High temperatures remaining near to slightly above seasonal normals through early next week, warmest Wednesday and Thursday. Decreasing precipitation chances into early next week with any light showers confined to the higher mountain peaks during the afternoons. There is the potential for increasing moisture and afternoon showers and thunderstorms towards the middle to end of next week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
Mid-level clouds continue to drift east and north across the region this morning. There are some weak returns on radar, but given the very dry layer below 700 mb and lack of any gauge reports, most if not all of this precipitation is likely not reaching the surface so expect a few sprinkles at best. Otherwise patchy low clouds continuing at the coast and up to 10-15 mi inland, clearing by mid morning. Given the mid-level cloud cover in place and a general drying trend with less instability, convective activity this afternoon will be extremely limited. A few light showers may develop over the higher peaks of the San Bernardino and Riverside County mountains, but thunderstorm chances are less than 10%.
Generally little change in the upper level pattern with broad ridging across the Western US and the upper high centered near CO and WY. Tropical Storm Elida, currently around 900 mi west of Cabo San Lucas, will move north off the West Coast and weaken into Tuesday. Based on the current track, no weather impacts are expected in Southern California. It will generate higher swell and surf though - see the Beaches section for more details.
Minor drying occurs through early next week with an monsoonal moisture gradually becoming higher based, limiting the potential for showers and thunderstorms each afternoon. Forecast maintains around a 15% chance over the San Bernardino Mountains through Tuesday. Aside from any monsoon activity, high temperatures will remain near seasonal normals through Tuesday - mid 70s to low 80s for the coastal areas, low 80s to mid 90s in the valleys, mid 70s to around 90 in the mountains, mid 90s to around 100 in the high desert, and 100-108 in the low desert. Areas of night and morning low clouds and fog will continue along the coast and far western valleys.
As we head into the middle of next week, the upper high sinks south towards TX and strengthens. There is still some spread in the ensembles on the position of the high and how far west the ridge axis will extend. This will dictate how much warming we see towards the middle of next week as well as how much moisture will be able to make it into the area. Ensemble mean Precipitable Water peaks sometime around Thu-Fri for the best chances of convection over the mountains, but if the ridge axis extends too far west it may be too stable for any showers or thunderstorms to develop. Otherwise slightly warmer for the middle to end of the week with highs a few degrees above normal, warmest Wednesday and Thursday.
180930z. Coast/Valleys, Mid-level clouds 15-20kft MSL are gradually clearing, with low-level clouds 1200-1400 ft MSL with tops to 1700-1900 ft MSL filling into coastal areas. Vis reductions 2-5 SM locally for higher coastal terrain. Low clouds clear 15-17Z, then reform at similar bases and move into coastal regions after 05Z Sun.
.Mountains/Deserts, VFR conditions expected through the period with SCT mid-level clouds AOA 15,000ft MSL gradually clearing overnight. SCT Cu based 10-12 kft MSL will develop over the Riverside and San Bernardino mtns after 18Z with chances for ISO-SCT SHRA/TSRA, most likely after 20Z through 01Z Sunday. Any storms that develop may produce lightning, gusty winds, and vis reductions.
No hazardous marine conditions are expected through Wednesday.
High amplitude southerly swell (4-5 ft with a period of 12-13 seconds) will build Sunday, bringing elevated to high surf and strong rip and longshore currents for Sunday through at least Tuesday. Highest surf, up to 7-9 ft, will be along south and southwest-facing beaches. Further details can be found in the High Surf Advisory. Surf falls a bit Tuesday and into Wednesday before another southerly swell (3-4 ft with a period of 15 seconds) brings another round of elevated surf for the end of the week and into the early weekend. The high risk for strong rip currents will remain from Sunday through next week.
Ca, High Surf Advisory from 5 PM Sunday to 11 PM PDT Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
