A cold Pacific storm out of the Gulf of Alaska took aim at the Southland Wednesday, threatening a wet afternoon commute Thursday, sharply colder temperatures, and whiteout conditions on mountain roads, National Weather Service forecasters said.
The storm is expected to produce widespread showers Thursday, when there also will be a slight chance of thunderstorms, some of which could produce small hail, according to an NWS advisory.
Rainfall totals resulting from the storm are expected to be up to a half- inch in coastal, valley and desert areas and up to an inch in the foothills and mountains, according to the NWS.
The storm will cause the snow level to fall to its lowest point so far this season, according to the advisory. It will start at 5,000 feet this afternoon and drop to between 4,000 and 3,500 feet by Thursday morning, likely leaving snow on roadways, including Interstate 5 through The Grapevine.
Between three and six inches of snow is expected above 5,000 feet, although between six and eight inches is possible, according to the advisory.
"Light accumulations are expected down to near 4,000 feet, including the Tejon Pass," it said. "The combination of wet snow and low temperatures in the mountains could create a dangerous situation for campers and outdoor enthusiasts who are not prepared ..."
Wednesday's forecast called for winds of between 15 and 25 miles per hour in mountain areas, gusting to 45 mph. A winter weather advisory warning of difficult travel conditions, caused in part by blowing snow and a resulting loss in visibility, will be in effect in the San Gabriel Mountains for 24 hours starting at 4 this afternoon.
The Seven-Day Outlook for Altadena from the National Weather Service:
- Thursday A 40 percent chance of showers, mainly before 4pm. Mostly cloudy, with a high near 57. South southwest wind 5 to 10 mph.
- Thursday Night A 20 percent chance of showers before 10pm. Partly cloudy, with a low around 45. South southwest wind around 5 mph becoming calm in the evening.
- Friday Partly sunny, with a high near 57. North wind 5 to 15 mph becoming south southwest in the afternoon.
- Friday Night A 40 percent chance of showers, mainly before 4am. Mostly cloudy, with a low around 47. South southeast wind around 5 mph becoming calm.
- Saturday A 20 percent chance of showers before 10am. Partly sunny, with a high near 60. Light southwest wind increasing to 5 to 10 mph in the morning.
- Saturday Night Partly cloudy, with a low around 46.
- Sunday A 20 percent chance of showers. Partly sunny, with a high near 61.
- Sunday Night Mostly cloudy, with a low around 48.
- Monday Mostly sunny, with a high near 64.
- Monday Night Partly cloudy, with a low around 50.
- Tuesday Mostly sunny, with a high near 62.
- Tuesday Night A slight chance of showers. Partly cloudy, with a low around 50.
- Wednesday Mostly sunny, with a high near 62.
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