This morning's sounding plot for TWC (above from SPC) indicates warm, dry, stable conditions locally, with PW well below an inch. Only threat of showers will remain well to our east this weekend.
The PW MIMIC analysis from CIMSS at University of Wisconsin (above for 12 UTC) shows very moist, tropical air lurking at the south end of GoC. Swirl near Hawaii is Hurricane Lester, which is forecast to avoid the Islands, passing off to their north.
The morning outlook from NHC (below) indicates high probabilities for a new tropical system to develop and head north toward Baja. This system could be a player in southern Arizona weather by mid-week next week. The GEFS plumes for QPF from 06 UTC last night (bottom) forecast the possibilities of significant rains for TUS after September 7th. The operational version of the model (blue) really doesn't pick up the tropical system and has one of the driest forecasts for the coming week - in contrast to the ECMWF operational forecast, which is very aggressive, bringing the tropical system all the way to the north end of Baja. Will perhaps become an interesting second half of the first full week of September (see the Cloud-maven blog post from August 30th - link to right).