More rain and wind in SLO County expected following a warm Christmas Day

My daughter Chloe is stationed on the USS Truman at Norfolk Naval Air Station, Virginia. She sent a text on Saturday morning proclaiming it was 13 degrees. I returned it by saying it would be close to 80 degrees in San Luis Obispo on Christmas. She will be a happy camper when she comes home on leave from the Navy next week. However, a significant change in our weather pattern is expected to start on Tuesday as a storm is forecast to produce gale-force southerly winds and much-needed rain.

In the meantime, a ridge of high pressure will produce fresh and strong (19 to 31 mph with gusts to 40 mph) Santa Lucia (northeasterly) winds on Christmas morning. These winds will create primarily clear skies. High temperatures will reach the mid to high-70s in the coastal valleys (San Luis Obispo), the low to mid-70s in the inland valleys (Paso Robles), and the high-60s along the beaches on Christmas Day. Tule fog will persist in the Central Valley.

Monday will be a transitional day as the area of high pressure responsible for the warm weather and gusty offshore winds breaks down, and a trough of low pressure develops along the West Coast. The winds will shift out of the south and decrease to gentle levels while mid to high-level clouds increase and temperatures drop.

An intense cold front strengthened by vigorous westerly upper-level winds across the Pacific will move through the Central Coast on Tuesday. This storm will produce moderate gale-force to fresh gale-force (32 to 46 mph with gusts to 50 mph) southerly winds and moderate to heavy rain on Tuesday morning and afternoon. The winds will decrease, and the rain will turn to showers on Tuesday night into Wednesday morning. This low-pressure system will tap into a plume of subtropical moisture, taking on the characteristics of an Atmospheric River (AR) which will keep air temperatures mild with snow levels above 5,000 feet. Total rainfall amounts should range between 1.5 and 2.5 inches, with higher amounts in the Santa Lucia mountains due to orographic enhancement.

An upper-level trough will follow Thursday into Friday with moderate to fresh (13 to 24 mph) southerly winds and widely scattered rain showers. The extended range models indicate another storm arriving along the Central Coast New Year’s Eve through New Year’s Day with gale-force southerly winds and more moderate to heavy rain.

Surf report

A 4- to 6-foot west-northwesterly (285-degree, deep-water) swell (with an 8- to 17-second period) is expected along our coastline on Sunday into Monday morning.

An 8- to 10-foot westerly (275-degree, deep-water) swell (with a 14- to 16-second period) will arrive along our coastline on Monday afternoon and night, increasing to 10- to 12-feet (with a 14- to 16-second period) on Tuesday. Combined with this westerly swell will be 5- to 7-foot southerly (180-degree, Shallow-water) sea on Tuesday.

This westerly swell is forecast to peak on Wednesday at 13- to 15-feet (with a 13- to 15-second period), decreasing on Thursday. This will be the highest wave event since spring of this year.

Seawater temperatures will range between 55 and 57 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 marine meteorologist. Email him at JohnLindseyLosOsos@gmail.com or follow him on Twitter @PGE_John.