High temperatures for inland areas of around 4 to 8 degrees above average through Friday will cool slightly to a few to around 5 degrees above average for early next week. Greater monsoonal moisture on Thursday and Friday and again around Monday of next week will bring a chance of afternoon showers and thunderstorms for the mountains and deserts. Night and morning low clouds will continue for the coastal waters into coastal areas.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
This afternoon, clear skies are prevailing across the region. The ridge is at its maximum westward reach today, yielding the hottest temperatures for the inland valleys this week. Widespread 100F to 105F readings are anticipated across the Inland Empire with mid to upper 90s in the interior valleys.
Highs Thursday may back off a degree or two, then remain very steady through early next week, only fluctuating by a degree or two each day. Today through early next week, highs will hover around 109-113F in the lower deserts with persistent areas of Major HeatRisk as a result of overnight lows only falling to the mid/upper 80s, about 5- 8 degrees above average.
The center of the ridge retracts slightly eastward, spinning around the Four Corners region and opening the door for monsoonal moisture. Around a 15-25% chance for afternoon isolated showers and a t-storm Thursday and Friday over the mountains, with lesser chances over the weekend as the ridge axis moves south and PWAT's decrease. Chances for more scattered shower/t-storm activity increase again early next week as the GFS shows the ridge access rotating and potentially re- opening the door to more mid-level moisture.
Throughout the forecast period, the marine layer will be fairly shallow, between 1,000-2000 feet deep, as the influence of the ridge continues. Low clouds should develop and push up to 20 miles inland as they typically do in the evening, except for nights with greater high cloud coverage, which could delay the formation of low clouds.
200000z. Coast, Patchy low clouds based 800-1200 ft MSL over coastal waters are expected to remain mostly offshore through early Thursday morning. Low clouds slowly push into coastal areas 06-09z Thu with coverage remaining patchy. Coverage of low clouds increases after 10z, especially in San Diego County with areas of clouds reaching 5-10 miles inland. Scatter out expected by 15-16z.
Otherwise, mostly clear through Thursday morning. Slight chance (15- 20%) of SHRA/TSRA over the mtns from 20z Thu - 01z Fri. SCT Cu based around 10 kft expected regardless of storm development.
No hazardous marine conditions are expected through Sunday.
Ca, Heat Advisory until 8 PM PDT Thursday for San Bernardino and Riverside County Valleys-The Inland Empire.
Extreme Heat Warning until 8 PM PDT Friday for Coachella Valley- San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, None.
