Big Picture Weather Pattern:

This is shaping up to be an active weather weekend across a larger portion of the Interior West, while fires will continue to burn across the far western states with smoke transport into the Central and Northern Rockies.

The jet stream will be stretched from Oregon across the Central Rockies, and this will contribute to gusty winds across the higher terrain of the Rockies. It will also act as a boundary of sorts between moisture types.

To the south of the jet stream, a significant surge of monsoonal moisture (perhaps the most significant surge of the season so far) will reach Utah and Colorado where numerous thunderstorms are expected along with locally heavy rain and the potential for flash flooding. Upslope winds blowing from the east in the lower atmosphere on the east side of the Continental Divide will also favor heavy rain in the Front Range and eastern ranges.

To the north of the jet stream, Pacific moisture will reach the east side of the Cascades and the Northern Rockies (with perhaps some residual monsoonal moisture mixed in), resulting in scattered thunderstorms. Locally heavy rain will occur with storms near and east of the Continental Divide in Montana and especially Wyoming, where more abundant moisture will be in place.

5-Day Temperature Forecast:

Temperatures will be cooler than average across the Central and Eastern Rockies, and a bit warmer than average across portions of the Southwest, Great Basin, and California. A cooling trend is expected near the West Coast by late in this period.

Wildfire Smoke Outlook:

Large and active wildfires continue to burn across the Far West from Washington to California, with a recent uptick in Idaho as well. Heavy smoke will impact areas immediately downwind of these fires, with significant smoke transport further downwind across Northern Utah, Idaho, Wyoming, and Southwest Montana. 

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

A similar pattern is expected on Saturday and Sunday. Below-average temperatures expected over the West Coast states next week could potentially lead to a reduction in fire intensity and smoke transport, but confidence is low this far out.

Rain and Thunderstorm Forecast for Fri (Aug 9) to Sun (Aug 11):

The Four Corners region will see the most widespread thunderstorm activity and heaviest rainfall totals this weekend, while the Northern Rockies will also be active. The Washington Cascades will see some showers and thunderstorms as well, with more widespread activity north of the border in Canada.

The Southern California mountains will also see an uptick in thunderstorm activity, especially on Saturday, while the Sierra will be drier with just some isolated storms for southern portions of the range.

Colorado:

Friday will be the most active day statewide with widespread thunderstorms. The San Juans and Sangres will be favored for the heaviest rainfall totals with an increased threat of flash flooding.

Saturday does not look quite as wet, but numerous thunderstorms can still be expected statewide with locally heavy rain expected.

On Sunday, a drying trend is expected near the Front Range with more isolated activity, while Western Colorado (especially the San Juans, Elks, Grand Mesa, and Flat Tops) will stay in an active thunderstorm pattern with heavy rain possible. 

Utah:

This will be an active thunderstorm pattern throughout Southern, Central, and Eastern Utah while the Wasatch Range will also see some storms.

Friday looks like the most active day statewide with numerous thunderstorms. Saturday and Sunday will also be active, though perhaps slightly less active than Friday. 

Flash flood potential will be higher throughout the weekend in slot canyons, dry washes, and small streams of Southern Utah.

Here is our forecast for the Capitol Reef National Park Visitor Center where thunderstorm potential looks high from Friday through early next week. 

Arizona:

The northward monsoon moisture surge will favor Northern Arizona, including the Flagstaff and Grand Canyon regions, with more isolated activity over Southern Arizona.

Friday and Sunday look like the two most active days, with slightly lower coverage of thunderstorms on Saturday.

New Mexico:

Northern New Mexico will be favored in this pattern with numerous thunderstorms and an elevated threat of flash flooding on Friday, including the Taos region.

Saturday and Sunday look a bit less active compared to Friday, but northern portions of the state will still see a good chance of thunderstorms.

Southern New Mexico will see more isolated thunderstorm activity in this pattern. 

Northern Rockies:

This will also be an active thunderstorm pattern across the Northern Rockies with the highest coverage of thunderstorms on Friday and Saturday, with a decrease in coverage for most areas on Sunday.

Areas near and east of the Continental Divide will be favored for the heaviest downpours with thunderstorms, especially in Wyoming and Southern Montana, including the Beartooths, Absarokas, Winds, and Bighorns. 

Forecast for Mon (Aug 12) to Tue (Aug 13):

An active pattern will continue as a trough of low pressure sets up near the West Coast, with south/southwest winds transporting monsoonal moisture from Arizona and New Mexico northward into Wyoming and Montana. Locally heavy downpours will remain possible, especially over the Southern Rockies.

The Northern Cascades will also see isolated showers and thunderstorms with more widespread activity north of the Canadian border.

Forecast for Wed (Aug 14) to Thu (Aug 15):

As the low pressure trough moves inland, drier air will work its way into Four Corners region, resulting in a significant reduction in thunderstorm chances over Utah and Arizona. Colorado and New Mexico will hang onto thunderstorm chances at least on Wednesday with drying possible by Thursday.

The Northern Rockies will see scattered thunderstorm chances persist with a chance of showers for the Northern Washington Cascades, while BC and Alberta look to see more widespread rain and thunderstorms.

Outlook for Fri (Aug 16) to Tue (Aug 20):

Monsoonal moisture will return to the Four Corners region and Wyoming, with an uptick in thunderstorm chances expected following the brief mid-week lull. Frequent disturbances will continue to track across the Northwest and Northern Rockies, keeping thunderstorm chances in the picture here as well.

Temperatures will be near to below average across the Far West which is good news for firefighting efforts. Temperatures will be above average across the Rockies, but no major heatwaves are expected.

Thanks so much for reading and have a great weekend! Next update on Monday (August 12).

Alan Smith