[citation needed] When a watch, warning or advisory (severe or non-severe) is disseminated by either the Storm Prediction Center (SPC) or a local National Weather Service Weather Forecast Office, a scroll with text moving right to left across the screen featuring information on the alert appears, usually accompanied by a three or six brief bursts of a 1050 Hz attention signal that last between three and eight seconds.
Although local offices of the National Weather Service have issued warnings for tornadoes and severe thunderstorms based on the path of a storm since October 2007,[4] most stations using the system display the affected jurisdictions on a per-county basis rather than delineating them by polygons.
This system's on-air design element is stylized depending on the television station using it (for example, until an upgrade of its system to allow widescreen overlays during broadcasts of high definition programming in March 2009, Oklahoma City NBC affiliate KFOR-TV's 4WARN Storm Alert variant displayed an "L"-bar surrounding a resized box display of the current program, containing a map of all 77 Oklahoma counties and accompanying legend, along with the name of a specific county above it – the country referenced in the assigned warning/watch color on the map is shown blinking for three seconds – and a ticker on the upper third of the screen; a live display of the station's Doppler radar system replaced the alert map when the alert ticker scrolled the second time).
[citation needed] Additional features were added to First Warning and its variants during the 2000s, including functions allowing the map to toggle between displays of current weather alerts and live or looped radar imagery, including radar images by individual county, which are often accompanied by warning information specific to the jurisdiction.
Although many stations have upgraded to HD-compatible versions of First Warning, the on-screen graphic map and/or scroll in some cases, may be displayed in anamorphic widescreen if the system is not properly set to a 16:9 display, causing partial cropping of the graphic outside of the safe area on 4:3 television sets.