High temperatures for inland areas will remain around 15 to 20 degrees above average into the weekend, with some record daily high temperatures continuing to be tied or broken, mainly for the mountains and deserts but occasionally for the inland valleys as well. The marine layer presence will continue, with some small day-to-day variations. Coastal low clouds not likely to spread as far inland on Friday and Saturday. Mid and high clouds will spread across the area for this weekend into early next week. High temperatures will lower only slightly during the weekend, with greater cooling spreading inland early next week as a low pressure system moves toward the California coast.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Update: At this hour, the marine layer is somewhat broken up along the coastal areas, although some of the clouds have pushed back east into the inland valleys of northern San Diego County. This should continue to fill in by later this evening and extend a little further inland. There could also be some locally dense areas of patchy fog developing within some of these inland areas and along the coastal slopes that intersect. There could be visibilities periodically reduced to less than a half a mile in some of this fog, especially along the I-15 corridor within some of the higher inland valleys. This should scatter out shortly after sunrise, and lead to mostly clear skies with just some passing high clouds.
The forecast appears to remain on track in terms to high pressure remaining in domination throughout the rest of the work week, and then a cooldown will follow this weekend into next week as the ridge finally breaks down and propagates eastward. This will allow for some troughing to possibly provide a chance of rain next Tuesday through Wednesday as deterministic models suggest. Even if the main energy from this major shortwave remains far enough to the north to not provide much in the way of precipitation as it passes through, it will bring a much more significant cooldown with it, with temperatures returning to closer values for where they should be for this time of year.
Previous discussion submitted at 125 PM:
Mostly clear this afternoon except for some low clouds over the coastal waters. Temperatures are within a few degrees of where they were at this time yesterday. The marine layer influence will persist through the weekend, with day-to-day variations on the depth and the inland extent of the low clouds and fog during the nights and mornings.
Daytime high temperatures will gradually trend higher through Saturday as the high pressure ridge persists over the Southwest. High temperatures today will range from around 5 degrees above average near the coast to around 20 degrees above average in the mountains and high desert. It looks like Saturday will be the warmest day with high temperatures ranging from around 10-12 degrees above average near the coast to 20-25 degrees above average in the San Diego County mountains. Saturday high temperatures will range from the 70s to low 80s near the coast to the upper 80s to mid 90s for the Inland Empire, with the upper 90s to 103 for the lower deserts.
Onshore flow today will be strong enough to produce southwest winds gusting 30-40 mph in the favored areas of the deserts and desert mtn slopes this afternoon and evening. Onshore flow will be noticeably weaker for Thursday then strengthen somewhat again on Friday.
For Sunday through next Wednesday, Temperatures will trend lower and clouds will generally increase as a low pressure system approaches the CA coast from the west, displacing the high pressure ridge to the southeast into TX. Next Wednesday will likely be the coolest day, with daytime high temps in the 60s-70s west of the mtns and in the 80s in the low deserts.
A significant percentage of ensemble members (most from the European model) indicate the potential for precip next Tue/Wed as the low pressure system moves inland. At this time, the National Blend of Models indicate up to a 35 percent chance (mainly in the mtns) for at least 0.01 inch. Any rainfall will likely be confined to areas from the mtns westward. Uncertainty is still high due to the spread among the model solutions.
260000z, Coast/Valleys, Low clouds based 800-1300 ft MSL are developing along the coast, pushing inland 01-03z up to the mountain foothills. Vis reduced 0-3SM in mountain foothills and 3-5 SM mainly over higher coastal terrain and valleys. Bases may lower a few hundred feet after 11z, yielding to patchy IFR cigs for coastal areas (higher confidence for SD County). There is a 30% chance for cigs to spread into the northwest IE vcnty KONT after 10Z, but higher confidence in misty conditions with MVFR vis but no cigs. Clouds scatter out Thu 15-17Z.
Mountains/Deserts, Breezy W/SW winds over desert slopes and mountain passes, gusting 25-35 kts (up to 45 kts locally) through 12z Thu.
Otherwise, mostly clear and VFR conditions will prevail through Thursday afternoon.
No hazardous marine conditions expected through Sunday.
Ca, None. PZ, None.
