{"id":5150,"date":"2026-09-09T17:45:27","date_gmt":"2026-09-09T17:45:27","guid":{"rendered":"https:\/\/discussions.weather.arizona.edu\/?p=5150"},"modified":"2026-09-09T17:45:27","modified_gmt":"2026-09-09T17:45:27","slug":"september-9th-2026-a-good-chance-of-thunderstorms-in-southeast-arizona-today-thunderstorms-will-move-into-the-tucson-metro-area-during-the-evening-hours-with-locally-heavy-rain-possible","status":"publish","type":"post","link":"https:\/\/discussions.weather.arizona.edu\/?p=5150","title":{"rendered":"September 9th, 2026: A\u00a0good chance of thunderstorms in southeast Arizona today; thunderstorms will move into the Tucson metro area during the evening hours, with locally heavy rain\u00a0possible.\u00a0Storm chances\u00a0decrease tomorrow as moisture moves south"},"content":{"rendered":"\n

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

Tropical storm Lowell recently affected Hawaii with strong winds and heavy rainfall, especially in mountainous regions. Meanwhile, the remnants of Marie brought rain and coastal impacts to southern California, but flooding was minimal. Upper-level water vapor satellite imagery shows moisture transport from remnants of Marie into California and another flow from Mexico into AZ\/NM. The subtropical high has reformed over the region, and moisture is available; mid-level temperatures are a bit high and will limit activity over most of Arizona except the southeastern corner. Thunderstorms will develop in Cochise, Graham, and Greenlee counties and move slowly west, reaching the Tucson metro between 7 and 9 pm. <\/p>\n\n\n\n

Forecasts indicate more precipitation today than tomorrow, with storms mainly in southern Arizona and along the international border by tomorrow. One long-range model (GEFS) suggests a chance of more storms early next week from tropical activity, though it differs from the European model (ECMWF), which takes the tropical moisture west away from the Southwest.<\/p>\n\n\n\n

Yesterday’s Weather<\/h2>\n\n\n\n

Visible satellite imagery overlaid with radar and lightning at 4:30 pm shows showers and thunderstorms extending from southeast Arizona northeast to southwest New Mexico and further northeast into southeast Colorado. Additional storms were on the Mogollon Rim, extending east into west-central New Mexico. Some light showers fell in the early morning hours in Pima and Graham counties. No severe weather was reported, and most of the heavier rain was confined to the mountains where precipitation was generally less than a half inch.<\/p>\n\n\n

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GOES-19 visible satellite imagery overlaid with radar reflectivity and GLM lightning from September 8th, 4;30 pm, College of DuPage.<\/figcaption><\/figure>\n<\/div>\n\n\n

The HRRR-UA WRF 12Z 24-hour accumulated precipitation forecast (left) and corresponding observed precipitation from MRMS (right) are shown below.\u00a0A good match between the forecast and observations, with only some of the totals in the sky islands underestimated in the forecast.\u00a0<\/p>\n\n\n

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HRRR-UA WRF 12Z 24-hour accumulated precipitation forecast (left) and corresponding observed precipitation from MRMS (right) for September 8th.<\/figcaption><\/figure>\n<\/div>\n\n\n

Analysis<\/h2>\n\n\n\n

The only remaining tropical system in the Pacific Basin is tropical storm Lowell, which brushed the western islands of Hawaii. Lihue Airport had a wind gust of 75 mph. Heavy rain fell in these areas, with up to 20 inches in the mountains.\u00a0More tropical systems are expected to develop well south of the Baja Peninsula over the next few weeks, with some potential to affect Arizona and California.\u00a0<\/p>\n\n\n

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National Hurricane Center outlook<\/a> for the Pacific basin<\/figcaption><\/figure>\n<\/div>\n\n\n

The remnants of Marie are still spinning 600 miles west of San Diego.\u00a0Marie did not hit the Los Angeles\u00a0area directly, but as shown by the Rainlog data, the\u00a0area did receive heavy rain. Rain falling from mid-level tropical systems does not fall at a fast rate, and flooding was minimal. The more significant effects from Marie were from heavy surf, beach erosion, and coastal flooding.<\/p>\n\n\n

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7-day precipitation totals for Los Angeles, September 2nd to 9th.<\/figcaption><\/figure>\n<\/div>\n\n\n

The\u00a08 am water vapor satellite imagery shows a polar low (blue “L”) and associated jet stream (black arrow) far off California’s west coast. The jet stream extends east into Montana. Moisture flows from the tropics to the remnants of Marie, then extends east into central California (red arrow).\u00a0Another moisture flow comes from central Mexico northwest to southern Arizona, then northeast into southwest Kansas (green arrow). A Tropical Upper Tropospheric Trough (TUTT) has several lows associated with it from the Caribbean Sea west into Mexico, then offshore of the Baja Peninsula (red dashed line).\u00a0<\/p>\n\n\n

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GOES-19 upper-level water vapor image September 9th at 8 am, College of DuPage.<\/figcaption><\/figure>\n<\/div>\n\n\n

The visible satellite picture from\u00a08 am this morning overlaid with radar and lightning images shows\u00a0showers over western Arizona and southeast California. Thunderstorms are south of the international border and will continue moving west towards Puerto Pe\u00f1asco.\u00a0A broken layer of mid-level clouds covers western Arizona, but it’s thinning east of I-10 in central Arizona, with only isolated clouds in New Mexico.<\/p>\n\n\n

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GOES-19 visible satellite imagery from September 9th at 8 am, College of DuPage.<\/figcaption><\/figure>\n<\/div>\n\n\n

Surface dewpoint temperatures are high over southern Arizona and southern New Mexico. Dry air is further north\u00a0near the Utah\/Colorado borders.<\/p>\n\n\n

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Surface weather station observations for Arizona and New Mexico at 7:00 am, NWS<\/a><\/figcaption><\/figure>\n<\/div>\n\n\n

The HRRR-UA WRF 12Z initialization (left) and observed (right) sounding for Phoenix at 5 am are below.\u00a0The soundings agree well. Negative factors include the dry pocket between 800 and 900 mb, the slightly warm 500 mb temperature of \u20134\u00b0C, and cooling from 810 mb to the surface.\u00a0<\/p>\n\n\n

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HRRR-UA WRF 12Z (left) initialization and observed sounding (right) at Phoenix for 5 am this morning.<\/figcaption><\/figure>\n<\/div>\n\n\n

At 250mb, high pressure is centered over central Pima County with very weak flow over the southern half of Arizona and New Mexico. An inverted trough is north-south oriented from the eastern Texas Panhandle south to near Laredo (red dashed line).<\/p>\n\n\n

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The high-pressure system is in Oklahoma, with the 500 mb axis extending to southeast Arizona, and a broad flow across northern Mexico into California. The flow in Arizona and New Mexico is weak.\u00a0Temperatures are warm\u00a0in the eastern third of New Mexico, which will prevent thunderstorms there.<\/p>\n\n\n

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At 700mb,\u00a0the high is east-west oriented from central Oklahoma across northern New Mexico and Arizona.\u00a0An easterly wave appears to be entering southeast Arizona and may be the focal point for today’s thunderstorms.\u00a0<\/p>\n\n\n

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Today<\/h2>\n\n\n\n

The Phoenix sounding (left) is for 4 am Thursday morning. There is too much Convective Inhibition (CIN)\u00a0during the day, but overnight the layer between 650 and 400 mb seems unstable enough to produce\u00a0some mid-level showers or a thunderstorm. In Tucson at 3:30 pm (right),\u00a0the CIN is less, and the storms will develop in the\u00a0mountains,\u00a0then move slowly west.<\/p>\n\n\n

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HRRR-UA WRF 12Z forecast soundings for Phoenix at 4 am (left) and Tucson at 3:30 pm (right).<\/figcaption><\/figure>\n<\/div>\n\n\n

The forecast radar reflectivity at 6:30 pm shows thunderstorms extending along a northeast-to-southwest axis from northeast New Mexico to Cochise and Santa Cruz counties in Arizona. The strongest storms in Arizona will be in southern and western\u00a0Cochise County, with the\u00a0forecast showing\u00a0storms in the Tucson area between 7 and 9 pm. The exact location of\u00a0the storms in the Tucson metro area is hard to predict, and different forecast runs have predicited precipitation ranging from\u00a00.25\u201d to 1″,\u00a0with Vail and the Rincon Mountains receiving\u00a0the\u00a0heaviest rain.\u00a0<\/p>\n\n\n\n