This blog post explains the lake-effect snow event sweeping the Great Lakes region from Sunday into Monday, why it forms, how it can produce intense and highly localized snow bands, and the rare phenomenon of thundersnow. Drawing on three decades of meteorological experience, I unpack the atmospheric mechanics, forecast challenges, and practical advice for residents and travelers in affected areas.
How lake-effect snow forms
Lake-effect snow develops when a mass of cold, dry air moves over the relatively warmer waters of the Great Lakes. This temperature contrast causes air to pick up moisture and heat from the lake surface, creating instability and strong upward motion.
The rising moist air cools and condenses, forming narrow, intense snow bands that stream downwind. These bands can produce heavy snowfall rates in very confined corridors.
Conditions can change rapidly over short distances.
The physics behind the bands
At the scale of a lake-effect event, small differences in wind direction, lake water temperature, and atmospheric stability determine where bands form and how intense they become. When the cold air is deep and the lake remains open (not frozen), the vertical motion is stronger and snowfall rates increase.
Key elements include fetch (how far the air travels over open water), lapse rates (how quickly temperature decreases with altitude), and low-level shear that can organize or disrupt band structure. The result is often a mosaic of heavy snow, light snow, and clear areas across the downwind shorelines.
Localized impacts and forecasting challenges
Lake-effect snow is uniquely challenging for forecasters because its impacts are so spatially variable. A road may be plowed and clear one mile and white-out with several inches of accumulation the next.
That unpredictability complicates travel planning, emergency response, and infrastructure operations. As a forecaster, I emphasize communicating the uncertainty: pinpoint forecasts are less reliable than probabilistic guidance showing where heavy bands are most likely.
Real-time observations and high-resolution models are crucial for short-term alerts.
What residents and travelers should know
Prepare for rapidly changing conditions and localized disruption when lake-effect snow is expected. Practical steps include:
Thundersnow: rare, loud, and telling
Meteorologists are also watching for thundersnow, a rare but dramatic component of some lake-effect storms. It occurs when the strong upward motion within a snow band is sufficient to generate electrical charge separation, producing lightning and thunder within a snow cloud.
Thundersnow is short-lived but signals very vigorous convection and often accompanies the heaviest snowfall rates. When it happens, snowfall can briefly intensify and visibility can drop precipitously.
When and why lightning appears in snow
As FOX Weather Meteorologist Bayne Froney noted, the critical ingredients for thundersnow mirror those for severe summer storms: cold air aloft, a warm moist source (the lake), and strong instability.
In the winter context the precipitation is snow rather than rain, but the dynamics that generate lightning are similar.
For observers, hearing thunder during snowfall is a clear signal to seek shelter and expect the heaviest accumulation nearby.
For forecasters and emergency managers, thundersnow is an unmistakable marker of a storm’s intensity and a cue to escalate warnings.
Lake-effect snow events like this one are vivid reminders of the Great Lakes’ influence on regional weather.
Here is the source article for this story: What is thundersnow and how does it happen? | Latest Weather Clips