textproduct: San Diego

SYNOPSIS

A weak low pressure system moving quickly inland through southern California will bring stronger onshore flow through Thursday. This will spread cooling inland and bring stronger and gusty southwest to west winds to the mountains and deserts. Winds will be strongest on Wednesday with gusts 40 to 50 mph. There will also be a chance of showers late today into Wednesday, with the chance for rainfall greatest in the mountains at 40 to 50 percent. Lower-level flow will go briefly offshore Friday and Saturday with drying and gusty north to northeast winds along and below the coastal slopes of the mountains gusting to 25 to 35 mph. This will be followed by warming through next weekend with high temperatures warming to 10 to 15 degrees above average for next Sunday.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

The afternoon...The marine layer has deepened to around 4000 ft and low clouds cover much of the area west of the mtns. Widespread mid and high clouds cover the region and will thicken through tonight as the moist layer deepens above 10,000 ft. The onshore flow is strengthening and the wind-favored locations in the mtns and adjacent desert slopes are currently reporting wind gusts of 25-35 mph. Temperatures are generally lower than at this time yesterday, as much as 10-12 degrees lower in the inland valleys. Radar is detecting the mid and high clouds but so far no measurable precipitation has been reported in SoCal.

The low pressure system moving in from the west will bring chances for light rain from this evening through Wednesday morning. Total accumulations will range from less than one tenth inch in the coastal areas and inland valleys to about two tenths inch in the San Bernardino Mountains. A snow level around 8500 feet will lower to 7000 to 7500 feet for Wednesday morning. This system will also bring stronger onshore flow through Thursday. Southwest to west winds will be strongest on Wednesday with gusts 40 to 50 mph in the mountains and on adjacent desert slopes. Temperatures will trend lower through Thursday with high temperatures a few degrees below average on Wednesday, ranging from the mid to upper 60s near the coast to the lower to mid 70s for the Inland Empire with the lower deserts in the 80s. Little change in temperatures is expected for Thursday.

A stronger low pressure system currently in the Gulf of Alaska will move inland over WA/OR Wed-Thu, reaching the northern Rockies by Friday. A sfc high will follow the low into the Great Basin producing offshore flow for Fri and Sat. Northeast to east winds begin to develop Friday morning and weaken on Saturday. The strength of the Santa Ana winds is still uncertain but with no upper level support, it will likely be relatively weak. North to northeast winds gusting to 25 to 35 mph along and below the coastal slopes of the mountains are expected on Friday. Conditions will trend warmer for Friday through Sunday. High temperatures on Sunday will be around 10 to 15 degrees above average ranging from the 70s near the coast to mid 80s to lower 90s for the Inland Empire with the lower deserts in the 90s.

Weak onshore flow will return for Monday and Tuesday, bringing cooler conditions to the coast and valleys. Elsewhere, temperatures will remain relatively unchanged.

AVIATION

311820Z...Low clouds 2000-3000 feet MSL will continue to cover areas within 15 miles of the coast. Higher chance for low clouds to scatter out this afternoon across the Inland Empire. Low clouds at coastal TAF sites may clear intermittently this afternoon with low to moderate confidence. Clouds lowering near 1800-2500 ft MSL pushing back inland across areas west of the mountains after 02Z Tues with higher coastal terrain obscured in fog. VCSH occurring from north to south between 00Z-12Z for all areas expect the lower deserts with moderate to high confidence.

Strong westerly winds 35-45 mph gusts 55 mph over mountain ridges, desert slopes and locally into deserts today into Wednesday; gusts near 30 kts possible VCTY KPSP/KTRM. MOD up/downdrafts in lee of mountains, and areas of vis reduced to 2-5SM in BLDU in deserts.

MARINE

No hazardous marine conditions expected through Wednesday. Northwest winds 20 to 25 knots late Thursday in the outer waters.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Wind Advisory from 8 PM this evening to 11 PM PDT Thursday for Apple and Lucerne Valleys-Coachella Valley-Riverside County Mountains-San Bernardino County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass near Banning.

PZ...None.