The heat is on across SoCal as high pressure strengthens over the area through the weekend, leading to areas of moderate to major heat risk. The marine layer will stay thin through this period, where night and morning low clouds will cover the coast each day. The area of high pressure will weaken some into next week and may move further east. This pattern will bring slightly cooler weather with a minimal chance for rainfall over the mountains.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Today through tomorrow night,
The latest satellite imagery at midnight reveals that the marine layer continues to struggle over the inner socal bight waters, thanks partially in part to an eddy that has developed near Catalina and has helped to create a stronger offshore flow for San Diego County as a result. This is also helping to erode some of the marine layer that has already developed over Orange County, as SE'ly surface winds have picked up due to the coastal eddy. There will still likely be some additional low cloud development, and skies may periodically go broken right along the coastal areas through this morning, with ceilings hovering around 1000 ft MSL. Otherwise, mostly clear skies will prevail and set up for another very warm day with temperatures still running generally around 5 to 10 degrees above the average for this time of year. There has also been some recycled mid-level monsoonal moisture that has been streaming over the region this morning, which may allow for a very slight chance of a shower or two to develop over the mountains (likely only confined to the highest elevations), although confidence is low given the lack of instability over the region. Hi-res guidance also does not suggest much in the way of development later on, although given that there is some moisture present, and a monsoonal wave transitioning towards the area, which may help to destabilize the mid-levels later on, a possible shower or two cannot be ruled out. However, it is a lot less likely with very little instability aloft that these would become thunderstorms. Under a strengthening ridge, highs will still be running around 5 to 10 degrees above the seasonal average for this time of year for today.
By tomorrow, winds in the mid-levels will begin to shift to become more southwesterly, and draw in drier air along with it. This will help to impede the chance of afternoon shower and thunderstorm development over the mountains. The troughing upstream will also begin to influence the area with slightly lower heights that will begin a gradual cooling trend beginning tomorrow. There will also begin the presence of a more predominant onshore flow, and this will likely help to draw in the marine layer a little sooner, and with better coverage for the following night. In addition, this is also going to allow for winds to increase through San Gorgonio Pass, and along the desert slopes, with gusts up around 40 mph through the early evening. This will continue to likely be the case through Wednesday as stronger onshore flow remains in place.
Monday through Friday,
Subtle cooling will continue through the mid half of next week and conditions will remain dry, with temperatures still being above average. Thereafter, mid-level winds will begin to shift back to being from a more easterly direction, with better positioning of the high pressure center aloft to allow for some of these monsoonal waves to develop and advect moisture over our region. Temperatures will also start to gradually warm again during this period, with increased humidity values and an increasing chance of getting thunderstorm activity for our mountains and deserts (and possibly even all the way to the coastal locations, depending on the propagation of these monsoonal waves as they develop over the deserts to our southeast and then transition over our region. During this period, the marine layer will likely struggle to develop, given the increased mid to high level clouds moving overhead, in addition, with better offshore flow overnight.
010600z. Coasts, Very patchy low clouds based around 1200ft MSL have developed offshore and along the coast. Brief CIGs have already been observed at KSAN and KCRQ and intermittent CIGs will likely persist through the next several hours as these patchy clouds move in and out. Guidance is indicating that clouds should become more consistent in coverage closer to 10-12z, with bases closer to 0800- 1100ft MSL and about 10 miles of inland extent. VIS restrictions to 3-5SM expected over mesas and higher coastal terrain when clouds are present. Clouds will scatter out around 16z Saturday morning, with VFR prevailing into the afternoon. Similarly patchy low clouds will form locally along the coast after 06z Sunday, initially based at 800-1100 ft MSL.
.Valleys/Mountains/Deserts, VFR conditions prevails throughout the period with FEW high clouds AOA 20000 feet MSL.
No hazardous marine conditions are expected through Wednesday.
A southerly swell from now Tropical Storm Genevieve will generate surf of 4-6 feet with sets up to 7 feet for south facing beaches today and tonight before diminishing Saturday. This will create hazardous conditions for inexperienced swimmers. In addition, the high tide tonight will be near 6 feet. The combination of the high tides and elevated surf increases the risk of coastal flooding. For more details, check the Coastal Hazard Message.
Ca, High Surf Advisory until 5 PM PDT this afternoon for Orange County Coastal Areas-San Diego County Coastal Areas.
Heat Advisory until 8 PM PDT Sunday for Orange County Coastal Areas-San Bernardino County Mountains-San Diego County Coastal Areas.
Extreme Heat Warning until 8 PM PDT Sunday for Apple and Lucerne Valleys-Orange County Inland Areas-Riverside County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains-San Diego County Valleys-Santa Ana Mountains and Foothills.
Extreme Heat Warning until 8 PM PDT Monday for Coachella Valley- San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, None.
