There were widespread storms (above shows CGs for 24-hours ending at 5 am this morning) last evening from northwest to southwest of the Tucson metro area. From here at the house there was a nice view, just after dark, of frequent lightning to the northwest. Of course, no rain yet again at the house. The summer pattern continues very marginal, with just enough heat and moisture for some CAPE and afternoon-evening storms around. Warm air lurks above 500 mb, keeping CAPE values low. At 6 am MST this morning only 16 ALERT stations, around the edges of the network, reported light rains in past 24-hours.
The morning sounding at Tucson (12 UTC skew-T above) has a decent shear profile with easterly steering winds and westerly winds in the upper-troposphere. However, CAPE appears marginal again. There was a run of the early WRF-NAM available this morning. The forecast of 10-m winds valid at 5 pm MST this afternoon (below) is impressive with a very strong outflow coming off the Rim Country to the north and a strong outflow blowing northward from convection in northern Mexico.
The forecast skew-T for TUS valid at 7 pm shows the shallow outflow from Mexico and convection just underway, but with very limited actual CAPE. The model's forecast of composite radar echoes valid at 8 pm (below) shows the most activity of the day over eastern Pima County, but it's not much. Forecast rain amounts are very slight. The outflows collide, but with only some moderate storms developing because of the limited CAPE. So a day with a bit more promise than last several, but the situation will have to evolve better than the model forecasts, if there are to be organized, strong thunderstorms late this afternoon and evening.
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