A ridge of high pressure will remain over the Desert Southwest for much of the week. Little day to day changes in temperatures is expected with warmer nights continuing. Monsoonal moisture and humidity will increase by Wednesday into the weekend, but chances for rainfall remain on the lower end.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
A 595 dm high has expanded over Southern California to New Mexico today. Models indicate this pressure system not moving very much through the work week, leading to minor day to day changes in the overall weather pattern. Temperatures will go down a touch through the middle of the week, but remain close to average for the coastal areas and adjacent valleys, with highs 5-10 degrees above normal for inland regions. Coastal low clouds will move into areas within 10 miles of the coast each night and morning as the marine layer depth remains relatively unchanged this week.
Subtle movements in the high's position, will dictate a change in the monsoonal moisture pattern. By Wednesday into the weekend, models indicate a slight shift in the high closer to the Four Corners region with better easterly flow aloft. This is looking more likely to occur, which will increase humidity overall for everyone; we will also see increasing yet subtle chances for showers and weak thunderstorms over the peninsular (Julian to Big Bear) mountain spine. Chances remain minimal to none by Thursday and Friday. Model agreement begins to diverge some on where the high exactly ends up by the weekend into early next week, somewhere between southern Nevada and the Four Corners. Ensemble members focus the best chance for rainfall by this weekend into early next week, but confidence on any rainfall occurring is low at this time. The high may strengthen again by later this week as well, which would increase temperatures slightly yet again. Our message remains the same that elevated heat risk continues through the week!
031730z. Coasts/Valleys, Low clouds based near 1300 ft MSL at the coastline will clear out within the next 1-2 hours. Low clouds based 1000-1400 ft MSL return to coastal San Diego County starting 01-02z Tue and coastal Orange County starting 04-06z Tue. Clouds extend 15- 20 miles inland by 10-11z. 20-30% chance for BKN cigs at KONT after 12z. Minor vis reductions (3-6SM) possible for elevated inland valleys. Clouds scatter back to the coastline by 17-18z.
.Mountains/Deserts, Expect mostly clear skies with unrestricted VIS.
No hazardous marine conditions are expected through Thursday.
Ca, Extreme Heat Warning until 8 PM PDT this evening for Riverside County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains.
Heat Advisory until 8 PM PDT this evening for San Bernardino County Mountains.
Extreme Heat Warning until 8 PM PDT Wednesday for Apple and Lucerne Valleys.
Extreme Heat Warning until 8 PM PDT Tuesday for Coachella Valley- San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, None.
