SLO County weather forecast for week of Dec. 27: First storm of season on the way

A change in the weather pattern will develop Sunday night into Monday morning as the season’s first storm slams into the Central Coast.

Moderate to fresh (13 to 24 mph) Santa Lucia (northeasterly) winds on Sunday morning will produce mostly clear skies and cool temperatures along the beaches and coastal valleys; however, areas of dense ground fog is expected in the inland valleys. Sunday’s high temperatures will range between the low to mid-60s.

1,002 millibar low-pressure system and associated cold front take aim at the Central Coast on Sunday night into Monday morning. This storm will produce increasing clouds Sunday afternoon and fresh to strong (19 to 31 mph) southeasterly winds. Moderate rain will start Sunday night and will continue into Monday morning. Combined with the rain on Monday morning will be strong to gale-force (25 to 38 mph) southwesterly winds and high westerly sea and swell. Rain showers will end by Monday afternoon. Total rainfall amounts will range between 0.75 and 1.50 inches throughout the San Luis Obispo and Santa Barbara counties. Snow elevations are expected to hover around 3,500 and 4,000 feet.

In this system’s wake, fresh to strong (19 to 31 mph) northeasterly winds, mostly clear skies and cooler temperatures are expected on Monday night into Wednesday. However, overnight dense valley ground fog away from beaches and persistent Tule fog in the San Joaquin Valley is forecast over this period.

A weak cold front will wash out over the Central Coast Wednesday night/Thursday morning with mostly cloudy skies and drizzle/light rain. This system will be followed by strong to gale-force (25 to 38 mph) northwesterly winds and partly cloudy skies on Thursday afternoon. Gusty Santa Lucia (northeasterly) winds and dry weather will return on New Year’s Day through Saturday.

The long-range models indicate the next wave of precipitation may develop during the first full work week of 2021 with mostly seasonable temperatures for the extended forecast period.

Surf report

An 8- to 10-foot northwesterly (295-degree, deep-water) swell (with an 8- to 16-secord period) is forecast on Sunday. Increasing southwesterly winds will generate a 15- to 17-foot westerly (265-degree, deep-water) sea and swell (with a 5- to 14-second period) on Monday morning and afternoon, decreasing to 10 to 12 feet by Monday night.

An 8- to 10-foot northwesterly (290-degree, deep-water) swell (with an 8- to 22-second period) will arrive along our coastline on Tuesday, increasing to 9- to 11-feet (with an 18- to 20-second period) on Wednesday into Thursday morning. A 10- to 12-foot northwesterly (310-degree, deep-water) sea and swell (with a 5- to 17-second period) is forecast on Thursday afternoon through Friday.

Seawater temperatures will range between 54 and 57 degrees through Saturday.

This week’s temperatures

LOWS AND HIGHS, PASO ROBLES

LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS

PG&E safety tip

Over the decades, I could count on one hand the number of times there has been a big southwesterly wind event. It is rare and seldom seen along the Central Coast. On those once-in-a-while occurrences when we do experience strong southwesterly wind events, the anomalous direction can cause havoc on our trees.



Many of our windswept trees along our coastline have grown into a quasi-aerodynamic profile pointed away from the prevailing northwesterly winds; when southwesterly winds develop, they can cause limbs to fall and even topple trees.

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.