Winter storm watch, warning or advisory: what each one means in Macomb County

What is the difference between a watch, a warning and an advisory?

NWS Detroit/Pontiac, the National Weather Service office in White Lake, issues southeast Michigan's winter alerts in three levels that differ in confidence and severity:

• Watch: conditions favor a storm that would meet warning criteria, but its track or timing is still uncertain. Under NWS policy a watch goes out once forecasters reach about 50 percent confidence, and not for a storm less than 12 hours away. By then it becomes a warning or an advisory, or it is canceled.
• Warning: a storm that threatens life or property is occurring, imminent or at least 80 percent likely.
• Advisory: the same confidence, for weather that causes significant inconvenience but stays below warning level.

The amounts behind each alert are guidance, not hard lines. Forecasters may issue a warning or advisory for less snow when timing makes a storm more dangerous, such as snow at rush hour or early in the season.

What does each alert mean in Macomb County?

Criteria from NWS Instruction 10-513 and the NWS heavy snow criteria map for the Macomb County zone (MIZ070). One storm event can last up to 48 hours.

Why does an advisory still mean the plow comes?

Snow removal is triggered by what is on the ground, not by the alert. Our residential trigger is over 2 inches and our commercial trigger is 1 inch, and past it every property on the route is dispatched without a call. Most snows in the advisory range clear a 2-inch trigger, and all of them clear a 1-inch commercial trigger.

So read the forecast amount, not the alert level. A Winter Weather Advisory for 3 to 5 inches is a plowed driveway. An advisory for a glaze of freezing drizzle is a salting decision, not a plowing one. See how much snow before a plow comes.

Why can a warning come in short?

A warning is a forecast, and forecasts are ranges. NWS policy takes the middle of the forecast range, rounded up, and compares it with the local criterion. A forecast of 6 to 8 inches has a middle of 7, so in Macomb County it carries a warning.

That is what happened on February 12 and 13, 2025. Macomb County was under a Winter Storm Warning for 6 to 8 inches. Measured totals came in at 4.0 inches in Clinton Township and New Baltimore, 4.8 in Washington Township and 6.0 in Shelby Township, with sleet and freezing drizzle mixing in along and south of I-94. The warning fell short, and every one of those reports was still double the residential trigger or more.

Your own driveway can also differ from any official report by an inch or two in either direction. How snowfall is measured explains why.

What should you do when a watch goes up?

Use the watch for the jobs that cannot be done in the middle of a storm:

1. Confirm your trigger and stop notes. A departure time, a paver apron or a buried light should already be on file with your snow company.
2. Decide where the cars go. Some Macomb County cities restrict street parking during snow emergencies. See snow emergency parking rules.
3. Stock traction and melt. Sand or grit, plus a de-icer that matches the coming temperatures.
4. Plan for ice, not just snow. If the watch mentions freezing rain, treating walks before it starts works better than treating after.
5. Property managers: confirm that accessible parking and entrances are cleared first, that service is timestamped, and who decides on closing.

How do blizzard and ice storm warnings change the work?

A blizzard is about wind and visibility, not depth. NWS policy notes that blizzard conditions do not require snow to be falling; blowing snow is enough. Driveways cleared during a blizzard drift shut again, so plan for a cleanup pass after the wind eases.

An Ice Storm Warning is the opposite problem: a glaze of a quarter inch or more and nothing for a blade to push. That is treatment and traction work, plus a real risk of falling limbs and downed power lines. See ice storm and power outage safety.

Are the alert names changing?

Some already have. On October 1, 2024, the National Weather Service replaced the Wind Chill Watch, Warning and Advisory with the Extreme Cold Watch, Extreme Cold Warning and Cold Weather Advisory. See what an Extreme Cold Warning means.

The next planned change is to the word "Advisory" itself. The NWS plans to replace Advisory headlines with plain-language headlines that describe the hazard, says the message content will stay the same, and has promised at least six months of public notice. Watches and warnings are not changing. Winter Weather Advisories were still being issued for Macomb County through the 2025-26 winter.