A new storm system is forecast to bring rain to Los Angeles starting Friday, with impacts expected to peak between 9 p.m. Saturday and 9 a.m. Sunday, according to the National Weather Service (NWS). The system is projected to deliver half an inch to an inch of rain across Southern California, with a 70% chance of precipitation during its peak period.
Halloween activities may be affected, though forecasters anticipate lighter rainfall earlier in the evening. The NWS in Oxnard stated that while traffic and minor roadway flooding are possible, the overall impacts are expected to be minimal. The last recorded Halloween rainfall in downtown Los Angeles occurred in 2014, with a quarter-inch of precipitation.
Storm Timeline and Forecast Details
The storm system is projected to arrive Friday, with stray showers possible in isolated areas and temperatures 5 to 10 degrees below normal, the NWS reported. Forecasters noted a 20% chance that rainfall totals could double or halve the projected amounts due to uncertainty in the storm’s track.
Meteorologist Ryan Kittell of the NWS in Oxnard emphasized that while Halloween activities should account for rain, the precipitation is currently expected to remain on the lighter side rather than moderate. The storm’s peak timing aligns with traditional trick-or-treating hours, raising concerns about outdoor plans.
Potential for Atmospheric River Conditions
AccuWeather and the National Oceanic and Atmospheric Administration (NOAA) have indicated that the storm could develop into an atmospheric river, a narrow band of concentrated moisture transporting tropical air from the Pacific. If the system aligns in a way that stretches from near Hawaii to the West Coast, it could form a Pineapple Express, a subset of atmospheric rivers known for delivering heavy rain and mountain snow.
While atmospheric rivers can provide valuable rainfall to drought-prone regions, they also pose risks of flash flooding, overwhelmed drainage systems, and rapid rises in rivers and streams. Mountain areas may experience heavy snowfall, particularly at higher elevations.
Historical Context and Preparedness
The NWS noted that Halloween rainfall in Los Angeles is uncommon, with the last measurable precipitation occurring in 2014. Forecasters have advised residents to plan for wet conditions, particularly during outdoor activities, though the storm’s intensity remains uncertain.
Officials recommend monitoring local weather updates and preparing for minor disruptions, such as delayed or altered Halloween events. No major evacuations or severe weather warnings have been issued as of the latest forecast.