SLO County weather clearing for Valentine’s Day. But that could change by the weekend

Last week’s weather pattern was one for the record books.

It all started when a 200-plus-mile-per-hour jetstream took aim at California from Japan and propelled commercial airliners across the Pacific at over the speed of sound ground speed in a classic El Niño fashion.

These winds carved out several low-pressure systems that merged into a 978-millibar bomb cyclone centered 100 miles west of the Bay Area that produced one of the strongest storms ever to slam into California, producing 102 mph southerly wind gusts at Pablo Point, a 1,200-foot peak north of Bolinas, in the Point Reyes National Seashore.

Locally, the PG&E TV towers weather station on the Cuesta Grade saw wind gusts of up to 79 mph last Sunday. These winds generated 17-foot southerly seas at the Diablo Canyon waverider buoy.

This system also created moderate to heavy rain throughout the Central Coast, with most locations recording between 2 and 4 inches last week.

However, the cold front associated with the 978-millibar storm interacted with a plume of subtropical moisture, an atmospheric river, which stalled over Southern California and created extraordinarily high rainfall amounts south of Point Conception.

In fact, many locations received more precipitation this last week than they would normally do throughout the entire rainfall season. The Cogswell Dam in Los Angeles County received the most, with 14.88 inches.

On Wednesday, an intense cold front associated with a deep and frigid upper-level low-pressure system moved through the Central Coast, producing gale-force southerly winds, unstable atmosphere conditions, thunderstorms, hail, and two confirmed EF1 tornadoes by the National Weather Service. One tornado was in Grover Beach, and the other occurred east of Los Osos.

In a break from the stormy weather, tranquil conditions will develop this Valentine’s Day week with gentle winds, partly cloudy to mostly clear skies, and gradually warmer temperatures. However, we could find ourselves back into a significant storm pattern by this upcoming weekend with gale-force southerly winds, heavy rains, and the chance of thunderstorms.

A 1,025-millibar area of high pressure centered 150 miles west of the Central Coast will force the storm track to the north, keeping San Luis Obispo and Santa Barbara counties dry through Friday.

A pattern of gentle to moderate (8 to 18 mph) Santa Lucia winds developing overnight and morning, shifting out of the northwest during the afternoon, will keep the marine layer to a minimum, with cold to cool mornings and mild afternoons. The inland valleys (Paso Robles) will drop to the low 30s, while the coastal valleys (San Luis Obispo) and beaches will cool to the low 40s. Highs will reach the mid-60s throughout the region.

The area of high pressure off the coastline responsible for the beautiful weather will weaken and move southward, opening the door to a series of storms that will impact Central California starting as early as Saturday and continuing through the following week. The numerical models are advertising that these systems will produce gale-force southerly winds, periods of moderate to heavy rain, increasing waves, and the chance of thunderstorms.

Surf report

A 5- to 7-foot northwesterly (295-degree, deep-water) swell (with an 11- to 20-second period) is forecast along our coastline on Sunday through Monday, decreasing to 4 to 6 feet (with an 8- to 16-second period) on Tuesday through Thursday.

Increasing southerly winds will generate a 6- to 8-foot southwesterly (245-degree, deep-water) sea and swell (with a 7- to 14-secomnd period) on Friday into Saturday afternoon, building to 15 to 17 feet on Saturday night through next Sunday and Monday.

Seawater temperatures will range between 57 and 58 degrees through Sunday, increasing to 59 to 61 degrees on Tuesday into Friday.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.