One last day of heat alerts with temperatures cooling near average by Friday into much of next week. Increasing monsoonal moisture will move into the region through Friday, with elevated chances over the mountains and locally into the deserts. Moisture decreases by the weekend into the first half of next week with minor chances over the mountain ridges, increasing again by late next week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Showers and weak thunderstorms are seen moving from NE to SW over Arizona and SE California. Some of these showers may reach the lower deserts by the early afternoon. Increased moisture and instability is seen in our sounding from this morning, aiding in a better set up for storms to pop over the mountains. Rain rates may near one half inch in some cells along the mountain desert slopes. A similar environment is seen on Friday, with elevated chances over the mountains and locally into the deserts. Pressure heights will fall by Friday into the weekend, providing slight cooling with high and low temperatures closer to average. The marine layer will be patchier with clouds forming near the coast nights and mornings, with better clearing each afternoon.
High pressure becomes centered over the Rockies and Central Plains, pivoting monsoonal moisture further to the east this weekend. This will lead to minimal chances for precipitation over the mountains during this time into the first half of next week. The pattern stays fairly similar through Tuesday, keeping temperatures closer to average with a healthy marine layer near the coast and far western valleys each night.
Models show a subtle increase in moisture by next Wednesday, potentially into the latter half of next week. Looking beyond this, models show a bit of spread on the monsoonal moisture feed. The major factor will be where the area of high pressure will be placed. Some models have this further east into the Southern Plains, which would shunt moisture further out of our region, or closer to the Central Rockies, which would favor a greater moisture set up. Nbm shows high temperatures sticking near average with 80s and 90s for many areas below 6000 feet with warmer/cooler temperatures for the lower deserts and along the coastal areas.
161800z. Coast/Valleys, Low clouds have mostly cleared out this morning, with FEW-SCT and occasionally BKN CIGs lingering along the immediate coastline. Otherwise, VFR prevails today with periods of FEW-SCT high clouds AOA 15,000ft MSL and southerly breezes. Expecting initially patchy low clouds to begin to push back ashore this evening after 06z Friday. Likely similar bases and coverage as seen this morning, though confidence is relatively low as mid-level monsoonal moisture/clouds move in overnight which may limit the coverage of the marine layer clouds.
.Mountains/Deserts, Periods of high clouds AOA 15,000 ft and VFR conditions expected throughout the period. SCT Cu based around 12,000ft MSL along with ISO TSRA over mountain ridges this afternoon after 21z through about 03z Fri.
No hazardous marine conditions are expected through Monday.
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 into early next week. Highest surf (up to 7-8 ft) will be along south and southwest-facing beaches.
Ca, Heat Advisory until 8 PM PDT this evening for Orange County Coastal Areas-San Diego County Coastal Areas.
Extreme Heat Warning until 8 PM PDT this evening for Coachella Valley-Orange County Inland Areas-Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Deserts-San Diego County Mountains-San Diego County Valleys-San Gorgonio Pass near Banning-Santa Ana Mountains and Foothills.
PZ, None.
