Big Picture:

A trough of low pressure centered over the Great Basin on Wednesday will work its way east late this week, eventually exiting out onto the plains by Saturday. Moisture and energy downstream of the trough as well as moist upslope winds east of the Continental Divide will act as focal points for thunderstorms, with coverage gradually shifting eastward from Wednesday to Friday.

Heading into the weekend, a ridge of high pressure will build along the West Coast, resulting in the first taste of summer heat for many areas. Central and Northern California will be the focal point for hot temperatures, while the Interior Northwest will experience the heat as well.

Forecast for Wednesday:

Showers and thunderstorms will favor the Sierra, Cascades, Western Canada, and Northern U.S. Rockies with locally heavy rain possible under stronger storms. A few severe thunderstorms are also possible across the eastern half of Wyoming with isolated incidents of large hail and damaging winds possible. 

Further south, isolated thunderstorms are possible across Northern Utah and the Northern Colorado Front Range, as well as Central/Northern New Mexico.

Forecast for Thursday:

The Sierra and Cascades will start to dry out, while Wyoming and Northeast Colorado will be the focal points of thunderstorm activity.

More isolated to scattered showers and thunderstorms can also be expected across Western Montana, Central and Eastern Idaho, and most of Utah with only a few storms across Southern Colorado and New Mexico.

Forecast for Friday:

Showers and thunderstorms will be most common along the Front Range and eastern ranges of Colorado and Wyoming with a chance of severe thunderstorms also existing east of the Rockies. Further west, only isolated showers/thunderstorms can be expected across Western Colorado/Wyoming and Northeast Utah.

Dry conditions and warm to hot temperatures will prevail across the remainder of the West.

Forecast for Saturday to Sunday:

Dry conditions will prevail across much of the West this weekend with the best chance of storms existing across the Colorado Front Range and Sangre de Christo Range, extending southward throughout Central New Mexico. 

Isolated storms are also possible across portions of the Central/Northern Rockies and perhaps the Sierra, but the first bout of summer heat will be the big story this weekend. 

Outlook for Monday (July 3) to Friday (July 7):

A ridge of high pressure will remain the dominant pattern across the Far West next week, thought it will gradually weaken over time.

A northwest flow pattern will set up further east with frequent shortwave disturbances and weak cold fronts leading to better chances of thunderstorms across the Northern and Eastern Rockies. Dry conditions are expected to prevail across the Southwest and Far West.

Temperatures are expected to be hotter than average across the Pacific Northwest, Sierra, Great Basin, and Southwest, while a cooling trend back to more seasonal temperatures is expected across Coastal California. Meanwhile, below-average temperatures are favored near and east of the Continental Divide.

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

Alan Smith