The McCollum Type II pattern continues and there does appear to be a shortwave trough digging southward over northwestern Colorado. The LUF sounding was the most unstable we have seen giving a BLI of -4.5. Considering that the pattern appeared to be the same and with more low level moisture, we forecasted a high risk of thunderstorms in the valley. P chart of the 12 UTC sounding from Luke Air Force Base on July 29, 1994.
Wind speeds are in knots.
The small box indicates the location of Phoenix, and the Salt and Verde River Basins are outlined. Observed Weather Thunderstorms developed in middle to late afternoon along the Rim and didn't move toward the Valley until late evening. Essentially, the Valley was quite suppressed given the high moisture and instability available. Some storms made it to Fountain Hills, but then dissipated in the early morning hours. Strongest storms were up along the Utah border and over eastern and southeastern portions of the state.