By this afternoon and tonight, he said the clouds should break somewhat, clearing the way for partly cloudy skies and intermittent thundershowers.
"Some of those could be very heavy, but I think the main rain event will be midday today," Christopherson said.
With temperatures continuing to drop — a high of 63 is expected today and 61 tomorrow — the National Weather Service is warning snow in the Laguna Mountains between here and San Diego could drop to the 4,500-foot mark.
According to the California Highway Patrol, the NWS predicted that 4,500-foot level could change as weather conditions were changing rapidly as of 8:30 this morning.
The CHP is recommending those traveling through the mountains between Imperial County and San Diego today carry snow chains as they could be required at any time. As of this morning chains were not being required on Interstate 8, but they were being required on highways 79 and 78 through Julian.
U.S. Border Patrol in the El Centro and San Diego sectors are preparing for the snow, placing agents on alert in the event undocumented immigrants attempt to cross the border in the snowy and frigid mountains south of I-8.
Border Patrol's San Diego sector-based BORSTAR, or border search trauma and rescue teams, have been placed on standby, ready to rescue and administer first-aid to immigrants found in the mountains, according to a press release issued by the El Centro sector Border Patrol.
In Imperial County, today's vegetable harvest could be at risk, Imperial Valley Vegetable Growers Association President John Hawk said this morning.
If the expected quarter-inch of rain falls today, harvesting of cauliflower, broccoli and lettuce could be curtailed until Friday.
Hawk added any more than a quarter-inch could do some serious damage to local crops, including slowing the harvest for the next two or three days and affecting the vegetable market, driving up the demand for such vegetables.
"The big news is if Oxnard and Santa Maria and Salinas and Bakersfield get serious rain," he said, adding damage to harvest in those areas would drive up the prices of broccoli and cauliflower.
Hawk added rain and colder weather in those cities could promote disease growth such as mildew and pinrot, further damaging crops.
If that happens local farmers would get paid more for their crops, he indicated.
Christopherson said this morning it should be partly cloudy and cool over the weekend, with no more rain expected.
Starting Wednesday, he added, temperatures should be back above normal.
Staff Writer Richard Montenegro can be reached at 337-3453.