20200813

Previous Forecast

There was a little bit more activity yesterday, mainly over eastern Arizona.  A few storms also developed over far western Arizona, which was a little surprising. (but not to the WRFGFS)

The GFS was the best performing model initialization.  The RR continues to not have enough activity in these marginal situations.

Discussion

It's the same old story.  The monsoon ridge is suppressed by the NW CONUS trough and Arizona is dominated by southwesterly flow.  PW has generally decreased since yesterday, but might be sufficient for storms over the higher terrain.

Initializations

The 12Z NAM initialized too many clouds over southeastern Arizona.  Other than that, the initiations look good.

Day 1

850mb moisture is marginal for storms today. 

Like yesterday, CAPE is low to moderate over much of southern and central Arizona.

The Tucson Skew-T has some favorable features such as a well-mixed CBL,  no strong inversions, decent mid-level steering, and upper winds to blow anvils away from the storm motion.   The only thing that is lacking for an active day is CAPE as it's only 200-500 J/kg.  It's still sufficient for some storms, mainly over high terrain, like yesterday.

Storms develop mainly over the higher terrain of SE Arizona.  A few may manage to drift into the Tucson area.

Day 2

It looks like more of the same as moisture continues to be marginal and CAPE is mostly low.  Significantly higher dewpoints are just south of the border though and CAPE is higher so it could be quite active there.

The Tucson Skew-T looks quite good as the wind profile is excellent with shear and mid-level steering.  CAPE is pretty good too.

Storms are mainly restricted to areas south of Tucson, but it is still possible that some may eventually develop.