SAN DIEGO — Though the week is expected to start with slightly warmer weather, the National Weather Service forecasts another wave of widespread rain and mountain snow come mid-week.

Sunday presented a fair weather day with a drier airmass overspreading the region, bringing stability, weather officials said. Nonetheless, temperatures were cooler with scattered cloud cover.

In fact, NWS says Sunday temperatures were expected to be around 10 degrees below average inland and two to 5 degrees below average near the coastal areas of the county.

Overnight Sunday, weather officials predict patchy frost in the sheltered valleys and some gusty westerly winds over the mountains and deserts.

The NWS forecasts Monday to be the warmest day of the week. Tuesday is still expected to be mild, but weather officials say a deep cyclone off the Northern California coast is expected to move south, eventually covering the state.

With this movement, NWS says another blanket of rain, snow and wind is expected to swing across Southern California by Thursday.

Precipitation may begin in northern areas Tuesday night and then is expected to cover the region on Wednesday, NWS said. Precipitation is forecast to be widespread and significant, but weather officials don’t expect it to be as heavy as the last storm.

Preliminary indications show modest snowfall accumulation above 5,000 feet in the mountains and NWS says this could turn out to be more significant.

The mid-week storm is anticipated to be a cold one, with weather officials predicting temperatures 15 to 20 degree below average inland.

Looking ahead to next weekend, NWS expects dry conditions and a modest warming trend throughout the region.