textproduct: San Diego

SYNOPSIS

Slightly cooler today with variable high clouds but temperatures will 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.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

There were a few patches of locally dense fog at the immediate coast in San Diego County earlier this morning. The fog has since lifted and the rest of the day will be mostly hazy sunshine with variable high clouds. Today will be generally cooler than yesterday as a weak upper level trough moves over the region, but high temperatures will still be 5 to 10 degrees above seasonal averages.

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.

AVIATION

021800...Coastal areas...VFR this afternoon, then low clouds based 400-700 ft MSL return after 02z Tue to the coast. VIS reductions expected 1-5SM for coastal sites after 03z, then VIS reductions 1/4- 2SM with FG for coastal mesas around I-15 and I-405 beginning 06- 08z, with a 40-50% chance of below 1/2SM at KCRQ. Low clouds and FG scatter out 15-17z Tue.

Otherwise, VFR conditions with SCT high clouds through Tuesday morning.

MARINE

Patchy fog with local visibility under 1 nautical mile tonight into Tuesday morning. Otherwise, no hazardous marine conditions are expected through Friday.

BEACHES

Surf of 3 to 6 feet with sets to 8 feet peaks today and tonight, and gradually diminishes Tuesday. A higher than average tide Tuesday morning will combine with this high surf to produce minor tidal overflow and flooding, along with strong rip currents and hazardous swimming conditions, most likely in San Diego County, through Tuesday morning. Check the Coastal Hazard Message for details on these multiple hazards.

SKYWARN

Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions.

SGX WATCHES/WARNINGS/ADVISORIES

CA...Coastal Flood Advisory until 10 AM PST Tuesday for San Diego County Coastal Areas.

High Surf 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.

High Surf Advisory until 10 AM PST Tuesday for Coastal Waters from San Mateo Point to the Mexican Border and out to 10 nm.