Week’s Weather Typical for Autumn: Gorgeous

The weather in the Valley this week is expected to be typical, predictable and, yes, wonderful.

Classic fall weather conditions--cool mornings and mild afternoons with mostly sunny skies--are expected through Friday, forecasters said.

“Nothing too unusual is expected for this week,” said Jonathan Slemmer, meteorologist with the National Weather Service.

The warmest spot in the Valley today is expected to be Chatsworth, which could see a high of 86 degrees. Slightly cooler temperatures are expected for Woodland Hills, Van Nuys and Burbank.

Morning lows through Friday should range from the low to upper 50s, Slemmer said.

Beginning Tuesday, an upper-level low pressure system from Northern California will bring a stronger onshore flow, resulting in low clouds and fog in the mornings and slightly cooler afternoon temperatures, said Jeff House, a meteorologist with WeatherData Inc., which provides forecast information to The Times.

The low pressure system, which is bordered by an upper-level high pressure system in British Columbia and a strong high pressure system to the northeast, is expected to hover over Southern California through Friday.

“What you have here is a cutoff low, or a blocked weather pattern,” House said. “Once it gets locked up like that, weather conditions generally tend to stay consistent.”

The Valley’s ultraviolet index level today at noon, when the sun’s rays are most direct, is expected to be four, a low level of exposure. Slemmer said individuals with fair complexions should be safe from sunburn for up to 20 minutes without protection.