Swell Matrix

Area Forecast Discussion

National Weather Service San Diego CA

1200 pm PDT Wed may 20 2026

Synopsis

A weak area of low pressure will stay over the area through Monday, bringing temperatures near to slightly above normal with night and morning clouds and fog for the coastal and western valley areas. A stronger area of low pressure moves by from the north, bringing cooler and breezier weather by the middle of next week.

Discussion

For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,

Low clouds and areas of dense fog occurred earlier this morning in coastal San Diego County. Low clouds will move slightly further inland to all coastal regions tonight through Thursday morning as the marine layer slightly deepens as a weak trough forms over Southern California. Temperatures will be fairly similar through he weekend as the weak area of low pressure hangs around with highs near to slightly above average across the region. As the weak trough moves in, low clouds will move around 15 miles inland each night, diminishing each morning. The weak troughing pattern will bring a return to light onshore winds from the southwest and west, gusting near 15-25 MPH each afternoon and evening.

By Monday into the first half of next week, a stronger troughing pattern develops over the West Coast as an area of low pressure passes to the north. This will bring in greater low cloud coverage each night and morning across the western valleys with temperatures cooling down further where 60s and 70s will occur from the mountains to the coast. Onshore flow will increase as the low moves into the Pac NW and Great Basin by Tuesday into the middle of the week. Nbm models show winds gusting near 30-45 MPH across most mountains and deserts, with locally higher winds in the passes.

Aviation

201630z, SKC expected across the region through this evening. Low clouds based 900-1500 ft MSL return to coastal areas overnight, starting in San Diego County around 06z and spreading northward. More uniform coverage than this morning with about 10-15 miles of inland extent. Minor vis reductions (1-5SM) along elevated coastal terrain. Low clouds scatter to the coast by 16-17z Thu.

Marine

No hazardous marine conditions are expected through Monday morning.

Watches, Warnings, Advisories

Ca, None. PZ, None.

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