Get ready for warm weather and thunderstorms this week, SLO County
Strengthening afternoon northwesterly winds will keep much of the Central Coast near seasonal temperatures through Monday. Then, another surge of subtropical moisture will bring increasing clouds, scattered showers and thunderstorms along with cooler conditions from Monday night through Wednesday morning.
Later on Wednesday and into Friday, clearing skies, warmer temperatures, and renewed northwesterly winds are expected.
Fresh to strong (19 to 31 mph) northwesterly winds will continue each afternoon through Monday, bringing mostly clear skies to the coast from late morning into the afternoon.
Low marine clouds will redevelop along the shoreline in the evening, which will push inland overnight and into the early morning.
Highs across the inland valleys (Paso Robles) will reach the upper 80s, while the coastal valleys (San Luis Obispo) climb into the upper 70s. Beaches will range from the mid-to-upper 60s, with Cayucos, Avila Beach and Shell Beach a bit warmer, reaching the mid-70s through Monday.
A 572 decameter upper-level, low-pressure system off the Southern California coast will draw insignificant monsoonal moisture from the south, bringing increasing southerly winds, higher dew-point temperatures, mid-and high-level clouds, warmer nights, cooler days, and a chance of convective showers and thunderstorms.
Rainfall totals of 0.25 to 0.75 inches are possible, with higher amounts near thunderstorms.
From Wednesday into Friday, northwesterly winds and temperatures will strengthen again.
Looking further ahead, a series of Pacific Northwest storms will send cold fronts across the Central Coast. While these fronts are unlikely to bring rain, they will tighten pressure gradients, leading to stronger northwest winds and cooler conditions during the second full week of fall.
Surf report
Fresh to strong (19 to 31 mph) northwesterly winds along the coastline will generate a 3- to 5-foot northwesterly (300-degree, deep water) sea and swell (with a 5- to 11-second period) through Monday.
A 3- to 5-foot northwesterly (290-degree, deep water) swell (with an 8- to 11-second period) is forecast for Tuesday.
If the southerly winds are strong enough on Tuesday, 1- to 2-foot southerly seas could develop.
Increasing northwesterly winds will generate 3- to 5-foot northwesterly (305-degree, deep water) sea and swell (with a 5- to 11-second period) later Wednesday through Friday.
A 1- to 2-foot Southern Hemisphere (220-degree, deep water) swell (with a 14- to 16-second period) will arrive along our coastline on Tuesday and remain at this level through Wednesday, fading away on Thursday.
Seawater temperatures will range between 59 and 63 degrees through Friday.
On this date in weather history (Sept. 21)
1894: A tornado picked up a heavy chicken house, which measured 16-feet-long and 16-feet-wide, and wedged the house between two trees. The hens were found the next day sitting on their eggs in the chicken house, with no windows broken, as though nothing had happened.
1954: The temperature at Deeth, Nevada, soared from a morning low of 12 degrees to a high of 87 degrees, a record daily warm up for the state.
2015: San Luis Obispo reached 99 degrees, breaking the previous record of 95 degrees set in 1946. The high air temperature at Paso Robles Municipal Airport reached 105 degrees, breaking the old record of 104 degrees set in 1949.
2021: The Baywood Park weather station near Morro Bay reached 88 degrees, the warmest temperature so far that year.
This week’s temperatures
LOWS AND HIGHS, PASO ROBLES
SUNDAY: 57, 88
MONDAY: 57, 89
TUESDAY: 61, 77
WEDNESDAY: 57, 89
THURSDAY: 57, 87
FRIDAY: 56, 85
SATURDAY: 56, 84
SUNDAY: 55, 82
LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS
SUNDAY: 57, 76
MONDAY: 58, 78
TUESDAY: 60, 68
WEDNESDAY: 59, 76
THURSDAY: 57, 80
FRIDAY: 58, 78
SATURDAY: 56, 75
SUNDAY: 55, 73
John Lindsey is a retired PG&E marine meteorologist. Email him at JohnLindseyLosOsos@gmail.com or follow him on X @PGE_John.