Another day of unstable air ushered in what National Weather Service forecasters say will be a pleasant weekend for the Bay Area.

By Thursday afternoon, with rain and even hail falling in areas of the South Bay and an ever-increasing number of thick and puffy clouds in other parts of the region, that outlook seemed a bit sketchy.

Still, the weather service said such a lead-up was entirely expected ahead of a weekend that promises sunny weather and high temperatures that may be 10 degrees warmer than the past week.

“The atmosphere is basically overturning,” NWS meteorologist Rick Canepa said Thursday afternoon as cold air from the higher parts of the atmosphere began to mix with temperatures that were starting to warm near the surface.

“That’s why it’s so sporadic in some places,” he said. “And less sporadic in others.”

The most consistent of the rain came in the South Bay and along the Central Coast, the weather service said. Periodic heavy showers occurred there, and Canepa said there were reports of hail near Watsonville, Santa Cruz and Capitola.

The East Bay and North Bay saw threatening clouds Thursday afternoon but did not report any measurable rain before 1 p.m.

So what about the weekend?

“It’s going to switch around pretty quickly Thursday evening,” Canepa said. “Upper-level high pressure is moving in from the west and the northwest, and that’s going to mean a quick clearing up by (Thursday night) that could leave some patches of fog Friday morning.”

The reversal is expected to send any hint of clouds far from the region today and Saturday and lift daytime temperatures into the mid- to high 60s, according to the weather service. The highs haven’t exceeded the mid-50s anywhere in the region since March began.

The extreme cold at night also is expected to rise by several degrees beginning Saturday. The weather service said a frost advisory was scheduled to be in effect this morning for East Bay and eastern Santa Clara Hills, as well as in the North Bay, the interior region of Monterey County, the Santa Lucia Range; and San Benito County.

According to forecasters, the atmosphere’s instability since March began may be setting the month up to be a wet one. As such, Canepa said the break from the wet stuff will not be a long one. Another low-pressure trough bearing down on the region with more rain is likely to arrive late Sunday night, he said.

Rain then remains in the weather forecast for much of the region through Wednesday.