Scattered rain showers, cloudy skies in the forecast for SLO County
Gentle west-southwesterly winds will persist through Monday, fostering a deep marine layer along the coast. The low clouds will push inland at night, bringing areas of mist and drizzle and keeping temperatures below normal.
A Gulf of Alaska storm will send several cold fronts to Oregon and Northern California early this week, delivering moderate to heavy rain to those regions. By the time the cold fronts reach the Central Coast on Tuesday and Wednesday, they will weaken, delivering partly to mostly cloudy skies with only a few scattered showers.
Behind the system, gale-force northwesterly winds and clearing skies are expected Thursday into Friday.
A 975-millibar low in the Gulf of Alaska will dig a trough along the West Coast, producing gentle to moderate (8 to 18 mph) west-southwest winds through Monday. The pattern will deepen the marine layer, pushing low clouds and pockets of mist and drizzle inland overnight.
Beaches will stay mostly overcast with partial afternoon clearing.
Highs across the inland valleys (Paso Robles) will reach the mid-70s, while the coastal valleys (San Luis Obispo) climb into the low 70s. Beaches will range from the low to mid-60s through Monday.
Two different cold fronts associated with the Gulf of Alaska storm will washout over the Central Coast Tuesday into Wednesday with increasing mid-to-high level clouds and few widely scattered rain showers.
In the mix, there could be some subtropical moisture from former hurricane Narda.
In the wake of these fronts, strong to gale force (25 to 38 mph) northwesterly winds and clearing skies and gradually warmer temperatures will develop on Thursday into Friday.
The northwesterly winds will decrease to fresh to strong (19 to 31 mph) levels next weekend, and temperatures will remain mild.
Looking ahead, the numerical weather models see no sign of October heat waves or additional rain the following week, with a “chamber of commerce” weather pattern expected to hold.
With October just around the corner, here’s a look back at Central Coast climate conditions for September:
At the Paso Robles Municipal Airport, the average temperature was 73.1 degrees, about 3 degrees warmer than normal. Rainfall totaled 0.31 inches, well above the typical 0.06 inches usually recorded for September.
Much like Paso Robles, San Luis Obispo County Regional Airport also saw above-average warmth. The average temperature reached 68.6 degrees, compared to the typical 66.5 degrees. Rainfall measured 0.36 inches, nearly nine times the normal 0.04 inches for the month.
At the Santa Maria Public Airport, rainfall was especially notable, totaling 0.73 inches — far above the usual 0.07 inches. The average temperature was 67 degrees, or 3.6 degrees warmer than normal.
Across all three stations, daytime highs were close to average, but overnight lows were much warmer, largely due to persistent subtropical moisture streaming over the region.
Surf report
Today’s 3- to 5-foot northwesterly (295-degree, deep water) swell (with an 8- to 15-second period) will continue at this level through Wednesday.
Gale force northwesterly winds will generate 6- to 8-foot northwesterly (305-degree, deep water) sea and swell (with a 5- to 14-second period) Thursday through Friday, decreasing to 5 to 7 feet with the same period next Saturday and Sunday.
Low swell conditions are forecast for the following week.
A 2- to 4-foot southerly (190-degree, deep water) swell (with a 12- to 14-second period) from former Hurricane Narda will arrive along our coastline Monday and remain at this level through Tuesday, fading away on Wednesday.
Seawater temperatures will range between 59 and 63 degrees through Wednesday, decreasing to 57 to 59 degrees on Thursday and will remain at this level through next Sunday.
On this date in weather history (Sept. 28)
1836: The first of three early season snows brought 4 inches of snow to Hamilton, New York, and two inches to Ashby, Massachusetts. (David Ludlum)
1988: Thunderstorms developing ahead of a cold front in the Central United States produced severe weather from northern Texas to the Lower Missouri Valley during the late afternoon and evening hours. Hail, 3 inches in diameter, was reported at Nolan, Texas, and wind gusts up to 80 mph were reported at Lawrence, Kansas. Thunderstorms drenched downtown Kansas City, Missouri, with up to 4 inches of rain, leaving some cars stranded in water 6 feet deep. (Storm Data)
2019: The morning’s upper-level trough produced areas of drizzle and light rain in the coastal regions. As this low-pressure system moved southward, a steep pressure gradient developed along the Central Coast and created moderate gale-force to fresh gale-force (32 to 46 mph with gust to 55 mph) northwesterly winds this afternoon into the night.
This week’s temperatures
LOWS AND HIGHS, PASO ROBLES
SUNDAY: 59, 76
MONDAY: 55, 75
TUESDAY: 55, 76
WEDNESDAY: 54, 79
THURSDAY: 52, 83
FRIDAY: 53, 82
SATURDAY: 55, 83
SUNDAY: 55, 81
LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS
SUNDAY: 59, 71
MONDAY: 58, 73
TUESDAY: 57, 70
WEDNESDAY: 56, 72
THURSDAY: 55, 74
FRIDAY: 56, 76
SATURDAY: 58, 77
SUNDAY: 56, 76
John Lindsey is a retired PG&E marine meteorologist. Email him at JohnLindseyLosOsos@gmail.com or follow him on X @PGE_John.