SLO County weather forecast for week of Sept. 27 — foggy at the coast, hot inland

Last week’s fog-free days and mild temperatures will give way to a persistent marine layer with night and morning mist and fog in the coastal regions, while triple-digit temperatures will continue in the inland areas this week.

Gentle to moderate (8 to 18) Santa Lucia (northeasterly) winds are expected Sunday morning which should be strong enough to produce clear skies along the coastline and hot temperatures in the coastal valleys (San Luis Obispo) and inland valleys (Paso Robles). Sunday’s high temperatures will range from the 70s along the coast, and high 90s to low 100s in the coastal and inland valleys.

The winds will shift out of the northwest which will allow the marine layer to redevelop along the immediate coastline by Sunday night and move further inland by Monday morning with areas of drizzle and dense fog. The gentle to moderate northwesterly to southwesterly winds will continue along the coastline through Tuesday. These winds will help to create a persistent marine layer along the beaches throughout the day with cooler temperatures, while an early-autumn heatwave continues in coastal and inland valleys through Tuesday.

Temperatures will start to drop off in the coastal valleys on Wednesday through Friday as the upper-level high-pressure ridge responsible for the autumn heatwave starts to break down and fresh to strong (19 to 31 mph) afternoon northwesterly winds develop along the coastline; however, the inland areas will remain hot through Saturday. These winds will produce a greater amount of clearing along the beaches.

A few of the models are indicating a chance of rain developing by October 6.

Surf report

A 6- to 8-foot northwesterly (295-degree, deep-water) swell (with an 8- to 11-second period) is forecast on Sunday, decreasing to 4 to 6 feet (with an 8- to 15-second period) on Monday through Tuesday. Increasing northwesterly winds will generate a 4- to 6-foot northwesterly (310-degree, deep-water) sea and swell (with a 5- to 12-second period) on Wednesday through Friday.

Seawater temperatures will range between 55 and 58 degrees through Friday.

This week’s temperatures

LOWS AND HIGHS, PASO ROBLES

LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS

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John Lindsey’s is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at pgeweather@pge.com or follow him on Twitter @PGE_John.

This story was originally published September 27, 2020 at 5:00 AM.