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Jonathan E. Thielen and William A. Gallus Jr.

1. Introduction Mesoscale convective systems (MCSs) play a crucial role climatologically in precipitation across the central United States. These systems account for roughly 30%–70% of the precipitation that occurs during the April–September period (warm season) in this region ( Ashley et al. 2003 ) and are therefore key phenomena of interest when seeking to improve the quantitative precipitation forecast (QPF) skill of models ( Fritsch et al. 1986 ). While this rainfall is essential to

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Aaron Johnson, Xuguang Wang, and Samuel Degelia

doing the DA on a coarser mesoscale grid without radar observations. Wheatley et al. (2015) focus on Warn-on-Forecast time and space scales and limit the forecast lead times to about 1 h. Both of these studies focus on severe weather prediction, which occurs primarily during the day. The prediction system described in this paper is unique in its focus on nocturnal convection. Furthermore, multiscale cycled EnKF is conducted using radar observations on the convection-permitting grid, and

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Aaron Johnson and Xuguang Wang

goals of PECAN was to improve the prediction of nocturnal CI, nocturnal mesoscale convective systems (MCSs), atmospheric bores, and nocturnal LLJs “with a particular focus on the next generation convective-permitting models and advanced assimilation techniques” ( Geerts et al. 2017 ). Much of the literature on model configurations for predicting convection in the Great Plains focuses primarily on daytime convection or discusses only the forecast lead time, with little or no mention of the

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Sean Stelten and William A. Gallus Jr.

-ARW model with 4-km horizontal grid spacing and 50 vertical levels. The domain spanned 1200 km × 1200 km and was centered on the initiation location of the observed PNCI. Initial and lateral boundary conditions were provided every 6 h from 12-km North American Mesoscale Forecast System (NAM) analyses. Runs began at 1200 UTC the day of the nocturnal initiation event, to capture the diurnal evolution of the boundary layer prior to the nocturnal events. The four PBL schemes used included two local mixing

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