Western US Daily Snow

Short Term Forecast

Big Picture Weather Pattern:

A trough of low pressure will move across the Northern Rockies early on Friday, then a second trough will move into Northern California before swinging inland later Friday and into Saturday.

Energy from these features will interact with monsoonal moisture to result in an active thunderstorm pattern across the Central Rockies, but dry air will work its way inland behind the second trough, helping to shunt monsoonal moisture southward toward the Mexico border by Sunday. 

5-Day Temperature Outlook:

We will see a break from the extreme heat from Friday to Tuesday. Temperatures will start to rebound to above-average values in the Rockies by early next week after a brief cooldown, while the West Coast and Pacific Northwest will be a little cooler than average.

Fire and Smoke Outlook:

It has been an active week for fire growth across the Northwest and California due to a combination of hot temperatures, gusty winds, and dry thunderstorms. 

Learn More → Western U.S. and Canada Wildfire Update

Winds aloft will generally blow from west/southwest to east/northeast downwind of the most active wildfires from Friday through early next week.

This will favor smoke transport across the Interior Northwest and Northern Rockies, with Northern Utah getting it at times too. Colorado looks less smoky in this pattern, though some occasional light haze is possible.

Smoke (Sky) Projection for Friday at 6pm (MT):

Smoke (Sky) Projection for Saturday at Noon (MT):

Around the middle of next week (July 31-August 1), a brief switch to northwest winds aloft is expected east of the wildfires, which could potentially transport some smoke into Colorado for a day or two, before shifting back to a west/southwest flow late next week (which would favor less smoke for Colorado).

The Interior Northwest and Northern Rockies look to stay smoky for the foreseeable future with day-to-day fluctuations in air quality.

Forecast for Fri (Jul 26) to Sun (Jul 28):

Friday and Saturday will be active thunderstorm days across the Central Rockies, with fewer storms expected in Utah and Nevada as drier air works its way in from the west. Significant drying is then expected across the Central Rockies starting on Sunday, though isolated storms with lighter rain will remain possible in some areas. 

Northern Rockies:

Storms will favor Western Wyoming and Southwest Montana, including the Winds, Tetons, and Beartooths. More isolated thunderstorms with less rainfall (i.e. dry thunderstorm potential) can be expected further north.

Colorado:

There will be a high chance of thunderstorms across all major mountain ranges of Colorado with locally heavy rain possible, while the Front Range cities east of the Divide are only expected to see isolated storms will lighter rainfall.

New Mexico:

There is also a high likelihood of thunderstorms throughout the mountainous regions of New Mexico with locally heavy rain and burn scar flash flooding possible. 

Arizona:

The main threat of thunderstorms with heavy rain potential will be confined to Southeast Arizona, including the Eastern Mogollon Rim and the mountain ranges near/east of Tucson. Northern areas including Flagstaff and the Grand Canyon will see only isolated thunderstorms and light rainfall. 

Utah:

Southern Utah will also begin to see a drying trend, though isolated thunderstorms will remain possible and flash flooding in slot canyons and dry washes couldn't be ruled out either (mainly on Friday). More numerous thunderstorms with heavier rain are expected over Northern Utah, including the Wasatch and Uinta Ranges.

Forecast for Mon (Jul 29) to Tue (Jul 30):

A trough of low pressure containing some moisture will move into the Pacific Northwest, with increasing potential for a soaking rain event across the Cascades, Olympics, and Western Washington lowlands, as well as Northwest Oregon.

Areas east of the Cascades crest, including Northeast Oregon, could pick up some light showers as well though it may not be enough to put much of a dent into the ongoing wildfires (most of which are located east of the Cascade crest).

The higher terrain of Northeast Washington and Northern Idaho could potentially pick up some beneficial rain as well, though confidence is lower. Rain chances will also be higher across British Columbia, which could potentially aid in firefighting efforts.

To the south, the monsoon will only slowly start to rebuild after Sunday's dry air surge. Arizona and New Mexico will have the best chance of seeing some storms, with locally heavy rain possible in the Southern Arizona ranges as well as the Mogollon Rim and Black Mountains.

Colorado should stay mostly dry in this pattern, though the Southern Sangres and San Juans could potentially see some thunderstorm activity.

Forecast for Wed (Jul 31) to Thu (Aug 1):

The Pacific Northwest will see a return to dry conditions, while the monsoon will ever so slightly move northward. Most of the action is still expected to stay in Arizona and New Mexico, but southern portions of Utah and Colorado could also see some isolated thunderstorms. 

Extended Forecast

Outlook for Fri (Aug 2) to Tue (Aug 6):

The heat will rebuild across the West during this period as a ridge of high pressure strengthens over the Rockies. The highest temperature anomalies are expected over the Northern Rockies with more modest warm anomalies over the West Coast.

The monsoon will also rebuild with an uptick in thunderstorm activity expected throughout the Four Corners region plus Southern Wyoming, while moisture could also extend into the Sierra and the Northern Rockies at times.

Thanks so much for reading and have a great weekend! I will be out on Monday, so check back in for my next forecast on Wednesday (July 31).

Alan Smith