{"id":3848,"date":"2026-07-21T17:44:27","date_gmt":"2026-07-21T17:44:27","guid":{"rendered":"https:\/\/discussions.weather.arizona.edu\/?p=3848"},"modified":"2026-07-22T17:14:06","modified_gmt":"2026-07-22T17:14:06","slug":"monsoon-weakening-scattered-storms-in-the-tucson-area-but-phoenix-should-remain-dry-warming-temperatures-into-the-weekend-july-21st-2026","status":"publish","type":"post","link":"https:\/\/discussions.weather.arizona.edu\/?p=3848","title":{"rendered":"Monsoon weakening; scattered storms in the Tucson area, but Phoenix should remain dry. Warming temperatures into the weekend: July 21st, 2026"},"content":{"rendered":"\n

Summary<\/h2>\n\n\n\n

The Tropical Upper Tropospheric Trough (TUTT) in southern California yesterday has moved north and dissipated. A new low has strengthened in eastern Arizona, aided by yesterday’s activity. Surface moisture remains high in parts of Arizona, leading to flash flood watches in areas of higher terrain northeast and southeast Arizona. Extreme heat warnings are in place in western Arizona. <\/p>\n\n\n\n

Forecasts indicate that Phoenix is unlikely to see storms today due to high convective inhibition, while Tucson has a higher chance for slow-moving storms with heavy rain. Most precipitation is expected in mountainous areas (about 0.5″), with valleys staying relatively dry unless a storm propagates and continues to develop from the southeast. <\/p>\n\n\n\n

Tomorrow, moisture and storm activity are predicted to decrease further, especially for Phoenix, while Tucson may still see scattered storms. By Thursday and into the weekend, monsoon activity is expected to lessen, with only isolated showers and a trend toward warmer temperatures. A possible return of moisture next week could bring renewed monsoon activity, but some down days are ahead. <\/p>\n\n\n\n

Yesterday’s Weather<\/h2>\n\n\n\n

Thunderstorms developed in eastern and northern Arizona in the areas that cleared out from remnant showers and clouds that persisted into Monday morning. Heavy rain\/flooding was reported at Payson with the thunderstorm circled in black.  The thunderstorm and associated outflow moved towards Phoenix, and produced a wind gust of 68 mph at Phoenix Sky Harbor Airport, but only a trace of rain.  After they moved from the mountains to the east, the thunderstorms ran out of Convective Available Potential Energy (CAPE), with new cells forming along the outflows and dying rather quickly.<\/p>\n\n\n

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GOES-19 visible satellite imagery overlaid with composite radar and GLM lightning flashes from July 20th at 6:30 pm, College of DuPage.<\/figcaption><\/figure>\n<\/div>\n\n\n

Storms moved into Tucson by 8 pm as shown by the observed radar reflectivity (below right). Wind gusts were near 40 mph with very little lightning, reflecting weak updrafts from the lack of CAPE. <\/p>\n\n\n\n