Weather Watch

SLO County weather forecast for the week of July 21

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

Subtropical moisture should continue to produce mid- to high level clouds today. The cloud cover likely will translate into cooler temperatures. However, this subtropical moisture will make it feel muggy.

Today’s high temperature is forecast to reach the mid-80s at the Mid-State Fair and the mid-70s for the coastal valleys. The beaches are expected to remain in the mid- to high 60s.

Thunderstorm development should continue along the southern Sierra and will likely intensify and spread northward along the crest throughout the day, with a slight chance for a few isolated thunderstorms  across lower elevations by this afternoon. The subtropical moisture is expected to move to the north and onshore winds will allow the marine layer to redevelop along our coastline by this evening.    

A relatively strong high-pressure ridge is forecast to build from the desert southwest over the Central Coast on Tuesday into Friday. This condition should bring warmer North County temperatures, with the Mid-State Fair reaching the high 90s and low 100s by Thursday and Friday. This ridge of high pressure should also reduce the marine layer and produce warmer temperatures in the coastal valleys, as well.

When temperatures are hot, avoid strenuous activities in direct sunlight and drink plenty of water. Pay attention to your body. Muscle cramps, dizziness and nausea may be signs of a heat-related illness.

Today’s surf report

Today’s 2- to 3-foot northwesterly (310-degree, deep-water) swell (with an 8- to 12-second period) will remain at this height through Tuesday morning.

Fresh to strong (19- to 31-mph) northwesterly winds will generate a 2- to 4-foot northwesterly (325-degree, deep-water) sea and swell (with a 4- to 8-second period) Tuesday afternoon through Wednesday morning. The northwesterly winds will further increase to strong to gale force (25- to 38-mph) levels, which will generate a 4- to 6-foot (325-degree, deep-water) sea and swell (with a 4- to 8-second period) Wednesday afternoon through Friday.

A 3- to 5-foot northwesterly (310-degree, deep-water) sea and swell (with a 5- to 9-second period) will develop along our coastline on Saturday and will remain at this height and period through next Monday.

Seawater temperatures

Offshore marine buoys north and south of Diablo Canyon reported seawater temperatures at 64-plus degrees. Seawater temperatures are forecast to range from 59 to 64 degrees through Tuesday.

Seawater temperatures are expected to decrease Wednesday through Friday.