Storm activity was on the wane yesterday across eastern Pima County. The plot above shows detected lightning strikes for 24-hours ending at 5 am MST this morning (July 17th). Most significant lightning was out in central Pima County and with a strong cell to the south of metro Tucson, near Green Valley. At 6 pm yesterday evening only 19 of 92 ALERT sites had reported any rain. During the night 14 additional stations recorded rain - so, about 20% coverage during both yesterday and last night - much lower than expectations, which had very high POPs forecast. The south sector of the ALERT network (below, 24-hours through 6 am this morning) had the only rain reports of significance, with two stations reporting over an inch.
The early WRF-GFS forecasts continued easterly winds below 700 mb (forecast TUS skew-T valid at 4 pm MST shown above), along with a drying trend. The model forecasts PW, which is at 41 mm this morning, to decrease to 30 or below during the mid-afternoon. Forecast composite radar echoes, below - also valid at 4 pm - indicate almost no storm echoes over southeastern Arizona and very little precipitation is forecast. The low elevations will have little to no CAPE and my main question re the model forecast is whether the drying will be significant enough to shut down convection over the mountains. Will watch the mountains this afternoon and also the evolution of the upper-low from New Mexico toward northern Sonora (what's left of the circulation is forecast to be located just south of Nogales at 5 pm MST tomorrow afternoon).
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