Climate & Environment
Polo’s remnants feed a widening flood threat from Southwest to Plains
Polo is weakening inland, but its tropical moisture is merging with a larger storm system. Saturated ground, burn scars and arroyos raise flash-flood concerns as the rain moves east.
Executive summary
- The current risk: The National Weather Service’s Weather Prediction Center said flash flooding could continue overnight from southeast Arizona and New Mexico into West Texas. Its latest outlook placed parts of the Southwest and central High Plains under a Moderate Risk of excessive rainfall, level 3 on a 4-level scale.[1][2]
- Why the threat is moving: Polo’s remnants are supplying tropical moisture as they interact with an upper-level low. The forecast calls for heavy rain to shift toward the southern Rockies and Southern Plains Wednesday and Thursday, with flood concerns extending farther into the central U.S.[1][3]
- Observed impacts: The Associated Press reported flooded roads, water rescues in Arizona and evacuations in New Mexico after concern about a dam. The forecast is not a report that flooding has occurred everywhere within the risk areas; the highest danger is localized where heavy rain meets saturated ground, burn scars and low-water crossings.[4][1]
Polo has weakened as it moved inland, but forecasters say its moisture is continuing northeast into a larger storm setup. In a forecast discussion issued Tuesday evening, the National Weather Service’s Weather Prediction Center said considerable flash flooding remained possible overnight from southeast Arizona and New Mexico into West Texas as Polo’s remnants merged with a strong upper-level low.[1][4]
The WPC’s excessive-rainfall outlook rated parts of the Southwest and central High Plains at Moderate Risk, level 3 of 4. The center also maintained moderate-risk areas for portions of the central and southern Plains and Corn Belt on Wednesday, and portions of the Southern Plains on Thursday. A risk category describes the forecast chance and potential footprint of excessive rain; it does not mean that every community inside the area will flood.[2]
Polo’s remnants are one part of the forecast pattern. The WPC said an upper-level low is drawing the tropical moisture northeast, while a strengthening low over the High Plains is expected to pull Gulf moisture northward. That broader system is why the rain threat can continue and shift east after Polo itself loses its tropical-cyclone identity.[1][2][5]
The Associated Press reported Tuesday that rain had flooded roads and left debris on New Mexico highways, while water rescues were reported in Arizona. Concern about a dam prompted evacuations in several small New Mexico communities, AP reported. These are reported impacts from Tuesday; the latest forecast describes the additional risk overnight and over the following days.[4]
Forecasters singled out saturated soils, burn scars, canyons and low-water crossings as especially vulnerable to rapid runoff. The WPC forecast heavy storms overnight in southern and eastern New Mexico and West Texas, then a shift toward the southern Rockies and Plains. AP and Weather.com also described a wider, multi-day rain and flood threat moving from the Southwest toward the central and southern United States.[1][4][3]
The forecast remains subject to change as storm bands move. The NWS advises people in affected areas to follow local warnings and avoid driving or walking through floodwater; a road that is passable before a storm can become dangerous quickly.[1][4]