Its for this coming Tuesday night into Wednesday morning, from our best computer model. As you can see by the caption, its valid, too.
If you visit the models day in and day out, you will have noticed by now that this has been a pretty normal rain year in model rain, model rain for Catalina often showing up 10-15 days in advance, but then disappears as the predicted rain day gets a little closer. This situation has gone in the reverse direction where no rain has been foretold in the models anywhere near us until this run from overnight, a nice change from the usual give and then take away aspect.
The difference from dry to wet is how the models have been foretelling where the jet stream in the middle of the troposphere will be located–in the SW, rain falls under and on the interior side1. All along they have been forecasting it to be north of Catalina/southern AZ. But now, without even looking yet, just seeing that rain on the map, you can bet that the jet is south of us. Let’s look and see if C-M is talking through his hat; big ranch, no cattle:
1Not so for most of the country. This relationship becomes exactly the opposite by the time you get into the East and southeast US: rain falls BEFORE the jet core in the middle of the troposphere gets to you as you can see on that same rain map above for the areas of the Midwest as humid tropical air streams north ahead of that big low forming in the Texas panhandle. There’ll be some big weather out there in the Plains States and eastward as our powerful trough exits AZ.