Summary:
- Average to cooler than average temperatures in May across most of the western US. Exceptions were a warmer than average month in central to northern California and portions of the southwest.
- It was a mostly dry month of May for much of the western US. A wetter than average month was experienced from northwest California into Oregon and across much of Montana.
- Snowpacks remain robust in much of the Rockies and near average in northern Oregon and portions of the Sierra Nevada mountains. In contrast, lower than average snowpacks are seen across the northern areas of Montana, Idaho, and most of Washington.
- Zonal flow and rain for the PNW and mild temperatures and dry south into California to start the month. The forecast has a ridge dominating for the rest of the month, tilting the odds to a warmer than average June over most of the west. The exception may be coastal California where cold offshore ocean temperatures may facilitate a stronger than normal marine layer resulting in slightly cooler coastal temperatures
- The dry season has started, but thunderstorm potential increases in the forecast for much of the interior west, while northwestern Washington will likely continue to see frontal rains for a portion of the month.
- Moving out of a coolish start to the growing season, the 90-day seasonal forecast has the western US headed into a likely warmer and drier than average summer.
- El Niño is likely to shift to neutral over the next month with La Niña developing during late summer to early fall. As such the seasonal models are favoring a warmer summer for much of the US, along with a more active hurricane season in the Atlantic and Gulf.
