Gradual cooling trend through the middle of the upcoming week. For Tuesday and Wednesday, increased high cloud cover continues to look likely, but precipitation chances have decreased. Gradual warming for the latter half of next week, with temperatures remaining near or slightly above average. Night and morning coastal low clouds expected most mornings this week, reaching into the western valleys at times. We're monitoring the potential for widespread precipitation over Labor Day Weekend, however there is high uncertainty in how the forecast will evolve.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
At 11 AM, temperatures were running 2 to 8 degrees cooler than they were at that time yesterday across the area. A gradual cooling is expected each day through Tuesday, with minor warming expected for the latter half of the week. Even with the warming, temperatures are expected to stay near to slightly above average for this time of year.
Broad troughing is expected prevail over the western United States through at least the middle of the week, which will keep the flow aloft southwesterly and cut down the humidity. In addition, winds will increase each afternoon with the sea breeze, most noticeable for mountains, passes, and canyons. Latest forecast has backed off on precipitation from Tropical Cyclone Karina, with current chances now less than 15 percent. The most likely scenario is there will be more widespread high cloud coverage Tuesday into Wednesday. The marine layer is expected to continue to rebuild over the next few days, with the potential for night and morning low clouds to reach into the western valleys. Depending on the extent of high cloud coverage mid-week, low cloud coverage may be disrupted again.
Late in the week, ensembles begin to diverge on the placement of the upper trough near the West Coast and the upper high over the Southern Rockies, with a trend towards a more eastward placement of each. This more eastward placement of the ridge and troughing closer to the coast would limit the amount of warming late in the week into next weekend. This would also affect the steering flow of a potential tropical system and any moisture and precipitation we'd receive from it over the weekend into early next week. While the National Hurricane Center has a 90% chance of this disturbance developing into a tropical cyclone off the coast of Mexico in the next 7 days, it is far too early to tell what, if any, impacts we'll see locally, especially given the ensemble spread in the upper level pattern. Current forecast has at least a chance of precipitation next weekend.
301800z, Coasts/Valleys, Clouds have fully cleared out this morning, with VFR conditions prevailing through the afternoon. Clouds based 1000-1500ft MSL redevelop after 02z Monday, with full CIGs expected across coastal San Diego County by 05-06z. Overnight, low clouds expected to fill inland through about 15 miles, with patchy CIGs spreading into Orange County after 09z. There is about a 60% chance of CIGs impacting KSNA between 11-16z Monday. VIS restrictions limited to where clouds intersect higher terrain. Clouds scatter out by 16-17z.
.Mtns/Deserts, Occasional FEW high lvl clouds AOA 20,000ft MSL through the period. Breezy west to southwest winds 20z this afternoon to about 05z Monday for the desert slopes into the deserts, with gusts to 20-30 kts, locally up to 35-40 kts through passes.
Gusts around 20 knots expected each afternoon through Thursday in the vicinity of San Clemente Island. Localized gusts near the island may reach 25 kts on Tuesday/Wednesday afternoons. Otherwise, no hazardous marine conditions are expected.
A 3-foot swell from the south-southwest (200 degrees) at 15 seconds will persist through today. This will bring localized elevated surf of 3-5 feet with sets to 6 feet, along with a high rip current risk to southwest-facing beaches, mostly in north San Diego County and Orange County. A new southerly swell (180-190 degrees) from Hurricane Karina will keep surf elevated at 3-5 feet with sets to 6 feet for Monday through Wednesday. Continued tropical swells look to keep surf elevated through the end of the week as well.
Ca, None. PZ, None.
