Heat wave scorches inland areas of Central Coast, while coastline remains cool

Just in time for the Mid-State Fair, an upper-level high-pressure system over California combined with moderate to fresh (13 to 24 mph) afternoon northwesterly winds along the coastline will bring triple-digit temperatures to San Luis Obispo County’s inland valleys on Sunday through this upcoming workweek.

In the coastal regions, these northwesterly (onshore) winds will create a persistent marine layer with pockets of fog and mist and extensive stratus clouds, keeping temperatures mild.

Sunday’s high temperatures will reach between 102 and 105 degrees in the inland valleys (Paso Robles) and the low 80s in the coastal valleys (San Luis Obispo). The beaches will warm up to the mid-60s under mostly overcast skies.

The models indicate variable amounts of subtropical moisture will stream northward over the Central Coast from Mexico. This condition should produce scattered mid- to high-level clouds, creating slightly cooler temperatures, but higher humidity levels will make it feel warmer from Monday through Wednesday.

The upper-level high is expected to strengthen to 599 decameters on Thursday through next Saturday, July 22, generating hotter inland temperatures, with Paso Robles reaching between 103 and 108 degrees. The coastline will remain shrouded in low-marine clouds, protecting it from the extreme heat.

Surf report

A 4- to 6-foot northwesterly (290-degree, deep-water) swell (with an 8- to 11-second period) is forecast along our coastline on Sunday through next Saturday, July 22.

Combined with this northwesterly swell will be 1- to 2-foot southerly (190-degree, deep-water) swell (with a 10- to 12-second period) from Hurricane Calvin, centered about 1.200 miles southwest of San Luis Obispo on Monday through Wednesday.

Seawater temperatures will range between 55 and 57 degrees through Thursday, increasing to 56 to 59 degrees by this weekend.

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.