When winter weather becomes active watches, warnings, and advisories can be issued at a moments notice. But what do they mean? If can often be hard to figure out what the difference between a Winter Storm Watch or a Winter Storm Warning is. Below is the criteria that the National Weather Service uses to determine which watch, warning, or advisory to issue.
Winter Storm Watch- Issued if there is a threat for heavy snow or sleet, significant accumulations of freezing rain or freezing drizzle, or any combination thereof. Usually issued for the second and third periods of a forecast (i.e., 12 to 36 hours in advance of the event). The definition of heavy snow in the Paducah forecast areais 4 inches or more in 12 hours, or 6 inches or more in 24 hours.
Winter Storm Warning- Issued if there is a high probablility that a mix of severe winter weather will occur, such as heavy snow or sleet, significant accumulation of freezing rain or freezing drizzle, or any combination thereof. Normally issued for the first forecast period (i.e., less than or equal to 12 hours in advance of the event). A Winter Storm Warning may be extended into the second period of the forecast if the weather situation warrants.
Winter Weather Advisory - Issued when a mixture of precipitation, such as snow, sleet, and freezing rain or drizzle, is expected but accumulations will not reach warning criteria. If all snow, accumulation should average at least 2 inches, but less than 4 inches. If only freezing rain or drizzle is expected, then the product is issued as a Freezing Rain or Freezing Drizzle Advisory. The criteria are subjective and may vary depending on the time of year and the public's perceived acclamation to winter weather conditions.
Blizzard Warning- Issued for winter storms with sustained winds or frequent gusts of 35mph or greater, and considerable falling and/or blowing snow reducing visibilities to 1/4 mile or less. These conditions should last for at least 3 hours.
Ice Storm Warning - Issued for those winter storms expected to produce damaging ice accumulation of 1/4 inch or more.
Wind Chill Warning - Issued when wind-chill temperatures are expected to reach -35 degrees or colder.
Wind Chill Advisory - Issued when wind-chill temperatures are expected to reach -20 to -34 degrees.
Freeze Advisory - Used during the growing season when air temperatures are expected to be at or below 32 degrees over a widespread area for a significant period of time. Adjectives such as killing, hard, or severe may be used as appropriate to describe the freeze.
Frost Advisory - Used during the growing season if overnight lows are expected to reach the lower to middle 30s with light winds. Used if a widespread killing frost is expected to pose a danger to growers. If a freeze and frost are both expected, then a Freeze Advisory supersedes a Frost Advisory.