High pressure will continue to dominate the region over the next week, bringing high temperatures well above normal with minor day to day changes. The marine layer remains shallow, leading to low clouds and fog near the coast, where the fog may be locally dense over the next couple of nights/mornings.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Morning update,
Low clouds and fog continue to persist throughout Orange County and have filled in within 5 miles of the coastline across San Diego County with several stations reporting visibility of 0.25-0.75 miles. The Dense Fog Advisory remains in effect until 10 AM when clouds/fog should be largely cleared out to the ocean or lifted enough to improve visibilities.
From previous discussion,
Low clouds and fog redevelop this evening, spreading back into the coastal areas tonight. With little change in the marine layer depth, patchy dense fog is likely to occur once again tonight into Sunday morning.
The upper level ridge of high pressure over the region breaks down this weekend, allowing a weak short wave trough to progress eastward across CA. This will bring slight cooling with a return of more predominant onshore flow through the weekend, though highs remain 10 to 15 degrees above normal. The upper ridge rebounds on Monday and Tuesday, combining with another round of weak Santa Ana winds to bring warming with highs locally up to 20 degrees above normal. Winds won't be particularly strong, remaining confined to the usual passes, canyons, and coastal slopes where peak gusts will be around 30 mph. Enough of an offshore push of drier air could occur to rid of us the marine layer low clouds and fog.
The upper high slowly weakens and onshore flow returns for the latter half of the week. There are subtle differences in the ensembles with how much the ridge weakens and is replaced by zonal flow, especially as we head into the end of the week. Around 60% of the ensemble members show zonal flow and therefore more cooling, while the remaining 40% maintain weak ridging for warmer weather. Either way, precipitation chances are zero through Friday. Ensembles are definitely trending wetter for next week, so we'll see if that holds.
131630z, Coast/Valleys, Low clouds with bases around 200-600 ft MSL and Fog are beginning their slow retreat and should be cleared along the coast by 18Z for San Diego County and by 18-20Z for Orange County. Low clouds and fog are expected to return this evening around 02-03Z along the coast and up to 15 SM inland with similar bases and visibilities as last night/this morning.
Mountains/Deserts, Clear skies and VFR conditions expected through the TAF period.
Patchy fog will continue over the local waters, improving by late this morning. Visibility reductions to 1 NM or less will be possible at times. A Marine Weather Statement is in effect until noon Saturday for the impacts from fog and contains more details. Otherwise, no hazardous marine conditions are expected through Thursday.
Ca, Dense Fog Advisory until 10 AM PST this morning for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
