Are more April showers on the way to SLO County? See this week’s weather forecast

Another late-season storm will bring gusty southerly winds, periods of rain and a chance of scattered thunderstorms from Monday night into Wednesday.

In the meantime, gentle southerly winds, variable clouds and cooler temperatures are expected Saturday night through Monday afternoon.

A 539 decameter, upper-level, low-pressure system cut off from the jet stream will gradually drift southward along the California coastline. Legendary KABC-TV meteorologist George Fischbeck often called this “a weatherman’s woe” because of the difficulty in predicting its track and speed.

This system will produce gentle southerly winds and increasing clouds late Saturday through Sunday and into Monday afternoon.

During this period, high temperatures will reach the low to mid-70s in the inland valleys, including Paso Robles, and the upper 60s to low 70s in coastal valleys such as San Luis Obispo. Beach temperatures will generally range from the low to mid-60s.

The upper-level low, along with its associated warm and cold fronts, will wobble across the Central Coast from Monday night into Tuesday, bringing strong to gale-force (25 to 38 mph) southerly winds and periods of rain. An upper-level trough will follow on Wednesday, bringing scattered rain showers and a chance of thunderstorms.

With the longer daylight hours of April, colder air associated with this upper low will increase atmospheric instability, raising the likelihood of thunderstorms. These convective cells could produce brief heavy downpours, hail and localized microbursts.

Daytime temperatures will only reach the 60s across the Central Coast on Tuesday and Wednesday.

Total rainfall is expected to range between 0.33 and 1.1 inches, with locally higher amounts in the Santa Lucia Range and other coastal mountains due to orographic enhancement.

A 1,019 millibar, Eastern Pacific high-pressure system will build about 1,000 miles west of Cape Mendocino on Thursday and Friday, creating a steep pressure gradient along the California coastline. This setup will generate strong to gale-force (25 to 38 mph, with gusts up to 45 mph) northwesterly winds during the afternoon and evening hours.

Winds will ease overnight and during the mornings, allowing areas of low marine clouds to develop along the coast.

The winds are expected to diminish next weekend as yet another low-pressure system approaches the Central Coast, bringing a slight chance of rain by next Sunday night into next Monday.

Surf report

It is unusual to see such low-swell conditions develop in April, when strong northwesterly winds are typically blowing along the coast.

Gentle southerly winds late Saturday through Sunday and into Monday afternoon will allow a 1- to 3-foot northwesterly (290-degree, deep water) swell (with a 7- to 11-second period) to develop along the Central Coast during this time frame.

Increasing southerly winds will generate a 5- to 7-foot westerly (260-degree, deep water) sea and swell (with a 5- to 12-second period) on Monday night into Wednesday.

Increasing northwesterly winds along the California coastline will generate 6- to 8-foot northwesterly (300-degree, deep water) sea and swell (with a 5- to 14-second period) on Thursday through Friday, decreasing to 3- to 5-feet (with 8- to 12-second period) next Saturday and Sunday.

Combined with this low northwesterly swell will be a 1- to 3-foot Southern Hemisphere (200-degree, deep water) swell (with a 13- to 15-second period) on Saturday through Tuesday.

Seawater temperatures are expected to range between 52 and 54 degrees through Sunday. From Monday through Wednesday, seawater temperatures will warm to 57 to 60 degrees as a northerly flowing current brings warmer water to the Central Coast.

Gale-force northwesterly winds along the California coastline will enhance coastal upwelling, leading to progressively cooler ocean temperatures on Thursday through Friday. Consequently, seawater temperatures will drop to 54 to 56 degrees.

On this date in weather history (April 19)

1775: The first engagement of the Revolutionary War took place under clear crisp weather at Lexington and Concord. (Sandra and TI Richard Sanders, 1987)

1973: Glenrock, Wyoming, received 41 inches of snow in just 24 hours, and a storm total of 58 inches, to establish two state records. (David Ludlum)

2017: Bill Coy’s rain gauge located in the Santa Lucia Mountains near Cayucos recorded 1.45 inches of rain from April 16 to 19. More importantly, his weather station had logged 57.1 inches during the rain season, the most he had ever seen. His rain records go back to 1979. Rocky Butte received 86.91 inches for the season, which runs from July 1 to June 30. Dawn Dunlap at Walter Ranch recorded 1.9 inches of rainfall between April 16 and 19, while Debby Mix at Circle 3 Ranch in the San Simeon Creek Watershed had seen over 100 inches. Cal Poly (home of climatology for San Luis Obispo) recorded more than 33 inches, or 150% of normal, for the entire rain season. The Paso Robles Municipal Airport saw 14.5 inches of rain. Generally, for the whole rain season, it receives 12.5 inches.

This week’s temperatures

LOWS AND HIGHS, PASO ROBLES

SUNDAY: 47, 75

MONDAY: 42, 71

TUESDAY: 41, 63

WEDNESDAY: 40, 67

THURSDAY: 42, 72

FRIDAY: 45,75

SATURDAY: 49, 76

SUNDAY: 50, 77

LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS

SUNDAY: 52, 71

MONDAY: 50, 68

TUESDAY: 48, 64

WEDNESDAY: 49, 73

THURSDAY: 50, 70

FRIDAY: 52, 72

SATURDAY: 53, 73

SUNDAY: 54, 74

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