| Day | Date | High/Low | Forecast |
| Fri | 12th | 77/62 | Hazy sunshine remainder of day and some afternoon mid/high clouds. Some evening high clouds possible. |
| Sat | 13th | 75/61 | Chance of early morning low clouds; Otherwise, mostly sunny day with some high clouds. Mostly clear evening. |
| Sun | 14th | 74/61 | Chance of early morning low clouds; Otherwise, sunny day. Mostly clear evening. |
| Mon | 15th | 75/62 | Chance of early morning low clouds; Otherwise, mostly sunny day with some high clouds possible. Some evening high clouds possible. |
| Tue | 16th | 76/63 | Chance of early morning low clouds; Otherwise, mostly sunny day with some high clouds. Mostly clear evening. |
Synopsis
[Note: Starting next week, forecast issuance will change to once a week for the summer.]
High pressure aloft covers much of the northeastern Pacific as well as the desert Southwest. However, a weak trough is embedded within this region of high pressure (trough lies west of Baja California but northern edge reaches southern California). Early this morning, radar detected some minor shower clouds over San Diego County. It was uncertain if any rain drops reached the ground since the moist air lay well aloft (dry air beneath except for a shallow marine layer near the ground). That minor, “monsoon” moisture well aloft should fade over the weekend (trough weakens further and passes westward).
It got warmer than I expected yesterday despite a decent strength, surface on-shore flow. Increased water vapor content at the surface might be explained by subtropical air aloft mixing down to the ground (aforementioned trough being the trigger). However, it might also be explained by the recent warming of ocean surface (68 degrees in parts of Santa Monica Bay…several degrees above normal for this time of year). In any case, temperatures yesterday/today have been higher than what I’d normally expect for the given, low level, wind flow pattern in place currently.
All the computer models predict minor day to day weather changes for the next several days (nothing unusual by this time of year). A shallow marine layer will be supported by moderate strength on-shore flow through the weekend. High pressure aloft does strengthen some late Sunday through Tuesday (at least). That should promote some renewed warming early next week in most areas. As usual, there is some uncertainty about how much warming/cooling will occur with waxing-waning of high pressure aloft. For this forecast I’ve kept campus temperatures slightly above normal, but if less vertical air mixing takes place on any given day, temperatures could be a few degrees lower (also applicable to other areas of the coastal plain).
Except for a chance by the coast (satellite imagery showed a return of low clouds in the South Bay area at mid-afternoon), I’m not predicting a relevant chance for “June Gloom” episodes through next week. No unusually strong, upper trough is forecast through next week, but the warmer than normal ocean should help support warmer than normal temperatures near the coast (strength of high pressure aloft being more influential for more well inland areas).
It’s far from certain, but there are some longer range model forecasts for strong high pressure aloft by the 25th (Astronomically speaking, summer begins on 21 June at 1:24 AM). If it happens, much warmer than normal weather can be expected for most of the Southland (beach areas, as usual, should escape the heat).
Next issued forecast/synopsis should be on Monday, 15 June.