| Day | Date | High/Low | Forecast |
| Mon | 15th | 71/60 | Sunny remainder of day. Clear evening. |
| Tue | 16th | 72/60 | Chance of some early morning low clouds; Otherwise, sunny day. Clear evening. |
| Wed | 17th | 70/59 | Chance of early morning low clouds; Otherwise, mostly sunny day. Mostly clear evening. |
| Thu | 18th | 69/59 | Chance of early morning low clouds; Otherwise, mostly sunny day. Mostly clear evening. |
| Fri | 19th | 68/58 | Chance of morning low clouds; Otherwise, mostly sunny day. Chance of evening low clouds. |
[Note: Issuance of forecasts/synopses will be just once a week for the summer.]
Synopsis
Like much of last week, high pressure aloft continues to dominate state weather. A weak, poorly defined trough also continues embedded within the high pressure region (now centered around or just west of San Luis Obispo County). All the computer models forecast a minor weakening of the aforementioned trough tomorrow, but the consequences on the surface on-shore flow pattern should be minimal. A little warming (relative to today) is anticipated for most areas tomorrow (most noticeable well inland areas), but a modest cooling trend should begin by the latter half of this week (temporary displacement of high pressure being the trigger).
Some upper level “monsoon” moisture worked its way into the Southland southern mountain region late last week. Sufficient moisture/instability remains for some afternoon cloud build-ups over the southern mountains. There shouldn’t be any shower clouds developing though (shower/thunderstorm threat stays to the south and east of the state). As upper level winds become westerly for a deep layer, drier air should return to that area (no further afternoon clouds expected by midweek).
The only other clouds of prominence will be marine layer clouds (mostly confined to the coast waters recently). The marine layer should be a tad shallower tomorrow (slight building of high pressure aloft), but a modest increase in on-shore flow later this week should allow for better areal coverage of coastal low clouds. By Friday and Saturday, some early morning low clouds may even reach some coastal valley locales. Of course, small unforeseen shifts in the low level, wind flow pattern may result in less clouds in some spots than others. Except for the coast, no persistent overcast (“June Gloom”) is currently anticipated.
High pressure aloft should begin to strengthen over the Southwest starting late Sunday. By the middle of next week, a number of model solutions show strong high pressure in the desert Southwest. If the high pressure center develops in western Arizona, it should get toasty for at least a few days over most of southern California (triple digits coastal valleys; topping 110 low deserts). Depending on how defined a shallow marine layer is next week, warming in the coastal plain may be modest (no more than about 80 degrees at UCLA for second half of next week). Since astronomical summer begins next week (21st at 1:24 AM), this warming period should be no surprise.
Next issued forecast/synopsis should be on Monday, 22 June.