Here is this week’s weather forecast by PG&E meteorologist John Lindsey.
The first in a series of late-season cold fronts will move onto the Central Coast this morning. Mist and drizzle will spread across the coastal regions San Luis Obispo County today. Due to the lack of any forcing mechanism in the atmosphere, significant rain and/or thunderstorms are not expected to develop. Today’s temperatures will only reach the high 70s in the North County and high 60s in the coastal valleys. Temperatures at the beaches will reach the low 60s.
Widespread mist/drizzle will develop tonight into Tuesday morning. The mist/drizzle is in response to a second and wetter cold front that will rotate into Northern California with rain. Rain will develop north of the Big Sur-Yosemite line by tonight. Possible June record amounts of rain could fall (between 2 and 3 inches) across the northern Sierra, Shasta and coastal mountains. For the Central Coast, only summer time mist and drizzle is expected. However, total precipitation amounts could reach a few hundredths of an inch along the San Luis Obispo County coastline. The relatively warm system will also keep snow levels well above 10,000 feet.
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Temperatures will warm slightly Tuesday before a more dramatic warm-up Wednesday as skies will clear throughout the day. Thursday, a ridge of high pressure will build from the east, providing us with clear skies and above-normal temperatures as we enter a warming trend; which is expected to continue through the weekend into the following week. The North County will see daytime temperatures return to triple-digits by the weekend with mild overnight lows. The hot conditions will likely continue into the Fourth of July holiday.
A 3- to 4-foot northwesterly (310-degree deep-water) swell (with a 7- to 9-second period) will develop along the coastline today and will remain at this height and period through Tuesday.
A 967-millibar storm developed near the Aleutian Islands last week. A 4- to 6-foot northwesterly (300-degree deep-water) swell (with a 16- to 18-second period) from this storm will arrive along our coastline Wednesday.
Increasing northwesterly winds along the coastline will generate a 5- to 7-foot northwesterly (310-degree deep-water) sea and swell (with a 5- to 16-second period) on Thursday. This northwesterly sea and swell will remain at this height but with a gradually shorter period through Sunday.
Arriving from the Southern Hemisphere:
A large storm developed near New Zealand last week. This storm will produce a 1-foot Southern Hemisphere (200-degree deep-water) swell (with a 19- to 21-second period) along our coastline Tuesday, building to 2 to 4 feet (with a 16- to 18-second period) on Wednesday. This swell will peak Thursday at 3 to 4 feet (with a 15- to 17-second period), gradually decreasing Friday through Saturday.
Last week, northwesterly wind gusts exceeded 50 mph almost every day at Diablo Canyon, producing a tremendous amount of upwelling along the Central Coast. This condition caused frigid late June seawater temperatures. In fact, they dropped to 49 degrees. Seawater temperatures will gradually increase to 51 and 53 degrees today, rising to 53 and 56 degrees by Tuesday. Seawater temperatures will decrease on Thursday through Sunday.