Marine Weather and Tide Forecast for Costa Mesa, CA

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

Temperatures at 1 PM were running mostly 5 to 10 degrees warmer than 1 PM yesterday across the area. Widespread moderate HeatRisk is impacting the inland valleys, mountain foothills, and High Desert today, with moderate to locally major HeatRisk in the low desert.
Make sure you're staying hydrated and seeking shade if you're spending time outdoors. If possible, avoid strenuous outdoor activity during the hottest part of the day (through 5pm). The ridge of high pressure over us today will begin to flatten Monday as an upper level trough moves inland across the West Coast. That will kick off a gradual cooling with highs Monday a few degrees cooler than today and additional cooling into Tuesday. Even with highs being knocked down a few degrees, they will remain 3 to 7 degrees above average Tuesday.

In addition to a few degrees of cooling, onshore flow will strengthen. That will bring breezy west winds to the desert mountain slopes, below the passes, and into the deserts during the afternoons and evenings. Strongest winds are expected Monday with gusts 30 to 45 mph, locally up to 50 mph through the San Gorgonio Pass.

Low clouds are expected to remain persistent each night and morning for the coast early this week, with areas of locally dense fog possible. The marine layer is expected to deepen for the middle to end of next week as a more amplified trough of low pressure approaches the West Coast.

Global ensemble clusters show a brief rebound in the ridge for Wednesday, which will bring a few degrees of warming to inland areas. NBM chances for the Inland Empire to exceed 100 degrees is 30 to 60 percent, with the higher chances in the eastern portions of the Inland Empire. In the low desert, NBM has a 60 to 80 percent chance of high temperatures exceeding 110 degrees. In the High Desert chances of exceeding 100 degrees are 70 to 80 percent. The warming on Wednesday will be short lived as there is good ensemble agreement in a more amplified trough moving into the Pacific Northwest Thursday through the weekend. While there is still some uncertainty in the finer details cooler conditions, increased winds, and a deeper marine layer can be expected for the end of the week.
There is high confidence in dry conditions with this passing trough.

AVIATION
151945Z
Coast/Valleys
Low clouds based around 400-700ft MSL are hugging the SD Co coastline this afternoon...these will dissipate over the next few hours from north to south. Moderate to high confidence in low clouds redeveloping tonight after 05Z Monday initially across southern coastal San Diego County, pushing northward. Confidence is lower that clouds make it to VCTY KSNA, which will yield a 40% chance of BKN cigs at KSNA. Bases likely a touch lower than this morning, around 300-600ft MSL. Vis 1-3 for coastal TAF sites and elevated coastal terrain in BR. Clouds clearing to the beaches after 16Z Mon.

Mountains/Deserts
FEW-SCT high clouds and mostly unrestricted VIS prevail through early Monday. Confidence moderate to high in seeing west wind gusts 20-30 kts, locally near 40 kts through the San Gorgonio Pass, leading to MOD UDDFS 18Z Mon-08Z Tue.

MARINE
Wind gusts up to 20-25 kts possible in the outer waters Monday afternoon near San Clemente Island. Otherwise, no hazardous marine conditions are expected through Thursday.

BEACHES
A 3 foot southerly (190 degrees) swell at 17-18 seconds will continue to produce elevated surf of 3 to 6 feet with local sets up to 7 feet, primarily for Orange County and northern San Diego County beaches. A Beach Hazard Statement remains in effect through late Sunday evening. Swell and surf heights wane late Sunday into Monday.

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



SGX WATCHES/WARNINGS/ADVISORIES
CA...Beach Hazards Statement until 11 PM PDT this evening for Orange County Coastal Areas.

PZ...None.