Marine Weather and Tide Forecast for Irvine, CA

DISCUSSION
FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

Morning Update

Low clouds and fog near the coast this morning will remain within a couple miles of the coast throughout the afternoon before pushing a bit further inland overnight into the morning hours, where another bout of dense fog is expected. This will continue again into the weekend as the weather pattern stays similar.
Otherwise, no major updates to the forecast.

.Previous Discussion (326 AM Friday)...

.SHORT TERM (Today through Sunday)...
Through the weekend, high pressure aloft will slowly weaken and weak onshore flow with slow deepening of a shallow marine layer will spread cooling inland, but with Sunday high temperatures will as much as 12 to 18 degrees above average for portions of the inland valleys and lower coastal slopes of the mountains. High temperatures on Sunday will range from around 70 near the coast to the mid 70s to lower 80s for the valleys and inland Orange County with the lower 80s for the lower deserts.

Satellite imagery shows widespread low clouds and dense fog over the coastal water extending locally inland along the coast in southern San Diego County and far northwestern Orange County. A Dense Fog Advisory continues for coastal areas until 9 AM. The dense fog is mostly expected to remain below higher coastal terrain such as the mesas in San Diego County. As the marine layer slowly deepens, the low clouds and fog are expected to cover more of the coastal areas for tonight into Saturday morning and might spread into the far western valleys for Saturday night into Sunday morning.

.LONG TERM (Monday through Thursday)...
Lower level flow will turn weakly offshore for Monday into Tuesday with warming and inland drying on Monday and slight cooling on Tuesday. Stronger onshore flow on Wednesday will spread cooling inland with high temperatures around 5 degrees cooler than Tuesday with additional slight cooling on Thursday.

For the middle and latter part of next week, cluster analysis continues to show the primary forecast variance is in the strength of the high pressure along the West Coast. Those that are weaker with high pressure aloft and stronger with onshore lower- level flow for southern California are more heavily represented with ensemble members of the GFS and Canadian models while those that maintain stronger high pressure aloft over southern California with weaker onshore flow are more heavily represented with members of the ECMWF.

For Ontario, the spread in the high temperature guidance between the 25th and 75th percentile remains three degrees or less through Monday, then increases to 8 degrees for next Wednesday, 9 degrees on Thursday, and 10 degrees on Friday.

AVIATION
121700Z
Coast/Valleys
Very low clouds that were along the immediate coast and nearshore waters this morning have largely backed off to the nearshore waters. These clouds (based around 100- 300ft MSL) will likely stick around within a few miles of the coast throughout the afternoon before pushing back ashore after 00z Saturday, eventually filling in 5-10 miles inland by 06z. Bases will be similar to this morning, about 100-200ft higher, sitting around 200-500 MSL. VIS restrictions generally 1/2-2SM at sea level with full obscurations of 0-1SM in FG expected along coastal mesas and locally within inland valleys. While some VIS restrictions improve after sunrise, low clouds and fog scatter out by 17-18z for San Diego County, with Orange County seeing clouds linger until 18-20z.

Mountains/Deserts...SKC and VFR conditions expected through Saturday morning.

MARINE
Low clouds/fog has become more patchy along the immediate coast as of 9AM this morning, though visibility reductions near 1 NM remain possible for the next hour or so before clouds lift enough to bring visibility back above 1 NM. The Marine Weather Statement contains more details for this risk, but is set to expire at 10AM. Clouds fill back in and settle late this afternoon/evening with areas of fog bringing visibility near 1 NM again tonight. Otherwise, no hazardous marine conditions are expected through Wednesday.

SKYWARN
Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions.



SGX WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...None.