SOUTHWEST — A powerful upper-level low off the California coast is pulling deep tropical moisture north from the eastern Pacific this week. Some of that moisture is tied to Trudy. Atmospheric moisture could reach record levels for this time of year across parts of the Southwest late Wednesday into Thursday. The setup will fuel rain, thunderstorms, mountain snow, and a risk of flash flooding and tornadoes.
Upper-Level Low Spins Off California
The storm system is centered over the Pacific west of Southern California and Baja California. Its counterclockwise spin is drawing moisture north along its eastern side. That moisture is streaming through Baja California and the Gulf of California into the Southwest.
Very warm ocean waters are helping supply even more moisture through evaporation. That gives the storm plenty of water to work with as it moves inland. The result could be an unusually wet stretch for late October.
Record Moisture Late Wednesday Into Thursday
Moisture levels in the atmosphere could hit record highs for this time of year late Wednesday into Thursday. The deepest moisture is shown flowing toward Southern California, southern Nevada, and Arizona. Areas near Santa Barbara, Indio, Las Vegas, Flagstaff, and Tucson sit in or near the moisture plume.
When the air holds this much water, storms can produce very heavy rain in a short time. Rainfall rates could overwhelm drainage systems in desert towns. Normally dry washes can flood with little warning.
Flash Flooding Is a Major Concern
Heavy downpours could lead to localized flash flooding across California and the Southwest. Burn scars, steep canyons, and desert washes face the greatest risk. Urban areas with limited drainage could also see quick street flooding…