More rain in the forecast? SLO County in for week of overcast skies, chance of showers

Last weekend’s heavy rain pushed precipitation totals well above average for this rainfall season (July 1, 2023, through June 30, 2024) throughout the Central Coast.

Rocky Butte, near Hearst Castle, has recorded 71.4 inches or 178% of normal this season. At the Paso Robles Airport, 18.2 inches of rain has fallen, or 141%of average, while the Santa Maria Airport has seen 17.3 inches, or 133% of the average. The Santa Barbara Municipal Airport has recorded an astounding 25.2 inches. Typically, the airport sees about 16 inches. Much like Santa Barbara, Cal Poly — home of climatology for San Luis Obispo since 1869 — has recorded 25.3 inches or 110% of normal.

This marks the second year in a row that the Central Coast has seen above-average rainfall, which leads to the question, have there ever been three consecutive years of above-average rainfall. The answer is yes.

Since 1869, the rainfall records at Cal Poly have recorded six occurrences of three or four straight years of above-average rainfall. This occurred last during the 1994 through 1997 rainfall seasons, which saw four years of above-average rainfall, and again in 1972 through 1974 and 1939 through 1942, on a seemingly 20- to 30-year cycle.

The Climate Prediction Center forecasts that a transition from El Niño to ENSO-neutral is likely by June 2024, with the increasing odds of La Niña developing by August 2024.

The majority of the time, a La Niña condition produces below-average rainfall along the Central Coast. However, after an El Niño cycle with two consecutive years of above-normal rainfall, a La Niña condition has produced below-average rainfall the following year for the Central Coast since 1950.

This week’s weather forecast: On Saturday, persistent northwesterly winds along the California coastline will allow the marine layer with pockets of fog and mist to develop in the coastal valleys and along the beaches. The low stratus clouds will clear from the coastal valleys during the late morning, but many beaches will remain overcast for most of the day. The inland valleys will warm up to the 80s under clear skies.

High pressure over California will produce Santa Lucia (northeasterly) winds on Sunday morning. This offshore flow will produce clear skies and warm temperatures throughout San Luis Obispo and Santa Barbara counties, reaching the 80s in the inland valleys (Paso Robles) and high 70s in the coastal valleys (San Luis Obispo) and along the beaches. The coastal regions will cool during the afternoon as fresh to strong (19 to 31 mph) northwesterly winds develop, except the southerly-facing beaches of Cayucos, Avila Beach and Shell Beach, which will remain warm.

A trough of low pressure will develop along the California coastline on Monday through Tuesday, creating persistent gentle to moderate (8 to 18 mph) northwesterly winds. This, in turn, will allow the low marine clouds to develop along the coastline and many of the coastal valleys during the night and morning. The beaches will remain mostly overcast with areas of mist and fog.

A weak cold front will move through Central California on Tuesday night into Wednesday morning with a deep marine layer. It will be followed by fresh to strong (19 to 31 mph) northwesterly winds and clearing skies on Wednesday afternoon into Thursday.

A late-season low-pressure system is forecast through the region on Friday with increasing clouds, scattered rain showers and the chance of thunderstorms. In this system’s wake, strong to gale-force (25 to 38 mph) northwesterly winds and clearing skies are forecast later Friday into next Saturday. Strong to gale-force northwesterly winds are expected for most of next week.

Surf report

A 6- to 8-foot northwesterly (295-degree deep-water) sea and swell (with a 5- to 11-second period) is forecast on Saturday through Sunday.

A 4- to 6-foot northwesterly (290-degree deep-water) swell (with an 8- to 12-second period) is forecast on Monday through Tuesday, becoming a 3- to 5-foot northwesterly sea and swell (with a 5- to 10-second period) on Wednesday into Thursday.

This northwesterly (290-degree deep-water) sea and swell will increase to 8- to 10-feet (with a 5- to 9-second period) Friday into next Saturday.

Combined with this northwesterly sea and swell, will be 1- to 2-foot southern hemisphere (215-degree deep-water) swell (with a 15- to 17-second period) on Sunday through Wednesday.

Seawater temperatures: Seawater temperatures will range between 53 and 55 degrees through Thursday, decreasing to 52 and 54 degrees on Friday through next Saturday.

This week’s temperatures

LOWS AND HIGHS, PASO ROBLES

LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS

John Lindsey is a retired PG&E marine meteorologist. Email him at JohnLindseyLosOsos@gmail.com or follow him on Twitter @PGE_John.