SLO County weather forecast: More rain through the week

As of Saturday, at noon, the Paso Robles Airport has recorded 2.36 inches of rain this rainfall season (July 1 through June 30), or 135% of the normal as of Dec. 3. The San Luis Obispo County Regional Airport has seen 3.23 inches of precipitation, or 80% of the seasonal average. These percentages should improve by Sunday, and here is why.

On Sunday, an intense 534 decameter upper-level low-pressure system off the northern California coastline will move southward toward the Central Coast. A cold front associated with this storm will interact with a plume of moisture extending southwestward across the pacific toward Hawaii and will produce rain and strong to gale-force (25 to 38 mph with gusts to 45 mph) southerly winds.

Most numerical forecast models indicate between 0.50 to 1.25 inches of rainfall throughout San Luis Obispo County, with up to 2 inches along the southerly-facing mountain slopes due to orographic enhancement by Sunday morning.

Overnight lows will drop to the mid to high-40s throughout the Central Coast, while daytime highs will range from the low-60s at the beaches, in the coastal valleys (San Luis Obispo), and in the inland valleys (Paso Robles) on Sunday.

Rain will turn to scattered showers late Sunday morning, ending by Sunday afternoon. The winds will decrease to gentle levels, and temperatures will remain mild on Sunday afternoon under mostly cloudy skies.

On Monday morning, the winds will increase out of the northeast (offshore). These offshore winds will produce partly cloudy skies throughout the day on Monday.

A cold front will move through the Central Coast on Tuesday with increasing mid to high-level clouds and a chance of rain showers. In the wake of the cold front, gentle to moderate (8 to 18 mph) northwesterly winds, cooler temperatures, and the marine layer with pockets of fog and mist will return to the coastal regions on Tuesday night and persist along the coastline through Thursday.

Another storm is forecast to produce gale-force southerly winds and moderate to heavy rain on Friday, Dec. 9.

An unsettled weather pattern with a chance of rain is expected to return on Dec. 17 and Dec. 19.

Surf report

Sunday’s 6- to 8-foot west-northwesterly (280-degree, deep-water) swell (with an 8- to 16-second period) will remain at this level into Monday morning.

A 4- to 6-foot northwesterly (295-degree, deep-water) swell (with an 8- to 14-second period) will develop along our coastline on Monday afternoon into Tuesday, decreasing to 3- to 5-feet with the same period on Wednesday through Thursday.

Increasing southerly seas along with a building northwesterly swell will develop along our coastline on Friday.

A strong northerly flowing current combined with less upwelling, has brought a warmer body of seawater to the Central Coast. Seawater temperatures will range between 55 and 59 degrees 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 December 4, 2022 at 5:30 AM.