An area of thundershowers moved across most of eastern Pima County around 11 pm to midnight last night, producing rains at some spots of 1 to 2 inches. Regional radar at midnight shown above from NCAR RAL - this product shows base reflectivity and tends to down-play the intensity of echoes because of clutter problems. The Rillito was flowing at 1000 cfs a bit after midnight at the Dodge gauge. Across the ALERT network 100% of the reporting gauges had rainfall during the past 24-hours. (Note that there were only 90 sites reporting - the Picture Rocks rain gauge has apparently been out of service for at least two months.) There were 50 sites with more than half an inch and 10 of these had over an inch. The max reported rain was 2.01" at the site at Altar Wash and 286. Here at the house we had 0.15" during midmorning showers and then another 0.15" around midnight with thunder - total rain for past 24-hours was only 0.30" here.
Skies were mostly clear this morning and PW was down quite a bit - above is time series of GPS derived PW at the Univ. of Arizona site. The CIRA blended PW product for 13 UTC this morning (below - Tuesday, September 10th) shows a distinct pocket of drier air over southeast Arizona - indicated by the darker green shades. So a key issue for the afternoon is that of how much will PW recover? There are considerably higher amounts of PW across the southwest third of the state. The early WRF forecasts from Atmo tend to keep the metro area PW low and afternoon storms decrease rapidly as they move toward eastern Pima County. It does appear that warm and dry air above 300 mb will limit CAPE this afternoon, but I suspect that things will recover a bit better than the midnight model runs forecast. It will be interesting to see what the morning forecasts from the WRF indicate for later today.
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