| Day | Date | High/Low | Forecast |
| Fri | 6th | 69/60 | Low clouds clearing to a sunny afternoon. Low clouds likely returning in the evening. |
| Sat | 7th | 70/59 | Low clouds clearing late morning; Sunny afternoon. Chance of evening low clouds. |
| Sun | 8th | 71/59 | Early morning low clouds likely; Otherwise, mostly sunny day. Chance of late evening low clouds. |
| Mon | 9th | 72/60 | Early morning low clouds likely; Otherwise, mostly sunny day. Chance of late evening low clouds. |
| Tue | 10th | 74/60 | Chance of early morning low clouds; Otherwise, sunny day. Chance of late evening low clouds. |
Synopsis
The upper air disturbance that triggered showers/thunderstorms this past Tuesday was more active than I expected (some of the computer model forecasts actually did a good job for the afternoon period…less so for morning and evening, however). Most storm totals were a tenth inch or less, but a few spots (mostly around or over the mountains) did receive up to about 0.8 inch rain). Totals in the one third to one half inch range were more common among the wetter locales. The UCLA auto-gauge recorded 0.03 inch (other nearby stations reported similar totals).
Currently, a weak, upper level low pressure is meandering west of central California (separate feature from the low pressure that existed early this week). Disturbances rotating about the “parent” circulation have promoted some afternoon showers/thunderstorms in the Sierras. In southern California, marine layer clouds are the main weather feature west of the mountains. Afternoon clouds in the interior have prevails these past two days, but no showers have resulted (to my knowledge). The off-shore low pressure is forecast to meander for a couple more days, but it should weaken through the whole period. So, its influence on Southland weather should diminish this weekend. High pressure aloft is expected to build off the coast late this weekend through early next week. That should start a noticeable warming trend for well inland areas.
Things this week turned out a little cooler than I anticipated earlier in the week. Although the current low pressure is weak, it’s still promoting a healthy strength, on-shore flow (more so than most models predicted early in the week). Even today, some parts of the coastal plain (Ventura County southward to San Diego County) have seen limited clearing this afternoon (none for some locales near the immediate coast, especially Oxnard plain and coastal San Diego County). Better daily clearing is expected this weekend through the first half of next week, but there is a chance that a shallow but effective marine layer will persist. This could result in continued “June Gloom” weather (i.e. persistent low clouds into the afternoon hours) near the coast Well inland areas should see much more sunshine and moderate warming this weekend though.
Once high pressure builds into the Southland early next week, a brief heat spell is likely for well inland areas, especially the interior (nothing unusual for June). Even areas near the coast should get at least slightly warmer than normal on Tuesday (possibly Wednesday too). If the warm air aloft can mix down into the marine layer to punch some holes in the low cloud field, significant warming could include areas near the coast (campus included). Confidence in this scenario, however, is low for now (not explicitly being forecast by the numerical models today).
Most of the longer range models predict a new, upper level trough developing over or just west of the state late in the week. It should be too weak to promote showers (exclude any chances for marine layer mist). However, a few days of good on-shore flow should occur in southern California (valid this weekend through early next week). Such a pattern usually results in widespread, marine layer clouds west of the mountains (maybe “June Gloom” for a couple days or more). Small details in the low level, wind flow pattern will likely dictate the actual “behavior” of the low clouds from one day to the next, but temperatures for much of next week may be at or slightly below normal levels (more so for the coastal plain).
Any new return to warmer than normal weather may hold off till mid-month or slightly later. That’s when some model solutions show high pressure building over the desert Southwest. Model agreement is rather poor on how far west the high pressure will get. A limited extension westward would largely keep the strong heating to the desert region (above normal west of the mountains but potentially just minor warming near the coast).
Next issued forecast/synopsis should be on Monday, 9 June. [Note: I plan on just a once a week issuance beginning next week and lasting through the summer.]