Western US Daily Snow
By Alan Smith, Meteorologist Posted 9 months ago August 11, 2025
Monsoon Finally Showing Some Signs of Life
Summary
Most areas will see a continued dry pattern to start the week, but monsoon moisture will gradually increase across the Southwest & the Rockies later this week, leading to an uptick in thunderstorm coverage. Initially, rainfall will be limited, but locally heavy downpours are possible later in the week. The PNW is also looking at a significant rain event on Fri-Sat as a frontal system arrives.
Short Term Forecast
Helpful Links:
Wildfire and Smoke Update:
Wildfires continue to burn across the Southwest, with limited fire activity over the Northwest. Northwest winds will result in NW to SE smoke transport from fires over the Southwest on Tuesday, then a transition to southwest winds is expected by Thursday, which will lead to SW to NE smoke transport.
Smoke (sky) forecast for 6 PM Tuesday:
5-Day Temperature Outlook:
Temperatures will be warmer than normal across much of the West over the next 5 days. However, the Northwest will see near-normal temperatures with a cooling trend over time, while portions of the Southwest will also see moderation from last week's extreme heat.
Tuesday (Aug 12):
This will be another quiet day for most of the West as limited monsoon moisture will retreat southward into New Mexico and Southern Arizona via north/northwest winds, while drier conditions will prevail across Utah, Western Colorado, and Northern Arizona.
Isolated to scattered afternoon thunderstorms will develop in New Mexico and Southeast Arizona, with most storms producing light rain and gusty winds. However, stronger storms will have the potential to produce locally heavy rain.
A few stray terrain-driven storms could also develop over Colorado, with the highest likelihood over southern and eastern ranges (San Juans, Sangres, Front Range).
Wednesday (Aug 13):
Monsoon moisture will expand westward a bit, favoring Arizona and Western New Mexico. Moisture levels will still not be overly impressive for August, but it will be enough for isolated to scattered thunderstorms across the green-shaded region.
Most storms will produce light to moderate rain with gusty winds, but stronger storms will be capable of producing locally heavy rain.
Thursday (Aug 14):
Monsoon moisture will begin to push northward with an increase in thunderstorm coverage expected across the Southwest and the Rockies.
Arizona and Southern Utah will be favored for heavy rainfall potential with scattered thunderstorms, with the greatest threat for heavy rain occurring later in the day as it will take some time for moisture to really increase in the lower atmosphere given the preceding dry airmass.
Moisture will also begin to increase further north with scattered thunderstorms developing across Utah, Colorado, and Wyoming. Storms in these areas will generally produce light to moderate rain and gusty winds. Lower moisture levels will also result in an increased threat of lightning-triggered wildfires.
Friday (Aug 15):
Moisture levels will continue to increase across the Southern and Central Rockies as southerly winds transport monsoonal moisture northward.
Meanwhile, a very wet (by August standards) storm system will impact the Pacific Northwest with moisture levels of 175 to 200% of normal.
Across the Rockies, more numerous thunderstorms can be expected, especially in the green-shaded region, with an increasing potential for heavy rainfall with storms. This includes most of New Mexico, Arizona, Utah, and Colorado along and west of the Continental Divide.
Further north, isolated to scattered thunderstorms can be expected in the yellow-shaded areas. Most storms in these areas will produce light to moderate rain, but stronger storms could produce locally heavy rain.
To the north, a powerful low pressure trough will make landfall in the Pacific Northwest, and a cold front will also move through. Abundant moisture arriving with this system will lead to a widespread rain event with heavy amounts possible along the West Coast, Olympic Peninsula, and Cascade Mountains.
Saturday (Aug 16):
Monsoonal moisture will remain in place over portions of the Rockies and Southwest with another active thunderstorm day possible. However, there are some model discrepancies in terms of which areas will be most favored and whether or not some areas start to dry out, so we will need to keep an eye on this later in the week.
To the north, lingering moisture over the Pacific Northwest will result in additional rain showers, though activity looks more intermittent with lighter rain amounts compared to Friday. Still, it looks like a cool and wet day across the region with a fall-like feel to it.
Extended Forecast
August 17-21:
Early next week, the monsoon should weaken somewhat with higher moisture levels confined to Arizona, New Mexico, and Southern Colorado. These areas will be the most favored for thunderstorms.
Further north, troughing is expected to persist off the coast of the Pacific Northwest, with medium-range models hinting at disturbances moving through. For now, it looks like Eastern Oregon to Northern Idaho and Montana would be favored for scattered showers and thunderstorms.
Temperatures are generally expected to be above normal across the Interior West and below normal along the West Coast. However, some moderation is also possible across the Southwest, depending on cloud cover as a result of the monsoon.
August 22-26:
Looking further out, most models are indicating a strengthening monsoon around this time, which could lead to an uptick in thunderstorm coverage across the Southwest, Rockies, and perhaps even the Sierra.
This includes the European AI Ensemble Model, which has performed better in the 10-15 day range lately than other models.
Temperatures are expected to be warmer than normal across most of the West, but with some localized cooling possible over the Four Corners region due to increased cloud cover associated with the monsoon.
Thanks so much for reading! Next update on Wednesday (August 13).
Alan Smith
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