The Role of the Great Plains Low‐Level Jet in Moisture Transport, Streamflow, and Flooding in the Missouri River Basin

Abstract The Missouri River Basin, one of the primary agricultural regions in North America, is prone to large hydroclimatic variability and extreme events. The Great Plains low‐level jet (GPLLJ) is one of the major sources of moisture transport into this region, and concerns over moisture extremes already seen in the interior U.S. have been linked to changes in GPLLJ. However, the relationship between GPLLJ and precipitation in this region remains uncertain, with studies showing conflicting results that may be related to distinct types of jet events. Here, we use daily GPLLJ data to study connections between different types of jet events and precipitation, integrated water vapor transport, and synoptic conditions to better understand GPLLJ‐streamflow linkages. We assess GPLLJ conditions during historical flood events and potential future changes using CMIP6 projections. We find: (a) in May–September, GPLLJ is associated with 29%–46% of monthly precipitation and with increased precipitation intensity; (b) GPLLJ has a consistently positive impact on Missouri River streamflow over the warm season; (c) coupled jets have a larger impact on moisture transport than uncoupled jets, but streamflow impact is reduced, likely due to seasonal timing; (d) unusual jet conditions preceded historical warm‐season flood events; and (e) future projections indicate relatively small changes in GPLLJ meridional wind velocities along with large increases in moisture transport driven by humidity increases. Although future streamflow will be partially dependent on snowmelt from the upper basin, the projected intensification of warm‐season moisture transport to the Missouri River suggests possible increases in future flood risk.