REFERENCE SHEET FOR WARNING/ADVISORY THRESHOLDS
Last Updated: April 26, 2010
The following are National Weather Service criteria for issuing Advisories and Warnings for various weather events. Watches generally are issued with
longer lead times in expectation of meeting Warning criteria.
| TYPE OF ISSUANCE |
WHEN ISSUED FOR SOUTHERN NEW ENGLAND |
| SMALL CRAFT ADVISORY |
Sustained winds 25-33 kts AND/OR Seas ≥ 5 feet within 24 hours |
| GALE WARNING |
Sustained winds 34-47 kts within 24 hrs from a non-tropical system |
| STORM WARNING |
Sustained winds ≥ 48 kts within 24 hours from a non tropical system |
| HURRICANE FORCE WIND WARNING |
Sustained winds or frequent gusts ≥ 64 kts (> 2 hrs) within 24 hours from a non-tropical system |
| TROPICAL STORM WARNING |
Sustained winds 39-73 mph (34-63 kts) (no gust criteria) associated with a tropical storm expected to affect a specified coastal zone within 24 hours |
| HURRICANE WARNING |
Sustained winds ≥ 74 mph (64 kts) (no gust criteria) associated with a hurricane expected to affect a specified coastal area within 24 hours |
| HURRICANE WIND WARNING (INLAND) |
Sustained winds ≥ 74 mph (no gust criteria) associated with a hurricane affecting areas beyond coastal zone (inland) within 24 hours |
| SPECIAL MARINE WARNING |
Brief/sudden occurrence of sustained wind or frequent gusts ≥ 34 knots, usually associated with thunderstorms;
AND/OR hail ≥3/4" in diameter; also issued for waterspouts |
| MARINE WEATHER STATEMENT |
Brief/sudden occurrence of sustained wind or frequent gusts = 25 knots,
usually associated with thunderstorms and/or back door cold fronts during the spring
|
| COASTAL FLOOD ADVISORY |
Minor coastal flooding expected within 12 hours. Examples include: splash over causing a few roads briefly impassable, standing water in parking lots, etc. |
| COASTAL FLOOD WARNING |
Coastal flooding expected within 12 hours; widespread serious coastal flooding which damages property AND/OR is a threat to life |
| DENSE FOG ADVISORY |
Widespread visibility ≤1/4 mile for at least 3 hours |
| HEAVY FREEZING SPRAY WARNING |
Ice accretion greater than 0.8 inches per hour |
| HIGH SURF ADVISORY |
When high surf poses a danger to life in the form RIP currents or breaking seas |
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