The marine layer in San Diego County was much stronger Sunday and was helping to keep the coastal eddy and the stratus hanging in tougher, the National Weather Service said.
Sunny skies Sunday afternoon were expected to give way quickly filling stratus clouds throughout the coastal basin in the evening, forecasters said.
Some gusty winds were possible through the passes and canyons and along the desert slopes, and a healthy sea breeze was forecast for Sunday afternoon in coastal and valley areas, the NWS said.
High temperatures along the coast Sunday were expected to be 64-69 degrees with overnight lows of 53-58, forecasters said. Highs in the western valleys will be 69-74 and near the foothills, 73-78 with overnight lows of 47-54.
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Mountain highs were expected to be 72-82 with overnight lows of 43-48. Desert highs will be 95-100 with overnight lows of 58-66.
A trough of low pressure across the northern Rockies was expected to maintain onshore flow with periods of gusty westerly winds over the mountains and deserts through Monday, forecasters said.
Low clouds and patchy fog were predicted to be extensive nights and mornings west of the mountains, clearing to the coast by afternoon.
Weak high pressure was expected to build over the Southwest on Tuesday, bringing warmer weather through the work week, the NWS said.
Cooler weather was likely to return by next weekend.