| Day | Date | High/Low | Forecast |
| Thu | 3rd | 76/64 | Mostly sunny remainder of day. Possible return of some low clouds in the evening. |
| Fri | 4th | 78/65 | Chance of early morning low clouds; Otherwise, mostly sunny day. Some evening low clouds possible. |
| Sat | 5th | 80/67 | Chance of some early morning low clouds; Otherwise, mostly sunny day. Becoming partly cloudy in the evening. |
| Sun | 6th | 80/66 | Partly to mostly cloudy through the evening. Chance of light showers, mainly in the morning. |
| Mon | 7th | 80/66 | Partly cloudy through the evening. |
Synopsis
An upper level trough continues along the West Coast today. It has produced some wet weather has far south as the northern most part of California (most numerous showers around/over mountains). While weak on its southern end, the trough has promoted cooler than normal weather in the Southland (welcome relief from the recent, hot and muggy weather). All the computer models show the upper trough weakening a bit tomorrow/Saturday. Although changes in the low level wind flow appear minor to negligible, the models forecast a minor warming for the subsequent two days (I followed the model output even though tomorrow could easily wind up the same as today, temperature-wise).
Hurricane Marie (category 1 storm though potentially capable of strengthening to category 2) was centered about 450 miles southwest of the southern tip of Baja California early this afternoon. A few models continue to show a weakened storm (down to tropical depression status) reaching the local waters (solutions vary from near San Diego to as far north as Santa Barbara)…valid time after Labor Day. However, not surprisingly, the vast remaining model solutions keep Marie’s surface circulation far from the state (at most, a remnant circulation may get as far north as several hundred miles west of San Diego).
The various models do show the aforementioned, West Coast trough siphoning off moisture from the hurricane and directing it toward southern California. At the least, the weather should turn cloudier and more humid over the Labor Day weekend (reaching San Diego area first by Saturday afternoon). A chance for showers could reach L.A. County as early as late Saturday evening, but the main threat in the County should be during the morning on Sunday. Isolated, brief-lived thunderstorms would be possible, but that threat should be mainly in the mountain/desert region (slightly greater instability expected there).
Run to run model consistency has been lacking so far with respect to how much rain may fall in the Southland. Widespread, heavy rain and wind appears an extremely low possibility now that most models keep Marie’s center far from the Southland, Isolated moderate to heavy showers/thunderstorms remain possible if upper air disturbances embedded within the West Coast trough are sufficiently strong. Today’s model consensus keeps L.A. County rainfall mostly under a quarter inch (mountains may get a little more). However, just where the showers fall remains to be seen. The predicted, southwest to northeast oriented shower bands may stay mostly to the south and east of L.A. County. In that case, L.A. County storm totals may be a few hundredths of an inch at most (maybe just trace amounts for some).
There are some model solutions that keep sufficient moisture around on Labor Day to support scattered showers. Since they should occur mostly in the mountain/desert region, I omitted any shower chances for the campus forecast. There are also some model solutions keeping a flow of “monsoon” moisture through next Thursday. However, that scenario is far from certain. In any case, the chief threat of showers/thunderstorms would be over the mountain/desert region anyway.
Most of the longer range models favor warmer weather for most of next week. There is a chance for widespread 90 degree weather in the inland, coastal plain by the middle of next week (return of some triple digit heat in the valleys). If today’s model consensus holds true (?), cooler weather will follow over the subsequent weekend (cooler than normal by mid-month).
Next issued forecast will be on Tuesday, 8 September, but possibly delayed to midday.