Officials with the National Weather Service Seattle office say thunderstorms sprung up in and around the Seattle metro area earlier this evening and are moving northward. This is occurring after record heat gripped much of western Washington today, August 16th.
The concern with this potential storm, according to the NWS, is the fire risk.
The concern with this type of convection is that due to their high based nature, not a lot of precipitation is expected out of them, but they are producing a fair amount of lightning, which can be fire starters. The prolonged period of hot and dry weather has dried the fuels out, therefore it would not take much to ignite some of these fuels that have had ample time to dry out and become much more combustible.
The main message for the next few hours is to play it safe with lightning and stay indoors.