SLO County could see 1 to 3 inches of rain as powerful storm moves in

All the eyes of the meteorological community were on a storm with hurricane-force winds that rapidly intensified as it traveled eastward across the southern Gulf of Alaska from 989 millibars to 943 millibars on Saturday.

This storm had explosive development and was consequently classified as a “bomb cyclone.” A low-pressure system needs to lower 24 millibars in 24 hours to be classified as a meteorological bomb.

The associated cold front is forecast to tap into subtropical moisture and take on the characteristics of an atmospheric river (AR) as it moves into Northern California with heavy rain on Sunday.

Expected precipitation totals in Northern California will range from 5-plus inches in the northern coastal mountains and the northern/central Sierra Nevada; 3 to 5 inches in lower elevations of the Bay Area and Sacramento Valley.

The ECMWF and GFS models continue to indicate that this intense cold front, strengthened by vigorous upper-level winds, will move through the Central Coast Sunday night into Monday morning.

This storm is forecast to produce moderate gale-force to fresh gale-force (32 to 46 mph with gusts to 60 mph) southerly winds and between 1 and 3 inches of rain in San Luis Obispo County. The Santa Lucia mountains above Cambria could see as much as 4 inches.

The strongest winds and heaviest rain are expected to occur between 2 a.m. and 6 a.m. on Monday with the frontal passage. This system will produce multiple feet of snow in the Sierra Nevada above 8,000 feet.

Wind advisories were issued for the Coastal Range starting at 11 a.m. Sunday through 11 a.m. Monday, with Highways 41, 46 and 33 at particular risk, according to the National Weather Service.

In the cold front’s wake, strong to gale-force (25 to 38 mph) northwesterly winds and clearing skies are forecast on Monday evening into Tuesday. Gusty Santa Lucia (northeasterly) winds, clear skies, and warmer temperatures are forecast on Wednesday through Friday. In fact, high temperatures could reach the low-80s in the coastal valleys and along the beaches by Thursday.

Surf report

A 5- to 7-foot northwesterly (290-degree, deep-water) swell (with an 8- to 13-second period) is forecast along our coastline on Sunday morning. Gale-force southerly winds along the Central California coastline will generate a 5- to 7-foot southerly (180-degree, shallow-water) seas on Sunday afternoon, building to 10- to 12-feet on Sunday night into early Monday morning.

These seas will be followed by a 10- to 12-foot westerly (280-degree, deep-water) swell (with an 18- to 20-second period) later Monday morning, building to 13- to 15- feet (with a 15- to 17-second period) by Monday afternoon through Tuesday morning. This swell will decrease to 9- to 11-feet (with a 13- to 15-second period) on Tuesday afternoon and night.

A 6- to 8-foot northwesterly (300-degree, deep-water) swell (with a 7- to 17-second period) is forecast along our coastline on Wednesday through Thursday.

Seawater temperatures will range between 56 and 58 degrees through Thursday.

This week’s temperatures

LOWS AND HIGHS, PASO ROBLES

LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS

PG&E safety tip

With oak trees heavily burdened with acorns and stressed from well below-average rain last season, fallen limbs and other debris is expected with Sunday’s night into Monday morning’s storm.

Never touch downed power lines. Stay away from the lines and keep others away from them.

Call 911 immediately to report the location of a downed line. After reporting the downed line, call Pacific Gas and Electric Co. toll-free at 800-743-5000.

John Lindsey’s is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at pgeweather@pge.com or follow him on Twitter @PGE_John.

This story was originally published October 24, 2021 at 9:00 AM.