Dry Air Knocking On The Door

Yesterday was another day with the best raining storms occurring mostly at higher elevations. Four of the regular reporting stations in southeast Arizona had measurable rainfall but amounts were quite light. In the ALERT network 57 sites had rainfall, with some nice amounts - 13 gauges measured more than half an inch and two sites had more than an inch - with higher amounts at higher elevations generally. Eight of the RAWS stations in southeastern Arizona had measurable, with Columbine and Guthrie having 1.27" and 1.28". Here at the house we had a nice cool outflow from the south-southwest at about 3;30 pm with gusts of 30 mph or a bit more; I could see some CGs as a new storm formed on the Catalinas; had a nice rainbow; but only a Trace of rain. Storms rapidly crashed before sunset and most of the rain occurred by 6 pm or so.

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Today, very dry air is over western Arizona, extending east to near the Phoenix area. The 14z surface plot is shown in the top image - note the low dewpoints over the western half of state. the visible satellite image in the middle shows that the dividing line between clear skies and partly cloudy conditions lies across central Pima County. Over eastern Pima County PW values are a bit over 30 mm while out west at Organ Pipe National Monument PW is around 15 mm - so a fairly distinct boundary separates the moist and dry air. Southerly winds at and below 700 mb are keeping an influx of low-level moisture into the southeast section of the state - see Tucson morning sounding at bottom. The very warm middle-level air that I mentioned yesterday is now overhead, with 500 mb temps at TUS of -3C and at PHX of -2C. Only the higher mountains are likely to generate enough CAPE this afternoon to pop some towers through this dry and hot upper-troposphere.
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It appears that - This is the end my friends of the summer thunderstorm season.