| Day | Date | High/Low | Forecast |
| Thu | 30th | 70/56 | Mostly sunny remainder of day. Chance of late evening low clouds. |
| Fri | 1st May | 72/55 | Mostly sunny day except chance of early morning low clouds. Chance of late evening low clouds. |
| Sat | 2nd | 71/57 | Mostly sunny day with some high clouds except chance of early morning low clouds. Chance of evening low clouds. |
| Sun | 3rd | 68/54 | Variable clouds but generally partly cloudy through the evening. |
| Mon | 4th | 65/53 | Variable clouds but generally partly cloudy day; Possibly breezy at times in the afternoon. Scattered evening clouds. |
Synopsis
An upper level trough exists across the Southwest today (axis oriented southwest to northwest). It’s responsible for the recent cool down and return of marine layer clouds. Generally speaking, only minor day to day changes affecting Southland weather are forecast through Saturday. Slightly weaker on-shore flow is expected tomorrow. Subtle shifts in the low level, wind flow pattern (such as placement of a coastal eddy circulation) may affect what weather occurs on a given day. I show minor warming for the campus area, but depending on the actual wind flow around the area, it may turn out no warmer tomorrow than it got today (68 degrees, as of this writing). And since we’re now well into the spring season, don’t be surprised if persistent, marine layer clouds occur in some locales (not necessarily same locales each day).
By Sunday, a “cut-off”, upper level low pressure is forecast to be off the northern California coast. It will be large enough to affect southern California weather. This particular low pressure won’t have access to abundant, deep layered, water vapor, but it should induce instability showers over parts of northern California through at least Tuesday. For a time, some model solutions predicted instability showers developing in the Southland (sometime Monday-Tuesday period). Recent model runs haven’t completely ruled out showers, but chances in the coastal plain should be extremely low (not worth including in the “official” forecast). In a worst case scenario (for my forecast), spotty, marine layer induced drizzle/light rain could occur Sunday morning. Isolated mountain showers might be possible Monday and Tuesday afternoons. Winds aloft on Monday would carry mountain shower clouds into the desert. Any showers Tuesday afternoon should remain to the east and south of L.A. County. Rainfall, if it occurs, should be under a quarter inch (includes mountain areas).
Cooler than normal temperatures should prevail Sunday through Tuesday (possibly Wednesday too). Warmer weather is expected next Thursday and Friday, but only modest warming is anticipated (at most, getting slightly warmer than normal). Another cool down is forecast for Mother’s Day weekend. How much cooling occurs remains to be seen, but there is a chance at some “May Gray” weather (i.e. persistent marine layer clouds west of the mountains). As with many marine layer patterns, I don’t have great confidence in weather details, be it one day or ten days into the future.
Next issued forecast/synopsis should be on Monday, 4 May.