Here is this week’s weather forecast by PG&E meteorologist John Lindsey.

Weather report

Monsoon moisture will continue to stream over San Luis Obispo County through Wednesday and will produce plenty of mid to high-level clouds. This subtropical moisture will also produce cooler daytime highs, but warmer and balmy Mid-State Fair nights.

Today’s high temperatures will reach the high 80s at the Mid-State Fair. The marine layer will keep maximum temperatures in the 70s in the coastal valleys and 60s along the coastline.

A weak low pressure system will rotate over the Central Coast today through Tuesday. Normally this type of system would have little effect on our weather. However, with the abundance of subtropical moisture, it could become the trigger mechanism to generate low-elevation isolated showers and thunderstorms. Unfortunately, this system may also produce dry lightning to the elevated terrain of San Luis Obispo County. The threat of low-elevation thunderstorms will taper off Wednesday but chances will continue over the higher terrain of the Sierra Nevada through Thursday.

High pressure will build later on Thursday through Saturday bringing gradually warmer temperatures to the North County. Increasing northwesterly (onshore) winds along the marine layer will continue to produce mild conditions near the coast.

Surf report

Today’s 4- to 6-foot northwesterly (310-degree deepwater) swell (with an 8- to 10-second period) will decrease to 2 to 4 feet on Tuesday and remain at this height and period through Wednesday morning.

Increasing northwesterly winds will generate a 3- to 4-foot northwesterly (320-degree deep-water) sea and swell (with a 5- to 9-second period) Wednesday afternoon through Saturday.

Arriving from the Southern Hemisphere: Today’s 1-to 2-foot Southern Hemisphere (190-degree deepwater) swell (with a 14- to 16-second period) will decrease Tuesday.

A 1- to 2-foot Southern Hemisphere (225-degree deep-water) swell (with a 15- to 17-second period) is forecast along our coastline Wednesday through Friday.

Water temperatures:

Seawater temperatures will range between 55 and 58 degrees through Wednesday, decreasing to 53 and 56 degrees on Thursday through Saturday.

John Lindsey’s Weekly Forecast is special to The Tribune. His Weather Watch column appears on Sundays. Contact him at pgeweather@pge.com.