At 1300 UTC this morning the blended PW product for the eastern Pacific (above) shows the closed low at around 30N and 130W, i.e., considerably west-southwest of San Diego. There is a broad plume of higher PW being pulled northward along about 120W. Thus, one would think that prospects are good for this system to impact southeastern Arizona with precipitation. However, all of the forecast models have a more negative solution. The models forecast the best moisture to push northward across northwestern Arizona into the Great Basin.
Above is Atmo's WRF-GFS forecast (from midnight last night) of accumulated precipitation from now through midnight on Thursday night. Basically, the model forecast leaves southeastern Arizona out of the precipitation action from this system (point forecast matrix indicates 0.01" for Mt. Lemmon). Below is the NAM precipitation forecast (from 5 am MST observations this morning) ending at the same time as the WRF-GFS, with a similar dry forecast for here. The GFS ensembles from 5 pm MST yesterday had no members forecasting rainfall over southeastern Arizona.
The graphic below shows the WRF-GFS forecast surface chart for the local Tucson area - valid at 3 pm tomorrow (Thursday afternoon). The forecast indicates warm and dry, with dewpoints remaining in the 40s, but with strong southwest winds. The timing of the front may be slow in the WRF-GFS, which doesn't bring it through the metro area until 5 to 6 pm tomorrow. The WRF-GFS does bring a frontal band of high RH, at 700 mb and above, across southeast Arizona. Thus, it appears that April's second weather event will likely bring winds, dust, virga, some possible sprinkles, and perhaps some nice mammatus clouds.
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