re: Deep South Severe Weather Thread (Enhanced)

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@RadarOmega

There are now THREE PDS TORNADO WARNINGS in effect for areas of Missouri and Illinois! These are confirmed LARGE and EXTREMELY DANGEROUS tornadoes! This is a life threatening situation! Seek shelter NOW! #MOwx #ILwx

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A particularly dangerous situation (PDS) tag is enhanced wording first used by the Storm Prediction Center (SPC), a national guidance center of the United States National Weather Service, for tornado watches and eventually expanded to use for other severe weather watches and warnings by local NWS forecast offices. It is issued at the discretion of the forecaster composing the watch or warning and implies that there is an enhanced risk of very severe and life-threatening weather, usually a major tornado outbreak or a long-lived, extreme derecho event, but possibly another weather hazard such as an exceptional flash flood or fire.[1][2]

PDS watches are quite uncommon; less than 3% of watches issued by the SPC from 1996 to 2005 were PDS watches, or an average of 24 each year.[3] When a PDS watch is issued, there are often more PDS watches issued for the same weather system, even on the same day during major outbreaks, so the number of days per year that a PDS watch is issued is significantly lower.

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PDS tornado warnings are currently issued on an experimental basis by the 38 National Weather Service Weather Forecast Offices within the Central Region.[15] The criteria for a PDS warning are when a tornado on the ground has been spotted or confirmed, or a significant tornado is expected based on radar signatures. While the intention of this experimental warning may be to replace the loosely defined tornado emergency, PDS tornado warnings are structured as the second highest level of tornado warning within the impact based warning system (an experiment – which also includes tags within warning products illustrating radar indications or physical observations of tornadoes, and damage potential – participated by the 33 Weather Forecast Offices within the Central Region, as well as eight additional offices within the Western, Eastern and Southern regions that began utilizing the system in the spring of 2014[16]); a tornado emergency, the highest warning level, is used within the United States for destructive tornadoes approaching more densely populated areas. These are the first warnings issued with PDS wording, and like PDS flash flood watches, are issued by local forecast offices.[17][18]

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