Western US Daily Snow
By Alan Smith, Meteorologist Posted 6 days ago June 9, 2025
Thunderstorm Activity Ramps Up Over the Northern Rockies
Summary
A trough-dominant pattern will set up over the Northwest this week, and downstream of this feature, a warm and unstable airmass will support an uptick in thunderstorm coverage & intensity over the Northern Rockies with Wed & Thu shaping up to be the most active days. The Southern Rockies (CO/NM) will continue to see t-storms early/mid week with coverage trending downward late in the week.
Short Term Forecast
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Monday Afternoon Conditions:
A moisture axis has been present across the Southern Rockies and Southwest, stretching into the Great Basin and California in recent days. This has contributed to daily rounds of thunderstorms across these regions.
On Monday, thunderstorms developed prior to noon over some of the higher terrain, especially in Southern Colorado and New Mexico, with coverage increasing into early afternoon.
Here was our Lightning Risk Map (dots indicating recent strikes) as of 1:23 pm MDT on Monday:
As of 3:48 pm MDT Monday, lightning activity has further increased across the West with mid-afternoon peaks noted over New Mexico, Nevada, and Northern California.
Tuesday (June 10) to Thursday (June 12):
A trough-dominant pattern will gradually take hold over the Northwest this week, with the high pressure ridge responsible for the recent heatwave shifting inland and flattening a bit. This will support a warm and unstable atmosphere across the Interior Northwest and Northern Rockies, which will be conducive to thunderstorms.
Temperatures are expected to be warmer than average across nearly the entire West this week, though cooling is expected compared to recent days over the Northwest lowlands.
Tuesday – A large portion of the West will see afternoon terrain-driven thunderstorms in response to several subtle weather features.
A trough will approach the West Coast while another trough tracks across Canada with a weakening high-pressure ridge, supporting an uptick in thunderstorms from Oregon to Montana. Most storms will produce light to moderate rain, but locally heavy downpours are possible along with strong wind gusts.
To the south, a lingering area of low pressure over Northern Mexico will reinforce moisture over New Mexico and Southern Colorado, where more numerous thunderstorms are expected, some of which will produce heavy rainfall.
Wednesday – This is shaping up to be an active day as a potent shortwave trough tracks across Idaho and Montana.
On the north side of the trough (green area), numerous thunderstorms are expected, including morning development over Oregon and Idaho, with coverage picking up over Wyoming and Montana heading into the afternoon.
Multiple rounds of thunderstorms are expected over the Northern Rockies, some of which will become strong to severe with 50-60+ mph wind gusts, medium to large hail, and heavy rain possible.
Over the Southern Rockies (yellow area), lingering moisture and remnant energy from the shortwave trough will contribute to scattered afternoon thunderstorms. Most storms will produce light to moderate rain, but locally heavy downpours are possible.
Thursday – The first trough will exit to the east out onto the plains, while a second trough approaching from the southwest will interact with lingering moisture to result in another active thunderstorm day across the Northern Rockies. Stronger storms will be capable of producing locally heavy rain and moderate to large hail.
Over the Southern Rockies, thunderstorm coverage will be more isolated compared to prior days, with most storms producing light to moderate rain. However, the Front Range foothills and Northeast Colorado plains could see strong to severe thunderstorms with large hail possible.
The map below shows projected 3-day rainfall totals from Tuesday through Thursday from the European weather model.
Extended Forecast
Friday (June 13) to Tuesday (June 17):
Troughing will continue to dominate the pattern over the Northwest with ridging over the Eastern Rockies and the Southwest. A deeper trough is also possible early next week (around the 16th-17th), which would favor cooler temperatures over the Northwest.
For this 5-day period, we are now expecting below-normal temperatures over the West Coast and Cascades, with above-normal temperatures for the remainder of the West.
From Friday (June 13) to Sunday (June 15), thunderstorm chances look to favor areas near and east of the Divide in Montana and Northern Wyoming. On June 16-17, we are seeing signs of a wetter pattern developing across the Pacific Northwest while the Northern Rockies could see additional showers and thunderstorms.
A notable drying trend is expected over the Southern Rockies, including Colorado and New Mexico, with only isolated thunderstorm activity favoring the Continental Divide, mainly early in this period.
June 17-23:
Looking further out, a trough-dominant pattern may persist over the Northwest with near to perhaps below normal temperatures projected for the Northwest and Far Northern Rockies, along with higher chances of rainfall.
Over the Southwest and Southern Rockies, above normal temperatures are expected along with drier conditions overall.
However, we are seeing some hints of early monsoonal moisture sneaking into Southern Arizona and New Mexico toward the end of this period. Confidence is low this far out, but it will be something to keep an eye on.
Thanks so much for reading! Next update on Wednesday (June 11).
Alan Smith
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