| Day | Date | High/Low | Forecast |
| Mon | 29th | 69/59 | Possible partial afternoon clearing; Otherwise, mostly cloudy through the evening. |
| Tue | 30th | 69/58 | Morning low clouds; Afternoon sunshine. Evening low clouds likely. |
| Wed | 1st July | 69/59 | Morning low clouds; Afternoon sunshine. Evening low clouds likely. |
| Thu | 2nd | 70/59 | Low clouds clearing by late morning. Late evening low clouds likely. |
| Fri | 3rd | 71/61 | Early morning low clouds; Otherwise, mostly sunny day. Chance of late evening low clouds. |
Synopsis
An upper level trough continues over the West Coast today (reason for relatively mild temperatures recently in the interior sections of the state). All the computer models maintain this trough for at least a couple of more days (gradually weakening though). So, any day to day weather changes in southern California should be minor (in theory). A general warming trend is anticipated by the 4th of July weekend.
As is often the case by this time of year, subtle changes in the low level, wind flow pattern can result in different “behavior” with the marine layer (one day to the next). There was good clearing of low clouds over much of the inner, coastal waters this morning but less so over land. Most areas west of the mountains have cleared out this afternoon but only partially in some spots. Tomorrow’s low cloud pattern could turn out differently in some locales (maybe starting out clear but clouding up for a time later in the morning). In any case, temperatures in most areas west of the mountains shouldn’t see more than a couple degrees difference (one day to the next). A healthy on-shore flow should help maintain brisk winds in the interior (stiff, afternoon sea breezes too in some coastal locales).
The southern end of the aforementioned, West Coast trough should give way to expanding high pressure from northern Mexico (forecast to happen second half of this week). By the holiday weekend, interior sections (i.e. mountain/desert region) should be seasonably warm or slightly warmer than normal. A return to seasonable temperatures for the coastal valleys and probably inland, coastal plain is anticipated. I’m less sure about areas closer to the coast. I over forecast the recent warming cycle last week (marine layer influence stayed stronger than I expected). While an unexpected, random disruption of the local, low cloud field potentially could mix warm air aloft down to the ground (producing warmer than normal weather), I’m staying on the conservative side (predicting UCLA will stay cooler than normal through the holiday weekend…normal afternoon temperature at UCLA 76 degrees).
Most of the longer range models show high pressure aloft anchored around four corner states (common for summer). Most model solutions don’t show the center of high pressure getting close to southern California. So, an excessive wave doesn’t appear probable next week (hot in the interior but not extremely so). As long as a defined marine layer sticks around, any warming cycle next week should be relatively mild (at most, slightly warmer than normal…includes over the subsequent weekend).
Some of the longer range models have predicted a “monsoon” moisture incursion in the Southland, but they keep putting it off with successive, model runs. The latest runs show some incursion possible by the 12th or 13th of July. Most solutions predict only a modest incursion (typical, isolated, afternoon showers/thunderstorms southern mountain/desert region). An uptick in muggy weather may also occur west of the mountains. Such weather is probable but whether this occurs before mid-July is still uncertain.
Next issued forecast/synopsis should be on Monday, 6 July.