{"id":4302,"date":"2026-08-05T17:55:35","date_gmt":"2026-08-05T17:55:35","guid":{"rendered":"https:\/\/discussions.weather.arizona.edu\/?p=4302"},"modified":"2026-08-05T17:55:35","modified_gmt":"2026-08-05T17:55:35","slug":"august-5th-2026-risk-of-severe-storms-possible-again-today-for-both-tucson-and-phoenix-strong-winds-and-heavy-rain-in-the-metro-areas-bring-a-threat-of-flash-floods","status":"publish","type":"post","link":"https:\/\/discussions.weather.arizona.edu\/?p=4302","title":{"rendered":"August 5th, 2026: Risk of severe storms possible again today\u00a0for both Tucson and Phoenix.\u00a0Strong winds and heavy rain in the metro areas\u00a0bring\u00a0a threat of flash floods."},"content":{"rendered":"\n

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

Surface moisture remains elevated across southern Arizona, with the Gulf Surge bringing higher dewpoints northward. Today, convective conditions are even more favorable than yesterday, with forecasts consistently predicting afternoon thunderstorms for the Tucson and Phoenix areas. These storms are expected to start in the mountains and move into the valleys, bringing heavy rain and strong winds; Tucson by 7 pm and Phoenix by 10 pm. Recent ensemble forecasts show rainfall totals could range from half an inch to nearly two inches, depending on storm organization. <\/p>\n\n\n\n

Tomorrow, storm activity will decrease in lower elevations, limited mostly to higher terrain, as is typical following a major storm day. Looking ahead, a quieter monsoon pattern will persist into the weekend, although a return of moisture may lead to renewed activity next week.<\/p>\n\n\n\n

Yesterday’s Weather<\/h2>\n\n\n\n

It was a bust! We have been having a good run of accurate forecasts this season, but yesterday was not one of them. Below is the 12Z HRRR-UA WRF forecast radar for 6 pm Tuesday, and below is the Tucson Doppler radar observation at the same time. Why did the storms not develop as forecast? The clue was in the Phoenix observed sounding at 5 am, where we\u00a0wrote the following comparing the model sounding to the observed sounding:\u00a0<\/p>\n\n\n\n

\u201cBut what is missing from the initialization is the cooling below 700mb caused by the Gulf Surge and thunderstorm outflow. This has increased the Convective Inhibition (CIN) to over \u2013500 [J\/kg], which can\u2019t be overcome with surface heating today.\u201d <\/p>\n\n\n

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HRRR-UA WRF 12Z simulated radar reflectivity forecast (left) and corresponding observed radar reflectivity from MRMS (right) for August 4th at 6 pm.<\/figcaption><\/figure>\n<\/div>\n\n\n

Since we do not have an observed sounding in Tucson to compare to the model initialization, we don\u2019t know if the same problem existed here at Tucson. So the state of the atmosphere that morning was one in which no amount of surface heating would allow storms to form. To make matters worse,\u00a0the low-level winds were from the northwest advecting stable air into Tucson. Standing outside at 4 pm yesterday afternoon, the wind was relatively cool even though it was over\u00a0100\u00b0F, and no cumulus was in the sky…a bad omen, showing convective initiation was not possible, likely due to CIN. \u00a0<\/p>\n\n\n\n

We were expecting severe weather in Tucson, but got none. We have been debating how important the observed sounding at 5 am is, since we don\u2019t have any from the Tucson location at the University of Arizona. Well, it was a false alarm,\u00a0so less of a big deal. But what would have happened if missing sounding data had resulted in a missed forecast where severe weather occurred in Arizona with no warning?\u00a0Below is an animation of the zoomed-in view of the Pima County 12Z HRRR-UAWRF forecast (left), the most conservative in rainfall prediction from yesterday, and the radar observations (right). <\/p>\n\n\n\n