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Wind Advisory, Fire Weather Watch and Red Flag Warning are familiar terms to all of us. That familiarity lessens, to a certain degree, the situational awareness and preparedness. Now, the National Weather Service in Sacramento is launching an overlay to Red Flag Warnings called Particularly Dangerous Situation (PDS.) The criteria for Red Flag Warnings remain unchanged.

The PDS designation will only be used for very rare events, within an existing Red Flag Warning. The decision matrix used by NWS Sacramento for Red Flag Warnings now has the additional magenta PDS option.

Red Flag Warning Weather Decision Matrix for Northern California West of the Cascade/Sierra Crest courtesy NWS Sacramento

Red Flag Warnings and Fire Weather Watches have been issued more frequently in recent years, as shown in the graphs below. Similar to the magenta “extreme” heat classification, the PDS magenta flag is in response to extreme weather events, amplified by climate change.

NWS Sacramento will issue the PDS as weather and fuel conditions warrant. In California, NWS Reno and NWS Los Angeles/Oxnard already have the capability to issue this product.

Most of the Red Flag Warnings in our area are issued between August and October when stronger wind events occur before the first substantial rains of the “wet” season.

NWS Sacramento will begin issuing PDS red flag warnings (should conditions warrant) this October.

The PDS addition to a Red Flag Warning will include: “Precautionary/Preparedness Action statement: This is a particularly dangerous situation with extremely low humidity and high winds. New fires will grow rapidly out of control. In some cases people may not be able to evacuate safely in time should a fire approach.

To reiterate, this is not a new product, only an addition to the existing Red Flag Warnings. Hopefully we won’t see magenta any time soon, but in case we do, now you know.