Some of these are different from the National weather Service (NOAA)
storm travel scale
1.road conditions/ minor travel delays. Some slippery spots. patches of snow or iced covered secondary/neighborhood roads. Minor visibility issues.
2 road conditions/ light travel delays. Slippery travel with secondary roadways being snow and or iced covered. Some limited visibility.
3 road conditions moderate travel delays try to stay on well-traveled roads Slippery travel. Snow and or ice build up on all roads. Reduced visibility.
4 road conditions heavy travel delays try to avoid travel… Snow and or Iced covered roads. Visibility less than a mile
5 road conditions severe travel delays stay off the roads. Roads could be unpassable. Visibility less than a 1/2 mile.
rainfall scale Ice scale snow scale (inches)
1 less than 1 inch 1 0-.1 inches level 1. minor 0-1
2 1-2 inches 2 .1- .25 inches level 2 light 1-4
3 2-3 inches 3 .25-.50 inches level 3 moderate 4-10
4 3-4 inches 4 .50– .75 inches level 4 heavy 10-20
5 4+ inches 5 .75+ inches level 5 severe 20+
detailed snow map is issued 2 days before storm depending on confidence level 60% +
Precautions, watches and warnings
winter weather precautions: chance of winter weather that could effect travel within the given time frame snowfall Level 2+ possible.
winter weather watch . Winter weather that causes travel delays is likely within the given time frame.
winter weather warning : winter weather that will reduce travel /effects travel will occur within the given time frame (level 3 snowfall or greater) 60% confidence or greater
winter weather advisory: winter weather slows travel (level 2 snowfall) 60% confidence or greater
Blizzard warning and Blizzard watch. ( National weather service definition)
strong wind precaution. winds or gusts of 30mph or higher is possible
Strong wind watch . Winds or gusts of 30+ likely .
Ice precaution accumulating ice possible
Ice advisory: chance of level 2 ice accumulation
ice watch chance of a quarter inch or greater within given period
ice warning 1/4 inch or greater is likely within the given period
Precautions can be issued 4 days before affected time if there is a chance 30-50%
watches can be issued 3 days out if its around 50% chance
warnings are issued 24 to 36 hours if there is a near 70% +
Merrimack valley weather 