| Day | Date | High/Low | Forecast |
| Mon | 2nd | 71/60 | Mostly sunny rest of day with some afternoon high clouds possible. Becoming mostly cloudy in the evening. |
| Tue | 3rd | 70/59 | Partly to mostly cloudy through the evening. Slight chance of light showers in the afternoon/evening. |
| Wed | 4th | 70/59 | Mostly cloudy morning with a slight chance of light showers early; Mostly sunny afternoon. Evening low clouds likely. |
| Thu | 5th | 70/60 | Good chance of morning low clouds but mostly sunny by afternoon. Chance of evening low clouds. |
| Fri | 6th | 71/61 | Chance of morning low clouds; Otherwise, mostly sunny remainder of day. Chance of evening low clouds. |
Synopsis
Although on-shore flow was on the increase yesterday, it wound up warmer than I expected in most locales. Apparently, an approaching upper low pressure (a few hundred miles west-southwest of Point Conception early this afternoon) didn’t exert enough atmospheric lifting to cool the lower atmosphere (until last night). Today’s weather has been more in line with what most of the computer models predicted last week.
Last week, the predicted, upper low pressure, now affecting Southland weather, would be too weak to threaten the region with showers, let alone thunderstorms forming. More recent model runs, however, have predicted scattered showers and even some thunderstorms in the interior for tomorrow into Wednesday (latter mainly for interior section). Some of the “monsoon” moisture aloft from former, tropical storm Alvin has lingered(came into the Southland over the weekend; produced some afternoon thunderstorms in the interior as well as some light showers in San Diego County). The upper low pressure, while relatively small in areal size, does possess a distinct circulation. Thus, I decided to write in a slight chance for light showers for the Tuesday afternoon/evening period. Some of the models do show showers by late in the morning hours in L.A. County, but that seems a little too quick (better atmospheric dynamics working on deep layered moisture arrive in the afternoon…or so, the models predict). Wherever the showers occur, most should be inconsequential (not measurable). Rainfall should be mostly under a tenth inch away from the mountains (up to a third inch there unless a thunderstorm occurs…up to half an inch, in a worst case scenario).
By the predawn hours on Wednesday, the shower threat in L.A. County should be winding down or ended (may take a little longer down in San Diego County; shower/thunderstorm threat in the interior may continue well into the afternoon). While I show a mostly sunny afternoon in the forecast, some areas may actually see only limited clearing.
The remainder of the week should have mundane weather (on-shore flow supporting marine layer clouds near the coast each day). A very weak trough, following on the heels of the now approaching low pressure, might support areas of stubborn low clouds Thursday morning, but a slow warming trend is anticipated later this week. By the weekend, subtropical high pressure aloft should exert more weather influence. That should result in moderate warming for well inland areas (possibly getting slightly warmer than normal). The temperature trend near the coast will depend on how well defined the marine layer will be at that time (decent strength on-shore flow usually supports limited warming nearer the coast).
Most of the longer range models show some form of trough nearing the state sometime next week. That should favor some cooling for at least a day or two (by midweek, based on today’s model consensus). However, there are some model solutions that keep the effects of the trough well to our north. In that scenario, local forces would dominate (daily sea breeze pattern of undetermined strength). I’m leaning toward near seasonable temperatures next week for the campus area but confidence isn’t high for now.
Next issued forecast/synopsis may be on Friday, 6 June. [Note: Like in the past, I plan on switching to a once a week issuance starting next week and lasting through the summer.]