As the New Year rolls in, residents across the southwestern parts of California, including Orange, San Diego, western Riverside, and southwestern San Bernardino counties, can expect a warmer start to 2025, with temperatures slightly nudging upwards. According to NWS San Diego, coastal regions will see highs in the mid-60s, while those further inland can look forward to temperatures ranging from the low to mid-70s, and those in the mountains will experience upper 50s to low 60s. For Thursday, the forecast suggests an even warmer range, with coastal areas reaching between 67 to 75 degrees and inland valleys hitting the bar at 73 to 81 degrees.
However, starting Friday, an onshore flow is expected to develop, ushering in cooler weather and more clouds through the weekend, "High pressure and offshore flow return next week to bring the next warming trend," states the synopsis from NWS San Diego's Area Forecast Discussion. Keep an eye out for possible Santa Ana winds, which are projected to potentially emerge around mid-week, although their strength and the consequent risk of fire weather conditions remain uncertain at this juncture.
Meanwhile, morning fog along the coast might pose challenges. The National Weather Service has reported dense fog across coastal mesas and western valleys, prompting a Dense Fog Advisory until 10 AM PST for various areas, including the Orange County Coastal Areas and San Diego County Valleys. The forecast discussion further notes weak offshore flow with northeast winds gusting between 20 to 30 mph, which should aid in lifting the coastal fog more effectively today.
In terms of aviation and marine conditions, visibility issues due to fog are imminent with the NWS San Diego warning of low stratus with bases 200-500 ft MSL that could reduce visibility to 1-2 SM along the immediate coasts; precautions are advised until conditions improve post-sunrise. Mariners, too, should be wary of patchy dense fog with visibility dropping to 1 NM or less close to shorelines until it clears shortly after sunrise.
