Winter weather alerts explained
Winter alerts can be confusing because the same amount of snow can lead to a warning in Atlanta and only an advisory in Minneapolis. Each local National Weather Service office sets criteria based on what disrupts daily life in its area.
The main winter alerts
| Alert | Meaning |
|---|---|
| Winter storm warning | Heavy snow, sleet or ice is expected or happening. Travel will be very difficult or impossible. |
| Winter storm watch | A significant winter storm is possible, usually 12 to 48 hours ahead. |
| Winter weather advisory | Snow, sleet or freezing rain will cause slippery roads and delays but stay below warning level. |
| Blizzard warning | Wind of 35 mph or more with snow cutting visibility under a quarter mile for three hours or more. |
| Ice storm warning | Damaging accumulations of ice from freezing rain. |
| Lake effect snow warning | Heavy, localized snow bands downwind of the Great Lakes. |
| Extreme cold warning | Life-threatening cold or wind chills (formerly the wind chill warning). |
| Cold weather advisory | Hazardous cold that can cause frostbite with long exposure. |
| Freeze warning | Temperatures of 32°F or lower that threaten crops and plants during the growing season. |
Why snowfall thresholds differ
A city that rarely sees snow has few plows and drivers with little winter experience, so two inches can shut it down. Offices in the South therefore use low thresholds for warnings, while offices in the northern Plains, Great Lakes and mountains use much higher ones. The text of every warning states the expected totals and timing, which matter more than the alert name.
How a storm usually unfolds
- One to two days before: a winter storm watch is issued.
- About a day before: the watch becomes a warning in the hardest-hit areas and an advisory at the edges.
- During the storm: warnings may be upgraded to blizzard or ice storm warnings, extended, or cancelled early.