WEST MICHIGAN - As we navigate our way through another winter in Michigan and a massive winter storm approaches, it's important to understand the various thresholds of a watch/warning/advisory that are issued by the National Weather Service. What do they mean? Each one has its own specific meaning, and all are issued based on the degree of severity and as a heightened awareness to the public. Most of our West Michigan counties are governed by the Grand Rapids NWS office, although our extreme southern counties of Berrien, Cass, St. Joseph, and Branch are overseen by the NWS office in North Webster, Indiana. Most of the time these offices communicate with each other on watches/warnings/advisories, so there's usually continuity across our viewing area. Keep in mind the criteria for all of these differ slightly across states/regions/nationally, but we'll focus on the NWS criteria from Grand Rapids.
These Winter Weather Alerts are used as a starting point. They provide a framework for NWS Meteorologists to issue an actual alert. Deviations to these guidelines can be made on a case by case basis (i.e. early/late season events, timing of day, etc.) Lets break each one down and their meaning.
WINTER WEATHER ADVISORY
- Issued for less than 3 inches of snow, but more than 8 inches in 18 hours or less. Two inches but less than 6 inches in 8 hours or less. Freezing Rain and Freezing Drizzle - Situations that cause significant inconveniences, and do not meet warning criteria. If caution is not used, this could lead to life-threatening situations. Ice accumulation causes driving or walking problems, but no damage to trees or power lines.Sleet - Situations that cause significant inconveniences, and do not meet warning criteria. If caution is not used, this is generally a 1/2 inch but less than 3 inches of sleet accumulation
WINTER STORM WATCH
- Issued in advance of the storm (usually at least 24 to 36 hours). It indicates the risk of a hazardous winter weather event has increased (at least a 50% chance of it occurring), but its occurrence, location, and/or timing is still uncertain. It is intended to provide enough lead time so you can make plans to stay safe. While rare for our area, a Blizzard Watch may be issued instead.
WINTER STORM WARNING
- Issued for 8 inches or more of snow in 18 hours or less. Six inches or more in 8 hours or less. An accumulation of sleet of at least 3 inches. Ice - A significant, and possibly damaging, accumulation of ice. Normally a coating of at least 1/4-inch.
BLIZZARD WARNING
- Blizzard Warnings are not always issued for meeting the traditional 1/4 mile visibility, sustained winds or gusts to 35 or greater, and falling/blowing snow for 3 or more hours. That is a starting point for sure, but impacts to society, regional scope/severity, and the time it will take the population to recover are a big factor when triggering a Blizzard Warning.
It's important to note that many watches/warnings/advisories have been deleted or are not used anymore by our local office in order to simplify things. I have been part of NWS Grand Rapids meetings with other media outlets for decades, and their goal is to make things easier for the general public to absorb and interpret. That means no more lake effect snow advisories, lake effect snow warnings, blizzard watches, ice storm watches, or ice storm warnings. Any type of winter weather we experience now falls under the categories above.
We do have some cold weather tips and winter storm tips from the National Weather Service as this storm approaches. See images below.
