Cooling conditions and increased westerly winds on the desert mountain slopes into the deserts tomorrow into Thursday. The marine layer will deepen into Thursday, spreading low clouds and fog into the valleys. Periods of northeasterly Santa Ana winds and warmer conditions this weekend, with less marine layer low clouds and fog. Moisture from the east could bring some showers for Sunday and Monday.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
(today through Friday), A low pressure system will move inland into northern California today and through the Great Basin on Thursday. This will strengthen the onshore flow across southern California for today into tonight. West winds will strengthen for the mountains and deserts and be strongest for tonight with gusts to 45 mph and isolated gusts to 65 mph.
The marine layer is around 2000 feet deep early this morning with patchy low clouds extending inland into portions of the western valleys. The low clouds are expected to spread into portions of the inland valleys for tonight as the marine layer deepens. Fairly rapid clearing from north to south is expected on Thursday morning as offshore flow develops with gusty north winds.
The coast and valleys will cool a few degrees today. On Thursday, high temperatures for the deserts onto the desert slopes of the mountains will be around 10 degrees cooler than today while coastal areas will warm a few to around 5 degrees as the lower-level flow goes offshore.
Offshore flow will continue on Friday with gusty northeast winds along and below the coastal slopes of the mountains. High temperatures on Friday will cool slightly for inland areaswith slight warming near the coast.
(Saturday through Tuesday), For the weekend, the center of a closed low pressure system will be somewhere over or offshore of northern Baja. Cluster analysis shows the solutions with greater chances for at least light precipitation for Sunday and Monday are those that are farther west with the center while those that are farther east are dry. The strength and placement of the stronger offshore winds for the weekend are also dependent on the placement of the upper low.
High temperatures will warm through the weekend with Sunday high temperatures as much as 8 to 12 degrees above average for coastal areas. As offshore flow weakens early next week, the coast and valleys will begin to cool while the deserts continue to slowly warm.
041030z. Coast/ western valleys, Areas of low clouds will gradually cover most of this area through 16Z. Bases will be around 1200-1500 feet MSL. Scatter out expected by 17-18Z. Low clouds will make an early return, around 00-05Z tonight into Thursday, and will spread farther into inland valleys. Bases will be similar, with some coastal higher terrain obscurations.
Otherwise, mostly clear and VFR conditions with some high clouds increasing later today.
Stronger northwest winds develop Thursday and continue into the evening, generating choppy and hazardous conditions. A Small Craft Advisory contains the details. Otherwise, no additional hazardous marine conditions are expected through Sunday.
Ca, Wind Advisory from 6 PM this evening to 4 AM PST Thursday for Apple and Lucerne Valleys-Riverside County Mountains-San Bernardino County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass near Banning.
PZ, Small Craft Advisory from 1 PM to 10 PM PST Thursday for Coastal Waters from San Mateo Point to the Mexican Border and out to 10 nm.
Small Craft Advisory from 7 AM to 10 PM PST Thursday for Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.
