- High pressure over western Canada brought a May heat wave to the PNW, while continued onshore flow south into California kept temperatures cool there. May ended substantially above average1 in the PNW, northern Basin, and Rockies, while coastal California was cooler than average, and elsewhere across the southern portion of the western US was near average.
• May saw a mixed bag in terms of precipitation in California with central to southern coastal and inland southern areas wetter than average while the central valley and northern coast were drier than average. The PNW west of the Cascades saw a dry May, while much of the eastern inland zones saw some much-needed precipitation.
• Short term forecast calls for mild conditions in the south and seasonal to warmer than average conditions in the north. Precipitation is most likely as thunderstorms build along the Sierra and Cascade mountains and eastside. A slight hint at a shift to a rain event later in June, but too early to detail further.
• SWE’s are still up over the west but melting fast in the north, a little slower in California. Drought coverage and intensity continue at low levels, but our seasonally dry period will likely tilt some regions back into drought.
• The June forecast points to the PNW and northern states likely seeing above average temperatures while California and southern states are likely to see average to below average temperatures. Precipitation during June is forecast to be largely driven by thunderstorm activity and likely more located along the mountains and inland. The 90-day forecast is tilting the odds to a warmer than average summer for the western US. The dry season is likely to be near average for most areas, slightly below average for the PNW and desert southwest. El Niño is likely with us through the end of the year, while the PDO remains in a strong negative phase. Neither are dominant influences in the summer months … but watchful, nevertheless.