SLO County Weather: Wind and rain on the way this week

NOAA’s Global Forecast System indicates between 0.33 and 0.75 of an inch of rainfall through the end of February. Little rain is expected into the first week of March. So far, the San Luis Obispo County Airport has recorded 0.38 of an inch of rain this month. Historically, it has recorded 3.54 inches for Feb. Let’s hope this forecast is incorrect. Not only has it been mostly dry, but it’s also been colder than usual. In fact, the temperature has averaged 51.7 degrees as of February 18; usually, it is 53.8 degrees for this month at the airport.

High pressure over the Great Basin will continue to produce gusty Santa Lucia (northeasterly/offshore) winds through Monday morning. This offshore flow will produce mostly clear skies with cool mornings and mild afternoons; however, an upper-level low-pressure system off the Central Coast will create a few scattered mid to high-level clouds. Highs this weekend will reach mid to high-60s, with lows lowering to the mid-30s in the inland valleys (Paso Robles) and mid-40s in the coastal valleys (San Luis Obispo).

The winds will shift out of the northwest (onshore) by Monday afternoon, allowing the marine layer areas of fog and mist to develop along the coastline and surge inland Monday night into Tuesday morning.

Batten down the hatches, and here’s why:

An upper-level low-pressure system from Canada will travel southward through the state of California and combined with 150-mph jet steam 20,000 feet above the Central Coast, will produce a few scattered rain showers on Tuesday night into Wednesday, with snow levels dropping to 3,000 feet. The main impact of this tempest will be to generate moderate gale-force to fresh gale-force (32 to 46 mph with gusts to 55 mph), northwesterly winds, and cooler temperatures on Tuesday evening into Wednesday. In fact, high temperatures will struggle to reach the low-50s on Wednesday.

An upper-level trough will follow Thursday afternoon into Friday with rain showers and even cooler temperatures, with snow levels dropping to 2,000 feet. Daytime highs in the inland valleys will only reach the high-40s and low-50s in the coastal valleys, with widespread frost overnight. Total rainfall amounts are expected to range between 0.33 and 0.50 of an inch.

The next chance for rain will be on Feb. 28.

Surf report

A 4- to 6-foot northwesterly (290-degree, deep-water) swell (with an 8- to 16-second period) is expected along our coastline on Sunday through Tuesday morning.

Increasing northwesterly winds off the California coastline will generate an 13- to 15-foot northwesterly (310-degree, deep-water) sea and swell (with a 5- to 14-second period) on Tuesday afternoon into Wednesday.

A 6- to 8-foot northwesterly swell (with an 8- to 11-second period) will arrive along our coastline on Thursday, decreasing to 4- to 6-feet on Friday.

Seawater temperatures will range between 51 and 53 degrees through Monday, decreasing to 49 to 52 degrees on Tuesday and will remain at this level through 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.

This story was originally published February 19, 2023 at 5:30 AM.