The forecast for this afternoon and evening is quite difficult for the Tucson metro area, but more straight forward for the Phoenix region.
The morning sounding plots (from the Univ. of WY page) for Phoenix (top) and Tucson (bottom) are shown above. Both appear quite supportive of severe thunderstorms, with excellent steering flow, a nice shear profile in lower half of troposphere that can support organized MCS/tropical-type squall. The upper winds will allow storm anvils to spread off to the northeast, or at worst be left behind by the convective cores. There appears to be substantial difluence aloft over Arizona, that will persist through most of the day. Both the soundings have moderate (for out here) CAPE for convection based around 600 to 700 mb - thus, excellent potential for severe macroburst windstorms. The most important aspect of the two soundings above is that while moisture and CAPE have increased substantially, there has NOT been significant low-level cooling. Thus, with abundant sunshine, the deserts should heat rapidly, storms should develop on mountains, and head toward the west. Often there is a day delay in intense storms after a GoC surge, because of low-level cooling and capping - not today!
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It appears that the primary, middle-level wave is off to the southwest of Tucson, over the GoC - exact details are unknown, since most of northern Mexico is devoid of soundings yet again. There does appear to be a trailing portion of the wave that will brush southeastern Arizona today. The cons for Tucson area are that there are still strong low-level easterly winds (however, these should diminish during the day), and the air mass is distinctly more stable over southwestern New Mexico. Key question is whether mountain storms develop from northeast to southeast of Tucson? Portions of south-central Arizona appear to have a moderate risk for severe thunderstorms today - say from Nogales to Phoenix and west to Colorado River. As for Tucson, I'd say it's a coin toss - my forecast for the house is 50% chance of thunderstorms with measureable rainfall, preceded by wind and dust.
The U of A, WRF-GFS forecast from the midnight run indicates MCSs over western Arizona at midnight tonight (top above is composite radar forecast). Accumulated precipitation at midnight (just above) is heaviest southwest of Tucson and in the Phoenix area. But the model indicates that storms initially developed east of Tucson - but barely. So, tough call for here - tomorrow's forecast, of course, will depend upon what happens during next 18 hours.
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