Another 500 mb cyclone will move eastward across southern Arizona, as the southern stream in the split flow remains active. The NAM 500 mb analysis at 12 UTC this morning (above) indicates the center of the cyclone is currently just a bit south of San Diego. The 7:08 am MST composite radar graphic from Yuma (below) shows that showers and thunderstorms ahead of the low extend across southwestern Arizona and have reached into far western Pima County.
The morning upper-air sounding from TWC (TWC is designation for the NWS office on the campus of the University of Arizona) above indicates little CAPE at sounding time, but moisture will be increasing from the west rapidly this morning and may approach an inch by later this afternoon. So, CAPE will increase and there appears to be an excellent chance of some more thunderstorms across our area.
The GEFS plumes (below from 06 UTC) for QPF are forecasting a similar event to that of Thursday night for today, and then another event on Monday night. The plumes may be a bit conservative, as the chance for thunderstorms across a larger portion of our area appears good for today.
The NWS forecast for low elevations of eastern Pima County again appears a bit conservative, with grid point POPs today of 60 to 70 percent for at least 0.01" of rain.
The 06 run of the WRF-GFS at Atmo forecasts a considerably better event for this second system. Above is forecast of composite radar echoes valid at 1:00 pm today and bottom shows forecast of accumulated precipitation through midnight tonight. So, I'm hopeful that I'll find more rain in the gauge here at sunrise tomorrow!
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