Severe Weather

Severe Weather

NWS Norman watch, warning and advisory criteria for severe weather
Severe Thunderstorm Warning
Issued when there is evidence based on radar or a reliable spotter report that a thunderstorm is producing, or about to produce, wind gusts of 58 mph or greater, structural wind damage, and/or hail 1 inch in diameter or greater.

Severe Thunderstorm Watch
Is issued by the Storm Prediction Center (SPC) when conditions are favorable for the development of severe thunderstorms over a larger-scale region. Tornadoes are not expected in such situations, but isolated tornado development cannot be ruled out.

PDS Severe Thunderstorm Watch
PDS stands for "Particularly Dangerous Situation" and is issued by the SPC when conditions are favorable for the development of high-end severe thunderstorms over a larger region.  In this situation the SPC believes multiple events of extreme severe weather with significant wind damage are likely to occur.  Citizens should alter their daily routine and listen for further updates when this watch is issued.  Tornadoes are not expected in such situations, but isolated tornado development cannot be ruled out and widespread straight-line wind damage is likely.

Tornado Warning - Observed or Radar Indicated
Issued when there is evidence based on radar or a reliable spotter report that a tornado is imminent or occurring.

Tornado Warning - Considerable
Issued when a reliable spotter reports the existence of a tornado (therefore, it is confirmed, not radar indicated) and it is doing considerable damage.

Tornado Warning - Catastrophic
Issued when a reliable spotter reports the existence of a tornado (therefore, it is confirmed, not radar indicated) and it is doing extreme damage that is considered catastrophic; complete destruction is possible.

Tornado Watch
Is issued by the Storm Prediction Center when conditions are favorable for the development of severe thunderstorms and tornadoes over a larger-scale region.

PDS Tornado Watch
PDS stands for "Particularly Dangerous Situation" and is issued when the SPC believes that a large outbreak of long-lived, large and violent tornadoes is likely.  This is a high-end tornado watch.  People in a PDS Tornado Watch should change their daily routines to ensure they are weather aware and prepared to take action with little notice.

Significant Weather Advisory
Issued for strong thunderstorms that are below severe levels, but still may have some adverse impacts. Usually issued for the threat of wind gusts of 40-58 mph or hail up to 1 inch in diameter.
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