Another round of monsoon thunderstorms is expected for the mountains on Tuesday with locally heavy rainfall rates. An isolated storm or two may pop up over the mountains again Wednesday, but otherwise drier conditions are expected for late week into the weekend. A cooling trend will bring below normal temperatures to the region from Wednesday onward along with breezy conditions for the mountains and deserts. For the coastal basin, the marine layer is expected to deepen each day through the weekend.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Today through tomorrow night,
Recycled monsoonal moisture is continuing to stream up over the region out of the southeast around the high positioned over the desert southwest. Given the amount of instability and abundance of moisture, there will be around a 40 to 50 percent chance of afternoon showers and thunderstorms developing, with the San Bernardinos mostly at play. Some of these storms will be capable of producing rainfall rates of 0.50 inches per hour. Expect that some of these storms will also produce strong and gusty winds due to outflows and high DCAPE values exceeding 1000 J/kg. There could also be some small hail associated with these storms. This will continue into the evening hours, with storms beginning to move towards the northeast by later in the day as mid-level flow begins to shift to being more out of a southwesterly direction. There may also be some isolated areas of flash flooding as a result of the storms, as they may rapidly intensity along the mountain/desert interface, especially where there are currently some SBCAPE values of 4000 J/kg, with temperatures/dews of low 90s over low 70s within the Coachella Valley. These showers and storms will likely make their way into the high deserts with skies continuing to clear as these showers/storms dissipate and move out of the CWA. The marine layer will be rather dispersed and then fill back in by late into the night. As troughing continues to influence the region from upstream, with should allow bases to slightly rise into the morning hours tomorrow.
Thursday through Wednesday,
Troughing from upstream will continue to influence the region with gradually cooling temperatures through the end of the week, and temperatures becoming as much as 10 degrees below the seasonal average for some areas. This will also increase surface gusty winds, especially during the afternoon for the high deserts, and mountain canyons/passes by later in the week, with gusts approaching 60 mph within Gorgonio Pass. There will also become more persistence with onshore flow, with the marine layer becoming more prevalent overnight and into the morning hours. Going into early next week, ensembles reflect a breakdown of the troughing over the E Pacific waters and thus a return to more seasonal temperatures, while remaining dry.
101800z. Coast/Valleys, Ongoing high cu AOA 20,000ft MSL through Wednesday. VFR through this evening before low clouds develop again tonight. Bases will be slightly higher, likely 1200-1500ft MSL after 03z Wed. Bases may lift from closer to 1000 to around 1500 MSL through 12z, and will spread up to 20 miles inland. Intermittent CIGs possible at inland TAF sites, KONT and KSBD between 12-15z. Low chances (10%) of impacts at inland TAF sites from nearby TSRA.
.Mountains/Deserts, Scattered TSRA over mountains and locally in deserts through this evening. Bases around 9000ft MSL with tops to 50000 feet with any storm. Any TSRA could produce lightning, strong up/downdrafts and associated VIS reductions. Otherwise, SCT-BKN clouds mostly above 15,000ft MSL through today.
No hazardous marine conditions are expected through Saturday.
High tides will exceed 7 feet this evening and again Wednesday evening between 800-930 PM, resulting in minor tidal overflow of low- lying areas along the beach. Surf will be low and is not expected to add much to the flooding potential. Check the Coastal Flood Advisory for details.
Ca, Coastal Flood Advisory until 11 PM PDT Wednesday for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
