Flood watches stretch across Arizona, New Mexico, Utah and Colorado as Pacific moisture surges in

Flood watches cover parts of Arizona, New Mexico, Utah and Colorado from October 30 into November 2, as successive surges of Pacific moisture raise the risk of flash flooding across the Four Corners. The Weather Prediction Center rated November 1 a Moderate Risk of excessive rainfall for the area. The ground there is still saturated from a destructive flood that began October 21.

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Forecasters describe three pushes of moisture rather than one: a Friday round centered on central Arizona, a second surge on Saturday, and a longer soaking over the San Juan Mountains on Sunday and Monday.

Arizona’s rounds of rain, from the Mogollon Rim to Phoenix

For October 30 the Weather Prediction Center placed portions of Arizona, southern Utah and southwestern New Mexico under a Slight Risk, with 1.5 to 3 inches of rain across many areas and the highest totals from the Mogollon Rim toward the White Mountains, according to The Watchers’ summary of the outlooks. The center said several instances of flash flooding were possible, especially in low-lying ground and slot canyons. The second surge, from midday October 31 into November 1, carries precipitable water of 1 to 1.5 inches, four to six standard deviations above normal, and an integrated vapor transport near 750 kg per meter per second that the center called near-record moisture for the season.

NWS Phoenix issued a Flood Watch for the Phoenix metro, rural Maricopa County and northwestern Pinal County from 6 a.m. to 6 p.m. MST on October 30, with rain rates of 1 to 2 inches an hour possible. Later watches begin late October 31 and run through early November 2, adding another 1 to 2 inches around Phoenix and 2 to 3 inches in higher terrain. NWS Flagstaff expects 1 to 3 inches more over saturated ground in Coconino, Navajo and Apache counties, including the Navajo Nation, while NWS Tucson forecast half an inch to an inch in southeastern Arizona valleys and 1 to 2 inches or more in the mountains. The nationwide NWS Flood Watch summary map lists the active watches.

The Saturday surge is the one forecasters flagged for timing. Rain of 1 to 2 inches is expected along the Mogollon Rim, with much of it falling after midnight when flash flooding is hardest to spot. NWS Phoenix also issued a separate watch for the higher terrain east of the city from noon through the evening of October 30. In Yavapai and northern Gila counties, NWS Flagstaff’s watch ran from 10 a.m. to 10 p.m. MST with general totals of half an inch to an inch and localized amounts up to 2 inches.

The San Juan Mountains Moderate Risk on November 1

The Moderate Risk window opens at 12:00 UTC on November 1 and closes at 12:00 UTC on November 2. Moisture four to five standard deviations above normal is forecast to stream into the San Juan Mountains, where persistent southwesterly flow could produce about 18 hours of steady heavy precipitation. Snow levels are expected to climb above roughly 11,000 feet, so the rain falls on most slopes instead of building snowpack. The center defines a Moderate Risk as at least a 40 percent chance of rainfall exceeding flash-flood guidance within 25 miles of a point, and it flagged that parts of central Arizona could need an upgrade. Its current excessive rainfall outlook page carries the latest risk maps.

NWS Grand Junction forecast 1 to 3 inches across parts of southeastern Utah and southwestern Colorado on November 1 and 2. Its watch covers the Four Corners, the Upper Dolores, Animas and San Juan river basins and the southwestern San Juan Mountains, with burn scars, low-water crossings and debris-blocked drains named as trouble spots. NWS Albuquerque expects 1 to 2 inches near and west of the Continental Divide, with a watch for north-central, northwestern and west-central New Mexico from early November 1 through the morning of November 2. River rises are expected there but should stay below those of the previous event.

A region still recovering from the October 21 flood

The earlier storm began on Wednesday, October 21, and by October 23 had triggered road closures, evacuations and emergency declarations in all four states, WUNC reported. Hurricane, Utah, declared an emergency after flooding damaged more than 100 homes and RVs. In San Juan County, New Mexico, responders rescued people from rooftops, and a county spokesperson, Devin Neeley, said flooding of that scale had not been seen there in generations. Colorado Gov. Jared Polis declared disaster emergencies in 12 counties. Climate scientist Daniel Swain linked the moisture to record-warm waters off the West Coast tied to a strong El Niño and a marine heat wave.

Kris Sanders, a meteorologist at the Grand Junction weather office, told reporters on October 25 that the soils were very saturated, so even modest rain could push small creeks and streams over their banks, as KUER relayed from the Associated Press. At that point the San Juan River was threatening Bluff, Montezuma Creek and Aneth, Utah, with evacuation warnings, and flooding at Shiprock on the Navajo Nation damaged wastewater facilities and released sewage into the river.

Two questions remain open as the watches run. One is whether central Arizona is bumped from a Slight to a Moderate Risk, as the Weather Prediction Center said might be necessary. The other is how high the rivers climb in New Mexico, where NWS Albuquerque expects rises that stay under the earlier event’s crests.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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