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Jake P. Mulholland, Jeffrey Frame, Stephen W. Nesbitt, Scott M. Steiger, Karen A. Kosiba, and Joshua Wurman

, (d) 0700, (e) 0800, and (f) 0900 UTC 7 Jan 2014. As the short-wave trough departs the region to the northeast and the midlevel short-wave ridge approaches, BL winds back from northwest (NW) to west (W), forcing the Georgian Bay band northward ( Fig. 18 ). Eventually, the winds back sufficiently for the connection to be lost ( Fig. 18d ). The shear zone and associated string of misovortices over Lake Ontario may have been influenced by this connection, at least during a portion of this event

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Daniel T. Eipper, George S. Young, Steven J. Greybush, Seth Saslo, Todd D. Sikora, and Richard D. Clark

wind shear, CBL depth, and synoptic-scale forcing ( Holroyd 1971 ; Niziol 1987 ; Byrd et al. 1991 ; Niziol et al. 1995 ; Ballentine et al. 1998 ; Campbell et al. 2016 ). An important focus of recent research has been the often-dramatic enhancement of lake-effect snowfall over the Tug Hill Plateau, which lies east of Lake Ontario (e.g., Veals and Steenburgh 2015 ). The recent Ontario Winter Lake-effect Systems (OWLeS) field campaign from December 2013 to January 2014 ( Kristovich et al. 2017

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Philip T. Bergmaier and Bart Geerts

lower boundary layer over the water. Over time (or with “fetch”), the depth of the boundary layer increases, either through continued modification by the lake or by other processes such as thermally driven surface convergence or even synoptic forcing, to the point that clouds and precipitation form. Over the North American Great Lakes, a lake-to-850-hPa temperature difference of at least 13 K (i.e., the dry adiabatic lapse rate) is typically required for the development of LE precipitation ( Holroyd

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Scott M. Steiger, Tyler Kranz, and Theodore W. Letcher

during OWLeS because of a very deep boundary layer. Although synoptic forcing largely caused the deep boundary layer, we speculate that the depth of the boundary layer may have been increased by an upwind elevated mixed layer (possibly formed by the deep boundary layer mixing over the upper Great Lakes). A comparison between upwind and downwind soundings taken around Lake Ontario indicates that this lake-modified boundary layer traversed the stable surface layer over the Canadian landmass between

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Leah S. Campbell, W. James Steenburgh, Peter G. Veals, Theodore W. Letcher, and Justin R. Minder

of convection was largest near the lake shore and decreased inland to Tug Hill ( Figs. 13 , 14a–c , 15 ). These factors enabled precipitation rates to be nearly as high in the coastal lowlands as over Tug Hill ( Fig. 13a ). We note, however, that there is a weak downstream broadening of the LLAP bands, so that snowfall occurs over a larger area as one moves inland over Tug Hill. In contrast, during nonbanded periods, the mesoscale forcing is weaker and there is a clear increase in echo

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Dan Welsh, Bart Geerts, Xiaoqin Jing, Philip T. Bergmaier, Justin R. Minder, W. James Steenburgh, and Leah S. Campbell

band organization is lesser or absent. This accentuates the role of lifting by these alternate mechanisms in the absence of strong convective forcing. Fig . 4. Data from radiosondes released nearly simultaneously from (a) Oswego, (b) SC, and (c) NR (locations shown in Fig. 2 ), plotted on a skew T –log p diagram. The wind is plotted on the right of each diagram (long barb = 5 m s −1 ). (d) Corresponding virtual potential temperature ( θ υ ) profiles. This research focuses on observations

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