The June weather in the West Coast is a fascinating and complex affair, with a strong Pacific jet stream driving a series of events that will have a significant impact on the region. The unusually active jet stream is a key factor in the region's weather patterns, with its strength and eastward extension contributing to the development of a broad and strong ridge of high pressure by mid-June. This ridge will bring a major shift to hotter and drier conditions, with a potential heatwave in the Pacific Northwest and Northern California. The ridge will not be centered over California, but its maximum impacts will be centered farther north, with a trend toward much warmer and drier conditions likely. The physical origins of this event are complex, with local mass accumulation near the jet exit region leading to surface high pressure, and diabatic heating warming the airmass and raising 500mb GPH heights. There may even be an indirect contribution from a recurving West Pacific typhoon, with past experience suggesting the models can struggle with the exact placement and magnitude of ridges under such conditions. The strong El Niño event by autumn is another key factor, with the updated June ensemble predictions indicating the potential for even more extreme outcomes than earlier forecast cycles. The recent research on Western U.S. sub-daily precipitation extremes confirms familiar spatiotemporal patterns and finds evidence of emerging increases in the heaviest downpours, with recent increases in potential atmospheric contributors to sub-daily downpours during 2000-2024 vs 1980-2024. This includes widespread increases in column water vapor despite mixed or even decreasing trends in surface humidity. The implications of these weather patterns are significant, with the potential for extreme heat and dry conditions, as well as the potential for heavy rainfall and lightning. The West Coast is a dynamic and ever-changing region, with the weather patterns and climate trends having a significant impact on the region's ecosystems and communities. It is important to stay informed and prepared for these changes, with the potential for extreme weather events and the need for adaptation and resilience.
