Scattered thunderstorms will remain in the forecast for at least another day as a weak low pressure center slides down the Sacramento Valley, adding just enough dynamics to daytime heating to stir things up in the afternoon. The low moves away Friday which should allow clearing conditions across the area which will stick around through Saturday. A slight chance of afternoon thundershowers comes back into the region Sunday and Monday.
View of intercloud lightning at night, late Twentieth Century. (Photo by Hulton Archive/Getty Images)
So what is the difference between lightning that is cloud to cloud vs cloud to ground? What occurs in both cases is the vertical motion of the strong updrafts creates a separation of electrical charges…. Positive on the tops of the clouds, and negative on the bottom. Envision a giant Duracell Battery and you’ll get the general idea. On a cloud to ground strike, the negative charge on the bottom of the cloud induces a positive charge on the ground, and since nature abhors big imbalances like that, there is a discharge to neutralize the electrical potential. The cloud to cloud does essentially the same thing, but the negative bottom of one cloud discharges into the positive top of another.
A Word of Weather 
Hi, I was thinking that if a lightning discharge depletes a cloud of a charge, the only way more lightning could come from that cloud is if the mechanics of the polarity differential are still occurring. So what I am asking is does lightning only come out of storm clouds that have updrafts that are growing? Also, does cloud to cloud lightning occur within the same cloud? Lastly, does the ground polarity change after a lightning strike? Is that why a bolt might travel many miles from a cloud to strike the ground, because the earth directly under the cloud has recently been discharged by a different strike?
Can you tell I like thunderstorms?
Mark Tadder
A Word of Weather wrote: > > >
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yes, you really need updrafts in order to have lightning, but you need rising air generally in order to get any kind of storm or precipitation in general. You can get cloud to cloud within the same storm cell, although defining where one “cloud” starts and another ends can get problematic. And the ground polarity doesn’t switch after a lightning strike, but the size of the charge does diminish (usually from strongly positive to near neutral.) And the reason a bolt travels many miles in rare instances is usually because it is a reverse polarity strike. It comes from the top of the thunderhead, and induces a negative charge on the ground. Those are rare, but can be very powerful.
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