record highs were broken, but it's still going to be hot.

Fire and Smoke Outlook:

Fire danger continues to rise with many areas now under High to Very High Danger west of the Continental Divide. The recent heatwave has led to increased evaporation rates, which have accelerated the drying out of vegetation. 

Fire activity has been on the rise across much of the West during the past week as well with a number of large fires burning from Utah to California to Washington to Montana. Heavy smoke is still confined to areas near and just downwind of large fires, but light smoke will lead to hazy skies across a significant portion of the West this weekend.

High-Res Smoke (Surface) Forecast for Friday PM:

Wildfire and Smoke Tracking Tools:

• Active Fires Map
• Real-Time Air Quality Map
• Smoke High-Res (Surface) Map
• Air Quality Forecast Map

Forecast for Fri (Jul 12) to Sat (Jul 13):

Friday will feature isolated terrain-driven thunderstorms across the Rockies and possibly the High Sierra, but most areas will see minimal rainfall. On Saturday, monsoonal moisture will increase with a better chance of thunderstorms across the High Sierra and the Four Corners. A mix of wet and dry thunderstorms can be expected.

Here is a zoomed-in rain forecast for the Sierra Nevada Range. Storms over the High Sierra could produce some heavy downpours on Saturday, with lighter rainfall further north around Tahoe.

Forecast for Sun (Jul 14) to Mon (Jul 15):

Thunderstorm coverage and rainfall potential will continue to expand across the West. Storms will be scattered in coverage and will favor the higher terrain.

Some storms will produce locally heavy downpours with a risk of flash flooding in slot canyons, dry washes, and burn scars (mainly in the Southwest), while other storms will produce little rainfall with greater potential for lightning-triggered wildfires.

Let's take a look at rainfall projections by region to get an idea of which areas will be more favored for thunderstorms and rainfall. Keep in mind that these are only projections, and will not always match reality as thunderstorms have an inherent degree of randomness. 

Sierra Nevada Range:

Arizona:

Utah:

Colorado:

Northern Rockies:

Forecast for Tue (Jul 16) to Wed (Jul 17):

Monsoon moisture will shift eastward with a drying trend for California and the Sierra Nevada Range, while New Mexico and Colorado will see an uptick in moisture with more widespread thunderstorms along with the potential for heavy rainfall.

Utah, Arizona, and Wyoming will hang onto some isolated or scattered thunderstorm activity.

Outlook for Thu (Jul 18) to Mon (Jul 22):

Above-average temperatures will persist across most of the West with the highest anomalies expected over the Northern Rockies. A typical monsoon pattern will also remain in place with near-daily thunderstorm chances for the Four Corners region, while fringe areas including the Sierra and the Northern Rockies could see occasional thunderstorms. 

Thanks so much for reading and have a great weekend! Next update on Monday (July 15).

Alan Smith