High pressure aloft will bring warmer temperatures for Thursday and Friday, primarily for inland areas where afternoon highs will be 5 to 10 degrees above average. Coastal low clouds will only extend into the western valleys for early Thursday and early Friday as the marine layer becomes a little shallower. A low pressure system moving into the western states will bring cooling and deepening of the marine layer for the weekend with coastal low clouds extending onto the coastal slopes of the mountains early Sunday.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Current satellite imagery this afternoon shows the marine layer clouds have retreated to the beaches or offshore with high cirrus clouds streaming in from the north. This northerly flow aloft is associated with a weak upper low west of Baja, which is progged to continue to drift south and east into Thursday. This allows weak ridging to build in, keeping weather quiet, trending temperatures warmer, and the marine layer locked in. The ridge axis peaks Thursday into Friday, with these days being the hottest of the week, high temperatures ranging 5-10 degrees above normal. Aside from the mild inland temperatures, the only other notable consequence of this pattern will be elevated winds in the mountains and deserts. The resulting pressure gradient from the nearby upper ridge is strongest on Friday and Saturday, which could bring 30-40 mph south-southwest wind gusts.
The next upper trough begins to push into the Pacific Northwest Friday into Saturday, helping to cool temperatures back down closer to average by Sunday. Ensembles begin to show some divergence in the strength/progression of this trough and a secondary/reinforcing upper low into early next week. Despite these subtle disagreements, the general consensus is that temperatures remain near to slightly below normal through mid-next week with typical June-gloom deep marine layer clouds.
031800z, Coast/Valleys, Satellite shows low clouds only around 2-5 miles inland, quickly retreating offshore. Bases currently around 1500ft MSL. SKC and VFR expected for all coastal sites by 19z. Low clouds move inland again tonight with lower bases around 1000-1200ft MSL and less inland extent, generally after 03z Thur. Low clouds may not make it up to KSNA until after 05z. Clouds will clear a little faster on Thursday, potentially by 16-18z.
Mountains/Deserts, VFR conditions through Thursday. FEW-SCT high clouds AOA 20,000ft MSL this afternoon, otherwise, SKC.
No hazardous marine conditions are expected through Sunday.
Ca, None. PZ, None.
