Moisture over southwestern California will slowly decrease today and Thursday, with decreasing chances for afternoon and early evening showers and thunderstorms in the mountains and high desert. Dry for Friday into next week, with a warming trend through the weekend. High temperatures will peak Sunday and Monday at a few to around 5 degrees above average for coastal areas and 5 to 10 degrees above average for the mountains and deserts. Night and morning coastal low clouds will cover much of the valleys into Thursday, then not spread as far into the valleys for the weekend into early next week as the marine layer becomes shallower.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
This afternoon, Satellite imagery shows cumulus cloud buildups over the local mtns but radar is yet to detect any precipitation, except over the mtns of northern Baja. There is still time for showers/tstms to develop this afternoon/evening in our local mtns. Any convective activity will likely dissipate around 7 pm. The marine layer low clouds are very slow to clear and continue to cover the coastal areas and the western portions of the San Diego County valleys.
From previous discussion, The atmosphere over SoCal will steadily become drier today through tomorrow for decreasing chances of afternoon showers/tstms as conditions become more stable.
In spite of broad troughing over the western US through Friday with a closed upper low developing off the CA coast on Sat, temperatures will slowly rise through the weekend. Friday high temperatures will be mostly within a few degrees of average, ranging from around 70 near the coast to the 80s for the Inland Empire, with 100 to 104 for the lower deserts.
As we move into the weekend, the sub-tropical high over northern Mexico will build over AZ and extreme southeastern CA. Slow warming will continue through the weekend with the heat peaking on Sunday and Monday. High temperatures for Sunday will range from a few to around 5 degrees above average for coastal areas and 5 to 10 degrees above average for the mountains and deserts. High temperatures on Sunday will range from the lower 70s near the coast to the mid 80s to mid 90s for the Inland Empire, with 105 to 110 for the lower deserts. The marine layer will become shallower with night and morning coastal low clouds not spreading as far into the valleys.
Not unexpectedly, model solutions diverge as we move into next week so there is measurable uncertainty in the forecast details. In general, we will see the sub-tropical ridge expand westward but remain to our south with weak ridging over the west coast. We can expect dry conditions to persist through the middle of next week with a shallower marine layer modifying temperatures near the coast. Inland temperatures will remain mostly several degrees above average.
042030z. Coast/Valleys, Low clouds based 1000-2000 ft MSL with tops to 2500 ft are present along most of the coast and locally to 20 miles inland. Some clearing for inland areas and the northern Orange County coast will continue through about 22Z, but clouds will otherwise linger along the San Diego County coast. Low clouds will push inland again after 00Z to fill most of the coastal basin overnight, with bases lowering to 1000-1500 ft MSL and inland vis reduced 3-5SM in BR. Clearing Thu morning 15-17Z for inland areas, 18-20Z for Orange County coast, and only partial clearing for San Diego County coastal areas 19-21Z, with KCRQ and KSAN likely remaining under cloud cover all day once again.
Mountains/Deserts, ISO SHRA/TSRA based at 10000 feet MSL possible over the mountains and high desert through 01Z this evening. Turning mostly clear thereafter.
No hazardous marine conditions are expected today through Monday.
Ca, None. PZ, None.
