20220722

 Previous Forecast

Activity remained over the higher terrain north and east of Phoenix and in far SE Arizona.  Another MCS moved across northern  Sonora, but it was weaker and didn't propagate as far as previous nights.  Not surprising as the atmosphere must be really worked over.  The various WRF forecasts did not have an MCS last night.

Discussion

PW has increased for central and eastern Arizona and is now 40-42mm around Tucson and 37-39mm near Phoenix.  It has decreased in far western Arizona.  Tucson has quite a bit of elevated CAPE at 1400 J/kg.  Steering winds are good as they are ENE at 10 to 20 knots.  Low-level winds could be better, but I'd guess they will come up from the NW by afternoon.  Anvil shading is an issue with easterly flow near the tropopause.  Based on the upper-air data, I'd say Tucson should have a good chance for storms today.

The subsidence inversion is gone, and the lower level cap is weak at Phoenix, but CAPE is lacking.  The wind profile looks good, with moderate mid-level easterly steering.  As with Tucson, anvil shading could be an issue. 

The 500mb anticyclone has weakened a little but remains in the same location.  Temperatures are slowly increasing, and around now, around -6 to -5C.  However, as seen on the Skew-T plots, the mid-level inversions are mostly gone, probably due to the slight weakening of the anticyclone.  A weak trough over north central Texas could come our way in a day or two.

Initializations

An MCV is spinning over north-central Sonora, along with an extensive debris cloud field.  The 6Z initializations did not have nearly enough clouds.  The 6Z GFS was missing the MCV.  9Z and beyond were all accurate, so those are today's favored runs.

Day 1

Thanks to the MCS, another outflow Surge is expected to begin sometime this morning.  Thus, the drying will be less than expected.

850mb dewpoints look good for much of far south-central and southeastern Arizona.  Southern NM has also moistened up, and despite easterly flow, there isn't any dry air advection into far SE Arizona.

CAPE is moderate from about central Pima to Cochise County, which will support a lot of activity today and tonight.  The model runs are mostly consistent with the magnitude and location.

Almost everything looks good for Tucson: 40mm PW, 1400 J/kg CAPE, deeply mixed PBL, low-level NW winds, and SE 15 to 20-knot steering flow.  The only problem is the upper winds are also southeasterly. Thus, anvil shading is a threat.

Most runs develop strong to isolated severe storms over the higher terrain of Santa Cruz, eastern Pima, and Cochise Counties by later in the afternoon.   They are split on moving storms into Tucson proper, but all have them near.

The 4-panel plot has the heaviest rain to the south and east of the valley.  Amounts could be pretty high, above 1.5".

Weaker activity continues for much of SE Arizona into the evening.

Day 2

The Gulf Surge continues into tomorrow, resulting in some of the highest PW values of the season so far for southcentral Arizona.

It's also one of the better(best?) CAPE days so far, with the best being in southeastern Arizona.

Another reason for a big day is that the trough I talked about earlier seems to make its way to Chihuahua by tomorrow afternoon, resulting in divergence and influence over southeastern Arizona.

All recent WRF runs are indicating another very active day for southeastern Arizona.  Some storms are likely to be severe.

Storms try and move towards the Phoenix area but die as they approach.  The forecast Skew-T is quite impressive with a deeply mixed PBL, 1900 J/kg of CAPE, and a good wind profile.  The only issue is the inversion at the top of the PBL, which looks pretty strong, and is why deep convection dies as it makes its way toward Phoenix.

48-hour accumulated precipitation is more than 3" for some locations, so widespread flash flooding could be a problem.