Still very warm conditions are in place with a subtle cooldown through the middle of the week. There will be increasing monsoonal moisture for the latter half of the week, with increasing chances of precipitation, although this looks to be only a slight chance, with above average temperatures continuing on into the upcoming weekend.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Today through tomorrow night,
The latest satellite imagery reveals that the marine layer has completely inundated all of the coastal areas of both Orange and San Diego counties, extending up to 10 miles inland for some portions of the inland areas, and even making its way far enough east for some areas of patchy fog in and around the I-15 corridor, so be advised and watch for quickly deteriorating visibilities if you happen to be traveling through some of these areas of fog this morning. Ceilings are generally hovering just under 1000 ft MSL for most locations , and a little lower from where they were yesterday. 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. Winds aloft in the mid-levels have began to shift and will become more southwesterly throughout today, drawing 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 that will continue through mid week. 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 tonight. 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 later today.
Tuesday through Saturday,
The pattern remains rather stagnant through mid week, with the subtle cooling and conditions remaining dry, and gusty winds in the passes during the afternoon. 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. Guidance has also been showing an increase in moisture content and precipitable water going into the beginning of the following weekend, which may further increase chances of developing thunderstorms during the afternoon over the mountains. 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.
021200z. Coasts, Low clouds have filled in completely for the coastal sites, with bases generally around 800-1000 ft MSL. Clouds extending around 10 miles inland with localized VIS restrictions to 3-5SM on higher coastal terrain. Any CIGs will begin scatter out by 16z Sunday. Slightly less patchy clouds with similar bases expected to develop again after 03z Mon, then continue to fill in throughout the rest of the forecast period, with similar CIGs, only slightly lower. These low clouds will begin to scatter out 17Z Monday.
.Valleys/Mountains/Deserts, Mostly clear and VFR conditions to continue through Sunday evening.
No hazardous marine conditions are expected through Wednesday.
Ca, Heat Advisory until 8 PM PDT this evening for Orange County Coastal Areas-San Bernardino County Mountains-San Diego County Coastal Areas.
Extreme Heat Warning until 8 PM PDT this evening 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.
