SLO County weather forecast: Pockets of fog and warm temperatures this week

A classic late spring pattern of night and morning low clouds with areas of fog and mist clearing during the afternoon will continue through Sunday. A late-season low-pressure system will significantly change the weather pattern starting on Monday and continuing into Wednesday.

Onshore flow (winds blowing from the Pacific to the land) will continue to produce a marine layer with pockets of fog and mist during the night and morning, clearing during the afternoon as the northwesterly (onshore) winds increase to fresh to strong (19 to 31 mph) levels along the coastline. Temperatures will reach the mid-80s in the inland valleys (Paso Robles), the low-70s in the coastal valleys (San Luis Obispo), and the low-60s along the beaches on Saturday through Sunday.

A late-season upper-level low-pressure (568 decameters) system will move southward along the Central California coastline and is forecast to produce gentle to moderate (8 to 18 mph) southerly winds and mostly cloudy skies with pockets of drizzle and rain along with a chance of thunderstorms in the afternoon and evening on Monday into Wednesday. Total precipitation amounts should range between 0.10 and 0.25 of an inch, with higher amounts in the mountains. Unsettled weather could continue into Thursday morning, depending on how fast this low-pressure system departs the area.

In this system’s wake, fresh to strong (19 to 31 mph) afternoon northwesterly winds will develop on Thursday through the following weekend. This condition is expected to produce clear skies during the late morning and afternoon, which will allow temperatures to reach the 80s in the inland valleys and 70s in the coastal valleys by Friday and Saturday.

Surf report

A 5- to 7-foot northwesterly (290-degree, deep-water) swell (with an 8- to 11-second period) is expected along our coastline on Saturday through Monday, decreasing to 3- to 5-feet on Tuesday into Wednesday. This northwesterly swell will further lower to 2- to 4-feet (with a 7- to 9-second period) on Thursday.

Increasing northwesterly winds along the coastline will generate a 5- to 7-foot northwesterly (310-degree, deep-water) sea and swell (with a 5- to 8-second period) on Friday, building to 6- to 8-feet next Saturday and Sunday.

Combined with this northwesterly sea and swell will be a 1- to 3-foot (195-degree, deep-water) southern hemisphere swell (with a 14- to 16-second period) on Tuesday through Thursday.

Seawater temperatures will range between 56 and 58 degrees through Thursday, decreasing to 54 to 56 degrees on Friday through next Sunday.

This week’s temperatures

LOWS AND HIGHS, PASO ROBLES

SUN

MON

TUE

WED

THU

FRI

SAT

53, 84

51, 68

52, 68

52, 72

51, 77

53, 80

54, 82

LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS

SUN

MON

TUE

WED

THU

FRI

SAT

54, 71

53, 62

55, 63

54, 65

54, 68

53, 72

54, 74

John Lindsey’s is a longtime meteorologist who lives in Los Osos. Email him at JohnLindseyLosOsos@gmail.com.