An elongated ridge of high pressure over the Great Plains is directing monsoonal moisture into the Great Basin and Central/Northern Rockies on Friday. We're also seeing an increase in moisture east of the Divide in Wyoming and Colorado.

As of early Friday afternoon, slow-moving thunderstorms were already ongoing throughout the West.

Our lightning density map is showing quite a bit of activity throughout the Rockies, Great Basin, and Sierra as well.

Current Radar

Lightning Density

Forecast Radar

Atmospheric moisture levels ("fuel" for thunderstorms and summertime convective rains) are very high across the Great Basin and portions of the Northern/Central Rockies on Friday.

The abundance of moisture combined with upper-level winds will result in slow-moving thunderstorms. As a result, Flash Flood Watches are in effect across a large portion of the West on Friday, highlighting the potential for heavy rains and runoff in steep/mountainous terrain, canyons, and wildfire burn scars. 

North of this moisture surge, a heatwave is underway across the Pacific Northwest and areas near the Canadian border, and heat advisories are currently in effect.

Heading into the weekend, monsoonal moisture will surge even farther north and northwest into Idaho, Eastern Oregon, and Eastern Washington. On the periphery of this surge, the Cascades will get in on the thunderstorm action as well.

Anomalously high levels of atmospheric moisture (compared to average) will extend northward toward the Canadian border on Saturday and Sunday.

On Monday, energy from a robust disturbance will move across the Northwest and Northern Rockies and will interact with monsoonal moisture in place to result in an active day across Wyoming, Utah, and Colorado. By Tuesday, we'll start to see a gradual drying trend from west to east in the wake of this disturbance.

The moist southerly flow across the West has reduced wildfire smoke across the West Central and Southwest U.S. while varying degrees of smoke remain across the Northwest and Northern Rockies. Some areas experiencing fires should see some relief in the form of wetting rains over the coming days, but farther west in the Cascades, there will also be a risk of dry thunderstorms and new lightning-triggered fires.

Forecast Smoke (surface)

Forecast Smoke (sky)

Our new air quality map shows good to moderate air quality across southern portions of the West and also areas along the West Coast, while the unhealthy air quality persists across much of the Interior Northwest and Northern Rockies.

Current Air Quality

The hottest temperatures relative to average will occur across the Pacific Northwest and far Northern Rockies over the next couple of days before gradually cooling off heading into early next week. Heavy cloud cover and significant rainfall associated with the monsoon will lead to more moderate temperatures across the remainder of the West, and areas east of the Divide in Colorado and New Mexico will see below-average temperatures.

Forecast for Friday, July 30th

Widespread slow-moving thunderstorms capable of producing heavy rainfall can be expected across the Central Rockies, Great Basin, and Sierra on Friday. Western Wyoming, Eastern Idaho, and Eastern Nevada are all areas that should see some of the heaviest rainfall amounts, especially the Wind River Range in Wyoming.

Forecast for Saturday, July 31st

Upslope flow will kick on across Eastern Colorado on Saturday with widespread thunderstorms and heavy rain expected for the Front Range, while Western and Central Colorado, Northern Utah, and Western Wyoming will see an active day with heavy rain as well. 

Farther west, moisture will surge northward into Western Idaho and Eastern Oregon with very heavy rains possible, which should both help with ongoing wildfires but also result in a significant threat for flash flooding.

More thunderstorms can be expected for the Sierra on Saturday, while the Cascades will likely see some thunderstorms as well – though lighter rain with Cascade thunderstorms also means there is a potential for lightning-triggered fires.

Forecast for Sunday, August 1st

Significant rains and thunderstorms will extend northward toward the Canadian border on Sunday and even the Cascades should see a mix of wet and dry thunderstorms, which could either be a blessing or a curse given the pre-existing fire danger and ongoing wildfires.

Heavy rain from thunderstorms can be expected across Idaho, Western Montana, Nevada, Utah, Western Wyoming, and much of Colorado and New Mexico.

Forecast for Monday, August 2nd

A disturbance in the upper atmosphere will move across the Northwest and Northern Rockies on Monday, with most of the action shifting into Eastern Idaho, Western Wyoming, Montana, Northern Utah, Colorado, and New Mexico. Energy from this disturbance will interact with the monsoonal moisture in place to result in widespread thunderstorms and heavy rain/flash flooding as winds aloft will remain weak.

Farther west, we'll start to see a drying trend on the backside of this disturbance.

Forecast for Tuesday, August 3rd

Moisture and thunderstorms/rain will continue to shift toward the east on Tuesday with areas near the Continental Divide in Wyoming, Colorado, and New Mexico likely to see the heaviest rainfall. Drier conditions will prevail farther west, though some isolated dry thunderstorms will be possible.

Outlook for Wed, Aug 4th - Sun, Aug 8th

The second half of next week is looking much drier as the disturbance will scour out most of the moisture in place across the Rockies. A stronger and drier westerly flow will take hold behind the disturbance and the bulk of the monsoonal moisture will retreat south toward the Mexico border.

A trough of low pressure is also expected to move into the Pacific Northwest later next week, ushering in cooler temperatures along with the potential for some rain showers.

Rain potential will be lower for most of the West during the second half of next week, except for New Mexico who could see some lingering heavy rains on Wednesday before drying out more afterward. Isolated thunderstorms with lighter rain will be the general rule of thumb across the Rockies and Southwest.

Farther north, Washington, Northern Idaho, and Northwest Montana could see some rain showers and perhaps a few thunderstorms.

Thanks so much for reading! Next update on Monday (8/2).

ALAN SMITH

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