Chances of showers, thunderstorms for San Diego County

SAN DIEGO (FOX 5/KUSI) -- Early Sunday morning, officials with the National Weather Service (NWS) reported that an upper-level low pressure system is moving east into Arizona, allowing a few showers to linger just north of Southern California.

While those showers are not expected to impact San Diego directly, residual mid-level moisture could spark isolated showers or thunderstorms over the mountain areas Sunday afternoon. Rainfall is expected to be light, with rates under a quarter inch per hour or less. This means any flooding risk is minimal.

In the meantime, a deep marine layer—currently estimated at around 4,000 feet— has brought widespread low clouds across coastal and inland valleys. A clear patch briefly appeared over southwestern San Diego County early Sunday morning, but weather officials say clouds are expected to fill in again before partial clearing by the afternoon hours.

Highs Sunday will remain several degrees below normal, making for a cooler end to the weekend, according to NWS predictions.

Looking ahead to Monday, a weak ridge of high pressure will briefly nudge temperatures upward and slightly reduce the depth of the marine layer. However, this warming will be short-lived as another disturbance moves in from the Pacific, bringing breezy conditions to the mountains and passes along with a slight dip in temperatures.

NWS officials say gradual warming is forecast midweek as high pressure builds from northern Mexico into the Desert Southwest. This should bring highs closer to seasonal averages by Wednesday and Thursday. However, forecasters are keeping an eye on another developing trough that could return cooler temperatures and increased cloud cover by the end of the week.