The National Weather Service (NWS) issues
Weather Warnings and Advisories when an imminent weather event has an 80-percent chance of occurring. “Take Action!” when you see one of these products issued for your area:
A Flash Flood Warning is issued when flash flooding is in progress, imminent or highly likely. The purpose of this particular product is to alert and inform the public, emergency management and other agencies that there is a weather event with a serious threat to life and/or property. These warnings can be issued minutes to hours ahead of the onset of flooding, and must be treated as urgent messages because dangerous, life-threatening flooding can develop within minutes. As of November 2019, Flash Flood Warnings trigger Wireless Emergency Alerts (WEAs) that send a free notification to your mobile device, alerting you of the hazardous conditions. Recently, the NWS has realized that they over-alert Flash Flood Warnings, and plan to scale back WEAs to only “considerable” or “catastrophic” events.
A Flood Warning, similar to a Flash Flood Warning, is also issued to convey the risk of serious flooding that poses a risk to life and/or property. The difference between the two is based on the location—flash flooding occurs when heavy rain quickly floods areas that are normally dry, while a Flood Warning is issued when a river is expected to overflow its banks and flood nearby roads and property. Typically, floods occurring along rivers are divided up based on the severity (minor, moderate or major) and details are added on the anticipated effects.
While a Flood Warning is issued when there is a serious threat, a Flood Advisory is broadcast when a flood event warrants advance notice but is less urgent than a warning. These advisories typically are issued when an event could cause significant inconveniences with notice, but potentially have life-threatening circumstances if caution isn’t exercised.
- Coastal/Lakeshore Hazardous Message
Coastal/Lakeshore Hazardous Messages are used to inform the public with detailed information on significant events impacting lake shores (such as the Great Lakes) and coastal locations or beachfronts of the United States. These hazard messages can be issued as a watch, warning or advisory. A watch is issued if significant impacts are possible while a warning is issued for a likely event.
- Special Weather Statement
Special Weather Statements provide information regarding ongoing or impending hazards that require public awareness, but do not pose the same threat level as a watch, warning or advisory. While these events are typically not life-threatening, caution should still be exercised.
Credit: National Weather Service
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