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Philip T. Bergmaier and Bart Geerts

initially forms upstream along a baroclinic boundary (i.e., LBF1) along the southern bulge of Lake Ontario. The cooler, shallow air mass south of LBF1 resembles a density current that advances northward over the lake while also being advected eastward. Such a current has just a single solenoidal circulation with horizontal vorticity pointing eastward along the isotherms. Differential surface friction ( Holroyd 1971 ; Steenburgh and Campbell 2017 ) initially contributes to the low-level convergence

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David A. R. Kristovich, Luke Bard, Leslie Stoecker, and Bart Geerts

intensity on each lake. The current study focuses on those influences that Mann et al. classified as direct. The most commonly cited processes by which upwind lakes are thought to have a direct influence on lake-effect convection over a downwind lake ( Niziol et al. 1995 ; Rose 2000 ; Rodriguez et al. 2007 ; Cordeira and Laird 2008 ) include 1) development of a low-stability, humid layer through mixing over the upwind lake, which allows the downwind lake-effect boundary layer to deepen and produce

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David A. R. Kristovich, Richard D. Clark, Jeffrey Frame, Bart Geerts, Kevin R. Knupp, Karen A. Kosiba, Neil F. Laird, Nicholas D. Metz, Justin R. Minder, Todd D. Sikora, W. James Steenburgh, Scott M. Steiger, Joshua Wurman, and George S. Young

the eastern Great Lakes; and 3) interactions between lake-effect systems (LeS) and Tug Hill east of Lake Ontario. These complementary components provided an opportunity to enhance the understanding and prediction of lake-effect snowstorms. Specifically, the scientific goals related to OWLeS research are to 1) understand the development of, and interactions between, internal planetary boundary layers (PBLs) and residual layers resulting from advection over multiple mesoscale water bodies and

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

typical organizations] occur when a continental/maritime polar (cP/mP) air mass is modified via heat and moisture fluxes by a large body of water (in this case, Lake Ontario), leading to the development of moist convection. The surface-based convective cloud tops generally range between 1 and 4 km above ground level (AGL), and the storms form in bands that are approximately 10–25 km wide and parallel to the mean boundary layer wind direction. b. Lake-effect lightning Winter lightning has been observed

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Philip T. Bergmaier, Bart Geerts, Leah S. Campbell, and W. James Steenburgh

. Further evidence for this interpretation comes from the tilting of this convergence zone with height between 43.7° and 43.75°N in Fig. 7c , toward the colder side of the land-breeze front (i.e., the left side). The shallow ~500-m-deep leading edge of the southerly flow (i.e., at 43.74°N) resembles a density current head, capped by front-to-rear northerly flow (shaded in blue) that rose over this leading edge within the primary updraft. This suggests a significant buoyancy gradient across the boundary

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

) depicted in scale at bottom. Box in (a) shows location of (b). Red circles represent COOP observing sites with annual average lake-effect snowfall (cm) from Veals and Steenburgh (2015) annotated. Black circles and blue diamonds indicate the locations of MRRs and meteorological stations (Met), respectively, at SIB, SC, NR, and UP. The green triangle represents the location of the KTYX Doppler radar. Lake-effect precipitation forms when boundary layer convection is initiated as cold air moves over a

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Leah S. Campbell and W. James Steenburgh

.1175/2008MWR2369.1 . 10.1175/2008MWR2369.1 Colle , B. A. , R. B. Smith , and D. A. Wesley , 2013 : Theory, observations, and predictions of orographic precipitation. Mountain Weather Research and Forecasting: Recent Progress and Current Challenges , F. K. Chow, S. F. J. De Wekker, and B. J. Snyder, Eds., Springer Atmospheric Sciences, Springer, 291–344. 10.1007/978-94-007-4098-3_6 Conrick , R. , H. D. Reeves , and S. Zhong , 2015 : The dependence of QPF on the choice of boundary and

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

2017 ; Steenburgh and Campbell 2017 ; Eipper et al. 2018 ). In particular, Eipper et al. (2018) found that cold air advection (CAA) in the upper portion of the boundary layer (BL) was strongly correlated with the inland penetration of lake-effect radar echoes. However, the influence of environmental baroclinity on the far-inland kinematic and dynamic structure of lake-effect snowbands has received little attention. Here we extend the investigation of Eipper et al. (2018) by evaluating

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

a relatively warm lake surface. If the lake–air temperature difference is sufficient, turbulent sensible and latent heat fluxes moisten and destabilize the boundary layer, leading to the formation of shallow, but often intense, convective clouds and snowfall. Lake-effect convection exhibits multiple modes of mesoscale organization, including widespread cellular convection, widespread wind-parallel linear roll circulations, localized wind-parallel bands, and localized mesoscale vortices

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