A thick layer of fog swirls around peaks in San Luis Obispo. John Lindsey
A trough of low pressure along the entire California coastline will produce a persistent marine layer with pockets of fog and mist during the overnight and morning hours and cooler temperatures starting Sunday and continuing through Friday.
A pattern of gentle variable winds during the overnight and morning, increasing out of the northwest to gentle to moderate (8 to 18 mph) levels later in the morning through the evening, will develop in response to a surface trough that will hug the California coastline Sunday through Friday.
This condition will create a deep and persistent marine layer along the coastline with overnight and morning dense fog, mist and even drizzle in the coastal regions. Over the period, most beaches will only see a partial clearing in weather patterns reminiscent of summer. Further inland, the marine layer will clear later in the morning through the afternoon.
Temperatures will range from the 70s in the inland valleys (Paso Robles) and 60s in the coastal valleys (San Luis Obispo), while many of the beaches will only reach the high 50s. Overnight lows will drop to the 40s throughout the Central Coast.
In springtime, Paso Robles has a 90 percent chance that there will be no 36-degree nights by May 24 and San Luis Obispo by May 10. Along the coastline, it is May 8. In other words, you can count on being safe from frost by that day, according to the National Gardeners Association.
Frost can develop when the air temperature is as high as 36 degrees or even 38 degrees. That happens because many things cool faster than the air surrounding them, like blades of grass, vines, car windshields, and roofs on buildings as their heat radiates to space, especially during clear, dry and windless conditions at night. If the night air is calm, denser cold air can flow downward along our mountain slopes and accumulate in the valleys.
A dry cold front will move through the Central Coast next Saturday and Sunday, creating a steep pressure gradient along the California coastline. In turn, moderate gale-force to fresh gale-force (32 to 46 mph) northwesterly winds will develop next weekend, peaking next Monday.
The long-range numerical models indicate a dry weather pattern through April; however, predicting precipitation in early spring tends to be very difficult, as the weather pattern can change on a dime.
Surf report
An 8- to 10-foot northwesterly (300-degree deep-water) sea and swell (with a 7- to 11-second period) was forecast on Saturday, decreasing to 5- to 7-feet by Sunday.
A 3- to 5-foot northwesterly (290-degree deep-water) swell (with an 8- to 16-second period) is forecast on Monday through Friday.
Increasing northwesterly winds will generate increasing northwesterly sea and swell next weekend. The peak could reach as high as 11- to 13-feet by next Sunday and Monday.
Combined with this northwesterly sea and swell will be a 2- to 3-foot Southern Hemisphere (205-degree deep-water) swell (with a 15- to 17-second period) on Saturday through Wednesday.
Surface seawater temperatures will range between 50 and 53 degrees through Tuesday, increasing to 52 and 55 degrees Wednesday through Friday. Seawater temperatures will lower to 48 to 50 degrees next weekend.
On this date in weather history (April 13):
1990: Thunderstorms developing along a cold front produced severe weather in central Oklahoma and north central Texas. Thunderstorms in Oklahoma produced up to 6 inches of golf ball-sized hail along I-40 near El Reno, with wind gusts to 75 mph at Okarche. Thunderstorms over north central Texas produced softball size hail northwest of Rotan, and high winds which injured two persons southeast of Itasca. (Storm Data)
2012: Thunderstorms developed out at sea and moved over San Luis Obispo County. These storms produced heavy rain, lightning and hail. Most Central Coast locations recorded over 1 inch of rain.
2022: Relentless northwesterly winds increased upwelling along the Central Coast. Consequently, seawater temperatures dropped to a chilly 49 degrees at the Diablo Canyon Waverider Buoy.
This week’s temperatures
LOWS AND HIGHS, PASO ROBLES
SUN
MON
TUE
WED
THU
FRI
SAT
SUN43, 81
57, 78
46, 73
45, 75
46, 73
45, 75
44, 76
43, 77
LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS
SUN
MON
TUE
WED
THU
FRI
SAT
SUN48, 72
48, 7250, 67
50, 6849, 68
51, 69
48, 7047, 71
John Lindsey is a retired PG&E marine meteorologist. Email him at [email protected] or follow him on X @PGE_John.
