| Day | Date | High/Low | Forecast |
| Mon | 14th | 77/65 | Low clouds clearing to a sunny afternoon. Chance of evening low clouds. |
| Tue | 15th | 76/65 | Morning low clouds but sunny afternoon. Chance of evening low clouds. |
| Wed | 16th | 75/65 | Morning low clouds likely but sunny afternoon. Chance of evening low clouds. |
| Thu | 17th | 75/64 | Morning low clouds likely but sunny afternoon. Chance of evening low clouds. |
| Fri | 18th | 76/64 | Good chance of early morning low clouds; Otherwise, mostly sunny day. Mostly clear evening. |
Synopsis
An upper level trough finally brought southern California, daytime temperatures down to or below normal yesterday (overnight temperatures most areas still higher than normal, though only slightly, as of this morning). A couple more troughs tomorrow and Wednesday should continue to promote “mild”, late summer weather. Temperatures should be a bit lower than it gets today. (FYI– It got a couple degrees warmer at UCLA than I predicted, but I kept the forecast for subsequent days unchanged…Today’s readings may be fluke though subtle, day to day wind shifts could influence actual, daily highs, up or down by a couple degrees).
Widespread, marine layer clouds prevailed in the coastal plain early today (partly due to a large, coastal eddy). Little change in the pattern is anticipated through at least Wednesday (potential for widespread coverage in the coastal valleys too). The marine layer is fairly deep for this time of year, but thanks to the “warm” ocean locally, low clouds dissipate more easily (reaching evaporation point more quickly than with a “cold” marine layer). The West Coast troughing pattern is expected to weaken in the second half of the week. In theory, weaker on-shore flow should lead to less extensive, marine layer clouds. A warming cycle is expected by Friday, but the computer model consensus favors only a brief, at best, modest warm up (mainly well inland areas). For areas near the coast (UCLA included), only minor warming is expected.
Any warming trend should be short-lived. Most model solutions show a new, upper level trough developing along the West Coast by Sunday. At the least, a return of weather similar to now should prevail early next week. With astronomical autumn arriving on Tuesday (5:05 PM PDT), some model solutions show some “cool” weather sometime next week (far from certain though). I wouldn’t necessarily describe it as sweater weather, but late afternoon hours may have a nippy feel relative to recent days.
While far from unanimous, most of the longer range models don’t favor any great, heat spells for the next couple of weeks. The window for “monsoon” moisture incursions into the Southland is nearing a close though a few model solutions do keep a window open for a time. In addition,there are no definitive signs so far in a model predicted, Santa Ana wind, but that season isn’t too far off normally (October).
Next issued forecast/synopsis should be on Monday, 21 September.