20160629

Previous Day
The late night/early morning storms did materialize as areas in and around Tucson saw storms after midnight.  The WRFRR handled this the best.

Initializations
This is going to be a tough day as the early morning activity has left behind lots of clouds and stable air in SE Arizona.  Bob has a excellent summary here.  The overnight runs have no clue regarding the modified air-mass as seen in the temperature plot below.

The 12Z NAM and GFS, while initializing too warm around Tucson, had a fair amount of clouds present.   There also appears to be a weak MCV over Santa Cruz county.   A large IT can be seen rotating over NW Mexico, similar to the WRFGFS from yesterday and this feature even shows up on the 12Z 500mb analysis.  The 12Z NAM  has it initialized well.

The 12Z RR struggled with the IPW initialization as much of Arizona was too dry and NW Mexico too wet.  The 12Z NAM and GFS were better with only minimal errors.

Confidence in the model runs, especially around Tucson is low due to the poor initialization of the rain cooled airmass and insufficient clouds.  However, clouds so seem to be dissipating which will allow some recovery. In other parts of the state, the model runs should be OK.  I'd say the best is the WRFNAM.

Day 1
Moisture continues to increase over all of the state with more than enough to support widespread activity this afternoon and evening.  With so much present, flash flooding potential with storms will be high.  The WRFNAM is a bit wetter as it has weak flow from the south while the WRFGFS has weak easterly flow over much of the eastern 1/2 of the state.

CAPE is moderate to high especially over the higher terrain of the Rim and White Mountains and as it's clear there this morning, storms should form rapidly and become strong.

Mid level winds continues to be somewhat favorable for propagation of storms into the lower elevations.  The direction is good, but the winds are weak.

The WRFGFS and NAM develop storms over far SE Arizona all along the Rim/Whites by early afternoon.  The big question is if deep convection will be present SE of Phoenix by late afternoon as that will be required for the generation of intersecting outflow boundaries needed for widespread Maricopa county storms.

WRFNAM

The afternoon Skew-T forecast indicates light easterly mid level steering, favorable upper flow, and a moderate amount of CAPE.  The issue is the PBL does not mix deep enough for convection, at least in the WRFNAM.

The WRFGFS has much more activity across SE Arizona by late afternoon than the WRFNAM.  I think the WRFGFS is overdone and is probably wrong.

WRFGFS

A big outbreak of strong/severe storms in Phoenix as predicted yesterday is now less likely as only one of the needed outflow boundaries is present by early evening.  The storms to the north of Phoenix did their part and a strong outflow moves south.

WRFNAM

As is so often the case, the actual events are many times somewhere in between the two model runs.  The WRFGFS has outflow boundaries moving in from the SE and N towards the Phoenix area.

WRFGFS

It's really a tough call for a major outbreak as Phoenix is primed and ready to go, even in the WRFNAM, as there is around 1500 J/Kg of CAPE.  I don't think a single strong outflow boundary is going to be enough to generate the lift needed, but if even a weak to moderate outflow boundary comes in from the SE, deep convection should initiate.

The WRFNAM does develop some activity in Pinal county during the evening.

The other extreme is the WRFGFS.  The wildcard is the IT that begins to eject into Arizona overnight.  The WRFGFS brings it into the state during the evening which helps organize convection.

Both runs continue activity into the early morning hours.

WRFGFS

Day 2 will follow later this morning