| Day | Date | High/Low | Forecast |
| Mon | 24th | 74/56 | Sunny day. Mostly clear evening. |
| Tue | 25th | 74/54 | Mostly sunny day with some high clouds. Some evening high clouds. |
| Wed | 26th | 67/53 | Chance of morning low clouds; Otherwise, partly cloudy with high clouds. Mostly cloudy evening. |
| Thu | 27th | 67/53 | Partly to mostly cloudy through the evening. |
| Fri | 28th | 66/52 | Partly cloudy morning; Mostly sunny afternoon. Partly cloudy evening. |
Synopsis
When I wrote the campus forecast this morning, my main concern was with marine layer clouds in Santa Monica Bay. Despite high pressure aloft inducing a marginal, off-shore flow (in this case, surface gradients off-shore toward the high desert but on-shore toward the low desert), satellite imagery showed low clouds/fog creeping closer to the coast. A shallow but effective marine layer could hinder significant warming near the coast (too shallow to really affect well inland locales though…reason for many coastal valleys reaching the 90 degree mark this afternoon). Thus, I decided to shave off some degrees to my forecast from last week (74 down from 79). Well, as it turned out, the campus warmed to 79 degrees briefly before noon. However, by 12:15, the sea breeze cooled the campus back to my revised high. Nearby Santa Monica airport did not warm pass the low 70s (a rather chilly 59 degrees with a few low clouds, as of this writing). Forecasting is often a matter of timing.
The marginal off-shore flow is forecast to transition to a full fledged, albeit weak, on-shore flow tomorrow afternoon. The current mass of low clouds/fog seen on satellite imagery may become entrenched tomorrow. I considered amending the forecast (valid for Tuesday) with a lower, daytime high and adding low clouds, but it wouldn’t take much vertical air mixing to punch holes in the current low cloud field (in Santa Monica Bay). Considering how warm it got at UCLA today (even nearby V.A. Hospital reached 77 degrees earlier today), I thought “74” as a reasonable compromise high…cooler but not too cool). Should the marine layer make a roaring comeback tomorrow, however, the campus will likely struggle to reach the upper 60s.
A very weak, sub-tropical, upper level trough will pass through southern California Wednesday morning. Besides variable high clouds associated with the trough, increasing on-shore flow (compared to tomorrow) should promote widespread, morning low clouds in the coastal plain (not necessarily as a solid overcast at first though). The marine layer should stick around for the remainder of this week. Hence, temperatures should be slightly cooler than normal (some chance that my chosen numbers will be a bit on the high side, depending on how persistent marine layer clouds get).
Beginning on Thursday and lasting into the first days of April (possibly longer), a series of fast moving, upper level troughs should promote on-shore flow and perhaps an occasional threat of marine layer induced drizzle/light rain. There could be the additional threat of cold air instability showers (mostly over/adjacent to higher mountains) by late in the weekend onward. These “waves” are more certain to bring occasional wet weather to northern California (most minor events, based on today’s computer model consensus). Because storm dynamics associated with the troughs should stay to the north of the Southland, it’s unclear (to me) if any widespread shower activity will get this far south. For this forecast, I left out mention of any shower threat. Despite a predicted, deepening marine layer Thursday, most areas should stay rain free (perhaps, some spotty drizzle along some coastal facing foothills/mountains). Friday’s trough may bring some light showers as close as Santa Barbara County. I do get more concerned for the Sunday and beyond period, but that’s outside of today’s forecast period. In any case, any predicted precipitation in southern California isn’t likely to be significant (based on recent model forecasts).
Next issued forecast/synopsis may be on Friday, 28 March.