COMING SOON: BIG CHILL.

Byline: Mary Beth Alexander and Stacy Finz Daily News Staff Writers

Gusts of up to 60 mph were expected to hammer the San Fernando Valley through this evening, but once the Santa Anas die down a winter chill will creep into the area.

Night temperatures are expected to drop into the low 40s tonight in the San Fernando Valley and the upper 30s by Thursday. In the Antelope Valley, the nighttime temperature could plunge as low as 17 degrees tonight, according to the National Weather Service.

``Seventeen degrees, that's unusual. That's got to be at least 10 degrees lower than we would normally expect,'' said meteorologist Mallory Ham.

A second wave of gusty winds blew through the San Fernando Valley on Tuesday, ending the brief calm after a violent weekend windstorm that felled up to 570 trees and contributed to two deaths.

The 20-30 mph winds were expected to continue until this evening, and weather officials warned some gusts could reach up to 60 mph.

City officials prepared for the onslaught, by keeping crews working round the clock, many of them still trying to clean up trees and branches felled over the weekend.

``We are in emergency mode,'' said Chuck Ellis, spokesman for the Department of Public Works. ``But we hope that we've seen the worst of it.''

As a precaution, Ellis warned people not to park their cars under trees that look unstable during the winds.

Wary homeowners around the Southland eyed precariously listing trees and loose branches, expecting them to crash to the ground with the next strong gust.

``The roots keep coming up every time the wind blows,'' said Milissa Ospina, who stood outside Tuesday watching a large tree shift in the wind in front of her home near the corner of Kuehner Drive and Katherine Road in Simi Valley.

Ospina said five trees already had fallen, blocking her yard.

Fire and utility crews also were on guard.

Los Angeles Fire Department spokesman Brian Humphrey said at least one extra crew would help fight any fire in the Valley, in case high winds sent sparks flying.

And, although no major outages had been reported, the city's Department of Water and Power crews were on call, prepared to deal with lines becoming tangled or knocked down by trees and branches.

``We're OK today, but we're ready,'' said DWP spokeswoman Karen Shepard-Grimes.

Tuesday's winds were created by a combination of swift-moving cold air from the Great Plains and warm weather off the coast, said Stewart Seto, a meteorology specialist for the National Weather Service.