Go With Persistence?

View of late afternoon storms developing over the Catalina Mountains yesterday (Monday August 24).

The rest of the western short-wave trough (which is most distinct up at 300 mb) will pull northeastward across northern Arizona today. The big unknown is whether upper-level subsidence will be strong enough to damp storm activity today. Otherwise there appears to have been little change since yesterday. Very moist, low-level air continues to flow intermittently northward from the Gulf of California; dewpoints and precipitable water have been holding steady out to California; the Phoenix and Tucson soundings continue to have CAPE. So, it appears that today will be much like yesterday with the mountains triggering storms that will try to move northeastward, but steering winds are weakening with time as the anticyclone rapidly rebuilds toward the Great Basin through next 36 hours, so storms may just drift.

The Phoenix morning sounding is quite unstable, indicating that there is some potential for storms to develop at lower elevations today. Storm activity the rest of the week probably depends to large degree on how much low-level drying occurs as the middle level anticyclone builds back northwestward. Tropical Storm Ignacio is forecast to move to the northwest but too far to the west to have very much influence on Arizona.