Good morning. We interrupt this lovely Sunday morning to bring you an update on the heavy rain chances we’ve been talking about for some time.
We’ll see fine weather today, and although Monday appears likely to be breezy with gusts up to 25 mph and cloudy, I don’t expect too much precipitation to fall. We’re going to have to wait for Tuesday, and more likely Tuesday night, for the action to begin. But first, a quick word about what’s driving this week’s heavy precipitation.
A very strong upper-level trough, an area of low pressure in the upper levels of the atmosphere, will move into Mexico this week. What’s so striking about this system is that it’s forecast to be as much as six standard deviations below normal, so these are really abnormally low pressures for March. Low pressure in the upper atmosphere allows air at the surface to rise. And generally more vigorous rising air leads to strong rain showers when there’s atmospheric moisture.