A ridge of high pressure is setting up over the Central Great Plains, and south/southwest flow around the High is transporting monsoonal moisture into the Central and Northern Rockies. Atmospheric moisture will be nearly 200% of average across this region, which will fuel widespread thunderstorm development, and weak winds aloft will result in slow-moving thunderstorms and heavy rainfall over the next several days.

Check out the projected rainfall totals over the next 5 days. While heavy rainfall is common at this time of year in Colorado and Southern/Central Utah, the typically drier Northern Rockies and Great Basin will see heavy rain and flash flooding potential as well. But the moisture is also needed due to ongoing drought and fire conditions.

The Tetons, Yellowstone, Wind Rivers, Sawtooths, Wasatch, Unitas, Sierra Nevada, and much of Colorado are in line to see intense thunderstorms with heavy rain and significant lightning risk for peak baggers. 

The Southern Rockies and desert regions will remain in an active pattern as well, and even portions of the Pacific Northwest could see some thunderstorms.

The abundance of moisture and cloud cover will knock temperatures down to values closer to average across a large portion of the West. Only the Pacific Northwest and areas near the Canadian border will see above-average temperatures during the next 5 days.

Forecast for Wednesday, July 28th

Widespread thunderstorms can be expected throughout the Rockies with the heaviest rainfall expected across the Tetons, Yellowstone, Wind Rivers, Uintas, and San Juans. Flash flooding will be a possibility across these ranges as well. The Sierra Nevada will see thunderstorms with wetting rains as well, while the Oregon Cascades could see dry thunderstorms.

Forecast for Thursday, July 29th

Another active thunderstorm day is expected across the Rockies with Wyoming and Northern Utah favored for the heaviest rain totals along with the potential for flash flooding. The Sierra Nevada and Great Basin will continue to experience wet thunderstorms, while the Oregon Cascades could see another round of dry thunderstorms.

Forecast for Friday, July 30th

Utah and Wyoming will continue to be the focal points for widespread thunderstorms and heavy rains, while the Great Basin, Sierra Nevada, and Northern Arizona should see a relative increase in thunderstorm activity as well. The Oregon and Southern Washington Cascades will see another risk of dry thunderstorms, which is not ideal given the current fire danger and ongoing fires across the region.

Forecast for Saturday, July 31st

Moisture will surge north into Eastern Oregon and Idaho with widespread thunderstorms and heavy rain expected along with flash flooding potential. This area could see some fire relief from the wetting rains, but the potential for mudslides and flash flooding in recent wildfire burn scars will also exist. The Washington Cascades could get in on the thunderstorm action as well.

Elsewhere, it will be another active day for thunderstorms across Wyoming, Utah, the Great Basin, and Sierra Nevada Range with heavy rains expected. Nearly all of Colorado will see an uptick in thunderstorm activity both west and east of the Divide. A cold front east of the Divide will be the culprit for thunderstorm activity over the Front Range.

Forecast for Sunday, August 1st

Sunday is looking wet and stormy across a large portion of the West with the focal point for heavy rains expected over Eastern Oregon and Idaho, including the Wallowa, Salmon River, and Sawtooth Ranges. Most of the major mountain ranges in Wyoming, Utah, and Colorado will continue to see numerous thunderstorms with locally heavy rains as well.

Outlook for Mon, Aug 2nd - Fri, Aug 6th

An active start to the week across the Rockies will gradually trend toward less widespread thunderstorms and lighter rainfall as high pressure retreats toward the Four Corners region and the flow of monsoonal moisture relaxes a bit.

Even so, daily rounds of thunderstorms are likely to continue across the Rockies, deserts, and Intermountain West. Western Colorado is most likely to be under the bullseye with more numerous thunderstorms across the San Juan, Elk, and Sawatch Ranges. 

Remnant monsoonal moisture will keep storm chances going across the Northern Rockies as well, though stronger winds aloft will result in faster-moving thunderstorms with less rainfall.

Thanks so much for reading! Next update on Friday (7/30).

ALAN SMITH

In addition to the wildfire smoke forecast maps, you can now view the real-time air quality index on OpenSummit to help you plan your next adventure.

The 'Air Quality Index' map overlay is the current US EPA PM2.5 air quality index from PurpleAir sensors. Shown as the 10-minute average. The higher the AQI value, the greater the level of air pollution and the greater the health concern.

Here is an example of the air quality index for the United States on July 26, 2021.

The map is updated every 10 minutes, with the average AQI value for the past 10 minutes.

View the air quality map on any device by upgrading to All-Access for $29.99/year (Single) or $39.99/year (Group). The subscription includes 5-day hourly forecasts, estimated trail conditions, and much more.

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Air Quality Map → OpenSummit.com/map