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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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Philip T. Bergmaier and Bart Geerts

1. Introduction Much attention has been devoted to understanding how large lakes (e.g., the North American Great Lakes) influence the weather and climate of the surrounding region. Lake-effect (LE) convection, which typically ensues when cold air masses migrate over relatively warmer open water during the fall and winter, often leads to heavy snowfall downwind of the lakes impacting local travel and commerce. More than a half century of research related to LE snowstorms has yielded significant

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

) the lake-effect mode along the transect, 2) the mean 950–850-hPa zonal wind speed , and 3) the LCAPE. The lake-effect mode was identified following Campbell et al. (2016) . Given a lack of regular upper-air sounding data directly upstream of Lake Ontario and the low temporal resolution (12 h) of sounding data, the data for and LCAPE came from the North American Regional Reanalysis (NARR; Mesinger et al. 2006 ), produced at a horizontal grid spacing of 32 km and available with a vertical

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Peter G. Veals and W. James Steenburgh

1. Introduction The Great Lakes of North America produce frequent, sometimes intense, lake-effect snowstorms during the cool season (e.g., Niziol et al. 1995 ). High snowfall rates, low visibility, and heavy accumulations impact commerce and transportation, but also contribute to a vibrant winter-sports economy ( Tug Hill Commission 2014 ). The region east of Lake Ontario, in particular, observes some of the most intense snowstorms in the world, many enhanced over the Tug Hill Plateau

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W. James Steenburgh and Leah S. Campbell

-effect convection organized on scales larger than individual cells or bands) can be generated during periods of relatively cold flow along the long axis of elongated lakes such as Lake Ontario in eastern North America ( Peace and Sykes 1966 ; Reinking et al. 1993 ; Ballentine et al. 1998 ; Steiger et al. 2013 ; Veals and Steenburgh 2015 ; Kristovich et al. 2017 ). These long-lake-axis-parallel (LLAP) systems have produced snowfall rates as high as 30.5 cm (12 in.) in 1 h, storm-total accumulations of 358

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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

2015 ). Much of the same region was blanketed by up to an additional 125 cm over the following three days (19–21 November 2014). The November 2014 Buffalo storms provide an example of the frequent, sometimes intense, lake-effect snowstorms produced by the Great Lakes of North America during the cool season (e.g., Niziol et al. 1995 ). The area to the east of Lake Ontario in particular experiences some of the most intense snowstorms in the world. High snowfall rates, low visibility, and heavy

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

1. Introduction Some of the world’s most intense lake-effect snow events occur downstream of the North American Great Lakes. Lake-effect snow events often only impact a relatively small area, but, within that narrow corridor, snowfall amounts and rates can be substantial. Lake-effect snowbands are relatively shallow, ~2–3 km deep, and, consequently, Weather Surveillance Radar-1988 Doppler (WRS-88D) coverage of these events from long ranges can be insufficient to capture many of the small

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

1. Introduction Cold-air outbreaks over the North American Great Lakes in late fall and early winter often lead to lake-effect (LE) snowfall, a phenomenon that occurs when relatively cool air moves across and is modified by a much warmer large body of water. Warming and moistening of the near-surface air produces a well-mixed boundary layer driven by moist convection and deepening with fetch from the upwind shore. Such convection tends to organize linearly into bands, parallel to the low

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Leah S. Campbell and W. James Steenburgh

1. Introduction Lake-effect snowstorms generated over the Great Lakes of North America and other bodies of water can produce intense, extremely localized snowfall (e.g., Andersson and Nilsson 1990 ; Steenburgh et al. 2000 ; Eito et al. 2005 ; Laird et al. 2009 ; Kindap 2010 ). Forecasters still struggle, however, to accurately predict the timing and location of the heaviest snowfall during lake-effect events, which disrupt local and regional transportation, education, utilities, and

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

-00016.1 . Barnes , S. L. , F. Caracena , and A. Marroquin , 1996 : Extracting synoptic-scale diagnostic information from mesoscale models: The Eta model, gravity waves, and quasigeostrophic diagnostics . Bull. Amer. Meteor. Soc. , 77 , 519 – 528 , doi: 10.1175/1520-0477(1996)077<0519:ESSDIF>2.0.CO;2 . Benjamin , S. G. , and Coauthors , 2016 : A North American hourly assimilation and model forecast cycle: The Rapid Refresh . Mon. Wea. Rev. , doi: 10.1175/MWR-D-15-0242.1 , in press . Bergeron

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