A flash flood warning was issued for parts of San Bernardino and Los Angeles counties Thursday during what could be an afternoon of potentially dangerous weather conditions.
A storm system out of the Pacific brought Southern California a chance of showers and thunderstorms, raising a risk of flash flooding and flows of mud and debris.
A warning in effect until 4:45 p.m. was issued for south central San Bernardino County, including Landers and Joshua Tree.
A secong warning was issued for nothern Los Angeles County, including Elizabeth Lake and Lake Hughes, in effect until 5:30 p.m.
Storms are possible elsewhere in Southern California Thursday evening, including the coast and valley areas. Most of the storm activity is expected in mountain and desert areas.
Any thunderstorm will have the potential to generate heavy downpours because a southerly air flow has been streaming into the area ahead of the storm system, bringing increasing moisture and atmospheric instability, NWS forecasters said. The air flow will weaken this afternoon, meaning any thunderstorm will linger.
In those conditions, heavy rain will produce "a risk of flash flooding and debris flows in recent burn areas," warned an NWS statement.
The chance of measurable precipitation this morning was generally set at 30 percent, although it was 40 percent in the Santa Clarita Valley and 50 percent in the Antelope Valley.