20161007

Another round of strong to possibly severe thunderstorms are possible over parts of the state tomorrow as moisture pools in the vicinity of a backdoor front. Activity gets off to an early start as a blob of moisture is forecast to be present over the Phoenix area around sunrise with some CAPE present.

Showers and few storms may form around 6-10am in the Phoenix vicinity.

This activity is being forced by a weak trough over SW Arizona as upper divergence is quite strong along the trough axis.

By early afternoon, moisture continues to increase over SE Arizona/SW NM with impressive 850 dewpoint temperatures around 10C.

CAPE is also impressive with 1000 J/Kg and higher over SE Arizona.  CAPE is also present over the White Mountains up towards Flagstaff which will also support strong storms.

As Bob Maddox pointed out, the wind profile is excellent with strong directional shear and with 1000+ CAPE, strong to severe storms are likely with isolated strong wind and some hail possible.  This is one of the more impressive vertical profiles I’ve seen this transition season due to high CAPE and good directional shear.

Deep convection develops over the high terrain of the Rim/White Mountains during the afternoon.

Later in the afternoon, deep convection forms over the higher terrain of SE Arizona.  Some of these storms become severe with the main threat being hail.  All the runs over the past 24 hours have been quite consistent with this solution.  The big question is if Tucson will see storms and the answer is unclear as some runs have storms in the valley while others (WRFNAM below) keep them over the higher terrain.

The WRFGFS does have strong storms in the Tucson valley and up into Pinal county by late afternoon.  So, the message is that some strong to severe storms are likely around SE Arizona, but exactly where is unclear.

A few strong storms continue over far eastern Arizona into the early evening.

The concern, as it always seems to be, is if there will be clouds restricting heating during the morning hours.  This is definitely a possibility as morning storm activity is possible around Phoenix as well as a large area of clouds overnight.  These clouds are forecast to move out during the morning hours thus there is nearly full heating in the model.