Will SLO County have a sunny Memorial Day? See the holiday weekend weather forecast

This past week, we’ve been under the influence of a deep marine layer known as “May Gray,” with mist and fog developing during the night and morning.

It’s been clearing from the inland and most of the coastal valleys during the afternoon, but keeping many beaches overcast throughout the day. This condition has also brought below-average temperatures, in fact, between 4 and 7 degrees cooler than normal for the middle of May.

However, there’s a silver lining.

Increasing north-to-northwesterly winds along the coastline and high pressure over California should bring a greater amount of sunshine along the beaches and warmer temperatures throughout the Central Coast starting on Tuesday and continuing through Thursday.

Gentle to moderate (8 to 18 mph) northwesterly winds on Saturday will produce mostly overcast skies along the beaches for most of the day, with slightly more clearing on Sunday afternoon as the northwesterly winds increase to moderate to fresh (13 to 24 mph) levels. The low marine stratus clouds will clear from the inland valleys later in the morning and the coastal valleys by the afternoon.

This weekend, high temperatures will reach the mid-70s in the inland valleys, mid-60s in the coastal valleys, and low-60s along the beaches.

Slightly warmer temperatures and a faster burn-off of the marine layer are expected to start on Monday and continue through Thursday. The northwesterly winds are forecast to increase to fresh to strong (19 to 31 mph) levels on Wednesday and Thursday afternoon, mixing out the temperature inversion layer and leaving behind mostly clear skies along the beaches during the afternoon. However, low marine clouds will redevelop during the night and morning.

The Memorial Day weekend is forecast to start with partly to mostly cloudy skies with areas of night and morning mist and drizzle on Friday as a cold front moves through the region. But don’t worry, it’s not all gloom. This will be followed by fresh to strong (19 to 31 mph) northwesterly winds and clearing skies next Saturday and Sunday with high temperatures reaching near seasonal levels.

Surf report

A 4- to 6-foot northwesterly (290-degree deep-water) swell (with an 8- to 11-second period) is expected on Saturday through Sunday morning, increasing to 6- to 8-feet with the same period on Sunday afternoon. This northwesterly swell will further build to 7- to 9-feet (with a 7- to 11-second period) on Sunday night and remain at this level through Wednesday morning.

A 6- to 8-foot northwesterly (310-degree deep-water) sea and swell (with a 5- to 10-second period) is expected on Wednesday afternoon through Thursday, becoming a 3- to 5-foot northwesterly swell (290-degree deep-water) swell (with an 8- to 11-second period) on Friday.

Combined with this northwesterly sea and swell, will be 2- to 4-foot southern hemisphere (220-degree deep-water) swell (with a 16- to 18-second period) on Saturday through Wednesday, decreasing on Thursday into Friday.

Seawater temperatures will decrease to 52 and 54 degrees through Friday.

On this date in Weather History (May 19):

1780 - The infamous “dark day” in New England tradition. At noon it was nearly as dark as night. Chickens went to roost and many persons were fearful of divine wrath. The phenomena was caused by forest fires to the west of New England. (David Ludlum)

2019 - Today’s convective rain showers and isolated thunderstorms produced periods of heavy rain and a few cloud to ground lightning strikes. The Diablo Canyon rain gauge recorded nearly one-half of an inch of rain in less than one hour. The most rain was recorded at See Canyon at 1.35 inches.

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.