Warmer weather on the way to SLO County — maybe even first triple-digits temps of the year

For most of this month, a ridge of high pressure over the Southeastern United States has produced record-breaking high temperatures in Florida and Texas, while most of the West Coast has been under the influence of a trough of low pressure, creating near-average seasonal temperatures.

However, a few longer-range models are advertising a strong upper-level ridge of high pressure developing over the Desert Southwest, resulting in much warmer weather throughout California during the first week of June.

Looking farther ahead, the Climate Prediction Center forecasts above-normal hurricane activity due to the development of La Niña conditions in the Equatorial Pacific. Historically, La Niña results in less wind shear — upper-level winds that can inhibit hurricane formation — and near-record warm ocean temperatures in the Atlantic.

Similar to the previous week, the Central Coast has been experiencing the effects of a deep marine layer known as “May gray.” This has led to mist and fog during the night and morning, clearing from the inland during the late morning and coastal valleys in the afternoon but keeping some of the beach communities overcast throughout the day.

However, a change is on the horizon.

Fresh to strong (19 to 31 mph) northwesterly winds will develop during the afternoon, combined with gentle Santa Lucia (northeasterly) winds during the early morning. This will result in a significant increase in clearing during the late morning and afternoon from this Memorial Day weekend through Tuesday.

Over this period, high temperatures will reach the mid-80s in the inland valleys (Paso Robles), mid-70s in the coastal valleys (San Luis Obispo), and 60s along the beaches, except for Cayucos, Avila Beach, and Shell Beach, which will reach the low 70s.

As we move into the following week, significant weather changes are expected.

Strong to gale-force (25 to 38 mph) northwesterly winds will develop on Wednesday into Thursday, leading to an even greater amount of clearing in the coastal regions.

A weak late-season cold front will move through the Central Coast on Friday into Saturday morning. This will bring gentle to moderate (8 to 18 mph) westerly winds and a deepening marine layer with pockets of mist and drizzle.

In the wake of this cold front, strong to gale-force northwesterly afternoon winds and clearing skies are forecast for next Sunday through the following week.

This will be accompanied by much warmer temperatures expected in the inland and coastal valleys. In fact, the inland valleys could reach triple-digit temperatures by the end of the following week for the first time this year, marking a significant shift in the weather conditions.

Surf report

A 4- to 6-foot northwesterly (300-degree deep-water) sea and swell (with a 5- to 8-second period) is expected on Saturday through Tuesday, increasing to 7 to 9 feet (with a 5- to 11-second period) on Wednesday into Thursday.

A 3- to 5-foot northwesterly (290-degree deep-water) swell (with an 8- to 11-second period) is forecast on Friday into next Saturday morning, followed by increasing northwesterly sea and swell next Saturday afternoon into the following week.

Combined with this northwesterly sea and swell will be 1- to 2-foot southern hemisphere (200-degree deep-water) swell (with a 15- to 17-second period) on Saturday throughout the upcoming week.

Seawater temperatures will decrease to 52 and 54 degrees through Tuesday, decreasing to 49 to 51 degrees on Wednesday and remaining at this level through next weekend.

This date in weather history (May 26)

2010: A dying frontal system produced sprinkles and a few light rain showers throughout our area. San Luis Obispo County Airport reported a couple hundreds of an inch of rain, while the Paso Robles airport and Diablo Canyon only reported a trace.

2014: Warm to hot conditions developed in the North County as a ridge of high pressure shifted eastward over San Luis Obispo County. In fact, Paso Robles hit 100 degrees.

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.