Here's What Determines the Type of Winter Precipitation That Falls
by David Moran, on Jan 3, 2019 2:42:24 PM
All precipitation develops in the same way, but in winter there can be quite a variety of types. Freezing rain, sleet, snow, are all possible when it gets cold outside.
Freezing rain forms when the air higher in the atmosphere is above freezing while the ground temp is below 32°F. Warmer air will cause falling snow to melt as it falls. When it makes contact with objects on or near the ground where the temps are at or below freezing, such as power lines or tree limbs, a coating of ice forms. This type of weather is extremely hazardous for travel and leads to extended power outages.
WeatherOps Freezing Rain Accumulation
Sleet forms in a similar way to freezing rain. In this case, the snowflakes only partially melt before refreezing. While it doesn't accumulate on power lines, sleet can build up on roads leading to traffic problems.
WeatherOps Sleet Accumulation
When the atmosphere is entirely below freezing, snow is the resulting precipitation type. Snowflakes develop in the dendritic growth zone. Here, no melting occurs, and snow begins to accumulate on the ground.
WeatherOps Snow Accumulation
In any winter weather event, there can be more than one precipitation type. For example, if freezing rain is occurring, air can cool because of the falling precipitation evaporating. This temperature change can allow the freezing rain to transition to sleet, and eventually snow, as the depth of the warm air decreases and erodes completely.
Schematic of Precipitation Types
All winter precipitation can cause hazards to travel and infrastructure. Understanding whether you will be dealing with rain, snow, or sleet can make a difference in transit times, how you prepare for a trip, possible cancellations, and outages.