Flash Flood Risk Rises for Las Vegas and Phoenix as Storm Moves In

While the northeastern corner of the country is expecting dry and sunny conditions this week, it will be the reverse situation unfolding in the opposite corner of the U.S. A massive storm system is gearing up to dump heavy rain and ignite thunderstorms across the Southwest starting on Wednesday and lasting through the rest of the week. This is what you need to know if you live in this corner of the country.

Southwestern U.S. Braces for Heavy Rain and Thunderstorms

A developing storm is forecast to churn into the Southwest in the days ahead, raising the risk of flash flooding, high winds, and travel disruptions. Although the moisture coming along with this weather maker will be beneficial to the areas struggling with drought and wildfire concerns, the pattern will also carry the threat of mudslides and other severe impacts.

Forecasters are warning that the rain will come in several waves that will stretch from the Pacific coastline and into the Rockies. In addition to the new storm, some of Trudy's remnants may also creep up into the interior portions of the Southwest.

The moisture machine fired up on Tuesday in some areas of Oregon and Northern California. San Francisco will remain under the threat of rain showers through at least Thursday.

The latest forecast models predict that the most potent bands of moisture will arrive in Southern California just in time for the Wednesday evening commute, sticking around through Thursday morning. The forecast is calling for widespread rain totals of 0.50 to 1 inch of rain across the lower elevations of coastal Southern California.

Heavier rain amounting to 1 to 2 inches is expected for the south- and west-facing slopes of the hills of this part of the Golden State. This mountainous terrain will also be at the greatest risk of mudslides and debris flows, particularly across the recent burn scars.

The Southwest cities such as Las Vegas and Phoenix are anticipating the rain to move in late Wednesday and into Thursday. Urban flash flooding will be a concern in these metro areas. Forecasters are warning that it will not take much rain for the normally dry streambeds to turn into rivers.

It has already been an especially wet October for Las Vegas. Sin City has picked up almost four times the historical average rainfall totals through Tuesday, with even more precipitation on the way.

The volatile weather will track farther east on Thursday, reaching parts of New Mexico and Colorado at this time. Spotty rain showers and storms will persist in the interior West well into the weekend.

Severe Weather Threat

The storm system responsible for the surge of moisture will also support the development of severe weather on Wednesday and Thursday. In addition to the risk of flash flooding, the greatest concern will be the strong winds and hail embedded in these storm cells.

Arizona will be under the umbrella of severe weather on Wednesday. By Thursday, this threat will expand to the north and east, reaching Utah, western New Mexico, and eastern Nevada.

The chance of thunderstorms along the Southern California coastline will also present the risk of waterspouts and tornadoes beginning Wednesday afternoon and lingering into early Thursday.

A southward dip in the jet stream over the western U.S. will also bring down chilly air from Canada for some parts of the region. This influx of colder temperatures will lay the groundwork for snow showers across the ridges and peaks of the Sierra Nevada. Any accumulation will be limited to the grassy areas.

Although this weather will cause its fair share of disruptions, the moisture is much-needed in the Colorado River Basin. Historically low water levels in Lake Powell have rebounded in recent weeks thanks to the wet pattern. Nearby Lake Mead has not been as lucky, as it has missed out on much of the rain.

The forecast of rain is good news for these major reservoirs, but it will take an entire winter of heavy snow to replenish these water stores during the annual spring thaw.

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