SAN DIEGO — Hello Friday and mostly clear morning skies — you made it to the weekend San Diegans!

Those in the valleys may have noticed what the National Weather Service described as “patchy radiation fog” to start the day, which is expected to dissipate under the sun’s rays.

Though much of the day is expected to remain dry, weather officials say isolated showers may begin as early as Friday afternoon across San Diego County.

This is due to an atmospheric river, or a “tropical moisture plume,” that’s anticipated to lift northward closer to the U.S./Mexico border, NWS explained in its area forecast discussion.

To explain this further, this describes what the American Meteorologist Society says is a “long, narrow, and transient corridor of strong horizontal water-vapor transport from lower latitudes.”

Some of these light showers could even make it into the lower deserts, according to weather officials. Overnight precipitation may occur as the upper level low finally lifts northeast as it becomes an open wave, meaning — for the most part — there is no closed circulation.

As for the final burst of widespread rain showers, which NWS says will mainly occur along and west of the mountains, that’s anticipated Friday night into Saturday.

As far as precipitation amounts, NWS says those have changed since the previous forecast with around 0.15 to 0.35 of an inch expected for the coasts and valleys.

In areas that may experience heavier showers, like the mountains, rainfall amounts could reach 0.25 to 0.50 of an inch, weather officials noted.

Looking ahead to the beginning of next week, NWS pointed to the return of Santa Anas. As for San Diego County, weather officials say a mild peak is expected to occur Tuesday morning as winds turn more easterly.