May 2024 was a chilly month for much of the West with high-elevation areas receiving significant late-season snow. However, it looks like we are going to see a big flip to summer weather during June with above-average warmth expected. 

May 2024 Review:

Winter did not exit quietly as many areas received significant late-season snow during the first week of May, including Tahoe, Utah, Colorado, and the Northern Rockies. The pattern was not quite as active for the remainder of the month, though higher terrain in the Rockies picked up additional snowfall during mid to late May.

Temperatures for the month of May were below average across the Northwest and the Northern and Central Rockies. The Central Rockies, in particular, were much cooler than average. Further south, temperatures were near to above average across the Southwest and the interior of California.

Precipitation anomalies were a mixed bag during May. Parts of the Northern Rockies (especially on the east side of the Continental Divide) received above-average precipitation. Other areas that were wetter (and snowier) than average include the west side of the Cascades, northern and eastern Oregon, and portions of Central Colorado.

Drier conditions prevailed across the Great Basin, Southwest, and the east side of the Cascades in Washington. Frequent dry and windy conditions contributed to wildfires in Arizona and New Mexico, as May through June (prior to monsoon season) is peak fire season in this region. 

Snowpack Update:

As of June 1, snowpack is near to above average across the Central Rockies and the Sierra, while snowpack is below average in the Pacific Northwest and Northwest Montana. Snowpack is also below average in New Mexico, due to rapid spring snowmelt despite a healthy winter snow season. 

June 2024 Outlook:

While spring took its time arriving in the mountains this year, it looks like we are going to see a quick transition to summer conditions in June.

Confidence is growing that high pressure ridging will be the dominant pattern through at least the first half of the month, with a strong signal toward above-average temperatures throughout the West, and especially in the Rockies. The one exception is the California Coast, where NOAA is projecting equal chances of above or below-average temperatures.

A strong above-average precipitation signal is noted across Western Washington and Northwest Oregon for the month of June. This is the result of a significant atmospheric river event that has impacted the region early this week with many areas already exceeding their monthly rainfall averages for June.  

Conditions are likely to be drier across the Northwest for the remainder of the month overall, while below-average signals are showing up across the Northern Rockies.

The Southwest U.S., California, and Southern Rockies typically do not see much rainfall during the month of June. There is not expected to be much deviation from climatology in these regions.

The eastern slopes of the Rockies are more likely to see thunderstorms in June due to moisture transport from the Gulf of Mexico. Equal chances of above or below-average rainfall are expected on the eastern slopes of the Rockies in New Mexico, Colorado, and Southern Wyoming with above-average rainfall expected further east on the plains.

Fire and Smoke Outlook:

Above-average fire activity is expected across portions of the Southwest (especially the southern half of Arizona and New Mexico) during June due to anticipated hot and dry conditions on the heels of a dry spring.

Below-average fire activity is expected across most of California. June tends to be a bit early for significant wildfires in the Northern Rockies and Pacific Northwest, and "near normal" fire potential is expected in these regions – meaning an early start to fire season is not anticipated.

North of the border, below-average fire potential is expected over the Coast Range of British Columbia, while a small area of above-average fire potential is noted over the Southeast BC/Southwest Alberta border region. Above-average fire potential is also expected further east on the Canadian Prairies. 

Thanks for reading and enjoy the start of summer! I will post the next monthly update in early July.

Alan Smith