Weekly Weather Event -Week of Jan. 20January 24, 2020
Winter Weather Advisories are in effect Friday night into Saturday for portions of southeast Wisconsin near the Milwaukee area and northeast Illinois. An estimated 3 to 6 inches of snow are expected to fall in this region with a potential for a wintery mix of snow and rain. Periods of moderate to heavy snowfall may also reduce visibility to less than a mile.
The National Weather Service issues winter weather advisories “for accumulations of snow, freezing rain, freezing drizzle, and sleet which will cause significant inconveniences and, if caution is not exercised, could lead to life-threatening situations.” The difference between the various types of frozen precipitation listed lies in the temperature of the air between the clouds and the ground. If the entire layer of air between the cloud and the ground remains below freezing, precipitation will reach the ground as snow.
Sleet and freezing rain are formed by a similar process, though these types of precipitation are distinct and have different end results. Occasionally, snowflakes will encounter a relatively thin layer in the atmosphere that is above freezing, and they will melt into raindrops. Sleet is formed when these raindrops meet a layer of air below freezing and refreeze into pellets of ice before reaching the ground. In contrast, freezing rain occurs when these raindrops fall through a layer of colder air but remain liquid until they come in contact with the ground.
Freezing rain is often considered the most dangerous form of frozen precipitation as it can create a solid sheet of ice on roads or accumulate on powerlines. Though not expected in the areas mentioned, all forms of frozen precipitation can result in slick roads and dangerous driving conditions. Drivers should take appropriate caution when on the roads.