Storms Avoid Metro Tucson Again

Yesterday afternoon the strong easterly surface winds weakened and turned some toward the south. As this happened a strong area of thunderstorms developed from south to west of Tucson. These storms produced heavy rains and prompted several severe thunderstorm warnings. There was a possible severe wind reported near Green Valley. There were 25 ALERT stations with rainfall, and six stations reported a half inch or more of rain. The rains were mostly in the southwestern portion of the ALERT network - see 24-hour rainfall reported at 6:30 am MST above. The storms ran westward as an organized line - see regional radar below from 7:00 pm MST. Thick anvil cloud from these storms pushed eastward across the metro, and a low-level outflow also pushed eastward across town about 3:30 pm. The low-level convergence over central Tucson forced weak showers over town (a trace here), but subsidence below the anvil apparently keep deep storms from developing. Essentially two mesoscale features were at battle overhead during the late afternoon and  evening. There was eventually a small cell, with lightning, over the Catalinas around 8:30 pm MST.

This morning extensive cloudiness covers almost all of the Southwest and extends northward across California, Nevada and Utah. The IR image above (for 13 UTC - 6 am MST) shows a large MCS over northern Mexico, and a smaller complex south of Las Vegas. The heavy cloud cover makes today's forecast very difficult, since much will depend on how the clouds evolve. Outflows have cooled the low-levels some and there is wet ground to the south and west - things are very complex.

The Tucson 12 UTC sounding (above) is very moist (in fact comparison with GPS indicates it's a bit too moist). The layer at and near surface is cool and stable, but the sounding indicates that there is an elevated layer at and below 700 mb with some CAPE. Is this real? The presence of light showers in the area (6:55 Tucson radar image below) seems to indicate that the elevated instability is likely present. Light sprinkles are falling here at the house. No early WF to evaluate. NAM keeps most significant precipitation out over central Pima County again. But the details of how the day evolves will be complicated....