Caribou National Weather Service - Significant Event Definitions/Thresholds

WARM SEASON EVENTS

THRESHOLDS

SEVERE THUNDERSTORM WARNING

WINDS>=58 mph (or implied by damage), and/or HAIL >= 3/4 inch

TORNADO WARNING

Radar Indicated and/or Spotter Report 

FLASH FLOOD WARNING

Life/Property threat within 6 hours. 

FLOOD WARNING

Widespread flooding of longer duration

FLOOD WARNING 
(MAIN STEM RIVER)

Life/Property threat beyond 12 hours. 

COLD SEASON EVENTS

THRESHOLDS

WINTER STORM OUTLOOK

Issued when a major storm could impact the area beyond 48 hours.

WINTER STORM WATCH

Issued when there is a likelihood a warning will eventually be issued. Watches are normally valid for possible events occurring within 12 to 48 hours.

WINTER STORM WARNING

Heavy Snow: 7" or more within 12 hours or 10" or more within 24 hours. Warnings may also be issued when greater than .5 inch of sleet or freezing rain accumulation is expected.

BLIZZARD WARNING 

Sustained winds or frequent gusts greater than or equal to 35 mph and falling or blowing snow with visibility less than 1/4 mile for greater at least 3 hours.

WIND CHILL WARNING

Widespread wind chills of 35 degrees below zero or lower with winds greater than 5 mph. 

WIND CHILL ADVISORY

Widespread wind chills of 20 to 34 degrees below zero with winds greater than 5 mph.

WINTER WEATHER ADVISORY

4" to 6" of snow within 12 hours, less than .5" of sleet or freezing rain, or blowing snow

BLOWING SNOW ADVISORY

Wind-driven snow resulting in visibilities occasionally 1/4 mile or lower.

COASTAL FLOOD WATCH

Coastal flooding not a associated with a tropical system possible within 12 to 36 hours.

COASTAL FLOOD WARNING

Coastal flooding not a associated with a tropical system expected within 12  hours.

MARINE

THRESHOLDS

HURRICANE WARNING

Sustained wind of 64 kts (74 mph) or greater resulting from a tropical storm system...may also be issued for coastal forecast zones (29 & 30).

TROPICAL STORM WARNING

Sustained wind of 34 - 63 kts (40 - 73 mph) resulting from a tropical system...may also be issued for coastal forecast zones (29 & 30).

STORM WARNING

Sustained wind of 48 kts or more not associated with a tropical system.

GALE WARNING

Sustained wind of 34 to 47 kts not associated with a tropical system.

SMALL CRAFT ADVISORY

Sustained winds of 25 to 33 kts and/or average seas of 5 feet or higher.

SPECIAL MARINE WARNING

Thunderstorm Winds of greater than 34 kts, water spouts, or any short duration wind greater than 34 kts not covered adequately in the marine forecast.

OTHER EVENTS

THRESHOLDS

HIGH WIND WARNING

Sustained winds at least 40 mph for 1 hour or more, or gusts to 58 mph or more for any duration. May be preceded by a High Wind Watch.

WIND ADVISORY

Sustained winds of 31 to 39 mph for 1 hour or more, or gusts from 46 to 57 mph for any duration. 

DENSE FOG ADVISORY

Widespread visibilities less than 1/4 mile.

FREEZE WARNING

Widespread temperatures below 30 degrees (a HARD FREEZE WARNING is issued for temperatures below 25). May or may not be accompanied by frost. Issued only during growing season.

FROST WARNING

Widespread temperatures 30 to 35 degrees. Widespread frost...may occur even though standard observing level temperatures (5 feet above ground) are above freezing. Issued only during growing season.

FROST ADVISORY

Widespread temperatures in the mid 30s. Scattered frost...may occur even though standard observing level temperatures (5 feet above ground) are above freezing. Issued only during growing season.

CIVIL EMERGENCY MESSAGE

Any emergency declared by city, county or state emergency management. Most often associated with nuclear or other hazardous materials. Issued at the request of emergency management.