Sun did come out late yesterday but it was not enough heating, or CAPE, for thunderstorms to build - note the significant lack of CGs over a VERY large area of Mexico and Arizona for 24-hours ending at 4 am this morning (above). The evening Tucson sounding indicated an extremely shallow boundary layer that only reached to 850 mb and indicated that the showers were based up at 600 to 700 mb. Thunderstorms got going mainly to the east in Cochise County and northward into the White Mountains. Across the ALERT network this morning 44 of 92 (almost 50% areal coverage) sites had light rainfall during past 24-hours. Only 5 stations had 0.25" or more and these were all in the Catalinas and Rincons - both Green Mountain and Manning Camp came in with 0.43". Sector plots below illustrate that the showers stuck to the east and mountainous parts of the network. Here at the house we had only a Trace through midnight and have picked up 0.02" from early am showers.
The early runs of the WRF model at Atmo indicate a somewhat similar day today. Atmosphere is moist but not very unstable, due to clouds and little in the way of a deep boundary layer. It is a damp and dreary morning across the metro area (Sunday, Sep. 8th). The PW values from Tucson west across southern Arizona are around 1.75 inches. The WRF-NAM appears to have forecast the morning shower coverage a bit better than the GFS version. Above is WRF-NAM forecast of radar echoes valid at 2 pm this afternoon and below is the forecast of rainfall totals through 5 am MST tomorrow morning. Models again forecast most significant showers to stay to the east and north. High temperature yesterday reached only 88F at TUS and WRF forecasts only 84F at the airport for today. So the dampness continues but CAPE will remain limited, unless we get some more serious sunshine this afternoon.
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