March ARB, CA 92518 Weather

Synopsis

A subtle cooling trend with cloudier skies and a rainier outlook is on tap as we head toward the weekend. The heaviest rainfall is expected later on Saturday into Sunday. Slightly warmer temperatures and dry weather is expected by Monday into the middle of next week.

Discussion

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

: UPDATED AVIATION, MARINE, AND BEACHES DISCUSSIONS:

A weak troughing pattern will continue across the region today into Thursday. This will bring temperatures near to slightly below normal with quiet weather. The marine layer will begin to build further in the days ahead with better chances for low clouds to fill parts of the coastal basin each night and morning.

A low pressure system currently over British Columbia will move southward Thursday into Friday, near the coasts of Washington and Oregon. As it does so, the troughing pattern will become stronger, bringing in slightly cooler weather and a deeper marine layer. The marine layer may become saturated enough by early Friday morning through Saturday morning produce isolated light showers for coastal areas and western valleys as high-res models are beginning to suggest, so chances for rain are around 15-25% in the forecast.

A large area of moisture in the form of a subtropical low pressure system that we have been watching the past few days, continues to look likely to form off to our southwest Friday into Saturday. There continues to be model differences on exactly where this system tracks into the Halloween weekend. Some show the system moving further north across SoCal, which would give us a more wet scenario. Others keep the system further south toward San Diego and into Baja California, which would not be as wet. Both these tales favor San Diego County receiving the most rain overall.

In terms of timing and how much rainfall we see is still in question. The heaviest rain may begin as early as Saturday afternoon starting from west to east, though would not be surprised if this is delayed toward an evening start. Chances for the heaviest rain greatly increase later Saturday night into Sunday morning area wide, with rain showers diminishing Sunday night. NBM shows chances for weekend rain totals over 1 inch to be near 55-70% across western San Diego County, as well as all mountain areas across SoCal. The chances lower near 35-45% for much of Orange County, the Inland Empire and the desert regions. These chances and the forecast will likely change some in the coming days, so please be prepared for wetter than normal Halloween weekend and keep an eye on the forecast.

Starting Monday into the middle next week, high pressure moves in from the west. This will bring temperatures closer to average near the coast, and about 5 degrees below normal for inland areas. Another low pressure system far off the coast may influence the weather later next week.

Aviation

281800Z: SCT-BKN high clouds above 20 kft throughout the TAF period. VFR conditions prevail into this evening, with deep marine layer clouds expected to filter in after 04z Thursday. Marine layer clouds will likely be based around 1500-2000ft. Coverage of these marine layer clouds will likely stretch into inland valleys and the Inland Empire, but is also expected to be very patchy with intermittent CIG coverage. There is higher confidence for more uniform CIG coverage along the coasts between 12-16z Thursday. Any CIGs will likely scatter out by 16-18z, with SCT marine layer clouds likely lingering into the afternoon hours.

Marine

No hazardous marine conditions are expected through Saturday. A storm system arriving Saturday night and Sunday could generate hazardous wind and sea conditions.

Beaches

High tides during the late mornings will generate significant coastal flooding this week. Tides will be anywhere from 1.4 to 1.6 feet above astronomical predictions, bringing high tides to near 7.7 feet for Thursday morning's high tide. A Coastal Flood Warning remains in effect through Thursday afternoon and contains more details.

While tides will continue to fall each day, a slight uptick in a southwesterly swell on Friday (3 ft at 15-16 seconds) will bring surf to 3-5 feet with sets to 6 feet. With the uptick in surf and high tides near 7.25 ft at noon on Friday, a Coastal Flood Advisory will replace the Coastal Flood Warning at 1 PM Thursday, in effect until 2 PM Friday.

Additionally, storm system is set to bring increased surf on Sunday. Stay tuned over the next few days for updates on expected surf as details become more clear.

Watches, warnings and advisories

CA: Coastal Flood Warning until 1 PM PDT Thursday for Orange County Coastal Areas-San Diego County Coastal Areas.

Coastal Flood Advisory from 1 PM Thursday to 2 PM PDT Friday for Orange County Coastal Areas-San Diego County Coastal Areas.

PZ: None.