Not as hot with high temperatures returning to near normal today into much of next week. Monsoonal moisture remains in place through next week for continued chances of showers and thunderstorms over the mountains and occasionally into the deserts each afternoon and early evening.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION/MARINE/BEACHES DISCUSSION,
Mid level clouds from earlier convection are moving across the region this morning. Based on current satellite trends, it does not appear that enough cloud cover will be in place to inhibit convection this afternoon. With weak southerly mid-level flow in place, expect convection to be focused over the mountains and locally into the high desert. The 00Z KNKX sounding had around 1.5 inch of precipitable water, which is forecast to increase slightly today. Sufficient PW combined with weak steering flow/near stationary storms will increase the risk of flash flooding this afternoon where stronger storms occur. Some CAMs are showing hourly rainfall amounts in excess of 1 inch, and 90th percentile 1 hour precipitation from the REFS is around 1.25 inch, though very localized.
For the remainder of the forecast area, low clouds and patchy fog along the coast and up to a few miles inland will clear by late morning. The upper level high continues to weaken with high temperatures returning to near normal, though continued humidity will keep nighttime temperatures elevated.
The upper level pattern remains largely unchanged this weekend through next week with broad upper level ridging across the Central US, weak troughing off the West Coast, and a pair of tropical systems passing by to the southwest. This will maintain southerly or easterly flow aloft and monsoonal moisture across the region. Moisture and instability decrease slightly this weekend into early next week for less widespread convection with lower rainfall rates each afternoon. Both the EC and GFS ensemble means show an increase in precipitable water towards the middle of next week, though the spread is somewhere on the order of 0.5" or more, likely due to differences in the placement in the upper level high. Around 51% of the members have the high in a more favorable position near the Four Corners region, while the remaining 49% have the high centered closer to Texas, putting us on the fringes of the moisture for lower precipiation chances. Otherwise just minor fluctuations in temperatures with highs generally in the mid to upper 70s along the coast, upper 80s to 90s in the valleys, upper 70s to low 90s in the mountains, upper 90s to low 100s in the high desert, and 100-110 in the low desert.
170930z. Coast/Valleys, Patchy low clouds based 700-1000 ft MSL impacting coastal areas this morning. Patchy minor vis reductions (2- 5SM) expected along elevated coastal terrain. Mid-level clouds will continue to lead to intermittent scatter out of low clouds through about 12Z, especially for San Diego Co. Low clouds will clear to the coast 15-17Z, with more southerly breezes expected near the coastline this afternoon. Low clouds similar in bases and coverage move into south SD coastal areas after 05Z Sat, moving north and inland through about 12Z Sat.
.Mountains/Deserts, Periods of high clouds AOA 15,000 ft and VFR conditions expected throughout the period. SCT Cu based 10-12 kft and ISO-SCT SHRA/TSRA redevelop over the mtns this afternoon, most likely 20Z Fri through 01Z Sat. Any storms that develop may produce lightning, gusty winds, and vis reductions.
No hazardous marine conditions are expected through Tuesday.
High amplitude southerly swell (4-5 ft with a period of 12-13 seconds) will build Saturday into Sunday, bringing elevated surf and strong rip and longshore currents for Sunday through at least Tuesday. Highest surf, up to 7-8 ft, will be along south and southwest-facing beaches.
Ca, None. PZ, None.
