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.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
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.
282330z, SCT-BKN marine layer clouds based 2500-3000 ft MSL are currently developing over coastal areas. These clouds will likely be transient with a period of clearing before areas of lower marine layer clouds based near 2000 ft MSL begin to develop 04-08z Thu. Coverage should become more uniform near the coast overnight with patchier coverage spreading into inland valleys. Low clouds scatter back to the coast 15-18z, though SCT low clouds may hang over coastal areas all day, especially in San Diego County. Low clouds based 2500-3000 ft MSL rush back inland early Thursday evening.
No hazardous marine conditions are expected through Saturday. A storm system arriving Saturday night and Sunday could generate hazardous wind and sea conditions.
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.
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.
