NWS Partial County Alerting information

One way NWS meets its missions to protect the public is to send weather warnings via NOAA Weather
Radio (NWR). The Emergency Alert System (EAS), in turn, uses NWR to get out life-saving alerts. Broadcasters use EAS to interrupt programming for vital NWS warnings. Users with NWR receivers equipped with Specific Area Message Encoding can program their radios with a 6-digit county code to receive alerts for one or more counties.

Because NWR is county based, if an NWS office forecasts that even a small part of a county is impacted by a storm, the entire county is alerted. This frequent alerting most strongly impacts large or uniquely-shaped (e.g., panhandle); or configured (e.g., islands) counties. The NWS has received complaints about receiving "too many EAS alerts" for a county and "too many warnings which are not applicable to my area of the county." Similarly, broadcasters have expressed concerns about sending EAS activations that do not apply to their broadcast service area.

Both NWR and EAS allow NWS to divide a county into 2-9 partitions, each with a unique 6-digit code. More than 10 years ago, four NWS offices (Duluth, MN; Glasgow, MT, Rapid City, SD,  and Tucson, AZ) successfully implemented partial county codes. Most SAME-equipped NWR receivers can read these codes. By using the SAME partial county location codes, these WFOs have successfully issued warnings for predefined parts of a county, substantially reducing the “False Alarm Area” and “listener fatigue.” Despite the success of these four partitioning efforts, Partial County Alerting is underused. Check out our 1-page Partial County Alerting fact sheet.

NWS restarted this program with Clark County, NV. NWS Las Vegas coordinated with Emergency Managers, the Nevada State Emergency Communications Committee, broadcasters, state and local government officials, EAS encoder/decoder manufacturers, and NWR receiver manufacturers to allow the office to use partitions for the following warnings:

• Dust Storm Warning (DSW)
• Flash Flood Warning (FFW)
• Severe Thunderstorm Warning (SVR)
• Tornado Warning (TOR)

More Information

• Overview
• Technical Discussion
• Partial County Implementation for Clark County, NV
• Benefits for Residents and Broadcasters
• PCA Example: Flash Flood Warning
• PCA In Action
• Outreach Resources and Contacts

Current NWR and EAS Dissemination Footprint Flash Flood Warning

This Warning, (depicted in green), currently activates NWR Specific Area Message Encoding (SAME) and EAS for the hatched area.