Very dry for the deserts into the mountains through Friday. The warming trend will continue for inland areas with the heat peaking on Wednesday and Thursday. There will be moderate to major HeatRisk for the lower deserts for Tuesday through Thursday. A few to around 5 degrees cooler for inland areas on Friday and Saturday, then slight warming with increasing humidity for Sunday through Tuesday of next week. The marine layer will keep coastal areas cooler with night and morning coastal low clouds spreading inland into portions of the western valleys at times.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, Today 7/6 to Thursday 7/9, Mid-level high pressure centered over southeast Arizona today have brought warm temperatures typical for this time of year and mostly clear skies to the entire region. Away from the immediate coast, temperatures this afternoon are 1 to about 6 degrees above those at this time yesterday. This warming trend will continue through Thursday as the high pressure expands and gradually shifts east, centering over southern California by Wednesday.
By Thursday, temperatures will be in the high 80s to mid 90s for inland Orange County/San Diego valleys/mountains, high 90s to just over 100 for the Inland Empire, around 105 degrees in the high desert, and 111-117 degrees in the low deserts (Coachella and San Diego desert). These temperatures are generally 5 to 10 degrees above average, and enough to bring locally moderate HeatRisk to the mountains westward (widespread moderate for the Inland Empire) and major HeatRisk for the low deserts.
Dry conditions will accompany hot ones in the deserts and mountains, with afternoon minimum humidities dipping into the teens today and gradually dropping through about Thursday, but generally moderate to good humidity overnight will moderate this. Winds will be typically breezy in the afternoons for this time of year. The marine layer will grow more shallow as the high pressure "pushes" it down, limiting it to coastal regions and western valleys, moving in in the late evening and scattering out around mid-morning each day. These will keep immediate coastal areas relatively cool and level, with highs in the 70s each day.
..Friday 7/10 through next week, While high pressure lingers over Southern California Friday, the ridge will start to weaken and move east, leading to 3-4 degrees of cooling from Thursday to Friday. The ridge continues to push east over the weekend, and temperatures continue to subtly cool through at least Saturday, when high temperatures will likely be within 5 degrees of average for most areas.
The center of the high continues to move to the northeast Sunday through early next week, and flow locally will turn south to southeasterly, advecting at least some moisture into the region starting Sunday and likely peaking (at least initially) Mon-Tue next week. At the least, this will lead to higher humidity in the deserts and mountains. Spread in exactly how much moisture will move in between global ensemble models (about an inch difference in PWAT between drier and wetter members) has lead to increased spread in temperature forecasts as well, both morning lows and afternoon highs. Increasing minimum temperatures for inland areas Sunday through early/mid next week is likely, while high temperature trends are more uncertain; temperatures may warm slightly for valley areas and level out for deserts.
Finally, a handful of global ensemble members have spotty, high- based precipitation over the region, with a pretty significant range of time periods between late this weekend into parts of next week. The National Blend of Models (NBM) has the highest chances over the deserts/mountains for Monday currently, but there are small chances for light precipitation over areas further west as well.
061800z. Coast/Valleys, SKC with VFR conditions expected through this evening. Patchy low clouds based 800-1200 ft MSL return to coastal San Diego County starting 06-09z Tue. Low clouds slowly push into Orange County and increase in coverage early Tuesday morning, reaching 10-15 miles inland by 13z. Patchy minor vis reductions (1- 5SM) for elevated coastal terrain and western valleys. Low clouds scatter back to the coastline 15-17z.
Otherwise, VFR conditions expected through the end of the TAF period.
Gusts around 20 to 25 kts are expected at times this afternoon and evening near San Clemente Island. See the Small Craft Advisory for more details. Similar gusts near 20 kts are possible Tuesday afternoon. Otherwise, no hazardous marine conditions are expected through Saturday.
Ca, Heat Advisory from 10 AM Wednesday to 8 PM PDT Thursday for San Bernardino and Riverside County Valleys-The Inland Empire.
Extreme Heat Warning from 10 AM Tuesday to 8 PM PDT Thursday for Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, Small Craft Advisory from 2 PM this afternoon to midnight PDT tonight for Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.
