Last week’s storm did manage to bring some thunderstorms and widespread moderate to heavy rainfall over coastal SoCal, with over 1-2 inches measured in the majority of locations. This is great news for local aquifers and those hoping for some free car washing, but unfortunately the more northern parts of the state–where water levels in reservoirs and aquifers are already very low–received very little to no rainfall, with less than 0.25 inches across the board and generally less than 0.10 in. And the outlook for the next couple of weeks isn’t particularly promising for any much-needed soaking rain or accumulating snowfall, either. Long-term indicators continue to behave strangely, and the models are continuing to have a hard time resolving anything smaller than semi-demi-hemispheric (that’s 1/16th of the globe) perturbations in the mean flow. What does this mean for the next two weeks? Well, first of all, a pesky little cutoff that has been cropping up in model solutions for the past few days could throw a wrench in current forecasts. I don’t currently think that it will have a significant impact on the weather in CA this week, but this prediction could well change if the low ends up being just a bit deeper or more offshore. Air aloft will be cold and there will be at least some instability, so we do need to keep an eye on the possibility of convection. At present, I think this is somewhat unlikely. After this low slinks offshore and spins harmlessly out to sea well southwest of San Diego, we enter yet another tranquil, mostly clear, and rather boring period for at least a week. The GFS, in particular, has been indicating that a strong Rex-blocking pattern will develop by day 7. As many of you know, Rex blocks often lead to very dry (and occasionally warm) weather over CA, and are often followed by a breakthrough of a West Pacific jet at some point 1-3 weeks after it’s initial setup. The alternate possibility, which is somewhat less common, if for such a block to orient itself in such a way that it drains frigid continental polar air from Canada from the N/NE into CA, bringing very cold temperatures and possibly low-elevation snow. Some of the recent GFS runs are indicating this possibility out towards day 13-16, so it’s worth keeping an eye on. I’m becoming increasingly worried about the water situation as the winter gets off to a dry start up here…
