SLO County weather forecast for the week of Sept. 18

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

A ridge of high pressure over California will produce gentle to moderate (8- to 18-mph) Santa Lucia (northeasterly) winds during the morning hours and gale-force northwesterly winds along the coastline during the afternoon hours Monday into Wednesday.

These northeasterly (offshore) winds will keep the marine layer out to sea during the morning hours, and strong to gale-force afternoon northwesterly winds will keep most of the beaches mild and blustery. In other words, the weather will have an autumn feel with crisp morning minimums followed by pleasant afternoons. Overall, afternoon highs will range from the high 80s to low 90s in the North County and high 70s to low 80s in the coastal valleys, The beaches will remain in the 60s, except the southerly facing beaches of Cayucos, Avila Beach and Shell Beach, which will reach the 70s.

Moderate gale-force to fresh gale-force (32 to 46 mph) northwesterly winds are forecast along our coastline later Thursday, which will keep the skies mostly clear and the temperatures mild. Warmer weather should return by the weekend, but no significant heat is expected.

Surf report

A 3- to 5-foot northwesterly (310-degree, deep-water) sea and swell (with a 5- to 11-second period) is forecast along our coastline through Monday.

A 975-millibar storm moved eastward and crossed the Aleutian Islands into the Gulf of Alaska on Saturday. Northwesterly swell from this storm reached 24 feet with a 14-second period Saturday morning. This northwesterly swell, combined with gale-force northwesterly winds along our coastline, will generate a 7- to 9-foot northwesterly (300-degree, deep-water) sea and swell (with a 5- to 17-second period) Tuesday and will remain at this height but with a gradually shorter period Wednesday into Thursday. This northwesterly sea and swell will decrease to 4 to 6 feet (with a 7- to 11-second period) Friday into next Sunday.

Seawater temperatures will range between 55 and 61 degrees through Monday, decreasing to 54 to 60 degrees Tuesday. Seawater temperatures will decrease to 52 and 56 degrees Wednesday into Friday.

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This story was originally published September 17, 2017 at 2:32 PM with the headline "SLO County weather forecast for the week of Sept. 18."