What might cause a wet drizzly weather pattern on the prairies?

A wet, drizzly weather pattern on the Canadian Prairies is most commonly caused by the presence of a large, slow-moving upper-level low pressure system positioned over the region^[1]. This system leads to unsettled, cool, and damp conditions, often persisting for days or weeks as it slowly moves and brings repeated chances for rain or drizzle^[1].

Essential supporting factors:

• Upper-level lows create conditions favoring extensive cloud cover and frequent precipitation such as light rain or drizzle, especially if the system is "cut-off" and moving sluggishly across the prairies^[1].
• Transitioning large-scale weather patterns, such as the weakening of an El Niño event, can "straighten" the jet stream, leading to increased precipitation and more persistent wet patterns^[2]. This shift from a blocking, dry weather pattern to a more zonal flow allows periodic rain systems to move in.
• Interaction of moist air masses with cooler air can enhance cloud formation and persistent light precipitation^[3]. When warm, moist air from the Gulf of Mexico or the Pacific meets cooler air over the prairies, condensation leads to drizzle and wet conditions.
• During periods when the jet stream becomes stagnant or meanders, the region can experience prolonged wet or dry periods depending on the position relative to the jet stream's waves^[4].
• Soil saturation from recent heavy rainfall or snowmelt can also enhance the persistence of wet, drizzly conditions, as evaporation from wet soils and surface water sustains local humidity.

In summary, the main causes of sustained wet, drizzly weather on the prairies are:

• Upper-level low pressure systems
• Transition or weakening of dominant weather patterns (such as the end of El Niño)
• Meandering or stagnant jet stream
• Collisions between moist and cool air masses^[1][2][3][4]

These meteorological conditions jointly create the extended periods of soggy, cloudy days typical of a drizzly prairie spring or summer.

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• https://www.producer.com/news/why-our-weather-has-been-cool-and-wet-recently/    
• https://www.cbc.ca/news/canada/saskatchewan/spring-moisture-prairies-1.7232163  
• https://www.manitobacooperator.ca/weather/what-causes-heavy-rainfall-on-the-prairies/  
• https://www.topcropmanager.com/drought-deluge-drought-deluge-18873/