20200826

 Day 1

I don't have the time (or energy) for a full discussion today, and considered taking the day off, but there is some potential for Phoenix to talk about.  There continues to be weak moist advection into the Phoenix area and to the north.  850mb dewpoints are high enough in these areas to support some strong thunderstorms.  SE Arizona continues to be SOL.

CAPE appears to be sufficient for storms to again form over the higher terrain to the north and northeast of Phoenix.  

As has been typical this year, the incursion of low-level moisture either results in a cap or a shallow mixed layer.  Today, it's a shallow mixed layer.  However, with enough localized convergence from outflow boundaries, a profile like this could develop deep convection.   Mid-level winds are favorable for moving storms from the higher terrain towards Phoenix, much like what happened yesterday.  However, this time, there is some CAPE to work with and some storms could move/develop over the lower elevations.

The WRFGFS develops strong storms to the north of Phoenix and tries to move them into the valley early this evening.  Other strong/severe storms develop later this afternoon over central and western Pima County.

The WRFGFS and NAM do develop some showers and weak storms in the Phoenix area this evening.  A few storms might be stronger than the model forecasts suggest as CAPE looks to be around 1000 J/kg.

Day 2

A weak surge is underway which results in increased moisture for much of the state.  The low-level easterlies in NM also weaken and allow this moisture to move into the Tucson area.

This surge also increases CAPE over much of south central Arizona moderate to high.  The high country also has enough CAPE/moisture for afternoon thunderstorm development.

Intense storms develop over far southern Arizona in the areas of highest CAPE.

I finally get to talk about Tucson again!  CAPE is more than enough to support strong storms in the Tucson area, but the mixed layer is shallow.  There are no inversions present, so all it would take is a strong outflow from a nearby storm.  (see above!)  Normally, steering flow wold be excellent, but it's dry to the east with no storms expected.  Also note that the end (did we even have a start?) of the monsoon can be seen at and above 350mb as southwesterly flow now dominates.  This flow may also result in anvils shearing off the top of the storms to the south, and moving over Tucson, resulting in shading and weak downward vertical velocities.  So, it is a mixed bag.

As often happens, storms move/develop over the higher terrain around Tucson, and skips the valley.

During the afternoon hours, model forecasts have broken to overcast skies for much of central and western Arizona, restricting heating.   CAPE is low at Phoenix so storms that are to the north and east have little support as they move closer to the lower elevations.

Most of the stronger storms remain over the higher terrain, but a few weak ones are possible for the Phoenix valley.