Marine Weather and Tide Forecast for Sunset Beach, CA

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

Update...

Skies were still clear at mid-evening across the area, though low clouds and fog were as close as about 50 miles southwest of San Diego. The models show a coastal eddy developing later tonight, which would move the low clouds and fog north into our coastal waters and eventually over land within a few miles of the beaches, though the eddy has yet to form, and timing of the eddy is a bit uncertain, though most likely starting before sunrise Sunday. The big story will be the Santa Ana Winds coming up Monday through Wednesday, with Tuesday morning having the strongest winds after the passage of an upper trough over the Desert Southwest as well as the time when the surface high peaks in strength over northern Nevada-- around 1044 mb. The low-level wind flow will initially be north- northeast Monday but switch more to the east late Monday night/Tuesday, so initially the Inland Empire and the Santa Ana Mountains will have the strongest winds Monday, but that will migrate towards San Diego County and below Banning Pass Tuesday. RH values will be quite low, 5-10% in many locations, during this event, and local wind gusts will be 60+ MPH from some of the mountain crests west through the foothills and into parts of the valleys below passes and canyons. Fuels will be dry as most of the area has had less than 10% of normal precipitation since the beginning of the water year on Oct 1 and generally not much of a summer monsoon either.

Previous discussion...

A weak ridge off the Pacific continues to snag to the NE over CA this afternoon as an upper level low moves into New Mexico. This has prompted weak offshore winds for interior areas with light onshore flow toward the coast. We've also seen warm temperatures out there for the date with some valleys in the lower 80s as of the noon hour. As the ridge of high pressure over the State weakens throughout the day, pressure heights will begin to fall, deepening the marine layer. Per latest HRRR guidance, clouds and fog will form tonight into Sunday morning with moderate confidence.
Some areas may see dense fog under 1/4 of a mile, so travel with care. The marine layer will deepen further into Sunday night and Monday, providing greater cooling for inland areas and clouds progressing further into the valleys by Monday morning, which will give a lesser chance of dense fog at lower elevations.

A trough of low pressure currently in Southeast Alaska will move southward into the Northern Rockies and the Desert Southwest by early next week. Upper level winds substantially increase as the trough digs through Nevada and Arizona. As the pressure gradient tightens and a surface high moves into the Great Basin, gusty Santa Ana winds and very dry air will result across Southern California.
Model projections depict near a 10mb gradient expected between San Diego and Las Vegas, indicating strong wind potential.

Latest hi-res model forecast guidance is getting a better grip on the start time of the these NE and E winds. Confidence is increasing that winds begin during mid Monday morning across mountain passes, pushing into western valleys by Monday afternoon and evening. Winds will be strongest and push farthest west toward portions of the coast on Tuesday morning and afternoon, decreasing throughout the day Wednesday. Valleys will see wind gusts primarily between 30 and 45 MPH, foothills 40-55 MPH, and locally over 60 MPH for mountain passes and canyons. Since this weather pattern favors a more easterly wind component, east-west oriented passes will see the highest winds, including the San Gorgonio Pass and across the San Diego County mountains/foothills. This will lead to critical fire weather conditions as dry fuels and low relative humidity values set in. Please take this time to secure any valuable property and practice wildfire safety measures by creating defensible space around residences and avoiding outdoor burning.

As the trough pushes eastward into the Plains, brief high pressure will move into the area, relaxing the pressure gradient. As it does so, we can expect calmer winds with fair weather. By around Friday, the weak ridge hangs on while a trough moves closer to the West Coast. Model guidance has shown a trend of this trough staying further north with the ridge staying over the West, so this would maintain a dry regime with temperatures slightly above average.
Chances are small, but light precipitation still not out of the question by next weekend if the trough dips south enough, though hopes are dwindling.

AVIATION
080315Z
Coasts
Clear skies and VFR currently prevailing. Low clouds and patchy FG may develop around 09-10z this evening, and push up to 5 miles inland. Cloud bases around 200-400 ft MSL and vis to be 0-2SM, with areas of dense FG and VIS to 1/2SM at times, especially for the higher coastal mesas. Confidence is low to moderate (20-40%) for CIGs at any specific TAF sites overnight, but if impacts do occur, clearing should begin by 17-18z. BR/HZ with VIS to 5-6SM may carry over into the afternoon hours. Confidence is higher for FG and low clouds Sunday evening, with CIGs likely at coastal sites as early as 01-03z Monday.

Valleys/Mountains/Deserts
Mostly clear skies and VFR prevail through Sunday evening.

MARINE
Patchy dense fog with visibilities around 1 nm or less expected to develop around 09z, continuing into Sunday morning. A Marine Weather Statement is in effect with more information. Another round of fog is possible Sunday night into Monday, but should be less dense over the waters. Increasing offshore winds on Tuesday with gusts up to 20- 25kts, primarily for the northern San Diego County coast.

FIRE WEATHER
A moderate to locally strong Santa Ana wind event will unfold with gusty northeast and east winds expected Monday through Wednesday.
Winds will begin late Monday morning and afternoon, peak in strength Tuesday morning and afternoon, and gradually fade through Wednesday. Riverside and San Diego County mountain foothills and adjacent inland valleys are expected to have the strongest winds.
Local gusts over 60 mph through favored passes and on mountain foothills. Gusts of 35-45 mph are expected in parts of the inland valleys. By Tuesday afternoon, relative humidity values should drop near 5-10% for inland areas and 15-25% at the coast.
Overnight recoveries will be poor increasing to only 15-30%. Low humidity, strong winds, and dry fuels will lead to critical fire weather conditions from Monday through Wednesday morning, highest risk on Tuesday. Wednesday and Thursday will see lighter winds, but humidity will still lower near 5-20% each afternoon.

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

SGX WATCHES/WARNINGS/ADVISORIES
CA...Red Flag Warning from 10 AM Monday to 4 AM PST Wednesday for Riverside County Mountains-Including The San Jacinto Ranger District Of The San Bernardino National Forest-San Bernardino County Mountains-Including The Mountain Top And Front Country Ranger Districts Of The San Bernardino National Forest-San Bernardino and Riverside County Valleys -The Inland Empire-San Diego County Inland Valleys-San Diego County Mountains-Including The Palomar And Descanso Ranger Districts of the Cleveland National Forest-San Gorgonio Pass Near Banning-Santa Ana Mountains-Including The Trabuco Ranger District of the Cleveland National Forest.

PZ...None.