Forecast Period: Wednesday through the Weekend (October 21–25)
Affected Regions: Central & Southern California, Four Corners, and Southern Rockies
An unstable upper-level low moving into the Western United States is drawing significant tropical and Pacific moisture northward, bringing a prolonged multi-day heavy rainfall event to parts of Central and Southern California, the Four Corners region, and the Southern Rockies.
While moisture is often welcome in the arid West, the convective intensity of these upcoming storms presents notable localized hazards.
Key Weather Hazards & Potential Impacts
- Flash Flooding & Urban Flooding
- Heavy convective downpours capable of rain rates over 1 inch per hour may quickly overwhelm drainage systems in urban areas, low-lying road crossings, and normally dry washes (arroyos).
- Travel delays and sudden road closures are likely during peak rainfall periods.
- Debris Flows & Mudslides Near Burn Scars
- Rain falling over recent burn scars poses a serious risk of fast-moving mud and debris flows.
- Communities downslope or downstream of burn scars should closely monitor local emergency alerts and evacuation warnings.
- Heavy Downpours & Isolated Thunderstorms
- Expect isolated strong-to-severe thunderstorms producing gusty surface winds, frequent lightning, and small hail embedded within the broader rain shield.
Timing & Regional Outlook
- California (Central & Southern): Rain and scattered embedded thunderstorms begin moving onshore midweek, with rainfall rates peaking through Thursday before spreading inland.
- Four Corners & Southern Rockies: Persistent surge of moisture will keep rain chances high through the weekend (Oct 21–25), keeping wash crossings dangerous and high-elevation routes slick.
Safety Tips for Residents & Travelers
- Turn Around, Don’t Drown: Never drive through flooded roadways or flowing washes. Deep water or collapsed roadbeds underneath can be invisible.
- Stay Clear of Canyons and Washes: Hikers and campers in canyon country should avoid narrow slot canyons and dry riverbeds, as upstream rain can send sudden flash floods miles downstream into clear weather areas.
- Monitor Local Updates: Stay tuned to local NWS offices and local emergency management for Flash Flood Watches, Warnings, and potential burn-scar evacuation directives.
