Storm Updates: Arizona Slight — Oct 21 Morning

Tropical: None · Severe: Slight · Flood: Slight

What Changed

• Compared with the October 21 afternoon desk (quiet-pulse-2026-10-21-afternoon): SPC Day 1 Convective Outlook (0100 UTC October 22 / 6:00 PM PDT October 21, 2026, valid 220100Z–221200Z) holds a SLIGHT RISK of severe thunderstorms for much of Arizona into far southeast Nevada and southwest Utah. Earlier Enhanced risk over central Arizona has closed with the end of peak diurnal heating; supercells remain possible overnight.
• Severe Thunderstorm Watches 689 and 690 remain active over central and southern Arizona. Multiple Severe Thunderstorm Warnings and Tornado Warnings verified earlier; LSRs include large hail (up to golf-ball size) and damaging winds in Yavapai, Coconino, and Maricopa Counties.
• WPC Day 1 Excessive Rainfall Outlook (updated 0015 UTC October 22, valid 01Z–12Z October 22) maintains a SLIGHT RISK over portions of southern California and the Southwest U.S. (including much of Arizona, southern Utah, southwest Colorado, western New Mexico). No upgrade to Moderate. Heavy rainfall rates continue with the moist plume and upper low.
• NHC continues advisories on Subtropical Storm Josephine (Advisory ~2: ~37.7°N 69.4°W, 65 mph, moving NNE at 6 mph, expected to accelerate northeast away from the U.S. and become extratropical with hurricane-force winds). No tropical storm or hurricane watch or warning on the U.S. coast or Gulf of America. Eastern Pacific Tropical Storm Vance remains well south of Mexico with no U.S. threat. Storm hub: Josephine 2026.
• Both severe and flood lanes remain open at Slight. Restoration focus stays on Arizona hail/wind/isolated tornado damage plus Southwest flash-flood potential from ongoing convection. Quiet Pulse remains closed.

Live Status

As of this Wednesday evening update to the morning desk, October 21, 2026 (approximately 9:12 PM PDT / 12:12 AM EDT October 22 / 0412Z October 22), the national picture centers on the Southwest. SPC Day 1 lists a Slight risk (Level 2 of 5) of severe thunderstorms across much of Arizona (including the Phoenix metro: Phoenix, Mesa, Glendale, Chandler, Scottsdale) into far southeast Nevada and southwest Utah for tonight. Marginal risk covers coastal central and southern California. Supercells are favored with elongated hodographs and 55–65 kt effective shear; large hail is the primary threat (locally 2+ inches possible), with a couple of tornadoes and damaging winds also possible given residual low-level shear and terrain influences. MUCAPE remains 1000–1500 J/kg under the advancing cold core of the deep upper low off the California coast. Additional development is expected across south-central Arizona overnight as shortwave energy approaches from Mexico.

Severe Thunderstorm Watch 689 covers central and southern Arizona until roughly 9:00 PM MST, with primary threats of scattered large hail (isolated very large), damaging winds to 70 mph, and a tornado or two. Watch 690 extends coverage further. Radar and local storm reports earlier today verified hail to 1.5 inches and 60 mph gusts near Prescott, Hawkins, Iron Springs, and other locations in Yavapai and Coconino Counties. Tornado warnings were issued in northern Arizona (first tornado watch products for the state in roughly 16 years). Convection is shifting eastward across Arizona into southwest New Mexico into early Thursday.

WPC Day 1 carries a Slight risk of excessive rainfall over southern California (focused on the Transverse Ranges, burn scars, and urban corridors north and northeast of Los Angeles) and the broader Southwest/Four Corners, including much of Arizona, southern Utah, and adjacent areas. Persistent southerly flow is advecting anomalous moisture; HREF probabilities for additional >1 inch rainfall remain high (>70%) through 12Z. Hourly rates of 0.5–1+ inches are possible, with higher amounts in terrain. Flash Flood Warnings have been issued in parts of Coconino County and southern Utah (including near Zion and Bryce areas). Residual Flood Watches cover higher terrain and burn scars. No Moderate or higher ERO is in effect on Day 1.

Tropical lane remains closed for the United States. Subtropical Storm Josephine is accelerating northeast away from the East Coast with no coastal watches or warnings. Residual high surf and coastal flood products may continue along portions of the East Coast from the parent system, but these do not open a tropical lane for this desk. Winter Storm Warnings remain active in parts of Alaska; these are outside the primary severe/flood focus.

Just-Hit

Preliminary local storm reports and media accounts document golf-ball-sized hail, shattered windows, dented vehicles, and downed trees across northern and central Arizona, including Flagstaff and Mesa areas. Strong winds toppled trees in the Coconino National Forest. Multiple tornado warnings and the first tornado watch for northern Arizona since 2010 verified earlier in the day. Flash Flood Warnings are active or recent over parts of Coconino County, southern Utah (including Zion National Park vicinity with reported muddy flows), and higher terrain/burn scars. No widespread major flooding has been reported as of this update, but the setup supports rapid runoff and urban/terrain flash flooding overnight. Primary ongoing restoration ticket is hail and wind damage to roofs, vehicles, and vegetation in the Phoenix metro and high country, with secondary flash-flood concerns in sensitive terrain.

Pulse Table

Rising Queries

Trends unreachable.

What This Means

The restoration ticket is driven by the Arizona Slight risk severe weather, with supporting flash-flood potential across the Southwest. Organized supercells continue into the evening and overnight with primary hazards of large hail and damaging winds, plus a couple of tornadoes possible. Phoenix metro and central Arizona remain in the threat area under active watches. Southern California sees a marginal severe threat from the approaching Pacific cyclone plus a Slight excessive rainfall risk focused on coastal ranges and urban areas. Named storm hub for Josephine is live even though no U.S. coastal threat. Monitor official sources for the latest warnings and local impacts.

Informational only — not an official warning. Always confirm with the latest official forecasts from weather.gov, spc.noaa.gov, wpc.ncep.noaa.gov, and nhc.noaa.gov. Turn around, don’t drown.