| Day | Date | High/Low | Forecast |
| Fri | 2nd | 65/57 | Becoming mostly sunny in the afternoon. Mostly cloudy evening. |
| Sat | 3rd | 64/55 | Possible partial afternoon clearing; Otherwise, mostly cloudy through the evening. Slight chance of light showers late afternoon and evening. |
| Sun | 4th | 64/54 | Partly to mostly cloudy day with a slight chance of brief showers. Partly cloudy evening. |
| Mon | 5th | 65/54 | Some morning clouds but mostly sunny day. Some evening clouds possible. |
| Tue | 6th | 67/55 | Mostly sunny day with some clouds possible. Mostly clear evening. |
Synopsis
Upper level low pressure continues over the Southwest (center east of Yuma, Arizona), but it’s weaker than yesterday. While still deep, I thought a slightly weaker on-shore flow would permit better clearing of low clouds today. That wasn’t the case. So, temperatures in most areas (so far) haven’t matched yesterday’s levels. Chalk it up to the eccentricities of the marine layer. At least, the aforementioned low pressure isn’t promoting as active a day of showers/thunderstorms in the interior as was the case yesterday (being weaker and further east of the area).
All the computer models show a new, Pacific trough moving south toward southern California. Renewed stronger on-shore flow should promote more persistent, low clouds tomorrow (in theory). Patchy morning mist/drizzle should occur (mostly around coastal facing foothills/mountains), but as the trough makes its way into the Southland late tomorrow, there should be an opportunity for marine layer induced showers (nothing heavy). The chance for marine layer showers should last into early Sunday morning. Since the various models have trended weaker with the approaching, new trough, I decided to limit the shower threat at “slight”.
Although the center circulation of the aforementioned, new trough should be east of L.A. County by late Sunday morning, there may be sufficient, atmospheric instability to promote some afternoon, mountain showers and isolated, brief-lived thunderstorms. The predicted north winds on the western half of the low pressure potentially could guide some of those showers into the L.A. County coastal valleys/plain. Hence, that’s the reason for my keeping a slight risk of showers through the afternoon hours. Any heavy intensity showers should rapidly weaken once it moves into the lowlands (much more stable air predicted west of the mountains).
By Monday afternoon, the low pressure center should be over eastern Arizona. Things should be drying out over most of the Southland, but sufficient, lingering instability might promote isolated showers in the interior that day. After that, dry weather in the interior should be the rule for the remainder of next week. The fate of the local, marine layer should be one of shallow and possibly diluted one as next week progresses. If the low cloud field manages to hang in, it should be more restricted in areal coverage (just near the coast by the middle of next week).
High pressure aloft is forecast to build into the Southwest by the middle of next week. It should hold strong through the end of next week (possibly through the subsequent weekend). No off-shore flow is currently being predicted, but the predicted strength of high pressure aloft should induce good subsidence warming for well inland areas. Warmer than normal weather should prevail by the middle of next week (lasting several days). 90 degree weather will be possible for some valley locales.
Warmer weather is anticipated closer to the coast too, but how much warming occurs will depend on how much of a marine layer lingers next week. A shallow but defined marine layer could greatly limit the warming trend (maybe only getting slightly warmer than normal (UCLA normal high in early May is 70 degrees). Even a diluted marine layer could keep areas near the coast from exceeding the mid-70s, provided the on-shore flow is strong enough.
Next issued forecast/synopsis may be on Monday, 5 May.