It looks like we might see one more round of thunderstorms Friday before the weekend clears up. Temperatures will cool to the lower 80s as clouds increase and scattered thunderstorms form on the western side of the Silver State. Morning winds should be light enough to allow the launching of the Balloon Race craft through the weekend. A warming trend picks up over the weekend with high temperatures rising to the upper 80s Saturday and the low 90s on Sunday.

Lightning 3

Yesterday I mentioned that most lightning is considered “negative polarity”, but there is “positive” lightning as well. Instead of originating from the negatively charged base of the cloud, positive lightning starts from the positively charged top of the thunderstorm cloud, usually up in the anvil portion. That huge positive charge induces a negative charge from the ground, and the stepped leader flows upward from the ground, instead of the other way around. As it reaches near the top of the anvil, the return stroke hits downward from the top of the cloud.

Lightning positive

Positive polarity lightning often forks upward.

Positive lightning can be much more dangerous than negative (not that negative is anything to sneeze at.) I’ll tell you why tomorrow.