PDS

PDS is short for Particularly Dangerous Situation. It is a heightened-awareness type of watch issued by the Storm Prediction Center. A PDS tornado watch may say, for example, "Destructive Tornadoes...Hail to 3 inches in diamater...thunderstorm wind gusts to 80mph...and dangerous lightning are possible in these areas."

...THIS IS A PARTICULARLY DANGEROUS SITUATION...
PDS watches are issued on high risk days, usually.