It will remain cooler and drier for inland areas through Friday, with patchy night and morning coastal low clouds spreading into portions of the western valleys at times. The center of Hurricane Marie will remain well to the south of the area. But a large increase in surf is expected for for Saturday into Sunday, then slowly subsiding for Labor Day into early next week. Mid and high level moisture from Marie will bring more clouds with increasing chances for showers for Saturday night into Sunday along with a slight chance of thunderstorms for the mountains, deserts, and inland valleys for Sunday afternoon.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
Today through Saturday,
Seasonably cool weather continues across the region with the upper level ridge displaced to the southeast US by a large trough across the West Coast. This large-scale trough features a strong upper low currently off the WA/OR coast. Consistent model guidance progs this feature to maintain intensity, and slowly meander into the Pacific Northwest into Saturday. Consequently, the cool mornings and below normal high temperatures will persist into Saturday with a fairly stagnant synoptic pattern overhead. Slightly elevated flow under this pattern will keep breezy west-southwesterly winds in place for the mountains and into the adjacent deserts through Saturday as well. Peak gusts generally 25-35 mph, locally up to 45 mph within mountain passes.
Of most interest continues to be the influence the aforementioned upper level pattern has for Hurricane Marie and the degree of its influence to southern California. With the coalescence of model guidance featuring the strong upper low maintaining latitude near the Pac NW and not pushing further south as guidance earlier in the week suggested was possible, the upper ridge across the south- central US is able to extend a ridge axis from the Desert Southwest into northern Mexico, helping steer Marie to the west and well out to sea. The only direct impacts from Hurricane Marie continues to be the elevated swell/surf arriving this weekend, see the Beaches section below for more details.
Late Saturday into early next week,
While the track for Hurricane Marie takes the storm out to sea and no direct impacts are anticipated, the larger-scale wave of mid level tropical moisture is set to move into the region during the day on Saturday. Combining this with the influence of the southwesterly flow aloft from the mid-latitude synoptic setup, widespread chances of rainfall this weekend remains the highlight of the forecast. There remains a great deal of spread in model guidance in how much, if any, rain falls, but confidence continues to slowly increase that at least most of the area will see some accumulations. Sunday looks to feature the greatest chances for rainfall. Within this uncertainty, even the higher-end of ensembles don't suggest a total wash-out, with the 90th percentile favoring 0.4-0.5" of total rainfall for the valleys and up to 0.5-1.0" for the coastal slopes/mountains. Ensemble means, however, are closer to 0.2-0.3". Until subtle differences in the placement of the large upper low in the PacNW and associated dynamical forcing are resolved and we stretch into the high resolution guidance window, a fair amount of uncertainty in the precipitation forecast will linger.
Despite the rainfall uncertainty, what is more certain is that the influx of tropical moisture and its influence on the temperatures. While the addition of moisture and clouds will help keep high temperatures near to below average into early next week, the cool mornings will trend warmer, with low temperatures returning back above normal come Sunday morning.
.AVIATION, 031800Z, Coast/Valleys, Patchy, intermittent low clouds based 1500- 2000 feet MSL will will develop tonight after 02z into Friday. Clouds may briefly move into coastal San Diego Co 03-05z before scattering again (40% chance), with the greatest chances for impacts 11-15Z. Any clouds will clear by 16Z Fri.
Mountains/Deserts, Mostly clear skies today and tomorrow. Breezy westerly winds mainly through mountain passes and along desert slopes 20-07Z. Gusts 25-35 kts with pockets of moderate up/downdrafts over and in lee of ridges.
031800z, Coast/Valleys, Patchy, intermittent low clouds based 1500- 2000 feet MSL will will develop tonight after 02z into Friday. Clouds may briefly move into coastal San Diego Co 03-05z before scattering again (40% chance), with the greatest chances for impacts 11-15Z. Any clouds will clear by 16Z Fri.
Mountains/Deserts, Mostly clear skies today and tomorrow. Breezy westerly winds mainly through mountain passes and along desert slopes 20-07Z. Gusts 25-35 kts with pockets of moderate up/downdrafts over and in lee of ridges.
040000Z, Coast/Valleys, Intermittent low clouds based 1500-2000ft MSL will will develop tonight after 03z, spreading up to 10 miles inland. Clouds will be extremely patchy. Clouds may briefly move into coastal San Diego Co 03-05z before scattering again (40% chance), with the greatest chances for 1 hour + impacts 11-15Z. Any clouds will clear by 16z Fri, with SKC thereafter. Another round of patchy clouds with bases generally around 2000ft MSL will develop again Friday evening, after 03z Sat.
Mountains/Deserts, Mostly SKC and VFR today and tomorrow. Breezy westerly winds mainly through mountain passes and along desert slopes through 07z. Gusts 25-35 kts with pockets of moderate up/downdrafts over and in lee of ridges.
No hazardous marine conditions are expected through Monday. However, wind gusts around 20 knots are expected this afternoon and evening around San Clemente Island.
A large south swell from Hurricane Marie will move into the region Friday night and Saturday, peaking Sunday into Monday, before gradually diminishing Tuesday. This will result in elevated to high surf and strong rip and longshore currents at majority of beaches. Additionally, waves will occasionally run much farther up the beach than expected, especially during increasing and evening high tides.
For south and southwest-facing beaches, expecting high surf 6-10 feet. This includes Orange County and north San Diego County beaches. For west-facing beaches, expecting elevated surf 4-7 feet. This includes most of southern San Diego County beaches.
High surf combined with high astronomical tides 6 to about 6.5 feet will lead to tidal overflow and coastal flooding Saturday through Tuesday during evening high tides, especially for those south and southwest-facing beaches as well as low-lying, typically impacted areas.
Ca, Coastal Flood Advisory from 6 AM Saturday to 11 PM PDT Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas.
High Surf Advisory from 6 AM Saturday to 11 PM PDT Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, Coastal Flood Advisory from 6 AM Saturday to 11 PM PDT Tuesday for Coastal Waters from San Mateo Point to the Mexican Border and out to 10 nm.
High Surf Advisory from 6 AM Saturday to 11 PM PDT Tuesday for Coastal Waters from San Mateo Point to the Mexican Border and out to 10 nm.
