lastAction Value Definition
New Used for an initial issuance of an event.
Extend Alert has been extended in time or area or both. An alert is extended (in time) when the valid time period of an existing event has been made longer or shorter by changing either or both the areas.startDateTime or areas.endDateTime. An alert is extended (in area) when the valid area of an existing event has been expanded from its previous issuance. An alert can also be extended in both area and time when the valid time period of an existing event has been changed (made longer or shorter) and the valid area has been expanded.
Cancel Active alert has been canceled prior to original expiration time.
Correct Alert has been modified to correct an error.

Alert has expired and is no longer active. Expire is primarily used in a concluding message, while the event is still active, to notify users that an event will be allowed to expire at the scheduled event ending time. It can also be used just after event expiration, to pass along final wrap-up information about the event.

Upgrade Upgrade is used when an existing event is upgraded for the same area to a higher eventClass, for example, from a watch to an advisory or warning, or from an advisory to a warning.
Continue Continue is used when providing updates to an existing event, where no changes were made to the area, valid time period, or eventClass.
Update Update to an active event.