Wet Weekend with Cold Nights

I'm sure that most of you have begun seeing rain chances pop up. Hopefully we can do a bit better than "probabilities" with this event. Rain accumulations on Friday will be insignificant. The Bulk of the rain will arrive Saturday. Currently there is one Model really blowing up with Rain amounts, but I am skeptical from this far out. Expect a wind shift out of the Southeast later in the week bringing in moisture as a precursor to the Rain Saturday.

I've posted regarding this topic before, but the driver for the next rain event is an Upper Level Trough of Cold air. You can see this pictured below.



Thunderstorms require 3 main ingredients: Moisture, Lift, and Instability. In the Delta, we typically have Moisture and Instability but an absence of Lift. Very small scale sources of Lift during the Summer are responsible for the apparent pop-up nature of Thunderstorms. A lifting mechanism can be a thermal boundary created by any number of phenomenon, or outflow from an old Thunderstorm. The problem with Convective forecasting is not diagnosing Moisture and Instability, but rather the lifting mechanism. Radar and Satellite must be scoured to locate boundaries. More often than not these boundaries are not visible until hours before the event.