Slightly cooler today with temperatures still be above seasonal averages. Patchy dense fog over the coastal waters could move ashore again this evening, becoming more widespread tonight into Tuesday morning. Warmer Tuesday through Thursday with periods of weak to locally moderate Santa Ana winds. Cooler with a return of onshore flow Friday through the weekend.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Update: The forecast in the short term has remained the same, with increasing Santa Ana Conditions from Wednesday into Thursday. The winds still look to be generally below the threshold of Wind Advisory, with the strongest gusts being located across the mountains of San Diego County, where gusts may occasionally over 50 mph through some of the passes as some of the high red guidance suggests. This will continued to be mentored in the upcoming days for possible issuance, as latest models have been trending to these winds being slightly stronger. After that, an upper level low transitioning over the region after a rex block cuts off the low to the south. This may allow for some showers, or even possibly a thunderstorm or two, to be possible during the afternoon on Friday. This could possibly hang around into Saturday as well, depending on where this upper level feature decides to propagate. There is also a slight better chance of the marine layer and fog penetrating into some of the coastal communities overnight. As offshore winds return by Wednesday, this should help mitigate the threat of foggy conditions along the coast as winds become more lightly offshore. There also appears to be a lot more indication of the broad area of troughing well upstream to begin to influence the region with much cooler and wetter conditions by the beginning next week as a series of troughs approach the region.
Previous discussion submitted at 407 PM:
Mostly sunny this afternoon with a few high clouds. Temperatures are generally lower than yesterday with some coastal and valley locations as much as 10-15 degrees lower than at this time yesterday. Surface pressure gradients are trending weaker offshore with -3.9 mb SAN-TPH. A weak sea breeze has developed west of the mtns.
From previous forecast, High-resolution models indicate a return of low clouds and fog to the coastal areas tonight into Tuesday morning. This is in spite of the surface pressure gradient trending stronger offshore during the next 24 hours as the upper level trough moves east and a sfc high moves into the Great Basin. The developing offshore flow will likely not be strong enough to push the marine layer clouds/fog offshore tonight/Tue morning. Wind gusts below the passes and on the coastal slopes will only peak at around 25-30 mph. Tuesday and Wednesday will be warmer as a Rex Block develops over the west coast, with an upper level low centered off the coast of central Baja and an upper high centered over the Bay Area. This pattern will provide easterly flow aloft over SoCal, enhancing the offshore flow on Wednesday and Thursday. Tuesday and Wednesday will likely be the warmest days with high temps 15-20 degrees above normal for the coastal areas and valleys and around 10-15 degrees above normal in the mountains and deserts. The national Blend of Models indicates a 25-45 percent chance of 90+ degrees on Wed for portions of inland OC. This drops to about 15 percent on Thu.
Temperatures begin to trend lower on Thu as the upper high shifts east in response to a low pressure trough approaching from the West. This trough will merge with the low to the south as it moves southeast over the region. The evolution of these systems remains very uncertain due to the spread among model solutions. Some previous solutions were indicating very small chances for precipitation Fri-Sat. Current solutions are mostly dry but the possibility of light precip on those days can't be eliminated. We can say with reasonable confidence that Fri-Sat will be cooler with increasing marine layer clouds as onshore flow returns.
A transient ridge will likely bring fair weather and a minor warmup on Sunday before a more significant low pressure trough moves in on Monday. This has the potential to bring precip to SoCal, mainly from the mtns westward. A majority of ensemble members across model platform indicate chances for precip on Monday. The NBM indicates about a 45 percent chance of measurable precip.
030330, Coast, Patchy low clouds based 400-700 ft MSL with vis 3-6 SM in BR have formed along parts of the coast this evening. Clouds will become more widespread along the coast through 10Z and spread inland up to 5-10 miles overnight. 70% chance for CIGs at KSAN/KSNA and 45% chance at KCRQ by 09Z. Bases likely to lower to 200-500 ft MSL overnight with areas of vis 1/4-2 SM, especially over coastal highlands, with a 50-60% chance for VIS < 1/2 SM at all coastal sites overnight. Low clouds and FG scatter out 14-17Z Tue, followed by widespread VFR conditions.
Elsewhere, VFR conditions with FEW-SCT high clouds through Tuesday afternoon.
Patchy fog with local visibility under 1 nautical mile expected through Tuesday morning. Otherwise, no hazardous marine conditions are expected through Friday.
Surf of 3 to 6 feet with sets to 8 feet peaks today then gradually diminishes Tuesday. A higher than average tide Tuesday morning will combine with the elevated surf to produce minor tidal overflow and flooding along with strong rip currents and hazardous swimming conditions through Tuesday morning, most likely in San Diego County. Check the Coastal Hazard Message for details on these hazards.
Ca, Coastal Flood Advisory until 10 AM PST Tuesday for San Diego County Coastal Areas.
Beach Hazards Statement until 9 PM PST this evening for Orange County Coastal Areas.
PZ, Coastal Flood Advisory until 10 AM PST Tuesday for Coastal Waters from San Mateo Point to the Mexican Border and out to 10 nm.
