An approaching trough will allow for notably cooler temperatures today. There will be stronger and gusty west winds this afternoon and evening in the mountains and deserts today. Gusts of 35 to 45 mph are likely in the wind-prone areas. Dry conditions will likely continue throughout the rest of the week, but then there could be a slight chance of precipitation by later this upcoming weekend.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Today through tomorrow night,
At 4 AM this morning, the GOES 18 Night Fog satellite imagery reveals that the marine layer is still rather dispersed, and not yet well formed up over the inner waters of the SoCal bight at this time. There are only a couple of patchy areas of fog and low clouds developing around La Jolla and Carlsbad at the moment. This will likely continue to struggle to develop through this morning, with weak offshore winds in place. There could be some patchy areas of fog developing within some of the wind-sheltered valleys through the early hours.
The ridge over the southwest region is continuing to break down and weaken as an area of troughing upstream, with an associated area of low pressure located over the E Pac waters west of northern California, continues to propagate eastward and will eventually move in over the Great Basin. This feature will begin to influence SoCal and provide us with increasing surface winds, which will become quite breezy by later in the afternoon across the higher elevations, and especially through the mountain canyons and passes, where there could be some gusts approaching 50 mph through the San Gorgonio pass and Banning. There will also be increasing mid to high level clouds, although the main energy will be far enough north that we are not expecting any precipitation with this. These strong and gusty winds will decouple by later this evening, and further diminish in strength going into tomorrow. Much cooler temperatures will be advected in behind this system, and therefore high temperatures for this afternoon will be notably cooler from where they have been in recent days, and much closer to the seasonal average for this time of year.
The onshore flow is going to become predominant, which will help to advect in lower level moisture, and therefore allow for there to be better marine layer coverage for later this evening into early tomorrow. These cloud bases will likely start out around roughly 1000 to 1500 ft, and then continue to gradually lift. There may possibly be a few areas of patchy light drizzle along some of the coastal slopes and the western-facing slopes of the inland foothills during the late evening hours today, and through the early morning hours tomorrow. There will be some weak upper level ridging moving in behind the exiting trough, which will bring about a brief warmup on Tuesday.
Wednesday through the upcoming weekend,
By Wednesday into Thursday, another trough is going to deepen and skirt across just to the north again, which will help to strengthen westerly winds again, and also reinforce some cooler temperatures. Then after the passage if this trough and brief building in of high pressure in its wake, there is going to be a deepening trough over the inner mountain west which will begin to deepen sharply and possibly become a cut-off upper level low just to south of the region as some of the deterministic models suggest. However, there is still such dispersion between these models that confidence is low if this will actually provide us with any measurable precip, though it is probably safe to say that there will be at least a slight chance by later in the upcoming weekend.
021000z. Coast, Patchy low clouds and fog most likely between 13- 16Z. Any cigs that form will be around 500 feet MSL with vis 2-5SM, but confidence is low for these impacts for any length of time. Better confidence in areas of low clouds after 06Z tonight into Tuesday. Cigs would be closer to 1500 feet MSL.
Otherwise, VFR with SCT high clouds. Areas of gusty southwest winds 25-35 knots in the mountains and deserts between 16-02Z. Mod up/downdrafts in lee of ridges. Locally reduced vis in BLDU in deserts.
Gusty northwest wind gusts exceeding 20 knots mainly around San Clemente Island will generate locally choppy seas this afternoon and evening. The Small Craft Advisory in effect contains the details. No additional marine hazards are expected late tonight through Friday.
Ca, None. PZ, Small Craft Advisory until 9 PM PST this evening for Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.
