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1. Climatology of Lake-Effect Snow Days Along the Southern Shore of Lake Michigan: What Is the Sensitivity to Environmental Factors and Snowband Morphology?

   https://doi.org/10.3389/frwa.2022.826293  

   Clark, Craig A.; Metz, Nicholas D.; Goebbert, Kevin H.; Ganesh-Babu, Bharath; Ballard, Nolan; Blackford, Andrew; Bottom, Andrew; Britt, Catherine; Carmer, Kelly; Davis, Quenten; et al (March 2022, Frontiers in Water)

   The Laurentian Great Lakes have substantial influences on regional climatology, particularly with impactful lake-effect snow events. This study examines the snowfall, cloud-inferred snow band morphology, and environment of lake-effect snow days along the southern shore of Lake Michigan for the 1997–2017 period. Suitable days for study were identified based on the presence of lake-effect clouds assessed in a previous study and extended through 2017, combined with an independent classification of likely lake-effect snow days based on independent snowfall data and weather map assessments. The primary goals are to identify lake-effect snow days and evaluate the snowfall distribution and modes of variability, the sensitivity to thermodynamic and flow characteristics within the upstream sounding at Green Bay, WI, and the influences of snowband morphology. Over 300 lake-effect days are identified during the study period, with peak mean snowfall within the lake belt extending from southwest Michigan to northern Indiana. Although multiple lake-effect morphological types are often observed on the same day, the most common snow band morphology is wind parallel bands. Relative to days with wind parallel bands, the shoreline band morphology is more common with a reduced lower-tropospheric zonal wind component within the upstream sounding at Green Bay, WI, as well as higher sea-level pressure and 500-hPa geopotential height anomalies to the north of the Great Lakes. Snowfall is sensitive to band morphology, with higher snowfall for shoreline band structures than for wind parallel bands, especially due south of Lake Michigan. Snowfall is also sensitive to thermodynamic and flow properties, with a greater sensitivity to temperature in southwest Michigan and to flow properties in northwest Indiana. 

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2. The Contribution of Lake-Effect Snow to Annual Snowfall Totals in the Vicinity of Lakes Erie, Michigan, and Ontario

   https://doi.org/10.3389/frwa.2022.782910  

   Jones, Erin A.; Lang, Carrie E.; Laird, Neil F. (March 2022, Frontiers in Water)

   In the Great Lakes region, total cold-season snowfall consists of contributions from both lake-effect systems (LES) and non-LES snow events. To enhance understanding of the regional hydroclimatology, this research examined these separate contributions with a focus on the cold seasons (October–March) of 2009/2010, a time period with the number of LES days substantially less than the mean, and 2012/2013, a time period with the number of LES days notably greater than the mean, for the regions surrounding Lakes Erie, Michigan, and Ontario. In general, LES snowfall exhibited a maximum contribution in near-shoreline areas surrounding each lake while non-LES snowfall tended to provide a more widespread distribution throughout the entire study regions with maxima often located in regions of elevated terrain. The percent contribution for LES snowfall to the seasonal snowfall varied spatially near each lake with localized maxima and ranged in magnitudes from 10% to over 70%. Although total LES snowfall amounts tended to be greater during the cold season with the larger number of LES days, the percent of LES snowfall contributing to the total cold-season snowfall was not directly dependent on the number of LES days. The LES snowfall contributions to seasonal totals were found to be generally larger for Lakes Erie and Ontario during the cold season with a greater number of LES days; however, LES contributions were similar or smaller for areas in the vicinity of Lake Michigan during the cold season with a smaller number of LES days. 

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3. Elevated Mixed Layers during Great Lake Lake-Effect Events: An Investigation and Case Study from OWLeS

   https://doi.org/10.1175/MWR-D-22-0344.1  

   Greybush, Steven J.; Sikora, Todd D.; Young, George S.; Mulhern, Quinlan; Clark, Richard D.; Jurewicz, Michael L. (January 2024, Monthly Weather Review)

   Abstract Data from rawinsondes launched during intensive observation periods (IOPs) of the Ontario Winter Lake-Effect Systems (OWLeS) field project reveal that elevated mixed layers (EMLs) in the lower troposphere were relatively common near Lake Ontario during OWLeS lake-effect events. Conservatively, EMLs exist in 193 of the 290 OWLeS IOP soundings. The distribution of EML base pressure derived from the OWLeS IOP soundings reveals two classes of EML, one that has a relatively low-elevation base (900–750 hPa) and one that has a relatively high-elevation base (750–500 hPa). It is hypothesized that the former class of EML, which is the focus of this research, is, at times, the result of mesoscale processes related to individual Great Lakes. WRF reanalysis fields from a case study during the OWLeS field project provide evidence of two means by which low-elevation base EMLs can originate from the lake-effect boundary layer convection and associated mesoscale circulations. First, such EMLs can form within the upper-level outflow branches of mesoscale solenoidal circulations. Evacuated Great Lakes–modified convective boundary layer air aloft then lies above ambient air of a greater static stability, forming EMLs. Second, such EMLs can form in the absence of a mesoscale solenoidal circulation when Great Lake–modified convective boundary layers overrun ambient air of a greater density. The reanalysis fields show that EMLs and layers of reduced static stability tied to Great Lakes–modified convective boundary layers can extend downwind for hundreds of kilometers from their areas of formation. Operational implications and avenues for future research are discussed. 

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4. Synoptic Conditions and Lake-to-Lake Connections for Days with Lake-Effect on All of the Great Lakes

   https://doi.org/10.1175/JAMC-D-23-0006.1  

   Laird, Neil F.; Crossett, Caitlin C.; Britt, Catherine J.; Metz, Nicholas D.; Carmer, Kelly; McBroom, Braedyn D. (April 2024, Journal of Applied Meteorology and Climatology)

   Abstract An investigation of lake-effect (LE) and the associated synoptic environment is presented for days when all five lakes in the Great Lakes (GL) region had LE bands (5LD). The study utilized an expanded database of observed LE clouds over the GL during 25 cold seasons (October–March) from 1997/1998 to 2021/2022. LE bands occurred on 2870 days (64% of all cold-season days). Nearly a third of all LE bands occurred during 5LD, although 5LD consisted of just 17.1% of LE days. A majority of 5LD (56.5%) had L2L and these days comprised 43.5% of all L2L occurrences. 5LD occurred with a mean of 26.1 (SD=6.2) days per cold season until 2008/2009 and then decreased to a mean of 13.8 (SD=5.5) days during subsequent cold seasons. January and February had the largest number of consecutive LE days in the GL with a mean of 5.7 and 5.4 days, respectively. As the number of consecutive LE days increase, both the number of 5LD and the occurrence of consecutive 5LD increase. This translates to an increased potential of heavy snowfall impacts in multiple, localized areas of the GL for extended time periods. The mean composite synoptic pattern of 5LD exhibited characteristics consistent with lake-aggregate disturbances and showed similarity to synoptic patterns favorable for LE over one or two of the GL found by previous studies. The results demonstrate that several additional areas of the GL are often experiencing LE bands when a localized area has active LE bands occurring. 

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5. A Climatology of Easterly Wind Lake-Effect and Lake-Enhanced Precipitation Events over the Western Lake Superior Region

   https://doi.org/10.1175/JAMC-D-22-0080.1  

   Sandstrom, Joshua D.; Cordeira, Jason M.; Hoffman, Eric G.; Metz, Nicholas D. (February 2023, Journal of Applied Meteorology and Climatology)

   Abstract Lake-effect precipitation is convective precipitation produced by relatively cold air passing over large and relatively warm bodies of water. This phenomenon most often occurs in North America over the southern and eastern shores of the Great Lakes, where high annual snowfalls and high-impact snowstorms frequently occur under prevailing west and northwest flow. Locally higher snow or rainfall amounts also occur due to lake-enhanced synoptic precipitation when conditionally unstable or neutrally stratified air is present in the lower troposphere. While likely less common, lake-effect and lake-enhanced precipitation can also occur with easterly winds, impacting the western shores of the Great Lakes. This study describes a 15-year climatology of easterly lake-effect (ELEfP) and lake-enhanced (ELEnP) precipitation (conjointly Easterly Lake Collective Precipitation: ELCP) events that developed in east-to-east-northeasterly flow over western Lake Superior from 2003 to 2018. ELCP occurs infrequently but often enough to have a notable climatological impact over western Lake Superior with an average of 14.6 events per year. The morphology favors both single shore-parallel ELEfP bands due to the convex western shoreline of Lake Superior and mixed-type banding due to ELEnP events occurring in association with “overrunning” synoptic-scale precipitation. ELEfP often occurs in association with a surface anticyclone to the north of Lake Superior. ELEnP typically features a similar northerly-displaced anticyclone and a surface cyclone located over the U.S. Upper Midwest that favor easterly boundary-layer winds over western Lake Superior. 

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