20200710

Discussion

Moisture and clouds have increased over Arizona due to the outflow from an MCS over Sonora from last night.  Dew-points were above 60F for awhile in Tucson, but are now generally in the mid-50's over much of the southern part of the state.   PW has slowly increased and is now around 32-38mm.  It is very moist in Sonora as the PW at Hermosillo is around 50mm.   Weakening Tropical Storm Christina is SW of the southern tip of Baja, moving WNW and weakening.  It may be close enough to initiate a Gulf Surge into Arizona over the next few days.

 The 500mb high is centered near the 4-corners with heights around 5960m.  Temperatures are around -6 to -4C which are quite warm and are not favorable for a lot of storm activity.

In spite of the moisture increase, there is only limited CAPE, due to the warm midlevel temperatures.  the substance inversion at 450mb is especially unfriendly!   At least the wind profile is looking more monsoon-like with the good southeasterly mid-level flow and weak winds aloft.

Model Initializations

Scattered to broken debris clouds are slowly decreasing over the state.  The 12Z initializations have clouds initialized well.   PW was initialized well, except for the NAM where it was too wet over far southern Arizona and into northern Sonora.  It looks like the RR and GFS have the best initializations.

Day 1

Moisture advection continues into southern Arizona today primarily due to the outflow surge from the overnight Sonoran MCS.  Dry air continues in New Mexico and far eastern Arizona.  

CAPE is low over much of the state, but there is a higher blob around the Flagstaff area which will support some afternoon deep convection.

The afternoon forecast Skew-T diagrams tell the story for Phoenix and Tucson.  As is typical with a moisture surge, the lower boundary layer is cooled which results in a pretty good cap.  Besides the one at 800mb, there is a second inversion around 500mb, which was also seen on the observed upper air data at 12Z.  So, in spite of some CAPE, deep convection, at least for the valleys, is very unlikely.

Very little activity is forecast for today except for a few storms over southern Coconino County.

Day 2

Weak moisture advection continues into the state, but PW generally decreases.  CAPE is also marginal for storms.

While the vertical wind profile is pretty good, CAPE is limited and there are multiple inversions present.  At least the moisture will knock a few degrees of the high temperatures compared to a few days ago.

Most afternoon activity is restricted to the White Mountains and Rim.

A few evening storms are possible for southeastern Arizona.  It's doubtful that they'll make it into the Tucson area.