An “extremely rare weather pattern” is set to hit the western U.S. in May, according to a Tuesday forecast.
The forecast, shared by amateur meteorologist Colin McCarthy, shows what appears to be a North American monsoon pattern that the western U.S. is used to — but there are key features missing. For example, McCarthy noted the “classic 4-Corners High” has yet to develop, but that the forecast would be a “true monsoon pattern” should it evolve.
Despite not being the “classic” monsoon forecast, McCarthy said the pattern is “extremely rare” for May.
This setup greatly resembles the North American Monsoon we see in summer with a moist southeast flow, but technically this is not a true monsoon pattern as the classic 4-Corners High hasn’t developed yet.
Nevertheless, an extremely rare weather pattern for May. pic.twitter.com/0Ih0sagoFo
— Colin McCarthy (@US_Stormwatch) May 9, 2023
The forecast followed some back-and-forth over whether a record-smashing heatwave would strike the Pacific Northwest during mid-May, or if it would trend toward a retrograding low-pressure system. The latter would tap “into an unusually moist atmosphere, bringing the potential for a prolonged thunderstorm outbreak which could lower daytime high,” according to McCarthy.
The western U.S. is already facing a fairly rare winter and spring seasonal weather fluctuation. California’s snowpack is 263% of normal, and threatening mass flooding throughout the region as summer starts to melt through, McCarthy said. (RELATED: California Braces For ‘The Big Melt.’ It Could Be Catastrophic)
Footage has already shown initial meltwaters refilling the once-lost Tulare Lake, halfway between San Francisco and Los Angeles. Reports suggest it could continue to flood until 2024, so emergency services in the area are remaining “vigilant” to deal with potential consequences.