A heat wave that already has produced record highs this week in part of Southern California was expected to generate more health-threatening temperatures across the Southland Friday, prompting an appeal to residents to use air conditioning judiciously and conserve electricity to avoid blackouts.
The appeal came in the form of a -- an urgent call for residents to conserve -- issued by the California Independent System Operator, which manages the state's power grid. Cal-ISO originally issued the alert for Friday through the weekend, but Friday lifted the warning for Saturday and Sunday.
According to Cal-ISO, its forecast peak electricity demands for the weekend were significantly lower than Friday. The agency still called on residents to conserve power over the weekend, but said the call was "not critical."
But the alert remained in effect for Friday, which was forecast to be the hottest day of the heat wave.
Cal-ISO officials said there is a "critical" need for residents throughout the state to cut their power usage, particularly between the hours of 11 a.m. and 6 p.m., when energy demand is expected to be noticeably high.
"Consumers are urged to reduce their energy use during the afternoon when air conditioners drive consumption," according to Cal-ISO, which recommended that residents set thermostats at 78 degrees or higher, use fans to cool rooms, close drapes and blinds, turn off unnecessary appliances and lights and use major appliances only in the morning or late evening.
The Los Angeles Department of Water and Power and Southern California Edison also urged customers to limit their electricity usage during the heat wave. Edison, whose power system is being hampered by the continuing closure of the San Onofre Nuclear Generating Station for repairs, announced it has been preparing for possible outages by having extra repair crews available throughout the weekend.
As was the case Thursday, an excessive heat warning issued by the National Weather Service to indicate oppressively high temperatures will be in force Friday from 11 a.m. until 8 p.m. in the San Gabriel, San Fernando and Santa Clarita valleys and the mountains of L.A. County -- both the San Gabriels and Santa Monicas.
The warning reflects that "the combination of hot temperatures and high humidity will combine to create a dangerous situation in which heat illnesses are possible," according to the NWS.
The NWS forecast highs today of 75 in Avalon; 78 in Newport Beach and at LAX; 89 on Mount Wilson; 90 in downtown L.A.; 91 in Anaheim; 92 in Long Beach; 93 in San Gabriel; 98 in Pasadena; 100 in Burbank; 107 in Woodland Hills and Saugus; and 108 in Palmdale and Lancaster. Temperatures are expected to be a few degrees lower Saturday and fall some more over subsequent days.
The above-normal daytime and overnight temperatures are the result of a hot air mass caused by a ridge of high pressure over the Southwestern United States, according to the NWS.
"Daytime temperatures well above 100 degrees across inland areas will be common through Saturday," according to an NWS advisory.
There will be a slight chance of afternoon and evening thunderstorms Friday and Saturday in the Antelope Valley and the San Gabriel mountains in Los Angeles and Ventura counties, NWS forecasters said.
"Any thunderstorms that develop would be capable of producing brief heavy rain, gusty winds, dangerous cloud-to-ground lightning and possibly small hail."
On Thursday, record highs for an Aug. 9 were set in Woodland Hills (109), Lancaster (109), and Sandberg (98).
Record highs were also set in Woodland Hills, Lancaster and Sandberg Tuesday.
To cope with the heat, the NWS urged Southland residents to drink plenty of fluids, stay out the sun and in an air-conditioned room as much as possible, check up on relatives and neighbors, never leave children, the elderly or pets in an enclosed vehicle in the heat, and take frequent breaks in the shade if working outdoors.