The 500 mb, short-wave trough we've been talking about has moved over the Great Basin this morning, with showers curving east and south (see visible satellite image above for 7:15 am MST). We had several periods of showers and thundershowers yesterday, but the heaviest rains across Tucson occurred with the morning band of rain. Across the ALERT network 24-hour coverage this morning was 100% - 45 sites measured more than half an inch and 8 locations had over an inch. Here at the house there was 0.88" in the gauge at 6 am this morning, but 0.82" of that fell yesterday from 9 am to noon. The air in low levels remains very moist (see CIRA blended PW below - yellows are over an inch and a half).
However, very dry air is intruding across the state in the upper-half of the troposphere. Above is the WRF-GFS skew-T at Tucson forecast for noon. The winds are westerly through the troposphere and the dry air aloft has mixed downward and extends below 500 mb. The model forecasts continuing CAPE, but developing storms will face a hostile environment above 600 or so mb. The convective towers the last two days have tended to be soft and fuzzy, somewhat tropical-like. Today it will be a battle of low-level CAPE versus warm, dry air aloft. The early WRF-GFS (forecast of total rainfall through midnight, below) forecasts that the back edge of storms and rain today will be just west of the Tucson area. It won't surprise me if the 12 UTC runs of the WRF shift the back edge further east.
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