The heat and humidity is expected to peak for the coast and valleys today with Extreme HeatRisk for portions of the coast into the western valleys. Gradual cooling of high temperatures will begin to spread inland on Thursday and Friday and will continue to spread inland through Sunday with not much change for Monday and Tuesday of next week. A tropical air mass will remain in place into Friday, then much drier for inland areas for this weekend through Tuesday with a return of the marine layer for coastal areas. There is a chance for showers and thunderstorms for this afternoon and a slight chance of showers for Thursday afternoon.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
(today through Friday), There were showers and thunderstorms on Tuesday afternoon with the heavier rainfall mostly tied to peak heating during the mid and late afternoon though there was some isolated development less tied to terrain. For Riverside and San Diego Counties, development was generally on convergence boundaries on the coastal slopes of the mountains with a slow drift of the thunderstorms toward the northwest. Rainfall near the core of the thunderstorms was generally 0.25 to 0.5 inch, locally exceeding one inch. There was a thunderstorm wind gust to 61 mph at 5:20 PM on Tuesday near Rainbow near the pass along Interstate 15 between Riverside and San Diego Counties.
It is once again a very warm night with temperatures at 2 AM of 5 to as much as 10 degrees warmer than 24 hours ago for the valleys and inland coastal areas with temperatures for the coast and valleys mostly in the 70s and 80s.
Today will once again be a very hot and humid day for the coast and valleys. High temperatures will range from the mid 80s to lower 90s near the beaches to 104 to 110 for the Inland Empire with 110 to 114 for the lower deserts with Extreme HeatRisk for portions of the coast and western valleys. There were a number of locations near the Orange County coast on Tuesday where the temperature warmed to around 95 to 100 during the early afternoon. When a weak seabreeze arrived in the afternoon, surface dewpoints increased into the mid 70s with heat index values increasing to around 110.
Low temperatures for the coast and valleys for today and Thursday will be mostly in the 70s with the most likely record-setting temperatures for record warm overnight temperatures. Cooling of high temperatures of a few degrees will begin to spread inland into the coast and valleys on Thursday and again on Friday.
(Saturday through Tuesday), Substantial drying aloft is expected for Saturday and Sunday. Precipitable water values exceeding 1.5 inch into Friday will decrease to around 1.25 inch on Saturday and 0.75 inch for Sunday through Tuesday.
In addition to the drying aloft, high temperatures on Saturday will cool a few to around 5 degrees with another few degrees of cooling on Sunday with slight day to day differences for Sunday through Tuesday. High temperatures for Sunday through Tuesday will be a few degrees below average at lower elevations to around 4 to 8 degrees below average for the inland valleys. High temperatures for Sunday through Tuesday will range from the 70s near the coast to the mid 80s to lower 90s for the Inland Empire with 100 to 104 for the lower deserts.
Nights will be cooler by Sunday and Monday with low pressure on Sunday and Monday mostly in the 50s for the inland valleys and in the 60s for coastal areas into the western valleys.
091800z, Mostly VFR conditions expected across the region through Thursday morning with SCT-BKN clouds between 10-20 kft. CBs based at 9 kft MSL with tops reaching to 35 kft will lead to some SHRA/TSRA mainly over mountains, but locally into deserts or inland valleys 19-01Z. Localized gusty winds and heavy rain in and near any TSRA.
No hazardous marine conditions are expected through Sunday.
Ca, Coastal Flood Advisory until 11 PM PDT this evening for Orange County Coastal Areas-San Diego County Coastal Areas.
Extreme Heat Warning until 8 PM PDT this evening for Orange County Coastal Areas-Orange County Inland Areas-San Bernardino and Riverside County Valleys-The Inland Empire- San Diego County Coastal Areas-San Diego County Valleys- Santa Ana Mountains and Foothills.
Heat Advisory from 8 PM this evening to 8 PM PDT Thursday for Orange County Coastal Areas-Orange County Inland Areas-San Bernardino and Riverside County Valleys-The Inland Empire- San Diego County Coastal Areas-San Diego County Valleys- Santa Ana Mountains and Foothills.
Heat Advisory until 8 PM PDT Thursday for Riverside County Mountains-San Diego County Mountains.
Extreme Heat Warning until 8 PM PDT Friday for Coachella Valley- San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, None.
