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Philip T. Bergmaier and Bart Geerts

1. Introduction During the cool season, lake-effect (LE) snowfall is common over and downwind of the Laurentian Great Lakes in North America when cold air masses are advected across the warmer lake surface. The large surface heat and moisture fluxes that result lead to destabilization of the boundary layer (BL) over the lake and the formation of clouds and precipitation. When the prevailing BL flow is oriented along the major axis of an elongated lake such as Lake Ontario, LE precipitation can

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

Ontario. Surface observations confirmed that, throughout the morning of 28 January, skies were clear west and south of Lake Erie and persistent low-level clouds extended from Lake Erie to Lake Ontario. It might be expected that, since Lake Erie was >95% ice covered ( GLERL 2017 ), lake-effect convection would be unlikely. However, observations from Gerbush et al. (2008) indicated that weak upward heat and moisture fluxes can occur even over ice-covered areas of Lake Erie. In addition, MODIS imagery

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Peter G. Veals, W. James Steenburgh, and Leah S. Campbell

of moisture and location of the saturated region ( Barcilon et al. 1979 ; Barcilon and Fitzjarrald 1985 ; Rotunno and Ferretti 2001 ; Jiang 2003 ). Microphysical processes and mountain wave dynamics also contribute to a highly nonlinear response in orographic precipitation, so caution must be used with simplistic treatment of these parameters (e.g., Jiang 2003 ; Jiang and Smith 2003 ; Colle 2004 ; Smith and Skyllingstad 2011 ). The effects of are not limited to the determination of flow

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Philip T. Bergmaier and Bart Geerts

insight into the processes controlling their development and evolution (e.g., Wiggin 1950 ; Peace and Sykes 1966 ; Holroyd 1971 ; Lavoie 1972 ; Kelly 1982 ; Byrd et al. 1991 ; Niziol et al. 1995 ; Laird et al. 2003 ; Veals and Steenburgh 2015 ; Welsh et al. 2016 ). For instance, it is well understood that heat and moisture fluxes between a warmer body of water, such as a lake, and colder ambient air above will gradually lead to warming and moistening, and therefore destabilization, of the

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

surface heat and moisture fluxes should cause convection to weaken as it moves inland. Several authors have suggested that the topography of Tug Hill plays an important role in locally enhancing lake-effect snowfall ( Reinking et al. 1993 ; Niziol et al. 1995 ; Veals and Steenburgh 2015 ). Modeling studies have diagnosed orographic enhancement of lake-effect snowfall over the modest topography (200–500-m relief) adjacent to Lakes Michigan and Erie and the much taller topography of the Wasatch

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

formulation of the latter to modulate by updraft speed and horizontal wind speed. Aside from its connection to the up–down model, a deeper CBL indicates a deeper layer of moisture available to LLAP bands [in typical near-saturated conditions (e.g., Byrd et al. 1991 ; Reinking et al. 1993 ; Minder et al. 2015 ; Campbell et al. 2016 )] and of snow generation through cloud microphysical processes. A deeper CBL also indicates higher values of CAPE for a given value of near-surface instability (resulting

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

1. Introduction Lake-effect snowfall impacts many regions downwind of the Great Lakes every winter, with locations such as the Tug Hill Plateau of upstate New York receiving average annual accumulations over 200 cm. As continental polar air masses cross the Great Lakes, vertical fluxes of heat and moisture from the lake surfaces into the overlying air masses moisten and destabilize the lower boundary layer (BL). This allows for the formation of sometimes vigorous BL convection, often manifested

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

moisture) that is accumulated in the boundary layer. Depending on the strength and orientation of the prevailing wind, land-breeze fronts of this type from opposing shorelines (e.g., the north and south shorelines of Lake Ontario) may converge near the middle of the lake, leading to the development of a single midlake band ( Passarelli and Braham 1981 ; Braham 1983 ). Alternatively, a land-breeze front may remain close to the shoreline where the prevailing wind has an onshore component, resulting in

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Karen A. Kosiba, Joshua Wurman, Kevin Knupp, Kyle Pennington, and Paul Robinson

R. M. Wakimoto , 2008a : Kinematic and moisture characteristics of a nonprecipitating cold front observed during IHOP. Part I: Across-front structures . Mon. Wea. Rev. , 136 , 147 – 172 , https://doi.org/10.1175/2007MWR1908.1 . 10.1175/2007MWR1908.1 Friedrich , K. , D. E. Kingsmill , C. Flamant , H. V. Murphey , and R. M. Wakimoto , 2008b : Kinematic and moisture characteristics of a nonprecipitating cold front observed during IHOP. Part II: Along-front structures . Mon

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W. James Steenburgh and Leah S. Campbell

, and mixed forest (not shown). Analyses from the NCEP North American Mesoscale Forecast System (NAM) provide initial atmospheric and land surface (soil moisture, soil temperature, and snow cover) conditions at 1200 UTC 10 December 2013, as well as lateral boundary conditions at 6-h intervals throughout the study period. For Great Lakes surface temperatures, we use the Great Lakes Environmental Research Laboratory (GLERL) Great Lakes Coastal Forecasting System analysis at 6-h intervals. In areas

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