For coastal areas, night and morning low clouds and dense fog will continue through Wednesday. A few degrees of cooling Wednesday followed by warming with weak offshore flow on Thursday. Onshore flow and weakening high pressure aloft will spread cooling inland for Friday through Monday, but high temperatures remain as much as 10 to 15 degrees above average for some inland areas.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
At 9 PM low clouds and areas of dense fog had developed along the coast and in the western valleys. Areas of dense fog are expected overnight into Wednesday morning. The chances of dense fog developing decreases Thursday and Friday. Three locations broke high temperature records today, Lake Cuyamaca, Campo, and Borrego. For more information check out the headline on our weather.gov/sandiego homepage. Highs Wednesday will be a few degrees cooler than today for most locations, with warmer conditions returning Thursday.
From Previous Discussion Issued at 2 PM December 16,
Thursday through early next week,
The ridge will continue to build ahead of an approaching major shortwave trough which will be approaching the region by this weekend. It will be considerably warmer on Friday as this occurs, with temperatures running around 20 degrees above average for the inland valley areas. As the trough continues to advance slowly eastward, with will help to bring about a cooling trend going into early next week, with the marine layer beginning to lift with strengthening onshore flow. Looking a little beyond the forecast, there is growing confidence with ensemble and deterministic models alike which show an increasing chance of precipitation across the region.
170330z, Coast/Western Valleys, Low clouds based 500-800 feet MSL have pushed to the I-15 corridor in SD County. Clouds start to develop over coastal and inland Orange County 05-07z. Areas of FG and VIS below 1/4SM for the coastal highlands; BR and VIS 1-4SM for lower coastal areas, with periods of VIS 1/4-1SM after 05z. VIS begins to improve everywhere 16-18z Wed as clouds clear to the coast 17-19z in SD County and 18-20z in Orange County. Patchy SCT-BKN clouds and VIS 4-6SM in HZ linger at the immediate coast throughout the day. Patchy low clouds return with slightly lower bases 00-02z Thu and coastal VIS reductions 0-4SM after 05-07z Thu.
Otherwise, VFR for interior valleys, mountains and deserts through the period with SCT clouds above 10k feet.
Areas of fog will redevelop tonight and continue through about 10 AM Wednesday morning. A Marine Weather Statement contains more details. Otherwise, no additional hazardous marine conditions are expected through Sunday.
Ca, Dense Fog Advisory until 10 AM PST Wednesday for Orange County Coastal Areas-Orange County Inland Areas-San Diego County Coastal Areas.
PZ, None.
