NWS Partial County Alerting information

The National Weather Service (NWS) broadcasts weather warnings and Non-Weather Emergency Messages (NWEMs) via NWR. NWR also serves as a primary source of information for the nation’s EAS.

The challenge:

NWR and EAS are both generally viewed as county-based systems. However, this is particularly problematic for select counties because even if only a small portion of a county is included in a warning, the warning’s NWR and EAS dissemination translates to the entire county. This issue is most common for very large, uniquely-shaped (e.g., rectangular) or uniquely-configured (e.g., islands) counties.

What NWS has done until now:

Both NWR and EAS allow a county to be divided into several fixed areas (partitions). Each partition is associated with a unique, six digit location code. Five WFOs have successfully assigned partial county codes to one or more of their counties (most recently by WFO Las Vegas for Clark County, NV). Details on what each of these WFOs are already doing are available through the link on the right side of this page. We refer to this more-targeted dissemination of warnings via NWR and EAS as Partial County Alerting (PCA). PCA implementation is not appropriate for every US county. The usefulness of PCA is generally reserved for very large or uniquely-shaped counties, such as elongated counties.

How Partial County Alerting improves information delivery via NWR and the EAS:

When PCA is implemented, NWR listeners with Specific Area Message Encoding (SAME)-equipped receivers carrying the Public Alert™ logo can easily select a unique, six digit location code for their local area and receive automated notifications of WFO-issued warnings only for the programmed partition(s). PCA reduces “listener fatigue” by reducing the receipt of warnings for distant parts of a county.

With PCA, broadcasters may choose to limit the activation of EAS to specific county areas.

How is Partial County Alerting changing beginning in 2024?

NWS will enhance the information we provide to the existing PCA service level. Details on these improvements are provided at the bottom of this page. For example, based on WFO decisions with local officials and emergency managers, PCA may also be used for NWEMs with this new service level.

How will I know if Partial County Alerting with the new service level begins for a county in 2024?

NWS will issue WFO-specific Service Change Notices. Announcements will be aired on NWR. Details will be provided on your WFO web page with county maps showing the partition boundaries, the SAME location codes to use with SAME-equipped NWR receivers and the complete list of warnings using PCA by the WFO.

What if I wish to continue receiving all the automated notifications of partial county warnings broadcast by a transmitter?

The implementation of PCA is an opt-in service for those who wish to receive warnings more applicable to their local area. If NWR listeners using Public Alert™ receivers wish to continue receiving all warnings broadcast by a specific station for their county, they do not need to make any SAME location code changes - they will retain the SAME code beginning with zero. Note that some stations do not broadcast warnings for every part of a county. NWR users are encouraged to consult each transmitter-specific page which details the “Areas Receiving Alert Tones.”

More Information

• PCA fact sheet (medium resolution)
• PCA fact sheet (high resolution)
• 6 WFOs using PCA
• Programming your NWR Receiver: Q&A
• SAME Location Codes for Counties
• SAME Location Code information for using PCA
• Information for broadcasters

Clark County, NV information:

• Clark County PCA implementation
• Public Service Announcement (video)
• Flash Flood Warning example