This feature has moved fairly rapidly west-northwestward toward the northern end of the Gulf of California. Southerly flow has just not strengthened over the northern Gulf of California, and Yuma remains fairly dry with only slow moistening occurring. The local Valley environment is well conditioned for downburst storms if we can ever get storms away from the mountains with updrafts rooted in the desert boundary layer. The McCollum Type II pattern has decayed today but will be briefly re-established tomorrow. P chart of the 12 UTC sounding from Luke Air Force Base on July 23, 1994.
Wind speeds are in knots.
The small box indicates the location of Phoenix, and the Salt and Verde River Basins are outlined. There were scattered storms over mostly the White Mountains and SE Mountains during the afternoon and evening. A significant area of storms developed over the Tucson area at dark and generated a fairly strong meso-outflow that moved across all of the Valley between about 0700 and 0800 UTC last night. However, there was little instability in the low deserts and only one brief and isolated cell developed over the Valley just northeast of Scottsdale - some lightning and a brief bit of thunder occurred around midnight.