textproduct: San Diego

SYNOPSIS

Easterly Santa Ana winds will continue into Thursday before weakening in the afternoon. A low pressure system off the northern Baja coast will direct mid and high level moisture and clouds into the area from the southeast Thursday into Friday with a slight chance of light showers over the mountains. The weekend will be dry and a little warmer. Another low pressure system will approach the California coast next Tuesday and Wednesday, with cooling and increasing chances for precipitation. Confidence is low on the timing and amounts of any precipitation.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Evening update... Skies are clear this evening, but a band of high clouds is beginning to approach from the south. East winds continue along the coastal mountain slopes and below the San Gorgonio Pass where the strongest gusts are between 30-40 mph. Offshore winds continue overnight, then weaken on Thursday as both surface pressure gradients the easterly winds aloft weaken. No changes to the forecast this evening.

Previous discussion... Temperatures will trend lower for Thu and Fri but will remain about 10-15 degrees above seasonal averages in the coastal areas and inland valleys. High temperatures on Thursday will range from the lower to mid 70s near the coast to the mid 70s to lower 80s for the valleys and inland Orange County. The coast and valleys will cool around 5 to 10 degrees on Friday with Friday high temperatures ranging from the mid to upper 60s near the coast to the upper 60s to mid 70s for the valleys.

The low pressure system off the northern Baja coast will draw mid and higher level subtropical moisture into the area from the southeast on Thursday into Friday. This will result in a slight chance of showers for late Thursday night into Friday. Showers will be mostly confined to the mountains. If any showers develop west of the mtns or lower deserts, precip is unlikely to reach the ground do to a deep and dry sub-cloud layer. Friday will likely be the coolest day, with daily high temps in the 60s and 70s west of the mtns. Some high-resolution models are also indicating the return of marine layer low clouds and fog to the coastal areas Thu night/Fri morning.

Temperatures will trend higher for the weekend, with Sunday high temperatures as much as 8 to 12 degrees above average for the valleys and lower coastal slopes of the mountains. High temperatures on Sunday will range from around 70 near the coast to the 70s to around 80 for the valleys and inland Orange County with the lower deserts in the lower to mid 80s. Onshore flow will continue into Sat, spreading marine layer low clouds and fog farther inland.

For next Mon-Wed...A more amplified low pressure trough will move in from the west bringing more significant cooling, increasing clouds and chances for widespread precipitation, mainly over and west of the mountains. Forecast details remain very uncertain due to the spread among model solutions. The National Blend of Models indicates a 48 hr probability of 0.01 or more of 50-70 percent west of the mtns for Tue- Wed, and a 25-35 percent chance for 0.25 inch or more.

AVIATION

050400Z...Mostly clear skies and VFR conditions will continue through Thursday, increasing clouds AOA 10,000 ft late Thursday. Gusty northerly to easterly winds will continue across the foothills, mountain passes, and into inland valleys through Thu afternoon, with surface gusts 35-45 kt near mountain passes and 20- 30 kts into the inland valleys. Mod up/downdrafts west of mountains. Localized BLDU intermittently reducing vis 3-5 SM in parts of the inland valleys. Areas LLWS in inland valleys and parts of the coast likely overnight through about 12Z.

MARINE

A building northwesterly swell (280 degrees) at 15-16 seconds may bring seas of 7-9 feet in the outer waters near/around San Clemente Island Friday and Saturday. This may also lead to localized steep, rough conditions near the entrance to the San Diego Bay/Zuniga Shoal. Otherwise, no hazardous marine conditions are expected through Monday.

BEACHES

Increasing long-period (15-16 second) swell from the west-northwest (280 degrees) will bring elevated to high surf of 5-8 feet with locally higher sets to 10 feet late Friday into Saturday. Impacts will be greatest at west facing beaches, especially across southern San Diego County. This may also lead to minor tidal overflow for low- lying beach areas during high tide late Friday into early Saturday.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Wind Advisory until noon PST Thursday for Orange County Inland Areas-Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains-San Diego County Valleys-San Gorgonio Pass near Banning-Santa Ana Mountains and Foothills.

PZ...None.