Today’s relatively weak system brought some interesting weather to NorCal this afternoon. The weak cold front was preceded by significant sunshine this morning and early afternoon, and cold temperatures aloft were apparently enough when combined with frontal lifting to produce two bands of strong showers and scattered thunderstorms this evening. Here in San Rafael, some very heavy rain fell this PM along with a lone clap of thunder. That’s the first “thunderstorm” in well over a year here. The skies were quite dramatic, in any case, and we recieved more than 1/2 inch in less that half an hour. Some scattered showers and possibly a few more isolated thunderstorms will linger into tomorrow morning (possibly a bit later in the Los Angeles area) before a drying trend ensues for the rest of the week. There’s not much to talk about for this period, escept that afternoon temperatures will rise considerably over interior areas. The most interesting part of the foreecast begins next weekend and last into next week. The GFS has been indicating, for several model runs now, that a weak upper low will develop off the coast SW of Los Angeles by week’s end and potentially draw some mid and upper-level moisture into the region from the southeast. This would be a very summer-like monsoonal patter, if it were to develop. I am more than a little suspicious at the moment, so will keep an eye on it. Otherwise, a cold upper trough is then forecast to pinch off and form a large cutoff low SW of CA by early next week, bringing the potential for rain to the entire state. Cutoffs are always hard to predict even a few days ahead of time, so it not worth trying to divine the details at this early date. SoCal stands a good chance of significant rainfall, however, if the low can get any sort of subtropical moisture tap. Beyond that: looks like some more disturbances are likely in cold NWly flow into CA for much of next week. Not gigantic storms are on the horizon still, but there could at least be some interesting weather over most/all of the state over the next 10 days….