Keep your rain jackets out, SLO County: More stormy weather is on the way

The Eastern Pacific High (1,033 millibars) has shifted westward, reaching nearly to the International Date Line, opening the door for storms in Central California.

Blustery, wet conditions are forecast to continue through Tuesday, then shift to dry conditions on Wednesday and should persist through mid-January as the Eastern Pacific High moves eastward toward the Central Coast.

A cold front associated with a 992 millibar surface low near Cape Mendocino will move through the Central Coast on Saturday morning, bringing strong to gale-force (25 to 38 mph with gusts to 45 mph) southeasterly winds and periods of heavy rain.

The winds will shift out of the south and decrease to fresh to strong (19 to 31 mph) levels, and rain will turn to showers on Saturday afternoon and night.

Total rainfall on Saturday is predicted to range from 0.75 to 2 inches, with higher amounts likely in the Santa Lucia Range and Coastal Mountains.

An upper-level trough will follow on Sunday, producing fresh to strong (19 to 31 mph) southerly winds in the morning, decreasing Sunday afternoon and night, with scattered rain showers. Total rainfall on Sunday is expected to range from 0.33 to 1 inch along the coast, with less precipitation in the inland valleys.

Another cold front will approach the Central Coast later Monday, bringing rain showers and increasing southerly winds. This system is forecast to move over the San Luis Obispo and Santa Barbara counties Monday night into Tuesday morning with strong to gale-force (25 to 38 mph) southeasterly winds, rain and a chance of thunderstorms.

Rainfall from Monday to Tuesday on the Central Coast will likely total between 0.75 to 1.5 inches.

In the cold front’s wake, combined with the Eastern Pacific High moving eastward, a steep pressure gradient will develop along the California coast, producing moderate gale-force to fresh gale-force (32 to 46 mph with gusts to 50 mph) northwesterly winds on Wednesday into Thursday.

These winds will bring in a colder air mass, with high temperatures only reaching the 50s throughout the Central Coast.

Overnight lows will drop to the low 30s in the inland valleys (Paso Robles) and to the upper 30s in the coastal valleys (San Luis Obispo), and along many of our beaches, with widespread frost expected during the overnight and morning on Thursday and Friday.

Increasing high pressure over the Great Basin will produce gusty Santa Lucia winds (northeasterly) during the overnight and morning starting on Friday into the following week under clear skies, except for dense valley fog during the night and morning with stratus clouds over the Santa Lucia and coastal mountains.

Tule Fog is expected to redevelop in the Central Valley.

Surf report

A 6- to 8-foot southerly (195-degree, deep water) sea and swell (with a 5- to 13-second period) is forecast along our coastline on Saturday, increasing out the of west to 9- to 11 feet (with a 14- to 16-second period) on Sunday.

Sunday’s high tide is predicted to be 6.6 feet at 9:44 a.m., but it could reach higher than 7 feet because tides are running about 6 inches higher due to thermal expansion of the water column.

Sea surface temperatures typically hover around 56 degrees at this time of the year, but are presently near 61 degrees.

This condition, combined with the high westerly swell, could produce coastal flooding.

A 5- to 7-foot southerly (200-degree, deep water) sea and swell (with a 5- to 11-second period) is forecast on Monday and will remain at this level through Tuesday.

Gale-force northwesterly winds will generate a 9- to 1-foot southerly (300-degree, deep water) sea and swell (with a 5- to 18-second period) later on Wednesday through Thursday, gradually decreasing on Friday through next Saturday.

Seawater temperatures will range between 60 and 62 degrees through Wednesday morning, lowering to 56 to 58 degrees by Thursday into Friday.

On this date in weather history (Jan. 4)

1910: A great flood in Utah and Nevada washed out 100 miles of railroad between Salt Lake City, Utah, and Los Angeles, California, causing $7 million of damage. (David Ludlum)

1961: The coldest temperature ever recorded in Hawaii was established with a reading of 14 degrees atop Haleakela Summit. (David Ludlum)

2006: During a 24-hour period, the Diablo Canyon Ocean Lab rain gauge recorded 3.8 inches of rain by 7 a.m. Other areas in San Luis Obispo County recorded more than 5 inches of precipitation since the morning prior. Sustained southerly winds reached 38 mph with gusts at 52 mph. Two low pressure systems, one over the area and the other one about 200 miles west of Diablo Canyon, both continued to tap into a plume of subtropical moisture.

2019: The morning’s low temperatures dropped to 30 degrees at the San Luis Obispo County Regional Airport, 29 degrees at PG&E EEC in Avila Valley, 25 degrees at the Paso Robles Airport and 20.5 degrees at Windrose Farm.

This week’s temperatures

LOWS AND HIGHS, PASO ROBLES

SUNDAY: 49, 56

MONDAY: 43, 56

TUESDAY: 41, 56

WEDNESDAY: 39, 54

THURSDAY: 34, 53

FRIDAY: 33, 54

SATURDAY: 34, 57

SUNDAY: 37, 61

LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS

SUNDAY: 54, 59

MONDAY: 49, 58

TUESDAY: 48, 57

WEDNESDAY: 46, 55

THURSDAY: 42, 56

FRIDAY: 38, 58

SATURDAY: 39, 56

SUNDAY: 39, 65

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