There will be a gradual warming trend through Saturday with slowly increasing HeatRisk. On Saturday, there will be moderate HeatRisk for the mountains and Inland Empire with major to locally extreme HeatRisk for the deserts. Night and morning low clouds will continue to spread into coastal areas and occasionally the far western valleys late each night. There will be slowly increasing monsoonal moisture in east to southeast flow aloft into early next week with a few showers over the mountains on Thursday afternoon and a slight chance of showers and thunderstorms for the mountains for each afternoon beginning on Friday. High temperatures for inland areas for Sunday and Monday will not be quite as hot.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
(today through Friday), Not much change in temperatures is expected for today with slight warming on Thursday and a little greater warming for Friday and Saturday. High temperatures for today through Saturday will warm a few degrees near the coast to around 5 degrees for inland areas.
Night and morning low clouds will continue to spread inland into coastal areas each night and into the far western valleys occasionally late each night.
There could be a few showers over the mountains on Thursday afternoon as shown by some of the higher-resolution models including the HRRR, CANSAC WRF, and RRFS with a few showers and isolated thunderstorms possible on Friday afternoon. Chances for measurable rainfall are 15 percent or less each day.
(Saturday through Tuesday), High temperatures on Saturday will range from few degrees above average near the coast to 5 to 10 degrees above average for the deserts. High temperatures on Saturday will range from the mid 70s to lower 80s near the coast to the mid 90s to 105 for the Inland Empire with 112 to 116 for the lower deserts. On Saturday, there will be moderate HeatRisk for the mountains and Inland Empire with major to locally extreme HeatRisk for the deserts.
For Sunday and Monday, high pressure will slowly weaken with the flow aloft becoming more southeasterly. Low-level moisture will slowly increase for the deserts with high temperatures becoming not quite as hot for inland areas.
High temperatures on Monday will be mostly within a few degrees of average to a few to around 5 degrees above average for the deserts. High temperatures on Monday will range from the mid 70s to lower 80s near the coast to the 90s to around 100 for the Inland Empire with 106 to 110 for the lower deserts.
051800z. Coasts/Valleys, Satellite shows low clouds are quickly eroding back towards the coast, with clearing expected for coastal TAF sites by 19z. Patchy stratus may linger at the beaches through the afternoon. Low clouds redevelop and move inland again this evening, likely after 03z Thur, with slightly lower bases around 1000-1500ft MSL. VIS down to 3-5SM for inland valleys and coastal terrain. Clearing on Thursday will occur a little earlier, likely by 16-18z.
.Mountains/Deserts, SCT-BKN clouds AOA 20,000ft MSL with unrestricted VIS through Thursday.
No hazardous marine conditions are expected through Saturday.
Ca, Heat Advisory until 8 PM PDT Saturday for Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains.
Extreme Heat Warning until 8 PM PDT Saturday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts- San Gorgonio Pass near Banning.
PZ, None.
