Before we jump into the forecast, I wanted to quickly share a fun graphic that shows the difference between the warmest day of the year (climate normals) and the summer solstice normal temp. The summer solstice is the longest day of the year, but it's not when summer temperatures peak for the Western United States.

Map courtesy of Brian Brettscheider.

You can see that most of the eastern half of the United States is nearing its peak summer temp, while a large swath of the Northern Rockies and Pacific Northwest still have anywhere from 4.5°F to 11.5°F of warming remaining. This seasonal lag in warmer temperatures into July and August following the summer solstice is flipped following the winter solstice, when we receive the coldest temperatures in January and February.

Looking ahead to the weather for the rest of this week, the Western U.S. will be influenced by a slow-moving system that will push eastward. This will help to usher in an increase in moisture and along with that, kick off several days of increased thunderstorm activity and times of gusty winds.

Forecast for Wednesday, June 23

The storm off the California Coast will pull in cooler temps on Wednesday for the Southwest, while well-above-average temps continue across the Northern Rockies and Interior Northwest.

As the energy continues to inch further east into California, the counter-clockwise rotation will pump moisture into Utah and into the high country of Colorado. This will bring an increased chance for thunderstorm activity on Wednesday afternoon, evening, and possibly into the overnight hours on Wednesday night.

Forecast for Thursday, June 24

The energy moving inland will bring cooler temps from California through the Colorado high country on Thursday, while a cold front dips south into Montana. Washington, Oregon, and Idaho will remain in the heat.

The cold front for Montana, along with the energy pushing further into the Intermountain West, will bring a decent chance for rain and thunderstorm activity during the second half of Thursday. Accumulating rainfall would be a major blessing for northern and central Colorado as wildfires continue to burn. We will need to watch for gusty winds during this afternoon/evening thunderstorm activity.

Forecast for Friday, June 25

Colder temperatures will continue to slide down the spine of the Rockies on Friday and provide a welcome relief for areas east of the Continental Divide in Wyoming and Colorado. During this same time, very warm temps will really take over the Pacific Northwest. This warming trend is very pronounced across the Cascade Range of Washington and Oregon.

The moisture bullseye will follow the colder temperatures down into Wyoming and Colorado, with the most widespread thunderstorm activity along and east of the Continental Divide on Friday.

This trend for late-week moisture and cooler temps is also clear in our 5-day hourly forecast for Longs Peak in Rocky Mountain National Park. Both Thursday and Friday have a heightened risk for precipitation and lightning, and you can see the large swing towards cooler temps on Friday compared to earlier in the week.

Forecast for Saturday, June 26 & Sunday, June 27

The trend for the upcoming weekend will be even warmer temps for the Pacific Northwest and cooler temps lingering for areas east of the divide in Colorado and Wyoming. Forecasted temps for Washington and Oregon are maxing out the scale come Sunday. This will also continue into the final days of June.

Isolated thunderstorms will continue to be the story across Colorado, New Mexico, and maybe Utah, though any rainfall is generally expected to be light. The upcoming weekend should be a great time to explore the high alpine across much of the Western United States.

Outlook for Mon, June 28 – Fri, July 2

For the week of June 28, we'll quickly return to "high and dry" conditions for most of the Western United States as a very strong ridge of high pressure is forecasted to settle in over the Pacific Northwest

If the current trend holds, we could be looking at record-breaking temperatures for Washington and Oregon. Areas east of the divide in Colorado and New Mexico could remain near normal, temperature-wise, and this will also be the region to watch for some afternoon thunderstorm activity.

Outlook for Independence Day

Looking ahead to July 4, I really don't see much change in the overall pattern. This will keep very high fire danger in place for nearly the entire Western United States so stay tuned to local law enforcement to see how this could impact your holiday weekend plans.

Thanks for reading! Next update on Friday (6/25).

SAM COLLENTINE

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